[Mesa-dev] [PATCH 3/3] glsl: don't always reject shaders with mismatching ifc blocks

[Timothy Arceri]

Since we store some member qualifiers in the interface type
we need to be more careful about rejecting shaders just because
the pointer doesn't match. Its perfectly valid for some qualifiers
such as precision to not match across shader interfaces.
---
 src/compiler/glsl/link_interface_blocks.cpp | 78 ++++++++++++++++++++++++++---
 1 file changed, 72 insertions(+), 6 deletions(-)

diff --git a/src/compiler/glsl/link_interface_blocks.cpp b/src/compiler/glsl/link_interface_blocks.cpp
index 9d36836..f868c99 100644
--- a/src/compiler/glsl/link_interface_blocks.cpp
+++ b/src/compiler/glsl/link_interface_blocks.cpp
@@ -81,6 +81,66 @@ intrastage_match(ir_variable *a,
    return true;
 }
 
+/**
+ * Return true if interface members mismatch and its not allowed by GLSL.
+ */
+static bool
+interstage_member_mismatch(struct gl_shader_program *prog,
+                           const glsl_type *c, const glsl_type *p) {
+
+   if (c->length != p->length)
+      return true;
+
+   for (unsigned i = 0; i < c->length; i++) {
+      if (c->fields.structure[i].type != p->fields.structure[i].type)
+         return true;
+      if (strcmp(c->fields.structure[i].name,
+                 p->fields.structure[i].name) != 0)
+         return true;
+      if (c->fields.structure[i].location
+          != p->fields.structure[i].location)
+         return true;
+      if (c->fields.structure[i].patch
+          != p->fields.structure[i].patch)
+         return true;
+
+      /* From Section 4.5 (Interpolation Qualifiers) 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 (prog->IsES || prog->Version < 440)
+         if (c->fields.structure[i].interpolation
+             != p->fields.structure[i].interpolation)
+            return true;
+
+      /* From Section 4.3.4 (Input Variables) of the GLSL ES 3.0 spec:
+       *
+       *    "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 table in Section 9.2.1 Linked Shaders of the GLSL ES 3.1 spec
+       * says that centroid no longer needs to match for varyings.
+       *
+       * The table in Section 9.2.1 Linked Shaders of the GLSL ES 3.2 spec
+       * says that sample need not match for varyings.
+       */
+      if (!prog->IsES || prog->Version < 310)
+         if (c->fields.structure[i].centroid
+             != p->fields.structure[i].centroid)
+            return true;
+      if (!prog->IsES || prog->Version < 320)
+         if (c->fields.structure[i].sample
+             != p->fields.structure[i].sample)
+            return true;
+   }
+
+   return false;
+}
 
 /**
  * Check if two interfaces match, according to interstage (in/out) interface
@@ -91,9 +151,8 @@ intrastage_match(ir_variable *a,
  * This is used for tessellation control and geometry shader consumers.
  */
 static bool
-interstage_match(ir_variable *producer,
-                 ir_variable *consumer,
-                 bool extra_array_level)
+interstage_match(struct gl_shader_program *prog, ir_variable *producer,
+                 ir_variable *consumer, bool extra_array_level)
 {
    /* Unsized arrays should not occur during interstage linking.  They
     * should have all been assigned a size by link_intrastage_shaders.
@@ -106,9 +165,16 @@ interstage_match(ir_variable *producer,
       /* Exception: if both the interface blocks are implicitly declared,
        * don't force their types to match.  They might mismatch due to the two
        * shaders using different GLSL versions, and that's ok.
+       *
+       * Also we store some member information in glsl_type that doesn't
+       * always have to match across shaders such as interpolation so we need
+       * to make a pass over members glsl_struct_field to make sure we don't
+       * reject shaders where fields don't need to match.
        */
-      if (consumer->data.how_declared != ir_var_declared_implicitly ||
-          producer->data.how_declared != ir_var_declared_implicitly)
+      if ((consumer->data.how_declared != ir_var_declared_implicitly ||
+           producer->data.how_declared != ir_var_declared_implicitly) &&
+          interstage_member_mismatch(prog, consumer->get_interface_type(),
+                                     producer->get_interface_type()))
          return false;
    }
 
@@ -311,7 +377,7 @@ validate_interstage_inout_blocks(struct gl_shader_program *prog,
       if (consumer_def == NULL)
          continue;
 
-      if (!interstage_match(var, consumer_def, extra_array_level)) {
+      if (!interstage_match(prog, var, consumer_def, extra_array_level)) {
          linker_error(prog, "definitions of interface block `%s' do not "
                       "match\n", var->get_interface_type()->name);
          return;
-- 
2.5.0