[RS6000] lqarx and stqcx. registers

lqarx RT and stqcx. RS are valid only with even numbered gprs.  The
predicate to enforce this happens to allow a loophole, closed by this
patch.

	PR target/69548
gcc/
	* config/rs6000/predicates.md (quad_int_reg_operand): Don't
	allow subregs.
gcc/testsuite/
	* gcc.target/powerpc/pr69548.c: New test.

From-SVN: r233065

gcc/ChangeLog

 2016-02-02  Alan Modra  <amodra@gmail.com>
 
+	PR target/69548
+	* config/rs6000/predicates.md (quad_int_reg_operand): Don't
+	allow subregs.
+
+2016-02-02  Alan Modra  <amodra@gmail.com>
+
 	PR target/68662
 	* config/rs6000/rs6000.c (need_toc_init): New var, set it
 	whenever toc_label_name used.

gcc/config/rs6000/predicates.md

@@ -375,20 +375,19 @@
 
 ;; Return 1 if op is a general purpose register that is an even register
 ;; which suitable for a load/store quad operation
+;; Subregs are not allowed here because when they are combine can
+;; create (subreg:PTI (reg:TI pseudo)) which will cause reload to
+;; think the innermost reg needs reloading, in TImode instead of
+;; PTImode.  So reload will choose a reg in TImode which has no
+;; requirement that the reg be even.
 (define_predicate "quad_int_reg_operand"
-  (match_operand 0 "register_operand")
+  (match_code "reg")
 {
   HOST_WIDE_INT r;
 
   if (!TARGET_QUAD_MEMORY && !TARGET_QUAD_MEMORY_ATOMIC)
     return 0;
 
-  if (GET_CODE (op) == SUBREG)
-    op = SUBREG_REG (op);
-
-  if (!REG_P (op))
-    return 0;
-
   r = REGNO (op);
   if (r >= FIRST_PSEUDO_REGISTER)
     return 1;

gcc/testsuite/ChangeLog

+2016-02-02  Alan Modra  <amodra@gmail.com>
+
+	PR target/69548
+	* gcc.target/powerpc/pr69548.c: New test.
+
 2016-02-01  Jakub Jelinek  <jakub@redhat.com>
 
 	PR rtl-optimization/69592

gcc/testsuite/gcc.target/powerpc/pr69548.c

+/* { dg-do assemble { target { powerpc*-*-* && lp64 } } } */
+/* { dg-skip-if "" { powerpc*-*-darwin* } { "*" } { "" } } */
+/* { dg-require-effective-target powerpc_p8vector_ok } */
+/* { dg-skip-if "do not override -mcpu" { powerpc*-*-* } { "-mcpu=*" } { "-mcpu=power8" } } */
+/* { dg-options "-mcpu=power8 -Os -mbig" } */
+
+__int128
+quad_exchange (__int128 *ptr, __int128 newval)
+{
+  return __atomic_exchange_n (ptr, newval, __ATOMIC_RELAXED);
+}