S/390: Don't fetch the return address early with ooo

We used to load the return address slot some time in advance.  This
helped on older machines to resolve the data dependencies in time.
However, it is pointless on out of order CPUs.  Disabled with that
patch.

gcc/ChangeLog:

2017-06-01  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* config/s390/s390.c (s390_emit_epilogue): Disable early return
	address fetch for z10 or later.

From-SVN: r248789

gcc/ChangeLog

+2017-06-01  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>
+
+	* config/s390/s390.c (s390_emit_epilogue): Disable early return
+	address fetch for z10 or later.
+
 2017-06-01  Claudiu Zissulescu  <claziss@synopsys.com>
 
 	* config/arc/arc.md (tst_movb): Add guard when splitting.

gcc/config/s390/s390.c

@@ -11410,8 +11410,6 @@ s390_emit_epilogue (bool sibcall)
 				gen_rtx_REG (Pmode, i), cfa_restores);
 	}
 
-      if (! sibcall)
-	{
       /* Fetch return address from stack before load multiple,
 	 this will do good for scheduling.
 
@@ -11419,8 +11417,12 @@ s390_emit_epilogue (bool sibcall)
 	 saved to a stack slot. (And not just because r14 happens to
 	 be in between two GPRs which need saving.)  Otherwise it
 	 would be difficult to take that decision back in
-	     s390_optimize_prologue.  */
-	  if (cfun_gpr_save_slot (RETURN_REGNUM) == SAVE_SLOT_STACK)
+	 s390_optimize_prologue.
+
+	 This optimization is only helpful on in-order machines.  */
+      if (! sibcall
+	  && cfun_gpr_save_slot (RETURN_REGNUM) == SAVE_SLOT_STACK
+	  && s390_tune <= PROCESSOR_2097_Z10)
 	{
 	  int return_regnum = find_unused_clobbered_reg();
 	  if (!return_regnum)
@@ -11437,12 +11439,11 @@ s390_emit_epilogue (bool sibcall)
 	  emit_move_insn (return_reg, addr);
 
 	  /* Once we did that optimization we have to make sure
-		 s390_optimize_prologue does not try to remove the
-		 store of r14 since we will not be able to find the
-		 load issued here.  */
+	     s390_optimize_prologue does not try to remove the store
+	     of r14 since we will not be able to find the load issued
+	     here.  */
 	  cfun_frame_layout.save_return_addr_p = true;
 	}
-	}
 
       insn = restore_gprs (frame_pointer,
 			   offset + cfun_frame_layout.gprs_offset