[FFmpeg-devel] Resubmit patch02 - [patch 4/4] Fix bug forPOWERLE: libswscale/ppc/swscale_altivec.c

Michael Niedermayer michaelni at gmx.at
Tue Nov 11 19:31:29 CET 2014


[...]

> @@ -140,31 +180,15 @@ static void hScale_altivec_real(SwsContext *c, int16_t *dst, int dstW,
>              for (i = 0; i < dstW; i++) {
>                  register int srcPos = filterPos[i];
>  
> -                vector unsigned char src_v0 = vec_ld(srcPos, src);
> -                vector unsigned char src_v1, src_vF;
> +                vector unsigned char src_vF = unaligned_load(srcPos, src);
>                  vector signed short src_v, filter_v;
>                  vector signed int val_vEven, val_s;
> -                if ((((uintptr_t)src + srcPos) % 16) > 12) {
> -                    src_v1 = vec_ld(srcPos + 16, src);
> -                }
> -                src_vF = vec_perm(src_v0, src_v1, vec_lvsl(srcPos, src));
> -
>                  src_v = // vec_unpackh sign-extends...
> -                        (vector signed short)(vec_mergeh((vector unsigned char)vzero, src_vF));
> +                        (vector signed short)(VEC_MERGEH((vector unsigned char)vzero, src_vF));
>                  // now put our elements in the even slots
>                  src_v = vec_mergeh(src_v, (vector signed short)vzero);
> -
> -                filter_v = vec_ld(i << 3, filter);
> -                // The 3 above is 2 (filterSize == 4) + 1 (sizeof(short) == 2).
> -
> -                // The neat trick: We only care for half the elements,
> -                // high or low depending on (i<<3)%16 (it's 0 or 8 here),
> -                // and we're going to use vec_mule, so we choose
> -                // carefully how to "unpack" the elements into the even slots.
> -                if ((i << 3) % 16)
> -                    filter_v = vec_mergel(filter_v, (vector signed short)vzero);
> -                else
> -                    filter_v = vec_mergeh(filter_v, (vector signed short)vzero);
> +                filter_v = (vector signed short)unaligned_load(i << 3, filter);
> +                filter_v = vec_mergeh(filter_v, (vector signed short)vzero);
>  
>                  val_vEven = vec_mule(src_v, filter_v);
>                  val_s     = vec_sums(val_vEven, vzero);

i see 3 vec_ld() before and 2 unaligned_load() each 2 vec_ld()
afterwards on big endian


