[InstCombine] sub(xor(x, y), or(x, y)) -> neg(and(x, y))

Summary:
```
Name: sub(xor(x, y), or(x, y)) -> neg(and(x, y))
%or = or i32 %y, %x
%xor = xor i32 %x, %y
%sub = sub i32 %xor, %or
  =>
%sub1 = and i32 %x, %y
%sub = sub i32 0, %sub1

Optimization: sub(xor(x, y), or(x, y)) -> neg(and(x, y))
Done: 1
Optimization is correct!
```

https://rise4fun.com/Alive/8OI

Reviewers: lebedev.ri

Reviewed By: lebedev.ri

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67188

llvm-svn: 370945

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index fbd0165cd2d..9d640e849dc 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1742,6 +1742,15 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
       return BinaryOperator::CreateAnd(A, B);
   }
 
+  // (sub (xor A, B) (or A, B)) --> neg (and A, B)
+  {
+    Value *A, *B;
+    if (match(Op0, m_Xor(m_Value(A), m_Value(B))) &&
+        match(Op1, m_c_Or(m_Specific(A), m_Specific(B))) &&
+        (Op0->hasOneUse() || Op1->hasOneUse()))
+      return BinaryOperator::CreateNeg(Builder.CreateAnd(A, B));
+  }
+
   {
     Value *Y;
     // ((X | Y) - X) --> (~X & Y)