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//===---- ScheduleDAGSDNodes.h - SDNode Scheduling --------------*- C++ -*-===//
// 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 implements the ScheduleDAGSDNodes class, which implements
// scheduling for an SDNode-based dependency graph.
#include "llvm/CodeGen/ISDOpcodes.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineValueType.h"
#include "llvm/CodeGen/ScheduleDAG.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/Support/Casting.h"
#include <cassert>
#include <string>
#include <vector>
namespace llvm {
class AAResults;
class InstrItineraryData;
/// ScheduleDAGSDNodes - A ScheduleDAG for scheduling SDNode-based DAGs.
/// Edges between SUnits are initially based on edges in the SelectionDAG,
/// and additional edges can be added by the schedulers as heuristics.
/// SDNodes such as Constants, Registers, and a few others that are not
/// interesting to schedulers are not allocated SUnits.
/// SDNodes with MVT::Glue operands are grouped along with the flagged
/// nodes into a single SUnit so that they are scheduled together.
/// SDNode-based scheduling graphs do not use SDep::Anti or SDep::Output
/// edges. Physical register dependence information is not carried in
/// the DAG and must be handled explicitly by schedulers.
class ScheduleDAGSDNodes : public ScheduleDAG {
MachineBasicBlock *BB = nullptr;
SelectionDAG *DAG = nullptr; // DAG of the current basic block
const InstrItineraryData *InstrItins;
/// The schedule. Null SUnit*'s represent noop instructions.
std::vector<SUnit*> Sequence;
explicit ScheduleDAGSDNodes(MachineFunction &mf);
~ScheduleDAGSDNodes() override = default;
/// Run - perform scheduling.
void Run(SelectionDAG *dag, MachineBasicBlock *bb);
/// isPassiveNode - Return true if the node is a non-scheduled leaf.
static bool isPassiveNode(SDNode *Node) {
if (isa<ConstantSDNode>(Node)) return true;
if (isa<ConstantFPSDNode>(Node)) return true;
if (isa<RegisterSDNode>(Node)) return true;
if (isa<RegisterMaskSDNode>(Node)) return true;
if (isa<GlobalAddressSDNode>(Node)) return true;
if (isa<BasicBlockSDNode>(Node)) return true;
if (isa<FrameIndexSDNode>(Node)) return true;
if (isa<ConstantPoolSDNode>(Node)) return true;
if (isa<TargetIndexSDNode>(Node)) return true;
if (isa<JumpTableSDNode>(Node)) return true;
if (isa<ExternalSymbolSDNode>(Node)) return true;
if (isa<MCSymbolSDNode>(Node)) return true;
if (isa<BlockAddressSDNode>(Node)) return true;
if (Node->getOpcode() == ISD::EntryToken ||
isa<MDNodeSDNode>(Node)) return true;
return false;
/// NewSUnit - Creates a new SUnit and return a ptr to it.
SUnit *newSUnit(SDNode *N);
/// Clone - Creates a clone of the specified SUnit. It does not copy the
/// predecessors / successors info nor the temporary scheduling states.
SUnit *Clone(SUnit *Old);
/// BuildSchedGraph - Build the SUnit graph from the selection dag that we
/// are input. This SUnit graph is similar to the SelectionDAG, but
/// excludes nodes that aren't interesting to scheduling, and represents
/// flagged together nodes with a single SUnit.
void BuildSchedGraph(AAResults *AA);
/// InitNumRegDefsLeft - Determine the # of regs defined by this node.
void InitNumRegDefsLeft(SUnit *SU);
/// computeLatency - Compute node latency.
virtual void computeLatency(SUnit *SU);
virtual void computeOperandLatency(SDNode *Def, SDNode *Use,
unsigned OpIdx, SDep& dep) const;
/// Schedule - Order nodes according to selected style, filling
/// in the Sequence member.
virtual void Schedule() = 0;
/// VerifyScheduledSequence - Verify that all SUnits are scheduled and
/// consistent with the Sequence of scheduled instructions.
void VerifyScheduledSequence(bool isBottomUp);
/// EmitSchedule - Insert MachineInstrs into the MachineBasicBlock
/// according to the order specified in Sequence.
virtual MachineBasicBlock*
EmitSchedule(MachineBasicBlock::iterator &InsertPos);
void dumpNode(const SUnit &SU) const override;
void dump() const override;
void dumpSchedule() const;
std::string getGraphNodeLabel(const SUnit *SU) const override;
std::string getDAGName() const override;
virtual void getCustomGraphFeatures(GraphWriter<ScheduleDAG*> &GW) const;
/// RegDefIter - In place iteration over the values defined by an
/// SUnit. This does not need copies of the iterator or any other STLisms.
/// The iterator creates itself, rather than being provided by the SchedDAG.
class RegDefIter {
const ScheduleDAGSDNodes *SchedDAG;
const SDNode *Node;
unsigned DefIdx = 0;
unsigned NodeNumDefs = 0;
MVT ValueType;
RegDefIter(const SUnit *SU, const ScheduleDAGSDNodes *SD);
bool IsValid() const { return Node != nullptr; }
MVT GetValue() const {
assert(IsValid() && "bad iterator");
return ValueType;
const SDNode *GetNode() const {
return Node;
unsigned GetIdx() const {
return DefIdx-1;
void Advance();
void InitNodeNumDefs();
/// ForceUnitLatencies - Return true if all scheduling edges should be given
/// a latency value of one. The default is to return false; schedulers may
/// override this as needed.
virtual bool forceUnitLatencies() const { return false; }
/// ClusterNeighboringLoads - Cluster loads from "near" addresses into
/// combined SUnits.
void ClusterNeighboringLoads(SDNode *Node);
/// ClusterNodes - Cluster certain nodes which should be scheduled together.
void ClusterNodes();
/// BuildSchedUnits, AddSchedEdges - Helper functions for BuildSchedGraph.
void BuildSchedUnits();
void AddSchedEdges();
void EmitPhysRegCopy(SUnit *SU, DenseMap<SUnit*, Register> &VRBaseMap,
MachineBasicBlock::iterator InsertPos);
} // end namespace llvm