.global bcd_add
bcd_add:
	xchg %rax, %rdi

	mov %cl, %ch
	mov %al, %ah
	and $0xF, %ch
	and $0xF, %ah
	and $0xF0, %cl
	and $0xF0, %al
	add %ah, %ch
	cmp $10, %ch
	jb no_adjust
	add $6, %ch
no_adjust:
	add %ch, %al
	add %al, %cl
	mov $0, %ch
	jc def_adjust
	cmp $0xA0, %cl
	jb no_adjust_h
def_adjust:
	add $0x60, %cl
	mov $1, %ch
no_adjust_h:

	mov %rdi, %rax
	ret

	.global bcd_sub
bcd_sub:
	xchg %rax, %rdi

	mov %cl, %ch
	mov %al, %ah
	and $0xF, %ch
	and $0xF, %ah
	and $0xF0, %cl
	and $0xF0, %al
	sub %ah, %ch
	cmp $10, %ch
	jb no_adjusts
	sub $6, %ch
no_adjusts:
	add %ch, %cl
	sub %al, %cl
	mov $0, %ch
	jc def_adjusts
	cmp $0xA0, %cl
	jb no_adjust_hs
def_adjusts:
	sub $0x60, %cl
	mov $1, %ch
no_adjust_hs:

	mov %rdi, %rax
	ret