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[RyuJit Wasm] fix off by one error for br_table #123565

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AndyAyersMS merged 2 commits into from
Jan 25, 2026
Merged

[RyuJit Wasm] fix off by one error for br_table #123565

AndyAyersMS merged 2 commits into from
Jan 25, 2026

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@AndyAyersMS AndyAyersMS commented Jan 23, 2026

The count of switch targets does not include the default.

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[RyuJit Wasm] fix off by one error for br_table
187e9b9 
The count of switch targets does not include the default.
Copilot AI review requested due to automatic review settings January 23, 2026 22:40
@github-actions github-actions bot added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label Jan 23, 2026
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AndyAyersMS commented Jan 23, 2026

@dotnet/jit PTAL

We can now run examples with switches, like so:

    static int sw(int n)
    {
        switch (n)
        {
            case 1: case 3: return 10;
            case 2: case 4: return 20;
            case 5: case 7: return 30;
            case 6: case 8: return 40;
            default: return 0;
        }
    }

via @kg's harness

Loading test-module.wasm...
Compiling test-module.wasm...
Instantiating test-module.wasm...
OK!
exports=["wasm_test_Program__addTwoFloats","wasm_test_Program__addTwoInts","wasm_test_Program__derefBytePtr","wasm_test_Program__derefIntPtr","wasm_test_Program__increaseFloat","wasm_test_Program__increment","wasm_test_Program__select","wasm_test_Program__sum","wasm_test_Program__sw"]
running 'exports.wasm_test_Program__sw(/* sp */ 1024, 6, /* pep */ 0)...
result was 40

Copilot AI reviewed Jan 23, 2026
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Pull request overview

This PR fixes an off-by-one error in the RyuJIT WASM code generation for switch statements using the br_table instruction.

Changes:

  • Fixed the count parameter passed to emitIns_I for INS_br_table to correctly exclude the default case from the count

adamperlin
adamperlin reviewed Jan 23, 2026
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kg
kg reviewed Jan 24, 2026
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This was referenced Jan 24, 2026
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@am11 am11 added the arch-wasm WebAssembly architecture label Jan 24, 2026
adamperlin
adamperlin approved these changes Jan 25, 2026
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This looks good to me!

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AndyAyersMS commented Jan 25, 2026

/ba-g infrastructure timeout

@AndyAyersMS AndyAyersMS merged commit 32cae38 into dotnet:main Jan 25, 2026
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@dotnet-maestro dotnet-maestro bot mentioned this pull request Jan 26, 2026
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