Use `_tpause` instead of `__builtin_ia32_tpause` by mocknen · Pull Request #27607 · microsoft/onnxruntime

mocknen · 2026-03-10T08:12:17Z

Description

Use _tpause function defined in waitpkgintrin.h instead of calling the compiler built-in function (__builtin_ia32_tpause) directly.

Motivation and Context

The _tpause is independent of the compiler, whereas its implementation via the built-in function __builtin_ia32_tpause varies by compiler. Therefore, it is advisable not to use it directly. For example, GCC and LLVM have different arguments, leading to portability issues.

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Pull request overview

This PR improves portability of the x86_64 spin-wait implementation by using the standardized _tpause intrinsic (from waitpkgintrin.h via existing headers) instead of directly invoking the compiler-specific built-in __builtin_ia32_tpause, which differs across compilers.

Changes:

Switch Linux tpause usage from __builtin_ia32_tpause to _tpause.
Consolidate the Windows/Linux tpause path under a single preprocessor branch.

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tianleiwu · 2026-03-10T17:33:26Z

Previously, I investigated an issue for clang build. Here is some information I got:
https://gemini.google.com/share/c1025d3447ee
The recommended change might need change in both cmake configuration and use #if defined(__WAITPKG__).

mocknen · 2026-03-11T04:17:35Z

@tianleiwu

Thanks for the advice!

I have changed the section to use __WAITPKG__ instead, and confirmed that it can be compiled both in GCC and LLVM.

However, I'm not sure if the defined(_WIN32) part is correct, but I've left it as is. A quick search suggests that MSVC doesn't support _tpause, so we'd need to use inline assembly. Unfortunately, I don't have a Windows environment available right now to verify this. If we need to change that, perhaps we should discuss it in a separate issue or pull request?

Additional info

__WAITPKG__ macro
- llvm
- gcc

generated code from GCC v14.2.0

bbf7d6:   74 28                   je     bbf800 <_ZN11onnxruntime11concurrency9SpinPauseEv+0x40>
bbf7d8:   0f 31                   rdtsc
bbf7da:   31 c9                   xor    ecx,ecx
bbf7dc:   48 c1 e2 20             shl    rdx,0x20
bbf7e0:   48 09 d0                or     rax,rdx
bbf7e3:   48 05 e8 03 00 00       add    rax,0x3e8
bbf7e9:   48 89 c2                mov    rdx,rax
bbf7ec:   48 c1 ea 20             shr    rdx,0x20
bbf7f0:   66 0f ae f1             tpause ecx

generated code from LLVM v21.1.8

1070643:   75 1e                   jne    1070663 <_ZN11onnxruntime11concurrency9SpinPauseEv+0x33>
1070645:   0f 31                   rdtsc
1070647:   48 c1 e2 20             shl    rdx,0x20
107064b:   48 09 d0                or     rax,rdx
107064e:   48 05 e8 03 00 00       add    rax,0x3e8
1070654:   48 89 c2                mov    rdx,rax
1070657:   48 c1 ea 20             shr    rdx,0x20
107065b:   31 c9                   xor    ecx,ecx
107065d:   66 0f ae f1             tpause ecx

mocknen · 2026-03-11T04:38:45Z

Regarding CMake C flags, since -march=native automatically enables -mwaitpkg as well, I don't think any special changes are necessary.

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Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 1 comment.

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onnxruntime/core/common/spin_pause.cc

mocknen · 2026-03-12T02:23:20Z

Rebased to include #27618.

tianleiwu

LGTM

tianleiwu · 2026-03-12T06:59:35Z

/azp run Linux QNN CI Pipeline, Win_TRT_Minimal_CUDA_Test_CI, Windows ARM64 QNN CI Pipeline,
Windows GPU Doc Gen CI Pipeline

azure-pipelines · 2026-03-12T06:59:55Z

Azure Pipelines successfully started running 4 pipeline(s).

