[FFmpeg-devel] [RFC] 'dsputil_arm_s.S' code review for possible improvements

Diego Biurrun diego
Sat Sep 15 05:20:16 CEST 2007

On Sat, Sep 15, 2007 at 12:53:29AM +0300, Siarhei Siamashka wrote:
> While waiting for a new armv5te idct patch review, took a look at
> 'dsputil_arm_s.S' source today.
> There are a number of problems and possible ways for improvements:
> ==========
> 1. This source uses '.align 8' directive everywhere. Actually '.align'
> is a not portable way to specify alignment and gnu assembler may interpret
> it either as an alignment in bytes or as an alignment of power of 2 of the 
> specified value depending on the target platform. The latter is true for 
> ARM and '.align 8' actually results in 256 bytes alignment! Such alignment
> blows up code size a lot and makes rather big holes in it, this is definitely
> not very good for cache.

The code should be using the ASMALIGN macro instead.  It takes these
platform differences into account.  Unfortunately only i386 seems to
have been fixed to use it.


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