Mark `simplify_aggregate_to_copy` mir-opt as unsound
Mark the `simplify_aggregate_to_copy` mir-opt added in #128299 as unsound as it seems to miscompile the MCVE reported in https://github.com/rust-lang/rust/issues/132353. The mir-opt can be re-enabled once this case is fixed.
```rs
fn pop_min(mut score2head: Vec<Option<usize>>) -> Option<usize> {
loop {
if let Some(col) = score2head[0] {
score2head[0] = None;
return Some(col);
}
}
}
fn main() {
let min = pop_min(vec![Some(1)]);
println!("min: {:?}", min);
// panic happens here on beta in release mode
// but not in debug mode
min.unwrap();
}
```
This MCVE is included as a `run-pass` ui regression test in the first commit. I built the ui test with a nightly manually, and can reproduce the behavioral difference with `-C opt-level=0` and `-C opt-level=1`. Locally, this ui test will fail unless it was run on a compiler built with the second commit marking the mir-opt as unsound thus disabling it by default.
This PR **partially reverts** commit e7386b3, reversing changes made to 02b1be1. The mir-opt implementation is just marked as unsound but **not** reverted to make reland reviews easier. Test changes are **reverted if they were not pure additions**. Tests added by the original PR received `-Z unsound-mir-opts` compile-flags.
cc `@DianQK` `@cjgillot` (PR author and reviewer of #128299)
Rename Receiver -> LegacyReceiver
As part of the "arbitrary self types v2" project, we are going to replace the current `Receiver` trait with a new mechanism based on a new, different `Receiver` trait.
This PR renames the old trait to get it out the way. Naming is hard. Options considered included:
* HardCodedReceiver (because it should only be used for things in the standard library, and hence is sort-of hard coded)
* LegacyReceiver
* TargetLessReceiver
* OldReceiver
These are all bad names, but fortunately this will be temporary. Assuming the new mechanism proceeds to stabilization as intended, the legacy trait will be removed altogether.
Although we expect this trait to be used only in the standard library, we suspect it may be in use elsehwere, so we're landing this change separately to identify any surprising breakages.
It's known that this trait is used within the Rust for Linux project; a patch is in progress to remove their dependency.
This is a part of the arbitrary self types v2 project,
https://github.com/rust-lang/rfcs/pull/3519https://github.com/rust-lang/rust/issues/44874
r? `@wesleywiser`
Set `signext` or `zeroext` for integer arguments on RISC-V and LoongArch64
This PR contains 3 commits:
- the first one introduces a new function `adjust_for_rust_abi` in `rustc_target`, and moves the x86 specific adjustment code into it;
- the second one adds RISC-V specific adjustment code into it, which sets `signext` or `zeroext` attribute for integer arguments.
- **UPDATE**: added the 3rd commit to apply the same adjustment for LoongArch64.
Optimize `Rc<T>::default`
The missing piece of https://github.com/rust-lang/rust/pull/131460.
Also refactored `Arc<T>::default` by using a safe `NonNull::from(Box::leak(_))` to replace the unnecessarily unsafe call to `NonNull::new_unchecked(Box::into_raw(_))`. The remaining unsafety is coming from `[Rc|Arc]::from_inner`, which is safe from the construction of `[Rc|Arc]Inner`.
x86-32 float return for 'Rust' ABI: treat all float types consistently
This helps with https://github.com/rust-lang/rust/issues/131819: for our own ABI on x86-32, we want to *never* use the float registers. The previous logic only considered F32 and F64, but skipped F16 and F128. So I made the logic just apply to all float types.
try-job: i686-gnu
try-job: i686-gnu-nopt
As part of the "arbitrary self types v2" project, we are going to
replace the current `Receiver` trait with a new mechanism based on a
new, different `Receiver` trait.
This PR renames the old trait to get it out the way. Naming is hard.
Options considered included:
* HardCodedReceiver (because it should only be used for things in the
standard library, and hence is sort-of hard coded)
* LegacyReceiver
* TargetLessReceiver
* OldReceiver
These are all bad names, but fortunately this will be temporary.
Assuming the new mechanism proceeds to stabilization as intended, the
legacy trait will be removed altogether.
Although we expect this trait to be used only in the standard library,
we suspect it may be in use elsehwere, so we're landing this change
separately to identify any surprising breakages.
It's known that this trait is used within the Rust for Linux project; a
patch is in progress to remove their dependency.
This is a part of the arbitrary self types v2 project,
https://github.com/rust-lang/rfcs/pull/3519https://github.com/rust-lang/rust/issues/44874
r? @wesleywiser
Always specify `llvm_abiname` for RISC-V targets
For RISC-V targets, when `llvm_abiname` is not specified LLVM will infer the ABI from the target features, causing #116344 to occur. This PR adds the correct `llvm_abiname` to all RISC-V targets where it is missing (which are all soft-float targets), and adds a test to prevent future RISC-V targets from accidentally omitting `llvm_abiname`. The only affect of this PR is that `-Ctarget-feature=+f` (or similar) will no longer affect the ABI on the modified targets.
<!-- homu-ignore:start -->
r? `@RalfJung`
<!--- homu-ignore:end -->
rust_for_linux: -Zregparm=<N> commandline flag for X86 (#116972)
Command line flag `-Zregparm=<N>` for X86 (32-bit) for rust-for-linux: https://github.com/rust-lang/rust/issues/116972
Implemented in the similar way as fastcall/vectorcall support (args are marked InReg if fit).
Return values larger than 2 registers using a return area pointer
LLVM and Cranelift disagree about how to return values that don't fit in the registers designated for return values. LLVM will force the entire return value to be passed by return area pointer, while Cranelift will look at each IR level return value independently and decide to pass it in a register or not, which would result in the return value being passed partially in registers and partially through a return area pointer.
While Cranelift may need to be fixed as the LLVM behavior is generally more correct with respect to the surface language, forcing this behavior in rustc itself makes it easier for other backends to conform to the Rust ABI and for the C ABI rustc already handles this behavior anyway.
In addition LLVM's decision to pass the return value in registers or using a return area pointer depends on how exactly the return type is lowered to an LLVM IR type. For example `Option<u128>` can be lowered as `{ i128, i128 }` in which case the x86_64 backend would use a return area pointer, or it could be passed as `{ i32, i128 }` in which case the x86_64 backend would pass it in registers by taking advantage of an LLVM ABI extension that allows using 3 registers for the x86_64 sysv call conv rather than the officially specified 2 registers.
This adjustment is only necessary for the Rust ABI as for other ABI's the calling convention implementations in rustc_target already ensure any return value which doesn't fit in the available amount of return registers is passed in the right way for the current target.
Helps with https://github.com/rust-lang/rustc_codegen_cranelift/issues/1525
cc https://github.com/bytecodealliance/wasmtime/issues/9250
Avoid superfluous UB checks in `IndexRange`
`IndexRange::len` is justified as an overall invariant, and
`take_prefix` and `take_suffix` are justified by local branch
conditions. A few more UB-checked calls remain in cases that are only
supported locally by `debug_assert!`, which won't do anything in
distributed builds, so those UB checks may still be useful.
We generally expect core's `#![rustc_preserve_ub_checks]` to optimize
away in user's release builds, but the mere presence of that extra code
can sometimes inhibit optimization, as seen in #131563.
llvm/llvm-project#91101 propagates range information across inlining,
resulting in more metadata in this test. Tolerate the range metadata if
it appears.
Support clobber_abi in MSP430 inline assembly
This supports `clobber_abi` which is one of the requirements of stabilization mentioned in #93335.
Refs: Section 3.2 "Register Conventions" in [MSP430 Embedded Application Binary Interface](https://www.ti.com/lit/an/slaa534a/slaa534a.pdf)
cc ``@cr1901``
r? ``@Amanieu``
``@rustbot`` label +O-msp430
`IndexRange::len` is justified as an overall invariant, and
`take_prefix` and `take_suffix` are justified by local branch
conditions. A few more UB-checked calls remain in cases that are only
supported locally by `debug_assert!`, which won't do anything in
distributed builds, so those UB checks may still be useful.
