WebAssembly / WebAssembly/binaryen
Use getMaxBits in comparisons
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- Dominant language
- WebAssembly
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- Merged PRs (30d)
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Description
E.g.
(i32.lt_u
(i32.ne
(local.get $0)
(i32.const 0)
)
(i32.const 128)
)
=->
(i32.const 1)
i32.ne returns 0 or 1, so it is max 1 bit, and that is always less than 128.
Found by the superoptimizer https://github.com/WebAssembly/binaryen/pull/4994 (for comparison to other findings: rule #20, benefit 13760).
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 by tracing the comparison optimization logic around getMaxBits and review the superoptimizer finding in pull request #4994, especially rule #20. Use the provided i32 example as a regression case; done means the comparison is recognized as always true and the result is reduced to i32.const 1.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp, wasm
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 42/100