[patch/rfc] frame_pc_unwind()

[Andrew Cagney <ac131313 at redhat dot com>]

Hello,

The attached patch adds a per-frame frame_pc_unwind() method.  This goes 
with the per-frame frame_register_unwind() method (notice how the 
names/meanings match - unlike frame_saved_pc() vs get_saved_register() :-).

For a dummy frame it uses the dummy-frame version.  For other frames it 
falls back to  the existing FRAME_SAVED_PC() version.

This patch means that both GET_SAVED_REGISTER() and FRAME_SAVED_PC() 
have now officially been `put on notice'.  Need to demonstrate the 
replacement before they can be made obsolete though :-)

Baring comments, I'll commit this in a few days,

Andrew
2002-11-08  Andrew Cagney  <ac131313@redhat.com>

	* frame.c (frame_pc_unwind): New function.
	(frame_saved_regs_pc_unwind): New function.
	(frame_register_unwind): Pass unwind_cache instead of
	register_unwind_cache.
	(set_unwind_by_pc): Add unwind_pc parameter, set.
	(create_new_frame): Pass frame->pc_unwind to set_unwind_by_pc.
	(get_prev_frame): Ditto.
	* frame.h (frame_pc_unwind_ftype): Declare.
	(struct frame_info): Add pc_unwind, pc_unwind_cache_p and
	pc_unwind_cache.  Rename register_unwind_cache to unwind_cache.
	(frame_pc_unwind): Declare.
	* dummy-frame.c (dummy_frame_pc_unwind): New function.
	(struct dummy_frame): Add comment mentioning that values are for
	previous frame.
	* dummy-frame.h (dummy_frame_pc_unwind): Declare.

	* blockframe.c (file_frame_chain_valid): Use frame_pc_unwind.
	(generic_file_frame_chain_valid): Ditto.
	* stack.c (frame_info): Ditto.

Index: blockframe.c
===================================================================
RCS file: /cvs/src/src/gdb/blockframe.c,v
retrieving revision 1.46
diff -u -r1.46 blockframe.c
--- blockframe.c	8 Nov 2002 20:48:55 -0000	1.46
+++ blockframe.c	9 Nov 2002 00:36:22 -0000
@@ -49,7 +49,7 @@
 file_frame_chain_valid (CORE_ADDR chain, struct frame_info *thisframe)
 {
   return ((chain) != 0
-	  && !inside_entry_file (FRAME_SAVED_PC (thisframe)));
+	  && !inside_entry_file (frame_pc_unwind (thisframe)));
 }
 
 /* Use the alternate method of avoiding running up off the end of the
@@ -753,12 +753,12 @@
 int
 generic_file_frame_chain_valid (CORE_ADDR fp, struct frame_info *fi)
 {
-  if (PC_IN_CALL_DUMMY (FRAME_SAVED_PC (fi), fp, fp))
+  if (PC_IN_CALL_DUMMY (frame_pc_unwind (fi), fp, fp))
     return 1;			/* don't prune CALL_DUMMY frames */
   else				/* fall back to default algorithm (see frame.h) */
     return (fp != 0
 	    && (INNER_THAN (fi->frame, fp) || fi->frame == fp)
-	    && !inside_entry_file (FRAME_SAVED_PC (fi)));
+	    && !inside_entry_file (frame_pc_unwind (fi)));
 }
 
 int
Index: dummy-frame.c
===================================================================
RCS file: /cvs/src/src/gdb/dummy-frame.c,v
retrieving revision 1.2
diff -u -r1.2 dummy-frame.c
--- dummy-frame.c	8 Nov 2002 23:12:52 -0000	1.2
+++ dummy-frame.c	9 Nov 2002 00:36:22 -0000
@@ -37,6 +37,8 @@
 {
   struct dummy_frame *next;
 
