re PR other/50925 ([avr] ICE at spill_failure, at reload1.c:2118)

re PR other/50925 ([avr] ICE at spill_failure, at reload1.c:2118)

	PR target/50925
	* config/avr/avr-protos.h (avr_hard_regno_nregs): Declare.
	* config/avr/avr.c (avr_can_eliminate): Simplify.
	(avr_initial_elimination_offset): Likewise.
	(avr_prologue_setup_frame): Use hard_frame_pointer_rtx.
	(expand_epilogue): Likewise.
	(avr_legitimize_address): Gut.
	(avr_legitimize_reload_address): Use hard_frame_pointer_rtx.
	(avr_hard_regno_nregs): New.
	(avr_hard_regno_ok): Allow only Pmode for arg and frame_pointers.
	(avr_regno_mode_code_ok_for_base_b): Handle arg and frame pointers.
	* config/avr/avr.h (FIXED_REGISTERS): Adjust arg pointer,
	add soft frame pointer.
	(CALL_USED_REGISTERS): Likewise.
	(REG_CLASS_CONTENTS): Likewise.
	(REGISTER_NAMES): Likewise.
	(HARD_REGNO_NREGS): Use avr_hard_regno_nregs.
	(HARD_FRAME_POINTER_REGNUM): New.
	(FRAME_POINTER_REGNUM): Use soft frame pointer.
	(ELIMINABLE_REGS): Eliminate from the soft frame pointer,
	remove the HARD_FRAME_POINTER self-elimination.

Co-Authored-By: Denis Chertykov <chertykov@gmail.com>
From-SVN: r183136