Auto merge of rust-lang#117749 - aliemjay:perf-canon-cache, r=lcnr

cache param env canonicalization

Canonicalize ParamEnv only once and store it. Then whenever we try to canonicalize `ParamEnvAnd<'tcx, T>` we only have to canonicalize `T` and then merge the results.

Prelimiary results show ~3-4% savings in diesel and serde benchmarks.

Best to review commits individually. Some commits have a short description.

Initial implementation had a soundness bug (rust-lang#117749 (comment)) due to cache invalidation:
- When canonicalizing `Ty<'?0>` we first try to resolve region variables in the current InferCtxt which may have a constraint `?0 == 'static`. This means that we register `Ty<'?0> => Canonical<Ty<'static>>` in the cache, which is obviously incorrect in another inference context.
- This is fixed by not doing region resolution when canonicalizing the query *input* (vs. response), which is the only place where ParamEnv is used, and then in a later commit we *statically* guard against any form of inference variable resolution of the cached canonical ParamEnv's.

r? `@ghost`

compiler/rustc_infer/src/infer/combine.rs

@@ -172,7 +172,7 @@ impl<'tcx> InferCtxt<'tcx> {
             // two const param's types are able to be equal has to go through a canonical query with the actual logic
             // in `rustc_trait_selection`.
             let canonical = self.canonicalize_query(
-                (relation.param_env(), a.ty(), b.ty()),
+                relation.param_env().and((a.ty(), b.ty())),
                 &mut OriginalQueryValues::default(),
             );
             self.tcx.check_tys_might_be_eq(canonical).map_err(|_| {

compiler/rustc_middle/src/infer/canonical.rs

@@ -21,17 +21,20 @@
 //!
 //! [c]: https://rust-lang.github.io/chalk/book/canonical_queries/canonicalization.html
 
+use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::sync::Lock;
 use rustc_macros::HashStable;
 use rustc_type_ir::Canonical as IrCanonical;
 use rustc_type_ir::CanonicalVarInfo as IrCanonicalVarInfo;
 pub use rustc_type_ir::{CanonicalTyVarKind, CanonicalVarKind};
 use smallvec::SmallVec;
+use std::collections::hash_map::Entry;
 use std::ops::Index;
 
 use crate::infer::MemberConstraint;
 use crate::mir::ConstraintCategory;
 use crate::ty::GenericArg;
-use crate::ty::{self, BoundVar, List, Region, Ty, TyCtxt};
+use crate::ty::{self, BoundVar, List, Region, Ty, TyCtxt, TypeFlags, TypeVisitableExt};
 
 pub type Canonical<'tcx, V> = IrCanonical<TyCtxt<'tcx>, V>;
 
@@ -291,3 +294,62 @@ impl<'tcx> Index<BoundVar> for CanonicalVarValues<'tcx> {
         &self.var_values[value.as_usize()]
     }
 }
+
+#[derive(Default)]
+pub struct CanonicalParamEnvCache<'tcx> {
+    map: Lock<
+        FxHashMap<
+            ty::ParamEnv<'tcx>,
+            (Canonical<'tcx, ty::ParamEnv<'tcx>>, &'tcx [GenericArg<'tcx>]),
+        >,
+    >,
+}
+
+impl<'tcx> CanonicalParamEnvCache<'tcx> {
+    /// Gets the cached canonical form of `key` or executes
+    /// `canonicalize_op` and caches the result if not present.
+    ///
+    /// `canonicalize_op` is intentionally not allowed to be a closure to
+    /// statically prevent it from capturing `InferCtxt` and resolving
+    /// inference variables, which invalidates the cache.
+    pub fn get_or_insert(
+        &self,
+        tcx: TyCtxt<'tcx>,
+        key: ty::ParamEnv<'tcx>,
+        state: &mut OriginalQueryValues<'tcx>,
+        canonicalize_op: fn(
+            TyCtxt<'tcx>,
+            ty::ParamEnv<'tcx>,
+            &mut OriginalQueryValues<'tcx>,
+        ) -> Canonical<'tcx, ty::ParamEnv<'tcx>>,
+    ) -> Canonical<'tcx, ty::ParamEnv<'tcx>> {
+        if !key.has_type_flags(
+            TypeFlags::HAS_INFER | TypeFlags::HAS_PLACEHOLDER | TypeFlags::HAS_FREE_REGIONS,
+        ) {
+            return Canonical {
+                max_universe: ty::UniverseIndex::ROOT,
+                variables: List::empty(),
+                value: key,
+            };
+        }
+
+        assert_eq!(state.var_values.len(), 0);
+        assert_eq!(state.universe_map.len(), 1);
+        debug_assert_eq!(&*state.universe_map, &[ty::UniverseIndex::ROOT]);
+
+        match self.map.borrow().entry(key) {
+            Entry::Occupied(e) => {
+                let (canonical, var_values) = e.get();
+                state.var_values.extend_from_slice(var_values);
+                canonical.clone()
+            }
+            Entry::Vacant(e) => {
+                let canonical = canonicalize_op(tcx, key, state);
+                let OriginalQueryValues { var_values, universe_map } = state;
+                assert_eq!(universe_map.len(), 1);
+                e.insert((canonical.clone(), tcx.arena.alloc_slice(var_values)));
+                canonical
+            }
+        }
+    }
+}

