LLVM really dislikes this and will assert, saying something along the
lines of:
```
rustc: llvm/lib/MC/MCSubtargetInfo.cpp:60: void ApplyFeatureFlag(
llvm::FeatureBitset&, llvm::StringRef, llvm::ArrayRef<llvm::SubtargetFeatureKV>
): Assertion
`SubtargetFeatures::hasFlag(Feature) && "Feature flags should start with '+' or '-'"`
failed.
```
No branch protection metadata unless enabled
Even if we emit metadata disabling branch protection, this metadata may
conflict with other modules (e.g. during LTO) that have different branch
protection metadata set.
This is an unstable flag and feature, so ideally the flag not being
specified should act as if the feature wasn't implemented in the first
place.
Additionally this PR also ensures we emit an error if
`-Zbranch-protection` is set on targets other than the supported
aarch64. For now the error is being output from codegen, but ideally it
should be moved to earlier in the pipeline before stabilization.
debuginfo: Simplify TypeMap used during LLVM debuginfo generation.
This PR simplifies the TypeMap that is used in `rustc_codegen_llvm::debuginfo::metadata`. It was unnecessarily complicated because it was originally implemented when types were not yet normalized before codegen. So it did it's own normalization and kept track of multiple unnormalized types being mapped to a single unique id.
This PR is based on https://github.com/rust-lang/rust/pull/93503, which is not merged yet.
The PR also removes the arena used for allocating string ids and instead uses `InlinableString` from the [inlinable_string](https://crates.io/crates/inlinable_string) crate. That might not be the best choice, since that crate does not seem to be very actively maintained. The [flexible-string](https://crates.io/crates/flexible-string) crate would be an alternative.
r? `@ghost`
Use undef for (some) partially-uninit constants
There needs to be some limit to avoid perf regressions on large arrays
with undef in each element (see comment in the code).
Fixes: #84565
Original PR: #83698
Depends on LLVM 14: #93577
properly handle fat pointers to uninhabitable types
Calculate the pointee metadata size by using `tcx.struct_tail_erasing_lifetimes` instead of duplicating the logic in `fat_pointer_kind`. Open to alternatively suggestions on how to fix this.
Fixes#94149
r? ````@michaelwoerister```` since you touched this code last, I think!
Partially move cg_ssa towards using a single builder
Not all codegen backends can handle hopping between blocks well. For example Cranelift requires blocks to be terminated before switching to building a new block. Rust-gpu requires a `RefCell` to allow hopping between blocks and cg_gcc currently has a buggy implementation of hopping between blocks. This PR reduces the amount of cases where cg_ssa switches between blocks before they are finished and mostly fixes the block hopping in cg_gcc. (~~only `scalar_to_backend` doesn't handle it correctly yet in cg_gcc~~ fixed that one.)
`@antoyo` please review the cg_gcc changes.
Change `char` type in debuginfo to DW_ATE_UTF
Rust previously encoded the `char` type as DW_ATE_unsigned_char. The more appropriate encoding is `DW_ATE_UTF`.
Clang also uses the DW_ATE_UTF for `char32_t` in C++.
This fixes the display of the `char` type in the Windows debuggers. Without this change, the variable did not show in the locals window.
LLDB 13 is also able to display the char value, when before it failed with `need to add support for DW_TAG_base_type 'char' encoded with DW_ATE = 0x8, bit_size = 32`
r? `@wesleywiser`
Rust previously encoded the `char` type as DW_ATE_unsigned_char. The more
appropriate encoding is DW_ATE_UTF.
Clang uses this same debug encoding for char32_t.
This fixes the display of `char` types in Windows debuggers as well as LLDB.
The previous implementation was written before types were properly
normalized for code generation and had to assume a more complicated
relationship between types and their debuginfo -- generating separate
identifiers for debuginfo nodes that were based on normalized types.
Since types are now already normalized, we can use them as identifiers
for debuginfo nodes.
Improve `unused_unsafe` lint
I’m going to add some motivation and explanation below, particularly pointing the changes in behavior from this PR.
_Edit:_ Looking for existing issues, looks like this PR fixes#88260.
_Edit2:_ Now also contains code that closes#90776.
Main motivation: Fixes some issues with the current behavior. This PR is
more-or-less completely re-implementing the unused_unsafe lint; it’s also only
done in the MIR-version of the lint, the set of tests for the `-Zthir-unsafeck`
version no longer succeeds (and is thus disabled, see `lint-unused-unsafe.rs`).
