rustc: Some small changes for the wasm32-wasip2 target
This commit has a few changes for the wasm32-wasip2 target. The first two are aimed at improving the compatibility of using `clang` as an external linker driver on this target. The default target to LLVM is updated to match the Rust target and additionally the `-fuse-ld=lld` argument is dropped since that otherwise interferes with clang's own linker detection. The only linker on wasm targets is LLD but on the wasip2 target a wrapper around LLD, `wasm-component-ld`, is used to drive the process and perform steps necessary for componentization.
The final commit changes the output of all objects on the wasip2 target to being PIC by default. This improves compatibilty with shared libaries but notably does not mean that there's a turnkey solution for shared libraries. The hope is that by having the standard libray work both with and without dynamic libraries will make experimentation easier.
This commit changes the new `wasm32-wasip2` target to being PIC by
default rather than the previous non-PIC by default. This change is
intended to make it easier for the standard library to be used in a
shared object in its precompiled form. This comes with a hypothetical
modest slowdown but it's expected that this is quite minor in most use
cases or otherwise wasm compilers and/or optimizing runtimes can elide
the cost.
LLVM has updated data layouts to specify `Fn32` on 64-bit ARM to avoid
C++ accidentally underaligning functions when trying to comply with
member function ABIs.
This should only affect Rust in cases where we had a similar bug (I
don't believe we have one), but our data layout must match to generate
code.
As a compatibility adaptatation, if LLVM is not version 19 yet, `Fn32`
gets voided from the data layout.
See llvm/llvm-project#90415
- Fixed std support in top-level docs.
- Added `*-apple-darwin` docs.
- Added `i686-apple-darwin` docs.
- Moved `aarch64-apple-ios-sim` to `*-apple-ios` and document all the
iOS targets there.
- Added `*-apple-ios-macabi` docs.
- Add myself (madsmtm) as co-maintainer of most of these targets.
Set non-leaf frame pointers on Fuchsia targets
This is part of our work to enable shadow call stack sanitization on Fuchsia, see [this Fuchsia issue](https://g-issues.fuchsia.dev/issues/327643884).
r? ``@tmandry``
Change `SIGPIPE` ui from `#[unix_sigpipe = "..."]` to `-Zon-broken-pipe=...`
In the stabilization [attempt](https://github.com/rust-lang/rust/pull/120832) of `#[unix_sigpipe = "sig_dfl"]`, a concern was [raised ](https://github.com/rust-lang/rust/pull/120832#issuecomment-2007394609) related to using a language attribute for the feature: Long term, we want `fn lang_start()` to be definable by any crate, not just libstd. Having a special language attribute in that case becomes awkward.
So as a first step towards the next stabilization attempt, this PR changes the `#[unix_sigpipe = "..."]` attribute to a compiler flag `-Zon-broken-pipe=...` to remove that concern, since now the language is not "contaminated" by this feature.
Another point was [also raised](https://github.com/rust-lang/rust/pull/120832#issuecomment-1987023484), namely that the ui should not leak **how** it does things, but rather what the **end effect** is. The new flag uses the proposed naming. This is of course something that can be iterated on further before stabilization.
Tracking issue: https://github.com/rust-lang/rust/issues/97889
This commit changes the LLVM target of for the Rust `wasm32-wasip2`
target to `wasm32-wasip2` as well. LLVM does a bit of detection on the
target string to know when to call `wasm-component-ld` vs `wasm-ld` so
otherwise clang is invoking the wrong linker.
In the stabilization attempt of `#[unix_sigpipe = "sig_dfl"]`, a concern
was raised related to using a language attribute for the feature: Long
term, we want `fn lang_start()` to be definable by any crate, not just
libstd. Having a special language attribute in that case becomes
awkward.
So as a first step towards towards the next stabilization attempt, this
PR changes the `#[unix_sigpipe = "..."]` attribute to a compiler flag
`-Zon-broken-pipe=...` to remove that concern, since now the language
is not "contaminated" by this feature.
Another point was also raised, namely that the ui should not leak
**how** it does things, but rather what the **end effect** is. The new
flag uses the proposed naming. This is of course something that can be
iterated on further before stabilization.
Upcoming mingw-w64 releases will contain small math functions refactor which moved implementation around.
As a result functions like `lgamma`
now depend on libraries in this order:
`libmingwex.a` -> `libmsvcrt.a` -> `libmingwex.a`.
Fixes#124221
Introduce perma-unstable `wasm-c-abi` flag
Now that `wasm-bindgen` v0.2.88 supports the spec-compliant C ABI, the idea is to switch to that in a future version of Rust. In the meantime it would be good to let people test and play around with it.
This PR introduces a new perma-unstable `-Zwasm-c-abi` compiler flag, which switches to the new spec-compliant C ABI when targeting `wasm32-unknown-unknown`.
Alternatively, we could also stabilize this and then deprecate it when we switch. I will leave this to the Rust maintainers to decide.
This is a companion PR to #117918, but they could be merged independently.
MCP: https://github.com/rust-lang/compiler-team/issues/703
Tracking issue: https://github.com/rust-lang/rust/issues/122532
To the best of my ability I believe that this is no longer necessary. I
don't fully recall why this was first added but I believe it had to do
with symbols all being exported by default and this was required to undo
that. Regardless nowadays the default output of rustc seems suitable so
it seems best to keep wasm in line with other targets.
Linker flavors next steps: linker features
This is my understanding of the first step towards `@petrochenkov's` vision for the future of linker flavors, described in https://github.com/rust-lang/rust/pull/119906#issuecomment-1895693162 and the discussion that followed.
To summarize: having `Cc` and `Lld` embedded in linker flavors creates tension about naming, and a combinatorial explosion of flavors for each new linker feature we'd want to use. Linker features are an extension mechanism that is complementary to principal flavors, with benefits described in #119906.
The most immediate use of this flag would be to turn self-contained linking on and off via features instead of flavors. For example, `-Clinker-features=+/-lld` would toggle using lld instead of selecting a precise flavor, and would be "generic" and work cross-platform (whereas linker flavors are currently more tied to targets). Under this scheme, MCP510 is expected to be `-Clink-self-contained=+linker -Zlinker-features=+lld -Zunstable-options` (though for the time being, the original flags using lld-cc flavors still work).
I purposefully didn't add or document CLI support for `+/-cc`, as it would be a noop right now. I only expect that we'd initially want to stabilize `+/-lld` to begin with.
r? `@petrochenkov`
You had requested that minimal churn would be done to the 230 target specs and this does none yet: the linker features are inferred from the flavor since they're currently isomorphic. We of course expect this to change sooner rather than later.
In the future, we can allow targets to define linker features independently from their flavor, and remove the cc and lld components from the flavors to use the features instead, this actually doesn't need to block stabilization, as we discussed.
