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Add -fno-dead-members and optimize dead class member functions. (#8330)

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This commit is contained in:
Wilson Snyder
2026-09-12 15:22:42 -04:00
committed by GitHub
parent 3bf0018354
commit 4fedb791ed
16 changed files with 1061 additions and 82 deletions
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src/V3Dead.cpp
+146 -37
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@@ -52,22 +52,28 @@ class DeadVertex final : public V3GraphVertex {
VL_RTTI_IMPL(DeadVertex, V3GraphVertex)
AstNode* const m_nodep; // Node that created vertex
uint64_t m_workPos = 0; // Position on DeadWorkList, 0 = not on list
bool m_removable; // Subject to dead removal
bool m_removable = false; // Subject to dead removal
bool m_isVirtual = false; // Virtual node, indirection
public:
DeadVertex(V3Graph* graphp, AstNode* nodep, bool removable)
DeadVertex(V3Graph* graphp, AstNode* nodep)
: V3GraphVertex{graphp}
, m_nodep{nodep}
, m_removable{removable} {}
, m_nodep{nodep} {}
~DeadVertex() override = default;
string dotShape() const override { return removable() ? "rectangle" : "ellipse"; }
string dotShape() const override {
return isVirtual() ? "diamond" : removable() ? "rectangle" : "ellipse";
}
AstNode* nodep() const VL_MT_STABLE { return m_nodep; }
string name() const override VL_MT_STABLE {
return (removable() ? "[R] "s : "") + nodep()->typeName() + ' ' + cvtToHex(nodep()) + ' '
+ nodep()->name();
return (isVirtual() ? "[VIRT] "
: removable() ? "[R] "s
: "[NR] ")
+ nodep()->typeName() + ' ' + cvtToHex(nodep()) + ' ' + nodep()->name();
}
bool removable() const { return m_removable; }
void removable(bool flag) { m_removable = flag; }
bool isVirtual() const { return m_isVirtual; }
void isVirtual(bool flag) { m_isVirtual = flag; }
uint64_t workPos() const { return m_workPos; }
void workPos(uint64_t value) { m_workPos = value; }
};
@@ -117,7 +123,13 @@ class DeadGraph final : public V3Graph {
// See const VNUser2InUse m_inuser2; inside DeadVisitor
// MEMBERS
DeadWorkList m_funcs; // Functions eligble for deletion
// Each virtual vertex by the ftask name()
std::unordered_map<std::string, DeadVertex*> m_virtualVtxsp;
void newEdge(DeadVertex* fromp, DeadVertex* top) {
new V3GraphEdge{this, fromp, top, 1, false};
if (top->removable()) m_funcs.erase(top); // Now has an input edge
}
void pushWorkMaybe(DeadVertex* vtxp, bool allowSize1) {
if (vtxp->removable()) {
if (VN_IS(vtxp->nodep(), NodeFTask)
@@ -130,18 +142,32 @@ public:
// METHODS
DeadGraph() = default;
~DeadGraph() override = default;
DeadVertex* findNewVertex(AstNode* nodep, bool removable) {
DeadVertex* findNewVertex(AstNode* nodep) {
DeadVertex* vtxp = nodep->user2u().to<DeadVertex*>();
if (!vtxp) {
vtxp = new DeadVertex{this, nodep, removable};
vtxp = new DeadVertex{this, nodep};
nodep->user2p(vtxp);
pushWorkMaybe(vtxp, false);
}
UASSERT_OBJ(vtxp->nodep() == nodep, nodep, "Vertex points at different node");
return vtxp;
}
DeadVertex* findVirtualVertex(AstNode* nodep) {
const auto it = m_virtualVtxsp.find(nodep->name());
DeadVertex* vtxp;
if (it != m_virtualVtxsp.end()) {
vtxp = it->second;
} else {
vtxp = new DeadVertex{this, nodep};
vtxp->removable(true);
vtxp->isVirtual(true);
pushWorkMaybe(vtxp, false);
m_virtualVtxsp.emplace(nodep->name(), vtxp);
}
return vtxp;
}
void findNewRemovableVertex(AstNode* nodep, bool removable) {
DeadVertex* const vtxp = findNewVertex(nodep, removable);
DeadVertex* const vtxp = findNewVertex(nodep);
// Wasn't removable before (due to earlier insert), make removable now
if (removable && !vtxp->removable()) {
vtxp->removable(true);
@@ -149,35 +175,65 @@ public:
}
}
void deleteNodeVertex(AstNode* nodep) {
if (DeadVertex* const vtxp = nodep->user2u().to<DeadVertex*>()) {
UINFO(9, "Delete vertex due to node deletion " << vtxp->name());
// Mark all about-to-empty downstream vertices onto worklist
for (const V3GraphEdge& oedge : vtxp->outEdges()) {
DeadVertex* const toVtxp = static_cast<DeadVertex*>(oedge.top());
