glsl: do not set the 'smooth' qualifier by default on ES shaders

It leads to surprising states with integer inputs and outputs on
vertex processing stages (e.g. geometry stages). Instead, rely on the
driver to choose smooth interpolation by default.

We still allow varyings to match when one stage declares it as smooth
and the other declares it without interpolation qualifiers.

Reviewed-by: Marek Olšák <[email protected]>
Tested-by: Dieter Nützel <[email protected]>

2 files changed, 16 insertions, 12 deletions

diff --git a/src/compiler/glsl/ast_to_hir.cpp b/src/compiler/glsl/ast_to_hir.cpp
index c46454956d7..1999e68158c 100644
--- a/src/compiler/glsl/ast_to_hir.cpp
+++ b/src/compiler/glsl/ast_to_hir.cpp
@@ -3126,17 +3126,6 @@ interpret_interpolation_qualifier(const struct ast_type_qualifier *qual,
       interpolation = INTERP_MODE_NOPERSPECTIVE;
    else if (qual->flags.q.smooth)
       interpolation = INTERP_MODE_SMOOTH;
-   else if (state->es_shader &&
-            ((mode == ir_var_shader_in &&
-              state->stage != MESA_SHADER_VERTEX) ||
-             (mode == ir_var_shader_out &&
-              state->stage != MESA_SHADER_FRAGMENT)))
-      /* Section 4.3.9 (Interpolation) of the GLSL ES 3.00 spec says:
-       *
-       *    "When no interpolation qualifier is present, smooth interpolation
-       *    is used."
-       */
-      interpolation = INTERP_MODE_SMOOTH;
    else
       interpolation = INTERP_MODE_NONE;
 
diff --git a/src/compiler/glsl/link_varyings.cpp b/src/compiler/glsl/link_varyings.cpp
index 656bf79ca9d..ed3bf416878 100644
--- a/src/compiler/glsl/link_varyings.cpp
+++ b/src/compiler/glsl/link_varyings.cpp
@@ -325,8 +325,23 @@ cross_validate_types_and_qualifiers(struct gl_shader_program *prog,
     *     "It is a link-time error if, within the same stage, the interpolation
     *     qualifiers of variables of the same name do not match.
     *
+    * Section 4.3.9 (Interpolation) of the GLSL ES 3.00 spec says:
+    *
+    *    "When no interpolation qualifier is present, smooth interpolation
+    *    is used."
+    *
+    * So we match variables where one is smooth and the other has no explicit
+    * qualifier.
     */
-   if (input->data.interpolation != output->data.interpolation &&
+   unsigned input_interpolation = input->data.interpolation;
+   unsigned output_interpolation = output->data.interpolation;
+   if (prog->IsES) {
+      if (input_interpolation == INTERP_MODE_NONE)
+         input_interpolation = INTERP_MODE_SMOOTH;
+      if (output_interpolation == INTERP_MODE_NONE)
+         output_interpolation = INTERP_MODE_SMOOTH;
+   }
+   if (input_interpolation != output_interpolation &&
        prog->data->Version < 440) {
       linker_error(prog,
                    "%s shader output `%s' specifies %s "