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Internals: Do not optimize variables with RW refs in Dfg

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This commit is contained in:
Geza Lore
2026-03-27 07:50:05 +00:00
parent f12cdac8da
commit 9ed7a9f98b
4 changed files with 60 additions and 38 deletions
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src/V3DfgOptimizer.cpp
+15 -1
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@@ -246,7 +246,8 @@ class DataflowOptimize final {
// - bit1: Written via AstVarXRef (hierarchical reference)
// - bit2: Read by logic in same module/netlist not represented in DFG
// - bit3: Written by logic in same module/netlist not represented in DFG
// - bit31-4: Reference count, how many DfgVertexVar represent this variable
// - bit4: Has READWRITE references
// - bit31-5: Reference count, how many DfgVertexVar represent this variable
//
// AstNode::user2/user3/user4 can be used by various DFG algorithms
const VNUser1InUse m_user1InUse;
@@ -285,6 +286,12 @@ class DataflowOptimize final {
senItemp->foreach([](const AstVarRef* refp) {
DfgVertexVar::setHasExtRdRefs(refp->varScopep());
});
return;
}
// Check direct references
if (const AstVarRef* const refp = VN_CAST(nodep, VarRef)) {
if (refp->access().isRW()) DfgVertexVar::setHasRWRefs(refp->varScopep());
return;
}
} else {
if (AstVar* const varp = VN_CAST(nodep, Var)) {
@@ -296,13 +303,20 @@ class DataflowOptimize final {
if (hasExtWr) DfgVertexVar::setHasExtWrRefs(varp);
return;
}
// Check direct references
if (const AstVarRef* const refp = VN_CAST(nodep, VarRef)) {
if (refp->access().isRW()) DfgVertexVar::setHasRWRefs(refp->varp());
return;
}
}
// Check hierarchical references
if (const AstVarXRef* const xrefp = VN_CAST(nodep, VarXRef)) {
AstVar* const tgtp = xrefp->varp();
if (!tgtp) return;
if (xrefp->access().isReadOrRW()) DfgVertexVar::setHasExtRdRefs(tgtp);
if (xrefp->access().isWriteOrRW()) DfgVertexVar::setHasExtWrRefs(tgtp);
if (xrefp->access().isRW()) DfgVertexVar::setHasRWRefs(tgtp);
return;
}
// Check cell ports