Re-associating constants can enable further simplification e.g. when
those constant become all zero/all ones. Run these patterns to fixed
point to capture the simplification, by revisiting the node.
V3Const eagerly deletes nodes (we want that in V3Const instead of using
pushDeletep, as otherwise the transient peak memory use during
verilation can be very high)
The std::map used to cache the predicate checking if a subtree contains
a member access then stale if a new node is allocated in the same address.
Fix by using unique node IDs stored in user4 as cache keys.
This is the bug uncovered by #8147
Related to #6963
Disable MULTIDRIVENPROC for static variables used as loop induction
variables. Same way as we disable similar warning in Dfg. While bad
style and bad for performance, it's common legacy code style.
The loops modelling the SystemVerilog scheduling regions are no longer
generated. They now live in 'VerilatedEvalLoop' in the runtime library.
The generated model holds one as a member, passing itself to it, and
exposes each evaluation entry point to it as a pure virtual method on
VerilatedModel. The model's 'eval' and 'eval_step' remain the top level
entry points, and are backward compatible.
V3Sched no longer emits '_eval' or '_eval_settle', etc.. Instead every
evaluation entry point called from the runtime is enumerated by 'VEval',
Scheduling creates all entry points, for all scheduling regions, even if
they are empty, and the runtime eval loop calls everything
unconditionally. If regions are empty, this is simply a call to an empty
function. This will hurt performance on very small models, but should
not be noticeable on anything meaningful, so it is likely best to keep
to reduce complexity.
A scheduling entry points evaluate a single iteration and returns
whether it did any work, they are effectively the previous
`_eval_phase_*` functions.
Notifications posted on pull requests now carry a marker naming their
source, as an HTML comment on their first line, which is invisible when
rendered. When posting, 'ci-pages-notify.bash' finds its own earlier
notifications with the same marker on that pull request, and deletes them.
A pull request therefore holds a single comment per source, rather than
accumulating one per run.
The superseded comments are not lost entirely. Each notification carries a
one line summary linking its report, stashed in an HTML comment, and the
notification superseding it inherits that summary, together with the
history the superseded one held itself, into a collapsed 'Workflow history'
section. That section therefore lists all the earlier reports, stays flat
however many runs a pull request sees, and holds no entry for the report
shown right above it.
The 'pr-notification' artifact is now uploaded via the new reusable
'upload-pr-notification' action, which validates the content the reporting
scripts produced, and records the source key and the pull request number
alongside it.
Fixes#8037
The following used to crash:
```systemverilog
class base #(type T = int); endclass
class derived extends base; endclass
derived #() d; // <- crash due to '#()'
```
Belt-and-braces in case GitHub apt mirrors start acting up again: On any
successful apt install, cache the deb files downloaded/needed for the
step, so on next run the mirrors need not be consulted. (That is: trade
apt mirror access with GitHub cache access, which is more reliable)
These tend to hang for hours on occasion. Install all apt dependencies
via ci-install.bash, and add a hard timeout and retry for each attempt.
Also removed unnecessary man-db config (GitHub has this off by default
now) and ineffective install path exclusions.
Re-associating constants can enable further simplification e.g. when
those constant become all zero/all ones. Run these patterns to fixed
point to capture the simplification, by revisiting the node.
Introduce a new DfgPrev vertex, representing the value of a variable
before any in-graph assignments. This can be used to break all remaining
cycles in the graph, so all Dfgs become acyclic after V3DfgBreakCycles.
The circular dataflow is still represented, and is taken care of by the
scheduler, it is just the DfgGraph that represents the logic that
becomes acyclic.
This makes V3DfgBreakCycles a mandatory transform, so drop the disabling
-fno-dfg-break-cycles option (still parsed, but has no effect).
Note the effect of this is small, as most cycles can be fixed up by
driver tracing, which is unchanged, but this is required for some
upcoming work.
AstScopeName is an AstNodeExpr, but V3Task stashed the DPI export scoping
marker into the enclosing AstCFunc's statement list (addStmtsp), placing an
expression in a statement position.
Give AstCFunc a dedicated 'scopeNamep' operand to hold the marker instead.
Part of #6280
An elaboration severity system task ($info/$warning/$error/$fatal used
as a module/generate/program/checker item), which is a module item,was
parsed as an AstInitial wrapping an AstElabDisplay. That put
AstElabDisplay (a non-statement) into the procedural statement list of
an AstInitial.
AstElabDisplay is evaluated by V3Width, which then deletes it. The
AstInitial wrapper is historic and has no effect.
Part of #6280
AstConstraintBefore ('solve x before y') is a constraint item that appears
in constraint bodies alongside its siblings AstConstraintExpr,
AstConstraintUnique and AstConstraintIf, all of which are AstNodeStmt.
Part of #6280.
The OrderGraph used during V3Order step deliberately omits some variable
accesses from the dependency graph. E.g.: a read of a variable that is
in the reading block's own hybrid sensitivity list emits no edge, nor
does a read ignored due to a force/release, nor an access to a variable
marked 'ignoreSchedWrite' and friends. For serial mode that is fine, the
logic runs one block at a time. In parallel mode two such blocks can run
concurrently, and if one writes what the other reads, that is a data
race at runtime.
These accesses cannot be recovered from the graph edges. They are now
collected from the AST while the OrderGraph is built, and held by the
OrderLogicVertex performing them.
FixDataHazards is reworked around these access lists stored in
OrderLogicVertex, so it is now aware of all variable accesses the logic
makes, including those not encoded by the dependency graph edges. The
previous heuristic of fixing data hazards by merging same-rank MTasks is
removed. Additional edges are inserted instead to prescribe a fixed
ordering of conflicting MTasks. To insert edges without unduly
increasing the critical path, or introducing cycles, new edges are
added such that they preserve topological ordering, and they are
inserted between vertices sorted by critical path length. See algorithm
details in the code.
Also add a data hazard checker under '--debug-partition', reporting every
unordered accessor pair left in the final MTask graph.
This fixes the race demonstrated by t_sched_hybrid_hazard (#7913),
which is no longer expected to fail.
Under ThreadSanitizer over the vltmt tests: 17 failing before, 3 after,
with no regressions. The 3 remaining are different defects.
This is a large refactor of the MTask graph and coarsening algorithm, in
prep for fixing the bug described in #7913, it can also improve the
resulting multi-threaded schedule.
Two major changes:
OrderMTaskGraph now maintains the critical paths of the MTasks through
mutation. There are 2 ways to mutate the graph, which are done via
methods on the graph itself: adding an edge (used during construction,
and will be used later during fixing data hazards), or merging an MTask
into another (used during contraction). All critical path measures are
automatically updated and propagated on any mutation, so no external
algorithm needs to maintain them explicitly.
The merge candidate scoreboard used during contraction is simplified to
remove deferral of updated scores. This simplifies the code and results
in a greedily more optimal schedule. (The previous tranched rescore was
an optimization to work around the previous std::set based scoreboard,
however since the algorithm now uses an efficient PairingHeap,
verilation time is not impacted by the more accurate scoring, while
yielding better results).
Combining these two into a single patch as the code is highly
interdependent and any one change without the other would be just a
noisy transit point with unclear performance implications. Together it
should be a clear improvement.
Also added a stronger validation step run with '--debug-partition',
which checks all invariants throughout the algorithms.
A '{N{bit}}' mask expands to a bit vector where every word is the same
value, obtained by negating the replicated bit. Recomputing that at each
use is no more expensive than loading it
splitCheck() cuts a function's top level statement list on node count
alone, ignoring AstVar declarations in that list. localizeVars() puts the
dynamic trigger temporaries there, which a 'wait fork' reaches, so the
declaration could land in one sub-function and its references in another.
Sub-functions are emitted as separate C++ functions, so the output failed
to compile:
error: '__Vtrigprevexpr_h5d9da2ce__0' was not declared in this scope
V3InlineCFuncs could also inline the sub-function holding the declaration
and free the AstVar while other sub-functions still referenced it, which
--debug reports as a broken link and which segfaults an -O3 build.
The existing "Can't split function with local variables" assertion only
checked AstCFunc::varsp(), not declarations among the statements.
Only allow a sub-function boundary where it does not separate a local
declaration from a reference to it. This keeps the temporaries function
local, as #6859 requires, while restoring the guarantee #5822 made that
splitting cannot orphan them.
Signed-off-by: Marco Brambilla <[email protected]>
MT scheduling used to round MTask costs to the nearest 5% to supposedly
reduce the amount of work required for propagating critical path change
updates. Profiling shows this doesn't actually save any verilation time,
as the floating point arithmetic itself is costly, and the propagation
savings only kick in when merging small tasks into large ones, which is
not the common case. (The float arithmetic also made this step
non-reproducible across host architectures and libm versions due to
numerical variance.)
Remove and use precise costs instead.
As the removed comment suggests, this is dubious and RTLMeter suggests
it makes no measurable difference on average (some designs improve, some
regress small amounts, on average ~1.0x)
Prep for further fixes that will remove the pre ranking.
Prep for fixing test added in #7913.
This is a large scale no functional change refactor, however, MT output
is perturbed as tied scores will be broken differently due to ordering
changes (still deterministic).
Split multi-threaded scheduling out of the monolithic
V3OrderParallel.cpp, into relatively independent parts, simplify the
data structures, and drop redundant or unused code.
New translation units:
- V3OrderMTaskGraph.h/.cpp: OrderMTaskGraph, the graph of LogicMTask
vertices and MTaskEdge edges. LogicMTask and MTaskEdge no longer
depend on the coarsening algorithm's merge candidate types;
per-algorithm auxiliary data is attached externally via the vertex and
edge user pointers.
- V3OrderMTaskFixHazards.cpp: data hazard fixup, was FixDataHazards.
- V3OrderMTaskContraction.cpp: graph coarsening, was Partitioner
together with PropagateCp and the merge candidate types.
- V3OrderParallel.cpp: now just the partitioning driver and ExecMTask
graph construction.
Data structure changes:
- Delete V3Scoreboard.h/.cpp. The generic template had a single user, now
a file-local MergeCandidateScoreboard in V3OrderMTaskContraction.cpp.
- Merge candidates are now MergeCandidate/SiblingMC/EdgeMC, distinguished
by a bit in the candidate id rather than by a vtable, and allocated by
the scoreboard, which owns their lifetime. This removes the multiple
inheritance previously used by MTaskEdge.
Move `hashGraphDebug` which prints the hash of a graph's shape for debugging
to generic `V3Graph::hashGraphDebug`.
Removed (can be added back later):
- Unnecesasry self tests that force special data stucture requirements.
- Per stage --stats output under --debug. (Final figures still reported.)
- Various debug dumps
The REPLACE_SHIFTL_SHIFTL and REPLACE_SHIFTR_SHIFTR peephole optimizations
fold '(a << b) << c' into 'a << (b + c)' (and likewise for '>>'), but computed
'b + c' in the width of the shift-amount operand. When 'b + c' overflows that
width it wraps around, producing a too-small shift amount and a wrong result.
Compute the sum one bit wider than the amounts so it cannot overflow.
Fixes#7955
PR #7902 uncovered a pre-existing bug in multi-threaded scheduling,
where we can end up with an un-ordered R-W hazard in the MTask graph,
resulting in non-deterministic runtime behaviour.
This is extremely hard to actually trigger on a small example, so using
ThreadSanitizer to flag it, which can identify the race reliably.
In this patch:
- Add configure and `verilator --get-supported TSAN` to check if the
configured compiler supports ThreadSanitizer
- Add a --tsan option to the test driver.py which builds the test with
thread sanitizer (similar idea to --gdbsim).
- Add a tests.enable_tsan() method to allow turning on TSan in the test
Python file.
- Add a suppressions file that waives TSan errors in the runtime library
- Finally add `t_sched_hybrid_hazard` that demonstrates the data race
triggered after #7902. This is currently expected failing, fix later.
With the suppression, there are 17 vltmt tests failing due races in the
generated code. (Using `driver.py --vltmt --tsan --quiet -j0`)
Change default debug build to use -O0 instead of -Og as the latter is
still not great debugging experience. Use -Og -gz, plus the new -ggdb1,
which together significantly cut down debug info size, to save CI cache
space, while still enabling -gdbbt tests to work.
Cache key isolation: Include the build flavour (ccwarn/asan/gcov) in the
build ccache key, so the coverage (gcov), asan, and RTLMeter
(ccwarn-off) configurations no longer share and thrash the single
'<runs-on>-<cc>' bucket, nor warm-start from each other's (near-useless)
caches.
Prune stale entries instead of a fixed size cap: After building/testing,
evict ccache entries this run did not touch (--evict-older-than, based
on the run's own duration). This bounds the saved cache to the current
working set, so CCACHE_MAXSIZE and CCACHE_LIMIT_MULTIPLE are no longer
needed and are removed (ccache falls back to its 5G default ceiling, but
is realistically much smaller).
ccache configuration:
- Drop CCACHE_COMPRESS (already the default in ccache 4.x).
- Add CCACHE_COMPILERCHECK=content, so a changed compiler mtime on a rebuilt
ephemeral runner image does not invalidate the whole restored cache.
- Hoist all ccache-related variables (CACHE_BASE_KEY, CCACHE_*, CXX) to the
workflow-level env.
Remove dead ccache scaffolding:
- reusable-lint-py: the job never compiles or caches; drop its ccache env.
- reusable-rtlmeter-run: remove the disabled persistent-cache step and its
storage variables; keep CCACHE_DISABLE=1, since caching must stay off to
keep RTLMeter timings representative.
Store test job ccache as artifacts for reuse
Code coverage and RTLMeter complete (concluding 'skipped') on branch
pushes where they do no work, and each completion fires the Pages
workflow_run trigger. Rebuilding and redeploying master's pages for
these no-op events is wasteful.
Gate the build job so a workflow_run whose upstream conclusion is
'skipped' does nothing; deploy and notify need build, so they
cascade-skip.
Route such no-op runs to their own throwaway concurrency group. In the
shared 'pages' group they would, as the newest queued run, cancel a
pending real run and then deploy nothing (concurrency keeps only the
in-progress and newest pending run). Real runs keep sharing 'pages' and
serialize as before.
Add retry to deploy step to reduce flakyness due to the Pages back end.
Fix trigger on workflow file changes.
The Windows build never actually used ccache; the '.ccache' directory
only ever held the win_flex_bison install, and cmake/MSVC did no compiler
caching. Clean this up:
- Drop the CCACHE_* environment variables from the job (meaningless here).
- Store win_flex_bison in a dedicated 'win_flex_bison' directory instead of
the misleadingly named '.ccache', and cache just that (static key, as it
is a fixed third-party tool).
- Set WIN_FLEX_BISON inside ci-win-compile.ps1 as an absolute path, rather
than in the workflow, making the script self-contained.
- Use the runner's processor count for build parallelism instead of a fixed
'-j 3', in both ci-win-compile.ps1 and ci-win-test.ps1.
- Remove the verilator-win.zip archive and upload steps; nothing consumes
that artifact.
- Build Verilator with the Ninja generator from an MSVC developer shell
instead of MSBuild. MSBuild only parallelizes across projects, and
Verilator is a single project, so it compiled serially; Ninja keeps all
cores busy. Also compile with /Od: this job only checks that Verilator
builds and can verilate an example, so an optimized binary is not needed
and the otherwise-dominant optimizer time is wasted.
- Merge reusable-rtlmeter-build.yml into reusable-build.yml, selected by
an 'install' flag: archive the installed Verilator for RTLMeter, or
the whole repository tree for the test jobs.
- Align reusable-test.yml input arguments with reusable-build.yml
- Pass build/test options as booleans instead of 0/1.
- Inline the single-entry build matrices, and hoist matrix keys that are
constant across a job.
- Split the monolithic ci-script.bash into ci-build.bash and
ci-test.bash, with shared setup in ci-common.bash.
- Pass job parameters as explicit command-line options rather than
environment variables (--compiler, --prefix, --suite, --asan,
--gcov, --reloc, --ccwarn).
- Detect the host OS and distribution at runtime (uname,
/etc/os-release) instead of the legacy Travis-era CI_OS_NAME,
CI_RUNS_ON and CI_BUILD_STAGE_NAME variables.
- Remove dead code: FreeBSD support, Windows wavediff install, the
unused CI_COMMIT variable, and various redundant operations.
- Inline the single-entry build-job matrices.
- Rename osx to macOS
- Refuse to run these ci scripts outside GitHub Actions to protect
developer checkouts.
PR #7776 removed Ubuntu 22.04 clang from the test matrix, which was the
only one testing the relocation of an installation. Add back under
Ubuntu 24.04 clang.
Restrict VL_RESTORER to be usable only with trivially copyable types.
Introduce VL_RESTORER_COPY and VL_RESTORER_CLEAR, which are more
efficient versions usable for non trivially copyable types.
VL_RESTORER_COPY semantically behaves the same as VL_RESTORER, but only
does one copy at initialization, and on scope exit restores via a move.
VL_RESTORER_CLEAR swaps the variable with an new one constructed via
the no-args constructor (e.g. empty collection), which does not require
any copying at any point.
Static assertions enforce picking one of the new flavours when copying
might be expensive.
Fetching a thread-local is relatively expensive. Random initializing
wides used to do it once or twice per word, and on short runs for
large designs can be noticeably expensive, so fetch once per variable
instead. Also remove unused VL_RAND_RESET_{Q,W} functions.
Rewrite module inlining decision to be based on a bipartite Module/Cell
graph, similar to V3InlineCFuncs. Preserved all old heuristics, but
added 2 new ones:
- If a module, and all the sub-hierarchy below it, is less than 10% the
total flattened size of the design, then flatten the contents of that
module (but the module itself is not necessarily inlined).
- If the flattened size of all instances of a module is less than 20% of
the total flattened size of the design, then inline all instances of
that module.
These are both relative to the total size of the design, so they
auto-scale with complexity. The net effect is that large shared
instances are preserved, but their contents are flattened out. E.g. in a
multi-core CPU this would keep the cores non-inlined but flatten out
most everything else. This still enables V3Combining and sharing those
later, but avoids potentially big overheads e.g. with small widely used
library modules.
Empirically this yields less generated C++ than the previous version
(due to removing lots of small functions), and can improve performance
10-20% while still having meaningful combining relative to the size of
the design.
Fix scheduling of writes in virtual interfaces, there were missing triggers (see added test).
Make V3SchedVirtIface handle writes done inside methods called through a virtual interface. The pass first records direct vif.member writes, VIF method calls, and candidate interface member VarScopes. It then walks the methods reachable from those VIF calls, writes to persistent interface variables in those method bodies are treated as VIF writes, and nested calls are followed with the same interface context. Function locals, temps, and events are ignored because they are not persistent interface storage observable through a later VIF read. Triggers are still created only from the intersection of (interface type, member name) writes and matching VarScopes, so unrelated interface variables and interfaces with no virtual access do not get extra triggers.
Recognize the common single-bit scan loop idioms in V3Unroll (before it
unrolls) and lower them to bit-reduction primitives, replacing a literal
W-iteration loop with one intrinsic-backed expression:
target=0; for (i=0;i<W;i++) if (vec[i]) target = i + 1; -> $mostsetbitp1(vec)
target=0; for (i=0;i<W;i++) if (vec[i]) target = target + 1; -> $countones(vec)
The leading-one form lowers to a new AstMostSetBitP1 node, emitted as
VL_MOSTSETBITP1_{I,Q,W}; those runtime helpers now use __builtin_clz where
available (same pattern as VL_REDXOR's __builtin_parity), with the existing
bit scan as fallback. The count-ones form reuses AstCountOnes ($countones,
popcount); as the DFG requires a 32-bit countones result it is built at 32
bits and narrowed to the accumulator width with a select.
Matching is structural to stay sound: the index must start at 0, increment
by exactly 1, and scan all W==width(vec) bits via a single 1-bit select of a
distinct vector, with the target pre-zeroed and no else branch. The loop
bound is accepted as a strict ascending 'idx < W' written either way and
signed or unsigned (Gt/GtS/Lt/LtS). Gated by -fbit-scan-loops (on at -O).
Adds t_bit_scan_loops (I/Q/W, count-ones and unsigned-index positives;
step-2, start-1, idx*2+1, vec[idx+1], target=idx and W!=width negatives, all
self-checked and asserted via --stats not to lower) plus t_bit_scan_loops_off
for the disable flag.
