Stabilize passing 128-bit integers via vector registers with asm! on x86

[folkertdev]

tracking issue: #133416
reference PR: rust-lang/reference#2313

Stabilization report

Summary

Stabilize passing 128-bit integers via vector registers with asm! on x86 and x86_64:

// Use 128-bit integers with vector registers.
let mut v = 0u128;

asm!("/* {:x} */", in(xmm_reg) v);
asm!("/* {:x} */", out(xmm_reg) v);

asm!("/* {:y} */", in(ymm_reg) v);
asm!("/* {:y} */", out(ymm_reg) v);

asm!("/* {:z} */", in(zmm_reg) v);
asm!("/* {:z} */", out(zmm_reg) v);

32-bit and 64-bit integer types can already be passed via vector registers. LLVM has supported 128-bit integers since 2019, see llvm/llvm-project#42502, so rustc not supporting them seems like an oversight.

This feature is part of asm_experimental_reg. We're not stabilizing that feature as a whole, but only pull out part of it.

History

• x86: support passing u128/i128 to inline assembly #151059

Open questions

None.

r? Amanieu

[traviscross]

Thanks @folkertdev.

@rfcbot fcp merge lang

[rust-rfcbot]

@traviscross has proposed to merge this. The next step is review by the rest of the tagged team members:

• @joshtriplett
• @nikomatsakis
• @scottmcm
• @tmandry
• @traviscross

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

cc @rust-lang/lang-advisors: FCP proposed for lang, please feel free to register concerns.
See this document for info about what commands tagged team members can give me.

[tmandry]

@rfcbot reviewed

[nikomatsakis]

@rfcbot reviewed

[rust-rfcbot]

🔔 This is now entering its final comment period, as per the review above. 🔔

[Amanieu]

r=me once FCP completes

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