[compiler] Properly guard the speculative optimizations for instanceof.

Add a general feedback slot for instanceof similar to what we already have
for for-in, which basically has a fast (indicated by the uninitialized
sentinel) and a slow (indicated by the megamorphic sentinel) mode. Now
we can only take the fast path when the feedback slot says it hasn't
seen any funky inputs and nothing funky appeared in the prototype chain.
In the TurboFan code we also deoptimize whenever we see a funky object
(i.e. a proxy or an object that requires access checks) in the prototype
chain (similar to what Crankshaft already did).

Drive-by-fix: Also make Crankshaft respect the mode and therefore
address the deopt loop in Crankshaft around instanceof.

We might want to introduce an InstanceOfIC mechanism at some point and
track the map of the right-hand side.

BUG=v8:5267
R=mvstanton@chromium.org

Review-Url: https://codereview.chromium.org/2370693002
Cr-Commit-Position: refs/heads/master@{#39718}
32 files changed
tree: 23d27939fffed1f416912e20d211b58139a2d042
  1. benchmarks/
  2. build_overrides/
  3. docs/
  4. gni/
  5. gypfiles/
  6. include/
  7. infra/
  8. samples/
  9. src/
  10. test/
  11. testing/
  12. third_party/
  13. tools/
  14. .clang-format
  15. .gitignore
  16. .gn
  17. .ycm_extra_conf.py
  18. AUTHORS
  19. BUILD.gn
  20. ChangeLog
  21. CODE_OF_CONDUCT.md
  22. codereview.settings
  23. DEPS
  24. LICENSE
  25. LICENSE.fdlibm
  26. LICENSE.strongtalk
  27. LICENSE.v8
  28. LICENSE.valgrind
  29. Makefile
  30. Makefile.android
  31. OWNERS
  32. PRESUBMIT.py
  33. README.md
  34. snapshot_toolchain.gni
  35. WATCHLISTS
README.md

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: https://github.com/v8/v8/wiki

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/*

Contributing

Please follow the instructions mentioned on the V8 wiki.