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[InstCombine] Properly combine metadata when replacing a load with another

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Not doing this can lead to misoptimizations down the line, e.g. because
of range metadata on the replacing load excluding values that are valid
for the load that is being replaced.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241886 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bjorn Steinbrink
2015-07-10 06:55:44 +00:00
parent dde12814c7
commit ad4d73941a
2 changed files with 49 additions and 1 deletions
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19
lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
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@@ -749,10 +749,27 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
// where there are several consecutive memory accesses to the same location,
// separated by a few arithmetic operations.
BasicBlock::iterator BBI = &LI;
if (Value *AvailableVal = FindAvailableLoadedValue(Op, LI.getParent(), BBI,6))
AAMDNodes AATags;
if (Value *AvailableVal = FindAvailableLoadedValue(Op, LI.getParent(), BBI,
6, nullptr, &AATags)) {
if (LoadInst *NLI = dyn_cast<LoadInst>(AvailableVal)) {
unsigned KnownIDs[] = {
LLVMContext::MD_tbaa,
LLVMContext::MD_alias_scope,
LLVMContext::MD_noalias,
LLVMContext::MD_range,
LLVMContext::MD_invariant_load,
LLVMContext::MD_nonnull,
};
combineMetadata(NLI, &LI, KnownIDs);
if (AATags)
NLI->setAAMetadata(AATags);
};
return ReplaceInstUsesWith(
LI, Builder->CreateBitOrPointerCast(AvailableVal, LI.getType(),
LI.getName() + ".cast"));
}
// load(gep null, ...) -> unreachable
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) {