MIPS Assembly/Pseudoinstructions

The MIPS instruction set is very small, so to do more complicated tasks we need to employ assembler macros called pseudoinstructions.

List of Pseudoinstructions

The following is a list of the standard MIPS instructions that are implemented as pseudoinstructions:

• blt
• bgt
• ble
• neg
• not
• bge
• li
• la
• move
• sge
• sgt

Branch Pseudoinstructions

Branch if less than (blt)

The blt instruction compares 2 registers, treating them as signed integers, and takes a branch if one register is less than another.

blt $8, $9, label

translates to

slt $1, $8, $9
bne $1, $0, label

Other Pseudoinstructions

Load Immediate (li)

The li pseudo instruction loads an immediate value into a register.

li $8, 0x3BF20

translates to

lui $8, 0x0003
ori $8, $8, 0xBF20

Move (move)

The move pseudo instruction moves the contents of one register into another register.

move $1, $2

translates to

add $1, $2, $0

Load Address (la)

la $a0,address

translates to

  lui $at, 4097 (0x1001 → upper 16 bits of $at).
  ori $a0,$at,disp 

where the immediate (“disp”) is the number of bytes between the first data location (always 0x 1001 0000) and the address of the first byte in the string.