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Use SSO_ARRAY_SIZE instead of 8 in SsoHashMap impl

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This commit is contained in:
Maybe Waffle 2023-04-11 10:56:35 +00:00
parent 0465201f77
commit a32959263c
1 changed files with 17 additions and 17 deletions
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34
compiler/rustc_data_structures/src/sso/map.rs
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@ -5,20 +5,20 @@
use std::hash::Hash;
use std::ops::Index;
// For pointer-sized arguments arrays
// are faster than set/map for up to 64
// arguments.
//
// On the other hand such a big array
// hurts cache performance, makes passing
// sso structures around very expensive.
//
// Biggest performance benefit is gained
// for reasonably small arrays that stay
// small in vast majority of cases.
//
// '8' is chosen as a sane default, to be
// reevaluated later.
/// For pointer-sized arguments arrays
/// are faster than set/map for up to 64
/// arguments.
///
/// On the other hand such a big array
/// hurts cache performance, makes passing
/// sso structures around very expensive.
///
/// Biggest performance benefit is gained
/// for reasonably small arrays that stay
/// small in vast majority of cases.
///
/// '8' is chosen as a sane default, to be
/// reevaluated later.
const SSO_ARRAY_SIZE: usize = 8;
/// Small-storage-optimized implementation of a map.
@ -407,7 +407,7 @@ fn extend_reserve(&mut self, additional: usize) {
impl<K, V> IntoIterator for SsoHashMap<K, V> {
type IntoIter = Either<
<ArrayVec<(K, V), 8> as IntoIterator>::IntoIter,
<ArrayVec<(K, V), SSO_ARRAY_SIZE> as IntoIterator>::IntoIter,
<FxHashMap<K, V> as IntoIterator>::IntoIter,
>;
type Item = <Self::IntoIter as Iterator>::Item;
@ -437,7 +437,7 @@ fn adapt_array_mut_it<K, V>(pair: &mut (K, V)) -> (&K, &mut V) {
impl<'a, K, V> IntoIterator for &'a SsoHashMap<K, V> {
type IntoIter = Either<
std::iter::Map<
<&'a ArrayVec<(K, V), 8> as IntoIterator>::IntoIter,
<&'a ArrayVec<(K, V), SSO_ARRAY_SIZE> as IntoIterator>::IntoIter,
fn(&'a (K, V)) -> (&'a K, &'a V),
>,
<&'a FxHashMap<K, V> as IntoIterator>::IntoIter,
@ -455,7 +455,7 @@ fn into_iter(self) -> Self::IntoIter {
impl<'a, K, V> IntoIterator for &'a mut SsoHashMap<K, V> {
type IntoIter = Either<
std::iter::Map<
<&'a mut ArrayVec<(K, V), 8> as IntoIterator>::IntoIter,
<&'a mut ArrayVec<(K, V), SSO_ARRAY_SIZE> as IntoIterator>::IntoIter,
fn(&'a mut (K, V)) -> (&'a K, &'a mut V),
>,
<&'a mut FxHashMap<K, V> as IntoIterator>::IntoIter,