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, Allocation},
17 use crate::ty::subst::SubstsRef;
18 use crate::ty::{self, 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 AllocId {
154 fn encode(&self, e: &mut E) -> Result<(), E::Error> {
155 e.encode_alloc_id(self)
159 macro_rules! encodable_via_deref {
161 $(impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for $t {
162 fn encode(&self, e: &mut E) -> Result<(), E::Error> {
169 encodable_via_deref! {
170 &'tcx ty::TypeckResults<'tcx>,
171 &'tcx traits::ImplSource<'tcx, ()>,
172 &'tcx mir::Body<'tcx>,
173 &'tcx mir::UnsafetyCheckResult,
174 &'tcx mir::BorrowCheckResult<'tcx>,
175 &'tcx mir::coverage::CodeRegion,
179 pub trait TyDecoder<'tcx>: Decoder {
180 const CLEAR_CROSS_CRATE: bool;
182 fn tcx(&self) -> TyCtxt<'tcx>;
184 fn peek_byte(&self) -> u8;
186 fn position(&self) -> usize;
188 fn cached_ty_for_shorthand<F>(&mut self, shorthand: usize, or_insert_with: F) -> Ty<'tcx>
190 F: FnOnce(&mut Self) -> Ty<'tcx>;
192 fn with_position<F, R>(&mut self, pos: usize, f: F) -> R
194 F: FnOnce(&mut Self) -> R;
196 fn positioned_at_shorthand(&self) -> bool {
197 (self.peek_byte() & (SHORTHAND_OFFSET as u8)) != 0
200 fn decode_alloc_id(&mut self) -> AllocId;
204 fn decode_arena_allocable<'tcx, D, T: ArenaAllocatable<'tcx> + Decodable<D>>(
210 decoder.tcx().arena.alloc(Decodable::decode(decoder))
214 fn decode_arena_allocable_slice<'tcx, D, T: ArenaAllocatable<'tcx> + Decodable<D>>(
220 decoder.tcx().arena.alloc_from_iter(<Vec<T> as Decodable<D>>::decode(decoder))
223 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for Ty<'tcx> {
224 #[allow(rustc::usage_of_ty_tykind)]
225 fn decode(decoder: &mut D) -> Ty<'tcx> {
226 // Handle shorthands first, if we have a usize > 0x80.
227 if decoder.positioned_at_shorthand() {
228 let pos = decoder.read_usize();
229 assert!(pos >= SHORTHAND_OFFSET);
230 let shorthand = pos - SHORTHAND_OFFSET;
232 decoder.cached_ty_for_shorthand(shorthand, |decoder| {
233 decoder.with_position(shorthand, Ty::decode)
236 let tcx = decoder.tcx();
237 tcx.mk_ty(ty::TyKind::decode(decoder))
242 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::Binder<'tcx, ty::PredicateKind<'tcx>> {
243 fn decode(decoder: &mut D) -> ty::Binder<'tcx, ty::PredicateKind<'tcx>> {
244 let bound_vars = Decodable::decode(decoder);
245 // Handle shorthands first, if we have a usize > 0x80.
246 ty::Binder::bind_with_vars(
247 if decoder.positioned_at_shorthand() {
248 let pos = decoder.read_usize();
249 assert!(pos >= SHORTHAND_OFFSET);
250 let shorthand = pos - SHORTHAND_OFFSET;
252 decoder.with_position(shorthand, ty::PredicateKind::decode)
254 ty::PredicateKind::decode(decoder)
261 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::Predicate<'tcx> {
262 fn decode(decoder: &mut D) -> ty::Predicate<'tcx> {
263 let predicate_kind = Decodable::decode(decoder);
264 decoder.tcx().mk_predicate(predicate_kind)
268 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for SubstsRef<'tcx> {
269 fn decode(decoder: &mut D) -> Self {
270 let len = decoder.read_usize();
271 let tcx = decoder.tcx();
273 (0..len).map::<ty::subst::GenericArg<'tcx>, _>(|_| Decodable::decode(decoder)),
278 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for mir::Place<'tcx> {
279 fn decode(decoder: &mut D) -> Self {
280 let local: mir::Local = Decodable::decode(decoder);
281 let len = decoder.read_usize();
282 let projection = decoder.tcx().mk_place_elems(
283 (0..len).map::<mir::PlaceElem<'tcx>, _>(|_| Decodable::decode(decoder)),
285 mir::Place { local, projection }
289 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::Region<'tcx> {
290 fn decode(decoder: &mut D) -> Self {
291 decoder.tcx().mk_region(Decodable::decode(decoder))
295 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for CanonicalVarInfos<'tcx> {
296 fn decode(decoder: &mut D) -> Self {
297 let len = decoder.read_usize();
298 let interned: Vec<CanonicalVarInfo<'tcx>> =
299 (0..len).map(|_| Decodable::decode(decoder)).collect();
300 decoder.tcx().intern_canonical_var_infos(interned.as_slice())
304 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for AllocId {
305 fn decode(decoder: &mut D) -> Self {
306 decoder.decode_alloc_id()
310 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::SymbolName<'tcx> {
311 fn decode(decoder: &mut D) -> Self {
312 ty::SymbolName::new(decoder.tcx(), &decoder.read_str())
316 macro_rules! impl_decodable_via_ref {
318 $(impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for $t {
319 fn decode(decoder: &mut D) -> Self {
320 RefDecodable::decode(decoder)
