[incremental] Patch: FYI: defer dwarf macro output

[Tom Tromey <tromey at redhat dot com>]

I'm checking this in on the incremental-compiler branch.

With the incremental compiler, it is not ok to emit any output to the
asm file until after the source file has been parsed and the
clear_binding_stack lang hook has been run.  This lets us defer
starting the assembler until relatively late, and is one of the keys
to implementing the (current choice of) incremental code generation
approach.

This restriction is enforced on the branch by using the file-local
dw_asm_out_file (rather than asm_out_file) in dwarf2out.c, and not
setting this until the appropriate time.

The test suite pointed out that the macro definition code was writing
to the assembly file during parsing.  This caused ICEs with -g3.

This patch fixes the problem by deferring all macro output until the
end of compilation.

Tom

ChangeLog:
2007-12-20  Tom Tromey  <tromey@redhat.com>

	* dwarf2out.c (macro_obstack): New global.
	(struct macro_entry): New.
	(first_macro_entry, last_macro_entry): New globals.
	(add_macro_entry): New function.
	(emit_macro_entries): Likewise.
	(dwarf2out_start_source_file): Use add_macro_entry.
	(dwarf2out_end_source_file): Likewise.
	(dwarf2out_define): Likewise.
	(dwarf2out_undef): Likewise.
	(dwarf2out_init): Clear macro_obstack if needed.
	(dwarf2out_finish): Call emit_macro_entries.

Index: dwarf2out.c
===================================================================
--- dwarf2out.c	(revision 130603)
+++ dwarf2out.c	(working copy)
@@ -138,6 +138,34 @@
 #define PTR_SIZE (POINTER_SIZE / BITS_PER_UNIT)
 #endif
 
+/* This is used when allocating entries for file enter/exit and macro
+   information.  */
+static struct obstack macro_obstack;
+
+/* An entry on the macro obstack takes this form.  */
+struct macro_entry
+{
+  /* The type of this entry.  */
+  enum dwarf_macinfo_record_type kind;
+
+  /* The line number.  */
+  unsigned int lineno;
+
+  /* The next entry.  */
+  struct macro_entry *next;
+
+  /* Associated string data, allocated using the struct hack.  */
+  char str[1];
+};
+
+/* The first macro entry, or NULL if no macro entry has been allocated
+   yet.  */
+static struct macro_entry *first_macro_entry;
+
+/* The most recently added macro entry, used to find the tail of the
+   list.  */
+static struct macro_entry *last_macro_entry;
+
 /* Array of RTXes referenced by the debugging information, which therefore
    must be kept around forever.  */
 static GTY(()) VEC(rtx,gc) *used_rtx_array;
@@ -14244,6 +14272,95 @@
     }
 }
 
+/* Add a new macro entry to the list.  */
+static void
+add_macro_entry (enum dwarf_macinfo_record_type kind, unsigned int lineno,
+		 const char *str)
+{
+  struct macro_entry *mac;
+  int len;
+
+  if (! first_macro_entry)
+    {
+      gcc_assert (! last_macro_entry);
+      gcc_obstack_init (&macro_obstack);
+    }
+
+  len = str ? strlen (str) : 0;
+  mac = (struct macro_entry *) obstack_alloc (&macro_obstack,
+					      sizeof (struct macro_entry)
+					      + len);
+  mac->kind = kind;
+  mac->lineno = lineno;
+  mac->next = NULL;
+  if (str)
+    strcpy (mac->str, str);
+
+  if (! first_macro_entry)
+    first_macro_entry = mac;
+  if (last_macro_entry)
+    last_macro_entry->next = mac;
+  last_macro_entry = mac;
+}
+
+/* Emit all the macro entries.  */
+static void
+emit_macro_entries (void)
+{
+  struct macro_entry *mac;
+
+  if (! first_macro_entry)
+    return;
+
+  gcc_assert (last_macro_entry);
+  gcc_assert (debug_info_level >= DINFO_LEVEL_VERBOSE);
+
+  switch_to_section (debug_macinfo_section);
+
+  for (mac = first_macro_entry; mac; mac = mac->next)
+    {
+      switch (mac->kind)
+	{
+	case DW_MACINFO_start_file:
+	  {
+	    int file_num = maybe_emit_file (lookup_filename (mac->str));
+
+	    dw2_asm_output_data (1, DW_MACINFO_start_file, "Start new file");
+	    dw2_asm_output_data_uleb128 (mac->lineno,
+					 "Included from line number %d",
+					 mac->lineno);
+	    dw2_asm_output_data_uleb128 (file_num, "file %s", mac->str);
+	  }
+	  break;
+
+	case DW_MACINFO_end_file:
+	  dw2_asm_output_data (1, DW_MACINFO_end_file, "End file");
+	  break;
+
+	case DW_MACINFO_define:
+	  dw2_asm_output_data (1, DW_MACINFO_define, "Define macro");
+	  dw2_asm_output_data_uleb128 (mac->lineno, "At line number %d",
+				       mac->lineno);
+	  dw2_asm_output_nstring (mac->str, -1, "The macro");
+	  break;
+
+	case DW_MACINFO_undef:
+	  dw2_asm_output_data (1, DW_MACINFO_undef, "Undefine macro");
+	  dw2_asm_output_data_uleb128 (mac->lineno, "At line number %d",
+				       mac->lineno);
+	  dw2_asm_output_nstring (mac->str, -1, "The macro");
+	  break;
+
+	default:
+	  gcc_unreachable ();
+	}
+    }
+
+  obstack_free (&macro_obstack, NULL);
+  first_macro_entry = NULL;
+  last_macro_entry = NULL;
+}
+
 /* Record the beginning of a new source file.  */
 
