Change SetProperty/SetSuperProperty to infer language mode when possible

In most cases, the language mode can be inferred from the closure and
the context. Computing the language mode instead of passing it around
simplifies the ICs and will make it possible to go towards lazily
allocating feedback vectors. Currently ICs obtain the language mode from
the feedback vectors and with lazy feedback allocation we may not always
have feedback vectors. Since computing language mode is a bit expensive
we want to defer it as far as possible.

In Array builtins and other builtins like Reflect.Set we need to force a
language mode when setting the properties. To support these cases the
SetProperty methods allow the language mode to be overridden when needed.

This is a first cl in a series of cls, that will defer the language mode
computation further and remove language mode where it is not needed.

BUG: v8:8580
Change-Id: I9c2396e3bcfe77c3c9d6760c46d86954d54744b9
Reviewed-by: Michael Lippautz <>
Reviewed-by: Jakob Gruber <>
Reviewed-by: Toon Verwaest <>
Commit-Queue: Mythri Alle <>
Cr-Commit-Position: refs/heads/master@{#58893}
22 files changed
tree: 7b6b03df609a3cef9eebd946c94c02cb7d169580
  1. .clang-format
  2. .clang-tidy
  3. .editorconfig
  4. .git-blame-ignore-revs
  5. .gitattributes
  6. .gitignore
  7. .gn
  8. .vpython
  13. ChangeLog
  14. DEPS
  16. LICENSE.fdlibm
  17. LICENSE.strongtalk
  18. LICENSE.v8
  19. LICENSE.valgrind
  20. OWNERS
  24. benchmarks/
  25. build_overrides/
  26. codereview.settings
  27. custom_deps/
  28. docs/
  29. gni/
  30. include/
  31. infra/
  32. samples/
  33. snapshot_toolchain.gni
  34. src/
  35. test/
  36. testing/
  37. third_party/
  38. 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.