style-guide: Some cleanups from the fmt-rfcs repo history
There were a few commits that seem to have gone missing between the fmt-rfcs repo and the style guide. Re-apply those commits to the version of the style-guide in `rust-lang/rust`.
All of these are cleanups that don't change meaning.
avoid clone path prefix when lowering to hir
Found this while trying to parallelize `lower_to_hir`.
When lowering to hir, `Nested` paths in `ast` will be split and the prefix segments will be cloned. This could be omited, since the only consequence is that the prefix segments in `Path`s in hir will have the same `HirId`s, and it seems harmless.
This simplifies the process of lowering to hir and avoids re-modification of `ResolverAstLowering`.
r? `@Aaron1011`
cc #99292
Substitute types before checking inlining compatibility.
Addresses https://github.com/rust-lang/rust/issues/112332 and https://github.com/rust-lang/rust/issues/113781
I don't have a minimal test, but I this seems to remove the ICE locally.
This whole pre-inlining validation mirrors the "real" MIR validation pass to verify that inlined MIR will still pass validation.
The debuginfo loop is added because MIR validation check projections in debuginfo.
Likewise, MIR validation only checks `is_subtype`, so there is no reason for a stronger check.
The types were not being substituted in `check_equal`, so we were not bailing out of inlining if the substituted MIR callee body would not pass validation.
Use SHA256 source file checksums by default when targeting MSVC
Currently, when targeting Windows (more specifically, the MSVC toolchain), Rust will use SHA1 source file checksums by default. SHA1 has been superseded by SHA256, and Microsoft recommends migrating to SHA256.
As of Visual Studio 2022, MSVC defaults to SHA256. This change aligns Rust and MSVC.
LLVM can already use SHA256 checksums, so this does not require any change to LLVM.
MSVC docs on source file checksums: https://learn.microsoft.com/en-us/cpp/build/reference/zh?view=msvc-170
Minor improvements to Windows TLS dtors
This does a few things:
* Moves keyless dtors into the same module as the `on_tls_callback` function because of dylib mess. We keep the `inline(never)` hints as a precaution (see also the issue they link to).
* Introduces the `HAS_DTORS` atomic as an optimization hint. This allows removing (most) of the TLS dtor code if no dtors are ever run. Otherwise it's always included because of a `#[used]`.
* Only run either keyed dtors or keyless dtors but not both. They should be mutually exclusive as keyed dtors are a fallback. I've also added an `assert` to make sure this is true.
Support `--print KIND=PATH` command line syntax
As is already done for `--emit KIND=PATH` and `-L KIND=PATH`.
In the discussion of #110785, it was pointed out that `--print KIND=PATH` is nicer than trying to apply the single global `-o` path to `--print`'s output, because in general there can be multiple print requests within a single rustc invocation, and anyway `-o` would already be used for a different meaning in the case of `link-args` and `native-static-libs`.
I am interested in using `--print cfg=PATH` in Buck2. Currently Buck2 works around the lack of support for `--print KIND=PATH` by [indirecting through a Python wrapper script](d43cf3a51a/prelude/rust/tools/get_rustc_cfg.py) to redirect rustc's stdout into the location dictated by the build system.
From skimming Cargo's usages of `--print`, it definitely seems like it would benefit from `--print KIND=PATH` too. Currently it is working around the lack of this by inserting `--crate-name=___ --print=crate-name` so that it can look for a line containing `___` as a delimiter between the 2 other `--print` informations it actually cares about. This is commented as a "HACK" and "abuse". 31eda6f7c3/src/cargo/core/compiler/build_context/target_info.rs (L242) (FYI `@weihanglo` as you dealt with this recently in https://github.com/rust-lang/cargo/pull/11633.)
Mentioning reviewers active in #110785: `@fee1-dead` `@jyn514` `@bjorn3`
Resurrect: rustc_llvm: Add a -Z `print-codegen-stats` option to expose LLVM statistics.
This resurrects PR https://github.com/rust-lang/rust/pull/104000, which has sat idle for a while. And I want to see the effect of stack-move optimizations on LLVM (like https://reviews.llvm.org/D153453) :).
I have applied the changes requested by `@oli-obk` and `@nagisa` https://github.com/rust-lang/rust/pull/104000#discussion_r1014625377 and https://github.com/rust-lang/rust/pull/104000#discussion_r1014642482 in the latest commits.
r? `@oli-obk`
-----
LLVM has a neat [statistics](https://llvm.org/docs/ProgrammersManual.html#the-statistic-class-stats-option) feature that tracks how often optimizations kick in. It's very handy for optimization work. Since we expose the LLVM pass timings, I thought it made sense to expose the LLVM statistics too.
-----
(Edit: fix broken link
(Edit2: fix segmentation fault and use malloc
If `rustc` is built with
```toml
[llvm]
assertions = true
```
Then you can see like
```
rustc +stage1 -Z print-codegen-stats -C opt-level=3 tmp.rs
===-------------------------------------------------------------------------===
... Statistics Collected ...
