Porting to GCC 17

The GCC 17 release series differs from previous GCC releases in a number of ways. Some of these are a result of bug fixing, and some old behaviors have been intentionally changed to support new standards, or relaxed in standards-conforming ways to facilitate compilation or run-time performance.

Some of these changes are user visible and can cause grief when porting to GCC 17. This document is an effort to identify common issues and provide solutions. Let us know if you have suggestions for improvements!

IA-32/x86-64 issues

Renamed AVX10.2 scalar saturating conversion intrinsics

The AVX10.2 scalar saturating conversion intrinsics were originally named with an _ep[i|u]{32,64} suffix. That suffix denotes packed elements, whereas these intrinsics convert a single scalar value and return a scalar integer, so the names did not follow the convention used by scalar conversion intrinsics since AVX-512F. The old names were never accepted by other x86 compilers. GCC 17 renames them to use the _[i|u]{32,64} suffix, with _si{32,64} aliases for the signed variants:

Removed in GCC 17	Use instead
`_mm_cvtts_sd_epi32`	`_mm_cvtts_sd_i32`, `_mm_cvtts_sd_si32`
`_mm_cvtts_sd_epu32`	`_mm_cvtts_sd_u32`
`_mm_cvtts_ss_epi32`	`_mm_cvtts_ss_i32`, `_mm_cvtts_ss_si32`
`_mm_cvtts_ss_epu32`	`_mm_cvtts_ss_u32`
`_mm_cvtts_roundsd_epi32`	`_mm_cvtts_roundsd_i32`, `_mm_cvtts_roundsd_si32`
`_mm_cvtts_roundsd_epu32`	`_mm_cvtts_roundsd_u32`
`_mm_cvtts_roundss_epi32`	`_mm_cvtts_roundss_i32`, `_mm_cvtts_roundss_si32`
`_mm_cvtts_roundss_epu32`	`_mm_cvtts_roundss_u32`
`_mm_cvtts_sd_epi64`	`_mm_cvtts_sd_i64`, `_mm_cvtts_sd_si64`
`_mm_cvtts_sd_epu64`	`_mm_cvtts_sd_u64`
`_mm_cvtts_ss_epi64`	`_mm_cvtts_ss_i64`, `_mm_cvtts_ss_si64`
`_mm_cvtts_ss_epu64`	`_mm_cvtts_ss_u64`
`_mm_cvtts_roundsd_epi64`	`_mm_cvtts_roundsd_i64`, `_mm_cvtts_roundsd_si64`
`_mm_cvtts_roundsd_epu64`	`_mm_cvtts_roundsd_u64`
`_mm_cvtts_roundss_epi64`	`_mm_cvtts_roundss_i64`, `_mm_cvtts_roundss_si64`
`_mm_cvtts_roundss_epu64`	`_mm_cvtts_roundss_u64`

The old names are still accepted on the GCC 15 and GCC 16 release branches.

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