[Mesa-dev] [PATCH 18/26] glsl: Fix linker checks for GLSL ES 3.00.

[Kenneth Graunke]

On 11/30/2012 10:07 AM, Ian Romanick wrote:
> From: Paul Berry <stereotype441 at gmail.com>
>
> This patch updates the following linker checks to do the right thing
> in GLSL 3.00 ES:
>
> - Failing to write to gl_Position is allowed in GLSL 1.40+ as well as
>    GLSL 3.00 ES.
>
> - It is an error to write to both gl_ClipVertex and gl_ClipDistance in
>    GLSL 1.30+.  This does not apply to GLSL 3.00 ES.
>
> - GLSL 3.00 ES uses the same varying counting rules as GLSL 1.00 ES.
>
> - In GLSL 1.30 and GLSL 3.00 ES, "discard" terminates the shader.
>
> - In GLSL 1.00 ES and GLSL 3.00 ES, both a fragment and a vertex
>    shader must be present.
>
> Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
> ---
>   src/glsl/linker.cpp | 22 +++++++++++++++-------
>   1 file changed, 15 insertions(+), 7 deletions(-)
>
> diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
> index d74911f..e2cd625 100644
> --- a/src/glsl/linker.cpp
> +++ b/src/glsl/linker.cpp
> @@ -289,8 +289,11 @@ validate_vertex_shader_executable(struct gl_shader_program *prog,
>       *      operations, if present, that operate on primitives after
>       *      vertex processing has occurred. Its value is undefined if
>       *      the vertex shader executable does not write gl_Position."
> +    *
> +    * GLSL ES 3.00 is similar to GLSL 1.40--failing to write to gl_Position is
> +    * not an error.
>       */
> -   if (prog->Version < 140) {
> +   if (prog->Version < (prog->IsEsProg ? 300 : 140)) {
>         find_assignment_visitor find("gl_Position");
>         find.run(shader->ir);
>         if (!find.variable_found()) {
> @@ -301,12 +304,15 @@ validate_vertex_shader_executable(struct gl_shader_program *prog,
>
>      prog->Vert.ClipDistanceArraySize = 0;
>
> -   if (prog->Version >= 130) {
> +   if (!prog->IsEsProg && prog->Version >= 130) {
>         /* From section 7.1 (Vertex Shader Special Variables) of the
>          * GLSL 1.30 spec:
>          *
>          *   "It is an error for a shader to statically write both
>          *   gl_ClipVertex and gl_ClipDistance."
> +       *
> +       * This does not apply to GLSL ES shaders, since GLSL ES defines neither
> +       * gl_ClipVertex not gl_ClipDistance.
>          */

Typo here: We want "neither...nor" rather than "neither...not".

Also, hooray for crippled APIs!

>         find_assignment_visitor clip_vertex("gl_ClipVertex");
>         find_assignment_visitor clip_distance("gl_ClipDistance");
> @@ -2144,7 +2150,7 @@ assign_varying_locations(struct gl_context *ctx,
>         }
>      }
>
> -   if (ctx->API == API_OPENGLES2 || prog->Version == 100) {
> +   if (ctx->API == API_OPENGLES2 || prog->IsEsProg) {
>         if (varying_vectors > ctx->Const.MaxVarying) {
>            if (ctx->Const.GLSLSkipStrictMaxVaryingLimitCheck) {
>               linker_warning(prog, "shader uses too many varying vectors "
> @@ -2539,8 +2545,10 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
>      /* Implement the GLSL 1.30+ rule for discard vs infinite loops Do
>       * it before optimization because we want most of the checks to get
>       * dropped thanks to constant propagation.
> +    *
> +    * This rule also applies to GLSL ES 3.00.
>       */
> -   if (max_version >= 130) {
> +   if (max_version >= (is_es_prog ? 300 : 130)) {
>         struct gl_shader *sh = prog->_LinkedShaders[MESA_SHADER_FRAGMENT];
>         if (sh) {
>   	 lower_discard_flow(sh->ir);
> @@ -2684,11 +2692,11 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
>         goto done;
>
>      /* OpenGL ES requires that a vertex shader and a fragment shader both be
> -    * present in a linked program.  By checking for use of shading language
> -    * version 1.00, we also catch the GL_ARB_ES2_compatibility case.
> +    * present in a linked program.  By checking prog->IsEsProg, we also
> +    * catch the GL_ARB_ES2_compatibility case.

Well.  GL_ARB_ES2/ES3_compatibility :)

>       */
>      if (!prog->InternalSeparateShader &&
> -       (ctx->API == API_OPENGLES2 || prog->Version == 100)) {
> +       (ctx->API == API_OPENGLES2 || prog->IsEsProg)) {
>         if (prog->_LinkedShaders[MESA_SHADER_VERTEX] == NULL) {
>   	 linker_error(prog, "program lacks a vertex shader\n");
>         } else if (prog->_LinkedShaders[MESA_SHADER_FRAGMENT] == NULL) {

Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>