[ARC]Fast interrupts support.

[ARC]Fast interrupts support.

When a processor enters a fast interrupts handler, and duplicate
register banks are configured, the processor saves the user context by
saving the registers in the main register bank to these additional
registers in the duplicate register bank.  In this fast interrupt
context, when you specify the rgf_banked_regs option,the compiler does
not save the registers duplicated in the additional register bank are
not saved.

gcc/
2017-05-09  Claudiu Zissulescu  <claziss@synopsys.com>
	    Andrew Burgess  <andrew.burgess@embecosm.com>

	* config/arc/arc.c (ARC_AUTOBLINK_IRQ_P): Consider fast interrupts
	case also.
	(ARC_AUTOFP_IRQ_P): Likewise.
	(ARC_AUTO_IRQ_P): Likewise.
	(rgf_banked_register_count): New variable.
	(parse_mrgf_banked_regs_option): New function.
	(arc_override_options): Handle rgf_banked_regs option.
	(arc_handle_interrupt_attribute): Add firq option.
	(arc_compute_function_type): Return fast irq type when required.
	(arc_must_save_register): Handle fast interrupts.
	(arc_expand_prologue): Do not emit dwarf info for fast interrupts.
	(arc_return_address_regs): Update.
	* config/arc/arc.h (arc_return_address_regs): Update.
	(arc_function_type): Add fast interrupt type.
	(ARC_INTERRUPT_P): Update.
	(RC_FAST_INTERRUPT_P): Define.
	* config/arc/arc.md (simple_return): Update for fast interrupts.
	(p_return_i): Likewise.
	* config/arc/arc.opt (mrgf-banked-regs): New option.
	* doc/invoke.texi (mrgf-banked-regs): Document.

testsuite/
2017-05-09  Claudiu Zissulescu  <claziss@synopsys.com>
	    Andrew Burgess  <andrew.burgess@embecosm.com>

	* gcc.target/arc/firq-1.c: New file.
	* gcc.target/arc/firq-2.c: Likewise.
	* gcc.target/arc/firq-3.c: Likewise.
	* gcc.target/arc/firq-4.c: Likewise.
	* gcc.target/arc/firq-5.c: Likewise.
	* gcc.target/arc/firq-6.c: Likewise.

Co-Authored-By: Andrew Burgess <andrew.burgess@embecosm.com>
From-SVN: r247796