[APX NF] Add a pass to convert legacy insn to NF insns

[APX NF] Add a pass to convert legacy insn to NF insns

For APX ccmp, current infrastructure will always generate cstore for
the ccmp flag user, like

	cmpe    %rcx, %r8
	ccmpnel %rax, %rbx
	seta	%dil
	add	%rcx, %r9
	add     %r9, %rdx
	testb   %dil, %dil
	je	.L2

For such case, the legacy add clobbers FLAGS_REG so there should have
extra cstore to avoid the flag be reset before using it. If the
instructions between flag producer and user are NF insns, the setcc/
test sequence is not required.

Add a pass to convert legacy flag clobber insns to their NF counterpart.
The convertion only happens when
1. APX_NF enabled.
2. For a BB, cstore was find, and there are insns between such cstore
and next explicit set insn to FLAGS_REG (test or cmp).
3. All the insns found should have NF counterpart.

The pass was added after rtl-ifcvt which eliminates some branch when
profitable, which could cause some flag-clobbering insn put between
cstore and jcc.

gcc/ChangeLog:

	* config/i386/i386.md (has_nf): New define_attr, add to all
	nf related patterns.
	* config/i386/i386-features.cc (apx_nf_convert): New function
	to convert Non-NF insns to their NF counterparts.
	(class pass_apx_nf_convert): New pass class.
	(make_pass_apx_nf_convert): New.
	* config/i386/i386-passes.def: Add pass_apx_nf_convert after
	rtl_ifcvt.
	* config/i386/i386-protos.h (make_pass_apx_nf_convert): Declare.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/apx-nf-2.c: New test.