[llvm-commits] [PATCH] Correct AVX detection in X86Subtarget::AutoDetectSubtargetFeatures()

[Craig Topper]

The check for XSAVE isn't necessary since all processors that support AVX
support XSAVE. Checking OSXSAVE isn't sufficient you would also need to
check XGETBV to make sure save/restore of XMM and YMM state is enabled by
the OS.

~Craig

On Sat, Aug 25, 2012 at 1:33 AM, Alex Rønne Petersen <alex at lycus.org> wrote:

> Hi LLVMers,
>
> The AVX detection code in X86Subtarget::AutoDetectSubtargetFeatures() only
> checked for the CPUID.{EAX = 1}.ECX.AVX bit previously. This is not enough;
> the XSAVE and OSXSAVE bits also need to be checked to be sure that the OS
> is aware of XMM/YMM registers and saves them during context switches. This
> patch fixes that.
>
> The patch was created with git diff - I was told svn should be able to
> work with that.
>
> This is my first patch submission, so if I did something wrong, please
> bear with me. :)
>
> Regards,
> Alex
>
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>


-- 
~Craig
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