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Refactor Dfg variable flags (#6259) 

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
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
8 changed files with 102 additions and 136 deletions
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27
src/V3Dfg.cpp
View File

@ -77,10 +77,6 @@ std::unique_ptr<DfgGraph> DfgGraph::clone() const {
break;
}
}
if (vp->hasDfgRefs()) cp->setHasDfgRefs();
if (vp->hasModRefs()) cp->setHasModRefs();
if (vp->hasExtRefs()) cp->setHasExtRefs();
}
// Clone operation vertices
for (const DfgVertex& vtx : m_opVertices) {
@ -262,8 +258,6 @@ static void dumpDotVertex(std::ostream& os, const DfgVertex& vtx) {
os << ", shape=box, style=filled, fillcolor=darkorange1"; // Orange
} else if (varVtxp->hasDfgRefs()) {
os << ", shape=box, style=filled, fillcolor=gold2"; // Yellow
} else if (varVtxp->keep()) {
os << ", shape=box, style=filled, fillcolor=grey";
} else {
os << ", shape=box";
}
@ -290,8 +284,6 @@ static void dumpDotVertex(std::ostream& os, const DfgVertex& vtx) {
os << ", shape=box3d, style=filled, fillcolor=darkorange1"; // Orange
} else if (arrVtxp->hasDfgRefs()) {
os << ", shape=box3d, style=filled, fillcolor=gold2"; // Yellow
} else if (arrVtxp->keep()) {
os << ", shape=box3d, style=filled, fillcolor=grey";
} else {
os << ", shape=box3d";
}
@ -597,16 +589,23 @@ DfgVertexVar* DfgVertex::getResultVar() {
resp = varp;
return;
}
// Prefer those variables that must be kept anyway
const bool keepOld = resp->keep() || resp->hasDfgRefs();
const bool keepNew = varp->keep() || varp->hasDfgRefs();
if (keepOld != keepNew) {
if (!keepOld) resp = varp;
if (resp->hasExtRefs() != varp->hasExtRefs()) {
if (!resp->hasExtRefs()) resp = varp;
return;
}
if (resp->hasModWrRefs() != varp->hasModWrRefs()) {
if (!resp->hasModWrRefs()) resp = varp;
return;
}
if (resp->hasDfgRefs() != varp->hasDfgRefs()) {
if (!resp->hasDfgRefs()) resp = varp;
return;
}
// Prefer those that already have module references
if (resp->hasModRefs() != varp->hasModRefs()) {
if (!resp->hasModRefs()) resp = varp;
if (resp->hasModRdRefs() != varp->hasModRdRefs()) {
if (!resp->hasModRdRefs()) resp = varp;
return;
}
// Prefer the earlier one in source order

