Wrap some query results in Lrc.

So that the frequent clones in `try_get` are cheaper.

Fixes #54274.

Author: nnethercote

src/librustc/infer/outlives/verify.rs

@@ -299,8 +299,8 @@ impl<'cx, 'gcx, 'tcx> VerifyBoundCx<'cx, 'gcx, 'tcx> {
         let assoc_item = tcx.associated_item(assoc_item_def_id);
         let trait_def_id = assoc_item.container.assert_trait();
         let trait_predicates = tcx.predicates_of(trait_def_id).predicates
-            .into_iter()
-            .map(|(p, _)| p)
+            .iter()
+            .map(|(p, _)| *p)
             .collect();
         let identity_substs = Substs::identity_for_item(tcx, assoc_item_def_id);
         let identity_proj = tcx.mk_projection(assoc_item_def_id, identity_substs);

src/librustc/traits/object_safety.rs

@@ -182,7 +182,7 @@ impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
         };
         predicates
             .predicates
-            .into_iter()
+            .iter()
             .map(|(predicate, _)| predicate.subst_supertrait(self, &trait_ref))
             .any(|predicate| {
                 match predicate {
@@ -302,9 +302,10 @@ impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
             return Some(MethodViolationCode::Generic);
         }
 
-        if self.predicates_of(method.def_id).predicates.into_iter()
+        if self.predicates_of(method.def_id).predicates.iter()
                 // A trait object can't claim to live more than the concrete type,
                 // so outlives predicates will always hold.
+                .cloned()
                 .filter(|(p, _)| p.to_opt_type_outlives().is_none())
                 .collect::<Vec<_>>()
                 // Do a shallow visit so that `contains_illegal_self_type_reference`

src/librustc/traits/specialize/mod.rs

@@ -407,7 +407,7 @@ fn to_pretty_impl_header(tcx: TyCtxt<'_, '_, '_>, impl_def_id: DefId) -> Option<
 
     // The predicates will contain default bounds like `T: Sized`. We need to
     // remove these bounds, and add `T: ?Sized` to any untouched type parameters.
-    let predicates = tcx.predicates_of(impl_def_id).predicates;
+    let predicates = &tcx.predicates_of(impl_def_id).predicates;
     let mut pretty_predicates = Vec::with_capacity(
         predicates.len() + types_without_default_bounds.len());
 

src/librustc/ty/mod.rs

@@ -2126,7 +2126,7 @@ impl<'a, 'gcx, 'tcx> AdtDef {
     }
 
     #[inline]
-    pub fn predicates(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> GenericPredicates<'gcx> {
+    pub fn predicates(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Lrc<GenericPredicates<'gcx>> {
         tcx.predicates_of(self.did)
     }
 
@@ -2369,8 +2369,8 @@ impl<'a, 'gcx, 'tcx> AdtDef {
                     def_id: sized_trait,
                     substs: tcx.mk_substs_trait(ty, &[])
                 }).to_predicate();
-                let predicates = tcx.predicates_of(self.did).predicates;
-                if predicates.into_iter().any(|(p, _)| p == sized_predicate) {
+                let predicates = &tcx.predicates_of(self.did).predicates;
+                if predicates.iter().any(|(p, _)| *p == sized_predicate) {
                     vec![]
                 } else {
                     vec![ty]

src/librustc/ty/query/mod.rs

@@ -127,17 +127,18 @@ define_queries! { <'tcx>
         /// predicate gets in the way of some checks, which are intended
         /// to operate over only the actual where-clauses written by the
         /// user.)
-        [] fn predicates_of: PredicatesOfItem(DefId) -> ty::GenericPredicates<'tcx>,
+        [] fn predicates_of: PredicatesOfItem(DefId) -> Lrc<ty::GenericPredicates<'tcx>>,
 
