Don't rerun goals if none of its vars have changed

Author: compiler-errors

compiler/rustc_infer/src/infer/context.rs

@@ -89,6 +89,57 @@ impl<'tcx> rustc_type_ir::InferCtxtLike for InferCtxt<'tcx> {
         self.inner.borrow_mut().unwrap_region_constraints().opportunistic_resolve_var(self.tcx, vid)
     }
 
+    fn is_changed_arg(&self, arg: ty::GenericArg<'tcx>) -> bool {
+        match arg.unpack() {
+            ty::GenericArgKind::Lifetime(_) => {
+                // Lifetimes should not change affect trait selection.
+                false
+            }
+            ty::GenericArgKind::Type(ty) => {
+                if let ty::Infer(infer_ty) = *ty.kind() {
+                    match infer_ty {
+                        ty::InferTy::TyVar(vid) => {
+                            !self.probe_ty_var(vid).is_err_and(|_| self.root_var(vid) == vid)
+                        }
+                        ty::InferTy::IntVar(vid) => {
+                            let mut inner = self.inner.borrow_mut();
+                            !matches!(
+                                inner.int_unification_table().probe_value(vid),
+                                ty::IntVarValue::Unknown
+                                    if inner.int_unification_table().find(vid) == vid
+                            )
+                        }
+                        ty::InferTy::FloatVar(vid) => {
+                            let mut inner = self.inner.borrow_mut();
+                            !matches!(
+                                inner.float_unification_table().probe_value(vid),
+                                ty::FloatVarValue::Unknown
+                                    if inner.float_unification_table().find(vid) == vid
+                            )
+                        }
+                        ty::InferTy::FreshTy(_)
+                        | ty::InferTy::FreshIntTy(_)
+                        | ty::InferTy::FreshFloatTy(_) => true,
+                    }
+                } else {
+                    true
+                }
+            }
+            ty::GenericArgKind::Const(ct) => {
+                if let ty::ConstKind::Infer(infer_ct) = ct.kind() {
+                    match infer_ct {
+                        ty::InferConst::Var(vid) => !self
+                            .probe_const_var(vid)
+                            .is_err_and(|_| self.root_const_var(vid) == vid),
+                        ty::InferConst::Fresh(_) => true,
+                    }
+                } else {
+                    true
+                }
+            }
+        }
+    }
+
     fn next_region_infer(&self) -> ty::Region<'tcx> {
         self.next_region_var(RegionVariableOrigin::MiscVariable(DUMMY_SP))
     }

compiler/rustc_infer/src/infer/opaque_types/table.rs

@@ -24,6 +24,12 @@ pub struct OpaqueTypeStorageEntries {
     duplicate_entries: usize,
 }
 
+impl rustc_type_ir::inherent::OpaqueTypeStorageEntries for OpaqueTypeStorageEntries {
+    fn needs_reevaluation(self, canonicalized: usize) -> bool {
+        self.opaque_types != canonicalized
+    }
+}
+
 impl<'tcx> OpaqueTypeStorage<'tcx> {
     #[instrument(level = "debug")]
     pub(crate) fn remove(

compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs

@@ -53,10 +53,10 @@ where
 {
     /// Canonicalizes the goal remembering the original values
     /// for each bound variable.
-    pub(super) fn canonicalize_goal<T: TypeFoldable<I>>(
+    pub(super) fn canonicalize_goal(
         &self,
-        goal: Goal<I, T>,
-    ) -> (Vec<I::GenericArg>, CanonicalInput<I, T>) {
+        goal: Goal<I, I::Predicate>,
+    ) -> (Vec<I::GenericArg>, CanonicalInput<I, I::Predicate>) {
         // We only care about one entry per `OpaqueTypeKey` here,
         // so we only canonicalize the lookup table and ignore
         // duplicate entries.
@@ -130,7 +130,12 @@ where
                     if goals.is_empty() {
                         assert!(matches!(goals_certainty, Certainty::Yes));
                     }
-                    (Certainty::Yes, NestedNormalizationGoals(goals))
+                    (
+                        Certainty::Yes,
+                        NestedNormalizationGoals(
+                            goals.into_iter().map(|(s, g, _)| (s, g)).collect(),
+                        ),
+                    )
                 }
                 _ => {
                     let certainty = shallow_certainty.and(goals_certainty);
@@ -272,7 +277,7 @@ where
     pub(super) fn instantiate_and_apply_query_response(
         &mut self,
         param_env: I::ParamEnv,
-        original_values: Vec<I::GenericArg>,
+        original_values: &[I::GenericArg],
         response: CanonicalResponse<I>,
     ) -> (NestedNormalizationGoals<I>, Certainty) {
         let instantiation = Self::compute_query_response_instantiation_values(

compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs

@@ -22,8 +22,9 @@ use crate::delegate::SolverDelegate;
 use crate::solve::inspect::{self, ProofTreeBuilder};
 use crate::solve::search_graph::SearchGraph;
 use crate::solve::{
-    CanonicalInput, Certainty, FIXPOINT_STEP_LIMIT, Goal, GoalEvaluationKind, GoalSource,
-    HasChanged, NestedNormalizationGoals, NoSolution, QueryInput, QueryResult,
+    CanonicalGoalCacheKey, CanonicalInput, Certainty, FIXPOINT_STEP_LIMIT, Goal,
+    GoalEvaluationKind, GoalSource, HasChanged, NestedNormalizationGoals, NoSolution, QueryInput,
+    QueryResult,
 };
 
 pub(super) mod canonical;
@@ -115,7 +116,7 @@ where
 
     pub(super) search_graph: &'a mut SearchGraph<D>,
 
-    nested_goals: Vec<(GoalSource, Goal<I, I::Predicate>)>,
+    nested_goals: Vec<(GoalSource, Goal<I, I::Predicate>, Option<CanonicalGoalCacheKey<I>>)>,
 
     pub(super) origin_span: I::Span,
 
@@ -147,8 +148,9 @@ pub trait SolverDelegateEvalExt: SolverDelegate {
         goal: Goal<Self::Interner, <Self::Interner as Interner>::Predicate>,
         generate_proof_tree: GenerateProofTree,
         span: <Self::Interner as Interner>::Span,
+        cache_key: Option<CanonicalGoalCacheKey<Self::Interner>>,
     ) -> (
-        Result<(HasChanged, Certainty), NoSolution>,
+        Result<(HasChanged, Certainty, CanonicalGoalCacheKey<Self::Interner>), NoSolution>,
         Option<inspect::GoalEvaluation<Self::Interner>>,
     );
 
@@ -171,8 +173,17 @@ pub trait SolverDelegateEvalExt: SolverDelegate {
         &self,
         goal: Goal<Self::Interner, <Self::Interner as Interner>::Predicate>,
         generate_proof_tree: GenerateProofTree,
+        cache_key: Option<CanonicalGoalCacheKey<Self::Interner>>,
     ) -> (
-        Result<(NestedNormalizationGoals<Self::Interner>, HasChanged, Certainty), NoSolution>,
+        Result<
+            (
+                NestedNormalizationGoals<Self::Interner>,
+                HasChanged,
+                Certainty,
+                CanonicalGoalCacheKey<Self::Interner>,
+            ),
+            NoSolution,
+        >,
         Option<inspect::GoalEvaluation<Self::Interner>>,
     );
 }
@@ -188,9 +199,13 @@ where
         goal: Goal<I, I::Predicate>,
         generate_proof_tree: GenerateProofTree,
         span: I::Span,
-    ) -> (Result<(HasChanged, Certainty), NoSolution>, Option<inspect::GoalEvaluation<I>>) {
+        cache_key: Option<CanonicalGoalCacheKey<I>>,
+    ) -> (
+        Result<(HasChanged, Certainty, CanonicalGoalCacheKey<I>), NoSolution>,
+        Option<inspect::GoalEvaluation<I>>,
+    ) {
         EvalCtxt::enter_root(self, self.cx().recursion_limit(), generate_proof_tree, span, |ecx| {
-            ecx.evaluate_goal(GoalEvaluationKind::Root, GoalSource::Misc, goal)
+            ecx.evaluate_goal(GoalEvaluationKind::Root, GoalSource::Misc, goal, cache_key)
         })
     }
 
