[AArch64] Add FFR and FFRT registers

[AArch64] Add FFR and FFRT registers

This patch adds the First Fault Register to the AArch64 port, as well
as a fake register known as the FFR Token or FFRT.  The main ACLE
patch explains what the FFRT does and how it works.

2019-10-29  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/aarch64/aarch64.md (FFR_REGNUM, FFRT_REGNUM): New constants.
	* config/aarch64/aarch64.h (FIRST_PSEUDO_REGISTER): Bump to
	FFRT_REGNUM + 1.
	(FFR_REGS, PR_AND_FFR_REGS): New register classes.
	(REG_CLASS_NAMES, REG_CLASS_CONTENTS): Add entries for them.
	* config/aarch64/aarch64.c (pr_or_ffr_regnum_p): New function.
	(aarch64_hard_regno_nregs): Handle the new register classes.
	(aarch64_hard_regno_mode_ok): Likewise.
	(aarch64_regno_regclass): Likewise.
	(aarch64_class_max_nregs): Likewise.
	(aarch64_register_move_cost): Likewise.
	(aarch64_conditional_register_usage): Don't treat FFR and FFRT
	as general register_operands.

From-SVN: r277561