Fix Access Violation when using lld & ThinLTO on windows-msvc
Users report an AV at runtime of the compiled binary when using lld and ThinLTO on windows-msvc. The AV occurs when accessing a static value which is defined in one crate but used in another. Based on the disassembly of the cross-crate use, it appears that the use is not correctly linked with the definition and is instead assigned a garbage pointer value.
If we look at the symbol tables for each crates' obj file, we can see what is happening:
*lib.obj*:
```
COFF SYMBOL TABLE
...
00E 00000000 SECT2 notype External | _ZN10reproducer7memrchr2FN17h612b61ca0e168901E
...
```
*bin.obj*:
```
COFF SYMBOL TABLE
...
010 00000000 UNDEF notype External | __imp__ZN10reproducer7memrchr2FN17h612b61ca0e168901E
...
```
The use of the symbol has the "import" style symbol name but the declaration doesn't generate any symbol with the same name. As a result, linking the files generates a warning from lld:
> rust-lld: warning: bin.obj: locally defined symbol imported: reproducer::memrchr::FN::h612b61ca0e168901 (defined in lib.obj) [LNK4217]
and the symbol reference remains undefined at runtime leading to the AV.
To fix this, we just need to detect that we are performing ThinLTO (and thus, static linking) and omit the `dllimport` attribute on the extern item in LLVM IR.
Fixes#81408
`CompiledModule` should not think a DWARF object was emitted when a
bitcode-only compilation has happened, this can confuse archive file
creation (which expects to create an archive containing non-existent dwo
files).
Signed-off-by: David Wood <david.wood@huawei.com>
LLVM 16: Update RISCV data layout
The RISCV data layout was changed in 974e2e690b.
This updates all `riscv64*` targets, though I don't really know what the difference between the `gc` and `imac` ones is.
Passes `x test codegen` at LLVM head and with the currently bundled LLVM version. Without this patch, some tests fail with:
> error: internal compiler error: compiler/rustc_codegen_llvm/src/context.rs:192:13: data-layout for target `riscv64gc-unknown-none-elf`, `e-m:e-p:64:64-i64:64-i128:128-n64-S128`, differs from LLVM target's `riscv64` default layout, `e-m:e-p:64:64-i64:64-i128:128-n32:64-S128
Moved type_array function to rustc_codegen_ssa::BaseTypeMethods trait.
This allows using normal alloca function to create arrays as suggested in
https://github.com/rust-lang/rust/pull/104022.
Signed-off-by: Ayush Singh <ayushsingh1325@gmail.com>
LLVM 16: Switch to using MemoryEffects
This adapts the compiler to the changes required by 304f1d59ca.
AFAICT, `WriteOnly` isn't used by the compiler, all `ReadNone` uses were migrated and the remaining use of `ReadOnly` is only for function parameters.
To simplify the FFI, this PR uses an enum to represent `MemoryEffects` across the FFI boundary, which then gets mapped to the matching static factory method when constructing the attribute.
Fixes#103961.
`@rustbot` label +llvm-main
r? `@nikic`
asm: Work around LLVM bug on AArch64
Upstream issue: https://github.com/llvm/llvm-project/issues/58384
LLVM gets confused if we assign a 32-bit value to a 64-bit register, so pass the 32-bit register name to LLVM in that case.
asm: Match clang behavior for inlateout fixed register operands
We have 2 options for representing LLVM constraints for `inlateout` operands on a fixed register (e.g. `r0`): `={r0},0` or `={r0},{r0}`.
This PR changes the behavior to the latter, which matches the behavior of Clang since https://reviews.llvm.org/D87279.
Users report an AV at runtime of the compiled binary when using lld and
ThinLTO on windows-msvc. The AV occurs when accessing a static value
which is defined in one crate but used in another. Based on the
disassembly of the cross-crate use, it appears that the use is not
correctly linked with the definition and is instead assigned a garbage
pointer value.
If we look at the symbol tables for each crates' obj file, we can see
what is happening:
*lib.obj*:
```
COFF SYMBOL TABLE
...
00E 00000000 SECT2 notype External | _ZN10reproducer7memrchr2FN17h612b61ca0e168901E
...
```
*bin.obj*:
```
COFF SYMBOL TABLE
...
010 00000000 UNDEF notype External | __imp__ZN10reproducer7memrchr2FN17h612b61ca0e168901E
...
```
The use of the symbol has the "import" style symbol name but the
declaration doesn't generate any symbol with the same name. As a result,
linking the files generates a warning from lld:
> rust-lld: warning: bin.obj: locally defined symbol imported: reproducer::memrchr::FN::h612b61ca0e168901 (defined in lib.obj) [LNK4217]
and the symbol reference remains undefined at runtime leading to the AV.
To fix this, we just need to detect that we are performing ThinLTO (and
thus, static linking) and omit the `dllimport` attribute on the extern
item in LLVM IR.
The new implementation doesn't use weak lang items and instead changes
`#[alloc_error_handler]` to an attribute macro just like
`#[global_allocator]`.