Motivated by a transformer inference design whose 80-bit leading-one detector
ran every cycle (~37% of runtime); the lowering is worth ~39% there.
The non *Ovr flavours of AstShift* have better downstream constant
folding, so keep using those if proven safe. Fold overshifts explicitly
instead of introducing *Ovr shifts.
Remove the expression combination counts from the default stats file,
and add a new `--dump-ast-patterns` option, which will dump new
`*_ast_patterns_*.txt` files. These contain the expression combinations
in a similar S-expression format as Dfg already produces with
`--dump-dfg-stats`. These dumps are not produced by just `--stats` as
they are fairly expensive to compute. Currently the new option will dump
at two points: just before we change to C types via widthMin usage, and
just before emit.
Previously V3InlineCFuncs inlined call sites but never deleted the now
dead callees. Also missed a lot of opportunities due to evaluation order.
Rewrite using a graph based algorithm, using only a single traversal of
the netlist. This is clearer, more accurate, and faster at compile time.
Also add a clean -fno-inline-cfuncs disable. Setting the limits to 0
still disables inlining, except of empty functions, which can be inlined
with 0 limits (they are no ops). It will also prune unused functions
without -fno-inline-cfuncs.
Pass now also respects `--output-split`
When a vertex is made acyclic, conservatively update the SCC map to
propagate and mark connected vertices as acyclic as much as possible.
This way we can stop early if the graph becomes acyclic after some
fixups. This can significantly reduce the number of fixups needing to be
applied, avoiding introducing redundancy.
Extend the decoder-pattern case optimization to selectors that are too
wide for a full 2^width lookup table. A decoder-pattern case (where
every case item assigns constants to a fixed set of LHSs) is lowered to
a new AstMachMasked expression. AstMachMasked is emitted as a run-time
VL_MATCHMASKEd_* function call. It contains a packed constant pool table,
'matchp', which is a list of '(mask, bits)' pairs. At runtime, the index of the
first matching entry is returned, and is used to index a value table. This single
(albeit complicated) expression can replace large if-else trees whole, resulting
in much more compact code with fewer static hard to predict branches. It
is worth about 10% speed and 30% code size in some designs.
Example:
```systemverilog
logic [39:0] sel;
always_comb
casez (sel)
40'b???????????????????????????????????????1: out = 8'h01;
40'b??????????????????????????????????????1?: out = 8'h02;
40'b?????????????????????????????????????1??: out = 8'h03;
default: out = 8'hff;
endcase
```
is compiled to:
```c++
out = TABLE_value[VL_MATCHMASKED_Q(sel, CONST_match)];
```
Where 'CONST_match' contains 4 entries, of a 40-bit mask and 40-bit bit
pattern each, and 'TABLE_value' contains 4 entries of the corresponding
8-bit results. (Entries are aligned to word boundaries to avoid runtime
bit swizzling)
Recognize "decoder" case statements (where every case item only assigns
constants to a fixed set of left-hand sides) and replace them with a
single packed constant lookup table indexed by the case expression.
Small tables are materialized inline in the generated code, and are
always optimized. Larger ones are placed in the constant pool and only
optimized if deemed beneficial over branches.
While this slightly conflicts with V3Table, and is not worth that much
on it's own, there will be a follow up patch that converts more cases of
this form which will be much more valuable. This patch does the
necessary analysis and the simple table conversion when possible.
Split -fcase into -fcase-table (this new conversion) and -fcase-tree (the
existing bitwise branch-tree conversion); -fno-case is now an alias for
both.
Default branches, assignments preceding the case (used as default values),
casez wildcards, multiple and partial left-hand sides, and both blocking and
non-blocking assignments are handled. Cases that cannot be safely tabled (e.g.
non-exhaustive with no default, overlapping writes to one variable, or mixed
blocking/non-blocking assignments) fall back to the existing if/else lowering.
Consequently disabled re-inlining of constant pool variables in V3Const,
and rebuild the constant pool hash in V3Dead (previously we didn't
create constant pool entries early enough for this to matter)
When a lot of combinational logic is driven from top level inputs,
work can be wasted evaluating that logic if the top level inputs don't
change.
This change adds an optimization by performing a change detect on the
top level inputs, and evaluate 'ico' logic only if the top level input
actually changed. This especially helps with --hierarchical/--lib-create
which runs the 'ico' of each sub-model in the eval settle loop.
This was observed to yield 40%+ run-time speedup on some partitioned
designs.
The added change detection is cheap, so it is emitted even if the 'ico'
region is small, and is on by default.
The optimization is only sound if the model itself does not write to the
top level inputs (otherwise the 'previous value' variables would be out
of sync, which are not updated by internal writes.). If we can detect a
top level input is written within the design, then for that input, we
fall back on always running the relevant logic. With --vpi we cannot
prove safety statically, so --vpi will disable this optimisation unless
explicitly enabled. (In which case it's the user's responsibility to not
write to top level inputs via the VPI.)
As per discussion. Remove the unsound V3SplitAs pass. The
isolate_assignments attribute/directive is now parsed and ignored in the
frontend for compatibility but otherwise have no effect.
Fixes#7144
This is still mostly refactoring of V3Case, but with functional changes.
Decouple the exhaustiveness/overlap analysis from the decision to
convert the case using the fast bitwise testing method. This enables
dropping the 'notParallel' assertions for those we can prove exhaustive
and unique, even if we decide to convert them using the generic if/else
ladder scheme.
Found by inspection, case inside used to threat 'x' as a value, not as a
wildcard. Per the standard it should behave as '==?' which treats both
'x' and 'z' as wildcards.
V3Gate used to inline too many expensive operations. One particularly
bad example is inlining `{<<{wide}}` (bit-reverse of a wide signal),
which is a single input node, but is quite expensive to compute, which
we always used to inline.
Change the heuristic to only inline single input nodes if they are not
wide, or a cheap wide operation, otherwise treat them the same as
multi-input ops and inline them only if they are used no more than once.
Add a simple Dfg pass that removes redundant bit selects early. This
can significantly cut down on downstream work and remove some temporary
variables introduced during synthesis.
Replace 3 DfgCond patterns with 2 more general ones that convert DfgCond
with common MSBs/LSBs in both branches into a DfgConcat with a narrower
DfgCond. This pattern arises frequently with Dfg synthesis.
Relax the live variable analysis performed by Dfg to bail on fewer
cases. This analysis was already conservative (meaning it might think
variables are live when they are not), which is good enough for Dfg use.
This change in particular enables synthesizing more complex logic
involving arrays, e.g. those introduce by V3Table creating lookup
tables.
- If any simulated cycle counts mismatch, report them and fail the job
- Keep "Elapsed" only in cppbuild
- Ignore "Elapsed" and "CPU" samples less than 30 seconds - too noisy
- Widen acceptable ranges on "Elapsed" and "Memory"
- Add badge legend
Teach DFG about CReset. This is not so much to optimize CReset itself, but to enable synthesizing logic involving CReset, which does appear with automatic variables used only in certain branches
The intention was to run scheduled with max 2 parallel jobs, however,
due to a bug they were run with 7 just like PR runs. This didn't seem to
cause problems, so change it all to 7, except for the hierarchical,
which runs on 6, for a total of a maximum 20 parallel RTLMeter run jobs
per workflow run.
When configured with --enable-partial-static (default on), only the
availability of static libraries were checked. Some platform only
package dynamic libs. If the static library is not found, fall back on
trying the dynamic one.
Small chance a bug gets through, but this will avoid multiple runs on the
common case of reformatting users' pull requests, and related run
cancellation problems.
Add a script that prints the job matrix of cases to run with RTLMeter.
This enables running different sets based on parameters. It will run
everything on scheduled nightly runs, but only a subset on PRs (to reduce
time and variance due to short cases).
Also prints the job matrix in descending duration order, which
effectively makes GitHub actions schedule longest jobs first to reduce
total workflow latency.
Combine consecutive assertOn() checks into one, and hoist past enclosing
'if' statements if possible. This enables combining a lot of them, which
can be worth 10% performance on some assertion heavy designs depending
on how the assertions are written.
Add an overload that takes `const char*` format string. This avoids
having to construct/destruct a temporary `std::string` at the call site
when calling these functions with a string literal, which is fairly
common. This is worth 25% code size on some assertion heavy design.
Also use `std::string::clear()` instead of assigning an empty string
which is more efficient.
Turn `x = $sformatf(...)` into `$sformat(x, ...)`. The former requires
checking and running a destructor for `x` at the call site, the later
does it in the callee VL_SFORMAT. This reduces the size of the call
site, which can be significant e.g. in the presence of many assertions.
Also added a rewrite of `$sformat(x, "const-string")` back into `x =
"const-string"` for the cases where the `$sformatf` would have been
folded into a constant string.
Treat AstSFormat as a special form of assignment in V3Life. This allows
eliminating earlier redundant assignments to strings when an $sformat
later sets the string. UVM has lot of these.
V3Premit extracts wide sub-expressions via temporaries, which is needed
for emitting wide operations to C++ (calls to `VL_*_W`). The previous
version used to extract both branches of an AstCond unconditionally,
meaning both branches were fully evaluated. Rewriting the AstCond into
an AstIf instead enables evaluating only the required branch. While
this does limit V3Subst, overall the resulting code is ~3% faster,
and contains ~25% fewer branches on a large design.
If the same statements appears in both branches of an 'if', put a single
copy after the 'if', apply recursively. This also has the effect of
getting rid of conditionals with identical branches, but is more widely
applicable.
* Fix wrong false assert in property local variable with cycle-delayed consequent
* factor helper for 100 line cov
* add return, should be 100 line cov now
This was a fudge to work around using VlWide in `if` conditions without
a `_ != 0` check. That check is actually inserted by V3Width (or an
equivalent reduction), so the offending code was only generated
internally. Hopefully fixed the single instance where this really
happened. (If not, C++ will fail to compile with "cannot convert VlWide
to bool in 'if (__HERE__)'" errors, still better than the old version
which used to silently not do the right test due to incorrect implicit
conversions.)
Change WDataInP/WDataOutP to be opaque handles types instead of aliases
to raw pointers. This subsequently eliminates needing an implicit cast
operator in VlWide, which is replaced with implicit constructors of
WDataInP/WDataOutP that can create a handle from a VlWide. This
eliminates some unsafe conversions that the previous implicit cast
operator unintentionally enabled (e.g. #7618). It also eliminates
having to insert ".data()" in various places int he generated code, which
simplifies internals (the only place ".data()" should be needed is in
calls to variadic functions where the expected type of the argument is
not WDataInP/WDataOutP).
The handles otherwise behave like pointers, implementing the minimal
amount of operators required to code the runtime. The handle is still
only a single pointer, and will be passed in registers as before, so
this patch should be performance neutral.
As part of this removed WData, which used to be an alias for EData.
All uses are now either EData*, WDataInP, WDataOutP, or VlWide directly.
When lowering dynamic event controls, destructive pre-clear updates were inserted with addHereThisAsNext() on the original node and then that node was replaced. This could leave leaked/orphaned nodes under leak-checking runs.
Build an explicit replacement stmt chain instead:
[pre-clear stmts] -> trigger loop -> awaitResumption,
and replace the original control with the chain head. Keep the loop-only path unchanged when no destructive pre-clear is needed.
- FOLD_SELF_SUB: x - x -> 0
- REMOVE_DIV_ONE / REMOVE_DIVS_ONE: x / 1 -> x (unsigned and signed)
- REMOVE_MUL_ZERO / REMOVE_MUL_ONE / REMOVE_MULS_ZERO / REMOVE_MULS_ONE:
0 * x -> 0 and 1 * x -> x (unsigned and signed)
- REPLACE_NOT_LT/GTE/GT/LTE and their signed counterparts: eliminate a
Not vertex by flipping the comparison operator
Test signals for the NOT-of-comparison GT/GTE variants use unique shift
amounts to prevent intra-pass CSE from merging their DfgGt/DfgGte vertices
with those produced when the complementary LT/LTE patterns fire, which
would otherwise trigger the !hasMultipleSinks() guard.
Unfortunate constellation of combinational assignments could be inlined
by V3Gate yielding an exponential expansion (added test used to consume
4GB+ memory and generate 3GB+ code).
Track AstMemberSel writes through virtual interface refs and connect them to matching interface-member VarScopes, so class-driven interface clocks get proper VCD activity updates.
Fixes#5044.
Explicitly annotate those AstNodeExpr subclasses that should have a
corresponding DfgVertex subclass generated by astgen. This avoids having
to tweak things in Dfg when adding new AstNode subclasses, which can
then be handled separately.
Dumping Dfg patterns can take a non-trivial amount of time, so do it
only with --dump-dfg-patterns, instead of with --stats.
Also further improve dumping format.
Remove parallel (using the FST library writer thread) and offloaded
(separate Verilator internal thread) tracing (only used by FST). These
are not compatible with #6992, and #5806 should yield better performance
in all cases.
Consequently mark '--trace-threads' and '--trace-fst-thread' options as
deprecated
Introduce a new DfgAstRd vertex, which holds an AstNodeExpr that is a
reference to a variable. This enables tracking all read references in
Dfg, which both enables more optimization, and allows inlining of
expressions in place of the reference more intelligently (e.g, when the
expression is only used once, and is not in a loop). This can get rid of
20-30% of temporary variables introduced in Dfg in some designs. Note
V3Gate later got rid of a lot of those, this is a step towards making
V3Gate redundant. The more intelligent expression inlining is worth ~10%
runtime speed on some designs.
Apple clang rejects `-o` when a precompiled header (.gch) is involved,
reporting "cannot specify -o when generating multiple output files".
Remove the unnecessary `-o $@` from the two PCH build rules; the
`%.o: %.cpp` pattern already implies the correct output name.
Always only replace the currently iterated node. This ensures it is not
on the work list, which simplifies upcoming work.
No functional of performance change intended.
Enable V3DfgCache to look up vertices without creating one. Reuse
existing terms in associative expression trees if they already exist
somewhere in the graph.
- Emit arrays under the new FST scope type FST_ST_SV_ARRAY
- Emit packed/unpacked 'array' attributes before FST_ST_SV_ARRAY,
including left and right indices of the array
- Emit packed/unpacked 'pack' attributes before FST_ST_VCD_STRUCT and
FST_ST_VCD_UNION, including the number of members in the types
All attributes apply to the immediately following scope definition (just
like enum dtype attributes).
Add jemalloc as an alternative malloc implementation for the Verilator
binary. When both tcmalloc and jemalloc are available, jemalloc is
preferred due to its better performance on RTLMeter.
The new --enable-jemalloc flag (default=check) mirrors the existing
--enable-tcmalloc behavior: auto-detected at configure time, supports
both static and dynamic linking, and is disabled when --enable-dev-asan
is active.
Factor out test execution into t/trace_*_common.py, which defines
a 'run' functions. All related t_trace_*py tests call this function.
Behaviour is partially encoded in the file name, which must be of the
form: t_trace_complex_<variant>_<mode>_<format>*.py, where '<variant>'
determines tracing options (default/params/structs), '<mode>' is the
compilation mode (--cc/--sc), and '<format>' determines the trace format
(vcd/fst/saif).
The part of the test name after '<format>' does not influence the test
directly and can be free form. If used, explicit 'verilator_flags2' is
passed to the 'run' function.
Used to incorrectly unroll 1D packed arrays of 'bit' or 'logic' into
elements when using --trace-structs if the array element type was given
via a typedef. Keep them as a single signal instead.
The lowerDistConstraints() function was not recursing into ConstraintIf
nodes, causing dist operators inside if-else blocks to remain unlowered
and trigger an internal error when ConstraintExprVisitor encountered them.
Fix by adding recursive handling of ConstraintIf nodes in lowerDistConstraints:
- Check for AstConstraintIf nodes before AstConstraintExpr
- Recursively process thensp() and elsesp() branches
- This ensures all dist operators are lowered regardless of nesting
Test case: t_randomize_dist_conditional.v demonstrates conditional dist:
constraint c {
if (randd) {
x dist { 8'd0 := 1, 8'd255 := 3 }; // 25% / 75%
} else {
x dist { 8'd0 := 3, 8'd255 := 1 }; // 75% / 25%
}
}
Fixes#7221
Also add array bounds and struct/union member counts to trace pushPrefix
(not used by vcd/fst/saif). Together these improve consistency in some
waveform formats.
- Allow reordering pure statements with DPI import calls iff no public
variables (including those read via a DPI export) are involved. This
ensures the DPI import can't observe the reordering
- Allow reordering of pure statements with AstDisplay and AstStop. This
requires an assumption that AstDisplay and AstStop will not read or
write model state other than via a VarRef explicitly present int the
Ast.
Overall this allows eliminating a lot of conditionals around assertions,
which were previously not possible.
Introduce new pass that converts impure expressions, or those with
function and method calls into simple assignment statements. Please see
the blurb at the top of the file why this is useful and how it works.
In particular currently it enables more Dfg optimization as functions
will be inlined without AstExprStmt.
Ideally we should enforce this lowering is applied to every procedural
statement (there are still a handful of exceptions). With that, long
term with this pass + #6820, there should be no need to ever use an
AstExprStmt past this new lowering pass, which should enable more easier
optimization down the line.
Also ideally this should be run earlier. Currently it's after V3Tristate
as that calls pinReconnectSimple so we don't have to touch Cell ports.
Currently disabled when code coverage is enabled due to #7119.
The recent V3InlineCFuncs only checks AstCFunc::varsp for locals, but
V3Reloop used to insert them into AstCFunc::stmtsp resulting in multiple
locals with the same name being inlined into the caller if the stars
align. Fix Reloop. Such things will also go away with #6280.
Rename AstSelLoopVars to AstForeachHeader, and make it a non-NodeExpr.
Tweak parser to always create an AstForeachHeader, so no need to fix it
up later.
After conversion of Ast to Dfg, but before synthesizing AstAlways into
primitives, run a pass to remove variables that are not observable, and
all logic that only computes such variables. This can get rid of a lot
of content early so we don't build redundant Dfgs, and also enables
synthesizing always blocks that use temporaries only in some branches,
which will come in a follow up.
This patch adds IEEE-1800 compliant scheduling support for the Inactive
scheduling region used for #0 delays.
Implementing this requires that **all** IEEE-1800 active region events
are placed in the internal 'act' section. This has simulation
performance implications. It prevents some optimizations (e.g.
V3LifePost), which reduces single threaded performance. It also reduces
the available work and parallelism in the internal 'nba' section, which
reduced the effectiveness of multi-threading severely.
Performance impact on RTLMeter when using scheduling adjusted to support
proper #0 delays is ~10-20% slowdown in single-threaded mode, and ~100%
(2x slower) with --threads 4.
To avoid paying this performance penalty unconditionally, the scheduling
is only adjusted if either:
1. The input contains a statically known #0 delay
2. The input contains a variable #x delay unknown at compile time
If no #0 is present, but #x variable delays are, a ZERODLY warning is
issued advising the use of '--no-sched-zero-delay' which is a promise
by the user that none of the variable delays will evaluate to a zero
delay at run-time. This warning is turned off if '--sched-zero-delay'
is explicitly given. This is similar to the '--timing' option.
If '--no-sched-zero-delay' was used at compile time, then executing
a zero delay will fail at runtime.
A ZERODLY warning is also issued if a static #0 if found, but the user
specified '--no-sched-zero-delay'. In this case the scheduling is not
adjusted to support #0, so executing it will fail at runtime. Presumably
the user knows it won't be executed.
The intended behaviour with all this is the following:
No #0, no #var in the design (#constant is OK)
-> Same as current behaviour, scheduling not adjusted,
same code generated as before
Has static #0 and '--no-sched-zero-delay' is NOT given:
-> No warnings, scheduling adjusted so it just works, runs slow
Has static #0 and '--no-sched-zero-delay' is given:
-> ZERODLY on the #0, scheduling not adjusted, fails at runtime if hit
No static #0, but has #var and no option is given:
-> ZERODLY on the #var advising use of '--no-sched-zero-delay' or
'--sched-zero-delay' (similar to '--timing'), scheduling adjusted
assuming it can be a zero delay and it just works
No static #0, but has #var and '--no-sched-zero-delay' is given:
-> No warning, scheduling not adjusted, fails at runtime if zero delay
No static #0, but has #var and '--sched-zero-delay' is given:
-> No warning, scheduling adjusted so it just works
AstCAwait is only ever uses in statement position, so model it as a
statement. We should never ever have a coroutine that returns a value.
