Remove cgu_reuse_tracker from Session
This removes a bit of global mutable state.
It will now miss post-lto cgu reuse when ThinLTO determines that a cgu doesn't get changed, but there weren't any tests for this anyway and a test for it would be fragile to the exact implementation of ThinLTO in LLVM.
Make `.rmeta` file in `dep-info` have correct name (`lib` prefix)
Since `filename_for_metadata()` and
`OutputFilenames::path(OutputType::Metadata)` had different logic for the name of the metadata file, the `.d` file contained a file name different from the actual name used. Share the logic to fix the out-of-sync name.
Without this fix, the `.d` file contained
dash-separated_something-extra.rmeta: dash-separated.rs
instead of
libdash_separated_something-extra.rmeta: dash-separated.rs
which is the name of the file that is actually written by the compiler.
Worth noting: It took me several iterations to get all tests to pass, so I am relatively confident that this PR does not break anything.
Closes#68839
Add CL and CMD into to pdb debug info
Partial fix for https://github.com/rust-lang/rust/issues/96475
The Arg0 and CommandLineArgs of the MCTargetOptions cpp class are not set within bb548f9645/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp (L378)
This causes LLVM to not neither output any compiler path (cl) nor the arguments that were used when invoking it (cmd) in the PDB file.
This fix adds the missing information to the target machine so LLVM can use it.
Since `filename_for_metadata()` and
`OutputFilenames::path(OutputType::Metadata)` had different logic for
the name of the metadata file, the `.d` file contained a file name
different from the actual name used. Share the logic to fix the
out-of-sync name.
Closes 68839.
Use conditional synchronization for Lock
This changes `Lock` to use synchronization only if `mode::is_dyn_thread_safe` could be true. This reduces overhead for the parallel compiler running with 1 thread.
The emitters are changed to use `DynSend` instead of `Send` so they can still use `Lock`.
A Rayon thread pool is not used with 1 thread anymore, as session globals contains `Lock`s which are no longer `Sync`.
Performance improvement with 1 thread and `cfg(parallel_compiler)`:
<table><tr><td rowspan="2">Benchmark</td><td colspan="1"><b>Before</b></th><td colspan="2"><b>After</b></th></tr><tr><td align="right">Time</td><td align="right">Time</td><td align="right">%</th></tr><tr><td>🟣 <b>clap</b>:check</td><td align="right">1.7665s</td><td align="right">1.7336s</td><td align="right">💚 -1.86%</td></tr><tr><td>🟣 <b>hyper</b>:check</td><td align="right">0.2780s</td><td align="right">0.2736s</td><td align="right">💚 -1.61%</td></tr><tr><td>🟣 <b>regex</b>:check</td><td align="right">0.9994s</td><td align="right">0.9824s</td><td align="right">💚 -1.70%</td></tr><tr><td>🟣 <b>syn</b>:check</td><td align="right">1.5875s</td><td align="right">1.5656s</td><td align="right">💚 -1.38%</td></tr><tr><td>🟣 <b>syntex_syntax</b>:check</td><td align="right">6.0682s</td><td align="right">5.9532s</td><td align="right">💚 -1.90%</td></tr><tr><td>Total</td><td align="right">10.6997s</td><td align="right">10.5083s</td><td align="right">💚 -1.79%</td></tr><tr><td>Summary</td><td align="right">1.0000s</td><td align="right">0.9831s</td><td align="right">💚 -1.69%</td></tr></table>
cc `@SparrowLii`
Add an (perma-)unstable option to disable vtable vptr
This flag is intended for evaluation of trait upcasting space cost for embedded use cases.
Compared to the approach in #112355, this option provides a way to evaluate end-to-end cost of trait upcasting. Rationale: https://github.com/rust-lang/rust/issues/112355#issuecomment-1658207769
## How this flag should be used (after merge)
Build your project with and without `-Zno-trait-vptr` flag. If you are using cargo, set `RUSTFLAGS="-Zno-trait-vptr"` in the environment variable. You probably also want to use `-Zbuild-std` or the binary built may be broken. Save both binaries somewhere.
### Evaluate the space cost
The option has a direct and indirect impact on vtable space usage. Directly, it gets rid of the trait vptr entry needed to store a pointer to a vtable of a supertrait. (IMO) this is a small saving usually. The larger saving usually comes with the indirect saving by eliminating the vtable of the supertrait (and its parent).
