RFC: Dwarf locations: analyze location before fetching stack top

[Jim Blandy <jimb@redhat.com>]

This is a minor rearrangement that will clean up an upcoming patch for
recognizing multi-piece expression values a bit.  I'll commit in a few
days.

(That upcoming patch is independent of the design for supporting
scattered values in GDB.  It is related only to recognizing, but not
handling, all possible results of Dwarf expression evaluation.)

2004-08-09  Jim Blandy  <jimb@redhat.com>

	* dwarf2loc.c (dwarf2_evaluate_loc_desc): Wait to fetch the top of
	the stack until we've decided what sort of result the evaluation
	has produced.  Use separate variables, with more specific names.

Index: gdb/dwarf2loc.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2loc.c,v
retrieving revision 1.15
diff -c -p -r1.15 dwarf2loc.c
*** gdb/dwarf2loc.c	13 May 2004 17:30:41 -0000	1.15
--- gdb/dwarf2loc.c	9 Aug 2004 23:41:15 -0000
*************** dwarf2_evaluate_loc_desc (struct symbol 
*** 205,211 ****
  			  unsigned char *data, unsigned short size,
  			  struct objfile *objfile)
  {
-   CORE_ADDR result;
    struct value *retval;
    struct dwarf_expr_baton baton;
    struct dwarf_expr_context *ctx;
--- 205,210 ----
*************** dwarf2_evaluate_loc_desc (struct symbol 
*** 228,248 ****
    ctx->get_tls_address = dwarf_expr_tls_address;
  
    dwarf_expr_eval (ctx, data, size);
-   result = dwarf_expr_fetch (ctx, 0);
  
    if (ctx->in_reg)
      {
!       int regnum = DWARF2_REG_TO_REGNUM (result);
!       retval = value_from_register (SYMBOL_TYPE (var), regnum, frame);
      }
    else
      {
        retval = allocate_value (SYMBOL_TYPE (var));
        VALUE_BFD_SECTION (retval) = SYMBOL_BFD_SECTION (var);
  
        VALUE_LVAL (retval) = lval_memory;
        VALUE_LAZY (retval) = 1;
!       VALUE_ADDRESS (retval) = result;
      }
  
    free_dwarf_expr_context (ctx);
--- 227,249 ----
    ctx->get_tls_address = dwarf_expr_tls_address;
  
    dwarf_expr_eval (ctx, data, size);
  
    if (ctx->in_reg)
      {
!       CORE_ADDR dwarf_regnum = dwarf_expr_fetch (ctx, 0);
!       int gdb_regnum = DWARF2_REG_TO_REGNUM (dwarf_regnum);
!       retval = value_from_register (SYMBOL_TYPE (var), gdb_regnum, frame);
      }
    else
      {
+       CORE_ADDR address = dwarf_expr_fetch (ctx, 0);
+ 
        retval = allocate_value (SYMBOL_TYPE (var));
        VALUE_BFD_SECTION (retval) = SYMBOL_BFD_SECTION (var);
  
        VALUE_LVAL (retval) = lval_memory;
        VALUE_LAZY (retval) = 1;
!       VALUE_ADDRESS (retval) = address;
      }
  
    free_dwarf_expr_context (ctx);