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llvm/lib/CodeGen/MachinePipeliner.cpp
Chandler Carruth e3e43d9d57 Sort the remaining #include lines in include/... and lib/.... 
I did this a long time ago with a janky python script, but now
clang-format has built-in support for this. I fed clang-format every
line with a #include and let it re-sort things according to the precise
LLVM rules for include ordering baked into clang-format these days.

I've reverted a number of files where the results of sorting includes
isn't healthy. Either places where we have legacy code relying on
particular include ordering (where possible, I'll fix these separately)
or where we have particular formatting around #include lines that
I didn't want to disturb in this patch.

This patch is *entirely* mechanical. If you get merge conflicts or
anything, just ignore the changes in this patch and run clang-format
over your #include lines in the files.

Sorry for any noise here, but it is important to keep these things
stable. I was seeing an increasing number of patches with irrelevant
re-ordering of #include lines because clang-format was used. This patch
at least isolates that churn, makes it easy to skip when resolving
conflicts, and gets us to a clean baseline (again).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304787 91177308-0d34-0410-b5e6-96231b3b80d8
2017-06-06 11:49:48 +00:00

3982 lines
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//===-- MachinePipeliner.cpp - Machine Software Pipeliner Pass ------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// An implementation of the Swing Modulo Scheduling (SMS) software pipeliner.
//
// Software pipelining (SWP) is an instruction scheduling technique for loops
// that overlap loop iterations and explioits ILP via a compiler transformation.
//
// Swing Modulo Scheduling is an implementation of software pipelining
// that generates schedules that are near optimal in terms of initiation
// interval, register requirements, and stage count. See the papers:
//
// "Swing Modulo Scheduling: A Lifetime-Sensitive Approach", by J. Llosa,
// A. Gonzalez, E. Ayguade, and M. Valero. In PACT '96 Processings of the 1996
// Conference on Parallel Architectures and Compilation Techiniques.
//
// "Lifetime-Sensitive Modulo Scheduling in a Production Environment", by J.
// Llosa, E. Ayguade, A. Gonzalez, M. Valero, and J. Eckhardt. In IEEE
// Transactions on Computers, Vol. 50, No. 3, 2001.
//
// "An Implementation of Swing Modulo Scheduling With Extensions for
// Superblocks", by T. Lattner, Master's Thesis, University of Illinois at
// Urbana-Chambpain, 2005.
//
//
// The SMS algorithm consists of three main steps after computing the minimal
// initiation interval (MII).
// 1) Analyze the dependence graph and compute information about each
// instruction in the graph.
// 2) Order the nodes (instructions) by priority based upon the heuristics
// described in the algorithm.
// 3) Attempt to schedule the nodes in the specified order using the MII.
//
// This SMS implementation is a target-independent back-end pass. When enabled,
// the pass runs just prior to the register allocation pass, while the machine
// IR is in SSA form. If software pipelining is successful, then the original
// loop is replaced by the optimized loop. The optimized loop contains one or
// more prolog blocks, the pipelined kernel, and one or more epilog blocks. If
// the instructions cannot be scheduled in a given MII, we increase the MII by
// one and try again.
//
// The SMS implementation is an extension of the ScheduleDAGInstrs class. We
// represent loop carried dependences in the DAG as order edges to the Phi
// nodes. We also perform several passes over the DAG to eliminate unnecessary
// edges that inhibit the ability to pipeline. The implementation uses the
// DFAPacketizer class to compute the minimum initiation interval and the check
// where an instruction may be inserted in the pipelined schedule.
//
// In order for the SMS pass to work, several target specific hooks need to be
// implemented to get information about the loop structure and to rewrite
// instructions.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/PriorityQueue.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/MemoryLocation.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/CodeGen/DFAPacketizer.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineInstrBundle.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterClassInfo.h"
#include "llvm/CodeGen/RegisterPressure.h"
#include "llvm/CodeGen/ScheduleDAG.h"
#include "llvm/CodeGen/ScheduleDAGInstrs.h"
#include "llvm/CodeGen/ScheduleDAGMutation.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/MC/MCInstrItineraries.h"
#include "llvm/PassAnalysisSupport.h"
#include "llvm/PassRegistry.h"
#include "llvm/PassSupport.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
#include <algorithm>
#include <cassert>
#include <climits>
#include <cstdint>
#include <deque>
#include <functional>
#include <iterator>
#include <map>
#include <tuple>
#include <utility>
#include <vector>
using namespace llvm;
#define DEBUG_TYPE "pipeliner"
STATISTIC(NumTrytoPipeline, "Number of loops that we attempt to pipeline");
STATISTIC(NumPipelined, "Number of loops software pipelined");
/// A command line option to turn software pipelining on or off.
