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Rollup merge of rust-lang#94699 - ssomers:btree_prune_insert, r=Dylan…
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…-DPC

BTree: remove dead data needlessly complicating insert

Possibly needless instructions generated

r? rust-lang/libs
r? `@Amanieu`
cc `@frank-king`
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@Dylan-DPC
Dylan-DPC authored Mar 9, 2022
2 parents f2b9fc2 + 36bb53d commit 0f880ef
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Showing 2 changed files with 19 additions and 40 deletions.
6 changes: 3 additions & 3 deletions library/alloc/src/collections/btree/map/entry.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@ use core::marker::PhantomData;
use core::mem;

use super::super::borrow::DormantMutRef;
use super::super::node::{marker, Handle, InsertResult::*, NodeRef};
use super::super::node::{marker, Handle, NodeRef};
use super::BTreeMap;

use Entry::*;
Expand Down Expand Up @@ -313,13 +313,13 @@ impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
#[stable(feature = "rust1", since = "1.0.0")]
pub fn insert(self, value: V) -> &'a mut V {
let out_ptr = match self.handle.insert_recursing(self.key, value) {
(Fit(_), val_ptr) => {
(None, val_ptr) => {
// SAFETY: We have consumed self.handle and the handle returned.
let map = unsafe { self.dormant_map.awaken() };
map.length += 1;
val_ptr
}
(Split(ins), val_ptr) => {
(Some(ins), val_ptr) => {
drop(ins.left);
// SAFETY: We have consumed self.handle and the reference returned.
let map = unsafe { self.dormant_map.awaken() };
Expand Down
53 changes: 16 additions & 37 deletions library/alloc/src/collections/btree/node.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -861,11 +861,10 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, mark
/// this edge. This method splits the node if there isn't enough room.
///
/// The returned pointer points to the inserted value.
fn insert(mut self, key: K, val: V) -> (InsertResult<'a, K, V, marker::Leaf>, *mut V) {
fn insert(mut self, key: K, val: V) -> (Option<SplitResult<'a, K, V, marker::Leaf>>, *mut V) {
if self.node.len() < CAPACITY {
let val_ptr = self.insert_fit(key, val);
let kv = unsafe { Handle::new_kv(self.node, self.idx) };
(InsertResult::Fit(kv), val_ptr)
(None, val_ptr)
} else {
let (middle_kv_idx, insertion) = splitpoint(self.idx);
let middle = unsafe { Handle::new_kv(self.node, middle_kv_idx) };
Expand All @@ -879,7 +878,7 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, mark
},
};
let val_ptr = insertion_edge.insert_fit(key, val);
(InsertResult::Split(result), val_ptr)
(Some(result), val_ptr)
}
}
}
Expand Down Expand Up @@ -923,13 +922,12 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>,
key: K,
val: V,
edge: Root<K, V>,
) -> InsertResult<'a, K, V, marker::Internal> {
) -> Option<SplitResult<'a, K, V, marker::Internal>> {
assert!(edge.height == self.node.height - 1);

if self.node.len() < CAPACITY {
self.insert_fit(key, val, edge);
let kv = unsafe { Handle::new_kv(self.node, self.idx) };
InsertResult::Fit(kv)
None
} else {
let (middle_kv_idx, insertion) = splitpoint(self.idx);
let middle = unsafe { Handle::new_kv(self.node, middle_kv_idx) };
Expand All @@ -943,7 +941,7 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>,
},
};
insertion_edge.insert_fit(key, val, edge);
InsertResult::Split(result)
Some(result)
}
}
}
Expand All @@ -953,32 +951,26 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, mark
/// this edge. This method splits the node if there isn't enough room, and tries to
/// insert the split off portion into the parent node recursively, until the root is reached.
///
/// If the returned result is a `Fit`, its handle's node can be this edge's node or an ancestor.
/// If the returned result is a `Split`, the `left` field will be the root node.
/// The returned pointer points to the inserted value.
/// If the returned result is some `SplitResult`, the `left` field will be the root node.
/// The returned pointer points to the inserted value, which in the case of `SplitResult`
/// is in the `left` or `right` tree.
pub fn insert_recursing(
self,
key: K,
value: V,
) -> (InsertResult<'a, K, V, marker::LeafOrInternal>, *mut V) {
) -> (Option<SplitResult<'a, K, V, marker::LeafOrInternal>>, *mut V) {
let (mut split, val_ptr) = match self.insert(key, value) {
(InsertResult::Fit(handle), ptr) => {
return (InsertResult::Fit(handle.forget_node_type()), ptr);
}
(InsertResult::Split(split), val_ptr) => (split.forget_node_type(), val_ptr),
(None, val_ptr) => return (None, val_ptr),
(Some(split), val_ptr) => (split.forget_node_type(), val_ptr),
};

loop {
split = match split.left.ascend() {
Ok(parent) => match parent.insert(split.kv.0, split.kv.1, split.right) {
InsertResult::Fit(handle) => {
return (InsertResult::Fit(handle.forget_node_type()), val_ptr);
}
InsertResult::Split(split) => split.forget_node_type(),
None => return (None, val_ptr),
Some(split) => split.forget_node_type(),
},
Err(root) => {
return (InsertResult::Split(SplitResult { left: root, ..split }), val_ptr);
}
Err(root) => return (Some(SplitResult { left: root, ..split }), val_ptr),
};
}
}
Expand Down Expand Up @@ -1529,14 +1521,6 @@ impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Leaf>, marker::K
}
}

impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::KV> {
pub fn forget_node_type(
self,
) -> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, marker::KV> {
unsafe { Handle::new_kv(self.node.forget_type(), self.idx) }
}
}

impl<BorrowType, K, V, Type> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, Type> {
/// Checks whether the underlying node is an `Internal` node or a `Leaf` node.
pub fn force(
Expand Down Expand Up @@ -1621,7 +1605,7 @@ pub enum ForceResult<Leaf, Internal> {
pub struct SplitResult<'a, K, V, NodeType> {
// Altered node in existing tree with elements and edges that belong to the left of `kv`.
pub left: NodeRef<marker::Mut<'a>, K, V, NodeType>,
// Some key and value split off, to be inserted elsewhere.
// Some key and value that existed before and were split off, to be inserted elsewhere.
pub kv: (K, V),
// Owned, unattached, new node with elements and edges that belong to the right of `kv`.
pub right: NodeRef<marker::Owned, K, V, NodeType>,
Expand All @@ -1639,11 +1623,6 @@ impl<'a, K, V> SplitResult<'a, K, V, marker::Internal> {
}
}

pub enum InsertResult<'a, K, V, NodeType> {
Fit(Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, marker::KV>),
Split(SplitResult<'a, K, V, NodeType>),
}

pub mod marker {
use core::marker::PhantomData;

Expand Down

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