wasm32-unknown-unknown stuck in infinite loop when compiling fluent-bundle at opt-level=3

[SOF3]

I failed to reproduce a minimum reproducible example for this bug, but the full steps to reproduce my scenario is found here: https://github.com/traffloat/traffloat/runs/4251506793

(Put simply: clone the repo, cd client, run cargo build --target wasm32-unknown-unknown )

Observation: when cargo compiles up to the fluemt-bundle crate, rustc keeps running for a few minutes on 100% CPU, using more and more RAM until the OOM killer from the OS stops it.

This only happens when I compile without the --releade flag. However, pay attention that I set opt-level=3 in the workspace Cargo.toml.

Furthermore, this only happens in the build stage with --target wasm32-unknown-unknown. This does not happen on x86_64-unknown-linux-gnu.

The issue cannot be reproduced by compiling a dummy crate that only includes that dependency.

Meta

rustc --version --verbose:

$ rustc --version --verbose                                                     rustc 1.58.0-nightly (d914f17ca 2021-11-16)
binary: rustc
commit-hash: d914f17ca71a33a89b2dc3436fca51b1a091559e
commit-date: 2021-11-16
host: x86_64-unknown-linux-gnu
release: 1.58.0-nightly
LLVM version: 13.0.0

Backtrace

error: could not compile `fluent-bundle`                                        
Caused by:
  process didn't exit successfully: `CARGO=/home/sofe/.rustup/toolchains/nightly-2021-11-17-x86_64-unknown-linux-gnu/bin/cargo CARGO_CRATE_NAME=fluent_bundle CARGO_MANIFEST_DIR=/home/sofe/.cargo/registry/src/github.com-1ecc6299db9ec823/fluent-bundle-0.15.2 CARGO_PKG_AUTHORS='Zibi Braniecki <[email protected]>:Staś Małolepszy <[email protected]>' CARGO_PKG_DESCRIPTION='A localization system designed to unleash the entire expressive power of
  natural language translations.
  ' CARGO_PKG_HOMEPAGE='http://www.projectfluent.org' CARGO_PKG_LICENSE=Apache-2.0/MIT CARGO_PKG_LICENSE_FILE='' CARGO_PKG_NAME=fluent-bundle CARGO_PKG_REPOSITORY='https://github.com/projectfluent/fluent-rs' CARGO_PKG_VERSION=0.15.2 CARGO_PKG_VERSION_MAJOR=0 CARGO_PKG_VERSION_MINOR=15 CARGO_PKG_VERSION_PATCH=2 CARGO_PKG_VERSION_PRE='' LD_LIBRARY_PATH='/home/sofe/proj/traffloat/target/debug/deps:/home/sofe/.rustup/toolchains/nightly-2021-11-17-x86_64-unknown-linux-gnu/lib:/home/sofe/.rustup/toolchains/nightly-2021-11-17-x86_64-unknown-linux-gnu/lib' rustc --crate-name fluent_bundle --edition=2018 /home/sofe/.cargo/registry/src/github.com-1ecc6299db9ec823/fluent-bundle-0.15.2/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts --crate-type lib --emit=dep-info,metadata,link -C opt-level=3 -C embed-bitcode=no -C debuginfo=2 -C debug-assertions=on --cfg 'feature="default"' -C metadata=d64013c212ea53c9 -C extra-filename=-d64013c212ea53c9 --out-dir /home/sofe/proj/traffloat/target/wasm32-unknown-unknown/debug/deps --target wasm32-unknown-unknown -L dependency=/home/sofe/proj/traffloat/target/wasm32-unknown-unknown/debug/deps -L dependency=/home/sofe/proj/traffloat/target/debug/deps --extern fluent_langneg=/home/sofe/proj/traffloat/target/wasm32-unknown-unknown/debug/deps/libfluent_langneg-20e6de4d2a5c2f31.rmeta --extern fluent_syntax=/home/sofe/proj/traffloat/target/wasm32-unknown-unknown/debug/deps/libfluent_syntax-6330210a26c5ec71.rmeta --extern intl_memoizer=/home/sofe/proj/traffloat/target/wasm32-unknown-unknown/debug/deps/libintl_memoizer-be378e2b3f9d6ab2.rmeta --extern intl_pluralrules=/home/sofe/proj/traffloat/target/wasm32-unknown-unknown/debug/deps/libintl_pluralrules-d90b40ad54dbd6fe.rmeta --extern rustc_hash=/home/sofe/proj/traffloat/target/wasm32-unknown-unknown/debug/deps/librustc_hash-e990337399c22a21.rmeta --extern self_cell=/home/sofe/proj/traffloat/target/wasm32-unknown-unknown/debug/deps/libself_cell-b546eeb8cbdb720e.rmeta --extern smallvec=/home/sofe/proj/traffloat/target/wasm32-unknown-unknown/debug/deps/libsmallvec-982c24cfab604cb7.rmeta --extern unic_langid=/home/sofe/proj/traffloat/target/wasm32-unknown-unknown/debug/deps/libunic_langid-a07d0b70489807ae.rmeta --cap-lints warn` (signal: 9, SIGKILL: kill)

[adrian17]

The issue cannot be reproduced by compiling a dummy crate that only includes that dependency.

Sounds very similar to what I experienced in #89647 , may be same as #89524 too.

[SOF3]

I have checked that disabling optimizations stops reproducing this issue.

Note that my workspace was configured like this:

[profile.dev]
opt-level = 3

[profile.dev.package]
my-first-package = {opt-level = 0}
my-second-package = {opt-level = 0}
my-other-packages = {opt-level = 0}

By applying the patch

 [profile.dev]
-opt-level = 3
+opt-level = 0

the issue is no longer reproduced.

Furthermore, this bug is also avoided by disabling optimizations for fluent-bundle only:

[profile.dev.package]
+fluent-bundle = {opt-level = 0}

The issue also doesn't occur in opt-level = 2. This seems to imply that the optimizations from level 2 to level 3 are causing the bug.

Strange thing is that the issue is not reproduced when I compile the whole project in release mode. Maybe something to do with the inconsistency of debug_assertions vs opt-level?

Note also that I have LTO enabled in release mode where this bug is not reproduced, but that seems unlikely to be relevant.

[apiraino]

Assigning priority as discussed in the Zulip thread of the Prioritization Working Group.

@rustbot label -I-prioritize +P-medium