Stabilize `-Zdwarf-version` as `-Cdwarf-version`
I propose stabilizing `-Zdwarf-version` as `-Cdwarf-version`. This PR adds a new `-Cdwarf-version` flag, leaving the unstable `-Z` flag as is to ease the transition period. The `-Z` flag will be removed in the future.
# `-Zdwarf-version` stabilization report
## What is the RFC for this feature and what changes have occurred to the user-facing design since the RFC was finalized?
No RFC/MCP, this flag was added in https://github.com/rust-lang/rust/pull/98350 and was not deemed large enough to require additional process.
The tracking issue for this feature is #103057.
## What behavior are we committing to that has been controversial? Summarize the major arguments pro/con.
None that has been extensively debated but there are a few questions that could have been chosen differently:
1. What should the flag name be?
The current flag name is very specific to DWARF. Other debuginfo formats exist (msvc's CodeView format or https://en.wikipedia.org/wiki/Stabs) so we could have chosen to generalize the flag name (`-{C,Z} debuginfo-version=dwarf-5` for example). While this would extend cleanly to support formats other than DWARF, there are some downsides to this design. Neither CodeView nor Stabs have specification or format versions so it's not clear what values would be supported beyond `dwarf-{2,3,4,5}` or `codeview`. We would also need to take care to ensure the name does not lead users to think they can pick a format other than one supported by the target. For instance, what would `--target x86_64-pc-windows-msvc -Cdebuginfo-version=dwarf-5` do?
2. What is the behavior when flag is used on targets that do not support DWARF?
Currently, passing `-{C,Z} dwarf-version` on targets like `*-windows-msvc` does not do anything. It may be preferable to emit a warning alerting the user that the flag has no effect on the target platform. Alternatively, we could emit an error but this could be annoying since it would require the use of target specific RUSTFLAGS to use the flag correctly (and there isn't a way to target "any platform that uses DWARF" using cfgs).
3. Does the precompiled standard library potentially using a different version of DWARF a problem?
I don't believe this is an issue as debuggers (and other such tools) already must deal with the possibility that an application uses different DWARF versions across its statically or dynamically linked libraries.
## Are there extensions to this feature that remain unstable? How do we know that we are not accidentally committing to those.
No extensions per se, although future DWARF versions could be considered as such. At present, we validate the requested DWARF version is between 2 and 5 (inclusive) so new DWARF versions will not automatically be supported until the validation logic is adjusted.
## Summarize the major parts of the implementation and provide links into the code (or to PRs)
- Targets define their preferred or default DWARF version: 34a5ea911c/compiler/rustc_target/src/spec/mod.rs (L2369)
- We use the target default but this can be overriden by `-{C,Z} dwarf-version` 34a5ea911c/compiler/rustc_session/src/session.rs (L738)
- The flag is validated 34a5ea911c/compiler/rustc_session/src/session.rs (L1253-L1258)
- When debuginfo is generated, we tell LLVM to use the requested value or the target default 34a5ea911c/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs (L106)
## Summarize existing test coverage of this feature
- Test that we actually generate the appropriate DWARF version
- https://github.com/rust-lang/rust/blob/master/tests/assembly/dwarf5.rs
- https://github.com/rust-lang/rust/blob/master/tests/assembly/dwarf4.rs
- Test that LTO with different DWARF versions picks the highest version
- https://github.com/rust-lang/rust/blob/master/tests/assembly/dwarf-mixed-versions-lto.rs
- Test DWARF versions 2-5 are valid while 0, 1 and 6 report an error
- https://github.com/rust-lang/rust/blob/master/tests/ui/debuginfo/dwarf-versions.rs
- Ensure LLVM does not report a warning when LTO'ing different DWARF versions together
- https://github.com/rust-lang/rust/blob/master/tests/ui/lto/dwarf-mixed-versions-lto.rs
## Has a call-for-testing period been conducted? If so, what feedback was received?
No call-for-testing has been conducted but Rust for Linux has been using this flag without issue.