(Best reviewed per commit)
Re-enable `has_thread_local` for i686-msvc
A few years back, `has_thread_local` was disabled as a workaround for a compiler issue. While the exact cause was never tracked down, it was suspected to be caused by the compiler inlining a thread local access across a dylib boundary. This should be fixed now so let's try again.
While they're isomorphic, we can flip the lld component where
applicable, so that downstream doesn't have to check both the flavor and
the linker features.
They are a flexible complementary mechanism to linker flavors,
that also avoid the combinatorial explosion of mapping linking features
to actual linker flavors.
Reduce Size of `ModifierInfo`
I added `ModifierInfo` in #121940 and had used a `u64` for the `size` field even though the largest value it holds is `512`.
This PR changes the type of the `size` field to `u16`.
The actual ABI implication here is that in some cases the values
are required to be "consecutive", i.e. must either all be passed
in registers or all on stack (without padding).
Adjust the code to either use Uniform::new() or Uniform::consecutive()
depending on which behavior is needed.
Then, when lowering this in LLVM, skip the [1 x i128] to i128
simplification if is_consecutive is set. i128 is the only case
I'm aware of where this is problematic right now. If we find
other cases, we can extend this (either based on target information
or possibly just by not simplifying for is_consecutive entirely).
When passing a 16 (or higher) aligned struct by value on ppc64le,
it needs to be passed as an array of `i128` rather than an array
of `i64`. This will force the use of an even starting register.
For the case of a 16 byte struct with alignment 16 it is important
that `[1 x i128]` is used instead of `i128` -- apparently, the
latter will get treated similarly to `[2 x i64]`, not exhibiting
the correct ABI. Add a `force_array` flag to `Uniform` to support
this.
The relevant clang code can be found here:
fe2119a7b0/clang/lib/CodeGen/Targets/PPC.cpp (L878-L884)fe2119a7b0/clang/lib/CodeGen/Targets/PPC.cpp (L780-L784)
I think the corresponding psABI wording is this:
> Fixed size aggregates and unions passed by value are mapped to as
> many doublewords of the parameter save area as the value uses in
> memory. Aggregrates and unions are aligned according to their
> alignment requirements. This may result in doublewords being
> skipped for alignment.
In particular the last sentence.
Fixes https://github.com/rust-lang/rust/issues/122767.
Fix incorrect 'llvm_target' value used on watchOS target
## Issue
`xcodebuild -create-xcframework` command doesn't recognize static libraries that are built on "arm64_32-apple-watchos" target.
Here are steps to reproduce the issue on a Mac:
1. Install nightly toolchain `nightly-2024-03-27`. Needs this specific version, because newer nightly versions are broken on watchos target.
1. Create an empty library: `mkdir watchos-lib && cd watchos-lib && cargo init --lib`.
1. Add configuration `lib.crate-type=["staticlib"]` to Cargo.toml.
1. Build the library: `cargo +nightly-2024-03-27 build --release -Zbuild-std --target arm64_32-apple-watchos`
1. Run `xcodebuild -create-xcframework` to put the static library into a xcframework, which results in an error:
```
$ xcodebuild -create-xcframework -library target/arm64_32-apple-watchos/release/libwatchos_lib.a -output test.xcframework
error: unable to determine the platform for the given binary '.../watchos-lib/target/arm64_32-apple-watchos/release/libwatchos_lib.a'; check your deployment version settings
```
## Fix
The root cause of this error is `xcodebuild` couldn't read `LC_BUILD_VERSION` from the static library to determine the library's target platform. And the reason it's missing is that an incorrect `llvm_target` value is used in `arm64_32-apple-watchos` target. The expected value is `<arch>-apple-watchos<major>.<minor>.0`, i.e. "arm64_32-apple-watchos8.0.0".
The [.../apple/mod.rs](43f4f2a3b1/compiler/rustc_target/src/spec/base/apple/mod.rs (L321)) file contains functions that construct such string. There is an existing function `watchos_sim_llvm_target` which returns llvm target value for watchOS simulator. But there is none for watchOS device. This PR adds that missing function to align watchOS with other Apple platform targets.
To verify the fix, you can simply build a toolchain on this PR branch and repeat the steps above using the built local toolchain to verify the `xcodebuild -create-xcframework` command can create a xcframework successfully.
Furthermore, you can verify `LC_BUILD_VERSION` contains correct info by using the simple shell script below to print `LC_BUILD_VERSION` of the static library that's built on watchos target:
```shell
bin=target/arm64_32-apple-watchos/release/libwatchos_lib.a
file=$(ar -t "$bin" | grep -E '\.o$' | head -n 1)
ar -x "$bin" "$file"
vtool -show-build-version "$file"
```
Here is an example output from my machine:
```
watchos_rust-495d6aaf3bccc08d.watchos_rust.35ba42bf9255ca9d-cgu.0.rcgu.o:
Load command 1
cmd LC_BUILD_VERSION
cmdsize 24
platform WATCHOS
minos 8.0
sdk n/a
ntools 0
```
MSVC targets should use COFF as their archive format
While adding support for Arm64EC I ran into an issue where the standard library's rlib was missing the "EC Symbol Table" which is required for the MSVC linker to find import library symbols (generated by Rust's `raw-dylib` feature) when building for EC.
The root cause of the issue is that LLVM only generated symbol tables (including the EC Symbol Table) if the `ArchiveKind` is `COFF`, but the MSVC targets didn't set their archive format, so it was defaulting to GNU.
Fix target-cpu fpu features on Arm R/M-profile
This is achieved by converting `+<fpu>,-d32,{,-fp64}` to `+<fpu>d16{,sp}`.
By using a single additive feature that captures `d16` vs `d32` and `sp` vs
`dp`, we prevent `-<feature>` from overriding `-C target-cpu` at build time.
Remove extraneous `-fp16` from `armv7r` targets, as this is not included in
`vfp3` anyway, but was preventing `fp16` from being enabled by e.g.,
`-C target-cpu=cortex-r7`, which does support `fp16`.
Add aarch64-apple-visionos and aarch64-apple-visionos-sim tier 3 targets
Introduces `aarch64-apple-visionos` and `aarch64-apple-visionos-sim` as tier 3 targets. This allows native development for the Apple Vision Pro's visionOS platform.
This work has been tracked in https://github.com/rust-lang/compiler-team/issues/642. There is a corresponding `libc` change https://github.com/rust-lang/libc/pull/3568 that is not required for merge.
Ideally we would be able to incorporate [this change](https://github.com/gimli-rs/object/pull/626) to the `object` crate, but the author has stated that a release will not be cut for quite a while. Therefore, the two locations that would reference the xrOS constant from `object` are hardcoded to their MachO values of 11 and 12, accompanied by TODOs to mark the code as needing change. I am open to suggestions on what to do here to get this checked in.
# 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 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.)
See [src/doc/rustc/src/platform-support/apple-visionos.md](e88379034a/src/doc/rustc/src/platform-support/apple-visionos.md)
> 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.
