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Rust's i128 return ABI does not agree with Clang and GCC on Windows targets #134288

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#137306
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Rust's i128 return ABI does not agree with Clang and GCC on Windows targets#134288
#137306
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A-ABIArea: Concerning the application binary interface (ABI)A-LLVMArea: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.C-bugCategory: This is a bug.O-windowsOperating system: WindowsT-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

Description

@tgross35
tgross35
opened on Dec 13, 2024

Originally reported at rust-lang/lang-team#255 (comment), Clang and GCC-MinGW return __int128 in xmm0. Rust currently returns it on the stack.

@wesleywiser has a proposed patch to make Clang return on the stack for -msvc targets, while keeping the behavior for MinGW wesleywiser/llvm-project@b2f8b83.

Rustc could probably just change the Windows ABI to always return in xmm0 for now, and then if the Clang patch lands we can change this to apply only to MinGW.

Demo: https://godbolt.org/z/o9h8We69o

Activity

  1. tgross35
    added
    A-ABIArea: Concerning the application binary interface (ABI)
    A-LLVMArea: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.
    C-bugCategory: This is a bug.
    O-windowsOperating system: Windows
    T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.
    on Dec 13, 2024
  2. rustbot
    added
    needs-triageThis issue may need triage. Remove when done. See docs forge.rust-lang.org/release/issue-triaging
    on Dec 13, 2024
  3. tgross35
    removed
    needs-triageThis issue may need triage. Remove when done. See docs forge.rust-lang.org/release/issue-triaging
    on Dec 13, 2024
  4. tgross35
    added 4 commits that reference this issue on Dec 14, 2024

    Windows x86: Change `i128` to return via the vector ABI

    c9e58b4

    Windows x86: Change `i128` to return via the vector ABI

    99092c5

    Windows x86: Change `i128` to return via the vector ABI

    8a6614e

    Windows x86: Change `i128` to return via the vector ABI

    706db2b
  5. bors
    added a commit that references this issue on Dec 14, 2024

    Auto merge of rust-lang#134290 - tgross35:windows-i128-callconv, r=<try>

    4c26894
  6. tgross35
    added 2 commits that reference this issue on Dec 15, 2024

    Windows x86: Change `i128` to return via the vector ABI

    c4e3300

    Windows x86: Change `i128` to return via the vector ABI with Cranelift

    0b63586
  7. bors
    added a commit that references this issue on Dec 15, 2024

    Auto merge of rust-lang#134290 - tgross35:windows-i128-callconv, r=<try>

    31dc001

  8. 28 remaining items

  9. lnicola
    added a commit that references this issue on Feb 10, 2025

    Auto merge of #134290 - tgross35:windows-i128-callconv, r=bjorn3,wesl…

    7066f1a
  10. tgross35
    added a commit that references this issue on Feb 20, 2025

    Remove `i128` and `u128` from `improper_ctypes_definitions`

    ce734ba
  11. tgross35
    added a commit that references this issue on May 18, 2025

    Remove `i128` and `u128` from `improper_ctypes_definitions`

    8d82555
  12. tgross35
    added a commit that references this issue on May 29, 2025

    Remove `i128` and `u128` from `improper_ctypes_definitions`

    0cba7fb
  13. matthiaskrgr
    added a commit that references this issue on Jun 4, 2025

    Rollup merge of rust-lang#137306 - tgross35:remove-i128-u128-improper…

    c5efc6a
  14. bors
    closed this as completedin 0cba7fbon Jun 4, 2025
  15. rust-timer
    added a commit that references this issue on Jun 4, 2025

    Unrolled build for #137306

    61fd398
  16. github-actions
    added a commit that references this issue on Jun 5, 2025

    Rollup merge of #137306 - tgross35:remove-i128-u128-improper-ctypes, …

    463af62
  17. kiseitai3
    added a commit that references this issue on Jun 6, 2025

    Remove `i128` and `u128` from `improper_ctypes_definitions`

    be0705c
  18. tautschnig
    added 2 commits that reference this issue on Jun 17, 2025

    Remove `i128` and `u128` from `improper_ctypes_definitions`

    2e47cec

    Rollup merge of rust-lang#137306 - tgross35:remove-i128-u128-improper…

    150f20c
  19. christian-schilling
    added 4 commits that reference this issue on Jan 27, 2026

    Windows x86: Change `i128` to return via the vector ABI

    894e068

    Auto merge of #134290 - tgross35:windows-i128-callconv, r=bjorn3,wesl…

    327fa21

    Windows x86: Change `i128` to return via the vector ABI

    c5b44a4

    Auto merge of #134290 - tgross35:windows-i128-callconv, r=bjorn3,wesl…

    50ffda9
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    A-ABIArea: Concerning the application binary interface (ABI)A-LLVMArea: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.C-bugCategory: This is a bug.O-windowsOperating system: WindowsT-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

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