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Optimize dead functions without references (#6380)

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This commit is contained in:
Artur Bieniek
2025-09-05 13:23:43 -04:00
committed by GitHub
parent a364704e3a
commit 905c0c4f6d
11 changed files with 207 additions and 18 deletions
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src/V3Dead.cpp
+42 -8
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@@ -37,6 +37,8 @@
#include "V3Dead.h"
#include "V3Stats.h"
#include <vector>
VL_DEFINE_DEBUG_FUNCTIONS;
@@ -51,6 +53,7 @@ class DeadVisitor final : public VNVisitor {
// AstVar::user1() -> int. Count of number of references
// AstVarScope::user1() -> int. Count of number of references
// AstNodeDType::user1() -> int. Count of number of references
// AstNodeFTask::user1() -> int. Non-zero if ever referenced (called)
const VNUser1InUse m_inuser1;
// TYPES
@@ -69,6 +72,7 @@ class DeadVisitor final : public VNVisitor {
std::vector<AstCell*> m_cellsp;
std::vector<AstClass*> m_classesp;
std::vector<AstTypedef*> m_typedefsp;
std::vector<AstNodeFTask*> m_tasksp; // All the tasks that could be removed if not called
AssignMap m_assignMap; // List of all simple assignments for each variable
bool m_sideEffect = false; // Side effects discovered in assign RHS
@@ -78,6 +82,9 @@ class DeadVisitor final : public VNVisitor {
AstNodeModule* m_modp = nullptr; // Current module
AstSelLoopVars* m_selloopvarsp = nullptr; // Current loop vars
// STATE - Statistic tracking
VDouble0 m_statFTasksDeadified;
// METHODS
void deleting(AstNode* nodep) {
@@ -166,6 +173,7 @@ class DeadVisitor final : public VNVisitor {
void visit(AstNodeFTaskRef* nodep) override {
iterateChildren(nodep);
checkAll(nodep);
if (nodep->taskp()) nodep->taskp()->user1(1);
if (nodep->classOrPackagep()) {
if (m_elimCells) {
nodep->classOrPackagep(nullptr);
@@ -174,9 +182,10 @@ class DeadVisitor final : public VNVisitor {
}
}
}
void visit(AstMethodCall* nodep) override {
void visit(AstModportFTaskRef* nodep) override {
iterateChildren(nodep);
checkAll(nodep);
if (nodep->ftaskp()) nodep->ftaskp()->user1(1);
}
void visit(AstRefDType* nodep) override {
iterateChildren(nodep);
@@ -312,6 +321,19 @@ class DeadVisitor final : public VNVisitor {
}
if (assignInAssign) m_sideEffect = true; // Parent assign shouldn't optimize
}
void visit(AstNodeFTask* nodep) override {
iterateChildren(nodep);
checkAll(nodep);
if (!nodep->taskPublic() && !nodep->dpiExport() && !nodep->dpiImport())
m_tasksp.push_back(nodep);
if (nodep->classOrPackagep()) {
if (m_elimCells) {
nodep->classOrPackagep(nullptr);
} else {
nodep->classOrPackagep()->user1Inc();
}
}
}
//-----
void visit(AstClockingItem* nodep) override {
@@ -342,6 +364,15 @@ class DeadVisitor final : public VNVisitor {
return m_elimCells && !typedefp->attrPublic();
}
void deadCheckTasks() {
for (AstNodeFTask* taskp : m_tasksp) {
if (!taskp->user1() && !taskp->classMethod()) {
deleting(taskp);
m_statFTasksDeadified++;
}
}
}
void deadCheckMod() {
// Kill any unused modules
// V3LinkCells has a graph that is capable of this too, but we need to do it
@@ -515,7 +546,7 @@ class DeadVisitor final : public VNVisitor {
public:
// CONSTRUCTORS
DeadVisitor(AstNetlist* nodep, bool elimUserVars, bool elimDTypes, bool elimScopes,
bool elimCells, bool elimTopIfaces)
bool elimCells, bool elimTopIfaces, bool elimTasks)
: m_elimUserVars{elimUserVars}
, m_elimDTypes{elimDTypes}
, m_elimCells{elimCells} {
@@ -534,6 +565,7 @@ public:
if (itr.first->user1()) itr.second->user1Inc();
}
if (elimTasks) deadCheckTasks();
deadCheckTypedefs();
deadCheckVar();
// We only eliminate scopes when in a flattened structure
@@ -549,7 +581,9 @@ public:
nodep->typeTablep()->repairCache();
VIsCached::clearCacheTree(); // Removing assignments may affect isPure
}
~DeadVisitor() override = default;
~DeadVisitor() override {
V3Stats::addStatSum("Optimizations, deadified FTasks", m_statFTasksDeadified);
};
};
//######################################################################
@@ -558,31 +592,31 @@ public:
void V3Dead::deadifyModules(AstNetlist* nodep) {
UINFO(2, __FUNCTION__ << ":");
{ // node, elimUserVars, elimDTypes, elimScopes, elimCells, elimTopIfaces
DeadVisitor{nodep, false, false, false, false, !v3Global.opt.topIfacesSupported()};
DeadVisitor{nodep, false, false, false, false, !v3Global.opt.topIfacesSupported(), false};
} // Destruct before checking
V3Global::dumpCheckGlobalTree("deadModules", 0, dumpTreeEitherLevel() >= 6);
}
void V3Dead::deadifyDTypes(AstNetlist* nodep) {
UINFO(2, __FUNCTION__ << ":");
{ DeadVisitor{nodep, false, true, false, false, false}; } // Destruct before checking
{ DeadVisitor{nodep, false, true, false, false, false, true}; } // Destruct before checking
V3Global::dumpCheckGlobalTree("deadDtypes", 0, dumpTreeEitherLevel() >= 3);
}
void V3Dead::deadifyDTypesScoped(AstNetlist* nodep) {
UINFO(2, __FUNCTION__ << ":");
{ DeadVisitor{nodep, false, true, true, false, false}; } // Destruct before checking
{ DeadVisitor{nodep, false, true, true, false, false, false}; } // Destruct before checking
V3Global::dumpCheckGlobalTree("deadDtypesScoped", 0, dumpTreeEitherLevel() >= 3);
}
void V3Dead::deadifyAll(AstNetlist* nodep) {
UINFO(2, __FUNCTION__ << ":");
{ DeadVisitor{nodep, true, true, false, true, false}; } // Destruct before checking
{ DeadVisitor{nodep, true, true, false, true, false, false}; } // Destruct before checking
V3Global::dumpCheckGlobalTree("deadAll", 0, dumpTreeEitherLevel() >= 3);
}
void V3Dead::deadifyAllScoped(AstNetlist* nodep) {
UINFO(2, __FUNCTION__ << ":");
{ DeadVisitor{nodep, true, true, true, true, false}; } // Destruct before checking
{ DeadVisitor{nodep, true, true, true, true, false, false}; } // Destruct before checking
V3Global::dumpCheckGlobalTree("deadAllScoped", 0, dumpTreeEitherLevel() >= 3);
}