This naming scheme matches `$ARCH-$VENDOR-$OS-$ABI` which is matches the iOS Apple Silicon simulator (`aarch64-apple-ios-sim`) and other Apple 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 must not introduce license incompatibilities.
> - Anything added to the Rust repository must be under the standard Rust license (`MIT OR Apache-2.0`).
> - 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 besubject to any new license requirements.
> - 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.
> - "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.
This contribution is fully available under the standard Rust license with no additional legal restrictions whatsoever. This PR does not introduce any new dependency less permissive than the Rust license policy.
The new targets do not depend on proprietary libraries.
> 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 new target mirrors the standard library for watchOS and iOS, with minor divergences.
> 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.
Documentation is provided in [src/doc/rustc/src/platform-support/apple-visionos.md](e88379034a/src/doc/rustc/src/platform-support/apple-visionos.md)
> 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.
> 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.
> 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.
I acknowledge these requirements and intend to ensure that they are met.
This target does not touch any existing tier 2 or tier 1 targets and should not break any other targets.
This is achieved by converting `+<fpu>,-d32,{,-fp64}` to `+<fpu>d16{,sp}`.
By using a single additive feature that captures `d16` vs `d32` and `sp` vs
`dp`, we prevent `-<feature>` from overriding `-C target-cpu` at build time.
Remove extraneous `-fp16` from `armv7r` targets, as this is not included in
`vfp3` anyway, but was preventing `fp16` from being enabled by e.g.,
`-C target-cpu=cortex-r7`, which does support `fp16`.
The expected value is "<arch>-apple-watchos<major>.<minor>.0", i.e.
"arm64_32-apple-watchos8.0.0".
compiler/rustc_target/src/spec/base/apple/mod.rs contains functions that
construct such string. There is an existing function
`watchos_sim_llvm_target` which returns llvm target value for watchOS
simulator. But there is none for watchOS device. This commit adds that
missing function to align watchOS with other Apple platform targets.
Check `x86_64` size assertions on `aarch64`, too
(Context: https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Checking.20size.20assertions.20on.20aarch64.3F)
Currently the compiler has around 30 sets of `static_assert_size!` for various size-critical data structures (e.g. various IR nodes), guarded by `#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]`.
(Presumably this cfg avoids having to maintain separate size values for 32-bit targets and unusual 64-bit targets. Apparently it may have been necessary before the i128/u128 alignment changes, too.)
This is slightly incovenient for people on aarch64 workstations (e.g. Macs), because the assertions normally aren't checked until we push to a PR. So this PR adds `aarch64` to the `#[cfg(..)]` guarding all of those assertions in the compiler.
---
Implemented with a simple find/replace. Verified by manually inspecting each `static_assert_size!` in `compiler/`, and checking that either the replacement succeeded, or adding aarch64 wouldn't have been appropriate.
This enables KCFI-based testing for all the CFI run-pass tests in the
suite today. We can add the test header on top of in-flight CFI tests
once they land.
It also enables KCFI as a sanitizer for x86_64 and aarch64 Linux to make
this possible. The sanitizer should likely be available for all aarch64,
x86_64, and riscv targets, but that isn't critical for initial testing.
Mention Register Size in `#[warn(asm_sub_register)]`
Fixes#121593
Displays the register size information obtained from `suggest_modifier()` and `default_modifier()`.
Remove `target_override`
Because the "target can override the backend" and "backend can override the target" situation is a mess. Details in the individual commits.
r? `@WaffleLapkin`
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 https://github.com/rust-lang/rust/pull/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.
Backend and target selection is a mess: the target can override the
backend (via `Target::default_codegen_backend`), *and* the backend can
override the target (via `CodegenBackend::target_override`).
The code that handles this is ugly. It calls `build_target_config`
twice, once before getting the backend and once again afterward. It also
must check that both overrides aren't triggering at the same time.
This commit removes the latter override. It's used in rust-gpu but
@eddyb said via Zulip that removing it would be ok. This simplifies the
code greatly, and will allow some nice follow-up refactorings.
This would trigger a `Size::sub: 0 - 8 would result in negative size` abort,
if `data.last_offset > offset`.
This is almost hilariously easy to trigger (https://godbolt.org/z/8rbv57xET):
```rust
#[repr(C)]
pub struct DoubleFloat {
f: f64,
g: f32,
}
#[no_mangle]
pub extern "C" fn foo(x: DoubleFloat) {}
```
Tests for this will be covered by the cast-target-abi.rs test added in a later commit.
Rename `wasm32-wasi-preview1-threads` to `wasm32-wasip1-threads`
This commit renames the current `wasm32-wasi-preview1-threads` target to `wasm32-wasip1-threads`. The need for this rename is a bit unfortunate as the previous name was chosen in an attempt to be future-compatible with other WASI targets. Originally this target was proposed to be `wasm32-wasi-threads`, and that's what was originally implemented in wasi-sdk as well. After discussion though and with the plans for the upcoming component-model target (now named `wasm32-wasip2`) the "preview1" naming was chosen for the threads-based target. The WASI subgroup later decided that it was time to drop the "preview" terminology and recommends "pX" instead, hence previous PRs to add `wasm32-wasip2` and rename `wasm32-wasi` to `wasm32-wasip1`.
So, with all that history, the "proper name" for this target is different than its current name, so one way or another a rename is required. This PR proposes renaming this target cold-turkey, unlike `wasm32-wasi` which is having a long transition period to change its name. The threads-based target is predicted to see only a fraction of the traffic of `wasm32-wasi` due to the unstable nature of the WASI threads proposal itself.
While I was here I updated the in-tree documentation in the target spec file itself as most of the documentation was copied from the original WASI target and wasn't as applicable to this target.
Also, as an aside, I can at least try to apologize for all the naming confusion here, but this is hopefully the last WASI-related rename.
Update /NODEFAUTLIB comment for msvc
I've tried to explain a bit more about the effects of `/NODEFAULTLIB` when using msvc link.exe (or compatible) as they're different from `-nodefaultlib` on gnu.
I also removed the part about licensing as I'm not sure licensing is an issue? Or rather, it's no more or less of an issue no matter how you link msvc libraries. The license is the one you get if using VS at all and even dynamic linking includes static code (e.g. startup/shutdown code, etc).
r? petrochenkov
Update Windows platform support
This should not be merged until Rust 1.76 but I'm told this may need an fcp in addition to [MCP 651](https://github.com/rust-lang/compiler-team/issues/651).
cc ```@rust-lang/compiler``` ```@rust-lang/release```
This commit renames the current `wasm32-wasi-preview1-threads` target to
`wasm32-wasip1-threads`. The need for this rename is a bit unfortunate
as the previous name was chosen in an attempt to be future-compatible
with other WASI targets. Originally this target was proposed to be
`wasm32-wasi-threads`, and that's what was originally implemented in
wasi-sdk as well. After discussion though and with the plans for the
upcoming component-model target (now named `wasm32-wasip2`) the
"preview1" naming was chosen for the threads-based target. The WASI
subgroup later decided that it was time to drop the "preview"
terminology and recommends "pX" instead, hence previous PRs to add
`wasm32-wasip2` and rename `wasm32-wasi` to `wasm32-wasip1`.
