Register conventions

register conventions and mnemonics

Number

Name

Use

0

$zero

hardwired 0 value

1

$at

used by assembler (pseudo-instructions)

2-3

$v0-1

subroutine return value

4-7

$a0-3

arguments: subroutine parameter value

8-15

$t0-7

temp: can be used by subroutine without saving

16-23

$s0-7

saved: must be saved and restored by subroutine

24-25

$t8-9

temp

26-27

$k0-1

kernel: interrupt/trap handler

28

$gp

global pointer (static or extern variables)

29

$sp

stack pointer

30

$fp

frame pointer

31

$ra

return address for subroutine

Hi, Lo

used in multiplication (provide 64 bits for result)

hidden registers

PC, the program counter, which stores the current address of the instruction

being executed

IR, which stores the instruction being executed