Reland "[wasm] Add feature counter for threads and shared memory"

This is a reland of b10a967f4b88e397728a8eda47d548a049911370

Original change's description:
> [wasm] Add feature counter for threads and shared memory
> This adds a feature counter for WASM shared memory (i.e. the presence
> of the "shared" bit in a WASM module's memory section) and the usage
> of WASM threads opcodes (i.e. wake/wait and atomics).
> This CL also plumbs the WasmFeatures through the compilation pipeline
> to detect features as functions are being compiled.
> BUG=chromium:868844
> Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
> Change-Id: I854f932d3adb16e4fd87196fe2a193950295b856
> Reviewed-on:
> Reviewed-by: Andreas Haas <>
> Reviewed-by: Ulan Degenbaev <>
> Commit-Queue: Ben Titzer <>
> Cr-Commit-Position: refs/heads/master@{#55337}

Bug: chromium:868844
Change-Id: Iac3a38d80fa71aadd7147704669a8fd671ecfae8
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Commit-Queue: Ben Titzer <>
Reviewed-by: Andreas Haas <>
Cr-Commit-Position: refs/heads/master@{#55363}
12 files changed
tree: 845a31dd27957376c2806ecaef2085aca54f1962
  1. .clang-format
  2. .editorconfig
  3. .git-blame-ignore-revs
  4. .gitattributes
  5. .gitignore
  6. .gn
  7. .vpython
  12. ChangeLog
  13. DEPS
  15. LICENSE.fdlibm
  16. LICENSE.strongtalk
  17. LICENSE.v8
  18. LICENSE.valgrind
  19. OWNERS
  23. benchmarks/
  24. build_overrides/
  25. codereview.settings
  26. custom_deps/
  27. docs/
  28. gni/
  29. include/
  30. infra/
  31. samples/
  32. snapshot_toolchain.gni
  33. src/
  34. test/
  35. testing/
  36. third_party/
  37. tools/

V8 JavaScript Engine

V8 is Google's open source JavaScript engine.

V8 implements ECMAScript as specified in ECMA-262.

V8 is written in C++ and is used in Google Chrome, the open source browser from Google.

V8 can run standalone, or can be embedded into any C++ application.

V8 Project page:

Getting the Code

Checkout depot tools, and run

    fetch v8

This will checkout V8 into the directory v8 and fetch all of its dependencies. To stay up to date, run

    git pull origin
    gclient sync

For fetching all branches, add the following into your remote configuration in .git/config:

    fetch = +refs/branch-heads/*:refs/remotes/branch-heads/*
    fetch = +refs/tags/*:refs/tags/*


Please follow the instructions mentioned on the V8 wiki.