glsl: add new type for compile time constants

In this patch we introduce a new ast type for holding the new
compile-time constant expressions. The main reason for this is that
we can no longer do merging of layout qualifiers before they have been
converted into GLSL IR so we need to store them to be proccessed later.

The new type has two helper functions:

- process_qualifier_constant()

 Used to merge and then evaluate qualifier expressions

- merge_qualifier()

 Simply appends a qualifier to a list to be merged later by
 process_qualifier_constant()

In order to avoid cascading error messages the process_qualifier_constant()
helpers return a bool

Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

src/glsl/ast.h

@@ -350,6 +350,26 @@ public:
    exec_list array_dimensions;
 };
 
+class ast_layout_expression : public ast_node {
+public:
+   ast_layout_expression(const struct YYLTYPE &locp, ast_expression *expr)
+   {
+      set_location(locp);
+      layout_const_expressions.push_tail(&expr->link);
+   }
+
+   bool process_qualifier_constant(struct _mesa_glsl_parse_state *state,
+                                   const char *qual_indentifier,
+                                   unsigned *value, bool can_be_zero);
+
+   void merge_qualifier(ast_layout_expression *l_expr)
+   {
+      layout_const_expressions.append_list(&l_expr->layout_const_expressions);
+   }
+
+   exec_list layout_const_expressions;
+};
+
 /**
  * C-style aggregate initialization class
  *

src/glsl/ast_type.cpp

@@ -467,3 +467,63 @@ ast_type_qualifier::merge_in_qualifier(YYLTYPE *loc,
 
    return true;
 }
+
+bool
+ast_layout_expression::process_qualifier_constant(struct _mesa_glsl_parse_state *state,
+                                                  const char *qual_indentifier,
+                                                  unsigned *value,
+                                                  bool can_be_zero)
+{
+   int min_value = 0;
+   bool first_pass = true;
+   *value = 0;
+
+   if (!can_be_zero)
+      min_value = 1;
+
+   for (exec_node *node = layout_const_expressions.head;
+           !node->is_tail_sentinel(); node = node->next) {
+
+      exec_list dummy_instructions;
+      ast_node *const_expression = exec_node_data(ast_node, node, link);
+
+      ir_rvalue *const ir = const_expression->hir(&dummy_instructions, state);
+
+      ir_constant *const const_int = ir->constant_expression_value();
+      if (const_int == NULL || !const_int->type->is_integer()) {
+         YYLTYPE loc = const_expression->get_location();
+         _mesa_glsl_error(&loc, state, "%s must be an integral constant "
+                          "expression", qual_indentifier);
+         return false;
+      }
+
+      if (const_int->value.i[0] < min_value) {
+         YYLTYPE loc = const_expression->get_location();
+         _mesa_glsl_error(&loc, state, "%s layout qualifier is invalid "
+                          "(%d < %d)", qual_indentifier,
+                          const_int->value.i[0], min_value);
+         return false;
+      }
+
+      if (!first_pass && *value != const_int->value.u[0]) {
+         YYLTYPE loc = const_expression->get_location();
+         _mesa_glsl_error(&loc, state, "%s layout qualifier does not "
+		          "match previous declaration (%d vs %d)",
+                          qual_indentifier, *value, const_int->value.i[0]);
+         return false;
+      } else {
+         first_pass = false;
+         *value = const_int->value.u[0];
+      }
+
+      /* If the location is const (and we've verified that
+       * it is) then no instructions should have been emitted
+       * when we converted it to HIR. If they were emitted,
+       * then either the location isn't const after all, or
+       * we are emitting unnecessary instructions.
+       */
+      assert(dummy_instructions.is_empty());
+   }
+
+   return true;
+}