The attribute will generate the `__rg_oom` function which is called by
the compiler-generated `__rust_alloc_error_handler`. If no `__rg_oom`
function is defined in any crate then the compiler shim will call
`__rdl_oom` in the alloc crate which will simply panic.
This also fixes link errors with `-C link-dead-code` with
`default_alloc_error_handler`: `__rg_oom` was previously defined in the
alloc crate and would attempt to reference the `oom` lang item, even if
it didn't exist. This worked as long as `__rg_oom` was excluded from
linking since it was not called.
This is a prerequisite for the stabilization of
`default_alloc_error_handler` (#102318).
Don't use usub.with.overflow intrinsic
The canonical form of a usub.with.overflow check in LLVM are separate sub + icmp instructions, rather than a usub.with.overflow intrinsic. Using usub.with.overflow will generally result in worse optimization potential.
The backend will attempt to form usub.with.overflow when it comes to actual instruction selection. This is not fully reliable, but I believe this is a better tradeoff than using the intrinsic in IR.
Fixes#103285.
The canonical form of a usub.with.overflow check in LLVM are
separate sub + icmp instructions, rather than a usub.with.overflow
intrinsic. Using usub.with.overflow will generally result in worse
optimization potential.
The backend will attempt to form usub.with.overflow when it comes
to actual instruction selection. This is not fully reliable, but
I believe this is a better tradeoff than using the intrinsic in
IR.
Fixes#103285.
We have 2 options for representing LLVM constraints for `inlateout`
operands on a fixed register (e.g. `r0`): `={r0},0` or `={r0},{r0}`.
This PR changes the behavior to the latter, which matches the behavior
of Clang since https://reviews.llvm.org/D87279.
More dupe word typos
I only picked those changes (from the regex search) that I am pretty certain doesn't change meaning and is just a typo fix. Do correct me if any fix is undesirable and I can revert those. Thanks.
Remove `-Ztime`
Because it has a lot of overlap with `-Ztime-passes` but is generally less useful. Plus some related cleanups.
Best reviewed one commit at a time.
r? `@davidtwco`
The compiler currently has `-Ztime` and `-Ztime-passes`. I've used
`-Ztime-passes` for years but only recently learned about `-Ztime`.
What's the difference? Let's look at the `-Zhelp` output:
```
-Z time=val -- measure time of rustc processes (default: no)
-Z time-passes=val -- measure time of each rustc pass (default: no)
```
The `-Ztime-passes` description is clear, but the `-Ztime` one is less so.
Sounds like it measures the time for the entire process?
No. The real difference is that `-Ztime-passes` prints out info about passes,
and `-Ztime` does the same, but only for a subset of those passes. More
specifically, there is a distinction in the profiling code between a "verbose
generic activity" and an "extra verbose generic activity". `-Ztime-passes`
prints both kinds, while `-Ztime` only prints the first one. (It took me
a close reading of the source code to determine this difference.)
In practice this distinction has low value. Perhaps in the past the "extra
verbose" output was more voluminous, but now that we only print stats for a
pass if it exceeds 5ms or alters the RSS, `-Ztime-passes` is less spammy. Also,
a lot of the "extra verbose" cases are for individual lint passes, and you need
to also use `-Zno-interleave-lints` to see those anyway.
Therefore, this commit removes `-Ztime` and the associated machinery. One thing
to note is that the existing "extra verbose" activities all have an extra
string argument, so the commit adds the ability to accept an extra argument to
the "verbose" activities.
resolve error when attempting to link a universal library on macOS
Previously attempting to link universal libraries into libraries (but not binaries) would produce an error that "File too small to be an archive". This works around this by invoking `lipo -thin` to extract a library for the target platform when passed a univeral library.
Fixes#55235
It's worth acknowledging that this implementation is kind of a horrible hack. Unfortunately I don't know how to do anything better, hopefully this PR will be a jumping off point.
Previously attempting to link universal libraries into libraries (but not binaries) would produce an error that "File too small to be an archive". This works around this by using `object` to extract a library for the target platform when passed a univeral library.
Fixes#55235
Declare `main` as visibility hidden on targets that default to hidden.
On targets with `default_hidden_visibility` set, which is currrently just WebAssembly, declare the generated `main` function with visibility hidden. This makes it consistent with clang's WebAssembly target, where `main` is just a user function that gets the same visibility as any other user function, which is hidden on WebAssembly unless explicitly overridden.
This will help simplify use cases which in the future may want to automatically wasm-export all visibility-"default" symbols. `main` isn't intended to be wasm-exported, and marking it hidden prevents it from being wasm-exported in that scenario.
LLVM [D131158] changed the SystemZ data layout to always set 64-bit
vector alignment, which used to be conditional on the "vector" feature.
[D131158]: https://reviews.llvm.org/D131158
On targets with `default_hidden_visibility` set, which is currrently
just WebAssembly, declare the generated `main` function with visibility
hidden. This makes it consistent with clang's WebAssembly target, where
`main` is just a user function that gets the same visibility as any
other user function, which is hidden on WebAssembly unless explicitly
overridden.
