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Avoid calling use_size() which could (in theory) be expensive if the global

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has a large number of users.  Instead, just keep track of whether we're
making changes as we do so.

This patch has no functionlity changes.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16874 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-10-10 16:43:46 +00:00
parent cbb9812d0d
commit 031955d462
1 changed files with 18 additions and 12 deletions
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30
lib/Transforms/IPO/GlobalOpt.cpp
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@ -231,8 +231,10 @@ static Constant *TraverseGEPInitializer(User *GEP, Constant *Init) {
/// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
/// users of the global, cleaning up the obvious ones. This is largely just a
/// quick scan over the use list to clean up the easy and obvious cruft.
static void CleanupConstantGlobalUsers(Value *V, Constant *Init) {
/// quick scan over the use list to clean up the easy and obvious cruft. This
/// returns true if it made a change.
static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) {
bool Changed = false;
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) {
User *U = *UI++;
@ -240,20 +242,27 @@ static void CleanupConstantGlobalUsers(Value *V, Constant *Init) {
// Replace the load with the initializer.
LI->replaceAllUsesWith(Init);
LI->getParent()->getInstList().erase(LI);
Changed = true;
} else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
// Store must be unreachable or storing Init into the global.
SI->getParent()->getInstList().erase(SI);
Changed = true;
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
if (CE->getOpcode() == Instruction::GetElementPtr) {
if (Constant *SubInit = TraverseGEPInitializer(CE, Init))
CleanupConstantGlobalUsers(CE, SubInit);
if (CE->use_empty()) CE->destroyConstant();
Changed |= CleanupConstantGlobalUsers(CE, SubInit);
if (CE->use_empty()) {
CE->destroyConstant();
Changed = true;
}
}
} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
if (Constant *SubInit = TraverseGEPInitializer(GEP, Init))
CleanupConstantGlobalUsers(GEP, SubInit);
if (GEP->use_empty())
Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
if (GEP->use_empty()) {
GEP->getParent()->getInstList().erase(GEP);
Changed = true;
}
} 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.
@ -261,10 +270,11 @@ static void CleanupConstantGlobalUsers(Value *V, Constant *Init) {
C->destroyConstant();
// This could have incalidated UI, start over from scratch.x
CleanupConstantGlobalUsers(V, Init);
return;
return true;
}
}
}
return Changed;
}
/// SRAGlobal - Perform scalar replacement of aggregates on the specified global
@ -472,14 +482,10 @@ static bool ProcessInternalGlobal(GlobalVariable *GV, Module::giterator &GVI) {
// Delete it now.
if (!GS.isLoaded) {
DEBUG(std::cerr << "GLOBAL NEVER LOADED: " << *GV);
unsigned NumUsers = GV->use_size();
// Delete any stores we can find to the global. We may not be able to
// make it completely dead though.
CleanupConstantGlobalUsers(GV, GV->getInitializer());
// Did we delete any stores?
bool Changed = NumUsers != GV->use_size();
bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer());
// If the global is dead now, delete it.
if (GV->use_empty()) {