         /// Maps from the def-id of an item (trait/struct/enum/fn) to the
         /// predicates (where clauses) directly defined on it. This is
         /// equal to the `explicit_predicates_of` predicates plus the
         /// `inferred_outlives_of` predicates.
-        [] fn predicates_defined_on: PredicatesDefinedOnItem(DefId) -> ty::GenericPredicates<'tcx>,
+        [] fn predicates_defined_on: PredicatesDefinedOnItem(DefId)
+            -> Lrc<ty::GenericPredicates<'tcx>>,
 
         /// Returns the predicates written explicit by the user.
         [] fn explicit_predicates_of: ExplicitPredicatesOfItem(DefId)
-            -> ty::GenericPredicates<'tcx>,
+            -> Lrc<ty::GenericPredicates<'tcx>>,
 
         /// Returns the inferred outlives predicates (e.g., for `struct
         /// Foo<'a, T> { x: &'a T }`, this would return `T: 'a`).
@@ -149,12 +150,12 @@ define_queries! { <'tcx>
         /// evaluate them even during type conversion, often before the
         /// full predicates are available (note that supertraits have
         /// additional acyclicity requirements).
-        [] fn super_predicates_of: SuperPredicatesOfItem(DefId) -> ty::GenericPredicates<'tcx>,
+        [] fn super_predicates_of: SuperPredicatesOfItem(DefId) -> Lrc<ty::GenericPredicates<'tcx>>,
 
         /// To avoid cycles within the predicates of a single item we compute
         /// per-type-parameter predicates for resolving `T::AssocTy`.
         [] fn type_param_predicates: type_param_predicates((DefId, DefId))
-            -> ty::GenericPredicates<'tcx>,
+            -> Lrc<ty::GenericPredicates<'tcx>>,
 
         [] fn trait_def: TraitDefOfItem(DefId) -> &'tcx ty::TraitDef,
         [] fn adt_def: AdtDefOfItem(DefId) -> &'tcx ty::AdtDef,

src/librustc_metadata/cstore_impl.rs

@@ -103,9 +103,9 @@ provide! { <'tcx> tcx, def_id, other, cdata,
     generics_of => {
         tcx.alloc_generics(cdata.get_generics(def_id.index, tcx.sess))
     }
-    predicates_of => { cdata.get_predicates(def_id.index, tcx) }
-    predicates_defined_on => { cdata.get_predicates_defined_on(def_id.index, tcx) }
-    super_predicates_of => { cdata.get_super_predicates(def_id.index, tcx) }
+    predicates_of => { Lrc::new(cdata.get_predicates(def_id.index, tcx)) }
+    predicates_defined_on => { Lrc::new(cdata.get_predicates_defined_on(def_id.index, tcx)) }
+    super_predicates_of => { Lrc::new(cdata.get_super_predicates(def_id.index, tcx)) }
     trait_def => {
         tcx.alloc_trait_def(cdata.get_trait_def(def_id.index, tcx.sess))
     }

src/librustc_traits/lowering/mod.rs

@@ -217,8 +217,9 @@ fn program_clauses_for_trait<'a, 'tcx>(
 
     let implemented_from_env = Clause::ForAll(ty::Binder::bind(implemented_from_env));
 
-    let where_clauses = &tcx.predicates_defined_on(def_id).predicates
-        .into_iter()
+    let predicates = &tcx.predicates_defined_on(def_id).predicates;
+    let where_clauses = &predicates
+        .iter()
         .map(|(wc, _)| wc.lower())
         .map(|wc| wc.subst(tcx, bound_vars))
         .collect::<Vec<_>>();
@@ -314,8 +315,9 @@ fn program_clauses_for_impl<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId
     let trait_pred = ty::TraitPredicate { trait_ref }.lower();
 
     // `WC`
-    let where_clauses = tcx.predicates_of(def_id).predicates
-        .into_iter()
+    let predicates = &tcx.predicates_of(def_id).predicates;
+    let where_clauses = predicates
+        .iter()
         .map(|(wc, _)| wc.lower())
         .map(|wc| wc.subst(tcx, bound_vars));
 