static cl::opt<bool> EnableSWP("enable-pipeliner", cl::Hidden, cl::init(true),
cl::ZeroOrMore,
cl::desc("Enable Software Pipelining"));
/// A command line option to enable SWP at -Os.
static cl::opt<bool> EnableSWPOptSize("enable-pipeliner-opt-size",
cl::desc("Enable SWP at Os."), cl::Hidden,
cl::init(false));
/// A command line argument to limit minimum initial interval for pipelining.
static cl::opt<int> SwpMaxMii("pipeliner-max-mii",
cl::desc("Size limit for the the MII."),
cl::Hidden, cl::init(27));
/// A command line argument to limit the number of stages in the pipeline.
static cl::opt<int>
SwpMaxStages("pipeliner-max-stages",
cl::desc("Maximum stages allowed in the generated scheduled."),
cl::Hidden, cl::init(3));
/// A command line option to disable the pruning of chain dependences due to
/// an unrelated Phi.
static cl::opt<bool>
SwpPruneDeps("pipeliner-prune-deps",
cl::desc("Prune dependences between unrelated Phi nodes."),
cl::Hidden, cl::init(true));
/// A command line option to disable the pruning of loop carried order
/// dependences.
static cl::opt<bool>
SwpPruneLoopCarried("pipeliner-prune-loop-carried",
cl::desc("Prune loop carried order dependences."),
cl::Hidden, cl::init(true));
#ifndef NDEBUG
static cl::opt<int> SwpLoopLimit("pipeliner-max", cl::Hidden, cl::init(-1));
#endif
static cl::opt<bool> SwpIgnoreRecMII("pipeliner-ignore-recmii",
cl::ReallyHidden, cl::init(false),
cl::ZeroOrMore, cl::desc("Ignore RecMII"));
namespace {
class NodeSet;
class SMSchedule;
class SwingSchedulerDAG;
/// The main class in the implementation of the target independent
/// software pipeliner pass.
class MachinePipeliner : public MachineFunctionPass {
public:
MachineFunction *MF = nullptr;
const MachineLoopInfo *MLI = nullptr;
const MachineDominatorTree *MDT = nullptr;
const InstrItineraryData *InstrItins;
const TargetInstrInfo *TII = nullptr;
RegisterClassInfo RegClassInfo;
#ifndef NDEBUG
static int NumTries;
#endif
/// Cache the target analysis information about the loop.
struct LoopInfo {
MachineBasicBlock *TBB = nullptr;
MachineBasicBlock *FBB = nullptr;
SmallVector<MachineOperand, 4> BrCond;
MachineInstr *LoopInductionVar = nullptr;
MachineInstr *LoopCompare = nullptr;
};
LoopInfo LI;
static char ID;
MachinePipeliner() : MachineFunctionPass(ID) {
initializeMachinePipelinerPass(*PassRegistry::getPassRegistry());
}
bool runOnMachineFunction(MachineFunction &MF) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<AAResultsWrapperPass>();
AU.addPreserved<AAResultsWrapperPass>();
AU.addRequired<MachineLoopInfo>();
AU.addRequired<MachineDominatorTree>();
AU.addRequired<LiveIntervals>();
MachineFunctionPass::getAnalysisUsage(AU);
}
private:
bool canPipelineLoop(MachineLoop &L);
bool scheduleLoop(MachineLoop &L);
bool swingModuloScheduler(MachineLoop &L);
};
/// This class builds the dependence graph for the instructions in a loop,
/// and attempts to schedule the instructions using the SMS algorithm.
class SwingSchedulerDAG : public ScheduleDAGInstrs {
MachinePipeliner &Pass;
/// The minimum initiation interval between iterations for this schedule.
unsigned MII;
/// Set to true if a valid pipelined schedule is found for the loop.
bool Scheduled;
MachineLoop &Loop;
LiveIntervals &LIS;
const RegisterClassInfo &RegClassInfo;
/// A toplogical ordering of the SUnits, which is needed for changing
/// dependences and iterating over the SUnits.
