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MIPS INSTRUCTIONS, REGISTERS AND SYSTEM CALLS
1. INTEGER and GENERAL INSTRUCTIONS

Call Arg 1 Arg 2 Arg3 Description

* abs rd rs put the absolute value of rs into rd
add rd rs rt rd = rs + rt (with overflow)
addu rd rs rt rd = rs + rt (without overflow)
addi rt rs imm rt = rs + imm (with overflow)
addiu rt rs imm rt = rs + imm (without overflow)
and rd rs rt put rs AND rt into rd
* b label branch to label
beq rs rt label branch to label if (rs==rt)
* beqz rs label branch to label if (rs==0)
* bge rs rt label branch to label if (rs>=rt)
bgez rs label branch to label if (rs>=0)
bgt rs rt label branch to label if (rs>rt)
bgtz rs label branch to label if (rs>0)
ble rs rt label branch to label if (rs<=rt)
blez rs label branch to label if (rs<=0)
* blt rs rt label branch to label if (rs<rt)
bltz rs label branch to label if (rs<0)
bne rs rt label branch to label if (rs!=rt)
* bnez rs label branch to label if (rs!=0)
div rd rs rt rd = rs DIV rt
j label jump to label
jal label jump to label and save next instruction in rd
jalr [rd] rs jump to instruction at (rs), save next in rd
jr rs jump to instruction at (rs)
* la rd label load address of word at label into rd
lb rt address load byte at address into rt, sign xtnd
lbu rt address load byte at address into rt
* li rd number load number into rd
lui rt number upper halfword of rt = 16-bit number
lw rd address load the word at address into rd
lw rd offset(base) load word at addr offset+base into rd
* move rd rs move rs to rd
* mul rd rs rt rd = rs * rt
* neg rd rs rd = - rs
nop do nothing
nor rd rs rt rd = rs NOR rt
* not rd rs rs = bitwise logical negation of rd
or rd rs rt rd = rs OR rt
ori rt rs imm rt = rs OR imm
* rem rd rs rt rd = rs MOD rt
* rol(ror) rd rs rt rd = rs rotated left(right) by rt
sb rt address store byte in rt to address
* seq rd rs rt if (rs==rt) rd=1;else rd=0
* sge rd rs rt if (rs>=rt) rd=1;else rd=0
* sgt rd rs rt if (rs>rt) rd=1;else rd=0
* sle rd rs rt if (rs<=rt) rd=1;else rd=0
sll rd rt sa rd = rt shifted left by distance sa
slt rd rs rt if (rs<rt) rd=1;else rd=0
* sne rd rs rt if (rs!=rt) rd=1;else rd=0
sra rd rt sa rd = rt shifted right by sa, sign-extended
srl rd rt sa rd = rt shifted right by sa, 0-extended
sub rd rs rt rd = rs - rt
sw rt address store the word in rt to address
sw rt offset(base) store word in rt to addr offset+base
syscall do a system call depending on contents of $v0
xor rd rs rt rd = rs XOR rt

* Indicates a pseudoinstruction (assembler generates more than one
instruction to produce the same result) (a pseudoinstruction has no opcode)
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2. FLOATING POINT INSTRUCTIONS
(single precision)

Call Arg 1 Arg 2 Arg3 Description

abs.s fd fs fd = absolute value of fs
add.s fd fs ft fd = fs + ft
bc1f label branch to label if float-flag is FALSE
bc1t label branch to label if float-flag is TRUE
c.eq.s fs ft if (fs==ft) then float-flag is TRUE, else its FALSE
c.le.s fs ft if (fs<=ft) then float-flag is TRUE,else its FALSE
c.lt.s fs ft if (fs<ft) then float-flag is TRUE, else its FALSE
cvt.s.w fd fs convert integer in fs to single-precision float in fd
cvt.w.s fd fs convert single-precisoin float in fs to integer in fd
div.s fd fs ft fd = fs / ft
l.s fd address load the single at address into fd
li.s fd number load the number fd
mov.s fd fs move single from fs to fd
mfc1 rd rs move integer rs to float rd
mtc1 rs rd move integer rs to float rd
mul.s fd fs ft fd = fs * ft
neg.s fd fs fd = - fs
s.s fd addresss store fd at in memory at address
sub.s fd fs ft fd = fs - ft

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3a. CPU REGISTERS

Name Register Function

$a0 4 used to pass the first of four arguments
$a1 5 used to pass the second of four arguments
$a2 6 used to pass the third of four arguments
$a3 7 used to pass the fourth of four arguments
$at 1 reserved for the operating system
$fp 30 frame pointer.
$gp 28 global memory pointer
$k0 26 reserved for the operating system
$k1 27 reserved for the operating system
$ra 31 return address
$s0 16 callee-saved registers
$s1 17 callee-saved registers
$s2 18 callee-saved registers
$s3 19 callee-saved registers
$s4 20 callee-saved registers
$s5 21 callee-saved registers
$s6 22 callee-saved registers
$s7 23 callee-saved registers
$sp 29 stack pointer to the first free location
$t0 8 used to hold temporary variables
$t1 9 used to hold temporary variables
$t2 10 used to hold temporary variables
$t3 11 used to hold temporary variables
$t4 12 used to hold temporary variables
$t5 13 used to hold temporary variables
$t6 14 used to hold temporary variables
$t7 15 used to hold temporary variables
$t8 24 used to hold temporary variables
$t9 25 used to hold temporary variables
$v0 2 used to pass values to and from functions
$v1 3 used to pass values to and from functions

3b. FPU (CP1) REGISTERS

Name Register Function

$f0 (float) hold floating point type function results
$f2 (float) hold floating poitn type function results
$f4 (float) temporary register
$f6 (float) temporary register
$f8 (float) temporary register
$f10 (float) temporary register
$f12 (float) pass the first of two float arguments
$f14 (float) pass the second of two float arguments
$f16 (float) temporary register
$f18 (float) temporary register
$f20 (float) saved register
$f22 (float) saved register
$f24 (float) saved register
$f26 (float) saved register
$f28 (float) saved register
$f30 (float) saved register

3c. CP0 REGISTERS

Register Function

13 Cause
14 EPC (Exception Program Counter)

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4. SYSTEM CALL INFORMATION

Call Code Event Arguments Result
(in $v0)

1 print int $a0 = integer $a0 is printed out
2 print float $f12 = float $f12 is printed out
4 print string $a0 = pointer to string string is printed out
5 read int $v0 holds integer read
6 read float $f0 holds float read
7 read double $f0 holds double read
8 read string $a0 = buffer,a1 = length string is read from console
9 sbrk $a0 = amount address of additional memory in $v0
10 exit program
11 print byte $a0 = byte byte is printed out


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Originally due to Eric Gauthier
Modified and expanded by C. D. Cantrell