[RS6000] rs6000_output_mi_thunk tidy

Since svn r123193 (git 327202e27a) the comment about scratch regs was
no longer correct, and I think gen_sibcall could have been used even
then.

	* gcc/config/rs6000/rs6000-call.c (rs6000_output_mi_thunk): Use
	gen_sibcall.

From-SVN: r273855

gcc/ChangeLog

 2019-07-28  Alan Modra  <amodra@gmail.com>
 
+	* gcc/config/rs6000/rs6000-call.c (rs6000_output_mi_thunk): Use
+	gen_sibcall.
+
+2019-07-28  Alan Modra  <amodra@gmail.com>
+
 	PR target/91135
 	* config/rs6000/linux.h (GNU_USER_TARGET_D_OS_VERSIONS): Don't
 	define.

gcc/config/rs6000/rs6000-call.c

@@ -8099,20 +8099,7 @@ rs6000_output_mi_thunk (FILE *file, tree thunk_fndecl ATTRIBUTE_UNUSED,
   funexp = XEXP (DECL_RTL (function), 0);
   funexp = gen_rtx_MEM (FUNCTION_MODE, funexp);
 
-#if TARGET_MACHO
-  if (MACHOPIC_INDIRECT)
-    funexp = machopic_indirect_call_target (funexp);
-#endif
-
-  /* gen_sibcall expects reload to convert scratch pseudo to LR so we must
-     generate sibcall RTL explicitly.  */
-  insn = emit_call_insn (
-	   gen_rtx_PARALLEL (VOIDmode,
-	     gen_rtvec (3,
-			gen_rtx_CALL (VOIDmode,
-				      funexp, const0_rtx),
-			gen_rtx_USE (VOIDmode, const0_rtx),
-			simple_return_rtx)));
+  insn = emit_call_insn (gen_sibcall (funexp, const0_rtx, const0_rtx));
   SIBLING_CALL_P (insn) = 1;
   emit_barrier ();