[PATCH/RFA] Fix returning small structs on OpenBSD/arm

[Mark Kettenis <mark.kettenis@xs4all.nl>]

On OpenBSD/arm, all structures are returned in memory, i.e. the
-fpcc-struct-return GCC option is the default.  There are a couple of
different ways we deal with pcc/reg struct return in GDB.  This adapts
the way things are done on i386 and m68k.  This makes it easy to
provide a user command to switch from one convention to the other like
i386 already has.  However, right now I don't actually see much reason
to add that option on arm.

Anyway, this shaves another 80 failures from the testsuite on
OpenBSD/arm.

ok?


Index: ChangeLog
===================================================================
RCS file: /cvs/src/src/gdb/ChangeLog,v
retrieving revision 1.7834
diff -u -p -r1.7834 ChangeLog
--- ChangeLog	19 Jul 2006 18:21:36 -0000	1.7834
+++ ChangeLog	19 Jul 2006 21:20:39 -0000
@@ -1,5 +1,15 @@
 2006-07-19  Mark Kettenis  <kettenis@gnu.org>
 
+	* arm-tdep.h (enum struct_return): New.
+	(struct gdbarch_tdep): Add struct_return member.
+	* arm-tdep.c (arm_return_value): Return
+	RETURN_VALUE_STRUCT_CONVENTION for aggregates when the ABI uses
+	pcc_struct_return.
+	(arm_gdbarch_init): Default to reg_struct_return.
+	* armobsd-tdep.c (armobsd_init_abi): Set pcc_struct_return.
+
+2006-07-19  Mark Kettenis  <kettenis@gnu.org>
+
 	* arm-tdep.c (arm_gdbarch_init): Get default floating-point model
 	from ELF flags for binaries produced by the GNU toolchain.
 
Index: arm-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/arm-tdep.c,v
retrieving revision 1.212
diff -u -p -r1.212 arm-tdep.c
--- arm-tdep.c	19 Jul 2006 18:21:36 -0000	1.212
+++ arm-tdep.c	19 Jul 2006 21:20:41 -0000
@@ -2259,11 +2259,14 @@ arm_return_value (struct gdbarch *gdbarc
 		  struct regcache *regcache, gdb_byte *readbuf,
 		  const gdb_byte *writebuf)
 {
+  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
+
   if (TYPE_CODE (valtype) == TYPE_CODE_STRUCT
       || TYPE_CODE (valtype) == TYPE_CODE_UNION
       || TYPE_CODE (valtype) == TYPE_CODE_ARRAY)
     {
-      if (arm_return_in_memory (gdbarch, valtype))
+      if (tdep->struct_return == pcc_struct_return
+	  || arm_return_in_memory (gdbarch, valtype))
 	return RETURN_VALUE_STRUCT_CONVENTION;
     }
 
@@ -2757,6 +2760,10 @@ arm_gdbarch_init (struct gdbarch_info in
   tdep->lowest_pc = 0x20;
   tdep->jb_pc = -1;	/* Longjump support not enabled by default.  */
 
+  /* The default, for both APCS and AAPCS, is to return small
+     structures in registers.  */
+  tdep->struct_return = reg_struct_return;
+
   set_gdbarch_push_dummy_call (gdbarch, arm_push_dummy_call);
   set_gdbarch_frame_align (gdbarch, arm_frame_align);
 
Index: arm-tdep.h
===================================================================
RCS file: /cvs/src/src/gdb/arm-tdep.h,v
retrieving revision 1.15
diff -u -p -r1.15 arm-tdep.h
--- arm-tdep.h	12 Jul 2006 20:46:32 -0000	1.15
+++ arm-tdep.h	19 Jul 2006 21:20:41 -0000
@@ -125,6 +125,14 @@ enum arm_abi_kind
   ARM_ABI_LAST
 };
 
+/* Convention for returning structures.  */
+
+enum struct_return
+{
+  pcc_struct_return,		/* Return "short" structures in memory.  */
+  reg_struct_return		/* Return "short" structures in registers.  */
+};
+
 /* Target-dependent structure in gdbarch.  */
 struct gdbarch_tdep
 {
@@ -147,10 +155,15 @@ struct gdbarch_tdep
 				   will be disabled.  */
   size_t jb_elt_size;		/* And the size of each entry in the buf.  */
 
+  /* Convention for returning structures.  */
+  enum struct_return struct_return;
+
   /* Cached core file helpers.  */
   struct regset *gregset, *fpregset;
 };
 
+
+
 #ifndef LOWEST_PC
 #define LOWEST_PC (gdbarch_tdep (current_gdbarch)->lowest_pc)
 #endif
Index: armobsd-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/armobsd-tdep.c,v
retrieving revision 1.3
diff -u -p -r1.3 armobsd-tdep.c
--- armobsd-tdep.c	18 Jul 2006 21:10:28 -0000	1.3
+++ armobsd-tdep.c	19 Jul 2006 21:20:41 -0000
@@ -88,6 +88,9 @@ armobsd_init_abi (struct gdbarch_info in
 
   tdep->jb_pc = 24;
   tdep->jb_elt_size = 4;
+
+  /* OpenBSD/arm uses -fpcc-struct-return by default.  */
+  tdep->struct_return = pcc_struct_return;
 }
 
 void