With Rust 1.73.0, some unit tests started to fail for mips-unknown-linux-musl target

[tatsuya6502]

Rust 1.73.0 has been released and some unit tests started to fail for 32-bit mips-unknown-linux-musl target.

Note that the CI is using QEMU's user space emulator, so emulation may not be accurate. However, as long as I can remember, these tests never failed with older versions of Rust.

https://github.com/moka-rs/moka/actions/runs/6436542687/job/17587394644

failures:

---- common::timer_wheel::tests::test_advance stdout ----
thread 'common::timer_wheel::tests::test_advance' panicked at src/common/timer_wheel.rs:667:22:
Expected an expired entry. Got Rescheduled(EntryInfo { key_hash: KeyHash { key: 1, hash: 1 }, is_admitted: false, is_dirty: true, last_accessed: AtomicInstant { instant: RwLock { data: Some(Instant(Instant { tv_sec: 434, tv_nsec: 814957001 })) } }, last_modified: AtomicInstant { instant: RwLock { data: Some(Instant(Instant { tv_sec: 434, tv_nsec: 814957001 })) } }, expiration_time: AtomicInstant { instant: RwLock { data: Some(Instant(Instant { tv_sec: 439, tv_nsec: 814957001 })) } }, policy_weight: 0 })
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

---- common::timer_wheel::tests::test_bucket_indices stdout ----
thread 'common::timer_wheel::tests::test_bucket_indices' panicked at src/common/timer_wheel.rs:586:9:
assertion `left == right` failed
  left: (0, 3)
 right: (0, 63)

---- sync::cache::tests::time_to_idle_by_expiry_type stdout ----
thread 'sync::cache::tests::time_to_idle_by_expiry_type' panicked at src/sync/cache.rs:2625:9:
assertion `left == right` failed
  left: 2
 right: 1


failures:
    common::timer_wheel::tests::test_advance
    common::timer_wheel::tests::test_bucket_indices
    sync::cache::tests::time_to_idle_by_expiry_type

test result: FAILED. 83 passed; 3 failed; 3 ignored; 0 measured; 0 filtered out; finished in 30.27s

[tatsuya6502]

• rust-lang >> t-compiler/help >> mipsel-unknown-linux-musl appears sad between 1.72.1/1.73.0

[tatsuya6502]

Update the Linux cross compiler tests:

main branch (for v0.12.x):

• Disable the fail-fast strategy (af7e5c3)

v0.11.x branch:

• Disable the fail-fast strategy. (357f767)
• Downgrade Rust to 1.72.1. (fa48f1c)

v0.10.x branch:

• Disable the fail-fast strategy. (73da63c)
• Downgrade Rust to 1.72.1. (86660b8)

v0.9.x branch:

• Disable the fail-fast strategy. (39c90c3)
• Downgrade Rust to 1.72.1. (3d8e0c5)

[tatsuya6502]

rust-lang >> t-compiler/help >> mipsel-unknown-linux-musl appears sad between 1.72.1/1.73.0 (near/396569490)

Both MIPS and MIPS64 are affected by a shift bug rust-lang/rust#116177 that happens when the size of the integer is twice as large as a register, and the two are getting swapped for some reason

[tatsuya6502]

Updated the Linux cross compiler tests:

main branch (for v0.12.x):

• Downgrade Rust to 1.72.1. (3c4e920)

[tatsuya6502]

Summary:

• Rust compiler 1.73.0 has a miscompilation issue for bit-wise shift in MIPS targets:
  • 64 bit shift is broken in nightly build for MIPS rust-lang/rust#116177
• It is caused by a LLVM bug:
  • [MIPS] miscompile of 64-bit shift with masked shift amount llvm/llvm-project#64794
  • They are trying to back-port the fix to the LLVM version that current Rust compiler uses.
• For now, we pinned Rust version to 1.72.1 for the Moka CI jobs with MIPS targets.
  • Branches: main, v0.11.0, v0.10.0, v0.9.0
  • Once the issue is resolved, we will switch the CI jobs back to use the latest Rust stable.

[tatsuya6502]

• Rust compiler 1.73.0 has a miscompilation issue for bit-wise shift in MIPS targets:
  • 64 bit shift is broken in nightly build for MIPS rust-lang/rust#116177
• It is caused by a LLVM bug:
  • [MIPS] miscompile of 64-bit shift with masked shift amount llvm/llvm-project#64794
    • They are trying to back-port the fix to the LLVM version that current Rust compiler uses.

The above issues have been resolved for Rust 1.76.0: rust-lang/rust#117907.

1.76.0 is currently Nightly and will be stable on February 8, 2024.

[tatsuya6502]

After upgrading Rust toolchain in my local environment to 1.75.0, I noticed rustup cannot install prebuilt std for the MIPS targets. This is because the MIPS targets have been demoted from tier 2 to tier 3. So the binary releases for these targets are no longer provided by the Rust project.

• Drop MIPS to tier 3 rust-lang/compiler-team#648
• Formally demote tier 2 MIPS targets to tier 3 rust-lang/rust#115238

Our CI is currently using Rust 1.72.1 for the MIPS targets, so it will continue running.

The above issues have been resolved for Rust 1.76.0: rust-lang/rust#117907.

1.76.0 is currently Nightly and will be stable on February 8, 2024.

When 1.76.0 is released, we will update our CI to use the latest stable for the MIPS targets again, by enabling build-std = true in the cross.toml.

• rust-std is not available for mips anymore (for ~2 days) cross-rs/cross#1336 (comment)