pushWorkMaybe(toVtxp, true);
}
nodep->user2p(nullptr); // Shouldn't be checked later as deleting, but in case
if (vtxp->removable()) m_funcs.erase(vtxp);
VL_DO_DANGLING(vtxp->unlinkDelete(this), vtxp);
if (DeadVertex* const vtxp = nodep->user2u().to<DeadVertex*>()) deleteVertex(vtxp);
}
void deleteVertex(DeadVertex* vtxp) {
UINFO(9, "Delete vertex " << vtxp->name());
// Mark all about-to-empty downstream vertices onto worklist
for (const V3GraphEdge& oedge : vtxp->outEdges()) {
DeadVertex* const toVtxp = static_cast<DeadVertex*>(oedge.top());
pushWorkMaybe(toVtxp, true); // size1 ok as about to delete below
}
// Node shouldn't be looking at user2p later as node being deleting, but in case
if (!vtxp->isVirtual()) vtxp->nodep()->user2p(nullptr);
if (vtxp->removable()) m_funcs.erase(vtxp);
VL_DO_DANGLING(vtxp->unlinkDelete(this), vtxp);
}
// This only tracks usage dependancy, not "containership",
// When all needs disappear the related node is eligble for deletion
void needs(AstNode* nodep, AstNode* parentp) {
if (parentp == nodep) return; // No need for tracking needs itself (recursion)
UINFO(9, "Edge node " << nodep << " -> " << parentp);
DeadVertex* const parentVtxp = findNewVertex(parentp, false);
DeadVertex* const nodeVtxp = findNewVertex(nodep, false);
DeadVertex* const parentVtxp = findNewVertex(parentp);
DeadVertex* const nodeVtxp = findNewVertex(nodep);
UINFO(9, "Edge need " << parentVtxp << " -> " << nodeVtxp);
new V3GraphEdge{this, parentVtxp, nodeVtxp, 1, false};
if (nodeVtxp->removable()) m_funcs.erase(nodeVtxp); // Now has an input edge
newEdge(parentVtxp, nodeVtxp);
}
void needsVirtual(AstNodeFTask* nodep, AstNode* parentp) {
// Virtual call can be to any function in the call hierarchy.
// For simplicity rather than tracking possible multiple base
// classes (due to 'implements' classes there can be more than
// one), we simply assume all virtual functions of the same name
// can call any other virtual function of the same name
// Track via an intermediate node.
// All calling parents' verticies -> Virtual Vertex -> all ftasks verticies
if (parentp == nodep) return; // No need for tracking needs itself (recursion)
DeadVertex* const parentVtxp = findNewVertex(parentp);
DeadVertex* const virtualVtxp = findVirtualVertex(nodep);
UINFO(9, "Edge needVirtual " << parentVtxp << " -> " << virtualVtxp);
newEdge(parentVtxp, virtualVtxp);
}
void funcVirtual(AstNodeFTask* nodep) {
// Virtual Vertex -> all ftasks verticies
DeadVertex* const virtualVtxp = findVirtualVertex(nodep);
DeadVertex* const nodeVtxp = findNewVertex(nodep);
UINFO(9, "Edge funcvirtual " << virtualVtxp << " -> " << nodeVtxp);
newEdge(virtualVtxp, nodeVtxp);
}
bool funcsEmpty() const { return m_funcs.empty(); }
AstNode* funcsGetPopFront() {
DeadVertex* const nodeVtxp = m_funcs.getPopFront();
AstNode* const nodep = nodeVtxp->nodep();
UASSERT_OBJ(nodeVtxp->inEmpty(), nodep, "Non-empty node on work list");
UASSERT_OBJ(nodeVtxp->removable(), nodep, "Non-removable node on work list");
DeadVertex* const vtxp = m_funcs.getPopFront();
UASSERT_OBJ(vtxp->inEmpty(), vtxp->nodep(), "Non-empty node on work list");
UASSERT_OBJ(vtxp->removable(), vtxp->nodep(), "Non-removable node on work list");
if (vtxp->isVirtual()) {
// Emptied (no inbound edge) virtual wrapper; all
// destinations verticies are now unused too (e.g. all virtual
// functions of this name may be deleted)
UINFO(9, "Removing virtual " << vtxp);
deleteVertex(vtxp);
return nullptr; // Caller will search again
}
AstNode* const nodep = vtxp->nodep();
return nodep;
}
};
@@ -225,7 +281,10 @@ class DeadVisitor final : public VNVisitor {
AstNode* m_containingFTaskRefp = nullptr; // Parent of ftaskref (e.g. task/module)
// STATE - Statistic tracking
VDouble0 m_statFTasksDeadified;
VDouble0 m_statFTasksDemoted;
VDouble0 m_statFTasksMDeadified;
VDouble0 m_statFTasksNMDeadified;
VDouble0 m_statFTasksVirtDeadified;
// METHODS
@@ -260,6 +319,14 @@ class DeadVisitor final : public VNVisitor {
if (AstNode* const subnodep = nodep->virtRefDTypep()) subnodep->user1Inc();
