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Use if SHARDS == 1 in a couple more places. #94111

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Use if SHARDS == 1 in a couple more places. #94111

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18 changes: 11 additions & 7 deletions compiler/rustc_data_structures/src/sharded.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -47,12 +47,12 @@ impl<T> Sharded<T> {

#[inline]
pub fn get_shard_by_hash(&self, hash: u64) -> &Lock<T> {
&self.shards[get_shard_index_by_hash(hash)].0
if SHARDS == 1 { &self.shards[0].0 } else { &self.shards[get_shard_index_by_hash(hash)].0 }
}

#[inline]
pub fn get_shard_by_index(&self, i: usize) -> &Lock<T> {
&self.shards[i].0
if SHARDS == 1 { &self.shards[0].0 } else { &self.shards[i].0 }
}

pub fn lock_shards(&self) -> Vec<LockGuard<'_, T>> {
Expand Down Expand Up @@ -142,9 +142,13 @@ fn make_hash<K: Hash + ?Sized>(val: &K) -> u64 {
/// consistently for each `Sharded` instance.
#[inline]
pub fn get_shard_index_by_hash(hash: u64) -> usize {
let hash_len = mem::size_of::<usize>();
// Ignore the top 7 bits as hashbrown uses these and get the next SHARD_BITS highest bits.
// hashbrown also uses the lowest bits, so we can't use those
let bits = (hash >> (hash_len * 8 - 7 - SHARD_BITS)) as usize;
bits % SHARDS
if SHARDS == 1 {
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https://godbolt.org/z/cq9nMvz1q This change is maybe redudant, since the optimizer will see that bits % 1 has to equal zero?

0
} else {
let hash_len = mem::size_of::<usize>();
// Ignore the top 7 bits as hashbrown uses these and get the next SHARD_BITS highest bits.
// hashbrown also uses the lowest bits, so we can't use those
let bits = (hash >> (hash_len * 8 - 7 - SHARD_BITS)) as usize;
bits % SHARDS
}
}