Avoid using simd_fmin/simd_fmax for AVX float min/max comparisons #1155
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These were not following the documented (albeit peculiar) semantics for the AVX intrinsics — the differences are around NaN and -0.0.
It was also causing suboptimal codegen, as LLVM needed to, for example, follow a
vminpswithvcmpunordps+vblendvpsto implement thellvm.minnumsemantics. (This is why I noticed it)The text quoted inside the tests is from the architecture manual (volume 2B) https://software.intel.com/content/dam/develop/external/us/en/documents-tps/253667-sdm-vol-2b.pdf. Essentially the same text can be found on websites like https://www.felixcloutier.com/x86/minps.
Somewhat surprisingly (or, it's surprising we'd get it right in one place, wrong in the other), we got this right for SSE min/max, so no change needed there.