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.
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.
In https://reviews.llvm.org/D125556 upstream changed sext() and zext()
to allow some no-op cases, which previously required use of the *OrSelf()
methods, which I assume is what was going on here. The *OrSelf() methods
got removed in https://reviews.llvm.org/D125559 after two weeks of
deprecation because they came with some bonus (probably-undesired)
behavior. Since the behavior of sext() and zext() changed slightly, I
kept the old *OrSelf() calls in LLVM 14 and earlier, and only use the
new version in LLVM 15.
r? @nikic
This new enum entry was introduced in https://reviews.llvm.org/D122268,
and if I'm reading correctly there's no case where we'd ever encounter
it in our uses of LLVM. To preserve the ability to compile this file
with -Werror -Wswitch we add an explicit case for this entry.
The majority of the code is only used by either rustbuild or
rustc_llvm's build script. Rust_build is compiled once for rustbuild and
once for every stage. This means that the majority of the code in this
crate is needlessly compiled multiple times. By moving only the code
actually used by the respective crates to rustbuild and rustc_llvm's
build script, this needless duplicate compilation is avoided.
Remove LLVM attribute removal
This was necessary before, because `declare_raw_fn` would always apply
the default optimization attributes to every declared function.
Then `attributes::from_fn_attrs` would have to remove the default
attributes in the case of, e.g. `#[optimize(speed)]` in a `-Os` build.
(see [`src/test/codegen/optimize-attr-1.rs`](03a8cc7df1/src/test/codegen/optimize-attr-1.rs (L33)))
However, every relevant callsite of `declare_raw_fn` (i.e. where we
actually generate code for the function, and not e.g. a call to an
intrinsic, where optimization attributes don't [?] matter)
calls `from_fn_attrs`, so we can remove the attribute setting
from `declare_raw_fn`, and rely on `from_fn_attrs` to apply the correct
attributes all at once.
r? `@ghost` (blocked on #94221)
`@rustbot` label S-blocked
This was necessary before, because `declare_raw_fn` would always apply
the default optimization attributes to every declared function,
and then `attributes::from_fn_attrs` would have to remove the default
attributes in the case of, e.g. `#[optimize(speed)]` in a `-Os` build.
However, every relevant callsite of `declare_raw_fn` (i.e. where we
actually generate code for the function, and not e.g. a call to an
intrinsic, where optimization attributes don't [?] matter)
calls `from_fn_attrs`, so we can simply remove the attribute setting
from `declare_raw_fn`, and rely on `from_fn_attrs` to apply the correct
attributes all at once.
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
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.
This doesn't handle `char` because it's a bit awkward to distinguish it
from u32 at this point in codegen.
Note that for some types (like `&Struct` and `&mut Struct`),
we already apply `dereferenceable`, which implies `noundef`,
so the IR does not change.
This agrees with Clang, and avoids an error when using LTO with mixed
C/Rust. LLVM considers different behaviour flags to be a mismatch,
even when the flag value itself is the same.
This also makes the flag setting explicit for all uses of
LLVMRustAddModuleFlag.
This was originally introduced in #10916 as a way to remove all landing
pads when performing LTO. However this is no longer necessary today
since rustc properly marks all functions and call-sites as nounwind
where appropriate.
In fact this is incorrect in the presence of `extern "C-unwind"` which
must create a landing pad when compiled with `-C panic=abort` so that
foreign exceptions are caught and properly turned into aborts.
RustWrapper: adapt to new AttributeMask API
Upstream LLVM change 9290ccc3c1a1 migrated attribute removal to use
AttributeMask instead of AttrBuilder, so we need to follow suit here.
r? ``@nagisa`` cc ``@nikic``
No functional changes intended.
The LLVM commit
ec501f15a8
removed the signed version of `createExpression`. This adapts the Rust
LLVM wrappers accordingly.
Mark drop calls in landing pads `cold` instead of `noinline`
Now that deferred inlining has been disabled in LLVM (#92110), this shouldn't cause catastrophic size blowup.
I confirmed that the test cases from https://github.com/rust-lang/rust/issues/41696#issuecomment-298696944 still compile quickly (<1s) after this change. ~Although note that I wasn't able to reproduce the original issue using a recent rustc/llvm with deferred inlining enabled, so those tests may no longer be representative. I was also unable to create a modified test case that reproduced the original issue.~ (edit: I reproduced it on CI by accident--the first commit timed out on the LLVM 12 builder, because I forgot to make it conditional on LLVM version)
r? `@nagisa`
cc `@arielb1` (this effectively reverts #42771 "mark calls in the unwind path as !noinline")
cc `@RalfJung` (fixes#46515)
edit: also fixes#87055
Add support for riscv64gc-unknown-freebsd
For https://doc.rust-lang.org/nightly/rustc/target-tier-policy.html#tier-3-target-policy:
* A 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.)
For all Rust targets on FreeBSD, it's [rust@FreeBSD.org](mailto:rust@FreeBSD.org).
* 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.
Done.
* 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.
Done
* 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.
Done.
* The target must not introduce license incompatibilities.
Done.
* Anything added to the Rust repository must be under the standard Rust license (MIT OR Apache-2.0).
Fine with me.
* 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.
Done.
* 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.
Done.
* Targets should not require proprietary (non-FOSS) components to link a functional binary or library.
Done.
* "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.
Fine with me.
