Allow try_split to split RTX_FRAME_RELATED_P insns

Allow try_split to split RTX_FRAME_RELATED_P insns

Instead of rejecting RTX_FRAME_RELATED_P insns, allow try_split to split
such insns, provided the split is after reload, and the result of the split
is a single insn.

recog.c:peep2_attempt already splits an RTX_FRAME_RELATED_P insn splitting
to a single insn. This patch refactors existing code copying frame related
info to a separate function (copy_frame_info_to_split_insn) and calls it
from both peep2_attempt and try_split.

2020-08-21  Senthil Kumar Selvaraj  <saaadhu@gcc.gnu.org>

gcc/ChangeLog:

	* emit-rtl.c (try_split): Call copy_frame_info_to_split_insn
	to split certain RTX_FRAME_RELATED_P insns.
	* recog.c (copy_frame_info_to_split_insn): New function.
	(peep2_attempt): Split copying of frame related info of
	RTX_FRAME_RELATED_P insns into above function and call it.
	* recog.h (copy_frame_info_to_split_insn): Declare it.