This will help simplify use cases which in the future may want to
automatically wasm-export all visibility-"default" symbols. `main` isn't
intended to be wasm-exported, and marking it hidden prevents it from
being wasm-exported in that scenario.
Remove support for legacy PM
This removes support for optimizing with LLVM's legacy pass manager, as well as the unstable `-Znew-llvm-pass-manager` option. We have been defaulting to the new PM since LLVM 13 (except for s390x that waited for 14), and LLVM 15 removed support altogether. The only place we still use the legacy PM is for writing the output file, just like `llc` does.
cc #74705
r? ``@nikic``
Implement simd_as for pointers
Expands `simd_as` (and `simd_cast`) to handle pointer-to-pointer, pointer-to-integer, and integer-to-pointer conversions.
cc ``@programmerjake`` ``@thomcc``
On later stages, the feature is already stable.
Result of running:
rg -l "feature.let_else" compiler/ src/librustdoc/ library/ | xargs sed -s -i "s#\\[feature.let_else#\\[cfg_attr\\(bootstrap, feature\\(let_else\\)#"
Add support for MIPS VZ ISA extension
[Link to relevant LLVM line where virt extension is specified](83fab8cee9/llvm/lib/Target/Mips/Mips.td (L172-L173))
This has been tested on mips-unknown-linux-musl with a target-cpu that is >= MIPS32 5 and `target-features=+virt`. The example was checked in a disassembler to ensure the correct assembly sequence was being generated using the virtualization instructions.
Needed additional work:
* MIPS is missing from [the Rust reference CPU feature lists](https://doc.rust-lang.org/reference/attributes/codegen.html#available-features)
Example docs for later:
```md
#### `mips` or `mips64`
This platform requires that `#[target_feature]` is only applied to [`unsafe`
functions][unsafe function]. This target's feature support is currently unstable
and must be enabled by `#![feature(mips_target_feature)]` ([Issue #44839])
[Issue #44839]: https://github.com/rust-lang/rust/issues/44839
Further documentation on these features can be found in the [MIPS Instruction Set
Reference Manual], or elsewhere on [mips.com].
[MIPS Instruction Set Reference Manual]: https://s3-eu-west-1.amazonaws.com/downloads-mips/documents/MD00086-2B-MIPS32BIS-AFP-6.06.pdf
[developer.arm.com]: https://www.mips.com/products/architectures/ase/
Feature | Implicitly Enables | Description
---------------|--------------------|-------------------
`fp64` | | 64-bit Floating Point
`msa` | | "MIPS SIMD Architecture"
`virt` | | Virtualization instructions (VZ ASE)
```
If the above is good I can also submit a PR for that if there's interest in documenting it while it's still unstable. Otherwise that can be dropped, I just wrote it before realizing it was possibly not a good idea.
Relevant to #44839
Add inline-llvm option for disabling/enabling LLVM inlining
In this PR, a new -Z option `inline-llvm` is added in order to be able to turn on/off LLVM inlining.
The capability of turning on/off inlining in LLVM backend is needed for testing performance implications of using recently enabled inlining in rustc's frontend (with -Z inline-mir=yes option, #91743). It would be interesting to see the performance effect using rustc's frontend inlining only without LLVM inlining enabled. Currently LLVM is still doing inlining no mater what value inline-mir is set to. With the option `inline-llvm` being added in this PR, user can turn off LLVM inlining by using `-Z inline-llvm=no` option (the default of inline-llvm is 'yes', LLVM inlining enabled).
Rollup of 5 pull requests
Successful merges:
- #99517 (Display raw pointer as *{mut,const} T instead of *-ptr in errors)
- #99928 (Do not leak type variables from opaque type relation)
- #100473 (Attempt to normalize `FnDef` signature in `InferCtxt::cmp`)
- #100653 (Move the cast_float_to_int fallback code to GCC)
- #100941 (Point at the string inside literal and mention if we need string inte…)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Move the cast_float_to_int fallback code to GCC
Now that we require at least LLVM 13, that codegen backend is always
using its intrinsic `fptosi.sat` and `fptoui.sat` conversions, so it
doesn't need the manual implementation. However, the GCC backend still
needs it, so we can move all of that code down there.
Use object instead of LLVM for reading bitcode from rlibs
Together with changes I plan to make as part of https://github.com/rust-lang/rust/pull/97485 this will allow entirely removing usage of LLVM's archive reader and thus allow removing `archive_ro.rs` and `ArchiveWrapper.cpp`.
Rollup of 9 pull requests
Successful merges:
- #95376 (Add `vec::Drain{,Filter}::keep_rest`)
- #100092 (Fall back when relating two opaques by substs in MIR typeck)
- #101019 (Suggest returning closure as `impl Fn`)
- #101022 (Erase late bound regions before comparing types in `suggest_dereferences`)
- #101101 (interpret: make read-pointer-as-bytes a CTFE-only error with extra information)
- #101123 (Remove `register_attr` feature)
- #101175 (Don't --bless in pre-push hook)
- #101176 (rustdoc: remove unused CSS selectors for `.table-display`)
- #101180 (Add another MaybeUninit array test with const)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
interpret: make read-pointer-as-bytes a CTFE-only error with extra information
Next step in the reaction to https://github.com/rust-lang/rust/issues/99923. Also teaches Miri to implicitly strip provenance in more situations when transmuting pointers to integers, which fixes https://github.com/rust-lang/miri/issues/2456.
