:- 32 General-Purpose -:
:- Registers -:
R3000 General-Purpose Registers
R3000 General-Purpose Registers
| Register No. |
|
Macro (2) | Assembler | Description |
|---|---|---|---|---|
| 0 | R_ZERO | R_R0 | zero/$0 | The contents of $0 register is always 0. |
| 1 | R_AT | R_R1 | at | Reserved
for the assembler.
This is the assembler temporary register, which is used in background. |
| 2-3 | R_V0-1 | R_R2-3 | v0-1 | Values
returned by functions. If a function
returns more than 2x32 bit values than memory has to be used. (later more) |
| 4-7 | R_A0-3 | R_R4-7 | a0-3 | Function
arguments. This register hold
the first function paramters. Parallel to this the same parameters are stored on stack. (later more) |
| 8-15 | R_T0-7 | R_R8-15 | t0-7 | t0-t9
can be used in functions without
carrying about the contents of them before the function was entered and after the function is left. |
| 16-23 | R_S0-7 | R_R16-23 | s0-7 | If
this register are used in functions, their
contents has to be saved before. It must be guaranted that the contents is the same after the function is left, as before it was entered. |
| 24-25 | R_T8-9 | R_R24-25 | t8-9 | See 8-15. |
| 26-27 | R_K0-1 | R_R26-27 | k0-1 | Reserved for the kernel |
| 28 | R_GP | R_R28 | gp | Global Pointer |
| 29 | R_SP | R_R29 | sp | Stack Pointer |
| 30 | R_FP | R_R30 | fp | Frame Pointer |
| 31 | R_RA | R_R31 | ra | This
register stores the return address at
which the programm will continue when the function is left. (jr ra). If a function is calling another function the contents of ra must be saved on stack before calling, otherwise lost in space. (crash!) |