Add tests for raw-dylib with vectorcall, and fix vectorcall code generation
* Adds tests for using `raw-dylib` (#58713) with `vectorcall`.
* Fixed code generation for `vectorcall` (parameters have to be marked with `InReg`, just like `fastcall`).
* Enabled running the `raw-dylib` `fastcall` tests when using MSVC (since I had to add support in the test for running MSVC-only tests since GCC doesn't support `vectorcall`).
Fix thumbv4t-none-eabi frame pointer setting
The `thumb_base` profile has changed since I last remember seeing it, and now it sets the frame pointer to "always keep", which is not desired for this target. Hooking a debugger to the running program is not really done, it's preferable to have the register available for actual program use, so the default "may omit" is now set.
I thought that the target was already using "may omit" when I checked on it last month, because I forgot that the target was previously based on `thumb_base` rather than `Default::default()`. I only noticed the issue just now when creating the `armv4t-none-eabi` target (https://github.com/rust-lang/rust/pull/99226), though this PR is not in any way conditional on that one.
This initial implementation handles transmutations between types with specified layouts, except when references are involved.
Co-authored-by: Igor null <m1el.2027@gmail.com>
Rollup of 6 pull requests
Successful merges:
- #99298 (Make `ui-fulldeps/gated-plugins` and `ui-fulldeps/multiple-plugins` tests stage 2 only)
- #99396 (Add some additional double-adjustment regression tests)
- #99449 (Do not resolve associated const when there is no provided value)
- #99595 (Mark atomics as unsupported on thumbv6m)
- #99627 (Lock stdout once when listing tests)
- #99638 (Remove Clean trait implementation for hir::Ty and middle::Ty)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Mark atomics as unsupported on thumbv6m
The thumbv6m target does not support atomics. Historically, LLVM
had a bug where atomic load/stores for this target were emitted
as plain load/stores rather than as libatomic calls. This was
fixed in https://reviews.llvm.org/D120026, which will be part of
LLVM 15. As we require that "atomic support" does not use libatomic,
we need to indicate that this target does not have native atomics.
Add support for LLVM ShadowCallStack.
LLVMs ShadowCallStack provides backward edge control flow integrity protection by using a separate shadow stack to store and retrieve a function's return address.
LLVM currently only supports this for AArch64 targets. The x18 register is used to hold the pointer to the shadow stack, and therefore this only works on ABIs which reserve x18. Further details are available in the [LLVM ShadowCallStack](https://clang.llvm.org/docs/ShadowCallStack.html) docs.
# Usage
`-Zsanitizer=shadow-call-stack`
# Comments/Caveats
* Currently only enabled for the aarch64-linux-android target
* Requires the platform to define a runtime to initialize the shadow stack, see the [LLVM docs](https://clang.llvm.org/docs/ShadowCallStack.html) for more detail.
The thumbv6m target does not support atomics. Historically, LLVM
had a bug where atomic load/stores for this target were emitted
as plain load/stores rather than as libatomic calls. This was
fixed in https://reviews.llvm.org/D120026, which will be part of
LLVM 15. As we require that "atomic support" does not use libatomic,
we need to indicate that this target does not have native atomics.
Use constant eval to do strict mem::uninit/zeroed validity checks
I'm not sure about the code organisation here, I just dumped the check in rustc_const_eval at the root. Not hard to move it elsewhere, in any case.
Also, this means cranelift codegen intrinsics lose the strict checks, since they don't seem to depend on rustc_const_eval, and I didn't see a point in keeping around two copies.
I also left comments in the is_zero_valid methods about "uhhh help how do i do this", those apply to both methods equally.
Also rustc_codegen_ssa now depends on rustc_const_eval... is this okay?
Pinging `@RalfJung` since you were the one who mentioned this to me, so I'm assuming you're interested.
Haven't had a chance to run full tests on this since it's really warm, and it's 1AM, I'll check out any failures/comments in the morning :)
DWARF version 5 brings a number of improvements over version 4. Quoting from
the announcement [1]:
> Version 5 incorporates improvements in many areas: better data compression,
> separation of debugging data from executable files, improved description of
> macros and source files, faster searching for symbols, improved debugging
> optimized code, as well as numerous improvements in functionality and
> performance.