85
src/V3DfgAstToDfg.cpp
View File

@ -87,8 +87,8 @@ template <bool T_Scoped>
class AstToDfgVisitor final : public VNVisitor {
// NODE STATE
// AstNode::user1p // DfgVertex for this AstNode
const VNUser1InUse m_user1InUse;
// AstNode::user2p // DfgVertex for this AstNode
const VNUser2InUse m_user2InUse;
// TYPES
using RootType = std::conditional_t<T_Scoped, AstNetlist, AstModule>;
@ -124,15 +124,12 @@ class AstToDfgVisitor final : public VNVisitor {
}
void markReferenced(AstNode* nodep) {
nodep->foreach([this](const AstVarRef* refp) {
// No need to (and in fact cannot) mark variables if:
if (!DfgVertex::isSupportedDType(refp->varp()->dtypep())) return; // unsupported type
if (refp->varp()->isSc()) return; // SystemC
nodep->foreach([](const AstVarRef* refp) {
VariableType* const tgtp = getTarget(refp);
// Mark vertex as having a module reference outside current DFG
getNet(tgtp)->setHasModRefs();
// Mark variable as written from non-DFG logic
if (refp->access().isWriteOrRW()) tgtp->user3(true);
// Mark as read from non-DFG logic
if (refp->access().isReadOrRW()) DfgVertexVar::setHasModRdRefs(tgtp);
// Mark as written from non-DFG logic
if (refp->access().isWriteOrRW()) DfgVertexVar::setHasModWrRefs(tgtp);
});
}
@ -144,27 +141,27 @@ class AstToDfgVisitor final : public VNVisitor {
}
DfgVertexVar* getNet(VariableType* vp) {
if (!vp->user1p()) {
if (!vp->user2p()) {
// vp DfgVertexVar vertices are not added to m_uncommittedVertices, because we
// want to hold onto them via AstVar::user1p, and the AstVar might be referenced via
// want to hold onto them via AstVar::user2p, and the AstVar might be referenced via
// multiple AstVarRef instances, so we will never revert a DfgVertexVar once
// created. We will delete unconnected variable vertices at the end.
if (VN_IS(vp->dtypep()->skipRefp(), UnpackArrayDType)) {
DfgVarArray* const vtxp = new DfgVarArray{*m_dfgp, vp};
vp->user1p();
vp->user2p();
m_varArrayps.push_back(vtxp);
vp->user1p(vtxp);
vp->user2p(vtxp);
} else {
DfgVarPacked* const vtxp = new DfgVarPacked{*m_dfgp, vp};
m_varPackedps.push_back(vtxp);
vp->user1p(vtxp);
vp->user2p(vtxp);
}
}
return vp->user1u().template to<DfgVertexVar*>();
return vp->user2u().template to<DfgVertexVar*>();
}
DfgVertex* getVertex(AstNode* nodep) {
DfgVertex* vtxp = nodep->user1u().to<DfgVertex*>();
DfgVertex* vtxp = nodep->user2u().to<DfgVertex*>();
UASSERT_OBJ(vtxp, nodep, "Missing Dfg vertex");
return vtxp;
}
@ -713,42 +710,6 @@ class AstToDfgVisitor final : public VNVisitor {
void visit(AstCell* nodep) override { markReferenced(nodep); }
void visit(AstNodeProcedure* nodep) override { markReferenced(nodep); }
void visit(AstVar* nodep) override {
if VL_CONSTEXPR_CXX17 (T_Scoped) {
return;
} else {
if (nodep->isSc()) return;
// No need to (and in fact cannot) handle variables with unsupported dtypes
if (!DfgVertex::isSupportedDType(nodep->dtypep())) return;
// Mark variables with external references
if (nodep->isIO() // Ports
|| nodep->user2() // Target of a hierarchical reference
|| nodep->isForced() // Forced
) {
getNet(reinterpret_cast<VariableType*>(nodep))->setHasExtRefs();
}
}
}
void visit(AstVarScope* nodep) override {
if VL_CONSTEXPR_CXX17 (!T_Scoped) {
return;
} else {
if (nodep->varp()->isSc()) return;
// No need to (and in fact cannot) handle variables with unsupported dtypes
if (!DfgVertex::isSupportedDType(nodep->dtypep())) return;
// Mark variables with external references
if (nodep->varp()->isIO() // Ports
|| nodep->user2() // Target of a hierarchical reference
|| nodep->varp()->isForced() // Forced
) {
getNet(reinterpret_cast<VariableType*>(nodep))->setHasExtRefs();
}
}
}
void visit(AstAssignW* nodep) override {
++m_ctx.m_inputEquations;
@ -820,7 +781,7 @@ class AstToDfgVisitor final : public VNVisitor {
}
void visit(AstVarRef* nodep) override {
UASSERT_OBJ(!nodep->user1p(), nodep, "Already has Dfg vertex");
UASSERT_OBJ(!nodep->user2p(), nodep, "Already has Dfg vertex");
if (unhandled(nodep)) return;
if (nodep->access().isRW() // Cannot represent read-write references
@ -853,19 +814,19 @@ class AstToDfgVisitor final : public VNVisitor {
return;
}
nodep->user1p(getNet(getTarget(nodep)));
nodep->user2p(getNet(getTarget(nodep)));
}
void visit(AstConst* nodep) override {
UASSERT_OBJ(!nodep->user1p(), nodep, "Already has Dfg vertex");
UASSERT_OBJ(!nodep->user2p(), nodep, "Already has Dfg vertex");
if (unhandled(nodep)) return;
DfgVertex* const vtxp = new DfgConst{*m_dfgp, nodep->fileline(), nodep->num()};
m_uncommittedVertices.push_back(vtxp);
nodep->user1p(vtxp);
nodep->user2p(vtxp);
}
void visit(AstSel* nodep) override {
UASSERT_OBJ(!nodep->user1p(), nodep, "Already has Dfg vertex");
UASSERT_OBJ(!nodep->user2p(), nodep, "Already has Dfg vertex");
if (unhandled(nodep)) return;
iterate(nodep->fromp());
@ -875,19 +836,19 @@ class AstToDfgVisitor final : public VNVisitor {
DfgVertex* vtxp = nullptr;
if (AstConst* const constp = VN_CAST(nodep->lsbp(), Const)) {
DfgSel* const selp = new DfgSel{*m_dfgp, flp, DfgVertex::dtypeFor(nodep)};
selp->fromp(nodep->fromp()->user1u().to<DfgVertex*>());
selp->fromp(nodep->fromp()->user2u().to<DfgVertex*>());
selp->lsb(constp->toUInt());
vtxp = selp;
} else {
iterate(nodep->lsbp());
if (m_foundUnhandled) return;
DfgMux* const muxp = new DfgMux{*m_dfgp, flp, DfgVertex::dtypeFor(nodep)};
muxp->fromp(nodep->fromp()->user1u().to<DfgVertex*>());
muxp->lsbp(nodep->lsbp()->user1u().to<DfgVertex*>());
muxp->fromp(nodep->fromp()->user2u().to<DfgVertex*>());
muxp->lsbp(nodep->lsbp()->user2u().to<DfgVertex*>());
vtxp = muxp;
}
m_uncommittedVertices.push_back(vtxp);
nodep->user1p(vtxp);
nodep->user2p(vtxp);
}
// The rest of the 'visit' methods are generated by 'astgen'