+  /* These values belong to the caller (the previous frame, the frame
+     that this unwinds back to).  */
   CORE_ADDR pc;
   CORE_ADDR fp;
   CORE_ADDR sp;
@@ -306,5 +308,13 @@
          register cache.  */
       regcache_cooked_read (dummy->regcache, regnum, bufferp);
     }
+}
+
+CORE_ADDR
+dummy_frame_pc_unwind (struct frame_info *frame,
+		       void **cache)
+{
+  struct dummy_frame *dummy = cached_find_dummy_frame (frame, cache);
+  return dummy->pc;
 }
 
Index: dummy-frame.h
===================================================================
RCS file: /cvs/src/src/gdb/dummy-frame.h,v
retrieving revision 1.2
diff -u -r1.2 dummy-frame.h
--- dummy-frame.h	8 Nov 2002 23:12:52 -0000	1.2
+++ dummy-frame.h	9 Nov 2002 00:36:22 -0000
@@ -54,6 +54,12 @@
 					 int *realnump,
 					 void *valuep);
 
+/* Assuming that FRAME is a dummy, return the resume address for the
+   previous frame.  */
+
+extern CORE_ADDR dummy_frame_pc_unwind (struct frame_info *frame,
+					void **unwind_cache);
+
 /* Return the regcache that belongs to the dummy-frame identifed by PC
    and FP, or NULL if no such frame exists.  */
 /* FIXME: cagney/2002-11-08: The function only exists because of
Index: frame.c
===================================================================
RCS file: /cvs/src/src/gdb/frame.c,v
retrieving revision 1.23
diff -u -r1.23 frame.c
--- frame.c	8 Nov 2002 23:12:52 -0000	1.23
+++ frame.c	9 Nov 2002 00:36:22 -0000
@@ -84,6 +84,17 @@
   return NULL;
 }
 
+CORE_ADDR
+frame_pc_unwind (struct frame_info *frame)
+{
+  if (!frame->pc_unwind_cache_p)
+    {
+      frame->pc_unwind_cache = frame->pc_unwind (frame, &frame->unwind_cache);
+      frame->pc_unwind_cache_p = 1;
+    }
+  return frame->pc_unwind_cache;
+}
+
 void
 frame_register_unwind (struct frame_info *frame, int regnum,
 		       int *optimizedp, enum lval_type *lvalp,
@@ -124,7 +135,7 @@
     }
 
   /* Ask this frame to unwind its register.  */
-  frame->register_unwind (frame, &frame->register_unwind_cache, regnum,
+  frame->register_unwind (frame, &frame->unwind_cache, regnum,
 			  optimizedp, lvalp, addrp, realnump, bufferp);
 }
 
@@ -524,6 +535,12 @@
     }
 }
 
+static CORE_ADDR
+frame_saved_regs_pc_unwind (struct frame_info *frame, void **cache)
+{
+  return FRAME_SAVED_PC (frame);
+}
+	
 /* Function: get_saved_register
    Find register number REGNUM relative to FRAME and put its (raw,
    target format) contents in *RAW_BUFFER.  
@@ -627,18 +644,28 @@
 
 static void
 set_unwind_by_pc (CORE_ADDR pc, CORE_ADDR fp,
-		  frame_register_unwind_ftype **unwind)
+		  frame_register_unwind_ftype **unwind_register,
+		  frame_pc_unwind_ftype **unwind_pc)
 {
   if (!USE_GENERIC_DUMMY_FRAMES)
-    /* Still need to set this to something.  The ``info frame'' code
-       calls this function to find out where the saved registers are.
-       Hopefully this is robust enough to stop any core dumps and
-       return vaguely correct values..  */
-    *unwind = frame_saved_regs_register_unwind;
+    {
+      /* Still need to set this to something.  The ``info frame'' code
+	 calls this function to find out where the saved registers are.
+	 Hopefully this is robust enough to stop any core dumps and
+	 return vaguely correct values..  */
+      *unwind_register = frame_saved_regs_register_unwind;
+      *unwind_pc = frame_saved_regs_pc_unwind;
+    }
   else if (PC_IN_CALL_DUMMY (pc, fp, fp))
-    *unwind = dummy_frame_register_unwind;
+    {
+      *unwind_register = dummy_frame_register_unwind;
+      *unwind_pc = dummy_frame_pc_unwind;
+    }
   else
-    *unwind = frame_saved_regs_register_unwind;
+    {
+      *unwind_register = frame_saved_regs_register_unwind;
+      *unwind_pc = frame_saved_regs_pc_unwind;
+    }
 }
 
