[PATCH 5/9] introduce per-bfd data for the objfile

[Tom Tromey <tromey at redhat dot com>]

If two objfiles represent the same underlying file, then they can
(eventually) share BFDs.  Once this is done, it also makes sense to
attach immutable data to the BFD rather than the objfile.  This
approach means less work (the data is only read once) and also less
memory use.

"Immutable" in this case really means read-only and
program-space-independent.  Eventually we'd like to change various
symbols to fit this criteria, but that is complicated, as my earlier
series shows.

This patch introduces a struct objfile_per_bfd_storage to store such
data.  Then it changes objfiles to refer to it; when a BFD is shared,
multiple objfiles will just share one of these objects.

This patch also switches the filename bcache to be shared.

	* elfread.c (elf_symtab_read): Update.
	* objfiles.c (objfiles_bfd_data): New global.
	(get_objfile_bfd_data, free_objfile_per_bfd_storage)
	(objfile_bfd_data_free, set_objfile_per_bfd): New functions.
	(allocate_objfile, free_objfile): Update.
	(_initialize_objfiles): Initialize objfiles_bfd_data.
	* objfiles.h (struct objfile_per_bfd_storage): New.
	(struct objfile) <per_bfd>: New field.
	<filename_cache>: Remove.
	(set_objfile_per_bfd): Declare.
	* symfile.c (reread_symbols): Update.  Call
	set_objfile_per_bfd.
	(allocate_symtab): Update.
	* symmisc.c (print_symbol_bcache_statistics): Update.
	(print_objfile_statistics): Print the size of the BFD obstack.
---
 gdb/elfread.c  |    2 +-
 gdb/objfiles.c |   66 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
 gdb/objfiles.h |   24 +++++++++++++++++++-
 gdb/symfile.c  |    6 ++--
 gdb/symmisc.c  |    7 ++++-
 5 files changed, 95 insertions(+), 10 deletions(-)

diff --git a/gdb/elfread.c b/gdb/elfread.c
index 22ac158..f3967d7 100644
--- a/gdb/elfread.c
+++ b/gdb/elfread.c
@@ -353,7 +353,7 @@ elf_symtab_read (struct objfile *objfile, int type,
 	    }
 	  filesym = sym;
 	  filesymname = bcache (filesym->name, strlen (filesym->name) + 1,
-				objfile->filename_cache);
+				objfile->per_bfd->filename_cache);
 	}
       else if (sym->flags & BSF_SECTION_SYM)
 	continue;
diff --git a/gdb/objfiles.c b/gdb/objfiles.c
index 57dd594..09268ff 100644
--- a/gdb/objfiles.c
+++ b/gdb/objfiles.c
@@ -106,6 +106,61 @@ get_objfile_pspace_data (struct program_space *pspace)
   return info;
 }
 
+
+
+/* Per-BFD data key.  */
+
+static const struct bfd_data *objfiles_bfd_data;
+
+static struct objfile_per_bfd_storage *
+get_objfile_bfd_data (struct objfile *objfile, struct bfd *abfd)
+{
+  struct objfile_per_bfd_storage *storage = NULL;
+
+  if (abfd != NULL)
+    storage = bfd_data (abfd, objfiles_bfd_data);
+
+  if (storage == NULL)
+    {
+      if (abfd != NULL)
+	{
+	  storage = bfd_zalloc (abfd, sizeof (struct objfile_per_bfd_storage));
+	  set_bfd_data (abfd, objfiles_bfd_data, storage);
+	}
+      else
+	storage = OBSTACK_ZALLOC (&objfile->objfile_obstack,
+				  struct objfile_per_bfd_storage);
+
+      obstack_init (&storage->storage_obstack);
+      storage->filename_cache = bcache_xmalloc (NULL, NULL);
+    }
+
+  return storage;
+}
+
+static void
+free_objfile_per_bfd_storage (struct objfile_per_bfd_storage *storage)
+{
+  bcache_xfree (storage->filename_cache);
+  obstack_free (&storage->storage_obstack, 0);
+}
+
+static void
+objfile_bfd_data_free (struct bfd *unused, void *d)
+{
+  free_objfile_per_bfd_storage (d);
+}
+
+/* This is a hack until we make reread_symbols create a new objfile.  */
+
+void
+set_objfile_per_bfd (struct objfile *objfile)
+{
+  objfile->per_bfd = get_objfile_bfd_data (objfile, objfile->obfd);
+}
+
+
+
 /* Called via bfd_map_over_sections to build up the section table that
    the objfile references.  The objfile contains pointers to the start
    of the table (objfile->sections) and to the first location after
@@ -184,7 +239,6 @@ allocate_objfile (bfd *abfd, int flags)
   objfile = (struct objfile *) xzalloc (sizeof (struct objfile));
   objfile->psymbol_cache = psymbol_bcache_init ();
   objfile->macro_cache = bcache_xmalloc (NULL, NULL);
-  objfile->filename_cache = bcache_xmalloc (NULL, NULL);
   /* We could use obstack_specify_allocation here instead, but
      gdb_obstack.h specifies the alloc/dealloc functions.  */
   obstack_init (&objfile->objfile_obstack);
@@ -214,6 +268,7 @@ allocate_objfile (bfd *abfd, int flags)
       objfile->name = xstrdup ("<<anonymous objfile>>");
     }
 
