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1 | // Copyright 2017 The Rust Project Developers. See the COPYRIGHT |
2 | // file at the top-level directory of this distribution and at | |
3 | // http://rust-lang.org/COPYRIGHT. | |
4 | // | |
5 | // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | |
6 | // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | |
7 | // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | |
8 | // option. This file may not be copied, modified, or distributed | |
9 | // except according to those terms. | |
10 | ||
11 | // This module contains some shared code for encoding and decoding various | |
12 | // things from the `ty` module, and in particular implements support for | |
13 | // "shorthands" which allow to have pointers back into the already encoded | |
14 | // stream instead of re-encoding the same thing twice. | |
15 | // | |
16 | // The functionality in here is shared between persisting to crate metadata and | |
17 | // persisting to incr. comp. caches. | |
18 | ||
19 | use hir::def_id::{DefId, CrateNum}; | |
0531ce1d | 20 | use infer::canonical::{CanonicalVarInfo, CanonicalVarInfos}; |
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21 | use rustc_data_structures::fx::FxHashMap; |
22 | use rustc_serialize::{Decodable, Decoder, Encoder, Encodable, opaque}; | |
23 | use std::hash::Hash; | |
24 | use std::intrinsics; | |
25 | use ty::{self, Ty, TyCtxt}; | |
26 | use ty::subst::Substs; | |
94b46f34 | 27 | use mir::interpret::Allocation; |
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28 | |
29 | /// The shorthand encoding uses an enum's variant index `usize` | |
30 | /// and is offset by this value so it never matches a real variant. | |
31 | /// This offset is also chosen so that the first byte is never < 0x80. | |
32 | pub const SHORTHAND_OFFSET: usize = 0x80; | |
33 | ||
34 | pub trait EncodableWithShorthand: Clone + Eq + Hash { | |
35 | type Variant: Encodable; | |
36 | fn variant(&self) -> &Self::Variant; | |
37 | } | |
38 | ||
39 | impl<'tcx> EncodableWithShorthand for Ty<'tcx> { | |
40 | type Variant = ty::TypeVariants<'tcx>; | |
41 | fn variant(&self) -> &Self::Variant { | |
42 | &self.sty | |
43 | } | |
44 | } | |
45 | ||
46 | impl<'tcx> EncodableWithShorthand for ty::Predicate<'tcx> { | |
47 | type Variant = ty::Predicate<'tcx>; | |
48 | fn variant(&self) -> &Self::Variant { | |
49 | self | |
50 | } | |
51 | } | |
52 | ||
53 | pub trait TyEncoder: Encoder { | |
54 | fn position(&self) -> usize; | |
55 | } | |
56 | ||
57 | impl<'buf> TyEncoder for opaque::Encoder<'buf> { | |
58 | #[inline] | |
59 | fn position(&self) -> usize { | |
60 | self.position() | |
61 | } | |
62 | } | |
63 | ||
64 | /// Encode the given value or a previously cached shorthand. | |
65 | pub fn encode_with_shorthand<E, T, M>(encoder: &mut E, | |
66 | value: &T, | |
67 | cache: M) | |
68 | -> Result<(), E::Error> | |
69 | where E: TyEncoder, | |
70 | M: for<'b> Fn(&'b mut E) -> &'b mut FxHashMap<T, usize>, | |
71 | T: EncodableWithShorthand, | |
72 | { | |
73 | let existing_shorthand = cache(encoder).get(value).cloned(); | |
