[patch/rfa:rs6000] Don't use ->prev

[Andrew Cagney <ac131313 at cygnus dot com>]

Hello,

A number of targets contained code that tested ``->prev'' as part of 
doing their frame analysis.  I think this ``cheating''.  The objective 
of the frame analysis code is to create the ->prev frame using 
information from the current frame, not to use the still being created 
->prev frame :-)

Two cases - frame_chain for z8k and s390 - were, I think, simply wrong. 
  The deleted z8k comment is telling - someone was 180 degrees out! :-)

The other two cases - get_saved_regs for SPARC and rs6000 - are more 
interesting.

The SPARC code clearly relies on there already being a ->prev frame so 
I've used get_prev_frame().  Since ->prev must exist, there is no risk 
of recursion - get_prev_frame() calling get_saved_regs() (yes, grotty).

The rs6000 has me puzzled. I think the ->frame contains the address of 
the wrong end of the frame!  If ->frame pointed at the frame's start, 
the code below wouldn't even be needed.  Anyway, I've changed it to use 
frame_chain() (I don't see regressions on NetBSD/PPC.  The other 
possability would be to risk a (recursive) get_prev_frame() call.

Anyway, is the rs6000 ok?

Andrew
2002-04-14  Andrew Cagney  <ac131313@redhat.com>

	* sparc-tdep.c (sparc_get_saved_register): Use get_prev_frame
	instead of ->prev.
	* z8k-tdep.c (z8k_frame_chain): Do not use ->prev.
	* s390-tdep.c (s390_frame_chain): Do not use ->prev.
	* rs6000-tdep.c (frame_get_saved_regs): Use rs6000_frame_chain()
	instead of ->prev.

Index: rs6000-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/rs6000-tdep.c,v
retrieving revision 1.55
diff -u -r1.55 rs6000-tdep.c
--- rs6000-tdep.c	12 Apr 2002 19:48:36 -0000	1.55
+++ rs6000-tdep.c	14 Apr 2002 16:48:56 -0000
@@ -1388,10 +1388,12 @@
       && fdatap->cr_offset == 0
       && fdatap->vr_offset == 0)
     frame_addr = 0;
-  else if (fi->prev && fi->prev->frame)
-    frame_addr = fi->prev->frame;
   else
-    frame_addr = read_memory_addr (fi->frame, wordsize);
+    /* NOTE: cagney/2002-04-14: The ->frame points to the inner-most
+       address of the current frame.  Things might be easier if the
+       ->frame pointed to the outer-most address of the frame.  In the
+       mean time, the address of the prev frame is used.  */
+    frame_addr = rs6000_frame_chain (fi);
 
   /* if != -1, fdatap->saved_fpr is the smallest number of saved_fpr.
      All fpr's from saved_fpr to fp31 are saved.  */
Index: s390-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/s390-tdep.c,v
retrieving revision 1.43
diff -u -r1.43 s390-tdep.c
--- s390-tdep.c	6 Apr 2002 00:02:50 -0000	1.43
+++ s390-tdep.c	14 Apr 2002 16:49:11 -0000
@@ -1009,9 +1009,7 @@
 {
   CORE_ADDR prev_fp = 0;
 
-  if (thisframe->prev && thisframe->prev->frame)
-    prev_fp = thisframe->prev->frame;
-  else if (generic_find_dummy_frame (thisframe->pc, thisframe->frame))
+  if (generic_find_dummy_frame (thisframe->pc, thisframe->frame))
     return generic_read_register_dummy (thisframe->pc, thisframe->frame,
                                         S390_SP_REGNUM);
   else
Index: sparc-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/sparc-tdep.c,v
retrieving revision 1.26
diff -u -r1.26 sparc-tdep.c
--- sparc-tdep.c	12 Apr 2002 18:18:57 -0000	1.26
+++ sparc-tdep.c	14 Apr 2002 16:49:23 -0000
@@ -829,11 +829,11 @@
 	    addr = frame1->frame + (regnum - G0_REGNUM) * SPARC_INTREG_SIZE
 	      - (FP_REGISTER_BYTES + 8 * SPARC_INTREG_SIZE);
 	  else if (regnum >= I0_REGNUM && regnum < I0_REGNUM + 8)
-	    addr = (frame1->prev->extra_info->bottom
+	    addr = (get_prev_frame (frame1)->extra_info->bottom
 		    + (regnum - I0_REGNUM) * SPARC_INTREG_SIZE
 		    + FRAME_SAVED_I0);
 	  else if (regnum >= L0_REGNUM && regnum < L0_REGNUM + 8)
-	    addr = (frame1->prev->extra_info->bottom
+	    addr = (get_prev_frame (frame1)->extra_info->bottom
 		    + (regnum - L0_REGNUM) * SPARC_INTREG_SIZE
 		    + FRAME_SAVED_L0);
 	  else if (regnum >= O0_REGNUM && regnum < O0_REGNUM + 8)
@@ -875,11 +875,11 @@
 	{
 	  /* Normal frame.  Local and In registers are saved on stack.  */
 	  if (regnum >= I0_REGNUM && regnum < I0_REGNUM + 8)
-	    addr = (frame1->prev->extra_info->bottom
+	    addr = (get_prev_frame (frame1)->extra_info->bottom
 		    + (regnum - I0_REGNUM) * SPARC_INTREG_SIZE
 		    + FRAME_SAVED_I0);
 	  else if (regnum >= L0_REGNUM && regnum < L0_REGNUM + 8)
-	    addr = (frame1->prev->extra_info->bottom
+	    addr = (get_prev_frame (frame1)->extra_info->bottom
 		    + (regnum - L0_REGNUM) * SPARC_INTREG_SIZE
 		    + FRAME_SAVED_L0);
 	  else if (regnum >= O0_REGNUM && regnum < O0_REGNUM + 8)
Index: z8k-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/z8k-tdep.c,v
retrieving revision 1.7
diff -u -r1.7 z8k-tdep.c
--- z8k-tdep.c	12 Apr 2002 18:18:57 -0000	1.7
+++ z8k-tdep.c	14 Apr 2002 16:49:25 -0000
@@ -160,10 +160,6 @@
 CORE_ADDR
 z8k_frame_chain (struct frame_info *thisframe)
 {
-  if (thisframe->prev == 0)
-    {
-      /* This is the top of the stack, let's get the sp for real */
-    }
   if (!inside_entry_file (thisframe->pc))
     {
       return read_memory_pointer (thisframe->frame);