glsl: Refactor handling of gl_ClipDistance/gl_ClipVertex linkage rules for GS.

This patch extracts the following logic from
validate_vertex_shader_executable():

(a) Generate an error if the shader writes to both gl_ClipDistance and
    gl_ClipVertex.

(b) Record whether the shader writes to gl_ClipDistance in
    gl_shader_program for use by the back-end.

(c) Record the size of gl_ClipDistance in gl_shader_program for use by
    transform feedback logic.

And moves it into a function that is shared between vertex and
geometry shaders.

Strictly speaking we only need to have shared logic for (b) and (c)
right now (since (a) only matters in compatibility contexts, and we're
only implementing geometry shaders in core contexts right now).  But
the three are closely related enough that it seems sensible to keep
them together.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>

3 files changed, 62 insertions, 29 deletions

diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index f87ae0eecf4..8430096aca8 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -373,6 +373,52 @@ link_invalidate_variable_locations(gl_shader *sh, int input_base,
 
 
 /**
+ * Set UsesClipDistance and ClipDistanceArraySize based on the given shader.
+ *
+ * Also check for errors based on incorrect usage of gl_ClipVertex and
+ * gl_ClipDistance.
+ *
+ * Return false if an error was reported.
+ */
+static void
+analyze_clip_usage(const char *shader_type, struct gl_shader_program *prog,
+                   struct gl_shader *shader, GLboolean *UsesClipDistance,
+                   GLuint *ClipDistanceArraySize)
+{
+   *ClipDistanceArraySize = 0;
+
+   if (!prog->IsES && 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 nor gl_ClipDistance.
+       */
+      find_assignment_visitor clip_vertex("gl_ClipVertex");
+      find_assignment_visitor clip_distance("gl_ClipDistance");
+
+      clip_vertex.run(shader->ir);
+      clip_distance.run(shader->ir);
+      if (clip_vertex.variable_found() && clip_distance.variable_found()) {
+         linker_error(prog, "%s shader writes to both `gl_ClipVertex' "
+                      "and `gl_ClipDistance'\n", shader_type);
+         return;
+      }
+      *UsesClipDistance = clip_distance.variable_found();
+      ir_variable *clip_distance_var =
+         shader->symbols->get_variable("gl_ClipDistance");
+      if (clip_distance_var)
+         *ClipDistanceArraySize = clip_distance_var->type->length;
+   } else {
+      *UsesClipDistance = false;
+   }
+}
+
+
+/**
  * Verify that a vertex shader executable meets all semantic requirements.
  *
  * Also sets prog->Vert.UsesClipDistance and prog->Vert.ClipDistanceArraySize
@@ -422,34 +468,8 @@ validate_vertex_shader_executable(struct gl_shader_program *prog,
       }
    }
 
-   prog->Vert.ClipDistanceArraySize = 0;
-
-   if (!prog->IsES && 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 nor gl_ClipDistance.
-       */
-      find_assignment_visitor clip_vertex("gl_ClipVertex");
-      find_assignment_visitor clip_distance("gl_ClipDistance");
-
-      clip_vertex.run(shader->ir);
-      clip_distance.run(shader->ir);
-      if (clip_vertex.variable_found() && clip_distance.variable_found()) {
-         linker_error(prog, "vertex shader writes to both `gl_ClipVertex' "
-                      "and `gl_ClipDistance'\n");
-         return;
-      }
-      prog->Vert.UsesClipDistance = clip_distance.variable_found();
-      ir_variable *clip_distance_var =
-         shader->symbols->get_variable("gl_ClipDistance");
-      if (clip_distance_var)
-         prog->Vert.ClipDistanceArraySize = clip_distance_var->type->length;
-   }
+   analyze_clip_usage("vertex", prog, shader, &prog->Vert.UsesClipDistance,
+                      &prog->Vert.ClipDistanceArraySize);
 }
 
 
@@ -480,7 +500,8 @@ validate_fragment_shader_executable(struct gl_shader_program *prog,
 /**
  * Verify that a geometry shader executable meets all semantic requirements
  *
- * Also sets prog->Geom.VerticesIn as a side effect.
+ * Also sets prog->Geom.VerticesIn, prog->Geom.UsesClipDistance, and
+ * prog->Geom.ClipDistanceArraySize as a side effect.
  *
  * \param shader Geometry shader executable to be verified
  */
@@ -493,6 +514,9 @@ validate_geometry_shader_executable(struct gl_shader_program *prog,
 
    unsigned num_vertices = vertices_per_prim(prog->Geom.InputType);
    prog->Geom.VerticesIn = num_vertices;
+
+   analyze_clip_usage("geometry", prog, shader, &prog->Geom.UsesClipDistance,
+                      &prog->Geom.ClipDistanceArraySize);
 }
 
 
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index 5f9b7f98394..22bb58c5fe2 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -1924,6 +1924,7 @@ struct gl_geometry_program
    GLenum InputType;  /**< GL_POINTS, GL_LINES, GL_LINES_ADJACENCY_ARB,
                            GL_TRIANGLES, or GL_TRIANGLES_ADJACENCY_ARB */
    GLenum OutputType; /**< GL_POINTS, GL_LINE_STRIP or GL_TRIANGLE_STRIP */
+   GLboolean UsesClipDistance;
 };
 
 
@@ -2348,6 +2349,13 @@ struct gl_shader_program
       GLenum InputType;  /**< GL_POINTS, GL_LINES, GL_LINES_ADJACENCY_ARB,
                               GL_TRIANGLES, or GL_TRIANGLES_ADJACENCY_ARB */
       GLenum OutputType; /**< GL_POINTS, GL_LINE_STRIP or GL_TRIANGLE_STRIP */
+      /**
+       * True if gl_ClipDistance is written to.  Copied into
+       * gl_geometry_program by _mesa_copy_linked_program_data().
+       */
+      GLboolean UsesClipDistance;
+      GLuint ClipDistanceArraySize; /**< Size of the gl_ClipDistance array, or
+                                         0 if not present. */
    } Geom;
 
    /** Vertex shader state */
diff --git a/src/mesa/main/shaderapi.c b/src/mesa/main/shaderapi.c
index d184b114cb9..4fe9d9ca252 100644
--- a/src/mesa/main/shaderapi.c
+++ b/src/mesa/main/shaderapi.c
@@ -1871,6 +1871,7 @@ _mesa_copy_linked_program_data(gl_shader_type type,
       dst_gp->VerticesOut = src->Geom.VerticesOut;
       dst_gp->InputType = src->Geom.InputType;
       dst_gp->OutputType = src->Geom.OutputType;
+      dst_gp->UsesClipDistance = src->Geom.UsesClipDistance;
    }
       break;
    default: