[Mesa-dev] [PATCH 1/2] util: Add util_memcpy_cpu_to_le()

[Patrick Baggett]

On Tue, Jul 15, 2014 at 11:19 AM, Tom Stellard <thomas.stellard at amd.com>
wrote:

> ---
>  src/gallium/auxiliary/util/u_math.h      | 22 ++++++++++++++++++++++
>  src/gallium/drivers/radeonsi/si_shader.c |  8 +-------
>  2 files changed, 23 insertions(+), 7 deletions(-)
>
> diff --git a/src/gallium/auxiliary/util/u_math.h
> b/src/gallium/auxiliary/util/u_math.h
> index b9ed197..cd3cf04 100644
> --- a/src/gallium/auxiliary/util/u_math.h
> +++ b/src/gallium/auxiliary/util/u_math.h
> @@ -812,6 +812,28 @@ util_bswap16(uint16_t n)
>            (n << 8);
>  }
>
> +static INLINE void*
> +util_memcpy_cpu_to_le(void *dest, void *src, size_t n)
> +{
> +#ifdef PIPE_ARCH_BIG_ENDIAN
> +       size_t i, e;
> +       for (i = 0, e = n % 8; i < e; i++) {
> +               char *d = (char*)dest;
> +               char *s = (char*)src;
> +               d[i] = s[e - i - 1];
> +       }
> +       dest += i;
> +       n -= i;
> +       for (i = 0, e = n / 8; i < e; i++) {
> +               uint64_t *d = (uint64_t*)dest;
> +               uint64_t *s = (uint64_t*)src;
> +               d[i] = util_bswap64(s[e - i - 1]);
> +       }
>

Doesn't this reverse all of the byte (as if it were a list) without
preserving word boundaries? e.g.

|a, b, c, d | e, f, g, h | i, j, k, l | m, n, o, p | ->
|p, o, n, m | l, j, k, i | h, g, f, e | d, c, b, a |

The old code did something like this, didn't it?:
|a, b, c, d | e, f, g, h | i, j, k, l | m, n, o, p | ->
|d, c, b, a | h, g, f, e | l, k, j, i | p, o, n, m |

I don't know which is correct, but it does seem like a behavior change. Or
am I misreading the code?

+       return dest;
> +#else
> +       return memcpy(dest, src, n);
> +#endif
> +}
>
>  /**
>   * Clamp X to [MIN, MAX].
> diff --git a/src/gallium/drivers/radeonsi/si_shader.c
> b/src/gallium/drivers/radeonsi/si_shader.c
> index f0650f4..6f0504b 100644
> --- a/src/gallium/drivers/radeonsi/si_shader.c
> +++ b/src/gallium/drivers/radeonsi/si_shader.c
> @@ -2559,13 +2559,7 @@ int si_compile_llvm(struct si_context *sctx, struct
> si_pipe_shader *shader,
>         }
>
>         ptr = (uint32_t*)sctx->b.ws->buffer_map(shader->bo->cs_buf,
> sctx->b.rings.gfx.cs, PIPE_TRANSFER_WRITE);
> -       if (SI_BIG_ENDIAN) {
> -               for (i = 0; i < binary.code_size / 4; ++i) {
> -                       ptr[i] =
> util_cpu_to_le32((*(uint32_t*)(binary.code + i*4)));
> -               }
> -       } else {
> -               memcpy(ptr, binary.code, binary.code_size);
> -       }
> +       util_memcpy_cpu_to_le(ptr, binary.code, binary.code_size);
>         sctx->b.ws->buffer_unmap(shader->bo->cs_buf);
>
>         free(binary.code);
> --
> 1.8.1.5
>
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