Code block jettisoning should be part of the GC's transitive closure
https://bugs.webkit.org/show_bug.cgi?id=72467
Reviewed by Geoff Garen.
Replaced JettisonedCodeBlocks with DFGCodeBlocks. The latter knows about all
DFG code blocks (i.e. those that may be jettisoned, and may have inlined weak
references) and helps track what state each of those code blocks is in during
GC. The state consists of two flags; mayBeExecuting, which tells if the code block
is live from call frames; and isJettisoned, which tells if the code block is
not owned by any executable and thus should be deleted as soon as it is not
mayBeExecuting.
- Not executing, Not jettisoned: The code block may or may not be reachable from
any executables, but it is owned by an executable, and hence should be
kept alive if its executable is live and if all of its weak references are
live. Otherwise it should be deleted during the current GC cycle, and its
outgoing references should not be scanned.
- Not executing but jettisoned: The code block should be deleted as soon as
possible and none of its outgoing references should be scanned.
- Executing but not jettisoned: The code block should be kept alive during this
GC cycle, and all of its outgoing references (including the weak ones)
should be scanned and marked strongly. The mayBeExecuting bit will be cleared at
the end of the GC cycle.
- Executing and jettisoned: The code block should be kept alive during this
GC cycle, and all of its outgoing references (including the weak ones)
should be scanned and marked strongly. However, on the next GC cycle, it
will have its mayBeExecuting bit cleared and hence it will become a candidate
for immediate deletion provided it is not executing again.
This is performance-neutral.
- CMakeLists.txt:
- GNUmakefile.list.am:
- JavaScriptCore.vcproj/JavaScriptCore/JavaScriptCore.vcproj:
- JavaScriptCore.xcodeproj/project.pbxproj:
- Target.pri:
- bytecode/CodeBlock.cpp:
(JSC::CodeBlock::~CodeBlock):
(JSC::CodeBlock::setJITCode):
(JSC::CodeBlock::DFGData::DFGData):
(JSC::DFGCodeBlocks::mark):
- heap/ConservativeRoots.cpp:
(JSC::ConservativeRoots::add):
- heap/ConservativeRoots.h:
- heap/DFGCodeBlocks.cpp: Added.
(JSC::DFGCodeBlocks::DFGCodeBlocks):
(JSC::DFGCodeBlocks::~DFGCodeBlocks):
(JSC::DFGCodeBlocks::jettison):
(JSC::DFGCodeBlocks::clearMarks):
(JSC::DFGCodeBlocks::deleteUnmarkedJettisonedCodeBlocks):
(JSC::DFGCodeBlocks::traceMarkedCodeBlocks):
- heap/DFGCodeBlocks.h: Added.
- heap/Heap.cpp:
(JSC::Heap::jettisonDFGCodeBlock):
(JSC::Heap::markRoots):
(JSC::Heap::collect):
- heap/Heap.h:
- heap/JettisonedCodeBlocks.cpp: Removed.
- heap/JettisonedCodeBlocks.h: Removed.
- interpreter/RegisterFile.cpp:
(JSC::RegisterFile::gatherConservativeRoots):
- interpreter/RegisterFile.h:
- runtime/Executable.cpp:
(JSC::jettisonCodeBlock):
