[Webkit-unassigned] [Bug 188135] [audio] Hard dependency on SSE instruction set

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=188135

--- Comment #1 from karogyoker2+webkit at gmail.com ---
Debian packages are built for 686 processors[1]. So, in theory WebKit should run on a Pentium Pro.

If the above code will eventually executed for somebody on a Pentium Pro or Pentium 2, it will crash due to SIGILL because these instructions are only available since Pentium 3.

But the fix is not that trivial. We cannot change (defined(__i386__) || defined(__x86_64__)) to __SSE__ because in that case Pentium 3, Pentium 4, Athlon and Athlon XP users would have degraded performance[2] because the package is built for Pentium Pro.

So we have 3 choices:
- Make it work on Pentium Pro with the disadvantage that it will be slower on newer CPUs
- Do some run time check if the CPU supports SSE and cache the result so it only gets this once by CPUID
- Leave it as it is until it is really causing some issues for somebody, probably this will never happen anyways. This bug would only trigger if somebody is using WebKit on a Pentium Pro or on a Pentium 2 and visits a website which is using the Web Audio API.

[1]: https://lists.debian.org/debian-devel/2015/09/msg00589.html
[2]: https://github.com/WebKit/webkit/blob/08b8a0b13504a2095cdfe0f8172c756f9776052c/Source/WebCore/platform/audio/DenormalDisabler.h#L32

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