/* 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.
==============================================================================*/

#ifndef TENSORFLOW_COMPILER_TF2XLA_XLA_OP_REGISTRY_H_
#define TENSORFLOW_COMPILER_TF2XLA_XLA_OP_REGISTRY_H_

#include <functional>
#include <memory>
#include <set>
#include <unordered_map>
#include <vector>

#include "tensorflow/core/common_runtime/device_factory.h"
#include "tensorflow/core/common_runtime/local_device.h"
#include "tensorflow/core/framework/device_base.h"
#include "tensorflow/core/framework/tensor.h"
#include "tensorflow/core/framework/types.pb.h"
#include "tensorflow/core/lib/core/status.h"
#include "tensorflow/core/platform/mem.h"
#include "tensorflow/core/platform/mutex.h"
#include "tensorflow/core/platform/thread_annotations.h"
#include "tensorflow/core/public/session_options.h"

namespace tensorflow {

// Names of the XLA compilation devices. These are not user-visible, and are
// used internally by the Tensorflow/XLA bridge to perform symbolic execution of
// a Tensorflow graph.

extern const char* const DEVICE_CPU_XLA_JIT;  // "CPU_XLA_JIT"
extern const char* const DEVICE_GPU_XLA_JIT;  // "GPU_XLA_JIT"

extern const char* const DEVICE_XLA_CPU;
extern const char* const DEVICE_XLA_GPU;

constexpr std::array<DataType, 4> kFloatTypes = {
    {DT_HALF, DT_FLOAT, DT_DOUBLE, DT_BFLOAT16}};
constexpr std::array<DataType, 12> kNumericTypes = {
    {DT_UINT8, DT_UINT32, DT_UINT64, DT_INT8, DT_INT32, DT_INT64, DT_HALF,
     DT_FLOAT, DT_DOUBLE, DT_COMPLEX64, DT_COMPLEX128, DT_BFLOAT16}};

constexpr std::array<DataType, 16> kCpuAllTypes = {
    {DT_UINT8, DT_QUINT8, DT_UINT32, DT_UINT64, DT_INT8, DT_QINT8, DT_INT32,
     DT_QINT32, DT_INT64, DT_HALF, DT_FLOAT, DT_DOUBLE, DT_COMPLEX64,
     DT_COMPLEX128, DT_BOOL, DT_BFLOAT16}};

constexpr std::array<DataType, 16> kGpuAllTypes = {
    {DT_UINT8, DT_QUINT8, DT_UINT32, DT_UINT64, DT_INT8, DT_QINT8, DT_INT32,
     DT_QINT32, DT_INT64, DT_HALF, DT_FLOAT, DT_DOUBLE, DT_COMPLEX64,
     DT_COMPLEX128, DT_BOOL, DT_BFLOAT16}};

// Class that manages registrations of operators and devices for the XLA JIT.
// Not thread-safe.
class XlaOpRegistry {
 public:
  typedef OpKernel* (*Factory)(OpKernelConstruction*);

  enum class AutoclusteringPolicy {
    // Enable autoclustering if the user requests it, e.g., via
    // experimental_jit_scope. Does not autocluster if the JIT is enabled
    // globally (e.g., via the OptimizerOptions in the TF session
    // configuration.)
    kIfExplicitlyRequested,
    // Enable autoclustering if explicitly requested, or if the JIT is enabled
    // globally in the session options, or via TF_XLA_FLAGS=--tf_xla_auto_jit=N.
    kIfEnabledGlobally,
    // Always try to autocluster ops placed on this device.
    kAlways,
  };

  // Describes how to compile operators assigned to a device.
  struct DeviceRegistration {
    // The name of the an XLA compilation device to use to compile code.
    string compilation_device_name;

    // When should we autocluster operators assigned to this device?
    AutoclusteringPolicy autoclustering_policy;

    // If we should ignore the resource variable memory model when clustering
    // resource variable reads and writes placed on this device.
    bool cluster_resource_variable_ops_unsafely = false;

    // If we should auto-cluster Stack operations placed on this device.
    bool cluster_stack_ops = false;

