[FFmpeg-devel] [PATCH] Fix overread in altivec DSP function sad16

[Måns Rullgård]

Vitor Sessak <vitor1001 at gmail.com> writes:

> Should fix "make fate-acodec-ac3_fixed" valgrind errors on PPC. See
> [1] and [2] for the altivec trick.
>
> -Vitor
>
> [1]
> http://fate.mkw.ru/report.cgi?time=20110129012153&slot=ppc-linux-gcc-valgrind
> [2] http://developer.apple.com/hardwaredrivers/ve/alignment.html
>
> From 3a30ae4b4152a9097070e18440896c34aa504c39 Mon Sep 17 00:00:00 2001
> From: Vitor Sessak <vitor1001 at gmail.com>
> Date: Sat, 29 Jan 2011 14:14:32 +0000
> Subject: [PATCH] Fix overread in altivec DSP function sad16
>
> ---
>  libavcodec/ppc/dsputil_altivec.c |   12 +++++++-----
>  1 files changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/libavcodec/ppc/dsputil_altivec.c b/libavcodec/ppc/dsputil_altivec.c
> index 1633232..6779312 100644
> --- a/libavcodec/ppc/dsputil_altivec.c
> +++ b/libavcodec/ppc/dsputil_altivec.c
> @@ -230,7 +230,7 @@ static int sad16_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_size, i
>      int i;
>      int s;
>      const vector unsigned int zero = (const vector unsigned int)vec_splat_u32(0);
> -    vector unsigned char perm1, perm2, *pix1v, *pix2v;
> +    vector unsigned char perm1, perm2, pix1v_low, pix1v_high, pix2v_low, pix2v_high;
>      vector unsigned char t1, t2, t3,t4, t5;
>      vector unsigned int sad;
>      vector signed int sumdiffs;
> @@ -241,11 +241,13 @@ static int sad16_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_size, i
>      for (i = 0; i < h; i++) {
>          /* Read potentially unaligned pixels into t1 and t2 */
>          perm1 = vec_lvsl(0, pix1);
> -        pix1v = (vector unsigned char *) pix1;
> +        pix1v_high = vec_ld( 0, pix1);
> +        pix1v_low  = vec_ld(15, pix1);
>          perm2 = vec_lvsl(0, pix2);
> -        pix2v = (vector unsigned char *) pix2;
> -        t1 = vec_perm(pix1v[0], pix1v[1], perm1);
> -        t2 = vec_perm(pix2v[0], pix2v[1], perm2);
> +        pix2v_high = vec_ld( 0, pix2);
> +        pix2v_low  = vec_ld(15, pix2);
> +        t1 = vec_perm(pix1v_high, pix1v_low, perm1);
> +        t2 = vec_perm(pix2v_high, pix2v_low, perm2);
>  
>          /* Calculate a sum of abs differences vector */
>          t3 = vec_max(t1, t2);
> -- 
> 1.7.3.5

Looks sane to me.

-- 
M?ns Rullg?rd
mans at mansr.com