rs6000.md (stfiwx): Change constraint to 'wu' to prevent generation of 'stxsiwx'…

rs6000.md (stfiwx): Change constraint to 'wu' to prevent generation of 'stxsiwx' on pre Power8 hardware.

	* config/rs6000/rs6000.md (stfiwx): Change constraint to 'wu' to
	prevent generation of 'stxsiwx' on pre Power8 hardware.

From-SVN: r238223

gcc/ChangeLog

+2016-07-11  Pat Haugen  <pthaugen@us.ibm.com>
+
+	PR target/71800
+	* config/rs6000/rs6000.md (stfiwx): Change constraint to 'wu' to
+	prevent generation of 'stxsiwx' on pre Power8 hardware.
+
 2016-07-11  David Malcolm  <dmalcolm@redhat.com>
 
 	* input.c: Include cpplib.h.

gcc/config/rs6000/rs6000.md

@@ -5747,9 +5747,11 @@
 })
 
 ; An UNSPEC is used so we don't have to support SImode in FP registers.
+; The 'wu' constraint is used for the 2nd alternative to ensure stxsiwx
+; is only generated for Power8 or later.
 (define_insn "stfiwx"
   [(set (match_operand:SI 0 "memory_operand" "=Z,Z")
-	(unspec:SI [(match_operand:DI 1 "gpc_reg_operand" "d,wv")]
+	(unspec:SI [(match_operand:DI 1 "gpc_reg_operand" "d,wu")]
 		   UNSPEC_STFIWX))]
   "TARGET_PPC_GFXOPT"
   "@