LLVM slowdown when building the libregex-automata rust crate for 32-bit x86 with asan
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- Dominant language
- LLVM
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Description
Here's the bitcode file which can reproduce the slowdown with
clang -target i686-unknown-linux-android libregex_automata.regex_automata.b5dfadd7c666403-cgu.0.rcgu.bc -c
Running it with -mllvm -opt-bisect-limit=-1 shows the pass and function where LLVM hangs:
BISECT: running pass (2021) remove-loads-into-fake-uses on function (_RNvNtNtCsYvqlNLYD0R_14regex_automata4meta8strategy3new)
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the attached libregex_automata bitcode and reproduce the slowdown using the clang -target i686-unknown-linux-android command in the report. Use -mllvm -opt-bisect-limit=-1 to inspect remove-loads-into-fake-uses on the named function, then verify that the reproducer no longer hangs or exhibits the slowdown.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100