src/dawn_native/d3d12/BufferD3D12.cpp - dawn - Git at Google

 // Copyright 2017 The Dawn Authors
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.

 #include "dawn_native/d3d12/BufferD3D12.h"

 #include "common/Assert.h"
 #include "common/Constants.h"
 #include "common/Math.h"
 #include "dawn_native/d3d12/CommandRecordingContext.h"
 #include "dawn_native/d3d12/D3D12Error.h"
 #include "dawn_native/d3d12/DeviceD3D12.h"
 #include "dawn_native/d3d12/HeapD3D12.h"
 #include "dawn_native/d3d12/ResidencyManagerD3D12.h"

 namespace dawn_native { namespace d3d12 {

     namespace {
         D3D12_RESOURCE_FLAGS D3D12ResourceFlags(wgpu::BufferUsage usage) {
             D3D12_RESOURCE_FLAGS flags = D3D12_RESOURCE_FLAG_NONE;

             if (usage & wgpu::BufferUsage::Storage) {
                 flags |= D3D12_RESOURCE_FLAG_ALLOW_UNORDERED_ACCESS;
             }

             return flags;
         }

         D3D12_RESOURCE_STATES D3D12BufferUsage(wgpu::BufferUsage usage) {
             D3D12_RESOURCE_STATES resourceState = D3D12_RESOURCE_STATE_COMMON;

             if (usage & wgpu::BufferUsage::CopySrc) {
                 resourceState |= D3D12_RESOURCE_STATE_COPY_SOURCE;
             }
             if (usage & wgpu::BufferUsage::CopyDst) {
                 resourceState |= D3D12_RESOURCE_STATE_COPY_DEST;
             }
             if (usage & (wgpu::BufferUsage::Vertex | wgpu::BufferUsage::Uniform)) {
                 resourceState |= D3D12_RESOURCE_STATE_VERTEX_AND_CONSTANT_BUFFER;
             }
             if (usage & wgpu::BufferUsage::Index) {
                 resourceState |= D3D12_RESOURCE_STATE_INDEX_BUFFER;
             }
             if (usage & wgpu::BufferUsage::Storage) {
                 resourceState |= D3D12_RESOURCE_STATE_UNORDERED_ACCESS;
             }
             if (usage & kReadOnlyStorageBuffer) {
                 resourceState |= (D3D12_RESOURCE_STATE_PIXEL_SHADER_RESOURCE |
                                   D3D12_RESOURCE_STATE_NON_PIXEL_SHADER_RESOURCE);
             }
             if (usage & wgpu::BufferUsage::Indirect) {
                 resourceState |= D3D12_RESOURCE_STATE_INDIRECT_ARGUMENT;
             }

             return resourceState;
         }

         D3D12_HEAP_TYPE D3D12HeapType(wgpu::BufferUsage allowedUsage) {
             if (allowedUsage & wgpu::BufferUsage::MapRead) {
                 return D3D12_HEAP_TYPE_READBACK;
             } else if (allowedUsage & wgpu::BufferUsage::MapWrite) {
                 return D3D12_HEAP_TYPE_UPLOAD;
             } else {
                 return D3D12_HEAP_TYPE_DEFAULT;
             }
         }
     }  // namespace

     Buffer::Buffer(Device* device, const BufferDescriptor* descriptor)
         : BufferBase(device, descriptor) {
     }

     MaybeError Buffer::Initialize() {
         D3D12_RESOURCE_DESC resourceDescriptor;
         resourceDescriptor.Dimension = D3D12_RESOURCE_DIMENSION_BUFFER;
         resourceDescriptor.Alignment = 0;
         // TODO(cwallez@chromium.org): Have a global "zero" buffer that can do everything instead
         // of creating a new 4-byte buffer?
         resourceDescriptor.Width = std::max(GetSize(), uint64_t(4u));
         resourceDescriptor.Height = 1;
         resourceDescriptor.DepthOrArraySize = 1;
         resourceDescriptor.MipLevels = 1;
         resourceDescriptor.Format = DXGI_FORMAT_UNKNOWN;
         resourceDescriptor.SampleDesc.Count = 1;
         resourceDescriptor.SampleDesc.Quality = 0;
         resourceDescriptor.Layout = D3D12_TEXTURE_LAYOUT_ROW_MAJOR;
         // Add CopyDst for non-mappable buffer initialization in CreateBufferMapped
         // and robust resource initialization.
         resourceDescriptor.Flags = D3D12ResourceFlags(GetUsage() | wgpu::BufferUsage::CopyDst);

         auto heapType = D3D12HeapType(GetUsage());
         auto bufferUsage = D3D12_RESOURCE_STATE_COMMON;

