[RFA] sparc-tdep.c: Fix `return' and `finish' from stop in call dummy

["Peter.Schauer" <Peter dot Schauer at regent dot e-technik dot tu-muenchen dot de>]

`return' and `finish' after a stop in a call dummy are currently not
handled correctly in sparc-tdep.c.

Here is a fix, it will be needed for the upcoming additional callfuncs
testcases:

	* sparc-tdep.c (sparc_fix_call_dummy):  Improve comments.
	Adjust call_dummy_breakpoint_offset, so that `finish' after a stop
	in a call dummy works.
	(sparc_gdbarch_init):  Fix setting of pc_in_call_dummy, it depends
	on SPARC32/64_CALL_DUMMY_ON_STACK, not DO_CALL_DUMMY_ON_STACK.

*** ./sparc-tdep.c.orig	Fri Sep 15 21:27:31 2000
--- ./sparc-tdep.c	Fri Sep 22 22:16:59 2000
***************
*** 2136,2149 ****
  			   | (((fun - (pc + CALL_DUMMY_CALL_OFFSET)) >> 2)
  			      & 0x3fffffff)));
  
!   /* Comply with strange Sun cc calling convention for struct-returning
!      functions.  */
!   if (!using_gcc
!       && (TYPE_CODE (value_type) == TYPE_CODE_STRUCT
! 	  || TYPE_CODE (value_type) == TYPE_CODE_UNION))
!     store_unsigned_integer (dummy + CALL_DUMMY_CALL_OFFSET + 8, 4,
! 			    TYPE_LENGTH (value_type) & 0x1fff);
  
    if (!(GDB_TARGET_IS_SPARC64))
      {
        /* If this is not a simulator target, change the first four
--- 2136,2163 ----
  			   | (((fun - (pc + CALL_DUMMY_CALL_OFFSET)) >> 2)
  			      & 0x3fffffff)));
  
!   /* If the called function returns an aggregate value, fill in the UNIMP
!      instruction containing the size of the returned aggregate return value,
!      which follows the call instruction.
!      For details see the SPARC Architecture Manual Version 8, Appendix D.3.
  
+      Adjust the call_dummy_breakpoint_offset for the bp_call_dummy breakpoint
+      to the proper address in the call dummy, so that `finish' after a stop
+      in a call dummy works.
+      Tweeking current_gdbarch is not an optimal solution, but the call to
+      sparc_fix_call_dummy is immediately followed by a call to run_stack_dummy,
+      which is the only function where dummy_breakpoint_offset is actually
+      used, if it is non-zero.  */
+   if (TYPE_CODE (value_type) == TYPE_CODE_STRUCT
+        || TYPE_CODE (value_type) == TYPE_CODE_UNION)
+     {
+       store_unsigned_integer (dummy + CALL_DUMMY_CALL_OFFSET + 8, 4,
+ 			      TYPE_LENGTH (value_type) & 0x1fff);
+       set_gdbarch_call_dummy_breakpoint_offset (current_gdbarch, 0x30);
+     }
+   else
+     set_gdbarch_call_dummy_breakpoint_offset (current_gdbarch, 0x2c);
+ 
    if (!(GDB_TARGET_IS_SPARC64))
      {
        /* If this is not a simulator target, change the first four
***************
*** 2961,2971 ****
    set_gdbarch_long_long_bit (gdbarch, 8 * TARGET_CHAR_BIT);
    set_gdbarch_max_register_raw_size (gdbarch, 8);
    set_gdbarch_max_register_virtual_size (gdbarch, 8);
- #ifdef DO_CALL_DUMMY_ON_STACK
-   set_gdbarch_pc_in_call_dummy (gdbarch, pc_in_call_dummy_on_stack);
- #else
-   set_gdbarch_pc_in_call_dummy (gdbarch, pc_in_call_dummy_at_entry_point);
- #endif
    set_gdbarch_pop_frame (gdbarch, sparc_pop_frame);
    set_gdbarch_push_return_address (gdbarch, sparc_push_return_address);
    set_gdbarch_push_dummy_frame (gdbarch, sparc_push_dummy_frame);
--- 2975,2980 ----
***************
*** 2999,3004 ****
--- 3008,3014 ----
        /* 32-bit machine types: */
  
  #ifdef SPARC32_CALL_DUMMY_ON_STACK
+       set_gdbarch_pc_in_call_dummy (gdbarch, pc_in_call_dummy_on_stack);
        set_gdbarch_call_dummy_address (gdbarch, sparc_call_dummy_address);
        set_gdbarch_call_dummy_breakpoint_offset (gdbarch, 0x30);
        set_gdbarch_call_dummy_length (gdbarch, 0x38);
***************
*** 3005,3010 ****
--- 3015,3021 ----
        set_gdbarch_call_dummy_location (gdbarch, ON_STACK);
        set_gdbarch_call_dummy_words (gdbarch, call_dummy_32);
  #else
+       set_gdbarch_pc_in_call_dummy (gdbarch, pc_in_call_dummy_at_entry_point);
        set_gdbarch_call_dummy_address (gdbarch, entry_point_address);
        set_gdbarch_call_dummy_breakpoint_offset (gdbarch, 0);
        set_gdbarch_call_dummy_length (gdbarch, 0);
***************
*** 3053,3058 ****
--- 3064,3070 ----
      default:	/* Any new machine type is likely to be 64-bit.  */
  
  #ifdef SPARC64_CALL_DUMMY_ON_STACK
+       set_gdbarch_pc_in_call_dummy (gdbarch, pc_in_call_dummy_on_stack);
        set_gdbarch_call_dummy_address (gdbarch, sparc_call_dummy_address);
        set_gdbarch_call_dummy_breakpoint_offset (gdbarch, 8 * 4);
        set_gdbarch_call_dummy_length (gdbarch, 192);
***************
*** 3060,3065 ****
--- 3072,3078 ----
        set_gdbarch_call_dummy_start_offset (gdbarch, 148);
        set_gdbarch_call_dummy_words (gdbarch, call_dummy_64);
  #else
+       set_gdbarch_pc_in_call_dummy (gdbarch, pc_in_call_dummy_at_entry_point);
        set_gdbarch_call_dummy_address (gdbarch, entry_point_address);
        set_gdbarch_call_dummy_breakpoint_offset (gdbarch, 0);
        set_gdbarch_call_dummy_length (gdbarch, 0);

-- 
Peter Schauer			pes@regent.e-technik.tu-muenchen.de