Pointer-to-int transmutation during CTFE now produces a message like this:
```
= help: this code performed an operation that depends on the underlying bytes representing a pointer
= help: the absolute address of a pointer is not known at compile-time, so such operations are not supported
```
r? ``@oli-obk``
rustc_middle: Remove `Visibility::Invisible`
It had a different meaning in the past, but now it's only used as an implementation detail of import resolution.
Add pointer masking convenience functions
This PR adds the following public API:
```rust
impl<T: ?Sized> *const T {
fn mask(self, mask: usize) -> *const T;
}
impl<T: ?Sized> *mut T {
fn mask(self, mask: usize) -> *const T;
}
// mod intrinsics
fn mask<T>(ptr: *const T, mask: usize) -> *const T
```
This is equivalent to `ptr.map_addr(|a| a & mask)` but also uses a cool llvm intrinsic.
Proposed in https://github.com/rust-lang/rust/pull/95643#issuecomment-1121562352
cc `@Gankra` `@scottmcm` `@RalfJung`
r? rust-lang/libs-api
Currently they try to be very precise. But they are wrong, i.e. they
don't match what's happening in the loop below. This code isn't hot
enough for it to matter that much.
Because `PassMode::Cast` is by far the largest variant, but is
relatively rare.
This requires making `PassMode` not impl `Copy`, and `Clone` is no
longer necessary. This causes lots of sigil adjusting, but nothing very
notable.
I couldn't find where exactly it's documented, but apperantly pointers to void
type are invalid in llvm - void is only allowed as a return type of functions.
This commit adds the following functions all of which have a signature
`pointer, usize -> pointer`:
- `<*mut T>::mask`
- `<*const T>::mask`
- `intrinsics::ptr_mask`
These functions are equivalent to `.map_addr(|a| a & mask)` but they
utilize `llvm.ptrmask` llvm intrinsic.
*masks your pointers*
Now that we require at least LLVM 13, that codegen backend is always
using its intrinsic `fptosi.sat` and `fptoui.sat` conversions, so it
doesn't need the manual implementation. However, the GCC backend still
needs it, so we can move all of that code down there.
Update the minimum external LLVM to 13
With this change, we'll have stable support for LLVM 13 through 15 (pending release).
For reference, the previous increase to LLVM 12 was #90175.
r? `@nagisa`
Add support for generating unique profraw files by default when using `-C instrument-coverage`
Currently, enabling the rustc flag `-C instrument-coverage` instruments the given crate and by default uses the naming scheme `default.profraw` for any instrumented profile files generated during the execution of a binary linked against this crate. This leads to multiple binaries being executed overwriting one another and causing only the last executable run to contain actual coverage results.
This can be overridden by manually setting the environment variable `LLVM_PROFILE_FILE` to use a unique naming scheme.
This PR adds a change to add support for a reasonable default for rustc to use when enabling coverage instrumentation similar to how the Rust compiler treats generating these same `profraw` files when PGO is enabled.
The new naming scheme is set to `default_%m_%p.profraw` to ensure the uniqueness of each file being generated using [LLVMs special pattern strings](https://clang.llvm.org/docs/SourceBasedCodeCoverage.html#running-the-instrumented-program).
Today the compiler sets the default for PGO `profraw` files to `default_%m.profraw` to ensure a unique file for each run. The same can be done for the instrumented profile files generated via the `-C instrument-coverage` flag as well which LLVM has API support for.
Linked Issue: https://github.com/rust-lang/rust/issues/100381
r? `@wesleywiser`
debuginfo: Generalize C++-like encoding for enums.
The updated encoding should be able to handle niche layouts where more than one variant has fields (as introduced in https://github.com/rust-lang/rust/pull/94075).
The new encoding is more uniform as there is no structural difference between direct-tag, niche-tag, and no-tag layouts anymore. The only difference between those cases is that the "dataful" variant in a niche-tag enum will have a `(start, end)` pair denoting the tag range instead of a single value.
The new encoding now also supports 128-bit tags, which occur in at least some standard library types. These tags are represented as `u64` pairs so that debuggers (which don't always have support for 128-bit integers) can reliably deal with them. The downside is that this adds quite a bit of complexity to the encoding and especially to the corresponding NatVis.
The new encoding seems to increase the size of (x86_64-pc-windows-msvc) debuginfo by 10-15%. The size of binaries is not affected (release builds were built with `-Cdebuginfo=2`, numbers are in kilobytes):
EXE | before | after | relative
-- | -- | -- | --
cargo (debug) | 40453 | 40450 | +0%
ripgrep (debug) | 10275 | 10273 | +0%
cargo (release) | 16186 | 16185 | +0%
ripgrep (release) | 4727 | 4726 | +0%
PDB | before | after | relative
-- | -- | -- | --
cargo (debug) | 236524 | 261412 | +11%
ripgrep (debug) | 53140 | 59060 | +11%
cargo (release) | 148516 | 169620 | +14%
ripgrep (release) | 10676 | 11804 | +11%
Given that the new encoding is more general, this is to be expected. Only platforms using C++-like debuginfo are affected -- which currently is only `*-pc-windows-msvc`.
