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Refactor Dfg variable flags (#6259)

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Store all flags in a DfgVertexVar relating to the underlying
AstVar/AstVarScope stored via AstNode::user1(). user2/user3/user4 are
then usable by DFG algorithms as needed.
This commit is contained in:
Geza Lore
2025-08-05 10:24:54 +01:00
committed by GitHub
parent d415757b0e
commit d2edab458e
8 changed files with 102 additions and 136 deletions
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src/V3DfgOptimizer.cpp
+14 -11
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@@ -296,16 +296,15 @@ void V3DfgOptimizer::optimize(AstNetlist* netlistp, const string& label) {
UINFO(2, __FUNCTION__ << ":");
// NODE STATE
// AstVar::user1 -> Used by:
// - V3DfgPasses::astToDfg,
// - V3DfgPasses::eliminateVars,
// - V3DfgPasses::dfgToAst,
// AstVar::user2 -> bool: Flag indicating referenced by AstVarXRef (set just below)
// AstVar::user3, AstVarScope::user3
// -> bool: Flag indicating written by logic not representable as DFG
// (set by V3DfgPasses::astToDfg)
const VNUser2InUse user2InUse;
const VNUser3InUse user3InUse;
// AstVar::user1, AstVarScope::user1 -> int, used as a bit-field
// - bit0: Read via AstVarXRef (hierarchical reference)
// - 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
// - bit4: Referenced by other DFG in same module/netlist
//
// AstNode::user2/user3/user4 can be used by various DFG algorithms
const VNUser1InUse user1InUse;
V3DfgContext ctx{label};
@@ -313,7 +312,11 @@ void V3DfgOptimizer::optimize(AstNetlist* netlistp, const string& label) {
// Pre V3Scope application. Run on each module separately.
// Mark cross-referenced variables
netlistp->foreach([](const AstVarXRef* xrefp) { xrefp->varp()->user2(true); });
netlistp->foreach([](const AstVarXRef* xrefp) {
AstVar* const tgtp = xrefp->varp();
if (xrefp->access().isReadOrRW()) DfgVertexVar::setHasRdXRefs(tgtp);
if (xrefp->access().isWriteOrRW()) DfgVertexVar::setHasWrXRefs(tgtp);
});
// Run the optimization phase
for (AstNode* nodep = netlistp->modulesp(); nodep; nodep = nodep->nextp()) {