Re: [PATCH] Use the new DWARF4 mandated DW_FORMs for -gdwarf-4

[Jakub Jelinek <jakub at redhat dot com>]

On Wed, Mar 31, 2010 at 05:40:21PM -0700, Cary Coutant wrote:
> > @@ -11538,12 +11509,6 @@ output_line_info (void)
> > ? unsigned long function;
> > ? int ver = dwarf_version;
> >
> > - ?/* Don't mark the output as DWARF-4 until we make full use of the
> > - ? ? version 4 extensions, and gdb supports them. ?For now, -gdwarf-4
> > - ? ? selects only a few extensions from the DWARF-4 spec. ?*/
> > - ?if (ver > 3)
> > - ? ?ver = 3;
> > -
> 
> Note that the format of the line number table header has changed
> between versions 3 and 4 (there's a new "maximum operations per
> instruction" field), so you don't want to change this to 4 until
> you've also changed the header accordingly. Since gas usually
> generates the line number table, it's going to need changing, too
> (eventually).

Oops, you're right.

Here is an updated patch (and ld/readelf patch will be posted soon).
For now it will just emit 1 as maximum ops per insn, it would need lots
of work on the GCC side to do any better for VLIWs and as gas
is generating that almost always anyway, it is really better to add that
support to gas.

Ok for trunk?

2010-04-01  Jakub Jelinek  <jakub@redhat.com>

	* dwarf2out.c (output_compilation_unit_header): For
	-gdwarf-4 use version 4 instead of version 3.
	(output_line_info): For version 4 and above emit additional
	maximum ops per insn header field.
	(DWARF_LINE_DEFAULT_MAX_OPS_PER_INSN): Define.

	* dwarf2out.c (is_c_family, is_java): Remove.
	(lower_bound_default): New function.
	(add_bound_info, gen_descr_array_type_die): Use it.

--- gcc/dwarf2out.c.jj	2010-03-31 17:44:06.000000000 +0200
+++ gcc/dwarf2out.c	2010-04-01 07:38:05.000000000 +0200
@@ -5689,6 +5689,11 @@ skeleton_chain_node;
    is not made available by the GCC front-end.  */
 #define	DWARF_LINE_DEFAULT_IS_STMT_START 1
 
+/* Maximum number of operations per instruction bundle.  */
+#ifndef DWARF_LINE_DEFAULT_MAX_OPS_PER_INSN
+#define DWARF_LINE_DEFAULT_MAX_OPS_PER_INSN 1
+#endif
+
 #ifdef DWARF2_DEBUGGING_INFO
 /* This location is used by calc_die_sizes() to keep track
    the offset of each DIE within the .debug_info section.  */
@@ -5964,9 +5969,7 @@ static const char *get_AT_string (dw_die
 static int get_AT_flag (dw_die_ref, enum dwarf_attribute);
 static unsigned get_AT_unsigned (dw_die_ref, enum dwarf_attribute);
 static inline dw_die_ref get_AT_ref (dw_die_ref, enum dwarf_attribute);
-static bool is_c_family (void);
 static bool is_cxx (void);
-static bool is_java (void);
 static bool is_fortran (void);
 static bool is_ada (void);
 static void remove_AT (dw_die_ref, enum dwarf_attribute);
@@ -7443,18 +7446,6 @@ get_AT_file (dw_die_ref die, enum dwarf_
   return a ? AT_file (a) : NULL;
 }
 
-/* Return TRUE if the language is C or C++.  */
-
-static inline bool
-is_c_family (void)
-{
-  unsigned int lang = get_AT_unsigned (comp_unit_die, DW_AT_language);
-
-  return (lang == DW_LANG_C || lang == DW_LANG_C89 || lang == DW_LANG_ObjC
-	  || lang == DW_LANG_C99
-	  || lang == DW_LANG_C_plus_plus || lang == DW_LANG_ObjC_plus_plus);
-}
-
 /* Return TRUE if the language is C++.  */
 
 static inline bool
@@ -7477,16 +7468,6 @@ is_fortran (void)
 	  || lang == DW_LANG_Fortran95);
 }
 
-/* Return TRUE if the language is Java.  */
-
-static inline bool
-is_java (void)
-{
-  unsigned int lang = get_AT_unsigned (comp_unit_die, DW_AT_language);
-
-  return lang == DW_LANG_Java;
-}
-
 /* Return TRUE if the language is Ada.  */
 
 static inline bool
@@ -10687,11 +10668,6 @@ output_compilation_unit_header (void)
 {
   int ver = dwarf_version;
 
