#define DEBUG_TYPE "globaldce"
#include "llvm/Transforms/IPO.h"
#include "llvm/Constants.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
using namespace llvm;
STATISTIC(NumAliases , "Number of global aliases removed");
STATISTIC(NumFunctions, "Number of functions removed");
STATISTIC(NumVariables, "Number of global variables removed");
namespace {
struct GlobalDCE : public ModulePass {
static char ID; GlobalDCE() : ModulePass(ID) {
initializeGlobalDCEPass(*PassRegistry::getPassRegistry());
}
bool runOnModule(Module &M);
private:
SmallPtrSet<GlobalValue*, 32> AliveGlobals;
void GlobalIsNeeded(GlobalValue *GV);
void MarkUsedGlobalsAsNeeded(Constant *C);
bool RemoveUnusedGlobalValue(GlobalValue &GV);
};
}
char GlobalDCE::ID = 0;
INITIALIZE_PASS(GlobalDCE, "globaldce",
"Dead Global Elimination", false, false)
ModulePass *llvm::createGlobalDCEPass() { return new GlobalDCE(); }
bool GlobalDCE::runOnModule(Module &M) {
bool Changed = false;
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
Changed |= RemoveUnusedGlobalValue(*I);
if (!I->hasLocalLinkage() && !I->hasLinkOnceLinkage() &&
!I->isDeclaration() && !I->hasAvailableExternallyLinkage())
GlobalIsNeeded(I);
}
for (Module::global_iterator I = M.global_begin(), E = M.global_end();
I != E; ++I) {
Changed |= RemoveUnusedGlobalValue(*I);
if (!I->hasLocalLinkage() && !I->hasLinkOnceLinkage() &&
!I->isDeclaration() && !I->hasAvailableExternallyLinkage())
GlobalIsNeeded(I);
}
for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
I != E; ++I) {
Changed |= RemoveUnusedGlobalValue(*I);
if (!I->hasLocalLinkage() && !I->hasLinkOnceLinkage())
GlobalIsNeeded(I);
}
std::vector<GlobalVariable*> DeadGlobalVars; for (Module::global_iterator I = M.global_begin(), E = M.global_end();
I != E; ++I)
if (!AliveGlobals.count(I)) {
DeadGlobalVars.push_back(I); I->setInitializer(0);
}
std::vector<Function*> DeadFunctions;
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
if (!AliveGlobals.count(I)) {
DeadFunctions.push_back(I); if (!I->isDeclaration())
I->deleteBody();
}
std::vector<GlobalAlias*> DeadAliases;
for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end(); I != E;
++I)
if (!AliveGlobals.count(I)) {
DeadAliases.push_back(I);
I->setAliasee(0);
}
if (!DeadFunctions.empty()) {
for (unsigned i = 0, e = DeadFunctions.size(); i != e; ++i) {
RemoveUnusedGlobalValue(*DeadFunctions[i]);
M.getFunctionList().erase(DeadFunctions[i]);
}
NumFunctions += DeadFunctions.size();
Changed = true;
}
if (!DeadGlobalVars.empty()) {
for (unsigned i = 0, e = DeadGlobalVars.size(); i != e; ++i) {
RemoveUnusedGlobalValue(*DeadGlobalVars[i]);
M.getGlobalList().erase(DeadGlobalVars[i]);
}
NumVariables += DeadGlobalVars.size();
Changed = true;
}
if (!DeadAliases.empty()) {
for (unsigned i = 0, e = DeadAliases.size(); i != e; ++i) {
RemoveUnusedGlobalValue(*DeadAliases[i]);
M.getAliasList().erase(DeadAliases[i]);
}
NumAliases += DeadAliases.size();
Changed = true;
}
AliveGlobals.clear();
return Changed;
}
void GlobalDCE::GlobalIsNeeded(GlobalValue *G) {
if (!AliveGlobals.insert(G))
return;
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G)) {
if (GV->hasInitializer())
MarkUsedGlobalsAsNeeded(GV->getInitializer());
} else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(G)) {
MarkUsedGlobalsAsNeeded(GA->getAliasee());
} else {
Function *F = cast<Function>(G);
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
for (User::op_iterator U = I->op_begin(), E = I->op_end(); U != E; ++U)
if (GlobalValue *GV = dyn_cast<GlobalValue>(*U))
GlobalIsNeeded(GV);
else if (Constant *C = dyn_cast<Constant>(*U))
MarkUsedGlobalsAsNeeded(C);
}
}
void GlobalDCE::MarkUsedGlobalsAsNeeded(Constant *C) {
if (GlobalValue *GV = dyn_cast<GlobalValue>(C))
return GlobalIsNeeded(GV);
for (User::op_iterator I = C->op_begin(), E = C->op_end(); I != E; ++I)
if (Constant *OpC = dyn_cast<Constant>(*I))
MarkUsedGlobalsAsNeeded(OpC);
}
bool GlobalDCE::RemoveUnusedGlobalValue(GlobalValue &GV) {
if (GV.use_empty()) return false;
GV.removeDeadConstantUsers();
return GV.use_empty();
}