ScheduleDAGTopologicalSort Topo;
struct NodeInfo {
int ASAP;
int ALAP;
NodeInfo() : ASAP(0), ALAP(0) {}
};
/// Computed properties for each node in the graph.
std::vector<NodeInfo> ScheduleInfo;
enum OrderKind { BottomUp = 0, TopDown = 1 };
/// Computed node ordering for scheduling.
SetVector<SUnit *> NodeOrder;
typedef SmallVector<NodeSet, 8> NodeSetType;
typedef DenseMap<unsigned, unsigned> ValueMapTy;
typedef SmallVectorImpl<MachineBasicBlock *> MBBVectorTy;
typedef DenseMap<MachineInstr *, MachineInstr *> InstrMapTy;
/// Instructions to change when emitting the final schedule.
DenseMap<SUnit *, std::pair<unsigned, int64_t>> InstrChanges;
/// We may create a new instruction, so remember it because it
/// must be deleted when the pass is finished.
SmallPtrSet<MachineInstr *, 4> NewMIs;
/// Ordered list of DAG postprocessing steps.
std::vector<std::unique_ptr<ScheduleDAGMutation>> Mutations;
/// Helper class to implement Johnson's circuit finding algorithm.
class Circuits {
std::vector<SUnit> &SUnits;
SetVector<SUnit *> Stack;
BitVector Blocked;
SmallVector<SmallPtrSet<SUnit *, 4>, 10> B;
SmallVector<SmallVector<int, 4>, 16> AdjK;
unsigned NumPaths;
static unsigned MaxPaths;
public:
Circuits(std::vector<SUnit> &SUs)
: SUnits(SUs), Stack(), Blocked(SUs.size()), B(SUs.size()),
AdjK(SUs.size()) {}
/// Reset the data structures used in the circuit algorithm.
void reset() {
Stack.clear();
Blocked.reset();
B.assign(SUnits.size(), SmallPtrSet<SUnit *, 4>());
NumPaths = 0;
}
void createAdjacencyStructure(SwingSchedulerDAG *DAG);
bool circuit(int V, int S, NodeSetType &NodeSets, bool HasBackedge = false);
void unblock(int U);
};
public:
SwingSchedulerDAG(MachinePipeliner &P, MachineLoop &L, LiveIntervals &lis,
const RegisterClassInfo &rci)
: ScheduleDAGInstrs(*P.MF, P.MLI, false), Pass(P), MII(0),
Scheduled(false), Loop(L), LIS(lis), RegClassInfo(rci),
Topo(SUnits, &ExitSU) {
P.MF->getSubtarget().getSMSMutations(Mutations);
}
void schedule() override;
void finishBlock() override;
/// Return true if the loop kernel has been scheduled.
bool hasNewSchedule() { return Scheduled; }
/// Return the earliest time an instruction may be scheduled.
int getASAP(SUnit *Node) { return ScheduleInfo[Node->NodeNum].ASAP; }
/// Return the latest time an instruction my be scheduled.
int getALAP(SUnit *Node) { return ScheduleInfo[Node->NodeNum].ALAP; }
/// The mobility function, which the the number of slots in which
/// an instruction may be scheduled.
int getMOV(SUnit *Node) { return getALAP(Node) - getASAP(Node); }
/// The depth, in the dependence graph, for a node.
int getDepth(SUnit *Node) { return Node->getDepth(); }
/// The height, in the dependence graph, for a node.
int getHeight(SUnit *Node) { return Node->getHeight(); }
/// Return true if the dependence is a back-edge in the data dependence graph.
/// Since the DAG doesn't contain cycles, we represent a cycle in the graph
/// using an anti dependence from a Phi to an instruction.
bool isBackedge(SUnit *Source, const SDep &Dep) {
if (Dep.getKind() != SDep::Anti)
return false;
return Source->getInstr()->isPHI() || Dep.getSUnit()->getInstr()->isPHI();
}
/// Return true if the dependence is an order dependence between non-Phis.
static bool isOrder(SUnit *Source, const SDep &Dep) {
if (Dep.getKind() != SDep::Order)
return false;
return (!Source->getInstr()->isPHI() &&
!Dep.getSUnit()->getInstr()->isPHI());
}
bool isLoopCarriedOrder(SUnit *Source, const SDep &Dep, bool isSucc = true);
/// The latency of the dependence.