Both impacts only affects vtables (notably the number of functions monomorphized should , however where vtable reside can depend on your relocation model. If the relocation model is static, then vtable is rodata (usually stored in Flash/ROM together with text in embedded scenario). If the binary is relocatable, however, the vtable will live in `.data` (more specifically, `.data.rel.ro`), and this will need to reside in RAM (which may be a more scarce resource in some cases), together with dynamic relocation info living in readonly segment.
For evaluation, you should run `size` on both binaries, with and without the flag. `size` would output three columns, `text`, `data`, `bss` and the sum `dec` (and it's hex version). As explained above, both `text` and `data` may change. `bss` shouldn't usually change. It'll be useful to see:
* Percentage change in text + data (indicating required flash/ROM size)
* Percentage change in data + bss (indicating required RAM size)
This reverts commit 4410868798, reversing
changes made to 249595b752.
This causes linker failures with the binutils version used by
cross (#115239), as well as miscompilations when using the mold
linker.
This option tells LLVM to emit relaxable relocation types
R_X86_64_GOTPCRELX/R_X86_64_REX_GOTPCRELX/R_386_GOT32X in applicable cases. True
matches Clang's CMake default since 2020-08 [1] and latest LLVM default[2].
This also works around a GNU ld<2.41 issue[3] when using
general-dynamic/local-dynamic TLS models in `-Z plt=no` mode with latest LLVM.
[1]: c41a18cf61
[2]: 2aedfdd9b8
[3]: https://sourceware.org/bugzilla/show_bug.cgi?id=24784
All of them are not exported from rustc_interface and used only during
global_ctxt(). Inlining them makes it easier to follow the order of
queries and slightly reduces line count.
new unstable option: -Zwrite-long-types-to-disk
This option guards the logic of writing long type names in files and instead using short forms in error messages in rustc_middle/ty/error behind a flag. The main motivation for this change is to disable this behaviour when running ui tests.
This logic can be triggered by running tests in a directory that has a long enough path, e.g. /my/very-long-path/where/rust-codebase/exists/
This means ui tests can fail depending on how long the path to their file is.
Some ui tests actually rely on this behaviour for their assertions, so for those we enable the flag manually.
This option guards the logic of writing long type names in files and
instead using short forms in error messages in rustc_middle/ty/error
behind a flag. The main motivation for this change is to disable this
behaviour when running ui tests.
This logic can be triggered by running tests in a directory that has a
long enough path, e.g. /my/very-long-path/where/rust-codebase/exists/
This means ui tests can fail depending on how long the path to their
file is.
Some ui tests actually rely on this behaviour for their assertions,
so for those we enable the flag manually.
Prototype: Add unstable `-Z reference-niches` option
MCP: rust-lang/compiler-team#641
Relevant RFC: rust-lang/rfcs#3204
This prototype adds a new `-Z reference-niches` option, controlling the range of valid bit-patterns for reference types (`&T` and `&mut T`), thereby enabling new enum niching opportunities. Like `-Z randomize-layout`, this setting is crate-local; as such, references to built-in types (primitives, tuples, ...) are not affected.
The possible settings are (here, `MAX` denotes the all-1 bit-pattern):
| `-Z reference-niches=` | Valid range |
|:---:|:---:|
| `null` (the default) | `1..=MAX` |
| `size` | `1..=(MAX- size)` |
| `align` | `align..=MAX.align_down_to(align)` |
| `size,align` | `align..=(MAX-size).align_down_to(align)` |
------
This is very WIP, and I'm not sure the approach I've taken here is the best one, but stage 1 tests pass locally; I believe this is in a good enough state to unleash this upon unsuspecting 3rd-party code, and see what breaks.
Resurrect: rustc_llvm: Add a -Z `print-codegen-stats` option to expose LLVM statistics.
This resurrects PR https://github.com/rust-lang/rust/pull/104000, which has sat idle for a while. And I want to see the effect of stack-move optimizations on LLVM (like https://reviews.llvm.org/D153453) :).