There is no need for it in SV, nor should we rely on it for internals.
Also reworks the fix for V3Life incorrectly constant propagating the
beforeTrig functions (#7072). The property that upsets V3Life is that
a function:
1. Is called from multiple static call sites (multiple AstCCall)
2. Reads model state directly (AstVarRef to non-locals/arguments)
Such function can only be created internally after scheduling (V3Task
throws an unsupported error on a non-inlined function that reads model
state), so added a flag to AstCFunc to mark the dangerous ones for
V3Life.
Many rules in the Dfg Peephole pass check if a node has more than one
sinks. Redundant variables that will ultimately be removed can prevent
these from matching. Remove such variables during the Peeophole pass
itself to enable more matches.
This is an attempt to generate an identical trace file scope hierarchy
both with and without -fno-inline. Primarily because it's needed for
testing in upcoming patch, but also improves consitency prior to #7001
This is primarily cleanup, but there are 2 functional changes included:
- It used to accidentally reorder bodies of AstNodeIf that were outside
an AstAlways. Now it will not touch anything outside an AstAlways.
- Removed one redundant edge from the graph which perturbs the result of
V3Graph::acyclic. This should make no difference for the actual
intended result of reordering NBAs to eliminate shadow variables.
Add a new Dfg pass 'pushDownSel'. This will try to move selects through
a tree of concatenations in order to eliminate temporary nodes holding
intermediate concatenation results. This can get rid of a lot of
variables when packed arrays are assigned in parts (e.g. bit-wise).
Use uint32_t max value instead of zero as sentinel value for a trace
code being unassigned. Prep for follow on patch.
Note the actual trace file will still start codes from one, the codes
in the model are just an offset from the base code.
We use special C++ types for ports, e.g. SystemC types in --sc mode, and native C arrays for unpacked arrays in --cc mode. These types are not substitutable for internal types, e.g. VlUnpacked, however all the runtime primitives expect internal types.
I think the intention was to use these special IO types only for top level ports, but the current implementation also uses them for the ports of all non-inlined modules. This means the output C++ will not compile if such a port is passed to a runtime primitive (e.g. array 'sort' as in the new test) or DPI import.
Changed to use the special IO types only on the top level ports.
Note these are likely still broken if attempting to invoke on a top level port (we might be saved by wrapTop, but later optimizations might eliminate the intermediary)
Re-inline ConstPool entries in V3Subst that have been expanded into
word-wise accessed by V3Expand. This enables downstream constant folding
on the word-wise expressions.
As V3Subst now understands ConstPool entries, we can also omit expanding
straight assignments with a ConstPool entry on the RHS. This allows the
C++ compiler to see the memcpy directly.
V3Expand wide SHIFTL and SHIFTR if the shift amount is know and is a
multiple of VL_EDATA_SIZE. This case results in each word requiring a
simple copy from the original, or store of a constant zero, which
subsequent V3Subst can then eliminate.
A temporary introduced by V3Premit could not be eliminated in V3Subst if
it was involved in an expression that did a write back to a
non-temporary. To enables removing these, we need to track all variables
in V3Subst, not just the ones we would consider for elimination. Note
the new implementation is marginally faster than the old one even though
it does more work. It can eliminate ~5% more of wide temporaries on some
designs. Algorithm is largely the same.
Concatenations that are only used by Sel expressions that do not consume
some bits on the edges can be narrowed to not compute the unused bits.
E.g.: `{a[4:0], b[4:0]}[5:4]` -> `{a[0], b[4]}[1:0]`
This is a superset or the PUSH_SEL_THROUGH_CONCAT DFG pattern, which is
removed.
Minor performance improvement, especially for assertions heavy code.
Strings are often used as temporaries in unlikely branches. Do not
localize them to avoid an unnecessary initialization on function entry.
PR #6704 introduced the getForceControlSignals function to
verilated_vpi.cpp. It returns a pair of vpiHandles. These handles were
not released, causing a memory leak. This commit fixes this, in addition
to other minor changes for speed and readability that did not make it
into #6704.
No functional change intended.
* logging for the unsatisfied constraints
* Apply 'make format'
* fix teh quote error in the array indexing
* Apply 'make format'
* Len change for the hash for randomity when named assertion is used
* seperate name assertion and satisfied case
* Apply 'make format'
* simply comments and display info
* refine code and fix protect case
* format
* update display in test and .out file
* add an enable flag and warning type, add a protect_id version test and update out files
* Apply 'make format'
* simplify some comments
* update out file, ready to be merged.
* update .py file to set the hash key solid
* rename and reformate the warning message to follow the verilator style
* add a nowarn test
* Apply 'make format'
* ordering
---------
Co-authored-by: Udaya Raj Subedi <[email protected]>
Co-authored-by: github action <[email protected]>
* Tests: Add a test whether signedness of a packed array is properly implemented.
* Fix signedness of a packed array when named type is not used.
* Fix signedness of the entire packed array.
Track the location based message/feature enable bits separately for code
and control file directives. A message/feature is disabled if disabled
either in the control file, or in code directives/metacomments. That is,
enabled only if both agree should be enabled.
Note this might miss some cases where a sub-tree within an And/Or/Xor
tree is optimizeable, but not the whole tree, but in practice this seems
to work better than the alternative of keeping a set of failed nodes and
bail early.
Now that we have an efficient algorithm to analyse which bits in a
combinational cycle are not dependent on the cycle, can simplify the
cycle fixup algorithms. Remove FixUpSelDrivers: this was a heuristic
to save on the expensive independent bits analysis, but itself can
cause a performance problem on certain inputs that result in a large
number of attempted fixups. Doing this simplifies the driver tracing
algorithm, and because we now only attempt to trace drivers that are
known to be independent of the cycles, it should always succeed...
Unless of course there is a mismatch between the independent bit
analysis ant the driver tracing algorithm. In such case (when we managed
to prove independence, but then fail to trace a driver), we will crash,
which is still easier to sv-bugpoint than a performance bug.
Fixes#6744
Forceable/externally written variables cannot be used as the canonical
result variable for a Dfg value as the variables value can be
inconsistent with its Dfg drivers (e.g. when forced).
This removes a factor N from DfgBreakCycles, by doing the necessary data
flow analysis for the entire graph up front, and resulting the result for
all subsequent cycle fixups in the current iteration.
Fixes#6731
The default stack size of secondary thread on macOS is 512k, which is
too small even to run some of the tests. Unfortunately changing the
thread size must happen via `pthred_create` attributes, which are not
available via the c++ threading APIs. Use pthreads directly on macOS,
and set the worker thread sizes to the same as the main thread stack.
Using `bind` into a parametrized hier_block used to be broken due to name
mangling, but was 'unintentionally' fixed by
916a89761e. Adding test to avoid
regressions.
Combined the 3 various APIs used in EmitC* passes to handle file
opening/splitting into a single one. This removes a lot of copy paste
and makes everything consistent.
All C++ file handling goes through `EmitCBaseVisitor` using the
`openNewOutputHeaderFile`, `openNewOutputSourceFile` and
`closOutputFile` methods.
To emit a new kind of file, always derive a new class from
`EmitCBaseVisitor`, and use the above APIs, they will take care of
everything else in a consistent matter.
Subsequently also removed V3OutSCFile, and instead included
verilated_sc.h (which included the systemc header itself) in the two
files that need it (the primary model header, and the root module
header).
Functional changes:
- The PCH header did not use to have a corresponding AstCFile. Now it
does, though this makes no difference in the output
- All 'slow' sources now have '__Slow' in the name automatically (the
only one missing was for the ConstPool files)
Rest of the output is identical except for the header line now being
present in all generated C++ files.
The Syms class can contain a very large number of VeriltedScope
instances if `--vpi` is used, all of which need a call to the default
constructor in the constructor of the Syms class. This can lead to very
long compilation times, even without optimization on some compilers.
To avoid the constructor calls, hold VeriltedScope via pointers in the
Syms class, and explicitly new and delete them in the Syms
constructor/destructor. These explicit new/delte can then be
automatically split up into sub functions when the Syms
constructor/destructor become large.
Regarding run-time performance, this should have no significant effect,
most interactions are either during construction/destruction of the Syms
object, or are via pointers already. The one place where we used to
refer to VerilatedScope instances is when emitting an AstScopeName for
things like $display %m. For those there will be an extra load
instruction at run-time, which should not make a big difference.
Patch 3 of 3 to fix long compile times of the Syms module in some
scenarios.
Splitting of the Syms constructor/destructor were a bit arbitrarily
enforced with some parts splitable, while others not. There was also an
issue that even if the constructor and destructor bodies were split, we
would still end up with both in the same file that was double the size of
the intended split limit.
To fix, first all statements required in the Syms constructor and
destructor are gathered into a vector, then if the total number of
statements required for both is bigger than the split limit, the
implementations are split into sub-functions, one per file, as before,
ensuring that none of the functions are bigger than the split limit.
Also add __Slow suffix to the names of the files.
Patch 2 of 3 to fix long compile times of the Syms module in some
scenarios.
In order to avoid long compile times of the Syms constructor due to
having a very large number of member constructor sto call, move to using
explicit ctor/dtor functions for all but the root VerilatedModule. The
root module needs a constructor as it has non-default-constructible
members. The other modules don't.
This is only part of the fix, as in order to avoid having a default
constructor call the VerilatedModule needs to be default constructible.
I think this is now true for modules that do not contain strings or
other non trivially constructible/destructible variables.
Patch 1 of 3 to fix long compile times of the Syms module in some
scenarios.
For handling $past and similar functions, we used to collect sampled
values of variables at the beginning of the main _eval function. If we
have many of these, this can grow _eval very large which can make C++
compilation very slow. Apply usual fix of emitting the necessary code in
a separate function and then splitting it based on size.
AstNode::unlinkFrBackWithNext is O(n) if the subject node is not the
head of the list. We sometimes want to unlink the rest of the list
starting at the node after the head (e.g.: in
V3Sched::util::splitCheck), this patch makes that O(1) as well.
AstMTaskBody is somewhat redundant and is problematic for #6280. We used
to wrap all MTasks in a CFunc before emit anyway. Now we create that
CFunc when we create the ExecMTask in V3OrderParallel, and subsequently
use the CFunc to represent the contents of the MTask. Final output and
optimizations are the same, but internals are simplified to move
towards #6280.
No functional change.
The 'act' region used to have 2 trigger vectors ('act' and 'pre'), now
it uses a single "extended" trigger vector where the top bits are what
used to be the used bits in the 'pre' trigger vector. Please see the
description above `TriggerKit`. Also move the extra triggers from the
low end to the high end in the trigger vectors.
Removed the VlTriggerVec type, and refactored to use an unpacked array
of 64-bit words instead. This means the trigger vector and its
operations are now the same as for any other unpacked array. The few
special functions required for operating on a trigger vector are now
generated in V3SchedTrigger as regular AstCFunc if needed.
No functional change intended, performance should be the same.
Instead of using the number of processors in the host, use the number of
processors available to the process, respecting cpu affinity
assignments. Without pthreads, fall back and use the number of
processors in the host as before.
This is now applied everywhere so runing `nuamctl -C 0-3 verilator` or
`numactl -C 0-3 Vsim` should behave as if the host has 4 cores (e.g.
like in CI jobs)
Used to fail with "can't use --exe with --lib-create", and we didn't
have any tests for it before. (The equivalent --main --exe --build
--timing works)
Add V3SchedUtil.cpp that contains common small utility functions.
Add V3SchedTrigger.cpp that contains functionality building the trigger
mechanism code.
No functional change, just code movement. Prep for some further work.
The AstIf nodes conditional on events being triggered used to be created
in V3Clock. Now it is in V3Sched*, in order to avoid having to pass
AstActive in CFunc or MTask bodies. No functional change intended, some
improved optimization due to simplifying timing triggers that were
previously missed, also fixes what seems like a bug in the original
timing commit code.
sched_forks.tree used to be dumped before sched.tree, while it's
basically after, so move transformForks in to a separate pass. Also
extract inlined visitors in V3SchedTiming.
Accessing the ports of hier_block instances directly under the current
hier_block (or top level) work just fine (the heir stub .sv has them),
and this can simplify hooking up dotted references into hier blocks:
push part of the reference under the hier block into the hier block, and
wire it to a port, then resolve the rest of the reference to the port of
the instance.
Cache already traced vertices and reuse them on subsequent traces. This
avoids a potential combinatorial explosion in the size of the resulting
circuit.
Internals: Refactor AstNodeBlock representation (#6280)
AstNodeBlock now has 2 child lists: 'declsp' to hold declarations within
the block, and 'stmtsp' to hold the procedural statements.
AstBegin is then just a simple subtype of AstNodeBlock.
AstFork is a proper superset of AstNodeBlock (and also AstBegin), and
adds 'forksp' which hold the parallel statements. Having the sequential
'stmtsp' in AstFork is required to properly implement variable
initializers in fork blocks (IEEE 1800-2023 9.3.2), this makes that
clear, while also separating the non AstNodeStmt declarations
(for #6280). The actual fork branches in 'AstFork::forkps()' are all
AstBegin nodes. This is required as lowering stages will introduce
additional statements in each parallel branch. (We used to wrap AstFork
statements into AstBegin in 3 different places, now they always are
AstBegin and this is enforced via the type checker/V3Broken).
Also fixes incorrect disabling of forked processes from within the `fork`.
- Delete 'finalsp'. It was used in one place, basically unnecessary and
safe to remove.
- Make 'argsp' a 'List[AstVar]'. This held before. It holds the function
argument and return variables.
- Replace 'intitsp' with 'varsp' and make it into 'List[AstVar]' to hold
the function local variables. This was most of its use before. The few
places we inserted statements here now moved into 'stmtsp' by
inserting at the front of the list.
Remove the large variety of ways raw "text" is represented in the Ast.
Particularly, the only thing that represents a string to be emitted in
the output is AstText.
There are 5 AstNodes that can contain AstText, and V3Emit will throw an
error if an AstText is encountered anywhere else:
- AstCStmt: Internally generated procedural statements involving raw
text.
- AstCStmtUser: This is the old AstUCStmt, renamed so it sorts next to
AstCStmt, as it's largely equivalent. We should never create this
internally unless used to represent user input. It is used for $c,
statements in the input, and for some 'systemc_* blocks.
- AstCExpr: Internally generaged expression involving raw text.
- AstCExprUser: This is the old AstUCFunc, renamed so it sorts next to
AstCExpr. It is largely equivalent, but also has more optimizations
disabled. This should never be created internally, it is only used for
$c expressions in the input.
- AstTextBlock: Use by V3ProtectLib only, to generate the hierarchical
wrappers.
Text "tracking" for indentation is always on for AstCStmt, AstCExpr, and
AstTextBlock, as these are always generated by us, and should always be
well formed.
Tracking is always off for AstCStmtUser and AstCExprUser, as these
contain arbitrary user input that might not be safe to parse for
indentation.
Remove subsequently redundant AstNodeSimpleText and AstNodeText types.
This patch also fixes incorrect indentation in emitted waveform tracing
functions, and makes the output more readable for hier block SV stubs.
With that, all raw text nodes are handled as a proper AstNodeStmt or
AstNodeExpr as required for #6280.
There was exactly one place in V3Task, handling DPI arguments when we
relied on cleanOut of AstCExpr being false for masking. Made that code
do the relevant masking via a few new run-time functions, which also
eliminates some special cases in the relevant V3Task functions.
Initial idea was to remodel AssignW as Assign under Alway. Trying that
uncovered some issues, the most difficult of them was that a delay
attached to a continuous assignment behaves differently from a delay
attached to a blocking assignment statement, so we need to keep the
knowledge of which flavour an assignment was until V3Timing.
So instead of removing AstAssignW, we always wrap it in an AstAlways,
with a special `keyword()` type. This makes it into a proper procedural
statement, which is almost equivalent to AstAssign, except for the case
when they contain a delay. We still gain the benefits of #6280 and can
simplify some code. Every AstNodeStmt should now be under an
AstNodeProcedure - which we should rename to AstProcess, or an
AstNodeFTask). As a result, V3Table can now handle AssignW for free.
Also uncovered and fixed a bug in handling intra-assignment delays if
a function is present on the RHS of an AssignW.
There is more work to be done towards #6280, and potentially simplifying
AssignW handing, but this is the minimal change required to tick it off
the TODO list for #6280.
I stared this because the emitted makefiles for hierarchical verilation
were non-deterministic (iterating unordered_map indexed by pointers).
Then I realized that the V3HierPlan is just a dependency graph encoded
in a slightly idiosyncratic way. We do have a data structure to use for
that instead.
With that the output should always be deterministic + have nicer dumps.
All code is built as C++ via CXX, but we still have some references to
CC. Trying to make sure we don't add plain C later by hiding the C
compiler. (So it's always enough to override CXX=... in configure)
Add an explicit 'sha' parameter to reusable-build, to define which
commit to build. This will be needed for PR coverage jobs. Consequently
use the 'archive' output from reusable-build to simplify retrieving the
resulting artifact in dependent jobs. Also fetch full history in
coverage builds.
Disable statuses and PR comments, make precision and ranges match lcov
reports generated by 'make coverage-report', remove unnecessary
contents. Rename codecov.yml -> .codecov.yml
This patch gets rid of over 80% of temporary dynamic memory allocations
(when a malloced node is immediately freed with no other malloc in
between). It also gets rid of over 20% of all calls to malloc.
It's worth ~3% average verilation speed up with tcmalloc, and more
without tcmalloc.
The default timeout for a job in GitHub Actions is 6 hours, which is
both too long, but more importantly, when reached the job is 'cancelled'
instead of 'failed'. Use the new `--timeout` option on `rtlmeter run`
instead to add a 60 minute timeout to compile and execute steps. (This
is ~3x longer than recent worst runs in the CI)
This patch implements #6480. All loop statements are represented using
AstLoop and AstLoopTest.
This necessitates rework of the loop unroller to handle loops of
arbitrary form. To enable this, I have split the old unroller used for
'generate for' statements and moved it into V3Param, and subsequently
rewrote V3Unroll to handle the new representation. V3Unroll can now
unroll more complex loops, including with loop conditions containing
multiple variable references or inlined functions.
Handling the more generic code also requires some restrictions. If a
loop contains any of the following, it cannot be unrolled:
- A timing control that might suspend the loop
- A non-inlined call to a non-pure function
These constructs can change the values of variables in the loop, so are
generally not safe to unroll if they are present. (We could still unroll
if all the variables needed for unrolling are automatic, however we
don't do that right now.)
These restrictions seem ok in the benchmark suite, where the new
unroller can generally unroll many more loops than before.
Internals: Refactor generate construct Ast handling (#6280)
We introduce AstNodeGen, the common base class of AstGenBlock,
AstGenCase, AstGenFor, and AstGenIf, which together represent all SV
generate constructs. Subsequently remove AstNodeFor, AstNodeCase
(AstCase is now directly derived from AstNodeStmt) and adjust internals
to work on the new representation.
Output is identical modulo hashes do to changed AstNode type ids, no
functional change intended.
Step towards #6280.
Rename AstAssignAlias to AstAlias and make it derive from AstNode
instead of AstNodeStmt.
Replace AstAlias with AstAssignW in V3LinkDot::linkDotScope, which is
the last place we need to be aware of the alias construct. Using
AstAssignW dowstream enables further optimization while preserving the
same functionality.
The only use for the clocker attribute and the AstVar::isUsedClock that
is actually necessary today for correctness is to mark top level inputs
of --lib-create blocks as being (or driving) a clock signal. Correctness
of --lib-create (and hence hierarchical blocks) actually used to depend
on having the right optimizations eliminate intermediate clocks (e.g.:
V3Gate), when the top level port was not used directly in a sensitivity
list, or marking top level signals manually via --clk or the clocker
attribute. However V3Sched::partition already needs to trace through the
logic to figure out what signals might drive a sensitivity list, so it
can very easily mark all top level inputs as such.
