x86 f16: implement rounding support

[TheNumbat]

Makes _mm_cvtps_ph/_mm256_cvtps_ph respect the rounding mode argument. Assumes _MM_FROUND_CUR_DIRECTION is always half-to-even, which isn't strictly correct, but is already assumed by various other functions.

Enables the rounding mode tests and adds a few more. There should be no behavior changes for the round-nearest and round-current cases.

[mr-c]

Some errors from Microsoft Visual Studio 2015 version 19.00.24241.7 and Visual Studio 2017 version 19.16.27035:

https://ci.appveyor.com/project/nemequ/simde/builds/53462546/job/ya2shs5yojpisa31#L4688

../test/x86/f16c.c:101: assertion failed: r0[1] == simde_x_mm_loadu_epi16(test_vec[i].r0)[1] (-512 == 32256)
../test/x86/f16c.c:313: assertion failed: r0[1] == simde_x_mm_loadu_epi16(test_vec[i].r0)[1] (-512 == 32256)

[TheNumbat]

Hmm, this is weird. It's rounding qnan to -qnan instead of qnan. Could be a compiler bug that was fixed in vs2019? Are there any other differences between those jobs?

[TheNumbat]

The only difference from 19.14 to 19.20 (which gives the expected answer) seems to be some spills: https://godbolt.org/z/Y59G5vK65

[TheNumbat]

Actually, it appears they changed NAN...https://godbolt.org/z/MGGfP5bfs

[TheNumbat]

I just removed the test since signed nan handling already differs between targets

[TheNumbat]

Looks like the Azure CI pipeline started timing out?

[mr-c]

@TheNumbat I will rebase this PR once #1384 is merged

[mr-c]

Thank you @TheNumbat !

[TheNumbat]

np! also, for context, I'm now using simde to run https://github.com/janestreet/ocaml_simd on arm 👍

[mr-c]

np! also, for context, I'm now using simde to run https://github.com/janestreet/ocaml_simd on arm 👍

Very cool, thank you for letting us know! Do you want to send them a PR to incorporate SIMDe directly?

[TheNumbat]

It's already incorporated internally (I work at Jane Street) - should appear in the repo soon-ish

[mr-c]

It's already incorporated internally (I work at Jane Street) - should appear in the repo soon-ish

Huzzah! Can you add an entry at https://github.com/simd-everywhere/simde/wiki/Projects-Using-SIMDe ? 💞