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Use rustc_data_structures::union_find.

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This commit is contained in:
Camille Gillot 2025-08-27 01:40:16 +00:00
parent 28ff5cf502
commit 5d0e66d451
1 changed files with 14 additions and 28 deletions
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42
compiler/rustc_mir_transform/src/dest_prop.rs
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@ -137,6 +137,7 @@
//! [attempt 3]: https://github.com/rust-lang/rust/pull/72632
//! [attempt 4]: https://github.com/rust-lang/rust/pull/96451
use rustc_data_structures::union_find::UnionFind;
use rustc_index::bit_set::DenseBitSet;
use rustc_index::interval::SparseIntervalMatrix;
use rustc_index::{IndexVec, newtype_index};
@ -225,13 +226,12 @@ impl<'tcx> crate::MirPass<'tcx> for DestinationPropagation {
merged_locals.insert(orig_dst);
// Replace `src` by `dst`.
relevant.union(src, dst);
live.union_rows(/* read */ src, /* write */ dst);
let head = relevant.union(src, dst);
live.union_rows(/* read */ src, /* write */ head);
live.union_rows(/* read */ dst, /* write */ head);
}
}
trace!(?merged_locals);
relevant.make_idempotent();
trace!(?relevant.renames);
if merged_locals.is_empty() {
@ -326,7 +326,7 @@ newtype_index! {
struct RelevantLocals {
original: IndexVec<RelevantLocal, Local>,
shrink: IndexVec<Local, Option<RelevantLocal>>,
renames: IndexVec<RelevantLocal, RelevantLocal>,
renames: UnionFind<RelevantLocal>,
}
impl RelevantLocals {
@ -345,35 +345,21 @@ impl RelevantLocals {
declare(dest)
}
let renames = IndexVec::from_fn_n(|l| l, original.len());
let renames = UnionFind::new(original.len());
RelevantLocals { original, shrink, renames }
}
fn find(&self, src: Local) -> Option<RelevantLocal> {
let mut src = self.shrink[src]?;
while let s2 = self.renames[src]
&& src != s2
{
src = s2
}
fn find(&mut self, src: Local) -> Option<RelevantLocal> {
let src = self.shrink[src]?;
let src = self.renames.find(src);
Some(src)
}
fn union(&mut self, lhs: RelevantLocal, rhs: RelevantLocal) {
self.renames[lhs] = rhs;
}
fn make_idempotent(&mut self) {
for l in self.renames.indices() {
let mut h = self.renames[l];
while let h2 = self.renames[h]
&& h != h2
{
h = h2
}
self.renames[l] = h;
debug_assert_eq!(h, self.renames[h], "non-idempotent for {l:?}");
}
fn union(&mut self, lhs: RelevantLocal, rhs: RelevantLocal) -> RelevantLocal {
let head = self.renames.unify(lhs, rhs);
// We need to ensure we keep the original local of the RHS, as it may be a required local.
self.original[head] = self.original[rhs];
head
}
}