Implement: -A*-B == A*B

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5740 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 79a551f70c887d83d2fbbb730d414cf11bec711f..067a884bc9d532a00165dc3a2783f02845798324 100644 (file)
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -342,6 +342,10 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
     }
   }
 
+  if (Value *Op0v = dyn_castNegVal(Op0))     // -X * -Y = X*Y
+    if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
+      return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
+
   return Changed ? &I : 0;
 }