specialize some collection and iterator operations to run in-place
This is a rebase and update of #66383 which was closed due inactivity.
Recent rustc changes made the compile time regressions disappear, at least for webrender-wrench. Running a stage2 compile and the rustc-perf suite takes hours on the hardware I have at the moment, so I can't do much more than that.
In the best case of the `vec::bench_in_place_recycle` synthetic microbenchmark these optimizations can provide a 15x speedup over the regular implementation which allocates a new vec for every benchmark iteration. [Benchmark results](https://gist.github.com/the8472/6d999b2d08a2bedf3b93f12112f96e2f). In real code the speedups are tiny, but it also depends on the allocator used, a system allocator that uses a process-wide mutex will benefit more than one with thread-local pools.
## What was changed
* `SpecExtend` which covered `from_iter` and `extend` specializations was split into separate traits
* `extend` and `from_iter` now reuse the `append_elements` if passed iterators are from slices.
* A preexisting `vec.into_iter().collect::<Vec<_>>()` optimization that passed through the original vec has been generalized further to also cover cases where the original has been partially drained.
* A chain of *Vec<T> / BinaryHeap<T> / Box<[T]>* `IntoIter`s through various iterator adapters collected into *Vec<U>* and *BinaryHeap<U>* will be performed in place as long as `T` and `U` have the same alignment and size and aren't ZSTs.
* To enable above specialization the unsafe, unstable `SourceIter` and `InPlaceIterable` traits have been added. The first allows reaching through the iterator pipeline to grab a pointer to the source memory. The latter is a marker that promises that the read pointer will advance as fast or faster than the write pointer and thus in-place operation is possible in the first place.
* `vec::IntoIter` implements `TrustedRandomAccess` for `T: Copy` to allow in-place collection when there is a `Zip` adapter in the iterator. TRA had to be made an unstable public trait to support this.
## In-place collectible adapters
* `Map`
* `MapWhile`
* `Filter`
* `FilterMap`
* `Fuse`
* `Skip`
* `SkipWhile`
* `Take`
* `TakeWhile`
* `Enumerate`
* `Zip` (left hand side only, `Copy` types only)
* `Peek`
* `Scan`
* `Inspect`
## Concerns
`vec.into_iter().filter(|_| false).collect()` will no longer return a vec with 0 capacity, instead it will return its original allocation. This avoids the cost of doing any allocation or deallocation but could lead to large allocations living longer than expected.
If that's not acceptable some resizing policy at the end of the attempted in-place collect would be necessary, which in the worst case could result in one more memcopy than the non-specialized case.
## Possible followup work
* split liballoc/vec.rs to remove `ignore-tidy-filelength`
* try to get trivial chains such as `vec.into_iter().skip(1).collect::<Vec<)>>()` to compile to a `memmove` (currently compiles to a pile of SIMD, see #69187 )
* improve up the traits so they can be reused by other crates, e.g. itertools. I think currently they're only good enough for internal use
* allow iterators sourced from a `HashSet` to be in-place collected into a `Vec`
rustdoc: do not use plain summary for trait impls
Fixes#38386.
Fixes#48332.
Fixes#49430.
Fixes#62741.
Fixes#73474.
Unfortunately this is not quite ready to go because the newly-working links trigger a bunch of linkcheck failures. The failures are tough to fix because the links are resolved relative to the implementor, which could be anywhere in the module hierarchy.
(In the current docs, these links end up rendering as uninterpreted markdown syntax, so I don't think these failures are any worse than the status quo. It might be acceptable to just add them to the linkchecker whitelist.)
Ideally this could be fixed with intra-doc links ~~but it isn't working for me: I am currently investigating if it's possible to solve it this way.~~ Opened #73829.
EDIT: This is now ready!
the test was sized to match external iteration only, since
vec's in-place collect now uses internal iteration we collect into
a different type now.
Note that any other try-fold based operation such as count() would also
have exceeded the type length limit for that iterator.