*TODO*
- [x] Properly update documentation
- [x] Add regression tests for new optimized enum layouts as introduced by #94075.
r? `@wesleywiser`
https://reviews.llvm.org/D120026 changed atomics on thumbv6m to
use libatomic, to ensure that atomic load/store are compatible with
atomic RMW/CAS. However, Rust wants to expose only load/store
without libcalls.
https://reviews.llvm.org/D130480 added support for this behind
the +atomics-32 target feature, so enable that feature.
Introduce an ArchiveBuilderBuilder
This avoids monomorphizing all linker code for each codegen backend and will allow passing in extra information to the archive builder from the codegen backend. I'm going to use this in https://github.com/rust-lang/rust/pull/97485 to allow passing in the right function to extract symbols from object files to a generic archive builder to be used by cg_llvm, cg_clif and cg_gcc.
This avoids monomorphizing all linker code for each codegen backend and
will allow passing in extra information to the archive builder from the
codegen backend.
codegen: use new {re,de,}allocator annotations in llvm
This obviates the patch that teaches LLVM internals about
_rust_{re,de}alloc functions by putting annotations directly in the IR
for the optimizer.
The sole test change is required to anchor FileCheck to the body of the
`box_uninitialized` method, so it doesn't see the `allocalign` on
`__rust_alloc` and get mad about the string `alloca` showing up. Since I
was there anyway, I added some checks on the attributes to prove the
right attributes got set.
r? `@nikic`
This obviates the patch that teaches LLVM internals about
_rust_{re,de}alloc functions by putting annotations directly in the IR
for the optimizer.
The sole test change is required to anchor FileCheck to the body of the
`box_uninitialized` method, so it doesn't see the `allocalign` on
`__rust_alloc` and get mad about the string `alloca` showing up. Since I
was there anyway, I added some checks on the attributes to prove the
right attributes got set.
While we're here, we also emit allocator attributes on
__rust_alloc_zeroed. This should allow LLVM to perform more
optimizations for zeroed blocks, and probably fixes#90032. [This
comment](https://github.com/rust-lang/rust/issues/24194#issuecomment-308791157)
mentions "weird UB-like behaviour with bitvec iterators in
rustc_data_structures" so we may need to back this change out if things
go wrong.
The new test cases require LLVM 15, so we copy them into LLVM
14-supporting versions, which we can delete when we drop LLVM 14.
Enable raw-dylib for bin crates
Fixes#93842
When `raw-dylib` is used in a `bin` crate, we need to collect all of the `raw-dylib` functions, generate the import library and add that to the linker command line.
I also changed the tests so that 1) the C++ dlls are created after the Rust dlls, thus there is no chance of accidentally using them in the Rust linking process and 2) disabled generating import libraries when building with MSVC.
Add fine-grained LLVM CFI support to the Rust compiler
This PR improves the LLVM Control Flow Integrity (CFI) support in the Rust compiler by providing forward-edge control flow protection for Rust-compiled code only by aggregating function pointers in groups identified by their return and parameter types.
Forward-edge control flow protection for C or C++ and Rust -compiled code "mixed binaries" (i.e., for when C or C++ and Rust -compiled code share the same virtual address space) will be provided in later work as part of this project by identifying C char and integer type uses at the time types are encoded (see Type metadata in the design document in the tracking issue https://github.com/rust-lang/rust/issues/89653).
LLVM CFI can be enabled with -Zsanitizer=cfi and requires LTO (i.e., -Clto).
Thank you again, `@eddyb,` `@nagisa,` `@pcc,` and `@tmiasko` for all the help!
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.
This commit improves the LLVM Control Flow Integrity (CFI) support in
the Rust compiler by providing forward-edge control flow protection for
Rust-compiled code only by aggregating function pointers in groups
identified by their return and parameter types.
Forward-edge control flow protection for C or C++ and Rust -compiled
code "mixed binaries" (i.e., for when C or C++ and Rust -compiled code
share the same virtual address space) will be provided in later work as
part of this project by identifying C char and integer type uses at the
time types are encoded (see Type metadata in the design document in the
tracking issue #89653).
LLVM CFI can be enabled with -Zsanitizer=cfi and requires LTO (i.e.,
-Clto).
make vtable pointers entirely opaque
This implements the scheme discussed in https://github.com/rust-lang/unsafe-code-guidelines/issues/338: vtable pointers should be considered entirely opaque and not even readable by Rust code, similar to function pointers.
- We have a new kind of `GlobalAlloc` that symbolically refers to a vtable.
- Miri uses that kind of allocation when generating a vtable.
- The codegen backends, upon encountering such an allocation, call `vtable_allocation` to obtain an actually dataful allocation for this vtable.
