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
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`
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
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 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.
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.
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.
Geza Lore
Yilou Wang
Artur Bieniek
Shashvat
Matthew Ballance
Zubin Jain
Yogish Sekhar
em2machine
github action
Wilson Snyder
Todd Strader
Geza Lore
Jose Drowne
Oleh Maksymenko
Dan Ruelas-Petrisko
Bartłomiej Chmiel