74 | if let Some(shorthand) = existing_shorthand { | |
75 | return encoder.emit_usize(shorthand); | |
76 | } | |
77 | ||
78 | let variant = value.variant(); | |
79 | ||
80 | let start = encoder.position(); | |
81 | variant.encode(encoder)?; | |
82 | let len = encoder.position() - start; | |
83 | ||
84 | // The shorthand encoding uses the same usize as the | |
85 | // discriminant, with an offset so they can't conflict. | |
86 | let discriminant = unsafe { intrinsics::discriminant_value(variant) }; | |
87 | assert!(discriminant < SHORTHAND_OFFSET as u64); | |
88 | let shorthand = start + SHORTHAND_OFFSET; | |
89 | ||
90 | // Get the number of bits that leb128 could fit | |
91 | // in the same space as the fully encoded type. | |
92 | let leb128_bits = len * 7; | |
93 | ||
94 | // Check that the shorthand is a not longer than the | |
95 | // full encoding itself, i.e. it's an obvious win. | |
96 | if leb128_bits >= 64 || (shorthand as u64) < (1 << leb128_bits) { | |
97 | cache(encoder).insert(value.clone(), shorthand); | |
98 | } | |
99 | ||
100 | Ok(()) | |
101 | } | |
102 | ||
103 | pub fn encode_predicates<'tcx, E, C>(encoder: &mut E, | |
104 | predicates: &ty::GenericPredicates<'tcx>, | |
105 | cache: C) | |
106 | -> Result<(), E::Error> | |
107 | where E: TyEncoder, | |
108 | C: for<'b> Fn(&'b mut E) -> &'b mut FxHashMap<ty::Predicate<'tcx>, usize>, | |
109 | { | |
110 | predicates.parent.encode(encoder)?; | |
111 | predicates.predicates.len().encode(encoder)?; | |
112 | for predicate in &predicates.predicates { | |
113 | encode_with_shorthand(encoder, predicate, &cache)? | |
114 | } | |
115 | Ok(()) | |
116 | } | |
117 | ||
118 | pub trait TyDecoder<'a, 'tcx: 'a>: Decoder { | |
119 | ||
120 | fn tcx(&self) -> TyCtxt<'a, 'tcx, 'tcx>; | |
121 | ||
122 | fn peek_byte(&self) -> u8; | |
123 | ||
124 | fn position(&self) -> usize; | |
125 | ||
126 | fn cached_ty_for_shorthand<F>(&mut self, | |
127 | shorthand: usize, | |
128 | or_insert_with: F) | |
129 | -> Result<Ty<'tcx>, Self::Error> | |
130 | where F: FnOnce(&mut Self) -> Result<Ty<'tcx>, Self::Error>; | |
131 | ||
132 | fn with_position<F, R>(&mut self, pos: usize, f: F) -> R | |
133 | where F: FnOnce(&mut Self) -> R; | |
134 | ||
135 | fn map_encoded_cnum_to_current(&self, cnum: CrateNum) -> CrateNum; | |
136 | ||
137 | fn positioned_at_shorthand(&self) -> bool { | |
138 | (self.peek_byte() & (SHORTHAND_OFFSET as u8)) != 0 | |
139 | } | |
140 | } | |
141 | ||
142 | #[inline] | |
143 | pub fn decode_cnum<'a, 'tcx, D>(decoder: &mut D) -> Result<CrateNum, D::Error> | |
144 | where D: TyDecoder<'a, 'tcx>, | |
145 | 'tcx: 'a, | |
146 | { | |
147 | let cnum = CrateNum::from_u32(u32::decode(decoder)?); | |
148 | Ok(decoder.map_encoded_cnum_to_current(cnum)) | |
149 | } | |
150 | ||
151 | #[inline] | |
152 | pub fn decode_ty<'a, 'tcx, D>(decoder: &mut D) -> Result<Ty<'tcx>, D::Error> | |
153 | where D: TyDecoder<'a, 'tcx>, | |
154 | 'tcx: 'a, | |
155 | { | |
156 | // Handle shorthands first, if we have an usize > 0x80. | |
157 | if decoder.positioned_at_shorthand() { | |
158 | let pos = decoder.read_usize()?; | |
159 | assert!(pos >= SHORTHAND_OFFSET); | |
