Oops, that took longer than expected. I tested the patch on a bunch of different uses of wasm from different toolchains and nothing seems to use duplicate imports, which is encouraging. Most wasm apps use Emscripten/LLVM, which Alon said doesn't intentionally generate duplicates. I also used about:telemetry and an artificial wasm module containing duplicates to confirm that USE_COUNTER2_JS_WASM_DUPLICATE_IMPORTS (under Histograms > Content) does indeed get bumped on duplicates.
Bug 1647791 Comment 8 Edit History
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Oops, that took me a while to get to. I tested the patch on a bunch of different uses of wasm from different toolchains and nothing seems to use duplicate imports, which is encouraging. Most wasm apps use Emscripten/LLVM, which Alon said doesn't intentionally generate duplicates. I also used about:telemetry and an artificial wasm module containing duplicates to confirm that USE_COUNTER2_JS_WASM_DUPLICATE_IMPORTS (under Histograms > Content) does indeed get bumped on duplicates.