[llvm] r215524 - InstCombine: Combine (xor (or %a, %b) (xor %a, %b)) to (add %a, %b)
Karthik Bhat
kv.bhat at samsung.com
Tue Aug 12 22:13:15 PDT 2014
Author: karthik
Date: Wed Aug 13 00:13:14 2014
New Revision: 215524
URL: http://llvm.org/viewvc/llvm-project?rev=215524&view=rev
Log:
InstCombine: Combine (xor (or %a, %b) (xor %a, %b)) to (add %a, %b)
Correctness proof of the transform using CVC3-
$ cat t.cvc
A, B : BITVECTOR(32);
QUERY BVXOR(A | B, BVXOR(A,B) ) = A & B;
$ cvc3 t.cvc
Valid.
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
llvm/trunk/test/Transforms/InstCombine/or-xor.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp?rev=215524&r1=215523&r2=215524&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp Wed Aug 13 00:13:14 2014
@@ -2508,6 +2508,18 @@ Instruction *InstCombiner::visitXor(Bina
if ((A == C && B == D) || (A == D && B == C))
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)))) {
+ if ((A == C && B == D) || (A == D && B == C))
+ return BinaryOperator::CreateAnd(A, B);
+ }
+ // (A | B)^(A ^ B) -> A & B
+ if (match(Op0I, m_Or(m_Value(A), m_Value(B))) &&
+ match(Op1I, m_Xor(m_Value(C), m_Value(D)))) {
+ if ((A == C && B == D) || (A == D && B == C))
+ return BinaryOperator::CreateAnd(A, B);
+ }
// (A & B) ^ (A ^ B) -> (A | B)
if (match(Op0I, m_And(m_Value(A), m_Value(B))) &&
match(Op1I, m_Xor(m_Specific(A), m_Specific(B))))
Modified: llvm/trunk/test/Transforms/InstCombine/or-xor.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/or-xor.ll?rev=215524&r1=215523&r2=215524&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/or-xor.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/or-xor.ll Wed Aug 13 00:13:14 2014
@@ -136,3 +136,14 @@ define i32 @test13(i32 %x, i32 %y) {
; CHECK-NEXT: %and = and i32 %x, %y
; CHECK-NEXT: ret i32 %and
}
+
+; ((x | y) ^ (x ^ y)) -> (x & y)
+define i32 @test15(i32 %x, i32 %y) {
+ %1 = xor i32 %y, %x
+ %2 = or i32 %y, %x
+ %3 = xor i32 %2, %1
+ ret i32 %3
+; CHECK-LABEL: @test15(
+; CHECK-NEXT: %1 = and i32 %y, %x
+; CHECK-NEXT: ret i32 %1
+}
More information about the llvm-commits
mailing list