         // D3D12 requires buffers on the READBACK heap to have the D3D12_RESOURCE_STATE_COPY_DEST
         // state
         if (heapType == D3D12_HEAP_TYPE_READBACK) {
             bufferUsage |= D3D12_RESOURCE_STATE_COPY_DEST;
             mFixedResourceState = true;
             mLastUsage = wgpu::BufferUsage::CopyDst;
         }

         // D3D12 requires buffers on the UPLOAD heap to have the D3D12_RESOURCE_STATE_GENERIC_READ
         // state
         if (heapType == D3D12_HEAP_TYPE_UPLOAD) {
             bufferUsage |= D3D12_RESOURCE_STATE_GENERIC_READ;
             mFixedResourceState = true;
             mLastUsage = wgpu::BufferUsage::CopySrc;
         }

         DAWN_TRY_ASSIGN(
             mResourceAllocation,
             ToBackend(GetDevice())->AllocateMemory(heapType, resourceDescriptor, bufferUsage));
         return {};
     }

     Buffer::~Buffer() {
         DestroyInternal();
     }

     ComPtr<ID3D12Resource> Buffer::GetD3D12Resource() const {
         return mResourceAllocation.GetD3D12Resource();
     }

     // When true is returned, a D3D12_RESOURCE_BARRIER has been created and must be used in a
     // ResourceBarrier call. Failing to do so will cause the tracked state to become invalid and can
     // cause subsequent errors.
     bool Buffer::TrackUsageAndGetResourceBarrier(CommandRecordingContext* commandContext,
                                                  D3D12_RESOURCE_BARRIER* barrier,
                                                  wgpu::BufferUsage newUsage) {
         // Track the underlying heap to ensure residency.
         Heap* heap = ToBackend(mResourceAllocation.GetResourceHeap());
         commandContext->TrackHeapUsage(heap, GetDevice()->GetPendingCommandSerial());

         // Return the resource barrier.
         return TransitionUsageAndGetResourceBarrier(commandContext, barrier, newUsage);
     }

     void Buffer::TrackUsageAndTransitionNow(CommandRecordingContext* commandContext,
                                             wgpu::BufferUsage newUsage) {
         D3D12_RESOURCE_BARRIER barrier;

         if (TrackUsageAndGetResourceBarrier(commandContext, &barrier, newUsage)) {
             commandContext->GetCommandList()->ResourceBarrier(1, &barrier);
         }
     }

     // When true is returned, a D3D12_RESOURCE_BARRIER has been created and must be used in a
     // ResourceBarrier call. Failing to do so will cause the tracked state to become invalid and can
     // cause subsequent errors.
     bool Buffer::TransitionUsageAndGetResourceBarrier(CommandRecordingContext* commandContext,
                                                       D3D12_RESOURCE_BARRIER* barrier,
                                                       wgpu::BufferUsage newUsage) {
         // Resources in upload and readback heaps must be kept in the COPY_SOURCE/DEST state
         if (mFixedResourceState) {
             ASSERT(mLastUsage == newUsage);
             return false;
         }

         D3D12_RESOURCE_STATES lastState = D3D12BufferUsage(mLastUsage);
         D3D12_RESOURCE_STATES newState = D3D12BufferUsage(newUsage);

         // If the transition is from-UAV-to-UAV, then a UAV barrier is needed.
         // If one of the usages isn't UAV, then other barriers are used.
         bool needsUAVBarrier = lastState == D3D12_RESOURCE_STATE_UNORDERED_ACCESS &&
                                newState == D3D12_RESOURCE_STATE_UNORDERED_ACCESS;

         if (needsUAVBarrier) {
             barrier->Type = D3D12_RESOURCE_BARRIER_TYPE_UAV;
             barrier->Flags = D3D12_RESOURCE_BARRIER_FLAG_NONE;
             barrier->UAV.pResource = GetD3D12Resource().Get();

             mLastUsage = newUsage;
             return true;
         }

         // We can skip transitions to already current usages.
         if ((mLastUsage & newUsage) == newUsage) {
             return false;
         }

         mLastUsage = newUsage;