compiler/rustc_middle/src/query/mod.rs

@@ -2177,7 +2177,9 @@ rustc_queries! {
     /// Used in `super_combine_consts` to ICE if the type of the two consts are definitely not going to end up being
     /// equal to eachother. This might return `Ok` even if the types are not equal, but will never return `Err` if
     /// the types might be equal.
-    query check_tys_might_be_eq(arg: Canonical<'tcx, (ty::ParamEnv<'tcx>, Ty<'tcx>, Ty<'tcx>)>) -> Result<(), NoSolution> {
+    query check_tys_might_be_eq(
+        arg: Canonical<'tcx, ty::ParamEnvAnd<'tcx, (Ty<'tcx>, Ty<'tcx>)>>
+    ) -> Result<(), NoSolution> {
         desc { "check whether two const param are definitely not equal to eachother"}
     }
 

compiler/rustc_middle/src/ty/context.rs

@@ -6,7 +6,7 @@ pub mod tls;
 
 use crate::arena::Arena;
 use crate::dep_graph::{DepGraph, DepKindStruct};
-use crate::infer::canonical::{CanonicalVarInfo, CanonicalVarInfos};
+use crate::infer::canonical::{CanonicalParamEnvCache, CanonicalVarInfo, CanonicalVarInfos};
 use crate::lint::struct_lint_level;
 use crate::metadata::ModChild;
 use crate::middle::codegen_fn_attrs::CodegenFnAttrs;
@@ -653,6 +653,8 @@ pub struct GlobalCtxt<'tcx> {
     pub new_solver_evaluation_cache: solve::EvaluationCache<'tcx>,
     pub new_solver_coherence_evaluation_cache: solve::EvaluationCache<'tcx>,
 
+    pub canonical_param_env_cache: CanonicalParamEnvCache<'tcx>,
+
     /// Data layout specification for the current target.
     pub data_layout: TargetDataLayout,
 
@@ -817,6 +819,7 @@ impl<'tcx> TyCtxt<'tcx> {
             evaluation_cache: Default::default(),
             new_solver_evaluation_cache: Default::default(),
             new_solver_coherence_evaluation_cache: Default::default(),
+            canonical_param_env_cache: Default::default(),
             data_layout,
             alloc_map: Lock::new(interpret::AllocMap::new()),
         }

compiler/rustc_trait_selection/src/traits/misc.rs

@@ -9,7 +9,7 @@ use rustc_infer::infer::canonical::Canonical;
 use rustc_infer::infer::{RegionResolutionError, TyCtxtInferExt};
 use rustc_infer::traits::query::NoSolution;
 use rustc_infer::{infer::outlives::env::OutlivesEnvironment, traits::FulfillmentError};
-use rustc_middle::ty::{self, AdtDef, GenericArg, List, ParamEnv, Ty, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{self, AdtDef, GenericArg, List, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::DUMMY_SP;
 
 use super::outlives_bounds::InferCtxtExt;
@@ -209,10 +209,10 @@ pub fn all_fields_implement_trait<'tcx>(
 
 pub fn check_tys_might_be_eq<'tcx>(
     tcx: TyCtxt<'tcx>,
-    canonical: Canonical<'tcx, (ParamEnv<'tcx>, Ty<'tcx>, Ty<'tcx>)>,
+    canonical: Canonical<'tcx, ty::ParamEnvAnd<'tcx, (Ty<'tcx>, Ty<'tcx>)>>,
 ) -> Result<(), NoSolution> {
-    let (infcx, (param_env, ty_a, ty_b), _) =
-        tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &canonical);
+    let (infcx, key, _) = tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &canonical);
+    let (param_env, (ty_a, ty_b)) = key.into_parts();
     let ocx = ObligationCtxt::new(&infcx);
 
     let result = ocx.eq(&ObligationCause::dummy(), param_env, ty_a, ty_b);

src/librustdoc/clean/blanket_impl.rs

@@ -14,7 +14,6 @@ pub(crate) struct BlanketImplFinder<'a, 'tcx> {
 impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
     pub(crate) fn get_blanket_impls(&mut self, item_def_id: DefId) -> Vec<Item> {
         let cx = &mut self.cx;
-        let param_env = cx.tcx.param_env(item_def_id);
         let ty = cx.tcx.type_of(item_def_id);
 
         trace!("get_blanket_impls({ty:?})");
@@ -40,7 +39,7 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                 let infcx = cx.tcx.infer_ctxt().build();
                 let args = infcx.fresh_args_for_item(DUMMY_SP, item_def_id);
                 let impl_ty = ty.instantiate(infcx.tcx, args);
-                let param_env = EarlyBinder::bind(param_env).instantiate(infcx.tcx, args);
+                let param_env = ty::ParamEnv::empty();
 
                 let impl_args = infcx.fresh_args_for_item(DUMMY_SP, impl_def_id);
                 let impl_trait_ref = trait_ref.instantiate(infcx.tcx, impl_args);

src/librustdoc/clean/mod.rs

@@ -26,7 +26,7 @@ use rustc_middle::middle::resolve_bound_vars as rbv;
 use rustc_middle::ty::fold::TypeFolder;
 use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::TypeVisitableExt;
-use rustc_middle::ty::{self, AdtKind, EarlyBinder, Ty, TyCtxt};
+use rustc_middle::ty::{self, AdtKind, Ty, TyCtxt};
 use rustc_middle::{bug, span_bug};
 use rustc_span::hygiene::{AstPass, MacroKind};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};