Implement AVX512_FP16

[sayantn]

This PR adds the AVX512_FP16 intrinsics in Rust. These intrinsics will be behind the feature gate #[feature(stdarch_x86_avx512_f16)] (rust-lang/rust#127213).

Progress:

• [x] Set intrinsics
• [x] Arithmetic operations (Add-Sub-Mul-Div on Real numbers)
• [x] FMA
• [x] Cast
• [x] Compare
• [x] Convert
• [x] Math (Reciprocal, Sqrt, RSqrt, Max, Min, Reduce)
• [x] FP-Support (FPClass, getexp, getmant, scale)
• [x] Load-Store
• [x] Complex number operations (mul-cmul-conj on Complex numbers)
• [x] AVX-NE-CONVERT

This also adds some missing inlining in avx512ifma and updates the x86-intel.xml file to v3.6.9

The set1_pch intrinsics were not implemented due to a lack of complex number type. cmpph and fpclassph intrinsics use inline asm because of no i1 support yet.

[rustbot]

r? @Amanieu

rustbot has assigned @Amanieu. They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[tgross35]

Have you run into any weird behavior with these, or do things seem to be working smoothly? (ignoring the ABI issue for system function calls, that is)

[sayantn]

No problems yet, just that simd_fabs doesn't accept a f16 argument, so i will just use an and operation. I am actively avoiding doing f16 operations in rust, but that's not a blocker for sure.

[bors]

:umbrella: The latest upstream changes (presumably 3dd9579da33db7fc9db68eb36969d387dd706517) made this pull request unmergeable. Please resolve the merge conflicts.

[sayantn]

cc @tgross35 @beetrees