On platforms where DWARF version 5 is supported (Linux, primarily), this commit
adds support for it behind a new `-Z dwarf-version=5` flag.
[1]: https://dwarfstd.org/Public_Review.php
rustc_target: Remove some redundant target properties
`is_like_emscripten` is equivalent to `os == "emscripten"`, so it's removed.
`is_like_fuchsia` is equivalent to `os == "fuchsia"`, so it's removed.
`is_like_osx` also falls into the same category and is equivalent to `vendor == "apple"`, but it's commonly used so I kept it as is for now.
`is_like_(solaris,windows,wasm)` are combinations of different operating systems or architectures (see compiler/rustc_target/src/spec/tests/tests_impl.rs) so they are also kept as is.
I think `is_like_wasm` (and maybe `is_like_osx`) are sufficiently closed sets, so we can remove these fields as well and replace them with methods like `fn is_like_wasm() { arch == "wasm32" || arch == "wasm64" }`.
On other hand, `is_like_solaris` and `is_like_windows` are sufficiently open and I can imagine custom targets introducing other values for `os`.
This is kind of a gray area.
Make debug_triple depend on target json file content rather than file path
This ensures that changes to target json files will force a recompilation. And more importantly that moving the files doesn't force a recompilation.
This should fix https://github.com/Rust-for-Linux/linux/issues/792 (cc ``@ojeda)``
Removes debug settings from wasm32_unknown_emscripten default link args
This is a debug setting. We should only make debug builds if user requests
a debug build. Currently this is inserted in release builds.
Furthermore, it would be better to insert these settings in --pre-link-args
because then it would be possible to override them if appropriate. Because
these are inserted at the end, it is necessary to patch emscripten to remove
them.
``@sbc100``
This is a debug setting. We should only make debug builds if user requests
a debug build. Currently this is inserted in release builds.
Furthermore, it would be better to insert these settings in --pre-link-args
because then it would be possible to override them if appropriate. Because
these are inserted at the end, it is necessary to patch emscripten to remove
them.
Relax mipsel-sony-psp's linker script
Previously, the linker script forcefully kept all `.lib.stub` sections, unnecessarily bloating the binary. Now, the script is LTO and `--gc-sections` friendly.
`--nmagic` was also added to the linker, because page alignment is not required on the PSP. This further reduces binary size.
Accompanying changes for the `psp` crate are found in: https://github.com/overdrivenpotato/rust-psp/pull/118
Previously, the linker script forcefully kept all `.lib.stub` sections,
unnecessarily bloating the binary. Now, the script is LTO and
`--gc-sections` friendly.
`--nmagic` was also added to the linker, because page alignment is not
required on the PSP. This further reduces binary size.
Accompanying changes for the PSP crate are found in:
https://github.com/overdrivenpotato/rust-psp/pull/118
Add support for emitting functions with `coldcc` to LLVM
The eventual goal is to try using this for things like the internal panicking stuff, to see whether it helps.
Remove migrate borrowck mode
Closes#58781Closes#43234
# Stabilization proposal
This PR proposes the stabilization of `#![feature(nll)]` and the removal of `-Z borrowck`. Current borrow checking behavior of item bodies is currently done by first infering regions *lexically* and reporting any errors during HIR type checking. If there *are* any errors, then MIR borrowck (NLL) never occurs. If there *aren't* any errors, then MIR borrowck happens and any errors there would be reported. This PR removes the lexical region check of item bodies entirely and only uses MIR borrowck. Because MIR borrowck could never *not* be run for a compiled program, this should not break any programs. It does, however, change diagnostics significantly and allows a slightly larger set of programs to compile.
Tracking issue: #43234
RFC: https://github.com/rust-lang/rfcs/blob/master/text/2094-nll.md
Version: 1.63 (2022-06-30 => beta, 2022-08-11 => stable).
## Motivation
Over time, the Rust borrow checker has become "smarter" and thus allowed more programs to compile. There have been three different implementations: AST borrowck, MIR borrowck, and polonius (well, in progress). Additionally, there is the "lexical region resolver", which (roughly) solves the constraints generated through HIR typeck. It is not a full borrow checker, but does emit some errors.