I have applied the changes requested by `@oli-obk` and `@nagisa` https://github.com/rust-lang/rust/pull/104000#discussion_r1014625377 and https://github.com/rust-lang/rust/pull/104000#discussion_r1014642482 in the latest commits.
r? `@oli-obk`
-----
LLVM has a neat [statistics](https://llvm.org/docs/ProgrammersManual.html#the-statistic-class-stats-option) feature that tracks how often optimizations kick in. It's very handy for optimization work. Since we expose the LLVM pass timings, I thought it made sense to expose the LLVM statistics too.
-----
(Edit: fix broken link
(Edit2: fix segmentation fault and use malloc
If `rustc` is built with
```toml
[llvm]
assertions = true
```
Then you can see like
```
rustc +stage1 -Z print-codegen-stats -C opt-level=3 tmp.rs
===-------------------------------------------------------------------------===
... Statistics Collected ...
===-------------------------------------------------------------------------===
3 aa - Number of MayAlias results
193 aa - Number of MustAlias results
531 aa - Number of NoAlias results
...
```
And the current default build emits only
```
$ rustc +stage1 -Z print-codegen-stats -C opt-level=3 tmp.rs
===-------------------------------------------------------------------------===
... Statistics Collected ...
===-------------------------------------------------------------------------===
$
```
This might be better to emit the message to tell assertion flag necessity, but now I can't find how to do that...
Implement rust-lang/compiler-team#578.
When an ICE is encountered on nightly releases, the new rustc panic
handler will also write the contents of the backtrace to disk. If any
`delay_span_bug`s are encountered, their backtrace is also added to the
file. The platform and rustc version will also be collected.
LLVM has a neat [statistics] feature that tracks how often optimizations kick
in. It's very handy for optimization work. Since we expose the LLVM pass
timings, I thought it made sense to expose the LLVM statistics too.
[statistics]: https://llvm.org/docs/ProgrammersManual.html#the-statistic-class-stats-option
Don't require each rustc_interface tool to opt-in to parallel_compiler
Previously, forgetting to call `interface::set_thread_safe_mode` would cause the following ICE:
```
thread 'rustc' panicked at 'uninitialized dyn_thread_safe mode!', /rustc/dfe0683138de0959b6ab6a039b54d9347f6a6355/compiler/rustc_data_structures/src/sync.rs:74:18
```
This calls `set_thread_safe_mode` in `interface::run_compiler` to avoid requiring it in the caller.
Fixes `tests/run-make-fulldeps/issue-19371` when parallel-compiler is enabled.
r? `@SparrowLii` cc https://github.com/rust-lang/rust/issues/75760
Previously, forgetting to call `interface::set_thread_safe_mode` would cause the following ICE:
```
thread 'rustc' panicked at 'uninitialized dyn_thread_safe mode!', /rustc/dfe0683138de0959b6ab6a039b54d9347f6a6355/compiler/rustc_data_structures/src/sync.rs:74:18
```
This calls `set_thread_safe_mode` in `interface::run_compiler` to avoid requiring it in the caller.
Fixes `tests/run-make-fulldeps/issue-19371` when parallel-compiler is enabled.
Because `Lrc<Box<T>>` is silly. (Clippy warns about `Rc<Box<T>>` and
`Arc<Box<T>>`, and it would warn here if (a) we used Clippy with rustc,
and (b) Clippy knew about `Lrc`.)
There's no need to store it in `Queries`. We can just use a local
variable, because it's always used shortly after it's produced.
The commit also removes the `tcx.analysis()` call in `ongoing_codegen`,
because it's easy to ensure that's done beforehand.
All this makes the dataflow within `run_compiler` easier to follow, at
the cost of making one test slightly more verbose, which I think is a
good tradeoff.
Write to stdout if `-` is given as output file
With this PR, if `-o -` or `--emit KIND=-` is provided, output will be written to stdout instead. Binary output (those of type `obj`, `llvm-bc`, `link` and `metadata`) being written this way will result in an error unless stdout is not a tty. Multiple output types going to stdout will trigger an error too, as they will all be mixded together.
This implements https://github.com/rust-lang/compiler-team/issues/431
The idea behind the changes is to introduce an `OutFileName` enum that represents the output - be it a real path or stdout - and to use this enum along the code paths that handle different output types.
If `-o -` or `--emit KIND=-` is provided, output will be written
to stdout instead. Binary output (`obj`, `llvm-bc`, `link` and
`metadata`) being written this way will result in an error unless
stdout is not a tty. Multiple output types going to stdout will
trigger an error too, as they will all be mixded together.
