diff options
Diffstat (limited to 'compiler/rustc_index/src/bit_set.rs')
| -rw-r--r-- | compiler/rustc_index/src/bit_set.rs | 12 |
1 files changed, 3 insertions, 9 deletions
diff --git a/compiler/rustc_index/src/bit_set.rs b/compiler/rustc_index/src/bit_set.rs index 3b03296e5c0..684bd34f909 100644 --- a/compiler/rustc_index/src/bit_set.rs +++ b/compiler/rustc_index/src/bit_set.rs @@ -491,18 +491,14 @@ pub struct ChunkedBitSet<T> { marker: PhantomData<T>, } -// Note: the chunk domain size is duplicated in each variant. This is a bit -// inconvenient, but it allows the type size to be smaller than if we had an -// outer struct containing a chunk domain size plus the `Chunk`, because the -// compiler can place the chunk domain size after the tag. +// NOTE: The chunk size is computed on-the-fly on each manipulation of a chunk. +// This avoids storing it, as it's almost always CHUNK_BITS except for the last one. #[derive(Clone, Debug, PartialEq, Eq)] enum Chunk { /// A chunk that is all zeros; we don't represent the zeros explicitly. - /// The `ChunkSize` is always non-zero. Zeros, /// A chunk that is all ones; we don't represent the ones explicitly. - /// `ChunkSize` is always non-zero. Ones, /// A chunk that has a mix of zeros and ones, which are represented @@ -514,9 +510,7 @@ enum Chunk { /// to store the length, which would make this type larger. These excess /// words are always zero, as are any excess bits in the final in-use word. /// - /// The first `ChunkSize` field is always non-zero. - /// - /// The second `ChunkSize` field is the count of 1s set in the chunk, and + /// The `ChunkSize` field is the count of 1s set in the chunk, and /// must satisfy `0 < count < chunk_domain_size`. /// /// The words are within an `Rc` because it's surprisingly common to |