- We need new intrinsics to obtain the size and align from a vtable (for some `ptr::metadata` APIs), since direct accesses are UB now.
I had to touch quite a bit of code that I am not very familiar with, so some of this might not make much sense...
r? `@oli-obk`
Allow to disable thinLTO buffer to support lto-embed-bitcode lld feature
Hello
This change is to fix issue (https://github.com/rust-lang/rust/issues/84395) in which passing "-lto-embed-bitcode=optimized" to lld when linking rust code via linker-plugin-lto doesn't produce the expected result.
Instead of emitting a single unified module into a llvmbc section of the linked elf, it emits multiple submodules.
This is caused because rustc emits the BC modules after running llvm `createWriteThinLTOBitcodePass` pass.
Which in turn triggers a thinLTO linkage and causes the said issue.
This patch allows via compiler flag (-Cemit-thin-lto=<bool>) to select between running `createWriteThinLTOBitcodePass` and `createBitcodeWriterPass`.
Note this pattern of selecting between those 2 passes is common inside of LLVM code.
The default is to match the old behavior.
Only compile #[used] as llvm.compiler.used for ELF targets
This returns `#[used]` to how it worked prior to the LLVM 13 update. The intention is not that this is a stable promise.
I'll add tests later today. The tests will test things that we don't actually promise, though.
It's a deliberately small patch, mostly comments. And assuming it's reviewed and lands in time, IMO it should at least be considered for uplifting to beta (so that it can be in 1.59), as the change broke many crates in the ecosystem, even if they are relying on behavior that is not guaranteed.
# Background
LLVM has two ways of preventing removal of an unused variable: `llvm.compiler.used`, which must be present in object files, but allows the linker to remove the value, and `llvm.used` which is supposed to apply to the linker as well, if possible.
Prior to LLVM 13, `llvm.used` and `llvm.compiler.used` were the same on ELF targets, although they were different elsewhere. Prior to our update to LLVM 13, we compiled `#[used]` using `llvm.used` unconditionally, even though we only ever promised behavior like `llvm.compiler.used`.
In LLVM 13, ELF targets gained some support for preventing linker removal of `llvm.used` via the SHF_RETAIN section flag. This has some compatibility issues though: Concretely: some older versions `ld.gold` (specifically ones prior to v2.36, released in Jan 2021) had a bug where it would fail to place a `#[used] #[link_section = ".init_array"]` static in between `__init_array_start`/`__init_array_end`, leading to code that does this failing to run a static constructor. This is technically not a thing we guarantee will work, is a common use case, and is needed in `libstd` (for example, to get access to `std::env::args()` even if Rust does not control `main`, such as when in a `cdylib` crate).
As a result, when updating to LLVM 13, we unconditionally switched to using `llvm.compiler.used`, which mirror the guarantees we make for `#[used]` and doesn't require the latest ld.gold. Unfortunately, this happened to break quite a bit of things in the ecosystem, as non-ELF targets had come to rely on `#[used]` being slightly stronger. In particular, there are cases where it will even break static constructors on these targets[^initinit] (and in fact, breaks way more use cases, as Mach-O uses special sections as an interface to the OS/linker/loader in many places).
As a result, we only switch to `llvm.compiler.used` on ELF[^elfish] targets. The rationale here is:
1. It is (hopefully) identical to the semantics we used prior to the LLVM13 update as prior to that update we unconditionally used `llvm.used`, but on ELF `llvm.used` was the same as `llvm.compiler.used`.
2. It seems to be how Clang compiles this, and given that they have similar (but stronger) compatibility promises, that makes sense.
[^initinit]: For Mach-O targets: It is not always guaranteed that `__DATA,__mod_init_func` is a GC root if it does not have the `S_MOD_INIT_FUNC_POINTERS` flag which we cannot add. In most cases, when ld64 transformed this section into `__DATA_CONST,__mod_init_func` it gets applied, but it's not clear that that is intentional (let alone guaranteed), and the logic is complex enough that it probably happens sometimes, and people in the wild report it occurring.
[^elfish]: Actually, there's not a great way to tell if it's ELF, so I've approximated it.
This is pretty ad-hoc and hacky! We probably should have a firmer set of guarantees here, but this change should relax the pressure on coming up with that considerably, returning it to previous levels.
---
Unsure who should review so leaving it open, but for sure CC `@nikic`
Remove branch target prologues from `#[naked] fn`
This patch hacks around rust-lang/rust#98768 for now via injecting appropriate attributes into the LLVMIR we emit for naked functions. I intend to pursue this upstream so that these attributes can be removed in general, but it's slow going wading through C++ for me.
Revert "Work around invalid DWARF bugs for fat LTO"
Since September, the toolchain has not been generating reliable DWARF
information for static variables when LTO is on. This has affected
projects in the embedded space where the use of LTO is typical. In our
case, it has kept us from bumping past the 2021-09-22 nightly toolchain
lest our debugger break. This has been a pretty dramatic regression for
people using debuggers and static variables. See #90357 for more info
and a repro case.
