Avoid undefined behavior in negation in LSR. Patch by Ahmed Charles.

Someone more familiar with LSR should double-check that the extra cast is actually doing the right thing in the overflow cases; I'm not completely confident that's that case.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141916 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index d03b86a..3e122c2 100644 (file)
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -1205,7 +1205,7 @@ static bool isLegalUse(const TargetLowering::AddrMode &AM,
     // If we have low-level target information, ask the target if it can fold an
     // integer immediate on an icmp.
     if (AM.BaseOffs != 0) {
-      if (TLI) return TLI->isLegalICmpImmediate(-AM.BaseOffs);
+      if (TLI) return TLI->isLegalICmpImmediate(-(uint64_t)AM.BaseOffs);
       return false;
     }
 
@@ -3593,7 +3593,7 @@ Value *LSRInstance::Expand(const LSRFixup &LF,
       // The other interesting way of "folding" with an ICmpZero is to use a
       // negated immediate.
       if (!ICmpScaledV)
-        ICmpScaledV = ConstantInt::get(IntTy, -Offset);
+        ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
       else {
         Ops.push_back(SE.getUnknown(ICmpScaledV));
         ICmpScaledV = ConstantInt::get(IntTy, Offset);