The AST borrowck was the original implementation of the borrow checker and was part of the initially stabilized Rust 1.0. In mid 2017, work began to implement the current MIR borrow checker and that effort ompleted by the end of 2017, for the most part. During 2018, efforts were made to migrate away from the AST borrow checker to the MIR borrow checker - eventually culminating into "migrate" mode - where HIR typeck with lexical region resolving following by MIR borrow checking - being active by default in the 2018 edition.
In early 2019, migrate mode was turned on by default in the 2015 edition as well, but with MIR borrowck errors emitted as warnings. By late 2019, these warnings were upgraded to full errors. This was followed by the complete removal of the AST borrow checker.
In the period since, various errors emitted by the MIR borrow checker have been improved to the point that they are mostly the same or better than those emitted by the lexical region resolver.
While there do remain some degradations in errors (tracked under the [NLL-diagnostics tag](https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3ANLL-diagnostics), those are sufficiently small and rare enough that increased flexibility of MIR borrow check-only is now a worthwhile tradeoff.
## What is stabilized
As said previously, this does not fundamentally change the landscape of accepted programs. However, there are a [few](https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3ANLL-fixed-by-NLL) cases where programs can compile under `feature(nll)`, but not otherwise.
There are two notable patterns that are "fixed" by this stabilization. First, the `scoped_threads` feature, which is a continutation of a pre-1.0 API, can sometimes emit a [weird lifetime error](https://github.com/rust-lang/rust/issues/95527) without NLL. Second, actually seen in the standard library. In the `Extend` impl for `HashMap`, there is an implied bound of `K: 'a` that is available with NLL on but not without - this is utilized in the impl.
As mentioned before, there are a large number of diagnostic differences. Most of them are better, but some are worse. None are serious or happen often enough to need to block this PR. The biggest change is the loss of error code for a number of lifetime errors in favor of more general "lifetime may not live long enough" error. While this may *seem* bad, the former error codes were just attempts to somewhat-arbitrarily bin together lifetime errors of the same type; however, on paper, they end up being roughly the same with roughly the same kinds of solutions.
## What isn't stabilized
This PR does not completely remove the lexical region resolver. In the future, it may be possible to remove that (while still keeping HIR typeck) or to remove it together with HIR typeck.
## Tests
Many test outputs get updated by this PR. However, there are number of tests specifically geared towards NLL under `src/test/ui/nll`
## History
* On 2017-07-14, [tracking issue opened](https://github.com/rust-lang/rust/issues/43234)
* On 2017-07-20, [initial empty MIR pass added](https://github.com/rust-lang/rust/pull/43271)
* On 2017-08-29, [RFC opened](https://github.com/rust-lang/rfcs/pull/2094)
* On 2017-11-16, [Integrate MIR type-checker with NLL](https://github.com/rust-lang/rust/pull/45825)
* On 2017-12-20, [NLL feature complete](https://github.com/rust-lang/rust/pull/46862)
* On 2018-07-07, [Don't run AST borrowck on mir mode](https://github.com/rust-lang/rust/pull/52083)
* On 2018-07-27, [Add migrate mode](https://github.com/rust-lang/rust/pull/52681)
* On 2019-04-22, [Enable migrate mode on 2015 edition](https://github.com/rust-lang/rust/pull/59114)
* On 2019-08-26, [Don't downgrade errors on 2015 edition](https://github.com/rust-lang/rust/pull/64221)
* On 2019-08-27, [Remove AST borrowck](https://github.com/rust-lang/rust/pull/64790)
interpret: better control over whether we read data with provenance
The resolution in https://github.com/rust-lang/unsafe-code-guidelines/issues/286 seems to be that when we load data at integer type, we implicitly strip provenance. So let's implement that in Miri at least for scalar loads. This makes use of the fact that `Scalar` layouts distinguish pointer-sized integers and pointers -- so I was expecting some wild bugs where layouts set this incorrectly, but so far that does not seem to happen.
This does not entirely implement the solution to https://github.com/rust-lang/unsafe-code-guidelines/issues/286; we still do the wrong thing for integers in larger types: we will `copy_op` them and then do validation, and validation will complain about the provenance. To fix that we need mutating validation; validation needs to strip the provenance rather than complaining about it. This is a larger undertaking (but will also help resolve https://github.com/rust-lang/miri/issues/845 since we can reset padding to `Uninit`).
