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If a global constant is dead then global's debug info should not prevent the optimizer in deleting the global. And while deleting global, delete global's debug info also.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@65994 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel
2009-03-04 01:22:23 +00:00
parent 0d6596b7bf
commit 7f6179d1d8
2 changed files with 72 additions and 6 deletions
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lib/Transforms/IPO/GlobalOpt.cpp
+20 -6
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@@ -137,15 +137,23 @@ struct VISIBILITY_HIDDEN GlobalStatus {
}
/// ConstantIsDead - Return true if the specified constant is (transitively)
/// dead. The constant may be used by other constants (e.g. constant arrays and
/// constant exprs) as long as they are dead, but it cannot be used by anything
/// else.
static bool ConstantIsDead(Constant *C) {
/// dead. The constant may be used by other constants (e.g. constant arrays,
/// constant exprs, constant global variables) as long as they are dead,
/// but it cannot be used by anything else. If DeadGVs is not null then
/// record dead constant GV users.
static bool ConstantIsDead(Constant *C,
SmallPtrSet<GlobalVariable *, 4> *DeadGVs = false) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
if (GV->hasLocalLinkage() && GV->use_empty()) {
if (DeadGVs)
DeadGVs->insert(GV);
return true;
}
if (isa<GlobalValue>(C)) return false;
for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI)
if (Constant *CU = dyn_cast<Constant>(*UI)) {
if (!ConstantIsDead(CU)) return false;
if (!ConstantIsDead(CU, DeadGVs)) return false;
} else
return false;
return true;
@@ -338,7 +346,13 @@ static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) {
} else if (Constant *C = dyn_cast<Constant>(U)) {
// If we have a chain of dead constantexprs or other things dangling from
// us, and if they are all dead, nuke them without remorse.
if (ConstantIsDead(C)) {
SmallPtrSet<GlobalVariable *, 4> DeadGVs;
if (ConstantIsDead(C, &DeadGVs)) {
for (SmallPtrSet<GlobalVariable *, 4>::iterator TI = DeadGVs.begin(),
TE = DeadGVs.end(); TI != TE; ) {
GlobalVariable *TGV = *TI; ++TI;
TGV->eraseFromParent();
}
C->destroyConstant();
// This could have invalidated UI, start over from scratch.
CleanupConstantGlobalUsers(V, Init);