Smart relaxation of TOP N counter.

	PR tree-optimization/92924
	* profile.c (compute_value_histograms): Divide
	all counter values.
	PR tree-optimization/92924
	* libgcov-driver.c (prune_topn_counter): New.
	(prune_counters): Likewise.
	(dump_one_gcov): Prune a run-time counter.
	* libgcov-profiler.c (__gcov_topn_values_profiler_body):
	For a known value, add GCOV_TOPN_VALUES to value.
	Otherwise, decrement all counters by one.

3 files changed, 77 insertions, 17 deletions

diff --git a/libgcc/ChangeLog b/libgcc/ChangeLog
index 5e8b506..441c8f0 100644
--- a/libgcc/ChangeLog
+++ b/libgcc/ChangeLog
@@ -1,3 +1,13 @@
+2020-01-22  Martin Liska  <mliska@suse.cz>
+
+	PR tree-optimization/92924
+	* libgcov-driver.c (prune_topn_counter): New.
+	(prune_counters): Likewise.
+	(dump_one_gcov): Prune a run-time counter.
+	* libgcov-profiler.c (__gcov_topn_values_profiler_body):
+	For a known value, add GCOV_TOPN_VALUES to value.
+	Otherwise, decrement all counters by one.
+
 2020-01-18  Hans-Peter Nilsson  <hp@axis.com>
 
 	* config/cris/arit.c (DS): Apply attribute __fallthrough__.
diff --git a/libgcc/libgcov-driver.c b/libgcc/libgcov-driver.c
index 1c07761..cdb611d 100644
--- a/libgcc/libgcov-driver.c
+++ b/libgcc/libgcov-driver.c
@@ -213,6 +213,56 @@ static struct gcov_fn_buffer *fn_buffer;
 /* Including system dependent components. */
 #include "libgcov-driver-system.c"
 
+/* Prune TOP N value COUNTERS.  It's needed in order to preserve
+   reproducibility of builds.  */
+
+static void
+prune_topn_counter (gcov_type *counters, gcov_type all)
+{
+  if (counters[1] == -1)
+    return;
+
+  for (unsigned i = 0; i < GCOV_TOPN_VALUES; i++)
+    {
+      if (counters[2 * i + 1] < all)
+	{
+	  counters[2 * i] = 0;
+	  counters[2 * i + 1] = 0;
+	}
+    }
+}
+
+/* Prune counters so that they are ready to store or merge.  */
+
+static void
+prune_counters (struct gcov_info *gi)
+{
+  for (unsigned i = 0; i < gi->n_functions; i++)
+    {
+      const struct gcov_fn_info *gfi = gi->functions[i];
+      const struct gcov_ctr_info *ci = gfi->ctrs;
+
+      for (unsigned j = 0; j < GCOV_COUNTERS; j++)
+	{
+	  if (gi->merge[j] == NULL)
+	    continue;
+
+	  if (gi->merge[j] == __gcov_merge_topn)
+	    {
+	      gcc_assert (!(ci->num % GCOV_TOPN_VALUES_COUNTERS));
+	      for (unsigned k = 0; k < (ci->num / GCOV_TOPN_VALUES_COUNTERS);
+		   k++)
+		{
+		  gcov_type *counters
+		    = ci->values + (k * GCOV_TOPN_VALUES_COUNTERS);
+		  prune_topn_counter (counters + 1, *counters);
+		}
+	    }
+	  ci++;
+	}
+    }
+}
+
 /* This function merges counters in GI_PTR to an existing gcda file.
    Return 0 on success.
    Return -1 on error. In this case, caller will goto read_fatal.  */
@@ -429,9 +479,11 @@ dump_one_gcov (struct gcov_info *gi_ptr, struct gcov_filename *gf,
   struct gcov_summary summary = {};
   int error;
   gcov_unsigned_t tag;
-
   fn_buffer = 0;
 
+  /* Prune current counters before we merge them.  */
+  prune_counters (gi_ptr);
+
   error = gcov_exit_open_gcda_file (gi_ptr, gf);
   if (error == -1)
     return;
diff --git a/libgcc/libgcov-profiler.c b/libgcc/libgcov-profiler.c
index 9417904..f45ef49 100644
--- a/libgcc/libgcov-profiler.c
+++ b/libgcc/libgcov-profiler.c
@@ -119,37 +119,35 @@ __gcov_topn_values_profiler_body (gcov_type *counters, gcov_type value,
 
   ++counters;
 
-  /* We have GCOV_TOPN_VALUES as we can keep multiple values
-     next to each other.  */
-  unsigned sindex = 0;
-
   for (unsigned i = 0; i < GCOV_TOPN_VALUES; i++)
     {
       if (value == counters[2 * i])
 	{
 	  if (use_atomic)
-	    __atomic_fetch_add (&counters[2 * i + 1], 1, __ATOMIC_RELAXED);
+	    __atomic_fetch_add (&counters[2 * i + 1], GCOV_TOPN_VALUES,
+				__ATOMIC_RELAXED);
 	  else
-	    counters[2 * i + 1]++;
+	    counters[2 * i + 1] += GCOV_TOPN_VALUES;
 	  return;
 	}
-      else if (counters[2 * i + 1] == 0)
+      else if (counters[2 * i + 1] <= 0)
 	{
 	  /* We found an empty slot.  */
 	  counters[2 * i] = value;
-	  counters[2 * i + 1] = 1;
+	  counters[2 * i + 1] = GCOV_TOPN_VALUES;
 	  return;
 	}
-
-      if (counters[2 * i + 1] < counters[2 * sindex + 1])
-	sindex = i;
     }
 
-  /* We haven't found an empty slot, then decrement the smallest.  */
-  if (use_atomic)
-    __atomic_fetch_sub (&counters[2 * sindex + 1], 1, __ATOMIC_RELAXED);
-  else
-    counters[2 * sindex + 1]--;
+  /* We haven't found an empty slot, then decrement all
+     counter values by one.  */
+  for (unsigned i = 0; i < GCOV_TOPN_VALUES; i++)
+    {
+      if (use_atomic)
+	__atomic_fetch_sub (&counters[2 * i + 1], 1, __ATOMIC_RELAXED);
+      else
+	counters[2 * i + 1]--;
+    }
 }
 
 #ifdef L_gcov_topn_values_profiler