On current nightly,
```rs
unsafe fn unsf() {}
fn inner_ignored() {
unsafe {
#[allow(unused_unsafe)]
unsafe {
unsf()
}
}
}
```
doesn’t create any warnings. This situation is not unrealistic to come by, the
inner `unsafe` block could e.g. come from a macro. Actually, this PR even
includes removal of one unused `unsafe` in the standard library that was missed
in a similar situation. (The inner `unsafe` coming from an external macro hides
the warning, too.)
The reason behind this problem is how the check currently works:
* While generating MIR, it already skips nested unsafe blocks (i.e. unsafe
nested in other unsafe) so that the inner one is always the one considered
unused
* To differentiate the cases of no unsafe operations inside the `unsafe` vs.
a surrounding `unsafe` block, there’s some ad-hoc magic walking up the HIR to
look for surrounding used `unsafe` blocks.
There’s a lot of problems with this approach besides the one presented above.
E.g. the MIR-building uses checks for `unsafe_op_in_unsafe_fn` lint to decide
early whether or not `unsafe` blocks in an `unsafe fn` are redundant and ought
to be removed.
```rs
unsafe fn granular_disallow_op_in_unsafe_fn() {
unsafe {
#[deny(unsafe_op_in_unsafe_fn)]
{
unsf();
}
}
}
```
```
error: call to unsafe function is unsafe and requires unsafe block (error E0133)
--> src/main.rs:13:13
|
13 | unsf();
| ^^^^^^ call to unsafe function
|
note: the lint level is defined here
--> src/main.rs:11:16
|
11 | #[deny(unsafe_op_in_unsafe_fn)]
| ^^^^^^^^^^^^^^^^^^^^^^
= note: consult the function's documentation for information on how to avoid undefined behavior
warning: unnecessary `unsafe` block
--> src/main.rs:10:5
|
9 | unsafe fn granular_disallow_op_in_unsafe_fn() {
| --------------------------------------------- because it's nested under this `unsafe` fn
10 | unsafe {
| ^^^^^^ unnecessary `unsafe` block
|
= note: `#[warn(unused_unsafe)]` on by default
```
Here, the intermediate `unsafe` was ignored, even though it contains a unsafe
operation that is not allowed to happen in an `unsafe fn` without an additional `unsafe` block.
Also closures were problematic and the workaround/algorithms used on current
nightly didn’t work properly. (I skipped trying to fully understand what it was
supposed to do, because this PR uses a completely different approach.)
```rs
fn nested() {
unsafe {
unsafe { unsf() }
}
}
```
```
warning: unnecessary `unsafe` block
--> src/main.rs:10:9
|
9 | unsafe {
| ------ because it's nested under this `unsafe` block
10 | unsafe { unsf() }
| ^^^^^^ unnecessary `unsafe` block
|
= note: `#[warn(unused_unsafe)]` on by default
```
vs
```rs
fn nested() {
let _ = || unsafe {
let _ = || unsafe { unsf() };
};
}
```
```
warning: unnecessary `unsafe` block
--> src/main.rs:9:16
|
9 | let _ = || unsafe {
| ^^^^^^ unnecessary `unsafe` block
|
= note: `#[warn(unused_unsafe)]` on by default
warning: unnecessary `unsafe` block
--> src/main.rs:10:20
|
10 | let _ = || unsafe { unsf() };
| ^^^^^^ unnecessary `unsafe` block
```
*note that this warning kind-of suggests that **both** unsafe blocks are redundant*
--------------------------------------------------------------------------------
I also dislike the fact that it always suggests keeping the outermost `unsafe`.
E.g. for
```rs
fn granularity() {
unsafe {
unsafe { unsf() }
unsafe { unsf() }
unsafe { unsf() }
}
}
```
I prefer if `rustc` suggests removing the more-course outer-level `unsafe`
instead of the fine-grained inner `unsafe` blocks, which it currently does on nightly:
```
warning: unnecessary `unsafe` block
--> src/main.rs:10:9
|
9 | unsafe {
| ------ because it's nested under this `unsafe` block
10 | unsafe { unsf() }
| ^^^^^^ unnecessary `unsafe` block
|
= note: `#[warn(unused_unsafe)]` on by default
warning: unnecessary `unsafe` block
--> src/main.rs:11:9
|
9 | unsafe {
| ------ because it's nested under this `unsafe` block
10 | unsafe { unsf() }
11 | unsafe { unsf() }
| ^^^^^^ unnecessary `unsafe` block
warning: unnecessary `unsafe` block
--> src/main.rs:12:9
|
9 | unsafe {
| ------ because it's nested under this `unsafe` block
...