    // If we should auto-cluster TensorArray operations placed on this device.
    bool cluster_tensor_array_ops = false;

    // If we should auto-cluster stateful RNG operations placed on this device.
    // Stateful RNG semantics are not properly supported by XLA so it is not
    // necessarily correct to auto-cluster stateful RNG ops in general.
    bool cluster_stateful_rng_ops = false;

    // If we should auto-cluster ControlTrigger operations placed on this
    // device.  ControlTrigger operations are not necessarily safe to cluster
    // since they affect deadness (a dead ControlTrigger produces a live
    // output).
    bool cluster_control_trigger = false;

    // If we should cluster Assert and CheckNumerics by eliding them (XLA does
    // not natively support Assert or CheckNumerics).
    bool elide_assert_and_checknumerics = false;

    // If we should cluster operations returning DT_VARIANT.
    bool cluster_variant_ops = false;

    // Whether ops known to be slow should be auto-clustered.
    bool cluster_slow_ops = false;

    // Whether ops known to have numerical accuracy issues should be
    // auto-clustered.
    bool cluster_inaccurate_ops = false;
  };

  // Registers an XLA backend. `compilation_device_name` is the name of the
  // device used for symbolic execution during compilation. `supported_types`
  // is the list of non-resource types supported by the device. Each operators
  // will be registered for the intersection of the operator's supported types
  // and the device's supported types. `backend_op_filter` is a function used
  // to exclude or modify operator registrations on the device; it may be
  // nullptr, in which case all ops are included.
  // `backend_op_filter` should return true if the op should be registered on
  // the device; it may optionally modify the KernelDef.
  typedef bool (*BackendOpFilter)(KernelDef* kdef);
  static void RegisterBackend(const string& compilation_device_name,
                              absl::Span<const DataType> supported_types,
                              BackendOpFilter op_filter);

  // Returns the names of the registered backends.
  static std::vector<string> BackendNames();

  // Returns true iff a backend with the given name is registered.
  static bool IsBackendRegistered(const string& name);

  // Registers `device_name` for XLA compilation, using information from
  // `registration`.
  // Does nothing if a registration for `device_name` already exists.
  static void RegisterCompilationDevice(const string& device_name,
                                        const DeviceRegistration& registration);

  // Returns the JIT device name associated with 'device_name', setting
  // 'jit_device_name', 'requires_jit', and 'enabled_jit_by_default', if they
  // are not null. Returns false and leaves the outputs unchanged if no matching
  // JIT device is registered.
  // '*enable_jit_by_default' is set to true if we should try to JIT using this
  // device when the JIT is enabled via the Session OptimizerOptions.
  static bool GetCompilationDevice(const string& device_name,
                                   const DeviceRegistration** registration);

  // Registers all JIT kernels on JIT devices, if not already registered.
  // Does nothing otherwise.
  static void RegisterCompilationKernels();

  // Returns KernelDefs for compilation ops registered on
  // 'compilation_device_name'.  Does not include kernels registered as
  // CompilationOnly, iff include_compilation_only_kernels=false.
  static std::vector<const KernelDef*> DeviceKernels(
      const string& compilation_device_name,
      bool include_compilation_only_kernels);

  // Returns all operations for which there are XLA kernels on any device.
  static std::vector<string> GetAllRegisteredOps();

  // Returns (via `result`) the indices of inputs to `node_def` that must be
  // compile-time constants. Returns an empty vector if the op is not
  // registered.
  //
  // `result` is sorted.
  static Status CompileTimeConstantInputs(const NodeDef& node_def,
                                          const OpDef& op_def,
                                          std::vector<int>* result) {
    return CompileTimeConstantInputs(node_def, /*op_kernel=*/nullptr, &op_def,
                                     result);
  }

  // Returns (via `result`) the indices of inputs to `op_kernel` that must be
  // compile-time constants.
  //
  // `result` is sorted.
  static Status CompileTimeConstantInputs(const OpKernel& op_kernel,
                                          std::vector<int>* result) {
    return CompileTimeConstantInputs(op_kernel.def(), /*op_kernel=*/&op_kernel,
                                     /*op_def=*/nullptr, result);
  }

