| Format | Description |
|---|
| N | no operands |
| RH | one register and the lower 16 bits of a word |
| RHH | one register and the upper 16 bits of a word |
| RRH | two registers and a zero-extended halfword |
| RRS | two registers and a sign-extended halfword |
| RRR | three registers |
| RRX | three registers, or two registers and a zero-extended halfword |
| RRY | three registers, or two registers and a sign-extended halfword |
| RRB | two registers and a sign-extended 16 bit offset |
| J | no registers and a sign-extended 26 bit offset |
| JR | one register |
| Mnemonic | Operands | Description | Format |
|---|
| add | dst, op1, op2 | dst := op1 + op2 | RRY |
| sub | dst, op1, op2 | dst := op1 - op2 | RRY |
| mul | dst, op1, op2 | dst := op1 * op2, signed | RRY |
| mulu | dst, op1, op2 | dst := op1 * op2, unsigned | RRX |
| div | dst, op1, op2 | dst := op1 / op2, signed | RRY |
| divu | dst, op1, op2 | dst := op1 / op2, unsigned | RRX |
| rem | dst, op1, op2 | dst := remainder of op1/op2, signed | RRY |
| remu | dst, op1, op2 | dst := remainder of op1/op2, unsigned | RRX |
| and | dst, op1, op2 | dst := bitwise AND of op1 and op2 | RRX |
| or | dst, op1, op2 | dst := bitwise OR of op1 and op2 | RRX |
| xor | dst, op1, op2 | dst := bitwise XOR of op1 and op2 | RRX |
| xnor | dst, op1, op2 | dst := bitwise XNOR of op1 and op2 | RRX |
| sll | dst, op1, op2 | dst := shift op1 logically left by op2 | RRX |
| slr | dst, op1, op2 | dst := shift op1 logically right by op2 | RRX |
| sar | dst, op1, op2 | dst := shift op1 arithmetically right by op2 | RRX |
| ldhi | dst, op1 | dst := op1 shifted left by 16 bits | RHH |
| beq | op1, op2, offset | branch to PC+4+offset*4 if op1 == op2 | RRB |
| bne | op1, op2, offset | branch to PC+4+offset*4 if op1 != op2 | RRB |
| ble | op1, op2, offset | branch to PC+4+offset*4 if op1 <= op2 (signed) | RRB |
| bleu | op1, op2, offset | branch to PC+4+offset*4 if op1 <= op2 (unsigned) | RRB |
| blt | op1, op2, offset | branch to PC+4+offset*4 if op1 < op2 (signed) | RRB |
| bltu | op1, op2, offset | branch to PC+4+offset*4 if op1 < op2 (unsigned) | RRB |
| bge | op1, op2, offset | branch to PC+4+offset*4 if op1 >= op2 (signed) | RRB |
| bgeu | op1, op2, offset | branch to PC+4+offset*4 if op1 >= op2 (unsigned) | RRB |
| bgt | op1, op2, offset | branch to PC+4+offset*4 if op1 > op2 (signed) | RRB |
| bgtu | op1, op2, offset | branch to PC+4+offset*4 if op1 > op2 (unsigned) | RRB |
| j | offset | jump to PC+4+offset*4 | J |
| jr | register | jump to register | JR |
| jal | offset | jump to PC+4+offset*4, store PC+4 in $31 | J |
| jalr | register | jump to register, store PC+4 in $31 | JR |
| trap | -/- | cause a trap, store PC in $30 | N |
| rfx | -/- | return from exception, restore PC from $30 | N |
| ldw | dst, reg, offset | dst := word @ (reg+offset) | RRS |
| ldh | dst, reg, offset | dst := sign-extended halfword @ (reg+offset) | RRS |
| ldhu | dst, reg, offset | dst := zero-extended halfword @ (reg+offset) | RRS |
| ldb | dst, reg, offset | dst := sign-extended byte @ (reg+offset) | RRS |
| ldbu | dst, reg, offset | dst := zero-extended byte @ (reg+offset) | RRS |
| stw | src, reg, offset | store src word @ (reg+offset) | RRS |
| sth | src, reg, offset | store src halfword @ (reg+offset) | RRS |
| stb | src, reg, offset | store src byte @ (reg+offset) | RRS |
| mvfs | dst, special | dst := contents of special register | RH |
| mvts | src, special | contents of special register := src | RH |
| tbs | -/- | TLB search | N |
| tbwr | -/- | TLB write random | N |
| tbri | -/- | TLB read index | N |
| tbwi | -/- | TLB write index | N |
| Integer Registers |
|---|
| $0 | always zero |
$8 | temporary register (caller-save) |
$16 | register variable (callee-save) |
$24 | temporary register (caller-save) |
| $1 | reserved for assembler |
$9 | temporary register (caller-save) |
$17 | register variable (callee-save) |
$25 | temporary register (caller-save) |
| $2 | func return value |
$10 | temporary register (caller-save) |
$18 | register variable (callee-save) |
$26 | reserved for OS kernel |
| $3 | func return value |
$11 | temporary register (caller-save) |
$19 | register variable (callee-save) |
$27 | reserved for OS kernel |
| $4 | proc/func argument |
$12 | temporary register (caller-save) |
$20 | register variable (callee-save) |
$28 | reserved for OS kernel |
| $5 | proc/func argument |
$13 | temporary register (caller-save) |
$21 | register variable (callee-save) |
$29 | stack pointer |
| $6 | proc/func argument |
$14 | temporary register (caller-save) |
$22 | register variable (callee-save) |
$30 | interrupt return address |
| $7 | proc/func argument |
$15 | temporary register (caller-save) |
$23 | register variable (callee-save) |
$31 | proc/func return address |