MIPS Instruction Set

Pavel I. Kryukov edited this page Jul 22, 2018 · 89 revisions

MIPS instructions are grouped by their semantics on this page.

If you want to get a list of instructions sorted by their opcodes, please check our C++ code file

If you want to see instructions in alphabet order, you may want to use MIPS IV reference and MIPS32 reference

Table of Contents

Instruction format

MIPS is a RISC processor, so every instruction has the same length — 32 bits (4 bytes). These bits have different meanings according to their displacement. They can be combined in following groups:

Name Size in bits Symbol Used for
Opcode 6 E Specification of instruction
Register specifications 5 s,t,d see below
Register-immediate 5 R Second part of opcode for instructions with 0x1 opcode
Shamt 5 S Constant value for shifts
Immediate constant value 16 C Immediate value for arithmetic and logical (AL) operations
Address 26 A Address for jumps and procedure calls
Funct 6 f Second part of opcode for instructions
Note: Even 26-bit field is called Address, it is never used for loads and stores!

Additionally, in tables below we may specify values explicitly:

  • 0|1 — plain bit values
  • - — ignored values

Register specificators

Register specificators are addresses of registers. They provide numbers of registers have source data and where machine should write result of instruction. MIPS supports instructions with up to 3 registers. They are named:

  • s-register (source)
  • t-register (target)
  • d-register (destination)
Note: s- and t- registers do not correspond to s0-s7 and t0-t7 registers described on MIPS Registers page. Here it is just notation

Additionally, MIPS RF contains a pair of special registers, HI and LO which are used to accumulate results of multiplication and division operations. In some cases they are concatenated to 2x size register notated as [HI, LO].

Address of register consists of 5 bits, so there can be 32 usable logical registers on one core.

Types of format

MIPS supports 5 main types of instruction format: R, I, RI, J, and SPECIAL2

Type name Max # of registers Immediate Instruction bits Used for
R 3 5 bits 000000ss sssttttt
dddddSSS SSffffff
AL and shift operations on registers
RI 1 16 bits 000001ss sssRRRRR
CCCCCCCC CCCCCCCC
Branches
I 2 16 bits EEEEEEss sssttttt
CCCCCCCC CCCCCCCC
AL operations with immediate values, load/stores, branches
J 0 26 bits EEEEEEAA AAAAAAAA
AAAAAAAA AAAAAAAA
Unconditional branches, procedure calls
Special2 3 5 bits 011100ss sssttttt
dddddSSS SSffffff
MIPS32 extenstions
Special3 3 5 bits 011111ss sssttttt
dddddSSS SSffffff
MIPS32 secret instructions

Reference sheet

Opcode

left\right digit 000 001 010 011 100 101 110 111
000 R RI j jal beq bne blez bgtz
001 addi addiu slti sltiu andi ori xori lui
010 COP0 COP1 COP2 COP1X beql bnel blezl bgtzl
011 daddi daddiu ldl ldr SPECIAL2 jalx SPECIAL3
100 lb lh lwl lw lbu lhu lwr lwu
101 sb sh swl sw sdl sdr swr cache
110 ll lwc1 lwc2 pref lld ldc1 ldc2 ld
111 sc swc1 swc2 scd sdc1 sdc2 sd

Functor R type

left\right digit 000 001 010 011 100 101 110 111
000 sll movci srl sra sllv srlv srav
001 jr jalr movz movn syscall break sync
010 mfhi mthi mflo mfhi dsllv dsrlv dsrav
011 mult multu div divu dmult dmultu ddiv ddivu
100 add addu sub subu and or xor nor
101 slt sltu dadd daddu dsub dsubu
110 tge tgeu tlt tltu teq tne
111 dsll dslr dsra dsll32 dsrl32 dsra32

Functor RI type

left\right digit 000 001 010 011 100 101 110 111
00 btlz bgez bltzl bgezl sllv
01 tgei jalr tlti tltiu teqi tnei
10 bltzal bgezal bltzall bgezall dsllv
11 synci

Special2

left\right digit 000 001 010 011 100 101 110 111
000 madd maddu mul msub msubu
001
010
011
100 clz clo dclz dclo
101
110
111 sdbbp

ALU

Add/subtract

All R-type

Name Syntax C code Funct Full format
add add $d, $s, $t d = s + t 0x20 000000ss
sssttttt
ddddd---
--100000
add unsigned addu $d, $s, $t d = s + t 0x21 000000ss
sssttttt
ddddd---
--100001
substract sub $d, $s, $t d = s - t 0x22 000000ss
sssttttt
ddddd---
--100010
substract unsigned subu $d, $s, $t d = s - t 0x23 000000ss
sssttttt
ddddd---
--100011

