Rollup merge of #140509 - tmiasko:merge-contiguous-ranges, r=jswrenn

transmutability: merge contiguous runs with a common destination Based on #140380. r? `@jswrenn` `@joshlf`

Author: matthiaskrgr

compiler/rustc_transmute/src/layout/dfa.rs

@@ -266,7 +266,7 @@ where
  }
 
  #[cfg(test)]
- pub(crate) fn from_edges<B: Copy + Into<Byte>>(
+ pub(crate) fn from_edges<B: Clone + Into<Byte>>(
  start: u32,
  accept: u32,
  edges: &[(u32, B, u32)],
@@ -275,8 +275,8 @@ where
  let accept = State(accept);
  let mut transitions: Map<State, Vec<(Byte, State)>> = Map::default();
 
- for (src, edge, dst) in edges.iter().copied() {
- transitions.entry(State(src)).or_default().push((edge.into(), State(dst)));
+ for &(src, ref edge, dst) in edges.iter() {
+ transitions.entry(State(src)).or_default().push((edge.clone().into(), State(dst)));
  }
 
  let transitions = transitions
@@ -401,12 +401,24 @@ mod edge_set {
  mut join: impl FnMut(Option<S>, Option<S>) -> S,
  ) -> EdgeSet<S>
  where
- S: Copy,
+ S: Copy + Eq,
  {
+ let mut runs: SmallVec<[(Byte, S); 1]> = SmallVec::new();
  let xs = self.runs.iter().copied();
  let ys = other.runs.iter().copied();
- // FIXME(@joshlf): Merge contiguous runs with common destination.
- EdgeSet { runs: union(xs, ys).map(|(range, (x, y))| (range, join(x, y))).collect() }
+ for (range, (x, y)) in union(xs, ys) {
+ let state = join(x, y);
+ match runs.last_mut() {
+ // Merge contiguous runs with a common destination.
+ Some(&mut (ref mut last_range, ref mut last_state))
+ if last_range.end == range.start && *last_state == state =>
+ {
+ last_range.end = range.end
+ }
+ _ => runs.push((range, state)),
+ }
+ }
+ EdgeSet { runs }
  }
  }
 }

compiler/rustc_transmute/src/maybe_transmutable/tests.rs

@@ -314,7 +314,7 @@ mod union {
  let u = s.clone().union(t.clone(), new_state);
 
  let expected_u =
- Dfa::from_edges(b, a, &[(b, 0, c), (b, 1, d), (d, 1, a), (d, 0, a), (c, 0, a)]);
+ Dfa::from_edges(b, a, &[(b, 0..=0, c), (b, 1..=1, d), (d, 0..=1, a), (c, 0..=0, a)]);
 
  assert_eq!(u, expected_u);