3 use rustc_data_structures::fingerprint::Fingerprint;
4 use rustc_hir::def::{CtorKind, CtorOf};
5 use rustc_index::vec::Idx;
6 use rustc_middle::ty::ParameterizedOverTcx;
7 use rustc_serialize::opaque::FileEncoder;
8 use rustc_serialize::Encoder as _;
9 use rustc_span::hygiene::MacroKind;
10 use std::marker::PhantomData;
11 use std::num::NonZeroUsize;
13 /// Helper trait, for encoding to, and decoding from, a fixed number of bytes.
14 /// Used mainly for Lazy positions and lengths.
15 /// Unchecked invariant: `Self::default()` should encode as `[0; BYTE_LEN]`,
16 /// but this has no impact on safety.
17 pub(super) trait FixedSizeEncoding: Default {
18 /// This should be `[u8; BYTE_LEN]`;
19 /// Cannot use an associated `const BYTE_LEN: usize` instead due to const eval limitations.
22 fn from_bytes(b: &Self::ByteArray) -> Self;
23 fn write_to_bytes(self, b: &mut Self::ByteArray);
26 impl FixedSizeEncoding for u32 {
27 type ByteArray = [u8; 4];
30 fn from_bytes(b: &[u8; 4]) -> Self {
31 Self::from_le_bytes(*b)
35 fn write_to_bytes(self, b: &mut [u8; 4]) {
36 *b = self.to_le_bytes();
40 macro_rules! fixed_size_enum {
41 ($ty:ty { $(($($pat:tt)*))* }) => {
42 impl FixedSizeEncoding for Option<$ty> {
43 type ByteArray = [u8;1];
46 fn from_bytes(b: &[u8;1]) -> Self {
52 $(${index()} => Some($($pat)*),)*
53 _ => panic!("Unexpected {} code: {:?}", stringify!($ty), b[0]),
58 fn write_to_bytes(self, b: &mut [u8;1]) {
62 $(Some($($pat)*) => 1 + ${index()},)*
93 ( ImplTraitPlaceholder )
100 ( Static(ast::Mutability::Not) )
101 ( Static(ast::Mutability::Mut) )
102 ( Ctor(CtorOf::Struct, CtorKind::Fn) )
103 ( Ctor(CtorOf::Struct, CtorKind::Const) )
104 ( Ctor(CtorOf::Variant, CtorKind::Fn) )
105 ( Ctor(CtorOf::Variant, CtorKind::Const) )
106 ( Macro(MacroKind::Bang) )
107 ( Macro(MacroKind::Attr) )
108 ( Macro(MacroKind::Derive) )
130 ( Default { has_value: false } )
131 ( Default { has_value: true } )
143 ty::AssocItemContainer {
157 // We directly encode `DefPathHash` because a `LazyValue` would incur a 25% cost.
158 impl FixedSizeEncoding for Option<DefPathHash> {
159 type ByteArray = [u8; 16];
162 fn from_bytes(b: &[u8; 16]) -> Self {
163 Some(DefPathHash(Fingerprint::from_le_bytes(*b)))
167 fn write_to_bytes(self, b: &mut [u8; 16]) {
168 let Some(DefPathHash(fingerprint)) = self else {
169 panic!("Trying to encode absent DefPathHash.")
171 *b = fingerprint.to_le_bytes();
175 // We directly encode RawDefId because using a `LazyValue` would incur a 50% overhead in the worst case.
176 impl FixedSizeEncoding for Option<RawDefId> {
177 type ByteArray = [u8; 8];
180 fn from_bytes(b: &[u8; 8]) -> Self {
181 let krate = u32::from_le_bytes(b[0..4].try_into().unwrap());
182 let index = u32::from_le_bytes(b[4..8].try_into().unwrap());
186 Some(RawDefId { krate: krate - 1, index })
190 fn write_to_bytes(self, b: &mut [u8; 8]) {
193 Some(RawDefId { krate, index }) => {
194 // CrateNum is less than `CrateNum::MAX_AS_U32`.
195 debug_assert!(krate < u32::MAX);
196 b[0..4].copy_from_slice(&(1 + krate).to_le_bytes());
197 b[4..8].copy_from_slice(&index.to_le_bytes());
203 impl FixedSizeEncoding for AttrFlags {
204 type ByteArray = [u8; 1];
207 fn from_bytes(b: &[u8; 1]) -> Self {
208 AttrFlags::from_bits_truncate(b[0])
212 fn write_to_bytes(self, b: &mut [u8; 1]) {
217 impl FixedSizeEncoding for bool {
218 type ByteArray = [u8; 1];
221 fn from_bytes(b: &[u8; 1]) -> Self {
226 fn write_to_bytes(self, b: &mut [u8; 1]) {
231 // NOTE(eddyb) there could be an impl for `usize`, which would enable a more
232 // generic `LazyValue<T>` impl, but in the general case we might not need / want
233 // to fit every `usize` in `u32`.