 /* Create an arbitrary (i.e. address specified by user) or innermost frame.
@@ -666,7 +693,8 @@
     INIT_EXTRA_FRAME_INFO (0, fi);
 
   /* Select/initialize an unwind function.  */
-  set_unwind_by_pc (fi->pc, fi->frame, &fi->register_unwind);
+  set_unwind_by_pc (fi->pc, fi->frame, &fi->register_unwind,
+		    &fi->pc_unwind);
 
   return fi;
 }
@@ -874,7 +902,8 @@
      (and probably other architectural information).  The PC lets you
      check things like the debug info at that point (dwarf2cfi?) and
      use that to decide how the frame should be unwound.  */
-  set_unwind_by_pc (prev->pc, prev->frame, &prev->register_unwind);
+  set_unwind_by_pc (prev->pc, prev->frame, &prev->register_unwind,
+		    &prev->pc_unwind);
 
   find_pc_partial_function (prev->pc, &name,
 			    (CORE_ADDR *) NULL, (CORE_ADDR *) NULL);
Index: frame.h
===================================================================
RCS file: /cvs/src/src/gdb/frame.h,v
retrieving revision 1.29
diff -u -r1.29 frame.h
--- frame.h	5 Nov 2002 21:44:05 -0000	1.29
+++ frame.h	9 Nov 2002 00:36:22 -0000
@@ -46,6 +46,12 @@
 					    int *realnump,
 					    void *valuep);
 
+/* Same as for registers above, but return the address at which the
+   calling frame would resume.  */
+
+typedef CORE_ADDR (frame_pc_unwind_ftype) (struct frame_info *frame,
+					   void **unwind_cache);
+
 /* Describe the saved registers of a frame.  */
 
 #if defined (EXTRA_FRAME_INFO) || defined (FRAME_FIND_SAVED_REGS)
@@ -135,10 +141,18 @@
        related unwind data.  */
     struct context *context;
 
-    /* See description above.  Return the register value for the
-       previous frame.  */
+    /* Unwind cache shared between the unwind functions - they had
+       better all agree as to the contents.  */
+    void *unwind_cache;
+
+    /* See description above.  The previous frame's registers.  */
     frame_register_unwind_ftype *register_unwind;
-    void *register_unwind_cache;
+
+    /* See description above.  The previous frame's resume address.
+       Save the previous PC in a local cache.  */
+    frame_pc_unwind_ftype *pc_unwind;
+    int pc_unwind_cache_p;
+    CORE_ADDR pc_unwind_cache;
 
     /* Pointers to the next (down, inner) and previous (up, outer)
        frame_info's in the frame cache.  */
@@ -340,6 +354,12 @@
 					       struct frame_info *frame,
 					       int regnum,
 					       enum lval_type *lval);
+
+/* Unwind the PC.  Strictly speaking return the resume address of the
+   calling frame.  For GDB, `pc' is the resume address and not a
+   specific register.  */
+
+extern CORE_ADDR frame_pc_unwind (struct frame_info *frame);
 
 /* Unwind the stack frame so that the value of REGNUM, in the previous
    frame is returned.  If VALUEP is NULL, don't fetch/compute the
Index: stack.c
===================================================================
RCS file: /cvs/src/src/gdb/stack.c,v
retrieving revision 1.46
diff -u -r1.46 stack.c
--- stack.c	3 Oct 2002 22:34:58 -0000	1.46
+++ stack.c	9 Nov 2002 00:36:22 -0000
@@ -866,7 +866,7 @@
   puts_filtered ("; ");
   wrap_here ("    ");
   printf_filtered ("saved %s ", REGISTER_NAME (PC_REGNUM));
-  print_address_numeric (FRAME_SAVED_PC (fi), 1, gdb_stdout);
+  print_address_numeric (frame_pc_unwind (fi), 1, gdb_stdout);
   printf_filtered ("\n");
 
   {