The reason this is useful is that we can now implement `addr` as a `transmute` from a pointer to an integer, and actually get the desired behavior of stripping provenance without exposing it!
riscv32imac-unknown-xous-elf: add target
This PR starts the process of upstreaming support for our operating system, thanks to a suggestion from `@yaahc` [on Twitter](https://twitter.com/yaahc_/status/1530558574706839567?s=20&t=Mgkn1LEYvGU6FEi5SpZRsA). We have maintained a fork of Rust and have made changes to improve support for our platform since Rust 1.51. Now we would like to upstream these changes.
Xous is a microkernel operating system designed to run on small systems. The kernel contains a wide range of userspace processes that provide common services such as console output, networking, and time access.
The kernel and its services are completely written in Rust using a custom build of libstd. This adds support for this target to upstream Rust so that we can drop support for our out-of-tree `target.json` file.
This first patch adds a Tier 3 target for Xous running on RISC-V. Future patches will add libstd support, but those patches require changes to `dlmalloc` and `compiler_builtins`.
> Tier 3 policy:
>
> A tier 3 target must have a designated developer or developers (the "target maintainers") on record to be CCed when issues arise regarding the target. (The mechanism to track and CC such developers may evolve over time.)
I will be the target maintainer for this target on matters that pertain to the `xous` part of the triple. For matters pertaining to the `riscv32imac` part of the triple, there should be no difference from all other `riscv` targets. If there are issues, I will address issues regarding the target.
> Targets must use naming consistent with any existing targets; for instance, a target for the same CPU or OS as an existing Rust target should use the same name for that CPU or OS. Targets should normally use the same names and naming conventions as used elsewhere in the broader ecosystem beyond Rust (such as in other toolchains), unless they have a very good reason to diverge. Changing the name of a target can be highly disruptive, especially once the target reaches a higher tier, so getting the name right is important even for a tier 3 target.
This is a new OS, so I have taken the `riscv32imac-unknown-none-elf` target and changed the `os` section of the triple. This follows convention on targets such as `riscv32gc-unknown-linux-gnu` and `mipsel-unknown-linux-uclibc`. An argument could be made for omitting the `-elf` section of the triple, such as `riscv32imc-esp-espidf`, however I'm not certain what benefit that has.
> Target names should not introduce undue confusion or ambiguity unless absolutely necessary to maintain ecosystem compatibility. For example, if the name of the target makes people extremely likely to form incorrect beliefs about what it targets, the name should be changed or augmented to disambiguate it.
I feel that the target name does not introduce any ambiguity.
> Tier 3 targets may have unusual requirements to build or use, but must not create legal issues or impose onerous legal terms for the Rust project or for Rust developers or users.
The only unusual requirement for building the `compiler-builtins` crate is a standard RISC-V C compiler supported by `cc-rs`, and using this target does not require any additional software beyond what is shipped by `rustup`.
> The target must not introduce license incompatibilities.
All of the additional code will use Apache-2.0.
> Anything added to the Rust repository must be under the standard Rust license (MIT OR Apache-2.0).
Agreed, and there is no problem here.
> The target must not cause the Rust tools or libraries built for any other host (even when supporting cross-compilation to the target) to depend on any new dependency less permissive than the Rust licensing policy. This applies whether the dependency is a Rust crate that would require adding new license exceptions (as specified by the tidy tool in the rust-lang/rust repository), or whether the dependency is a native library or binary. In other words, the introduction of the target must not cause a user installing or running a version of Rust or the Rust tools to be subject to any new license requirements.
The only new dependency will be the `xous` crate, which is licensed `MIT OR Apache-2.0`
> Compiling, linking, and emitting functional binaries, libraries, or other code for the target (whether hosted on the target itself or cross-compiling from another target) must not depend on proprietary (non-FOSS) libraries. Host tools built for the target itself may depend on the ordinary runtime libraries supplied by the platform and commonly used by other applications built for the target, but those libraries must not be required for code generation for the target; cross-compilation to the target must not require such libraries at all. For instance, rustc built for the target may depend on a common proprietary C runtime library or console output library, but must not depend on a proprietary code generation library or code optimization library. Rust's license permits such combinations, but the Rust project has no interest in maintaining such combinations within the scope of Rust itself, even at tier 3.