> @@ -172,25 +196,16 @@ static void hScale_altivec_real(SwsContext *c, int16_t *dst, int dstW,
>                  dst[i] = FFMIN(tempo[3] >> 7, (1 << 15) - 1);
>              }
>          break;
> -
>          case 8:
>              for (i = 0; i < dstW; i++) {
>                  register int srcPos = filterPos[i];
>  
> -                vector unsigned char src_v0 = vec_ld(srcPos, src);
> -                vector unsigned char src_v1, src_vF;
> +                vector unsigned char src_vF = unaligned_load(srcPos, src);
>                  vector signed short src_v, filter_v;
>                  vector signed int val_v, val_s;
> -                if ((((uintptr_t)src + srcPos) % 16) > 8) {
> -                    src_v1 = vec_ld(srcPos + 16, src);
> -                }
> -                src_vF = vec_perm(src_v0, src_v1, vec_lvsl(srcPos, src));
> -
>                  src_v = // vec_unpackh sign-extends...
> -                        (vector signed short)(vec_mergeh((vector unsigned char)vzero, src_vF));
> +                        (vector signed short)(VEC_MERGEH((vector unsigned char)vzero, src_vF));
>                  filter_v = vec_ld(i << 4, filter);
> -                // the 4 above is 3 (filterSize == 8) + 1 (sizeof(short) == 2)
> -
>                  val_v = vec_msums(src_v, filter_v, (vector signed int)vzero);
>                  val_s = vec_sums(val_v, vzero);
>                  vec_st(val_s, 0, tempo);
> @@ -202,25 +217,20 @@ static void hScale_altivec_real(SwsContext *c, int16_t *dst, int dstW,
>              for (i = 0; i < dstW; i++) {
>                  register int srcPos = filterPos[i];
>  
> -                vector unsigned char src_v0 = vec_ld(srcPos, src);
> -                vector unsigned char src_v1 = vec_ld(srcPos + 16, src);
> -                vector unsigned char src_vF = vec_perm(src_v0, src_v1, vec_lvsl(srcPos, src));
> -
> +                vector unsigned char src_vF = unaligned_load(srcPos, src);
>                  vector signed short src_vA = // vec_unpackh sign-extends...
> -                                             (vector signed short)(vec_mergeh((vector unsigned char)vzero, src_vF));
> +                                             (vector signed short)(VEC_MERGEH((vector unsigned char)vzero, src_vF));
>                  vector signed short src_vB = // vec_unpackh sign-extends...
> -                                             (vector signed short)(vec_mergel((vector unsigned char)vzero, src_vF));
> -
> +                                             (vector signed short)(VEC_MERGEL((vector unsigned char)vzero, src_vF));
>                  vector signed short filter_v0 = vec_ld(i << 5, filter);
>                  vector signed short filter_v1 = vec_ld((i << 5) + 16, filter);
> -                // the 5 above are 4 (filterSize == 16) + 1 (sizeof(short) == 2)
>  
>                  vector signed int val_acc = vec_msums(src_vA, filter_v0, (vector signed int)vzero);
>                  vector signed int val_v   = vec_msums(src_vB, filter_v1, val_acc);
>  
>                  vector signed int val_s = vec_sums(val_v, vzero);
>  
> -                vec_st(val_s, 0, tempo);
> +                VEC_ST(val_s, 0, tempo);
>                  dst[i] = FFMIN(tempo[3] >> 7, (1 << 15) - 1);
>              }
>          break;
> @@ -231,56 +241,34 @@ static void hScale_altivec_real(SwsContext *c, int16_t *dst, int dstW,
>                  register int srcPos = filterPos[i];
>  
>                  vector signed int val_s, val_v = (vector signed int)vzero;
> -                vector signed short filter_v0R = vec_ld(i * 2 * filterSize, filter);
> -                vector unsigned char permF     = vec_lvsl((i * 2 * filterSize), filter);
> -
> -                vector unsigned char src_v0 = vec_ld(srcPos, src);
> -                vector unsigned char permS  = vec_lvsl(srcPos, src);
>  

>                  for (j = 0; j < filterSize - 15; j += 16) {
> -                    vector unsigned char src_v1 = vec_ld(srcPos + j + 16, src);
> -                    vector unsigned char src_vF = vec_perm(src_v0, src_v1, permS);
> -
> +                    vector unsigned char src_vF = unaligned_load(srcPos + j, src);
>                      vector signed short src_vA = // vec_unpackh sign-extends...
> -                                                 (vector signed short)(vec_mergeh((vector unsigned char)vzero, src_vF));
> +                                                 (vector signed short)(VEC_MERGEH((vector unsigned char)vzero, src_vF));
>                      vector signed short src_vB = // vec_unpackh sign-extends...
> -                                                 (vector signed short)(vec_mergel((vector unsigned char)vzero, src_vF));
> -
> -                    vector signed short filter_v1R = vec_ld((i * 2 * filterSize) + (j * 2) + 16, filter);
> -                    vector signed short filter_v2R = vec_ld((i * 2 * filterSize) + (j * 2) + 32, filter);
> -                    vector signed short filter_v0  = vec_perm(filter_v0R, filter_v1R, permF);
> -                    vector signed short filter_v1  = vec_perm(filter_v1R, filter_v2R, permF);
> +                                                 (vector signed short)(VEC_MERGEL((vector unsigned char)vzero, src_vF));
> +                    vector signed short filter_v0  = (vector signed short)unaligned_load((i * 2 * filterSize) + (j * 2), filter);
> +                    vector signed short filter_v1  = (vector signed short)unaligned_load((i * 2 * filterSize) + (j * 2) + 16, filter);
>  
>                      vector signed int val_acc = vec_msums(src_vA, filter_v0, val_v);
>                      val_v = vec_msums(src_vB, filter_v1, val_acc);
> -
> -                    filter_v0R = filter_v2R;
> -                    src_v0     = src_v1;
>                  }

i count 3 vec_ld() before and 6 (2 for each unaligned_load())
after the change for big endian

[...]


-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Awnsering whenever a program halts or runs forever is
On a turing machine, in general impossible (turings halting problem).
On any real computer, always possible as a real computer has a finite number
of states N, and will either halt in less than N cycles or never halt.
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