In this patch we remove the AstVar::attrClocker and AstVar::isUsedClock
attributes, and replace them with AstVar::isPrimaryClock, automatically
set by V3Sched::partition. This eliminates all need for manual
annotation so we are deprecating the --clk/--no-clk options and the
clocker/no_clocker attributes.
This also eliminates the opportunity for any further mis-optimization
similar to #6453.
Regarding the other uses of the removed AstVar attributes:
- As of 5.000, initial edges are triggered via a separate mechanism
applied in V3Sched, so the use in V3EmitCFunc.cpp is redundant
- Also as of 5.000, we can handle arbitrary sensitivity expressions, so
the restriction on eliminating clock signals in V3Gate is unnecessary
- Since the recent change when Dfg is applied after V3Scope, it does
perform the equivalent of GateClkDecomp, so we can delete that pass.
Chores:
- Remove ci-ccache-maint. This has never been useful and is just cruft.
- Remove then unused CI_COMMIT
- Change job names so they come out nicer in the web views
- Make os-name input to reusable-build always explicit
Improvements:
- Have at most build-test job in progress per branch
- Cancel in-progress build-test jobs on PRs
- In forks (that is, not on 'verilator/verilator'), cancel any
in-progress build-test jobs on push to the branch
These are no longer required for correct scheduling. They are still
accepted for backward compatibility, but have no effect on simulation
and are dropped in the front-end. Also removed the then redundant
AstAlwaysPublic class.
Fixes#6442
Added a lock around the table used to detect memory leaks. Note the only
part that is multi-threaded at the moment is V3Emit where we create
AstCFiles and the like, so the lock should be almost always uncontested.
This code is not thread safe. Specifically AstNode constructors are not
thread safe, as they may create entries in the shared Dtype table via
which can be racy.
Replace std::exit with v3Global.exit, and make V3Error::vlAbort call
v3Global.shutdown. This gives us an opportunity to release resources to
facilitate leak checking even when exiting early on an error.
Note we still don't release most resources by default without
VL_LEAK_CHECKS, so there is no behaviour change there.
Combined Dfg variable elimination into the regularization pass that runs
before converting back to Ast. This avoids introducing some unnecessary
temporaries.
Added replacing of variables with constants in the Ast if after the
Dfg passes they are known to be constants. This is only done in final
scoped Dfg application.
Avoid introducing temporaries for common sub-expressions that are
cheaper to re-compute than store in a temporary variable.
Enable removal of redundant unpacked array variables.
Also fixes#6394 as this patch involved changes to that code.
Do not apply V3Const in V3Expand after a function if nothing was
expanded in it.
Also fix statistics counter while at it.
Inspired by #6379, follow up from #6111
1. Move class V3ParseGrammar into V3ParseGrammar.h so editors understand
it as c++ code
2. Fix #line directives in the bison output file
This together enables us to gdb through V3ParseGrammar, verilog.y, and
the bison generated C code step by step, with all source annotations in
the debug info pointing to the right place (e.g.: you will step to the
right place in verilog.y, then step back to the bison generated switch
statement/loop, and then step into calls in V3ParseGrammar as kind of
expected.
These are all genuine bugs, brief descriptions.
1. V3OrderCFuncEmitter.h used to delete a node early that was still
reference in a graph dump later. Not a big deal, it can be deleted
later at the end of V3Order.
2. V3Param.cpp: this one is tricky. The variable referenced by
AstVarXRef was deleted at the end of `visit(AstGenCase*)`, but then
`visit(AstVarXRef*)` checks `nodep->varp()` (already deleted) to see
if it's in an interface.
3. V3String::wildMatch is sometimes called with an empty 's' (the string
we are matching against tha pattern 'p'), in which case it used to go
off into the woods. Added check on call. An arbitrary number of `*`
will still match the empty string.
4. V3Task.cpp: There was an error reported for an unsupported construct,
then a subsequent SEGV. Just signal the error upward so we bail on an
error in a more graceful way.
5. verylog.y: Some unsupported constructs failed to set the parsed node,
so some memory thrash made it into some code downstream. Just parse
these into nullptr.
Also increased the timeout on one test, which sometimes tripped with
asan on GCC during heavy host load.
Added a mini type system for Dfg using DfgDataType to replace Dfg's use
of AstNodeDType. This is much more restricted and represents only the
types Dfg can handle in a canonical form. This will be needed when
adding more support for unpacked arrays and maybe unpacked structs one
day.
Also added an internal type checker for DfgGraphs which encodes all the
assumptions the code makes about type relationships in the graph. Run
this in a few places with --debug-check. Fix resulting fallout.
Reduce set of synthesized logic to be more in-line with what Dfg used to
handle before + drivers of circular variables. This was always the
intention but the previous algorithm was both a bit too eager, and also
missed some circular variables. We can add back more heuristics based on
performance measurements for non-circular logic later.
Parts of this algorithm were distributed over many files some
masquerading as re-usable APIs, they were not. Move everything into one
file and avoid unnecessary virtual functions.
- Remove _ENUM_END, so -Wswitch does not demand it's covered. Use the
new NUM_TYPES constexpr member instead.
- Remove 'at' prefix. This seems historical and is not particularly useful.
- Fix some cppcheck warts while at it
Add DfgUserMap as a handle around the one pointer worth of algorithm
specific 'user' storage in each DfgVertex. This reduces verbosity,
improves type safety and correctness. Also enables us to remove one
pointer from DfgVertex to reduce memory use. No functional change.
Large scale refactoring to simplify some of the more obtuse internals of
DFG. Remove multiple redundant internal APIs, simplify representation of
variables, fix potential unsoundness in circular decomposition. No
functional change intended.
Workflows triggered for a PR from a fork can never have write
permissions, so to post a comment on a PR, it must be done from a
separate workflow triggered by 'workflow_run' in the main repository.
* Fix broken support of unassigned virtual interfaces
Unassigned virtual interface support added by #6245 is broken - PR marks
dead module as alive - we can't do that as once a module is dead it
needs to remain dead because earlier steps (e.g. port resolution) have
already been skipped.
This commit handles unassigned virtual interfaces at the beginning of
first pass of LinkDot (so it is never marked as dead, and no linking
steps are getting skipped).
Fixes#6253.
* Apply suggestions from code review
Co-authored-by: Wilson Snyder <[email protected]>
* Apply 'make format'
* Revert add of redundant iterateChildren() call
* Add original test case
---------
Co-authored-by: Wilson Snyder <[email protected]>
Co-authored-by: github action <[email protected]>
The previous algorithm was designed to handle the general case where a
full control flow path predicate is required to select which value to
use when synthesizing control flow join point in an always block.
Here we add a better algorithm that tries to use the predicate of
the closest dominating branch if the branch paths dominate the joining
paths. This is almost universally true in synthesizable logic (RTLMeter
has no exceptions), however there are cases where this is not
applicable, for which we fall back on the previous generic algorithm.
Overall this significantly simplifies the synthesized Dfg graphs and
enables further optimization.
* Skip profiling tests on non-glibc platforms
* Enforce dumb terminal in tests
* Include POSIX headers whenever __unix__ macro is defined
* Treat no procfs as normal condition
* Respect MAKE variable when running make
There were a couple corner case bugs in V3Inline, and one in Dfg when
dealing with inlining of modules/variables.
V3Inline:
- Invalid code generated when inlining an input that also had an
assignment to it (Throws an ASSIGNIN, but this is sometimes reasonable
to do, e.g. hiererchical reference to an unonnected input port)
- Inlining (aliasing) publicly writeable input port.
- Inlining forcable port connected to constant.
Dfg:
- Inining publicly writeable variables
The tests that cover these are the same and fixing one will trigger the
other bug, so fixing them all in one go. Also cleanup V3Inline to be less
out of order and rely less on unique APIs only used by V3Inine (will
remove those in follow up patch).
Small step towards #6280.
cppcheck provides best results when analysing the whole program. It also
has a builtin `-j` option to run on multiple threads.
Replace existing cppcheck-* targets with cppcheck-verilator,
cppcheck-runtime, cppcheck-example and cppcheck-vlc that checks each of
those components as a whole. Each of these runs on the maximum available
logical processors on the host by default, as reported by `nproc`, but
can be manually overridden with `make CPPCHECK_JOBS=<number>` instead.
The `make cppcheck` target runs the 4 cppcheck-* targets listed above
sequentially (but each of them uses the specified CPPCHECK_JOBS threads)
Rewrite with much less running around in the templates. Use private
methods only + friend functions that do the actual type check. This
avoids cppcheck warnings.
Added cppcheck-suppressions.txt in the repo root. You can add new
patterns in there instead of having to parse the XML output.
Also configure to add the -D__GNUC__ preprocessor macro, which makes it
understand UASSERT (it understands the 'noreturn' function attribute).
Added some case by case specific suppressions and fixed up other code,
especially in V3Ast*h and V3Dfg*.h, including code generated by astgen
that had some no-ops that irks cppcheck.
One thing it does not seem to like is `const` class members with default
initializers in the class. It will assume that's always the value, even
if overridden in the constructor. We had few so removed them.
With that a lot of files in `src/` are now clean or only have a handful
of issues. Therefore, I have also deleted cppcheck_filtered, and made it
produce human readable output straight to the terminal.
Regarding cleaning up the reported nits, I kind of got bored after
V3[A-E] so pausing here. Apologies for the merge conflicts.
Tested with cppcheck 2.13.0
This patch adds DfgLogic, which is a vertex that represents a whole,
arbitrarily complex combinational AstAlways or AstAssignW in the
DfgGraph.
Implementing this requires computing the variables live at entry to the
AstAlways (variables read by the block), so there is a new
ControlFlowGraph data structure and a classical data-flow analysis based
live variable analysis to do that at the variable level (as opposed to
bit/element level).
The actual CFG construction and live variable analysis is best effort,
and might fail for currently unhandled constructs or data types. This
can be extended later.
V3DfgAstToDfg is changed to convert the Ast into an initial DfgGraph
containing only DfgLogic, DfgVertexSplice and DfgVertexVar vertices.
The DfgLogic are then subsequently synthesized into primitive operations
by the new V3DfgSynthesize pass, which is a combination of the old
V3DfgAstToDfg conversion and new code to handle AstAlways blocks with
complex flow control.
V3DfgSynthesize by default will synthesize roughly the same constructs
as V3DfgAstToDfg used to handle before, plus any logic that is part of a
combinational cycle within the DfgGraph. This enables breaking up these
cycles, for which there are extensions to V3DfgBreakCycles in this patch
as well. V3DfgSynthesize will then delete all non synthesized or non
synthesizable DfgLogic vertices and the rest of the Dfg pipeline is
identical, with minor changes to adjust for the changed representation.
Because with this change we can now eliminate many more UNOPTFLAT, DFG
has been disabled in all the tests that specifically target testing the
scheduling and reporting of circular combinational logic.
Rewrote V3LifePost to not depend on having AstAssignPre and
AstAssignPost types, but work with generic AstNodeAssign. There is an
extra flag in AstVarScope to denote it's part of an NBA and should be
considered.
Step towards #6280.
NBAs targeting a variable in a different scope are now allocated
temporary variables for captured values in the scope of the NBA, not the
scope of the target variable.
Fixes#6286
Runs RTLMeter on PRs if the PR has the 'pr: rtlmeter' label applied to
it. This should make it easy to selectively require the RTLMeter
workflows to pass on a PR that is potentially invasive, per our own
judgement.
Both V3DfgBreakCycles.cpp and V3DfgDecomposition.cpp used to contain an
implementation of the same algorithm to color strongly connected
components. Now there is only one, and it lives in V3DfgColorSCCs.cpp.
After making a cyclic DFG component acyclic, merge that component back
into the acyclic sub-graph of the input graph. This enables optimizing
through the components that were made acyclic in their larger context.
Store all flags in a DfgVertexVar relating to the underlying
AstVar/AstVarScope stored via AstNode::user1(). user2/user3/user4 are
then usable by DFG algorithms as needed.
When we had a `{a, b} = ...`, and the DFG conversion of `a = ...`
succeeded, but `b = ...` failed, we still used to include `a = ...` in
the DFG, which then caused a spurious multi-driver error for `a` on
a subsequent DFG pass, as the original `{a, b} = ...` was still present
in the Ast, but we also had the extra `a = ...` from converting out of
DFG on the previous pass.
In this patch we only convert assignments with a concatenation on the
LHS, if all target LValues can be converted into DFG.
This is the proper fix for #4231
Introduce V3OutStream as a V3OutFormatter that writes to a stream
instead of a file. This can be used to emit formatted code fragments
e.g. in debug prints and graph dumps.
Limits columns to 16M columns, or may report wrong column on such long lines.
Limits single token to 64K lines, or may report wrong line for that token.
Remove AstJumpLabel
AstJumpGo now references one if its enclosing AstJumpBlocks, and
branches straight after the referenced block.
That is:
```
JumpBlock a {
...
JumpGo(a);
...
}
// <--- the JumpGo(a) goes here
```
This is sufficient for all use cases and makes control flow much easier to
reason about. As a result, V3Const can optimize a bit more aggressively.
Second half of, and fixes#6216
Added test for a particularly convoluted case requiring fixup in
V3Premit. To help with statistics stability, also prevent V3Premit from
introducing temporaries for assignment where the RHS reads the LHS, but
the assignment is known to be atomic (by emitted C++ semantics).
Also rename `createWideTemp` to `createTemp`, as it is used for non-wide
expressions as well.
This used to be restricted to variable vertices, but now can handle
arbitrary circular vertices that represent packed values. It also
converges faster than the earlier version. Prep for resolving loops
through arrays.
SystemC variables are fairly special (they can only be assigned to/from,
but not otherwise participate in expressions), which complicates some
DFG code. These variables only ever appear as port on the top level
wrapper, so excluding them from DFG does not make us loose any
optimizations, but simplifies internals.
Previously DFG was limited to having a Sel, or an ArraySel potentially
under a Concat on the LHS of combinational assignments. Other forms or
combinations were not representable in the graph.
This adds support for arbitrary combinations of the above by
combining DfgSplicePacked and DfgSpliceArray vertices introduced in
#6176. In particular, Sel(ArraySel(VarRef,_),_) enables a lot more code
to be represented in DFG.
This is mostly a refactoring, but also enables handling some more
UNOPTFLAT, when the variable is only partially assigned in the cycle.
Previously the way partial assignments to variables were handled were
through the DfgVerexVar types themselves, which kept track of all
drivers. This has been replaced by DfgVertexSplice (which always drives
a DfgVeretexVar), and all DfgVertexVar now only have a single source,
either a DfgVertexSplice, if partially assigned, or an arbitrary
DfgVertex when updated as a whole.
Added a second algorithm to break cycles in DFG by identifying which
bits of a circular variable are actually independent of the variable,
then reuse the existing (but extended) driver tracing algorithm to
eliminate them.
This can fix up things like: `assign gray = binary ^ (gray >> 1)`
Added an algorithm that can break some combinational cycles in DFG, by
attempting to trace driver logic until we escape the cycle. This can
eliminate a decent portion of UNOPTFLAT warnings. E.g. due to this code:
```systemverilog
assign a[0] = .....;
assign a[1] = ~a[0];
```
The manual for the BLKANDNBLK warning describes that it is safe to
disable that error if the updated ranges are non-overlapping. This
however was not true (see the added t_nba_mixed_update* tests).
In this patch we change V3Delayed to use a new ShadowVarMasked
scheme for variables that have mixed blocking and non-blocking
updates (or the FlagUnique scheme for unpacked variables), which
is in fact safe to use when the updated parts are non-overlapping.
Furthermore, mixed assignments are safe as far as scheduling is
concerned if either:
- They are to independent parts (bits/members/etc) (with this patch)
- Or if the blocking assignment is in clocked (or suspendable) logic.
The risk in scheduling is a race between the Post scheduled NBA
commit, and blocking assignments in combinational logic, which might
order incorrectly.
The second point highlights that we can handle stuff like this safely,
which is sometimes used in testbenches:
```systemverilog
always @(posedge clk) begin
if ($time == 0) a = 0;
end
always @(posedge clk) begin
if ($time > 0) a <= 2;
end
````
The only dangerous case is:
```systemverilog
always @(posedge clk) foo[idx] <= val;
assign foo[0] = bar;
```
Whit this patch, this will still resolve fine at run-time if 'idx' is
never zero, but might resolve incorrectly if 'idx' is zero.
With the above in mind, the BLKANDNBLK warning is now only issued if:
- We can't prove that the assignments are to non-overlapping bits
- And the blocking assignment is in combinational logic
These are the cases that genuinely require user attention to resolve.
With this patch, there are no more BLKANDNBLK warnings in the RTLMeter
designs.
Fixes#6122.
These passes blow up the Ast size on some designs, so delaying running V3Const
until after the whole pass can notably increase peak memory usage. In this
patch we apply V3Const per CFunc within these passes, which saves on memory.
Added -fno-const-eager to disable the intra-pass V3Const application, for
debugging.
Somewhat commonly, there is code out there that compares an expression (or
variable) against many different constants, e.g. a one-hot decoder:
```systemverilog
assign oneHot = {x == 3, x == 2, x == 1, x == 0};
```
If the width of the expression is sufficiently large, this can blow up
a GCC pass and take an egregious amount of memory and time to compile.
Adding a new DFG pass that will generate a cheap one-hot decoder:
to compute:
```systemverilog
wire [$bits(x)-1:0] idx = <the expression being compared many times>
reg tab [1<<$bits(x)] = '{default: 0};
reg [$bits(x)-1:0] pre = '0;
always_comb begin
tab[pre] = 0;
tab[idx] = 1;
pre = idx ; // This assignment marked to avoid a false UNOPFTLAT
end
```
We then replace the comparisons `x == CONST` with `tab[CONST]`.
This is generally performance neutral, but avoids the compile time and memory
blowup with GCC (128GB+ -> 1GB in one example).
We do not apply this if the comparisons seem to be part of a `COMPARE ?
val : COND` conditional tree, which the C++ compilers can turn into jump
tables.
This enables all XiangShan configurations from RTLMeter to now build with GCC,
so in this patch we enabled those in the nightly runs.
Failing to reset the work list pointer in vertices leads to not removing
some redundant variables if they become redundant after having been
considered once already.
To run scheduled instances of the RTLMeter or coverage workflows, the
ENABLE_SCHEDULED_JOBS variable must explicitly be set to 'true' in the
repository settings. This enables each fork to decide whether to run the
scheduled instances or not.
During V3Expand, some w32/1 (width == 32, widthMin == 1), nodes (e.g.:
RedOr) are replaced with w1 nodes (width == widthMin == 1) (e.g.: Neq).
However, V3Expand runs after V3Clean, when we are in C++ width world,
so we need to preserve the width/widthMin distinction, otherwise a later
constant folding can eliminate e.g. a necessary AstAnd used clear an
intermediate result (isAllOnes is true for a Const 1 with w1, but false
for a Const 1 with w32/1).
Attempting to fix by preserving all width/widthMin during a replacement
in V3Expand.
DFG itself is fine, but the transformed code hits the above.
Fixes#5953
Add the GitHub Actions workflows for running RTLMeter.
Runs start daily, at 02:00 UTC, on ubuntu-24.04. There are 2 runs:
- Using GCC, with default verilator options
- Using Clang, with "--threads 4"
Each run uses a maximum of 2 runners in parallel (so max 4 in total),
and takes slightly over 2 hours to complete.
The jobs will fail if a benchmark is broken, so this already serves as a
regression test for the included designs.
For now, performance metrics are recorded as artefacts of the run but
not otherwise published.
Performance metrics are always recorded for all successful jobs, even if
some cases are failing.
Lately ccache was mostly missing when using clang. Add '-Xclang
-fno-pch-timestamp' as recommended in the ccache manual. This indeed
fixes the caching.
Having many triggers still hits a bottleneck in LLVM leading to long
compile times.
Instead of setting triggers bit-wise, set them as a whole 64-bit word
when possible. This improves C++ compile times by ~4x on some large
designs and has minor run-time performance benefit.
This patch adds a heuristic to V3SplitVar, and it attempts to split up
packed variables that are only referenced via constant index,
non-overlapping bit/range selects. This can eliminate some UNOPTFLAT cases.
