[m68k] return values

[Nathan Sidwell <nathan@codesourcery.com>]

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this is a reworking of my recent return value patch.  this patch just contains 
changes to select which register contains a pointer value, and how structure 
return values are located.

I've added tdep field 'ptr_value_regnum' to accommodate the different ABIs that 
return in %d0 or %a0.

Most of the patch is adding the necessary pieces to the os sniffers to 
initialize that value.

ok?

nathan
-- 
Nathan Sidwell    ::   http://www.codesourcery.com   ::         CodeSourcery
nathan@codesourcery.com    ::     http://www.planetfall.pwp.blueyonder.co.uk


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2006-06-09  Nathan Sidwell  <nathan@codesourcery.com>

	* configure.tgt (gdb_osabi): uclinux is like linux.
	* m68k-tdep.c (m68k_svr4_extract_return_value): Use
	tdep->ptr_value_regnum for pointer returns.
	(m68k_svr4_store_return_value): Likewise.
	(m68k_svr4_init_abi, m68k_aout_init_abi): Set ptr_value_regnum.
	(m68k_gdbarch_init): Likewise.
	* m68k-tdep.h (struct gdbarch_tdep): Add ptr_value_regnum
	field.
	* m68kbsd-tdep.c (m68kbsd_aout_init_abi): Use m68k_aout_init_abi.
	(m68kbsd_elf_init_abi): Add comment.
	* m68klinux-tdep.c (m68k_linux_init_abi): Just set the struct
	pointer register here.

Index: configure.tgt
===================================================================
RCS file: /cvs/src/src/gdb/configure.tgt,v
retrieving revision 1.172
diff -c -3 -p -r1.172 configure.tgt
*** configure.tgt	20 Apr 2006 23:18:48 -0000	1.172
--- configure.tgt	9 Jun 2006 12:45:08 -0000
*************** esac
*** 223,228 ****
--- 223,229 ----
  case "${target}" in
  *-*-freebsd*)	gdb_osabi=GDB_OSABI_FREEBSD_ELF ;;
  *-*-linux*)	gdb_osabi=GDB_OSABI_LINUX ;;
+ *-*-uclinux*)	gdb_osabi=GDB_OSABI_LINUX ;;
  *-*-nto*)	gdb_osabi=GDB_OSABI_QNXNTO ;;
  m68*-*-openbsd* | m88*-*-openbsd* | vax-*-openbsd*) ;;
  *-*-openbsd*)	gdb_osabi=GDB_OSABI_OPENBSD_ELF ;;
Index: m68k-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/m68k-tdep.c,v
retrieving revision 1.106
diff -c -3 -p -r1.106 m68k-tdep.c
*** m68k-tdep.c	8 Jun 2006 19:11:45 -0000	1.106
--- m68k-tdep.c	9 Jun 2006 12:45:09 -0000
*************** m68k_svr4_extract_return_value (struct t
*** 253,259 ****
        convert_typed_floating (buf, builtin_type_m68881_ext, valbuf, type);
      }
    else if (TYPE_CODE (type) == TYPE_CODE_PTR && len == 4)
!     regcache_raw_read (regcache, M68K_A0_REGNUM, valbuf);
    else
      m68k_extract_return_value (type, regcache, valbuf);
  }
--- 253,261 ----
        convert_typed_floating (buf, builtin_type_m68881_ext, valbuf, type);
      }
    else if (TYPE_CODE (type) == TYPE_CODE_PTR && len == 4)
!     regcache_raw_read (regcache,
! 		       gdbarch_tdep (current_gdbarch)->ptr_value_regnum,
! 		       valbuf);
    else
      m68k_extract_return_value (type, regcache, valbuf);
  }
*************** m68k_svr4_store_return_value (struct typ
*** 292,301 ****
        regcache_raw_write (regcache, M68K_FP0_REGNUM, buf);
      }
    else if (TYPE_CODE (type) == TYPE_CODE_PTR && len == 4)
!     {
!       regcache_raw_write (regcache, M68K_A0_REGNUM, valbuf);
!       regcache_raw_write (regcache, M68K_D0_REGNUM, valbuf);
!     }
    else
      m68k_store_return_value (type, regcache, valbuf);
  }
--- 294,302 ----
        regcache_raw_write (regcache, M68K_FP0_REGNUM, buf);
      }
    else if (TYPE_CODE (type) == TYPE_CODE_PTR && len == 4)
!     regcache_raw_write (regcache,
! 			gdbarch_tdep (current_gdbarch)->ptr_value_regnum,
! 			valbuf);
    else
      m68k_store_return_value (type, regcache, valbuf);
  }
*************** m68k_svr4_return_value (struct gdbarch *
*** 370,394 ****
    if ((code == TYPE_CODE_STRUCT || code == TYPE_CODE_UNION)
        && !m68k_reg_struct_return_p (gdbarch, type))
      {
!       /* The System V ABI says that:
! 
! 	 "A function returning a structure or union also sets %a0 to
! 	 the value it finds in %a0.  Thus when the caller receives
! 	 control again, the address of the returned object resides in
! 	 register %a0."
! 
! 	 So the ABI guarantees that we can always find the return
! 	 value just after the function has returned.  */
! 
!       if (readbuf)
! 	{
! 	  ULONGEST addr;
! 
! 	  regcache_raw_read_unsigned (regcache, M68K_A0_REGNUM, &addr);
! 	  read_memory (addr, readbuf, TYPE_LENGTH (type));
! 	}
! 
!       return RETURN_VALUE_ABI_RETURNS_ADDRESS;
      }
  
