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

[Chandler Carruth via llvm-commits]

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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