  // Returns true if `op` is a "metadata" op, one that only looks at the shapes
  // of its operands and not their values.
  static bool IsMetadataOp(const string& op);

 private:
  friend class XlaBackendRegistrar;
  friend class XlaOpRegistrar;
  friend class XlaOpRegistrationBuilder;

  static XlaOpRegistry& Instance();

  XlaOpRegistry();
  ~XlaOpRegistry();

  mutex mutex_;

  // Describes an XLA backend.
  struct Backend {
    // Which types are supported by this device?
    std::set<DataType> supported_types;

    // The per-backend operator filter function. See the comment on
    // RegisterBackend() for details.
    BackendOpFilter op_filter;

    // KernelDefs built by RegisterCompilationKernels() for each op supported
    // by the device.
    std::vector<std::unique_ptr<KernelDef>> kernel_defs;
  };

  // Map from compilation device names to a description of the backend.
  std::unordered_map<string, Backend> backends_ GUARDED_BY(mutex_);

  // Map from Tensorflow device names to the corresponding JIT device metadata.
  std::unordered_map<string, DeviceRegistration> compilation_devices_
      GUARDED_BY(mutex_);

  // A description of a Tensorflow operator that can be compiled to XLA.
  struct OpRegistration {
    string name;

    // Should this operator be registered only on compilation devices, without a
    // dummy kernel registered on the corresponding XLA device?
    bool compilation_only = false;

    // Should we allow resource types for type attributes? Used by _Arg to
    // allow DT_RESOURCE.
    bool allow_resource_types = false;

    // Should we allow variant types for type attributes? Used by While to
    // allow TensorList which is of type DT_VARIANT.
    bool allow_variant_types = false;

    // Should we allow string type for type attributes? Used by PartitionedCall
    // to allow DT_STRING.
    bool allow_string_type = false;

    // Mapping from attribute name to a list of supported types.
    std::unordered_map<string, std::set<DataType>> type_constraints;

    // An optional whitelist of devices. If there is no whitelist, all devices
    // are permitted.
    bool has_device_whitelist = false;
    std::unordered_set<string> device_whitelist;

    // Names of arguments that must be compile-time constants.
    std::unordered_set<string> compile_time_constant_inputs;

    // True if this is a "metadata" op, one that only looks at the shapes of its
    // operands and not their values.
    bool is_metadata_op = false;

    // Factory used to build OpKernels that perform symbolic execution.
    Factory factory;
  };

  // Returns true if registrations x and y can both be added to the registry.
  // This is always the case if they refer to different ops. If they refer to
  // the same op name, they must: have the same values for compilation_only,
  // allow_resource_types and allow_variant_types; use a device_whitelist; and
  // their whitelists must not intersect.
  static bool IsCompatible(const OpRegistration& x, const OpRegistration& y);

  static Status CompileTimeConstantInputs(const NodeDef& node_def,
                                          const OpKernel* op_kernel,
                                          const OpDef* op_def,
                                          std::vector<int>* result);

  // Map from operator name to OpRegistrations, populated by REGISTER_XLA_OP.
  // Registrations present under the same key must satisfy IsCompatible above,
  // and this is checked during registration.
  std::unordered_map<string, std::vector<std::unique_ptr<OpRegistration>>> ops_
      GUARDED_BY(mutex_);

  // Have we already registered the JIT kernels on the JIT devices?
  bool jit_kernels_registered_ = false;

  // Holds ownership of OpKernelRegistrars that represent the Tensorflow kernel
  // registrations created by RegisterCompilationKernels() and
  // RegisterDeviceKernels().
  std::vector<std::unique_ptr<kernel_factory::OpKernelRegistrar>>
      kernel_registrars_ GUARDED_BY(mutex_);
};

// REGISTER_XLA_OP() registers an XLA OpKernel by name, for example:
// REGISTER_XLA_OP(Name("Add"), AddOp);
// where 'AddOp' is the name of a JIT OpKernel class that implements "Add".
//
// We don't use a variadic macro here because we don't expect JIT operators to
// be templated.