So, with all that history, the "proper name" for this target is
different than its current name, so one way or another a rename is
required. This PR proposes renaming this target cold-turkey, unlike
`wasm32-wasi` which is having a long transition period to change its
name. The threads-based target is predicted to see only a fraction of
the traffic of `wasm32-wasi` due to the unstable nature of the WASI
threads proposal itself.
While I was here I updated the in-tree documentation in the target spec
file itself as most of the documentation was copied from the original
WASI target and wasn't as applicable to this target.
Also, as an aside, I can at least try to apologize for all the naming
confusion here, but this is hopefully the last WASI-related rename.
LLVM Bitcode Linker: A self contained linker for nvptx and other targets
This PR introduces a new linker named `llvm-bitcode-linker`. It is a `self-contained` linker that can be used to link programs in `llbc` before optimizing and compiling to native code. It will first be used internally in the Rust compiler to enable tests for the `nvptx64-nvidia-cuda` target as the original `rust-ptx-linker` is deprecated. It will then be provided to users of the `nvptx64-nvidia-cuda` target with the purpose of linking ptx. More targets than nvptx will also be supported eventually.
The PR introduces a new unstable `LinkerFlavor` for the compiler. The compiler will also not be shipped with rustc but most likely instead be shipped in it's own unstable component (a follow up PR will be opened for this). This means that merging this PR should not add any stability guarantees.
When more details of `self-contained` is implemented it will only be possible to use the linker when `-Clink-self-contained=+linker` is passed.
<details>
<summary>Original Description</summary>
**When this PR was created it was focused a bit differently. The original text is preserved here in case there's some interests in it**
I have experimenting with approaches to replace the ptx-linker and enable the nvptx target tests again. I think it's time to get some feedback on the approach.
### The problem
The only useful linker for the nvptx target is [this crate](https://github.com/denzp/rust-ptx-linker). Since this linker performs linking on llvm bitcode it needs to track the llvm version of rustc and use the same format. It has not been maintained for 3+ years and must be considered abandoned. Over the years rust have upgraded LLVM while the linker has been left to bitrot. It is no longer in a usable state.
Due to the difficulty of keeping the ptx-linker up to date outside of tree the nvptx tests was [disabled a long time ago](f8f9a2869c). It was [previously discussed](https://github.com/rust-lang/rust/pull/96842#issuecomment-1146470177) if adding the ptx-linker to the rust repo would be a possibility. My efforts in doing this stopped at getting an answered if the license would prohibit it from inclusion in the [Rust repo](https://github.com/rust-lang/rust/pull/96842#issuecomment-1148397554). I therefore concluded that a re-write would be necessary.
### The possible solution presented here
The llvm tools know perfectly well how to link and optimize llvm bitcode. Each of them only perform a single task, and are therefore a bit cumbersome to call with the current linker approach rustc takes.
This PR adds a simple tool (current name `embedded-linker`) which can link self contained (often embedded) programs in llvm bitcode before compiling to the target format. Optimization will also be performed if lto is enabled. The rust compiler will make a single invocation to this tool, while the tool will orchestrate the many calls to the llvm tools.
### The questions
- Is having control over the nvptx linking and therefore also tests worth it to add such tool? or should the tool live outside the rust repo?
- Is the approach of calling llvm tools acceptable? Or would we want to keep the ptx-linker approach of using the llvm library? The tools seems to provide more simplicity and stability, but more intermediate files are being written. Perhaps there also are some performance penalty for the calling tools approach.
- What is the process for adding such tool? MCP?
- Does adding `llvm-link` to the llvm-tool component require any process?
- Does it require some sort of FCP to remove ptx-linker as the default linker for ptx? Or is it sufficient that using the upstream ptx-linker is broken in its current state. it is possible to use a somewhat patched version of ptx-linker.
</details>
Add metadata to targets
follow up to #121905 and #122157
This adds four pieces of metadata to every target:
- description
- tier
- host tools
- std
This information is currently scattered across target docs and both
- not machine readable, making validation harder
- sometimes subtly encoding by the table it's in, causing mistakes and making it harder to review changes to the properties
By putting it in the compiler, we improve this. Later, we will use this canonical information to generate target documentation from it.
I used find-replace for all the `description: None`.
One thing I'm not sure about is the behavior for the JSON. It doesn't really make sense that custom targets supply this information, especially the tier. But for the roundtrip tests, we do need to print and parse it. Maybe emit a warning when a custom target provides the metadata key? Either way, I don't think that's important right now, this PR should get merged ASAP or it will conflict all over the place.
r? davidtwco
Stop using LLVM struct types for byval/sret
For `byval` and `sret`, the type has no semantic meaning, only the size matters\*†. Using `[N x i8]` is a more direct way to specify that we want `N` bytes, and avoids relying on LLVM's struct layout.
\*: The alignment would matter, if we didn't explicitly specify it. From what I can tell, we always specified the alignment for `sret`; for `byval`, we didn't until #112157.
†: For `byval`, the hidden copy may be impacted by padding in the LLVM struct type, i.e. padding bytes may not be copied. (I'm not sure if this is done today, but I think it would be legal.) But we manually pad our LLVM struct types specifically to avoid there ever being LLVM-visible padding, so that shouldn't be an issue.
Split out from #121577.
r? `@nikic`
This adds four pieces of metadata to every target:
- description
- tier
- host tools
- std
This information is currently scattered across target docs and both
- not machine readable, making validation harder
- sometimes subtly encoding by the table it's in, causing mistakes and
making it harder to review changes to the properties
By putting it in the compiler, we improve this. Later, we will use this
canonical information to generate target documentation from it.
Add the new description field to Target::to_json, and add descriptions for some MSVC targets
The original PR to add a `description` field to `Target` (<https://github.com/rust-lang/rust/pull/121905>) didn't add the field to `Target::to_json`, which meant that the `check_consistency` testwould fail if you tried to set a description as it wouldn't survive round-tripping via JSON: https://github.com/rust-lang/rust/actions/runs/8180997936/job/22370052535#step:27:4967
This change adds the field to `Target::to_json`, and sets some descriptions to verify that it works correctly.
Add arm64ec-pc-windows-msvc target
Introduces the `arm64ec-pc-windows-msvc` target for building Arm64EC ("Emulation Compatible") binaries for Windows.
For more information about Arm64EC see <https://learn.microsoft.com/en-us/windows/arm/arm64ec>.
## 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 maintainer for this 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.
Target uses the `arm64ec` architecture to match LLVM and MSVC, and the `-pc-windows-msvc` suffix to indicate that it targets Windows via the MSVC environment.