+  objfile->per_bfd = get_objfile_bfd_data (objfile, abfd);
   objfile->pspace = current_program_space;
 
   /* Initialize the section indexes for this objfile, so that we can
@@ -557,7 +612,10 @@ free_objfile (struct objfile *objfile)
      still may reference objfile->obfd.  */
   objfile_free_data (objfile);
 
-  gdb_bfd_unref (objfile->obfd);
+  if (objfile->obfd)
+    gdb_bfd_unref (objfile->obfd);
+  else
+    free_objfile_per_bfd_storage (objfile->per_bfd);
 
   /* Remove it from the chain of all objfiles.  */
 
@@ -606,7 +664,6 @@ free_objfile (struct objfile *objfile)
   /* Free the obstacks for non-reusable objfiles.  */
   psymbol_bcache_free (objfile->psymbol_cache);
   bcache_xfree (objfile->macro_cache);
-  bcache_xfree (objfile->filename_cache);
   if (objfile->demangled_names_hash)
     htab_delete (objfile->demangled_names_hash);
   obstack_free (&objfile->objfile_obstack, 0);
@@ -1383,4 +1440,7 @@ _initialize_objfiles (void)
   objfiles_pspace_data
     = register_program_space_data_with_cleanup (NULL,
 						objfiles_pspace_data_cleanup);
+
+  objfiles_bfd_data = register_bfd_data_with_cleanup (NULL,
+						      objfile_bfd_data_free);
 }
diff --git a/gdb/objfiles.h b/gdb/objfiles.h
index 097f4db..7caff48 100644
--- a/gdb/objfiles.h
+++ b/gdb/objfiles.h
@@ -160,6 +160,22 @@ extern void print_symbol_bcache_statistics (void);
 /* Number of entries in the minimal symbol hash table.  */
 #define MINIMAL_SYMBOL_HASH_SIZE 2039
 
+/* Some objfile data is hung off the BFD.  This enables sharing of the
+   data across all objfiles using the BFD.  The data is stored in an
+   instance of this structure, and associated with the BFD using the
+   registry system.  */
+
+struct objfile_per_bfd_storage
+{
+  /* The storage has an obstack of its own.  */
+
+  struct obstack storage_obstack;
+  
+  /* Byte cache for file names.  */
+
+  struct bcache *filename_cache;
+};
+
 /* Master structure for keeping track of each file from which
    gdb reads symbols.  There are several ways these get allocated: 1.
    The main symbol file, symfile_objfile, set by the symbol-file command,
@@ -222,6 +238,11 @@ struct objfile
 
     bfd *obfd;
 