Update books
## reference
4 commits in 1b6c4b0afab97c0230433466c97167bbbe8445f6..25391dba46262f882fa846beefaff54a966a8fa5
2020-08-18 17:04:28 -0700 to 2020-09-02 07:22:55 -0700
- clarify when reading uninititalized memory is allowed (rust-lang-nursery/reference#852)
- Update patterns chapter, add rest patterns. (rust-lang-nursery/reference#876)
- Improve Type-Coersion Documentation (rust-lang-nursery/reference#843)
- Added variable back into example. (rust-lang-nursery/reference#880)
## book
3 commits in c0a6a61b8205da14ac955425f74258ffd8ee065d..e5ed97128302d5fa45dbac0e64426bc7649a558c
2020-08-14 14:21:49 -0500 to 2020-08-31 12:53:40 -0500
- Fix type mismatch in listing 10-5 (rust-lang/book#2441)
- Update ppendix-06-translation.md (rust-lang/book#2437)
- Correct no-listing-10-result-in-tests: Take tests module out of the main function (rust-lang/book#2430)
## rust-by-example
3 commits in 80a10e22140e28392b99d24ed02f4c6d8cb770a0..19f0a0372af497b34369cf182d9d16156cab2969
2020-08-08 09:56:46 -0300 to 2020-08-26 09:38:48 -0300
- prefer `length` over `size` when talking about number of elements vs. bytesize (rust-lang/rust-by-example#1372)
- Split out variable shadowing into a separate example (rust-lang/rust-by-example#1370)
- Update extern crate related sections (rust-lang/rust-by-example#1369)
## edition-guide
1 commits in bd6e4a9f59c5c1545f572266af77f5c7a5bad6d1..81f16863014de60b53de401d71ff904d163ee030
2020-07-12 17:37:08 -0500 to 2020-08-27 13:56:31 -0700
- Fix a small typo. (rust-lang/edition-guide#218)
inliner: Avoid query cycles when optimizing generators
The HIR Id trick is insufficient to prevent query cycles when optimizing
generators, since merely requesting a layout of a generator also
computes its `optimized_mir`.
Make no attempts to inline functions into generators within the same
crate to avoid query cycles.
Fixes#76181.
Make all methods of `std::net::Ipv4Addr` const
Make the following methods of `std::net::Ipv4Addr` unstable const under the `const_ipv4` feature:
- `octets`
- `is_loopback`
- `is_private`
- `is_link_local`
- `is_global` (unstable)
- `is_shared` (unstable)
- `is_ietf_protocol_assignment` (unstable)
- `is_benchmarking` (unstable)
- `is_reserved` (unstable)
- `is_multicast`
- `is_broadcast`
- `is_documentation`
- `to_ipv6_compatible`
- `to_ipv6_mapped`
This would make all methods of `Ipv6Addr` const.
Of these methods, `is_global`, `is_broadcast`, `to_ipv6_compatible`, and `to_ipv6_mapped` require a change in implementation.
Part of #76205
Improve recovery on malformed format call
The token following a format expression should be a comma. However, when it is replaced with a similar token (such as a dot), then the corresponding error is emitted, but the token is treated as a comma, and the parsing step continues.
r? @petrochenkov
lexer: Tiny improvement to shebang detection
Lexer now discerns between regular comments and doc comments, so use that.
The change only affects the choice of reported errors.
Make all methods of `std::net::Ipv6Addr` const
Make the following methods of `std::net::Ipv6Addr` unstable const under the `const_ipv6` feature:
- `segments`
- `is_unspecified`
- `is_loopback`
- `is_global` (unstable)
- `is_unique_local`
- `is_unicast_link_local_strict`
- `is_documentation`
- `multicast_scope`
- `is_multicast`
- `to_ipv4_mapped`
- `to_ipv4`
This would make all methods of `Ipv6Addr` const.
Changed the implementation of `is_unspecified` and `is_loopback` to use a `match` instead of `==`, all other methods did not require a change.
All these methods are dependent on `segments`, the current implementation of which requires unstable `const_fn_transmute` ([PR#75085](https://github.com/rust-lang/rust/pull/75085)).
Part of #76205
Give a better error message for duplicate built-in macros
Minor follow-up to https://github.com/rust-lang/rust/pull/75176 giving a better error message for duplicate builtin macros. This would have made it a little easier to debug.
r? @petrochenkov
Use "Fira Sans" for crate list font
Fira Sans is what's used for module lists and other item lists.
Previously, the default body font, "Source Serif Pro", was used for
crate lists, which didn't visually match other item lists.
@rustbot modify labels: T-rustdoc
Add new `-Z dump-mir-spanview` option
Similar to `-Z dump-mir-graphviz`, this adds the option to write
HTML+CSS files that allow users to analyze the spans associated with MIR
elements (by individual statement, just terminator, or overall basic
block).
This PR was split out from PR #76004, and exposes an API for spanview
HTML+CSS files that is also used to analyze code regions chosen for
coverage instrumentation (in a follow-on PR).
Rust compiler MCP rust-lang/compiler-team#278
Relevant issue: #34701 - Implement support for LLVMs code coverage
instrumentation
r? @tmandry
FYI @wesleywiser
The HIR Id trick is insufficient to prevent query cycles when optimizing
generators, since merely requesting a layout of a generator also
computes its `optimized_mir`.
Make no attempts to inline functions into generators within the same
crate to avoid query cycles.
Makes the following methods of `std::net::Ipv4Addr` unstable const under the `const_ipv4` feature:
- `is_global`
- `is_reserved`
- `is_broadcast`
- `to_ipv6_compatible`
- `to_ipv6_mapped`
This results in all methods of `Ipv4Addr` being const.
