/* Copyright 2025 The OpenXLA 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.
==============================================================================*/

#ifndef XLA_BACKENDS_GPU_AUTOTUNER_CUDNN_H_
#define XLA_BACKENDS_GPU_AUTOTUNER_CUDNN_H_

#include <memory>
#include <vector>

#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/strings/string_view.h"
#include "xla/backends/autotuner/codegen_backend.h"
#include "xla/backends/gpu/autotuner/gpu_codegen_backend.h"
#include "xla/hlo/ir/hlo_instruction.h"
#include "xla/service/compiler.h"
#include "xla/stream_executor/stream_executor.h"
#include "xla/xla.pb.h"

namespace xla {
namespace gpu {

// A codegen backend for cuDNN.
// Determines execution plan id. Requires a device with cuDNN >= 9.0.
// Note: We support cudnn fusions containing a dot and cudnn convolutions.
//
// A Cudnn fusion is a fusion with a custom call target of "__cudnn$fusion":
// ```
// fusion {
//   p0 = f32[3,28,32] parameter(0)
//   p1 = f32[3,28,32] parameter(1)
//   ROOT d = f32[3,32,32] dot(p0, p1),
//     lhs_batch_dims={0}, rhs_batch_dims={0},
//     lhs_contracting_dims={1}, rhs_contracting_dims={1}
// }

// ENTRY e {
//   p0 = f32[3,28,32] parameter(0)
//   p1 = f32[3,28,32] parameter(1)
//   ROOT _ = f32[3,32,32] fusion(p0, p1), kind=kCustom, calls=fusion,
//     backend_config={"fusion_backend_config": {kind: "__cudnn$fusion"}}
// })";
// ```

class CudnnBackend : public GpuCodegenBackend {
 public:
  explicit CudnnBackend(stream_executor::StreamExecutor* stream_executor,
                        const DebugOptions* debug_options, Compiler* compiler,
                        const Compiler::GpuTargetConfig* target_config)
      : GpuCodegenBackend("Cudnn", debug_options, compiler, target_config,
                          stream_executor) {}

  absl::StatusOr<std::vector<std::unique_ptr<BackendConfig>>>
  GetSupportedConfigs(const HloInstruction& instr) override;

  absl::StatusOr<std::unique_ptr<BackendConfig>> GetDefaultConfig(
      const HloInstruction& instr) override;

  // Can replace the instruction with a new one in the parent computation, to
  // apply the configs with non-zero workspace size.
  absl::Status ApplyConfig(HloInstruction& instr,
                           const BackendConfig& config) override;

 private:
  bool IsSupported(const HloInstruction& instr) override;
};

}  // namespace gpu
}  // namespace xla

#endif  // XLA_BACKENDS_GPU_AUTOTUNER_CUDNN_H_