if (AstNode* const subnodep = nodep->virtRefDType2p()) subnodep->user1Inc();
}
void needsTask(AstNodeFTask* taskp, AstNode* containerp) {
if (!taskp) return; // Unlinked
if (taskp->isVirtual()) {
m_graph.needsVirtual(taskp, containerp);
} else {
m_graph.needs(taskp, containerp);
}
}
// VISITORS
void visit(AstNodeModule* nodep) override {
@@ -319,7 +386,7 @@ class DeadVisitor final : public VNVisitor {
iterateChildren(nodep);
if (!m_sideEffect && !nodep->isPure()) m_sideEffect = true;
checkAll(nodep);
if (nodep->taskp()) m_graph.needs(nodep->taskp(), m_containingFTaskRefp);
needsTask(nodep->taskp(), m_containingFTaskRefp);
if (nodep->classOrPackagep()) {
if (m_elimCells) {
nodep->classOrPackagep(nullptr);
@@ -331,7 +398,7 @@ class DeadVisitor final : public VNVisitor {
void visit(AstModportFTaskRef* nodep) override {
iterateChildren(nodep);
checkAll(nodep);
if (nodep->ftaskp()) m_graph.needs(nodep->ftaskp(), m_containingFTaskRefp);
needsTask(nodep->ftaskp(), m_containingFTaskRefp);
}
void visit(AstRefDType* nodep) override {
iterateChildren(nodep);
@@ -472,13 +539,15 @@ class DeadVisitor final : public VNVisitor {
}
void visit(AstNodeFTask* nodep) override {
const bool removable = !(nodep->taskPublic() || nodep->dpiExport() || nodep->dpiImport()
|| nodep->classMethod());
|| nodep->keepAlive() || nodep->isConstructor()
|| (!v3Global.opt.fDeadMethods() && nodep->classMethod()));
m_graph.findNewRemovableVertex(nodep, removable);
//
VL_RESTORER(m_containingFTaskRefp);
m_containingFTaskRefp = nodep;
iterateChildren(nodep);
checkAll(nodep);
if (nodep->isVirtual()) m_graph.funcVirtual(nodep);
if (!removable) {
if (m_modp && !m_modp->dead() && !m_modp->verilatorLib())
m_modp->user1Inc(); // Keep container
@@ -523,10 +592,41 @@ class DeadVisitor final : public VNVisitor {
void deadCheckTasks() {
while (!m_graph.funcsEmpty()) {
AstNode* const taskp = m_graph.funcsGetPopFront();
UINFO(9, "Dead task " << taskp);
deleting(taskp);
++m_statFTasksDeadified;
AstNode* const nodep = m_graph.funcsGetPopFront();
if (!nodep) continue;
UINFO(9, "Dead " << nodep);
if (AstNodeFTask* const taskp = VN_CAST(nodep, NodeFTask)) {
if (taskp->isVirtual()) {
++m_statFTasksVirtDeadified;
} else if (taskp->classMethod()) {
++m_statFTasksMDeadified;
} else {
++m_statFTasksNMDeadified;
}
}
deleting(nodep);
}
}
void deadCheckDemote() {
for (V3GraphVertex& gvtx : m_graph.vertices()) {
DeadVertex* const vtxp = gvtx.cast<DeadVertex>();
// A isVirtual vertex with single out means there's only one target virtual function
// that can be virtually called, so can make it non-virtual for faster execution
// (UVM benefits from this)
if (!vtxp->outSize1()) continue;
if (!vtxp->isVirtual()) continue;
for (V3GraphEdge& edge : vtxp->outEdges()) { // Always a single one
AstNode* const nodep = edge.top()->as<DeadVertex>()->nodep();
AstNodeFTask* const funcp = VN_AS(nodep, NodeFTask);
UASSERT_OBJ(funcp->isVirtual(), funcp,
"Only virtual ftasks should be under DeadVirtualVertex");
if (v3Global.opt.fDeadMethods()) {
funcp->isVirtual(false);
UINFO(9, "Demote to non-virtual " << funcp);
++m_statFTasksDemoted;
}
}
}
}
@@ -746,13 +846,22 @@ public:
if (!elimTopIfaces) preserveTopIfaces(nodep);
deadCheckMod();
// After deleting as much as can, demote some virtual functions
if (elimTasks) deadCheckDemote();
// We may have removed some datatypes, cleanup
nodep->typeTablep()->repairCache();
VIsCached::clearCacheTree(); // Removing assignments may affect isPure
nodep->constPoolp()->rebuildVarScopesAndCache();
}
~DeadVisitor() override {
V3Stats::addStatSum("Optimizations, deadified FTasks", m_statFTasksDeadified);
V3Stats::addStatSum("Optimizations, FTasks, virtual-to-nonvirtual demotion",
m_statFTasksDemoted);
V3Stats::addStatSum("Optimizations, FTasks, deadified, methods", m_statFTasksMDeadified);
V3Stats::addStatSum("Optimizations, FTasks, deadified, non-methods",
m_statFTasksNMDeadified);
V3Stats::addStatSum("Optimizations, FTasks, deadified, virtual",
m_statFTasksVirtDeadified);
};
};