[google] add a new parameter to control icall promotion strategy

[Xinliang David Li]

The attached patch defines a new parameter to decide if icall
promotion (LIPO) is using a new hotness based heuristic or not.   (See
Honza's speculative call support patch for reference).


David

Index: params.def
===================================================================
--- params.def  (revision 201420)
+++ params.def  (working copy)
@@ -903,6 +903,13 @@ DEFPARAM (PARAM_ALWAYS_INLINE_ICALL_TARG
          "force inline indirect call target when promoted",
           0, 0, 0)
 
+/* Do not check the icall target count distribution, but use
+   hotness info to decide if promotion should be done.  */
+DEFPARAM (PARAM_ICALL_USE_HOTNESS_HEUR,
+         "icall-use-hotness-heur",
+         "use hotness based heuristics to match inliner",
+          0, 0, 0)
+
 /* Force the compiler to be in LIPO mode even there is no
  profile data available. -fripa is also needed. */
 DEFPARAM (PARAM_FORCE_LIPO_MODE, 
Index: value-prof.c
===================================================================
--- value-prof.c        (revision 201419)
+++ value-prof.c        (working copy)
@@ -1558,6 +1558,7 @@ gimple_ic_transform_mult_targ (gimple st
   gimple modify1, modify2;
   struct cgraph_node *direct_call1 = 0, *direct_call2 = 0;
   int perc_threshold, count_threshold, always_inline;
+  int use_hotness_heur = false;
   location_t locus;
 
   val1 = histogram->hvalue.counters [1];
@@ -1576,9 +1577,18 @@ gimple_ic_transform_mult_targ (gimple st
   perc_threshold = PARAM_VALUE (PARAM_ICALL_PROMOTE_PERCENT_THRESHOLD);
   count_threshold = PARAM_VALUE (PARAM_ICALL_PROMOTE_COUNT_THRESHOLD);
   always_inline = PARAM_VALUE (PARAM_ALWAYS_INLINE_ICALL_TARGET);
+  use_hotness_heur = PARAM_VALUE (PARAM_ICALL_USE_HOTNESS_HEUR);
 
-  if (100 * count1 < all * perc_threshold || count1 < count_threshold)
-    return false;
+  if (!use_hotness_heur)
+    {
+      if (100 * count1 < all * perc_threshold || count1 < count_threshold)
+        return false;
+    }
+  else
+    {
+      if (!maybe_hot_count_p (cfun, count1))
+        return false;
+    }
 
   if (check_ic_counter (stmt, &count1, &count2, all))
     return false;
@@ -1597,9 +1607,17 @@ gimple_ic_transform_mult_targ (gimple st
 
   direct_call1 = find_func_by_global_id (val1, flag_auto_profile);
 
-  if (val2 && (100 * count2 >= all * perc_threshold)
-      && count2 > count_threshold)
-    direct_call2 = find_func_by_global_id (val2, flag_auto_profile);
+  if (!use_hotness_heur)
+    {
+      if (val2 && (100 * count2 >= all * perc_threshold)
+          && count2 > count_threshold)
+        direct_call2 = find_func_by_global_id (val2, flag_auto_profile);
+    }
+  else
+    {
+      if (maybe_hot_count_p (cfun, count2))
+        direct_call2 = find_func_by_global_id (val2, flag_auto_profile);
+    }
 
   locus = (stmt != NULL) ? gimple_location (stmt)
       : DECL_SOURCE_LOCATION (current_function_decl);