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(cherry picked from commit e245570def155191b61f73647eb543dd45685b2f)
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rustc_target: document public AbiMap-related fn and variants
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workingjubilee:redescribe-rustc_target-more-accurately, r=wesleywiser
Refresh module-level docs for `rustc_target::spec`
We have long since gone on a curveball from the flexible-target-specification RFC by introducing stability and soundness promises to the language and compiler which we often struggle with extending to target-specific implementation details. Indeed, we often *literally cannot*. We also have modified the search algorithm details. Update the comments for `rustc_target::spec` considerably.
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add `extern "custom"` functions
tracking issue: rust-lang/rust#140829
previous discussion: https://github.com/rust-lang/rust/issues/140566
In short, an `extern "custom"` function is a function with a custom ABI, that rust does not know about. Therefore, such functions can only be defined with `#[unsafe(naked)]` and `naked_asm!`, or via an `extern "C" { /* ... */ }` block. These functions cannot be called using normal rust syntax: calling them can only be done from inline assembly.
The motivation is low-level scenarios where a custom calling convention is used. Currently, we often pick `extern "C"`, but that is a lie because the function does not actually respect the C calling convention.
At the moment `"custom"` seems to be the name with the most support. That name is not final, but we need to pick something to actually implement this.
r? `@traviscross`
cc `@tgross35`
try-job: x86_64-apple-2
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r=workingjubilee
Add (back) `unsupported_calling_conventions` lint to reject more invalid calling conventions
This adds back the `unsupported_calling_conventions` lint that was removed in https://github.com/rust-lang/rust/pull/129935, in order to start the process of dealing with https://github.com/rust-lang/rust/issues/137018. Specifically, we are going for the plan laid out [here](https://github.com/rust-lang/rust/issues/137018#issuecomment-2672118326):
- thiscall, stdcall, fastcall, cdecl should only be accepted on x86-32
- vectorcall should only be accepted on x86-32 and x86-64
The difference to the status quo is that:
- We stop accepting stdcall, fastcall on targets that are windows && non-x86-32 (we already don't accept these on targets that are non-windows && non-x86-32)
- We stop accepting cdecl on targets that are non-x86-32
- (There is no difference for thiscall, this was already a hard error on non-x86-32)
- We stop accepting vectorcall on targets that are windows && non-x86-*
Vectorcall is an unstable ABI so we can just make this a hard error immediately. The others are stable, so we emit the `unsupported_calling_conventions` forward-compat lint. I set up the lint to show up in dependencies via cargo's future-compat report immediately, but we could also make it show up just for the local crate first if that is preferred.
try-job: i686-msvc-1
try-job: x86_64-msvc-1
try-job: test-various
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store `target.min_global_align` as an `Align`
Parse the alignment properly when the target is defined/parsed, and error out on invalid alignment values. That means this work doesn't need to happen for every global in each backend.
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compiler: Add track_caller to AbiMapping::unwrap
Same reason as it is on Option's.
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Add new Tier-3 targets: `loongarch32-unknown-none*`
MCP: https://github.com/rust-lang/compiler-team/issues/865
NOTE: LoongArch32 ELF object support is available starting with object v0.37.0.
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calling conventions
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workingjubilee:apple-likes-frame-pointers-but-not-that-much, r=madsmtm
compiler: set Apple frame pointers by architecture
All Apple targets stop overriding this configuration and instead use the default base of FramePointer::NonLeaf, which means some Apples will have less frame pointers in leaf functions.
r? ``@madsmtm``
cc ``@thomcc``
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Apple targets can now overriding this configuration and instead use the
default based on their architecture, which means aarch64 targets now
have less frame pointers in leaf functions.
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Same reason as it is on Option's.
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MCP: https://github.com/rust-lang/compiler-team/issues/865
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Replace ad-hoc ABI "adjustments" with an `AbiMap` to `CanonAbi`
Our `conv_from_spec_abi`, `adjust_abi`, and `is_abi_supported` combine to give us a very confusing way of reasoning about what _actual_ calling convention we want to lower our code to and whether we want to compile the resulting code at all. Instead of leaving this code as a miniature adventure game in which someone tries to combine stateful mutations into a Rube Goldberg machine that will let them escape the maze and arrive at the promised land of codegen, we let `AbiMap` devour this complexity. Once you have an `AbiMap`, you can answer which `ExternAbi`s will lower to what `CanonAbi`s (and whether they will lower at all).
Removed:
- `conv_from_spec_abi` replaced by `AbiMap::canonize_abi`
- `adjust_abi` replaced by same
- `Conv::PreserveAll` as unused
- `Conv::Cold` as unused
- `enum Conv` replaced by `enum CanonAbi`
target-spec.json changes:
- If you have a target-spec.json then now your "entry-abi" key will be specified in terms of one of the `"{abi}"` strings Rust recognizes, e.g.
