Struct Opcodes

pub struct Opcodes {
    pub prefixes: Prefixes,
    pub escape: bool,
    pub primary: u8,
    pub secondary: Option<u8>,
}

Describe an instruction’s opcodes. From section 2.1.2 “Opcodes” in the reference manual:

A primary opcode can be 1, 2, or 3 bytes in length. An additional 3-bit opcode field is sometimes encoded in the ModR/M byte. Smaller fields can be defined within the primary opcode. Such fields define the direction of operation, size of displacements, register encoding, condition codes, or sign extension. Encoding fields used by an opcode vary depending on the class of operation.

Two-byte opcode formats for general-purpose and SIMD instructions consist of one of the following:

• An escape opcode byte 0FH as the primary opcode and a second opcode byte.
• A mandatory prefix (66H, F2H, or F3H), an escape opcode byte, and a second opcode byte (same as previous bullet).

For example, CVTDQ2PD consists of the following sequence: F3 0F E6. The first byte is a mandatory prefix (it is not considered as a repeat prefix).

Three-byte opcode formats for general-purpose and SIMD instructions consist of one of the following:

• An escape opcode byte 0FH as the primary opcode, plus two additional opcode bytes.
• A mandatory prefix (66H, F2H, or F3H), an escape opcode byte, plus two additional opcode bytes (same as previous bullet).

For example, PHADDW for XMM registers consists of the following sequence: 66 0F 38 01. The first byte is the mandatory prefix.

Fields

prefixes: Prefixes

The prefix bytes for this instruction.

escape: bool

Indicates the use of an escape opcode byte, 0x0f.

primary: u8

The primary opcode.

secondary: Option<u8>

Some instructions (e.g., SIMD) may have a secondary opcode.

Trait Implementations

impl<const N: usize> From<[u8; N]> for Opcodes

fn from(bytes: [u8; N]) -> Self

Converts to this type from the input type.

impl From<u8> for Opcodes

fn from(primary: u8) -> Opcodes

Converts to this type from the input type.