326 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for ty::List<Ty<'tcx>> {
327 fn decode(decoder: &mut D) -> &'tcx Self {
328 let len = decoder.read_usize();
329 decoder.tcx().mk_type_list((0..len).map::<Ty<'tcx>, _>(|_| Decodable::decode(decoder)))
333 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D>
334 for ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>
336 fn decode(decoder: &mut D) -> &'tcx Self {
337 let len = decoder.read_usize();
338 decoder.tcx().mk_poly_existential_predicates(
339 (0..len).map::<ty::Binder<'tcx, _>, _>(|_| Decodable::decode(decoder)),
344 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::Const<'tcx> {
345 fn decode(decoder: &mut D) -> Self {
346 decoder.tcx().mk_const(Decodable::decode(decoder))
350 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [ty::ValTree<'tcx>] {
351 fn decode(decoder: &mut D) -> &'tcx Self {
352 decoder.tcx().arena.alloc_from_iter(
353 (0..decoder.read_usize()).map(|_| Decodable::decode(decoder)).collect::<Vec<_>>(),
358 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for Allocation {
359 fn decode(decoder: &mut D) -> &'tcx Self {
360 decoder.tcx().intern_const_alloc(Decodable::decode(decoder))
364 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [(ty::Predicate<'tcx>, Span)] {
365 fn decode(decoder: &mut D) -> &'tcx Self {
366 decoder.tcx().arena.alloc_from_iter(
367 (0..decoder.read_usize()).map(|_| Decodable::decode(decoder)).collect::<Vec<_>>(),
372 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [thir::abstract_const::Node<'tcx>] {
373 fn decode(decoder: &mut D) -> &'tcx Self {
374 decoder.tcx().arena.alloc_from_iter(
375 (0..decoder.read_usize()).map(|_| Decodable::decode(decoder)).collect::<Vec<_>>(),
380 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [thir::abstract_const::NodeId] {
381 fn decode(decoder: &mut D) -> &'tcx Self {
382 decoder.tcx().arena.alloc_from_iter(
383 (0..decoder.read_usize()).map(|_| Decodable::decode(decoder)).collect::<Vec<_>>(),
388 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for ty::List<ty::BoundVariableKind> {
389 fn decode(decoder: &mut D) -> &'tcx Self {
390 let len = decoder.read_usize();
391 decoder.tcx().mk_bound_variable_kinds(
392 (0..len).map::<ty::BoundVariableKind, _>(|_| Decodable::decode(decoder)),
397 impl_decodable_via_ref! {
398 &'tcx ty::TypeckResults<'tcx>,
399 &'tcx ty::List<Ty<'tcx>>,
400 &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
401 &'tcx traits::ImplSource<'tcx, ()>,
403 &'tcx mir::Body<'tcx>,
404 &'tcx mir::UnsafetyCheckResult,
405 &'tcx mir::BorrowCheckResult<'tcx>,
406 &'tcx mir::coverage::CodeRegion,
407 &'tcx ty::List<ty::BoundVariableKind>,
412 macro_rules! __impl_decoder_methods {
413 ($($name:ident -> $ty:ty;)*) => {
416 fn $name(&mut self) -> $ty {
423 macro_rules! impl_arena_allocatable_decoder {
425 ([decode $(, $attrs:ident)*]
426 [$name:ident: $ty:ty]) => {
427 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for $ty {
429 fn decode(decoder: &mut D) -> &'tcx Self {
430 decode_arena_allocable(decoder)
434 impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [$ty] {
436 fn decode(decoder: &mut D) -> &'tcx Self {
437 decode_arena_allocable_slice(decoder)
441 ([$ignore:ident $(, $attrs:ident)*]$args:tt) => {
442 impl_arena_allocatable_decoder!([$($attrs),*]$args);
446 macro_rules! impl_arena_allocatable_decoders {
447 ([$($a:tt $name:ident: $ty:ty,)*]) => {
449 impl_arena_allocatable_decoder!($a [$name: $ty]);
454 rustc_hir::arena_types!(impl_arena_allocatable_decoders);
455 arena_types!(impl_arena_allocatable_decoders);
458 macro_rules! implement_ty_decoder {
459 ($DecoderName:ident <$($typaram:tt),*>) => {
460 mod __ty_decoder_impl {
461 use std::borrow::Cow;
462 use rustc_serialize::Decoder;
464 use super::$DecoderName;
466 impl<$($typaram ),*> Decoder for $DecoderName<$($typaram),*> {
467 $crate::__impl_decoder_methods! {
490 fn read_raw_bytes(&mut self, len: usize) -> &[u8] {
491 self.opaque.read_raw_bytes(len)
498 macro_rules! impl_binder_encode_decode {
499 ($($t:ty),+ $(,)?) => {
501 impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ty::Binder<'tcx, $t> {
502 fn encode(&self, e: &mut E) -> Result<(), E::Error> {
503 self.bound_vars().encode(e)?;
504 self.as_ref().skip_binder().encode(e)
507 impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::Binder<'tcx, $t> {
508 fn decode(decoder: &mut D) -> Self {
509 let bound_vars = Decodable::decode(decoder);
510 ty::Binder::bind_with_vars(Decodable::decode(decoder), bound_vars)
517 impl_binder_encode_decode! {
518 &'tcx ty::List<Ty<'tcx>>,
520 ty::ExistentialPredicate<'tcx>,
522 Vec<ty::GeneratorInteriorTypeCause<'tcx>>,