         // The COMMON state represents a state where no write operations can be pending, which makes
         // it possible to transition to and from some states without synchronizaton (i.e. without an
         // explicit ResourceBarrier call). A buffer can be implicitly promoted to 1) a single write
         // state, or 2) multiple read states. A buffer that is accessed within a command list will
         // always implicitly decay to the COMMON state after the call to ExecuteCommandLists
         // completes - this is because all buffer writes are guaranteed to be completed before the
         // next ExecuteCommandLists call executes.
         // https://docs.microsoft.com/en-us/windows/desktop/direct3d12/using-resource-barriers-to-synchronize-resource-states-in-direct3d-12#implicit-state-transitions

         // To track implicit decays, we must record the pending serial on which a transition will
         // occur. When that buffer is used again, the previously recorded serial must be compared to
         // the last completed serial to determine if the buffer has implicity decayed to the common
         // state.
         const Serial pendingCommandSerial = ToBackend(GetDevice())->GetPendingCommandSerial();
         if (pendingCommandSerial > mLastUsedSerial) {
             lastState = D3D12_RESOURCE_STATE_COMMON;
             mLastUsedSerial = pendingCommandSerial;
         }

         // All possible buffer states used by Dawn are eligible for implicit promotion from COMMON.
         // These are: COPY_SOURCE, VERTEX_AND_COPY_BUFFER, INDEX_BUFFER, COPY_DEST,
         // UNORDERED_ACCESS, and INDIRECT_ARGUMENT. Note that for implicit promotion, the
         // destination state cannot be 1) more than one write state, or 2) both a read and write
         // state. This goes unchecked here because it should not be allowed through render/compute
         // pass validation.
         if (lastState == D3D12_RESOURCE_STATE_COMMON) {
             return false;
         }

         barrier->Type = D3D12_RESOURCE_BARRIER_TYPE_TRANSITION;
         barrier->Flags = D3D12_RESOURCE_BARRIER_FLAG_NONE;
         barrier->Transition.pResource = GetD3D12Resource().Get();
         barrier->Transition.StateBefore = lastState;
         barrier->Transition.StateAfter = newState;
         barrier->Transition.Subresource = D3D12_RESOURCE_BARRIER_ALL_SUBRESOURCES;

         return true;
     }

     D3D12_GPU_VIRTUAL_ADDRESS Buffer::GetVA() const {
         return mResourceAllocation.GetGPUPointer();
     }

     bool Buffer::IsMapWritable() const {
         // TODO(enga): Handle CPU-visible memory on UMA
         return (GetUsage() & (wgpu::BufferUsage::MapRead | wgpu::BufferUsage::MapWrite)) != 0;
     }

     MaybeError Buffer::MapAtCreationImpl(uint8_t** mappedPointer) {
         // The mapped buffer can be accessed at any time, so it must be locked to ensure it is never
         // evicted. This buffer should already have been made resident when it was created.
         Heap* heap = ToBackend(mResourceAllocation.GetResourceHeap());
         DAWN_TRY(ToBackend(GetDevice())->GetResidencyManager()->LockAllocation(heap));

         mWrittenMappedRange = {0, static_cast<size_t>(GetSize())};
         DAWN_TRY(CheckHRESULT(GetD3D12Resource()->Map(0, &mWrittenMappedRange,
                                                       reinterpret_cast<void**>(mappedPointer)),
                               "D3D12 map at creation"));
         mMappedData = reinterpret_cast<char*>(mappedPointer);
         return {};
     }

     MaybeError Buffer::MapReadAsyncImpl(uint32_t serial) {
         // The mapped buffer can be accessed at any time, so we must make the buffer resident and
         // lock it to ensure it is never evicted.
         Heap* heap = ToBackend(mResourceAllocation.GetResourceHeap());
         DAWN_TRY(ToBackend(GetDevice())->GetResidencyManager()->LockAllocation(heap));

         mWrittenMappedRange = {};
         D3D12_RANGE readRange = {0, static_cast<size_t>(GetSize())};
         DAWN_TRY(CheckHRESULT(
             GetD3D12Resource()->Map(0, &readRange, reinterpret_cast<void**>(&mMappedData)),
             "D3D12 map read async"));
         // There is no need to transition the resource to a new state: D3D12 seems to make the GPU
         // writes available when the fence is passed.
         return {};
     }

