MIPS Assembly/Register File

This page will talk about the structural details of the MIPS register file.

Zero Register

The zero register ($zero or $0) always contains a value of 0. It is built into the hardware and therefore cannot be modified.

$at Register

The $at (Assembler Temporary) register is used for temporary values within pseudo commands. It is not preserved across function calls.

$v Registers

The $v Registers are used for returning values from functions. They are not preserved across function calls.

Argument Registers

The $a registers are used for passing arguments to functions. They are not preserved across function calls.

Temporaries

The temporary registers are used by the assembler or assembly language programmer to store intermediate values. They are not preserved across function calls.

Saved Temporaries

Saved Temporary registers are used to store longer lasting values. They are preserved across function calls.

$k Registers

The k registers are reserved for use by the OS kernel.

Pointer Registers

• Global Pointer ($gp)
• Stack Pointer ($sp) - Used to store the value of the stack pointer.
• Frame Pointer ($fp) - Used to store the value of the frame pointer.
• Return Address ($ra) - Stores the return address (the location in the program that a function needs to return to).

All Pointer Registers are preserved accross function calls.