rustc crashes when trying to bench upcoming neon-support in RustFFT with latest stdarch.

[HEnquist]

I'm working on adding neon support to RustFFT, and wanted to try the vld* and vst* instrinsics added here: #1224

First results were promising, but now I'm having a hard time running benchmarks because rustc crashes when building the benches. It crashes quite hard, without giving any useful error message. I'm using rust commit d14731c (simply master from yesterday, have also tried with a version from a couple of days ago with the same result), with stdarch updated to commit 931cdfb.

I would like to investigate this and try to at least help solve it, but I have no idea were to start. Any advice?

I'm trying to bench this branch: https://github.com/HEnquist/RustFFT/tree/vldx

I have tried on both a raspberry pi, and on an Oracle Ampere VM, with the same results.

Error:

pi@raspberrypi:~/RustFFT $ cargo bench --features neon neon_
   Compiling rustfft v6.0.1 (/home/pi/RustFFT)
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x826e48)[0x7f919b2e48]
linux-vdso.so.1(__kernel_rt_sigreturn+0x0)[0x7f96f1a788]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x11b83a4)[0x7f923443a4]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x16b1810)[0x7f9283d810]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x246e1f4)[0x7f935fa1f4]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x246e350)[0x7f935fa350]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x246f570)[0x7f935fb570]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xb5d674)[0x7f91ce9674]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xb48ba4)[0x7f91cd4ba4]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xb4cfe8)[0x7f91cd8fe8]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xa24380)[0x7f91bb0380]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xa1eb14)[0x7f91baab14]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xa95048)[0x7f91c21048]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xaf9320)[0x7f91c85320]
/mount/ssd/rustc/lib/libstd-ba7780e7efc39bcb.so(rust_metadata_std_2d103c436cd22770+0x8c380)[0x7f9108b380]
/lib/aarch64-linux-gnu/libpthread.so.0(+0x77e4)[0x7f90e3d7e4]
/lib/aarch64-linux-gnu/libc.so.6(+0xcfadc)[0x7f90f48adc]
error: could not compile `rustfft`

Caused by:
  process didn't exit successfully: `rustc --crate-name rustfft --edition=2018 src/lib.rs --error-format=json --json=diagnostic-rendered-ansi --emit=dep-info,link -C opt-level=3 -C embed-bitcode=no --test --cfg 'feature="avx"' --cfg 'feature="default"' --cfg 'feature="neon"' --cfg 'feature="sse"' -C metadata=541f3979c27e3f0a -C extra-filename=-541f3979c27e3f0a --out-dir /home/pi/RustFFT/target/release/deps -L dependency=/home/pi/RustFFT/target/release/deps --extern num_complex=/home/pi/RustFFT/target/release/deps/libnum_complex-d7ededc7dd339a27.rlib --extern num_integer=/home/pi/RustFFT/target/release/deps/libnum_integer-0edf0ad8b3f42ac1.rlib --extern num_traits=/home/pi/RustFFT/target/release/deps/libnum_traits-7542682cf91f65c6.rlib --extern paste=/home/pi/RustFFT/target/release/deps/libpaste-49b243a423c645cd.so --extern primal_check=/home/pi/RustFFT/target/release/deps/libprimal_check-d5a43e363432ab49.rlib --extern rand=/home/pi/RustFFT/target/release/deps/librand-5cd04db47872812e.rlib --extern strength_reduce=/home/pi/RustFFT/target/release/deps/libstrength_reduce-1c2f1a65415e918e.rlib --extern transpose=/home/pi/RustFFT/target/release/deps/libtranspose-226cfc662b715315.rlib` (signal: 11, SIGSEGV: invalid memory reference)
warning: build failed, waiting for other jobs to finish...
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x826e48)[0x7f7f990e48]
linux-vdso.so.1(__kernel_rt_sigreturn+0x0)[0x7f84ef8788]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x11b83a4)[0x7f803223a4]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x16b1810)[0x7f8081b810]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x246e1f4)[0x7f815d81f4]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x246e350)[0x7f815d8350]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x246f570)[0x7f815d9570]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xb5d674)[0x7f7fcc7674]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xb48ba4)[0x7f7fcb2ba4]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xb4cfe8)[0x7f7fcb6fe8]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xa24380)[0x7f7fb8e380]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xa1eb14)[0x7f7fb88b14]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xa95048)[0x7f7fbff048]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xaf9320)[0x7f7fc63320]
/mount/ssd/rustc/lib/libstd-ba7780e7efc39bcb.so(rust_metadata_std_2d103c436cd22770+0x8c380)[0x7f7f069380]
/lib/aarch64-linux-gnu/libpthread.so.0(+0x77e4)[0x7f7ee1b7e4]
/lib/aarch64-linux-gnu/libc.so.6(+0xcfadc)[0x7f7ef26adc]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x826e48)[0x7fafd07e48]
linux-vdso.so.1(__kernel_rt_sigreturn+0x0)[0x7fb526f788]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x11b83a4)[0x7fb06993a4]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x16b1810)[0x7fb0b92810]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x246e1f4)[0x7fb194f1f4]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x246e350)[0x7fb194f350]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x246f570)[0x7fb1950570]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xb5d674)[0x7fb003e674]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xb48ba4)[0x7fb0029ba4]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xb4cfe8)[0x7fb002dfe8]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xa24380)[0x7faff05380]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xa1eb14)[0x7fafeffb14]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xa95048)[0x7faff76048]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xaf9320)[0x7faffda320]
/mount/ssd/rustc/lib/libstd-ba7780e7efc39bcb.so(rust_metadata_std_2d103c436cd22770+0x8c380)[0x7faf3e0380]
/lib/aarch64-linux-gnu/libpthread.so.0(+0x77e4)[0x7faf1927e4]
/lib/aarch64-linux-gnu/libc.so.6(+0xcfadc)[0x7faf29dadc]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x826e48)[0x7faa5c3e48]
linux-vdso.so.1(__kernel_rt_sigreturn+0x0)[0x7fafb2b788]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x11b83a4)[0x7faaf553a4]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x16b1810)[0x7fab44e810]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x246e1f4)[0x7fac20b1f4]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x246e350)[0x7fac20b350]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0x246f570)[0x7fac20c570]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xb5d674)[0x7faa8fa674]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xb48ba4)[0x7faa8e5ba4]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xb4cfe8)[0x7faa8e9fe8]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xa24380)[0x7faa7c1380]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xa1eb14)[0x7faa7bbb14]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xa95048)[0x7faa832048]
/mount/ssd/rustc/lib/librustc_driver-b200c9ef89c7aa6a.so(+0xaf9320)[0x7faa896320]
/mount/ssd/rustc/lib/libstd-ba7780e7efc39bcb.so(rust_metadata_std_2d103c436cd22770+0x8c380)[0x7fa9c9c380]
/lib/aarch64-linux-gnu/libpthread.so.0(+0x77e4)[0x7fa9a4e7e4]
/lib/aarch64-linux-gnu/libc.so.6(+0xcfadc)[0x7fa9b59adc]
error: build failed