160 | let shorthand = pos - SHORTHAND_OFFSET; | |
161 | ||
162 | decoder.cached_ty_for_shorthand(shorthand, |decoder| { | |
163 | decoder.with_position(shorthand, Ty::decode) | |
164 | }) | |
165 | } else { | |
166 | let tcx = decoder.tcx(); | |
167 | Ok(tcx.mk_ty(ty::TypeVariants::decode(decoder)?)) | |
168 | } | |
169 | } | |
170 | ||
171 | #[inline] | |
172 | pub fn decode_predicates<'a, 'tcx, D>(decoder: &mut D) | |
173 | -> Result<ty::GenericPredicates<'tcx>, D::Error> | |
174 | where D: TyDecoder<'a, 'tcx>, | |
175 | 'tcx: 'a, | |
176 | { | |
177 | Ok(ty::GenericPredicates { | |
178 | parent: Decodable::decode(decoder)?, | |
179 | predicates: (0..decoder.read_usize()?).map(|_| { | |
180 | // Handle shorthands first, if we have an usize > 0x80. | |
181 | if decoder.positioned_at_shorthand() { | |
182 | let pos = decoder.read_usize()?; | |
183 | assert!(pos >= SHORTHAND_OFFSET); | |
184 | let shorthand = pos - SHORTHAND_OFFSET; | |
185 | ||
186 | decoder.with_position(shorthand, ty::Predicate::decode) | |
187 | } else { | |
188 | ty::Predicate::decode(decoder) | |
189 | } | |
190 | }) | |
191 | .collect::<Result<Vec<_>, _>>()?, | |
192 | }) | |
193 | } | |
194 | ||
195 | #[inline] | |
196 | pub fn decode_substs<'a, 'tcx, D>(decoder: &mut D) -> Result<&'tcx Substs<'tcx>, D::Error> | |
197 | where D: TyDecoder<'a, 'tcx>, | |
198 | 'tcx: 'a, | |
199 | { | |
200 | let len = decoder.read_usize()?; | |
201 | let tcx = decoder.tcx(); | |
202 | Ok(tcx.mk_substs((0..len).map(|_| Decodable::decode(decoder)))?) | |
203 | } | |
204 | ||
205 | #[inline] | |
206 | pub fn decode_region<'a, 'tcx, D>(decoder: &mut D) -> Result<ty::Region<'tcx>, D::Error> | |
207 | where D: TyDecoder<'a, 'tcx>, | |
208 | 'tcx: 'a, | |
209 | { | |
210 | Ok(decoder.tcx().mk_region(Decodable::decode(decoder)?)) | |
211 | } | |
212 | ||
213 | #[inline] | |
214 | pub fn decode_ty_slice<'a, 'tcx, D>(decoder: &mut D) | |
215 | -> Result<&'tcx ty::Slice<Ty<'tcx>>, D::Error> | |
216 | where D: TyDecoder<'a, 'tcx>, | |
217 | 'tcx: 'a, | |
218 | { | |
219 | let len = decoder.read_usize()?; | |
220 | Ok(decoder.tcx().mk_type_list((0..len).map(|_| Decodable::decode(decoder)))?) | |
221 | } | |
222 | ||
223 | #[inline] | |
224 | pub fn decode_adt_def<'a, 'tcx, D>(decoder: &mut D) | |
225 | -> Result<&'tcx ty::AdtDef, D::Error> | |
226 | where D: TyDecoder<'a, 'tcx>, | |
227 | 'tcx: 'a, | |
228 | { | |
229 | let def_id = DefId::decode(decoder)?; | |
230 | Ok(decoder.tcx().adt_def(def_id)) | |
231 | } | |
232 | ||
233 | #[inline] | |
234 | pub fn decode_existential_predicate_slice<'a, 'tcx, D>(decoder: &mut D) | |
235 | -> Result<&'tcx ty::Slice<ty::ExistentialPredicate<'tcx>>, D::Error> | |
236 | where D: TyDecoder<'a, 'tcx>, | |
237 | 'tcx: 'a, | |
238 | { | |
239 | let len = decoder.read_usize()?; | |
240 | Ok(decoder.tcx() | |
241 | .mk_existential_predicates((0..len).map(|_| Decodable::decode(decoder)))?) | |
242 | } | |
243 | ||
244 | #[inline] | |
0531ce1d XL |
245 | pub fn decode_canonical_var_infos<'a, 'tcx, D>(decoder: &mut D) |
246 | -> Result<CanonicalVarInfos<'tcx>, D::Error> | |
abe05a73 XL |