unsigned getLatency(SUnit *Source, const SDep &Dep) {
// Anti dependences represent recurrences, so use the latency of the
// instruction on the back-edge.
if (Dep.getKind() == SDep::Anti) {
if (Source->getInstr()->isPHI())
return Dep.getSUnit()->Latency;
if (Dep.getSUnit()->getInstr()->isPHI())
return Source->Latency;
return Dep.getLatency();
}
return Dep.getLatency();
}
/// The distance function, which indicates that operation V of iteration I
/// depends on operations U of iteration I-distance.
unsigned getDistance(SUnit *U, SUnit *V, const SDep &Dep) {
// Instructions that feed a Phi have a distance of 1. Computing larger
// values for arrays requires data dependence information.
if (V->getInstr()->isPHI() && Dep.getKind() == SDep::Anti)
return 1;
return 0;
}
/// Set the Minimum Initiation Interval for this schedule attempt.
void setMII(unsigned mii) { MII = mii; }
MachineInstr *applyInstrChange(MachineInstr *MI, SMSchedule &Schedule,
bool UpdateDAG = false);
/// Return the new base register that was stored away for the changed
/// instruction.
unsigned getInstrBaseReg(SUnit *SU) {
DenseMap<SUnit *, std::pair<unsigned, int64_t>>::iterator It =
InstrChanges.find(SU);
if (It != InstrChanges.end())
return It->second.first;
return 0;
}
void addMutation(std::unique_ptr<ScheduleDAGMutation> Mutation) {
Mutations.push_back(std::move(Mutation));
}
private:
void addLoopCarriedDependences(AliasAnalysis *AA);
void updatePhiDependences();
void changeDependences();
unsigned calculateResMII();
unsigned calculateRecMII(NodeSetType &RecNodeSets);
void findCircuits(NodeSetType &NodeSets);
void fuseRecs(NodeSetType &NodeSets);
void removeDuplicateNodes(NodeSetType &NodeSets);
void computeNodeFunctions(NodeSetType &NodeSets);
void registerPressureFilter(NodeSetType &NodeSets);
void colocateNodeSets(NodeSetType &NodeSets);
void checkNodeSets(NodeSetType &NodeSets);
void groupRemainingNodes(NodeSetType &NodeSets);
void addConnectedNodes(SUnit *SU, NodeSet &NewSet,
SetVector<SUnit *> &NodesAdded);
void computeNodeOrder(NodeSetType &NodeSets);
bool schedulePipeline(SMSchedule &Schedule);
void generatePipelinedLoop(SMSchedule &Schedule);
void generateProlog(SMSchedule &Schedule, unsigned LastStage,
MachineBasicBlock *KernelBB, ValueMapTy *VRMap,
MBBVectorTy &PrologBBs);
void generateEpilog(SMSchedule &Schedule, unsigned LastStage,
MachineBasicBlock *KernelBB, ValueMapTy *VRMap,
MBBVectorTy &EpilogBBs, MBBVectorTy &PrologBBs);
void generateExistingPhis(MachineBasicBlock *NewBB, MachineBasicBlock *BB1,
MachineBasicBlock *BB2, MachineBasicBlock *KernelBB,
SMSchedule &Schedule, ValueMapTy *VRMap,
InstrMapTy &InstrMap, unsigned LastStageNum,
unsigned CurStageNum, bool IsLast);
void generatePhis(MachineBasicBlock *NewBB, MachineBasicBlock *BB1,
MachineBasicBlock *BB2, MachineBasicBlock *KernelBB,
SMSchedule &Schedule, ValueMapTy *VRMap,
InstrMapTy &InstrMap, unsigned LastStageNum,
unsigned CurStageNum, bool IsLast);
void removeDeadInstructions(MachineBasicBlock *KernelBB,
MBBVectorTy &EpilogBBs);
void splitLifetimes(MachineBasicBlock *KernelBB, MBBVectorTy &EpilogBBs,
SMSchedule &Schedule);
