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Specialize HashStable for [u8] slices

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Particularly for ctfe-stress-4, the hashing of byte slices as part of the
MIR Allocation is quite hot. Previously, we were falling back on byte-by-byte
copying of the slice into the SipHash buffer (64 bytes long) before hashing a 64
byte chunk, and then doing that again and again.

This should hopefully be an improvement for that code.
This commit is contained in:
Mark Rousskov 2021-10-23 12:11:05 -04:00
parent 514b387795
commit 3cd5c95ab0
1 changed files with 7 additions and 0 deletions
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7
compiler/rustc_data_structures/src/stable_hasher.rs
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@ -301,6 +301,13 @@ impl<T: HashStable<CTX>, CTX> HashStable<CTX> for [T] {
}
}
impl<CTX> HashStable<CTX> for [u8] {
fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
self.len().hash_stable(ctx, hasher);
hasher.write(self);
}
}
impl<T: HashStable<CTX>, CTX> HashStable<CTX> for Vec<T> {
#[inline]
fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {