1 //===---- LatencyPriorityQueue.h - A latency-oriented priority queue ------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file declares the LatencyPriorityQueue class, which is a
11 // SchedulingPriorityQueue that schedules using latency information to
12 // reduce the length of the critical path through the basic block.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_CODEGEN_LATENCYPRIORITYQUEUE_H
17 #define LLVM_CODEGEN_LATENCYPRIORITYQUEUE_H
18 
19 #include "llvm/CodeGen/ScheduleDAG.h"
20 
21 namespace llvm {
22   class LatencyPriorityQueue;
23 
24   /// Sorting functions for the Available queue.
25   struct latency_sort : public std::binary_function<SUnit*, SUnit*, bool> {
26     LatencyPriorityQueue *PQ;
latency_sortlatency_sort27     explicit latency_sort(LatencyPriorityQueue *pq) : PQ(pq) {}
28 
29     bool operator()(const SUnit* left, const SUnit* right) const;
30   };
31 
32   class LatencyPriorityQueue : public SchedulingPriorityQueue {
33     // SUnits - The SUnits for the current graph.
34     std::vector<SUnit> *SUnits;
35 
36     /// NumNodesSolelyBlocking - This vector contains, for every node in the
37     /// Queue, the number of nodes that the node is the sole unscheduled
38     /// predecessor for.  This is used as a tie-breaker heuristic for better
39     /// mobility.
40     std::vector<unsigned> NumNodesSolelyBlocking;
41 
42     /// Queue - The queue.
43     std::vector<SUnit*> Queue;
44     latency_sort Picker;
45 
46   public:
LatencyPriorityQueue()47     LatencyPriorityQueue() : Picker(this) {
48     }
49 
isBottomUp()50     bool isBottomUp() const override { return false; }
51 
initNodes(std::vector<SUnit> & sunits)52     void initNodes(std::vector<SUnit> &sunits) override {
53       SUnits = &sunits;
54       NumNodesSolelyBlocking.resize(SUnits->size(), 0);
55     }
56 
addNode(const SUnit * SU)57     void addNode(const SUnit *SU) override {
58       NumNodesSolelyBlocking.resize(SUnits->size(), 0);
59     }
60 
updateNode(const SUnit * SU)61     void updateNode(const SUnit *SU) override {
62     }
63 
releaseState()64     void releaseState() override {
65       SUnits = nullptr;
66     }
67 
getLatency(unsigned NodeNum)68     unsigned getLatency(unsigned NodeNum) const {
69       assert(NodeNum < (*SUnits).size());
70       return (*SUnits)[NodeNum].getHeight();
71     }
72 
getNumSolelyBlockNodes(unsigned NodeNum)73     unsigned getNumSolelyBlockNodes(unsigned NodeNum) const {
74       assert(NodeNum < NumNodesSolelyBlocking.size());
75       return NumNodesSolelyBlocking[NodeNum];
76     }
77 
empty()78     bool empty() const override { return Queue.empty(); }
79 
80     void push(SUnit *U) override;
81 
82     SUnit *pop() override;
83 
84     void remove(SUnit *SU) override;
85 
86     // scheduledNode - As nodes are scheduled, we look to see if there are any
87     // successor nodes that have a single unscheduled predecessor.  If so, that
88     // single predecessor has a higher priority, since scheduling it will make
89     // the node available.
90     void scheduledNode(SUnit *Node) override;
91 
92 private:
93     void AdjustPriorityOfUnscheduledPreds(SUnit *SU);
94     SUnit *getSingleUnscheduledPred(SUnit *SU);
95   };
96 }
97 
98 #endif
99