This commit is a mechanical revert of
d5de680e20 from PR #89041, which caused
the issue. (Note on that PR that the commit's author has requested it be
reverted.)
I have locally verified that this fixes#90357 by restoring the
functionality of both the repro case I posted on that bug, and debugger
behavior on real programs. There do not appear to be test cases for this
in the toolchain; if I've missed them, point me at 'em and I'll update
them.
Adding the option to control from rustc CLI
if the resulted ".o" bitcode module files are with
thinLTO info or regular LTO info.
Allows using "-lto-embed-bitcode=optimized" during linkage
correctly.
Signed-off-by: Ziv Dunkelman <ziv.dunkelman@nextsilicon.com>
Keep unstable target features for asm feature checking
Inline assembly uses the target features to determine which registers
are available on the current target. However it needs to be able to
access unstable target features for this.
Fixes#99071
Inline assembly uses the target features to determine which registers
are available on the current target. However it needs to be able to
access unstable target features for this.
Fixes#99071
There are several indications that we should not ZST as a ScalarInt:
- We had two ways to have ZST valtrees, either an empty `Branch` or a `Leaf` with a ZST in it.
`ValTree::zst()` used the former, but the latter could possibly arise as well.
- Likewise, the interpreter had `Immediate::Uninit` and `Immediate::Scalar(Scalar::ZST)`.
- LLVM codegen already had to special-case ZST ScalarInt.
So instead add new ZST variants to those types that did not have other variants
which could be used for this purpose.
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
Use less string interning
This removes string interning in a couple of places where doing so won't result in perf improvements. I also switched one place to use pre-interned symbols.
Change enum->int casts to not go through MIR casts.
follow-up to https://github.com/rust-lang/rust/pull/96814
this simplifies all backends and even gives LLVM more information about the return value of `Rvalue::Discriminant`, enabling optimizations in more cases.
Work around llvm 12's memory ordering restrictions.
Older llvm has the pre-C++17 restriction on success and failure memory ordering, requiring the former to be at least as strong as the latter. So, for llvm 12, this upgrades the success ordering to a stronger one if necessary.
See https://github.com/rust-lang/rust/issues/68464
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.
Older llvm has the pre-C++17 restriction on success and failure memory
ordering, requiring the former to be at least as strong as the latter.
So, for llvm 12, this upgrades the success ordering to a stronger one if
necessary.
Remove the source archive functionality of ArchiveWriter
We now build archives through strictly additive means rather than taking an existing archive and potentially substracting parts. This is simpler and makes it easier to swap out the archive writer in https://github.com/rust-lang/rust/pull/97485.
once cell renamings
This PR does the renamings proposed in https://github.com/rust-lang/rust/issues/74465#issuecomment-1153703128
- Move/rename `lazy::{OnceCell, Lazy}` to `cell::{OnceCell, LazyCell}`
- Move/rename `lazy::{SyncOnceCell, SyncLazy}` to `sync::{OnceLock, LazyLock}`
(I used `Lazy...` instead of `...Lazy` as it seems to be more consistent, easier to pronounce, etc)
```@rustbot``` label +T-libs-api -T-libs
Support lint expectations for `--force-warn` lints (RFC 2383)
Rustc has a `--force-warn` flag, which overrides lint level attributes and forces the diagnostics to always be warn. This means, that for lint expectations, the diagnostic can't be suppressed as usual. This also means that the expectation would not be fulfilled, even if a lint had been triggered in the expected scope.
This PR now also tracks the expectation ID in the `ForceWarn` level. I've also made some minor adjustments, to possibly catch more bugs and make the whole implementation more robust.
This will probably conflict with https://github.com/rust-lang/rust/pull/97718. That PR should ideally be reviewed and merged first. The conflict itself will be trivial to fix.
---
r? `@wesleywiser`
cc: `@flip1995` since you've helped with the initial review and also discussed this topic with me. 🙃
Follow-up of: https://github.com/rust-lang/rust/pull/87835
Issue: https://github.com/rust-lang/rust/issues/85549
Yeah, and that's it.
This adds the typeid and `vcall_visibility` metadata to vtables when the
-Cvirtual-function-elimination flag is set.
The typeid is generated in the same way as for the
`llvm.type.checked.load` intrinsic from the trait_ref.
The offset that is added to the typeid is always 0. This is because LLVM
assumes that vtables are constructed according to the definition in the
Itanium ABI. This includes an "address point" of the vtable. In C++ this
is the offset in the vtable where information for RTTI is placed. Since
there is no RTTI information in Rust's vtables, this "address point" is
always 0. This "address point" in combination with the offset passed to
the `llvm.type.checked.load` intrinsic determines the final function
that should be loaded from the vtable in the
`WholeProgramDevirtualization` pass in LLVM. That's why the
`llvm.type.checked.load` intrinsics are generated with the typeid of the
trait, rather than with that of the function that is called. This
matches what `clang` does for C++.
The vcall_visibility metadata depends on three factors:
1. LTO level: Currently this is always fat LTO, because LLVM only
supports this optimization with fat LTO.
