[PATCH] D100091: [X86] Fix wrong handle with "-mno-x87"

Wed Apr 21 23:40:21 PDT 2021

LiuChen3 added a comment.

In D100091#2677235 <https://reviews.llvm.org/D100091#2677235>, @craig.topper wrote:

> In D100091#2675996 <https://reviews.llvm.org/D100091#2675996>, @LiuChen3 wrote:
>
>> In D100091#2675968 <https://reviews.llvm.org/D100091#2675968>, @craig.topper wrote:
>>
>>> What about cases that use x87 to do float/double conversions? I think it’s i64 conversions in 32-bit mode. But maybe other cases. Does gcc disable those with -mno-80387?
>>
>> You are right! GCC can do the conversions: https://godbolt.org/z/87ez838oc . 
>> With this patch, llvm will fail in ISEL. I want to make another patch to do this.
>
> I'm more concerned about these cases that don't use long double and aren't missed constant folding. https://godbolt.org/z/qGv54ef34

It seems not easy to handle this. I want fix a bug in this patch. For this part, It looks more like a feature. We want to do that in another patch. What's your opinion here?

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  https://reviews.llvm.org/D100091/new/

https://reviews.llvm.org/D100091