/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

/*!
 * \file tir/analysis/calculate_workspace.cc
 * \brief Calculate any intermediary memory required by PrimFuncs.
 */
#include <tvm/arith/analyzer.h>
#include <tvm/runtime/device_api.h>
#include <tvm/tir/analysis.h>
#include <tvm/tir/function.h>
#include <tvm/tir/stmt_functor.h>

namespace tvm {
namespace tir {

class WorkspaceCalculator : public StmtExprVisitor {
 public:
  WorkspaceCalculator() = default;
  size_t operator()(const PrimFunc& func);
  size_t byte_alignment = tvm::runtime::kDefaultWorkspaceAlignment;

 private:
  void VisitStmt_(const AllocateNode* op) override;
  size_t CalculateExtentsSize(const AllocateNode* op);
  size_t GetByteAlignedSize(size_t non_aligned_size);
  size_t current_size = 0;
  size_t max_size = 0;
};

size_t WorkspaceCalculator::operator()(const PrimFunc& func) {
  this->VisitStmt(func->body);
  return this->max_size;
}

size_t WorkspaceCalculator::GetByteAlignedSize(size_t non_aligned_size) {
  return ((non_aligned_size + byte_alignment - 1) / byte_alignment) * byte_alignment;
}

size_t WorkspaceCalculator::CalculateExtentsSize(const AllocateNode* op) {
  size_t element_size_bytes = op->dtype.bytes();
  size_t num_elements = 1;
  for (const auto& ext : op->extents) {
    if (ext->IsInstance<IntImmNode>()) {
      num_elements *= Downcast<IntImm>(ext)->value;
    } else {
      // We cant statically calculate workspace for dynamic shapes
      num_elements = 0;
    }
  }
  return GetByteAlignedSize(num_elements * element_size_bytes);
}

void WorkspaceCalculator::VisitStmt_(const AllocateNode* op) {
  auto size = CalculateExtentsSize(op);
  current_size += size;
  if (current_size > max_size) {
    max_size = current_size;
  }
  StmtExprVisitor::VisitStmt(op->body);
  current_size -= size;
}

size_t CalculateWorkspaceBytes(const PrimFunc& func, const Integer& workspace_byte_alignment) {
  WorkspaceCalculator wc;
  wc.byte_alignment = workspace_byte_alignment->value;
  return wc(func);
}

TVM_REGISTER_GLOBAL("tir.analysis.calculate_workspace_bytes")
    .set_body_typed([](PrimFunc func, Integer workspace_byte_alignment) {
      return static_cast<int>(CalculateWorkspaceBytes(func, workspace_byte_alignment));
    });

}  // namespace tir
}  // namespace tvm