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InstCombine: Don't shrink allocas when combining with a bitcast.

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When considering folding a bitcast of an alloca into the alloca itself,
make sure we don't shrink the amount of memory being allocated, or
things rapidly go sideways.

rdar://13324424

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176547 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jim Grosbach
2013-03-06 05:44:53 +00:00
parent 508d11b19c
commit 186d8a3d67
3 changed files with 52 additions and 1 deletions
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6
lib/Transforms/InstCombine/InstCombineCasts.cpp
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@@ -104,6 +104,12 @@ Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI,
uint64_t CastElTySize = TD->getTypeAllocSize(CastElTy);
if (CastElTySize == 0 || AllocElTySize == 0) return 0;
// If the allocation has multiple uses, only promote it if we're not
// shrinking the amount of memory being allocated.
uint64_t AllocElTyStoreSize = TD->getTypeStoreSize(AllocElTy);
uint64_t CastElTyStoreSize = TD->getTypeStoreSize(CastElTy);
if (!AI.hasOneUse() && CastElTyStoreSize < AllocElTyStoreSize) return 0;
// See if we can satisfy the modulus by pulling a scale out of the array
// size argument.
unsigned ArraySizeScale;