[hpux] Improve handling of unwind records for hp compiler

[Randolph Chung <randolph at tausq dot org>]

As discussed recently on the gdb mailing list, current gdb has problems 
unwinding code generated by the HP compiler. The attached patch teaches 
the hppa unwinder about two additional flags in the unwind record 
generated by the HP toolchain.

For some reason in the gdb code, the "alloca_frame" bit is called 
Pseudo_SP_Set; most HP docs refer to it as alloca_frame. I'll submit a 
separate change to improve the "maint print unwind" command to print out 
all the unwind record flags and change the name of the alloca_frame flag 
to match the documentation.

This patch was tested with no regressions against GNU tools on 
hppa2.0w-hp-hpux11.11 and hppa64-hp-hpux11.11. I only tested it against 
one HP compiled program I have on hand (wdb).

I'll commit this in a couple of days if there are no additional comments.

thanks
randolph

P.S. wdb doesn't handle this case correctly either.
2005-12-15  Randolph Chung  <tausq@debian.org>

	* hppa-tdep.c (hppa_frame_cache): Handle Region_Description and
	Pseudo_SP_Set in unwind record.

Index: hppa-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/hppa-tdep.c,v
retrieving revision 1.216
diff -u -p -r1.216 hppa-tdep.c
--- hppa-tdep.c	9 Dec 2005 11:13:34 -0000	1.216
+++ hppa-tdep.c	15 Dec 2005 14:41:17 -0000
@@ -1857,7 +1857,7 @@ hppa_frame_cache (struct frame_info *nex
      GCC code.  */
   {
     int final_iteration = 0;
-    CORE_ADDR pc, end_pc;
+    CORE_ADDR pc, start_pc, end_pc;
     int looking_for_sp = u->Save_SP;
     int looking_for_rp = u->Save_RP;
     int fp_loc = -1;
@@ -1877,9 +1877,19 @@ hppa_frame_cache (struct frame_info *nex
     /* We used to use frame_func_unwind () to locate the beginning of the
        function to pass to skip_prologue ().  However, when objects are 
        compiled without debug symbols, frame_func_unwind can return the wrong 
-       function (or 0).  We can do better than that by using unwind records.  */
+       function (or 0).  We can do better than that by using unwind records.  
+       This only works if the Region_description of the unwind record
+       indicates that it includes the entry point of the function.  
+       HP compilers sometimes generate unwind records for regions that
+       do not include the entry or exit point of a function.  GNU tools
+       do not do this.  */
 
-    prologue_end = skip_prologue_hard_way (u->region_start, 0);
+    if ((u->Region_description & 0x2) == 0)
+      start_pc = u->region_start;
+    else
+      start_pc = frame_func_unwind (next_frame);
+
+    prologue_end = skip_prologue_hard_way (start_pc, 0);
     end_pc = frame_pc_unwind (next_frame);
 
     if (prologue_end != 0 && end_pc > prologue_end)
@@ -1887,7 +1897,7 @@ hppa_frame_cache (struct frame_info *nex
 
     frame_size = 0;
 
-    for (pc = u->region_start;
+    for (pc = start_pc;
 	 ((saved_gr_mask || saved_fr_mask
 	   || looking_for_sp || looking_for_rp
 	   || frame_size < (u->Total_frame_size << 3))
@@ -2054,9 +2064,12 @@ hppa_frame_cache (struct frame_info *nex
 	instead of Save_SP.  */
  
      fp = frame_unwind_register_unsigned (next_frame, HPPA_FP_REGNUM);
+
+     if (u->Pseudo_SP_Set)
+       fp -= u->Total_frame_size << 3;
  
      if (frame_pc_unwind (next_frame) >= prologue_end
-         && u->Save_SP && fp != 0)
+         && (u->Save_SP || u->Pseudo_SP_Set) && fp != 0)
       {
  	cache->base = fp;