text: /* Copyright 2017 The TensorFlow Authors. All Rights Reserved.
  
  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 "tensorflow/compiler/jit/xla_device.h"
  
  #include <stdlib.h>
  #include <unordered_set>
  
  #include "tensorflow/compiler/jit/defs.h"
  #include "tensorflow/compiler/jit/xla_device_context.h"
  #include "tensorflow/compiler/jit/xla_device_ops.h"
  #include "tensorflow/compiler/tf2xla/dump_graph.h"
  #include "tensorflow/compiler/tf2xla/xla_op_registry.h"
  #include "tensorflow/compiler/xla/client/client_library.h"
  #include "tensorflow/core/common_runtime/device.h"
  #include "tensorflow/core/common_runtime/device_factory.h"
  #include "tensorflow/core/common_runtime/dma_helper.h"
  #include "tensorflow/core/common_runtime/function.h"
  #include "tensorflow/core/common_runtime/renamed_device.h"
  #include "tensorflow/core/framework/allocator.h"
  #include "tensorflow/core/framework/device_base.h"
  #include "tensorflow/core/framework/function.h"
  #include "tensorflow/core/framework/kernel_def.pb.h"
  #include "tensorflow/core/framework/node_def_builder.h"
  #include "tensorflow/core/framework/op_kernel.h"
  #include "tensorflow/core/framework/tensor.h"
  #include "tensorflow/core/framework/tensor.pb.h"
  #include "tensorflow/core/framework/types.h"
  #include "tensorflow/core/graph/graph_constructor.h"
  #include "tensorflow/core/lib/core/notification.h"
  #include "tensorflow/core/lib/core/status.h"
  #include "tensorflow/core/platform/logging.h"
  #include "tensorflow/core/platform/stream_executor_no_cuda.h"
  #include "tensorflow/core/platform/tracing.h"
  #include "tensorflow/core/public/session_options.h"
  #include "tensorflow/core/public/version.h"
  #include "tensorflow/core/util/device_name_utils.h"
  #include "tensorflow/core/util/stream_executor_util.h"
  
  namespace se = ::perftools::gputools;
  
  namespace tensorflow {
  
  // Caches a XlaDeviceAllocator per <backend, device ordinal> pair. A
  // XlaDeviceAllocator is created on demand and is associated with a
  // XlaDevice. It outlives the device itself (for instance, the buffer
  // backing a tensor holds a pointer to the allocator for book-keeping,
  // and this buffer can outlast the device).
  class XlaDeviceAllocatorState {
   public:
    // Creates or returns a cached XlaDeviceAllocator for a given
    // backend and device_ordinal.
    static XlaDeviceAllocator* GetOrCreateXlaDeviceAllocator(
        const xla::Backend* backend, int device_ordinal);
  
   private:
    // Returns the singleton instance of XlaDeviceAllocatorState.
    static XlaDeviceAllocatorState& Singleton();
    XlaDeviceAllocatorState();
    ~XlaDeviceAllocatorState();
  
    mutex allocator_mutex_;  // Guards the singleton allocator state.
    std::unordered_map<std::pair<const xla::Backend*, int>,
                       std::unique_ptr<XlaDeviceAllocator>,
                       hash<std::pair<const xla::Backend*, int>>>
        allocators_ GUARDED_BY(allocator_mutex_);
  
    TF_DISALLOW_COPY_AND_ASSIGN(XlaDeviceAllocatorState);
  };
  
  /* static */ XlaDeviceAllocatorState& XlaDeviceAllocatorState::Singleton() {
    static auto a = new XlaDeviceAllocatorState;
    return *a;
  }
  
  XlaDeviceAllocatorState::XlaDeviceAllocatorState() = default;
  XlaDeviceAllocatorState::~XlaDeviceAllocatorState() = default;
  
  XlaDeviceAllocator* XlaDeviceAllocatorState::GetOrCreateXlaDeviceAllocator(
      const xla::Backend* backend, int device_ordinal) {
    XlaDeviceAllocatorState& state = Singleton();
    mutex_lock lock(state.allocator_mutex_);
  
    auto it = state.allocators_.find({backend, device_ordinal});
    if (it != state.allocators_.end()) {
      return it->second.get();
    }
  
    std::unique_ptr<XlaDeviceAllocator> alloc =
        xla::MakeUnique<XlaDeviceAllocator>(backend, device_ordinal);
    XlaDeviceAllocator* alloc_ptr = alloc.get();
    state.allocators_[{backend, device_ordinal}] = std::move(alloc);
    return alloc_ptr;
  }
  
