ARMv8

ARMv8 is the machine architecture that the Nintendo Switch uses to process compiled code. It has a very large instruction set and register components.

Registers

The architecture includes a variety of registers.

GPR

The GPRs have two varieties, 64-bit GPRs and 32-bit GPRs.

Name	Size	Description
X0-X7	64-bit	Used to pass parameters to a function and to return a result. Can be used as scratch.
X8	64-bit	Indirect result register. Passes the address of an indirect result.
X9-X15	64-bit	Caller-saved temporary registers.
X16	64-bit	IP0 (Intra-Procedure Call) temporary register. Can be used for call veneers and as a caller-saved temporary register.
X17	64-bit	IP1 (Intra-Procedure Call) temporary register. Can be used for call veneers and as a caller-saved temporary register.
X18	64-bit	Platform register, reserved by the platform ABI. For platforms that do not utilize the register, it can be used as a temporary register.
X19-X29	64-bit	Callee-saved temporary registers.
X30	64-bit	Link register (LR).

The 32-bit registers use the exact same register types, where it starts with W rather than X.

FPR

The architecture has multiple types of registers for floating point.

Name	Size	Description
S0-S7	32-bit	Used to pass parameters to a function and to return a result. Can be used as scratch.
S8-S15	32-bit	Callee-preserved registers.
S16-S31	32-bit	These registers do not need to be preserved by the caller, nor the callee.

The following types of floating point registers exist (only the prefixes):

Name	Size
B	8-bit
H	16-bit
S	32-bit
D or V	64-bit
Q	128-bit

Special Registers

Name	Size	Description
WZR	32-bit	Zero register. Always contains a 32-bit 0x0 value.
XZR	64-bit	Zero register. Always contains a 64-bit 0x0 value.
WSP	32-bit	Current stack pointer.
SP	64-bit	Current stack pointer.
PC	64-bit	Program counter.