Enum OptLevel 

pub enum OptLevel {
    None,
    Size,
    Aggressive,
}

Optimization level for encoding.

The levels differ in what an optimization is allowed to change, not just in how hard it tries:

Level	May shrink encodings	May change architectural state
None	no	no
Size (default)	yes	no
Aggressive	yes	yes (FLAGS only)

Size is the default because every transform it performs is observationally equivalent: the rewritten instruction leaves registers, memory and FLAGS exactly as the original would.

Aggressive additionally permits rewrites that clobber FLAGS — notably the zero idiom mov reg, 0 → xor reg, reg. That is a real semantic change: it silently breaks sequences such as

cmp  eax, ebx
mov  eax, 0     ; must not disturb FLAGS
sete al

so it must be opted into explicitly, and only where FLAGS are known dead.

Variants

None

No optimizations — byte-for-byte predictable output.

Size

Prefer shortest encodings, but only via transforms that preserve all architectural state including FLAGS (default).

Aggressive

Also allow transforms that clobber FLAGS (e.g. the mov reg, 0 zero idiom). Only safe when FLAGS are dead after the rewritten instruction.

Trait Implementations

impl Clone for OptLevel

fn clone(&self) -> OptLevel

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for OptLevel

impl Debug for OptLevel

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

Formats the value using the given formatter.

impl Default for OptLevel

fn default() -> OptLevel

Returns the “default value” for a type.

impl Eq for OptLevel

impl PartialEq for OptLevel

fn eq(&self, other: &OptLevel) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for OptLevel