     MaybeError Buffer::MapWriteAsyncImpl(uint32_t serial) {
         // The mapped buffer can be accessed at any time, so we must make the buffer resident and
         // lock it to ensure it is never evicted.
         Heap* heap = ToBackend(mResourceAllocation.GetResourceHeap());
         DAWN_TRY(ToBackend(GetDevice())->GetResidencyManager()->LockAllocation(heap));

         mWrittenMappedRange = {0, static_cast<size_t>(GetSize())};
         DAWN_TRY(CheckHRESULT(GetD3D12Resource()->Map(0, &mWrittenMappedRange,
                                                       reinterpret_cast<void**>(&mMappedData)),
                               "D3D12 map write async"));
         // There is no need to transition the resource to a new state: D3D12 seems to make the CPU
         // writes available on queue submission.
         return {};
     }

     void Buffer::UnmapImpl() {
         GetD3D12Resource()->Unmap(0, &mWrittenMappedRange);
         // When buffers are mapped, they are locked to keep them in resident memory. We must unlock
         // them when they are unmapped.
         Heap* heap = ToBackend(mResourceAllocation.GetResourceHeap());
         ToBackend(GetDevice())->GetResidencyManager()->UnlockAllocation(heap);
         mWrittenMappedRange = {};
         mMappedData = nullptr;
     }

     void* Buffer::GetMappedPointerImpl() {
         return mMappedData;
     }

     void Buffer::DestroyImpl() {
         // We must ensure that if a mapped buffer is destroyed, it does not leave a dangling lock
         // reference on its heap.
         if (IsMapped()) {
             Heap* heap = ToBackend(mResourceAllocation.GetResourceHeap());
             ToBackend(GetDevice())->GetResidencyManager()->UnlockAllocation(heap);
         }

         ToBackend(GetDevice())->DeallocateMemory(mResourceAllocation);
     }

     bool Buffer::CheckIsResidentForTesting() const {
         Heap* heap = ToBackend(mResourceAllocation.GetResourceHeap());
         return heap->IsInList() || heap->IsResidencyLocked();
     }

     bool Buffer::CheckAllocationMethodForTesting(AllocationMethod allocationMethod) const {
         return mResourceAllocation.GetInfo().mMethod == allocationMethod;
     }

 }}  // namespace dawn_native::d3d12
	// Copyright 2017 The Dawn Authors
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.

	#include "dawn_native/d3d12/BufferD3D12.h"

	#include "common/Assert.h"
	#include "common/Constants.h"
	#include "common/Math.h"
	#include "dawn_native/d3d12/CommandRecordingContext.h"
	#include "dawn_native/d3d12/D3D12Error.h"
	#include "dawn_native/d3d12/DeviceD3D12.h"
	#include "dawn_native/d3d12/HeapD3D12.h"
	#include "dawn_native/d3d12/ResidencyManagerD3D12.h"

	namespace dawn_native { namespace d3d12 {

	namespace {
	D3D12_RESOURCE_FLAGS D3D12ResourceFlags(wgpu::BufferUsage usage) {
	D3D12_RESOURCE_FLAGS flags = D3D12_RESOURCE_FLAG_NONE;

	if (usage & wgpu::BufferUsage::Storage) {
	flags \|= D3D12_RESOURCE_FLAG_ALLOW_UNORDERED_ACCESS;
	}

	return flags;
	}

	D3D12_RESOURCE_STATES D3D12BufferUsage(wgpu::BufferUsage usage) {
	D3D12_RESOURCE_STATES resourceState = D3D12_RESOURCE_STATE_COMMON;

	if (usage & wgpu::BufferUsage::CopySrc) {
	resourceState \|= D3D12_RESOURCE_STATE_COPY_SOURCE;
	}
	if (usage & wgpu::BufferUsage::CopyDst) {
	resourceState \|= D3D12_RESOURCE_STATE_COPY_DEST;
	}
	if (usage & (wgpu::BufferUsage::Vertex \| wgpu::BufferUsage::Uniform)) {
	resourceState \|= D3D12_RESOURCE_STATE_VERTEX_AND_CONSTANT_BUFFER;
	}
	if (usage & wgpu::BufferUsage::Index) {
	resourceState \|= D3D12_RESOURCE_STATE_INDEX_BUFFER;
	}
	if (usage & wgpu::BufferUsage::Storage) {
	resourceState \|= D3D12_RESOURCE_STATE_UNORDERED_ACCESS;
	}
	if (usage & kReadOnlyStorageBuffer) {
	resourceState \|= (D3D12_RESOURCE_STATE_PIXEL_SHADER_RESOURCE \|
	D3D12_RESOURCE_STATE_NON_PIXEL_SHADER_RESOURCE);
	}
	if (usage & wgpu::BufferUsage::Indirect) {
	resourceState \|= D3D12_RESOURCE_STATE_INDIRECT_ARGUMENT;
	}