## What outstanding bugs in the issue tracker involve this feature? Are they stabilization-blocking?
All reported bugs have been resolved.
## Summarize contributors to the feature by name for recognition and assuredness that people involved in the feature agree with stabilization
- Initial implementation in https://github.com/rust-lang/rust/pull/98350 by `@pcwalton`
- Stop emitting `.debug_pubnames` and `.debug_pubtypes` when using DWARF 5 in https://github.com/rust-lang/rust/pull/117962 by `@weihanglo.`
- Refactoring & cleanups (#135739), fix LLVM warning on LTO with different DWARF versions (#136659) and argument validation (#136746) by `@wesleywiser`
## What FIXMEs are still in the code for that feature and why is it ok to leave them there?
No FIXMEs related to this feature.
## What static checks are done that are needed to prevent undefined behavior?
This feature cannot cause undefined behavior.
We ensure the DWARF version is one of the supported values [here](34a5ea911c/compiler/rustc_session/src/session.rs (L1255-L1257)).
## In what way does this feature interact with the reference/specification, and are those edits prepared?
No changes to reference/spec, unstable rustc docs are moved to the stable book as part of the stabilization PR.
## Does this feature introduce new expressions and can they produce temporaries? What are the lifetimes of those temporaries?
No.
## What other unstable features may be exposed by this feature?
`-Zembed-source` requires use of DWARF 5 extensions but has its own feature gate.
## What is tooling support like for this feature, w.r.t rustdoc, clippy, rust-analzyer, rustfmt, etc.?
No support needed for rustdoc, clippy, rust-analyzer, rustfmt or rustup.
Cargo could expose this as an option in build profiles but I would expect the decision as to what version should be used would be made for the entire crate graph at build time rather than by individual package authors.
cc-rs has support for detecting the presence of `-{C,Z} dwarf-version` in `RUSTFLAGS` and providing the corresponding flag to Clang/gcc (https://github.com/rust-lang/cc-rs/pull/1395).
---
Closes#103057
Some architectures (like s390x) require strings to be 2 byte aligned.
Therefor the section name will be marked with a .2 postfix on this
architectures.
Allowing a section name with a .1 or .2 postfix will make the test pass
on either platform.
Fix breakage when running compiletest with `--test-args=--edition=2015`
Compiletest has an `--edition` flag to change the default edition tests are run with. Unfortunately no test suite successfully executes when that flag is passed. If the edition is set to something greater than 2015 the breakage is expected, since the test suite currently supports only edition 2015 (Ferrous Systems will open an MCP about fixing that soonish). Surprisingly, the test suite is also broken if `--edition=2015` is passed to compiletest. This PR focuses on fixing the latter.
This PR fixes the two categories of failures happening when `--edition=2015` is passed:
* Some edition-specific tests set their edition through `//@ compile-flags` instead of `//@ edition`. Compiletest doesn't parse the compile flags, so it would see no `//@ edition` and add another `--edition` flag, leading to a rustc error.
* Compiletest would add the edition after `//@ compile-flags`, while some tests depend on flags passed to `//@ compile-flags` being the last flags in the rustc invocation.
Note that for the first category, I opted to manually go and replace all `//@ compile-flags` setting an edition with an explicit `//@ edition`. We could've changed compiletest to instead check whether an edition was set in `//@ compile-flags`, but I thought it was better to enforce a consistent way to set the edition in tests.
I also added the edition to the stamp, so that changing `--edition` results in tests being re-executed.
r? `@jieyouxu`
rustc_target: update x86_win64 to match the documented calling convention for f128
llvm/llvm-project@5ee1c0b714 updates llvm to match the documented calling convention to pass f128 indirectly. This change makes us do that on all versions of LLVM, not just starting with LLVM 21.
