Struct Budget 

pub struct Budget { /* private fields */ }

A budget of work steps that every pass draws from.

A step is one unit of analysis or rewrite work (roughly: one instruction, block, edge, or value visited). Each pass charges its cost before it changes anything; a pass that cannot be paid for does nothing and marks the budget exhausted, so the function is always left valid. Every pass is linear in the function except where noted on PassKind, and those non-linear parts (nested loops in LICM, repeated re-examination in copy propagation, hash collisions in GVN) are charged step by step, so a hostile function cannot make optimization take more than budget steps.

Examples

use opt_lang::Budget;

let mut b = Budget::new(10);
assert_eq!(b.remaining(), 10);
assert!(!b.is_exhausted());
assert!(Budget::unlimited().remaining() > 1 << 60);

Implementations

impl Budget

pub const fn new(steps: u64) -> Budget

A budget of steps steps.

Examples

assert_eq!(opt_lang::Budget::new(5).remaining(), 5);

pub const fn unlimited() -> Budget

A budget that never runs out in practice (u64::MAX steps).

Examples

assert!(!opt_lang::Budget::unlimited().is_exhausted());

pub const fn remaining(&self) -> u64

The steps left.

Examples

assert_eq!(opt_lang::Budget::new(0).remaining(), 0);

pub const fn is_exhausted(&self) -> bool

Whether a pass was refused (or stopped early) because the budget ran out.

Examples

use ir_lang::{Linkage, Module, Signature};
use opt_lang::{Budget, PassKind};

let mut m = Module::new("m");
let f = m.declare_function("f", &Signature::new(&[], &[]), Linkage::Export)?;
m.build(f)?.ret(&[])?;
let mut budget = Budget::new(0);
let changed = opt_lang::run_pass(&mut m.edit(f)?, PassKind::Dce, &mut budget)?;
assert!(!changed && budget.is_exhausted());

Trait Implementations

impl Clone for Budget

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for Budget

impl Debug for Budget

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

Formats the value using the given formatter.

impl Eq for Budget

impl PartialEq for Budget

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Budget