[メモ]mips reference #MIPS

参考リンク

Computer Organization and Design MIPS Edition, Fifth Edition: The Hardware/Software Interface (The Morgan Kaufmann Series in Computer Architecture and Design)
MIPS Reference Data Card 上の本の付録
qtspim .. http://spimsimulator.sourceforge.net/
qtspim tutorial .. https://ecs-network.serv.pacific.edu/ecpe-170/tutorials/qtspim-tutorial

instruction

jal .. The instruction actually saves PC+4 in register $ra to link to the following instruction to set up the procedure return (as call in x86)

jr $ra .. Same as ret in x86

mnemonic

Mnemonic	Meaning	Type	Opcode	Funct
add	Add	R	0x00	0x20
addi	Add immediate	I	0x08	NA
addiu	Addi unsigned	I	0x09	NA
addu	Add unsigned	R	0x00	0x21
and	Bitwise AND	R	0x00	0x24
andi	Bitwise AND Immediate	I	0x0C	NA
beq	Branch if Equal	I	0x04	NA
blez	Branch if Less Than or Equal to Zero	I	0x06	NA
bne	Branch if Not Equal	I	0x05	NA
div	Divide	R	0x00	0x1A
divu	Unsigned Divide	R	0x00	0x1B
j	Jump to Address	J	0x02	NA
jal	Jump and Link	J	0x03	NA
jr	Jump to Address in Register	R	0x00	0x08
lbu	Load Byte Unsigned	I	0x24	NA
lhu	Load Halfword Unsigned	I	0x25	NA
lui	Load Upper Immediate	I	0x0F	NA
lw	Load Word	I	0x23	NA
mfhi	Move from HI Register	R	0x00	0x10
mflo	Move from LO Register	R	0x00	0x12
mfc0	Move from Coprocessor 0	R	0x10	NA
mult	Multiply	R	0x00	0x18
multu	Unsigned Multiply	R	0x00	0x19
nor	Bitwise NOR (NOT-OR)	R	0x00	0x27
xor	Bitwise XOR (Exclusive-OR)	R	0x00	0x26
or	Bitwise OR	R	0x00	0x25
ori	Bitwise OR Immediate	I	0x0D	NA
sb	Store Byte	I	0x28	NA
sh	Store Halfword	I	0x29	NA
slt	Set to 1 if Less Than	R	0x00	0x2A
slti	Set to 1 if Less Than Immediate	I	0x0A	NA
sltiu	Set to 1 if Less Than Unsigned Immediate	I	0x0B	NA
sltu	Set to 1 if Less Than Unsigned	R	0x00	0x2B
sll	Logical Shift Left	R	0x00	0x00
srl	Logical Shift Right (0-extended)	R	0x00	0x02
sra	Arithmetic Shift Right (sign-extended)	R	0x00	0x03
sub	Subtract	R	0x00	0x22
subu	Unsigned Subtract	R	0x00	0x23
sw	Store Word	I	0x2B	NA

https://inst.eecs.berkeley.edu/~cs61c/resources/MIPS_help.html もいい感じにまとまっている

example

I-type

instruction	instr	opcode	rs	rt	immediate	remarks
bits	31:0	31:26	25:21	20:16	15:0
`addi $s0, $0, 5`	`addi $rt, $rs, imm`	0x08	0x00($0)	0x10	0x05
`lw $s0, 100($1)`	`lw $rt, imm($rs)`	0x23	0x11	0x10	0x64
`sw $s0, 100($1)`	`sw $rt, imm($rs)`	0x2B	0x11	0x10	0x64	lwと逆の操作だが、rs, rtは同じ

R-type

instruction	instr	opcode	rs	rt	rd	shamt	funct
bits	31:0	31:26	25:21	20:16	15:11	10:6	5:0
`sll $t2, $s0, 4`	`sll $rd, $rt, shamt`	0x00	0x00	0x10	0x0a	0x04	0x00
`and $t2, $s0, $s1`	`and $rd, $rs, $rt`	0x00	0x10	0x11	0x0a	0x00	0x24

addressing

registers

$at .. assembler temporary. This is used to store the immediate number that is parted by the 32-Bit Immediate Operands like lui(load upper immediate).
PC(Program counter): Instruction address register. The register holds the address of the current instruction being executed.
$k0-$k1 Reserved for OS Kernel

syscall

spim はあくまでmipsシミュレータなので、本格的なオペレーティングシステムはもっていないが、入出力ができないと不便なので、簡単なOS的な機能を持っている。それを呼び出すと入出力ができる。

exec

memory layout

Fig2.13 The MIPS memory allocation for program and data.

R29 [sp] = 7fffeffcとあるので、stack領域-0x1000で0x1000[byte]分なんかに使っているみたい(環境変数が入ってる??)

main

mainのentrypointは0x00400024でそれまで何をしてるか。

# Register number
## $v0-$v1 .. 2-3, $a0-$a3 .. 4-7, $sp .. 29, $ra .. 31
User Text Segment [00400000]..[00440000]
## argc
[00400000] 8fa40000  lw $4, 0($29)            ; 183: lw $a0 0($sp)
## argv
[00400004] 27a50004  addiu $5, $29, 4         ; 184: addiu $a1 $sp 4
## envp 
[00400008] 24a60004  addiu $6, $5, 4          ; 185: addiu $a2 $a1 4 
# Shift left by constant
[0040000c] 00041080  sll $2, $4, 2            ; 186: sll $v0 $a0 2 
[00400010] 00c23021  addu $6, $6, $2          ; 187: addu $a2 $a2 $v0 
# For procedure call(jump and link)
[00400014] 0c100009  jal 0x00400024 [main]    ; 188: jal main 
[00400018] 00000000  nop                      ; 189: nop
# no longer execute
## syscall 10 (exit)
[0040001c] 3402000a  ori $2, $0, 10           ; 191: li $v0 10 
[00400020] 0000000c  syscall                  ; 192: syscall
# この後、mainのentrypoint