  /* static */ Status XlaDevice::Create(
      const string& platform_name, const string& device_name, int device_ordinal,
      const string& jit_device_name, const SessionOptions& options,
      const string& name_prefix, bool register_device_for_compilation,
      std::unique_ptr<XlaDevice>* device) {
    VLOG(1) << "XlaDevice::Create " << platform_name << " " << device_name << ":"
            << device_ordinal;
  
    if (register_device_for_compilation) {
      // These are no-ops if they have already been done previously for
      // this device_name/compilation_device_name pair.
      XlaOpRegistry::DeviceRegistration registration;
      registration.compilation_device_name = jit_device_name;
      registration.requires_compilation = true;
      registration.enable_jit_by_default = false;
      registration.compile_resource_ops = true;
      XlaOpRegistry::RegisterCompilationDevice(device_name, registration);
    }
  
    auto platform = se::MultiPlatformManager::PlatformWithName(platform_name);
    if (!platform.ok()) {
      return StreamExecutorUtil::ConvertStatus(platform.status());
    }
  
    const DeviceAttributes attrs = Device::BuildDeviceAttributes(
        strings::StrCat(name_prefix, "/device:", device_name, ":",
                        device_ordinal),
        DeviceType(device_name), Bytes(16ULL << 30), DeviceLocality(),
        strings::StrCat("device: ", device_name, " device"));
  
    device->reset(new XlaDevice(options, attrs, device_ordinal,
                                DeviceType(jit_device_name),
                                platform.ValueOrDie()));
    return Status::OK();
  }
  
  XlaDevice::Metadata::Metadata(int device_ordinal, se::Platform* platform,
                                const DeviceType& device_type)
      : device_ordinal_(device_ordinal),
        device_type_(device_type),
        platform_(platform) {}
  
  int XlaDevice::Metadata::device_ordinal() const { return device_ordinal_; }
  
  se::Platform* XlaDevice::Metadata::platform() const { return platform_; }
  
  xla::LocalClient* XlaDevice::Metadata::client() const {
    auto client = xla::ClientLibrary::GetOrCreateLocalClient(platform_);
    return client.ValueOrDie();
  }
  
  const DeviceType& XlaDevice::Metadata::jit_device_type() const {
    return device_type_;
  }
  
  /* static */ Status XlaDevice::GetMetadata(OpKernelContext* ctx,
                                             const Metadata** metadata) {
    XlaDevice* xla_device =
        dynamic_cast<XlaDevice*>(ctx->device()->UnderlyingDevice());
    if (xla_device == nullptr) {
      return errors::Internal(
          "Cannot get XLA metadata from non-XLA device \"", ctx->device()->name(),
          "\". GetMetadata must only be called on an XLA device. Either an "
          "internal bug has been triggered, or an XLA-specific op has been "
          "placed on the wrong device.");
    }
    *metadata = &(xla_device->xla_metadata_);
    return Status::OK();
  }
  
  XlaDevice::XlaDevice(const SessionOptions& options,
                       const DeviceAttributes& attrs, int device_ordinal,
                       const DeviceType& jit_device_name, se::Platform* platform)
      : LocalDevice(options, attrs),
        xla_metadata_(device_ordinal, platform, jit_device_name),
        device_ordinal_(device_ordinal),
        jit_device_name_(jit_device_name),
        xla_allocator_(nullptr),
        platform_(platform) {}
  
  XlaDevice::~XlaDevice() {}
  
  xla::LocalClient* XlaDevice::client() const {
    // We lazily create the client because the platform commits to the
    // details of the host hardware when the client is created, so we
    // don't want to do it until we get a chance to hook the platform up
    // to a simulator.
  
