static libraries with ar_archive_writer

Fixes rust-lang#107495

SeqCst is unnecessary here.

SeqCst is unnecessary here.

Relaxed is enough here.

SeqCst is unnecessary.

Relaxed is enough to make sure this `swap` results in `true` only once.

No need for SeqCst. Release+Acquire is the right memory ordering for a
mutex.

SeqCst is unnecessary here.

SeqCst is unnecessary here.

SeqCst is unnecessary. Release+Acquire is the right ordering for a
mutex.

Relaxed is enough to ensure fetch_add(1) returns each integer exactly
once.

SeqCst is unnecessary. Release+Acquire is the right ordering for a
mutex.

The SeqCst wasn't synchronizing with anything. Relaxed is enough.

rustc is just one tool/executable, even if at the center of the toolchain

These assertions detect situations where a BCB node would have both a physical
counter and one or more in-edge counters/expressions.

For most BCBs that situation would indicate an implementation bug. However,
it's perfectly fine in the case of a BCB having an edge that loops back to
itself.

Given the complexity and risk involved in fixing the assertions, and the fact
that nothing relies on them actually being true, this patch just removes them
instead.

SeqCst isn't necessary in any of these cases.

Relaxed is enough to have fetch_add(1) return each value only once
(until it wraps around).

Relaxed memory ordering is fine because spawn()/join() already provides
all the synchronization we need.

Relaxed is enough here. Synchronization is done by the mutex.

…iler-errors

pattern analysis: add a custom test harness

There are two features of the pattern analysis code that are hard to test: the newly-added pattern complexity limit, and the computation of arm intersections. This PR adds some crate-specific tests for that, including an unmaintainable but pretty macro to help construct patterns.

r? ```@compiler-errors```

Add bare metal riscv32 target.

I asked in the embedded Rust matrix if it would be OK to clone a PR to add another riscv32 configuration. The riscv32ima in this case. `@MabezDev` was open to this suggestion as a maintainer for the Riscv targets.

I now took rust-lang#117958 for inspiration and added/edited the appropriate files.

# [Tier 3 target policy](https://doc.rust-lang.org/nightly/rustc/target-tier-policy.html#tier-3-target-policy)

> At this tier, the Rust project provides no official support for a target, so we place minimal requirements on the introduction of targets.
>
> A proposed new tier 3 target must be reviewed and approved by a member of the compiler team based on these requirements. The reviewer may choose to gauge broader compiler team consensus via a [Major Change Proposal (MCP)](https://forge.rust-lang.org/compiler/mcp.html).
>
> A proposed target or target-specific patch that substantially changes code shared with other targets (not just target-specific code) must be reviewed and approved by the appropriate team for that shared code before acceptance.

> * A tier 3 target must have a designated developer or developers (the "target maintainers") on record to be CCed when issues arise regarding the target. (The mechanism to track and CC such developers may evolve over time.)

The target being added is using riscv32 as a basis, with added extensions. The riscv32 targets already have a maintainer and are named in the description file.

> * Targets must use naming consistent with any existing targets; for instance, a target for the same CPU or OS as an existing Rust target should use the same name for that CPU or OS. Targets should normally use the same names and naming conventions as used elsewhere in the broader ecosystem beyond Rust (such as in other toolchains), unless they have a very good reason to diverge. Changing the name of a target can be highly disruptive, especially once the target reaches a higher tier, so getting the name right is important even for a tier 3 target.
>   * Target names should not introduce undue confusion or ambiguity unless absolutely necessary to maintain ecosystem compatibility. For example, if the name of the target makes people extremely likely to form incorrect beliefs about what it targets, the name should be changed or augmented to disambiguate it.
>   * If possible, use only letters, numbers, dashes and underscores for the name. Periods (.) are known to cause issues in Cargo.

Name is derived from the extensions used in the target.
> * Tier 3 targets may have unusual requirements to build or use, but must not create legal issues or impose onerous legal terms for the Rust project or for Rust developers or users.
>   * The target must not introduce license incompatibilities.

Same conditions apply compared to other riscv32 targets.
>   * Anything added to the Rust repository must be under the standard Rust license (MIT OR Apache-2.0).

Same conditions apply compared to other riscv32 targets.
>   * The target must not cause the Rust tools or libraries built for any other host (even when supporting cross-compilation to the target) to depend on any new dependency less permissive than the Rust licensing policy. This applies whether the dependency is a Rust crate that would require adding new license exceptions (as specified by the tidy tool in the rust-lang/rust repository), or whether the dependency is a native library or binary. In other words, the introduction of the target must not cause a user installing or running a version of Rust or the Rust tools to be subject to any new license requirements.

Same conditions apply compared to other riscv32 targets.
>   * Compiling, linking, and emitting functional binaries, libraries, or other code for the target (whether hosted on the target itself or cross-compiling from another target) must not depend on proprietary (non-FOSS) libraries. Host tools built for the target itself may depend on the ordinary runtime libraries supplied by the platform and commonly used by other applications built for the target, but those libraries must not be required for code generation for the target; cross-compilation to the target must not require such libraries at all. For instance, rustc built for the target may depend on a common proprietary C runtime library or console output library, but must not depend on a proprietary code generation library or code optimization library. Rust's license permits such combinations, but the Rust project has no interest in maintaining such combinations within the scope of Rust itself, even at tier 3.