```json
"entry-abi": "C",
"entry-abi": "win64",
"entry-abi": "aapcs",
```
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`adjust_abi` is not needed and `is_abi_supported` can be a 1-liner.
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makes entry_abi a lowering of the ABI string, so now it can be
```json
"entry_abi": "C",
"entry_abi": "win64",
"entry_abi": "aapcs",
```
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- Add AbiMapping for encoding the nuance of deprecated ABIs
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* https://maskray.me/blog/2023-06-18-port-llvm-xray-to-apple-systems
* https://github.com/llvm/llvm-project/blob/llvmorg-20.1.4/clang/lib/Driver/XRayArgs.cpp#L31
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workingjubilee:aarch64-linux-should-use-frame-pointers, r=compiler-errors
aarch64-linux: Default to FramePointer::NonLeaf
For aarch64-apple and aarch64-windows, platform docs state that code must use frame pointers correctly. This is because the AAPCS64 mandates that a platform specify its frame pointer conformance requirements:
- Apple: https://developer.apple.com/documentation/xcode/writing-arm64-code-for-apple-platforms#Respect-the-purpose-of-specific-CPU-registers
- Windows: https://learn.microsoft.com/en-us/cpp/build/arm64-windows-abi-conventions?view=msvc-170#integer-registers
- AAPCS64: https://github.com/ARM-software/abi-aa/blob/4492d1570eb70c8fd146623e0db65b2d241f12e7/aapcs64/aapcs64.rst#the-frame-pointer
Unwinding code either requires unwind tables or frame pointers, and on aarch64 the expectation is that one can use frame pointers for this. Most Linux targets represent a motley variety of possible distributions, so it is unclear who to defer to on conformance, other than perhaps Arm. In the absence of a specific edict for a given aarch64-linux target, Rust will assume aarch64-linux targets also use non-leaf frame pointers. This reflects what compilers like clang do.
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[win][arm64] Remove 'Arm64 Hazard' undocumented MSVC option and instead disable problematic test
PR #140758 added the undocumented `/arm64hazardfree` MSVC linker flag to work around a test failure where LLVM generated code that would trip a hazard in an outdated ARM processor.
Adding this flag caused issues with LLD, as it doesn't recognize it.
Rethinking the issue, using the undocumented flag seems like the incorrect solution: there's no guarantee that the flag won't be removed in the future, or change its meaning.
Instead, I've disabled the problematic test for Arm64 Windows and have filed a bug with the MSVC team to have the check removed: <https://developercommunity.microsoft.com/t/Remove-checking-for-and-fixing-Cortex-A/10905134>
This PR supersedes #140977
r? ```@jieyouxu```
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For aarch64-apple and aarch64-windows, platform docs state that code
must use frame pointers correctly. This is because the AAPCS64 mandates
that a platform specify its frame pointer conformance requirements:
- Apple: https://developer.apple.com/documentation/xcode/writing-arm64-code-for-apple-platforms#Respect-the-purpose-of-specific-CPU-registers
- Windows: https://learn.microsoft.com/en-us/cpp/build/arm64-windows-abi-conventions?view=msvc-170#integer-registers
- AAPCS64: https://github.com/ARM-software/abi-aa/blob/4492d1570eb70c8fd146623e0db65b2d241f12e7/aapcs64/aapcs64.rst#the-frame-pointer
Unwinding code either requires unwind tables or frame pointers, and
on aarch64 the expectation is that one can use frame pointers for this.
Most Linux targets represent a motley variety of possible distributions,
so it is unclear who to defer to on conformance, other than perhaps Arm.
In the absence of a specific edict for a given aarch64-linux target,
Rust will assume aarch64-linux targets use non-leaf frame pointers.
This reflects what compilers like clang do.
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disable problematic test
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Unfortunately, multiple people are reporting linker warnings related to
`__rust_no_alloc_shim_is_unstable` after this change. The solution isn't
quite clear yet, let's revert to green for now, and try a reland with a
determined solution for `__rust_no_alloc_shim_is_unstable`.
This reverts commit c8b7f32434c0306db5c1b974ee43443746098a92, reversing
changes made to 667247db71ea18c4130dd018d060e7f09d589490.
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Enable non-leaf Frame Pointers for Arm64 Windows
Microsoft recommends enabling frame pointers for Arm64 Windows as it enables fast stack walking, from <https://learn.microsoft.com/en-us/cpp/build/arm64-windows-abi-conventions?view=msvc-170#integer-registers>:
> The frame pointer (x29) is required for compatibility with fast stack walking used by ETW and other services. It must point to the previous {x29, x30} pair on the stack.
I'm setting this to "non-leaf" as leaf functions shouldn't be spilling registers and so won't touch the frame pointer.
