Struct Instruction 

#[repr(C)]
pub struct Instruction {
    pub opcode: u32,
    pub instruction_type: InstructionType,
    pub operands: SmallVec<[Operand; 4]>,
}

PowerPC instruction representation with optimized memory layout.

Memory Layout

• opcode: 6 bits (bits 26-31 of instruction word)
• instruction_type: 1 byte (enum with #[repr(u8)])
• operands: SmallVec with inline capacity for 4 operands (most instructions have ≤4)

Fields

opcode: u32

Primary opcode (6 bits, stored as u32 for alignment but only uses 6 bits)

instruction_type: InstructionType

Instruction type category (1 byte enum)

operands: SmallVec<[Operand; 4]>

Instruction operands (register, immediate, address, etc.) Uses SmallVec to avoid heap allocation for common case (≤4 operands)

Implementations

impl Instruction

pub fn decode(word: u32, address: u32) -> Result<DecodedInstruction>

Decode a 32-bit PowerPC instruction word into a structured representation.

Algorithm

1. Extract primary opcode (bits 26-31)
2. For opcode 31 (extended), extract secondary opcode (bits 1-10)
3. Extract operands based on instruction format
4. Return decoded instruction with type and operands

Arguments

• word - 32-bit instruction word in big-endian format
• address - Memory address where this instruction is located (for function mapping)

Returns

Result<DecodedInstruction> - Decoded instruction or error if invalid

Errors

Returns error if instruction cannot be decoded (invalid opcode, malformed format)

Examples

// Decode an addi instruction: addi r3, r4, 42
let word: u32 = 0x3864002A; // addi r3, r4, 42
let address: u32 = 0x80000000;
let decoded = Instruction::decode(word, address)?;
assert_eq!(decoded.instruction.instruction_type, InstructionType::Arithmetic);
assert_eq!(decoded.address, address);

Trait Implementations

impl Clone for Instruction

fn clone(&self) -> Instruction

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Instruction

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.