diff options
Diffstat (limited to 'compiler/rustc_data_structures/src/obligation_forest')
| -rw-r--r-- | compiler/rustc_data_structures/src/obligation_forest/mod.rs | 19 |
1 files changed, 16 insertions, 3 deletions
diff --git a/compiler/rustc_data_structures/src/obligation_forest/mod.rs b/compiler/rustc_data_structures/src/obligation_forest/mod.rs index 91abdaada..27a869eb7 100644 --- a/compiler/rustc_data_structures/src/obligation_forest/mod.rs +++ b/compiler/rustc_data_structures/src/obligation_forest/mod.rs @@ -97,7 +97,17 @@ pub trait ObligationProcessor { type Error: Debug; type OUT: OutcomeTrait<Obligation = Self::Obligation, Error = Error<Self::Obligation, Self::Error>>; - fn needs_process_obligation(&self, obligation: &Self::Obligation) -> bool; + /// Implementations can provide a fast-path to obligation-processing + /// by counting the prefix of the passed iterator for which + /// `needs_process_obligation` would return false. + fn skippable_obligations<'a>( + &'a self, + _it: impl Iterator<Item = &'a Self::Obligation>, + ) -> usize { + 0 + } + + fn needs_process_obligation(&self, _obligation: &Self::Obligation) -> bool; fn process_obligation( &mut self, @@ -416,6 +426,10 @@ impl<O: ForestObligation> ObligationForest<O> { loop { let mut has_changed = false; + // This is the super fast path for cheap-to-check conditions. + let mut index = + processor.skippable_obligations(self.nodes.iter().map(|n| &n.obligation)); + // Note that the loop body can append new nodes, and those new nodes // will then be processed by subsequent iterations of the loop. // @@ -424,9 +438,8 @@ impl<O: ForestObligation> ObligationForest<O> { // `for index in 0..self.nodes.len() { ... }` because the range would // be computed with the initial length, and we would miss the appended // nodes. Therefore we use a `while` loop. - let mut index = 0; while let Some(node) = self.nodes.get_mut(index) { - // This test is extremely hot. + // This is the moderately fast path when the prefix skipping above didn't work out. if node.state.get() != NodeState::Pending || !processor.needs_process_obligation(&node.obligation) { |