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Fix NBA shared flag reuse (#5848)

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Fixes #5847
This commit is contained in:
Geza Lore
2025-03-11 07:40:21 -04:00
committed by GitHub
parent 8157f21c3e
commit 6ecdd14fdb
3 changed files with 115 additions and 4 deletions
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src/V3Delayed.cpp
+25 -4
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@@ -155,6 +155,7 @@ class DelayedVisitor final : public VNVisitor {
struct { // Stuff needed for Scheme::FlagShared
AstActive* activep; // The active block for the Pre/Post logic
AstAlwaysPost* postp; // The post block for commiting results
AstVarScope* commitFlagp; // The commit flag variable, for reuse
AstIf* commitIfp; // The previous if statement for committing, for reuse
} m_flagSharedKit;
struct { // Stuff needed for Scheme::FlagUnique
@@ -421,6 +422,9 @@ class DelayedVisitor final : public VNVisitor {
AstAlwaysPost* const postp = new AstAlwaysPost{flp};
activep->addStmtsp(postp);
vscpInfo.flagSharedKit().postp = postp;
// Initialize
vscpInfo.flagSharedKit().commitFlagp = nullptr;
vscpInfo.flagSharedKit().commitIfp = nullptr;
}
void convertSchemeFlagShared(AstAssignDly* nodep, AstVarScope* vscp, VarScopeInfo& vscpInfo) {
UASSERT_OBJ(vscpInfo.m_scheme == Scheme::FlagShared, vscp, "Inconsistent NBA scheme");
@@ -443,14 +447,16 @@ class DelayedVisitor final : public VNVisitor {
const bool consecutive = nodep == m_nextDlyp;
m_nextDlyp = VN_CAST(nodep->nextp(), AssignDly);
VarScopeInfo* const prevVscpInfop = consecutive ? &m_vscpInfo(m_prevVscp) : nullptr;
// We can reuse the flag of the previous assignment if:
const bool reuseTheFlag =
// Consecutive NBAs
consecutive
// ... that use the same scheme
&& m_vscpInfo(m_prevVscp).m_scheme == Scheme::FlagShared
&& prevVscpInfop->m_scheme == Scheme::FlagShared
// ... and share the same overall update domain
&& m_vscpInfo(m_prevVscp).senTreep()->sameTree(vscpInfo.senTreep());
&& prevVscpInfop->senTreep()->sameTree(vscpInfo.senTreep());
if (!reuseTheFlag) {
// Create new flag
@@ -466,10 +472,25 @@ class DelayedVisitor final : public VNVisitor {
// Add the 'Post' scheduled commit
AstIf* const ifp = new AstIf{flp, new AstVarRef{flp, flagVscp, VAccess::READ}};
vscpInfo.flagSharedKit().postp->addStmtsp(ifp);
vscpInfo.flagSharedKit().commitFlagp = flagVscp;
vscpInfo.flagSharedKit().commitIfp = ifp;
} else {
// Reuse the commit block of the previous assignment
vscpInfo.flagSharedKit().commitIfp = m_vscpInfo(m_prevVscp).flagSharedKit().commitIfp;
if (vscp != m_prevVscp) {
// Different variable, ensure the commit block exists for this variable,
// can reuse existing one with the same flag, otherwise create a new one.
AstVarScope* const flagVscp = prevVscpInfop->flagSharedKit().commitFlagp;
UASSERT_OBJ(flagVscp, nodep, "Commit flag of previous assignment should exist");
if (vscpInfo.flagSharedKit().commitFlagp != flagVscp) {
AstIf* const ifp = new AstIf{flp, new AstVarRef{flp, flagVscp, VAccess::READ}};
vscpInfo.flagSharedKit().postp->addStmtsp(ifp);
vscpInfo.flagSharedKit().commitFlagp = flagVscp;
vscpInfo.flagSharedKit().commitIfp = ifp;
}
} else {
// Same variable, reuse the commit block of the previous assignment
vscpInfo.flagSharedKit().commitFlagp = prevVscpInfop->flagSharedKit().commitFlagp;
vscpInfo.flagSharedKit().commitIfp = prevVscpInfop->flagSharedKit().commitIfp;
}
++m_nSharedSetFlags;
}
// Commit the captured value to the captured destination