492 lines
16 KiB
Rust
492 lines
16 KiB
Rust
// This module contains some shared code for encoding and decoding various
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// things from the `ty` module, and in particular implements support for
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// "shorthands" which allow to have pointers back into the already encoded
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// stream instead of re-encoding the same thing twice.
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//
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// The functionality in here is shared between persisting to crate metadata and
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// persisting to incr. comp. caches.
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use crate::arena::ArenaAllocatable;
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use crate::hir::def_id::{DefId, CrateNum};
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use crate::infer::canonical::{CanonicalVarInfo, CanonicalVarInfos};
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use rustc_data_structures::fx::FxHashMap;
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use rustc_serialize::{Decodable, Decoder, Encoder, Encodable, opaque};
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use std::hash::Hash;
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use std::intrinsics;
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use crate::ty::{self, List, Ty, TyCtxt};
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use crate::ty::subst::SubstsRef;
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use crate::mir::{self, interpret::Allocation};
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use syntax_pos::Span;
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/// The shorthand encoding uses an enum's variant index `usize`
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/// and is offset by this value so it never matches a real variant.
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/// This offset is also chosen so that the first byte is never < 0x80.
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pub const SHORTHAND_OFFSET: usize = 0x80;
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pub trait EncodableWithShorthand: Clone + Eq + Hash {
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type Variant: Encodable;
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fn variant(&self) -> &Self::Variant;
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}
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#[allow(rustc::usage_of_ty_tykind)]
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impl<'tcx> EncodableWithShorthand for Ty<'tcx> {
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type Variant = ty::TyKind<'tcx>;
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fn variant(&self) -> &Self::Variant {
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&self.kind
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}
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}
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impl<'tcx> EncodableWithShorthand for ty::Predicate<'tcx> {
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type Variant = ty::Predicate<'tcx>;
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fn variant(&self) -> &Self::Variant {
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self
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}
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}
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pub trait TyEncoder: Encoder {
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fn position(&self) -> usize;
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}
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impl TyEncoder for opaque::Encoder {
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#[inline]
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fn position(&self) -> usize {
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self.position()
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}
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}
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/// Encode the given value or a previously cached shorthand.
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pub fn encode_with_shorthand<E, T, M>(encoder: &mut E,
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value: &T,
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cache: M)
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-> Result<(), E::Error>
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where E: TyEncoder,
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M: for<'b> Fn(&'b mut E) -> &'b mut FxHashMap<T, usize>,
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T: EncodableWithShorthand,
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{
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let existing_shorthand = cache(encoder).get(value).cloned();
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if let Some(shorthand) = existing_shorthand {
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return encoder.emit_usize(shorthand);
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}
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let variant = value.variant();
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let start = encoder.position();
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variant.encode(encoder)?;
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let len = encoder.position() - start;
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// The shorthand encoding uses the same usize as the
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// discriminant, with an offset so they can't conflict.
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let discriminant = unsafe { intrinsics::discriminant_value(variant) };
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assert!(discriminant < SHORTHAND_OFFSET as u64);
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let shorthand = start + SHORTHAND_OFFSET;
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// Get the number of bits that leb128 could fit
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// in the same space as the fully encoded type.
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let leb128_bits = len * 7;
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// Check that the shorthand is a not longer than the
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// full encoding itself, i.e., it's an obvious win.
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if leb128_bits >= 64 || (shorthand as u64) < (1 << leb128_bits) {
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cache(encoder).insert(value.clone(), shorthand);
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}
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Ok(())
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}
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pub fn encode_spanned_predicates<'tcx, E, C>(
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encoder: &mut E,
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predicates: &'tcx [(ty::Predicate<'tcx>, Span)],
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cache: C,
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) -> Result<(), E::Error>
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where E: TyEncoder,
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C: for<'b> Fn(&'b mut E) -> &'b mut FxHashMap<ty::Predicate<'tcx>, usize>,
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{
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predicates.len().encode(encoder)?;
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for (predicate, span) in predicates {
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encode_with_shorthand(encoder, predicate, &cache)?;
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span.encode(encoder)?;
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}
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Ok(())
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}
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pub trait TyDecoder<'tcx>: Decoder {
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fn tcx(&self) -> TyCtxt<'tcx>;
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fn peek_byte(&self) -> u8;
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fn position(&self) -> usize;
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fn cached_ty_for_shorthand<F>(&mut self,
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shorthand: usize,
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or_insert_with: F)
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-> Result<Ty<'tcx>, Self::Error>
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where F: FnOnce(&mut Self) -> Result<Ty<'tcx>, Self::Error>;
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fn with_position<F, R>(&mut self, pos: usize, f: F) -> R
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where F: FnOnce(&mut Self) -> R;
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fn map_encoded_cnum_to_current(&self, cnum: CrateNum) -> CrateNum;
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fn positioned_at_shorthand(&self) -> bool {
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(self.peek_byte() & (SHORTHAND_OFFSET as u8)) != 0
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}
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}
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#[inline]
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pub fn decode_arena_allocable<D, T: ArenaAllocatable + Decodable>(
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decoder: &mut D,
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) -> Result<&'tcx T, D::Error>
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where
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D: TyDecoder<'tcx>,
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{
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Ok(decoder.tcx().arena.alloc(Decodable::decode(decoder)?))
