Introduce ChunkedBitSet
and use it for some dataflow analyses.
This reduces peak memory usage significantly for some programs with very large functions, such as: - `keccak`, `unicode_normalization`, and `match-stress-enum`, from the `rustc-perf` benchmark suite; - `http-0.2.6` from crates.io. The new type is used in the analyses where the bitsets can get huge (e.g. 10s of thousands of bits): `MaybeInitializedPlaces`, `MaybeUninitializedPlaces`, and `EverInitializedPlaces`. Some refactoring was required in `rustc_mir_dataflow`. All existing analysis domains are either `BitSet` or a trivial wrapper around `BitSet`, and access in a few places is done via `Borrow<BitSet>` or `BorrowMut<BitSet>`. Now that some of these domains are `ClusterBitSet`, that no longer works. So this commit replaces the `Borrow`/`BorrowMut` usage with a new trait `BitSetExt` containing the needed bitset operations. The impls just forward these to the underlying bitset type. This required fiddling with trait bounds in a few places. The commit also: - Moves `static_assert_size` from `rustc_data_structures` to `rustc_index` so it can be used in the latter; the former now re-exports it so existing users are unaffected. - Factors out some common "clear excess bits in the final word" functionality in `bit_set.rs`. - Uses `fill` in a few places instead of loops.
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14 changed files with 806 additions and 75 deletions
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@ -1,10 +1,12 @@
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//! Random access inspection of the results of a dataflow analysis.
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use crate::framework::BitSetExt;
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use std::borrow::Borrow;
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use std::cmp::Ordering;
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#[cfg(debug_assertions)]
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use rustc_index::bit_set::BitSet;
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use rustc_index::vec::Idx;
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use rustc_middle::mir::{self, BasicBlock, Location};
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use super::{Analysis, Direction, Effect, EffectIndex, Results};
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@ -209,13 +211,13 @@ where
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}
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}
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impl<'mir, 'tcx, A, R, T> ResultsCursor<'mir, 'tcx, A, R>
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impl<'mir, 'tcx, A, R> ResultsCursor<'mir, 'tcx, A, R>
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where
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A: Analysis<'tcx, Domain = BitSet<T>>,
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T: Idx,
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A: crate::GenKillAnalysis<'tcx>,
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A::Domain: BitSetExt<A::Idx>,
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R: Borrow<Results<'tcx, A>>,
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{
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pub fn contains(&self, elem: T) -> bool {
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pub fn contains(&self, elem: A::Idx) -> bool {
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self.get().contains(elem)
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}
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}
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