Linking is performed by `rust-lld`
> "onerous" here is an intentionally subjective term. At a minimum, "onerous" legal/licensing terms include but are not limited to: non-disclosure requirements, non-compete requirements, contributor license agreements (CLAs) or equivalent, "non-commercial"/"research-only"/etc terms, requirements conditional on the employer or employment of any particular Rust developers, revocable terms, any requirements that create liability for the Rust project or its developers or users, or any requirements that adversely affect the livelihood or prospects of the Rust project or its developers or users.
There are no terms. Xous is completely open. It runs on open hardware. We even provide the source to the CPU.
> 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 paragraph makes sense, but I don't think it's directed at me.
> 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.
This paragraph also does not appear to be directed at me.
> 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.
So far we have:
* Thread
* Mutexex
* Condvar
* TcpStream
* TcpListener
* UdpSocket
* DateTime
* alloc
These will be merged as part of libstd in a future patch once I submit support for Xous in `dlmalloc` and `compiler-builtins`.
> 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.
Testing is currently done on real hardware or in a Renode emulator. I can add documentation on how to do this in a future patch, and I would need instructions on where to add said documentation.
> 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.
Alright.
> 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.
Sounds good.
> 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.
This shouldn't affect any other targets, so this is understood.
> 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 shouldn't come up right away. `xous` is a new operating system, and most features are keyed off of `target(os = "xous")` rather than a given architecture.
Xous is a microkernel operating system designed to run on small systems.
The kernel contains a wide range of userspace processes that provide
common services such as console output, networking, and time access.
The kernel and its services are completely written in Rust using a
custom build of libstd. This adds support for this target to upstream
Rust so that we can drop support for our out-of-tree `target.json` file.
Add a Tier 3 target for Xous running on RISC-V.
Signed-off-by: Sean Cross <sean@xobs.io>
- The logic is now unified for all targets (wasm targets should also be supported now)
- Additional "symlink" files like `ld64` are eliminated
- lld-wrapper is used for propagating the correct lld flavor
- Cleanup "unwrap or exit" logic in lld-wrapper
Fix codegen bug in "ptx-kernel" abi related to arg passing
I found a codegen bug in the nvptx abi related to that args are passed as ptrs ([see comment](https://github.com/rust-lang/rust/issues/38788#issuecomment-1048999928)), this is not as specified in the [ptx-interoperability doc](https://docs.nvidia.com/cuda/ptx-writers-guide-to-interoperability/) or how C/C++ does it. It will also almost always fail in practice since device/host uses different memory spaces for most hardware.
This PR fixes the bug and add tests for passing structs to ptx kernels.
I observed that all nvptx assembly tests had been marked as [ignore a long time ago](https://github.com/rust-lang/rust/pull/59752#issuecomment-501713428). I'm not sure if the new one should be marked as ignore, it passed on my computer but it might fail if ptx-linker is missing on the server? I guess this is outside scope for this PR and should be looked at in a different issue/PR.
I only fixed the nvptx64-nvidia-cuda target and not the potential code paths for the non-existing 32bit target. Even though 32bit nvptx is not a supported target there are still some code under the hood supporting codegen for 32 bit ptx. I was advised to create an MCP to find out if this code should be removed or updated.
Perhaps ``@RDambrosio016`` would have interest in taking a quick look at this.
asm: Add a kreg0 register class on x86 which includes k0
Previously we only exposed a kreg register class which excludes the k0
register since it can't be used in many instructions. However k0 is a
valid register and we need to have a way of marking it as clobbered for
clobber_abi.
Fixes#94977
Previously we only exposed a kreg register class which excludes the k0
register since it can't be used in many instructions. However k0 is a
valid register and we need to have a way of marking it as clobbered for
clobber_abi.
