KittyArm32 Namespace Reference

Namespace containing utility functions for ARM32 instructions. More...

Functions
int32_t	signExtend (uint32_t val, int bits)
	Sign-extends a 32-bit unsigned integer to a 32-bit signed integer.
std::string	regName (unsigned r)
	Returns the name of an ARM32 general-purpose register.
int	regIndex (const std::string &name)
	Inverse of regName(): maps a decoded register name back to its index.
std::string	branchCondName (uint32_t cond)
	Returns the name of a conditional execution flag.
std::string	typeToString (EKittyInsnTypeArm32 t)
	Converts an EKittyInsnTypeArm32 to a string representation.
uint8_t	loadStoreWidth (EKittyInsnTypeArm32 t)
	Load/Store access width in bytes for an ARM32 instruction type.
bool	isLoad (EKittyInsnTypeArm32 t)
	True when t is one of the load instruction types.
bool	isStore (EKittyInsnTypeArm32 t)
	True when t is one of the store instruction types.
EKittyInsnTypeArm32	decodeInsnType (uint32_t instr)
	Decodes type of an ARM32 instruction.
KittyInsnArm32	decodeInsn (uint32_t instr, uint32_t address=0)
	Decodes an ARM32 instruction.

Variables
constexpr uint32_t	kInstructionStride = 4
constexpr uint32_t	kPcBias = 8
constexpr int	kLinkRegister = 14
constexpr int	kNumGPRegisters = 15

Detailed Description

Namespace containing utility functions for ARM32 instructions.

This namespace provides utility functions for decoding ARM32 instructions,

Function Documentation

branchCondName()

std::string KittyArm32::branchCondName ( uint32_t cond )

inline

Returns the name of a conditional execution flag.

Parameters

cond	The conditional execution flag value (0-15).

Returns

The name of the conditional execution flag as a string.

decodeInsn()

KittyInsnArm32 KittyArm32::decodeInsn	(	uint32_t	instr,
		uint32_t	address = 0 )

Decodes an ARM32 instruction.

Parameters

instr	The 32-bit instruction value.
address	The address of the instruction (optional).

Returns

The details of the decoded instruction.

decodeInsnType()

EKittyInsnTypeArm32 KittyArm32::decodeInsnType

(

uint32_t

instr

)

Decodes type of an ARM32 instruction.

Parameters

instr

The 32-bit instruction value.

Returns

The type of the instruction.

isLoad()

bool KittyArm32::isLoad

(

EKittyInsnTypeArm32

t

)

True when t is one of the load instruction types.

Parameters

t	The instruction type to query.

isStore()

bool KittyArm32::isStore

(

EKittyInsnTypeArm32

t

)

True when t is one of the store instruction types.

Parameters

t	The instruction type to query.

loadStoreWidth()

uint8_t KittyArm32::loadStoreWidth

(

EKittyInsnTypeArm32

t

)

Load/Store access width in bytes for an ARM32 instruction type.

Parameters

t	The instruction type to query.

Returns

1 for the byte forms, 2 for the halfword forms, 4 for everything else (word loads/stores, and LDR_LITERAL); 0 for a type that is not a load or store at all.

regIndex()

int KittyArm32::regIndex

(

const std::string &

name

)

Inverse of regName(): maps a decoded register name back to its index.

Parameters

name	Register name as produced by regName() - "sp"/"lr"/"pc" for 13/14/15, "r0".."r15" otherwise.

Returns

The register index (0-15), or -1 for anything unrecognised. Note that 15 (PC) is a valid answer here while being one past kNumGPRegisters: PC is nameable but not trackable, so a caller sizing an array by kNumGPRegisters must bound-check the result rather than index with it directly.

regName()

std::string KittyArm32::regName ( unsigned r )

inline

Returns the name of an ARM32 general-purpose register.

Parameters

r	The register number (0-15).

Returns

The name of the register as a string.

signExtend()

int32_t KittyArm32::signExtend ( uint32_t val, int bits )

inline

Sign-extends a 32-bit unsigned integer to a 32-bit signed integer.

Parameters

val	The input 32-bit unsigned integer.
bits	The number of bits to sign-extend.

Returns

The sign-extended 32-bit signed integer.

typeToString()

std::string KittyArm32::typeToString

(

EKittyInsnTypeArm32

t

)

Converts an EKittyInsnTypeArm32 to a string representation.

Parameters

t	The instruction type to convert.

Returns

The string representation of the instruction type.

Variable Documentation

kInstructionStride

uint32_t KittyArm32::kInstructionStride = 4

constexpr

A32 instruction size. Fixed at 4 bytes, which is what makes a linear sweep possible at all - and is exactly the assumption that does not hold for Thumb/Thumb-2, whose mixed 16/32-bit encoding this decoder does not handle. The one source of truth for anything stepping through A32 code.

kLinkRegister

int KittyArm32::kLinkRegister = 14

constexpr

R14, the link register: BX LR is how an A32 function returns, so a consumer looking for returns has to name this register.

kNumGPRegisters

int KittyArm32::kNumGPRegisters = 15

constexpr

ARM32 general-purpose register count: R0-R14. R15 (PC) is deliberately excluded - every consumer of this constant tracks live register state, and PC's value changes every instruction rather than being something register-tracking can hold, so it is never a valid array index here. The one source of truth for register-array sizing and regIndex's bound check.

kPcBias

uint32_t KittyArm32::kPcBias = 8

constexpr

What A32 reads the PC as: the instruction's own address plus 8, an artefact of the original three-stage pipeline that the architecture keeps for compatibility. Every PC-relative form here is biased by it, so the number lives in one place rather than as a literal 8 at each use.