Add a Fence opcode to B3
https://bugs.webkit.org/show_bug.cgi?id=162343
Reviewed by Geoffrey Garen.
Source/JavaScriptCore:
This adds the most basic fence support to B3. Currently, this is optimal on x86 and correct
on ARM. It also happens to be sufficient and optimal for what we'll do in the concurrent GC.
The idea of Fence is that it can represent any standalone fence instruction by having two
additional params: a read range and a write range. If the write range is empty, this is
taken to be a store-store fence, which turns into zero code on x86 and a cheaper fence on
ARM.
It turns out that this is powerful enough to express store-load and store-store fences. For
load-store and load-load fences, you wouldn't have wanted to use any code on x86 and you
wouldn't have wanted a standalone barrier on ARM. For those cases, you'd want either a
fenced load (load acquire) or a dependency. See bug 162349 and bug 162350, respectively.
This isn't yet optimized for store-store fences on ARM because we don't have the
MacroAssembler support. Also, the support for "dmb ish" is not really what we want (it seems
to use a heavier fence). I don't think that this is urgent because of how the concurrent GC
will use this facility. I've left that to bug 162342.
* CMakeLists.txt:
* JavaScriptCore.xcodeproj/project.pbxproj:
* assembler/MacroAssemblerCodeRef.cpp:
(JSC::MacroAssemblerCodeRef::tryToDisassemble):
(JSC::MacroAssemblerCodeRef::disassembly):
* assembler/MacroAssemblerCodeRef.h:
(JSC::MacroAssemblerCodeRef::size): Deleted.
(JSC::MacroAssemblerCodeRef::tryToDisassemble): Deleted.
* b3/B3Compilation.h:
(JSC::B3::Compilation::codeRef):
(JSC::B3::Compilation::disassembly):
(JSC::B3::Compilation::code): Deleted.
* b3/B3Effects.h:
* b3/B3FenceValue.cpp: Added.
(JSC::B3::FenceValue::~FenceValue):
(JSC::B3::FenceValue::cloneImpl):
(JSC::B3::FenceValue::FenceValue):
* b3/B3FenceValue.h: Added.
* b3/B3LowerToAir.cpp:
(JSC::B3::Air::LowerToAir::lower):
* b3/B3Opcode.cpp:
(WTF::printInternal):
* b3/B3Opcode.h:
* b3/B3Validate.cpp:
* b3/B3Value.cpp:
(JSC::B3::Value::effects):
* b3/air/AirOpcode.opcodes:
* b3/testb3.cpp:
(JSC::B3::checkUsesInstruction):
(JSC::B3::checkDoesNotUseInstruction):
(JSC::B3::testX86MFence):
(JSC::B3::testX86CompilerFence):
(JSC::B3::run):
Websites/webkit.org:
* docs/b3/intermediate-representation.html:
git-svn-id: http://svn.webkit.org/repository/webkit/trunk@206226 268f45cc-cd09-0410-ab3c-d52691b4dbfc
19 files changed
