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[Ada] Fix fallout of bitfields ABI change on Windows

Message ID 201204301005.36732.ebotcazou@adacore.com
State New
Headers show

Commit Message

Eric Botcazou April 30, 2012, 8:05 a.m. UTC 
The MS bitfields ABI and its stringent rules totally break packing in Ada, so 
we cannot use the C layout in this case.  The i386.c hunk fixes an oversight 
which would result in gazillions of warnings for QUAL_UNION_TYPE.

Tested on i586-suse-linux and i686-pc-mingw32, applied on the mainline and the 
4.7 branch (as obvious for the i386.c hunk).


2012-04-30  Eric Botcazou  <ebotcazou@adacore.com>

	* config/i386/i386.c (ix86_handle_struct_attribute): Use the proper
	predicate to discriminate types.


2012-04-30  Eric Botcazou  <ebotcazou@adacore.com>

	* gcc-interface/utils.c (finish_record_type): Force the traditional GCC
	layout for bitfields on the type if it is packed or has a representation
	clause and an alternate layout is available.
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Patch

Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c	(revision 186907)
+++ config/i386/i386.c	(working copy)
@@ -32465,8 +32465,7 @@  ix86_handle_struct_attribute (tree *node
   else
     type = node;
 
-  if (!(type && (TREE_CODE (*type) == RECORD_TYPE
-		 || TREE_CODE (*type) == UNION_TYPE)))
+  if (!(type && RECORD_OR_UNION_TYPE_P (*type)))
     {
       warning (OPT_Wattributes, "%qE attribute ignored",
 	       name);
Index: ada/gcc-interface/utils.c
===================================================================
--- ada/gcc-interface/utils.c	(revision 186956)
+++ ada/gcc-interface/utils.c	(working copy)
@@ -721,6 +721,19 @@  finish_record_type (tree record_type, tr
 	 case where there is a rep clause but all fields have errors and
 	 no longer have a position.  */
       TYPE_SIZE (record_type) = 0;
+
+      /* Ensure we use the traditional GCC layout for bitfields when we need
+	 to pack the record type or have a representation clause.  The other
+	 possible layout (Microsoft C compiler), if available, would prevent
+	 efficient packing in almost all cases.  */
+#ifdef TARGET_MS_BITFIELD_LAYOUT
+      if (TARGET_MS_BITFIELD_LAYOUT && TYPE_PACKED (record_type))
+	decl_attributes (&record_type,
+			 tree_cons (get_identifier ("gcc_struct"),
+				    NULL_TREE, NULL_TREE),
+			 ATTR_FLAG_TYPE_IN_PLACE);
+#endif
+
       layout_type (record_type);
     }