1 //! This module contains some shared code for encoding and decoding various
2 //! things from the `ty` module, and in particular implements support for
3 //! "shorthands" which allow to have pointers back into the already encoded
4 //! stream instead of re-encoding the same thing twice.
6 //! The functionality in here is shared between persisting to crate metadata and
7 //! persisting to incr. comp. caches.
9 use crate::arena::ArenaAllocatable;
10 use crate::infer::canonical::{CanonicalVarInfo, CanonicalVarInfos};
13 interpret::{AllocId, ConstAllocation},
17 use crate::ty::subst::SubstsRef;
18 use crate::ty::{self, AdtDef, Ty, TyCtxt};
19 use rustc_data_structures::fx::FxHashMap;
20 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
24 use std::marker::DiscriminantKind;
26 /// The shorthand encoding uses an enum's variant index `usize`
27 /// and is offset by this value so it never matches a real variant.
28 /// This offset is also chosen so that the first byte is never < 0x80.
29 pub const SHORTHAND_OFFSET: usize = 0x80;
31 pub trait EncodableWithShorthand<'tcx, E: TyEncoder<'tcx>>: Copy + Eq + Hash {
32 type Variant: Encodable<E>;
33 fn variant(&self) -> &Self::Variant;
36 #[allow(rustc::usage_of_ty_tykind)]
37 impl<'tcx, E: TyEncoder<'tcx>> EncodableWithShorthand<'tcx, E> for Ty<'tcx> {
38 type Variant = ty::TyKind<'tcx>;
41 fn variant(&self) -> &Self::Variant {
46 impl<'tcx, E: TyEncoder<'tcx>> EncodableWithShorthand<'tcx, E> for ty::PredicateKind<'tcx> {
47 type Variant = ty::PredicateKind<'tcx>;
50 fn variant(&self) -> &Self::Variant {
55 pub trait TyEncoder<'tcx>: Encoder {
56 const CLEAR_CROSS_CRATE: bool;
58 fn position(&self) -> usize;
59 fn type_shorthands(&mut self) -> &mut FxHashMap<Ty<'tcx>, usize>;
60 fn predicate_shorthands(&mut self) -> &mut FxHashMap<ty::PredicateKind<'tcx>, usize>;
61 fn encode_alloc_id(&mut self, alloc_id: &AllocId) -> Result<(), Self::Error>;
64 /// Trait for decoding to a reference.
66 /// This is a separate trait from `Decodable` so that we can implement it for
67 /// upstream types, such as `FxHashSet`.
69 /// The `TyDecodable` derive macro will use this trait for fields that are
70 /// references (and don't use a type alias to hide that).
72 /// `Decodable` can still be implemented in cases where `Decodable` is required
74 pub trait RefDecodable<'tcx, D: TyDecoder<'tcx>> {
75 fn decode(d: &mut D) -> &'tcx Self;
78 /// Encode the given value or a previously cached shorthand.
79 pub fn encode_with_shorthand<'tcx, E, T, M>(
83 ) -> Result<(), E::Error>
86 M: for<'b> Fn(&'b mut E) -> &'b mut FxHashMap<T, usize>,
87 T: EncodableWithShorthand<'tcx, E>,
88 // The discriminant and shorthand must have the same size.
89 T::Variant: DiscriminantKind<Discriminant = isize>,
91 let existing_shorthand = cache(encoder).get(value).copied();
92 if let Some(shorthand) = existing_shorthand {
93 return encoder.emit_usize(shorthand);
96 let variant = value.variant();
98 let start = encoder.position();
99 variant.encode(encoder)?;
100 let len = encoder.position() - start;
102 // The shorthand encoding uses the same usize as the
103 // discriminant, with an offset so they can't conflict.
104 let discriminant = intrinsics::discriminant_value(variant);
105 assert!(SHORTHAND_OFFSET > discriminant as usize);
107 let shorthand = start + SHORTHAND_OFFSET;
109 // Get the number of bits that leb128 could fit
110 // in the same space as the fully encoded type.
111 let leb128_bits = len * 7;
113 // Check that the shorthand is a not longer than the
114 // full encoding itself, i.e., it's an obvious win.
