[Ffmpeg-devel] [RFC] port cabac asm to AMD64

Guillaume POIRIER poirierg
Sat Oct 21 23:56:19 CEST 2006


On 10/21/06, Reimar D?ffinger <Reimar.Doeffinger at stud.uni-karlsruhe.de> wrote:
> Hello,
> On Sat, Oct 21, 2006 at 03:33:00PM -0600, Loren Merritt wrote:
> > On Sat, 21 Oct 2006, Reimar D?ffinger wrote:
> >
> > >though it should be possible to optimize further, mixing use of 64 and
> > >32 bit registers is said to be quite slow.
> >
> > How so? My AMD optimization manual says that you _should_ mix 32bit and
> > 64bit registers, because there's no penalty and the 32bit opcodes are
> > smaller.
> > (http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/25112.PDF
> > page 68)
> Maybe I confused that with access to 32 bit and 64 bit stuff at the same
> memory address, that definitely had some problems.

Or also partial register stall problems that happen when you do a
write operation to a partial register and then a read operation from
its larger version of this register.

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