`@rustbot` label llvm-main
try-job: dist-x86_64-msvc
try-job: dist-x86_64-mingw
try-job: x86_64-msvc-1
try-job: x86_64-msvc-2
try-job: x86_64-mingw-1
try-job: x86_64-mingw-2
Avoid wrapping constant allocations in packed structs when not necessary
This way LLVM will set the string merging flag if the alloc is a nul terminated string, reducing binary sizes.
try-job: armhf-gnu
Lower BinOp::Cmp to llvm.{s,u}cmp.* intrinsics
Lowers `mir::BinOp::Cmp` (`three_way_compare` intrinsic) to the corresponding LLVM `llvm.{s,u}cmp.i8.*` intrinsics.
These are the intrinsics mentioned in https://github.com/rust-lang/rust/pull/118310, which are now available in LLVM 19.
I couldn't find any follow-up PRs/discussions about this, please let me know if I missed something.
r? `@scottmcm`
Some tests expect to be compiled for a specific CPU or require certain
target features to be present (or absent). These tests work fine with
default CPUs but fail in downstream builds for RHEL and Fedora, where
we use non-default CPUs such as z13 on s390x, pwr9 on ppc64le, or
x86-64-v2/x86-64-v3 on x86_64.
attempt to support `BinaryFormat::Xcoff` in `naked_asm!`
Fixes https://github.com/rust-lang/rust/issues/137219
So, the inline assembly support for xcoff is extremely limited. The LLVM [XCOFFAsmParser](1b25c0c4da/llvm/lib/MC/MCParser/XCOFFAsmParser.cpp) does not support many of the attributes that LLVM itself emits, and that should exist based on [the assembler docs](https://www.ibm.com/docs/en/ssw_aix_71/assembler/assembler_pdf.pdf). It also does accept some that should not exist based on those docs.
So, I've tried to do the best I can given those limitations. At least it's better than emitting the directives for elf and having that fail somewhere deep in LLVM. Given that inline assembly for this target is incomplete (under `asm_experimental_arch`), I think that's OK (and again I don't see how we can do better given the limitations in LLVM).
r? ```@Noratrieb``` (given that you reviewed https://github.com/rust-lang/rust/pull/136637)
It seems reasonable to ping the [`powerpc64-ibm-aix` target maintainers](https://doc.rust-lang.org/rustc/platform-support/aix.html), hopefully they have thoughts too: ```@daltenty``` ```@gilamn5tr```
Remove i586-pc-windows-msvc
See [MCP 840](https://github.com/rust-lang/compiler-team/issues/840).
I left a specialized error message that should help users that hit this in the wild (for example, because they use it in their CI).
```
error: Error loading target specification: the `i586-pc-windows-msvc` target has been removed. Use the `i686-pc-windows-msvc` target instead.
Windows 10 (the minimum required OS version) requires a CPU baseline of at least i686 so you can safely switch. Run `rustc --print target-list` for a list of built-in targets
```
``@workingjubilee`` ``@calebzulawski`` fyi portable-simd uses this target in CI, if you wanna remove it already before this happens
Remove `:` from `stack-protector-heuristics-effect.rs` Filecheck Pattern
With function sections, the assembly label does not necessarily end in `:`.
Remove trailing `:` to be more consistent with the rest of the existing Filecheck patterns.
```
// CHECK-LABEL: local_string_addr_taken
#[no_mangle]
pub fn local_string_addr_taken(f: fn(&String)) {
let x = String::new();
f(&x);
```
Make x86 QNX target name consistent with other Rust targets
Rename target to be consistent with other Rust targets: Use `i686` instead of `i586`
See also
- #136495
- #109173
CC: `@jonathanpallant` `@japaric` `@gh-tr` `@samkearney`
Create a generic AVR target: avr-none
This commit removes the `avr-unknown-gnu-atmega328` target and replaces it with a more generic `avr-none` variant that must be specialized using `-C target-cpu` (e.g. `-C target-cpu=atmega328p`).
