EVOLUTION-MANAGER

Edit File: deadness_analysis.h

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==============================================================================*/

#ifndef TENSORFLOW_COMPILER_JIT_DEADNESS_ANALYSIS_H_
#define TENSORFLOW_COMPILER_JIT_DEADNESS_ANALYSIS_H_

#include "tensorflow/core/graph/graph.h"
#include "tensorflow/stream_executor/lib/statusor.h"

namespace tensorflow {

// This analyzes a TensorFlow graph to identify nodes which may have partially
// dead inputs (i.e. these nodes may have some dead inputs and some alive
// inputs).
//
// For example, the ADD node in the following graph
//
//      V0  PRED0    V1  PRED1
//       |    |       |    |
//       v    v       v    v
//       SWITCH       SWITCH
//          |            |
//          +---+   + ---+
//              |   |
//              v   v
//               ADD
//
// can have its inputs independently dead or alive based on the runtime values
// of PRED0 and PRED1.
//
// It is tempting to call this a liveness analysis but I avoided that because
// "liveness" already has other connotations.
class DeadnessAnalysis {
 public:
  // An opaque representation of a predicate.  DeadnessPredicate
  // instances that compare equal via operator== represent predicates
  // that always evaluate to the same value.
  struct DeadnessPredicate {
   public:
    DeadnessPredicate(const DeadnessPredicate&) = default;
    DeadnessPredicate(DeadnessPredicate&&) = default;

DeadnessPredicate& operator=(const DeadnessPredicate&) = default;
    DeadnessPredicate& operator=(DeadnessPredicate&&) = default;

bool operator==(const DeadnessPredicate& other) const {
      return other.pred_ == pred_;
    }

bool operator!=(const DeadnessPredicate& other) const {
      return other.pred_ != pred_;
    }

private:
    explicit DeadnessPredicate(void* pred) : pred_(pred) {}

// This is really a Predicate*, but we don't want to expose that
    // implementation detail to our clients.  `pred_` has pointer equality so we
    // can just compare the pointer in operator== and operator!=.
    void* pred_;

friend class DeadnessAnalysis;
  };

virtual se::port::StatusOr<DeadnessPredicate> GetPredicateFor(
      Node* n, int oidx) const = 0;

// Prints out the internal state of this instance.  For debugging purposes
  // only.
  virtual void Print() const = 0;
  virtual ~DeadnessAnalysis();

string DebugString(DeadnessPredicate predicate) const;

// Run the deadness analysis over `graph` and returns an error or a populated
  // instance of DeadnessAnalysis in `result`.
  static Status Run(const Graph& graph,
                    std::unique_ptr<DeadnessAnalysis>* result);

protected:
  static DeadnessPredicate MakeDeadnessPredicate(void* pred) {
    return DeadnessPredicate(pred);
  }
};

}  // namespace tensorflow

#endif  // TENSORFLOW_COMPILER_JIT_DEADNESS_ANALYSIS_H_