[PATCH] D126273: [DAGCombiner][VP] Add DAGCombine for merging VP_FADD and VP_FMUL to VP_FMA.

Tue May 24 08:46:42 PDT 2022

liaolucy added a comment.

In D126273#3534429 <https://reviews.llvm.org/D126273#3534429>, @craig.topper wrote:

> In D126273#3533580 <https://reviews.llvm.org/D126273#3533580>, @liaolucy wrote:
>
>> When I test tsvc.
>>
>> The IR is:
>>
>>   @llvm.fmuladd.nxv2f32(<vscale x 2 x float>.....
>>
>> Not
>>
>>   @llvm.riscv.vfmul.nxv2f32.nxv2f32(<vscale x 2 x float> ......
>>   @llvm.riscv.vfadd.nxv2f32.nxv2f32(<vscale x 2 x float> ......
>>    
>>
>> So I am not sure, we need merge vp.fmul and vp.fadd to vp.fma.  maybe vp.fma is enough?
>
> fmuladd is use with -ffp-contract=on(the default). fmul+fadd is used with -ffast-math or -ffp-contract=fast or -Ofast.

Got it. Thank you very much.

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https://reviews.llvm.org/D126273