Introduce `tcx.get_diagnostic_name`
Introduces a "reverse lookup" for diagnostic items. This is mainly intended for `@rust-lang/clippy` which often does a long series of `is_diagnostic_item` calls for the same `DefId`.
r? `@oli-obk`
Array `.len()` MIR optimization pass
This pass kind-of works back the `[T; N].len()` call that at the moment is first coerced as `&[T; N]` -> `&[T]` and then uses `&[T].len()`. Depends on #86383
Add two inline annotations for hot functions
These two functions are essentially no-ops (and compile to just a load and
return), but show up in process_obligations profiles with a high call count --
so worthwhile to try and inline them. This is not normally possible as they're
non-generic, so they don't get offered for inlining by our current algorithm.
perf: only check for `rustc_trivial_field_reads` attribute on traits, not items, impls, etc.
The checks that are removed in this PR (originally added in #85200) caused a small perf regression: https://github.com/rust-lang/rust/pull/88824#issuecomment-932664761
Since the attribute is currently only applied to traits, I don't think it's worth keeping the additional checks for now.
If/when we decide to apply the attribute somewhere else, we can (partially) revert this and reevaluate the perf impact.
r? `@nikomatsakis` cc `@FabianWolff`
Rollup of 12 pull requests
Successful merges:
- #87601 (Add functions to add unsigned and signed integers)
- #88523 (Expand documentation for `FpCategory`.)
- #89050 (refactor: VecDeques Drain fields to private)
- #89245 (refactor: make VecDeque's IterMut fields module-private, not just crate-private)
- #89324 (Rename `std:🧵:available_conccurrency` to `std:🧵:available_parallelism`)
- #89329 (print-type-sizes: skip field printing for primitives)
- #89501 (Note specific regions involved in 'borrowed data escapes' error)
- #89506 (librustdoc: Use correct heading levels.)
- #89528 (Fix suggestion to borrow when casting from pointer to reference)
- #89531 (library std, libc dependency update)
- #89588 (Add a test for generic_const_exprs)
- #89591 (fix: alloc-optimisation is only for rust llvm)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
fix: alloc-optimisation is only for rust llvm
As discussed at the bottom of #83485.
On a separate note I'll take this chance ask, is it worth pulling in that patch (to recognise `__rust_dealloc`) into Debian's system LLVM? The main factors for us to consider would be (1) is the optimisation significant and (2) is there not any significant negative impact to non-rust packages that use LLVM.
librustdoc: Use correct heading levels.
Closes#89309
This fixes the `<h#>` header tags throughout the docs to reflect a semantic hierarchy.
- I ran a script to manually check that we don't have any files with multiple `<h1>` tags.
- Also checked that we never incorrectly nest e.g. a `<h2>` under an `<h3>`.
- I also spot-checked a bunch of pages (`trait.Read`, `enum.Ordering`, `primitive.isize`, `trait.Iterator`).
Note specific regions involved in 'borrowed data escapes' error
Fixes#67007
Currently, a 'borrowed data escapes' error does not mention
the specific lifetime involved (except indirectly through a suggestion
about adding a lifetime bound). We now explain the specific lifetime
relationship that failed to hold, which improves otherwise vague
error messages.
Rename `std:🧵:available_conccurrency` to `std:🧵:available_parallelism`
_Tracking issue: https://github.com/rust-lang/rust/issues/74479_
This PR renames `std:🧵:available_conccurrency` to `std:🧵:available_parallelism`.
## Rationale
The API was initially named `std:🧵:hardware_concurrency`, mirroring the [C++ API of the same name](https://en.cppreference.com/w/cpp/thread/thread/hardware_concurrency). We eventually decided to omit any reference to the word "hardware" after [this comment](https://github.com/rust-lang/rust/pull/74480#issuecomment-662045841). And so we ended up with `available_concurrency` instead.
---
For a talk I was preparing this week I was reading through ["Understanding and expressing scalable concurrency" (A. Turon, 2013)](http://aturon.github.io/academic/turon-thesis.pdf), and the following passage stood out to me (emphasis mine):
> __Concurrency is a system-structuring mechanism.__ An interactive system that deals with disparate asynchronous events is naturally structured by division into concurrent threads with disparate responsibilities. Doing so creates a better fit between problem and solution, and can also decrease the average latency of the system by preventing long-running computations from obstructing quicker ones.
> __Parallelism is a resource.__ A given machine provides a certain capacity for parallelism, i.e., a bound on the number of computations it can perform simultaneously. The goal is to maximize throughput by intelligently using this resource. For interactive systems, parallelism can decrease latency as well.
