Mesa (master): glsl: TCS outputs can not be transform feedback candidates on GLES

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Module: Mesa
Branch: master
Commit: bf1f49482d677e562993543cd9a9367597ce3ccc
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=bf1f49482d677e562993543cd9a9367597ce3ccc

Author: Jose Maria Casanova Crespo <jmcasanova at igalia.com>
Date:   Wed Nov 21 18:23:03 2018 +0100

glsl: TCS outputs can not be transform feedback candidates on GLES

Avoids regression on:

KHR-GLES*.core.tessellation_shader.single.xfb_captures_data_from_correct_stage

that is uncovered by the following patch.

"glsl: fix recording of variables for XFB in TCS shaders"

v2: Rebased over glsl: fix recording of variables for XFB in TCS shaders
v3: Move this patch before "glsl: fix recording of variables for XFB in TCS
    shaders" to avoid temporal regressions. (Illia Mirkin)

Cc: 19.0 <mesa-stable at lists.freedesktop.org>
Reviewed-by: Timothy Arceri <tarceri at itsqueeze.com>

---

 src/compiler/glsl/link_varyings.cpp | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/compiler/glsl/link_varyings.cpp b/src/compiler/glsl/link_varyings.cpp
index 3969c0120b3..272e1239d27 100644
--- a/src/compiler/glsl/link_varyings.cpp
+++ b/src/compiler/glsl/link_varyings.cpp
@@ -2504,7 +2504,27 @@ assign_varying_locations(struct gl_context *ctx,
 
          if (num_tfeedback_decls > 0) {
             tfeedback_candidate_generator g(mem_ctx, tfeedback_candidates);
-            g.process(output_var);
+            /* From OpenGL 4.6 (Core Profile) spec, section 11.1.2.1
+             * ("Vertex Shader Variables / Output Variables")
+             *
+             * "Each program object can specify a set of output variables from
+             * one shader to be recorded in transform feedback mode (see
+             * section 13.3). The variables that can be recorded are those
+             * emitted by the first active shader, in order, from the
+             * following list:
+             *
+             *  * geometry shader
+             *  * tessellation evaluation shader
+             *  * tessellation control shader
+             *  * vertex shader"
+             *
+             * But on OpenGL ES 3.2, section 11.1.2.1 ("Vertex Shader
+             * Variables / Output Variables") tessellation control shader is
+             * not included in the stages list.
+             */
+            if (!prog->IsES || producer->Stage != MESA_SHADER_TESS_CTRL) {
+               g.process(output_var);
+            }
          }
 
          ir_variable *const input_var =