Same conditions apply compared to other riscv32 targets.
>   * "onerous" here is an intentionally subjective term. At a minimum, "onerous" legal/licensing terms include but are not limited to: non-disclosure requirements, non-compete requirements, contributor license agreements (CLAs) or equivalent, "non-commercial"/"research-only"/etc terms, requirements conditional on the employer or employment of any particular Rust developers, revocable terms, any requirements that create liability for the Rust project or its developers or users, or any requirements that adversely affect the livelihood or prospects of the Rust project or its developers or users.

Same conditions apply compared to other riscv32 targets.
> * Neither this policy nor any decisions made regarding targets shall create any binding agreement or estoppel by any party. If any member of an approving Rust team serves as one of the maintainers of a target, or has any legal or employment requirement (explicit or implicit) that might affect their decisions regarding a target, they must recuse themselves from any approval decisions regarding the target's tier status, though they may otherwise participate in discussions.
>   * This requirement does not prevent part or all of this policy from being cited in an explicit contract or work agreement (e.g. to implement or maintain support for a target). This requirement exists to ensure that a developer or team responsible for reviewing and approving a target does not face any legal threats or obligations that would prevent them from freely exercising their judgment in such approval, even if such judgment involves subjective matters or goes beyond the letter of these requirements.

Same conditions apply compared to other riscv32 targets.
> * Tier 3 targets should attempt to implement as much of the standard libraries as possible and appropriate (core for most targets, alloc for targets that can support dynamic memory allocation, std for targets with an operating system or equivalent layer of system-provided functionality), but may leave some code unimplemented (either unavailable or stubbed out as appropriate), whether because the target makes it impossible to implement or challenging to implement. The authors of pull requests are not obligated to avoid calling any portions of the standard library on the basis of a tier 3 target not implementing those portions.

This target is build on top of existing riscv32 targets and inherits these implementations.
> * The target must provide documentation for the Rust community explaining how to build for the target, using cross-compilation if possible. If the target supports running binaries, or running tests (even if they do not pass), the documentation must explain how to run such binaries or tests for the target, using emulation if possible or dedicated hardware if necessary.

The documentation of this target is shared along with targets that target riscv32 with a different configuration of extensions.
> * Tier 3 targets must not impose burden on the authors of pull requests, or other developers in the community, to maintain the target. In particular, do not post comments (automated or manual) on a PR that derail or suggest a block on the PR based on a tier 3 target. Do not send automated messages or notifications (via any medium, including via `@)` to a PR author or others involved with a PR regarding a tier 3 target, unless they have opted into such messages.

I now understand, apologies for the mention before.
>   * Backlinks such as those generated by the issue/PR tracker when linking to an issue or PR are not considered a violation of this policy, within reason. However, such messages (even on a separate repository) must not generate notifications to anyone involved with a PR who has not requested such notifications.

I now understand, apologies for the link to a similar PR before.
> * Patches adding or updating tier 3 targets must not break any existing tier 2 or tier 1 target, and must not knowingly break another tier 3 target without approval of either the compiler team or the maintainers of the other tier 3 target.
>   * In particular, this may come up when working on closely related targets, such as variations of the same architecture with different features. Avoid introducing unconditional uses of features that another variation of the target may not have; use conditional compilation or runtime detection, as appropriate, to let each target run code supported by that target.

This should not cause issues, as the target has similarities to other configurations of the riscv32 targets.
> * Tier 3 targets must be able to produce assembly using at least one of rustc's supported backends from any host target.

This should not cause issues, as the target has similarities to other configurations of the riscv32 targets.

…thercote

Use same file permissions for ar_archive_writer as the LLVM archive writer

This is required to switch to ar_archive_writer in the future without regressions. In addition to this PR support for reading thin archives needs to be added (rust-lang#107407) to fix all known regressions.

Fixes rust-lang#107495

Relax SeqCst ordering in standard library.

Every single SeqCst in the standard library is unnecessary. In all cases, Relaxed or Release+Acquire was sufficient.

As I [wrote](https://marabos.nl/atomics/memory-ordering.html#common-misconceptions) in my book on atomics:

> [..] when reading code, SeqCst basically tells the reader: "this operation depends on the total order of every single SeqCst operation in the program," which is an incredibly far-reaching claim. The same code would likely be easier to review and verify if it used weaker memory ordering instead, if possible. For example, Release effectively tells the reader: "this relates to an acquire operation on the same variable," which involves far fewer considerations when forming an understanding of the code.
>
> It is advisable to see SeqCst as a warning sign. Seeing it in the wild often means that either something complicated is going on, or simply that the author did not take the time to analyze their memory ordering related assumptions, both of which are reasons for extra scrutiny.

r? ``@Amanieu`` ``@joboet``

use more accurate terminology

rustc is just one tool/executable, even if at the center of the toolchain

coverage: Remove incorrect assertions from counter allocation

These assertions detect situations where a BCB node (in the coverage graph) would have both a physical counter and one or more in-edge counters/expressions.

For most BCBs that situation would indicate an implementation bug. However, it's perfectly fine in the case of a BCB having an edge that loops back to itself.

Given the complexity and risk involved in fixing the assertions, and the fact that nothing relies on them actually being true, this patch just removes them instead.

Fixes rust-lang#122738.

```@rustbot``` label +A-code-coverage

…ng-usize-max, r=Nilstrieb

Add `usize::MAX` arg tests for Vec

Tests to prevent recurrence of the UB from the rust-lang#122760 issue.

I skipped the `with_capacity`, `drain`, `reserve`, etc. APIs because they actually had a good assortment of tests earlier in the same file.

r? Nilstrieb

…li-obk

Rename `hir::Let` into `hir::LetExpr`

As discussed on [zulip](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Improve.20naming.20of.20.60ExprKind.3A.3ALet.60.3F).

r? ```@Zalathar```