Re: m68k-elf return value registers

[Vladimir Prus <vladimir at codesourcery dot com>]

On Tuesday, January 25, 2011 19:49:15 Vladimir Prus wrote:

> How about this split:
> 
> - Register used to return structures
> - Logic used to decide whether a structure is returned in register
> - Adjusting register used for returning pointers

And here's the patch that adjusts the register used to return structures.

Earlier, you said:

> > Also, you should make sure that that code doesn't get used for
> > OpenBSD/m68k a.out, since it will be wrong.

but I've lost track of what bit of the patch you meant. Could you clarify
that, as part of reviewing whatever individual patch is applicable?

- Volodya

-- 
Vladimir Prus
Mentor Graphics
+7 (812) 677-68-40

commit 6dfd0b7446fce82dba3ae07e24fadb89b9908455
Author: Vladimir Prus <vladimir@codesourcery.com>
Date:   Fri Jan 14 00:10:12 2011 +0300

    Use the right structure and pointer return registers on m68k-elf.
    
    	* m68k-tdep.c (m68k_gdbarch_init): Use A0 for structure
    	returns on ELF targets, A1 otherwise.
    	(m68k_svr4_init_abi): No need to specify %a0 for structure
    	returns here.
    	* m68kbsd-tdep.c (m68kbsd_elf_init_abi): Use A1 for struct return on OpenBSD.

diff --git a/gdb/m68k-tdep.c b/gdb/m68k-tdep.c
index 736bf5b..accffc8 100644
--- a/gdb/m68k-tdep.c
+++ b/gdb/m68k-tdep.c
@@ -1114,8 +1114,7 @@ m68k_svr4_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
   /* SVR4 uses a different calling convention.  */
   set_gdbarch_return_value (gdbarch, m68k_svr4_return_value);
 
-  /* SVR4 uses %a0 instead of %a1.  */
-  tdep->struct_value_regnum = M68K_A0_REGNUM;
+  tdep->ptr_value_regnum = M68K_A0_REGNUM;
 
   tdep->ptr_value_regnum = M68K_A0_REGNUM;
 }
@@ -1291,7 +1290,16 @@ m68k_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   /* Function call & return.  */
   set_gdbarch_push_dummy_call (gdbarch, m68k_push_dummy_call);
   set_gdbarch_return_value (gdbarch, m68k_return_value);
+  tdep->struct_return = reg_struct_return;
 
+  /* These register numbers may be overridden by an OSABI
+     sniffer.  */
+  if (info.abfd == NULL)
+    tdep->struct_value_regnum = M68K_A0_REGNUM;
+  else if (bfd_get_flavour (info.abfd) == bfd_target_elf_flavour)
+    tdep->struct_value_regnum = M68K_A0_REGNUM;
+  else
+    tdep->struct_value_regnum = M68K_A1_REGNUM;
   tdep->ptr_value_regnum = M68K_D0_REGNUM;
 
   /* Disassembler.  */
@@ -1303,8 +1311,6 @@ m68k_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
 #else
   tdep->jb_pc = -1;
 #endif
-  tdep->struct_value_regnum = M68K_A1_REGNUM;
-  tdep->struct_return = reg_struct_return;
 
   /* Frame unwinder.  */
   set_gdbarch_dummy_id (gdbarch, m68k_dummy_id);
diff --git a/gdb/m68kbsd-tdep.c b/gdb/m68kbsd-tdep.c
index 3b5f5e0..f5bfa1a 100644
--- a/gdb/m68kbsd-tdep.c
+++ b/gdb/m68kbsd-tdep.c
@@ -234,6 +234,15 @@ m68kbsd_elf_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
   /* NetBSD ELF uses SVR4-style shared libraries.  */
   set_solib_svr4_fetch_link_map_offsets
     (gdbarch, svr4_ilp32_fetch_link_map_offsets);
+
+  /* OpenBSD uses %a1to return structures.  */
+  if (info.abfd)
+    {
+      enum gdb_osabi osabi = gdbarch_lookup_osabi (info.abfd);
+
+      if (osabi == GDB_OSABI_OPENBSD_ELF)
+	tdep->struct_value_regnum = M68K_A1_REGNUM;
+    }
 }