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InstCombine: ((A | ~B) ^ (~A | B)) to A ^ B

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Proof using CVC3 follows:
$ cat t.cvc
A, B : BITVECTOR(32);
QUERY BVXOR((A | ~B),(~A |B)) = BVXOR(A,B);
$ cvc3 t.cvc
Valid.

Patch by Mayur Pandey!

Differential Revision: http://reviews.llvm.org/D4883

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215621 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer 2014-08-14 06:46:25 +00:00
parent 8c651f5c26
commit eb323b2b3c
2 changed files with 23 additions and 0 deletions
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10
lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -2512,6 +2512,16 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
if ((A == C && B == D) || (A == D && B == C))
return BinaryOperator::CreateXor(A, B);
}
// (A | ~B) ^ (~A | B) -> A ^ B
if (match(Op0I, m_Or(m_Value(A), m_Not(m_Value(B)))) &&
match(Op1I, m_Or(m_Not(m_Specific(A)), m_Specific(B)))) {
return BinaryOperator::CreateXor(A, B);
}
// (~A | B) ^ (A | ~B) -> A ^ B
if (match(Op0I, m_Or(m_Not(m_Value(A)), m_Value(B))) &&
match(Op1I, m_Or(m_Specific(A), m_Not(m_Specific(B))))) {
return BinaryOperator::CreateXor(A, B);
}
// (A ^ B)^(A | B) -> A & B
if (match(Op0I, m_Xor(m_Value(A), m_Value(B))) &&
match(Op1I, m_Or(m_Value(C), m_Value(D)))) {

13
test/Transforms/InstCombine/or-xor.ll
View File

@ -147,3 +147,16 @@ define i32 @test15(i32 %x, i32 %y) {
; CHECK-NEXT: %1 = and i32 %y, %x
; CHECK-NEXT: ret i32 %1
}
; ((x | ~y) ^ (~x | y)) -> x ^ y
define i32 @test16(i32 %x, i32 %y) {
%noty = xor i32 %y, -1
%notx = xor i32 %x, -1
%or1 = or i32 %x, %noty
%or2 = or i32 %notx, %y
%xor = xor i32 %or1, %or2
ret i32 %xor
; CHECK-LABEL: @test16(
; CHECK-NEXT: %xor = xor i32 %x, %y
; CHECK-NEXT: ret i32 %xor
}