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//===---- LatencyPriorityQueue.h - A latency-oriented priority queue ------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// 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.
#include "llvm/CodeGen/ScheduleDAG.h"
#include "llvm/Config/llvm-config.h"
namespace llvm {
class LatencyPriorityQueue;
/// Sorting functions for the Available queue.
struct latency_sort {
LatencyPriorityQueue *PQ;
explicit latency_sort(LatencyPriorityQueue *pq) : PQ(pq) {}
bool operator()(const SUnit* LHS, const SUnit* RHS) 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;
/// Queue - The queue.
std::vector<SUnit*> Queue;
latency_sort Picker;
LatencyPriorityQueue() : Picker(this) {
bool isBottomUp() const override { return false; }
void initNodes(std::vector<SUnit> &sunits) override {
SUnits = &sunits;
NumNodesSolelyBlocking.resize(SUnits->size(), 0);
void addNode(const SUnit *SU) override {
NumNodesSolelyBlocking.resize(SUnits->size(), 0);
void updateNode(const SUnit *SU) override {
void releaseState() override {
SUnits = nullptr;
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];
bool empty() const override { return Queue.empty(); }
void push(SUnit *U) override;
SUnit *pop() override;
void remove(SUnit *SU) override;
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD void dump(ScheduleDAG *DAG) const override;
// 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 *SU) override;
void AdjustPriorityOfUnscheduledPreds(SUnit *SU);
SUnit *getSingleUnscheduledPred(SUnit *SU);