LLVM Assertion failed when optimizing SIMD code on aarch64.apple.darwin

[bk-eclipse]

Code

#![feature(portable_simd)]
use core::simd::Simd;

type BASE=u64;
fn test(
    value: [Simd<BASE, 1>; 2]
) -> Simd<BASE, 1> {
    rotate_right(Simd::splat(1) ^ value[0], 8)
}

fn rotate_right(v: Simd<BASE, 1>, count: BASE) -> Simd<BASE, 1> {
    (v >> count) | (v << (64-count))
}

fn main() {
    let v = [Simd::splat(1); 2];
    assert_eq!(test(v), Simd::splat(1));
}

Meta

rustc --version --verbose:

rustc 1.89.0-nightly (dcecb9917 2025-05-09)

Error output

error: rustc interrupted by SIGILL, printing backtrace

Backtrace

Thread 9 "lto cgu.0" received signal SIGILL, Illegal instruction.
[Switching to Thread 0x7fffdcbff6c0 (LWP 481356)]
0x00007fffed215dbb in llvm::AArch64InstrInfo::copyPhysReg(llvm::MachineBasicBlock&, llvm::MachineInstrBundleIterator<llvm::MachineInstr, false>, llvm::DebugLoc const&, llvm::MCRegister, llvm::MCRegister, bool, bool, bool) const ()
   from ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/libLLVM.so.20.1-rust-1.89.0-nightly
(gdb) bt
#0  0x00007fffed215dbb in llvm::AArch64InstrInfo::copyPhysReg(llvm::MachineBasicBlock&, llvm::MachineInstrBundleIterator<llvm::MachineInstr, false>, llvm::DebugLoc const&, llvm::MCRegister, llvm::MCRegister, bool, bool, bool) const ()
   from ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/libLLVM.so.20.1-rust-1.89.0-nightly
#1  0x00007fffef8b6eac in llvm::TargetInstrInfo::lowerCopy(llvm::MachineInstr*, llvm::TargetRegisterInfo const*) const [clone .cold] ()
   from ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/libLLVM.so.20.1-rust-1.89.0-nightly
#2  0x00007fffeec34b8d in (anonymous namespace)::ExpandPostRA::runOnMachineFunction(llvm::MachineFunction&) ()
   from ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/libLLVM.so.20.1-rust-1.89.0-nightly
#3  0x00007fffee828f91 in llvm::FPPassManager::runOnFunction(llvm::Function&) ()
   from ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/libLLVM.so.20.1-rust-1.89.0-nightly
#4  0x00007fffee8283ef in llvm::FPPassManager::runOnModule(llvm::Module&) ()
   from ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/libLLVM.so.20.1-rust-1.89.0-nightly
#5  0x00007fffeee5d7c3 in llvm::legacy::PassManagerImpl::run(llvm::Module&) ()
   from ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/libLLVM.so.20.1-rust-1.89.0-nightly
#6  0x00007ffff6830302 in LLVMRustWriteOutputFile ()
   from ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-9dc9f9e211dbb3c2.so
#7  0x00007ffff682fe61 in rustc_codegen_llvm::back::write::write_output_file ()
   from ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-9dc9f9e211dbb3c2.so
#8  0x00007ffff682d426 in rustc_codegen_llvm::back::write::codegen ()
   from ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-9dc9f9e211dbb3c2.so
#9  0x00007ffff682d0f4 in rustc_codegen_ssa::back::write::finish_intra_module_work::<rustc_codegen_llvm::LlvmCodegenBackend> ()
   from ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-9dc9f9e211dbb3c2.so
#10 0x00007ffff682be2a in std::sys::backtrace::__rust_begin_short_backtrace::<<rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::ExtraBackendMethods>::spawn_named_thread<rustc_codegen_ssa::back::write::spawn_work<rustc_codegen_llvm::LlvmCodegenBackend>::{closure#0}, ()>::{closure#0}, ()> ()
   from ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-9dc9f9e211dbb3c2.so
#11 0x00007ffff68f8c5c in <<std::thread::Builder>::spawn_unchecked_<<rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::ExtraBackendMethods>::spawn_named_thread<rustc_codegen_ssa::back::write::spawn_work<rustc_codegen_llvm::LlvmCodegenBackend>::{closure#0}, ()>::{closure#0}, ()>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0} ()
   from ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-9dc9f9e211dbb3c2.so
#12 0x00007ffff68f8feb in std::sys::pal::unix::thread::Thread::new::thread_start ()
   from ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-9dc9f9e211dbb3c2.so
#13 0x00007ffff069c043 in start_thread (arg=<optimized out>) at ./nptl/pthread_create.c:447
#14 0x00007ffff071a778 in __GI___clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:78

[bk-eclipse]

Bisecting showed that this bug was introduced on nightly at 2024-02-13 - the same day LLVM 18 was merged.

[bk-eclipse]

A workaround is to disable the target feature sha3:

RUSTFLAGS="-C target-feature=-sha3" cargo b --release --target aarch64-apple-darwin

[moxian]

@rustbot label: +A-SIMD +A-LLVM +O-Apple -needs-triage

[appetrosyan]

I replicated this bug on Mac OS. The same code on the same (and newer) nightlies compiles on Linux. This is a Darwin-specific problem

[bk-eclipse]

It looks like the compiler tries to optimize this code with a special xar instruction. This seem to fails because the SIMD requires only one lane here.