115 if leb128_bits >= 64 || (shorthand as u64) < (1 << leb128_bits) {
116 cache(encoder).insert(*value, shorthand);
122 impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for Ty<'tcx> {
123 fn encode(&self, e: &mut E) -> Result<(), E::Error> {
124 encode_with_shorthand(e, self, TyEncoder::type_shorthands)
128 impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ty::Binder<'tcx, ty::PredicateKind<'tcx>> {
129 fn encode(&self, e: &mut E) -> Result<(), E::Error> {
130 self.bound_vars().encode(e)?;
131 encode_with_shorthand(e, &self.skip_binder(), TyEncoder::predicate_shorthands)
135 impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ty::Predicate<'tcx> {
136 fn encode(&self, e: &mut E) -> Result<(), E::Error> {
137 self.kind().encode(e)
141 impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ty::Region<'tcx> {
142 fn encode(&self, e: &mut E) -> Result<(), E::Error> {
143 self.kind().encode(e)
147 impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ty::Const<'tcx> {
148 fn encode(&self, e: &mut E) -> Result<(), E::Error> {
153 impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ConstAllocation<'tcx> {
154 fn encode(&self, e: &mut E) -> Result<(), E::Error> {
155 self.inner().encode(e)
159 impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for AdtDef<'tcx> {
160 fn encode(&self, e: &mut E) -> Result<(), E::Error> {
165 impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for AllocId {
166 fn encode(&self, e: &mut E) -> Result<(), E::Error> {
167 e.encode_alloc_id(self)
171 pub trait TyDecoder<'tcx>: Decoder {
172 const CLEAR_CROSS_CRATE: bool;
174 fn tcx(&self) -> TyCtxt<'tcx>;
176 fn peek_byte(&self) -> u8;
178 fn position(&self) -> usize;
180 fn cached_ty_for_shorthand<F>(&mut self, shorthand: usize, or_insert_with: F) -> Ty<'tcx>
182 F: FnOnce(&mut Self) -> Ty<'tcx>;
184 fn with_position<F, R>(&mut self, pos: usize, f: F) -> R
186 F: FnOnce(&mut Self) -> R;
188 fn positioned_at_shorthand(&self) -> bool {
189 (self.peek_byte() & (SHORTHAND_OFFSET as u8)) != 0
192 fn decode_alloc_id(&mut self) -> AllocId;
196 fn decode_arena_allocable<'tcx, D, T: ArenaAllocatable<'tcx> + Decodable<D>>(
202 decoder.tcx().arena.alloc(Decodable::decode(decoder))
206 fn decode_arena_allocable_slice<'tcx, D, T: ArenaAllocatable<'tcx> + Decodable<D>>(
212 decoder.tcx().arena.alloc_from_iter(<Vec<T> as Decodable<D>>::decode(decoder))
215 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for Ty<'tcx> {
216 #[allow(rustc::usage_of_ty_tykind)]
217 fn decode(decoder: &mut D) -> Ty<'tcx> {
218 // Handle shorthands first, if we have a usize > 0x80.
219 if decoder.positioned_at_shorthand() {
220 let pos = decoder.read_usize();
221 assert!(pos >= SHORTHAND_OFFSET);
222 let shorthand = pos - SHORTHAND_OFFSET;
224 decoder.cached_ty_for_shorthand(shorthand, |decoder| {
225 decoder.with_position(shorthand, Ty::decode)
228 let tcx = decoder.tcx();
229 tcx.mk_ty(ty::TyKind::decode(decoder))
234 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::Binder<'tcx, ty::PredicateKind<'tcx>> {
235 fn decode(decoder: &mut D) -> ty::Binder<'tcx, ty::PredicateKind<'tcx>> {
236 let bound_vars = Decodable::decode(decoder);
237 // Handle shorthands first, if we have a usize > 0x80.
