Hi Emily, those "SimdSeeds" are just blobs of bytes which are used to drive the generation of the wasm module, see the "data" argument on `GenerateRandomWasmModule` <https://source.chromium.org/chromium/chromium/src/+/main:v8/src/wasm/fuzzing/random-module-generation.cc;l=5121;drc=4124cdcb1bc693e8ea6001f8d6aa554965de75a1>. The interpretation of those bytes often changes when additions or modifications to this random generation are made, so it's not ideal to hard-code them anywhere (but we sometimes do it anyway if there is no better regression test we have).
I see two options: 1. You could look at simd-cross-compiler-determinism-fuzztest.cc <https://source.chromium.org/chromium/chromium/src/+/main:v8/test/unittests/wasm/simd-cross-compiler-determinism-fuzztest.cc> and float32-cross-compiler-determinism-fuzztest.cc <https://source.chromium.org/chromium/chromium/src/+/main:v8/test/unittests/wasm/float32-cross-compiler-determinism-fuzztest.cc>, which generate some code in different compilers very deterministically and compare the results against each other. Maybe you can generate some interesting patterns explicitly in a similar way. 2. Generally the "random module generation" fuzzers *are* what we use to find differences between compilers which are not covered by simpler tests. But they are not targeting specific patterns. We do have some variants nowadays (GenerateWasmModuleForInitExpressions, GenerateWasmModuleForDeopt, GenerateWasmModuleForRevec), but it does not scale to add a variant for every new feature or optimization. You could just run this fuzzer over night, maybe commenting out parts which are not interesting to you. Since you are interested in SIMD operations, I would start with the v8_wasm_compile_simd_fuzzer (using libfuzzer, only works in a chromium checkout), or the centipede variant of that (this "ModuleGenerationTest.TestSimd" which also works in V8). Let me know if you need more details on that and I can support you off-list. -Clemens On Mon, Feb 2, 2026 at 1:21 PM Emily Boarer <[email protected]> wrote: > Hi All, > cc: Matthias Liedtke, Clemens Backes > > I am working on adding AddReduce / arm64 SIMD ADDV instruction support in > this patch: https://chromium-review.googlesource.com/c/v8/v8/+/7462509 . > For this patch, I am looking to add a fuzztest to compare correctness > between turboshaft and liftoff executions of some simple wasm code, which > can exercise the pre-optimized instructions in question here (to prove that > any optimizations retain correctness). > > This problem doesn't seem to really have an example/comparable solution > already V8 to my knowledge (I will gladly be corrected on that!). > > `test/unittests/wasm/module-generation-fuzztest.cc`'s `SimdSeeds()` could > be an example of how to achieve something like this? I am not entirely sure > what's going on with that function, but perhaps it is a wasm blob? In > general this seems a very non-obvious addition to be made, and I could do > with all the help and suggestions on offer. > > Thanks, > Emily > > -- > -- > v8-dev mailing list > [email protected] > http://groups.google.com/group/v8-dev > --- > You received this message because you are subscribed to the Google Groups > "v8-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion visit > https://groups.google.com/d/msgid/v8-dev/59abf3f7-4c1c-4454-a101-1000a8eceaean%40googlegroups.com > <https://groups.google.com/d/msgid/v8-dev/59abf3f7-4c1c-4454-a101-1000a8eceaean%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- Clemens Backes Software Engineer [email protected] Google Germany GmbH Erika-Mann-Straße 33 80636 München Geschäftsführer: Paul Manicle, Liana Sebastian Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg Diese E-Mail ist vertraulich. Falls sie diese fälschlicherweise erhalten haben sollten, leiten Sie diese bitte nicht an jemand anderes weiter, löschen Sie alle Kopien und Anhänge davon und lassen Sie mich bitte wissen, dass die E-Mail an die falsche Person gesendet wurde. This e-mail is confidential. If you received this communication by mistake, please don't forward it to anyone else, please erase all copies and attachments, and please let me know that it has gone to the wrong person. -- -- v8-dev mailing list [email protected] http://groups.google.com/group/v8-dev --- You received this message because you are subscribed to the Google Groups "v8-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/v8-dev/CAGO%3DqhCye9Ttc%2BfaiA0gtd9dyBBNcYembpGpjC%2BdFryXBPcR_Q%40mail.gmail.com.
