[x264-devel] Re: [PATCH] IDCT8 and SA8D routines in Altivec

[Manuel Rommel]

Hi,

Guillaume, in your second post this was added to your patch:

> -      CFLAGS="$CFLAGS -faltivec -fastf -mcpu=G4"
> +      CFLAGS="$CFLAGS -faltivec -fastf -mcpu=G5"


It might be dangerous to specify -mcpu=G5 on every PPC since then gcc  
produces instructions which are only valid on a G5, so x264 is likely  
crash on a G4 oder G3.


And I have a question about the use of VEC_ABS in your SA8D code, for  
example:

> +    vec_s16_t abs6v = VEC_ABS(sa8d6v);

As far as I understand, this gets transformed to

vec_s16_t abs6v =     sa8d6v     = vec_max( sa8d6v, vec_sub 
( zero_s16v, sa8d6v ) );

This shouldn't alter the output but it could be possible to get rid  
of some instructions, if I understand it right.

Thank you!

Regards,
manuelro

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