Method writeVolatileBuffer

src/vulkan/vulkan-buffer.cpp:271–381

    }

    void CommandList::writeVolatileBuffer(Buffer* buffer, const void* data, size_t dataSize)
    {
        VolatileBufferState& state = m_VolatileBufferStates[buffer];

        if (!state.initialized)
        {
            state.minVersion = int(buffer->desc.maxVersions);
            state.maxVersion = -1;
            state.initialized = true;
        }
        
        std::array<uint64_t, uint32_t(CommandQueue::Count)> queueCompletionValues = {
            getQueueLastFinishedID(m_Device, CommandQueue::Graphics),
            getQueueLastFinishedID(m_Device, CommandQueue::Compute),
            getQueueLastFinishedID(m_Device, CommandQueue::Copy)
        };

        uint32_t searchStart = buffer->versionSearchStart;
        uint32_t maxVersions = buffer->desc.maxVersions;
        uint32_t version = 0;

        uint64_t originalVersionInfo = 0;

        // Since versionTracking[] can be accessed by multiple threads concurrently,
        // perform the search in a loop ending with compare_exchange until the exchange is successful.
        while (true)
        {
            bool found = false;

            // Search through the versions of this buffer, looking for either unused (0)
            // or submitted and already finished versions

            for (uint32_t searchIndex = 0; searchIndex < maxVersions; searchIndex++)
            {
                version = searchIndex + searchStart;
                version = (version >= maxVersions) ? (version - maxVersions) : version;

                originalVersionInfo = buffer->versionTracking[version];

                if (originalVersionInfo == 0)
                {
                    // Previously unused version - definitely available
                    found = true;
                    break;
                }

                // Decode the bitfield
                bool isSubmitted = (originalVersionInfo & c_VersionSubmittedFlag) != 0;
                uint32_t queueIndex = uint32_t(originalVersionInfo >> c_VersionQueueShift) & c_VersionQueueMask;
                uint64_t id = originalVersionInfo & c_VersionIDMask;

                // If the version is in a recorded but not submitted command list,
                // we can't use it. So, only compare the version ID for submitted CLs.
                if (isSubmitted)
                {
                    // Versions can potentially be used in CLs submitted to different queues.
                    // So we store the queue index and use look at the last finished CL in that queue.