[Mesa-dev] [PATCH 2/2] glsl: Don't require matching interpolation qualifiers for newer GLSL

[Jordan Justen]

The OpenGLES GLSL 3.1 and OpenGL GLSL 4.3 specifications both remove
the requirement for the output and input interpolation qualifiers to
match.

Note: I'm changing desktop OpenGL to allow the interpolation to
differ, starting with 4.3, whereas the code previously used 4.4. (This
was first added in 32a220f1f60980de50ecefb3b9ab1f754ade8c83.)

The OpenGL 4.2 spec says: "the last active shader stage output
variables and fragment shader input variables of the same name must
match in type and qualification (other than out matching to in)"

The OpenGL 4.3 spec says: "interpolation qualification (e.g., flat)
and auxiliary qualification (e.g. centroid) may differ."

The OpenGLES GLSL 3.00.4 specification says: "The output of the vertex
shader and the input of the fragment shader form an interface. For
this interface, vertex shader output variables and fragment shader
input variables of the same name must match in type and qualification
(other than precision and out matching to in)."

The OpenGLES GLSL 3.10 Specification says: "interpolation
qualification (e.g., flat) and auxiliary qualification (e.g. centroid)
may differ"

Signed-off-by: Jordan Justen <jordan.l.justen at intel.com>
Cc: Tapani Pälli <tapani.palli at intel.com>
---
 src/compiler/glsl/link_varyings.cpp | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/src/compiler/glsl/link_varyings.cpp b/src/compiler/glsl/link_varyings.cpp
index 9d7177d..0938cf1 100644
--- a/src/compiler/glsl/link_varyings.cpp
+++ b/src/compiler/glsl/link_varyings.cpp
@@ -172,17 +172,9 @@ cross_validate_types_and_qualifiers(struct gl_shader_program *prog,
       return;
    }
 
-   /* GLSL >= 4.40 removes text requiring interpolation qualifiers
-    * to match cross stage, they must only match within the same stage.
-    *
-    * From page 84 (page 90 of the PDF) of the GLSL 4.40 spec:
-    *
-    *     "It is a link-time error if, within the same stage, the interpolation
-    *     qualifiers of variables of the same name do not match.
-    *
-    */
-   if (input->data.interpolation != output->data.interpolation &&
-       prog->Version < 440) {
+   /* Interpolation must match until OpenGL 4.3 and OpenGLES 3.1 */
+   if (prog->Version < (prog->IsES ? 310 : 430) &&
+       input->data.interpolation != output->data.interpolation) {
       linker_error(prog,
                    "%s shader output `%s' specifies %s "
                    "interpolation qualifier, "
-- 
2.7.0