intern offsetof fields

compiler/rustc_const_eval/src/transform/validate.rs

@@ -719,7 +719,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
 
                 let mut current_ty = *container;
 
-                for &field in fields {
+                for field in fields.iter() {
                     match current_ty.kind() {
                         ty::Tuple(fields) => {
                             let Some(&f_ty) = fields.get(field.as_usize()) else {

compiler/rustc_middle/src/mir/syntax.rs

@@ -1115,7 +1115,7 @@ pub enum Rvalue<'tcx> {
     CheckedBinaryOp(BinOp, Box<(Operand<'tcx>, Operand<'tcx>)>),
 
     /// Computes a value as described by the operation.
-    NullaryOp(NullOp, Ty<'tcx>),
+    NullaryOp(NullOp<'tcx>, Ty<'tcx>),
 
     /// Exactly like `BinaryOp`, but less operands.
     ///
@@ -1212,13 +1212,13 @@ pub enum AggregateKind<'tcx> {
 }
 
 #[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
-pub enum NullOp {
+pub enum NullOp<'tcx> {
     /// Returns the size of a value of that type
     SizeOf,
     /// Returns the minimum alignment of a type
     AlignOf,
     /// Returns the offset of a field
-    OffsetOf(Vec<FieldIdx>),
+    OffsetOf(&'tcx List<FieldIdx>),
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
@@ -1288,6 +1288,6 @@ mod size_asserts {
     static_assert_size!(Operand<'_>, 24);
     static_assert_size!(Place<'_>, 16);
     static_assert_size!(PlaceElem<'_>, 24);
-    static_assert_size!(Rvalue<'_>, 48);
+    static_assert_size!(Rvalue<'_>, 40);
     // tidy-alphabetical-end
 }

compiler/rustc_middle/src/mir/type_foldable.rs

@@ -16,7 +16,6 @@ TrivialTypeTraversalAndLiftImpls! {
     UserTypeAnnotationIndex,
     BorrowKind,
     CastKind,
-    NullOp,
     hir::Movability,
     BasicBlock,
     SwitchTargets,
@@ -26,6 +25,7 @@ TrivialTypeTraversalAndLiftImpls! {
 
 TrivialTypeTraversalImpls! {
     ConstValue<'tcx>,
+    NullOp<'tcx>,
 }
 
 impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for &'tcx [InlineAsmTemplatePiece] {

compiler/rustc_middle/src/thir.rs

@@ -20,7 +20,7 @@ use rustc_middle::mir::interpret::AllocId;
 use rustc_middle::mir::{self, BinOp, BorrowKind, FakeReadCause, Mutability, UnOp};
 use rustc_middle::ty::adjustment::PointerCast;
 use rustc_middle::ty::subst::SubstsRef;
-use rustc_middle::ty::{self, AdtDef, FnSig, Ty, UpvarSubsts};
+use rustc_middle::ty::{self, AdtDef, FnSig, List, Ty, UpvarSubsts};
 use rustc_middle::ty::{CanonicalUserType, CanonicalUserTypeAnnotation};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::{sym, Span, Symbol, DUMMY_SP};
@@ -484,7 +484,7 @@ pub enum ExprKind<'tcx> {
     /// Field offset (`offset_of!`)
     OffsetOf {
         container: Ty<'tcx>,
-        fields: Vec<FieldIdx>,
+        fields: &'tcx List<FieldIdx>,
     },
     /// An expression taking a reference to a thread local.
     ThreadLocalRef(DefId),

compiler/rustc_middle/src/ty/codec.rs

@@ -19,6 +19,7 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_middle::ty::TyCtxt;
 use rustc_serialize::{Decodable, Encodable};
 use rustc_span::Span;
+use rustc_target::abi::FieldIdx;
 pub use rustc_type_ir::{TyDecoder, TyEncoder};
 use std::hash::Hash;
 use std::intrinsics;
@@ -401,6 +402,15 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<ty
     }
 }
 
+impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<FieldIdx> {
+    fn decode(decoder: &mut D) -> &'tcx Self {
+        let len = decoder.read_usize();
+        decoder
+            .interner()
+            .mk_fields_from_iter((0..len).map::<FieldIdx, _>(|_| Decodable::decode(decoder)))
+    }
+}
+
 impl_decodable_via_ref! {
     &'tcx ty::TypeckResults<'tcx>,
     &'tcx ty::List<Ty<'tcx>>,
@@ -412,6 +422,7 @@ impl_decodable_via_ref! {
     &'tcx mir::coverage::CodeRegion,
     &'tcx ty::List<ty::BoundVariableKind>,
     &'tcx ty::List<ty::Predicate<'tcx>>,
+    &'tcx ty::List<FieldIdx>,
 }
 
 #[macro_export]

compiler/rustc_middle/src/ty/context.rs

@@ -155,6 +155,7 @@ pub struct CtxtInterners<'tcx> {
     layout: InternedSet<'tcx, LayoutS>,
     adt_def: InternedSet<'tcx, AdtDefData>,
     external_constraints: InternedSet<'tcx, ExternalConstraintsData<'tcx>>,
+    fields: InternedSet<'tcx, List<FieldIdx>>,
 }
 
 impl<'tcx> CtxtInterners<'tcx> {
@@ -178,6 +179,7 @@ impl<'tcx> CtxtInterners<'tcx> {
             layout: Default::default(),
             adt_def: Default::default(),
             external_constraints: Default::default(),
+            fields: Default::default(),
         }
     }
 
@@ -1585,6 +1587,7 @@ slice_interners!(
     projs: pub mk_projs(ProjectionKind),
     place_elems: pub mk_place_elems(PlaceElem<'tcx>),
     bound_variable_kinds: pub mk_bound_variable_kinds(ty::BoundVariableKind),
+    fields: pub mk_fields(FieldIdx),
 );
 
 impl<'tcx> TyCtxt<'tcx> {
@@ -2253,6 +2256,14 @@ impl<'tcx> TyCtxt<'tcx> {
         T::collect_and_apply(iter, |xs| self.mk_place_elems(xs))
     }
 
+    pub fn mk_fields_from_iter<I, T>(self, iter: I) -> T::Output
+    where
+        I: Iterator<Item = T>,
+        T: CollectAndApply<FieldIdx, &'tcx List<FieldIdx>>,
+    {
+        T::collect_and_apply(iter, |xs| self.mk_fields(xs))
+    }
+
     pub fn mk_substs_trait(
         self,
         self_ty: Ty<'tcx>,

compiler/rustc_mir_build/src/build/expr/as_rvalue.rs

@@ -481,8 +481,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 }))))
             }
 
-            ExprKind::OffsetOf { container, ref fields } => {
-                block.and(Rvalue::NullaryOp(NullOp::OffsetOf(fields.clone()), container))
+            ExprKind::OffsetOf { container, fields } => {
+                block.and(Rvalue::NullaryOp(NullOp::OffsetOf(fields), container))
             }
 
             ExprKind::Literal { .. }

compiler/rustc_mir_build/src/thir/cx/expr.rs

@@ -667,7 +667,7 @@ impl<'tcx> Cx<'tcx> {
             hir::ExprKind::OffsetOf(_, _) => {
                 let data = self.typeck_results.offset_of_data();
                 let &(container, ref indices) = data.get(expr.hir_id).unwrap();
-                let fields = indices.iter().copied().collect();
+                let fields = tcx.mk_fields_from_iter(indices.iter().copied());
 
                 ExprKind::OffsetOf { container, fields }
             }