Fixes#94977
allow large Size again
This basically reverts most of https://github.com/rust-lang/rust/pull/80042, and instead does the panic in `bits()` with a `#[cold]` function to make sure it does not get inlined.
https://github.com/rust-lang/rust/pull/80042 added a comment about an invariant ("The top 3 bits are ALWAYS zero") that is not actually enforced, and if it were enforced that would be a problem for https://github.com/rust-lang/rust/pull/95388. So I think we should not have that invariant, and I adjusted the code accordingly.
r? `@oli-obk` Cc `@sivadeilra`
ARMv6K Horizon OS has_thread_local support
cc. ```@ian-h-chamberlain```
cc. ```@AzureMarker```
Being an ARM target, it has always had built-in support for `#[thread_local]`. This PR comes in just now because we were testing `std::thread` support with `thread_local_dtor`s. This will hopefully be the last PR for the target specification, unless anymore features will be needed as time goes on.
Fold aarch64 feature +fp into +neon
Arm's FEAT_FP and Feat_AdvSIMD describe the same thing on AArch64:
The Neon unit, which handles both floating point and SIMD instructions.
Moreover, a configuration for AArch64 must include both or neither.
Arm says "entirely proprietary" toolchains may omit floating point:
https://developer.arm.com/documentation/102374/0101/Data-processing---floating-point
In the Programmer's Guide for Armv8-A, Arm says AArch64 can have
both FP and Neon or neither in custom implementations:
https://developer.arm.com/documentation/den0024/a/AArch64-Floating-point-and-NEON
In "Bare metal boot code for Armv8-A", enabling Neon and FP
is just disabling the same trap flag:
https://developer.arm.com/documentation/dai0527/a
In an unlikely future where "Neon and FP" become unrelated,
we can add "[+-]fp" as its own feature flag.
Until then, we can simplify programming with Rust on AArch64 by
folding both into "[+-]neon", which is valid as it supersets both.
"[+-]neon" is retained for niche uses such as firmware, kernels,
"I just hate floats", and so on.
I am... pretty sure no one is relying on this.
An argument could be made that, as we are not an "entirely proprietary" toolchain, we should not support AArch64 without floats at all. I think that's a bit excessive. However, I want to recognize the intent: programming for AArch64 should be simplified where possible. For x86-64, programmers regularly set up illegal feature configurations because it's hard to understand them, see https://github.com/rust-lang/rust/issues/89586. And per the above notes, plus the discussion in https://github.com/rust-lang/rust/issues/86941, there should be no real use cases for leaving these features split: the two should in fact always go together.
- Fixesrust-lang/rust#95002.
- Fixesrust-lang/rust#95064.
- Fixesrust-lang/rust#95122.
Arm's FEAT_FP and Feat_AdvSIMD describe the same thing on AArch64:
The Neon unit, which handles both floating point and SIMD instructions.
Moreover, a configuration for AArch64 must include both or neither.
Arm says "entirely proprietary" toolchains may omit floating point:
https://developer.arm.com/documentation/102374/0101/Data-processing---floating-point
In the Programmer's Guide for Armv8-A, Arm says AArch64 can have
both FP and Neon or neither in custom implementations:
https://developer.arm.com/documentation/den0024/a/AArch64-Floating-point-and-NEON
In "Bare metal boot code for Armv8-A", enabling Neon and FP
is just disabling the same trap flag:
https://developer.arm.com/documentation/dai0527/a
In an unlikely future where "Neon and FP" become unrelated,
we can add "[+-]fp" as its own feature flag.
Until then, we can simplify programming with Rust on AArch64 by
folding both into "[+-]neon", which is valid as it supersets both.
"[+-]neon" is retained for niche uses such as firmware, kernels,
"I just hate floats", and so on.
`Layout` is another type that is sometimes interned, sometimes not, and
we always use references to refer to it so we can't take any advantage
of the uniqueness properties for hashing or equality checks.
This commit renames `Layout` as `LayoutS`, and then introduces a new
`Layout` that is a newtype around an `Interned<LayoutS>`. It also
interns more layouts than before. Previously layouts within layouts
(via the `variants` field) were never interned, but now they are. Hence
the lifetime on the new `Layout` type.
Unlike other interned types, these ones are in `rustc_target` instead of
`rustc_middle`. This reflects the existing structure of the code, which
does layout-specific stuff in `rustc_target` while `TyAndLayout` is
generic over the `Ty`, allowing the type-specific stuff to occur in
`rustc_middle`.
The commit also adds a `HashStable` impl for `Interned`, which was
needed. It hashes the contents, unlike the `Hash` impl which hashes the
pointer.
