Handle WORD_REGISTER_OPERATIONS when reloading (subreg (reg))

gcc/
	PR target/78660
	* lra-constraints.c (curr_insn_transform): Handle
	WORD_REGISTER_OPERATIONS requirements when reloading SUBREGs.

From-SVN: r245598

gcc/ChangeLog

+2017-02-20  Matthew Fortune  <matthew.fortune@imgtec.com>
+
+	PR target/78660
+	* lra-constraints.c (curr_insn_transform): Handle
+	WORD_REGISTER_OPERATIONS requirements when reloading SUBREGs.
+
 2017-02-19  Uros Bizjak  <ubizjak@gmail.com>
 
 	Revert:

gcc/lra-constraints.c

@@ -4130,7 +4130,15 @@ curr_insn_transform (bool check_only_p)
 			  && (goal_alt[i] == NO_REGS
 			      || (simplify_subreg_regno
 				  (ira_class_hard_regs[goal_alt[i]][0],
-				   GET_MODE (reg), byte, mode) >= 0)))))
+				   GET_MODE (reg), byte, mode) >= 0)))
+		      /* WORD_REGISTER_OPERATIONS targets require the register
+			 to be reloaded when the outer mode is strictly
+			 narrower than the inner mode.  Note: It may be
+			 necessary to always reload the inner mode here but it
+			 requires further investigation.  */
+		      || (GET_MODE_PRECISION (mode)
+			  < GET_MODE_PRECISION (GET_MODE (reg))
+			  && WORD_REGISTER_OPERATIONS)))
 		{
 		  if (type == OP_OUT)
 		    type = OP_INOUT;