[RFA] Delete another call to dwarf2read.c:decode_locdesc

[Daniel Jacobowitz <drow at mvista dot com>]

The global variables set according to the DW_OP_frame_base are no longer
used anywhere except decode_locdesc, and decode_locdesc is never called when
we should expect a frame-relative object; see the updated comments in the
patch below.  This function is now only used for member offsets, etc.;
partial symbols (DW_TAG_variable only); and common blocks, which act as
global variables.  The partial symbol case should either be eliminated or
changed to use computed locations.  The common block case probably likewise.
And the remaining cases expect constants.

So DW_OP_breg* and DW_OP_fbreg are dead wood at this point and can be
removed from this function.  They're handled entirely in the LOC_COMPUTED
support code.

These happened to be next on my campaign to whack global state from the
dwarf2 reader; marching slowly down the file.  Tested on i386-linux/dwarf2.
OK?

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

2003-11-18  Daniel Jacobowitz  <drow@mvista.com>

	* dwarf2read.c (offreg, basereg, isderef, frame_base_reg)
	(frame_base_offset): Delete.
	(read_func_scope): Delete call to decode_locdesc.
	(decode_locdesc): Update comments.  Don't set the removed variables.
	Complain for DW_OP_reg* not at the end.  Remove DW_OP_breg* and
	DW_OP_fbreg support.

Index: dwarf2read.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2read.c,v
retrieving revision 1.113
diff -u -p -r1.113 dwarf2read.c
--- dwarf2read.c	18 Nov 2003 21:51:38 -0000	1.113
+++ dwarf2read.c	19 Nov 2003 01:19:53 -0000
@@ -446,20 +446,6 @@ static struct pending **list_in_scope = 
 static int isreg;		/* Object lives in register.
 				   decode_locdesc's return value is
 				   the register number.  */
-static int offreg;		/* Object's address is the sum of the
-				   register specified by basereg, plus
-				   the offset returned.  */
-static int basereg;		/* See `offreg'.  */
-static int isderef;		/* Value described by flags above is
-				   the address of a pointer to the object.  */
-
-/* DW_AT_frame_base values for the current function.
-   frame_base_reg is -1 if DW_AT_frame_base is missing, otherwise it
-   contains the register number for the frame register.
-   frame_base_offset is the offset from the frame register to the
-   virtual stack frame. */
-static int frame_base_reg;
-static CORE_ADDR frame_base_offset;
 
 /* This value is added to each symbol value.  FIXME:  Generalize to
    the section_offsets structure used by dbxread (once this is done,
@@ -2149,50 +2135,12 @@ read_func_scope (struct die_info *die, s
       objfile->ei.entry_func_highpc = highpc;
     }
 
-  /* Decode DW_AT_frame_base location descriptor if present, keep result
-     for DW_OP_fbreg operands in decode_locdesc.  */
-  frame_base_reg = -1;
-  frame_base_offset = 0;
-  attr = dwarf_attr (die, DW_AT_frame_base);
-  if (attr)
-    {
-      CORE_ADDR addr;
-
-      /* Support the .debug_loc offsets */
-      if (attr_form_is_block (attr))
-        {
-          addr = decode_locdesc (DW_BLOCK (attr), cu);
-        }
-      else if (attr->form == DW_FORM_data4 || attr->form == DW_FORM_data8)
-        {
-	  dwarf2_complex_location_expr_complaint ();
-          addr = 0;
-        }
-      else
-        {
-	  dwarf2_invalid_attrib_class_complaint ("DW_AT_frame_base", name);
-          addr = 0;
-        }
-    
-      if (isderef)
-	dwarf2_unsupported_at_frame_base_complaint (name);
-      else if (isreg)
-	frame_base_reg = addr;
-      else if (offreg)
-	{
-	  frame_base_reg = basereg;
-	  frame_base_offset = addr;
-	}
-      else
-	dwarf2_unsupported_at_frame_base_complaint (name);
-    }
-
   new = push_context (0, lowpc);
   new->name = new_symbol (die, die->type, cu);
 
-  /* If there was a location expression for DW_AT_frame_base above,
-     record it.  We still need to decode it above because not all
-     symbols use location expressions exclusively.  */
+  /* If there is a location expression for DW_AT_frame_base, record
+     it.  */
+  attr = dwarf_attr (die, DW_AT_frame_base);
   if (attr)
     dwarf2_symbol_mark_computed (attr, new->name, cu);
 
@@ -6876,14 +6824,17 @@ dwarf2_fundamental_type (struct objfile 
    Given a pointer to a dwarf block that defines a location, compute
    the location and return the value.
 
-   FIXME: This is a kludge until we figure out a better
-   way to handle the location descriptions.
-   Gdb's design does not mesh well with the DWARF2 notion of a location
-   computing interpreter, which is a shame because the flexibility goes unused.
-   FIXME: Implement more operations as necessary.
+   NOTE drow/2003-11-18: This function is called in two situations
+   now: for the address of static or global variables (partial symbols
+   only) and for offsets into structures which are expected to be
+   (more or less) constant.  The partial symbol case should go away,
+   and only the constant case should remain.  That will let this
+   function complain more accurately.  A few special modes are allowed
+   without complaint for global variables (for instance, global
+   register values and thread-local values).
 
