Replace LZCNT with BSR instruction in hdr_histogram#230
Replace LZCNT with BSR instruction in hdr_histogram#230mpenick merged 3 commits intoapache:masterfrom
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The LZCNT instruction produced by __lzcnt on Windows is not available on many CPUs in use today. BSR is a safe replacement requiring only minimal additional work.
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Hi @SeverinLeonhardt, thanks for your contribution! In order for us to evaluate and accept your PR, we ask that you sign a contribution license agreement. It's all electronic and will take just minutes. Sincerely, |
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Thank you @SeverinLeonhardt for signing the Contribution License Agreement. Cheers, |
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@SeverinLeonhardt Thanks for researching and getting a pull request together. I just had one issue compiling on Windows, otherwise, LGTM. |
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This shouldn't be const because it's reused for the next BSR.
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I noticed another issue too that's unrelated to the changes you made. For GCC-based compilers |
__builtin_clzll is undefined for 0 so this case must be handled separately.
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Updated the pull request as you've suggested. |
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Thanks for updating. Looks good. |
Replace LZCNT with BSR instruction in hdr_histogram
3 participants
The LZCNT instruction produced by __lzcnt on Windows is not available
on many CPUs in use today. BSR is a safe replacement requiring only
minimal additional work.