combine.c (subst): Use simplify_subreg_regno rather than REG_CANNOT_CHANGE_MODE_P to detect...

gcc/
	* combine.c (subst): Use simplify_subreg_regno rather than
	REG_CANNOT_CHANGE_MODE_P to detect invalid mode changes.

From-SVN: r215448

gcc/ChangeLog

 2014-09-22  Richard Sandiford  <richard.sandiford@arm.com>
 
+	* combine.c (subst): Use simplify_subreg_regno rather than
+	REG_CANNOT_CHANGE_MODE_P to detect invalid mode changes.
+
+2014-09-22  Richard Sandiford  <richard.sandiford@arm.com>
+
 	* rtl.h (subreg_info): Expand commentary
 	* rtlanal.c (subreg_get_info): Likewise.
 

gcc/combine.c

@@ -5121,15 +5121,13 @@ subst (rtx x, rtx from, rtx to, int in_dest, int in_cond, int unique_copy)
 		      )
 		    return gen_rtx_CLOBBER (VOIDmode, const0_rtx);
 
-#ifdef CANNOT_CHANGE_MODE_CLASS
 		  if (code == SUBREG
 		      && REG_P (to)
 		      && REGNO (to) < FIRST_PSEUDO_REGISTER
-		      && REG_CANNOT_CHANGE_MODE_P (REGNO (to),
-						   GET_MODE (to),
-						   GET_MODE (x)))
+		      && simplify_subreg_regno (REGNO (to), GET_MODE (to),
+						SUBREG_BYTE (x),
+						GET_MODE (x)) < 0)
 		    return gen_rtx_CLOBBER (VOIDmode, const0_rtx);
-#endif
 
 		  new_rtx = (unique_copy && n_occurrences ? copy_rtx (to) : to);
 		  n_occurrences++;