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Auto merge of #120076 - Mark-Simulacrum:unhash, r=cjgillot

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Use UnhashMap for a few more maps

This avoids a few cases of hashing data that's already hashed.

cc https://github.com/rust-lang/rust/issues/56308
This commit is contained in:
bors 2024-01-19 04:43:17 +00:00
commit 1bd42be8cb
4 changed files with 28 additions and 6 deletions
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12
compiler/rustc_data_structures/src/hashes.rs
View file

@ -75,11 +75,21 @@ impl fmt::LowerHex for Hash64 {
}
}
#[derive(Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord, Default)]
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Default)]
pub struct Hash128 {
inner: u128,
}
// We expect Hash128 to be well mixed. So there's no point in hashing both parts.
//
// This also allows using Hash128-containing types in UnHash-based hashmaps, which would otherwise
// debug_assert! that we're hashing more than a single u64.
impl std::hash::Hash for Hash128 {
fn hash<H: std::hash::Hasher>(&self, h: &mut H) {
h.write_u64(self.truncate().as_u64());
}
}
impl Hash128 {
#[inline]
pub fn truncate(self) -> Hash64 {

14
compiler/rustc_data_structures/src/stable_hasher.rs
View file

@ -314,7 +314,19 @@ impl_stable_traits_for_trivial_type!(char);
impl_stable_traits_for_trivial_type!(());
impl_stable_traits_for_trivial_type!(Hash64);
impl_stable_traits_for_trivial_type!(Hash128);
// We need a custom impl as the default hash function will only hash half the bits. For stable
// hashing we want to hash the full 128-bit hash.
impl<CTX> HashStable<CTX> for Hash128 {
#[inline]
fn hash_stable(&self, _: &mut CTX, hasher: &mut StableHasher) {
self.as_u128().hash(hasher);
}
}
unsafe impl StableOrd for Hash128 {
const CAN_USE_UNSTABLE_SORT: bool = true;
}
impl<CTX> HashStable<CTX> for ! {
fn hash_stable(&self, _ctx: &mut CTX, _hasher: &mut StableHasher) {