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Optimize DFG before V3Gate (#6141)

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This commit is contained in:
Geza Lore
2025-07-01 17:55:08 -04:00
committed by GitHub
parent e015805194
commit 7a3f1f16ca
26 changed files with 555 additions and 181 deletions
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src/V3DfgPasses.cpp
+33 -17
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@@ -232,6 +232,8 @@ void V3DfgPasses::removeUnused(DfgGraph& dfg) {
}
void V3DfgPasses::binToOneHot(DfgGraph& dfg, V3DfgBinToOneHotContext& ctx) {
UASSERT(dfg.modulep(), "binToOneHot only works with unscoped DfgGraphs for now");
const auto userDataInUse = dfg.userDataInUse();
// Structure to keep track of comparison details
@@ -372,7 +374,7 @@ void V3DfgPasses::binToOneHot(DfgGraph& dfg, V3DfgBinToOneHotContext& ctx) {
DfgVarPacked* varp = srcp->getResultVar();
if (!varp) {
const std::string name = dfg.makeUniqueName("BinToOneHot_Idx", nTables);
varp = dfg.makeNewVar(flp, name, idxDTypep)->as<DfgVarPacked>();
varp = dfg.makeNewVar(flp, name, idxDTypep, nullptr)->as<DfgVarPacked>();
varp->varp()->isInternal(true);
varp->addDriver(flp, 0, srcp);
}
@@ -392,7 +394,8 @@ void V3DfgPasses::binToOneHot(DfgGraph& dfg, V3DfgBinToOneHotContext& ctx) {
// The table variable
DfgVarArray* const tabVtxp = [&]() {
const std::string name = dfg.makeUniqueName("BinToOneHot_Tab", nTables);
DfgVarArray* const varp = dfg.makeNewVar(flp, name, tabDTypep)->as<DfgVarArray>();
DfgVarArray* const varp
= dfg.makeNewVar(flp, name, tabDTypep, nullptr)->as<DfgVarArray>();
varp->varp()->isInternal(true);
varp->varp()->noReset(true);
varp->setHasModRefs();
@@ -496,9 +499,10 @@ void V3DfgPasses::eliminateVars(DfgGraph& dfg, V3DfgEliminateVarsContext& ctx) {
workListp = &vtx;
};
// List of variables we are replacing
std::vector<AstVar*> replacedVariables;
// 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;
// Process the work list
@@ -541,7 +545,7 @@ void V3DfgPasses::eliminateVars(DfgGraph& dfg, V3DfgEliminateVarsContext& ctx) {
// If it is only referenced in this DFG, it can be removed
++ctx.m_varsRemoved;
varp->replaceWith(varp->source(0));
varp->varp()->unlinkFrBack()->deleteTree();
varp->nodep()->unlinkFrBack()->deleteTree();
} else if (DfgVarPacked* const driverp = varp->source(0)->cast<DfgVarPacked>()) {
// If it's driven from another variable, it can be replaced by that. However, we do not
// want to propagate SystemC variables into the design.
@@ -549,9 +553,11 @@ void V3DfgPasses::eliminateVars(DfgGraph& dfg, V3DfgEliminateVarsContext& ctx) {
// Mark it for replacement
++ctx.m_varsReplaced;
UASSERT_OBJ(!varp->hasSinks(), varp, "Variable inlining should make this impossible");
UASSERT(!varp->varp()->user1p(), "Replacement already exists");
replacedVariables.emplace_back(varp->varp());
varp->varp()->user1p(driverp->varp());
// Grab the AstVar/AstVarScope
AstNode* const nodep = varp->nodep();
UASSERT_OBJ(!nodep->user1p(), nodep, "Replacement already exists");
replacedVariables.emplace_back(nodep);
nodep->user1p(driverp->nodep());
} else {
// Otherwise this *is* the canonical var
continue;
@@ -566,16 +572,24 @@ void V3DfgPasses::eliminateVars(DfgGraph& dfg, V3DfgEliminateVarsContext& ctx) {
// Job done if no replacements possible
if (replacedVariables.empty()) return;
// Apply variable replacements in the module
VNDeleter deleter;
dfg.modulep()->foreach([&](AstVarRef* refp) {
AstVar* varp = refp->varp();
while (AstVar* const replacementp = VN_AS(varp->user1p(), Var)) varp = replacementp;
refp->varp(varp);
});
// Apply variable replacements
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;
refp->varp(varp);
});
} else {
v3Global.rootp()->foreach([&](AstVarRef* refp) {
AstVarScope* vscp = refp->varScopep();
while (AstVarScope* const replacep = VN_AS(vscp->user1p(), VarScope)) vscp = replacep;
refp->varScopep(vscp);
refp->varp(vscp->varp());
});
}
// Remove the replaced variables
for (AstVar* const varp : replacedVariables) varp->unlinkFrBack()->deleteTree();
for (AstNode* const nodep : replacedVariables) nodep->unlinkFrBack()->deleteTree();
}
void V3DfgPasses::optimize(DfgGraph& dfg, V3DfgOptimizationContext& ctx) {
@@ -599,7 +613,9 @@ void V3DfgPasses::optimize(DfgGraph& dfg, V3DfgOptimizationContext& ctx) {
apply(3, "input ", [&]() {});
apply(4, "inlineVars ", [&]() { inlineVars(dfg); });
apply(4, "cse0 ", [&]() { cse(dfg, ctx.m_cseContext0); });
apply(4, "binToOneHot ", [&]() { binToOneHot(dfg, ctx.m_binToOneHotContext); });
if (dfg.modulep()) {
apply(4, "binToOneHot ", [&]() { binToOneHot(dfg, ctx.m_binToOneHotContext); });
}
if (v3Global.opt.fDfgPeephole()) {
apply(4, "peephole ", [&]() { peephole(dfg, ctx.m_peepholeContext); });
// We just did CSE above, so without peephole there is no need to run it again these