    /* This special case is for structures consisting of a single
--- 371,381 ----
    if ((code == TYPE_CODE_STRUCT || code == TYPE_CODE_UNION)
        && !m68k_reg_struct_return_p (gdbarch, type))
      {
!       /* Although they SYSV ABI specifies that a function returning a
! 	 structure this way should preserve %a0, GCC doesn't do that.
! 	 Furthermore there's no point changeing GCC to make it do it,
! 	 as that would just be bloat. */
!       return RETURN_VALUE_STRUCT_CONVENTION;
      }
  
    /* This special case is for structures consisting of a single
*************** m68k_svr4_init_abi (struct gdbarch_info 
*** 1124,1131 ****
    /* 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;
  }
  \f
  
--- 1111,1137 ----
    /* SVR4 uses a different calling convention.  */
    set_gdbarch_return_value (gdbarch, m68k_svr4_return_value);
  
!   /* SVR4 uses %a0.  */
    tdep->struct_value_regnum = M68K_A0_REGNUM;
+   tdep->struct_return = reg_struct_return;
+   /* Pointers are returned in %a0 */
+   tdep->ptr_value_regnum = M68K_A0_REGNUM;
+ }
+ 
+ /* a.out */
+ 
+ void
+ m68k_aout_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
+ {
+   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
+ 
+   set_gdbarch_return_value (gdbarch, m68k_return_value);
+ 
+   /* aout uses %a1 */
+   tdep->struct_value_regnum = M68K_A1_REGNUM;
+   tdep->struct_return = reg_struct_return;
+   /* Pointers are returned in %a0 */
+   tdep->ptr_value_regnum = M68K_A0_REGNUM;
  }
  \f
  
*************** m68k_gdbarch_init (struct gdbarch_info i
*** 1175,1182 ****
    set_gdbarch_register_to_value (gdbarch,  m68k_register_to_value);
    set_gdbarch_value_to_register (gdbarch, m68k_value_to_register);
  
    set_gdbarch_push_dummy_call (gdbarch, m68k_push_dummy_call);
!   set_gdbarch_return_value (gdbarch, m68k_return_value);
  
    /* Disassembler.  */
    set_gdbarch_print_insn (gdbarch, print_insn_m68k);
--- 1181,1194 ----
    set_gdbarch_register_to_value (gdbarch,  m68k_register_to_value);
    set_gdbarch_value_to_register (gdbarch, m68k_value_to_register);
  
+   /* Function call & return */
    set_gdbarch_push_dummy_call (gdbarch, m68k_push_dummy_call);
!   /* These values are for bare metal -- os specific ABIs can override
!      them */
!   set_gdbarch_return_value (gdbarch, m68k_svr4_return_value);
!   tdep->struct_value_regnum = M68K_A0_REGNUM;
!   tdep->struct_return = reg_struct_return;
!   tdep->ptr_value_regnum = M68K_D0_REGNUM;
  
