[Libre-soc-bugs] [Bug 231] Video Opcodes Standards writeup

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Wed Sep 2 22:27:10 BST 2020


--- Comment #6 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
folks, just to clarify: this bugreport is for discussion of audio/video
encode/decode specific instructions, and for their documentation and to track
their submission to an OpenPOWER Foundation ISA Working Group. 

3D GPU instructions, such as triangle detection, unless they can be
demonstrated as needed for a video CODEC, are out of scope for this bugreport. 
there will be another bugreport for discussion of 3D opcodes to be documented
and submitted to OPF ISA WG.

also, Cole: the technique used by Jeff Bush in his Nyuzi paper is the most
effective technique (calculating the pixels per clock achieved for a given
enhancement).   measuring the effectiveness of an *existing* instruction set
merely gives us a comparative baseline.  as we are doing a software-accelerated
augmented ISA then just as in Jeff's Nyuzi work we can "profile" different
areas of a CODEC and target those areas where alternative opcodes would give
the highest bang per buck.

Lauri is correct in that we need at least binutils support (gnu as) for SV even
to begin to start that assessment.  or at the very least a really bad hack
which pre-processes assembler

that in turn means that we need realistically to do the SV-i-fication of POWER9
before being able to start this work in earnest.

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