_Chapter 2.1: Concurrency is not Parallelism. Page 30._
---
_"Concurrency is a system-structuring mechanism. Parallelism is a resource."_ — It feels like this accurately captures the way we should be thinking about these APIs. What this API returns is not "the amount of concurrency available to the program" which is a property of the program, and thus even with just a single thread is effectively unbounded. But instead it returns "the amount of _parallelism_ available to the program", which is a resource hard-constrained by the machine's capacity (and can be further restricted by e.g. operating systems).
That's why I'd like to propose we rename this API from `available_concurrency` to `available_parallelism`. This still meets the criteria we previously established of not attempting to define what exactly we mean by "hardware", "threads", and other such words. Instead we only talk about "concurrency" as an abstract resource available to our program.
r? `@joshtriplett`
refactor: make VecDeque's IterMut fields module-private, not just crate-private
Made the fields of VecDeque's IterMut private by creating a IterMut::new(...) function to create a new instance of IterMut and migrating usage to use IterMut::new(...).
refactor: VecDeques Drain fields to private
Made the fields of VecDeque's Drain private by creating a Drain::new(...) function to create a new instance of Drain and migrating usage to use Drain::new(...).
Expand documentation for `FpCategory`.
I intend these changes to be helpful to readers who are not yet familiar with the quirks of floating-point numbers. Additionally, I felt it was misleading to describe `Nan` as being the result of division by zero, since most divisions by zero (except for 0/0) produce `Infinite` floats, so I moved that remark to the `Infinite` variant with adjustment.
The first sentence of the `Nan` documentation is copied from `f32`; I followed the example of the `f64` documentation by referring to `f32` for general concepts, rather than duplicating the text.
----
I considered making similar changes to the documentation of the `is_*` methods of floats, but decided that that was a much larger and trickier problem; here, each of the variants' descriptions can be expected to be read in context of being mutually exclusive with the others.
Switch to our own mirror of libisl plus `ct-ng oldconfig` fixes
Switching to mirror the ISL libs (#89594) unearthed a (possibly long-standing?) issue with `ct-ng oldconfig`. It always overwrites the mirror config values. This PR adds the ISL mirror, gets rid of `ct-ng oldconfig` and adds crosstools-ng config files which can be used directly. (Edited)
Fixes#89593.
r? `@pietroalbini`
Consider unfulfilled obligations in binop errors
When encountering a binop where the types would have been accepted, if
all the predicates had been fulfilled, include information about the
predicates and suggest appropriate `#[derive]`s if possible.
Fix#84515.
When encountering a binop where the types would have been accepted, if
all the predicates had been fulfilled, include information about the
predicates and suggest appropriate `#[derive]`s if possible.
Point at trait(s) that needs to be `impl`emented.
Rollup of 10 pull requests
Successful merges:
- #88706 (Normalize associated type projections when checking return type of main)
- #88828 (Use `libc::sigaction()` instead of `sys::signal()` to prevent a deadlock)
- #88871 (Fix suggestion for nested struct patterns)
- #89317 (Move generic error message to separate branches)
- #89351 (for signed wrapping remainder, do not compare lhs with MIN)
- #89442 (Add check for duplicated doc aliases)
- #89502 (Fix Lower/UpperExp formatting for integers and precision zero)
- #89523 (Make `proc_macro_derive_resolution_fallback` a future-breakage lint)
- #89532 (Document behavior of `MaybeLiveLocals` regarding enums and field-senstivity)
- #89546 (Make an initial guess for metadata size to reduce buffer resizes)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Make an initial guess for metadata size to reduce buffer resizes
When reading metadata, the compiler starts with a `Vec::new()`, which will need to grow repeatedly as the metadata gets decompressed into it. Reduce the number of resizes by starting out at the size of the compressed data.
Document behavior of `MaybeLiveLocals` regarding enums and field-senstivity
This arose from a [discussion on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/189540-t-compiler.2Fwg-mir-opt/topic/MaybeLiveLocals.20and.20Discriminants) where a new contributor attempted to implement a dead-store elimination pass using this analysis. They ran into a nasty hack around `SetDiscriminant` the effect of which is to lets handle assignments of literals to enum-typed locals (e.g. `x = Some(4)`) correctly. This took me a while to figure out.
Document this oddity, so the next person will have an easier time, and add a test to enshrine the current behavior.
r? ``@tmiasko``
