[Mesa-dev] [PATCH 4/8] glsl: Add new builtins required by GL_ARB_sample_shading

[Ian Romanick]

On 10/14/2013 10:12 AM, Anuj Phogat wrote:
> New builtins added by GL_ARB_sample_shading:
> in vec2 gl_SamplePosition
> in int gl_SampleID
> in int gl_NumSamples
> out int gl_SampleMask[]
> 
> Signed-off-by: Anuj Phogat <anuj.phogat at gmail.com>
> ---
>  src/glsl/builtin_variables.cpp | 11 +++++++++++
>  src/glsl/link_varyings.cpp     |  2 ++
>  src/mesa/main/mtypes.h         |  7 ++++++-
>  src/mesa/program/prog_print.c  |  5 +++++
>  4 files changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/src/glsl/builtin_variables.cpp b/src/glsl/builtin_variables.cpp
> index ae0a03f..c886840 100644
> --- a/src/glsl/builtin_variables.cpp
> +++ b/src/glsl/builtin_variables.cpp
> @@ -30,6 +30,9 @@
>  #include "program/prog_statevars.h"
>  #include "program/prog_instruction.h"
>  
> +static struct gl_builtin_uniform_element gl_NumSamples_elements[] = {
> +   {NULL, {STATE_NUM_SAMPLES, 0, 0}, SWIZZLE_XYZW}
> +};
>  
>  static struct gl_builtin_uniform_element gl_DepthRange_elements[] = {
>     {"near", {STATE_DEPTH_RANGE, 0, 0}, SWIZZLE_XXXX},
> @@ -236,6 +239,7 @@ static struct gl_builtin_uniform_element gl_NormalMatrix_elements[] = {
>  #define STATEVAR(name) {#name, name ## _elements, Elements(name ## _elements)}
>  
>  static const struct gl_builtin_uniform_desc _mesa_builtin_uniform_desc[] = {
> +   STATEVAR(gl_NumSamples),
>     STATEVAR(gl_DepthRange),
>     STATEVAR(gl_ClipPlane),
>     STATEVAR(gl_Point),
> @@ -613,6 +617,7 @@ builtin_variable_generator::generate_constants()
>  void
>  builtin_variable_generator::generate_uniforms()
>  {
> +   add_uniform(int_t, "gl_NumSamples");
>     add_uniform(type("gl_DepthRangeParameters"), "gl_DepthRange");
>     add_uniform(array(vec4_t, VERT_ATTRIB_MAX), "gl_CurrentAttribVertMESA");
>     add_uniform(array(vec4_t, VARYING_SLOT_MAX), "gl_CurrentAttribFragMESA");
> @@ -789,6 +794,12 @@ builtin_variable_generator::generate_fs_special_vars()
>        if (state->AMD_shader_stencil_export_warn)
>           var->warn_extension = "GL_AMD_shader_stencil_export";
>     }
> +
> +   if (state->ARB_sample_shading_enable) {
> +      add_input(VARYING_SLOT_SAMPLE_ID, int_t, "gl_SampleID");
> +      add_input(VARYING_SLOT_SAMPLE_POS, vec2_t, "gl_SamplePosition");
> +      add_output(FRAG_RESULT_SAMPLE_MASK, array(int_t, 1), "gl_SampleMask");

I don't see code anywhere in this patch series that correctly sizes this
array.  I thought gl_SampleMask.length() == gl_NumSamples... except you
can't use .length() on gl_SampleMask because the size can't be known at
compile-time.  We should have a test that 'gl_SampleMask.length()' fails
to compile. :)

The only other array that works like this is gl_TexCoord.  That array is
sized to 0 (line 837 of builtin_variables.cpp).  I believe gl_SampleMask
should do the same.

