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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/V3DfgPasses.cpp
+14 -13
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@@ -294,7 +294,7 @@ void V3DfgPasses::binToOneHot(DfgGraph& dfg, V3DfgBinToOneHotContext& ctx) {
varp->varp()->isInternal(true);
varp->srcp(srcp);
}
varp->setHasModRefs();
varp->setHasModRdRefs();
return varp;
}();
// The previous index variable - we don't need a vertex for this
@@ -314,7 +314,7 @@ void V3DfgPasses::binToOneHot(DfgGraph& dfg, V3DfgBinToOneHotContext& ctx) {
= dfg.makeNewVar(flp, name, tabDTypep, nullptr)->as<DfgVarArray>();
varp->varp()->isInternal(true);
varp->varp()->noReset(true);
varp->setHasModRefs();
varp->setHasModWrRefs();
return varp;
}();
@@ -417,9 +417,9 @@ void V3DfgPasses::eliminateVars(DfgGraph& dfg, V3DfgEliminateVarsContext& ctx) {
// List of variables (AstVar or AstVarScope) we are replacing
std::vector<AstNode*> replacedVariables;
// AstVar::user1p() : AstVar* -> The replacement variables
// AstVarScope::user1p() : AstVarScope* -> The replacement variables
const VNUser1InUse user1InUse;
// AstVar::user2p() : AstVar* -> The replacement variables
// AstVarScope::user2p() : AstVarScope* -> The replacement variables
const VNUser2InUse user2InUse;
// Process the work list
while (workListp != sentinelp) {
@@ -448,10 +448,11 @@ void V3DfgPasses::eliminateVars(DfgGraph& dfg, V3DfgEliminateVarsContext& ctx) {
// Can't remove if it has external drivers
if (!varp->isDrivenFullyByDfg()) continue;
// Can't remove if must be kept (including external, non module references)
if (varp->keep()) continue;
// Can't remove if referenced in other DFGs of the same module (otherwise might rm twice)
// Can't remove if referenced external to the module/netlist
if (varp->hasExtRefs()) continue;
// Can't remove if written in the module
if (varp->hasModWrRefs()) continue;
// Can't remove if referenced in other DFGs of the same module
if (varp->hasDfgRefs()) continue;
// If it has multiple sinks, it can't be eliminated
@@ -469,9 +470,9 @@ void V3DfgPasses::eliminateVars(DfgGraph& dfg, V3DfgEliminateVarsContext& ctx) {
UASSERT_OBJ(!varp->hasSinks(), varp, "Variable inlining should make this impossible");
// Grab the AstVar/AstVarScope
AstNode* const nodep = varp->nodep();
UASSERT_OBJ(!nodep->user1p(), nodep, "Replacement already exists");
UASSERT_OBJ(!nodep->user2p(), nodep, "Replacement already exists");
replacedVariables.emplace_back(nodep);
nodep->user1p(driverp->nodep());
nodep->user2p(driverp->nodep());
} else {
// Otherwise this *is* the canonical var
continue;
@@ -490,13 +491,13 @@ void V3DfgPasses::eliminateVars(DfgGraph& dfg, V3DfgEliminateVarsContext& ctx) {
if (AstModule* const modp = dfg.modulep()) {
modp->foreach([&](AstVarRef* refp) {
AstVar* varp = refp->varp();
while (AstVar* const replacep = VN_AS(varp->user1p(), Var)) varp = replacep;
while (AstVar* const replacep = VN_AS(varp->user2p(), Var)) varp = replacep;
refp->varp(varp);
});
} else {
v3Global.rootp()->foreach([&](AstVarRef* refp) {
AstVarScope* vscp = refp->varScopep();
while (AstVarScope* const replacep = VN_AS(vscp->user1p(), VarScope)) vscp = replacep;
while (AstVarScope* const replacep = VN_AS(vscp->user2p(), VarScope)) vscp = replacep;
refp->varScopep(vscp);
refp->varp(vscp->varp());
});