[Mesa-dev] [PATCH 2/3] svga: fix CMP translation for vertex shaders

[Jose Fonseca]

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

----- Original Message -----
> Converting CMP to SLT+LRP didn't work when src2 or src3 was Inf/NaN.
> That's the case for GLSL sqrt(0).  sqrt(0) actually happens in many
> piglit auto-generated tests that use the distance() function.
> 
> v2: remove debug/devel code, per Jose
> ---
>  src/gallium/drivers/svga/svga_tgsi_insn.c |   73
>  +++++++++++++++--------------
>  1 files changed, 37 insertions(+), 36 deletions(-)
> 
> diff --git a/src/gallium/drivers/svga/svga_tgsi_insn.c
> b/src/gallium/drivers/svga/svga_tgsi_insn.c
> index 595b06d..a2d6b51 100644
> --- a/src/gallium/drivers/svga/svga_tgsi_insn.c
> +++ b/src/gallium/drivers/svga/svga_tgsi_insn.c
> @@ -896,42 +896,6 @@ static boolean emit_ceil(struct
> svga_shader_emitter *emit,
>  }
>  
>  
> -/* Translate the following TGSI CMP instruction.
> - *    CMP  DST, SRC0, SRC1, SRC2
> - * To the following SVGA3D instruction sequence.
> - *    CMP  DST, SRC0, SRC2, SRC1
> - */
> -static boolean emit_cmp(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] );
> -   const struct src_register src1 = translate_src_register(
> -      emit, &insn->Src[1] );
> -   const struct src_register src2 = translate_src_register(
> -      emit, &insn->Src[2] );
> -
> -   if (emit->unit == PIPE_SHADER_VERTEX) {
> -      SVGA3dShaderDestToken temp = get_temp(emit);
> -      struct src_register zero = scalar(get_zero_immediate(emit),
> TGSI_SWIZZLE_X);
> -
> -      /* Since vertex shaders don't support the CMP instruction,
> -       * simulate it with SLT and LRP instructions.
> -       *    SLT  TMP, SRC0, 0.0
> -       *    LRP  DST, TMP, SRC1, SRC2
> -       */
> -      if (!submit_op2(emit, inst_token(SVGA3DOP_SLT), temp, src0,
> zero))
> -         return FALSE;
> -      return submit_lrp(emit, dst, src(temp), src1, src2);
> -   }
> -
> -   /* CMP  DST, SRC0, SRC2, SRC1 */
> -   return submit_op3( emit, inst_token( SVGA3DOP_CMP ), dst, src0,
> src2, src1);
> -}
> -
> -
> -
>  /* Translate the following TGSI DIV instruction.
>   *    DIV  DST.xy, SRC0, SRC1
>   * To the following SVGA3D instruction sequence.
> @@ -1421,6 +1385,43 @@ static boolean emit_select_op(struct
> svga_shader_emitter *emit,
>  }
>  
>  
> +/**
> + * Translate TGSI CMP instruction.
> + */
> +static boolean
> +emit_cmp(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] );
> +   const struct src_register src1 =
> +      translate_src_register(emit, &insn->Src[1] );
> +   const struct src_register src2 =
> +      translate_src_register(emit, &insn->Src[2] );
> +
> +   if (emit->unit == PIPE_SHADER_VERTEX) {
> +      struct src_register zero =
> +         scalar(get_zero_immediate(emit), TGSI_SWIZZLE_X);
> +      /* We used to simulate CMP with SLT+LRP.  But that didn't work
> when
> +       * src1 or src2 was Inf/NaN.  In particular, GLSL sqrt(0)
> failed
> +       * because it involves a CMP to handle the 0 case.
> +       * Use a conditional expression instead.
> +       */
> +      return emit_conditional(emit, PIPE_FUNC_LESS, dst,
> +                              src0, zero, src1, src2);
> +   }
> +   else {
> +      assert(emit->unit == PIPE_SHADER_FRAGMENT);
> +
> +      /* CMP  DST, SRC0, SRC2, SRC1 */
> +      return submit_op3( emit, inst_token( SVGA3DOP_CMP ), dst,
> +                         src0, src2, src1);
> +   }
> +
> +}
> +
> +
>  /* Translate texture instructions to SVGA3D representation.
>   */
>  static boolean emit_tex2(struct svga_shader_emitter *emit,
> --
> 1.7.3.4
> 
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