### Description Use `_tpause` function defined in `waitpkgintrin.h` instead of calling the compiler built-in function (`__builtin_ia32_tpause`) directly. ### Motivation and Context The [`_tpause`][intel-intrinsics-guide] is independent of the compiler, whereas its implementation via the built-in function `__builtin_ia32_tpause` varies by compiler. Therefore, it is advisable not to use it directly. For example, [GCC][waitpkgintrin-gcc] and [LLVM][waitpkgintrin-llvm] have different arguments, leading to portability issues. [intel-intrinsics-guide]: https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=tpause&techs=Other&ig_expand=6888 [waitpkgintrin-gcc]: https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/config/i386/waitpkgintrin.h;h=42c6b0cd02866eccdfe3308f4792f17fe8c6ae38;hb=HEAD#l51 [waitpkgintrin-llvm]: https://github.com/llvm/llvm-project/blob/a682073ae7a49de4b95498ba01b9ea32e6b5f607/clang/lib/Headers/waitpkgintrin.h#L33-L38

This cherry-picks the following commits for the release: | Commit ID | PR Number | Commit Title | |-----------|-----------|-------------| | eb23be8 | #27354 | Update python_requires | | d626b56 | #27479 | [QNN EP] Enable offline x64 compilation with memhandle IO type | | 60ce0e6 | #27607 | Use `_tpause` instead of `__builtin_ia32_tpause` | | 69feb84 | #27591 | Add PCI bus fallback for Linux GPU device discovery in containerized environments | | de92668 | #27650 | Revert "[QNN EP] Fix error messages being logged as VERBOSE instead o… | | 0f66526 | #27644 | [Plugin EP] Check for nullptr before dereferencing | | 929f73e | #27666 | Plugin EP: Fix bug that incorrectly assigned duplicate MetDef IDs to fused nodes in different GraphViews | --------- Co-authored-by: XXXXRT666 <157766680+XXXXRT666@users.noreply.github.com> Co-authored-by: derdeljan-msft <derdeljan@microsoft.com> Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com> Co-authored-by: Shogo Yamazaki <f9ifphmiz7i8akhowc8l5t1x9qp0lfu4@mocknen.net> Co-authored-by: Copilot <198982749+Copilot@users.noreply.github.com> Co-authored-by: baijumeswani <12852605+baijumeswani@users.noreply.github.com> Co-authored-by: edgchen1 <18449977+edgchen1@users.noreply.github.com> Co-authored-by: Baiju Meswani <bmeswani@microsoft.com> Co-authored-by: Artur Wojcik <artur.wojcik@amd.com> Co-authored-by: Adrian Lizarraga <adlizarraga@microsoft.com>

tianleiwu requested a review from Copilot March 10, 2026 16:25

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mocknen force-pushed the mocknen/replace-builtin-tpause branch from ed7fa32 to fe170b5 Compare March 11, 2026 03:36

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onnxruntime/core/common/spin_pause.cc Show resolved Hide resolved

mocknen force-pushed the mocknen/replace-builtin-tpause branch from fe170b5 to 7cabbc7 Compare March 11, 2026 06:02

Use _tpause instead of __builtin_ia32_tpause

2d87f10

mocknen force-pushed the mocknen/replace-builtin-tpause branch from 7cabbc7 to 2d87f10 Compare March 12, 2026 02:18

tianleiwu approved these changes Mar 12, 2026

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tianleiwu enabled auto-merge (squash) March 12, 2026 03:45

tianleiwu merged commit 60ce0e6 into microsoft:main Mar 12, 2026
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tianleiwu mentioned this pull request Mar 12, 2026

Use _tpause also for clang #27442

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tianleiwu added the release:1.24.4 label Mar 13, 2026

tianleiwu mentioned this pull request Mar 16, 2026

ORT 1.24.4 release cherry pick round 1 #27682

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dependabot bot mentioned this pull request Mar 30, 2026

deps(nuget): Bump the microsoft-packages group with 11 updates Ellerbach/azure-ai-search-simulator#86

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Use `_tpause` instead of `__builtin_ia32_tpause`#27607

Use `_tpause` instead of `__builtin_ia32_tpause`#27607
tianleiwu merged 1 commit intomicrosoft:mainfrom
mocknen:mocknen/replace-builtin-tpause

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mocknen commented Mar 10, 2026

Description

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Pull request overview

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mocknen commented Mar 11, 2026

Additional info

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