Use a generational allocator for reusing AstConst across
V3Simulate::clear(), instead of using user1 (which is also used
to store values of nodes).
Also fix invalid lookup on array initializer
This happened to work before #5516, by creating a whole shadow copy of
the entire array. Revert back to that behaviour for now, it will be
slow, but works still.
Fixes#5590
Add a new pass to split up (recursively):
foo = {l, r};
into the following, with the right indices, iff the concatenation
straddles a wide word boundary.
foo[_:_] = r;
foo[_:_] = l;
This eliminates more wide temporaries.
Another 23% speedup on VeeR EH2 high_perf. Also brings the predicted
stack size from 8M to 40k.
The DFG peephole pass converts all associative trees into right leaning,
which is good for simplifying pattern recognition, but can lead to an
excessive amount of wide intermediate results being constructed for
right leaning concatenations.
Add a new pass to balance concatenation trees by trying to:
- Create VL_EDATASIZE (32-bit) sub-terms, so words can then be packed
easily afterwards
- Try to ensure the operands of a concat are roughly the same width
within a concatenation tree. This does not yield the shortest tree,
but it ensures it has many sub-nodes that are small enough to fit into
machine registers.
This can eliminate a lot of wide intermediate results, which would need
temporaries, and also increases ILP within sub-expressions (assuming the
C compiler can't figure that out itself).
This is over 2x run-time speedup on the high_perf configuration of
VeeR EH2 (which you could arguably also get with -fno-dfg, but oh well).
Instead of installing redirect scripts in to bindir, and real
executables in to pkgdatadir/bin, we now put the real executables into
bindir, and add redirect scripts into pkgdatadir/bin. (That is, we
redirect in the opposite direction as before).
This enables the same relocatable and testable installations as before
without putting architecture specific binaries into pkgdatadir, so
hopefully we now conform to the Linux Filesystem Hierarchy Standard.
This requires a small fixup in the installed `verilator` script to
hardcode the relative path between bindir and pkgdatadir.
Fixes#5140
An ordering constraint between NBA commit blocks ('Post' logic) and the
written variable were previously added as soft constraints (cutable
edges). However these are required for correctness, so if it ever is
cut we will have incorrect simulation results.
Change these into hard constraints instead. This necessitates adding a
flag on AstVar to ignore special variables constructed during V3Delayed
that might otherwise appear as degenerate logic loops. E.g.:
if (VdlySet) {
VdlySet = 0; // <- This write to VdlySet can and must be ignored
LHS = VdlyVal;
}
No functional change, but you might get an error if this constraint was
ever violated. (Theoretically it should never be, as these variables
were inserted in a way that does not require violating these constraints
...)
* Refactor V3Delay for extensibility
Introduce the concept of an "NBA Scheme", which is the lowering pattern
we can use for various variables that are the targets of NBAs.
E.g.:
- ShadowVariable (old default scheme)
- FlagShared (old array set flag scheme)
- ValueQueueWhole (recent dynamic commit queue)
We now analyse all AstAssignDly before making any decisions on which
scheme to apply. We then choose a specific scheme for each variable that
is the target of an NBA, and then all NBAs targeting that variable use
the same scheme. This enables easy mix and match of schemes as needed,
while remaining consistent by design after extensions.
Output is perturbed due to node insertion order, but no functional
or performance change is intended.
Due to out of range selects, V3Table attempted to create a table in the
constant pool with an 'x' value in it, which caused an internal error.
Ensure V3Table behaves the same for out of range selects as the original
logic would.
There is a related bug #5490, about leaving partially out of range
selects in the logic after inserting bounds checks in V3Unknown.
This change gets rid of most of the shared pointers and useless memory
allocations. Also takes advantage of higher-arity bvxor/concat to
reduce amount of data sent to the solver.
Signed-off-by: Arkadiusz Kozdra <[email protected]>
V3ConfigWildcardResolver::resolve used to only cache the result of a
name lookup if there were any directives applied to the queried name.
This can be a performance problem. E.g. the module resolver is invoked
for every variable to check for attributes. If you had 'n' variables in
the design, and you also had 'k' directives that apply to specific
modules not involving most of the 'n' variables, then checking the
attributes involved O(n*k) operations. This can be very expensive
for large 'n' and 'k'.
In this patch we resolve every name exactly once, so the same above is
now O(n) in the worst case, and often a lot smaller due to repeat
lookups.
According to IEEE 1800-2023 12.7.3, the loop creates an implicit block
around it, containing declarations of the loop variables with automatic
lifetime.
No functional change intended.
Signed-off-by: Arkadiusz Kozdra <[email protected]>
The necessary options to support C++ coroutines vary greatly between
compilers, its versions, and the standard library being used. This
patch makes the check for coroutine support more robust by adding a
declaration of a coroutine variable, instead of just including the
header. It also makes sure that the HAVE_COROUTINE and
CFG_CXXFLAGS_COROUTINES flags are always set together, and only when
coroutine support is detected.
The two most useless warning classes are llvmlibc-* on virtually every
identifier use that it does not resolve to __llvm_libc:: namespace, and
altera-* ones that warn on virtually every loop statement that it could
be unrolled with a pragma. No functional change.
Signed-off-by: Arkadiusz Kozdra <[email protected]>
Documentation states that minimum of all reported coverage of all signals in a line should be taken.
Previous logic would break if there were any signals with zero coverage followed by signals with
nonzero coverage - a minimum from those nonzero toggle count would be taken, disregarding zero
coverage of previous signals.
Internal-tag: [#62193]
Signed-off-by: Krzysztof Obłonczek <[email protected]>
Not sure why this was disabled before, but it seems legal to me to
change
'forced A' -> 'B' -> 'C'
into
'forced A' -> 'B',
'forced A' -> 'C'
Fixes#5249
After the V3Timing refactoring the V3SchedTiming phase could apparently
move away all awaits from a coroutine without adding a co_return
statement.
Signed-off-by: Arkadiusz Kozdra <[email protected]>
`$psprintf` is a non-standard system function present in some other
simulators, and has been rejected for standardization by IEEE because
of being basically the same as `$sformatf`.
To encourage users to fix their codebase, a warning is emitted by
default, but it gets otherwise interpreted as `$sformatf` as early as
during lexing.
Signed-off-by: Arkadiusz Kozdra <[email protected]>
* wording/formatting
Signed-off-by: Arkadiusz Kozdra <[email protected]>
---------
Signed-off-by: Arkadiusz Kozdra <[email protected]>
* Support 2D dynamic array initialization (#4700)
- new[] on sub arrays (as per original issue)
- Built-in methods for sub-arrays
- Initialization and literals assignmensts
- Dynamic array as an element for other arrays and queues
libcxx has removed the experimental/coroutine include file in favor of
the C++20-standard coroutine include. If the latter is available we
use it otherwise falling back to the existing experimental version (in
which case we also disable the deprecated-experimental-coroutine warning).
(See also https://reviews.llvm.org/D108697.)
operand order reversed for AstCMethodHard "neq"
interface between C-style arrays and VlUnpacked
overloads added to VlUnpacked::neq(), VlUnpacked::assign()
VlUnpacked::operator=() added
Fixes #5125
* Internals: Move getenvStr to verilatedos. No functional change intended.
* Fix POS34-C. Do not call putenv() with a pointer to an automatic variable as the argument.
Signed-off-by: Arkadiusz Kozdra <[email protected]>
For NBAs that might execute a dynamic number of times in a single
evaluation (specifically: those that assign to array elements inside
loops), we introduce a new run-time VlNBACommitQueue data-structure
(currently a vector), which stores all pending updates and the necessary
info to reconstruct the LHS reference of the AstAssignDly at run-time.
All variables needing a commit queue has their corresponding unique
commit queue.
All NBAs to a variable that requires a commit queue go through the
commit queue. This is necessary to preserve update order in sequential
code, e.g.:
a[7] <= 10
for (int i = 1 ; i < 10; ++i) a[i] <= i;
a[2] <= 10
needs to end with array elements 1..9 being 1, 10, 3, 4, 5, 6, 7, 8, 9.
This enables supporting common forms of NBAs to arrays on the left hand
side of <= in non-suspendable/non-fork code. (Suspendable/fork
implementation is unclear to me so I left it unchanged, see #5084).
Any NBA that does not need a commit queue (i.e.: those that were
supported before), use the same scheme as before, and this patch should
have no effect on the generated code for those NBAs.
No functional change. Postpone the conversion of all AstAssignDlys that
use the 'VdlySet' scheme for array LHSs until after the complete
traversal of the netlist. The next patch takes advantage of this by
using some extra information also gathered through the traversal to
change the conversion.
AstAssignDlys inside suspendable or fork are not deferred and are
processed identical to the previous version.
There are some TODOs in this patch that are fixed in the next patch.
Output code perturbed due to variable ordering.
MULTIDRIVEN message ordering perturbed due to processing order change.
No functional change.
This patch is just cleanup with some non-functional changes to enable
the next patch. Most importantly createDlyOnSet, which implements NBAs
for arrays, has a new streamlined implementation that does the same
thing. Some output code is perturbed due to statement/local variable
insertion order.
Also renamed Vdlyvfoo to VdlyFoo for easier readability of the generated
code.
Checking the wrong node meant we never actually pushed constant
bit-select indices into the delayed update, as was the intention, but
always generated a temporary instead.
This adheres more to the wording used in IEEE 1800-2017 22.5.1,
specifying the join operator to be more of a delimiter than join:
> A `` delimits lexical tokens without introducing white space,
> allowing identifiers to be constructed from arguments.
Before, string RHS arguments to the join operator were silently dropped.
Signed-off-by: Arkadiusz Kozdra <[email protected]>
The goal here is to use as single ordering heuristic (which can be
improved later) within MTasks as we do for serial code ordering. The
heuristic itself is factored out into the new OrderMoveGraphSerializer.
This also yields slightly nicer ordering than the previously use
GraphStream, so we end up with fewer trigger (domain) conditionals in
the MTasks, this can be worth a few percent speedup.
This has the somewhat nice side-effect of reusing OrderMoveGraphVertex
for both serial and parallel mode, so MTaskMoveGraphVertex can be
removed.
Serial mode yields identical output.
- Adds support for C-style for-loop initializers
- Current implementation supports: for (x a = 1, y b = 2, ...)
- This patch extends support to: for (x a = 1, b = 2, ...)
- Adds unit test for new feature
Instead of carrying around MTask affinity from scheduling, compute it in
V3VariableOrder (where it is used), by tracing through the code. This
simplifies some code and has the benefit of handling variables
introduced after scheduling. It's worth a few % speed at run-time, and
the new implementation of V3VariableOrder is slightly more efficient,
though the speed/space is still dominated by the TSP sort.
There is no strong need to re-map LogicMTask IDs and it just adds extra
processing. Instead we just allocate a separate set of ExecMTask IDs as
they are created, which can also be used as the unique profiling ID as
well. The only effect on the output of this is the change in mtask IDs
emitted, which was fairly arbitrary to begin with.
Wrapping the functions in #4933 broke --prof-exec report as the
predicted MTask times are computed during thread packing, but are
emitted in the wrapping functions.
V3Partition used to contain 2 conceptually separate set of algorithms
- The MTask partitioning/coarsening algorithm used by V3Order. This has
been moved to V3OrderParallel.cpp
- The lowering of AstExecGraph into per thread functions by packing
tasks into threads and creating additional code
(V3Partition::finalize). This has been moved to the new
V3ExecGraph.cpp
This patch is just code movement/rename with minimal fixes required to
do so.
Continuing the idea of decoupling the implementations of the various algorithms.
The main points:
-Move the former "processDomain" stuff, dealing with assigning combinational logic into the relevant sensitivity domains into V3OrderProcessDomains.cpp
-Move the parallel code construction in V3OrderParallel.cpp (Could combine this with some parts of V3Partition - those not called from V3Partition::finalize - but that's not for this patch).
-Move the serial code construction into V3OrderSerial.cpp
-Factored the very small common code between the parallel and serial code construction (processMoveOneLogic) into V3OrderCFuncEmitter.cpp
Move OrderBuildVisitor into V3OrderGraphBuilder.cpp (and rename to
V3OrderGraphBuilder). Move ProcessMoveBuildGraph to
V3OrderMoveGraphBuilder.cpp (and rename to V3OrderGraphBuilder).
This patch is pure code movement/rename, no refactoring at all.
Add a new data-structure V3DfgCache, which can be used to retrieve
existing vertices with some given inputs vertices. Use this in
V3DfgPeephole to eliminate the creation of redundant vertices.
Overall this is performance neutral, but is in prep for some future
work.
DFG could remove forceable signals by replacing them with their
in-design driver. This is a bit of a pain to prevent, and ideally the
forcing transform should happen before DFG, but implementing it there is
a pain due to having to rewrite ports based on direction. This is an
attempted fix in DFG. More cases might remain.
This functionality used to be distributed in the removeVars pass and the
final dfgToAst conversion. Instead added a new 'regularize' pass to
convert DFGs into forms that can be trivially converted back to Ast, and
a new 'eliminateVars' pass to remove/repalce redundant variables. This
simplifies dfgToAst significantly and makes the code a bit easier to
follow.
The new 'regularize' pass will ensure that every sub-expression with
multiple uses is assigned to a temporary (unless it's a trivial memory
reference or constant), and will also eliminate or replace redundant
variables. Overall it is a performance neutral change but it does
enable some later improvements which required the graph to be in this
form, and this also happens to be the form required for the dfgToAst
conversion.
With --stats, we will print DFG pattern combinations, one per line, as
S-expressions to new stat files, together with their frequency, to aid
discovery of new peephole patterns.
When the condition of an AstWhile loop contains a statement (e.g.
through an AstExprStmt), temporaries inserted in that statement need to
go before that statement, not in the AstWhile precondition.
devcontainers are a convenient way to provide users a reproducible
build environment. It is currently supported by Visual Studio Code,
Visual Studio and IntelliJ.
When the user opens the verilator repo in VSCode with the standard
devcontainer extension installed, VSCode will ask the user if they
want to reopen in the devcontainer, then build the Docker image as per
our definition and then restart VSCode 'remotely' attached to the
Docker container.
More information:
https://code.visualstudio.com/docs/devcontainers/containers
Also:
- zlibc is missing on Debian-based systems now
- Add non-root user to Dockerfile and make default
- Enable creating constant pool entries for RHS of simple
var = const assignments
- Never extract ArraySel (it's just pointer arithmetic)
- Remove unnecessary AstTraceInc precond child tree
- Always fully recurse expressions (fix transplanted from #4617)
- General cleanup
Overall the patch is performance neutral to slightly positive, but saves
~10% peak Verialtor memory usage due to not creating temporaries (which
are later expanded) for any ArraySels.
Adds a new field to `AstSenItem` that stores the `iff` condition which is then handled by `SenExprBuilder`.
Signed-off-by: Krzysztof Bieganski <[email protected]>
This patch addresses two issues with NBAs in non-inlined functions/tasks:
- If the NBA writes to a local automatic var, the var could cease to exist before the NBA executes. This is normally addressed by fork dynscopes (#4356), but NBA-to-fork transformation happens way after `V3Fork` (in `V3Timing`). To solve this, we put NBAs that write to locals under forks in `V3Fork` already. This way, such locals will be put in dynscopes, and will still exist after the task containing the NBA exits.
- The above change means that any writes in forks other than `fork..join` should be handled by `V3Fork`. Thus, in `V3SchedTiming`, we only have to worry about read references, so we can simply copy all remaining locals. Because we copy, lifetimes are not an issue. This fixes a bug that allowed assignment intravals to be overwritten if they go out of scope in the containing function.
This patch enforces the use of the most specific accessors for operands
which have an '@astgen alias' declaration, by making the superclass
accessors of the same operands private. This ensures client code is
cleaner as you can't use multiple different methods to reference the
same operands (which we used to in some places). Also prep for some
refactoring.
V3Subst is currently the pass responsible for peak memory usage. This
patch saves ~16% of peak memory on OpenTitan.
2 changes:
- It is actually safe to delete the substituted expressions immediately,
but this is the lesser contribution
- More importantly, we only ever substitute STMTTEMP variables, which
are always defined within the same CFunc, so we can limit the scope of
the optimization to CFunc. This allows us to reclaim the SubstVarEntry
structures at the end of every CFunc, rather than at the end of the
whole pass, which gives us most of the memory savings.
Generated output is identical
Used to set the wrong public flag on forceEn/forceVal, which means they
were not included in ICO as necessary, but V3Gate tended to inline them,
so this was hard to hit.
Fixes#4577
This saves about 5% memory. V3AstUserAllocator is appropriate for most use
cases, performance is marginally up as we are mostly D-cache bound on
large designs.
The typical find/if-not-exists-insert pattern can be achieved with 1
lookup instead of 2 using emplace with a sentinel value. Also maps value
initialize their values when inserted with the [] operator, this is
defined and so there is no need to explicitly insert zeroes for integer
values.
This patch adds some abstract enums to pass to the trace decl* APIs, so
the VCD/FST specific code can be kept in verilated_{vcd,fst}_*.cc, and
removed from V3Emit*. It also reworks the generation of the trace init
functions (those that call 'decl*' for the signals) such that the scope
hierarchy is traversed precisely once during initialization, which
simplifies the FST writer. This later change also has the side effect of
fixing tracing of nested interfaces when traced via an interface
reference - see the change in the expected t_interface_ref_trace - which
previously were missed.
Some values emitted to the trace files are constant (e.g.: actual
parameter values), and never change. Previously we used to trace these
in the 'full' dumps, which also included all other truly variable
signals. This patch introduces a new generated trace function 'const',
to complement the 'full' and 'chg' flavour, and 'const' now only
contains the constant signals, while 'full' and 'chg' contain only the
truly variable signals. The generate 'full' and 'chg' trace functions
now have exactly the same shape. Note that 'const' signals are still
traced using the 'full*' dump methods of the trace buffers, so there is
no need for a third flavour of those.
V3Stats for "fast" code have bit-rotted a little and is causing some
problems with tests that rely on stats outputs. The problem is that not
all code is necessarily reachable from eval() any more (due to the
complexity of some the features added over the past few years), so it
might miss some things, as for measuring the "fast" code, it is trying
to trace the execution paths via calls, starting from eval(). It also
appears the fast code can also contain calls to slow code in some
circumstances.
To avoid all that, removed trying to trace dynamic execution, and simply
report the static node counts, which is enough for testing.
Similarly, the variable counts are somewhat dubious, as they don't
include all data types, or all instances of a module in some stages.
Removing these as they are not widely used nor dependable. More specific
stats can be added if required and can be well defined.
Prior to this we failed to create implicit nets for inputs of gate
primitives, which is required by the standard (IEEE 1800-2017 6.10).
Note: outputs were covered due to being modeled as the LHS of
assignments, which do create implicit nets.
Again --prof-exec have bit-rotted a little with all the recent changes
to the structure of the generated code. This patch contains a few
improvements:
- Repalce the eval/evl_loop begin/end events with generic
section_push/section_pop events, that can be arbitrarily sprinkled
into the generate code (so long as they are matched correctly) to
measure various sections. The report then contains a nested profile
of the sections, and the VCD trace shows the section names.
- Better handling of exec graphs
- Clearer overall statistics
Still some remains of the --threads 0 mode. Remove unnecessary complexity
from V3EmitCModel. (Also don't pretend there is an MTask in single
threaded mode, when there really isn't.)
It's unlikely one value fits all use case, so making VL_LOCK_SPINS
configurable at model build time.
For testing, we reduce the value as we expect high contention.
Previously V3InstrCount used to completely ignore an AstConcat,
including its children (see the rational in the comment). The problem is
the operands can be huge and expensive compound expressions (especially
since DFG), and not just a simple variable reference. This fix gains
some MT speed improvement.
Since we removed --threads 0 support, the 'threads()' option always
returns a value >= 1. Remove corresponding dead code.
Some of the coverage counters appear to use atomics even if the model is
single threaded. I'm under the impression this was a bug originally so
those ones I changed to use threads() > 1 instead.
According to 1800-2017 36.3, 1800-2017 A.9.3, 1364-2005 20.2 and 1364-2005 A.9.3, user defined system task and function identifiers can use the same character set for the second character as all the following characters.
