* config/avr/avr.c (avr_override_options, avr_init_once,
function_prologue, function_epilogue, frame_pointer_required_p,
class_likely_spilled_p, order_regs_for_local_alloc,
avr_address_cost, avr_ret_register): Use K&R style arguments.
(initial_elimination_offset, gas_output_limited_string):
Remove ATTRIBUTE_UNUSED from the used arguments.
(output_mov*, out_mov*_r_mr, out_mov*_mr_r, output_reload_insisf):
Use local variables src, dest, base to access operands[].
Rename reg_dest to reg_src if that's what it is.
(output_movhi, output_movsisf): Optimize loading 8-bit immediate
constants to LD_REGS if reg_was_0.
(output_reload_insisf): Change arg 3 to insn length and set it.
(out_movhi_r_mr, out_movhi_mr_r): Use in/out for more efficient
access to 16-bit I/O register pairs.
(avr_address_cost): Lower cost for the above case.
(out_tsthi): Use "or" (faster) instead of "sbiw" if the operand
may be clobbered, also for LD_REGS.
(adjust_insn_length): Correct insn length for iorhi3 and iorsi3
with a CONST_INT.
* config/avr/avr.h (PTRDIFF_TYPE): Make signed.
* config/avr/avr.md: Change all uses of the TEST_HARD_REG_CLASS
macro to test_hard_reg_class function.
(*movsi, *movsf): Change "cc" attribute from "clobber" to "none"
for loading immediate constants to LD_REGS.
(andsi3, cmphi, cmpsi): Add return statements to avoid warnings.