WebAssembly / WebAssembly/binaryen

Once Reduction Pass improvement

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#4,124 0 comments 0 reactions 0 assignees View on GitHub

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Dominant language
WebAssembly
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Forks
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Avg merge
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Merged PRs (30d)
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Description

Recent Once Reduction pass properly handled following CFG in pseudocode:

bool initialized = false;
void boo() {
  if (initialized) return;
  ...
  initialized = true;
}

but unsound for this:

bool initialized = false;
void boo() {
  if (!initialized) {
    ...
    initialized = true;
  }
}

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the linked PR #4111 and locate the Once Reduction pass implementation, then compare its handling of the two CFG shapes shown in the issue. Add a regression test for the second example and verify that the optimization no longer produces unsound behavior.

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
35/100

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