> 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.
Target name exactly specifies the type of code that will be produced.
> If possible, use only letters, numbers, dashes and underscores for the name. Periods (.) are known to cause issues in Cargo.
Done.
> 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.
Uses the same dependencies, requirements and licensing as the other `*-pc-windows-msvc` targets.
> Anything added to the Rust repository must be under the standard Rust license (MIT OR Apache-2.0).
Understood.
> 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.
> 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.
> "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.
Uses the same dependencies, requirements and licensing as the other `*-pc-windows-msvc` 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.
Understood, I am not a member of the Rust team.
> 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.
Both `core` and `alloc` are supported.
Support for `std` depends on making changes to the standard library, `stdarch` and `backtrace` which cannot be done yet as they require fixes coming in LLVM 18.
> 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.
Documentation is provided in src/doc/rustc/src/platform-support/arm64ec-pc-windows-msvc.md
> 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.
> 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.
Understood.
Introduces the `arm64ec-pc-windows-msvc` target for building Arm64EC ("Emulation Compatible") binaries for Windows.
For more information about Arm64EC see <https://learn.microsoft.com/en-us/windows/arm/arm64ec>.
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 maintainer for this 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.
Target uses the `arm64ec` architecture to match LLVM and MSVC, and the `-pc-windows-msvc` suffix to indicate that it targets Windows via the MSVC environment.
> 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.
Target name exactly specifies the type of code that will be produced.
> If possible, use only letters, numbers, dashes and underscores for the name. Periods (.) are known to cause issues in Cargo.
Done.
> 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.
Uses the same dependencies, requirements and licensing as the other `*-pc-windows-msvc` targets.
> Anything added to the Rust repository must be under the standard Rust license (MIT OR Apache-2.0).
Understood.
> 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.
> 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.
> "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.
Uses the same dependencies, requirements and licensing as the other `*-pc-windows-msvc` 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.
Understood, I am not a member of the Rust team.
> 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.
Both `core` and `alloc` are supported.
Support for `std` dependends on making changes to the standard library, `stdarch` and `backtrace` which cannot be done yet as the bootstrapping compiler raises a warning ("unexpected `cfg` condition value") for `target_arch = "arm64ec"`.
> 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.
Documentation is provided in src/doc/rustc/src/platform-support/arm64ec-pc-windows-msvc.md
> 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.
> 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.
Understood.
This is the short description (`64-bit MinGW (Windows 7+)`) including
the platform requirements.
The reason for doing it like this is that this PR will be quite prone to
conflicts whenever targets get added, so it should be as simple as
possible to get it merged. Future PRs which migrate targets are scoped
to groups of targets, so they will not conflict as they can just touch
these.
This moves some of the information from the rustc book into the
compiler.
It cannot be queried yet, that is future work. It is also future work to
fill out all the descriptions, which will coincide with the work of
moving over existing target docs to the new format.
Add a new `wasm32-wasip1` target to rustc
This commit adds a new target called `wasm32-wasip1` to rustc. This new target is explained in these two MCPs:
* https://github.com/rust-lang/compiler-team/issues/607
* https://github.com/rust-lang/compiler-team/issues/695
In short, the previous `wasm32-wasi` target is going to be renamed to `wasm32-wasip1` to better live alongside the [new `wasm32-wasip2` target](https://github.com/rust-lang/rust/pull/119616). This new target is added alongside the `wasm32-wasi` target and has the exact same definition as the previous target. This PR is effectively a rename of `wasm32-wasi` to `wasm32-wasip1`. Note, however, that as explained in rust-lang/compiler-team#695 the previous `wasm32-wasi` target is not being removed at this time. This change will reach stable Rust before even a warning about the rename will be printed. At this time this change is just the start where a new target is introduced and users can start migrating if they support only Nightly for example.
This commit adds a new target called `wasm32-wasip1` to rustc.
This new target is explained in these two MCPs:
* https://github.com/rust-lang/compiler-team/issues/607
* https://github.com/rust-lang/compiler-team/issues/695
In short, the previous `wasm32-wasi` target is going to be renamed to
`wasm32-wasip1` to better live alongside the [new
`wasm32-wasip2` target](https://github.com/rust-lang/rust/pull/119616).
This new target is added alongside the `wasm32-wasi` target and has the
exact same definition as the previous target. This PR is effectively a
rename of `wasm32-wasi` to `wasm32-wasip1`. Note, however, that
as explained in rust-lang/compiler-team#695 the previous `wasm32-wasi`
target is not being removed at this time. This change will reach stable
Rust before even a warning about the rename will be printed. At this
time this change is just the start where a new target is introduced and
users can start migrating if they support only Nightly for example.
Adds initial support for DataFlowSanitizer to the Rust compiler. It
currently supports `-Zsanitizer-dataflow-abilist`. Additional options
for it can be passed to LLVM command line argument processor via LLVM
arguments using `llvm-args` codegen option (e.g.,
`-Cllvm-args=-dfsan-combine-pointer-labels-on-load=false`).
Add stubs in IR and ABI for `f16` and `f128`
This is the very first step toward the changes in https://github.com/rust-lang/rust/pull/114607 and the [`f16` and `f128` RFC](https://rust-lang.github.io/rfcs/3453-f16-and-f128.html). It adds the types to `rustc_type_ir::FloatTy` and `rustc_abi::Primitive`, and just propagates those out as `unimplemented!` stubs where necessary.
These types do not parse yet so there is no feature gate, and it should be okay to use `unimplemented!`.
The next steps will probably be AST support with parsing and the feature gate.
r? `@compiler-errors`
cc `@Nilstrieb` suggested breaking the PR up in https://github.com/rust-lang/rust/pull/120645#issuecomment-1925900572
Stabilize `cfg_target_abi`
This stabilizes the `cfg` option called `target_abi`:
```rust
#[cfg(target_abi = "eabihf")]
```
Tracking issue: #80970fixes#78791resolves#80970
Fixes:
$ MAGIC_EXTRA_RUSTFLAGS=-Zmove-size-limit=4096 ./x test compiler/rustc_target
error: moving 6216 bytes
--> compiler/rustc_target/src/spec/base/apple/tests.rs:17:19
|
17 | for target in all_sim_targets {
| ^^^^^^^^^^^^^^^ value moved from here
|
= note: The current maximum size is 4096, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
= note: `-D large-assignments` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(large_assignments)]`
mark `min_exhaustive_patterns` as complete
This is step 1 and 2 of my [proposal](https://github.com/rust-lang/rust/issues/119612#issuecomment-1918097361) to move `min_exhaustive_patterns` forward. The vast majority of in-tree use cases of `exhaustive_patterns` are covered by `min_exhaustive_patterns`. There are a few cases that still require `exhaustive_patterns` in tests and they're all behind references.
r? ``@ghost``
Fix `cfg(target_abi = "sim")` on `i386-apple-ios`
Since https://github.com/rust-lang/rust/issues/80970 is stabilizing, I went and had a look, and found that the result was wrong on `i386-apple-ios`.
r? rust-lang/macos
These crates all needed specialization for `newtype_index!`, which will no
longer be necessary when the current nightly eventually becomes the next
bootstrap compiler.
