ADDIU - MIPS instruction reference

addiuAdd immediate unsigned (no overflow trap) 
Adds a sign-extended immediate to $t2 and puts the sum in $t1, wrapping on overflow instead of trapping.
Used in Exceptions and coprocessor 0MIPS assembly
Sum of an arrayMIPS assembly
The largest elementMIPS assembly
Byte length of a stringMIPS assembly
Reverse a string in placeMIPS assembly
 
Forms  addiu , ,   
Pseudo-instructionsThe assembler turns these into one or more real instructions.
  addiu , ,   
Set $t1 to ($t2 plus 32-bit immediate), no overflow
 addiu , , %lo()  
Set $t1 to $t2 plus the lower 16 bits of label's address
Operands $t1 Any general-purpose register, $0 to $31, using its numeric or named spelling, such as $8 or $t0 ($zero is $0; $ra is $31). 
$t2 A general-purpose register. It may be the same register as $t1. 
imm16 A signed 16-bit immediate, -32768 to 32767. 
imm32 A 32-bit immediate, -2147483648 to 4294967295. Pseudoinstruction expansion may overwrite $at, losing its previous value. 
label A named address in the program, such as the start of a loop or a variable in .data. 
The immediate is a signed 16-bit value sign-extended to 32 bits; no overflow exception is raised. Despite the name the immediate is sign-extended, not zero-extended. The most common add-immediate instruction.
 # Add immediate 1 across the signed boundary without trapping. Inspect $t2: 0x80000000.
li $t0, 0x7FFFFFFF
addiu $t2, $t0, 1