 static void
@@ -14259,16 +14376,7 @@
     }
 
   if (debug_info_level >= DINFO_LEVEL_VERBOSE)
-    {
-      int file_num = maybe_emit_file (lookup_filename (filename));
-
-      switch_to_section (debug_macinfo_section);
-      dw2_asm_output_data (1, DW_MACINFO_start_file, "Start new file");
-      dw2_asm_output_data_uleb128 (lineno, "Included from line number %d",
-				   lineno);
-
-      dw2_asm_output_data_uleb128 (file_num, "file %s", filename);
-    }
+    add_macro_entry (DW_MACINFO_start_file, lineno, filename);
 }
 
 /* Record the end of a source file.  */
@@ -14281,10 +14389,7 @@
     new_die (DW_TAG_GNU_EINCL, comp_unit_die, NULL);
 
   if (debug_info_level >= DINFO_LEVEL_VERBOSE)
-    {
-      switch_to_section (debug_macinfo_section);
-      dw2_asm_output_data (1, DW_MACINFO_end_file, "End file");
-    }
+    add_macro_entry (DW_MACINFO_end_file, 0, NULL);
 }
 
 /* Called from debug_define in toplev.c.  The `buffer' parameter contains
@@ -14292,16 +14397,10 @@
    initial whitespace, #, whitespace, directive-name, whitespace part.  */
 
 static void
-dwarf2out_define (unsigned int lineno ATTRIBUTE_UNUSED,
-		  const char *buffer ATTRIBUTE_UNUSED)
+dwarf2out_define (unsigned int lineno, const char *buffer)
 {
   if (debug_info_level >= DINFO_LEVEL_VERBOSE)
-    {
-      switch_to_section (debug_macinfo_section);
-      dw2_asm_output_data (1, DW_MACINFO_define, "Define macro");
-      dw2_asm_output_data_uleb128 (lineno, "At line number %d", lineno);
-      dw2_asm_output_nstring (buffer, -1, "The macro");
-    }
+    add_macro_entry (DW_MACINFO_define, lineno, buffer);
 }
 
 /* Called from debug_undef in toplev.c.  The `buffer' parameter contains
@@ -14309,16 +14408,10 @@
    initial whitespace, #, whitespace, directive-name, whitespace part.  */
 
 static void
-dwarf2out_undef (unsigned int lineno ATTRIBUTE_UNUSED,
-		 const char *buffer ATTRIBUTE_UNUSED)
+dwarf2out_undef (unsigned int lineno, const char *buffer)
 {
   if (debug_info_level >= DINFO_LEVEL_VERBOSE)
-    {
-      switch_to_section (debug_macinfo_section);
-      dw2_asm_output_data (1, DW_MACINFO_undef, "Undefine macro");
-      dw2_asm_output_data_uleb128 (lineno, "At line number %d", lineno);
-      dw2_asm_output_nstring (buffer, -1, "The macro");
-    }
+    add_macro_entry (DW_MACINFO_undef, lineno, buffer);
 }
 
 /* Set up for Dwarf output at the start of compilation.  */
@@ -14357,6 +14450,15 @@
   cold_text_section_used = false;
   cold_text_section = NULL;
 
+  /* FIXME: should have a cleanup function in the server so this can
+     be free while the server is quiescent.  */
+  if (first_macro_entry)
+    {
+      obstack_free (&macro_obstack, NULL);
+      first_macro_entry = NULL;
+      last_emitted_file = NULL;
+    }
+
   /* Allocate the file_table.  */
   file_table = htab_create_ggc (50, file_table_hash,
 				file_table_eq, NULL);
@@ -14805,6 +14907,9 @@
   limbo_die_node *node, *next_node;
   dw_die_ref die = 0;
 
+  /* Emit the macro information.  */
+  emit_macro_entries ();
+
   /* Add the name for the main input file now.  We delayed this from
      dwarf2out_init to avoid complications with PCH.  */
   add_name_attribute (comp_unit_die, remap_debug_filename (filename));