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Fix linking statics on Arm64EC
Arm64EC builds recently started to fail due to the linker not finding a symbol:
```
symbols.o : error LNK2001: unresolved external symbol #_ZN3std9panicking11EMPTY_PANIC17hc8d2b903527827f1E (EC Symbol)
C:\Code\hello-world\target\arm64ec-pc-windows-msvc\debug\deps\hello_world.exe : fatal error LNK1120: 1 unresolved externals
```
It turns out that `EMPTY_PANIC` is a new static variable that was being exported then imported from the standard library, but when exporting LLVM didn't prepend the name with `#` (as only functions are prefixed with this character), whereas Rust was prefixing with `#` when attempting to import it.
The fix is to have Rust not prefix statics with `#` when importing.
Adding tests discovered another issue: we need to correctly mark static exported from dylibs with `DATA`, otherwise MSVC's linker assumes they are functions and complains that there is no exit thunk for them.
CI found another bug: we only apply `DllImport` to non-local statics that aren't foreign items (i.e., in an `extern` block), that is we want to use `DllImport` for statics coming from other Rust crates. However, `__rust_no_alloc_shim_is_unstable` is a static generated by the Rust compiler if required, but downstream crates consider it a foreign item since it is declared in an `extern "Rust"` block, thus they do not apply `DllImport` to it and so fails to link if it is exported by the previous crate as `DATA`. The fix is to apply `DllImport` to foreign items that are marked with the `rustc_std_internal_symbol` attribute (i.e., we assume they aren't actually foreign and will be in some Rust crate).
Fixes #138541
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try-job: dist-aarch64-msvc
try-job: dist-x86_64-msvc
try-job: x86_64-msvc-1
try-job: x86_64-msvc-2
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Co-authored-by: Jubilee <workingjubilee@gmail.com>
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mitigate MSVC alignment issue on x86-32
This implements mitigation for https://github.com/rust-lang/rust/issues/112480 by stopping to emit `align` attributes on loads and function arguments when building for a win32 MSVC target. MSVC is known to not properly align `u64` and similar types, and claiming to LLVM that everything is properly aligned increases the chance that this will cause problems.
Of course, the misalignment is still a bug, but we can't fix that bug, only MSVC can.
Also add an errata note to the platform support page warning users about this known problem.
try-job: `i686-msvc*`
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Rollup of 8 pull requests
Successful merges:
- #138934 (support config extensions)
- #139091 (Rewrite on_unimplemented format string parser.)
- #139753 (Make `#[naked]` an unsafe attribute)
- #139762 (Don't assemble non-env/bound candidates if projection is rigid)
- #139834 (Don't canonicalize crate paths)
- #139868 (Move `pal::env` to `std::sys::env_consts`)
- #139978 (Add citool command for generating a test dashboard)
- #139995 (Clean UI tests 4 of n)
r? `@ghost`
`@rustbot` modify labels: rollup
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Move `pal::env` to `std::sys::env_consts`
Combine the `std::env::consts` platform implementations as a single file. Use the Unix file as the base, since it has 28 entries, and fold the 8 singleton platforms into it. The Unix file was roughly grouped into Linux, Apple, BSD, and everything else, roughly in alphabetical order. Alphabetically order them to make it easier to maintain and discard the Unix-specific groups to generalize it to all platforms.
I'd prefer to have no fallback implementation, as I consider it a bug; however TEEOS, Trusty, and Xous have no definitions here. Since they otherwise have `pal` abstractions, that indicates that there are several platforms without `pal` abstractions which are also missing here. To support unsupported, create a little macro to handle the fallback case and not introduce ordering between the `cfg`s like `cfg_if!`.
I've named the module `std::sys::env_consts`, because they are used in `std::env::consts` and I intend to use the name `std::sys::env` for the combination of `Args` and `Vars`.
cc `@joboet` `@ChrisDenton`
Tracked in #117276.
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On Windows 7 32-bit, the alignment characteristic of the TLS Directory
don't appear to be respected by the PE Loader, leading to crashes. As
a result, let's disable has_thread_local to make sure TLS goes through
the emulation layer.
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Rollup of 9 pull requests
Successful merges:
- #135340 (Add `explicit_extern_abis` Feature and Enforce Explicit ABIs)
- #139440 (rustc_target: RISC-V: feature addition batch 2)
- #139667 (cfi: Remove #[no_sanitize(cfi)] for extern weak functions)
- #139828 (Don't require rigid alias's trait to hold)
- #139854 (Improve parse errors for stray lifetimes in type position)
- #139889 (Clean UI tests 3 of n)
- #139894 (Fix `opt-dist` CLI flag and make it work without LLD)
- #139900 (stepping into impls for normalization is unproductive)
- #139915 (replace some #[rustc_intrinsic] usage with use of the libcore declarations)
r? `@ghost`
`@rustbot` modify labels: rollup
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The "B" extension is ratified as a combination of three extensions: "Zba",
"Zbb" and "Zbs". To maximize discoverability of the RISC-V target features,
this commit makes use of the "B" extension instead of its three members.
This way, `#[cfg(target_feature = "b")]` can also be used instead of:
`#[cfg(all(target_feature = "zba", target_feature = "zbb", target_feature = "zbs"))]`
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