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Fix component numbers of new Vertices in V3DfgBreakCycles 

Fix part of #6225
This commit is contained in:
Geza Lore 2025-07-24 09:37:51 +01:00
parent 4882a3c827
commit 887863ca8c
1 changed files with 26 additions and 6 deletions
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32
src/V3DfgBreakCycles.cpp
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@ -210,7 +210,12 @@ class TraceDriver final : public DfgVisitor {
// Create and return a new Vertex and add it to m_newVtxps. Fileline is
// taken from 'refp', but 'refp' is otherwise not used. You should
// always use this to create new vertices, so unused ones (if a trace
// eventually fails) can be cleaned up at the end.
// eventually fails) can be cleaned up at the end. This also sets the
// vertex user<uint32_t> to 0, indicating the new vertex is not part of a
// strongly connected component. This should always be true, as all the
// vertices we create here are driven from outside the component we are
// trying to escape, and will sink into that component. Given those are
// separate SCCs, these new vertices must be acyclic.
template <typename Vertex>
Vertex* make(const DfgVertex* refp, uint32_t width) {
static_assert(std::is_base_of<DfgVertex, Vertex>::value //
@ -229,6 +234,7 @@ class TraceDriver final : public DfgVisitor {
if VL_CONSTEXPR_CXX17 (std::is_same<DfgConst, Vertex>::value) {
DfgConst* const vtxp = new DfgConst{m_dfg, refp->fileline(), width};
vtxp->template setUser<uint32_t>(0);
m_newVtxps.emplace_back(vtxp);
return reinterpret_cast<Vertex*>(vtxp);
} else {
@ -239,6 +245,7 @@ class TraceDriver final : public DfgVisitor {
Vertex>::type;
AstNodeDType* const dtypep = DfgVertex::dtypeForWidth(width);
Vtx* const vtxp = new Vtx{m_dfg, refp->fileline(), dtypep};
vtxp->template setUser<uint32_t>(0);
m_newVtxps.emplace_back(vtxp);
return reinterpret_cast<Vertex*>(vtxp);
}
@ -276,7 +283,7 @@ class TraceDriver final : public DfgVisitor {
// Trace the vertex
onStackr = true;
if (vtxp->user<uint32_t>() != m_component) {
if (vtxp->getUser<uint32_t>() != m_component) {
// If the currently traced vertex is in a different component,
// then we found what we were looking for.
if (msb != vtxp->width() - 1 || lsb != 0) {
@ -579,7 +586,7 @@ public:
// waste a lot of compute.
static DfgVertex* apply(DfgGraph& dfg, DfgVertex* vtxp, uint32_t lsb, uint32_t width,
bool aggressive) {
TraceDriver traceDriver{dfg, vtxp->user<uint32_t>(), aggressive};
TraceDriver traceDriver{dfg, vtxp->getUser<uint32_t>(), aggressive};
// Find the out-of-component driver of the given vertex
DfgVertex* const resultp = traceDriver.trace(vtxp, lsb + width - 1, lsb);
// Delete unused newly created vertices (these can be created if a
@ -852,7 +859,7 @@ class FixUpSelDrivers final {
// Only handle Sel
DfgSel* const selp = sink.cast<DfgSel>();
if (!selp) return;
// Try to find of the driver of the selected bits outside the cycle
// Try to find the driver of the selected bits outside the cycle
DfgVertex* const fixp
= TraceDriver::apply(dfg, vtxp, selp->lsb(), selp->width(), false);
if (!fixp) return;
@ -968,6 +975,8 @@ class FixUpIndependentRanges final {
if (!termp) {
AstNodeDType* const dtypep = DfgVertex::dtypeForWidth(width);
DfgSel* const selp = new DfgSel{dfg, vtxp->fileline(), dtypep};
// Same component as 'vtxp', as reads 'vtxp' and will replace 'vtxp'
selp->setUser<uint32_t>(vtxp->getUser<uint32_t>());
// Do not connect selp->fromp yet, need to do afer replacing 'vtxp'
selp->lsb(lsb);
termp = selp;
@ -1022,7 +1031,9 @@ class FixUpIndependentRanges final {
nImprovements += gatherTerms(termps, dfg, vtxp, indpBits, msb, lsb);
} else {
// The range is not used, just use constant 0 as a placeholder
termps.emplace_back(new DfgConst{dfg, flp, msb - lsb + 1});
DfgConst* const constp = new DfgConst{dfg, flp, msb - lsb + 1};
constp->setUser<uint32_t>(0);
termps.emplace_back(constp);
}
// Next iteration
isUsed = !isUsed;
@ -1033,6 +1044,7 @@ class FixUpIndependentRanges final {
if (nImprovements) {
// Concatenate all the terms to create the replacement
DfgVertex* replacementp = termps.front();
const uint32_t vComp = vtxp->getUser<uint32_t>();
for (size_t i = 1; i < termps.size(); ++i) {
DfgVertex* const termp = termps[i];
const uint32_t catWidth = replacementp->width() + termp->width();
@ -1040,6 +1052,14 @@ class FixUpIndependentRanges final {
DfgConcat* const catp = new DfgConcat{dfg, flp, dtypep};
catp->rhsp(replacementp);
catp->lhsp(termp);
// Need to figure out which component the replacement vertex
// belongs to. If any of the terms are of the original
// component, it's part of that component, otherwise its not
// cyclic (all terms are from outside the original component,
// and feed into the original component).
const uint32_t tComp = termp->getUser<uint32_t>();
const uint32_t rComp = replacementp->getUser<uint32_t>();
catp->setUser<uint32_t>(tComp == vComp || rComp == vComp ? vComp : 0);
replacementp = catp;
}
@ -1071,7 +1091,7 @@ public:
// For array variables, fix up element-wise
const uint32_t component = varp->getUser<uint32_t>();
varp->forEachSink([&](DfgVertex& sink) {
// Ignore if sink is not part of cycle
// Ignore if sink is not part of same cycle
if (sink.getUser<uint32_t>() != component) return;
// Only handle ArraySels with constant index
DfgArraySel* const aselp = sink.cast<DfgArraySel>();