[incremental] Patch: FYI: print some statistics

[Tom Tromey]

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

This adds a function to print statistics about decl sharing.
I use this from the debugger to make sure that we're actually doing
something vaguely sensible.

The stats for gdb show that there is only one compilation job that has
more unshared decls than shared.  That seems pretty good.

Does it bug anybody else that hash table iteration has to be done via
callbacks?  I keep having to invent these throwaway state-holding
structs, which tend to obscure the code.

Tom

ChangeLog:
2008-03-27  Tom Tromey  <tromey@redhat.com>

	* c-tree.h (c_parser_print_job_statistics): Declare.
	* c-parser.c (struct job_statistics): New struct.
	(update_shared_from_hunk): New function.
	(update_shared_from_job): Likewise.
	(c_parser_print_job_statistics): Likewise.

Index: c-tree.h
===================================================================
--- c-tree.h	(revision 132956)
+++ c-tree.h	(working copy)
@@ -460,6 +460,8 @@
 extern void c_parser_lookup_callback (tree, tree, bool);
 extern void c_parse_file_wrapper (int);
 
+extern void c_parser_print_job_statistics (void);
+
 extern htab_t c_parser_create_smash_map (void);
 
 /* Only for use by the GC.  */
Index: c-parser.c
===================================================================
--- c-parser.c	(revision 133494)
+++ c-parser.c	(working copy)
@@ -9442,6 +9442,84 @@
   htab_traverse_noresize (used, insert_single_binding, NULL);
 }
 
+/* User data structure for statistics gathering.  */
+struct job_statistics
+{
+  /* False if we are updating reference counts; true if we are
+     updating decl counts.  */
+  bool update_decls;
+
+  /* This maps hunk bindings to a reference count.  */
+  struct pointer_map_t *binding_refc;
+
+  /* Counters used to compute the number of shared and unshared decls
+     in a given job.  */
+  int shared;
+  int unshared;
+};
+
+/* Helper for statistics printer.  */
+static int
+update_shared_from_hunk (void **slot, void *user_data)
+{
+  struct hunk_binding *hunk = (struct hunk_binding *) *slot;
+  struct job_statistics *stats = (struct job_statistics *) user_data;
+
+  if (stats->update_decls)
+    {
+      int num = htab_elements (hunk->binding_map);
+      void **slot = pointer_map_contains (stats->binding_refc, hunk);
+      if ((int) *slot == 1)
+	stats->unshared += num;
+      else
+	stats->shared += num;
+    }
+  else
+    {
+      /* Update the reference count info.  */
+      void **slot = pointer_map_insert (stats->binding_refc, hunk);
+      *slot = (void *) ((int) *slot + 1);
+    }
+
+  return 1;
+}
+
+/* Helper for statistics printer.  */
+static int
+update_shared_from_job (void **slot, void *user_data)
+{
+  struct c_compile_job *job = (struct c_compile_job *) *slot;
+  struct job_statistics *stats = (struct job_statistics *) user_data;
+  stats->shared = 0;
+  stats->unshared = 0;
+  htab_traverse_noresize (job->hunks, update_shared_from_hunk, stats);
+  if (stats->update_decls)
+    fprintf (stderr, "%-20s %10d %10d\n", lbasename (job->object_file_name),
+	     stats->shared, stats->unshared);
+  return 1;
+}
+
+/* Print some statistics about the current compile jobs.  */
+void
+c_parser_print_job_statistics (void)
+{
+  struct job_statistics stats;
+
+  stats.update_decls = false;
+  stats.binding_refc = pointer_map_create ();
+  stats.shared = 0;
+
+  htab_traverse_noresize (all_compile_jobs, update_shared_from_job, &stats);
+
+  fprintf (stderr, "%-20s %10s %10s\n", "Filename", "Shared", "Unshared");
+  fprintf (stderr, "%-20s %10s %10s\n", "========", "======", "========");
+
+  stats.update_decls = true;
+  htab_traverse_noresize (all_compile_jobs, update_shared_from_job, &stats);
+
+  pointer_map_destroy (stats.binding_refc);
+}
+
 
 /* Parse a single source file.  */