Change default for jump_table expansion ratio to 8.

2018-06-20  Martin Liska  <mliska@suse.cz>

	* tree-switch-conversion.c (jump_table_cluster::can_be_handled):
        Change default ratio from 10 to 8.

From-SVN: r261795

gcc/ChangeLog

 2018-06-20  Martin Liska  <mliska@suse.cz>
 
+	* tree-switch-conversion.c (jump_table_cluster::can_be_handled):
+        Change default ratio from 10 to 8.
+
+2018-06-20  Martin Liska  <mliska@suse.cz>
+
 	* tree-switch-conversion.c (jump_table_cluster::find_jump_tables):
         New.
 	(bit_test_cluster::find_bit_tests): Likewise.

gcc/tree-switch-conversion.c

@@ -1165,17 +1165,11 @@ jump_table_cluster::can_be_handled (const vec<cluster *> &clusters,
      make a sequence of conditional branches instead of a dispatch.
 
      The definition of "much bigger" depends on whether we are
-     optimizing for size or for speed.  If the former, the maximum
-     ratio range/count = 3, because this was found to be the optimal
-     ratio for size on i686-pc-linux-gnu, see PR11823.  The ratio
-     10 is much older, and was probably selected after an extensive
-     benchmarking investigation on numerous platforms.  Or maybe it
-     just made sense to someone at some point in the history of GCC,
-     who knows...  */
+     optimizing for size or for speed.  */
   if (!flag_jump_tables)
     return false;
 
-  unsigned HOST_WIDE_INT max_ratio = optimize_insn_for_size_p () ? 3 : 10;
+  unsigned HOST_WIDE_INT max_ratio = optimize_insn_for_size_p () ? 3 : 8;
 
   unsigned HOST_WIDE_INT range = get_range (clusters[start]->get_low (),
 					    clusters[end]->get_high ());