Come up with jump_table ratio constants used in jump_table_cluster.

2018-06-28  Martin Liska  <mliska@suse.cz>

	* tree-switch-conversion.c (jump_table_cluster::can_be_handled):
        Use newly introduced constants.
	* tree-switch-conversion.h (struct jump_table_cluster):
        Define max_ratio_for_size and max_ratio_for_speed.

From-SVN: r262212

gcc/ChangeLog

 2018-06-28  Martin Liska  <mliska@suse.cz>
 
+	* tree-switch-conversion.c (jump_table_cluster::can_be_handled):
+        Use newly introduced constants.
+	* tree-switch-conversion.h (struct jump_table_cluster):
+        Define max_ratio_for_size and max_ratio_for_speed.
+
+2018-06-28  Martin Liska  <mliska@suse.cz>
+
 	* tree-switch-conversion.c (jump_table_cluster::find_jump_tables):
         Add new checking assert to catch invalid state.
 	(jump_table_cluster::can_be_handled): Handle single case

gcc/tree-switch-conversion.c

@@ -1180,7 +1180,8 @@ jump_table_cluster::can_be_handled (const vec<cluster *> &clusters,
   if (start == end)
     return true;
 
-  unsigned HOST_WIDE_INT max_ratio = optimize_insn_for_size_p () ? 3 : 8;
+  unsigned HOST_WIDE_INT max_ratio
+    = optimize_insn_for_size_p () ? max_ratio_for_size : max_ratio_for_speed;
   unsigned HOST_WIDE_INT range = get_range (clusters[start]->get_low (),
 					    clusters[end]->get_high ());
   /* Check overflow.  */

gcc/tree-switch-conversion.h

@@ -257,6 +257,12 @@ struct jump_table_cluster: public group_cluster
 
   /* Return whether jump table expansion is allowed.  */
   static bool is_enabled (void);
+
+  /* Max growth ratio for code that is optimized for size.  */
+  static const unsigned HOST_WIDE_INT max_ratio_for_size = 3;
+
+  /* Max growth ratio for code that is optimized for speed.  */
+  static const unsigned HOST_WIDE_INT max_ratio_for_speed = 8;
 };
 
 /* A GIMPLE switch statement can be expanded to a short sequence of bit-wise