[rust-compiler] Use rustc-hash FxHasher for all maps and sets#36811
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Boshen wants to merge 1 commit into
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[rust-compiler] Use rustc-hash FxHasher for all maps and sets#36811Boshen wants to merge 1 commit into
Boshen wants to merge 1 commit into
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Replace std HashMap/HashSet with rustc_hash FxHashMap/FxHashSet and switch indexmap to the FxBuildHasher hasher across all compiler crates. Adds rustc-hash = "2" to every crate and consolidates the imports to single brace imports at the top of each file.
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Swaps the default hashers across the Rust compiler crates for rustc-hash's faster
FxHasher.Why
FxHasheris a simple, fast, non-cryptographic hasher. std's default (SipHash) is DoS-resistant but heavy — the compiler keys maps/sets almost entirely on small integer IDs (IdentifierId,BlockId,ScopeId, …) where that protection buys nothing. Switching gives:HashMap/HashSet.Changes
std::collections::HashMap/HashSet→rustc_hash::FxHashMap/FxHashSetindexmapIndexMap/IndexSetnow useFxBuildHasher, inlined asIndexMap<K, V, FxBuildHasher>(noFxIndexMaptype aliases)rustc-hash = "2"added to all 12 crate manifestsrustc_hash/indexmapimports consolidated into single brace imports at the top of each fileThe change is serde-neutral:
FxHashMapandIndexMap<_, _, FxBuildHasher>serialize to byte-identical JSON, andIndexMapkeeps insertion order.cargo check,cargo fmt --check, andcargo testall pass with no warnings.