===-------------------------------------------------------------------------===
3 aa - Number of MayAlias results
193 aa - Number of MustAlias results
531 aa - Number of NoAlias results
...
```
And the current default build emits only
```
$ rustc +stage1 -Z print-codegen-stats -C opt-level=3 tmp.rs
===-------------------------------------------------------------------------===
... Statistics Collected ...
===-------------------------------------------------------------------------===
$
```
This might be better to emit the message to tell assertion flag necessity, but now I can't find how to do that...
style-guide: clean up "must"/"should"/"may"
Avoid using "should" or "may" for required parts of the default style.
The style guide inconsistently used language like "there should be a space" or
"it should be on its own line", or "may be written on a single line", for
things that are required components of the default Rust style. "should" and
especially "may" come across as optional. While the style guide overall now has
a statement at the top that the default style itself is a *recommendation*, the
*definition* of the default style should not be ambiguous about what's part of
the default style.
Rewrite language in the style guide to only use "should" and "may" and similar
for truly optional components of the style (e.g. things a tool cannot or should
not enforce in its default configuration).
In their place, either use "must", or rewrite in imperative style ("put a
space", "start it on the same line"). The latter also substantially reduces the
use of passive voice.
Looking for "should"s also flagged some recommendations the style guide made
for configurability of tools (e.g. a tool "should" have a given configuration
option). I've removed those recommendations, per discussion with the style
team; it's not the domain of the style guide to make such recommendations, only
to define the default Rust style.
In the process of making this change, I also fixed a typo, fixed a text structure
issue, fixed an example that didn't match the Rust style (missing a trailing
comma), and added an additional example for clarity. (Those changes would have
conflicted with this one.) Those changes appear in separate commits.
These are all purely editorial changes, and do not affect the semantic
definition of the Rust style.
std: remove an allocation in `Path::with_extension`
`Path::with_extension` used to reallocate (and copy) paths twice per call, now it does it once, by checking the size of the previous and new extensions it's possible to call `PathBuf::with_capacity` and pass the exact capacity required.
This also reduces the memory consumption of the path returned from `Path::with_extension` by using exact capacity instead of using amortized exponential growth.
remove the unstable `core::sync::atomic::ATOMIC_*_INIT` constants
Tracking issue: #99069
It would be weird to ever stabilise these as they are already deprecated.
The style guide inconsistently used language like "there should be a
space" or "it should be on its own line", or "may be written on a single
line", for things that are required components of the default Rust
style. "should" and especially "may" come across as optional. While the
style guide overall now has a statement at the top that the default
style itself is a *recommendation*, the *definition* of the default
style should not be ambiguous about what's part of the default style.
Rewrite language in the style guide to only use "should" and "may" and
similar for truly optional components of the style (e.g. things a tool
cannot or should not enforce in its default configuration).
In their place, either use "must", or rewrite in imperative style ("put
a space", "start it on the same line"). The latter also substantially
reduces the use of passive voice.
This is a purely editorial change, and does not affect the semantic
definition of the Rust style.
The style guide requires a trailing comma on where clause components,
but then gives an example that doesn't include one. Add the missing
trailing comma.
Get `!nonnull` metadata on slice iterators, without `assume`s
This updates the non-ZST paths to read the end pointer through a pointer-to-`NonNull`, so that they all get `!nonnull` metadata.
That means that the last `assume(!ptr.is_null())` can be deleted, without impacting codegen -- the codegen tests confirm the LLVM-IR ends up exactly the same as before.
Always const-prop scalars and scalar pairs
This removes some complexity from the pass.
The limitation to propagate ScalarPairs only for tuple comes from https://github.com/rust-lang/rust/pull/67015, when ScalarPair constant were modeled using `Rvalue::Aggregate`. Nowadays, we use `ConstValue::ByRef`, which does not care about the underlying type.
The justification for not propagating in all cases was perf. This seems not to be a clear cut any more: https://github.com/rust-lang/rust/pull/113858#issuecomment-1642396746
Refactor vtable encoding and optimize it for the case of multiple marker traits
This PR does two things
- Refactor `prepare_vtable_segments` (this was motivated by the other change, `prepare_vtable_segments` was quite hard to understand and while trying to edit it I've refactored it)
- Mostly remove `loop`s labeled `break`s/`continue`s whenever there is a simpler solution
- Also use `?`
- Make vtable format a bit more efficient wrt to marker traits
- See the tests for an example
Fixes https://github.com/rust-lang/rust/issues/113840
cc `@crlf0710`
----
Review wise it's probably best to review each commit individually, as then it's more clear why the refactoring is correct.
I can split the last two commits (which change behavior) into a separate PR if it makes reviewing easier
Querify unused trait check.
This code transitively loads information for all bodies, and from resolutions. As it does not return a value, it should be beneficial to have it as a query.