* 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.
Ok.
* 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.
Ok.
* 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.
std is implemented.
* 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.
Building is possible the same way as other Rust on FreeBSD targets.
* 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.
Ok.
* 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.
Ok.
* 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.
Ok.
* 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.
Ok.
Add support for LLVM coverage mapping format versions 5 and 6
This PR cherry-pick's Swatinem's initial commit in unsubmitted PR #90047.
My additional commit augments Swatinem's great starting point, but adds full support for LLVM
Coverage Mapping Format version 6, conditionally, if compiling with LLVM 13.
Version 6 requires adding the compilation directory when file paths are
relative, and since Rustc coverage maps use relative paths, we should
add the expected compilation directory entry.
Note, however, that with the compilation directory, coverage reports
from `llvm-cov show` can now report file names (when the report includes
more than one file) with the full absolute path to the file.
This would be a problem for test results, but the workaround (for the
rust coverage tests) is to include an additional `llvm-cov show`
parameter: `--compilation-dir=.`
Emit LLVM optimization remarks when enabled with `-Cremark`
The default diagnostic handler considers all remarks to be disabled by
default unless configured otherwise through LLVM internal flags:
`-pass-remarks`, `-pass-remarks-missed`, and `-pass-remarks-analysis`.
This behaviour makes `-Cremark` ineffective on its own.
Fix this by configuring a custom diagnostic handler that enables
optimization remarks based on the value of `-Cremark` option. With
`-Cremark=all` enabling all remarks.
Fixes#90924.
r? `@nikic`
LLVM has built-in heuristics for adding stack canaries to functions. These
heuristics can be selected with LLVM function attributes. This patch adds a
rustc option `-Z stack-protector={none,basic,strong,all}` which controls the use
of these attributes. This gives rustc the same stack smash protection support as
clang offers through options `-fno-stack-protector`, `-fstack-protector`,
`-fstack-protector-strong`, and `-fstack-protector-all`. The protection this can
offer is demonstrated in test/ui/abi/stack-protector.rs. This fills a gap in the
current list of rustc exploit
mitigations (https://doc.rust-lang.org/rustc/exploit-mitigations.html),
originally discussed in #15179.
Stack smash protection adds runtime overhead and is therefore still off by
default, but now users have the option to trade performance for security as they
see fit. An example use case is adding Rust code in an existing C/C++ code base
compiled with stack smash protection. Without the ability to add stack smash
protection to the Rust code, the code base artifacts could be exploitable in
ways not possible if the code base remained pure C/C++.
Stack smash protection support is present in LLVM for almost all the current
tier 1/tier 2 targets: see
test/assembly/stack-protector/stack-protector-target-support.rs. The one
exception is nvptx64-nvidia-cuda. This patch follows clang's example, and adds a
warning message printed if stack smash protection is used with this target (see
test/ui/stack-protector/warn-stack-protector-unsupported.rs). Support for tier 3
targets has not been checked.
Since the heuristics are applied at the LLVM level, the heuristics are expected
to add stack smash protection to a fraction of functions comparable to C/C++.
Some experiments demonstrating how Rust code is affected by the different
heuristics can be found in
test/assembly/stack-protector/stack-protector-heuristics-effect.rs. There is
potential for better heuristics using Rust-specific safety information. For
example it might be reasonable to skip stack smash protection in functions which
transitively only use safe Rust code, or which uses only a subset of functions
the user declares safe (such as anything under `std.*`). Such alternative
heuristics could be added at a later point.
LLVM also offers a "safestack" sanitizer as an alternative way to guard against
stack smashing (see #26612). This could possibly also be included as a
stack-protection heuristic. An alternative is to add it as a sanitizer (#39699).
This is what clang does: safestack is exposed with option
`-fsanitize=safe-stack`.
The options are only supported by the LLVM backend, but as with other codegen
options it is visible in the main codegen option help menu. The heuristic names
"basic", "strong", and "all" are hopefully sufficiently generic to be usable in
other backends as well.
Reviewed-by: Nikita Popov <nikic@php.net>
Extra commits during review:
- [address-review] make the stack-protector option unstable
- [address-review] reduce detail level of stack-protector option help text
- [address-review] correct grammar in comment
- [address-review] use compiler flag to avoid merging functions in test
- [address-review] specify min LLVM version in fortanix stack-protector test
Only for Fortanix test, since this target specifically requests the
`--x86-experimental-lvi-inline-asm-hardening` flag.
- [address-review] specify required LLVM components in stack-protector tests
- move stack protector option enum closer to other similar option enums
- rustc_interface/tests: sort debug option list in tracking hash test
- add an explicit `none` stack-protector option
Revert "set LLVM requirements for all stack protector support test revisions"
This reverts commit a49b74f92a4e7d701d6f6cf63d207a8aff2e0f68.
`Module::getOrInsertGlobal` returns a `Constant*`, which is a super
class of `GlobalVariable`, but if the given type doesn't match an
existing declaration, it returns a bitcast of that global instead.
This causes UB when we pass that to `LLVMGetVisibility` which
unconditionally casts the opaque argument to a `GlobalValue*`.
Instead, we can do our own get-or-insert without worrying whether
existing types match exactly. It's not relevant when we're just trying
to get/set the linkage and visibility, and if types are needed we can
bitcast or error nicely from `rustc_codegen_llvm` instead.