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}
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#[inline]
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pub fn decode_arena_allocable_slice<D, T: ArenaAllocatable + Decodable>(
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decoder: &mut D,
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) -> Result<&'tcx [T], D::Error>
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where
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D: TyDecoder<'tcx>,
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{
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Ok(decoder.tcx().arena.alloc_from_iter(<Vec<T> as Decodable>::decode(decoder)?))
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}
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#[inline]
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pub fn decode_cnum<D>(decoder: &mut D) -> Result<CrateNum, D::Error>
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where
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D: TyDecoder<'tcx>,
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{
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let cnum = CrateNum::from_u32(u32::decode(decoder)?);
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Ok(decoder.map_encoded_cnum_to_current(cnum))
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}
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#[allow(rustc::usage_of_ty_tykind)]
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#[inline]
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pub fn decode_ty<D>(decoder: &mut D) -> Result<Ty<'tcx>, D::Error>
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where
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D: TyDecoder<'tcx>,
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{
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// Handle shorthands first, if we have an usize > 0x80.
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if decoder.positioned_at_shorthand() {
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let pos = decoder.read_usize()?;
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assert!(pos >= SHORTHAND_OFFSET);
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let shorthand = pos - SHORTHAND_OFFSET;
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decoder.cached_ty_for_shorthand(shorthand, |decoder| {
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decoder.with_position(shorthand, Ty::decode)
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})
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} else {
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let tcx = decoder.tcx();
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Ok(tcx.mk_ty(ty::TyKind::decode(decoder)?))
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}
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}
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#[inline]
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pub fn decode_spanned_predicates<D>(
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decoder: &mut D,
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) -> Result<&'tcx [(ty::Predicate<'tcx>, Span)], D::Error>
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where
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D: TyDecoder<'tcx>,
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{
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let tcx = decoder.tcx();
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Ok(tcx.arena.alloc_from_iter(
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(0..decoder.read_usize()?).map(|_| {
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// Handle shorthands first, if we have an usize > 0x80.
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let predicate = if decoder.positioned_at_shorthand() {
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let pos = decoder.read_usize()?;
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assert!(pos >= SHORTHAND_OFFSET);
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let shorthand = pos - SHORTHAND_OFFSET;
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decoder.with_position(shorthand, ty::Predicate::decode)
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} else {
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ty::Predicate::decode(decoder)
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}?;
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Ok((predicate, Decodable::decode(decoder)?))
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})
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.collect::<Result<Vec<_>, _>>()?,
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))
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}
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#[inline]
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pub fn decode_substs<D>(decoder: &mut D) -> Result<SubstsRef<'tcx>, D::Error>
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where
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D: TyDecoder<'tcx>,
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{
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let len = decoder.read_usize()?;
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let tcx = decoder.tcx();
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Ok(tcx.mk_substs((0..len).map(|_| Decodable::decode(decoder)))?)
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}
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#[inline]
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pub fn decode_place<D>(decoder: &mut D) -> Result<mir::Place<'tcx>, D::Error>
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where
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D: TyDecoder<'tcx>,
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{
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let base: mir::PlaceBase<'tcx> = Decodable::decode(decoder)?;
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let len = decoder.read_usize()?;
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let projection: &'tcx List<mir::PlaceElem<'tcx>> =
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decoder.tcx().mk_place_elems((0..len).map(|_| Decodable::decode(decoder)))?;
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Ok(mir::Place { base, projection })
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}
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#[inline]
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pub fn decode_region<D>(decoder: &mut D) -> Result<ty::Region<'tcx>, D::Error>
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where
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D: TyDecoder<'tcx>,
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{
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Ok(decoder.tcx().mk_region(Decodable::decode(decoder)?))
