[compiler] Don't assume a HeapConstant context input is a Context.

In a generator containing loops, there are always certain control flow
paths that are impossible, due to the way we represent generators at the
bytecode level.  Unfortunately, the graph builder can't tell that these
paths are impossible.  In combination with dead code, it can then happen
that we build a subgraph (for unreachable code) whose incoming context
is the undefined oddball.  JSContextSpecialization did not expect that.

Bug: chromium:794822
Change-Id: I259be5ae6c5f5adc8fca19c64bf71285ee922b7a
Reviewed-on: https://chromium-review.googlesource.com/828954
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50129}
2 files changed
tree: de7ff0ddf99361ed34ce7f0f5f48436c30f59697
  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. .editorconfig
  16. .git-blame-ignore-revs
  17. .gitignore
  18. .gn
  19. .vpython
  20. .ycm_extra_conf.py
  21. AUTHORS
  22. BUILD.gn
  23. ChangeLog
  24. CODE_OF_CONDUCT.md
  25. codereview.settings
  26. DEPS
  27. LICENSE
  28. LICENSE.fdlibm
  29. LICENSE.strongtalk
  30. LICENSE.v8
  31. LICENSE.valgrind
  32. Makefile
  33. Makefile.android
  34. OWNERS
  35. PRESUBMIT.py
  36. README.md
  37. snapshot_toolchain.gni
  38. 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.