[workingjubilee]

Please include rustc --version --verbose.

[HEnquist]

Sure! It doesn't say that much unfortunately.

pi@raspberrypi:~ $ /mount/ssd/rustc/bin/rustc --version --verbose
rustc 1.57.0-dev
binary: rustc
commit-hash: unknown
commit-date: unknown
host: aarch64-unknown-linux-gnu
release: 1.57.0-dev
LLVM version: 13.0.0

[SparrowLii]

Can you find out which lines of code in the bench caused the crash? This might help to find the root cause.

[workingjubilee]

LLVM version: 13.0.0

This is what I wanted to make sure of.
The last "official" LLVM 13.0.0 (Rust was merging the "release candidate" versions to be able to get a head start on testing) was pulled in shortly after you posted this, so it may be a good idea to try today's rustc.

[HEnquist]

It doesn't seem to matter much what my benches contain, it fails no matter what. I just started building rustc from today, will try it as soon as it's ready (tomorrow probably, takes some time on a Raspberry Pi..)

[workingjubilee]

aarch64-unknown-linux-gnu is a tier 1 target: It should be possible to download the latest nightly via rustup, no? No need to recompile it.

[HEnquist]

I need a newer stdarch than in the latest nightly, with all the vld* and vst* intrinsics.

[HEnquist]

The updated llvm unfortunately made no difference. If I go back to the RustFFT version just before I started using the vld* and vst* intrinsics builds and benches fine. I'll try to figure out exactly what change triggers the crash. Unfortunately I'm a bit short on time these days, so may take a while.

[HEnquist]

The crash seems to come when I compile a benchmark if my FFTs use this function: https://github.com/HEnquist/RustFFT/blob/vldx/src/neon/neon_vector.rs#L156
It only fails with cargo bench, with cargo test it's all good.

[SparrowLii]

We can replace vld2q_f64 with a fn with equivalent behavior and see if the crash will still happen:

pub unsafe fn vld2q_f64_fake(a: *const f64) -> float64x2x2_t {
    let x: [f64; 4] = core::ptr::read_unaligned(a.cast());
    transmute([x[0], x[2], x[1], x[3]])
}

[HEnquist]

Using the vld2q_f64_fake instead of vld2q_f64 makes the benches build and run fine!

[HEnquist]

By the way, vld3q_f64 and vld4q_f64 cause no problems. No need for fake-versions of those to make the benches ok.