The WebAssembly targets of rustc have weird issues around name mangling
and import the same name from different modules. This all largely stems
from the fact that we're using literal symbol names in LLVM IR to
represent what a function is called when it's imported, and we're not
using the wasm-specific `wasm-import-name` attribute. This in turn leads
to two issues:
* If, in the same codegen unit, the same FFI symbol is referenced twice
then rustc, when translating to LLVM IR, will only reference one
symbol from the first wasm module referenced.
* There's also a bug in LLD [1] where even if two codegen units
reference different modules, having the same symbol names means that
LLD coalesces the symbols and only refers to one wasm module.
Put another way, all our imported wasm symbols from the environment are
keyed off their LLVM IR symbol name, which has lots of collisions today.
This commit fixes the issue by implementing two changes:
1. All wasm symbols with `#[link(wasm_import_module = "...")]` are
mangled by default in LLVM IR. This means they're all given unique names.
2. Symbols then use the `wasm-import-name` attribute to ensure that the
WebAssembly file uses the correct import name.
When put together this should ensure we don't trip over the LLD bug [1]
and we also codegen IR correctly always referencing the right symbols
with the right import module/name pairs.
Closes#50021Closes#56309Closes#63562
[1]: https://bugs.llvm.org/show_bug.cgi?id=44316
.gitignore: Don't ignore a file that exists in the repository
.gitignore should not ignore files that exist in the repository. The
ignore of .cargo applies to the committed .cargo directory used in an
example:
$ git ls-files --exclude-standard --ignored
src/test/run-make/thumb-none-qemu/example/.cargo/config
Explicitly un-ignore that file.
make transparent enums more ordinary
By recognizing that structs & unions have one variant, we can make the treatment of transparent enums less ad-hoc.
cc https://github.com/rust-lang/rust/issues/60405
r? @davidtwco
Delete flaky test net::tcp::tests::fast_rebind
This test is unreliable for at least 3 users on two platforms: see #57509 and #51006. It was added 5 years ago in #22015. Do we know whether this is testing something important that would indicate a bug in our implementation, or if it's fine to remove?
r? @sfackler @alexcrichton because this somewhat resembles #59018Closes#57509. Closes#51006.
Improve code generated for `starts_with(<literal char>)`
This PR includes two minor improvements to the code generated when checking for string prefix/suffix.
The first commit simplifies the str/str operation, by taking advantage of the raw UTF-8 representation.
The second commit replaces the current str/char matching logic with a char->str encoding and then the previous method.
The resulting code should be equivalent in the generic case (one char is being encoded versus one char being decoded), but it becomes easy to optimize in the case of a literal char, which in most cases a developer might expect to be at least as simple as that of a literal string.
This PR should fix#41993
.gitignore should not ignore files that exist in the repository. The
ignore of .cargo applies to the committed .cargo directory used in an
example:
$ git ls-files --exclude-standard --ignored
src/test/run-make/thumb-none-qemu/example/.cargo/config
Explicitly un-ignore that file.
Stabilize the `core::panic` module
`std::panic` is already stable.
`core::panic::PanicInfo` and `core::panic::Location` are stable and can be used through that path because of a bug in stability checking: #15702
Stabilize `std::{rc,sync}::Weak::{weak_count, strong_count}`
* Original PR: #56696
* Tracking issue: #57977Closes: #57977
Supporting comments:
> Although these were added for testing, it is occasionally useful to have a way to probe optimistically for whether a weak pointer has become dangling, without actually taking the overhead of manipulating atomics. Are there any plans to stabilize this?
_Originally posted by @bdonlan in https://github.com/rust-lang/rust/issues/57977#issuecomment-516970921_
> Having this stabilized would help. Currently, the only way to check if a weak pointer has become dangling is to call `upgrade`, which is by far expensive.
_Originally posted by @glebpom in https://github.com/rust-lang/rust/issues/57977#issuecomment-526934709_
Not sure if stabilizing these warrants a full RFC, so throwing this out here as a start for now.
Note: per CONTRIBUTING.md, I ran the tidy checks, but they seem to be failing on unchanged files (primarily in `src/stdsimd`).
This code was added to avoid UB in LLVM 6 and earlier, but we no longer support those LLVM versions.
Since https://reviews.llvm.org/D47807 (released in LLVM 7), uitofp does exactly what we need.
Closes#51872
Restore original implementation of Vec::retain
This PR reverts #48065, which aimed to optimize `Vec::retain` by making use of `Vec::drain_filter`. Unfortunately at that time, `drain_filter` was unsound.
The soundness hole in `Vec::drain_filter` was fixed in #61224 by guaranteeing that cleanup logic runs via a nested `Drop`, even in the event of a panic. Implementing this nested drop affects codegen (apparently?) and results in slower code.
Fixes#65970
Enable `loop` and `while` in constants behind a feature flag
This PR is an initial implementation of #52000. It adds a `const_loop` feature gate, which allows `while` and `loop` expressions through both HIR and MIR const-checkers if enabled. `for` expressions remain forbidden by the HIR const-checker, since they desugar to a call to `IntoIterator::into_iter`, which will be rejected anyways.
`while` loops also require [`#![feature(const_if_match)]`](https://github.com/rust-lang/rust/pull/66507), since they have a conditional built into them. The diagnostics from the HIR const checker will suggest this to the user.
r? @oli-obk
cc @rust-lang/wg-const-eval
