re PR target/46278 (avr-gcc 4.5.1 doing suboptimal reloads using X)

re PR target/46278 (avr-gcc 4.5.1 doing suboptimal reloads using X)

	PR target/46278
	* doc/invoke.texi (AVR Options): Document -mstrict-X.
	* config/avr/avr.opt (-mstrict-X): New option.
	(avr_strict_X): New variable reflecting -mstrict-X.
	* config/avr/avr.c (avr_reg_ok_for_addr_p): Add parameter
	outer_code and pass it down to avr_regno_mode_code_ok_for_base_p.
	(avr_legitimate_address_p): Pass outer_code to
	avr_reg_ok_for_addr_p and use that function in case PLUS.
	(avr_mode_code_base_reg_class): Depend on avr_strict_X.
	(avr_regno_mode_code_ok_for_base_p): Ditto, and depend on outer_code.
	(avr_option_override): Disable -fcaller-saves if -mstrict-X is on.

From-SVN: r179993