void addBranches(MBBVectorTy &PrologBBs, MachineBasicBlock *KernelBB,
MBBVectorTy &EpilogBBs, SMSchedule &Schedule,
ValueMapTy *VRMap);
bool computeDelta(MachineInstr &MI, unsigned &Delta);
void updateMemOperands(MachineInstr &NewMI, MachineInstr &OldMI,
unsigned Num);
MachineInstr *cloneInstr(MachineInstr *OldMI, unsigned CurStageNum,
unsigned InstStageNum);
MachineInstr *cloneAndChangeInstr(MachineInstr *OldMI, unsigned CurStageNum,
unsigned InstStageNum,
SMSchedule &Schedule);
void updateInstruction(MachineInstr *NewMI, bool LastDef,
unsigned CurStageNum, unsigned InstStageNum,
SMSchedule &Schedule, ValueMapTy *VRMap);
MachineInstr *findDefInLoop(unsigned Reg);
unsigned getPrevMapVal(unsigned StageNum, unsigned PhiStage, unsigned LoopVal,
unsigned LoopStage, ValueMapTy *VRMap,
MachineBasicBlock *BB);
void rewritePhiValues(MachineBasicBlock *NewBB, unsigned StageNum,
SMSchedule &Schedule, ValueMapTy *VRMap,
InstrMapTy &InstrMap);
void rewriteScheduledInstr(MachineBasicBlock *BB, SMSchedule &Schedule,
InstrMapTy &InstrMap, unsigned CurStageNum,
unsigned PhiNum, MachineInstr *Phi,
unsigned OldReg, unsigned NewReg,
unsigned PrevReg = 0);
bool canUseLastOffsetValue(MachineInstr *MI, unsigned &BasePos,
unsigned &OffsetPos, unsigned &NewBase,
int64_t &NewOffset);
void postprocessDAG();
};
/// A NodeSet contains a set of SUnit DAG nodes with additional information
/// that assigns a priority to the set.
class NodeSet {
SetVector<SUnit *> Nodes;
bool HasRecurrence;
unsigned RecMII = 0;
int MaxMOV = 0;
int MaxDepth = 0;
unsigned Colocate = 0;
SUnit *ExceedPressure = nullptr;
public:
typedef SetVector<SUnit *>::const_iterator iterator;
NodeSet() : Nodes(), HasRecurrence(false) {}
NodeSet(iterator S, iterator E) : Nodes(S, E), HasRecurrence(true) {}
bool insert(SUnit *SU) { return Nodes.insert(SU); }
void insert(iterator S, iterator E) { Nodes.insert(S, E); }
template <typename UnaryPredicate> bool remove_if(UnaryPredicate P) {
return Nodes.remove_if(P);
}
unsigned count(SUnit *SU) const { return Nodes.count(SU); }
bool hasRecurrence() { return HasRecurrence; };
unsigned size() const { return Nodes.size(); }
bool empty() const { return Nodes.empty(); }
SUnit *getNode(unsigned i) const { return Nodes[i]; };
void setRecMII(unsigned mii) { RecMII = mii; };
void setColocate(unsigned c) { Colocate = c; };
void setExceedPressure(SUnit *SU) { ExceedPressure = SU; }
bool isExceedSU(SUnit *SU) { return ExceedPressure == SU; }
int compareRecMII(NodeSet &RHS) { return RecMII - RHS.RecMII; }
int getRecMII() { return RecMII; }
/// Summarize node functions for the entire node set.
void computeNodeSetInfo(SwingSchedulerDAG *SSD) {
for (SUnit *SU : *this) {
MaxMOV = std::max(MaxMOV, SSD->getMOV(SU));
MaxDepth = std::max(MaxDepth, SSD->getDepth(SU));
}
}
void clear() {
Nodes.clear();
RecMII = 0;
HasRecurrence = false;
MaxMOV = 0;
MaxDepth = 0;
Colocate = 0;
ExceedPressure = nullptr;
}
operator SetVector<SUnit *> &() { return Nodes; }
/// Sort the node sets by importance. First, rank them by recurrence MII,
/// then by mobility (least mobile done first), and finally by depth.
