[PATCH] Fix part of PR gcov-profile/54487

[tejohnson, 2012-09-07 05:51:18]

This fixes part of the issue described in PR gcov-profile/54487 where
there were warnings about mismatches due to slight differences in the
merged histograms in different object files. This can happen due to
the truncating integer division in the merge routine, which could result
in slightly different histograms when summaries are merged in different
orders.

Tested with bootstrap and profiledbootstrap on x86_64-unknown-linux-gnu.
Ok for trunk?

Teresa

2012-09-06  Teresa Johnson  <tejohnson@google.com>

        PR gcov-profile/54487
	* libgcc/libgcov.c (gcov_exit): Avoid warning on histogram
        differences.

Index: libgcc/libgcov.c
===================================================================
--- libgcc/libgcov.c	(revision 191035)
+++ libgcc/libgcov.c	(working copy)
@@ -707,7 +707,13 @@ gcov_exit (void)
 	    memcpy (cs_all, cs_prg, sizeof (*cs_all));
 	  else if (!all_prg.checksum
 		   && (!GCOV_LOCKED || cs_all->runs == cs_prg->runs)
-		   && memcmp (cs_all, cs_prg, sizeof (*cs_all)))
+                   /* Don't compare the histograms, which may have slight
+                      variations depending on the order they were updated
+                      due to the truncating integer divides used in the
+                      merge.  */
+                   && memcmp (cs_all, cs_prg,
+                              sizeof (*cs_all) - (sizeof (gcov_bucket_type)
+                                                  * GCOV_HISTOGRAM_SIZE)))
 	    {
 	      fprintf (stderr, "profiling:%s:Invocation mismatch - some data files may
have been removed%s\n",
 		       gi_filename, GCOV_LOCKED

--
This patch is available for review at http://codereview.appspot.com/6501100

[hubicka_ucw.cz, 2012-09-07 10:55:27]

> This fixes part of the issue described in PR gcov-profile/54487 where
> there were warnings about mismatches due to slight differences in the
> merged histograms in different object files. This can happen due to
> the truncating integer division in the merge routine, which could result
> in slightly different histograms when summaries are merged in different
> orders.
> 
> Tested with bootstrap and profiledbootstrap on x86_64-unknown-linux-gnu.
> Ok for trunk?

OK,
thanks!
Honza
> 
> Teresa
> 
> 2012-09-06  Teresa Johnson  <tejohnson@google.com>
> 
>         PR gcov-profile/54487
> 	* libgcc/libgcov.c (gcov_exit): Avoid warning on histogram
>         differences.
> 
> Index: libgcc/libgcov.c
> ===================================================================
> --- libgcc/libgcov.c	(revision 191035)
> +++ libgcc/libgcov.c	(working copy)
> @@ -707,7 +707,13 @@ gcov_exit (void)
>  	    memcpy (cs_all, cs_prg, sizeof (*cs_all));
>  	  else if (!all_prg.checksum
>  		   && (!GCOV_LOCKED || cs_all->runs == cs_prg->runs)
> -		   && memcmp (cs_all, cs_prg, sizeof (*cs_all)))
> +                   /* Don't compare the histograms, which may have slight
> +                      variations depending on the order they were updated
> +                      due to the truncating integer divides used in the
> +                      merge.  */
> +                   && memcmp (cs_all, cs_prg,
> +                              sizeof (*cs_all) - (sizeof (gcov_bucket_type)
> +                                                  * GCOV_HISTOGRAM_SIZE)))
>  	    {
>  	      fprintf (stderr, "profiling:%s:Invocation mismatch - some data files
may have been removed%s\n",
>  		       gi_filename, GCOV_LOCKED
> 
> --
> This patch is available for review at http://codereview.appspot.com/6501100