Fix INT_MIN gotcha pointed out by Eli Friedman.

llvm-svn: 128028

1 files changed, 4 insertions, 3 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index c36f68c2aeb..0f4bfb7b0d9 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -725,9 +725,10 @@ bool llvm::isPowerOfTwo(Value *V, const TargetData *TD, unsigned Depth) {
       isPowerOfTwo(SI->getFalseValue(), TD, Depth);
 
   // An exact divide or right shift can only shift off zero bits, so the result
-  // is a power of two only if the first operand is a power of two.
-  if (match(V, m_Shr(m_Value(), m_Value())) ||
-      match(V, m_IDiv(m_Value(), m_Value()))) {
+  // is a power of two only if the first operand is a power of two and not
+  // copying a sign bit (sdiv int_min, 2).
+  if (match(V, m_LShr(m_Value(), m_Value())) ||
+      match(V, m_UDiv(m_Value(), m_Value()))) {
     BinaryOperator *BO = cast<BinaryOperator>(V);
     if (BO->isExact())
       return isPowerOfTwo(BO->getOperand(0), TD, Depth);