[InstCombine] Fold sub (and A, B) (or A, B)) to neg (xor A, B)

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

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

https://rise4fun.com/Alive/VI6

Found by @lebedev.ri. Also author of the proof.

Reviewers: lebedev.ri, spatel

Reviewed By: lebedev.ri

Subscribers: llvm-commits, lebedev.ri

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67155

llvm-svn: 370934

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index 776bef36abf..fbd0165cd2d 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1725,6 +1725,15 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
       return BinaryOperator::CreateXor(A, B);
   }
 
+  // (sub (and A, B) (or A, B)) --> neg (xor A, B)
+  {
+    Value *A, *B;
+    if (match(Op0, m_And(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.CreateXor(A, B));
+  }
+
   // (sub (or A, B), (xor A, B)) --> (and A, B)
   {
     Value *A, *B;