#include "llvm/Instructions.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
-#include "Support/Debug.h"
-#include "Support/Statistic.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/ADT/Statistic.h"
+#include <set>
using namespace llvm;
namespace {
Pass *llvm::createGlobalConstifierPass() { return new Constifier(); }
+/// A lot of global constants are stored only in trivially dead setter
+/// functions. Because we don't want to cycle between globaldce and this pass,
+/// just do a simple check to catch the common case.
+static bool ContainingFunctionIsTriviallyDead(Instruction *I) {
+ Function *F = I->getParent()->getParent();
+ if (!F->hasInternalLinkage()) return false;
+ F->removeDeadConstantUsers();
+ return F->use_empty();
+}
+
/// isStoredThrough - Return false if the specified pointer is provably never
/// stored through. If we can't tell, we must conservatively assume it might.
///
-static bool isStoredThrough(Value *V) {
+static bool isStoredThrough(Value *V, std::set<PHINode*> &PHIUsers) {
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) {
- if (isStoredThrough(CE))
+ if (isStoredThrough(CE, PHIUsers))
return true;
} else if (Instruction *I = dyn_cast<Instruction>(*UI)) {
- if (I->getOpcode() == Instruction::GetElementPtr) {
- if (isStoredThrough(I)) return true;
- } else if (!isa<LoadInst>(*UI) && !isa<SetCondInst>(*UI))
- return true; // Any other non-load instruction might store!
+ if (!ContainingFunctionIsTriviallyDead(I)) {
+ if (I->getOpcode() == Instruction::GetElementPtr ||
+ I->getOpcode() == Instruction::Select) {
+ if (isStoredThrough(I, PHIUsers)) return true;
+ } else if (PHINode *PN = dyn_cast<PHINode>(I)) {
+ // PHI nodes we can check just like select or GEP instructions, but we
+ // have to be careful about infinite recursion.
+ if (PHIUsers.insert(PN).second) // Not already visited.
+ if (isStoredThrough(I, PHIUsers)) return true;
+
+ } else if (!isa<LoadInst>(I) && !isa<SetCondInst>(I)) {
+ return true; // Any other non-load instruction might store!
+ }
+ }
} else {
// Otherwise must be a global or some other user.
return true;
bool Constifier::run(Module &M) {
bool Changed = false;
+ std::set<PHINode*> PHIUsers;
for (Module::giterator GV = M.gbegin(), E = M.gend(); GV != E; ++GV)
if (!GV->isConstant() && GV->hasInternalLinkage() && GV->hasInitializer()) {
- if (!isStoredThrough(GV)) {
+ if (!isStoredThrough(GV, PHIUsers)) {
DEBUG(std::cerr << "MARKING CONSTANT: " << *GV << "\n");
GV->setConstant(true);
++NumMarked;
Changed = true;
}
+ PHIUsers.clear();
}
return Changed;
}