Index: lto-cgraph.c
===================================================================
--- lto-cgraph.c	(revision 193909)
+++ lto-cgraph.c	(working copy)
@@ -46,6 +46,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-streamer.h"
 #include "gcov-io.h"
 #include "tree-pass.h"
+#include "profile.h"
 
 static void output_cgraph_opt_summary (void);
 static void input_cgraph_opt_summary (vec<symtab_node>  nodes);
@@ -593,14 +594,49 @@ lto_output_ref (struct lto_simple_output_block *ob
 static void
 output_profile_summary (struct lto_simple_output_block *ob)
 {
+  unsigned h_ix, bv_ix, h_cnt = 0;
+  unsigned histo_bitvector[GCOV_HISTOGRAM_BITVECTOR_SIZE];
+
   if (profile_info)
     {
-      /* We do not output num, sum_all and run_max, they are not used by
-	 GCC profile feedback and they are difficult to merge from multiple
-	 units.  */
+      /* We do not output num and run_max, they are not used by
+         GCC profile feedback and they are difficult to merge from multiple
+         units.  */
       gcc_assert (profile_info->runs);
       streamer_write_uhwi_stream (ob->main_stream, profile_info->runs);
       streamer_write_uhwi_stream (ob->main_stream, profile_info->sum_max);
+
+      /* sum_all is needed for computing the working set with the
+         histogram.  */
+      streamer_write_uhwi_stream (ob->main_stream, profile_info->sum_all);
+
+      /* Count number of non-zero histogram entries, and fill in a bit vector
+         of non-zero indices.  */
+         counters.  */
+      for (bv_ix = 0; bv_ix < GCOV_HISTOGRAM_BITVECTOR_SIZE; bv_ix++)
+        histo_bitvector[bv_ix] = 0;
+      for (h_ix = 0; h_ix < GCOV_HISTOGRAM_SIZE; h_ix++)
+        {
+          if (profile_info->histogram[h_ix].num_counters > 0)
+            {
+              histo_bitvector[h_ix / 32] |= 1 << (h_ix % 32);
+              h_cnt++;
+            }
+        }
+      /* Output the bitvector and the non-zero entries.  */
+      for (bv_ix = 0; bv_ix < GCOV_HISTOGRAM_BITVECTOR_SIZE; bv_ix++)
+        streamer_write_uhwi_stream (ob->main_stream, histo_bitvector[bv_ix]);
+      for (h_ix = 0; h_ix < GCOV_HISTOGRAM_SIZE; h_ix++)
+        {
+          if (!profile_info->histogram[h_ix].num_counters)
+            continue;
+          streamer_write_uhwi_stream (ob->main_stream,
+                                      profile_info->histogram[h_ix].num_counters);
+          streamer_write_uhwi_stream (ob->main_stream,
+                                      profile_info->histogram[h_ix].min_value);
+          streamer_write_uhwi_stream (ob->main_stream,
+                                      profile_info->histogram[h_ix].cum_value);
+        }
     }
   else
     streamer_write_uhwi_stream (ob->main_stream, 0);
@@ -1227,11 +1263,58 @@ static void
 input_profile_summary (struct lto_input_block *ib,
 		       struct lto_file_decl_data *file_data)
 {
+  unsigned h_ix, bv_ix, h_cnt = 0;
+  unsigned histo_bitvector[GCOV_HISTOGRAM_BITVECTOR_SIZE];
+  unsigned cur_bitvector;
   unsigned int runs = streamer_read_uhwi (ib);
   if (runs)
     {
       file_data->profile_info.runs = runs;
       file_data->profile_info.sum_max = streamer_read_uhwi (ib);
+      file_data->profile_info.sum_all = streamer_read_uhwi (ib);
+
+      memset (file_data->profile_info.histogram, 0,
+              sizeof (gcov_bucket_type) * GCOV_HISTOGRAM_SIZE);
+      /* Input the bitvector of non-zero histogram indices.  */
+      for (bv_ix = 0; bv_ix < GCOV_HISTOGRAM_BITVECTOR_SIZE; bv_ix++)
+        {
+          histo_bitvector[bv_ix] = streamer_read_uhwi (ib);
+          h_cnt += __builtin_popcountll (histo_bitvector[bv_ix]);
+        }
+      bv_ix = 0;
+      h_ix = 0;
+      cur_bitvector = 0;
+      while (h_cnt--)
+        {
+          /* Find the index corresponding to the next entry we will read in.
+             First find the next non-zero bitvector and re-initialize
+             the histogram index accordingly, then right shift and increment
+             the index until we find a set bit.  */
+          while (!cur_bitvector)
+            {
+              h_ix = bv_ix * 32;
+              gcc_assert(bv_ix < GCOV_HISTOGRAM_BITVECTOR_SIZE);
+              cur_bitvector = histo_bitvector[bv_ix++];
+            }
+          while (!(cur_bitvector & 0x1))
+            {
+              h_ix++;
+              cur_bitvector >>= 1;
+            }
+          gcc_assert(h_ix < GCOV_HISTOGRAM_SIZE);
+
+          file_data->profile_info.histogram[h_ix].num_counters
+              = streamer_read_uhwi (ib);
+          file_data->profile_info.histogram[h_ix].min_value
+              = streamer_read_uhwi (ib);
+          file_data->profile_info.histogram[h_ix].cum_value
+              = streamer_read_uhwi (ib);
+
+          /* Shift off the index we are done with and increment to the
+             corresponding next histogram entry.  */
+          cur_bitvector >>= 1;
+          h_ix++;
+        }
     }
 
