[llvm] r215524 - InstCombine: Combine (xor (or %a, %b) (xor %a, %b)) to (add %a, %b)

[Karthik Bhat]

Hi David,
Apologies for the bad variable name in the test cases. I somehow missed the
comments. Will update the test case along with next patch.
Regards
Karthik Bhat



On Thu, Aug 14, 2014 at 4:54 AM, Jonathan Roelofs <jonathan at codesourcery.com
> wrote:

>
>
> On 8/13/14, 5:05 PM, David Majnemer wrote:
>
>> On Tue, Aug 12, 2014 at 10:13 PM, Karthik Bhat <kv.bhat at samsung.com
>> <mailto:kv.bhat at samsung.com>> wrote:
>>
>>     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)
>>
> s/add/and/
>
> Unfortunately too late to fix as it's in the commit message.
>
>>
>>     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
>>
>>
>> I LGTM'd this differential under the understanding that you would clean
>> up the
>> variable names used: http://reviews.llvm.org/D4866#inline-40056
>>
>> Please fix test15.
>>
>>     +}
>>
>>
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>>
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> --
> Jon Roelofs
> jonathan at codesourcery.com
> CodeSourcery / Mentor Embedded
>
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