APPENDIX C. MIPS APPENDIX C. MIPS

Appendix C

MIPS

C.1 Registers.

( O32 calling convention )

C.1.1 General purpose registersGPR

Number Pseudoname Description

$0 $ZERO Always zero. Writing to this register is effectively an idle instruction (NOP).

$1 $AT Used as a temporary register for assembly macros and pseudoinstructions.

$2 ...$3 $V0 ...$V1 Function result is returned here.

$4 ...$7 $A0 ...$A3 Function arguments.

$8 ...$15 $T0 ...$T7 Used for temporary data.

$16 ...$23 $S0 ...$S7 Used for temporary data∗.

$24 ...$25 $T8 ...$T9 Used for temporary data.

$26 ...$27 $K0 ...$K1 Reserved forOSkernel.

$28 $GP Global Pointer∗∗.

$29 $SP SP∗.

$30 $FP FP∗.

$31 $RA RA.

n/a PC PC.

n/a HI high 32 bit of multiplication or division remainder∗∗∗.

n/a LO low 32 bit of multiplication and division remainder∗∗∗.

C.1.2 Floating-point registers

Name Description

$F0..$F1 Function result returned here.

$F2..$F3 Not used.

$F4..$F11 Used for temporary data.

$F12..$F15 First two function arguments.

$F16..$F19 Used for temporary data.

$F20..$F31 Used for temporary data∗.

∗—Calleemust preserve the value.

∗∗—Calleemust preserve the value ( except inPICcode).

∗∗∗—accessible using theMFHIandMFLOinstructions.

C.2 Instructions

There are 3 kinds of instructions:

• R-type: those which have 3 registers. R-instruction usually have the following form: