[gcc r11-6910] libgcov: improve profile reproducibility

[gcc r11-6910] libgcov: improve profile reproducibility

[Martin Liska]

https://gcc.gnu.org/g:d40b21eebc9d41c3cb9ccbdf6338968436550621

commit r11-6910-gd40b21eebc9d41c3cb9ccbdf6338968436550621
Author: Martin Liska <mliska@suse.cz>
Date:   Tue Jan 26 12:44:34 2021 +0100

    libgcov: improve profile reproducibility
    
    libgcc/ChangeLog:
    
            PR gcov-profile/98739
            * libgcov.h (gcov_topn_add_value): Do not train when
            we have a merged profile with a negative number of total
            value.

Diff:
---
 libgcc/libgcov.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/libgcc/libgcov.h b/libgcc/libgcov.h
index df08e882dd7..ddc688509bd 100644
--- a/libgcc/libgcov.h
+++ b/libgcc/libgcov.h
@@ -443,7 +443,13 @@ gcov_topn_add_value (gcov_type *counters, gcov_type value, gcov_type count,
 		     int use_atomic, int increment_total)
 {
   if (increment_total)
-    gcov_counter_add (&counters[0], 1, use_atomic);
+    {
+      /* In the multi-threaded mode, we can have an already merged profile
+	 with a negative total value.  In that case, we should bail out.  */
+      if (counters[0] < 0)
+	return 0;
+      gcov_counter_add (&counters[0], 1, use_atomic);
+    }
 
   struct gcov_kvp *prev_node = NULL;
   struct gcov_kvp *minimal_node = NULL;