[FFmpeg-devel] [PATCH] x86: use raw opcode for xgetbv instruction

Måns Rullgård mans
Sun Feb 20 16:43:04 CET 2011

Luca Barbato <lu_zero at gentoo.org> writes:

> On 02/20/2011 03:39 PM, Mans Rullgard wrote:
>> This allows the CPU detection to work with assemblers not supporting
>> the xgetbv mnemonic.  These include clang and some BSD versions.
>> All AVX code will be written for yasm, where the main assembler
>> is not involved.
> We'd better put a notice about this somewhere and/or prepare a configure
> check in case somebody provides inline avx asm.

Note that xgetbv is not an avx instruction as such.  As for inline asm,
we should discourage its use.

> The patch looks ok (given the opcode is that one).

I got it from the manual, and objdump agrees.

BTW, there is an open clang bug on this already.

M?ns Rullg?rd
mans at mansr.com

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