[SFI] Add support for flushing old Bytecode from SharedFunctionInfos.

This change makes the SFI to bytecode link pseudo-weak. The marking visitors
check whether the bytecode is old, and if so, don't mark it and instead
push the SFI onto a bytecode_flushing_candidates worklist. Once marking
is complete, this list is walked, and for any of the candidates who's bytecode
has not been marked (i.e., is only referenced by the shared function info),
the bytecode is flushed and the SFI has the function data replaced with
an UncompiledData (which overwrites the flushed bytecode array).

Since we don't track JSFunctions, these can still think the underlying
function is compiled, and so calling them will invoke
InterpreterEntryTrampoline. As such, logic is added to
InterpreterEntryTrampoline to detect flushed functions, and enter
CompileLazy instead.

BUG=v8:8395

Change-Id: I4afba79f814ca9a92dec45d59485935845a6669d
Reviewed-on: https://chromium-review.googlesource.com/c/1348433
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58158}
19 files changed
tree: 93014dba1995bb9af48a3eedba10751ab12bfbbc
  1. .clang-format
  2. .clang-tidy
  3. .editorconfig
  4. .git-blame-ignore-revs
  5. .gitattributes
  6. .gitignore
  7. .gn
  8. .vpython
  9. .ycm_extra_conf.py
  10. AUTHORS
  11. BUILD.gn
  12. CODE_OF_CONDUCT.md
  13. ChangeLog
  14. DEPS
  15. LICENSE
  16. LICENSE.fdlibm
  17. LICENSE.strongtalk
  18. LICENSE.v8
  19. LICENSE.valgrind
  20. OWNERS
  21. PRESUBMIT.py
  22. README.md
  23. WATCHLISTS
  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/
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.