`getCommonClassTypep` and its helper code has been moved to AstNode
class. This is a lot better place for this functionality. Moreover, it
allowed to get rid of the dependency on V3Width from generic AST-related
code.
This API is used if the user copies the process using `fork`
and similar OS-level mechanisms. The `at_clone` member function
ensures that all model-allocated resources are re-allocated, such
that the copied child process/model can simulate correctly.
A typical allocated resource is the thread pool, which every model
has its own pool.
* Ignore CLion project files and CMake outputs
* Supporting stripping file path that contains backslash
* Set /bigobj flag and increase stack size for windows platform
* Fix MSVC warnings
Multiple edge timing controls in class methods would cause compilation errors on
the generated C++ code. This is because the `SenExprBuilder` used for these
would get recreated per timing control, resulting in duplicate variable names.
The fix is to have a single `SenExprBuilder` per scope.
Multiple edge timing controls in class methods would cause compilation errors on the generated C++ code. This is because the `SenExprBuilder` used for these would get recreated per timing control, resulting in duplicate variable names. The fix is to have a single `SenExprBuilder` per scope.
* Add VL_ASSERT_CAPABILITY; add assumeLocked and pretendUnlock to V3Mutex.
* Pass jobs as template-arguments and use std::packaged_task.
* Add and use V3ThreadPool::ScopedExclusiveAccess.
Given nested forks, if the inner fork had a `join` or `join_any` at the end,
`V3Sched::transformForks()` would decide that the fork's `VlForkSync` variable
should be passed in from the outside. This resulted in the `VlForkSync` getting
redeclared as a function argument. Ultimately, it led to C++ compilation errors
due to variable redeclaration.
Fixed by rearranging the `if`s that decide whether a variable should be passed
in or left as-is.
`stopRequested()` reads only atomic variables. It doesn't need a mutex
to do this.
This function is called in `waitIfStopRequested()`, which in turn
is called before execution of every job, and inside some jobs. With this
change the mutex inside `waitIfStopRequested` needs to be locked only in
very rare cases instead of every time.
Event-triggered coroutines live in two stages: 'uncommitted' and 'ready'. First
they land in 'uncommitted', meaning they can't be resumed yet. Only after
coroutines from the 'ready' queue are resumed, the 'uncommitted' ones are moved
to the 'ready' queue, and can be resumed. This is to avoid self-triggering in
situations like waiting for an event immediately after triggering it.
However, there is an issue with `wait` statements. If you have a `wait(b)`, it's
being translated into a loop that awaits a change in `b` as long as `b` is
false. If `b` is false at first, the coroutine is put into the `uncommitted`
queue. If `b` is set to true before it's committed, the coroutine won't get
resumed.
This patch fixes that by immediately committing event controls created from
`wait` statements. That means the coroutine from the example above will get
resumed from now on.
This makes the implementation of the detection and propagation of the
suspendable property simpler and easier to read. More importantly, there are no
more jumps around the AST with the `visit` functions, which in some cases could
result in incorrect visitor context while in the `visit` function. See the added
test, which would cause Verilator to segfault before this patch.
In testing, verilation performance was not shown to be affected by this change.
Though there is a slight performance improvement from this patch, due to adding
one more check before refreshing class member cache.
Signed-off-by: Krzysztof Bieganski <[email protected]>
* V3Common.cpp::makeVlToString: fix `VL_TOSTRING_W` statement generation to include width argument
* fix contribution name
* add testcase for long struct `VL_TO_STRING_W` bug
This patch fixes two cases where methods in base classes were not being marked
as coroutines, even though they were being overridden by coroutines.
- One case is the class member cache not getting refreshed for searched classes.
- The other is when the overriding methods are not declared as `virtual`. In
that case, the `isVirtual()` getter on such a method returns false, which led
to `V3Timing` skipping the step of searching for overridden methods.
Signed-off-by: Krzysztof Bieganski <[email protected]>
Static variables of functions are created in the function. When blocks
in a function use identical names for static variables, we need to name
those variables properly.
Pack the elements of VlTriggerVec as dense bits (instead of a 1 byte
bool per bit), and check whether they are set on a word granularity.
This effectively transforms conditions of the form `if (trig.at(0) |
trig.at(2) | trig.at(64))` into `if (trig.word(0) & 0x5 | trig.word(1) &
0x1)`. This improves OpenTitan ST by about 1%, worth more on some other
designs.
`VlNow{}` is completely unnecessary, as coroutines are always on the
heap (unless optimized out). Also fix access of var ref passed to forked processes.
Given an await at the end of a block, e.g. at the end of a loop body, a trace
activity setter was not inserted, as there were no following statements. This
patch makes the activity update unconditional.
Before this patch, it was possible to access non-static class members using
static access, which resulted in C++ compilation errors. This adds
verilation-time checks for such situations.
1. Fixes passing a null reference as a task argument. Before this patch it would
cause a C++ compile error like `cannot convert ‘VlNull’ to ‘VlClassRef<...>’`.
2. Fixes passing a class reference as a task argument when the argument is a
reference to a base class. Before the patch it would cause a C++ compile
error like `cannot convert ‘VlClassRef<{DERIVED_CLASS}>’ to ‘VlClassRef<{BASE_CLASS}>`.
Before this patch, calling tasks directly under forks would result in each
statement of these tasks being executed concurrently. This was due to Verilator
inlining tasks most of the time. Such inlined tasks' statements would simply
replace the original call, and there would be no indication that these used to
be grouped together. Ultimately resulting in `V3Timing` treating each statement
as a separate process.
The solution is simply to wrap each fork sub-statement in a begin in `V3Begin`
(except for the ones that are begins, as that would be pointless). `V3Begin` is
already aware of forks, and is supposed to avoid issues like this one, so it
seems like a natural fit. This also protects us from similar bugs, i.e. if some
statement gets replaced or expanded into multiple statements.
Signed-off-by: Krzysztof Bieganski <[email protected]>
The baked in DEFENV paths might end up with extra NULL characters
at the end if the binaries are installed by something that patches them
for relocatable installs (e.g. conda). Avoid this issue by immediately
passing them through std::string::c_str() method to stop at the first NULL
* Support method class without parenthesis
Signed-off-by: Ryszard Rozak <[email protected]>
* Delete replaced nodes
Signed-off-by: Ryszard Rozak <[email protected]>
---------
Signed-off-by: Ryszard Rozak <[email protected]>
This backs out #606b35853b, which is believed no longer needed due to
(#3881) being fixed.
If this proves wrong and additional OS dependencies are needed, we should
use a feature test macro so that the OS test doesn't need upkeep.
Fixes#3872.
Testing this is a bit tricky, as the front-end fixes up the operand
widths in shifts to match, and we need V3Const to introduce a mismatched
one by reducing `4'd2 ** x` (with x being 2 2-bit wide signal) to `4'd1
<< x`, but t_dfg_peephole runs with V3Const disabled exactly because it
makes it hard to write tests. Rather than fixing this one case in
V3Const (which we should do systematically at some point), I fixed DFG
to accept these just in case V3Const generates more of them. The
assertions were there only because of paranoia (as I thought these were
not possible inputs), the code otherwise works.
In order to avoid unexpected breakage on multi-driven variables, we
resolve in DFG construction by using only the first driver encountered.
Also issues the MULTIDRIVEN error for these signals.
Replace the 'run to fixed point' algorithm with a work list driven
approach. Instead of marking the graph as changed, we explicitly add
vertices to the work list, to be visited, when a vertex is changed. This
improves both memory locality (as the work list is processed in last in
first out order), and removed unnecessary visitations when only a few
nodes changes.
Folding an AstLogAnd with a non-zero constant operand used to coerce the
type of the other operand, yielding an ill-typed node that DFG was then
unhappy about. Add a RedOr instead if the width of the replacement
operand is greater than zero.
Fixes#3726
Apart from the representational changes below, this patch renames
AstNodeMath to AstNodeExpr, and AstCMath to AstCExpr.
Now every expression (i.e.: those AstNodes that represent a [possibly
void] value, with value being interpreted in a very general sense) has
AstNodeExpr as a super class. This necessitates the introduction of an
AstStmtExpr, which represents an expression in statement position, e.g :
'foo();' would be represented as AstStmtExpr(AstCCall(foo)). In exchange
we can get rid of isStatement() in AstNodeStmt, which now really always
represent a statement
Peak memory consumption and verilation speed are not measurably changed.
Partial step towards #3420
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"Builds both the debug and release binaries, overriding CMAKE_BUILD_TYPE. Not supported under MSBuild."
)
find_package(Python3COMPONENTSInterpreter)
set(PYTHON3${Python3_EXECUTABLE})
# See also CMake built-in; CMAKE_INSTALL_PREFIX is applied by the install command.
set(CMAKE_INSTALL_DATADIR.)
include(GNUInstallDirs)
include(CMakePackageConfigHelpers)
include(CheckStructHasMember)
include(ExternalProject)
include(FindThreads)
if(NOTWIN32)
message(WARNING"CMake support on Linux/OSX is experimental.")
endif()
if(WIN32)
if(DEFINEDENV{WIN_FLEX_BISON})
set(WIN_FLEX_BISON"$ENV{WIN_FLEX_BISON}")
endif()
if(IS_DIRECTORY${WIN_FLEX_BISON})
list(APPENDCMAKE_PREFIX_PATH${WIN_FLEX_BISON})
else()
message(
FATAL_ERROR
"The path specified by WIN_FLEX_BISON environment variable is not an existing folder: ${WIN_FLEX_BISON}"
)
endif()
if(NOTWIN_FLEX_BISON)
message(
FATAL_ERROR
"Please install https://github.com/lexxmark/winflexbison and set WIN_FLEX_BISON environment variable. Please use install cmake target after a successful build."
)
endif()
set(CMAKE_CXX_STANDARD20)
endif()
set(OBJCACHE""CACHESTRING"Path for ccache, auto-detected if empty")
option(OBJCACHE_ENABLED"Compile Verilator with ccache"ON)
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A “User Product” is either (1) a “consumer product”, which means any tangible personal property which is normally used for personal, family, or household purposes, or (2) anything designed or sold for incorporation into a dwelling. In determining whether a product is a consumer product, doubtful cases shall be resolved in favor of coverage. For a particular product received by a particular user, “normally used” refers to a typical or common use of that class of product, regardless of the status of the particular user or of the way in which the particular user actually uses, or expects or is expected to use, the product. A product is a consumer product regardless of whether the product has substantial commercial, industrial or non-consumer uses, unless such uses represent the only significant mode of use of the product.
“Installation Information” for a User Product means any methods, procedures, authorization keys, or other information required to install and execute modified versions of a covered work in that User Product from a modified version of its Corresponding Source. The information must suffice to ensure that the continued functioning of the modified object code is in no case prevented or interfered with solely because modification has been made.
If you convey an object code work under this section in, or with, or specifically for use in, a User Product, and the conveying occurs as part of a transaction in which the right of possession and use of the User Product is transferred to the recipient in perpetuity or for a fixed term (regardless of how the transaction is characterized), the Corresponding Source conveyed under this section must be accompanied by the Installation Information. But this requirement does not apply if neither you nor any third party retains the ability to install modified object code on the User Product (for example, the work has been installed in ROM).
The requirement to provide Installation Information does not include a requirement to continue to provide support service, warranty, or updates for a work that has been modified or installed by the recipient, or for the User Product in which it has been modified or installed. Access to a network may be denied when the modification itself materially and adversely affects the operation of the network or violates the rules and protocols for communication across the network.
Corresponding Source conveyed, and Installation Information provided, in accord with this section must be in a format that is publicly documented (and with an implementation available to the public in source code form), and must require no special password or key for unpacking, reading or copying.
7. Additional Terms.
“Additional permissions” are terms that supplement the terms of this License by making exceptions from one or more of its conditions. Additional permissions that are applicable to the entire Program shall be treated as though they were included in this License, to the extent that they are valid under applicable law. If additional permissions apply only to part of the Program, that part may be used separately under those permissions, but the entire Program remains governed by this License without regard to the additional permissions.
When you convey a copy of a covered work, you may at your option remove any additional permissions from that copy, or from any part of it. (Additional permissions may be written to require their own removal in certain cases when you modify the work.) You may place additional permissions on material, added by you to a covered work, for which you have or can give appropriate copyright permission.
Notwithstanding any other provision of this License, for material you add to a covered work, you may (if authorized by the copyright holders of that material) supplement the terms of this License with terms:
a) Disclaiming warranty or limiting liability differently from the terms of sections 15 and 16 of this License; or
b) Requiring preservation of specified reasonable legal notices or author attributions in that material or in the Appropriate Legal Notices displayed by works containing it; or
c) Prohibiting misrepresentation of the origin of that material, or requiring that modified versions of such material be marked in reasonable ways as different from the original version; or
d) Limiting the use for publicity purposes of names of licensors or authors of the material; or
e) Declining to grant rights under trademark law for use of some trade names, trademarks, or service marks; or
f) Requiring indemnification of licensors and authors of that material by anyone who conveys the material (or modified versions of it) with contractual assumptions of liability to the recipient, for any liability that these contractual assumptions directly impose on those licensors and authors.
All other non-permissive additional terms are considered “further restrictions” within the meaning of section 10. If the Program as you received it, or any part of it, contains a notice stating that it is governed by this License along with a term that is a further restriction, you may remove that term. If a license document contains a further restriction but permits relicensing or conveying under this License, you may add to a covered work material governed by the terms of that license document, provided that the further restriction does not survive such relicensing or conveying.
If you add terms to a covered work in accord with this section, you must place, in the relevant source files, a statement of the additional terms that apply to those files, or a notice indicating where to find the applicable terms.
Additional terms, permissive or non-permissive, may be stated in the form of a separately written license, or stated as exceptions; the above requirements apply either way.
8. Termination.
You may not propagate or modify a covered work except as expressly provided under this License. Any attempt otherwise to propagate or modify it is void, and will automatically terminate your rights under this License (including any patent licenses granted under the third paragraph of section 11).
However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.
Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.
Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, you do not qualify to receive new licenses for the same material under section 10.
9. Acceptance Not Required for Having Copies.
You are not required to accept this License in order to receive or run a copy of the Program. Ancillary propagation of a covered work occurring solely as a consequence of using peer-to-peer transmission to receive a copy likewise does not require acceptance. However, nothing other than this License grants you permission to propagate or modify any covered work. These actions infringe copyright if you do not accept this License. Therefore, by modifying or propagating a covered work, you indicate your acceptance of this License to do so.
10. Automatic Licensing of Downstream Recipients.
Each time you convey a covered work, the recipient automatically receives a license from the original licensors, to run, modify and propagate that work, subject to this License. You are not responsible for enforcing compliance by third parties with this License.
An “entity transaction” is a transaction transferring control of an organization, or substantially all assets of one, or subdividing an organization, or merging organizations. If propagation of a covered work results from an entity transaction, each party to that transaction who receives a copy of the work also receives whatever licenses to the work the party's predecessor in interest had or could give under the previous paragraph, plus a right to possession of the Corresponding Source of the work from the predecessor in interest, if the predecessor has it or can get it with reasonable efforts.
You may not impose any further restrictions on the exercise of the rights granted or affirmed under this License. For example, you may not impose a license fee, royalty, or other charge for exercise of rights granted under this License, and you may not initiate litigation (including a cross-claim or counterclaim in a lawsuit) alleging that any patent claim is infringed by making, using, selling, offering for sale, or importing the Program or any portion of it.
11. Patents.
A “contributor” is a copyright holder who authorizes use under this License of the Program or a work on which the Program is based. The work thus licensed is called the contributor's “contributor version”.
A contributor's “essential patent claims” are all patent claims owned or controlled by the contributor, whether already acquired or hereafter acquired, that would be infringed by some manner, permitted by this License, of making, using, or selling its contributor version, but do not include claims that would be infringed only as a consequence of further modification of the contributor version. For purposes of this definition, “control” includes the right to grant patent sublicenses in a manner consistent with the requirements of this License.
Each contributor grants you a non-exclusive, worldwide, royalty-free patent license under the contributor's essential patent claims, to make, use, sell, offer for sale, import and otherwise run, modify and propagate the contents of its contributor version.
In the following three paragraphs, a “patent license” is any express agreement or commitment, however denominated, not to enforce a patent (such as an express permission to practice a patent or covenant not to sue for patent infringement). To “grant” such a patent license to a party means to make such an agreement or commitment not to enforce a patent against the party.
If you convey a covered work, knowingly relying on a patent license, and the Corresponding Source of the work is not available for anyone to copy, free of charge and under the terms of this License, through a publicly available network server or other readily accessible means, then you must either (1) cause the Corresponding Source to be so available, or (2) arrange to deprive yourself of the benefit of the patent license for this particular work, or (3) arrange, in a manner consistent with the requirements of this License, to extend the patent license to downstream recipients. “Knowingly relying” means you have actual knowledge that, but for the patent license, your conveying the covered work in a country, or your recipient's use of the covered work in a country, would infringe one or more identifiable patents in that country that you have reason to believe are valid.
If, pursuant to or in connection with a single transaction or arrangement, you convey, or propagate by procuring conveyance of, a covered work, and grant a patent license to some of the parties receiving the covered work authorizing them to use, propagate, modify or convey a specific copy of the covered work, then the patent license you grant is automatically extended to all recipients of the covered work and works based on it.
A patent license is “discriminatory” if it does not include within the scope of its coverage, prohibits the exercise of, or is conditioned on the non-exercise of one or more of the rights that are specifically granted under this License. You may not convey a covered work if you are a party to an arrangement with a third party that is in the business of distributing software, under which you make payment to the third party based on the extent of your activity of conveying the work, and under which the third party grants, to any of the parties who would receive the covered work from you, a discriminatory patent license (a) in connection with copies of the covered work conveyed by you (or copies made from those copies), or (b) primarily for and in connection with specific products or compilations that contain the covered work, unless you entered into that arrangement, or that patent license was granted, prior to 28 March 2007.
Nothing in this License shall be construed as excluding or limiting any implied license or other defenses to infringement that may otherwise be available to you under applicable patent law.
12. No Surrender of Others' Freedom.
If conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot convey a covered work so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not convey it at all. For example, if you agree to terms that obligate you to collect a royalty for further conveying from those to whom you convey the Program, the only way you could satisfy both those terms and this License would be to refrain entirely from conveying the Program.
13. Use with the GNU Affero General Public License.
Notwithstanding any other provision of this License, you have permission to link or combine any covered work with a work licensed under version 3 of the GNU Affero General Public License into a single combined work, and to convey the resulting work. The terms of this License will continue to apply to the part which is the covered work, but the special requirements of the GNU Affero General Public License, section 13, concerning interaction through a network will apply to the combination as such.
14. Revised Versions of this License.
The Free Software Foundation may publish revised and/or new versions of the GNU General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.
Each version is given a distinguishing version number. If the Program specifies that a certain numbered version of the GNU General Public License “or any later version” applies to it, you have the option of following the terms and conditions either of that numbered version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of the GNU General Public License, you may choose any version ever published by the Free Software Foundation.
If the Program specifies that a proxy can decide which future versions of the GNU General Public License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Program.
Later license versions may give you additional or different permissions. However, no additional obligations are imposed on any author or copyright holder as a result of your choosing to follow a later version.
15. Disclaimer of Warranty.
THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
16. Limitation of Liability.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
17. Interpretation of Sections 15 and 16.
If the disclaimer of warranty and limitation of liability provided above cannot be given local legal effect according to their terms, reviewing courts shall apply local law that most closely approximates an absolute waiver of all civil liability in connection with the Program, unless a warranty or assumption of liability accompanies a copy of the Program in return for a fee.
END OF TERMS AND CONDITIONS
How to Apply These Terms to Your New Programs
If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively state the exclusion of warranty; and each file should have at least the “copyright” line and a pointer to where the full notice is found.
<one line to give the program's name and a brief idea of what it does.>
Copyright (C) <year> <name of author>
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.
Also add information on how to contact you by electronic and paper mail.
If the program does terminal interaction, make it output a short notice like this when it starts in an interactive mode:
<program> Copyright (C) <year> <name of author>
This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the appropriate parts of the General Public License. Of course, your program's commands might be different; for a GUI interface, you would use an “about box”.
