[RFA] PPC ABI compliance fix

[Elena Zannoni <ezannoni at redhat dot com>]

Back in November, gcc changed the way structures <= 8 bytes are
returned on the PPC. The change was made to be compliant with the
SVR4 ABI.

http://gcc.gnu.org/ml/gcc-patches/2001-11/msg01468.html

The abi specifies that such structures are passed in r3 and r4.
Bigger structures are passed in memory.

Gcc was passing every structure in memory.  The change was made for
embedded targets, but not for natives (PowerPC Linux, NetBSD, and
FreeBSD).

Of course this change breaks binary compatibility with older gcc's.
Not sure what to do about that, if anything, the case it covers is a
corner case, anyway.


Elena


2002-03-21  Elena Zannoni  <ezannoni@redhat.com>

        * ppc-linux-tdep.c (ppc_sysv_abi_use_struct_convention): New
        function.  
	* ppc-tdep.h (ppc_sysv_abi_use_struct_convention): Export.
        * rs6000-tdep.c (rs6000_gdbarch_init): Use different
        structure returning convention for SYSV ABI case, but not
        for GNU/Linux, FreeBSD, or NetBSD.

Index: rs6000-tdep.c
===================================================================
RCS file: /cvs/uberbaum/gdb/rs6000-tdep.c,v
retrieving revision 1.38
diff -u -r1.38 rs6000-tdep.c
--- rs6000-tdep.c	2002/02/14 15:13:53	1.38
+++ rs6000-tdep.c	2002/03/22 18:46:53
@@ -2563,8 +2563,6 @@
   set_gdbarch_store_struct_return (gdbarch, rs6000_store_struct_return);
   set_gdbarch_store_return_value (gdbarch, rs6000_store_return_value);
   set_gdbarch_extract_struct_value_address (gdbarch, rs6000_extract_struct_value_address);
-  set_gdbarch_use_struct_convention (gdbarch, generic_use_struct_convention);
-
   set_gdbarch_pop_frame (gdbarch, rs6000_pop_frame);
 
   set_gdbarch_skip_prologue (gdbarch, rs6000_skip_prologue);
@@ -2576,6 +2574,27 @@
   /* Not sure on this. FIXMEmgo */
   set_gdbarch_frame_args_skip (gdbarch, 8);
 
+  /* Until November 2001, gcc was not complying to the SYSV ABI for
+     returning structures less than or equal to 8 bytes in size. It was
+     returning everything in memory. When this was corrected, it wasn't
+     fixed for native platforms. */
+  if (sysv_abi)
+    {
+      if (osabi == ELFOSABI_LINUX
+          || osabi == ELFOSABI_NETBSD
+          || osabi == ELFOSABI_FREEBSD)
+	set_gdbarch_use_struct_convention (gdbarch,
+					   generic_use_struct_convention);
+      else
+	set_gdbarch_use_struct_convention (gdbarch,
+					   ppc_sysv_abi_use_struct_convention);
+    }
+  else
+    {
+      set_gdbarch_use_struct_convention (gdbarch,
+					  generic_use_struct_convention);
+    }
+
   set_gdbarch_frame_chain_valid (gdbarch, file_frame_chain_valid);
   if (osabi == ELFOSABI_LINUX)
     {

Index: ppc-linux-tdep.c
===================================================================
RCS file: /cvs/uberbaum/gdb/ppc-linux-tdep.c,v
retrieving revision 1.13
diff -u -r1.13 ppc-linux-tdep.c
--- ppc-linux-tdep.c	2002/02/24 22:31:19	1.13
+++ ppc-linux-tdep.c	2002/03/22 18:48:39
@@ -414,6 +414,14 @@
    it may be used generically by ports which use either the SysV ABI or
    the EABI */
 
+/* Structures 8 bytes or less long are returned in the r3 & r4
+   registers, according to the SYSV ABI. */
+int
+ppc_sysv_abi_use_struct_convention (int gcc_p, struct type *value_type)
+{
+  return (TYPE_LENGTH (value_type) > 8);
+}
+
 /* round2 rounds x up to the nearest multiple of s assuming that s is a
    power of 2 */
 
Index: ppc-tdep.h
===================================================================
RCS file: /cvs/uberbaum/gdb/ppc-tdep.h,v
retrieving revision 1.6
diff -u -r1.6 ppc-tdep.h
--- ppc-tdep.h	2001/12/30 00:14:50	1.6
+++ ppc-tdep.h	2002/03/22 18:49:05
@@ -31,6 +31,7 @@
 int ppc_linux_frameless_function_invocation (struct frame_info *);
 void ppc_linux_frame_init_saved_regs (struct frame_info *);
 CORE_ADDR ppc_linux_frame_chain (struct frame_info *);
+int ppc_sysv_abi_use_struct_convention (int, struct type *);
 CORE_ADDR ppc_sysv_abi_push_arguments (int, struct value **, CORE_ADDR, int,
 				       CORE_ADDR);
 int ppc_linux_memory_remove_breakpoint (CORE_ADDR addr, char *contents_cache);