238 ty::Binder::bind_with_vars(
239 if decoder.positioned_at_shorthand() {
240 let pos = decoder.read_usize();
241 assert!(pos >= SHORTHAND_OFFSET);
242 let shorthand = pos - SHORTHAND_OFFSET;
244 decoder.with_position(shorthand, ty::PredicateKind::decode)
246 ty::PredicateKind::decode(decoder)
253 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::Predicate<'tcx> {
254 fn decode(decoder: &mut D) -> ty::Predicate<'tcx> {
255 let predicate_kind = Decodable::decode(decoder);
256 decoder.tcx().mk_predicate(predicate_kind)
260 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for SubstsRef<'tcx> {
261 fn decode(decoder: &mut D) -> Self {
262 let len = decoder.read_usize();
263 let tcx = decoder.tcx();
265 (0..len).map::<ty::subst::GenericArg<'tcx>, _>(|_| Decodable::decode(decoder)),
270 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for mir::Place<'tcx> {
271 fn decode(decoder: &mut D) -> Self {
272 let local: mir::Local = Decodable::decode(decoder);
273 let len = decoder.read_usize();
274 let projection = decoder.tcx().mk_place_elems(
275 (0..len).map::<mir::PlaceElem<'tcx>, _>(|_| Decodable::decode(decoder)),
277 mir::Place { local, projection }
281 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::Region<'tcx> {
282 fn decode(decoder: &mut D) -> Self {
283 decoder.tcx().mk_region(Decodable::decode(decoder))
287 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for CanonicalVarInfos<'tcx> {
288 fn decode(decoder: &mut D) -> Self {
289 let len = decoder.read_usize();
290 let interned: Vec<CanonicalVarInfo<'tcx>> =
291 (0..len).map(|_| Decodable::decode(decoder)).collect();
292 decoder.tcx().intern_canonical_var_infos(interned.as_slice())
296 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for AllocId {
297 fn decode(decoder: &mut D) -> Self {
298 decoder.decode_alloc_id()
302 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::SymbolName<'tcx> {
303 fn decode(decoder: &mut D) -> Self {
304 ty::SymbolName::new(decoder.tcx(), &decoder.read_str())
308 macro_rules! impl_decodable_via_ref {
310 $(impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for $t {
311 fn decode(decoder: &mut D) -> Self {
312 RefDecodable::decode(decoder)
318 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for ty::List<Ty<'tcx>> {
319 fn decode(decoder: &mut D) -> &'tcx Self {
320 let len = decoder.read_usize();
321 decoder.tcx().mk_type_list((0..len).map::<Ty<'tcx>, _>(|_| Decodable::decode(decoder)))
325 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D>
326 for ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>
328 fn decode(decoder: &mut D) -> &'tcx Self {
329 let len = decoder.read_usize();
330 decoder.tcx().mk_poly_existential_predicates(
331 (0..len).map::<ty::Binder<'tcx, _>, _>(|_| Decodable::decode(decoder)),
336 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::Const<'tcx> {
337 fn decode(decoder: &mut D) -> Self {
338 decoder.tcx().mk_const(Decodable::decode(decoder))
342 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [ty::ValTree<'tcx>] {
343 fn decode(decoder: &mut D) -> &'tcx Self {
344 decoder.tcx().arena.alloc_from_iter(
345 (0..decoder.read_usize()).map(|_| Decodable::decode(decoder)).collect::<Vec<_>>(),
350 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ConstAllocation<'tcx> {
351 fn decode(decoder: &mut D) -> Self {
352 decoder.tcx().intern_const_alloc(Decodable::decode(decoder))
356 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for AdtDef<'tcx> {
357 fn decode(decoder: &mut D) -> Self {
358 decoder.tcx().intern_adt_def(Decodable::decode(decoder))
362 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [(ty::Predicate<'tcx>, Span)] {
363 fn decode(decoder: &mut D) -> &'tcx Self {
364 decoder.tcx().arena.alloc_from_iter(
365 (0..decoder.read_usize()).map(|_| Decodable::decode(decoder)).collect::<Vec<_>>(),