You should also get your employer (if you work as a programmer) or school, if any, to sign a “copyright disclaimer” for the program, if necessary. For more information on this, and how to apply and follow the GNU GPL, see <http://www.gnu.org/licenses/>.
The GNU General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Lesser General Public License instead of this License. But first, please read <http://www.gnu.org/philosophy/why-not-lgpl.html>.
TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
1. Definitions.
"License" shall mean the terms and conditions for use, reproduction, and distribution as defined by Sections 1 through 9 of this document.
"Licensor" shall mean the copyright owner or entity authorized by the copyright owner that is granting the License.
"Legal Entity" shall mean the union of the acting entity and all other entities that control, are controlled by, or are under common control with that entity. For the purposes of this definition, "control" means (i) the power, direct or indirect, to cause the direction or management of such entity, whether by contract or otherwise, or (ii) ownership of fifty percent (50%) or more of the outstanding shares, or (iii) beneficial ownership of such entity.
"You" (or "Your") shall mean an individual or Legal Entity exercising permissions granted by this License.
"Source" form shall mean the preferred form for making modifications, including but not limited to software source code, documentation source, and configuration files.
"Object" form shall mean any form resulting from mechanical transformation or translation of a Source form, including but not limited to compiled object code, generated documentation, and conversions to other media types.
"Work" shall mean the work of authorship, whether in Source or Object form, made available under the License, as indicated by a copyright notice that is included in or attached to the work (an example is provided in the Appendix below).
"Derivative Works" shall mean any work, whether in Source or Object form, that is based on (or derived from) the Work and for which the editorial revisions, annotations, elaborations, or other modifications represent, as a whole, an original work of authorship. For the purposes of this License, Derivative Works shall not include works that remain separable from, or merely link (or bind by name) to the interfaces of, the Work and Derivative Works thereof.
"Contribution" shall mean any work of authorship, including the original version of the Work and any modifications or additions to that Work or Derivative Works thereof, that is intentionally submitted to Licensor for inclusion in the Work by the copyright owner or by an individual or Legal Entity authorized to submit on behalf of the copyright owner. For the purposes of this definition, "submitted" means any form of electronic, verbal, or written communication sent to the Licensor or its representatives, including but not limited to communication on electronic mailing lists, source code control systems, and issue tracking systems that are managed by, or on behalf of, the Licensor for the purpose of discussing and improving the Work, but excluding communication that is conspicuously marked or otherwise designated in writing by the copyright owner as "Not a Contribution."
"Contributor" shall mean Licensor and any individual or Legal Entity on behalf of whom a Contribution has been received by Licensor and subsequently incorporated within the Work.
2. Grant of Copyright License. Subject to the terms and conditions of this License, each Contributor hereby grants to You a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare Derivative Works of, publicly display, publicly perform, sublicense, and distribute the Work and such Derivative Works in Source or Object form.
3. Grant of Patent License. Subject to the terms and conditions of this License, each Contributor hereby grants to You a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable (except as stated in this section) patent license to make, have made, use, offer to sell, sell, import, and otherwise transfer the Work, where such license applies only to those patent claims licensable by such Contributor that are necessarily infringed by their Contribution(s) alone or by combination of their Contribution(s) with the Work to which such Contribution(s) was submitted. If You institute patent litigation against any entity (including a cross-claim or counterclaim in a lawsuit) alleging that the Work or a Contribution incorporated within the Work constitutes direct or contributory patent infringement, then any patent licenses granted to You under this License for that Work shall terminate as of the date such litigation is filed.
4. Redistribution. You may reproduce and distribute copies of the Work or Derivative Works thereof in any medium, with or without modifications, and in Source or Object form, provided that You meet the following conditions:
(a) You must give any other recipients of the Work or Derivative Works a copy of this License; and
(b) You must cause any modified files to carry prominent notices stating that You changed the files; and
(c) You must retain, in the Source form of any Derivative Works that You distribute, all copyright, patent, trademark, and attribution notices from the Source form of the Work, excluding those notices that do not pertain to any part of the Derivative Works; and
(d) If the Work includes a "NOTICE" text file as part of its distribution, then any Derivative Works that You distribute must include a readable copy of the attribution notices contained within such NOTICE file, excluding those notices that do not pertain to any part of the Derivative Works, in at least one of the following places: within a NOTICE text file distributed as part of the Derivative Works; within the Source form or documentation, if provided along with the Derivative Works; or, within a display generated by the Derivative Works, if and wherever such third-party notices normally appear. The contents of the NOTICE file are for informational purposes only and do not modify the License. You may add Your own attribution notices within Derivative Works that You distribute, alongside or as an addendum to the NOTICE text from the Work, provided that such additional attribution notices cannot be construed as modifying the License.
You may add Your own copyright statement to Your modifications and may provide additional or different license terms and conditions for use, reproduction, or distribution of Your modifications, or for any such Derivative Works as a whole, provided Your use, reproduction, and distribution of the Work otherwise complies with the conditions stated in this License.
5. Submission of Contributions. Unless You explicitly state otherwise, any Contribution intentionally submitted for inclusion in the Work by You to the Licensor shall be under the terms and conditions of this License, without any additional terms or conditions. Notwithstanding the above, nothing herein shall supersede or modify the terms of any separate license agreement you may have executed with Licensor regarding such Contributions.
6. Trademarks. This License does not grant permission to use the trade names, trademarks, service marks, or product names of the Licensor, except as required for reasonable and customary use in describing the origin of the Work and reproducing the content of the NOTICE file.
7. Disclaimer of Warranty. Unless required by applicable law or agreed to in writing, Licensor provides the Work (and each Contributor provides its Contributions) on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. You are solely responsible for determining the appropriateness of using or redistributing the Work and assume any risks associated with Your exercise of permissions under this License.
8. Limitation of Liability. In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall any Contributor be liable to You for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising as a result of this License or out of the use or inability to use the Work (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if such Contributor has been advised of the possibility of such damages.
9. Accepting Warranty or Additional Liability. While redistributing the Work or Derivative Works thereof, You may choose to offer, and charge a fee for, acceptance of support, warranty, indemnity, or other liability obligations and/or rights consistent with this License. However, in accepting such obligations, You may act only on Your own behalf and on Your sole responsibility, not on behalf of any other Contributor, and only if You agree to indemnify, defend, and hold each Contributor harmless for any liability incurred by, or claims asserted against, such Contributor by reason of your accepting any such warranty or additional liability.
END OF TERMS AND CONDITIONS
APPENDIX: How to apply the Apache License to your work.
To apply the Apache License to your work, attach the following boilerplate notice, with the fields enclosed by brackets "[]" replaced with your own identifying information. (Don't include the brackets!) The text should be enclosed in the appropriate comment syntax for the file format. We also recommend that a file or class name and description of purpose be included on the same "printed page" as the copyright notice for easier identification within third-party archives.
Copyright [yyyy] [name of copyright owner]
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
Preamble
This license establishes the terms under which a given free software Package may be copied, modified, distributed, and/or redistributed. The intent is that the Copyright Holder maintains some artistic control over the development of that Package while still keeping the Package available as open source and free software.
You are always permitted to make arrangements wholly outside of this license directly with the Copyright Holder of a given Package. If the terms of this license do not permit the full use that you propose to make of the Package, you should contact the Copyright Holder and seek a different licensing arrangement.
Definitions
"Copyright Holder" means the individual(s) or organization(s) named in the copyright notice for the entire Package.
"Contributor" means any party that has contributed code or other material to the Package, in accordance with the Copyright Holder's procedures.
"You" and "your" means any person who would like to copy, distribute, or modify the Package.
"Package" means the collection of files distributed by the Copyright Holder, and derivatives of that collection and/or of those files. A given Package may consist of either the Standard Version, or a Modified Version.
"Distribute" means providing a copy of the Package or making it accessible to anyone else, or in the case of a company or organization, to others outside of your company or organization.
"Distributor Fee" means any fee that you charge for Distributing this Package or providing support for this Package to another party. It does not mean licensing fees.
"Standard Version" refers to the Package if it has not been modified, or has been modified only in ways explicitly requested by the Copyright Holder.
"Modified Version" means the Package, if it has been changed, and such changes were not explicitly requested by the Copyright Holder.
"Original License" means this Artistic License as Distributed with the Standard Version of the Package, in its current version or as it may be modified by The Perl Foundation in the future.
"Source" form means the source code, documentation source, and configuration files for the Package.
"Compiled" form means the compiled bytecode, object code, binary, or any other form resulting from mechanical transformation or translation of the Source form.
Permission for Use and Modification Without Distribution
(1) You are permitted to use the Standard Version and create and use Modified Versions for any purpose without restriction, provided that you do not Distribute the Modified Version.
Permissions for Redistribution of the Standard Version
(2) You may Distribute verbatim copies of the Source form of the Standard Version of this Package in any medium without restriction, either gratis or for a Distributor Fee, provided that you duplicate all of the original copyright notices and associated disclaimers. At your discretion, such verbatim copies may or may not include a Compiled form of the Package.
(3) You may apply any bug fixes, portability changes, and other modifications made available from the Copyright Holder. The resulting Package will still be considered the Standard Version, and as such will be subject to the Original License.
Distribution of Modified Versions of the Package as Source
(4) You may Distribute your Modified Version as Source (either gratis or for a Distributor Fee, and with or without a Compiled form of the Modified Version) provided that you clearly document how it differs from the Standard Version, including, but not limited to, documenting any non-standard features, executables, or modules, and provided that you do at least ONE of the following:
(a) make the Modified Version available to the Copyright Holder of the Standard Version, under the Original License, so that the Copyright Holder may include your modifications in the Standard Version.
(b) ensure that installation of your Modified Version does not prevent the user installing or running the Standard Version. In addition, the Modified Version must bear a name that is different from the name of the Standard Version.
(c) allow anyone who receives a copy of the Modified Version to make the Source form of the Modified Version available to others under
(i) the Original License or
(ii) a license that permits the licensee to freely copy, modify and redistribute the Modified Version using the same licensing terms that apply to the copy that the licensee received, and requires that the Source form of the Modified Version, and of any works derived from it, be made freely available in that license fees are prohibited but Distributor Fees are allowed.
Distribution of Compiled Forms of the Standard Version or Modified Versions without the Source
(5) You may Distribute Compiled forms of the Standard Version without the Source, provided that you include complete instructions on how to get the Source of the Standard Version. Such instructions must be valid at the time of your distribution. If these instructions, at any time while you are carrying out such distribution, become invalid, you must provide new instructions on demand or cease further distribution. If you provide valid instructions or cease distribution within thirty days after you become aware that the instructions are invalid, then you do not forfeit any of your rights under this license.
(6) You may Distribute a Modified Version in Compiled form without the Source, provided that you comply with Section 4 with respect to the Source of the Modified Version.
Aggregating or Linking the Package
(7) You may aggregate the Package (either the Standard Version or Modified Version) with other packages and Distribute the resulting aggregation provided that you do not charge a licensing fee for the Package. Distributor Fees are permitted, and licensing fees for other components in the aggregation are permitted. The terms of this license apply to the use and Distribution of the Standard or Modified Versions as included in the aggregation.
(8) You are permitted to link Modified and Standard Versions with other works, to embed the Package in a larger work of your own, or to build stand-alone binary or bytecode versions of applications that include the Package, and Distribute the result without restriction, provided the result does not expose a direct interface to the Package.
Items That are Not Considered Part of a Modified Version
(9) Works (including, but not limited to, modules and scripts) that merely extend or make use of the Package, do not, by themselves, cause the Package to be a Modified Version. In addition, such works are not considered parts of the Package itself, and are not subject to the terms of this license.
General Provisions
(10) Any use, modification, and distribution of the Standard or Modified Versions is governed by this Artistic License. By using, modifying or distributing the Package, you accept this license. Do not use, modify, or distribute the Package, if you do not accept this license.
(11) If your Modified Version has been derived from a Modified Version made by someone other than you, you are nevertheless required to ensure that your Modified Version complies with the requirements of this license.
(12) This license does not grant you the right to use any trademark, service mark, tradename, or logo of the Copyright Holder.
(13) This license includes the non-exclusive, worldwide, free-of-charge patent license to make, have made, use, offer to sell, sell, import and otherwise transfer the Package with respect to any patent claims licensable by the Copyright Holder that are necessarily infringed by the Package. If you institute patent litigation (including a cross-claim or counterclaim) against any party alleging that the Package constitutes direct or contributory patent infringement, then this Artistic License to you shall terminate on the date that such litigation is filed.
(14) Disclaimer of Warranty:
THE PACKAGE IS PROVIDED BY THE COPYRIGHT HOLDER AND CONTRIBUTORS "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES. THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT ARE DISCLAIMED TO THE EXTENT PERMITTED BY YOUR LOCAL LAW. UNLESS REQUIRED BY LAW, NO COPYRIGHT HOLDER OR CONTRIBUTOR WILL BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING IN ANY WAY OUT OF THE USE OF THE PACKAGE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Copyright (c) 2004-2010 by Internet Systems Consortium, Inc. ("ISC")
Copyright (c) 1995-2003 by Internet Software Consortium
Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
This version of the GNU Lesser General Public License incorporates the terms and conditions of version 3 of the GNU General Public License, supplemented by the additional permissions listed below.
0. Additional Definitions.
As used herein, "this License" refers to version 3 of the GNU Lesser General Public License, and the "GNU GPL" refers to version 3 of the GNU General Public License.
"The Library" refers to a covered work governed by this License, other than an Application or a Combined Work as defined below.
An "Application" is any work that makes use of an interface provided by the Library, but which is not otherwise based on the Library. Defining a subclass of a class defined by the Library is deemed a mode of using an interface provided by the Library.
A "Combined Work" is a work produced by combining or linking an Application with the Library. The particular version of the Library with which the Combined Work was made is also called the "Linked Version".
The "Minimal Corresponding Source" for a Combined Work means the Corresponding Source for the Combined Work, excluding any source code for portions of the Combined Work that, considered in isolation, are based on the Application, and not on the Linked Version.
The "Corresponding Application Code" for a Combined Work means the object code and/or source code for the Application, including any data and utility programs needed for reproducing the Combined Work from the Application, but excluding the System Libraries of the Combined Work.
1. Exception to Section 3 of the GNU GPL.
You may convey a covered work under sections 3 and 4 of this License without being bound by section 3 of the GNU GPL.
2. Conveying Modified Versions.
If you modify a copy of the Library, and, in your modifications, a facility refers to a function or data to be supplied by an Application that uses the facility (other than as an argument passed when the facility is invoked), then you may convey a copy of the modified version:
a) under this License, provided that you make a good faith effort to ensure that, in the event an Application does not supply the function or data, the facility still operates, and performs whatever part of its purpose remains meaningful, or
b) under the GNU GPL, with none of the additional permissions of this License applicable to that copy.
3. Object Code Incorporating Material from Library Header Files.
The object code form of an Application may incorporate material from a header file that is part of the Library. You may convey such object code under terms of your choice, provided that, if the incorporated material is not limited to numerical parameters, data structure layouts and accessors, or small macros, inline functions and templates (ten or fewer lines in length), you do both of the following:
a) Give prominent notice with each copy of the object code that the Library is used in it and that the Library and its use are covered by this License.
b) Accompany the object code with a copy of the GNU GPL and this license document.
4. Combined Works.
You may convey a Combined Work under terms of your choice that, taken together, effectively do not restrict modification of the portions of the Library contained in the Combined Work and reverse engineering for debugging such modifications, if you also do each of the following:
a) Give prominent notice with each copy of the Combined Work that the Library is used in it and that the Library and its use are covered by this License.
b) Accompany the Combined Work with a copy of the GNU GPL and this license document.
c) For a Combined Work that displays copyright notices during execution, include the copyright notice for the Library among these notices, as well as a reference directing the user to the copies of the GNU GPL and this license document.
d) Do one of the following:
0) Convey the Minimal Corresponding Source under the terms of this License, and the Corresponding Application Code in a form suitable for, and under terms that permit, the user to recombine or relink the Application with a modified version of the Linked Version to produce a modified Combined Work, in the manner specified by section 6 of the GNU GPL for conveying Corresponding Source.
1) Use a suitable shared library mechanism for linking with the Library. A suitable mechanism is one that (a) uses at run time a copy of the Library already present on the user's computer system, and (b) will operate properly with a modified version of the Library that is interface-compatible with the Linked Version.
e) Provide Installation Information, but only if you would otherwise be required to provide such information under section 6 of the GNU GPL, and only to the extent that such information is necessary to install and execute a modified version of the Combined Work produced by recombining or relinking the Application with a modified version of the Linked Version. (If you use option 4d0, the Installation Information must accompany the Minimal Corresponding Source and Corresponding Application Code. If you use option 4d1, you must provide the Installation Information in the manner specified by section 6 of the GNU GPL for conveying Corresponding Source.)
5. Combined Libraries.
You may place library facilities that are a work based on the Library side by side in a single library together with other library facilities that are not Applications and are not covered by this License, and convey such a combined library under terms of your choice, if you do both of the following:
a) Accompany the combined library with a copy of the same work based on the Library, uncombined with any other library facilities, conveyed under the terms of this License.
b) Give prominent notice with the combined library that part of it is a work based on the Library, and explaining where to find the accompanying uncombined form of the same work.
6. Revised Versions of the GNU Lesser General Public License.
The Free Software Foundation may publish revised and/or new versions of the GNU Lesser General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.
Each version is given a distinguishing version number. If the Library as you received it specifies that a certain numbered version of the GNU Lesser General Public License "or any later version" applies to it, you have the option of following the terms and conditions either of that published version or of any later version published by the Free Software Foundation. If the Library as you received it does not specify a version number of the GNU Lesser General Public License, you may choose any version of the GNU Lesser General Public License ever published by the Free Software Foundation.
If the Library as you received it specifies that a proxy can decide whether future versions of the GNU Lesser General Public License shall
apply, that proxy's public statement of acceptance of any version is permanent authorization for you to choose that version for the Library.
Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
Preamble
The GNU General Public License is a free, copyleft license for software and other kinds of works.
The licenses for most software and other practical works are designed to take away your freedom to share and change the works. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change all versions of a program--to make sure it remains free software for all its users. We, the Free Software Foundation, use the GNU General Public License for most of our software; it applies also to any other work released this way by its authors. You can apply it to your programs, too.
When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for them if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs, and that you know you can do these things.
To protect your rights, we need to prevent others from denying you these rights or asking you to surrender the rights. Therefore, you have certain responsibilities if you distribute copies of the software, or if you modify it: responsibilities to respect the freedom of others.
For example, if you distribute copies of such a program, whether gratis or for a fee, you must pass on to the recipients the same freedoms that you received. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.
Developers that use the GNU GPL protect your rights with two steps: (1) assert copyright on the software, and (2) offer you this License giving you legal permission to copy, distribute and/or modify it.
For the developers' and authors' protection, the GPL clearly explains that there is no warranty for this free software. For both users' and authors' sake, the GPL requires that modified versions be marked as changed, so that their problems will not be attributed erroneously to authors of previous versions.
Some devices are designed to deny users access to install or run modified versions of the software inside them, although the manufacturer can do so. This is fundamentally incompatible with the aim of protecting users' freedom to change the software. The systematic pattern of such abuse occurs in the area of products for individuals to use, which is precisely where it is most unacceptable. Therefore, we have designed this version of the GPL to prohibit the practice for those products. If such problems arise substantially in other domains, we stand ready to extend this provision to those domains in future versions of the GPL, as needed to protect the freedom of users.
Finally, every program is threatened constantly by software patents. States should not allow patents to restrict development and use of software on general-purpose computers, but in those that do, we wish to avoid the special danger that patents applied to a free program could make it effectively proprietary. To prevent this, the GPL assures that patents cannot be used to render the program non-free.
The precise terms and conditions for copying, distribution and modification follow.
TERMS AND CONDITIONS
0. Definitions.
“This License” refers to version 3 of the GNU General Public License.
“Copyright” also means copyright-like laws that apply to other kinds of works, such as semiconductor masks.
“The Program” refers to any copyrightable work licensed under this License. Each licensee is addressed as “you”. “Licensees” and “recipients” may be individuals or organizations.