 }
@@ -1242,10 +1325,13 @@ static void
 merge_profile_summaries (struct lto_file_decl_data **file_data_vec)
 {
   struct lto_file_decl_data *file_data;
-  unsigned int j;
+  unsigned int j, h_ix;
   gcov_unsigned_t max_runs = 0;
   struct cgraph_node *node;
   struct cgraph_edge *edge;
+  gcov_type saved_sum_all = 0;
+  gcov_ctr_summary *saved_profile_info = 0;
+  int saved_scale = 0;
 
   /* Find unit with maximal number of runs.  If we ever get serious about
      roundoff errors, we might also consider computing smallest common
@@ -1269,6 +1355,8 @@ merge_profile_summaries (struct lto_file_decl_data
   profile_info = &lto_gcov_summary;
   lto_gcov_summary.runs = max_runs;
   lto_gcov_summary.sum_max = 0;
+  memset (lto_gcov_summary.histogram, 0,
+          sizeof (gcov_bucket_type) * GCOV_HISTOGRAM_SIZE);
 
   /* Rescale all units to the maximal number of runs.
      sum_max can not be easily merged, as we have no idea what files come from
@@ -1284,8 +1372,46 @@ merge_profile_summaries (struct lto_file_decl_data
 					 * scale
 					 + REG_BR_PROB_BASE / 2)
 					/ REG_BR_PROB_BASE);
+	lto_gcov_summary.sum_all = MAX (lto_gcov_summary.sum_all,
+					(file_data->profile_info.sum_all
+					 * scale
+					 + REG_BR_PROB_BASE / 2)
+					/ REG_BR_PROB_BASE);
+        /* Save a pointer to the profile_info with the largest
+           scaled sum_all and the scale for use in merging the
+           histogram.  */
+        if (lto_gcov_summary.sum_all > saved_sum_all)
+          {
+            saved_profile_info = &file_data->profile_info;
+            saved_sum_all = lto_gcov_summary.sum_all;
+            saved_scale = scale;
+          }
       }
 