5
src/V3DfgDecomposition.cpp
View File

@ -330,13 +330,10 @@ class ExtractCyclicComponents final {
}
}
UASSERT_OBJ(clonep, &vtx, "Unhandled 'DfgVertexVar' sub-type");
if (vtx.hasModRefs()) clonep->setHasModRefs();
if (vtx.hasExtRefs()) clonep->setHasExtRefs();
VertexState& cloneStatep = allocState(*clonep);
cloneStatep.component = component;
// We need to mark both the original and the clone as having references in other DFGs
// Mark variable as having references in other DFGs
vtx.setHasDfgRefs();
clonep->setHasDfgRefs();
}
return *clonep;
}

14
src/V3DfgDfgToAst.cpp
View File

@ -129,8 +129,8 @@ template <bool T_Scoped>
class DfgToAstVisitor final : DfgVisitor {
// NODE STATE
// AstScope::user1p // The combinational AstActive under this scope
const VNUser1InUse m_user1InUse;
// AstScope::user2p // The combinational AstActive under this scope
const VNUser2InUse m_user2InUse;
// TYPES
using VariableType = std::conditional_t<T_Scoped, AstVarScope, AstVar>;
@ -152,28 +152,28 @@ class DfgToAstVisitor final : DfgVisitor {
}
static AstActive* getCombActive(AstScope* scopep) {
if (!scopep->user1p()) {
if (!scopep->user2p()) {
// Try to find the existing combinational AstActive
for (AstNode* nodep = scopep->blocksp(); nodep; nodep = nodep->nextp()) {
AstActive* const activep = VN_CAST(nodep, Active);
if (!activep) continue;
if (activep->hasCombo()) {
scopep->user1p(activep);
scopep->user2p(activep);
break;
}
}
// If there isn't one, create a new one
if (!scopep->user1p()) {
if (!scopep->user2p()) {
FileLine* const flp = scopep->fileline();
AstSenTree* const senTreep
= new AstSenTree{flp, new AstSenItem{flp, AstSenItem::Combo{}}};
AstActive* const activep = new AstActive{flp, "", senTreep};
activep->sensesStorep(senTreep);
scopep->addBlocksp(activep);
scopep->user1p(activep);
scopep->user2p(activep);
}
}
return VN_AS(scopep->user1p(), Active);
return VN_AS(scopep->user2p(), Active);
}
AstNodeExpr* convertDfgVertexToAstNodeExpr(DfgVertex* vtxp) {