@@ -352,7 +354,7 @@ pub fn program_clauses_for_type_def<'a, 'tcx>(
 
     // `WC`
     let where_clauses = tcx.predicates_of(def_id).predicates
-        .into_iter()
+        .iter()
         .map(|(wc, _)| wc.lower())
         .map(|wc| wc.subst(tcx, bound_vars))
         .collect::<Vec<_>>();

src/librustc_typeck/astconv.rs

@@ -24,6 +24,7 @@ use rustc::traits;
 use rustc::ty::{self, Ty, TyCtxt, ToPredicate, TypeFoldable};
 use rustc::ty::{GenericParamDef, GenericParamDefKind};
 use rustc::ty::wf::object_region_bounds;
+use rustc_data_structures::sync::Lrc;
 use rustc_target::spec::abi;
 use std::collections::BTreeSet;
 use std::slice;
@@ -45,7 +46,7 @@ pub trait AstConv<'gcx, 'tcx> {
     /// Returns the set of bounds in scope for the type parameter with
     /// the given id.
     fn get_type_parameter_bounds(&self, span: Span, def_id: DefId)
-                                 -> ty::GenericPredicates<'tcx>;
+                                 -> Lrc<ty::GenericPredicates<'tcx>>;
 
     /// What lifetime should we use when a lifetime is omitted (and not elided)?
     fn re_infer(&self, span: Span, _def: Option<&ty::GenericParamDef>)
@@ -1119,8 +1120,8 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
     {
         let tcx = self.tcx();
 
-        let bounds = self.get_type_parameter_bounds(span, ty_param_def_id)
-            .predicates.into_iter().filter_map(|(p, _)| p.to_opt_poly_trait_ref());
+        let predicates = &self.get_type_parameter_bounds(span, ty_param_def_id).predicates;
+        let bounds = predicates.iter().filter_map(|(p, _)| p.to_opt_poly_trait_ref());
 
         // Check that there is exactly one way to find an associated type with the
         // correct name.

src/librustc_typeck/check/mod.rs

@@ -1869,15 +1869,15 @@ impl<'a, 'gcx, 'tcx> AstConv<'gcx, 'tcx> for FnCtxt<'a, 'gcx, 'tcx> {
     fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> { self.tcx }
 
     fn get_type_parameter_bounds(&self, _: Span, def_id: DefId)
-                                 -> ty::GenericPredicates<'tcx>
+                                 -> Lrc<ty::GenericPredicates<'tcx>>
     {
         let tcx = self.tcx;
         let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
         let item_id = tcx.hir.ty_param_owner(node_id);
         let item_def_id = tcx.hir.local_def_id(item_id);
         let generics = tcx.generics_of(item_def_id);
         let index = generics.param_def_id_to_index[&def_id];
-        ty::GenericPredicates {
+        Lrc::new(ty::GenericPredicates {
             parent: None,
             predicates: self.param_env.caller_bounds.iter().filter_map(|&predicate| {
                 match predicate {
@@ -1890,7 +1890,7 @@ impl<'a, 'gcx, 'tcx> AstConv<'gcx, 'tcx> for FnCtxt<'a, 'gcx, 'tcx> {
                     _ => None
                 }
             }).collect()
-        }
+        })
     }
 
     fn re_infer(&self, span: Span, def: Option<&ty::GenericParamDef>)

src/librustc_typeck/check/wfcheck.rs

@@ -910,8 +910,8 @@ fn check_false_global_bounds<'a, 'gcx, 'tcx>(
 
     let def_id = fcx.tcx.hir.local_def_id(id);
     let predicates = fcx.tcx.predicates_of(def_id).predicates
-        .into_iter()
-        .map(|(p, _)| p)
+        .iter()
+        .map(|(p, _)| *p)
         .collect();
     // Check elaborated bounds
     let implied_obligations = traits::elaborate_predicates(fcx.tcx, predicates);