On Thu, 2009-07-30 at 02:52 -0700, Micha?? Kr??l wrote:
> Module: Mesa
> Branch: master
> Commit: b724dd28e24ec1c38af1082f5e16cd9a12d1653d
> URL:    
> http://cgit.freedesktop.org/mesa/mesa/commit/?id=b724dd28e24ec1c38af1082f5e16cd9a12d1653d
> 
> Author: Michal Krol <[email protected]>
> Date:   Thu Jul 30 10:12:09 2009 +0200
> 
> tgsi: Document LOOP/ENDLOOP instruction operation.
> 
> ---
> 
>  .../auxiliary/tgsi/tgsi-instruction-set.txt        |   20 
> ++++++++++++++++++--
>  1 files changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/src/gallium/auxiliary/tgsi/tgsi-instruction-set.txt 
> b/src/gallium/auxiliary/tgsi/tgsi-instruction-set.txt
> index a3f4947..5f88cc2 100644
> --- a/src/gallium/auxiliary/tgsi/tgsi-instruction-set.txt
> +++ b/src/gallium/auxiliary/tgsi/tgsi-instruction-set.txt
> @@ -667,7 +667,16 @@ TGSI Instruction Specification
>  
>  1.9.8  LOOP - Loop
>  
> -  TBD
> +  dst.x = floor(src.x)
> +  dst.y = floor(src.y)
> +  dst.z = floor(src.z)
> +
> +  if (dst.y <= 0)
> +    pc = [matching ENDLOOP] + 1
> +  endif
> +
> +  Note: The destination must be a loop register.
> +        The source must be a constant register.
>  
> 
>  1.9.9  REP - Repeat
> @@ -687,7 +696,14 @@ TGSI Instruction Specification
>  
>  1.9.12  ENDLOOP - End Loop
>  
> -  TBD
> +  dst.x = dst.x + dst.z
> +  dst.y = dst.y - 1.0
> +
> +  if (dst.y > 0)
> +    pc = [matching LOOP instruction] + 1
> +  endif
> +
> +  Note: The destination must be a loop register.

Michal,

Does ENDLOOP (now known as as ENDFOR) really benefits from a destination
register? There is none in
http://msdn.microsoft.com/en-us/library/ms800316.aspx . It seems that a
destination register here only adds redundancy/inconsistency to the
shader.

Also, I don't think there is any point in describing what's in dst.x,
dst.y, dst.z, AFAICT, D3D LOOP variables can only be used for relative
addressing, and cannot have swizzles, i.e., are scalar, so they should
be described as such.

Jose


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