When user code intentionally dereferences null, the alignment of the
dereference is theoretically infinite. Put a cap on the computed
alignment to avoid overflow, noticed by John Regehr.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109596 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index fc62bb0..0d5e302 100644
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -96,12 +96,17 @@
/// increase the alignment of the ultimate object, making this check succeed.
unsigned InstCombiner::GetOrEnforceKnownAlignment(Value *V,
unsigned PrefAlign) {
- unsigned BitWidth = TD ? TD->getTypeSizeInBits(V->getType()) :
- sizeof(PrefAlign) * CHAR_BIT;
+ assert(V->getType()->isPointerTy() &&
+ "GetOrEnforceKnownAlignment expects a pointer!");
+ unsigned BitWidth = TD ? TD->getPointerSizeInBits() : 64;
APInt Mask = APInt::getAllOnesValue(BitWidth);
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
ComputeMaskedBits(V, Mask, KnownZero, KnownOne);
unsigned TrailZ = KnownZero.countTrailingOnes();
+
+ // LLVM doesn't support alignments larger than this currently.
+ TrailZ = std::min(TrailZ, unsigned(sizeof(unsigned) * CHAR_BIT - 1));
+
unsigned Align = 1u << std::min(BitWidth - 1, TrailZ);
if (PrefAlign > Align)