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perf: outline and make reserve as cold #562

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perf: outline and make reserve as cold #562

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45 changes: 30 additions & 15 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1111,7 +1111,7 @@ impl<T, const N: usize> SmallVec<T, N> {
pub fn push_mut(&mut self, value: T) -> &mut T {
let len = self.len();
if len == self.capacity() {
self.reserve(1);
self.reserve_cold(1);
}

// SAFETY: `len < capacity` after the reserve,
Expand Down Expand Up @@ -1231,16 +1231,22 @@ impl<T, const N: usize> SmallVec<T, N> {
pub fn reserve(&mut self, additional: usize) {
// can't overflow since len <= capacity
if additional > self.capacity() - self.len() {
let new_capacity = infallible(
self.len()
.checked_add(additional)
.and_then(usize::checked_next_power_of_two)
.ok_or(CollectionAllocErr::CapacityOverflow)
);
self.grow(new_capacity);
self.reserve_cold(additional);
}
}

#[cold]
#[inline(never)]
fn reserve_cold(&mut self, additional: usize) {
let new_capacity = infallible(
self.len()
.checked_add(additional)
.and_then(usize::checked_next_power_of_two)
.ok_or(CollectionAllocErr::CapacityOverflow)
);
self.grow(new_capacity);
}

#[inline]
pub fn try_reserve(&mut self, additional: usize) -> Result<(), CollectionAllocErr> {
if additional > self.capacity() - self.len() {
Expand All @@ -1259,15 +1265,21 @@ impl<T, const N: usize> SmallVec<T, N> {
pub fn reserve_exact(&mut self, additional: usize) {
// can't overflow since len <= capacity
if additional > self.capacity() - self.len() {
let new_capacity = infallible(
self.len()
.checked_add(additional)
.ok_or(CollectionAllocErr::CapacityOverflow)
);
self.grow(new_capacity);
self.reserve_exact_cold(additional);
}
}

#[cold]
#[inline(never)]
fn reserve_exact_cold(&mut self, additional: usize) {
let new_capacity = infallible(
self.len()
.checked_add(additional)
.ok_or(CollectionAllocErr::CapacityOverflow)
);
self.grow(new_capacity);
}

#[inline]
pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), CollectionAllocErr> {
if additional > self.capacity() - self.len() {
Expand Down Expand Up @@ -1441,8 +1453,11 @@ impl<T, const N: usize> SmallVec<T, N> {
if index > len {
assert_failed(index, len);
}
self.reserve(1);

// reserve one if there is no capacity left
if len == self.capacity() {
self.reserve_cold(1);
}
// SAFETY: `index <= len <= capacity`,
// so the offset stays in bounds of the allocation.
let ptr = unsafe { self.as_mut_ptr().add(index) };
Expand Down