	return resourceState;
	}

	D3D12_HEAP_TYPE D3D12HeapType(wgpu::BufferUsage allowedUsage) {
	if (allowedUsage & wgpu::BufferUsage::MapRead) {
	return D3D12_HEAP_TYPE_READBACK;
	} else if (allowedUsage & wgpu::BufferUsage::MapWrite) {
	return D3D12_HEAP_TYPE_UPLOAD;
	} else {
	return D3D12_HEAP_TYPE_DEFAULT;
	}
	}
	} // namespace

	Buffer::Buffer(Device* device, const BufferDescriptor* descriptor)
	: BufferBase(device, descriptor) {
	}

	MaybeError Buffer::Initialize() {
	D3D12_RESOURCE_DESC resourceDescriptor;
	resourceDescriptor.Dimension = D3D12_RESOURCE_DIMENSION_BUFFER;
	resourceDescriptor.Alignment = 0;
	// TODO(cwallez@chromium.org): Have a global "zero" buffer that can do everything instead
	// of creating a new 4-byte buffer?
	resourceDescriptor.Width = std::max(GetSize(), uint64_t(4u));
	resourceDescriptor.Height = 1;
	resourceDescriptor.DepthOrArraySize = 1;
	resourceDescriptor.MipLevels = 1;
	resourceDescriptor.Format = DXGI_FORMAT_UNKNOWN;
	resourceDescriptor.SampleDesc.Count = 1;
	resourceDescriptor.SampleDesc.Quality = 0;
	resourceDescriptor.Layout = D3D12_TEXTURE_LAYOUT_ROW_MAJOR;
	// Add CopyDst for non-mappable buffer initialization in CreateBufferMapped
	// and robust resource initialization.
	resourceDescriptor.Flags = D3D12ResourceFlags(GetUsage() \| wgpu::BufferUsage::CopyDst);

	auto heapType = D3D12HeapType(GetUsage());
	auto bufferUsage = D3D12_RESOURCE_STATE_COMMON;

	// D3D12 requires buffers on the READBACK heap to have the D3D12_RESOURCE_STATE_COPY_DEST
	// state
	if (heapType == D3D12_HEAP_TYPE_READBACK) {
	bufferUsage \|= D3D12_RESOURCE_STATE_COPY_DEST;
	mFixedResourceState = true;
	mLastUsage = wgpu::BufferUsage::CopyDst;
	}

	// D3D12 requires buffers on the UPLOAD heap to have the D3D12_RESOURCE_STATE_GENERIC_READ
	// state
	if (heapType == D3D12_HEAP_TYPE_UPLOAD) {
	bufferUsage \|= D3D12_RESOURCE_STATE_GENERIC_READ;
	mFixedResourceState = true;
	mLastUsage = wgpu::BufferUsage::CopySrc;
	}

	DAWN_TRY_ASSIGN(
	mResourceAllocation,
	ToBackend(GetDevice())->AllocateMemory(heapType, resourceDescriptor, bufferUsage));
	return {};
	}

	Buffer::~Buffer() {
	DestroyInternal();
	}

	ComPtr<ID3D12Resource> Buffer::GetD3D12Resource() const {
	return mResourceAllocation.GetD3D12Resource();
	}

	// When true is returned, a D3D12_RESOURCE_BARRIER has been created and must be used in a
	// ResourceBarrier call. Failing to do so will cause the tracked state to become invalid and can
	// cause subsequent errors.
	bool Buffer::TrackUsageAndGetResourceBarrier(CommandRecordingContext* commandContext,
	D3D12_RESOURCE_BARRIER* barrier,
	wgpu::BufferUsage newUsage) {
	// Track the underlying heap to ensure residency.
	Heap* heap = ToBackend(mResourceAllocation.GetResourceHeap());
	commandContext->TrackHeapUsage(heap, GetDevice()->GetPendingCommandSerial());

