InstSimplify: X >> X -> 0

[oota-llvm.git] / lib / Analysis / InstructionSimplify.cpp

diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index bf7745143da7d551ff54f02facdf2afbd6f63af1..d66ecca928aa854e66d5f76113d81557e95433cd 100644 (file)
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -1363,6 +1363,10 @@ static Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact,
   if (Value *V = SimplifyShift(Instruction::LShr, Op0, Op1, Q, MaxRecurse))
     return V;
 
+  // X >> X -> 0
+  if (Op0 == Op1)
+    return Constant::getNullValue(Op0->getType());
+
   // undef >>l X -> 0
   if (match(Op0, m_Undef()))
     return Constant::getNullValue(Op0->getType());
@@ -1391,6 +1395,10 @@ static Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact,
   if (Value *V = SimplifyShift(Instruction::AShr, Op0, Op1, Q, MaxRecurse))
     return V;
 
+  // X >> X -> 0
+  if (Op0 == Op1)
+    return Constant::getNullValue(Op0->getType());
+
   // all ones >>a X -> all ones
   if (match(Op0, m_AllOnes()))
     return Op0;