12 | unsafe { unsf() }
| ^^^^^^ unnecessary `unsafe` block
```
--------------------------------------------------------------------------------
Needless to say, this PR addresses all these points. For context, as far as my
understanding goes, the main advantage of skipping inner unsafe blocks was that
a test case like
```rs
fn top_level_used() {
unsafe {
unsf();
unsafe { unsf() }
unsafe { unsf() }
unsafe { unsf() }
}
}
```
should generate some warning because there’s redundant nested `unsafe`, however
every single `unsafe` block _does_ contain some statement that uses it. Of course
this PR doesn’t aim change the warnings on this kind of code example, because
the current behavior, warning on all the inner `unsafe` blocks, makes sense in this case.
As mentioned, during MIR building all the unsafe blocks *are* kept now, and usage
is attributed to them. The way to still generate a warning like
```
warning: unnecessary `unsafe` block
--> src/main.rs:11:9
|
9 | unsafe {
| ------ because it's nested under this `unsafe` block
10 | unsf();
11 | unsafe { unsf() }
| ^^^^^^ unnecessary `unsafe` block
|
= note: `#[warn(unused_unsafe)]` on by default
warning: unnecessary `unsafe` block
--> src/main.rs:12:9
|
9 | unsafe {
| ------ because it's nested under this `unsafe` block
...
12 | unsafe { unsf() }
| ^^^^^^ unnecessary `unsafe` block
warning: unnecessary `unsafe` block
--> src/main.rs:13:9
|
9 | unsafe {
| ------ because it's nested under this `unsafe` block
...
13 | unsafe { unsf() }
| ^^^^^^ unnecessary `unsafe` block
```
in this case is by emitting a `unused_unsafe` warning for all of the `unsafe`
blocks that are _within a **used** unsafe block_.
The previous code had a little HIR traversal already anyways to collect a set of
all the unsafe blocks (in order to afterwards determine which ones are unused
afterwards). This PR uses such a traversal to do additional things including logic
like _always_ warn for an `unsafe` block that’s inside of another **used**
unsafe block. The traversal is expanded to include nested closures in the same go,
this simplifies a lot of things.
The whole logic around `unsafe_op_in_unsafe_fn` is a little complicated, there’s
some test cases of corner-cases in this PR. (The implementation involves
differentiating between whether a used unsafe block was used exclusively by
operations where `allow(unsafe_op_in_unsafe_fn)` was active.) The main goal was
to make sure that code should compile successfully if all the `unused_unsafe`-warnings
are addressed _simultaneously_ (by removing the respective `unsafe` blocks)
no matter how complicated the patterns of `unsafe_op_in_unsafe_fn` being
disallowed and allowed throughout the function are.
--------------------------------------------------------------------------------
One noteworthy design decision I took here: An `unsafe` block
with `allow(unused_unsafe)` **is considered used** for the purposes of
linting about redundant contained unsafe blocks. So while
```rs
fn granularity() {
unsafe { //~ ERROR: unnecessary `unsafe` block
unsafe { unsf() }
unsafe { unsf() }
unsafe { unsf() }
}
}
```
warns for the outer `unsafe` block,
```rs
fn top_level_ignored() {
#[allow(unused_unsafe)]
unsafe {
#[deny(unused_unsafe)]
{
unsafe { unsf() } //~ ERROR: unnecessary `unsafe` block
unsafe { unsf() } //~ ERROR: unnecessary `unsafe` block
unsafe { unsf() } //~ ERROR: unnecessary `unsafe` block
}
}
}
```
warns on the inner ones.
Move ty::print methods to Drop-based scope guards
Primary goal is reducing codegen of the TLS access for each closure, which shaves ~3 seconds of bootstrap time over rustc as a whole.
Adopt let else in more places
Continuation of #89933, #91018, #91481, #93046, #93590, #94011.
I have extended my clippy lint to also recognize tuple passing and match statements. The diff caused by fixing it is way above 1 thousand lines. Thus, I split it up into multiple pull requests to make reviewing easier. This is the biggest of these PRs and handles the changes outside of rustdoc, rustc_typeck, rustc_const_eval, rustc_trait_selection, which were handled in PRs #94139, #94142, #94143, #94144.
Even if we emit metadata disabling branch protection, this metadata may
conflict with other modules (e.g. during LTO) that have different branch
protection metadata set.
This is an unstable flag and feature, so ideally the flag not being
specified should act as if the feature wasn't implemented in the first
place.
Additionally this PR also ensures we emit an error if
`-Zbranch-protection` is set on targets other than the supported
aarch64. For now the error is being output from codegen, but ideally it
should be moved to earlier in the pipeline before stabilization.
