[PATCH] D141074: [X86] Avoid converting 64-bit integers to floating point using x87 on Windows

Mon Jan 9 15:19:35 PST 2023

craig.topper added a comment.

In D141074#4037902 <https://reviews.llvm.org/D141074#4037902>, @icedrocket wrote:

> In D141074#4037854 <https://reviews.llvm.org/D141074#4037854>, @lebedev.ri wrote:
>
>> In D141074#4037831 <https://reviews.llvm.org/D141074#4037831>, @icedrocket wrote:
>>
>>> If SSE2 is available, we only need to use library calls to convert between 64-bit integers and floating point. However, if only x87 is available, precision issues are unavoidable. What I meant was to just use the x87 implementation and print a warning in this case.
>>
>> Why are they unavoidable?
>
> As long as the precision control is low, x87 has low precision.

If the precision control is set to more than 24-bit precision, x87 actually has more precision than SSE for fp32.

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