[Mesa-dev] [PATCH 1/3] svga: properly implement TRUNC instruction

[Jose Fonseca]

Reviewed-by: Jose Fonseca <jfonseca at vmware.com>

----- Original Message -----
> Was previously implemented with FLOOR.
> Fixes quite a few piglit tests of float->int conversion, integer
> division, etc.
> 
> v2: clean up left over debug/devel code, per Jose
> ---
>  src/gallium/drivers/svga/svga_tgsi_insn.c |   55
>  ++++++++++++++++++++++++++++-
>  1 files changed, 54 insertions(+), 1 deletions(-)
> 
> diff --git a/src/gallium/drivers/svga/svga_tgsi_insn.c
> b/src/gallium/drivers/svga/svga_tgsi_insn.c
> index 75853aa..595b06d 100644
> --- a/src/gallium/drivers/svga/svga_tgsi_insn.c
> +++ b/src/gallium/drivers/svga/svga_tgsi_insn.c
> @@ -2374,6 +2374,57 @@ static boolean emit_log(struct
> svga_shader_emitter *emit,
>  }
>  
>  
> +/**
> + * Translate TGSI TRUNC instruction.
> + * We need to truncate toward zero. Ex: trunc(-1.9) = -1
> + * Different approaches are needed for VS versus PS.
> + */
> +static boolean
> +emit_trunc(struct svga_shader_emitter *emit,
> +           const struct tgsi_full_instruction *insn)
> +{
> +   SVGA3dShaderDestToken dst = translate_dst_register(emit, insn,
> 0);
> +   const struct src_register src0 =
> +      translate_src_register(emit, &insn->Src[0] );
> +   SVGA3dShaderDestToken t1 = get_temp(emit);
> +
> +   /* t1 = fract(abs(src0)) */
> +   if (!submit_op1(emit, inst_token(SVGA3DOP_FRC), t1,
> absolute(src0)))
> +      return FALSE;
> +
> +   /* t1 = abs(src0) - t1 */
> +   if (!submit_op2(emit, inst_token(SVGA3DOP_ADD), t1,
> absolute(src0),
> +                   negate(src(t1))))
> +      return FALSE;
> +
> +   /*
> +    * Now we need to multiply t1 by the sign of the original value.
> +   */
> +   if (emit->unit == PIPE_SHADER_VERTEX) {
> +      /* For VS: use SGN instruction */
> +      /* Need another temp plus two extra/dummy registers */
> +      SVGA3dShaderDestToken t2 = get_temp(emit), t3 =
> get_temp(emit),
> +         t4 = get_temp(emit);
> +
> +      /* t2 = sign(src0) */
> +      if (!submit_op3(emit, inst_token(SVGA3DOP_SGN), t2, src0,
> +                      src(t3), src(t4)))
> +         return FALSE;
> +
> +      /* dst = t1 * t2 */
> +      if (!submit_op2(emit, inst_token(SVGA3DOP_MUL), dst, src(t1),
> src(t2)))
> +         return FALSE;
> +   }
> +   else {
> +      /* For FS: Use CMP instruction */
> +      return submit_op3(emit, inst_token( SVGA3DOP_CMP ), dst,
> +                        src0, src(t1), negate(src(t1)));
> +   }
> +
> +   return TRUE;
> +}
> +
> +
>  static boolean emit_bgnsub( struct svga_shader_emitter *emit,
>                             unsigned position,
>                             const struct tgsi_full_instruction *insn
>                             )
> @@ -2464,9 +2515,11 @@ static boolean svga_emit_instruction( struct
> svga_shader_emitter *emit,
>        return emit_call( emit, insn );
>  
>     case TGSI_OPCODE_FLR:
> -   case TGSI_OPCODE_TRUNC:        /* should be TRUNC, not FLR */
>        return emit_floor( emit, insn );
>  
> +   case TGSI_OPCODE_TRUNC:
> +      return emit_trunc( emit, insn );
> +
>     case TGSI_OPCODE_CEIL:
>        return emit_ceil( emit, insn );
>  
> --
> 1.7.3.4
> 
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