@@ -201,7 +216,7 @@ where
     ) -> bool {
         self.probe(|| {
             EvalCtxt::enter_root(self, root_depth, GenerateProofTree::No, I::Span::dummy(), |ecx| {
-                ecx.evaluate_goal(GoalEvaluationKind::Root, GoalSource::Misc, goal)
+                ecx.evaluate_goal(GoalEvaluationKind::Root, GoalSource::Misc, goal, None)
             })
             .0
         })
@@ -213,16 +228,22 @@ where
         &self,
         goal: Goal<I, I::Predicate>,
         generate_proof_tree: GenerateProofTree,
+        cache_key: Option<CanonicalGoalCacheKey<I>>,
     ) -> (
-        Result<(NestedNormalizationGoals<I>, HasChanged, Certainty), NoSolution>,
+        Result<
+            (NestedNormalizationGoals<I>, HasChanged, Certainty, CanonicalGoalCacheKey<I>),
+            NoSolution,
+        >,
         Option<inspect::GoalEvaluation<I>>,
     ) {
         EvalCtxt::enter_root(
             self,
             self.cx().recursion_limit(),
             generate_proof_tree,
             I::Span::dummy(),
-            |ecx| ecx.evaluate_goal_raw(GoalEvaluationKind::Root, GoalSource::Misc, goal),
+            |ecx| {
+                ecx.evaluate_goal_raw(GoalEvaluationKind::Root, GoalSource::Misc, goal, cache_key)
+            },
         )
     }
 }
@@ -447,11 +468,12 @@ where
         goal_evaluation_kind: GoalEvaluationKind,
         source: GoalSource,
         goal: Goal<I, I::Predicate>,
-    ) -> Result<(HasChanged, Certainty), NoSolution> {
-        let (normalization_nested_goals, has_changed, certainty) =
-            self.evaluate_goal_raw(goal_evaluation_kind, source, goal)?;
+        cache_key: Option<CanonicalGoalCacheKey<I>>,
+    ) -> Result<(HasChanged, Certainty, CanonicalGoalCacheKey<I>), NoSolution> {
+        let (normalization_nested_goals, has_changed, certainty, cache_key) =
+            self.evaluate_goal_raw(goal_evaluation_kind, source, goal, cache_key)?;
         assert!(normalization_nested_goals.is_empty());
-        Ok((has_changed, certainty))
+        Ok((has_changed, certainty, cache_key))
     }
 
     /// Recursively evaluates `goal`, returning the nested goals in case
@@ -466,7 +488,27 @@ where
         goal_evaluation_kind: GoalEvaluationKind,
         source: GoalSource,
         goal: Goal<I, I::Predicate>,
-    ) -> Result<(NestedNormalizationGoals<I>, HasChanged, Certainty), NoSolution> {
+        cache_key: Option<CanonicalGoalCacheKey<I>>,
+    ) -> Result<
+        (NestedNormalizationGoals<I>, HasChanged, Certainty, CanonicalGoalCacheKey<I>),
+        NoSolution,
+    > {
+        if let Some(cache_key) = cache_key {
+            if !cache_key.stalled_vars.iter().any(|value| self.delegate.is_changed_arg(*value))
+                && !self
+                    .delegate
+                    .opaque_types_storage_num_entries()
+                    .needs_reevaluation(cache_key.num_opaques)
+            {
+                return Ok((
+                    NestedNormalizationGoals::empty(),
+                    HasChanged::No,
+                    cache_key.certainty,
+                    cache_key,
+                ));
+            }
+        }
+
         let (orig_values, canonical_goal) = self.canonicalize_goal(goal);
         let mut goal_evaluation =
             self.inspect.new_goal_evaluation(goal, &orig_values, goal_evaluation_kind);
@@ -489,7 +531,7 @@ where
             if !has_only_region_constraints(response) { HasChanged::Yes } else { HasChanged::No };
 
         let (normalization_nested_goals, certainty) =
-            self.instantiate_and_apply_query_response(goal.param_env, orig_values, response);
+            self.instantiate_and_apply_query_response(goal.param_env, &orig_values, response);
         self.inspect.goal_evaluation(goal_evaluation);
 
         // FIXME: We previously had an assert here that checked that recomputing
@@ -502,7 +544,33 @@ where
         // Once we have decided on how to handle trait-system-refactor-initiative#75,
         // we should re-add an assert here.
 
