This is xnu-8019. See this file in:
Directory listing for xnu-8019//iokit/Kernel
IOBufferMemoryDescriptor.cpp
IOCPU.cpp
IOCatalogue.cpp
IOCommand.cpp
IOCommandGate.cpp
IOCommandPool.cpp
IOCommandQueue.cpp
IOConditionLock.cpp
IODMACommand.cpp
IODMAController.cpp
IODMAEventSource.cpp
IODataQueue.cpp
IODeviceMemory.cpp
IODeviceTreeSupport.cpp
IOEventSource.cpp
IOFilterInterruptEventSource.cpp
IOGuardPageMemoryDescriptor.cpp
IOHibernateIO.cpp
IOHibernateInternal.h
IOHibernateRestoreKernel.c
IOHistogramReporter.cpp
IOInterleavedMemoryDescriptor.cpp
IOInterruptAccounting.cpp
IOInterruptController.cpp
IOInterruptEventSource.cpp
IOKitDebug.cpp
IOKitKernelInternal.h
IOLib.cpp
IOLocks.cpp
IOMapper.cpp
IOMemoryCursor.cpp
IOMemoryDescriptor.cpp
IOMultiMemoryDescriptor.cpp
IONVRAM.cpp
IOPMGR.cpp
IOPMPowerSource.cpp
IOPMPowerSourceList.cpp
IOPMPowerStateQueue.cpp
IOPMPowerStateQueue.h
IOPMinformee.cpp
IOPMinformeeList.cpp
IOPMrootDomain.cpp
IOPMrootDomainInternal.h
IOPerfControl.cpp
IOPlatformActions.cpp
IOPlatformExpert.cpp
IOPlatformIO.cpp
IOPolledInterface.cpp
IOPowerConnection.cpp
IORTC.cpp
IORangeAllocator.cpp
IORegistryEntry.cpp
IOReportLegend.cpp
IOReporter.cpp
IOReporterDefs.h
IOService.cpp
IOServicePM.cpp
IOServicePMPrivate.h
IOServicePrivate.h
IOSharedDataQueue.cpp
IOSimpleReporter.cpp
IOStartIOKit.cpp
IOStateReporter.cpp
IOStatistics.cpp
IOStringFuncs.c
IOSubMemoryDescriptor.cpp
IOSyncer.cpp
IOTimerEventSource.cpp
IOUserClient.cpp
IOUserServer.cpp
IOWorkLoop.cpp
PassthruInterruptController.cpp
RootDomainUserClient.cpp
RootDomainUserClient.h
arm/
i386/
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x86_64/