    // For now GetOrCreateLocalClient always returns success when passed
    // a non-null platform. If that changes we may have to plumb in some
    // way to pass Status back.
    return xla::ClientLibrary::GetOrCreateLocalClient(platform_).ValueOrDie();
  }
  
  Allocator* XlaDevice::GetAllocator(AllocatorAttributes attr) {
    if (attr.on_host()) {
      return cpu_allocator();
    }
  
    if (xla_allocator_ == nullptr) {
      xla::Backend* backend = client()->mutable_backend();
      xla_allocator_ = XlaDeviceAllocatorState::GetOrCreateXlaDeviceAllocator(
          backend, device_ordinal_);
    }
    return xla_allocator_;
  }
  
  xla::StatusOr<se::Stream*> XlaDevice::GetStream() {
    if (!stream_) {
      xla::Backend* backend = client()->mutable_backend();
      TF_ASSIGN_OR_RETURN(stream_, backend->BorrowStream(device_ordinal_));
    }
    return stream_.get();
  }
  
  Status XlaDevice::FillContextMap(const Graph* graph,
                                   DeviceContextMap* device_context_map) {
    VLOG(1) << "XlaDevice::FillContextMap";
    device_context_map->resize(graph->num_node_ids());
    TF_ASSIGN_OR_RETURN(se::Stream * stream, GetStream());
    auto ctx = new XlaDeviceContext(stream);
    for (Node* n : graph->nodes()) {
      VLOG(2) << n->id() << " : " << n->type_string() << " : " << n->name();
      ctx->Ref();
      (*device_context_map)[n->id()] = ctx;
    }
    ctx->Unref();
    return Status::OK();
  }
  
  void XlaDevice::Compute(OpKernel* op_kernel, OpKernelContext* context) {
    VLOG(1) << "XlaDevice::Compute " << op_kernel->name() << ":"
            << op_kernel->type_string();
    // When TraceMe profiling is off (which is the default), the
    // following TraceMe constructor is simply a conditional test of
    // false value. Measurements show that its overhead is negligible.
    port::Tracing::TraceMe trace_me(op_kernel->name(), op_kernel->type_string(),
                                    op_kernel->IsExpensive());
    op_kernel->Compute(context);
  }
  
  void XlaDevice::ComputeAsync(AsyncOpKernel* op_kernel, OpKernelContext* context,
                               AsyncOpKernel::DoneCallback done) {
    VLOG(1) << "XlaDevice::ComputeAsync " << op_kernel->name() << ":"
            << op_kernel->type_string();
    port::Tracing::TraceMe trace_me(op_kernel->name(), op_kernel->type_string(),
                                    op_kernel->IsExpensive());
    op_kernel->ComputeAsync(context, done);
  }
  
  Status XlaDevice::MakeTensorFromProto(const TensorProto& tensor_proto,
                                        const AllocatorAttributes alloc_attrs,
                                        Tensor* tensor) {
    VLOG(1) << "XlaDevice::MakeTensorFromProto";
  
    Tensor parsed(tensor_proto.dtype());
    if (!parsed.FromProto(cpu_allocator(), tensor_proto)) {
      return errors::InvalidArgument("Cannot parse tensor from proto: ",
                                     tensor_proto.DebugString());
    }
  
    Status status;
    if (alloc_attrs.on_host()) {
      *tensor = parsed;
    } else {
      Tensor copy(GetAllocator(alloc_attrs), parsed.dtype(), parsed.shape());
      Notification n;
      TF_ASSIGN_OR_RETURN(se::Stream * stream, GetStream());
      XlaTransferManager manager(stream);
      manager.CopyCPUTensorToDevice(&parsed, this, &copy,
                                    [&n, &status](const Status& s) {
                                      status = s;
                                      n.Notify();
                                    });
      n.WaitForNotification();
      *tensor = copy;
    }
    VLOG(2) << "Allocated tensor at " << DMAHelper::base(tensor);
    return status;
  }
  
  XlaDeviceOpRegistrations* RegisterXlaDeviceKernels(const char* device,
                                                     const char* jit_device) {
    XlaOpRegistry::RegisterCompilationKernels();
    XlaDeviceOpRegistrations* registrations = new XlaDeviceOpRegistrations;
    auto dummy_factory = [](OpKernelConstruction* context) -> OpKernel* {
      return new XlaDeviceDummyOp(context);
    };
    for (const KernelDef* jit_def : XlaOpRegistry::DeviceKernels(
             jit_device,
             /*include_compilation_only_kernels=*/false)) {
      KernelDef* def = new KernelDef(*jit_def);
      def->set_device_type(device);
      registrations->op_kernel_registrars.emplace_back(
          new kernel_factory::OpKernelRegistrar(def, "XlaDeviceDummyOp",
                                                dummy_factory));
    }
    return registrations;
  }
  
  }  // namespace tensorflow
  