bjoernager/rust
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Limit creation of tracked place directly.

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This commit is contained in:
Camille GILLOT 2023-01-28 11:23:18 +00:00
parent 9a6c04f5d0
commit c48756cdbf
2 changed files with 22 additions and 11 deletions
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11
compiler/rustc_mir_transform/src/dataflow_const_prop.rs
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@ -37,9 +37,6 @@ impl<'tcx> MirPass<'tcx> for DataflowConstProp {
return;
}
// Decide which places to track during the analysis.
let map = Map::from_filter(tcx, body, Ty::is_scalar);
// We want to have a somewhat linear runtime w.r.t. the number of statements/terminators.
// Let's call this number `n`. Dataflow analysis has `O(h*n)` transfer function
// applications, where `h` is the height of the lattice. Because the height of our lattice
@ -48,10 +45,10 @@ impl<'tcx> MirPass<'tcx> for DataflowConstProp {
// `O(num_nodes * tracked_places * n)` in terms of time complexity. Since the number of
// map nodes is strongly correlated to the number of tracked places, this becomes more or
// less `O(n)` if we place a constant limit on the number of tracked places.
if tcx.sess.mir_opt_level() < 4 && map.tracked_places() > PLACE_LIMIT {
debug!("aborted dataflow const prop due to too many tracked places");
return;
}
let place_limit = if tcx.sess.mir_opt_level() < 4 { Some(PLACE_LIMIT) } else { None };
// Decide which places to track during the analysis.
let map = Map::from_filter(tcx, body, Ty::is_scalar, place_limit);
// Perform the actual dataflow analysis.
let analysis = ConstAnalysis::new(tcx, body, map);