	// Return the resource barrier.
	return TransitionUsageAndGetResourceBarrier(commandContext, barrier, newUsage);
	}

	void Buffer::TrackUsageAndTransitionNow(CommandRecordingContext* commandContext,
	wgpu::BufferUsage newUsage) {
	D3D12_RESOURCE_BARRIER barrier;

	if (TrackUsageAndGetResourceBarrier(commandContext, &barrier, newUsage)) {
	commandContext->GetCommandList()->ResourceBarrier(1, &barrier);
	}
	}

	// When true is returned, a D3D12_RESOURCE_BARRIER has been created and must be used in a
	// ResourceBarrier call. Failing to do so will cause the tracked state to become invalid and can
	// cause subsequent errors.
	bool Buffer::TransitionUsageAndGetResourceBarrier(CommandRecordingContext* commandContext,
	D3D12_RESOURCE_BARRIER* barrier,
	wgpu::BufferUsage newUsage) {
	// Resources in upload and readback heaps must be kept in the COPY_SOURCE/DEST state
	if (mFixedResourceState) {
	ASSERT(mLastUsage == newUsage);
	return false;
	}

	D3D12_RESOURCE_STATES lastState = D3D12BufferUsage(mLastUsage);
	D3D12_RESOURCE_STATES newState = D3D12BufferUsage(newUsage);

	// If the transition is from-UAV-to-UAV, then a UAV barrier is needed.
	// If one of the usages isn't UAV, then other barriers are used.
	bool needsUAVBarrier = lastState == D3D12_RESOURCE_STATE_UNORDERED_ACCESS &&
	newState == D3D12_RESOURCE_STATE_UNORDERED_ACCESS;

	if (needsUAVBarrier) {
	barrier->Type = D3D12_RESOURCE_BARRIER_TYPE_UAV;
	barrier->Flags = D3D12_RESOURCE_BARRIER_FLAG_NONE;
	barrier->UAV.pResource = GetD3D12Resource().Get();

	mLastUsage = newUsage;
	return true;
	}

	// We can skip transitions to already current usages.
	if ((mLastUsage & newUsage) == newUsage) {
	return false;
	}

	mLastUsage = newUsage;

	// The COMMON state represents a state where no write operations can be pending, which makes
	// it possible to transition to and from some states without synchronizaton (i.e. without an
	// explicit ResourceBarrier call). A buffer can be implicitly promoted to 1) a single write
	// state, or 2) multiple read states. A buffer that is accessed within a command list will
	// always implicitly decay to the COMMON state after the call to ExecuteCommandLists
	// completes - this is because all buffer writes are guaranteed to be completed before the
	// next ExecuteCommandLists call executes.
	// https://docs.microsoft.com/en-us/windows/desktop/direct3d12/using-resource-barriers-to-synchronize-resource-states-in-direct3d-12#implicit-state-transitions

	// To track implicit decays, we must record the pending serial on which a transition will
	// occur. When that buffer is used again, the previously recorded serial must be compared to
	// the last completed serial to determine if the buffer has implicity decayed to the common
	// state.
	const Serial pendingCommandSerial = ToBackend(GetDevice())->GetPendingCommandSerial();
	if (pendingCommandSerial > mLastUsedSerial) {
	lastState = D3D12_RESOURCE_STATE_COMMON;
	mLastUsedSerial = pendingCommandSerial;
	}

	// All possible buffer states used by Dawn are eligible for implicit promotion from COMMON.
	// These are: COPY_SOURCE, VERTEX_AND_COPY_BUFFER, INDEX_BUFFER, COPY_DEST,
	// UNORDERED_ACCESS, and INDIRECT_ARGUMENT. Note that for implicit promotion, the
	// destination state cannot be 1) more than one write state, or 2) both a read and write
	// state. This goes unchecked here because it should not be allowed through render/compute
	// pass validation.
	if (lastState == D3D12_RESOURCE_STATE_COMMON) {
	return false;
	}

	barrier->Type = D3D12_RESOURCE_BARRIER_TYPE_TRANSITION;
	barrier->Flags = D3D12_RESOURCE_BARRIER_FLAG_NONE;
	barrier->Transition.pResource = GetD3D12Resource().Get();
	barrier->Transition.StateBefore = lastState;
	barrier->Transition.StateAfter = newState;
	barrier->Transition.Subresource = D3D12_RESOURCE_BARRIER_ALL_SUBRESOURCES;

	return true;
	}

	D3D12_GPU_VIRTUAL_ADDRESS Buffer::GetVA() const {
	return mResourceAllocation.GetGPUPointer();
	}

	bool Buffer::IsMapWritable() const {
	// TODO(enga): Handle CPU-visible memory on UMA
	return (GetUsage() & (wgpu::BufferUsage::MapRead \| wgpu::BufferUsage::MapWrite)) != 0;
	}