Fix dependency tracking for debugger visualizers
This PR fixes dependency tracking for debugger visualizer files by changing the `debugger_visualizers` query to an `eval_always` query that scans the AST while it is still available. This way the set of visualizer files is already available when dep-info is emitted. Since the query is turned into an `eval_always` query, dependency tracking will now reliably detect changes to the visualizer script files themselves.
TODO:
- [x] perf.rlo
- [x] Needs a bit more documentation in some places
- [x] Needs regression test for the incr. comp. case
Fixes https://github.com/rust-lang/rust/issues/111226
Fixes https://github.com/rust-lang/rust/issues/111227
Fixes https://github.com/rust-lang/rust/issues/111295
r? `@wesleywiser`
cc `@gibbyfree`
Only depend on CFG_VERSION in rustc_interface
This avoids having to rebuild the whole compiler on each commit when `omit-git-hash = false`.
cc https://github.com/rust-lang/rust/issues/76720 - this won't fix it, and I'm not suggesting we turn this on by default, but it will make it less painful for people who do have `omit-git-hash` on as a workaround.
Error message all end up passing into a function as an `impl
Into<{D,Subd}iagnosticMessage>`. If an error message is creatd as
`&format("...")` that means we allocate a string (in the `format!`
call), then take a reference, and then clone (allocating again) the
reference to produce the `{D,Subd}iagnosticMessage`, which is silly.
This commit removes the leading `&` from a lot of these cases. This
means the original `String` is moved into the
`{D,Subd}iagnosticMessage`, avoiding the double allocations. This
requires changing some function argument types from `&str` to `String`
(when all arguments are `String`) or `impl
Into<{D,Subd}iagnosticMessage>` (when some arguments are `String` and
some are `&str`).
Use dynamic dispatch for queries
This replaces most concrete query values `V` with `MaybeUninit<[u8; { size_of::<V>() }]>` reducing the code instantiated by queries. The compile time of `rustc_query_impl` is reduced by 27%. It is an alternative to https://github.com/rust-lang/rust/pull/107937 which uses unstable const generics while this uses a `EraseType` trait which maps query values to their erased variant.
This is achieved by introducing an `Erased` type which does sanity check with `cfg(debug_assertions)`. The query caches gets instantiated with these erased types leaving the code in `rustc_query_system` unaware of them. `rustc_query_system` is changed to use instances of `QueryConfig` so that `rustc_query_impl` can pass in `DynamicConfig` which holds a pointer to a virtual table.
<table><tr><td rowspan="2">Benchmark</td><td colspan="1"><b>Before</b></th><td colspan="2"><b>After</b></th></tr><tr><td align="right">Time</td><td align="right">Time</td><td align="right">%</th></tr><tr><td>🟣 <b>clap</b>:check</td><td align="right">1.7055s</td><td align="right">1.6949s</td><td align="right"> -0.62%</td></tr><tr><td>🟣 <b>hyper</b>:check</td><td align="right">0.2547s</td><td align="right">0.2528s</td><td align="right"> -0.73%</td></tr><tr><td>🟣 <b>regex</b>:check</td><td align="right">0.9590s</td><td align="right">0.9553s</td><td align="right"> -0.39%</td></tr><tr><td>🟣 <b>syn</b>:check</td><td align="right">1.5457s</td><td align="right">1.5440s</td><td align="right"> -0.11%</td></tr><tr><td>🟣 <b>syntex_syntax</b>:check</td><td align="right">5.9092s</td><td align="right">5.9009s</td><td align="right"> -0.14%</td></tr><tr><td>Total</td><td align="right">10.3741s</td><td align="right">10.3479s</td><td align="right"> -0.25%</td></tr><tr><td>Summary</td><td align="right">1.0000s</td><td align="right">0.9960s</td><td align="right"> -0.40%</td></tr></table>
