Document WebAssembly target feature expectations
This commit is a result of the discussion on #128475 and incorporates parts of #109807 as well. This is all done as a new page of documentation for the `wasm32-unknown-unknown` target which previously did not exist. This new page goes into details about the preexisting target and additionally documents the expectations for WebAssembly features and code generation.
The tl;dr is that LLVM will enable features over time after most engines have had support for awhile. Compiling without features requires `-Ctarget-cpu=mvp` to rustc plus `-Zbuild-std` to Cargo.
Closes#109807Closes#119811Closes#128475
Promote Mac Catalyst targets to Tier 2, and ship with rustup
Promote the Mac Catalyst targets `x86_64-apple-ios-macabi` and `aarch64-apple-ios-macabi` to Tier 2, as per [the MCP](https://github.com/rust-lang/compiler-team/issues/761) (see that for motivation and details).
These targets are now also distributed with rustup, although without the sanitizer runtime, as that currently has trouble building, see https://github.com/rust-lang/rust/issues/129069.
Unconditionally allow shadow call-stack sanitizer for AArch64
It is possible to do so whenever `-Z fixed-x18` is applied.
cc ``@Darksonn`` for context
The reasoning is that, as soon as reservation on `x18` is forced through the flag `fixed-x18`, on AArch64 the option to instrument with [Shadow Call Stack sanitizer](https://clang.llvm.org/docs/ShadowCallStack.html) is then applicable regardless of the target configuration.
At the every least, we would like to relax the restriction on specifically `aarch64-unknonw-none`. For this option, we can include a documentation change saying that users of compiled objects need to ensure that they are linked to runtime with Shadow Call Stack instrumentation support.
Related: #121972
Add powerpc-unknown-linux-muslspe compile target
This is almost identical to already existing targets:
- powerpc_unknown_linux_musl.rs
- powerpc_unknown_linux_gnuspe.rs
It has support for PowerPC SPE (muslspe), which
can be used with GCC version up to 8. It is useful for Freescale or IBM cores like e500.
This was verified to be working with OpenWrt build system for CZ.NIC's Turris 1.x routers, which are using Freescale P2020, e500v2, so add it as a Tier 3 target.
Follow-up of https://github.com/rust-lang/rust/pull/100860
Promote aarch64-apple-darwin to Tier 1
This promotes aarch64-apple-darwin to Tier 1 status as per rust-lang/rfcs#3671 and tracking issue #73908. Not sure what else is necessary for this to impement the aforementioned RFC, however I figured I'd try. I did read in previous issues and PRs that the necessary infrastructure was already in place for the aarch64-apple-darwin target, and the RFC mentions the same. So this should be all thats necessary in order for the target to be promoted.
This is a recreation of my previous PR because I accidentally did an incorrect git rebase which caused unnecessary changes to various commit SHAs. So this PR is a recreation of my previous PR without said stumble. My bad.
This commit is a result of the discussion on #128475 and incorporates
parts of #109807 as well. This is all done as a new page of
documentation for the `wasm32-unknown-unknown` target which previously
did not exist. This new page goes into details about the preexisting
target and additionally documents the expectations for WebAssembly
features and code generation.
The tl;dr is that LLVM will enable features over time after most engines
have had support for awhile. Compiling without features requires
`-Ctarget-cpu=mvp` to rustc plus `-Zbuild-std` to Cargo.
Closes#109807Closes#128475
Add target page for riscv64gc-unknown-linux-gnu
I was reading https://github.com/rust-lang/rust/issues/113739 and realized I knew most of the information necessary to create the `riscv64gc-unknown-linux-gnu` target page.
Apache NuttX is a real-time operating system (RTOS) with an emphasis on standards compliance and small footprint. It is scalable from 8-bit to 64-bit microcontroller environments. The primary governing standards in NuttX are POSIX and ANSI standards.
NuttX adopts additional standard APIs from Unix and other common RTOSs, such as VxWorks. These APIs are used for functionality not available under the POSIX and ANSI standards. However, some APIs, like fork(), are not appropriate for deeply-embedded environments and are not implemented in NuttX.
For brevity, many parts of the documentation will refer to Apache NuttX as simply NuttX.
I'll be adding libstd support for NuttX in the future, but for now I'll just add the targets.
Tier 3 policy:
> 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.)
I will be the target maintainer for this target on matters that pertain to the NuttX part of the triple.
For matters pertaining to the riscv or arm part of the triple, there should be no difference from all other targets. If there are issues, I will address issues regarding the target.
> 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.
This is a new supported OS, so I have taken the origin target like `riscv32imac-unknown-none-elf` or `thumbv7m-none-eabi`
and changed the `os` section to `nuttx`.
> 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.
I feel that the target name does not introduce any ambiguity.
> 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 only unusual requirement for building the compiler-builtins crate is a standard RISC-V or ARM C compiler supported by cc-rs, and using this target does not require any additional software beyond what is shipped by rustup.
> The target must not introduce license incompatibilities.
All of the additional code will use Apache-2.0.
> Anything added to the Rust repository must be under the standard Rust
> license (`MIT OR Apache-2.0`).
Agreed, and there is no problem here.
> 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.
No new dependencies are added.
> 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.
Linking is performed by rust-lld
> "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.
There are no terms. NuttX is distributed under the Apache 2.0 license.
> 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.
