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

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

Differential Revision: http://reviews.llvm.org/D4898

llvm-svn: 215974
This commit is contained in:
Mayur Pandey 2014-08-19 08:19:19 +00:00
parent 97ebe53032
commit 960507beb4
2 changed files with 23 additions and 0 deletions
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10
llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -2522,6 +2522,16 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
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_And(m_Value(A), m_Not(m_Value(B)))) &&
match(Op1I, m_And(m_Not(m_Specific(A)), m_Specific(B)))) {
return BinaryOperator::CreateXor(A, B);
}
// (~A & B) ^ (A & ~B) -> A ^ B
if (match(Op0I, m_And(m_Not(m_Value(A)), m_Value(B))) &&
match(Op1I, m_And(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
llvm/test/Transforms/InstCombine/or-xor.ll
View File

@ -160,3 +160,16 @@ define i32 @test16(i32 %x, i32 %y) {
; CHECK-NEXT: %xor = xor i32 %x, %y
; CHECK-NEXT: ret i32 %xor
}
; ((x & ~y) ^ (~x & y)) -> x ^ y
define i32 @test17(i32 %x, i32 %y) {
%noty = xor i32 %y, -1
%notx = xor i32 %x, -1
%and1 = and i32 %x, %noty
%and2 = and i32 %notx, %y
%xor = xor i32 %and1, %and2
ret i32 %xor
; CHECK-LABEL: @test17(
; CHECK-NEXT: %xor = xor i32 %x, %y
; CHECK-NEXT: ret i32 %xor
}