re PR tree-optimization/84740 (ICE in build_constructors, at tree-switch-conversion.c:965)

	PR tree-optimization/84740
	* tree-switch-conversion.c (process_switch): Call build_constructors
	only if info.phi_count is non-zero.

	* gcc.dg/torture/pr84740.c: New test.

From-SVN: r258354

gcc/ChangeLog

 2018-03-08  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/84740
+	* tree-switch-conversion.c (process_switch): Call build_constructors
+	only if info.phi_count is non-zero.
+
 	PR tree-optimization/84739
 	* tree-tailcall.c (find_tail_calls): Check call arguments against
 	DECL_ARGUMENTS (current_function_decl) rather than

gcc/testsuite/ChangeLog

 2018-03-08  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/84740
+	* gcc.dg/torture/pr84740.c: New test.
+
 	PR tree-optimization/84739
 	* gcc.dg/pr84739.c: New test.
 

gcc/testsuite/gcc.dg/torture/pr84740.c

+/* PR tree-optimization/84740 */
+
+void
+frobulate_for_gcc (unsigned int v)
+{
+  const char *s;
+  switch (v)
+    {
+    case 0:
+      s = "foo";
+      break;
+    case 1:
+      s = "bar";
+      break;
+    case 2:
+      s = "spam";
+      break;
+    default:
+      s = (const char *) 0;
+      break;
+    }
+  if (!s)
+    __builtin_printf ("%s\n", s);
+}

gcc/tree-switch-conversion.c

@@ -1563,7 +1563,8 @@ process_switch (gswitch *swtch)
   gather_default_values (info.default_case_nonstandard
 			 ? gimple_switch_label (swtch, 1)
 			 : gimple_switch_default_label (swtch), &info);
-  build_constructors (swtch, &info);
+  if (info.phi_count)
+    build_constructors (swtch, &info);
 
   build_arrays (swtch, &info); /* Build the static arrays and assignments.   */
   gen_inbound_check (swtch, &info);	/* Build the bounds check.  */