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rustc::hir::map::definitions - fix O(n^2) when disambiguating

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Instead of finding the next free disambiguator by incrementing it until
you find a place, store the next available disambiguator in an hash-map.

This avoids O(n^2) performance when lots of items have the same
un-disambiguated `DefPathData` - e.g. all `use` items have
`DefPathData::Misc`.
This commit is contained in:
Ariel Ben-Yehuda 2017-08-01 14:44:20 +03:00
parent c9d14a846f
commit 70478ca5c8
1 changed files with 16 additions and 16 deletions
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32
src/librustc/hir/map/definitions.rs
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@ -18,7 +18,7 @@ use hir;
use hir::def_id::{CrateNum, DefId, DefIndex, LOCAL_CRATE, DefIndexAddressSpace,
CRATE_DEF_INDEX};
use ich::Fingerprint;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::indexed_vec::IndexVec;
use rustc_data_structures::stable_hasher::StableHasher;
use serialize::{Encodable, Decodable, Encoder, Decoder};
@ -153,7 +153,7 @@ pub struct Definitions {
pub(super) node_to_hir_id: IndexVec<ast::NodeId, hir::HirId>,
macro_def_scopes: FxHashMap<Mark, DefId>,
expansions: FxHashMap<DefIndex, Mark>,
keys_created: FxHashSet<DefKey>,
next_disambiguator: FxHashMap<(DefIndex, DefPathData), u32>,
}
// Unfortunately we have to provide a manual impl of Clone because of the
@ -170,7 +170,7 @@ impl Clone for Definitions {
node_to_hir_id: self.node_to_hir_id.clone(),
macro_def_scopes: self.macro_def_scopes.clone(),
expansions: self.expansions.clone(),
keys_created: self.keys_created.clone(),
next_disambiguator: self.next_disambiguator.clone(),
}
}
}
@ -402,7 +402,7 @@ impl Definitions {
node_to_hir_id: IndexVec::new(),
macro_def_scopes: FxHashMap(),
expansions: FxHashMap(),
keys_created: FxHashSet(),
next_disambiguator: FxHashMap(),
}
}
@ -516,20 +516,20 @@ impl Definitions {
// The root node must be created with create_root_def()
assert!(data != DefPathData::CrateRoot);
// Find a unique DefKey. This basically means incrementing the disambiguator
// until we get no match.
let mut key = DefKey {
parent: Some(parent),
disambiguated_data: DisambiguatedDefPathData {
data,
disambiguator: 0
}
// Find the next free disambiguator for this key.
let disambiguator = {
let next_disamb = self.next_disambiguator.entry((parent, data.clone())).or_insert(0);
let disambiguator = *next_disamb;
*next_disamb = next_disamb.checked_add(1).expect("disambiguator overflow");
disambiguator
};
while self.keys_created.contains(&key) {
key.disambiguated_data.disambiguator += 1;
}
self.keys_created.insert(key.clone());
let key = DefKey {
parent: Some(parent),
disambiguated_data: DisambiguatedDefPathData {
data, disambiguator
}
};
let parent_hash = self.table.def_path_hash(parent);
let def_path_hash = key.compute_stable_hash(parent_hash);