[llvm] r299658 - [InstCombine] Fix a case where we weren't checking that an instruction had a single use resulting in extra instructions being created.

[Friedman, Eli via llvm-commits]

On 4/6/2017 9:42 AM, Craig Topper via llvm-commits wrote:
> Author: ctopper
> Date: Thu Apr  6 11:42:46 2017
> New Revision: 299658
>
> URL: http://llvm.org/viewvc/llvm-project?rev=299658&view=rev
> Log:
> [InstCombine] Fix a case where we weren't checking that an instruction had a single use resulting in extra instructions being created.

Testcase?

-Eli

>
> Modified:
>      llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
>
> Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp?rev=299658&r1=299657&r2=299658&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp (original)
> +++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp Thu Apr  6 11:42:46 2017
> @@ -1332,18 +1332,21 @@ Instruction *InstCombiner::visitAnd(Bina
>           // ((A & N) + B) & AndRHS -> (A + B) & AndRHS iff N&AndRHS == AndRHS.
>           // ((A | N) + B) & AndRHS -> (A + B) & AndRHS iff N&AndRHS == 0
>           // ((A ^ N) + B) & AndRHS -> (A + B) & AndRHS iff N&AndRHS == 0
> -        if (Value *V = FoldLogicalPlusAnd(Op0LHS, Op0RHS, AndRHS, false, I))
> -          return BinaryOperator::CreateAnd(V, AndRHS);
> -        if (Value *V = FoldLogicalPlusAnd(Op0RHS, Op0LHS, AndRHS, false, I))
> -          return BinaryOperator::CreateAnd(V, AndRHS);  // Add commutes
> +        if (Op0I->hasOneUse()) {
> +          if (Value *V = FoldLogicalPlusAnd(Op0LHS, Op0RHS, AndRHS, false, I))
> +            return BinaryOperator::CreateAnd(V, AndRHS);
> +          if (Value *V = FoldLogicalPlusAnd(Op0RHS, Op0LHS, AndRHS, false, I))
> +            return BinaryOperator::CreateAnd(V, AndRHS);  // Add commutes
> +        }
>           break;
>   
>         case Instruction::Sub:
>           // ((A & N) - B) & AndRHS -> (A - B) & AndRHS iff N&AndRHS == AndRHS.
>           // ((A | N) - B) & AndRHS -> (A - B) & AndRHS iff N&AndRHS == 0
>           // ((A ^ N) - B) & AndRHS -> (A - B) & AndRHS iff N&AndRHS == 0
> -        if (Value *V = FoldLogicalPlusAnd(Op0LHS, Op0RHS, AndRHS, true, I))
> -          return BinaryOperator::CreateAnd(V, AndRHS);
> +        if (Op0I->hasOneUse())
> +          if (Value *V = FoldLogicalPlusAnd(Op0LHS, Op0RHS, AndRHS, true, I))
> +            return BinaryOperator::CreateAnd(V, AndRHS);
>   
>           // -x & 1 -> x & 1
>           if (AndRHSMask == 1 && match(Op0LHS, m_Zero()))
>
>
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