25
src/V3DfgOptimizer.cpp
View File

@ -296,16 +296,15 @@ void V3DfgOptimizer::optimize(AstNetlist* netlistp, const string& label) {
UINFO(2, __FUNCTION__ << ":");
// NODE STATE
// AstVar::user1 -> Used by:
// - V3DfgPasses::astToDfg,
// - V3DfgPasses::eliminateVars,
// - V3DfgPasses::dfgToAst,
// AstVar::user2 -> bool: Flag indicating referenced by AstVarXRef (set just below)
// AstVar::user3, AstVarScope::user3
// -> bool: Flag indicating written by logic not representable as DFG
// (set by V3DfgPasses::astToDfg)
const VNUser2InUse user2InUse;
const VNUser3InUse user3InUse;
// AstVar::user1, AstVarScope::user1 -> int, used as a bit-field
// - bit0: Read via AstVarXRef (hierarchical reference)
// - bit1: Written via AstVarXRef (hierarchical reference)
// - bit2: Read by logic in same module/netlist not represented in DFG
// - bit3: Written by logic in same module/netlist not represented in DFG
// - bit4: Referenced by other DFG in same module/netlist
//
// AstNode::user2/user3/user4 can be used by various DFG algorithms
const VNUser1InUse user1InUse;
V3DfgContext ctx{label};
@ -313,7 +312,11 @@ void V3DfgOptimizer::optimize(AstNetlist* netlistp, const string& label) {
// Pre V3Scope application. Run on each module separately.
// Mark cross-referenced variables
netlistp->foreach([](const AstVarXRef* xrefp) { xrefp->varp()->user2(true); });
netlistp->foreach([](const AstVarXRef* xrefp) {
AstVar* const tgtp = xrefp->varp();
if (xrefp->access().isReadOrRW()) DfgVertexVar::setHasRdXRefs(tgtp);
if (xrefp->access().isWriteOrRW()) DfgVertexVar::setHasWrXRefs(tgtp);
});
// Run the optimization phase
for (AstNode* nodep = netlistp->modulesp(); nodep; nodep = nodep->nextp()) {

27
src/V3DfgPasses.cpp
View File

@ -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());
});