+  gcc_assert (saved_profile_info);
+
+  /* Scale up the histogram from the profile that had the largest
+     scaled sum_all above.  */
+  for (h_ix = 0; h_ix < GCOV_HISTOGRAM_SIZE; h_ix++)
+    {
+      /* Scale up the min value as we did the corresponding sum_all
+         above. Use that to find the new histogram index.  */
+      int scaled_min = (saved_profile_info->histogram[h_ix].min_value
+                        * saved_scale + REG_BR_PROB_BASE / 2)
+                       / REG_BR_PROB_BASE;
+      unsigned new_ix = gcov_histo_index (scaled_min);
+      lto_gcov_summary.histogram[new_ix].min_value = scaled_min;
+      /* Some of the scaled counter values would ostensibly need to be placed
+         into different (larger) histogram buckets, but we keep things simple
+         here and place the scaled cumulative counter value in the bucket
+         corresponding to the scaled minimum counter value.  */
+      lto_gcov_summary.histogram[new_ix].cum_value
+          = (saved_profile_info->histogram[h_ix].cum_value
+             * saved_scale + REG_BR_PROB_BASE / 2) / REG_BR_PROB_BASE;
+      lto_gcov_summary.histogram[new_ix].num_counters
+          = saved_profile_info->histogram[h_ix].num_counters;
+    }
+
   /* Watch roundoff errors.  */
   if (lto_gcov_summary.sum_max < max_runs)
     lto_gcov_summary.sum_max = max_runs;
@@ -1365,7 +1491,9 @@ input_symtab (void)
     }
 
   merge_profile_summaries (file_data_vec);
+  compute_working_sets ();
 
+
   /* Clear out the aux field that was used to store enough state to
      tell which nodes should be overwritten.  */
   FOR_EACH_FUNCTION (node)
Index: gcov-io.c
===================================================================
--- gcov-io.c	(revision 193909)
+++ gcov-io.c	(working copy)
@@ -622,10 +622,10 @@ gcov_time (void)
 }
 #endif /* IN_GCOV */
 
-#if IN_LIBGCOV || !IN_GCOV
+#if !IN_GCOV
 /* Determine the index into histogram for VALUE. */
 
-static unsigned
+GCOV_LINKAGE unsigned
 gcov_histo_index(gcov_type value)
 {
   gcov_type_unsigned v = (gcov_type_unsigned)value;
@@ -801,4 +801,4 @@ static void gcov_histogram_merge(gcov_bucket_type
   /* Finally, copy the merged histogram into tgt_histo.  */
   memcpy(tgt_histo, tmp_histo, sizeof (gcov_bucket_type) * GCOV_HISTOGRAM_SIZE);
 }
-#endif /* IN_LIBGCOV || !IN_GCOV */
+#endif /* !IN_GCOV */
Index: gcov-io.h
===================================================================
--- gcov-io.h	(revision 193909)
+++ gcov-io.h	(working copy)
@@ -608,6 +608,7 @@ GCOV_LINKAGE void gcov_sync (gcov_position_t /*bas
 #if !IN_GCOV
 /* Available outside gcov */
 GCOV_LINKAGE void gcov_write_unsigned (gcov_unsigned_t) ATTRIBUTE_HIDDEN;
+GCOV_LINKAGE unsigned gcov_histo_index (gcov_type value);
 #endif
 
 #if !IN_GCOV && !IN_LIBGCOV
Index: profile.c
===================================================================
--- profile.c	(revision 193909)
+++ profile.c	(working copy)
@@ -207,7 +207,7 @@ instrument_values (histogram_values values)
    the number of counters required to cover that working set percentage and
    the minimum counter value in that working set.  */
 
-static void
+void
 compute_working_sets (void)
 {
   gcov_type working_set_cum_values[NUM_GCOV_WORKING_SETS];
Index: profile.h
===================================================================
--- profile.h	(revision 193909)
+++ profile.h	(working copy)
@@ -47,4 +47,6 @@ extern gcov_type sum_edge_counts (vec<edge, va_gc>
 extern void init_node_map (void);
 extern void del_node_map (void);
 
+extern void compute_working_sets (void);
+
 #endif /* PROFILE_H */
