Support using multiple registers to hold the frame pointer

Support using multiple registers to hold the frame pointer

When multiple hard registers are required to hold the frame pointer,
ensure that the registers after the first are marked as non-allocatable,
live and eliminable as well.

2019-11-07  Kwok Cheung Yeung  <kcy@codesourcery.com>

	gcc/
	* ira.c (setup_alloc_regs): Setup no_unit_alloc_regs for
	frame pointer in multiple registers.
	(ira_setup_eliminable_regset): Setup eliminable_regset,
	ira_no_alloc_regs and regs_ever_live for frame pointer in
	multiple registers.

From-SVN: r277895