[x264-devel] libx264 for Blackfin?

[Måns Rullgård]

Harald Krapfenbauer <harald.krapfenbauer at bluetechnix.com> writes:

>>>> The Blackfin is not particularly suited to running x264.
>>>
>>> Is this documented anywhere? Or was there some research, discussion
>>> about it?
>>
>>It is a dual-issue architecture with no SIMD capabilities.
>
> From the reference manual:
>
> "Instruction Overview
> This chapter discusses the instructions that control vector operations.
> Users can take advantage of these instructions to perform simultaneous
> operations on multiple 16-bit values, including add, subtract, multiply,
> shift, negate, pack, and search. Compare-Select and Add-On-Sign are also
> included in this chapter."
>
> Simultaneous operations on multiple 16-bit values...do you mean this
> by "dual-issue". I had thought, these vector operations are kind of
> SIMD...

Depends on what you expect from SIMD.  To call something a SIMD
architecture, I expect a full complement of arithmetic operations on 8-,
16- and 32-bit element sizes.  The instructions you refer to operate on
32-bit registers, and only a select few operations are possible.  What
the manual calls vector operations are restricted to pairs of 16-bit
values.

Comparing to other architectures, this pseudo-SIMD does not even match
the capabilities of ARMv6.

-- 
Måns Rullgård
mans at mansr.com