#define REGISTER_XLA_OP(NAME, OP) \
  REGISTER_XLA_OP_UNIQ_HELPER(__COUNTER__, NAME, OP)

class XlaOpRegistrationBuilder {
 public:
  // Starts an operator registration chain.
  static XlaOpRegistrationBuilder Name(absl::string_view name);

  // Specifies a whitelist of devices on which the operator may run.
  XlaOpRegistrationBuilder& Device(absl::string_view devices);
  XlaOpRegistrationBuilder& Device(absl::Span<const absl::string_view> devices);

  // Specifies a type constraint for a type variable attribute. Each constraint
  // specifies the set of types that the type variable may assume.
  XlaOpRegistrationBuilder& TypeConstraint(absl::string_view attr_name,
                                           DataType allowed);

  XlaOpRegistrationBuilder& TypeConstraint(absl::string_view attr_name,
                                           absl::Span<const DataType> allowed);

  // Specifies that a dummy copy of this operator should not be registered on
  // XLA_* devices, but may be used during compilation.
  XlaOpRegistrationBuilder& CompilationOnly();

  // Allow DT_RESOURCE types for type parameters.
  XlaOpRegistrationBuilder& AllowResourceTypes();

  // Allow DT_VARIANT types for type parameters.
  XlaOpRegistrationBuilder& AllowVariantTypes();

  // Allow DT_STRING type for type parameters.
  XlaOpRegistrationBuilder& AllowStringType();

  // Mark 'input_name' as an argument whose value must be known at compile-time.
  XlaOpRegistrationBuilder& CompileTimeConstantInput(
      absl::string_view input_name);

  // Mark this op as a "metadata" op, one that only looks at the shapes of its
  // operands and not their values.
  XlaOpRegistrationBuilder& IsMetadataOp();

  std::unique_ptr<XlaOpRegistry::OpRegistration> Build(
      XlaOpRegistry::Factory factory);

 private:
  XlaOpRegistrationBuilder(absl::string_view name);

  std::unique_ptr<XlaOpRegistry::OpRegistration> registration_;
};

// REGISTER_XLA_BACKEND() registers an XLA backend. Example usage:
// REGISTER_XLA_BACKEND(DEVICE_GPU_XLA_JIT, kGpuAllTypes, GpuOpFilter);
#define REGISTER_XLA_BACKEND(NAME, ...) \
  REGISTER_XLA_BACKEND_UNIQ_HELPER(__COUNTER__, NAME, __VA_ARGS__)

// Implementation details.

class XlaOpRegistrar {
 public:
  XlaOpRegistrar(std::unique_ptr<XlaOpRegistry::OpRegistration> registration);
};

#define REGISTER_XLA_OP_UNIQ_HELPER(COUNTER, BUILDER, OP) \
  REGISTER_XLA_OP_UNIQ(COUNTER, BUILDER, OP)

#define REGISTER_XLA_OP_UNIQ(CTR, BUILDER, OP)                                 \
  static ::tensorflow::XlaOpRegistrar xla_op_registrar__body__##CTR##__object( \
      ::tensorflow::XlaOpRegistrationBuilder::BUILDER.Build(                   \
          [](::tensorflow::OpKernelConstruction* context)                      \
              -> ::tensorflow::OpKernel* { return new OP(context); }));

class XlaBackendRegistrar {
 public:
  XlaBackendRegistrar(absl::string_view name, absl::Span<const DataType> types,
                      XlaOpRegistry::BackendOpFilter op_filter = nullptr);
};

#define REGISTER_XLA_BACKEND_UNIQ_HELPER(COUNTER, NAME, ...) \
  REGISTER_XLA_BACKEND_UNIQ(COUNTER, NAME, __VA_ARGS__)

#define REGISTER_XLA_BACKEND_UNIQ(CTR, NAME, ...) \
  static ::tensorflow::XlaBackendRegistrar        \
      xla_backend_registrar__body__##CTR##__object(NAME, __VA_ARGS__);

}  // namespace tensorflow

#endif  // TENSORFLOW_COMPILER_TF2XLA_XLA_OP_REGISTRY_H_