We generally expect core's `#![rustc_preserve_ub_checks]` to optimize
away in user's release builds, but the mere presence of that extra code
can sometimes inhibit optimization, as seen in #131563.
Use Default visibility for rustc-generated C symbol declarations
Non-default visibilities should only be used for definitions, not declarations, otherwise linking can fail.
This is based on https://github.com/rust-lang/rust/pull/123994.
Issue https://github.com/rust-lang/rust/issues/123427
When I changed `default-hidden-visibility` to `default-visibility` in https://github.com/rust-lang/rust/pull/130005, I updated all places in the code that used `default-hidden-visibility`, replicating the hidden-visibility bug to also happen for protected visibility.
Without this change, trying to build rustc with `-Z default-visibility=protected` fails with a link error.
This hack was intended to handle the case where `-Clto=thin` causes the
compiler to emit multiple output files (when producing LLVM-IR or assembly).
The hack only affects 4 tests, of which 3 are just meta-tests for the hack
itself. The one remaining test that motivated the hack currently doesn't even
need it!
(`tests/codegen/issues/issue-81408-dllimport-thinlto-windows.rs`)
Non-default visibilities should only be used for definitions, not
declarations, otherwise linking can fail.
Co-authored-by: Collin Baker <collinbaker@chromium.org>
LLVM and Cranelift disagree about how to return values that don't fit
in the registers designated for return values. LLVM will force the
entire return value to be passed by return area pointer, while
Cranelift will look at each IR level return value independently and
decide to pass it in a register or not, which would result in the
return value being passed partially in registers and partially through
a return area pointer.
While Cranelift may need to be fixed as the LLVM behavior is generally
more correct with respect to the surface language, forcing this
behavior in rustc itself makes it easier for other backends to conform
to the Rust ABI and for the C ABI rustc already handles this behavior
anyway.
In addition LLVM's decision to pass the return value in registers or
using a return area pointer depends on how exactly the return type is
lowered to an LLVM IR type. For example `Option<u128>` can be lowered
as `{ i128, i128 }` in which case the x86_64 backend would use a return
area pointer, or it could be passed as `{ i32, i128 }` in which case
the x86_64 backend would pass it in registers by taking advantage of an
LLVM ABI extension that allows using 3 registers for the x86_64 sysv
call conv rather than the officially specified 2 registers.
This adjustment is only necessary for the Rust ABI as for other ABI's
the calling convention implementations in rustc_target already ensure
any return value which doesn't fit in the available amount of return
registers is passed in the right way for the current target.
The `Box<T: Default>` impl currently calls `T::default()` before allocating
the `Box`.
Most `Default` impls are trivial, which should in theory allow
LLVM to construct `T: Default` directly in the `Box` allocation when calling
`<Box<T>>::default()`.
However, the allocation may fail, which necessitates calling `T's` destructor if it has one.
If the destructor is non-trivial, then LLVM has a hard time proving that it's
sound to elide, which makes it construct `T` on the stack first, and then copy it into the allocation.
Create an uninit `Box` first, and then write `T::default` into it, so that LLVM now only needs to prove
that the `T::default` can't panic, which should be trivial for most `Default` impls.
Add missing module flags for `-Zfunction-return=thunk-extern`
This fixes a bug in the `-Zfunction-return=thunk-extern` flag. The flag needs to be passed onto LLVM to ensure that functions such as `asan.module_ctor` and `asan.module_dtor` that are created internally in LLVM have the mitigation applied to them.
This was originally discovered [in the Linux kernel](https://lore.kernel.org/all/CANiq72myZL4_poCMuNFevtpYYc0V0embjSuKb7y=C+m3vVA_8g@mail.gmail.com/).
Original flag PR: #116892
PR for similar issue: #129373
Tracking issue: #116853
cc ``@ojeda``
r? ``@wesleywiser``
- fix for divergence
- fix error message
- fix another cranelift test
- fix some cranelift things
- don't set the NORETURN option for naked asm
- fix use of naked_asm! in doc comment
- fix use of naked_asm! in run-make test
- use `span_bug` in unreachable branch