    /* Disassembler.  */
    set_gdbarch_print_insn (gdbarch, print_insn_m68k);
*************** m68k_gdbarch_init (struct gdbarch_info i
*** 1187,1194 ****
  #else
    tdep->jb_pc = -1;
  #endif
-   tdep->struct_value_regnum = M68K_A1_REGNUM;
-   tdep->struct_return = reg_struct_return;
  
    /* Frame unwinder.  */
    set_gdbarch_unwind_dummy_id (gdbarch, m68k_unwind_dummy_id);
--- 1199,1204 ----
Index: m68k-tdep.h
===================================================================
RCS file: /cvs/src/src/gdb/m68k-tdep.h,v
retrieving revision 1.10
diff -c -3 -p -r1.10 m68k-tdep.h
*** m68k-tdep.h	17 Dec 2005 22:34:01 -0000	1.10
--- m68k-tdep.h	9 Jun 2006 12:45:09 -0000
*************** struct gdbarch_tdep
*** 76,85 ****
--- 76,90 ----
  
    /* Convention for returning structures.  */
    enum struct_return struct_return;
+   
+   /* Register in which pointers are returned.  */
+   int ptr_value_regnum;
  };
  
  /* Initialize a SVR4 architecture variant.  */
  extern void m68k_svr4_init_abi (struct gdbarch_info, struct gdbarch *);
+ /* Initialize a aout architecture variant.   */
+ extern void m68k_aout_init_abi (struct gdbarch_info, struct gdbarch *);
  \f
  
  /* Functions exported from m68kbsd-tdep.c.  */
Index: m68kbsd-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/m68kbsd-tdep.c,v
retrieving revision 1.7
diff -c -3 -p -r1.7 m68kbsd-tdep.c
*** m68kbsd-tdep.c	17 Dec 2005 22:34:01 -0000	1.7
--- m68kbsd-tdep.c	9 Jun 2006 12:45:09 -0000
*************** m68kbsd_aout_init_abi (struct gdbarch_in
*** 206,212 ****
  
    m68kbsd_init_abi (info, gdbarch);
  
!   tdep->struct_return = reg_struct_return;
  
    tramp_frame_prepend_unwinder (gdbarch, &m68kobsd_sigtramp);
  }
--- 206,212 ----
  
    m68kbsd_init_abi (info, gdbarch);
  
!   m68k_aout_init_abi (info, gdbarch);
  
    tramp_frame_prepend_unwinder (gdbarch, &m68kobsd_sigtramp);
  }
*************** m68kbsd_elf_init_abi (struct gdbarch_inf
*** 222,227 ****
--- 222,228 ----
  
    /* NetBSD ELF uses the SVR4 ABI.  */
    m68k_svr4_init_abi (info, gdbarch);
+   /* But with pcc structure return */
    tdep->struct_return = pcc_struct_return;
  
    /* NetBSD ELF uses SVR4-style shared libraries.  */
Index: m68klinux-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/m68klinux-tdep.c,v
retrieving revision 1.18
diff -c -3 -p -r1.18 m68klinux-tdep.c
*** m68klinux-tdep.c	20 Apr 2006 17:29:47 -0000	1.18
--- m68klinux-tdep.c	9 Jun 2006 12:45:09 -0000
*************** m68k_linux_init_abi (struct gdbarch_info
*** 291,298 ****
       address to store a structure value.  It also returns small
       structures in registers instead of memory.  */
    m68k_svr4_init_abi (info, gdbarch);
    tdep->struct_value_regnum = M68K_A1_REGNUM;
-   tdep->struct_return = reg_struct_return;
  
    frame_unwind_append_sniffer (gdbarch, m68k_linux_sigtramp_frame_sniffer);
  
--- 291,298 ----
       address to store a structure value.  It also returns small
       structures in registers instead of memory.  */
    m68k_svr4_init_abi (info, gdbarch);
+   /* But the struct pointer is in %a1 */
    tdep->struct_value_regnum = M68K_A1_REGNUM;
  
    frame_unwind_append_sniffer (gdbarch, m68k_linux_sigtramp_frame_sniffer);