Invert diagnostic lints.
That is, change `diagnostic_outside_of_impl` and `untranslatable_diagnostic` from `allow` to `deny`, because more than half of the compiler has been converted to use translated diagnostics.
This commit removes more `deny` attributes than it adds `allow` attributes, which proves that this change is warranted.
r? ````@davidtwco````
That is, change `diagnostic_outside_of_impl` and
`untranslatable_diagnostic` from `allow` to `deny`, because more than
half of the compiler has be converted to use translated diagnostics.
This commit removes more `deny` attributes than it adds `allow`
attributes, which proves that this change is warranted.
target: default to the medium code model on LoongArch targets
The Rust LoongArch targets have been using the default LLVM code model so far, which is "small" in LLVM-speak and "normal" in LoongArch-speak. As [described][1] in the "Code Model" section of LoongArch ELF psABI spec v20231219, one can only make function calls as far as ±128MiB with the "normal" code model; this is insufficient for very large software containing Rust components that needs to be linked into the big text section, such as Chromium.
Because:
* we do not want to ask users to recompile std if they are to build such software,
* objects compiled with larger code models can be linked with those with smaller code models without problems, and
* the "medium" code model is comparable to the "small"/"normal" one performance-wise (same data access pattern; each function call becomes 2-insn long and indirect, but this may be relaxed back into the direct 1-insn form in a future LLVM version), but is able to perform function calls within ±128GiB,
it is better to just switch the targets to the "medium" code model, which is also "medium" in LLVM-speak.
[1]: https://github.com/loongson/la-abi-specs/blob/v2.30/laelf.adoc#code-models
riscv only supports split_debuginfo=off for now
Disable packed/unpacked options for riscv linux/android. Other riscv targets already only have the off option.
The packed/unpacked options might be supported in the future. See upstream issue for more details:
https://github.com/llvm/llvm-project/issues/56642Fixes#110224
The Rust LoongArch targets have been using the default LLVM code model
so far, which is "small" in LLVM-speak and "normal" in LoongArch-speak.
As described in the "Code Model" section of LoongArch ELF psABI spec
v20231219 [1], one can only make function calls as far as ±128MiB with
the "normal" code model; this is insufficient for very large software
containing Rust components that needs to be linked into the big text
section, such as Chromium.
Because:
* we do not want to ask users to recompile std if they are to build
such software,
* objects compiled with larger code models can be linked with those
with smaller code models without problems, and
* the "medium" code model is comparable to the "small"/"normal" one
performance-wise (same data access pattern; each function call
becomes 2-insn long and indirect, but this may be relaxed back into
the direct 1-insn form in a future LLVM version), but is able to
perform function calls within ±128GiB,
it is better to just switch the targets to the "medium" code model,
which is also "medium" in LLVM-speak.
[1]: https://github.com/loongson/la-abi-specs/blob/v2.30/laelf.adoc#code-models
Disable packed/unpacked options for riscv linux/android.
Other riscv targets already only have the off option.
The packed/unpacked options might be supported in the future.
See upstream issue for more details:
https://github.com/llvm/llvm-project/issues/56642Fixes#110224
Remove --fatal-warnings on wasm targets
These were added with good intentions, but a recent change in LLVM 18 emits a warning while examining .rmeta sections in .rlib files. Since this flag is a nice-to-have and users can update their LLVM linker independently of rustc's LLVM version, we can just omit the flag.
See [this comment on wasm targets' uses of `--fatal-warnings`](https://github.com/llvm/llvm-project/pull/78658#issuecomment-1906651390).
Add a new `wasm32-wasi-preview2` target
This is the initial implementation of the MCP https://github.com/rust-lang/compiler-team/issues/694 creating a new tier 3 target `wasm32-wasi-preview2`. That MCP has been seconded and will most likely be approved in a little over a week from now. For more information on the need for this target, please read the [MCP](https://github.com/rust-lang/compiler-team/issues/694).
There is one aspect of this PR that will become insta-stable once these changes reach a stable compiler:
* A new `target_family` named `wasi` is introduced. This target family incorporates all wasi targets including `wasm32-wasi` and its derivative `wasm32-wasi-preview1-threads`. The difference between `target_family = wasi` and `target_os = wasi` will become much clearer when `wasm32-wasi` is renamed to `wasm32-wasi-preview1` and the `target_os` becomes `wasm32-wasi-preview1`. You can read about this target rename in [this MCP](https://github.com/rust-lang/compiler-team/issues/695) which has also been seconded and will hopefully be officially approved soon.
Additional technical details include:
* Both `std::sys::wasi_preview2` and `std::os::wasi_preview2` have been created and mostly use `#[path]` annotations on their submodules to reach into the existing `wasi` (soon to be `wasi_preview1`) modules. Over time the differences between `wasi_preview1` and `wasi_preview2` will grow and most like all `#[path]` based module aliases will fall away.
* Building `wasi-preview2` relies on a [`wasi-sdk`](https://github.com/WebAssembly/wasi-sdk) in the same way that `wasi-preview1` does (one must include a `wasi-root` path in the `Config.toml` pointing to sysroot included in the wasi-sdk). The target should build against [wasi-sdk v21](https://github.com/WebAssembly/wasi-sdk/releases/tag/wasi-sdk-21) without modifications. However, the wasi-sdk itself is growing [preview2 support](https://github.com/WebAssembly/wasi-sdk/pull/370) so this might shift rapidly. We will be following along quickly to make sure that building the target remains possible as the wasi-sdk changes.
* This requires a [patch to libc](https://github.com/rylev/rust-libc/tree/wasm32-wasi-preview2) that we'll need to land in conjunction with this change. Until that patch lands the target won't actually build.
These were added with good intentions, but a recent change in LLVM 18
emits a warning while examining .rmeta sections in .rlib files. Since
this flag is a nice-to-have and users can update their LLVM linker
independently of rustc's LLVM version, we can just omit the flag.
This also adds changes in the rust test suite in order to get a few of them to
pass.
Co-authored-by: Frank Laub <flaub@risc0.com>
Co-authored-by: Urgau <3616612+Urgau@users.noreply.github.com>
With https://reviews.llvm.org/D86310 LLVM now has i128 aligned to
16-bytes on x86 based platforms. This will be in LLVM-18. This patch
updates all our spec targets to be 16-byte aligned, and removes the
alignment when speaking to older LLVM.
This results in Rust overaligning things relative to LLVM on older LLVMs.
This alignment change was discussed in rust-lang/compiler-team#683
See #54341 for additional information about why this is happening and
where this will be useful in the future.
