[Headers][X86] Allow SSE/AVX integer comparison intrinsics to be used in constexpr

[RKSimon]

Split off from #152490

_mm_cmpeq_epi8 _mm_cmpeq_epi16 _mm_cmpeq_epi32 _mm_cmpeq_epi64
_mm_cmpgt_epi8 _mm_cmpgt_epi16 _mm_cmpgt_epi32 _mm_cmpgt_epi64
_mm_cmplt_epi8 _mm_cmplt_epi16 _mm_cmplt_epi32 _mm_cmplt_epi64

_mm256_cmpeq_epi8 _mm256_cmpeq_epi16 _mm256_cmpeq_epi32 _mm256_cmpeq_epi64
_mm256_cmpgt_epi8 _mm256_cmpgt_epi16 _mm256_cmpgt_epi32 _mm256_cmpgt_epi64

The pre-AVX512 integer comparison intrinsics are all safe to be used in constexpr - use #152296 for reference

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. Check that no other contributor is working on this issue. If someone is assigned to the issue or claimed to be working on it, ping the person. After one week without a response, the assignee may be changed.
2. Leave a comment indicating that you are working on the issue, or just create a pull request after following the steps below. Mention this issue in the description of the pull request.
3. Fix the issue locally.
4. Run the test suite locally. Remember that the subdirectories under test/ create fine-grained testing targets, so you can e.g. use make check-clang-ast to only run Clang's AST tests.
5. Create a Git commit.
6. Run git clang-format HEAD~1 to format your changes.
7. Open a pull request to the upstream repository on GitHub. Detailed instructions can be found in GitHub's documentation. Mention this issue in the description of the pull request.

If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Simon Pilgrim (RKSimon)

Split off from https://github.com//issues/152490 ``` _mm_cmpeq_epi8 _mm_cmpeq_epi16 _mm_cmpeq_epi32 _mm_cmpeq_epi64 _mm_cmpgt_epi8 _mm_cmpgt_epi16 _mm_cmpgt_epi32 _mm_cmpgt_epi64 _mm_cmplt_epi8 _mm_cmplt_epi16 _mm_cmplt_epi32 _mm_cmplt_epi64

_mm256_cmpeq_epi8 _mm256_cmpeq_epi16 _mm256_cmpeq_epi32 _mm256_cmpeq_epi64
_mm256_cmpgt_epi8 _mm256_cmpgt_epi16 _mm256_cmpgt_epi32 _mm256_cmpegt_epi64

The pre-AVX512 integer comparison intrinsics are all safe to be used in constexpr - use #<!-- -->152296 for reference
</details>

[llvmbot]

@llvm/issue-subscribers-backend-x86

Author: Simon Pilgrim (RKSimon)

Split off from https://github.com//issues/152490 ``` _mm_cmpeq_epi8 _mm_cmpeq_epi16 _mm_cmpeq_epi32 _mm_cmpeq_epi64 _mm_cmpgt_epi8 _mm_cmpgt_epi16 _mm_cmpgt_epi32 _mm_cmpgt_epi64 _mm_cmplt_epi8 _mm_cmplt_epi16 _mm_cmplt_epi32 _mm_cmplt_epi64

_mm256_cmpeq_epi8 _mm256_cmpeq_epi16 _mm256_cmpeq_epi32 _mm256_cmpeq_epi64
_mm256_cmpgt_epi8 _mm256_cmpgt_epi16 _mm256_cmpgt_epi32 _mm256_cmpegt_epi64

The pre-AVX512 integer comparison intrinsics are all safe to be used in constexpr - use #<!-- -->152296 for reference
</details>

[sivk-kex]

Hello, I would like to work on this issue.

[sivk-kex]

Thank you.

[sivk-kex]

@RKSimon Sorry, I have a personal emergency. Can you reassign this?