<table><tr><td rowspan="2">Benchmark</td><td colspan="1"><b>Before</b></th><td colspan="2"><b>After</b></th></tr><tr><td align="right">Time</td><td align="right">Time</td><td align="right">%</th></tr><tr><td>🟣 <b>clap</b>:check:initial</td><td align="right">2.0605s</td><td align="right">2.0575s</td><td align="right"> -0.15%</td></tr><tr><td>🟣 <b>hyper</b>:check:initial</td><td align="right">0.3218s</td><td align="right">0.3216s</td><td align="right"> -0.07%</td></tr><tr><td>🟣 <b>regex</b>:check:initial</td><td align="right">1.1848s</td><td align="right">1.1839s</td><td align="right"> -0.07%</td></tr><tr><td>🟣 <b>syn</b>:check:initial</td><td align="right">1.9409s</td><td align="right">1.9376s</td><td align="right"> -0.17%</td></tr><tr><td>🟣 <b>syntex_syntax</b>:check:initial</td><td align="right">7.3105s</td><td align="right">7.2928s</td><td align="right"> -0.24%</td></tr><tr><td>Total</td><td align="right">12.8185s</td><td align="right">12.7935s</td><td align="right"> -0.20%</td></tr><tr><td>Summary</td><td align="right">1.0000s</td><td align="right">0.9986s</td><td align="right"> -0.14%</td></tr></table>
<table><tr><td rowspan="2">Benchmark</td><td colspan="1"><b>Before</b></th><td colspan="2"><b>After</b></th></tr><tr><td align="right">Time</td><td align="right">Time</td><td align="right">%</th></tr><tr><td>🟣 <b>clap</b>:check:unchanged</td><td align="right">0.4606s</td><td align="right">0.4617s</td><td align="right"> 0.24%</td></tr><tr><td>🟣 <b>hyper</b>:check:unchanged</td><td align="right">0.1335s</td><td align="right">0.1336s</td><td align="right"> 0.08%</td></tr><tr><td>🟣 <b>regex</b>:check:unchanged</td><td align="right">0.3324s</td><td align="right">0.3346s</td><td align="right"> 0.65%</td></tr><tr><td>🟣 <b>syn</b>:check:unchanged</td><td align="right">0.6268s</td><td align="right">0.6307s</td><td align="right"> 0.64%</td></tr><tr><td>🟣 <b>syntex_syntax</b>:check:unchanged</td><td align="right">1.8248s</td><td align="right">1.8508s</td><td align="right">💔 1.43%</td></tr><tr><td>Total</td><td align="right">3.3779s</td><td align="right">3.4113s</td><td align="right"> 0.99%</td></tr><tr><td>Summary</td><td align="right">1.0000s</td><td align="right">1.0061s</td><td align="right"> 0.61%</td></tr></table>
It's based on https://github.com/rust-lang/rust/pull/108167.
r? `@cjgillot`
Introduce `DynSend` and `DynSync` auto trait for parallel compiler
part of parallel-rustc #101566
This PR introduces `DynSend / DynSync` trait and `FromDyn / IntoDyn` structure in rustc_data_structure::marker. `FromDyn` can dynamically check data structures for thread safety when switching to parallel environments (such as calling `par_for_each_in`). This happens only when `-Z threads > 1` so it doesn't affect single-threaded mode's compile efficiency.
r? `@cjgillot`
Fix mishandled `--check-cfg` arguments order
This PR fixes a bug in `--check-cfg` where the order of `--check-cfg=names(a)` and `--check-cfg=values(a,…)` would trip the compiler.
Fixes https://github.com/rust-lang/rust/issues/111291
cc `@taiki-e` `@petrochenkov`
Add `force` option for `--extern` flag
When `--extern force:foo=libfoo.so` is passed to `rustc` and `foo` is not actually used in the crate, ~inject an `extern crate foo;` statement into the AST~ force it to be resolved anyway in `CrateLoader::postprocess()`. This allows you to, for instance, inject a `#[panic_handler]` implementation into a `#![no_std]` crate without modifying its source so that it can be built as a `dylib`. It may also be useful for `#![panic_runtime]` or `#[global_allocator]`/`#![default_lib_allocator]` implementations.
My work previously involved integrating Rust into an existing C/C++ codebase which was built with Buck and shipped on, among other platforms, Android. When targeting Android, Buck builds all "native" code with shared linkage* so it can be loaded from Java/Kotlin. My project was not itself `#![no_std]`, but many of our dependencies were, and they would fail to build with shared linkage due to a lack of a panic handler. With this change, that project can add the new `force` option to the `std` dependency it already explicitly provides to every crate to solve this problem.
