Don't add DW_AT_low_pc if the CU has no associated code.

        * dwarf2out.c (dwarf2out_finish): Don't add low_pc and/or
        high_pc attribute if the CU has no associated code. Only output
        DW_AT_entry_pc for CU if not generating strict dwarf and
        dwarf_version < 4.

From-SVN: r171846

gcc/ChangeLog

+2011-03-31  Mark Wielaard  <mjw@redhat.com>
+
+	* dwarf2out.c (dwarf2out_finish): Don't add low_pc and/or
+	high_pc attribute if the CU has no associated code. Only output
+	DW_AT_entry_pc for CU if not generating strict dwarf and
+	dwarf_version < 4.
+
 2011-04-01  Bernd Schmidt  <bernds@codesourcery.com>
 
 	* dwarf2out.h (dwarf2out_frame_debug_init): Declare.

gcc/dwarf2out.c

@@ -23588,23 +23588,18 @@ dwarf2out_finish (const char *filename)
   if (!have_multiple_function_sections 
       || (dwarf_version < 3 && dwarf_strict))
     {
+      /* Don't add if the CU has no associated code.  */
+      if (text_section_used)
+	{
 	  add_AT_lbl_id (comp_unit_die (), DW_AT_low_pc, text_section_label);
 	  add_AT_lbl_id (comp_unit_die (), DW_AT_high_pc, text_end_label);
 	}
-
+    }
   else
     {
       unsigned fde_idx = 0;
       bool range_list_added = false;
 
-      /* We need to give .debug_loc and .debug_ranges an appropriate
-	 "base address".  Use zero so that these addresses become
-	 absolute.  Historically, we've emitted the unexpected
-	 DW_AT_entry_pc instead of DW_AT_low_pc for this purpose.
-	 Emit both to give time for other tools to adapt.  */
-      add_AT_addr (comp_unit_die (), DW_AT_low_pc, const0_rtx);
-      add_AT_addr (comp_unit_die (), DW_AT_entry_pc, const0_rtx);
-
       if (text_section_used)
 	add_ranges_by_labels (comp_unit_die (), text_section_label,
 			      text_end_label, &range_list_added);
@@ -23625,8 +23620,19 @@ dwarf2out_finish (const char *filename)
 	}
 
       if (range_list_added)
+	{
+	  /* We need to give .debug_loc and .debug_ranges an appropriate
+	     "base address".  Use zero so that these addresses become
+	     absolute.  Historically, we've emitted the unexpected
+	     DW_AT_entry_pc instead of DW_AT_low_pc for this purpose.
+	     Emit both to give time for other tools to adapt.  */
+	  add_AT_addr (comp_unit_die (), DW_AT_low_pc, const0_rtx);
+	  if (! dwarf_strict && dwarf_version < 4)
+	    add_AT_addr (comp_unit_die (), DW_AT_entry_pc, const0_rtx);
+
 	  add_ranges (NULL);
 	}
+    }
 
   if (debug_info_level >= DINFO_LEVEL_NORMAL)
     add_AT_lineptr (comp_unit_die (), DW_AT_stmt_list,