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Use delayed error handling for Encodable and Encoder infallible.

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There are two impls of the `Encoder` trait: `opaque::Encoder` and
`opaque::FileEncoder`. The former encodes into memory and is infallible, the
latter writes to file and is fallible.

Currently, standard `Result`/`?`/`unwrap` error handling is used, but this is a
bit verbose and has non-trivial cost, which is annoying given how rare failures
are (especially in the infallible `opaque::Encoder` case).

This commit changes how `Encoder` fallibility is handled. All the `emit_*`
methods are now infallible. `opaque::Encoder` requires no great changes for
this. `opaque::FileEncoder` now implements a delayed error handling strategy.
If a failure occurs, it records this via the `res` field, and all subsequent
encoding operations are skipped if `res` indicates an error has occurred. Once
encoding is complete, the new `finish` method is called, which returns a
`Result`. In other words, there is now a single `Result`-producing method
instead of many of them.

This has very little effect on how any file errors are reported if
`opaque::FileEncoder` has any failures.

Much of this commit is boring mechanical changes, removing `Result` return
values and `?` or `unwrap` from expressions. The more interesting parts are as
follows.
- serialize.rs: The `Encoder` trait gains an `Ok` associated type. The
  `into_inner` method is changed into `finish`, which returns
  `Result<Vec<u8>, !>`.
- opaque.rs: The `FileEncoder` adopts the delayed error handling
  strategy. Its `Ok` type is a `usize`, returning the number of bytes
  written, replacing previous uses of `FileEncoder::position`.
- Various methods that take an encoder now consume it, rather than being
  passed a mutable reference, e.g. `serialize_query_result_cache`.
This commit is contained in:
Nicholas Nethercote
2022-06-07 13:30:45 +10:00
parent 582b9cbc45
commit 1acbe7573d
45 changed files with 611 additions and 682 deletions
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4
compiler/rustc_middle/src/mir/graph_cyclic_cache.rs
View File

@@ -38,8 +38,8 @@ impl GraphIsCyclicCache {
impl<S: serialize::Encoder> serialize::Encodable<S> for GraphIsCyclicCache {
#[inline]
fn encode(&self, s: &mut S) -> Result<(), S::Error> {
serialize::Encodable::encode(&(), s)
fn encode(&self, s: &mut S) {
serialize::Encodable::encode(&(), s);
}
}

15
compiler/rustc_middle/src/mir/interpret/mod.rs
View File

@@ -207,27 +207,26 @@ pub fn specialized_encode_alloc_id<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>>(
encoder: &mut E,
tcx: TyCtxt<'tcx>,
alloc_id: AllocId,
) -> Result<(), E::Error> {
) {
match tcx.global_alloc(alloc_id) {
GlobalAlloc::Memory(alloc) => {
trace!("encoding {:?} with {:#?}", alloc_id, alloc);
AllocDiscriminant::Alloc.encode(encoder)?;
alloc.encode(encoder)?;
AllocDiscriminant::Alloc.encode(encoder);
alloc.encode(encoder);
}
GlobalAlloc::Function(fn_instance) => {
trace!("encoding {:?} with {:#?}", alloc_id, fn_instance);
AllocDiscriminant::Fn.encode(encoder)?;
fn_instance.encode(encoder)?;
AllocDiscriminant::Fn.encode(encoder);
fn_instance.encode(encoder);
}
GlobalAlloc::Static(did) => {
assert!(!tcx.is_thread_local_static(did));
// References to statics doesn't need to know about their allocations,
// just about its `DefId`.
AllocDiscriminant::Static.encode(encoder)?;
did.encode(encoder)?;
AllocDiscriminant::Static.encode(encoder);
did.encode(encoder);
}
}
Ok(())
}
// Used to avoid infinite recursion when decoding cyclic allocations.

