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Internals: Improve DFG implementation details (#6355)

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Large scale refactoring to simplify some of the more obtuse internals of
DFG. Remove multiple redundant internal APIs, simplify representation of
variables, fix potential unsoundness in circular decomposition. No
functional change intended.
This commit is contained in:
Geza Lore
2025-09-02 16:50:40 +01:00
committed by GitHub
parent 67f26508ba
commit a6f26b85b3
24 changed files with 1763 additions and 1733 deletions
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src/V3DfgPasses.cpp
+17 -13
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@@ -84,8 +84,7 @@ void V3DfgPasses::inlineVars(DfgGraph& dfg) {
for (DfgVertexVar& vtx : dfg.varVertices()) {
if (DfgVarPacked* const varp = vtx.cast<DfgVarPacked>()) {
if (varp->hasSinks() && varp->isDrivenFullyByDfg()) {
DfgVertex* const driverp = varp->srcp();
varp->forEachSinkEdge([=](DfgEdge& edge) { edge.relinkSource(driverp); });
varp->replaceWith(varp->srcp());
}
}
}
@@ -148,16 +147,17 @@ void V3DfgPasses::removeUnused(DfgGraph& dfg) {
if (varp->hasDfgRefs()) continue;
}
// Add sources of unused vertex to work list
vtxp->forEachSource([&](DfgVertex& src) {
vtxp->foreachSource([&](DfgVertex& src) {
// We only remove actual operation vertices and synthesis temporaries in this loop
if (src.is<DfgConst>()) return;
if (src.is<DfgConst>()) return false;
const DfgVertexVar* const varp = src.cast<DfgVertexVar>();
if (varp && !varp->tmpForp()) return;
if (varp && !varp->tmpForp()) return false;
// If already in work list then nothing to do
if (src.getUser<DfgVertex*>()) return;
if (src.getUser<DfgVertex*>()) return false;
// Actually add to work list.
src.setUser<DfgVertex*>(workListp);
workListp = &src;
return false;
});
// Remove the unused vertex
vtxp->unlinkDelete(dfg);
@@ -214,10 +214,13 @@ void V3DfgPasses::binToOneHot(DfgGraph& dfg, V3DfgBinToOneHotContext& ctx) {
if (DfgVertex* const sinkp = vtxp->singleSink()) {
if (sinkp->is<DfgNot>()) return useOk(sinkp, !inv);
}
return !vtxp->findSink<DfgCond>([vtxp, inv](const DfgCond& sink) {
if (sink.condp() != vtxp) return false;
return inv ? sink.thenp()->is<DfgCond>() : sink.elsep()->is<DfgCond>();
const bool condTree = vtxp->foreachSink([&](const DfgVertex& sink) {
const DfgCond* const condp = sink.cast<DfgCond>();
if (!condp) return false;
if (condp->condp() != vtxp) return false;
return inv ? condp->thenp()->is<DfgCond>() : condp->elsep()->is<DfgCond>();
});
return !condTree;
};
// Look at all comparison nodes and build the 'Val2Terms' map for each source vertex
@@ -306,7 +309,7 @@ void V3DfgPasses::binToOneHot(DfgGraph& dfg, V3DfgBinToOneHotContext& ctx) {
// Required data types
AstNodeDType* const idxDTypep = srcp->dtypep();
AstNodeDType* const bitDTypep = DfgGraph::dtypePacked(1);
AstNodeDType* const bitDTypep = V3Dfg::dtypePacked(1);
AstUnpackArrayDType* const tabDTypep = new AstUnpackArrayDType{
flp, bitDTypep, new AstRange{flp, static_cast<int>(nBits - 1), 0}};
v3Global.rootp()->typeTablep()->addTypesp(tabDTypep);
@@ -438,10 +441,11 @@ void V3DfgPasses::eliminateVars(DfgGraph& dfg, V3DfgEliminateVarsContext& ctx) {
const auto addToWorkList = [&](DfgVertex& vtx) {
// If already in work list then nothing to do
DfgVertex*& nextInWorklistp = vtx.user<DfgVertex*>();
if (nextInWorklistp) return;
if (nextInWorklistp) return false;
// Actually add to work list.
nextInWorklistp = workListp;
workListp = &vtx;
return false;
};
// List of variables (AstVar or AstVarScope) we are replacing
@@ -467,7 +471,7 @@ void V3DfgPasses::eliminateVars(DfgGraph& dfg, V3DfgEliminateVarsContext& ctx) {
// Remove unused non-variable vertices
if (!vtxp->is<DfgVertexVar>() && !vtxp->hasSinks()) {
// Add sources of removed vertex to work list
vtxp->forEachSource(addToWorkList);
vtxp->foreachSource(addToWorkList);
// Remove the unused vertex
vtxp->unlinkDelete(dfg);
continue;
@@ -517,7 +521,7 @@ void V3DfgPasses::eliminateVars(DfgGraph& dfg, V3DfgEliminateVarsContext& ctx) {
}
// Add sources of redundant variable to the work list
vtxp->forEachSource(addToWorkList);
vtxp->foreachSource(addToWorkList);
// Remove the redundant variable
vtxp->unlinkDelete(dfg);
}