2. Visibility of the trait: If the trait is publicly visible, VFE
can only act on its vtables after linking.
3. Number of CGUs: if there is more than one CGU, also vtables with
restricted visibility could be seen outside of the CGU, so VFE can
only act on them after linking.
To reflect this, there are three visibility levels: Public, LinkageUnit,
and TranslationUnit.
Add the intrinsic
declare {i8*, i1} @llvm.type.checked.load(i8* %ptr, i32 %offset, metadata %type)
This is used in the VFE optimization when lowering loading functions
from vtables to LLVM IR. The `metadata` is used to map the function to
all vtables this function could belong to. This ensures that functions
from vtables that might be used somewhere won't get removed.
To apply the optimization the `Virtual Function Elim` module flag has to
be set. To apply this optimization post-link the `LTOPostLink` module
flag has to be set.
Add Apple WatchOS compile targets
Hello,
I would like to add the following target triples for Apple WatchOS as Tier 3 platforms:
armv7k-apple-watchos
arm64_32-apple-watchos
x86_64-apple-watchos-sim
There are some pre-requisites Pull Requests:
https://github.com/rust-lang/compiler-builtins/pull/456 (merged)
https://github.com/alexcrichton/cc-rs/pull/662 (pending)
https://github.com/rust-lang/libc/pull/2717 (merged)
There will be a subsequent PR with standard library changes for WatchOS. Previous compiler and library changes were in a single PR (https://github.com/rust-lang/rust/pull/94736) which is now closed in favour of separate PRs.
Many thanks!
Vlad.
### Tier 3 Target Requirements
Adds support for Apple WatchOS compile targets.
Below are details on how this target meets the requirements for tier 3:
> 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.)
`@deg4uss3r` has volunteered to be the target maintainer. I am also happy to help if a second maintainer is required.
> 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.
Uses the same naming as the LLVM target, and the same convention as other Apple targets.
> 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 don't believe there is any ambiguity here.
> 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.
I don't see any legal issues here.
> The target must not introduce license incompatibilities.
> Anything added to the Rust repository must be under the standard Rust license (MIT OR Apache-2.0).
> 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.
> If the target supports building host tools (such as rustc or cargo), those host tools must not depend on proprietary (non-FOSS) libraries, other than ordinary runtime libraries supplied by the platform and commonly used by other binaries built for the target. 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.
> Targets should not require proprietary (non-FOSS) components to link a functional binary or library.
> "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.
I see no issues with any of the above.
> 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 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.
Only relevant to those making approval decisions.
> 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.
core and alloc can be used. std support will be added in a subsequent PR.
> 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 tests (even if they do not pass), the documentation must explain how to run tests for the target, using emulation if possible or dedicated hardware if necessary.
Use --target=<target> option to cross compile, just like any target. Tests can be run using the WatchOS simulator (see https://developer.apple.com/documentation/xcode/running-your-app-in-the-simulator-or-on-a-device).
> 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.
> 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.
I don't foresee this being a problem.
> 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.
> 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.
No other targets should be affected by the pull request.
Make -Cpasses= only apply to pre-link optimization
This change causes passes specified in -Cpasses= to be applied
only during pre-link optimization, not during LTO. This avoids
such passes running multiple times, which they may not be
designed for.
Fixes https://github.com/rust-lang/rust/issues/97713
This change causes passes specified in -Cpasses= to be applied
only during pre-link optimization, not during LTO. This avoids
such passes running multiple times, which they may not be
designed for.
Fixes https://github.com/rust-lang/rust/issues/97713
Specify DWARF alignment in bits, not bytes.
In DWARF, alignment of types is specified in bits, as is made clear by the
parameter name `AlignInBits`. However, `rustc` was incorrectly passing a byte
alignment. This commit fixes that.
This was noticed in upstream LLVM when I tried to check in a test consisting of
LLVM IR generated from `rustc` and it triggered assertions [1].
[1]: https://reviews.llvm.org/D126835
In DWARF, alignment of types is specified in bits, as is made clear by the
parameter name `AlignInBits`. However, `rustc` was incorrectly passing a byte
alignment. This commit fixes that.
This was noticed in upstream LLVM when I tried to check in a test consisting of
LLVM IR generated from `rustc` and it triggered assertions [1].
[1]: https://reviews.llvm.org/D126835
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)
Finish bumping stage0
It looks like the last time had left some remaining cfg's -- which made me think
that the stage0 bump was actually successful. This brings us to a released 1.62
beta though.
This now brings us to cfg-clean, with the exception of check-cfg-features in bootstrap;
I'd prefer to leave that for a separate PR at this time since it's likely to be more tricky.
cc https://github.com/rust-lang/rust/pull/97147#issuecomment-1132845061
r? `@pietroalbini`
Prepare Rust for opaque pointers
Fix one codegen bug with opaque pointers, and update our IR tests to accept both typed pointer and opaque pointer IR. This is a bit annoying, but unavoidable if we want decent test coverage on both LLVM 14 and LLVM 15.
This prepares Rust for when LLVM will enable opaque pointers by default.
