Re: Order symbols before section copying in the lto streamer

[Jan Hubicka <hubicka@ucw.cz>]

> Hi,
> this patch orders symbols where we copy sections to match the order
> of files in the command line.  This optimizes streaming process since we
> are not opening and closing files randomly and also we read them more
> sequentially.  This saves some kernel time though I think more can be
> done if we avoid doing pair of mmap/unmap for every file section we
> read.
> 
> We also read files in random order in ipa-cp and during devirt.
> I guess also summary streaming can be refactored to stream all summaries
> for a given file instead of reading one sumarry from all files.
> 
> Bootstrapped/regtested x86_64-linux, plan to commit it this afternoon if
> there are no complains.
> 
> Honza
> 
> 	* lto-common.c (lto_file_finalize): Add order attribute.
> 	(lto_create_files_from_ids): Pass order.
> 	(lto_file_read): UPdate call of lto_create_files_from_ids.
> 	* lto-streamer-out.c (output_constructor): Push CTORS_OUT timevar.
> 	(cmp_symbol_files): New.
> 	(lto_output): Copy sections in file order.
> 	* lto-streamer.h (lto_file_decl_data): Add field order.
Hi,
I have commited the patch but messed up testing so it broke builds with
static libraries and checking enabled. This is fixes by this patch

	* lto-streamer-out.c (cmp_symbol_files): Watch for overflow.
Index: lto-streamer-out.c
===================================================================
--- lto-streamer-out.c	(revision 277346)
+++ lto-streamer-out.c	(working copy)
@@ -2447,7 +2447,12 @@ cmp_symbol_files (const void *pn1, const
 
   /* Order within static library.  */
   if (n1->lto_file_data && n1->lto_file_data->id != n2->lto_file_data->id)
-    return n1->lto_file_data->id - n2->lto_file_data->id;
+    {
+      if (n1->lto_file_data->id > n2->lto_file_data->id)
+	return 1;
+      if (n1->lto_file_data->id < n2->lto_file_data->id)
+	return -1;
+    }
 
   /* And finaly order by the definition order.  */
   return n1->order - n2->order;