370 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [thir::abstract_const::Node<'tcx>] {
371 fn decode(decoder: &mut D) -> &'tcx Self {
372 decoder.tcx().arena.alloc_from_iter(
373 (0..decoder.read_usize()).map(|_| Decodable::decode(decoder)).collect::<Vec<_>>(),
378 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [thir::abstract_const::NodeId] {
379 fn decode(decoder: &mut D) -> &'tcx Self {
380 decoder.tcx().arena.alloc_from_iter(
381 (0..decoder.read_usize()).map(|_| Decodable::decode(decoder)).collect::<Vec<_>>(),
386 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for ty::List<ty::BoundVariableKind> {
387 fn decode(decoder: &mut D) -> &'tcx Self {
388 let len = decoder.read_usize();
389 decoder.tcx().mk_bound_variable_kinds(
390 (0..len).map::<ty::BoundVariableKind, _>(|_| Decodable::decode(decoder)),
395 impl_decodable_via_ref! {
396 &'tcx ty::TypeckResults<'tcx>,
397 &'tcx ty::List<Ty<'tcx>>,
398 &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
399 &'tcx traits::ImplSource<'tcx, ()>,
400 &'tcx mir::Body<'tcx>,
401 &'tcx mir::UnsafetyCheckResult,
402 &'tcx mir::BorrowCheckResult<'tcx>,
403 &'tcx mir::coverage::CodeRegion,
404 &'tcx ty::List<ty::BoundVariableKind>
408 macro_rules! __impl_decoder_methods {
409 ($($name:ident -> $ty:ty;)*) => {
412 fn $name(&mut self) -> $ty {
419 macro_rules! impl_arena_allocatable_decoder {
421 ([decode $(, $attrs:ident)*]
422 [$name:ident: $ty:ty]) => {
423 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for $ty {
425 fn decode(decoder: &mut D) -> &'tcx Self {
426 decode_arena_allocable(decoder)
430 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [$ty] {
432 fn decode(decoder: &mut D) -> &'tcx Self {
433 decode_arena_allocable_slice(decoder)
439 macro_rules! impl_arena_allocatable_decoders {
440 ([$($a:tt $name:ident: $ty:ty,)*]) => {
442 impl_arena_allocatable_decoder!($a [$name: $ty]);
447 rustc_hir::arena_types!(impl_arena_allocatable_decoders);
448 arena_types!(impl_arena_allocatable_decoders);
450 macro_rules! impl_arena_copy_decoder {
451 (<$tcx:tt> $($ty:ty,)*) => {
452 $(impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for $ty {
454 fn decode(decoder: &mut D) -> &'tcx Self {
455 decoder.tcx().arena.alloc(Decodable::decode(decoder))
459 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [$ty] {
461 fn decode(decoder: &mut D) -> &'tcx Self {
462 decoder.tcx().arena.alloc_from_iter(<Vec<_> as Decodable<D>>::decode(decoder))
468 impl_arena_copy_decoder! {<'tcx>
470 rustc_span::symbol::Ident,
472 rustc_span::def_id::DefId,
473 rustc_span::def_id::LocalDefId,
474 (rustc_middle::middle::exported_symbols::ExportedSymbol<'tcx>, rustc_middle::middle::exported_symbols::SymbolExportInfo),
478 macro_rules! implement_ty_decoder {
479 ($DecoderName:ident <$($typaram:tt),*>) => {
480 mod __ty_decoder_impl {
481 use std::borrow::Cow;
482 use rustc_serialize::Decoder;
484 use super::$DecoderName;
486 impl<$($typaram ),*> Decoder for $DecoderName<$($typaram),*> {
487 $crate::__impl_decoder_methods! {
510 fn read_raw_bytes(&mut self, len: usize) -> &[u8] {
511 self.opaque.read_raw_bytes(len)
518 macro_rules! impl_binder_encode_decode {
519 ($($t:ty),+ $(,)?) => {
521 impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ty::Binder<'tcx, $t> {
522 fn encode(&self, e: &mut E) -> Result<(), E::Error> {
523 self.bound_vars().encode(e)?;
524 self.as_ref().skip_binder().encode(e)
527 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::Binder<'tcx, $t> {
528 fn decode(decoder: &mut D) -> Self {
529 let bound_vars = Decodable::decode(decoder);
530 ty::Binder::bind_with_vars(Decodable::decode(decoder), bound_vars)
537 impl_binder_encode_decode! {
538 &'tcx ty::List<Ty<'tcx>>,
540 ty::ExistentialPredicate<'tcx>,
542 Vec<ty::GeneratorInteriorTypeCause<'tcx>>,