combine: Don't make an intermediate reg for assigning to sfp (PR87871)

The code with an intermediate register is perfectly fine, but LRA
apparently cannot handle the resulting code, or perhaps something else
is wrong.  In either case, making an extra temporary will not likely
help here, so let's just skip it.


	PR rtl-optimization/87871
	* combine.c (make_more_copies): Skip if dest is frame_pointer_rtx.

From-SVN: r265821

gcc/ChangeLog

+2018-11-05  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR rtl-optimization/87871
+	* combine.c (make_more_copies): Skip if dest is frame_pointer_rtx.
+
 2018-11-05  Paul Koning  <ni1d@arrl.net>
 
 	* doc/sourcebuild.texi (target attributes): Document new "inf"

gcc/combine.c

@@ -14959,6 +14959,9 @@ make_more_copies (void)
 	  rtx dest = SET_DEST (set);
 	  if (dest == pc_rtx)
 	    continue;
+	  /* See PR87871.  */
+	  if (dest == frame_pointer_rtx)
+	    continue;
 	  rtx src = SET_SRC (set);
 	  if (!(REG_P (src) && HARD_REGISTER_P (src)))
 	    continue;