[llvm] r310186 - [InstCombine] Fold (C - X) ^ signmask -> (C + signmask - X).

[Chandler Carruth via llvm-commits]

Doh, you landed the fix as I wrote the email, sorry for that and thanks!

On Sat, Aug 5, 2017 at 3:46 PM Chandler Carruth <chandlerc at gmail.com> wrote:

> Pretty sure this broke most of the build bots:
> http://lab.llvm.org:8011/builders/clang-x86_64-debian-fast/builds/5829
>
> On Sat, Aug 5, 2017 at 1:01 PM Craig Topper via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Author: ctopper
>> Date: Sat Aug  5 13:00:44 2017
>> New Revision: 310186
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=310186&view=rev
>> Log:
>> [InstCombine] Fold (C - X) ^ signmask -> (C + signmask - X).
>>
>> Modified:
>>     llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
>>     llvm/trunk/test/Transforms/InstCombine/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=310186&r1=310185&r2=310186&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
>> (original)
>> +++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp Sat
>> Aug  5 13:00:44 2017
>> @@ -2422,11 +2422,17 @@ Instruction *InstCombiner::visitXor(Bina
>>    if (ConstantInt *RHSC = dyn_cast<ConstantInt>(Op1)) {
>>      if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
>>        // ~(c-X) == X-c-1 == X+(-c-1)
>> -      if (Op0I->getOpcode() == Instruction::Sub && RHSC->isMinusOne())
>> -        if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
>> -          Constant *NegOp0I0C = ConstantExpr::getNeg(Op0I0C);
>> -          return BinaryOperator::CreateAdd(Op0I->getOperand(1),
>> -                                           SubOne(NegOp0I0C));
>> +      if (Op0I->getOpcode() == Instruction::Sub)
>> +        if (ConstantInt *Op0I0C =
>> dyn_cast<ConstantInt>(Op0I->getOperand(0))) {
>> +          if (RHSC->isMinusOne()) {
>> +            Constant *NegOp0I0C = ConstantExpr::getNeg(Op0I0C);
>> +            return BinaryOperator::CreateAdd(Op0I->getOperand(1),
>> +                                             SubOne(NegOp0I0C));
>> +          } else if (RHSC->getValue().isSignMask()) {
>> +            // (C - X) ^ signmask -> (C + signmask - X)
>> +            Constant *C = Builder.getInt(RHSC->getValue() +
>> Op0I0C->getValue());
>> +            return BinaryOperator::CreateSub(C, Op0I->getOperand(1));
>> +          }
>>          }
>>
>>        if (ConstantInt *Op0CI =
>> dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
>> @@ -2440,7 +2446,6 @@ Instruction *InstCombiner::visitXor(Bina
>>              // (X + C) ^ signmask -> (X + C + signmask)
>>              Constant *C = Builder.getInt(RHSC->getValue() +
>> Op0CI->getValue());
>>              return BinaryOperator::CreateAdd(Op0I->getOperand(0), C);
>> -
>>            }
>>          } else if (Op0I->getOpcode() == Instruction::Or) {
>>            // (X|C1)^C2 -> X^(C1|C2) iff X&~C1 == 0
>>
>> Modified: llvm/trunk/test/Transforms/InstCombine/xor.ll
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/xor.ll?rev=310186&r1=310185&r2=310186&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/test/Transforms/InstCombine/xor.ll (original)
>> +++ llvm/trunk/test/Transforms/InstCombine/xor.ll Sat Aug  5 13:00:44 2017
>> @@ -353,6 +353,15 @@ define i32 @test28(i32 %indvar) {
>>    ret i32 %t214
>>  }
>>
>> +define i32 @test28_sub(i32 %indvar) {
>> +; CHECK-LABEL: @test28_sub(
>> +; CHECK-NEXT:    ret i32 -2147483648 <(214)%20748-3648>
>> +;
>> +  %t7 = sub i32 -2147483647 <(214)%20748-3647>, %indvar
>> +  %t214 = xor i32 %t7, -2147483648 <(214)%20748-3648>
>> +  ret i32 %t214
>> +}
>> +
>>  define i32 @test29(i1 %C) {
>>  ; CHECK-LABEL: @test29(
>>  ; CHECK-NEXT:    [[V:%.*]] = select i1 [[C:%.*]], i32 915, i32 113
>>
>>
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>>
>
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