Introduce `DynSend` and `DynSync` auto trait for parallel compiler
part of parallel-rustc #101566
This PR introduces `DynSend / DynSync` trait and `FromDyn / IntoDyn` structure in rustc_data_structure::marker. `FromDyn` can dynamically check data structures for thread safety when switching to parallel environments (such as calling `par_for_each_in`). This happens only when `-Z threads > 1` so it doesn't affect single-threaded mode's compile efficiency.
r? `@cjgillot`
- only borrow the refcell once per loop
- avoid complex matches to reduce branch paths in the hot loop
- use a by-ref fast path that avoids mutations at the expense of having false negatives
Use a lock-free datastructure for source_span
follow up to the perf regression in https://github.com/rust-lang/rust/pull/105462
The main regression is likely the CStore, but let's evaluate the perf impact of this on its own
`rustc_data_structures::thin_vec::ThinVec` looks like this:
```
pub struct ThinVec<T>(Option<Box<Vec<T>>>);
```
It's just a zero word if the vector is empty, but requires two
allocations if it is non-empty. So it's only usable in cases where the
vector is empty most of the time.
This commit removes it in favour of `thin_vec::ThinVec`, which is also
word-sized, but stores the length and capacity in the same allocation as
the elements. It's good in a wider variety of situation, e.g. in enum
variants where the vector is usually/always non-empty.
The commit also:
- Sorts some `Cargo.toml` dependency lists, to make additions easier.
- Sorts some `use` item lists, to make additions easier.
- Changes `clean_trait_ref_with_bindings` to take a
`ThinVec<TypeBinding>` rather than a `&[TypeBinding]`, because this
avoid some unnecessary allocations.
Since RFC 3052 soft deprecated the authors field anyway, hiding it from
crates.io, docs.rs, and making Cargo not add it by default, and it is
not generally up to date/useful information, we should remove it from
crates in this repo.
rustc_data_structures has a dependency on crossbeam-utils but never uses
it. It appears to have originally had this dependency in order to set
the "nightly" feature; however, its other dependencies use a different
version of crossbeam-utils, so this doesn't actually affect anything.
Furthermore, in current crossbeam-utils, the "nightly" feature has
become a no-op.
don't enable parking_lot nightly features
Having the compiler itself depend on external libraries that use nightly features can lead to "fun" bootstrap situations. Within the rustc repo we use `cfg(bootstrap)` to resolve those, but that is not a reasonable option for external dependencies.
So I propose we stop enabling the "nightly" feature of `parking_lot` here. In my experiments, this then indeed leads to the feature not being enabled (i.e., nothing else enables it), and everything still builds. However, this means parking_lot's `RwLock` will no longer have hardware lock elision for readers -- I hope that is okay to lose in exchange for less bootstrap brain twisting. ;)
Cc `@Amanieu`
With the arrival of min const generics, many alt-vec libraries have
updated to use it in some way and arrayvec is no exception. Use the
latest with minor refactoring.
Also, rustc_workspace_hack is the only user of smallvec 0.6 in the
entire tree, so drop it.
This pulls in rust-lang/rustc-rayon#8 to fix#81425. (h/t @ammaraskar)
That revealed weak constraints on `rustc_arena::DropArena`, because its
`DropType` was holding type-erased raw pointers to generic `T`. We can
implement `Send` for `DropType` (under `cfg(parallel_compiler)`) by
requiring all `T: Send` before they're type-erased.
This version adds the ability to use `rdpmc` hardware-based performance
counters instead of wall-clock time for measuring duration. This also
introduces a dependency on the `perf-event-open-sys` crate on Linux
which is used when using hardware counters.
