[Mesa-dev] [PATCH v2 2/3] glsl: allow built-in variables to be explicitly declared

[Timothy Arceri]

Mesa seems to be the only implementation that doesn't allow builtins
to be explicitly declared. The GLSL 1.30 spec seems to imply that
buitins may be explicitly declared.

This this allows the game "Full Bore" the be playable (when using
MESA_GL_VERSION_OVERRIDE=3.3COMPAT). It will also allow us to
remove the allow_glsl_builtin_variable_redeclaration dri override.

>From the GLSL 1.30 spec Section 7.2 (Fragment Shader Special
Variables):

    "Both gl_FragColor and gl_FragData are deprecated; the preferred
    usage is to explicitly declare these outputs in the fragment
    shader using the out storage qualifier."

To avoid some GLSL ES tests failing we add a check to make sure
precision matches on the redeclared builtin.
---
 src/compiler/glsl/ast_to_hir.cpp | 32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/src/compiler/glsl/ast_to_hir.cpp b/src/compiler/glsl/ast_to_hir.cpp
index a7a9ac80769..54d0816a986 100644
--- a/src/compiler/glsl/ast_to_hir.cpp
+++ b/src/compiler/glsl/ast_to_hir.cpp
@@ -4390,14 +4390,8 @@ get_variable_being_redeclared(ir_variable **var_ptr, YYLTYPE loc,
       earlier->data.precision = var->data.precision;
       earlier->data.memory_coherent = var->data.memory_coherent;
 
-   } else if (earlier->data.how_declared == ir_var_declared_implicitly &&
-              state->allow_builtin_variable_redeclaration) {
-      /* Allow verbatim redeclarations of built-in variables. Not explicitly
-       * valid, but some applications do it.
-       */
-      if (earlier->data.mode != var->data.mode &&
-          !(earlier->data.mode == ir_var_system_value &&
-            var->data.mode == ir_var_shader_in)) {
+   } else if (allow_all_redeclarations) {
+      if (earlier->data.mode != var->data.mode) {
          _mesa_glsl_error(&loc, state,
                           "redeclaration of `%s' with incorrect qualifiers",
                           var->name);
@@ -4406,8 +4400,22 @@ get_variable_being_redeclared(ir_variable **var_ptr, YYLTYPE loc,
                           "redeclaration of `%s' has incorrect type",
                           var->name);
       }
-   } else if (allow_all_redeclarations) {
-      if (earlier->data.mode != var->data.mode) {
+   } else if (earlier->data.how_declared == ir_var_declared_implicitly) {
+      /* Allow verbatim redeclarations of built-in variables. The GLSL 1.30
+       * spec seems to imply that buitins may be explicitly declared.
+       *
+       * From the GLSL 1.30 spec Section 7.2 (Fragment Shader Special
+       * Variables):
+       *
+       *    "Both gl_FragColor and gl_FragData are deprecated; the preferred
+       *    usage is to explicitly declare these outputs in the fragment
+       *    shader using the out storage qualifier."
+       */
+      enum ir_variable_mode builtin_mode =
+         glsl_external_mode((ir_variable_mode) earlier->data.mode,
+                            state->stage, earlier->data.location);
+
+      if (builtin_mode != var->data.mode) {
          _mesa_glsl_error(&loc, state,
                           "redeclaration of `%s' with incorrect qualifiers",
                           var->name);
@@ -4415,6 +4423,10 @@ get_variable_being_redeclared(ir_variable **var_ptr, YYLTYPE loc,
          _mesa_glsl_error(&loc, state,
                           "redeclaration of `%s' has incorrect type",
                           var->name);
+      } else if (earlier->data.precision != var->data.precision) {
+         _mesa_glsl_error(&loc, state,
+                          "redeclaration of `%s' has incorrect precision",
+                          var->name);
       }
    } else {
       _mesa_glsl_error(&loc, state, "`%s' redeclared", var->name);
-- 
2.17.0