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
