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Improve Dfg type system (#6390)

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Added a mini type system for Dfg using DfgDataType to replace Dfg's use
of AstNodeDType. This is much more restricted and represents only the
types Dfg can handle in a canonical form. This will be needed when
adding more support for unpacked arrays and maybe unpacked structs one
day.

Also added an internal type checker for DfgGraphs which encodes all the
assumptions the code makes about type relationships in the graph. Run
this in a few places with --debug-check. Fix resulting fallout.
This commit is contained in:
Geza Lore
2025-09-07 20:38:50 +01:00
committed by GitHub
parent f67534069c
commit 6bc48fcdb3
27 changed files with 778 additions and 394 deletions
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src/V3DfgBreakCycles.cpp
+7 -11
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@@ -123,8 +123,7 @@ class TraceDriver final : public DfgVisitor {
// Vertex is DfgConst, in which case this code is unreachable ...
using Vtx = typename std::conditional<std::is_same<DfgConst, Vertex>::value, DfgSel,
Vertex>::type;
AstNodeDType* const dtypep = V3Dfg::dtypePacked(width);
Vtx* const vtxp = new Vtx{m_dfg, refp->fileline(), dtypep};
Vtx* const vtxp = new Vtx{m_dfg, refp->fileline(), DfgDataType::packed(width)};
m_vtx2Scc[vtxp] = 0;
m_newVtxps.emplace_back(vtxp);
return reinterpret_cast<Vertex*>(vtxp);
@@ -137,10 +136,9 @@ class TraceDriver final : public DfgVisitor {
if (!nodep) nodep = v3Global.rootp();
const std::string name = m_dfg.makeUniqueName(prefix, nodep->user2Inc());
FileLine* const flp = vtxp->fileline();
AstNodeDType* const dtypep = vtxp->dtypep();
DfgVertex::ScopeCache scopeCache;
AstScope* const scopep = m_dfg.modulep() ? nullptr : vtxp->scopep(scopeCache);
DfgVertexVar* const varp = m_dfg.makeNewVar(flp, name, dtypep, scopep);
DfgVertexVar* const varp = m_dfg.makeNewVar(flp, name, vtxp->dtype(), scopep);
varp->varp()->isInternal(true);
varp->tmpForp(varp->nodep());
return varp;
@@ -151,8 +149,8 @@ class TraceDriver final : public DfgVisitor {
// return after the call. 'visit' methods should not call 'iterate', call
// this method instead, which checks for cycles.
DfgVertex* trace(DfgVertex* const vtxp, const uint32_t msb, const uint32_t lsb) {
UASSERT_OBJ(!vtxp->isArray(), vtxp, "Cannot trace array type vertices");
UASSERT_OBJ(vtxp->width() > msb, vtxp, "Traced Vertex too narrow");
UASSERT_OBJ(vtxp->isPacked(), vtxp, "Can only trace packed type vertices");
UASSERT_OBJ(vtxp->size() > msb, vtxp, "Traced Vertex too narrow");
// Push to stack
m_stack.emplace_back(vtxp, msb, lsb);
@@ -958,7 +956,7 @@ class IndependentBits final : public DfgVisitor {
DfgVertex* const currp = workList.front();
workList.pop_front();
if (VN_IS(currp->dtypep(), UnpackArrayDType)) {
if (currp->isArray()) {
// For an unpacked array vertex, just enque it's sinks.
// (There can be no loops through arrays directly)
currp->foreachSink([&](DfgVertex& vtx) {
@@ -1146,8 +1144,7 @@ class FixUpIndependentRanges final {
}
// Fall back on using the part of the variable (if dependent, or trace failed)
if (!termp) {
AstNodeDType* const dtypep = V3Dfg::dtypePacked(width);
DfgSel* const selp = new DfgSel{m_dfg, vtx.fileline(), dtypep};
DfgSel* const selp = new DfgSel{m_dfg, vtx.fileline(), DfgDataType::packed(width)};
// Same component as 'vtxp', as reads 'vtxp' and will replace 'vtxp'
m_vtx2Scc[selp] = m_vtx2Scc.at(vtx);
// Do not connect selp->fromp yet, need to do afer replacing 'vtxp'
@@ -1225,8 +1222,7 @@ class FixUpIndependentRanges final {
for (size_t i = 1; i < termps.size(); ++i) {
DfgVertex* const termp = termps[i];
const uint32_t catWidth = replacementp->width() + termp->width();
AstNodeDType* const dtypep = V3Dfg::dtypePacked(catWidth);
DfgConcat* const catp = new DfgConcat{m_dfg, flp, dtypep};
DfgConcat* const catp = new DfgConcat{m_dfg, flp, DfgDataType::packed(catWidth)};
catp->rhsp(replacementp);
catp->lhsp(termp);
// Need to figure out which component the replacement vertex