Relax limits of early inliner for the forwarder functions

[Jan Hubicka <hubicka@ucw.cz>]

Hi,
in 4.6 timeframe I limited early inlier growth to apply only for leaf functions.
This does not work really well, because with less propagation of address expressions
we are really not 100% succesfull on detecting C++ forwarders and predicting them
zero cost.   This patch simply makes the cost to be divided by number of callees, similarly
as in LLVM.

Bootstrapped/regtested x86_64-linux, benchmarked and comitted.
The patch seems consistent win in all benchmarks, most noticeably in tramp3d.

	* ipa-inline.c (leaf_node_p): Rename to ...
	(num_calls) ... this one.
	(want_early_inline_function_p): Allow smal growth on non-leafs.
Index: ipa-inline.c
===================================================================
--- ipa-inline.c	(revision 193134)
+++ ipa-inline.c	(working copy)
@@ -380,17 +380,18 @@ can_early_inline_edge_p (struct cgraph_e
 }
 
 
-/* Return true when N is leaf function.  Accept cheap builtins
-   in leaf functions.  */
+/* Return number of calls in N.  Ignore cheap builtins.  */
 
-static bool
-leaf_node_p (struct cgraph_node *n)
+static int
+num_calls (struct cgraph_node *n)
 {
   struct cgraph_edge *e;
+  int num = 0;
+
   for (e = n->callees; e; e = e->next_callee)
     if (!is_inexpensive_builtin (e->callee->symbol.decl))
-      return false;
-  return true;
+      num++;
+  return num;
 }
 
 
@@ -414,6 +415,8 @@ want_early_inline_function_p (struct cgr
   else
     {
       int growth = estimate_edge_growth (e);
+      int n;
+
       if (growth <= 0)
 	;
       else if (!cgraph_maybe_hot_edge_p (e)
@@ -427,22 +430,23 @@ want_early_inline_function_p (struct cgr
 		     growth);
 	  want_inline = false;
 	}
-      else if (!leaf_node_p (callee)
-	       && growth > 0)
+      else if (growth > PARAM_VALUE (PARAM_EARLY_INLINING_INSNS))
 	{
 	  if (dump_file)
 	    fprintf (dump_file, "  will not early inline: %s/%i->%s/%i, "
-		     "callee is not leaf and code would grow by %i\n",
+		     "growth %i exceeds --param early-inlining-insns\n",
 		     xstrdup (cgraph_node_name (e->caller)), e->caller->uid,
 		     xstrdup (cgraph_node_name (callee)), callee->uid,
 		     growth);
 	  want_inline = false;
 	}
-      else if (growth > PARAM_VALUE (PARAM_EARLY_INLINING_INSNS))
+      else if ((n = num_calls (callee)) != 0
+	       && growth * (n + 1) > PARAM_VALUE (PARAM_EARLY_INLINING_INSNS))
 	{
 	  if (dump_file)
 	    fprintf (dump_file, "  will not early inline: %s/%i->%s/%i, "
-		     "growth %i exceeds --param early-inlining-insns\n",
+		     "growth %i exceeds --param early-inlining-insns "
+		     "divided by number of calls\n",
 		     xstrdup (cgraph_node_name (e->caller)), e->caller->uid,
 		     xstrdup (cgraph_node_name (callee)), callee->uid,
 		     growth);