All I-type

Name Syntax C code Opcode Full format
add immediate addi $t, $s, C t = s + C 0x8 001000ss
sssttttt
CCCCCCCC
CCCCCCCC
add immediate unsigned addiu $t, $s, C t = s + C 0x9 001001ss
sssttttt
CCCCCCCC
CCCCCCCC

Multiplication/division

All R-type

Name Syntax C code Funct Full format
multiply mult $s, $t [HI, LO] = s * t 0x18 000000ss
sssttttt
--------
--011000
multiply unsigned multu $s, $t [HI, LO] = s * t 0x19 000000ss
sssttttt
--------
--011001
divide div $s, $t LO = s / t; HI = s % t 0x1A 000000ss
sssttttt
--------
--011010
divide unsigned divu $s, $t LO = s / t; HI = s % t 0x1B 000000ss
sssttttt
--------
--011011
move from HI mfhi $d d = HI 0x10 000000--
--------
ddddd---
--010000
move to HI mthi $s HI = s 0x11 000000ss
sss-----
--------
--010001
move from LO mflo $d d = LO 0x12 000000--
--------
ddddd---
--010010
move to LO mtlo $s LO = s 0x13 000000ss
sss-----
--------
--010011

Special2 type (MIPS32)

Name Syntax C code Funct Full format
multiply and add madd $s, $t [HI, LO] += s * t 0x00 011100ss
sssttttt
--------
--000000
multiply and add unsigned maddu $s, $t [HI, LO] += s * t 0x01 011100ss
sssttttt
--------
--000000
multiply to low mul $d, $s, $t d = s * t 0x02 011100ss
sssttttt
ddddd---
--000010
multiply and sub msub $s, $t [HI, LO] -= s * t 0x04 011100ss
sssttttt
--------
--000100
multiply and sub unsigned msubu $s, $t [HI, LO] -= s * t 0x05 011100ss
sssttttt
--------
--000101

Shifts

All R-type

Name Syntax C code Funct Full format
shift left logical immediate sll $d, $t, S d = t << S 0x0 000000--
---ttttt
dddddSSS
SS000000
shift right logical immediate srl $d, $t, S d = t >> S 0x2 000000--
---ttttt
dddddSSS
SS000010
shift right arithmetic immediate sra $d, $t, S d = (int32)t >> S 0x3 000000--
---ttttt
dddddSSS
SS000011
shift left logical sllv $d, $t, $s d = t << s 0x4 000000ss
sssttttt
ddddd---
--000100
shift right logical srlv $d, $t, $s d = t >> s 0x6 000000ss
sssttttt
ddddd---
--000110
shift right arithmetic srav $d, $t, $s d = (int32)t >> s 0x7 000000ss
sssttttt
ddddd---
--000111

Comparisons

All R-type

Name Syntax C code Funct Full format
set on less than slt $d, $s, $t d = (s < t) 0x2A 000000ss
sssttttt
ddddd---
--101010
set on
less than
unsigned
sltu $d, $s, $t d = (s < t) 0x2B 000000ss
sssttttt
ddddd---
--101011

All I-type

Name Syntax C code Opcode Full format
set on
less than
immediate
slti $s, $t, C t = (s < C) 0xA 001010ss
sssttttt
CCCCCCCC
CCCCCCCC
set on
less than
immediate unsigned
sltiu $s, $t, C t = (s < C) 0xB 001011ss
sssttttt
CCCCCCCC
CCCCCCCC

Logical operations

All R-type

Name Syntax C code Funct Full format
and and $d, $t, $s d = s & t 0x24 000000ss
sssttttt
ddddd---
--100100
or or $d, $t, $s d = s l t 0x25 000000ss
sssttttt
ddddd---
--100101
xor xor $d, $t, $s d = s ^ t 0x26 000000ss
sssttttt
ddddd---
--100110
nor nor $d, $t, $s d = ~ (s l t) 0x27 000000ss
sssttttt
ddddd---
--100111

All I-type

Name Syntax C code Opcode Full format
and with immediate andi $s, $t, C t = s & C 0xC 001100ss
sssttttt
CCCCCCCC
CCCCCCCC
or with immediate ori $s, $t, C t = s l C 0xD 001101ss
sssttttt
CCCCCCCC
CCCCCCCC
xor with immediate xori $s, $t, C t = s ^ C 0xE 001110ss
sssttttt
CCCCCCCC
CCCCCCCC
load upper immediate lui $t, C t = C << 16 0xF 001111--
---ttttt
CCCCCCCC
CCCCCCCC

