Struct PrefetchHint 

pub struct PrefetchHint {
    pub write: bool,
    pub locality: u8,
}

What a crate::Opcode::Prefetch says about the access it is a hint for.

Two facts, both of them out of __builtin_prefetch’s own arguments, and neither of them a promise. A prefetch that says the wrong thing, or a target that ignores it, changes how long the program takes and nothing else, so nothing downstream may read either of these as a fact about what the program will do.

Fields

write: bool

Whether the access being prepared for will write, which is the second argument.

It matters on a machine that has separate instructions for the two, because a line fetched for writing is fetched in a state that does not have to be asked for again when the write happens. x86-64 has one for it, prefetchw, and only on a processor that says it has it, so this reaches the back end and the back end decides.

locality: u8

How much of the data will still be wanted after the access, from zero for none of it to three for all of it, which is the third argument.

Three is the default and is what a program that writes the one argument form means. Zero is the one that is a different instruction rather than a different cache level on x86-64: it says the line is wanted once, so prefetchnta fetches it in a way that does not push anything else out.

Implementations

impl PrefetchHint

pub const MOST: u8 = 3

The highest locality, which is the one the one argument form of the builtin means.

pub const fn read() -> Self

The hint a call that said nothing beyond the address means, which is a read that will want all of the data afterwards.

pub const fn access(self) -> &'static str

The word for which half of the access this is about, which is how it prints.

pub const fn is_valid(self) -> bool

Whether the locality is one of the four the builtin has.

Asked by the verifier. Nothing here clamps an out of range one, because a number this did not come from __builtin_prefetch’s third argument is a bug in whoever built the instruction rather than something a program wrote.

Trait Implementations

impl Clone for PrefetchHint

fn clone(&self) -> PrefetchHint

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for PrefetchHint

impl Debug for PrefetchHint

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

Formats the value using the given formatter.

impl Default for PrefetchHint

fn default() -> PrefetchHint

Returns the “default value” for a type.

impl Display for PrefetchHint

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

Formats the value using the given formatter.

impl Eq for PrefetchHint

impl Hash for PrefetchHint

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for PrefetchHint

fn cmp(&self, other: &PrefetchHint) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

fn clamp_to<R>(self, range: R) -> Self

where Self: Sized, R: ClampBounds<Self>,

🔬This is a nightly-only experimental API. (clamp_to)

Restrict a value to a certain range.

impl PartialEq for PrefetchHint

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

Equality operator ==.

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

Inequality operator !=.

impl PartialOrd for PrefetchHint

fn partial_cmp(&self, other: &PrefetchHint) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

Tests less than (for self and other) and is used by the < operator.

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

Tests less than or equal to (for self and other) and is used by the <= operator.

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

Tests greater than (for self and other) and is used by the > operator.

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

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl StructuralPartialEq for PrefetchHint