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[wasm] Wasm encoding of reading from array is unnecessarily large #134465

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#135146
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[wasm] Wasm encoding of reading from array is unnecessarily large#134465
#135146
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adamperlin
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arch-wasmWebAssembly architecturearea-CodeGen-coreclrCLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI
Milestone
12.0.0

Description

@davidwrighton
davidwrighton
opened on Sep 22, 2026

When encoding a load from an array of integers, the codegen is bigger than it needs to be.

What I'm seeing today is

          local.get 6 ;; Load _array from WASM temp
          local.get 4 ;; Load index
          i32.const 2
          i32.shl ;; Scale index * 4
          i32.const 8
          i32.add
          i32.add
          i32.load align=1 ;; Load data from array, with 8 byte offset

What I'd like to see

          local.get 6 ;; Load _array from WASM temp
          local.get 4 ;; Load index
          i32.const 2
          i32.shl ;; Scale index * 4
          i32.add
          i32.load offset=8 align=1 ;; Load data from array, with 8 byte offset

Behavior of these 2 sequences is identical, but the one below is 12 bytes, and the upper one is 15 bytes.

Activity

  1. davidwrighton
    added
    area-CodeGen-coreclrCLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI
    arch-wasmWebAssembly architecture
    on Sep 22, 2026

  2. dotnet-policy-service commented on Sep 22, 2026

    @dotnet-policy-service
    dotnet-policy-serviceBot
    on Sep 22, 2026 – with Dotnet Policy Service
    Contributor

    Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
    See info in area-owners.md if you want to be subscribed.

  3. davidwrighton
    added
    untriagedNew issue has not been triaged by the area owner
    on Sep 22, 2026

  4. dotnet-policy-service commented on Sep 22, 2026

    @dotnet-policy-service
    dotnet-policy-serviceBot
    on Sep 22, 2026 – with Dotnet Policy Service
    Contributor

    Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
    See info in area-owners.md if you want to be subscribed.

  5. adamperlin
    self-assigned this
    on Sep 24, 2026
  6. pavelsavara
    added this to the 12.0.0 milestone on Sep 24, 2026
  7. pavelsavara
    removed
    untriagedNew issue has not been triaged by the area owner
    on Sep 24, 2026
  8. adamperlin
    added a commit that references this issue on Oct 20, 2026

    [wasm] [JIT] Contain Array Data Offsets (#135146)

    845ed4c
  9. adamperlin
    closed this as completedin #135146on Oct 20, 2026
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