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Optimize atomic_thread_fence #740

Merged
merged 8 commits into from
Apr 30, 2020
Merged

Optimize atomic_thread_fence #740

merged 8 commits into from
Apr 30, 2020

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AlexGuteniev
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Fix #739 (without saving stack variable)

@AlexGuteniev AlexGuteniev requested a review from a team as a code owner April 23, 2020 14:28
@AlexGuteniev AlexGuteniev mentioned this pull request Apr 24, 2020
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@StephanTLavavej StephanTLavavej added the performance Must go faster label Apr 24, 2020
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StephanTLavavej approved these changes Apr 24, 2020
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I suggest minor comment edits and sorting the suppressed warnings; other than that, this looks good to me. Assuming that interlocked operations on separate guard variables provide a sufficient fence, there should be no ODR concerns with mixing-and-matching; older TUs will share a single separate guard variable.

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@AlexGuteniev
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After @pcordes comment, I'm now thinking that _InterlockedXor(reinterpret_cast<volatile long*>(_AddressOfReturnAddress()), 0); may be a slightly better alternative, and in this case no suppression needed.

But I'll need to add intrinsic include (_AddressOfReturnAddress() is not <intrin0.h>), and you have already approved the current approach, so let's go with that.

@StephanTLavavej StephanTLavavej self-assigned this Apr 29, 2020
@StephanTLavavej StephanTLavavej merged commit a5a9e49 into microsoft:master Apr 30, 2020
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Thanks for this performance improvement - I'm really glad you noticed it! 😸

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AlexGuteniev commented Apr 30, 2020 •
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Thanks to @pcordes for great explanations on this subject!

@AlexGuteniev AlexGuteniev deleted the optimize_atomic_thread_fence branch April 30, 2020 10:44
@AlexGuteniev AlexGuteniev mentioned this pull request Jun 9, 2020
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@BillyONeal BillyONeal BillyONeal approved these changes

@StephanTLavavej StephanTLavavej StephanTLavavej approved these changes

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<atomic>: Optimize atomic_thread_fence
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