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 <[email protected]>
Reviewed-by: Ian Romanick <[email protected]>
Reviewed-by: Matt Turner <[email protected]>

2 files changed, 9 insertions, 0 deletions

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: