>From section 7.1 (Built-In Language Variables) of the GLSL 4.10
spec:

    Also, if a built-in interface block is redeclared, no member of
    the built-in declaration can be redeclared outside the block
    redeclaration.

We have been regarding this text as a clarification to the behaviour
established for gl_PerVertex by GLSL 1.50, so we apply it regardless
of GLSL version.

This patch enforces the rule by adding a boolean to ir_variable to
track how the variable was declared: implicitly, normally, or in an
interface block.

Fixes piglit tests:
- gs-redeclares-pervertex-out-after-global-redeclaration.geom
- vs-redeclares-pervertex-out-after-global-redeclaration.vert
- gs-redeclares-pervertex-out-after-other-global-redeclaration.geom
- vs-redeclares-pervertex-out-after-other-global-redeclaration.vert
- gs-redeclares-pervertex-out-before-global-redeclaration
- vs-redeclares-pervertex-out-before-global-redeclaration

Cc: "10.0" <mesa-sta...@lists.freedesktop.org>
---
 src/glsl/ast_to_hir.cpp        | 20 ++++++++++++++++++++
 src/glsl/builtin_variables.cpp |  3 +++
 src/glsl/ir.cpp                |  3 ++-
 src/glsl/ir.h                  | 36 ++++++++++++++++++++++++++++++++++++
 4 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
index 76b256c..0128047 100644
--- a/src/glsl/ast_to_hir.cpp
+++ b/src/glsl/ast_to_hir.cpp
@@ -3355,6 +3355,15 @@ ast_declarator_list::hir(exec_list *instructions,
       ir_variable *earlier =
          get_variable_being_redeclared(var, decl->get_location(), state,
                                        false /* allow_all_redeclarations */);
+      if (earlier != NULL) {
+         if (strncmp(var->name, "gl_", 3) == 0 &&
+             earlier->how_declared == ir_var_declared_in_block) {
+            _mesa_glsl_error(&loc, state,
+                             "`%s' has already been redeclared using "
+                             "gl_PerVertex", var->name);
+         }
+         earlier->how_declared = ir_var_declared_normally;
+      }
 
       if (decl->initializer != NULL) {
         result = process_initializer((earlier == NULL) ? var : earlier,
@@ -5048,6 +5057,7 @@ ast_interface_block::hir(exec_list *instructions,
             _mesa_glsl_error(&loc, state, "`%s' redeclared",
                              this->instance_name);
          }
+         earlier->how_declared = ir_var_declared_normally;
          earlier->type = var->type;
          earlier->reinit_interface_type(block_type);
          delete var;
@@ -5078,7 +5088,11 @@ ast_interface_block::hir(exec_list *instructions,
                _mesa_glsl_error(&loc, state,
                                 "redeclaration of gl_PerVertex can only "
                                 "include built-in variables");
+            } else if (earlier->how_declared == ir_var_declared_normally) {
+               _mesa_glsl_error(&loc, state,
+                                "`%s' has already been redeclared", var->name);
             } else {
+               earlier->how_declared = ir_var_declared_in_block;
                earlier->reinit_interface_type(block_type);
             }
             continue;
@@ -5125,6 +5139,12 @@ ast_interface_block::hir(exec_list *instructions,
             if (var != NULL &&
                 var->get_interface_type() == earlier_per_vertex &&
                 var->mode == var_mode) {
+               if (var->how_declared == ir_var_declared_normally) {
+                  _mesa_glsl_error(&loc, state,
+                                   "redeclaration of gl_PerVertex cannot "
+                                   "follow a redeclaration of `%s'",
+                                   var->name);
+               }
                state->symbols->disable_variable(var->name);
                var->remove();
             }
diff --git a/src/glsl/builtin_variables.cpp b/src/glsl/builtin_variables.cpp
index 4d44104..257a36d 100644
--- a/src/glsl/builtin_variables.cpp
+++ b/src/glsl/builtin_variables.cpp
@@ -434,6 +434,7 @@ builtin_variable_generator::add_variable(const char *name,
                                          enum ir_variable_mode mode, int slot)
 {
    ir_variable *var = new(symtab) ir_variable(type, name, mode);
+   var->how_declared = ir_var_declared_implicitly;
 
    switch (var->mode) {
    case ir_var_auto:
@@ -472,6 +473,7 @@ builtin_variable_generator::add_uniform(const glsl_type 
*type,
                                         const char *name)
 {
    ir_variable *const uni = add_variable(name, type, ir_var_uniform, -1);
+   uni->how_declared = ir_var_declared_implicitly;
 
    unsigned i;
    for (i = 0; _mesa_builtin_uniform_desc[i].name != NULL; i++) {
@@ -520,6 +522,7 @@ builtin_variable_generator::add_const(const char *name, int 
value)
 {
    ir_variable *const var = add_variable(name, glsl_type::int_type,
                                         ir_var_auto, -1);
+   var->how_declared = ir_var_declared_implicitly;
    var->constant_value = new(var) ir_constant(value);
    var->constant_initializer = new(var) ir_constant(value);
    var->has_initializer = true;
diff --git a/src/glsl/ir.cpp b/src/glsl/ir.cpp
index 1b49736..ffff297 100644
--- a/src/glsl/ir.cpp
+++ b/src/glsl/ir.cpp
@@ -1586,7 +1586,8 @@ ir_variable::ir_variable(const struct glsl_type *type, 
const char *name,
                         ir_variable_mode mode)
    : max_array_access(0), max_ifc_array_access(NULL),
      read_only(false), centroid(false), invariant(false),
-        mode(mode), interpolation(INTERP_QUALIFIER_NONE), atomic()
+     how_declared(ir_var_declared_normally), mode(mode),
+     interpolation(INTERP_QUALIFIER_NONE), atomic()
 {
    this->ir_type = ir_type_variable;
    this->type = type;
diff --git a/src/glsl/ir.h b/src/glsl/ir.h
index 7859702..4f775da 100644
--- a/src/glsl/ir.h
+++ b/src/glsl/ir.h
@@ -294,6 +294,34 @@ enum ir_variable_mode {
 };
 
 /**
+ * Enum keeping track of how a variable was declared.  For error checking of
+ * the gl_PerVertex redeclaration rules.
+ */
+enum ir_var_declaration_type {
+   /**
+    * Normal declaration (for most variables, this means an explicit
+    * declaration.  Exception: temporaries are always implicitly declared, but
+    * they still use ir_var_declared_normally).
+    *
+    * Note: an ir_variable that represents a named interface block uses
+    * ir_var_declared_normally.
+    */
+   ir_var_declared_normally = 0,
+
+   /**
+    * Variable was explicitly declared (or re-declared) in an unnamed
+    * interface block.
+    */
+   ir_var_declared_in_block,
+
+   /**
+    * Variable is an implicitly declared built-in that has not been explicitly
+    * re-declared by the shader.
+    */
+   ir_var_declared_implicitly,
+};
+
+/**
  * \brief Layout qualifiers for gl_FragDepth.
  *
  * The AMD/ARB_conservative_depth extensions allow gl_FragDepth to be 
redeclared
@@ -526,6 +554,14 @@ public:
    unsigned assigned:1;
 
    /**
+    * Enum indicating how the variable was declared.  See
+    * ir_var_declaration_type.
+    *
+    * This is used to detect certain kinds of illegal variable redeclarations.
+    */
+   unsigned how_declared:2;
+
+   /**
     * Storage class of the variable.
     *
     * \sa ir_variable_mode
-- 
1.8.4.2

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