[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
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index 776bef3..fbd0165 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1725,6 +1725,15 @@
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;