To “modify” a work means to copy from or adapt all or part of the work in a fashion requiring copyright permission, other than the making of an exact copy. The resulting work is called a “modified version” of the earlier work or a work “based on” the earlier work.
A “covered work” means either the unmodified Program or a work based on the Program.
To “propagate” a work means to do anything with it that, without permission, would make you directly or secondarily liable for infringement under applicable copyright law, except executing it on a computer or modifying a private copy. Propagation includes copying, distribution (with or without modification), making available to the public, and in some countries other activities as well.
To “convey” a work means any kind of propagation that enables other parties to make or receive copies. Mere interaction with a user through a computer network, with no transfer of a copy, is not conveying.
An interactive user interface displays “Appropriate Legal Notices” to the extent that it includes a convenient and prominently visible feature that (1) displays an appropriate copyright notice, and (2) tells the user that there is no warranty for the work (except to the extent that warranties are provided), that licensees may convey the work under this License, and how to view a copy of this License. If the interface presents a list of user commands or options, such as a menu, a prominent item in the list meets this criterion.
1. Source Code.
The “source code” for a work means the preferred form of the work for making modifications to it. “Object code” means any non-source form of a work.
A “Standard Interface” means an interface that either is an official standard defined by a recognized standards body, or, in the case of interfaces specified for a particular programming language, one that is widely used among developers working in that language.
The “System Libraries” of an executable work include anything, other than the work as a whole, that (a) is included in the normal form of packaging a Major Component, but which is not part of that Major Component, and (b) serves only to enable use of the work with that Major Component, or to implement a Standard Interface for which an implementation is available to the public in source code form. A “Major Component”, in this context, means a major essential component (kernel, window system, and so on) of the specific operating system (if any) on which the executable work runs, or a compiler used to produce the work, or an object code interpreter used to run it.
The “Corresponding Source” for a work in object code form means all the source code needed to generate, install, and (for an executable work) run the object code and to modify the work, including scripts to control those activities. However, it does not include the work's System Libraries, or general-purpose tools or generally available free programs which are used unmodified in performing those activities but which are not part of the work. For example, Corresponding Source includes interface definition files associated with source files for the work, and the source code for shared libraries and dynamically linked subprograms that the work is specifically designed to require, such as by intimate data communication or control flow between those subprograms and other parts of the work.
The Corresponding Source need not include anything that users can regenerate automatically from other parts of the Corresponding Source.
The Corresponding Source for a work in source code form is that same work.
2. Basic Permissions.
All rights granted under this License are granted for the term of copyright on the Program, and are irrevocable provided the stated conditions are met. This License explicitly affirms your unlimited permission to run the unmodified Program. The output from running a covered work is covered by this License only if the output, given its content, constitutes a covered work. This License acknowledges your rights of fair use or other equivalent, as provided by copyright law.
You may make, run and propagate covered works that you do not convey, without conditions so long as your license otherwise remains in force. You may convey covered works to others for the sole purpose of having them make modifications exclusively for you, or provide you with facilities for running those works, provided that you comply with the terms of this License in conveying all material for which you do not control copyright. Those thus making or running the covered works for you must do so exclusively on your behalf, under your direction and control, on terms that prohibit them from making any copies of your copyrighted material outside their relationship with you.
Conveying under any other circumstances is permitted solely under the conditions stated below. Sublicensing is not allowed; section 10 makes it unnecessary.
3. Protecting Users' Legal Rights From Anti-Circumvention Law.
No covered work shall be deemed part of an effective technological measure under any applicable law fulfilling obligations under article 11 of the WIPO copyright treaty adopted on 20 December 1996, or similar laws prohibiting or restricting circumvention of such measures.
When you convey a covered work, you waive any legal power to forbid circumvention of technological measures to the extent such circumvention is effected by exercising rights under this License with respect to the covered work, and you disclaim any intention to limit operation or modification of the work as a means of enforcing, against the work's users, your or third parties' legal rights to forbid circumvention of technological measures.
4. Conveying Verbatim Copies.
You may convey verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice; keep intact all notices stating that this License and any non-permissive terms added in accord with section 7 apply to the code; keep intact all notices of the absence of any warranty; and give all recipients a copy of this License along with the Program.
You may charge any price or no price for each copy that you convey, and you may offer support or warranty protection for a fee.
5. Conveying Modified Source Versions.
You may convey a work based on the Program, or the modifications to produce it from the Program, in the form of source code under the terms of section 4, provided that you also meet all of these conditions:
a) The work must carry prominent notices stating that you modified it, and giving a relevant date.
b) The work must carry prominent notices stating that it is released under this License and any conditions added under section 7. This requirement modifies the requirement in section 4 to “keep intact all notices”.
c) You must license the entire work, as a whole, under this License to anyone who comes into possession of a copy. This License will therefore apply, along with any applicable section 7 additional terms, to the whole of the work, and all its parts, regardless of how they are packaged. This License gives no permission to license the work in any other way, but it does not invalidate such permission if you have separately received it.
d) If the work has interactive user interfaces, each must display Appropriate Legal Notices; however, if the Program has interactive interfaces that do not display Appropriate Legal Notices, your work need not make them do so.
A compilation of a covered work with other separate and independent works, which are not by their nature extensions of the covered work, and which are not combined with it such as to form a larger program, in or on a volume of a storage or distribution medium, is called an “aggregate” if the compilation and its resulting copyright are not used to limit the access or legal rights of the compilation's users beyond what the individual works permit. Inclusion of a covered work in an aggregate does not cause this License to apply to the other parts of the aggregate.
6. Conveying Non-Source Forms.
You may convey a covered work in object code form under the terms of sections 4 and 5, provided that you also convey the machine-readable Corresponding Source under the terms of this License, in one of these ways:
a) Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by the Corresponding Source fixed on a durable physical medium customarily used for software interchange.
b) Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by a written offer, valid for at least three years and valid for as long as you offer spare parts or customer support for that product model, to give anyone who possesses the object code either (1) a copy of the Corresponding Source for all the software in the product that is covered by this License, on a durable physical medium customarily used for software interchange, for a price no more than your reasonable cost of physically performing this conveying of source, or (2) access to copy the Corresponding Source from a network server at no charge.
c) Convey individual copies of the object code with a copy of the written offer to provide the Corresponding Source. This alternative is allowed only occasionally and noncommercially, and only if you received the object code with such an offer, in accord with subsection 6b.
d) Convey the object code by offering access from a designated place (gratis or for a charge), and offer equivalent access to the Corresponding Source in the same way through the same place at no further charge. You need not require recipients to copy the Corresponding Source along with the object code. If the place to copy the object code is a network server, the Corresponding Source may be on a different server (operated by you or a third party) that supports equivalent copying facilities, provided you maintain clear directions next to the object code saying where to find the Corresponding Source. Regardless of what server hosts the Corresponding Source, you remain obligated to ensure that it is available for as long as needed to satisfy these requirements.
e) Convey the object code using peer-to-peer transmission, provided you inform other peers where the object code and Corresponding Source of the work are being offered to the general public at no charge under subsection 6d.
A separable portion of the object code, whose source code is excluded from the Corresponding Source as a System Library, need not be included in conveying the object code work.
A “User Product” is either (1) a “consumer product”, which means any tangible personal property which is normally used for personal, family, or household purposes, or (2) anything designed or sold for incorporation into a dwelling. In determining whether a product is a consumer product, doubtful cases shall be resolved in favor of coverage. For a particular product received by a particular user, “normally used” refers to a typical or common use of that class of product, regardless of the status of the particular user or of the way in which the particular user actually uses, or expects or is expected to use, the product. A product is a consumer product regardless of whether the product has substantial commercial, industrial or non-consumer uses, unless such uses represent the only significant mode of use of the product.
“Installation Information” for a User Product means any methods, procedures, authorization keys, or other information required to install and execute modified versions of a covered work in that User Product from a modified version of its Corresponding Source. The information must suffice to ensure that the continued functioning of the modified object code is in no case prevented or interfered with solely because modification has been made.
If you convey an object code work under this section in, or with, or specifically for use in, a User Product, and the conveying occurs as part of a transaction in which the right of possession and use of the User Product is transferred to the recipient in perpetuity or for a fixed term (regardless of how the transaction is characterized), the Corresponding Source conveyed under this section must be accompanied by the Installation Information. But this requirement does not apply if neither you nor any third party retains the ability to install modified object code on the User Product (for example, the work has been installed in ROM).
The requirement to provide Installation Information does not include a requirement to continue to provide support service, warranty, or updates for a work that has been modified or installed by the recipient, or for the User Product in which it has been modified or installed. Access to a network may be denied when the modification itself materially and adversely affects the operation of the network or violates the rules and protocols for communication across the network.
Corresponding Source conveyed, and Installation Information provided, in accord with this section must be in a format that is publicly documented (and with an implementation available to the public in source code form), and must require no special password or key for unpacking, reading or copying.
7. Additional Terms.
“Additional permissions” are terms that supplement the terms of this License by making exceptions from one or more of its conditions. Additional permissions that are applicable to the entire Program shall be treated as though they were included in this License, to the extent that they are valid under applicable law. If additional permissions apply only to part of the Program, that part may be used separately under those permissions, but the entire Program remains governed by this License without regard to the additional permissions.
When you convey a copy of a covered work, you may at your option remove any additional permissions from that copy, or from any part of it. (Additional permissions may be written to require their own removal in certain cases when you modify the work.) You may place additional permissions on material, added by you to a covered work, for which you have or can give appropriate copyright permission.
Notwithstanding any other provision of this License, for material you add to a covered work, you may (if authorized by the copyright holders of that material) supplement the terms of this License with terms:
a) Disclaiming warranty or limiting liability differently from the terms of sections 15 and 16 of this License; or
b) Requiring preservation of specified reasonable legal notices or author attributions in that material or in the Appropriate Legal Notices displayed by works containing it; or
c) Prohibiting misrepresentation of the origin of that material, or requiring that modified versions of such material be marked in reasonable ways as different from the original version; or
d) Limiting the use for publicity purposes of names of licensors or authors of the material; or
e) Declining to grant rights under trademark law for use of some trade names, trademarks, or service marks; or
f) Requiring indemnification of licensors and authors of that material by anyone who conveys the material (or modified versions of it) with contractual assumptions of liability to the recipient, for any liability that these contractual assumptions directly impose on those licensors and authors.
All other non-permissive additional terms are considered “further restrictions” within the meaning of section 10. If the Program as you received it, or any part of it, contains a notice stating that it is governed by this License along with a term that is a further restriction, you may remove that term. If a license document contains a further restriction but permits relicensing or conveying under this License, you may add to a covered work material governed by the terms of that license document, provided that the further restriction does not survive such relicensing or conveying.
If you add terms to a covered work in accord with this section, you must place, in the relevant source files, a statement of the additional terms that apply to those files, or a notice indicating where to find the applicable terms.
Additional terms, permissive or non-permissive, may be stated in the form of a separately written license, or stated as exceptions; the above requirements apply either way.
8. Termination.
You may not propagate or modify a covered work except as expressly provided under this License. Any attempt otherwise to propagate or modify it is void, and will automatically terminate your rights under this License (including any patent licenses granted under the third paragraph of section 11).
However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.
Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.
Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, you do not qualify to receive new licenses for the same material under section 10.
9. Acceptance Not Required for Having Copies.
You are not required to accept this License in order to receive or run a copy of the Program. Ancillary propagation of a covered work occurring solely as a consequence of using peer-to-peer transmission to receive a copy likewise does not require acceptance. However, nothing other than this License grants you permission to propagate or modify any covered work. These actions infringe copyright if you do not accept this License. Therefore, by modifying or propagating a covered work, you indicate your acceptance of this License to do so.
10. Automatic Licensing of Downstream Recipients.
Each time you convey a covered work, the recipient automatically receives a license from the original licensors, to run, modify and propagate that work, subject to this License. You are not responsible for enforcing compliance by third parties with this License.
An “entity transaction” is a transaction transferring control of an organization, or substantially all assets of one, or subdividing an organization, or merging organizations. If propagation of a covered work results from an entity transaction, each party to that transaction who receives a copy of the work also receives whatever licenses to the work the party's predecessor in interest had or could give under the previous paragraph, plus a right to possession of the Corresponding Source of the work from the predecessor in interest, if the predecessor has it or can get it with reasonable efforts.
You may not impose any further restrictions on the exercise of the rights granted or affirmed under this License. For example, you may not impose a license fee, royalty, or other charge for exercise of rights granted under this License, and you may not initiate litigation (including a cross-claim or counterclaim in a lawsuit) alleging that any patent claim is infringed by making, using, selling, offering for sale, or importing the Program or any portion of it.
11. Patents.
A “contributor” is a copyright holder who authorizes use under this License of the Program or a work on which the Program is based. The work thus licensed is called the contributor's “contributor version”.
A contributor's “essential patent claims” are all patent claims owned or controlled by the contributor, whether already acquired or hereafter acquired, that would be infringed by some manner, permitted by this License, of making, using, or selling its contributor version, but do not include claims that would be infringed only as a consequence of further modification of the contributor version. For purposes of this definition, “control” includes the right to grant patent sublicenses in a manner consistent with the requirements of this License.
Each contributor grants you a non-exclusive, worldwide, royalty-free patent license under the contributor's essential patent claims, to make, use, sell, offer for sale, import and otherwise run, modify and propagate the contents of its contributor version.
In the following three paragraphs, a “patent license” is any express agreement or commitment, however denominated, not to enforce a patent (such as an express permission to practice a patent or covenant not to sue for patent infringement). To “grant” such a patent license to a party means to make such an agreement or commitment not to enforce a patent against the party.
If you convey a covered work, knowingly relying on a patent license, and the Corresponding Source of the work is not available for anyone to copy, free of charge and under the terms of this License, through a publicly available network server or other readily accessible means, then you must either (1) cause the Corresponding Source to be so available, or (2) arrange to deprive yourself of the benefit of the patent license for this particular work, or (3) arrange, in a manner consistent with the requirements of this License, to extend the patent license to downstream recipients. “Knowingly relying” means you have actual knowledge that, but for the patent license, your conveying the covered work in a country, or your recipient's use of the covered work in a country, would infringe one or more identifiable patents in that country that you have reason to believe are valid.
If, pursuant to or in connection with a single transaction or arrangement, you convey, or propagate by procuring conveyance of, a covered work, and grant a patent license to some of the parties receiving the covered work authorizing them to use, propagate, modify or convey a specific copy of the covered work, then the patent license you grant is automatically extended to all recipients of the covered work and works based on it.
A patent license is “discriminatory” if it does not include within the scope of its coverage, prohibits the exercise of, or is conditioned on the non-exercise of one or more of the rights that are specifically granted under this License. You may not convey a covered work if you are a party to an arrangement with a third party that is in the business of distributing software, under which you make payment to the third party based on the extent of your activity of conveying the work, and under which the third party grants, to any of the parties who would receive the covered work from you, a discriminatory patent license (a) in connection with copies of the covered work conveyed by you (or copies made from those copies), or (b) primarily for and in connection with specific products or compilations that contain the covered work, unless you entered into that arrangement, or that patent license was granted, prior to 28 March 2007.
Nothing in this License shall be construed as excluding or limiting any implied license or other defenses to infringement that may otherwise be available to you under applicable patent law.
12. No Surrender of Others' Freedom.
If conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot convey a covered work so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not convey it at all. For example, if you agree to terms that obligate you to collect a royalty for further conveying from those to whom you convey the Program, the only way you could satisfy both those terms and this License would be to refrain entirely from conveying the Program.
13. Use with the GNU Affero General Public License.
Notwithstanding any other provision of this License, you have permission to link or combine any covered work with a work licensed under version 3 of the GNU Affero General Public License into a single combined work, and to convey the resulting work. The terms of this License will continue to apply to the part which is the covered work, but the special requirements of the GNU Affero General Public License, section 13, concerning interaction through a network will apply to the combination as such.
14. Revised Versions of this License.
The Free Software Foundation may publish revised and/or new versions of the GNU General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.
Each version is given a distinguishing version number. If the Program specifies that a certain numbered version of the GNU General Public License “or any later version” applies to it, you have the option of following the terms and conditions either of that numbered version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of the GNU General Public License, you may choose any version ever published by the Free Software Foundation.
If the Program specifies that a proxy can decide which future versions of the GNU General Public License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Program.
Later license versions may give you additional or different permissions. However, no additional obligations are imposed on any author or copyright holder as a result of your choosing to follow a later version.
15. Disclaimer of Warranty.
THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
16. Limitation of Liability.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
17. Interpretation of Sections 15 and 16.
If the disclaimer of warranty and limitation of liability provided above cannot be given local legal effect according to their terms, reviewing courts shall apply local law that most closely approximates an absolute waiver of all civil liability in connection with the Program, unless a warranty or assumption of liability accompanies a copy of the Program in return for a fee.
END OF TERMS AND CONDITIONS
How to Apply These Terms to Your New Programs
If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively state the exclusion of warranty; and each file should have at least the “copyright” line and a pointer to where the full notice is found.
<one line to give the program's name and a brief idea of what it does.>
Copyright (C) <year> <name of author>
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.
Also add information on how to contact you by electronic and paper mail.
If the program does terminal interaction, make it output a short notice like this when it starts in an interactive mode:
<program> Copyright (C) <year> <name of author>
This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the appropriate parts of the General Public License. Of course, your program's commands might be different; for a GUI interface, you would use an “about box”.
You should also get your employer (if you work as a programmer) or school, if any, to sign a “copyright disclaimer” for the program, if necessary. For more information on this, and how to apply and follow the GNU GPL, see <http://www.gnu.org/licenses/>.
The GNU General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Lesser General Public License instead of this License. But first, please read <http://www.gnu.org/philosophy/why-not-lgpl.html>.
This is free and unencumbered software released into the public domain.
Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.
In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and
successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
For more information, please refer to <http://unlicense.org/>
# Good checks: -checks='-*,bugprone-assignment-in-if-condition,google-build-using-namespace,google-readability-casting,modernize-use-default-member-init,modernize-use-emplace,modernize-use-equals-default,modernize-use-equals-delete,modernize-use-nullptr,performance-faster-string-find,readability-isolate-declaration,readability-redundant-control-flow,readability-redundant-member-init,readability-redundant-string-cstr,readability-uppercase-literal-suffix
$(grep -E "(lines|branches)\.*:" ${MAKE_LOG} | sed "s/\.*:/:/" || true)
</pre>
Report: [${RUN_ID}](${REPORT_URL})
Please get to 100% line coverage, and understand all branches; see the [developer docs](https://github.com/verilator/verilator/blob/master/docs/internals.rst#code-coverage-results)
When to check: before editing anything under `docs/`.
Read the repository-root [AGENTS.md](../AGENTS.md) first for process and cross-cutting rules.
## Writing rules
- Rewrap paragraphs after editing -- keep consistent line length in `*.rst` files.
- Document only stable, implemented features -- never planned or in-development capabilities; prevents user confusion and support burden.
- Explain WHAT and WHEN, not HOW -- conceptual purpose and practical use cases over implementation mechanics; describe behavior ("optimized as pure", not "treated as pure") and clarify ambiguous referents ("in the internals of Verilator").
- Keep terminology consistent -- one term per concept; update docs when renaming code constructs; spell out full terms, avoiding abbreviations like "sim"/"sims".
- Use "how many" for countable nouns (threads, tasks, workers) and "how much" for uncountable quantities.
- Mark internal or experimental features "for internal use only" -- prevents user dependence and forced deprecation cycles later.
- Use specific IEEE references: `IEEE {number}-{year}` plus the section (e.g. `Annex I`) -- a vague "IEEE spec requires" is unverifiable.
- Document all flags with descriptions, not just syntax.
## reStructuredText mechanics
- Use the `:vlopt:` role for Verilator option references -- makes cross-references clickable and consistent.
- Escape angle brackets (`\<`, `\>`) in link targets -- prevents broken links to command-line options.
- Generate documentation examples with `test.extract` from `test_regress` test files -- examples stay synced with actually tested behavior.
## Hard constraint
- Never edit `docs/CONTRIBUTORS` -- only humans may, after reading and agreeing to its statement; remind the user instead.
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