Simplify FunctionKind, saving 4 bits in SharedFunctionInfo

Since we only need to store 18 different function kinds,
the bitfield approach was wasting space (requiring 11 bits).

This patch replaces the bitfield with a regular enum, and
updates all the FunctionKind predicates to use comparisons
instead of bitwise ops.

For the small amount of builtin code that depended upon being
able to do masking to determine whether something is a class
constructor, we still store two extra bits on FunctionKind,
which are computed when the SFI is initialized.

If this approach causes performance regressions (i.e., if it
turns out that other code was implicitly depending on masking
for fast checks), we can revert this or address it in
other ways (e.g., by doing similar caching of repeated checks
in the caller).

Change-Id: Iebb3214f564ea8bd7b21e78fda33517d63247124
Commit-Queue: Adam Klein <>
Reviewed-by: Sathya Gunasekaran <>
Cr-Commit-Position: refs/heads/master@{#50559}
13 files changed
tree: 960543b075c3d6d9cd9cdf6322c658dcf3cb0bd9
  1. .clang-format
  2. .editorconfig
  3. .git-blame-ignore-revs
  4. .gitignore
  5. .gn
  6. .vpython
  11. ChangeLog
  12. DEPS
  14. LICENSE.fdlibm
  15. LICENSE.strongtalk
  16. LICENSE.v8
  17. LICENSE.valgrind
  18. Makefile
  20. OWNERS
  24. benchmarks/
  25. build_overrides/
  26. codereview.settings
  27. docs/
  28. gni/
  29. gypfiles/
  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.