[Mesa-dev] [PATCH 28/29] i965: Drop random 32-bit assembly implementation of memcpy().

[Ian Romanick]

On 09/27/2013 04:46 PM, Kenneth Graunke wrote:
> This was only used for uploading batchbuffer data, and only on 32-bit
> systems.  If this is actually useful, we might want to use it more
> widely.  But more than likely, it isn't.

This probably is still useful, alas.  The glibc memcpy wants to do an
Atom-friendly backwards walk of the addresses.  For some kinds of
mappings (uncached?), this breaks write combining and ruins performance.

We didn't need this for 64-bit because, at the time, there were no
64-bit Atoms.  I don't know what glibc does for memcpy on 64-bit these days.

We should at least measure this in some 32-bit games on a couple platforms.

> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> ---
>  src/mesa/drivers/dri/i965/intel_batchbuffer.c |  2 +-
>  src/mesa/drivers/dri/i965/intel_context.h     | 28 ---------------------------
>  2 files changed, 1 insertion(+), 29 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/intel_batchbuffer.c b/src/mesa/drivers/dri/i965/intel_batchbuffer.c
> index 77f3ada..a1e5ffc 100644
> --- a/src/mesa/drivers/dri/i965/intel_batchbuffer.c
> +++ b/src/mesa/drivers/dri/i965/intel_batchbuffer.c
> @@ -343,7 +343,7 @@ intel_batchbuffer_data(struct brw_context *brw,
>  {
>     assert((bytes & 3) == 0);
>     intel_batchbuffer_require_space(brw, bytes, is_blit);
> -   __memcpy(brw->batch.map + brw->batch.used, data, bytes);
> +   memcpy(brw->batch.map + brw->batch.used, data, bytes);
>     brw->batch.used += bytes >> 2;
>  }
>  
> diff --git a/src/mesa/drivers/dri/i965/intel_context.h b/src/mesa/drivers/dri/i965/intel_context.h
> index 58a6e86..89cbb7f 100644
> --- a/src/mesa/drivers/dri/i965/intel_context.h
> +++ b/src/mesa/drivers/dri/i965/intel_context.h
> @@ -97,34 +97,6 @@ struct intel_batchbuffer {
>  };
>  
>  /* ================================================================
> - * From linux kernel i386 header files, copes with odd sizes better
> - * than COPY_DWORDS would:
> - * XXX Put this in src/mesa/main/imports.h ???
> - */
> -#if defined(i386) || defined(__i386__)
> -static INLINE void * __memcpy(void * to, const void * from, size_t n)
> -{
> -   int d0, d1, d2;
> -   __asm__ __volatile__(
> -      "rep ; movsl\n\t"
> -      "testb $2,%b4\n\t"
> -      "je 1f\n\t"
> -      "movsw\n"
> -      "1:\ttestb $1,%b4\n\t"
> -      "je 2f\n\t"
> -      "movsb\n"
> -      "2:"
> -      : "=&c" (d0), "=&D" (d1), "=&S" (d2)
> -      :"0" (n/4), "q" (n),"1" ((long) to),"2" ((long) from)
> -      : "memory");
> -   return (to);
> -}
> -#else
> -#define __memcpy(a,b,c) memcpy(a,b,c)
> -#endif
> -
> -
> -/* ================================================================
>   * intel_context.c:
>   */
>  
>