Similarly to the earlier patch that defers constant folding on optimized
logic, now we also defer the variable substitutions as well. This again
eliminates a lot of traversals, and yields another ~10x speedup of V3Gate
on a design where V3Gate used to dominate while producing identical
results.
Rather than constant folding each logic block after every substitution,
only constant fold updated blocks when re-analysed, or at the end. This
removes a lot of invocations of V3Const on large blocks that can be
optimized well, and should yield the same result.
This speeds up V3Gate by ~4x on a design where V3Gate dominates.
Fail at compile time if the result of these macros can be statically
determined (i.e.: they aways succeed or always fail). Remove unnecessary
casts discovered. No functional change.
Rework Ast hashing to be stable
Eliminated reliance on pointer values in AstNode hashes in order to make
them stable. This requires moving the sameHash functions into a visitor,
as nodes pointed to via members (and not child nodes) need to be hashed
themselves.
The hashes are now stable (as far as I could test them), and the impact
on verilation time is small enough not to be reliably measurable.
V3Hasher is responsible for computing AstNode hashes, while V3DupFinder
can be used to find duplicate trees based on hashes. Interface of
V3DupFinder simplified somewhat. No functional change intended at this
point, but hash computation might differ in minor details, this however
should have no perceivable effect on output/runtime.
Implements (#2964)
The main goal of this patch is to enable splitting the full and
incremental tracing functions into multiple functions, which can then be
run in parallel at a later stage. It also simplifies further
experimentation as all of the interesting trace code construction now
happens in V3Trace. No functional change is intended by this patch, but
there are some implementation changes in the generated code.
Highlights:
- Pass symbol table directly to trace callbacks for simplicity.
- A new traceRegister function is generated which adds each trace
function as an individual callback, which means we can have multiple
callbacks for each trace function type.
- A new traceCleanup function is generated which clears the activity
flags, as the trace callbacks might be implemented as multiple functions.
- Re-worked sub-function handling so there is no separate sub-function
for each trace activity class. Sub-functions are generate when required
by splitting.
- traceFull/traceChg are now created in V3Trace rather than V3TraceDecl,
this requires carrying the trace value tree in TraceDecl until it
reaches V3Trace where the TraceInc nodes are created (previously a
TraceInc was also created in V3TraceDecl which carries the value).
Geza Lore
Wilson Snyder