This *does not* stabilize `i128`/`u128` for FFI.
In LLVM 17, PowerPC targets started including function pointer alignments
in data layouts, and in Rust's update to that version (#114048), we added
the function pointer alignments. `powerpc64-unknown-linux-musl` had
`Fi64` set but this seems incorrect, and the code in LLVM would always
have computed `Fn32` because it is a MUSL target.
Signed-off-by: David Wood <david@davidtw.co>
Adds a basic assembly test checking that each target can produce assembly
and update the target tier policy to require this.
Signed-off-by: David Wood <david@davidtw.co>
Varargs support for system ABI
This PR allows functions with the `system` ABI to be variadic (under the `extended_varargs_abi_support` feature tracked in #100189). On x86 windows, the `system` ABI is equivalent to `C` for variadic functions. On other platforms, `system` is already equivalent to `C`.
Fixes#110505
This removes emit_enum_variant and the emit_usize calls that resulted
in. In libcore this eliminates 17% of leb128, taking us from 8964488 to
7383842 leb128's serialized.
Rollup of 10 pull requests
Successful merges:
- #118521 (Enable address sanitizer for MSVC targets using INFERASANLIBS linker flag)
- #119026 (std::net::bind using -1 for openbsd which in turn sets it to somaxconn.)
- #119195 (Make named_asm_labels lint not trigger on unicode and trigger on format args)
- #119204 (macro_rules: Less hacky heuristic for using `tt` metavariable spans)
- #119362 (Make `derive(Trait)` suggestion more accurate)
- #119397 (Recover parentheses in range patterns)
- #119417 (Uplift some miscellaneous coroutine-specific machinery into `check_closure`)
- #119539 (Fix typos)
- #119540 (Don't synthesize host effect args inside trait object types)
- #119555 (Add codegen test for RVO on MaybeUninit)
r? `@ghost`
`@rustbot` modify labels: rollup
Support reg_addr register class in s390x inline assembly
In s390x, `r0` cannot be used as an address register (it is evaluated as zero in an address context).
Therefore, currently, in assemblies involving memory accesses, `r0` must be [marked as clobbered](1a1155653a/src/arch/s390x.rs (L58)) or [explicitly used to a non-address](1a1155653a/src/arch/s390x.rs (L135)) or explicitly use an address register to prevent `r0` from being allocated to a register for the address.
This patch adds a register class for allocating general-purpose registers, except `r0`, to make it easier to use address registers. (powerpc already has a register class (reg_nonzero) for a similar purpose.)
This is identical to the `a` constraint in LLVM and GCC:
https://llvm.org/docs/LangRef.html#supported-constraint-code-list
> a: A 32, 64, or 128-bit integer address register (excludes R0, which in an address context evaluates as zero).
https://gcc.gnu.org/onlinedocs/gcc/Machine-Constraints.html
> a
> Address register (general purpose register except r0)
cc ``@uweigand``
r? ``@Amanieu``
Fix: Properly set vendor in i686-win7-windows-msvc target
In #118150 , setting the `vendor` field of the `i686-win7-windows-msvc` target was forgotten, preventing us from easily checking the target using `cfg(target_vendor)`.
With this PR, we set the target vendor to "win7".
This involves lots of breaking changes. There are two big changes that
force changes. The first is that the bitflag types now don't
automatically implement normal derive traits, so we need to derive them
manually.
Additionally, bitflags now have a hidden inner type by default, which
breaks our custom derives. The bitflags docs recommend using the impl
form in these cases, which I did.
Add illumos aarch64 target for rust.
This adds the newly being developed illumos aarch64 target to the rust compiler.
`@rmustacc` `@citrus-it` `@richlowe` As promissed before my hiatus :)
Enable stack probes on aarch64 for LLVM 18
I tested this on `aarch64-unknown-linux-gnu` with LLVM main (~18).
cc #77071, to be closed once we upgrade our LLVM submodule.
Add new targets {x86_64,i686}-win7-windows-msvc
This PR adds two new Tier 3 targets, x86_64-win7-windows-msvc and i686-win7-windows-msvc, that aim to support targeting Windows 7 after the `*-pc-windows-msvc` target drops support for it (slated to happen in 1.76.0).
# 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.)
This is me, `@roblabla` on github.
> - 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.
I went with naming the target `x86_64-win7-windows-msvc`, inserting the `win7` in the vendor field (usually set to to `pc`). This is done to avoid ecosystem churn, as quite a few crates have `cfg(target_os = "windows")` or `cfg(target_env = "msvc")`, but nearly no `cfg(target_vendor = "pc")`. Since my goal is to be able to seamlessly swap to the `win7` target, I figured it'd be easier this way.
> - 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 believe the naming is pretty explicit.
> - If possible, use only letters, numbers, dashes and underscores for the name. Periods (`.`) are known to cause issues in Cargo.
The name comforms to this requirement.
> - 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.
> - Anything added to the Rust repository must be under the standard Rust license (`MIT OR Apache-2.0`).
> - 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.
> - 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.
> - "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.
As far as I understand it, this target has exactly the same legal situation as the existing Tier 1 x86_64-pc-windows-msvc.
> - 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.
This target supports the whole libstd surface, since it's essentially reusing all of the x86_64-pc-windows-msvc target. Understood.
> - 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.
Wrote some documentation on how to build, test and cross-compile the target in the `platform-support` part. Hopefully it's enough to get started.
> - 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.
Understood.
> If a tier 3 target stops meeting these requirements, or the target maintainers no longer have interest or time, or the target shows no signs of activity and has not built for some time, or removing the target would improve the quality of the Rust codebase, we may post a PR to remove it; any such PR will be CCed to the target maintainers (and potentially other people who have previously worked on the target), to check potential interest in improving the situation.
Understood.
Add emulated TLS support
This is a reopen of https://github.com/rust-lang/rust/pull/96317 . many android devices still only use 128 pthread keys, so using emutls can be helpful.
Currently LLVM uses emutls by default for some targets (such as android, openbsd), but rust does not use it, because `has_thread_local` is false.
This commit has some changes to allow users to enable emutls:
1. add `-Zhas-thread-local` flag to specify that std uses `#[thread_local]` instead of pthread key.
2. when using emutls, decorate symbol names to find thread local symbol correctly.
3. change `-Zforce-emulated-tls` to `-Ztls-model=emulated` to explicitly specify whether to generate emutls.
r? `@Amanieu`
These files were added to the repository but never wired up so they could
be used - and that was a few years ago without anyone noticing - so let's
remove these, they can be re-added if someone wants them.
Signed-off-by: David Wood <david@davidtw.co>
`riscv32` platform support
This PR adds the following RISCV targets to the tier 2 list of targets:
- riscv32imafc-unknown-none-elf
- riscv32im-unknown-none-elf
The rationale behind adding them directly to tier 2, is that the other bare metal targets already exist at tier 2, and these new targets are the same with an additional target feature enabled.