Seizing the day, I'm adding myself as the maintainer of this target - I've been already fixing the bugs anyway, might as well make it official 🙂
Related discussions:
- https://github.com/rust-lang/rust/pull/131171
- https://github.com/rust-lang/compiler-team/issues/800
try-job: x86_64-gnu-debug
This commit removes the `avr-unknown-gnu-atmega328` target and replaces
it with a more generic `avr-none` variant that must be specialized with
the `-C target-cpu` flag (e.g. `-C target-cpu=atmega328p`).
Stabilize target_feature_11
# Stabilization report
This is an updated version of https://github.com/rust-lang/rust/pull/116114, which is itself a redo of https://github.com/rust-lang/rust/pull/99767. Most of this commit and report were copied from those PRs. Thanks ```@LeSeulArtichaut``` and ```@calebzulawski!```
## Summary
Allows for safe functions to be marked with `#[target_feature]` attributes.
Functions marked with `#[target_feature]` are generally considered as unsafe functions: they are unsafe to call, cannot *generally* be assigned to safe function pointers, and don't implement the `Fn*` traits.
However, calling them from other `#[target_feature]` functions with a superset of features is safe.
```rust
// Demonstration function
#[target_feature(enable = "avx2")]
fn avx2() {}
fn foo() {
// Calling `avx2` here is unsafe, as we must ensure
// that AVX is available first.
unsafe {
avx2();
}
}
#[target_feature(enable = "avx2")]
fn bar() {
// Calling `avx2` here is safe.
avx2();
}
```
Moreover, once https://github.com/rust-lang/rust/pull/135504 is merged, they can be converted to safe function pointers in a context in which calling them is safe:
```rust
// Demonstration function
#[target_feature(enable = "avx2")]
fn avx2() {}
fn foo() -> fn() {
// Converting `avx2` to fn() is a compilation error here.
avx2
}
#[target_feature(enable = "avx2")]
fn bar() -> fn() {
// `avx2` coerces to fn() here
avx2
}
```
See the section "Closures" below for justification of this behaviour.
## Test cases
Tests for this feature can be found in [`tests/ui/target_feature/`](f6cb952dc1/tests/ui/target-feature).
## Edge cases
### Closures
* [target-feature 1.1: should closures inherit target-feature annotations? #73631](https://github.com/rust-lang/rust/issues/73631)
Closures defined inside functions marked with #[target_feature] inherit the target features of their parent function. They can still be assigned to safe function pointers and implement the appropriate `Fn*` traits.
```rust
#[target_feature(enable = "avx2")]
fn qux() {
let my_closure = || avx2(); // this call to `avx2` is safe
let f: fn() = my_closure;
}
```
This means that in order to call a function with #[target_feature], you must guarantee that the target-feature is available while the function, any closures defined inside it, as well as any safe function pointers obtained from target-feature functions inside it, execute.
This is usually ensured because target features are assumed to never disappear, and:
- on any unsafe call to a `#[target_feature]` function, presence of the target feature is guaranteed by the programmer through the safety requirements of the unsafe call.
- on any safe call, this is guaranteed recursively by the caller.
If you work in an environment where target features can be disabled, it is your responsibility to ensure that no code inside a target feature function (including inside a closure) runs after this (until the feature is enabled again).
**Note:** this has an effect on existing code, as nowadays closures do not inherit features from the enclosing function, and thus this strengthens a safety requirement. It was originally proposed in #73631 to solve this by adding a new type of UB: “taking a target feature away from your process after having run code that uses that target feature is UB” .
This was motivated by userspace code already assuming in a few places that CPU features never disappear from a program during execution (see i.e. 2e29bdf908/crates/std_detect/src/detect/arch/x86.rs); however, concerns were raised in the context of the Linux kernel; thus, we propose to relax that requirement to "causing the set of usable features to be reduced is unsafe; when doing so, the programmer is required to ensure that no closures or safe fn pointers that use removed features are still in scope".
