[RFA] mips_store_struct_return, mips_extract_struct_value_address

[Michael Snyder]

These two new functions serve as the gdbarch-ification of the 
corresponding macros, but also add functionality.  The existing
macros didn't work, because they depended on the value of the
struct_return address being preserved in $v0 (which the compiler
was not constrained to do).  Instead we borrow an implementation
from numerous other targets, and save the value when gdb sets it
(which ought to be in store_struct_return, but in our case is in
push_arguments), and then return it later via
extract_struct_value_address.

A future improvement would be to move the code that sets 
struct_return from push_arguments into store_struct_return.
-------------- next part --------------
2002-08-19  Michael Snyder  <msnyder@redhat.com>

	* mips-tdep.c (struct_return_addr): New variable.  Address
	of struct_return as recorded by push_arguments.
	(mips_eabi_push_arguments, mips_o32_push_arguments, 
	mips_o64_push_arguments, mips_n32n64_push_arguments): Store
	value of struct_return address.
	(mips_extract_struct_value_address): New function. 
	Return struct_return_addr as saved by push_arguments.
	(mips_store_struct_return): New function, empty stub.
	(mips_gdbarch_init): Set store_struct_return and
	extract_struct_value_address.

Index: mips-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/mips-tdep.c,v
retrieving revision 1.108
diff -p -r1.108 mips-tdep.c
*** mips-tdep.c	19 Aug 2002 23:22:17 -0000	1.108
--- mips-tdep.c	20 Aug 2002 01:50:53 -0000
*************** mips_type_needs_double_align (struct typ
*** 2536,2541 ****
--- 2536,2543 ----
  #define ROUND_DOWN(n,a) ((n) & ~((a)-1))
  #define ROUND_UP(n,a) (((n)+(a)-1) & ~((a)-1))
  
+ static CORE_ADDR struct_return_addr;
+ 
  CORE_ADDR
  mips_eabi_push_arguments (int nargs,
  			  struct value **args,
*************** mips_eabi_push_arguments (int nargs,
*** 2557,2562 ****
--- 2559,2566 ----
  
    sp = ROUND_DOWN (sp, 16);
    struct_addr = ROUND_DOWN (struct_addr, 16);
+   /* Save struct_addr for EXTRACT_STRUCT_VALUE_ADDRESS.  */
+   struct_return_addr = struct_addr;
  
    /* Now make space on the stack for the args.  We allocate more
       than necessary for EABI, because the first few arguments are
*************** mips_n32n64_push_arguments (int nargs,
*** 2810,2815 ****
--- 2814,2821 ----
  
    sp = ROUND_DOWN (sp, 16);
    struct_addr = ROUND_DOWN (struct_addr, 16);
+   /* Save struct_addr for EXTRACT_STRUCT_VALUE_ADDRESS.  */
+   struct_return_addr = struct_addr;
  
    /* Now make space on the stack for the args.  */
    for (argnum = 0; argnum < nargs; argnum++)
*************** mips_o32_push_arguments (int nargs,
*** 3036,3041 ****
--- 3042,3049 ----
  
    sp = ROUND_DOWN (sp, 16);
    struct_addr = ROUND_DOWN (struct_addr, 16);
+   /* Save struct_addr for EXTRACT_STRUCT_VALUE_ADDRESS.  */
+   struct_return_addr = struct_addr;
  
    /* Now make space on the stack for the args.  */
    for (argnum = 0; argnum < nargs; argnum++)
*************** mips_o64_push_arguments (int nargs,
*** 3335,3340 ****
--- 3343,3350 ----
  
    sp = ROUND_DOWN (sp, 16);
    struct_addr = ROUND_DOWN (struct_addr, 16);
+   /* Save struct_addr for EXTRACT_STRUCT_VALUE_ADDRESS.  */
+   struct_return_addr = struct_addr;
  
    /* Now make space on the stack for the args.  */
    for (argnum = 0; argnum < nargs; argnum++)
*************** mips_n32n64_store_return_value (struct t
*** 4760,4765 ****
--- 4770,4794 ----
    mips_n32n64_xfer_return_value (type, current_regcache, NULL, valbuf);
  }
  
+ static CORE_ADDR
+ mips_extract_struct_value_address (struct regcache *ignore)
+ {
+   CORE_ADDR ret = struct_return_addr;
+   /* We can't count on the struct return value being returned 
+      in v0 -- which is why we use mips_store_struct_return
+      to stash it in a private cache.  FIXME this really calls
+      for a stack.  */
+ 
+   struct_return_addr = 0;
+   return ret;
+ }
+ 
+ static void
+ mips_store_struct_return (CORE_ADDR addr, CORE_ADDR sp)
+ {
+   /* Nothing to do -- push_arguments does all the work.  */
+ }
+ 
  /* Exported procedure: Is PC in the signal trampoline code */
  
  static int
*************** mips_gdbarch_init (struct gdbarch_info i
*** 5832,5837 ****
--- 5861,5871 ----
  
    set_gdbarch_do_registers_info (gdbarch, mips_do_registers_info);
    set_gdbarch_pc_in_sigtramp (gdbarch, mips_pc_in_sigtramp);
+ 
+   set_gdbarch_store_struct_return (gdbarch, mips_store_struct_return);
+   set_gdbarch_extract_struct_value_address (gdbarch, 
+ 					    mips_extract_struct_value_address);
+ 
  
    /* Hook in OS ABI-specific overrides, if they have been registered.  */
    gdbarch_init_osabi (info, gdbarch, osabi);