-  /* Don't mark the output as DWARF-4 until we make full use of the
-     version 4 extensions, and gdb supports them.  For now, -gdwarf-4
-     selects only a few extensions from the DWARF-4 spec.  */
-  if (ver > 3)
-    ver = 3;
   if (DWARF_INITIAL_LENGTH_SIZE - DWARF_OFFSET_SIZE == 4)
     dw2_asm_output_data (4, 0xffffffff,
       "Initial length escape value indicating 64-bit DWARF extension");
@@ -11538,12 +11514,6 @@ output_line_info (void)
   unsigned long function;
   int ver = dwarf_version;
 
-  /* Don't mark the output as DWARF-4 until we make full use of the
-     version 4 extensions, and gdb supports them.  For now, -gdwarf-4
-     selects only a few extensions from the DWARF-4 spec.  */
-  if (ver > 3)
-    ver = 3;
-
   ASM_GENERATE_INTERNAL_LABEL (l1, LINE_NUMBER_BEGIN_LABEL, 0);
   ASM_GENERATE_INTERNAL_LABEL (l2, LINE_NUMBER_END_LABEL, 0);
   ASM_GENERATE_INTERNAL_LABEL (p1, LN_PROLOG_AS_LABEL, 0);
@@ -11571,6 +11541,9 @@ output_line_info (void)
   dw2_asm_output_data (1, 1,
 		       "Minimum Instruction Length");
 
+  if (ver >= 4)
+    dw2_asm_output_data (1, DWARF_LINE_DEFAULT_MAX_OPS_PER_INSN,
+			 "Maximum Operations Per Instruction");
   dw2_asm_output_data (1, DWARF_LINE_DEFAULT_IS_STMT_START,
 		       "Default is_stmt_start flag");
   dw2_asm_output_data (1, DWARF_LINE_BASE,
@@ -16339,6 +16312,42 @@ add_comp_dir_attribute (dw_die_ref die)
     add_AT_string (die, DW_AT_comp_dir, remap_debug_filename (wd));
 }
 
+/* Return the default for DW_AT_lower_bound, or -1 if there is not any
+   default.  */
+
+static int
+lower_bound_default (void)
+{
+  switch (get_AT_unsigned (comp_unit_die, DW_AT_language))
+    {
+    case DW_LANG_C:
+    case DW_LANG_C89:
+    case DW_LANG_C99:
+    case DW_LANG_C_plus_plus:
+    case DW_LANG_ObjC:
+    case DW_LANG_ObjC_plus_plus:
+    case DW_LANG_Java:
+      return 0;
+    case DW_LANG_Fortran77:
+    case DW_LANG_Fortran90:
+    case DW_LANG_Fortran95:
+      return 1;
+    case DW_LANG_UPC:
+    case DW_LANG_D:
+      return dwarf_version >= 4 ? 0 : -1;
+    case DW_LANG_Ada95:
+    case DW_LANG_Ada83:
+    case DW_LANG_Cobol74:
+    case DW_LANG_Cobol85:
+    case DW_LANG_Pascal83:
+    case DW_LANG_Modula2:
+    case DW_LANG_PLI:
+      return dwarf_version >= 4 ? 1 : -1;
+    default:
+      return -1;
+    }
+}
+
 /* Given a tree node describing an array bound (either lower or upper) output
    a representation for that bound.  */
 
@@ -16356,11 +16365,13 @@ add_bound_info (dw_die_ref subrange_die,
     case INTEGER_CST:
       {
 	unsigned int prec = simple_type_size_in_bits (TREE_TYPE (bound));
+	int dflt;
 
 	/* Use the default if possible.  */
 	if (bound_attr == DW_AT_lower_bound
-	    && (((is_c_family () || is_java ()) && integer_zerop (bound))
-	        || (is_fortran () && integer_onep (bound))))
+	    && host_integerp (bound, 0)
+	    && (dflt = lower_bound_default ()) != -1
+	    && tree_low_cst (bound, 0) == dflt)
 	  ;
 
 	/* Otherwise represent the bound as an unsigned value with the
@@ -17261,11 +17272,11 @@ gen_descr_array_type_die (tree type, str
       if (info->dimen[dim].lower_bound)
 	{
 	  /* If it is the default value, omit it.  */
-	  if ((is_c_family () || is_java ())
-	      && integer_zerop (info->dimen[dim].lower_bound))
-	    ;
-	  else if (is_fortran ()
-		   && integer_onep (info->dimen[dim].lower_bound))
+	  int dflt;
+
+	  if (host_integerp (info->dimen[dim].lower_bound, 0)
+	      && (dflt = lower_bound_default ()) != -1
+	      && tree_low_cst (info->dimen[dim].lower_bound, 0) == dflt)
 	    ;
 	  else
 	    add_descr_info_field (subrange_die, DW_AT_lower_bound,


	Jakub