* [Fix #[inline(always)] on closures with target feature 1.1 #111836](https://github.com/rust-lang/rust/pull/111836)
Closures accept `#[inline(always)]`, even within functions marked with `#[target_feature]`. Since these attributes conflict, `#[inline(always)]` wins out to maintain compatibility.
### ABI concerns
* [The extern "C" ABI of SIMD vector types depends on target features #116558](https://github.com/rust-lang/rust/issues/116558)
The ABI of some types can change when compiling a function with different target features. This could have introduced unsoundness with target_feature_11, but recent fixes (#133102, #132173) either make those situations invalid or make the ABI no longer dependent on features. Thus, those issues should no longer occur.
### Special functions
The `#[target_feature]` attribute is forbidden from a variety of special functions, such as main, current and future lang items (e.g. `#[start]`, `#[panic_handler]`), safe default trait implementations and safe trait methods.
This was not disallowed at the time of the first stabilization PR for target_features_11, and resulted in the following issues/PRs:
* [`#[target_feature]` is allowed on `main` #108645](https://github.com/rust-lang/rust/issues/108645)
* [`#[target_feature]` is allowed on default implementations #108646](https://github.com/rust-lang/rust/issues/108646)
* [#[target_feature] is allowed on #[panic_handler] with target_feature 1.1 #109411](https://github.com/rust-lang/rust/issues/109411)
* [Prevent using `#[target_feature]` on lang item functions #115910](https://github.com/rust-lang/rust/pull/115910)
## Documentation
* Reference: [Document the `target_feature_11` feature reference#1181](https://github.com/rust-lang/reference/pull/1181)
---
cc tracking issue https://github.com/rust-lang/rust/issues/69098
cc ```@workingjubilee```
cc ```@RalfJung```
r? ```@rust-lang/lang```
tests: `-Copt-level=3` instead of `-O` in assembly tests
An effective blocker for redefining the meaning of `-O` is to stop reusing this somewhat ambiguous alias in our own assembly test suite. The choice between `-Copt-level=2` and `-Copt-level=3` is arbitrary for most of our tests. In most cases it makes no difference, so I set most of them to `-Copt-level=3`, as it will lead to slightly more "normalized" assembly.
Add amdgpu target
Add amdgpu target to rustc and enable the LLVM target.
Fix compiling `core` with the amdgpu:
The amdgpu backend makes heavy use of different address spaces. This
leads to situations, where a pointer in one addrspace needs to be casted
to a pointer in a different addrspace. `bitcast` is invalid for this
case, `addrspacecast` needs to be used.
Fix compilation failures that created bitcasts for such cases by
creating pointer casts (which creates an `addrspacecast` under the hood)
instead.
MCP: https://github.com/rust-lang/compiler-team/issues/823
Tracking issue: #135024
Kinda related to the original amdgpu tracking issue #51575 (though that one has been closed for a while).
Pick the max DWARF version when LTO'ing modules with different versions
Currently, when rustc compiles code with `-Clto` enabled that was built
with different choices for `-Zdwarf-version`, a warning will be
reported. It's very easy to observe this by compiling most anything (eg,
"hello world") and specifying `-Clto -Zdwarf-version=5` since the
standard library is distributed with `-Zdwarf-version=4`.
This behavior isn't actually useful for a few reasons:
- From observation, LLVM chooses to pick the highest DWARF version
anyway after issuing the warning.
- Clang specifies that in this case, the max version should be picked
without a warning and as a general principle, we want to support
x-lang LTO with Clang which implies using the same module flag merge
behaviors.
- Debuggers need to be able to handle a variety of versions within the
same debugging session as you can easily have some parts of a binary
(or some dynamic libraries within an application) all compiled with
different DWARF versions.
This commit changes the module flag merge behavior to match Clang and
use the highest version of DWARF. It also adds a test to ensure this
behavior is respected in the case of two crates being LTO'd together and
adds a test to ensure no warning is printed.
Fixes#130041 which fails due to these warnings being printed
cc #103057
