[Mesa-dev] [PATCH 4/8] glsl: Support gl_TessLevelInner/Outer[] as TES input variables.

[Kenneth Graunke]

Upcoming reworks in i965 are going to make it easy to handle this
like any other input.  Having it as a system value will just require
additional code for no benefit.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/compiler/glsl/builtin_variables.cpp | 15 +++++++++++----
 src/mesa/main/mtypes.h                  |  6 ++++++
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/compiler/glsl/builtin_variables.cpp b/src/compiler/glsl/builtin_variables.cpp
index ca266a4c37c..d6dac6d7de5 100644
--- a/src/compiler/glsl/builtin_variables.cpp
+++ b/src/compiler/glsl/builtin_variables.cpp
@@ -1075,10 +1075,17 @@ builtin_variable_generator::generate_tes_special_vars()
    add_system_value(SYSTEM_VALUE_PRIMITIVE_ID, int_t, "gl_PrimitiveID");
    add_system_value(SYSTEM_VALUE_VERTICES_IN, int_t, "gl_PatchVerticesIn");
    add_system_value(SYSTEM_VALUE_TESS_COORD, vec3_t, "gl_TessCoord");
-   add_system_value(SYSTEM_VALUE_TESS_LEVEL_OUTER, array(float_t, 4),
-                    "gl_TessLevelOuter");
-   add_system_value(SYSTEM_VALUE_TESS_LEVEL_INNER, array(float_t, 2),
-                    "gl_TessLevelInner");
+   if (this->state->ctx->Const.GLSLTessLevelsAsInputs) {
+      add_input(VARYING_SLOT_TESS_LEVEL_OUTER, array(float_t, 4),
+                "gl_TessLevelOuter")->data.patch = 1;
+      add_input(VARYING_SLOT_TESS_LEVEL_INNER, array(float_t, 2),
+                "gl_TessLevelInner")->data.patch = 1;
+   } else {
+      add_system_value(SYSTEM_VALUE_TESS_LEVEL_OUTER, array(float_t, 4),
+                       "gl_TessLevelOuter");
+      add_system_value(SYSTEM_VALUE_TESS_LEVEL_INNER, array(float_t, 2),
+                       "gl_TessLevelInner");
+   }
    if (state->ARB_shader_viewport_layer_array_enable) {
       var = add_output(VARYING_SLOT_LAYER, int_t, "gl_Layer");
       var->data.interpolation = INTERP_MODE_FLAT;
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index c7535a37761..419be7c5c24 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -3643,6 +3643,12 @@ struct gl_constants
    bool GLSLFrontFacingIsSysVal;
 
    /**
+    * True if gl_TessLevelInner/Outer[] in the TES should be inputs
+    * (otherwise, they're system values).
+    */
+   bool GLSLTessLevelsAsInputs;
+
+   /**
     * Always use the GetTransformFeedbackVertexCount() driver hook, rather
     * than passing the transform feedback object to the drawing function.
     */
-- 
2.11.0