I'm not the reviewer here.
> 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.
Again I'm not the reviewer here.
> 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.
> 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.
Building is described in platform support doc, but libstd is not supported now,
I'll implement it later.
> 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.
Understood.
> 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.
Understood.
> 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.
I believe I didn't break any other 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.
I think there are no such problems in this PR.
> Tier 3 targets must be able to produce assembly using at least one of
> rustc's supported backends from any host target. (Having support in a fork
> of the backend is not sufficient, it must be upstream.)
Yes, it use standard RISCV or ARM backend to generate assembly.
Signed-off-by: Huang Qi <huangqi3@xiaomi.com>
This is almost identical to already existing targets:
- powerpc_unknown_linux_musl.rs
- powerpc_unknown_linux_gnuspe.rs
It has support for PowerPC SPE (muslspe), which
can be used with GCC version up to 8. It is useful for Freescale or IBM
cores like e500.
This was verified to be working with OpenWrt build system for CZ.NIC's
Turris 1.x routers, which are using Freescale P2020, e500v2, so add it as
a Tier 3 target.
In particular, remove the note saying cdylibs can't link against dylibs — that hasn't been true for over four years.
* 2019-11-07: note is written: b54e8ecc2e
* 2020-01-23: restriction is lifted (without updating docs): 72aaa3a414
use "bootstrap" instead of "rustbuild" in comments and docs
Let's stick with the single name "bootstrap" to refer to the bootstrap project to avoid confusion. This should make it clearer, especially for new contributors.
Ensure floats are returned losslessly by the Rust ABI on 32-bit x86
Solves #115567 for the (default) `"Rust"` ABI. When compiling for 32-bit x86, this PR changes the `"Rust"` ABI to return floats indirectly instead of in x87 registers (with the exception of single `f32`s, which this PR returns in general purpose registers as they are small enough to fit in one). No change is made to the `"C"` ABI as that ABI requires x87 register usage and therefore will need a different solution.
Update the LoongArch target documentation
The docs for the LoongArch targets are a bit dated since their introduction, and the prose has some room for improvement as well. Streamline a bit, referring to the neighboring targets' docs, and provide up-to-date information as much as I can come up with.
cc fellow target maintainer `@heiher` for review of target-specific bits
The docs for the LoongArch targets are a bit dated since their
introduction, and the prose has some room for improvement as well.
Streamline a bit, referring to the neighboring targets' docs, and
provide up-to-date information as much as I can come up with.
Deprecate no-op codegen option `-Cinline-threshold=...`
This deprecates `-Cinline-threshold` since using it has no effect. This has been the case since the new LLVM pass manager started being used, more than 2 years ago.
Recommend using `-Cllvm-args=--inline-threshold=...` instead.
Closes#89742 which is E-help-wanted.
Tier 2 std support must always be known
We should never have a tier 2 target without knowing its support status so I think this line in the tier 2 section is a bit wrong:
> ? indicates the standard library support is unknown or a work-in-progress.
My first inclination was just to drop the "unknown or" part. However, after thinking about it some more, I think we should just use `✓` for this. The only affected targets are UEFI and frankly there are targets with worse std support that are marked with `✓` (e.g. wasm).
I think a `✓` should mean "this supports building with std (and is checked in CI for tier 2+)". The target errata can detail the current limitations or special requirements for doing so.
Add `powerpc-unknown-openbsd` maintenance status
As noted in https://github.com/rust-lang/rust/issues/126451#issuecomment-2167211749 `powerpc-unknown-openbsd` is not maintained by the OpenBSD devs. If a maintainer is found this can be updated with their information but we should document the current status and note explicitly that it's different from other OpenBSD targets.
Add std Xtensa targets support
Adds std Xtensa targets. This enables using Rust on ESP32, ESP32-S2 and ESP32-S3 chips.
Tier 3 policy:
> 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.)
`@MabezDev,` `@ivmarkov` and I (`@SergioGasquez)` will maintain the targets.
> 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.
The target triple is consistent with other targets.
> 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.
We follow the same naming convention as other targets.
> 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 does not introduce any legal issues.
> The target must not introduce license incompatibilities.
There are no license incompatibilities
> Anything added to the Rust repository must be under the standard Rust license (MIT OR Apache-2.0).
Everything added is under that licenses
> 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.
Requirements are not changed for any other target.
> 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.
The linker used by the targets is the GCC linker from the GCC toolchain cross-compiled for Xtensa.
GNU GPL.
> "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.
No such terms exist for this target
> 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.
Understood
> 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.
The targets implement libStd almost in its entirety, except for the missing support for process, as
this is a bare metal platform. The process `sys\unix` module is currently stubbed to return "not
implemented" errors.
> 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.
Here is how to build for the target https://docs.esp-rs.org/book/installation/riscv-and-xtensa.html
and it also covers how to run binaries on the target.
> 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.
> 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.
Understood
> 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.
No other targets should be affected
> Tier 3 targets must be able to produce assembly using at least one of rustc's supported backends
from any host target.
It can produce assembly, but it requires a custom LLVM with Xtensa support
(https://github.com/espressif/llvm-project/). The patches are trying to be upstreamed
(https://github.com/espressif/llvm-project/issues/4)
This deprecates `-Cinline-threshold` since using it has no effect. This
has been the case since the new LLVM pass manager started being used,
more than 2 years ago.
