instructions.md

Instructions in assembler and in the VM

Here is a list of available instructions.

Arithmetic and logical operations

OPCODE	Mnemonic	Function	Semantics	Format
2	add rd rs1 rs2	addition	rd <= rs1 + rs2	R
3	add rd rs im	addition	rd <= rs1 + im	I
4	sub rd rs1 rs2	substraction	rd <= rs1 - rs2	R
5	sub rd rs im	substraction	rd <= rs1 - im	I
6	mul rd rs1 rs2	multiplication signed	rd <= rs1 * rs2	R
7	mul rd rs im	multiplication signed	rd <= rs1 * im	I
8	div rd rs1 rs2	signed integer division	rd <= rs1 / rs2	R
9	div rd rs im	signed integer division	rd <= rs1 / im	I
10	and rd rs1 rs2	logical bitwise AND	rd <= rs1 & rs2	R
11	and rd rs im	logical bitwise AND	rd <= rs1 & im	I
12	or rd rs1 rs2	logical bitwise OR	rd <= rs1 | rs2	R
13	or rd rs im	logical bitwise OR	rd <= rs1 | im	I
14	xor rd rs1 rs2	exclusive logical bitwise OR	rd <= rs1 ^ rs2	R
15	xor rd rs im	exclusive logical bitwise OR	rd <= rs1 ^ im	I
16	shl rd rs1 rs2	shift left	rd <= rs1 << rs2	R
17	shl rd rs im	shift left	rd <= rs1 << im	I
18	shr rd rs1 rs2	shift right	rd <= rs1 >> rs2	R
19	shr rd rs im	shift right	rd <= rs1 >> im	I

Comparison operations

OPCODE	Mnemonic	Function	Semantics	Format
20	slt rd rs1 rs2	set lower than	rd <= (rs1 < rs2) ? 1 : 0	R
21	slt rd rs im	set lower than	rd <= (rs1 < im) ? 1 : 0	I
22	sle rd rs1 rs2	set lower equal	rd <= (rs1 <= rs2) ? 1 : 0	R
23	sle rd rs im	set lower equal	rd <= (rs1 <= im) ? 1 : 0	I
24	seq rd rs1 rs2	set equal	rd <= (rs1 = rs2) ? 1 : 0	R
25	seq rd rs im	set equal	rd <= (rs1 = im) ? 1 : 0	I

Load and Store

OPCODE	Mnemonic	Function	Semantics	Format
27	load rd ra offset	read memory	rd <= mem[ra + offset]	I
29	store rs ra offset	write memory	mem[ra + offset] <= rs	I

Connections

OPCODE	Mnemonic	Function	Semantics	Format
30	jmp rd ra	jump and link register	rd <= PC ; PC <= ra	JR
31	jmp rd addr	jump and link immediate	rd <= PC ; PC <= addr	JI
32	braz rs addr	branch if zero	if (rs = 0) {PC <= addr}	B
33	branz rs addr	branch if not zero	if (rs != 0) {PC <= addr}	B

System calls

OPCODE	Mnemonic	Function	Semantics	Format
34	scall n	System call		S
	scall 0	Read number	r20 <= number from keyboard
	scall 1	Write number	print r20 on screen
	scall 3	Write char	print r20 as a 7-bit character
	scall 4	Write string	write string pointed to by r20

Stop the machine

OPCODE	Mnemonic	Function	Semantics	Format
35	stop	Stop the processor		H