InstCombine: Don't shrink allocas when combining with a bitcast.
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
diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp
index a960ab2..d162223 100644
--- a/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -104,6 +104,12 @@
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;