[Webkit-unassigned] [Bug 174232] Reimplement bmalloc::log2 for MSVC

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=174232

Yusuke Suzuki <utatane.tea at gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |utatane.tea at gmail.com

--- Comment #2 from Yusuke Suzuki <utatane.tea at gmail.com> ---
Comment on attachment 314788
  --> https://bugs.webkit.org/attachment.cgi?id=314788
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=314788&action=review

> Source/bmalloc/bmalloc/Algorithm.h:137
> -    return bitCount<unsigned long>() - 1 - __builtin_clzl(value);
> +    return value < 2 ? 0 : 1 + log2(value / 2);

We should keep the current efficient log2 for non-Windows environment.
If this is not constexpr, in Windows, you can use _BitScanReverse64 / _BitScanReverse. But maybe they are not constexpr.

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