[Mesa-dev] [PATCH] mesa: add const flags to skip MaxVarying and MaxUniform linker checks

[Marek Olšák]

This is only temporary until a better solution is available.
---

I haven't given up yet because reporting incorrect driver limits
may cause more troubles than this. I made it pretty small this
time.

It doesn't change any driver besides Gallium. Please review,
especially the part in st_extensions.c whether it's acceptable
or whether some other conditions should be used instead.
(e.g. strcmp(get_vendor(), "X.Org R300 Project") is possible too)

I plan to implement a better solution, so that this code can go
away.

I see only two ways out of this.

The first one is:
- Let Gallium drivers report an error when they can't run
  a certain shader.

The second one is:
- Remove the Mesa IR.
- Replace TGSI by the GLSL IR completely.
- Move the dead-constant elimination pass from the R300 compiler
  to the GLSL IR.
- Implement a GLSL optimization pass which breaks varying arrays
  into separate elements when possible.

Thanks.

 src/glsl/linker.cpp                    |    9 ++++++---
 src/mesa/main/mtypes.h                 |    9 +++++++++
 src/mesa/state_tracker/st_extensions.c |    8 ++++++++
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index 3527088..fe35ed3 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -1814,7 +1814,8 @@ assign_varying_locations(struct gl_context *ctx,
    }
 
    if (ctx->API == API_OPENGLES2 || prog->Version == 100) {
-      if (varying_vectors > ctx->Const.MaxVarying) {
+      if (varying_vectors > ctx->Const.MaxVarying &&
+          !ctx->Const.GLSLSkipStrictMaxVaryingLimitCheck) {
 	 linker_error(prog, "shader uses too many varying vectors "
 		      "(%u > %u)\n",
 		      varying_vectors, ctx->Const.MaxVarying);
@@ -1822,7 +1823,8 @@ assign_varying_locations(struct gl_context *ctx,
       }
    } else {
       const unsigned float_components = varying_vectors * 4;
-      if (float_components > ctx->Const.MaxVarying * 4) {
+      if (float_components > ctx->Const.MaxVarying * 4 &&
+          !ctx->Const.GLSLSkipStrictMaxVaryingLimitCheck) {
 	 linker_error(prog, "shader uses too many varying components "
 		      "(%u > %u)\n",
 		      float_components, ctx->Const.MaxVarying * 4);
@@ -1959,7 +1961,8 @@ check_resources(struct gl_context *ctx, struct gl_shader_program *prog)
 		      shader_names[i]);
       }
 
-      if (sh->num_uniform_components > max_uniform_components[i]) {
+      if (sh->num_uniform_components > max_uniform_components[i] &&
+          !ctx->Const.GLSLSKipStrictMaxUniformLimitCheck) {
          linker_error(prog, "Too many %s shader uniform components",
 		      shader_names[i]);
       }
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index fc494f7..7e9f6ca 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -2829,6 +2829,15 @@ struct gl_constants
     * Texture borders are deprecated in GL 3.0.
     **/
    GLboolean StripTextureBorder;
+
+   /**
+    * For drivers which can do a better job at eliminating unused varyings
+    * and uniforms than the GLSL compiler.
+    *
+    * XXX Remove these as soon as a better solution is available.
+    */
+   GLboolean GLSLSkipStrictMaxVaryingLimitCheck;
+   GLboolean GLSLSKipStrictMaxUniformLimitCheck;
 };
 
 
diff --git a/src/mesa/state_tracker/st_extensions.c b/src/mesa/state_tracker/st_extensions.c
index 37fb3e7..fdaffa8 100644
--- a/src/mesa/state_tracker/st_extensions.c
+++ b/src/mesa/state_tracker/st_extensions.c
@@ -224,6 +224,14 @@ void st_init_limits(struct st_context *st)
    c->UniformBooleanTrue = ~0;
 
    c->StripTextureBorder = GL_TRUE;
+
+   c->GLSLSKipStrictMaxUniformLimitCheck =
+      screen->get_shader_param(screen, PIPE_SHADER_FRAGMENT,
+                               PIPE_SHADER_CAP_MAX_CONSTS) <= 256;
+
+   c->GLSLSkipStrictMaxVaryingLimitCheck =
+      screen->get_shader_param(screen, PIPE_SHADER_FRAGMENT,
+                               PIPE_SHADER_CAP_MAX_INPUTS) <= 10;
 }
 
 
-- 
1.7.5.4