	MaybeError Buffer::MapAtCreationImpl(uint8_t** mappedPointer) {
	// The mapped buffer can be accessed at any time, so it must be locked to ensure it is never
	// evicted. This buffer should already have been made resident when it was created.
	Heap* heap = ToBackend(mResourceAllocation.GetResourceHeap());
	DAWN_TRY(ToBackend(GetDevice())->GetResidencyManager()->LockAllocation(heap));

	mWrittenMappedRange = {0, static_cast<size_t>(GetSize())};
	DAWN_TRY(CheckHRESULT(GetD3D12Resource()->Map(0, &mWrittenMappedRange,
	reinterpret_cast<void**>(mappedPointer)),
	"D3D12 map at creation"));
	mMappedData = reinterpret_cast<char*>(mappedPointer);
	return {};
	}

	MaybeError Buffer::MapReadAsyncImpl(uint32_t serial) {
	// The mapped buffer can be accessed at any time, so we must make the buffer resident and
	// lock it to ensure it is never evicted.
	Heap* heap = ToBackend(mResourceAllocation.GetResourceHeap());
	DAWN_TRY(ToBackend(GetDevice())->GetResidencyManager()->LockAllocation(heap));

	mWrittenMappedRange = {};
	D3D12_RANGE readRange = {0, static_cast<size_t>(GetSize())};
	DAWN_TRY(CheckHRESULT(
	GetD3D12Resource()->Map(0, &readRange, reinterpret_cast<void**>(&mMappedData)),
	"D3D12 map read async"));
	// There is no need to transition the resource to a new state: D3D12 seems to make the GPU
	// writes available when the fence is passed.
	return {};
	}

	MaybeError Buffer::MapWriteAsyncImpl(uint32_t serial) {
	// The mapped buffer can be accessed at any time, so we must make the buffer resident and
	// lock it to ensure it is never evicted.
	Heap* heap = ToBackend(mResourceAllocation.GetResourceHeap());
	DAWN_TRY(ToBackend(GetDevice())->GetResidencyManager()->LockAllocation(heap));

	mWrittenMappedRange = {0, static_cast<size_t>(GetSize())};
	DAWN_TRY(CheckHRESULT(GetD3D12Resource()->Map(0, &mWrittenMappedRange,
	reinterpret_cast<void**>(&mMappedData)),
	"D3D12 map write async"));
	// There is no need to transition the resource to a new state: D3D12 seems to make the CPU
	// writes available on queue submission.
	return {};
	}

	void Buffer::UnmapImpl() {
	GetD3D12Resource()->Unmap(0, &mWrittenMappedRange);
	// When buffers are mapped, they are locked to keep them in resident memory. We must unlock
	// them when they are unmapped.
	Heap* heap = ToBackend(mResourceAllocation.GetResourceHeap());
	ToBackend(GetDevice())->GetResidencyManager()->UnlockAllocation(heap);
	mWrittenMappedRange = {};
	mMappedData = nullptr;
	}

	void* Buffer::GetMappedPointerImpl() {
	return mMappedData;
	}

	void Buffer::DestroyImpl() {
	// We must ensure that if a mapped buffer is destroyed, it does not leave a dangling lock
	// reference on its heap.
	if (IsMapped()) {
	Heap* heap = ToBackend(mResourceAllocation.GetResourceHeap());
	ToBackend(GetDevice())->GetResidencyManager()->UnlockAllocation(heap);
	}

	ToBackend(GetDevice())->DeallocateMemory(mResourceAllocation);
	}

	bool Buffer::CheckIsResidentForTesting() const {
	Heap* heap = ToBackend(mResourceAllocation.GetResourceHeap());
	return heap->IsInList() \|\| heap->IsResidencyLocked();
	}

	bool Buffer::CheckAllocationMethodForTesting(AllocationMethod allocationMethod) const {
	return mResourceAllocation.GetInfo().mMethod == allocationMethod;
	}

	}} // namespace dawn_native::d3d12