247 | where D: TyDecoder<'a, 'tcx>, |
248 | 'tcx: 'a, | |
249 | { | |
0531ce1d XL |
250 | let len = decoder.read_usize()?; |
251 | let interned: Result<Vec<CanonicalVarInfo>, _> = (0..len).map(|_| Decodable::decode(decoder)) | |
252 | .collect(); | |
253 | Ok(decoder.tcx() | |
254 | .intern_canonical_var_infos(interned?.as_slice())) | |
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255 | } |
256 | ||
257 | #[inline] | |
258 | pub fn decode_const<'a, 'tcx, D>(decoder: &mut D) | |
259 | -> Result<&'tcx ty::Const<'tcx>, D::Error> | |
260 | where D: TyDecoder<'a, 'tcx>, | |
261 | 'tcx: 'a, | |
262 | { | |
263 | Ok(decoder.tcx().mk_const(Decodable::decode(decoder)?)) | |
264 | } | |
265 | ||
94b46f34 XL |
266 | #[inline] |
267 | pub fn decode_allocation<'a, 'tcx, D>(decoder: &mut D) | |
268 | -> Result<&'tcx Allocation, D::Error> | |
269 | where D: TyDecoder<'a, 'tcx>, | |
270 | 'tcx: 'a, | |
271 | { | |
272 | Ok(decoder.tcx().intern_const_alloc(Decodable::decode(decoder)?)) | |
273 | } | |
274 | ||
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275 | #[macro_export] |
276 | macro_rules! __impl_decoder_methods { | |
277 | ($($name:ident -> $ty:ty;)*) => { | |
278 | $(fn $name(&mut self) -> Result<$ty, Self::Error> { | |
279 | self.opaque.$name() | |
280 | })* | |
281 | } | |
282 | } | |
283 | ||
284 | #[macro_export] | |
285 | macro_rules! implement_ty_decoder { | |
286 | ($DecoderName:ident <$($typaram:tt),*>) => { | |
287 | mod __ty_decoder_impl { | |
288 | use super::$DecoderName; | |
0531ce1d | 289 | use $crate::infer::canonical::CanonicalVarInfos; |
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290 | use $crate::ty; |
291 | use $crate::ty::codec::*; | |
292 | use $crate::ty::subst::Substs; | |
293 | use $crate::hir::def_id::{CrateNum}; | |
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294 | use rustc_serialize::{Decoder, SpecializedDecoder}; |
295 | use std::borrow::Cow; | |
296 | ||
297 | impl<$($typaram ),*> Decoder for $DecoderName<$($typaram),*> { | |
298 | type Error = String; | |
299 | ||
300 | __impl_decoder_methods! { | |
301 | read_nil -> (); | |
302 | ||
303 | read_u128 -> u128; | |
304 | read_u64 -> u64; | |
305 | read_u32 -> u32; | |
306 | read_u16 -> u16; | |
307 | read_u8 -> u8; | |
308 | read_usize -> usize; | |
309 | ||
310 | read_i128 -> i128; | |
311 | read_i64 -> i64; | |
312 | read_i32 -> i32; | |
313 | read_i16 -> i16; | |
314 | read_i8 -> i8; | |
315 | read_isize -> isize; | |
316 | ||
317 | read_bool -> bool; | |
318 | read_f64 -> f64; | |
319 | read_f32 -> f32; | |
320 | read_char -> char; | |
321 | read_str -> Cow<str>; | |
322 | } | |
323 | ||
324 | fn error(&mut self, err: &str) -> Self::Error { | |
325 | self.opaque.error(err) | |
326 | } | |
327 | } | |
328 | ||
329 | // FIXME(#36588) These impls are horribly unsound as they allow | |
330 | // the caller to pick any lifetime for 'tcx, including 'static, | |
331 | // by using the unspecialized proxies to them. | |
332 | ||
333 | impl<$($typaram),*> SpecializedDecoder<CrateNum> | |
334 | for $DecoderName<$($typaram),*> { | |
335 | fn specialized_decode(&mut self) -> Result<CrateNum, Self::Error> { | |