Control Flow

Conditional branches

All I-type

Name Syntax PC advance Opcode Full format
branch on equal beq $s, $t, C PC += 4;
if (s == t)
PC += (C << 2)
0x4 000100ss
sssttttt
CCCCCCCC
CCCCCCCC
branch on not equal bne $s, $t, C PC += 4;
if (s != t)
PC += (C << 2)
0x5 000101ss
sssttttt
CCCCCCCC
CCCCCCCC
branch less than
or equal than zero
blez $s, C PC += 4;
if (s <= 0)
PC += (C << 2)
0x6 000110ss
sss-----
CCCCCCCC
CCCCCCCC
branch greater than zero bgtz $s, C PC += 4;
if (s > 0)
PC += (C << 2)
0x7 000111ss
sss-----
CCCCCCCC
CCCCCCCC

All RI-type

Name Syntax PC advance REGIMM Full format
branch on less than zero bltz $s, C PC += 4;
if (s < 0)
PC += (C << 2);
0x0 000001ss
sss00000
CCCCCCCC
CCCCCCCC
branch on greater than
or equal to zero
bgez $s, C PC += 4;
if (s >= 0)
PC += (C << 2);
0x1 000001ss
sss00001
CCCCCCCC
CCCCCCCC
branch on less than
zero and link
bltzal $s, C PC += 4;
if (s < 0)
PC += (C << 2);
0x10 000001ss
sss10000
CCCCCCCC
CCCCCCCC
branch on greater than
or equal to zero and link
bgezal $s, C PC += 4;
if (s >= 0)
PC += (C << 2);
0x11 000001ss
sss10001
CCCCCCCC
CCCCCCCC

Likely conditional branches (MIPS II)

These branches may be assumed as taken by branch prediction unit

All I-type

Name Syntax PC advance Opcode Full format
branch on equal likely beql $s, $t, C PC += 4;
if (s == t)
PC += (C << 2)
0x14 010100ss
sssttttt
CCCCCCCC
CCCCCCCC
branch on
not equal likely
bnel $s, $t, C PC += 4;
if (s != t)
PC += (C << 2)
0x15 010101ss
sssttttt
CCCCCCCC
CCCCCCCC
branch less than
or equal than zero likely
blezl $s, C PC += 4;
if (s <= 0)
PC += (C << 2)
0x16 010110ss
sss-----
CCCCCCCC
CCCCCCCC
branch greater
than zero likely
bgtzl $s, C PC += 4;
if (s > 0)
PC += (C << 2)
0x17 010111ss
sss-----
CCCCCCCC
CCCCCCCC

All RI-type

Name Syntax PC advance REGIMM Full format
branch on less
than zero likely
bltzl $s, C PC += 4;
if (s < 0)
PC += (C << 2);
0x2 000001ss
sss00010
CCCCCCCC
CCCCCCCC
branch on greater than
or equal to zero likely
bgezl $s, C PC += 4;
if (s >= 0)
PC += (C << 2);
0x3 000001ss
sss00011
CCCCCCCC
CCCCCCCC
branch on less than
zero and link likely
bltzall $s, C PC += 4;
if (s < 0)
PC += (C << 2);
0x12 000001ss
sss10010
CCCCCCCC
CCCCCCCC
branch on greater than
or equal to zero and link likely
bgezall $s, C PC += 4;
if (s >= 0)
PC += (C << 2);
0x13 000001ss
sss10011
CCCCCCCC
CCCCCCCC

Unconditional jumps

All J-type

Name Syntax C code PC advance Opcode Full format
jump j A PC = (PC & 0xf0000000) l (A << 2) 0x2 000010AA
AAAAAAAA
AAAAAAAA
AAAAAAAA
jump and link jal A ra = PC + 4 PC = (PC & 0xf0000000) l (A << 2) 0x3 000011AA
AAAAAAAA
AAAAAAAA
AAAAAAAA

Indirect jumps

All R-type

Name Syntax C code PC advance Funct Full format
jump register jr $s PC = s 0x8 000000ss
sss-----
--------
--001000
jump register and link jalr $s, $d d = PC + 4 PC = s 0x9 000000ss
sss-----
ddddd---
--001001

Conditional moves (MIPS IV)

All R-type

Name Syntax C code Funct Full format
move if zero movz $d, $s, $t if (t == 0) d = s 0xA 000000ss
sssttttt
ddddd---
--001010
move if not zero movn $d, $s, $t if (t != 0) d = s 0xB 000000ss
sssttttt
ddddd---
--001011