*This is an oversimplification - Buck has a couple features for aggregating dependencies into larger shared libraries, but none that I think sustainably solve this problem.
~The AST injection happens after macro expansion around where we similarly inject a test harness and proc-macro harness. The resolver's list of actually-used extern flags is populated during macro expansion, and if any of our `--extern` arguments have the `force` option and weren't already used, we inject an `extern crate` statement for them. The injection logic was added in `rustc_builtin_macros` as that's where similar injections for tests, proc-macros, and std/core already live.~
(New contributor - grateful for feedback and guidance!)
Stabilize raw-dylib, link_ordinal, import_name_type and -Cdlltool
This stabilizes the `raw-dylib` feature (#58713) for all architectures (i.e., `x86` as it is already stable for all other architectures).
Changes:
* Permit the use of the `raw-dylib` link kind for x86, the `link_ordinal` attribute and the `import_name_type` key for the `link` attribute.
* Mark the `raw_dylib` feature as stable.
* Stabilized the `-Zdlltool` argument as `-Cdlltool`.
* Note the path to `dlltool` if invoking it failed (we don't need to do this if `dlltool` returns an error since it prints its path in the error message).
* Adds tests for `-Cdlltool`.
* Adds tests for being unable to find the dlltool executable, and dlltool failing.
* Fixes a bug where we were checking the exit code of dlltool to see if it failed, but dlltool always returns 0 (indicating success), so instead we need to check if anything was written to `stderr`.
NOTE: As previously noted (https://github.com/rust-lang/rust/pull/104218#issuecomment-1315895618) using dlltool within rustc is temporary, but this is not the first time that Rust has added a temporary tool use and argument: https://github.com/rust-lang/rust/pull/104218#issuecomment-1318720482
Big thanks to ``````@tbu-`````` for the first version of this PR (#104218)
Improve check-cfg implementation
This PR makes multiple improvements into the implementation of check-cfg, it is a prerequisite to a follow-up PR that will introduce a simpler and more explicit syntax.
The 2 main area of improvements are:
1. Internal representation of expected values:
- now uses `FxHashSet<Option<Symbol>>` instead of `FxHashSet<Symbol>`, it made the no value expected case only possible when no values where in the `HashSet` which is now represented as `None` (same as cfg represent-it).
- a enum with `Some` and `Any` makes it now clear if some values are expected or not, necessary for `feature` and `target_feature`.
2. Diagnostics: Improve the diagnostics in multiple case and fix case where a missing value could have had a new name suggestion instead of the value diagnostic; and some drive by improvements
I highly recommend reviewing commit by commit.
r? `@petrochenkov`
This is done to simplify to relationship between names() and values()
but also make thing clearer (having an Any to represent that any values
are allowed) but also to allow the (none) + values expected cases that
wasn't possible before.
Add cross-language LLVM CFI support to the Rust compiler
This PR adds cross-language LLVM Control Flow Integrity (CFI) support to the Rust compiler by adding the `-Zsanitizer-cfi-normalize-integers` option to be used with Clang `-fsanitize-cfi-icall-normalize-integers` for normalizing integer types (see https://reviews.llvm.org/D139395).
It provides 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). For more information about LLVM CFI and cross-language LLVM CFI support for the Rust compiler, see design document in the tracking issue #89653.
Cross-language LLVM CFI can be enabled with -Zsanitizer=cfi and -Zsanitizer-cfi-normalize-integers, and requires proper (i.e., non-rustc) LTO (i.e., -Clinker-plugin-lto).
Thank you again, ``@bjorn3,`` ``@nikic,`` ``@samitolvanen,`` and the Rust community for all the help!
This commit adds cross-language LLVM Control Flow Integrity (CFI)
support to the Rust compiler by adding the
`-Zsanitizer-cfi-normalize-integers` option to be used with Clang
`-fsanitize-cfi-icall-normalize-integers` for normalizing integer types
(see https://reviews.llvm.org/D139395).
It provides 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). For more
information about LLVM CFI and cross-language LLVM CFI support for the
Rust compiler, see design document in the tracking issue #89653.
Cross-language LLVM CFI can be enabled with -Zsanitizer=cfi and
-Zsanitizer-cfi-normalize-integers, and requires proper (i.e.,
non-rustc) LTO (i.e., -Clinker-plugin-lto).
