commit 1a8d5c3d1f43ebf7b07f1f009797e7d3eccebc60
author Sanjay Patel <spatel@rotateright.com> Sat Mar 03 17:53:25 2018 +0000
committer Sanjay Patel <spatel@rotateright.com> Sat Mar 03 17:53:25 2018 +0000
tree d0e252005e765d494b52480803e9eb14238216f3
parent 73eb2d255529c83e94b2e36d67060a14f60ce1a0

[InstCombine] (~X) - (~Y) --> Y - X

llvm-svn: 326660

llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index c47ebb3..b37b201 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1511,6 +1511,11 @@
   if (match(Op0, m_AllOnes()))
     return BinaryOperator::CreateNot(Op1);
 
+  // (~X) - (~Y) --> Y - X
+  Value *X, *Y;
+  if (match(Op0, m_Not(m_Value(X))) && match(Op1, m_Not(m_Value(Y))))
+    return BinaryOperator::CreateSub(Y, X);
+
   if (Constant *C = dyn_cast<Constant>(Op0)) {
     Value *X;
     // C - zext(bool) -> bool ? C - 1 : C