[PATCH] Bits from Early LTO debug merge -- move stuff from late to early finish

[Richard Biener <rguenther@suse.de>]

This merges moving of unused type pruning from late to early finish as 
well as handling of debug types and dwarf2 dups elimination.  It adds
a flag to DIEs so we can mark them as removed in case sth after
early finish tries to lookup a DIE for a removed DIE again - we shouldn't
re-use the removed DIE (w/o parent) there.

I suppose at some point we should re-think how pruning of "unused"
stuff is supposed to work.  Given my grand plan is to get rid of
debug hooks and allow FEs direct control over the DWARF it should
be ultimatively their decision what to remove (err, not create, in
the first place).

Bootstrap and regtest running on x86_64-unknown-linux-gnu, ok for trunk?

I believe this is the last part I can reasonably split out (but I'll
have a second look after merging back from trunk once this and the other
pending patch is approved).

Thanks,
Richard.

2016-09-22  Richard Biener  <rguenther@suse.de>

	* dwarf2out.c (struct die_struct): Add removed flag.
	(lookup_type_die): If the DIE is marked as removed, clear
	TYPE_SYMTAB_DIE and return NULL.
	(lookup_decl_die): If the DIE is marked as removed, remove it
	from the hash and return NULL.
	(mark_removed): New helper.
	(prune_unused_types_prune): Call it for removed DIEs.
	(dwarf2out_finish): Move unused type pruning debug_types handling
	and breaking out includes ...
	(dwarf2out_early_finish): ... here.

Index: gcc/dwarf2out.c
===================================================================
--- gcc/dwarf2out.c	(revision 240353)
+++ gcc/dwarf2out.c	(working copy)
@@ -2705,6 +2705,10 @@ typedef struct GTY((chain_circular ("%h.
   /* Die is used and must not be pruned as unused.  */
   BOOL_BITFIELD die_perennial_p : 1;
   BOOL_BITFIELD comdat_type_p : 1; /* DIE has a type signature */
+  /* Whether this DIE was removed from the DIE tree, for example via
+     prune_unused_types.  We don't consider those present from the
+     DIE lookup routines.  */
+  BOOL_BITFIELD removed : 1;
   /* Lots of spare bits.  */
 }
 die_node;
@@ -5098,7 +5102,13 @@ new_die (enum dwarf_tag tag_value, dw_di
 static inline dw_die_ref
 lookup_type_die (tree type)
 {
-  return TYPE_SYMTAB_DIE (type);
+  dw_die_ref die = TYPE_SYMTAB_DIE (type);
+  if (die && die->removed)
+    {
+      TYPE_SYMTAB_DIE (type) = NULL;
+      return NULL;
+    }
+  return die;
 }
 
 /* Given a TYPE_DIE representing the type TYPE, if TYPE is an
@@ -5163,7 +5173,16 @@ decl_die_hasher::equal (die_node *x, tre
 static inline dw_die_ref
 lookup_decl_die (tree decl)
 {
-  return decl_die_table->find_with_hash (decl, DECL_UID (decl));
+  dw_die_ref *die = decl_die_table->find_slot_with_hash (decl, DECL_UID (decl),
+							 NO_INSERT);
+  if (!die)
+    return NULL;
+  if ((*die)->removed)
+    {
+      decl_die_table->clear_slot (die);
+      return NULL;
+    }
+  return *die;
 }
 
 /* Returns a hash value for X (which really is a var_loc_list).  */
@@ -26195,6 +26214,16 @@ prune_unused_types_update_strings (dw_di
       }
 }
 
+/* Mark DIE and its children as removed.  */
+
+static void
+mark_removed (dw_die_ref die)
+{
+  dw_die_ref c;
+  die->removed = true;
+  FOR_EACH_CHILD (die, c, mark_removed (c));
+}
+
 /* Remove from the tree DIE any dies that aren't marked.  */
 
 static void
@@ -26224,12 +26253,14 @@ prune_unused_types_prune (dw_die_ref die
 	      die->die_child = prev;
 	    }
 	  c->die_sib = NULL;
+	  mark_removed (c);
 	  return;
 	}
       else
 	{
 	  next = c->die_sib;
 	  c->die_sib = NULL;
+	  mark_removed (c);
 	}
 
     if (c != prev->die_sib)
@@ -27835,37 +27866,6 @@ dwarf2out_finish (const char *)
   resolve_addr (comp_unit_die ());
   move_marked_base_types ();
 
-  if (flag_eliminate_unused_debug_types)
-    prune_unused_types ();
-
-  /* Generate separate COMDAT sections for type DIEs. */
-  if (use_debug_types)
-    {
-      break_out_comdat_types (comp_unit_die ());
-
-      /* Each new type_unit DIE was added to the limbo die list when created.
-         Since these have all been added to comdat_type_list, clear the
-         limbo die list.  */
-      limbo_die_list = NULL;
-
-      /* For each new comdat type unit, copy declarations for incomplete
-         types to make the new unit self-contained (i.e., no direct
-         references to the main compile unit).  */
-      for (ctnode = comdat_type_list; ctnode != NULL; ctnode = ctnode->next)
-        copy_decls_for_unworthy_types (ctnode->root_die);
-      copy_decls_for_unworthy_types (comp_unit_die ());
-
-      /* In the process of copying declarations from one unit to another,
-         we may have left some declarations behind that are no longer
-         referenced.  Prune them.  */
-      prune_unused_types ();
-    }
-
-  /* Generate separate CUs for each of the include files we've seen.
-     They will go into limbo_die_list.  */
-  if (flag_eliminate_dwarf2_dups)
-    break_out_includes (comp_unit_die ());
-
   /* Traverse the DIE's and add sibling attributes to those DIE's that
      have children.  */
   add_sibling_attributes (comp_unit_die ());
@@ -28193,6 +28193,38 @@ dwarf2out_early_finish (const char *file
     }
   deferred_asm_name = NULL;
 
+  if (flag_eliminate_unused_debug_types)
+    prune_unused_types ();
+
+  /* Generate separate COMDAT sections for type DIEs. */
+  if (use_debug_types)
+    {
+      break_out_comdat_types (comp_unit_die ());
+
+      /* Each new type_unit DIE was added to the limbo die list when created.
+         Since these have all been added to comdat_type_list, clear the
+         limbo die list.  */
+      limbo_die_list = NULL;
+
+      /* For each new comdat type unit, copy declarations for incomplete
+         types to make the new unit self-contained (i.e., no direct
+         references to the main compile unit).  */
+      for (comdat_type_node *ctnode = comdat_type_list;
+	   ctnode != NULL; ctnode = ctnode->next)
+        copy_decls_for_unworthy_types (ctnode->root_die);
+      copy_decls_for_unworthy_types (comp_unit_die ());
+
+      /* In the process of copying declarations from one unit to another,
+         we may have left some declarations behind that are no longer
+         referenced.  Prune them.  */
+      prune_unused_types ();
+    }
+
+  /* Generate separate CUs for each of the include files we've seen.
+     They will go into limbo_die_list.  */
+  if (flag_eliminate_dwarf2_dups)
+    break_out_includes (comp_unit_die ());
+
   /* The early debug phase is now finished.  */
   early_dwarf_finished = true;
 }