src/dawn/native/d3d12/CommandAllocatorManager.cpp

// Copyright 2017 The Dawn & Tint Authors
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#include "dawn/native/d3d12/CommandAllocatorManager.h"

#include "dawn/native/d3d/D3DError.h"
#include "dawn/native/d3d12/DeviceD3D12.h"
#include "dawn/native/d3d12/QueueD3D12.h"

#include "dawn/common/Assert.h"
#include "dawn/common/BitSetIterator.h"

namespace dawn::native::d3d12 {

CommandAllocatorManager::CommandAllocatorManager(Queue* queue) : mQueue(queue), mAllocatorCount(0) {
    mFreeAllocators.set();
}

ResultOrError<ID3D12CommandAllocator*> CommandAllocatorManager::ReserveCommandAllocator() {
    // If there are no free allocators, get the oldest serial in flight and wait on it
    if (mFreeAllocators.none()) {
        const ExecutionSerial firstSerial = mInFlightCommandAllocators.FirstSerial();
        DAWN_TRY(mQueue->WaitForSerial(firstSerial));
        DAWN_TRY(Tick(firstSerial));
    }

    DAWN_ASSERT(mFreeAllocators.any());

    // Get the index of the first free allocator from the bitset
    unsigned int firstFreeIndex = *(IterateBitSet(mFreeAllocators).begin());

    if (firstFreeIndex >= mAllocatorCount) {
        DAWN_ASSERT(firstFreeIndex == mAllocatorCount);
        mAllocatorCount++;

        ID3D12Device* d3d12Device = ToBackend(mQueue->GetDevice())->GetD3D12Device();
        DAWN_TRY(CheckHRESULT(
            d3d12Device->CreateCommandAllocator(D3D12_COMMAND_LIST_TYPE_DIRECT,
                                                IID_PPV_ARGS(&mCommandAllocators[firstFreeIndex])),
            "D3D12 create command allocator"));
    }

    // Mark the command allocator as used
    mFreeAllocators.reset(firstFreeIndex);

    // Enqueue the command allocator. It will be scheduled for reset after the next
    // ExecuteCommandLists
    mInFlightCommandAllocators.Enqueue({mCommandAllocators[firstFreeIndex], firstFreeIndex},
                                       mQueue->GetPendingCommandSerial());
    return mCommandAllocators[firstFreeIndex].Get();
}

MaybeError CommandAllocatorManager::Tick(ExecutionSerial lastCompletedSerial) {
    // Reset all command allocators that are no longer in flight
    for (auto it : mInFlightCommandAllocators.IterateUpTo(lastCompletedSerial)) {
        DAWN_TRY(CheckHRESULT(it.commandAllocator->Reset(), "D3D12 reset command allocator"));
        mFreeAllocators.set(it.index);
    }
    mInFlightCommandAllocators.ClearUpTo(lastCompletedSerial);
    return {};
}

}  // namespace dawn::native::d3d12