Memory

All I-type unless noted otherwise

Loads

Name Syntax C code Opcode Full format
load byte lb $t, C($s) t = *(int8*)(s + C) 0x20 100000ss
sssttttt
CCCCCCCC
CCCCCCCC
load half word lh $t, C($s) t = *(int16*)(s + C) 0x21 100001ss
sssttttt
CCCCCCCC
CCCCCCCC
load word left lwl $t, C($s) 0x22 100010ss
sssttttt
CCCCCCCC
CCCCCCCC
load word lw $t, C($s) t = *(int32*)(s + C) 0x23 100011ss
sssttttt
CCCCCCCC
CCCCCCCC
load byte unsigned lbu $t, C($s) t = *(uint8*)(s + C) 0x24 100100ss
sssttttt
CCCCCCCC
CCCCCCCC
load half word unsigned lhu $t, C($s) t = *(uint16*)(s + C) 0x25 100101ss
sssttttt
CCCCCCCC
CCCCCCCC
load word right lwl $t, C($s) 0x26 100010ss
sssttttt
CCCCCCCC
CCCCCCCC

Stores

Name Syntax C code Opcode Full format
store byte sb $t, C($s) *(uint8*)(s + C) = (t & 0xff) 0x28 101000ss
sssttttt
CCCCCCCC
CCCCCCCC
store half sh $t, C($s) *(uint16*)(s + C) = (t & 0xffff) 0x29 101000ss
sssttttt
CCCCCCCC
CCCCCCCC
store word
left
swl $t, C($s) 0x2A 101010ss
sssttttt
CCCCCCCC
CCCCCCCC
store word sw $t, C($s) *(uint32*)(s + C) = t 0x2B 101011ss
sssttttt
CCCCCCCC
CCCCCCCC
store word
right
swr $t, C($s) 0x2E 101110ss
sssttttt
CCCCCCCC
CCCCCCCC

Atomics (MIPS II)

Name Syntax C code Opcode Full format
load linked word ll $t, C($s) 0x30 110000ss
sssttttt
CCCCCCCC
CCCCCCCC
store conditional sc $t, C($s) 0x38 111000ss
sssttttt
CCCCCCCC
CCCCCCCC

Prefetch (MIPS IV)

Name Syntax C code Opcode Full format
prefetch pref H, C($s) 0x33 110011ss
sssHHHHH
CCCCCCCC
CCCCCCCC

Memory Order (MIPS II)

R-type

Name Syntax C code Funct Full format
syncronization barrier sync 0xF 000000--
--------
-----000
00001111

Operating system

Special instructions

Name Syntax PC advance T Opcode/Funct Full format
system call syscall PC += 4 R 0xC 000000--
--------
--------
--001100
breakpoint break PC += 4 R 0xD 000000--
--------
--------
--001101

Conditional traps (MIPS II)

All R-type

Name Syntax C++ code Funct Full format
trap on
greater or equal
tge $s, $t if (s >= t) throw 0x30 000000ss
sssttttt
--------
--110000
trap on
greater or equal
unsigned
tgeu $s, $t if (s >= t) throw 0x31 000000ss
sssttttt
--------
--110001
trap on less than tlt $s, $t if (s < t) throw 0x32 000000ss
sssttttt
--------
--110010
trap on
less than
unsigned
tltu $s, $t if (s < t) throw 0x33 000000ss
sssttttt
--------
--110011
trap on equal teq $s, $t if (s == t) throw 0x34 000000ss
sssttttt
--------
--110100
trap on not equal tne $s, $t if (s != t) throw 0x36 000000ss
sssttttt
--------
--110110

All RI-type

Name Syntax C++ code REGIMM Full format
trap on greater than
or equal immediate unsigned
tgei $s, C if (s >= C) throw 0x8 000001ss
sss01000
CCCCCCCC
CCCCCCCC
trap on greater than
or equal immediate unsigned
tgeiu $s, C if (s >= C) throw 0x9 000001ss
sss01001
CCCCCCCC
CCCCCCCC
trap on less
than immediate
tlti $s, C if (s < C) throw 0xA 000001ss
sss01010
CCCCCCCC
CCCCCCCC
trap on less
than immediate unsigned
tltiu $s, C if (s < C) throw 0xB 000001ss
sss01011
CCCCCCCC
CCCCCCCC
trap on equal to immediate teqi $s, C if (s == C) throw 0xC 000001ss
sss01100
CCCCCCCC
CCCCCCCC
trap on not equal to immediate tnei $s, C if (s != C) throw 0xE 000001ss
sss01110
CCCCCCCC
CCCCCCCC
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