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merge: micro-optimize allocation of Merge object for resolved value

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It's super common that a Merge object holds a resolved value, so let's inline
up to 1 element. T of Merge<T> usually consists of a couple of pointer-sized
fields. I don't see any measurable speed up, but it's no worse than the
original.
This commit is contained in:
Yuya Nishihara 2023-11-03 17:32:39 +09:00
parent 1140295829
commit 09987c1d27
1 changed files with 6 additions and 5 deletions
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11
lib/src/merge.rs
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@ -21,10 +21,11 @@ use std::fmt::{Debug, Formatter};
use std::hash::Hash;
use std::io::Write;
use std::iter::zip;
use std::slice;
use std::sync::Arc;
use std::{slice, vec};
use itertools::Itertools;
use smallvec::{smallvec_inline, SmallVec};
use crate::backend;
use crate::backend::{BackendError, FileId, ObjectId, TreeId, TreeValue};
@ -115,7 +116,7 @@ where
#[derive(PartialEq, Eq, Hash, Clone)]
pub struct Merge<T> {
/// Alternates between positive and negative terms, starting with positive.
values: Vec<T>,
values: SmallVec<[T; 1]>,
}
impl<T: Debug> Debug for Merge<T> {
@ -143,7 +144,7 @@ impl<T> Merge<T> {
/// Creates a `Merge` with a single resolved value.
pub fn resolved(value: T) -> Self {
Merge {
values: vec![value],
values: smallvec_inline![value],
}
}
@ -321,7 +322,7 @@ impl<T> Merge<T> {
/// the checking until after `from_iter()` (to `MergeBuilder::build()`).
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct MergeBuilder<T> {
values: Vec<T>,
values: SmallVec<[T; 1]>,
}
impl<T> Default for MergeBuilder<T> {
@ -345,7 +346,7 @@ impl<T> MergeBuilder<T> {
impl<T> IntoIterator for Merge<T> {
type Item = T;
type IntoIter = vec::IntoIter<T>;
type IntoIter = smallvec::IntoIter<[T; 1]>;
fn into_iter(self) -> Self::IntoIter {
self.values.into_iter()