The recent patch to defer substitutions on V3Gate crashes on circular
logic that has cycle length >= 3 with all inlineable signals (cycle
length 2 is detected correctly and is not inlined). Fix by stopping
recursion at the loop-back edge.
Fixes#3543
This is detritus from when V3TraceDecl used to run after V3Gate, today
V3TraceDecl runs before V3Gate and this value has no function at all.
No functional change intended.
dynamic_cast is not free. Replace obvious instances (where the result is
unconditionally dereferenced) with static_cast in contexts with
performance implications.
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)
Geza Lore
Wilson Snyder