As well as the additional targets, this PR fills out the platform support document(s) that were previously missing.
~~The RISC-V bare metal targets don't currently have a platform support document, but this will change soon as the RISC-V team from the Rust-embedded working group will maintain these once https://github.com/davidtwco/rust/pull/1 is merged (and `@davidtwco's` upstream PR is merged after). For the time being you can cc myself or any other member of the RISC-V team: https://github.com/orgs/rust-embedded/teams/riscv.~~
> A tier 2 target must have value to people other than its maintainers. (It may still be a niche target, but it must not be exclusively useful for an inherently closed group.)
RISC-V is an open specification, used and accessible to anyone including individuals.
> A tier 2 target must have a designated team of developers (the "target maintainers") available to consult on target-specific build-breaking issues, or if necessary to develop target-specific language or library implementation details. This team must have at least 2 developers.
This rust-embedded working group's [RISCV team](https://github.com/orgs/rust-embedded/teams/riscv) will maintain these targets.
> The target must not place undue burden on Rust developers not specifically concerned with that target. Rust developers are expected to not gratuitously break a tier 2 target, but are not expected to become experts in every tier 2 target, and are not expected to provide target-specific implementations for every tier 2 target.
I don't forsee this being an issue, the RISCV team will ensure we avoid undue burden for the general Rust community.
> The target must provide documentation for the Rust community explaining how to build for the target using cross-compilation, and explaining how to run tests for the target. If at all possible, this documentation should show how to run Rust programs and tests for the target using emulation, to allow anyone to do so. If the target cannot be feasibly emulated, the documentation should explain how to obtain and work with physical hardware, cloud systems, or equivalent.
There are links to resources we maintain in the re wg org in the platform support document.
> The target must document its baseline expectations for the features or versions of CPUs, operating systems, libraries, runtime environments, and similar.
Documented in the platform support document.
> If introducing a new tier 2 or higher target that is identical to an existing Rust target except for the baseline expectations for the features or versions of CPUs, operating systems, libraries, runtime environments, and similar, then the proposed target must document to the satisfaction of the approving teams why the specific difference in baseline expectations provides sufficient value to justify a separate target.
New target features in RISCV can drastically change the capability of a CPU, hence the need for a separate target to support different variants. We aim to support any ratified RISCV extensions.
> Tier 2 targets must not leave any significant portions of core or the standard library unimplemented or stubbed out, unless they cannot possibly be supported on the target.
`core` is fully implemented.
> The code generation backend for the target should not have deficiencies that invalidate Rust safety properties, as evaluated by the Rust compiler team. (This requirement does not apply to arbitrary security enhancements or mitigations provided by code generation backends, only to those properties needed to ensure safe Rust code cannot cause undefined behavior or other unsoundness.) If this requirement does not hold, the target must clearly and prominently document any such limitations as part of the target's entry in the target tier list, and ideally also via a failing test in the testsuite. The Rust compiler team must be satisfied with the balance between these limitations and the difficulty of implementing the necessary features.
RISCV is a well-established and well-maintained LLVM backend. To the best of my knowledge, the backend won't cause the generated code to have undefined behaviour.
> If the target supports C code, and the target has an interoperable calling convention for C code, the Rust target must support that C calling convention for the platform via extern "C". The C calling convention does not need to be the default Rust calling convention for the target, however.
The C calling convention is supported by RISCV.
> The target must build reliably in CI, for all components that Rust's CI considers mandatory.
For the last 4-5 years many of these RISCV targets have been building in CI without any known issues.
> The approving teams may additionally require that a subset of tests pass in CI, such as enough to build a functional "hello world" program, ./x.py test --no-run, or equivalent "smoke tests". In particular, this requirement may apply if the target builds host tools, or if the tests in question provide substantial value via early detection of critical problems.
Not applicable, in the future we may wish to add qemu tests but this is out of scope for now.
> Building the target in CI must not take substantially longer than the current slowest target in CI, and should not substantially raise the maintenance burden of the CI infrastructure. This requirement is subjective, to be evaluated by the infrastructure team, and will take the community importance of the target into account.
To the best of my knowledge, this will not induce a burden on the current CI infra.
> Tier 2 targets should, if at all possible, support cross-compiling. Tier 2 targets should not require using the target as the host for builds, even if the target supports host tools.
Cross-compilation is supported and documented in the platform support document.
> In addition to the legal requirements for all targets (specified in the tier 3 requirements), because a tier 2 target typically involves the Rust project building and supplying various compiled binaries, incorporating the target and redistributing any resulting compiled binaries (e.g. built libraries, host tools if any) must not impose any onerous license requirements on any members of the Rust project, including infrastructure team members and those operating CI systems. This is a subjective requirement, to be evaluated by the approving teams.
There are no additional license issues to worry about.
> Tier 2 targets must not impose burden on the authors of pull requests, or other developers in the community, to ensure that tests pass for 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 tests failing for the target. Do not send automated messages or notifications (via any medium, including via `@)` to a PR author or others involved with a PR regarding the PR breaking tests on a tier 2 target, unless they have opted into such messages.
The RISCV team agrees not to do this.
> The target maintainers should regularly run the testsuite for the target, and should fix any test failures in a reasonably timely fashion.
The RISCV team will fix any issues in a timely manner.
Currently LLVM uses emutls by default
for some targets (such as android, openbsd),
but rust does not use it, because `has_thread_local` is false.
This commit has some changes to allow users to enable emutls:
1. add `-Zhas-thread-local` flag to specify
that std uses `#[thread_local]` instead of pthread key.
2. when using emutls, decorate symbol names
to find thread local symbol correctly.
3. change `-Zforce-emulated-tls` to `-Ztls-model=emulated`
to explicitly specify whether to generate emutls.
Use `unwinding` crate for unwinding on Xous platform
This patch adds support for using [unwinding](https://github.com/nbdd0121/unwinding) on platforms where libunwinding isn't viable. An example of such a platform is `riscv32imac-unknown-xous-elf`.
### Background
The Rust project maintains a fork of llvm at [llvm-project](https://github.com/rust-lang/llvm-project/) where it applies patches on top of the llvm project. This mostly seems to be to get unwinding support for the SGX project, and there may be other patches that I'm unaware of.
There is a lot of machinery in the build system to support compiling `libunwind` on other platforms, and I needed to add additional patches to llvm in order to add support for Xous.
Rather than continuing down this path, it seemed much easier to use a Rust-based library. The `unwinding` crate by `@nbdd0121` fits this description perfectly.
### Future work
This could potentially replace the custom patches for `libunwind` on other platforms such as SGX, and could enable unwinding support on many more exotic platforms.
### Anti-goals
This is not designed to replace `libunwind` on tier-one platforms or those where unwinding support already exists. There is already a well-established approach for unwinding there. Instead, this aims to enable unwinding on new platforms where C++ code may be difficult to compile.
