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Regression: explicit TCO and Fat LTO jump table size explosion with inline #162118

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Regression: explicit TCO and Fat LTO jump table size explosion with inline#162118
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C-bugCategory: This is a bug.I-heavyIssue: Problems and improvements with respect to binary size of generated code.I-prioritizeIssue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}needs-triageThis issue may need triage. Remove when done. See docs forge.rust-lang.org/release/issue-triagingregression-untriagedUntriaged performance or correctness regression.

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@stevefan1999-personal
stevefan1999-personal
opened on Sep 1, 2026

On fat LTO, it seems like the jump table generation is not taken in effect, or rather taken too literally.

For thin LTO however, did seems to work.

Reported as of explodingcamera/tinywasm#55 (comment)

rustc version: nightly 1.100.0

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  1. stevefan1999-personal
    added
    C-bugCategory: This is a bug.
    on Sep 1, 2026
  2. rustbot
    added
    needs-triageThis issue may need triage. Remove when done. See docs forge.rust-lang.org/release/issue-triaging
    on Sep 1, 2026
  3. theemathas
    added
    I-heavyIssue: Problems and improvements with respect to binary size of generated code.
    regression-untriagedUntriaged performance or correctness regression.
    on Sep 1, 2026
  4. rustbot
    added
    I-prioritizeIssue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}
    on Sep 1, 2026

  5. apiraino commented on Sep 2, 2026

    @apiraino
    apiraino
    on Sep 2, 2026
    Contributor

    hi @stevefan1999-personal I'm not too familiar with wasm. could you drop a reproducible to allow us bisecting to where this started? thanks

  6. stevefan1999-personal commented on Sep 3, 2026

    @stevefan1999-personal
    stevefan1999-personal
    on Sep 3, 2026
    Author

    hi @stevefan1999-personal I'm not too familiar with wasm. could you drop a reproducible to allow us bisecting to where this started? thanks

    https://github.com/stevefan1999-personal/rust-162118-repro

    here you go

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    C-bugCategory: This is a bug.I-heavyIssue: Problems and improvements with respect to binary size of generated code.I-prioritizeIssue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}needs-triageThis issue may need triage. Remove when done. See docs forge.rust-lang.org/release/issue-triagingregression-untriagedUntriaged performance or correctness regression.

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