Re: [rfa:ppc] Eliminate write_sp, but how?

[Andrew Cagney <ac131313@redhat.com>]

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>> So, in addition to eliminating deprecated write_sp, would it be ok to 
>> move the write SP code to the end of the push_dummy_call methods?
> 
> 
> I can't think of any problems that would arise from moving the "write
> SP" code to the end of the various push_dummy_call() methods.  But
> just in case, when you change it, please note how it used to be done
> and why doing it in a different location *shouldn't* be a problem. 
> (It may someday make it easier to debug that obscure target which
> randomly picks a stopped thread's stack to service an interrupt...)

This is what I've checked in.

Andrew


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2003-09-11  Andrew Cagney  <cagney@redhat.com>

	* rs6000-tdep.c (rs6000_push_dummy_call): Use
	regcache_raw_write_signed to set SP_REGNUM, move the operation to
	near the function's end.
	(rs6000_gdbarch_init): Do not set "deprecated_dummy_write_sp".
	* ppc-sysv-tdep.c (ppc_sysv_abi_push_dummy_call): Use
	regcache_raw_write_signed to set SP_REGNUM.

Index: ppc-sysv-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/ppc-sysv-tdep.c,v
retrieving revision 1.8
diff -u -r1.8 ppc-sysv-tdep.c
--- ppc-sysv-tdep.c	9 Sep 2003 22:41:47 -0000	1.8
+++ ppc-sysv-tdep.c	11 Sep 2003 19:23:29 -0000
@@ -189,8 +189,8 @@
   /* Make sure that we maintain 16 byte alignment */
   sp &= ~0x0f;
 
-  /* Update %sp before proceeding any further */
-  write_register (SP_REGNUM, sp);
+  /* Update %sp before proceeding any further.   */
+  regcache_raw_write_signed (regcache, SP_REGNUM, sp);
 
   /* write the backchain */
   store_unsigned_integer (old_sp_buf, 4, saved_sp);
Index: rs6000-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/rs6000-tdep.c,v
retrieving revision 1.155
diff -u -r1.155 rs6000-tdep.c
--- rs6000-tdep.c	9 Sep 2003 22:41:47 -0000	1.155
+++ rs6000-tdep.c	11 Sep 2003 19:23:34 -0000
@@ -1246,14 +1246,6 @@
       space = (space + 15) & -16;
       sp -= space;
 
-      /* This is another instance we need to be concerned about
-         securing our stack space. If we write anything underneath %sp
-         (r1), we might conflict with the kernel who thinks he is free
-         to use this area. So, update %sp first before doing anything
-         else.  */
-
-      write_register (SP_REGNUM, sp);
-
       /* If the last argument copied into the registers didn't fit there 
          completely, push the rest of it into stack.  */
 
@@ -1294,14 +1286,17 @@
 	  ii += ((len + 3) & -4) / 4;
 	}
     }
-  else
-    /* Secure stack areas first, before doing anything else.  */
-    write_register (SP_REGNUM, sp);
 
   /* set back chain properly */
   store_unsigned_integer (tmp_buffer, 4, saved_sp);
   write_memory (sp, tmp_buffer, 4);
 
+  /* Set the stack pointer.  According to the ABI, the SP is ment to
+     be set _before_ the corresponding stack space is used.  No need
+     for that here though - the target has been completly stopped - it
+     isn't possible for an exception handler to stomp on the stack.  */
+  regcache_raw_write_signed (regcache, SP_REGNUM, sp);
+
   /* Point the inferior function call's return address at the dummy's
      breakpoint.  */
   regcache_raw_write_signed (regcache, tdep->ppc_lr_regnum, bp_addr);
@@ -2896,7 +2891,6 @@
     set_gdbarch_print_insn (gdbarch, gdb_print_insn_powerpc);
 
   set_gdbarch_write_pc (gdbarch, generic_target_write_pc);
-  set_gdbarch_deprecated_dummy_write_sp (gdbarch, deprecated_write_sp);
 
   set_gdbarch_num_regs (gdbarch, v->nregs);
   set_gdbarch_num_pseudo_regs (gdbarch, v->npregs);