Fix PR ada/21952

[Eric Botcazou <ebotcazou at adacore dot com>]

It's a regression present on mainline and 4.1 branch for Alpha platforms.
The Alpha back-end unconditionally uses a couple of machine-independent
attributes that originally come from the C family of languages, leading to a 
flood of warnings for the Ada compiler.

This is fixed by adding minimal support for these attributes to Gigi. 
Bootstrapped/regtested on i586-suse-linux, applied to the mainline and 4.1 
branch.


2006-09-13  Eric Botcazou  <ebotcazou@adacore.com>

	PR ada/21952
	* gigi.h (gnat_internal_attribute_table): Declare.
	* misc.c (LANG_HOOKS_ATTRIBUTE_TABLE): Define to above.
	* utils.c (gnat_internal_attribute_table): New global variable.
	(builtin_function): Always call decl_attributes on the builtin.
	(handle_const_attribute): New static function.
	(handle_nothrow_attribute): Likewise.


-- 
Eric Botcazou

Index: gigi.h
===================================================================
RCS file: /gnat.dev/cvs/Dev/gnat/gigi.h,v
retrieving revision 1.20.2.41
retrieving revision 1.20.2.42
diff -u -r1.20.2.41 -r1.20.2.42
--- gigi.h	4 Mar 2006 18:18:19 -0000	1.20.2.41
+++ gigi.h	17 Mar 2006 11:25:59 -0000	1.20.2.42
@@ -309,7 +309,6 @@
    type whose bit width is Pmode.  Assume "long" is such a type here.  */
 #undef SIZE_TYPE
 #define SIZE_TYPE "long int"
-
 
 /* Data structures used to represent attributes.  */
 
@@ -332,6 +331,9 @@
   Node_Id error_point;
 };
 
+/* Table of machine-independent internal attributes.  */
+extern const struct attribute_spec gnat_internal_attribute_table[];
+
 /* Define the entries in the standard data array.  */
 enum standard_datatypes
 {
Index: misc.c
===================================================================
RCS file: /gnat.dev/cvs/Dev/gnat/misc.c,v
retrieving revision 1.44.2.70
retrieving revision 1.44.2.71
diff -u -p -r1.44.2.70 -r1.44.2.71
--- misc.c	14 Feb 2006 22:18:15 -0000	1.44.2.70
+++ misc.c	17 Mar 2006 11:26:02 -0000	1.44.2.71
@@ -158,6 +158,8 @@ static tree gnat_type_max_size		(tree);
 #define LANG_HOOKS_UNSIGNED_TYPE	gnat_unsigned_type
 #undef  LANG_HOOKS_SIGNED_OR_UNSIGNED_TYPE
 #define LANG_HOOKS_SIGNED_OR_UNSIGNED_TYPE gnat_signed_or_unsigned_type
+#undef  LANG_HOOKS_ATTRIBUTE_TABLE
+#define LANG_HOOKS_ATTRIBUTE_TABLE	gnat_internal_attribute_table
 
 const struct lang_hooks lang_hooks = LANG_HOOKS_INITIALIZER;
 
Index: utils.c
===================================================================
RCS file: /gnat.dev/cvs/Dev/gnat/utils.c,v
retrieving revision 1.48.2.112
retrieving revision 1.48.2.113
diff -u -p -r1.48.2.112 -r1.48.2.113
--- utils.c	15 Mar 2006 08:01:31 -0000	1.48.2.112
+++ utils.c	17 Mar 2006 11:26:07 -0000	1.48.2.113
@@ -79,6 +79,21 @@ tree gnat_raise_decls[(int) LAST_REASON_
 tree static_ctors;
 tree static_dtors;
 
+/* Forward declarations for handlers of attributes.  */
+static tree handle_const_attribute (tree *, tree, tree, int, bool *);
+static tree handle_nothrow_attribute (tree *, tree, tree, int, bool *);
+
+/* Table of machine-independent internal attributes for Ada.  We support
+   this minimal set ot attributes to accomodate the Alpha back-end which
+   unconditionally puts them on its builtins.  */
+const struct attribute_spec gnat_internal_attribute_table[] =
+{
+  /* { name, min_len, max_len, decl_req, type_req, fn_type_req, handler } */
+  { "const",   0, 0, true,  false, false, handle_const_attribute   },
+  { "nothrow", 0, 0, true,  false, false, handle_nothrow_attribute },
+  { NULL,      0, 0, false, false, false, NULL }
+};
+
 /* Associates a GNAT tree node to a GCC tree node. It is used in
    `save_gnu_tree', `get_gnu_tree' and `present_gnu_tree'. See documentation
    of `save_gnu_tree' for more info.  */
@@ -1844,11 +1859,48 @@ builtin_function (const char *name, tree
   gnat_pushdecl (decl, Empty);
   DECL_BUILT_IN_CLASS (decl) = class;
   DECL_FUNCTION_CODE (decl) = function_code;
+
+  /* Possibly apply some default attributes to this built-in function.  */
   if (attrs)
-      decl_attributes (&decl, attrs, ATTR_FLAG_BUILT_IN);
+    decl_attributes (&decl, attrs, ATTR_FLAG_BUILT_IN);
+  else
+    decl_attributes (&decl, NULL_TREE, 0);
+
   return decl;
 }
 
+/* Handle a "const" attribute; arguments as in
+   struct attribute_spec.handler.  */
+
+static tree
+handle_const_attribute (tree *node, tree ARG_UNUSED (name),
+			tree ARG_UNUSED (args), int ARG_UNUSED (flags),
+			bool *no_add_attrs)
+{
+  if (TREE_CODE (*node) == FUNCTION_DECL)
+    TREE_READONLY (*node) = 1;
+  else
+    *no_add_attrs = true;
+
+  return NULL_TREE;
+}
+
+/* Handle a "nothrow" attribute; arguments as in
+   struct attribute_spec.handler.  */
+
+static tree
+handle_nothrow_attribute (tree *node, tree ARG_UNUSED (name),
+			  tree ARG_UNUSED (args), int ARG_UNUSED (flags),
+			  bool *no_add_attrs)
+{
+  if (TREE_CODE (*node) == FUNCTION_DECL)
+    TREE_NOTHROW (*node) = 1;
+  else
+    *no_add_attrs = true;
+
+  return NULL_TREE;
+}
+
 /* Return an integer type with the number of bits of precision given by
    PRECISION.  UNSIGNEDP is nonzero if the type is unsigned; otherwise
    it is a signed type.  */