-        Ok((normalization_nested_goals, has_changed, certainty))
+        // Remove the unconstrained RHS arg, which is expected to have changed.
+        let mut stalled_vars = orig_values;
+        if let Some(normalizes_to) = goal.predicate.as_normalizes_to() {
+            let normalizes_to = normalizes_to.skip_binder();
+            let rhs_arg: I::GenericArg = normalizes_to.term.into();
+            let idx = stalled_vars
+                .iter()
+                .rposition(|arg| *arg == rhs_arg)
+                .expect("expected unconstrained arg");
+            stalled_vars.swap_remove(idx);
+        }
+
+        Ok((
+            normalization_nested_goals,
+            has_changed,
+            certainty,
+            CanonicalGoalCacheKey {
+                num_opaques: canonical_goal
+                    .canonical
+                    .value
+                    .predefined_opaques_in_body
+                    .opaque_types
+                    .len(),
+                stalled_vars,
+                certainty,
+            },
+        ))
     }
 
     fn compute_goal(&mut self, goal: Goal<I, I::Predicate>) -> QueryResult<I> {
@@ -602,7 +670,7 @@ where
         let cx = self.cx();
         // If this loop did not result in any progress, what's our final certainty.
         let mut unchanged_certainty = Some(Certainty::Yes);
-        for (source, goal) in mem::take(&mut self.nested_goals) {
+        for (source, goal, cache_key) in mem::take(&mut self.nested_goals) {
             if let Some(has_changed) = self.delegate.compute_goal_fast_path(goal, self.origin_span)
             {
                 if matches!(has_changed, HasChanged::Yes) {
@@ -630,11 +698,16 @@ where
                 let unconstrained_goal =
                     goal.with(cx, ty::NormalizesTo { alias: pred.alias, term: unconstrained_rhs });
 
-                let (NestedNormalizationGoals(nested_goals), _, certainty) =
-                    self.evaluate_goal_raw(GoalEvaluationKind::Nested, source, unconstrained_goal)?;
+                let (NestedNormalizationGoals(nested_goals), _, certainty, cache_key) = self
+                    .evaluate_goal_raw(
+                        GoalEvaluationKind::Nested,
+                        source,
+                        unconstrained_goal,
+                        cache_key,
+                    )?;
                 // Add the nested goals from normalization to our own nested goals.
                 trace!(?nested_goals);
-                self.nested_goals.extend(nested_goals);
+                self.nested_goals.extend(nested_goals.into_iter().map(|(s, g)| (s, g, None)));
 
                 // Finally, equate the goal's RHS with the unconstrained var.
                 //
@@ -660,6 +733,8 @@ where
                 // looking at the "has changed" return from evaluate_goal,
                 // because we expect the `unconstrained_rhs` part of the predicate
                 // to have changed -- that means we actually normalized successfully!
+                // FIXME: Do we need to eagerly resolve here? Or should we check
+                // if the cache key has any changed vars?
                 let with_resolved_vars = self.resolve_vars_if_possible(goal);
                 if pred.alias != goal.predicate.as_normalizes_to().unwrap().skip_binder().alias {
                     unchanged_certainty = None;
@@ -668,21 +743,21 @@ where
                 match certainty {
                     Certainty::Yes => {}
                     Certainty::Maybe(_) => {
-                        self.nested_goals.push((source, with_resolved_vars));
+                        self.nested_goals.push((source, with_resolved_vars, Some(cache_key)));
                         unchanged_certainty = unchanged_certainty.map(|c| c.and(certainty));
                     }
                 }
             } else {
-                let (has_changed, certainty) =
-                    self.evaluate_goal(GoalEvaluationKind::Nested, source, goal)?;
+                let (has_changed, certainty, cache_key) =
+                    self.evaluate_goal(GoalEvaluationKind::Nested, source, goal, cache_key)?;
                 if has_changed == HasChanged::Yes {
                     unchanged_certainty = None;
                 }
 
                 match certainty {
                     Certainty::Yes => {}
                     Certainty::Maybe(_) => {
-                        self.nested_goals.push((source, goal));
+                        self.nested_goals.push((source, goal, Some(cache_key)));
                         unchanged_certainty = unchanged_certainty.map(|c| c.and(certainty));
                     }
                 }
@@ -706,7 +781,7 @@ where
         goal.predicate =
             goal.predicate.fold_with(&mut ReplaceAliasWithInfer::new(self, source, goal.param_env));
         self.inspect.add_goal(self.delegate, self.max_input_universe, source, goal);
-        self.nested_goals.push((source, goal));
+        self.nested_goals.push((source, goal, None));
     }
 
     #[instrument(level = "trace", skip(self, goals))]