    A location description containing no operations indicates that the
-   object is optimized out.  The return value is meaningless for that case.
+   object is optimized out.  The return value is 0 for that case.
    FIXME drow/2003-11-16: No callers check for this case any more; soon all
    callers will only want a very basic result and this can become a
    complaint.
@@ -6891,12 +6842,6 @@ dwarf2_fundamental_type (struct objfile 
    When the result is a register number, the global isreg flag is set,
    otherwise it is cleared.
 
-   When the result is a base register offset, the global offreg flag is set
-   and the register number is returned in basereg, otherwise it is cleared.
-
-   When the DW_OP_fbreg operation is encountered without a corresponding
-   DW_AT_frame_base attribute, we complain.
-
    Note that stack[0] is unused except as a default error return.
    Note that stack overflow is not yet handled.  */
 
@@ -6917,8 +6862,6 @@ decode_locdesc (struct dwarf_block *blk,
   stacki = 0;
   stack[stacki] = 0;
   isreg = 0;
-  offreg = 0;
-  isderef = 0;
 
   while (i < size)
     {
@@ -6994,6 +6937,8 @@ decode_locdesc (struct dwarf_block *blk,
 	case DW_OP_reg31:
 	  isreg = 1;
 	  stack[++stacki] = op - DW_OP_reg0;
+	  if (i < size)
+	    dwarf2_complex_location_expr_complaint ();
 	  break;
 
 	case DW_OP_regx:
@@ -7001,68 +6946,8 @@ decode_locdesc (struct dwarf_block *blk,
 	  unsnd = read_unsigned_leb128 (NULL, (data + i), &bytes_read);
 	  i += bytes_read;
 	  stack[++stacki] = unsnd;
-	  break;
-
-	case DW_OP_breg0:
-	case DW_OP_breg1:
-	case DW_OP_breg2:
-	case DW_OP_breg3:
-	case DW_OP_breg4:
-	case DW_OP_breg5:
-	case DW_OP_breg6:
-	case DW_OP_breg7:
-	case DW_OP_breg8:
-	case DW_OP_breg9:
-	case DW_OP_breg10:
-	case DW_OP_breg11:
-	case DW_OP_breg12:
-	case DW_OP_breg13:
-	case DW_OP_breg14:
-	case DW_OP_breg15:
-	case DW_OP_breg16:
-	case DW_OP_breg17:
-	case DW_OP_breg18:
-	case DW_OP_breg19:
-	case DW_OP_breg20:
-	case DW_OP_breg21:
-	case DW_OP_breg22:
-	case DW_OP_breg23:
-	case DW_OP_breg24:
-	case DW_OP_breg25:
-	case DW_OP_breg26:
-	case DW_OP_breg27:
-	case DW_OP_breg28:
-	case DW_OP_breg29:
-	case DW_OP_breg30:
-	case DW_OP_breg31:
-	  offreg = 1;
-	  basereg = op - DW_OP_breg0;
-	  stack[++stacki] = read_signed_leb128 (NULL, (data + i), &bytes_read);
-	  i += bytes_read;
-	  break;
-
-	case DW_OP_bregx:
-	  offreg = 1;
-	  basereg = read_unsigned_leb128 (NULL, (data + i), &bytes_read);
-	  i += bytes_read;
-	  stack[++stacki] = read_signed_leb128 (NULL, (data + i), &bytes_read);
-	  i += bytes_read;
-	  break;
-
-	case DW_OP_fbreg:
-	  stack[++stacki] = read_signed_leb128 (NULL, (data + i), &bytes_read);
-	  i += bytes_read;
-	  if (frame_base_reg >= 0)
-	    {
-	      offreg = 1;
-	      basereg = frame_base_reg;
-	      stack[stacki] += frame_base_offset;
-	    }
-	  else
-	    {
-	      complaint (&symfile_complaints,
-			 "DW_AT_frame_base missing for DW_OP_fbreg");
-	    }
+	  if (i < size)
+	    dwarf2_complex_location_expr_complaint ();
 	  break;
 
 	case DW_OP_addr:
@@ -7133,9 +7018,10 @@ decode_locdesc (struct dwarf_block *blk,
 	  break;
 
 	case DW_OP_deref:
-	  isderef = 1;
 	  /* If we're not the last op, then we definitely can't encode
-	     this using GDB's address_class enum.  */
+	     this using GDB's address_class enum.  This is valid for partial
+	     global symbols, although the variable's address will be bogus
+	     in the psymtab.  */
 	  if (i < size)
 	    dwarf2_complex_location_expr_complaint ();
 	  break;
@@ -7145,6 +7031,8 @@ decode_locdesc (struct dwarf_block *blk,
 	     of the thread control block at which the variable is located.  */
 	  /* Nothing should follow this operator, so the top of stack would
 	     be returned.  */
+	  /* This is valid for partial global symbols, but the variable's
+	     address will be bogus in the psymtab.  */
 	  if (i < size)
 	    dwarf2_complex_location_expr_complaint ();
           break;