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Avoid calling use_size() which could (in theory) be expensive if the global
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
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@ -231,8 +231,10 @@ static Constant *TraverseGEPInitializer(User *GEP, Constant *Init) {
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/// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
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/// users of the global, cleaning up the obvious ones. This is largely just a
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/// quick scan over the use list to clean up the easy and obvious cruft.
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static void CleanupConstantGlobalUsers(Value *V, Constant *Init) {
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/// quick scan over the use list to clean up the easy and obvious cruft. This
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/// returns true if it made a change.
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static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) {
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bool Changed = false;
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for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) {
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User *U = *UI++;
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@ -240,20 +242,27 @@ static void CleanupConstantGlobalUsers(Value *V, Constant *Init) {
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// Replace the load with the initializer.
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LI->replaceAllUsesWith(Init);
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LI->getParent()->getInstList().erase(LI);
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Changed = true;
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} else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
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// Store must be unreachable or storing Init into the global.
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SI->getParent()->getInstList().erase(SI);
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Changed = true;
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} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
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if (CE->getOpcode() == Instruction::GetElementPtr) {
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if (Constant *SubInit = TraverseGEPInitializer(CE, Init))
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CleanupConstantGlobalUsers(CE, SubInit);
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if (CE->use_empty()) CE->destroyConstant();
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Changed |= CleanupConstantGlobalUsers(CE, SubInit);
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if (CE->use_empty()) {
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CE->destroyConstant();
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Changed = true;
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}
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}
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} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
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if (Constant *SubInit = TraverseGEPInitializer(GEP, Init))
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CleanupConstantGlobalUsers(GEP, SubInit);
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if (GEP->use_empty())
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Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
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if (GEP->use_empty()) {
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GEP->getParent()->getInstList().erase(GEP);
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Changed = true;
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}
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} else if (Constant *C = dyn_cast<Constant>(U)) {
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// If we have a chain of dead constantexprs or other things dangling from
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// us, and if they are all dead, nuke them without remorse.
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@ -261,10 +270,11 @@ static void CleanupConstantGlobalUsers(Value *V, Constant *Init) {
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C->destroyConstant();
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// This could have incalidated UI, start over from scratch.x
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CleanupConstantGlobalUsers(V, Init);
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return;
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return true;
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}
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}
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}
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return Changed;
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}
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/// SRAGlobal - Perform scalar replacement of aggregates on the specified global
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@ -472,14 +482,10 @@ static bool ProcessInternalGlobal(GlobalVariable *GV, Module::giterator &GVI) {
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// Delete it now.
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if (!GS.isLoaded) {
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DEBUG(std::cerr << "GLOBAL NEVER LOADED: " << *GV);
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unsigned NumUsers = GV->use_size();
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// Delete any stores we can find to the global. We may not be able to
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// make it completely dead though.
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CleanupConstantGlobalUsers(GV, GV->getInitializer());
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// Did we delete any stores?
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bool Changed = NumUsers != GV->use_size();
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bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer());
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// If the global is dead now, delete it.
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if (GV->use_empty()) {
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