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}
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#[inline]
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pub fn decode_ty_slice<D>(decoder: &mut D) -> Result<&'tcx ty::List<Ty<'tcx>>, D::Error>
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where
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D: TyDecoder<'tcx>,
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{
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let len = decoder.read_usize()?;
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Ok(decoder.tcx().mk_type_list((0..len).map(|_| Decodable::decode(decoder)))?)
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}
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#[inline]
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pub fn decode_adt_def<D>(decoder: &mut D) -> Result<&'tcx ty::AdtDef, D::Error>
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where
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D: TyDecoder<'tcx>,
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{
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let def_id = DefId::decode(decoder)?;
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Ok(decoder.tcx().adt_def(def_id))
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}
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#[inline]
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pub fn decode_existential_predicate_slice<D>(
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decoder: &mut D,
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) -> Result<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>, D::Error>
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where
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D: TyDecoder<'tcx>,
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{
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let len = decoder.read_usize()?;
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Ok(decoder.tcx()
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.mk_existential_predicates((0..len).map(|_| Decodable::decode(decoder)))?)
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}
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#[inline]
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pub fn decode_canonical_var_infos<D>(decoder: &mut D) -> Result<CanonicalVarInfos<'tcx>, D::Error>
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where
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D: TyDecoder<'tcx>,
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{
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let len = decoder.read_usize()?;
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let interned: Result<Vec<CanonicalVarInfo>, _> = (0..len).map(|_| Decodable::decode(decoder))
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.collect();
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Ok(decoder.tcx()
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.intern_canonical_var_infos(interned?.as_slice()))
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}
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#[inline]
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pub fn decode_const<D>(decoder: &mut D) -> Result<&'tcx ty::Const<'tcx>, D::Error>
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where
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D: TyDecoder<'tcx>,
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{
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Ok(decoder.tcx().mk_const(Decodable::decode(decoder)?))
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}
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#[inline]
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pub fn decode_allocation<D>(decoder: &mut D) -> Result<&'tcx Allocation, D::Error>
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where
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D: TyDecoder<'tcx>,
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{
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Ok(decoder.tcx().intern_const_alloc(Decodable::decode(decoder)?))
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}
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#[macro_export]
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macro_rules! __impl_decoder_methods {
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($($name:ident -> $ty:ty;)*) => {
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$(
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fn $name(&mut self) -> Result<$ty, Self::Error> {
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self.opaque.$name()
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}
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)*
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}
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}
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#[macro_export]
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macro_rules! impl_arena_allocatable_decoder {
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([]$args:tt) => {};
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([decode $(, $attrs:ident)*]
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[[$DecoderName:ident [$($typaram:tt),*]], [$name:ident: $ty:ty], $tcx:lifetime]) => {
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impl<$($typaram),*> SpecializedDecoder<&$tcx $ty> for $DecoderName<$($typaram),*> {
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#[inline]
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fn specialized_decode(&mut self) -> Result<&$tcx $ty, Self::Error> {
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decode_arena_allocable(self)
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}
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}
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impl<$($typaram),*> SpecializedDecoder<&$tcx [$ty]> for $DecoderName<$($typaram),*> {
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#[inline]
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fn specialized_decode(&mut self) -> Result<&$tcx [$ty], Self::Error> {
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decode_arena_allocable_slice(self)
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}
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}
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};
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([$ignore:ident $(, $attrs:ident)*]$args:tt) => {
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impl_arena_allocatable_decoder!([$($attrs),*]$args);
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};
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}
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#[macro_export]
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macro_rules! impl_arena_allocatable_decoders {
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($args:tt, [$($a:tt $name:ident: $ty:ty,)*], $tcx:lifetime) => {
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$(
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impl_arena_allocatable_decoder!($a [$args, [$name: $ty], $tcx]);
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)*
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}
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}
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#[macro_export]
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macro_rules! implement_ty_decoder {
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($DecoderName:ident <$($typaram:tt),*>) => {
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mod __ty_decoder_impl {
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use std::borrow::Cow;
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use rustc_serialize::{Decoder, SpecializedDecoder};
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use $crate::infer::canonical::CanonicalVarInfos;
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use $crate::ty;
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use $crate::ty::codec::*;
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use $crate::ty::subst::SubstsRef;
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use $crate::hir::def_id::{CrateNum};
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use syntax_pos::Span;
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use super::$DecoderName;
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impl<$($typaram ),*> Decoder for $DecoderName<$($typaram),*> {
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type Error = String;
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__impl_decoder_methods! {
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read_nil -> ();
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read_u128 -> u128;
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read_u64 -> u64;
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read_u32 -> u32;
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read_u16 -> u16;
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read_u8 -> u8;
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read_usize -> usize;
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read_i128 -> i128;
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read_i64 -> i64;
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read_i32 -> i32;
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read_i16 -> i16;
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read_i8 -> i8;
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read_isize -> isize;
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read_bool -> bool;
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read_f64 -> f64;
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read_f32 -> f32;
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read_char -> char;
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read_str -> Cow<'_, str>;
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}
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fn error(&mut self, err: &str) -> Self::Error {
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self.opaque.error(err)
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}
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}
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// FIXME(#36588): These impls are horribly unsound as they allow
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// the caller to pick any lifetime for `'tcx`, including `'static`,
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// by using the unspecialized proxies to them.