8
compiler/rustc_middle/src/mir/mod.rs
View File

@@ -672,16 +672,16 @@ const TAG_CLEAR_CROSS_CRATE_SET: u8 = 1;
impl<E: TyEncoder, T: Encodable<E>> Encodable<E> for ClearCrossCrate<T> {
#[inline]
fn encode(&self, e: &mut E) -> Result<(), E::Error> {
fn encode(&self, e: &mut E) {
if E::CLEAR_CROSS_CRATE {
return Ok(());
return;
}
match *self {
ClearCrossCrate::Clear => TAG_CLEAR_CROSS_CRATE_CLEAR.encode(e),
ClearCrossCrate::Set(ref val) => {
TAG_CLEAR_CROSS_CRATE_SET.encode(e)?;
val.encode(e)
TAG_CLEAR_CROSS_CRATE_SET.encode(e);
val.encode(e);
}
}
}

4
compiler/rustc_middle/src/mir/predecessors.rs
View File

@@ -56,9 +56,7 @@ impl PredecessorCache {
impl<S: serialize::Encoder> serialize::Encodable<S> for PredecessorCache {
#[inline]
fn encode(&self, _s: &mut S) -> Result<(), S::Error> {
Ok(())
}
fn encode(&self, _s: &mut S) {}
}
impl<D: serialize::Decoder> serialize::Decodable<D> for PredecessorCache {

4
compiler/rustc_middle/src/mir/switch_sources.rs
View File

@@ -56,9 +56,7 @@ impl SwitchSourceCache {
impl<S: serialize::Encoder> serialize::Encodable<S> for SwitchSourceCache {
#[inline]
fn encode(&self, _s: &mut S) -> Result<(), S::Error> {
Ok(())
}
fn encode(&self, _s: &mut S) {}
}
impl<D: serialize::Decoder> serialize::Decodable<D> for SwitchSourceCache {

4
compiler/rustc_middle/src/mir/traversal.rs
View File

@@ -367,9 +367,7 @@ impl PostorderCache {
impl<S: serialize::Encoder> serialize::Encodable<S> for PostorderCache {
#[inline]
fn encode(&self, _s: &mut S) -> Result<(), S::Error> {
Ok(())
}
fn encode(&self, _s: &mut S) {}
}
impl<D: serialize::Decoder> serialize::Decodable<D> for PostorderCache {

47
compiler/rustc_middle/src/ty/codec.rs
View File

@@ -69,11 +69,7 @@ pub trait RefDecodable<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> {
}
/// Encode the given value or a previously cached shorthand.
pub fn encode_with_shorthand<'tcx, E, T, M>(
encoder: &mut E,
value: &T,
cache: M,
) -> Result<(), E::Error>
pub fn encode_with_shorthand<'tcx, E, T, M>(encoder: &mut E, value: &T, cache: M)
where
E: TyEncoder<I = TyCtxt<'tcx>>,
M: for<'b> Fn(&'b mut E) -> &'b mut FxHashMap<T, usize>,
@@ -83,13 +79,14 @@ where
{
let existing_shorthand = cache(encoder).get(value).copied();
if let Some(shorthand) = existing_shorthand {
return encoder.emit_usize(shorthand);
encoder.emit_usize(shorthand);
return;
}
let variant = value.variant();
let start = encoder.position();
variant.encode(encoder)?;
variant.encode(encoder);
let len = encoder.position() - start;
// The shorthand encoding uses the same usize as the
@@ -108,57 +105,55 @@ where
if leb128_bits >= 64 || (shorthand as u64) < (1 << leb128_bits) {
cache(encoder).insert(*value, shorthand);
}
Ok(())
}
impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for Ty<'tcx> {
fn encode(&self, e: &mut E) -> Result<(), E::Error> {
encode_with_shorthand(e, self, TyEncoder::type_shorthands)
fn encode(&self, e: &mut E) {
encode_with_shorthand(e, self, TyEncoder::type_shorthands);
}
}
impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E>
for ty::Binder<'tcx, ty::PredicateKind<'tcx>>
{
fn encode(&self, e: &mut E) -> Result<(), E::Error> {
self.bound_vars().encode(e)?;
encode_with_shorthand(e, &self.skip_binder(), TyEncoder::predicate_shorthands)
fn encode(&self, e: &mut E) {
self.bound_vars().encode(e);
encode_with_shorthand(e, &self.skip_binder(), TyEncoder::predicate_shorthands);
}
}
impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Predicate<'tcx> {
fn encode(&self, e: &mut E) -> Result<(), E::Error> {
self.kind().encode(e)
fn encode(&self, e: &mut E) {
self.kind().encode(e);
}
}
impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Region<'tcx> {
fn encode(&self, e: &mut E) -> Result<(), E::Error> {
self.kind().encode(e)
fn encode(&self, e: &mut E) {
self.kind().encode(e);
}
}
impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Const<'tcx> {
fn encode(&self, e: &mut E) -> Result<(), E::Error> {
self.0.0.encode(e)
fn encode(&self, e: &mut E) {
self.0.0.encode(e);
}
}
impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ConstAllocation<'tcx> {
fn encode(&self, e: &mut E) -> Result<(), E::Error> {
fn encode(&self, e: &mut E) {
self.inner().encode(e)
}
}
impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for AdtDef<'tcx> {
fn encode(&self, e: &mut E) -> Result<(), E::Error> {
fn encode(&self, e: &mut E) {
self.0.0.encode(e)
}
}
impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for AllocId {
fn encode(&self, e: &mut E) -> Result<(), E::Error> {
fn encode(&self, e: &mut E) {
e.encode_alloc_id(self)
}
}
@@ -508,9 +503,9 @@ macro_rules! impl_binder_encode_decode {
($($t:ty),+ $(,)?) => {
$(
impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Binder<'tcx, $t> {
fn encode(&self, e: &mut E) -> Result<(), E::Error> {
self.bound_vars().encode(e)?;
self.as_ref().skip_binder().encode(e)
fn encode(&self, e: &mut E) {
self.bound_vars().encode(e);
self.as_ref().skip_binder().encode(e);
}
}
impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Binder<'tcx, $t> {

