re PR target/84406 ([MSP430] ICE on valid code in…

re PR target/84406 ([MSP430] ICE on valid code in find_widening_optab_handler_and_mode, at optabs-query.c:476)

	PR middle-end/84406
	* optabs-query.c (find_widening_optab_handler_and_mode): If from_mode
	is a scalar_int_mode, assert that to_mode is a scalar_int_mode with
	greater precision.  If to_mode is a MODE_PARTIAL_INT, stop the
	search at the associated MODE_INT.

From-SVN: r257858

gcc/ChangeLog

+2018-02-20  Richard Sandiford  <richard.sandiford@linaro.org>
+
+	PR middle-end/84406
+	* optabs-query.c (find_widening_optab_handler_and_mode): If from_mode
+	is a scalar_int_mode, assert that to_mode is a scalar_int_mode with
+	greater precision.  If to_mode is a MODE_PARTIAL_INT, stop the
+	search at the associated MODE_INT.
+
 2018-02-20  Jeff Law  <law@redhat.com>
 
 	PR middle-end/82123

gcc/optabs-query.c

@@ -473,9 +473,23 @@ find_widening_optab_handler_and_mode (optab op, machine_mode to_mode,
 				      machine_mode from_mode,
 				      machine_mode *found_mode)
 {
-  gcc_checking_assert (GET_MODE_CLASS (from_mode) == GET_MODE_CLASS (to_mode));
-  gcc_checking_assert (from_mode < to_mode);
-  FOR_EACH_MODE (from_mode, from_mode, to_mode)
+  machine_mode limit_mode = to_mode;
+  if (is_a <scalar_int_mode> (from_mode))
+    {
+      gcc_checking_assert (is_a <scalar_int_mode> (to_mode)
+			   && known_lt (GET_MODE_PRECISION (from_mode),
+					GET_MODE_PRECISION (to_mode)));
+      /* The modes after FROM_MODE are all MODE_INT, so the only
+	 MODE_PARTIAL_INT mode we consider is FROM_MODE itself.
+	 If LIMIT_MODE is MODE_PARTIAL_INT, stop at the containing
+	 MODE_INT.  */
+      if (GET_MODE_CLASS (limit_mode) == MODE_PARTIAL_INT)
+	limit_mode = GET_MODE_WIDER_MODE (limit_mode).require ();
+    }
+  else
+    gcc_checking_assert (GET_MODE_CLASS (from_mode) == GET_MODE_CLASS (to_mode)
+			 && from_mode < to_mode);
+  FOR_EACH_MODE (from_mode, from_mode, limit_mode)
     {
       enum insn_code handler = convert_optab_handler (op, to_mode, from_mode);