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arena_types!(impl_arena_allocatable_decoders, [$DecoderName [$($typaram),*]], 'tcx);
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impl<$($typaram),*> SpecializedDecoder<CrateNum>
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for $DecoderName<$($typaram),*> {
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fn specialized_decode(&mut self) -> Result<CrateNum, Self::Error> {
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decode_cnum(self)
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}
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}
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impl<$($typaram),*> SpecializedDecoder<ty::Ty<'tcx>>
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for $DecoderName<$($typaram),*> {
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fn specialized_decode(&mut self) -> Result<ty::Ty<'tcx>, Self::Error> {
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decode_ty(self)
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}
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}
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impl<$($typaram),*> SpecializedDecoder<&'tcx [(ty::Predicate<'tcx>, Span)]>
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for $DecoderName<$($typaram),*> {
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fn specialized_decode(&mut self)
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-> Result<&'tcx [(ty::Predicate<'tcx>, Span)], Self::Error> {
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decode_spanned_predicates(self)
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}
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}
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impl<$($typaram),*> SpecializedDecoder<SubstsRef<'tcx>>
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for $DecoderName<$($typaram),*> {
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fn specialized_decode(&mut self) -> Result<SubstsRef<'tcx>, Self::Error> {
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decode_substs(self)
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}
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}
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impl<$($typaram),*> SpecializedDecoder<$crate::mir::Place<'tcx>>
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for $DecoderName<$($typaram),*> {
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fn specialized_decode(
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&mut self
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) -> Result<$crate::mir::Place<'tcx>, Self::Error> {
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decode_place(self)
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}
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}
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impl<$($typaram),*> SpecializedDecoder<ty::Region<'tcx>>
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for $DecoderName<$($typaram),*> {
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fn specialized_decode(&mut self) -> Result<ty::Region<'tcx>, Self::Error> {
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decode_region(self)
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}
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}
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impl<$($typaram),*> SpecializedDecoder<&'tcx ty::List<ty::Ty<'tcx>>>
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for $DecoderName<$($typaram),*> {
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fn specialized_decode(&mut self)
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-> Result<&'tcx ty::List<ty::Ty<'tcx>>, Self::Error> {
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decode_ty_slice(self)
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}
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}
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impl<$($typaram),*> SpecializedDecoder<&'tcx ty::AdtDef>
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for $DecoderName<$($typaram),*> {
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fn specialized_decode(&mut self) -> Result<&'tcx ty::AdtDef, Self::Error> {
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decode_adt_def(self)
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}
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}
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impl<$($typaram),*> SpecializedDecoder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>
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for $DecoderName<$($typaram),*> {
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fn specialized_decode(&mut self)
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-> Result<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>, Self::Error> {
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decode_existential_predicate_slice(self)
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}
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}
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impl<$($typaram),*> SpecializedDecoder<CanonicalVarInfos<'tcx>>
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for $DecoderName<$($typaram),*> {
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fn specialized_decode(&mut self)
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-> Result<CanonicalVarInfos<'tcx>, Self::Error> {
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decode_canonical_var_infos(self)
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}
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}
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impl<$($typaram),*> SpecializedDecoder<&'tcx $crate::ty::Const<'tcx>>
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for $DecoderName<$($typaram),*> {
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fn specialized_decode(&mut self) -> Result<&'tcx ty::Const<'tcx>, Self::Error> {
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decode_const(self)
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}
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}
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impl<$($typaram),*> SpecializedDecoder<&'tcx $crate::mir::interpret::Allocation>
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for $DecoderName<$($typaram),*> {
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fn specialized_decode(
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&mut self
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) -> Result<&'tcx $crate::mir::interpret::Allocation, Self::Error> {
|
|
decode_allocation(self)
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|