LatencyPriorityQueue.h

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//===---- LatencyPriorityQueue.h - A latency-oriented priority queue ------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file declares the LatencyPriorityQueue class, which is a
// SchedulingPriorityQueue that schedules using latency information to
// reduce the length of the critical path through the basic block.
//
//===----------------------------------------------------------------------===//

#ifndef LATENCY_PRIORITY_QUEUE_H
#define LATENCY_PRIORITY_QUEUE_H

#include "llvm/CodeGen/ScheduleDAG.h"
#include "llvm/ADT/PriorityQueue.h"

namespace llvm {
  class LatencyPriorityQueue;
  
  /// Sorting functions for the Available queue.
  struct latency_sort : public std::binary_function<SUnit*, SUnit*, bool> {
    LatencyPriorityQueue *PQ;
    explicit latency_sort(LatencyPriorityQueue *pq) : PQ(pq) {}
    
    bool operator()(const SUnit* left, const SUnit* right) const;
  };

  class LatencyPriorityQueue : public SchedulingPriorityQueue {
    // SUnits - The SUnits for the current graph.
    std::vector<SUnit> *SUnits;
    
    /// NumNodesSolelyBlocking - This vector contains, for every node in the
    /// Queue, the number of nodes that the node is the sole unscheduled
    /// predecessor for.  This is used as a tie-breaker heuristic for better
    /// mobility.
    std::vector<unsigned> NumNodesSolelyBlocking;

    PriorityQueue<SUnit*, std::vector<SUnit*>, latency_sort> Queue;
public:
    LatencyPriorityQueue() : Queue(latency_sort(this)) {
    }
    
    void initNodes(std::vector<SUnit> &sunits) {
      SUnits = &sunits;
      NumNodesSolelyBlocking.resize(SUnits->size(), 0);
    }

    void addNode(const SUnit *SU) {
      NumNodesSolelyBlocking.resize(SUnits->size(), 0);
    }

    void updateNode(const SUnit *SU) {
    }

    void releaseState() {
      SUnits = 0;
    }
    
    unsigned getLatency(unsigned NodeNum) const {
      assert(NodeNum < (*SUnits).size());
      return (*SUnits)[NodeNum].getHeight();
    }
    
    unsigned getNumSolelyBlockNodes(unsigned NodeNum) const {
      assert(NodeNum < NumNodesSolelyBlocking.size());
      return NumNodesSolelyBlocking[NodeNum];
    }
    
    unsigned size() const { return Queue.size(); }

    bool empty() const { return Queue.empty(); }
    
    virtual void push(SUnit *U) {
      push_impl(U);
    }
    void push_impl(SUnit *U);
    
    void push_all(const std::vector<SUnit *> &Nodes) {
      for (unsigned i = 0, e = Nodes.size(); i != e; ++i)
        push_impl(Nodes[i]);
    }
    
    SUnit *pop() {
      if (empty()) return NULL;
      SUnit *V = Queue.top();
      Queue.pop();
      return V;
    }

    void remove(SUnit *SU) {
      assert(!Queue.empty() && "Not in queue!");
      Queue.erase_one(SU);
    }

    // ScheduledNode - As nodes are scheduled, we look to see if there are any
    // successor nodes that have a single unscheduled predecessor.  If so, that
    // single predecessor has a higher priority, since scheduling it will make
    // the node available.
    void ScheduledNode(SUnit *Node);

private:
    void AdjustPriorityOfUnscheduledPreds(SUnit *SU);
    SUnit *getSingleUnscheduledPred(SUnit *SU);
  };
}

#endif