Stage-3 bootstrap

Implements a full assembler that supports text-format instructions, macros, and labels up to 15 characters long.

TODO

• Multi-file support
• Multiple register push/pop

Syntax

The first character read from a line determines the behaviour of this assembler:

• #: Comment (ignore text until newline)
• =abcd: Defines a 2-byte (16-bit) hex constant
• :abcdefgh: Defines a global label
• .abcdefgh: Defines a local label (local to the enclosing global)
• tab: Assemble (copy) chars to output until a newline
• newline: Blank line, skipped

Instruction set

Instruction	Expansion	Notes
data ...	...	Literal data. Use backslash hex for escapes (\00, \ff)
mov? r1, r2	=?12	Loads a register from another
ldc r1,	=\$1	Load constant
ldh r1, #2345	=#1 2345	Load register
ldh r1, 'c'	=!1c	Load char constant
ldb [r1], r2	=[12	Load byte
ldw [r1], r2	={12	Load word
ldd [r1], r2	=(12	Load double word
stb [r1], r2	[=12	Store byte
stw [r1], r2	{=12	Store word
std [r1], r2	(=12	Store double word
add? r1, r2	+?12	Add with optional condition
sub? r1, r2	-?12	Subtract with optional condition
mul? r1, r2	*?12	Multiply with optional condition
div? r1, r2	/?12	Divide with optional condition
mod? r1, r2	%?12	Modulo with optional condition
or? r1, r2	|?12	Bitwise OR with optional condition
and? r1, r2	&?12	Bitwise AND with optional condition
xor? r1, r2	^?12	Bitwise XOR with optional condition
eq r1, r2	?=12	Compare equal
ne r1, r2	?!12	Compare not equal
gt r1, r2	?>12	Compare greater than
lt r1, r2	?<12	Compare less than
push r1	- yd(=y1	Push to stack
pop r1	=(1y+ yd	Pop from stack
sys r1	S 1	System call with 1 argument
sys r1, r2	S 12	System call with 2 arguments
sys r1, r2, r3	S+123	System call with 3 arguments
sys r1, r2, r3, r4	S+1234	System call with 4 arguments
sys r1, r2, r3, r4, r5	S+12345	System call with 5 arguments
sys r1, r2, r3, r4, r5, r6	S+123456	System call with 6 arguments
jump	=$z	Unconditional jump
jump^	+?ze=$z	Jump if flag
jump?	+^ze=$z	Jump if not zero
ret	=(xy+ yd= zx	Unconditional return
ret?	=(xy+?yd=?zx	Conditional return
call	- yd=#x 000c+ xz(=yx=$z	Function call
db 0	\00	Define zero byte
dw 0	\00\00	Define zero word
dd 0	\00\00\00\00	Define zero double word