> +   }
>  }
>  
>  
> diff --git a/src/glsl/link_varyings.cpp b/src/glsl/link_varyings.cpp
> index 4ba6d8a..3595a58 100644
> --- a/src/glsl/link_varyings.cpp
> +++ b/src/glsl/link_varyings.cpp
> @@ -938,6 +938,8 @@ is_varying_var(GLenum shaderType, const ir_variable *var)
>        case VARYING_SLOT_POS:
>        case VARYING_SLOT_FACE:
>        case VARYING_SLOT_PNTC:
> +      case VARYING_SLOT_SAMPLE_ID:
> +      case VARYING_SLOT_SAMPLE_POS:
>           return false;
>        default:
>           return true;
> diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
> index 5520e86..65ec829 100644
> --- a/src/mesa/main/mtypes.h
> +++ b/src/mesa/main/mtypes.h
> @@ -236,6 +236,8 @@ typedef enum
>     VARYING_SLOT_LAYER, /* Appears as VS or GS output */
>     VARYING_SLOT_FACE, /* FS only */
>     VARYING_SLOT_PNTC, /* FS only */
> +   VARYING_SLOT_SAMPLE_ID, /* FS only */
> +   VARYING_SLOT_SAMPLE_POS, /* FS only */
>     VARYING_SLOT_VAR0, /* First generic varying slot */
>     VARYING_SLOT_MAX = VARYING_SLOT_VAR0 + MAX_VARYING
>  } gl_varying_slot;
> @@ -272,6 +274,8 @@ typedef enum
>  #define VARYING_BIT_FACE BITFIELD64_BIT(VARYING_SLOT_FACE)
>  #define VARYING_BIT_PNTC BITFIELD64_BIT(VARYING_SLOT_PNTC)
>  #define VARYING_BIT_VAR(V) BITFIELD64_BIT(VARYING_SLOT_VAR0 + (V))
> +#define VARYING_BIT_SAMPLE_ID BITFIELD64_BIT(VARYING_SLOT_SAMPLE_ID)
> +#define VARYING_BIT_SAMPLE_POS BITFIELD64_BIT(VARYING_SLOT_SAMPLE_POS)
>  /*@}*/
>  
>  
> @@ -306,12 +310,13 @@ typedef enum
>      * register is written.  No FRAG_RESULT_DATAn will be written.
>      */
>     FRAG_RESULT_COLOR = 2,
> +   FRAG_RESULT_SAMPLE_MASK = 3,
>  
>     /* FRAG_RESULT_DATAn are the per-render-target (GLSL gl_FragData[n]
>      * or ARB_fragment_program fragment.color[n]) color results.  If
>      * any are written, FRAG_RESULT_COLOR will not be written.
>      */
> -   FRAG_RESULT_DATA0 = 3,
> +   FRAG_RESULT_DATA0 = 4,
>     FRAG_RESULT_MAX = (FRAG_RESULT_DATA0 + MAX_DRAW_BUFFERS)
>  } gl_frag_result;
>  
> diff --git a/src/mesa/program/prog_print.c b/src/mesa/program/prog_print.c
> index cf85213..0c56ae6 100644
> --- a/src/mesa/program/prog_print.c
> +++ b/src/mesa/program/prog_print.c
> @@ -150,6 +150,8 @@ arb_input_attrib_string(GLint index, GLenum progType)
>        "fragment.(twenty)", /* VARYING_SLOT_LAYER */
>        "fragment.(twenty-one)", /* VARYING_SLOT_FACE */
>        "fragment.(twenty-two)", /* VARYING_SLOT_PNTC */
> +      "fragment.(twenty-three)", /* VARYING_SLOT_SAMPLE_ID */
> +      "fragment.(twenty-four)", /* VARYING_SLOT_SAMPLE_POS */

Can we just call these "fragment.sampleid" and "fragment.samplepos"?

>        "fragment.varying[0]",
>        "fragment.varying[1]",
>        "fragment.varying[2]",
> @@ -274,6 +276,8 @@ arb_output_attrib_string(GLint index, GLenum progType)
>        "result.(twenty)", /* VARYING_SLOT_LAYER */
>        "result.(twenty-one)", /* VARYING_SLOT_FACE */
>        "result.(twenty-two)", /* VARYING_SLOT_PNTC */
> +      "result.(twenty-three)", /* VARYING_SLOT_SAMPLE_ID */
> +      "result.(twenty-four)", /* VARYING_SLOT_SAMPLE_POS */

Since these should never appear in a vertex shader, I think it's okay to
leave these as "result.(twenty-...)".

>        "result.varying[0]",
>        "result.varying[1]",
>        "result.varying[2]",
> @@ -311,6 +315,7 @@ arb_output_attrib_string(GLint index, GLenum progType)
>        "result.depth", /* FRAG_RESULT_DEPTH */
>        "result.(one)", /* FRAG_RESULT_STENCIL */
>        "result.color", /* FRAG_RESULT_COLOR */
> +      "result.sample_mask", /* FRAG_RESULT_SAMPLE_MASK */

NV_gpu_shader5 doesn't have the _, so I think "result.samplemask" is
slightly better.

>        "result.color[0]", /* FRAG_RESULT_DATA0 (named for GLSL's gl_FragData) */
>        "result.color[1]",
>        "result.color[2]",
>