Rollup of 10 pull requests
Successful merges:
- #89892 (Suggest `impl Trait` return type when incorrectly using a generic return type)
- #91675 (Add MemTagSanitizer Support)
- #92806 (Add more information to `impl Trait` error)
- #93497 (Pass `--test` flag through rustdoc to rustc so `#[test]` functions can be scraped)
- #93814 (mips64-openwrt-linux-musl: correct soft-foat)
- #93847 (kmc-solid: Use the filesystem thread-safety wrapper)
- #93877 (asm: Allow the use of r8-r14 as clobbers on Thumb1)
- #93892 (Only mark projection as ambiguous if GAT substs are constrained)
- #93915 (Implement --check-cfg option (RFC 3013), take 2)
- #93953 (Add the `known-bug` test directive, use it, and do some cleanup)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Add MemTagSanitizer Support
Add support for the LLVM [MemTagSanitizer](https://llvm.org/docs/MemTagSanitizer.html).
On hardware which supports it (see caveats below), the MemTagSanitizer can catch bugs similar to AddressSanitizer and HardwareAddressSanitizer, but with lower overhead.
On a tag mismatch, a SIGSEGV is signaled with code SEGV_MTESERR / SEGV_MTEAERR.
# Usage
`-Zsanitizer=memtag -C target-feature="+mte"`
# Comments/Caveats
* MemTagSanitizer is only supported on AArch64 targets with hardware support
* Requires `-C target-feature="+mte"`
* LLVM MemTagSanitizer currently only performs stack tagging.
# TODO
* Tests
* Example
This should provide a small perf improvement for debug builds,
and should more than cancel out the regression from adding noundef,
which was only significant in debug builds.
Fix ICE when using Box<T, A> with pointer sized A
Fixes#78459
Note that using `Box<T, A>` with a more than pointer sized `A` or using a pointer sized `A` with a Box of a DST will produce a different ICE (#92054) which is not fixed by this PR.
Add support for control-flow protection
This change adds a flag for configuring control-flow protection in the LLVM backend. In Clang, this flag is exposed as `-fcf-protection` with options `none|branch|return|full`. This convention is followed for `rustc`, though as a codegen option: `rustc -Z cf-protection=<none|branch|return|full>`. Tracking issue for future work is #93754.
llvm: migrate to new parameter-bearing uwtable attr
In https://reviews.llvm.org/D114543 the uwtable attribute gained a flag
so that we can ask for sync uwtables instead of async, as the former are
much cheaper. The default is async, so that's what I've done here, but I
left a TODO that we might be able to do better.
While in here I went ahead and dropped support for removing uwtable
attributes in rustc: we never did it, so I didn't write the extra C++
bridge code to make it work. Maybe I should have done the same thing
with the `sync|async` parameter but we'll see.
Specifically, change `Ty` from this:
```
pub type Ty<'tcx> = &'tcx TyS<'tcx>;
```
to this
```
pub struct Ty<'tcx>(Interned<'tcx, TyS<'tcx>>);
```
There are two benefits to this.
- It's now a first class type, so we can define methods on it. This
means we can move a lot of methods away from `TyS`, leaving `TyS` as a
barely-used type, which is appropriate given that it's not meant to
be used directly.
- The uniqueness requirement is now explicit, via the `Interned` type.
E.g. the pointer-based `Eq` and `Hash` comes from `Interned`, rather
than via `TyS`, which wasn't obvious at all.
Much of this commit is boring churn. The interesting changes are in
these files:
- compiler/rustc_middle/src/arena.rs
- compiler/rustc_middle/src/mir/visit.rs
- compiler/rustc_middle/src/ty/context.rs
- compiler/rustc_middle/src/ty/mod.rs
Specifically:
- Most mentions of `TyS` are removed. It's very much a dumb struct now;
`Ty` has all the smarts.
- `TyS` now has `crate` visibility instead of `pub`.
- `TyS::make_for_test` is removed in favour of the static `BOOL_TY`,
which just works better with the new structure.
- The `Eq`/`Ord`/`Hash` impls are removed from `TyS`. `Interned`s impls
of `Eq`/`Hash` now suffice. `Ord` is now partly on `Interned`
(pointer-based, for the `Equal` case) and partly on `TyS`
(contents-based, for the other cases).
- There are many tedious sigil adjustments, i.e. adding or removing `*`
or `&`. They seem to be unavoidable.
In https://reviews.llvm.org/D114543 the uwtable attribute gained a flag
so that we can ask for sync uwtables instead of async, as the former are
much cheaper. The default is async, so that's what I've done here, but I
left a TODO that we might be able to do better.
While in here I went ahead and dropped support for removing uwtable
attributes in rustc: we never did it, so I didn't write the extra C++
bridge code to make it work. Maybe I should have done the same thing
with the `sync|async` parameter but we'll see.
