Designate the widest case label to be the default label

gcc/ChangeLog:

	* gimple.c (preprocess_case_label_vec_for_gimple): When the case
	labels are exhaustive, designate the label with the widest
	range to be the default label.

gcc/testsuite/ChangeLog:

	* gcc.dg/switch-10.c: New test.

From-SVN: r239146

gcc/ChangeLog

+2016-08-04  Patrick Palka  <ppalka@gcc.gnu.org>
+
+	* gimple.c (preprocess_case_label_vec_for_gimple): When the case
+	labels are exhaustive, designate the label with the widest
+	range to be the default label.
+
 2016-08-04  Andrew Pinski  <apinski@cavium.com>
 
 	* config/aarch64/aarch64.c (thunderx_vector_cost): New variable.

gcc/gimple.c

@@ -2946,18 +2946,30 @@ preprocess_case_label_vec_for_gimple (vec<tree> labels,
 	    high = CASE_LOW (labels[len - 1]);
 	  if (tree_int_cst_equal (high, TYPE_MAX_VALUE (index_type)))
 	    {
+	      tree widest_label = labels[0];
 	      for (i = 1; i < len; i++)
 		{
 		  high = CASE_LOW (labels[i]);
 		  low = CASE_HIGH (labels[i - 1]);
 		  if (!low)
 		    low = CASE_LOW (labels[i - 1]);
+
+		  if (CASE_HIGH (labels[i]) != NULL_TREE
+		      && (CASE_HIGH (widest_label) == NULL_TREE
+			  || wi::gtu_p (wi::sub (CASE_HIGH (labels[i]),
+						 CASE_LOW (labels[i])),
+					wi::sub (CASE_HIGH (widest_label),
+						 CASE_LOW (widest_label)))))
+		    widest_label = labels[i];
+
 		  if (wi::add (low, 1) != high)
 		    break;
 		}
 	      if (i == len)
 		{
-		  tree label = CASE_LABEL (labels[0]);
+		  /* Designate the label with the widest range to be the
+		     default label.  */
+		  tree label = CASE_LABEL (widest_label);
 		  default_case = build_case_label (NULL_TREE, NULL_TREE,
 						   label);
 		}

gcc/testsuite/ChangeLog

+2016-08-04  Patrick Palka  <ppalka@gcc.gnu.org>
+
+	* gcc.dg/switch-10.c: New test.
+
 2016-08-04  James Greenhalgh  <james.greenhalgh@arm.com>
 
 	* gcc.c-torture/execute/pr70903.c: Remove duplicate test body.

gcc/testsuite/gcc.dg/switch-10.c

+/* { dg-options "-O2 -fdump-tree-cfg" }  */
+/* { dg-final { scan-tree-dump "case 0:" "cfg" } }  */
+/* { dg-final { scan-tree-dump-not "case 1 ... 255:" "cfg" } }  */
+#include <stdint.h>
+
+void foo (void);
+void bar (void);
+
+void
+test (uint8_t ch)
+{
+  switch (ch)
+   {
+   case 0:
+     foo ();
+     break;
+
+   case 1 ... 255:
+     bar ();
+     break;
+   }
+}