Introduce -fprofile-reproducibility and support it with TOP N.

	PR ipa/92924
	* common.opt: Add -fprofile-reproducibility.
	* doc/invoke.texi: Document it.
	* value-prof.c (dump_histogram_value):
	Document and support behavior for counters[0]
	being a negative value.
	(get_nth_most_common_value): Handle negative
	counters[0] in respect to flag_profile_reproducible.
	PR ipa/92924
	* libgcov-merge.c (merge_topn_values_set): Record
	when a TOP N counter becomes invalid.  When merging
	remove a smallest value if the space is needed.

2 files changed, 42 insertions, 15 deletions

diff --git a/libgcc/ChangeLog b/libgcc/ChangeLog
index 7b46ccb..dedc308 100644
--- a/libgcc/ChangeLog
+++ b/libgcc/ChangeLog
@@ -1,3 +1,10 @@
+2020-02-18  Martin Liska  <mliska@suse.cz>
+
+	PR ipa/92924
+	* libgcov-merge.c (merge_topn_values_set): Record
+	when a TOP N counter becomes invalid.  When merging
+	remove a smallest value if the space is needed.
+
 2020-02-12  Sandra Loosemore  <sandra@codesourcery.com>
 
 	PR libstdc++/79193
diff --git a/libgcc/libgcov-merge.c b/libgcc/libgcov-merge.c
index 19b8ee7..c0785b0 100644
--- a/libgcc/libgcov-merge.c
+++ b/libgcc/libgcov-merge.c
@@ -86,36 +86,47 @@ __gcov_merge_time_profile (gcov_type *counters, unsigned n_counters)
 
 #ifdef L_gcov_merge_topn
 
+/* To merging of TOPN profiles.
+   counters[0] is the number of executions
+   for i in 0 ... TOPN-1
+     counters[2 * i + 1] is target
+     counters[2 * i + 2] is corresponding hitrate counter.
+
+   Because we prune counters only those with probability >= 1/TOPN are
+   present now.
+
+   We use sign of counters[0] to track whether the number of different
+   targets exceeds TOPN.  */
+
 static void
 merge_topn_values_set (gcov_type *counters)
 {
   /* First value is number of total executions of the profiler.  */
-  gcov_type all = gcov_get_counter_ignore_scaling (-1);
-  counters[0] += all;
+  gcov_type all = gcov_get_counter ();
+  gcov_type *total = &counters[0];
   ++counters;
 
+  /* Negative value means that counter is missing some of values.  */
+  if (all < 0)
+    *total = -(*total);
+
+  *total += all;
+
   /* Read all part values.  */
   gcov_type read_counters[2 * GCOV_TOPN_VALUES];
-
   for (unsigned i = 0; i < GCOV_TOPN_VALUES; i++)
     {
       read_counters[2 * i] = gcov_get_counter_target ();
       read_counters[2 * i + 1] = gcov_get_counter_ignore_scaling (-1);
     }
 
-  if (read_counters[1] == -1)
-    {
-      counters[1] = -1;
-      return;
-    }
-
   for (unsigned i = 0; i < GCOV_TOPN_VALUES; i++)
     {
       if (read_counters[2 * i + 1] == 0)
 	continue;
 
       unsigned j;
-      int slot = -1;
+      int slot = 0;
 
       for (j = 0; j < GCOV_TOPN_VALUES; j++)
 	{
@@ -124,13 +135,15 @@ merge_topn_values_set (gcov_type *counters)
 	      counters[2 * j + 1] += read_counters[2 * i + 1];
 	      break;
 	    }
-	  else if (counters[2 * j + 1] == 0)
+	  else if (counters[2 * j + 1] < counters[2 * slot + 1])
 	    slot = j;
 	}
 
       if (j == GCOV_TOPN_VALUES)
 	{
-	  if (slot > 0)
+	  gcov_type slot_count = counters[2 * slot + 1];
+	  /* We found an empty slot.  */
+	  if (slot_count == 0)
 	    {
 	      /* If we found empty slot, add the value.  */
 	      counters[2 * slot] = read_counters[2 * i];
@@ -138,9 +151,16 @@ merge_topn_values_set (gcov_type *counters)
 	    }
 	  else
 	    {
-	      /* We haven't found a slot, bail out.  */
-	      counters[1] = -1;
-	      return;
+	      /* Here we are loosing some values.  */
+	      if (*total >= 0)
+		*total = -(*total);
+	      if (read_counters[2 * i + 1] > slot_count)
+		{
+		  counters[2 * slot] = read_counters[2 * i];
+		  counters[2 * slot + 1] = read_counters[2 * i + 1];
+		}
+	      else
+		counters[2 * slot + 1] -= read_counters[2 * i + 1];
 	    }
 	}
     }