6
compiler/rustc_middle/src/ty/consts/int.rs
View File

@@ -140,9 +140,9 @@ impl<CTX> crate::ty::HashStable<CTX> for ScalarInt {
}
impl<S: Encoder> Encodable<S> for ScalarInt {
fn encode(&self, s: &mut S) -> Result<(), S::Error> {
s.emit_u128(self.data)?;
s.emit_u8(self.size)
fn encode(&self, s: &mut S) {
s.emit_u128(self.data);
s.emit_u8(self.size);
}
}

6
compiler/rustc_middle/src/ty/context.rs
View File

@@ -87,7 +87,7 @@ pub trait OnDiskCache<'tcx>: rustc_data_structures::sync::Sync {
fn drop_serialized_data(&self, tcx: TyCtxt<'tcx>);
fn serialize(&self, tcx: TyCtxt<'tcx>, encoder: &mut FileEncoder) -> FileEncodeResult;
fn serialize(&self, tcx: TyCtxt<'tcx>, encoder: FileEncoder) -> FileEncodeResult;
}
#[allow(rustc::usage_of_ty_tykind)]
@@ -1466,8 +1466,8 @@ impl<'tcx> TyCtxt<'tcx> {
)
}
pub fn serialize_query_result_cache(self, encoder: &mut FileEncoder) -> FileEncodeResult {
self.on_disk_cache.as_ref().map_or(Ok(()), |c| c.serialize(self, encoder))
pub fn serialize_query_result_cache(self, encoder: FileEncoder) -> FileEncodeResult {
self.on_disk_cache.as_ref().map_or(Ok(0), |c| c.serialize(self, encoder))
}
/// If `true`, we should use lazy normalization for constants, otherwise

4
compiler/rustc_middle/src/ty/list.rs
View File

@@ -117,8 +117,8 @@ impl<T: fmt::Debug> fmt::Debug for List<T> {
impl<S: Encoder, T: Encodable<S>> Encodable<S> for List<T> {
#[inline]
fn encode(&self, s: &mut S) -> Result<(), S::Error> {
(**self).encode(s)
fn encode(&self, s: &mut S) {
(**self).encode(s);
}
}

2
compiler/rustc_middle/src/ty/subst.rs
View File

@@ -217,7 +217,7 @@ impl<'tcx> TypeFoldable<'tcx> for GenericArg<'tcx> {
}
impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for GenericArg<'tcx> {
fn encode(&self, e: &mut E) -> Result<(), E::Error> {
fn encode(&self, e: &mut E) {
self.unpack().encode(e)
}
}