Rationalize and optimize storage allocation
https://bugs.webkit.org/show_bug.cgi?id=91303
Reviewed by Oliver Hunt.
This implements a backwards bump allocator for copied space storage
allocation, shown in pseudo-code below:
pointer bump(size) {
pointer tmp = allocator->remaining;
tmp -= size;
if (tmp < 0)
fail;
allocator->remaining = tmp;
return allocator->payloadEnd - tmp - size;
}
The advantage of this allocator is that it:
- Only requires one comparison in the common case where size is known to
not be huge, and this comparison can be done by checking the sign bit
of the subtraction.
- Can be implemented even when only one register is available. This
register is reused for both temporary storage during allocation and
for the result.
- Preserves the behavior that memory in a block is filled in from lowest
address to highest address, which allows for a cheap reallocation fast
path.
- Is resilient against the block used for allocation being the last one
in virtual memory, thereby otherwise leading to the risk of overflow
in the bump pointer, despite only doing one branch.
In order to implement this allocator using the smallest possible chunk
of code, I refactored the copied space code so that all of the allocation
logic is in CopiedAllocator, and all of the state is in either
CopiedBlock or CopiedAllocator. This should make changing the allocation
fast path easier in the future.
In order to do this, I needed to add some new assembler support,
particularly for various forms of add(address, register) and negPtr().
This is performance neutral. The purpose of this change is to facilitate
further inlining of storage allocation without having to reserve
additional registers or emit too much code.
* assembler/MacroAssembler.h:
(JSC::MacroAssembler::addPtr):
(MacroAssembler):
(JSC::MacroAssembler::negPtr):
* assembler/MacroAssemblerARMv7.h:
(MacroAssemblerARMv7):
(JSC::MacroAssemblerARMv7::add32):
* assembler/MacroAssemblerX86.h:
(JSC::MacroAssemblerX86::add32):
(MacroAssemblerX86):
* assembler/MacroAssemblerX86_64.h:
(MacroAssemblerX86_64):
(JSC::MacroAssemblerX86_64::addPtr):
(JSC::MacroAssemblerX86_64::negPtr):
* assembler/X86Assembler.h:
(X86Assembler):
(JSC::X86Assembler::addl_mr):
(JSC::X86Assembler::addq_mr):
(JSC::X86Assembler::negq_r):
* heap/CopiedAllocator.h:
(CopiedAllocator):
(JSC::CopiedAllocator::isValid):
(JSC::CopiedAllocator::CopiedAllocator):
(JSC::CopiedAllocator::tryAllocate):
(JSC):
(JSC::CopiedAllocator::tryReallocate):
(JSC::CopiedAllocator::forceAllocate):
(JSC::CopiedAllocator::resetCurrentBlock):
(JSC::CopiedAllocator::setCurrentBlock):
(JSC::CopiedAllocator::currentCapacity):
* heap/CopiedBlock.h:
(CopiedBlock):
(JSC::CopiedBlock::create):
(JSC::CopiedBlock::zeroFillWilderness):
(JSC::CopiedBlock::CopiedBlock):
(JSC::CopiedBlock::payloadEnd):
(JSC):
(JSC::CopiedBlock::payloadCapacity):
(JSC::CopiedBlock::data):
(JSC::CopiedBlock::dataEnd):
(JSC::CopiedBlock::dataSize):
(JSC::CopiedBlock::wilderness):
(JSC::CopiedBlock::wildernessEnd):
(JSC::CopiedBlock::wildernessSize):
(JSC::CopiedBlock::size):
* heap/CopiedSpace.cpp:
(JSC::CopiedSpace::tryAllocateSlowCase):
(JSC::CopiedSpace::tryAllocateOversize):
(JSC::CopiedSpace::tryReallocate):
(JSC::CopiedSpace::doneFillingBlock):
(JSC::CopiedSpace::doneCopying):
* heap/CopiedSpace.h:
(CopiedSpace):
* heap/CopiedSpaceInlineMethods.h:
(JSC::CopiedSpace::startedCopying):
(JSC::CopiedSpace::allocateBlockForCopyingPhase):
(JSC::CopiedSpace::allocateBlock):
(JSC::CopiedSpace::tryAllocate):
(JSC):
* heap/MarkStack.cpp:
(JSC::SlotVisitor::startCopying):
(JSC::SlotVisitor::allocateNewSpace):
(JSC::SlotVisitor::doneCopying):
* heap/SlotVisitor.h:
(JSC::SlotVisitor::SlotVisitor):
* jit/JIT.h:
* jit/JITInlineMethods.h:
(JSC::JIT::emitAllocateBasicStorage):
(JSC::JIT::emitAllocateJSArray):
git-svn-id: http://svn.webkit.org/repository/webkit/trunk@122677 268f45cc-cd09-0410-ab3c-d52691b4dbfc
diff --git a/Source/JavaScriptCore/assembler/MacroAssemblerX86.h b/Source/JavaScriptCore/assembler/MacroAssemblerX86.h
index 45de813..da9dd8f 100644
--- a/Source/JavaScriptCore/assembler/MacroAssemblerX86.h
+++ b/Source/JavaScriptCore/assembler/MacroAssemblerX86.h
@@ -63,6 +63,11 @@
m_assembler.addl_im(imm.m_value, address.m_ptr);
}
+ void add32(AbsoluteAddress address, RegisterID dest)
+ {
+ m_assembler.addl_mr(address.m_ptr, dest);
+ }
+
void add64(TrustedImm32 imm, AbsoluteAddress address)
{
m_assembler.addl_im(imm.m_value, address.m_ptr);
@@ -78,7 +83,7 @@
{
m_assembler.orl_im(imm.m_value, address.m_ptr);
}
-
+
void sub32(TrustedImm32 imm, AbsoluteAddress address)
{
m_assembler.subl_im(imm.m_value, address.m_ptr);