336 | decode_cnum(self) | |
337 | } | |
338 | } | |
339 | ||
340 | impl<$($typaram),*> SpecializedDecoder<ty::Ty<'tcx>> | |
341 | for $DecoderName<$($typaram),*> { | |
342 | fn specialized_decode(&mut self) -> Result<ty::Ty<'tcx>, Self::Error> { | |
343 | decode_ty(self) | |
344 | } | |
345 | } | |
346 | ||
347 | impl<$($typaram),*> SpecializedDecoder<ty::GenericPredicates<'tcx>> | |
348 | for $DecoderName<$($typaram),*> { | |
349 | fn specialized_decode(&mut self) | |
350 | -> Result<ty::GenericPredicates<'tcx>, Self::Error> { | |
351 | decode_predicates(self) | |
352 | } | |
353 | } | |
354 | ||
355 | impl<$($typaram),*> SpecializedDecoder<&'tcx Substs<'tcx>> | |
356 | for $DecoderName<$($typaram),*> { | |
357 | fn specialized_decode(&mut self) -> Result<&'tcx Substs<'tcx>, Self::Error> { | |
358 | decode_substs(self) | |
359 | } | |
360 | } | |
361 | ||
362 | impl<$($typaram),*> SpecializedDecoder<ty::Region<'tcx>> | |
363 | for $DecoderName<$($typaram),*> { | |
364 | fn specialized_decode(&mut self) -> Result<ty::Region<'tcx>, Self::Error> { | |
365 | decode_region(self) | |
366 | } | |
367 | } | |
368 | ||
369 | impl<$($typaram),*> SpecializedDecoder<&'tcx ty::Slice<ty::Ty<'tcx>>> | |
370 | for $DecoderName<$($typaram),*> { | |
371 | fn specialized_decode(&mut self) | |
372 | -> Result<&'tcx ty::Slice<ty::Ty<'tcx>>, Self::Error> { | |
373 | decode_ty_slice(self) | |
374 | } | |
375 | } | |
376 | ||
377 | impl<$($typaram),*> SpecializedDecoder<&'tcx ty::AdtDef> | |
378 | for $DecoderName<$($typaram),*> { | |
379 | fn specialized_decode(&mut self) -> Result<&'tcx ty::AdtDef, Self::Error> { | |
380 | decode_adt_def(self) | |
381 | } | |
382 | } | |
383 | ||
384 | impl<$($typaram),*> SpecializedDecoder<&'tcx ty::Slice<ty::ExistentialPredicate<'tcx>>> | |
385 | for $DecoderName<$($typaram),*> { | |
386 | fn specialized_decode(&mut self) | |
387 | -> Result<&'tcx ty::Slice<ty::ExistentialPredicate<'tcx>>, Self::Error> { | |
388 | decode_existential_predicate_slice(self) | |
389 | } | |
390 | } | |
391 | ||
0531ce1d XL |
392 | impl<$($typaram),*> SpecializedDecoder<CanonicalVarInfos<'tcx>> |
393 | for $DecoderName<$($typaram),*> { | |
394 | fn specialized_decode(&mut self) | |
395 | -> Result<CanonicalVarInfos<'tcx>, Self::Error> { | |
396 | decode_canonical_var_infos(self) | |
abe05a73 XL |
397 | } |
398 | } | |
399 | ||
400 | impl<$($typaram),*> SpecializedDecoder<&'tcx $crate::ty::Const<'tcx>> | |
401 | for $DecoderName<$($typaram),*> { | |
402 | fn specialized_decode(&mut self) -> Result<&'tcx ty::Const<'tcx>, Self::Error> { | |
403 | decode_const(self) | |
404 | } | |
405 | } | |
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406 | |
407 | impl<$($typaram),*> SpecializedDecoder<&'tcx $crate::mir::interpret::Allocation> | |
408 | for $DecoderName<$($typaram),*> { | |
409 | fn specialized_decode( | |
410 | &mut self | |
411 | ) -> Result<&'tcx $crate::mir::interpret::Allocation, Self::Error> { | |
412 | decode_allocation(self) | |
413 | } | |
414 | } | |
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415 | } |
416 | } | |
417 | } | |
418 |