stor-layout.c (update_alignment_for_field): Use targetm.align_anon_bitfield.

* stor-layout.c (update_alignment_for_field): Use
	targetm.align_anon_bitfield.
	* target-def.h (TARGET_ALIGN_ANON_BITFIELD): Define.
	(TARGET_INITIALIZER): Use it.
	* target.h (struct gcc_target): Add align_anon_bitfield.
	* config/arm/arm.c (arm_align_anon_bitfield):  New function.
	(TARGET_ALIGN_ANON_BITFIELD): Define.
	* doc/tm.texi: Document TARGET_ALIGN_ANON_BITFIELD.

From-SVN: r81838

gcc/ChangeLog

@@ -1,3 +1,14 @@
+2004-05-14  Paul Brook  <paul@codesourcery.com>
+
+	* stor-layout.c (update_alignment_for_field): Use
+	targetm.align_anon_bitfield.
+	* target-def.h (TARGET_ALIGN_ANON_BITFIELD): Define.
+	(TARGET_INITIALIZER): Use it.
+	* target.h (struct gcc_target): Add align_anon_bitfield.
+	* config/arm/arm.c (arm_align_anon_bitfield):  New function.
+	(TARGET_ALIGN_ANON_BITFIELD): Define.
+	* doc/tm.texi: Document TARGET_ALIGN_ANON_BITFIELD.
+
 2004-05-13  Zack Weinberg  <zack@codesourcery.com>
 
 	* tree.def (documentation): Remove mention of class 'b'.

gcc/config/arm/arm.c

@@ -160,6 +160,7 @@ static void arm_setup_incoming_varargs (CUMULATIVE_ARGS *, enum machine_mode,
 					tree, int *, int);
 static bool arm_promote_prototypes (tree);
 static bool arm_default_short_enums (void);
+static bool arm_align_anon_bitfield (void);
 
 
 /* Initialize the GCC target structure.  */
@@ -260,6 +261,9 @@ static bool arm_default_short_enums (void);
 #undef TARGET_DEFAULT_SHORT_ENUMS
 #define TARGET_DEFAULT_SHORT_ENUMS arm_default_short_enums
 
+#undef TARGET_ALIGN_ANON_BITFIELD
+#define TARGET_ALIGN_ANON_BITFIELD arm_align_anon_bitfield
+
 struct gcc_target targetm = TARGET_INITIALIZER;
 
 /* Obstack for minipool constant handling.  */
@@ -14565,3 +14569,12 @@ arm_default_short_enums (void)
 {
   return TARGET_AAPCS_BASED;
 }
+
+
+/* AAPCS requires that anonymous bitfields affect structure alignment.  */
+
+static bool
+arm_align_anon_bitfield (void)
+{
+  return TARGET_AAPCS_BASED;
+}

gcc/doc/tm.texi

@@ -1301,6 +1301,13 @@ Like @code{PCC_BITFIELD_TYPE_MATTERS} except that its effect is limited
 to aligning a bit-field within the structure.
 @end defmac
 
+@deftypefn {Target Hook} bool TARGET_ALIGN_ANON_BITFIELDS (void)
+When @code{PCC_BITFIELD_TYPE_MATTERS} is true this hook will determine
+whether unnamed bitfields affect the alignment of the containing
+structure.  The hook should return true if the structure should inherit
+the alignment requirements of an unnamed bitfield's type.
+@end deftypefn
+
 @defmac MEMBER_TYPE_FORCES_BLK (@var{field}, @var{mode})
 Return 1 if a structure or array containing @var{field} should be accessed using
 @code{BLKMODE}.

gcc/stor-layout.c

@@ -771,8 +771,10 @@ update_alignment_for_field (record_layout_info rli, tree field,
   else if (is_bitfield && PCC_BITFIELD_TYPE_MATTERS)
     {
       /* Named bit-fields cause the entire structure to have the
-	 alignment implied by their type.  */
-      if (DECL_NAME (field) != 0)
+	 alignment implied by their type.  Some targets also apply the same
+	 rules to unnamed bitfields.  */
+      if (DECL_NAME (field) != 0
+	  || targetm.align_anon_bitfield ())
 	{
 	  unsigned int type_align = TYPE_ALIGN (type);
 

gcc/target-def.h

@@ -310,6 +310,7 @@ Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 #define TARGET_INSERT_ATTRIBUTES hook_void_tree_treeptr
 #define TARGET_FUNCTION_ATTRIBUTE_INLINABLE_P hook_bool_tree_false
 #define TARGET_MS_BITFIELD_LAYOUT_P hook_bool_tree_false
+#define TARGET_ALIGN_ANON_BITFIELD hook_bool_void_false
 #define TARGET_RTX_COSTS hook_bool_rtx_int_int_intp_false
 #define TARGET_MANGLE_FUNDAMENTAL_TYPE hook_constcharptr_tree_null
 
@@ -384,6 +385,7 @@ Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
   TARGET_INSERT_ATTRIBUTES,			\
   TARGET_FUNCTION_ATTRIBUTE_INLINABLE_P,	\
   TARGET_MS_BITFIELD_LAYOUT_P,			\
+  TARGET_ALIGN_ANON_BITFIELD,			\
   TARGET_INIT_BUILTINS,				\
   TARGET_EXPAND_BUILTIN,			\
   TARGET_MANGLE_FUNDAMENTAL_TYPE,		\

gcc/target.h

@@ -307,6 +307,9 @@ struct gcc_target
      Microsoft Visual C++ bitfield layout rules.  */
   bool (* ms_bitfield_layout_p) (tree record_type);
 
+  /* Return true if anonymous bitfields affect structure alignment.  */
+  bool (* align_anon_bitfield) (void);
+
   /* Set up target-specific built-in functions.  */
   void (* init_builtins) (void);