[PATCH] D38288: [InstCombine] Restrict transforming shared selects using SimplifySelectsFeedingBinaryOp when we cannot simplify the binary op.

[Michael Berg via Phabricator via llvm-commits]

mcberg2017 added inline comments.


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Comment at: lib/Transforms/InstCombine/InstructionCombining.cpp:740
     Value *V2 = SimplifyBinOp(Opcode, B, D, SQ.getWithInstruction(&I));
     if (V1 && V2)
       SI = Builder.CreateSelect(A, V2, V1);
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mcrosier wrote:
> I wonder if something like this would work:
> 
>     bool SelectsHaveOneUse = LHS->hasOneUse() && RHS->hasOneUse();
>     if (V1 && V2)
>       SI = Builder.CreateSelect(A, V2, V1);
>     else if (V2 && SelectsHaveOneUse)
>       SI = Builder.CreateSelect(A, V2, Builder.CreateBinOp(Opcode, C, E));
>     else if (V1 && SelectsHaveOneUse)
>       SI = Builder.CreateSelect(A, Builder.CreateBinOp(Opcode, B, D), V1);
An earlier review was opened here: https://reviews.llvm.org/D38263, from which the snippet above originates.  Just to let folks know that are two reviews open on this topic.


https://reviews.llvm.org/D38288