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 #include "llvm/Config/llvm-config.h"
21 
22 namespace llvm {
23   class LatencyPriorityQueue;
24 
25   /// Sorting functions for the Available queue.
26   struct latency_sort {
27     LatencyPriorityQueue *PQ;
latency_sortlatency_sort28     explicit latency_sort(LatencyPriorityQueue *pq) : PQ(pq) {}
29 
30     bool operator()(const SUnit* LHS, const SUnit* RHS) const;
31   };
32 
33   class LatencyPriorityQueue : public SchedulingPriorityQueue {
34     // SUnits - The SUnits for the current graph.
35     std::vector<SUnit> *SUnits;
36 
37     /// NumNodesSolelyBlocking - This vector contains, for every node in the
38     /// Queue, the number of nodes that the node is the sole unscheduled
39     /// predecessor for.  This is used as a tie-breaker heuristic for better
40     /// mobility.
41     std::vector<unsigned> NumNodesSolelyBlocking;
42 
43     /// Queue - The queue.
44     std::vector<SUnit*> Queue;
45     latency_sort Picker;
46 
47   public:
LatencyPriorityQueue()48     LatencyPriorityQueue() : Picker(this) {
49     }
50 
isBottomUp()51     bool isBottomUp() const override { return false; }
52 
initNodes(std::vector<SUnit> & sunits)53     void initNodes(std::vector<SUnit> &sunits) override {
54       SUnits = &sunits;
55       NumNodesSolelyBlocking.resize(SUnits->size(), 0);
56     }
57 
addNode(const SUnit * SU)58     void addNode(const SUnit *SU) override {
59       NumNodesSolelyBlocking.resize(SUnits->size(), 0);
60     }
61 
updateNode(const SUnit * SU)62     void updateNode(const SUnit *SU) override {
63     }
64 
releaseState()65     void releaseState() override {
66       SUnits = nullptr;
67     }
68 
getLatency(unsigned NodeNum)69     unsigned getLatency(unsigned NodeNum) const {
70       assert(NodeNum < (*SUnits).size());
71       return (*SUnits)[NodeNum].getHeight();
72     }
73 
getNumSolelyBlockNodes(unsigned NodeNum)74     unsigned getNumSolelyBlockNodes(unsigned NodeNum) const {
75       assert(NodeNum < NumNodesSolelyBlocking.size());
76       return NumNodesSolelyBlocking[NodeNum];
77     }
78 
empty()79     bool empty() const override { return Queue.empty(); }
80 
81     void push(SUnit *U) override;
82 
83     SUnit *pop() override;
84 
85     void remove(SUnit *SU) override;
86 
87 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
88     LLVM_DUMP_METHOD void dump(ScheduleDAG *DAG) const override;
89 #endif
90 
91     // scheduledNode - As nodes are scheduled, we look to see if there are any
92     // successor nodes that have a single unscheduled predecessor.  If so, that
93     // single predecessor has a higher priority, since scheduling it will make
94     // the node available.
95     void scheduledNode(SUnit *SU) override;
96 
97 private:
98     void AdjustPriorityOfUnscheduledPreds(SUnit *SU);
99     SUnit *getSingleUnscheduledPred(SUnit *SU);
100   };
101 }
102 
103 #endif
104