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[InstCombine] Fold IntToPtr and PtrToInt into preceding loads.

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Currently we only fold a BitCast into a Load when the BitCast is its
only user.

Do the same for any no-op cast.

Differential Revision: http://reviews.llvm.org/D9152

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238452 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer
2015-05-28 18:39:17 +00:00
parent ef1de3295a
commit 967f6ad3e1
3 changed files with 167 additions and 5 deletions
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15
lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
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@@ -483,12 +483,17 @@ static Instruction *combineLoadToOperationType(InstCombiner &IC, LoadInst &LI) {
}
// Fold away bit casts of the loaded value by loading the desired type.
// We can do this for BitCastInsts as well as casts from and to pointer types,
// as long as those are noops (i.e., the source or dest type have the same
// bitwidth as the target's pointers).
if (LI.hasOneUse())
if (auto *BC = dyn_cast<BitCastInst>(LI.user_back())) {
LoadInst *NewLoad = combineLoadToNewType(IC, LI, BC->getDestTy());
BC->replaceAllUsesWith(NewLoad);
IC.EraseInstFromFunction(*BC);
return &LI;
if (auto* CI = dyn_cast<CastInst>(LI.user_back())) {
if (CI->isNoopCast(DL)) {
LoadInst *NewLoad = combineLoadToNewType(IC, LI, CI->getDestTy());
CI->replaceAllUsesWith(NewLoad);
IC.EraseInstFromFunction(*CI);
return &LI;
}
}
// FIXME: We should also canonicalize loads of vectors when their elements are