+    /* The per-BFD data.  Note that this is treated specially if OBFD
+       is NULL.  */
+
+    struct objfile_per_bfd_storage *per_bfd;
+
     /* The gdbarch associated with the BFD.  Note that this gdbarch is
        determined solely from BFD information, without looking at target
        information.  The gdbarch determined from a running target may
@@ -249,7 +270,6 @@ struct objfile
 
     struct psymbol_bcache *psymbol_cache; /* Byte cache for partial syms.  */
     struct bcache *macro_cache;           /* Byte cache for macros.  */
-    struct bcache *filename_cache;	  /* Byte cache for file names.  */
 
     /* Hash table for mapping symbol names to demangled names.  Each
        entry in the hash table is actually two consecutive strings,
@@ -649,4 +669,6 @@ extern void default_iterate_over_objfiles_in_search_order
 
 #define MULTI_OBJFILE_P() (object_files && object_files->next)
 
+void set_objfile_per_bfd (struct objfile *obj);
+
 #endif /* !defined (OBJFILES_H) */
diff --git a/gdb/symfile.c b/gdb/symfile.c
index 95ed480..1aa3927 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -2550,8 +2550,6 @@ reread_symbols (void)
 	  objfile->psymbol_cache = psymbol_bcache_init ();
 	  bcache_xfree (objfile->macro_cache);
 	  objfile->macro_cache = bcache_xmalloc (NULL, NULL);
-	  bcache_xfree (objfile->filename_cache);
-	  objfile->filename_cache = bcache_xmalloc (NULL,NULL);
 	  if (objfile->demangled_names_hash != NULL)
 	    {
 	      htab_delete (objfile->demangled_names_hash);
@@ -2572,6 +2570,8 @@ reread_symbols (void)
 	  memset (&objfile->msymbol_demangled_hash, 0,
 		  sizeof (objfile->msymbol_demangled_hash));
 
+	  set_objfile_per_bfd (objfile);
+
 	  /* obstack_init also initializes the obstack so it is
 	     empty.  We could use obstack_specify_allocation but
 	     gdb_obstack.h specifies the alloc/dealloc functions.  */
@@ -2856,7 +2856,7 @@ allocate_symtab (const char *filename, struct objfile *objfile)
     obstack_alloc (&objfile->objfile_obstack, sizeof (struct symtab));
   memset (symtab, 0, sizeof (*symtab));
   symtab->filename = (char *) bcache (filename, strlen (filename) + 1,
-				      objfile->filename_cache);
+				      objfile->per_bfd->filename_cache);
   symtab->fullname = NULL;
   symtab->language = deduce_language_from_filename (filename);
   symtab->debugformat = "unknown";
diff --git a/gdb/symmisc.c b/gdb/symmisc.c
index d3028e6..3e9ca82 100644
--- a/gdb/symmisc.c
+++ b/gdb/symmisc.c
@@ -93,7 +93,8 @@ print_symbol_bcache_statistics (void)
     print_bcache_statistics (psymbol_bcache_get_bcache (objfile->psymbol_cache),
                              "partial symbol cache");
     print_bcache_statistics (objfile->macro_cache, "preprocessor macro cache");
-    print_bcache_statistics (objfile->filename_cache, "file name cache");
+    print_bcache_statistics (objfile->per_bfd->filename_cache,
+			     "file name cache");
   }
 }
 
@@ -147,13 +148,15 @@ print_objfile_statistics (void)
 		       OBJSTAT (objfile, sz_strtab));
     printf_filtered (_("  Total memory used for objfile obstack: %d\n"),
 		     obstack_memory_used (&objfile->objfile_obstack));
+    printf_filtered (_("  Total memory used for BFD obstack: %d\n"),
+		     obstack_memory_used (&objfile->per_bfd->storage_obstack));
     printf_filtered (_("  Total memory used for psymbol cache: %d\n"),
 		     bcache_memory_used (psymbol_bcache_get_bcache
 		                          (objfile->psymbol_cache)));
     printf_filtered (_("  Total memory used for macro cache: %d\n"),
 		     bcache_memory_used (objfile->macro_cache));
     printf_filtered (_("  Total memory used for file name cache: %d\n"),
-		     bcache_memory_used (objfile->filename_cache));
+		     bcache_memory_used (objfile->per_bfd->filename_cache));
   }
 }
 
-- 
1.7.7.6