Also adds tests for these methods in a const context.
Fira Sans is what's used for module lists and other item lists.
Previously, the default body font, "Source Serif Pro", was used for
crate lists, which didn't visually match other item lists.
Run cfg-stripping on generic parameters before invoking derive macros
Fixes#75930
This changes the tokens seen by a proc-macro. However, ising a `#[cfg]` attribute
on a generic paramter is unusual, and combining it with a proc-macro
derive is probably even more unusual. I don't expect this to cause any
breakage.
Move ninja requirements to a dynamic check, when actually building
It isn't practical to determine whether we'll build LLVM very early in the
pipeline, so move the ninja checking to a dynamic check.
r? @pietroalbini -- this should fix nightlies
Eliminate some other bound checks when index comes from an enum
#36962 introduced an assumption for the upper limit of the enum's value. This PR adds an assumption to the lower value as well.
I've modified the original codegen test to show that derived (in that case, adding 1) values also don't generate bounds checks.
However, this test is actually carefully crafted to not hit a bug: if the enum's variants are modified to 1 and 2 instead of 2 and 3, the test fails by adding a bounds check. I suppose this is an LLVM issue and #75525, while not exactly in this context should be tracking it.
I'm not at all confident if this patch can be accepted, or even if it _should_ be accepted in this state. But I'm curious about what others think :)
~Improves~ Should improve #13926 but does not close it because it's not exactly predictable, where bounds checks may pop up against the assumptions.
Previously, this would say no such macro existed, but this was
misleading, since the macro _did_ exist, it was just already seen.
- Say where the macro was previously defined
- Add long-form error message
Similar to `-Z dump-mir-graphviz`, this adds the option to write
HTML+CSS files that allow users to analyze the spans associated with MIR
elements (by individual statement, just terminator, or overall basic
block).
This PR was split out from PR #76004, and exposes an API for spanview
HTML+CSS files that is also used to analyze code regions chosen for
coverage instrumentation (in a follow-on PR).
Rust compiler MCP rust-lang/compiler-team#278
Relevant issue: #34701 - Implement support for LLVMs code coverage
instrumentation
Update expect-test to 1.0
The only change is that `expect_file` now uses path relative to the
current file (same as `include!`). Before, it used paths relative to
the workspace root, which makes no sense.
Make `cow_is_borrowed` methods const
Constify the following methods of `alloc::borrow::Cow`:
- `is_borrowed`
- `is_owned`
Analogous to the const methods `is_some` and `is_none` for Option, and `is_ok` and `is_err` for Result.
These methods are still unstable under `cow_is_borrowed`.
Possible because of #49146 (Allow if and match in constants).
Tracking issue: #65143
Update cargo
8 commits in 51b66125ba97d2906f461b3f4e0408f206299bb6..126907a7cfccbe93778530e6a6bbaa3adb6c515c
2020-08-19 20:22:52 +0000 to 2020-08-31 20:42:11 +0000
- Fix flakiness in close_output test (rust-lang/cargo#8668)
- Reload unstable table from config file in `reload_rooted_at` (rust-lang/cargo#8656)
- Bump to 0.49.0, update changelog (rust-lang/cargo#8659)
- Fix LTO with doctests. (rust-lang/cargo#8657)
- Add spaces after -C and -Z flags for consistency (rust-lang/cargo#8648)
- Fix cache_messages::rustdoc test broken on beta. (rust-lang/cargo#8653)
- fix: remove unnecessary allocations (rust-lang/cargo#8641)
- Fixed a spelling and some clippy warnings (rust-lang/cargo#8637)
Move `#[cfg(test)]` modules into separate files to save recompiling the `std` crate
Implements an accepted proposal: https://github.com/rust-lang/compiler-team/issues/344
Some notes for reviewers:
* `mod tests` nested in `mod foo` in `mod bar`, I move `foo` to a new file, `tests` is a new file in foo: For example library/std/src/sys/sgx/abi/tls.rs
* `mod test` (not `mod tests`) also is moved.
* `mod benches` are moved.
* `mod tests` is placed before any `use` statements: The topic is discussed in https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Code.20Style.20process
* Some files in cloudabi was changed too. But I notice copyright banners in those files, should we ping cloudabi people?
* I formatted files after moving tests around. I think that may make it easier to review :p .
* Some files don't need `ignore-tidy-filelength` anymore.
The only change is that `expect_file` now uses path relative to the
current file (same as `include!`). Before, it used paths relative to
the workspace root, which makes no sense.
`parse_stream_from_source_str` is a more stable API to convert a
string into a bunch of tokens, and it also catches errors about
mismatched parenthesis.
bors