234 impl<T> FixedSizeEncoding for Option<LazyValue<T>> {
235 type ByteArray = [u8; 4];
238 fn from_bytes(b: &[u8; 4]) -> Self {
239 let position = NonZeroUsize::new(u32::from_bytes(b) as usize)?;
240 Some(LazyValue::from_position(position))
244 fn write_to_bytes(self, b: &mut [u8; 4]) {
245 let position = self.map_or(0, |lazy| lazy.position.get());
246 let position: u32 = position.try_into().unwrap();
247 position.write_to_bytes(b)
251 impl<T> FixedSizeEncoding for Option<LazyArray<T>> {
252 type ByteArray = [u8; 8];
255 fn from_bytes(b: &[u8; 8]) -> Self {
256 let ([ref position_bytes, ref meta_bytes],[])= b.as_chunks::<4>() else { panic!() };
257 let position = NonZeroUsize::new(u32::from_bytes(position_bytes) as usize)?;
258 let len = u32::from_bytes(meta_bytes) as usize;
259 Some(LazyArray::from_position_and_num_elems(position, len))
263 fn write_to_bytes(self, b: &mut [u8; 8]) {
264 let ([ref mut position_bytes, ref mut meta_bytes],[])= b.as_chunks_mut::<4>() else { panic!() };
266 let position = self.map_or(0, |lazy| lazy.position.get());
267 let position: u32 = position.try_into().unwrap();
268 position.write_to_bytes(position_bytes);
270 let len = self.map_or(0, |lazy| lazy.num_elems);
271 let len: u32 = len.try_into().unwrap();
272 len.write_to_bytes(meta_bytes);
276 /// Helper for constructing a table's serialization (also see `Table`).
277 pub(super) struct TableBuilder<I: Idx, T: FixedSizeEncoding> {
278 blocks: IndexVec<I, T::ByteArray>,
279 _marker: PhantomData<T>,
282 impl<I: Idx, T: FixedSizeEncoding> Default for TableBuilder<I, T> {
283 fn default() -> Self {
284 TableBuilder { blocks: Default::default(), _marker: PhantomData }
288 impl<I: Idx, const N: usize, T> TableBuilder<I, Option<T>>
290 Option<T>: FixedSizeEncoding<ByteArray = [u8; N]>,
292 pub(crate) fn set(&mut self, i: I, value: T) {
293 self.set_nullable(i, Some(value))
297 impl<I: Idx, const N: usize, T: FixedSizeEncoding<ByteArray = [u8; N]>> TableBuilder<I, T> {
298 pub(crate) fn set_nullable(&mut self, i: I, value: T) {
299 // FIXME(eddyb) investigate more compact encodings for sparse tables.
300 // On the PR @michaelwoerister mentioned:
301 // > Space requirements could perhaps be optimized by using the HAMT `popcnt`
302 // > trick (i.e. divide things into buckets of 32 or 64 items and then
303 // > store bit-masks of which item in each bucket is actually serialized).
304 self.blocks.ensure_contains_elem(i, || [0; N]);
305 value.write_to_bytes(&mut self.blocks[i]);
308 pub(crate) fn encode(&self, buf: &mut FileEncoder) -> LazyTable<I, T> {
309 let pos = buf.position();
310 for block in &self.blocks {
311 buf.emit_raw_bytes(block);
313 let num_bytes = self.blocks.len() * N;
314 LazyTable::from_position_and_encoded_size(
315 NonZeroUsize::new(pos as usize).unwrap(),
321 impl<I: Idx, const N: usize, T: FixedSizeEncoding<ByteArray = [u8; N]> + ParameterizedOverTcx>
324 for<'tcx> T::Value<'tcx>: FixedSizeEncoding<ByteArray = [u8; N]>,
326 /// Given the metadata, extract out the value at a particular index (if any).
328 pub(super) fn get<'a, 'tcx, M: Metadata<'a, 'tcx>>(&self, metadata: M, i: I) -> T::Value<'tcx> {
329 debug!("LazyTable::lookup: index={:?} len={:?}", i, self.encoded_size);
331 let start = self.position.get();
332 let bytes = &metadata.blob()[start..start + self.encoded_size];
333 let (bytes, []) = bytes.as_chunks::<N>() else { panic!() };
334 match bytes.get(i.index()) {
335 Some(bytes) => FixedSizeEncoding::from_bytes(bytes),
336 None => FixedSizeEncoding::from_bytes(&[0; N]),
340 /// Size of the table in entries, including possible gaps.
341 pub(super) fn size(&self) -> usize {
342 self.encoded_size / N