47
src/V3DfgVertices.h
View File

@ -41,9 +41,6 @@
class DfgVertexVar VL_NOT_FINAL : public DfgVertexUnary {
AstVar* const m_varp; // The AstVar associated with this vertex (not owned by this vertex)
AstVarScope* const m_varScopep; // The AstVarScope associated with this vertex (not owned)
bool m_hasDfgRefs = false; // This AstVar is referenced in a different DFG of the module
bool m_hasModRefs = false; // This AstVar is referenced outside the DFG, but in the module
bool m_hasExtRefs = false; // This AstVar is referenced from outside the module
// Location of driver of this variable. Only used for converting back to Ast. Might be nullptr.
FileLine* m_driverFileLine = nullptr;
@ -62,13 +59,6 @@ public:
AstNode* nodep() const {
return m_varScopep ? static_cast<AstNode*>(m_varScopep) : static_cast<AstNode*>(m_varp);
}
bool hasDfgRefs() const { return m_hasDfgRefs; }
void setHasDfgRefs() { m_hasDfgRefs = true; }
bool hasModRefs() const { return m_hasModRefs; }
void setHasModRefs() { m_hasModRefs = true; }
bool hasExtRefs() const { return m_hasExtRefs; }
void setHasExtRefs() { m_hasExtRefs = true; }
bool hasNonLocalRefs() const { return hasDfgRefs() || hasModRefs() || hasExtRefs(); }
FileLine* driverFileLine() const { return m_driverFileLine; }
void driverFileLine(FileLine* flp) { m_driverFileLine = flp; }
@ -77,17 +67,32 @@ public:
return srcp() && !srcp()->is<DfgVertexSplice>() && !varp()->isForced();
}
// Variable cannot be removed, even if redundant in the DfgGraph (might be used externally)
bool keep() const {
// Keep if referenced outside this module
if (hasExtRefs()) return true;
// Keep if traced
if (v3Global.opt.trace() && varp()->isTrace()) return true;
// Keep if public
if (varp()->isSigPublic()) return true;
// Keep if written in non-DFG code
if (nodep()->user3()) return true;
// Otherwise it can be removed
// Variable referenced via an AstVarXRef (hierarchical reference)
bool hasXRefs() const { return nodep()->user1() & 0x03; }
static void setHasRdXRefs(AstNode* nodep) { nodep->user1(nodep->user1() | 0x01); }
static void setHasWrXRefs(AstNode* nodep) { nodep->user1(nodep->user1() | 0x02); }
// Variable referenced from Ast code in the same module/netlist
bool hasModRdRefs() const { return nodep()->user1() & 0x04; }
bool hasModWrRefs() const { return nodep()->user1() & 0x08; }
bool hasModRefs() const { return nodep()->user1() & 0x0c; }
static void setHasModRdRefs(AstNode* nodep) { nodep->user1(nodep->user1() | 0x04); }
static void setHasModWrRefs(AstNode* nodep) { nodep->user1(nodep->user1() | 0x08); }
void setHasModRdRefs() const { setHasModRdRefs(nodep()); }
void setHasModWrRefs() const { setHasModWrRefs(nodep()); }
// Variable referenced from other DFG in the same module/netlist
bool hasDfgRefs() const { return nodep()->user1() & 0x10; }
void setHasDfgRefs() { nodep()->user1(nodep()->user1() | 0x10); }
// Variable referenced outside the containing module/netlist.
bool hasExtRefs() const {
if (m_varp->isIO()) return true; // Ports
if (m_varp->isTrace()) return true; // Traced
if (m_varp->isForced()) return true; // Forced
if (hasXRefs()) return true; // Target of a hierarchical reference
if (m_varp->isPrimaryIO()) return true; // Top level ports
if (m_varp->isSigPublic()) return true; // Public
return false;
}
};

8
src/astgen
View File

@ -1250,13 +1250,13 @@ def write_dfg_ast_to_dfg(filename):
continue
fh.write("void visit(Ast{t}* nodep) override {{\n".format(t=node.name))
fh.write(' UASSERT_OBJ(!nodep->user1p(), nodep, "Already has Dfg vertex");\n\n')
fh.write(' UASSERT_OBJ(!nodep->user2p(), nodep, "Already has Dfg vertex");\n\n')
fh.write(" if (unhandled(nodep)) return;\n\n")
for i in range(node.arity):
fh.write(" iterate(nodep->op{j}p());\n".format(j=i + 1))
fh.write(" if (m_foundUnhandled) return;\n")
fh.write(
' UASSERT_OBJ(nodep->op{j}p()->user1p(), nodep, "Child {j} missing Dfg vertex");\n'
' UASSERT_OBJ(nodep->op{j}p()->user2p(), nodep, "Child {j} missing Dfg vertex");\n'
.format(j=i + 1))
fh.write("\n")
fh.write(" Dfg{t}* const vtxp = makeVertex<Dfg{t}>(nodep, *m_dfgp);\n".format(
@ -1268,11 +1268,11 @@ def write_dfg_ast_to_dfg(filename):
fh.write(" }\n\n")
for i in range(node.arity):
fh.write(
" vtxp->relinkSource<{i}>(nodep->op{j}p()->user1u().to<DfgVertex*>());\n".
" vtxp->relinkSource<{i}>(nodep->op{j}p()->user2u().to<DfgVertex*>());\n".
format(i=i, j=i + 1))
fh.write("\n")
fh.write(" m_uncommittedVertices.push_back(vtxp);\n")
fh.write(" nodep->user1p(vtxp);\n")
fh.write(" nodep->user2p(vtxp);\n")
fh.write("}\n")