/// Each node set may contain a colocate value which is used as the first
/// tie breaker, if it's set.
bool operator>(const NodeSet &RHS) const {
if (RecMII == RHS.RecMII) {
if (Colocate != 0 && RHS.Colocate != 0 && Colocate != RHS.Colocate)
return Colocate < RHS.Colocate;
if (MaxMOV == RHS.MaxMOV)
return MaxDepth > RHS.MaxDepth;
return MaxMOV < RHS.MaxMOV;
}
return RecMII > RHS.RecMII;
}
bool operator==(const NodeSet &RHS) const {
return RecMII == RHS.RecMII && MaxMOV == RHS.MaxMOV &&
MaxDepth == RHS.MaxDepth;
}
bool operator!=(const NodeSet &RHS) const { return !operator==(RHS); }
iterator begin() { return Nodes.begin(); }
iterator end() { return Nodes.end(); }
void print(raw_ostream &os) const {
os << "Num nodes " << size() << " rec " << RecMII << " mov " << MaxMOV
<< " depth " << MaxDepth << " col " << Colocate << "\n";
for (const auto &I : Nodes)
os << " SU(" << I->NodeNum << ") " << *(I->getInstr());
os << "\n";
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD void dump() const { print(dbgs()); }
#endif
};
/// This class repesents the scheduled code. The main data structure is a
/// map from scheduled cycle to instructions. During scheduling, the
/// data structure explicitly represents all stages/iterations. When
/// the algorithm finshes, the schedule is collapsed into a single stage,
/// which represents instructions from different loop iterations.
///
/// The SMS algorithm allows negative values for cycles, so the first cycle
/// in the schedule is the smallest cycle value.
class SMSchedule {
private:
/// Map from execution cycle to instructions.
DenseMap<int, std::deque<SUnit *>> ScheduledInstrs;
/// Map from instruction to execution cycle.
std::map<SUnit *, int> InstrToCycle;
/// Map for each register and the max difference between its uses and def.
/// The first element in the pair is the max difference in stages. The
/// second is true if the register defines a Phi value and loop value is
/// scheduled before the Phi.
std::map<unsigned, std::pair<unsigned, bool>> RegToStageDiff;
/// Keep track of the first cycle value in the schedule. It starts
/// as zero, but the algorithm allows negative values.
int FirstCycle;
/// Keep track of the last cycle value in the schedule.
int LastCycle;
/// The initiation interval (II) for the schedule.
int InitiationInterval;
/// Target machine information.
const TargetSubtargetInfo &ST;
/// Virtual register information.
MachineRegisterInfo &MRI;
std::unique_ptr<DFAPacketizer> Resources;
public:
SMSchedule(MachineFunction *mf)
: ST(mf->getSubtarget()), MRI(mf->getRegInfo()),
Resources(ST.getInstrInfo()->CreateTargetScheduleState(ST)) {
FirstCycle = 0;
LastCycle = 0;
InitiationInterval = 0;
}
void reset() {
ScheduledInstrs.clear();
InstrToCycle.clear();
RegToStageDiff.clear();
FirstCycle = 0;
LastCycle = 0;
InitiationInterval = 0;
}
/// Set the initiation interval for this schedule.
void setInitiationInterval(int ii) { InitiationInterval = ii; }
/// Return the first cycle in the completed schedule. This
/// can be a negative value.
int getFirstCycle() const { return FirstCycle; }
/// Return the last cycle in the finalized schedule.
int getFinalCycle() const { return FirstCycle + InitiationInterval - 1; }
/// Return the cycle of the earliest scheduled instruction in the dependence
/// chain.
int earliestCycleInChain(const SDep &Dep);
/// Return the cycle of the latest scheduled instruction in the dependence
/// chain.
int latestCycleInChain(const SDep &Dep);
void computeStart(SUnit *SU, int *MaxEarlyStart, int *MinLateStart,
int *MinEnd, int *MaxStart, int II, SwingSchedulerDAG *DAG);
bool insert(SUnit *SU, int StartCycle, int EndCycle, int II);
/// Iterators for the cycle to instruction map.
typedef DenseMap<int, std::deque<SUnit *>>::iterator sched_iterator;
typedef DenseMap<int, std::deque<SUnit *>>::const_iterator
const_sched_iterator;
/// Return true if the instruction is scheduled at the specified stage.
bool isScheduledAtStage(SUnit *SU, unsigned StageNum) {
return (stageScheduled(SU) == (int)StageNum);
}
/// Return the stage for a scheduled instruction. Return -1 if
/// the instruction has not been scheduled.
int stageScheduled(SUnit *SU) const {
std::map<SUnit *, int>::const_iterator it = InstrToCycle.find(SU);
if (it == InstrToCycle.end())
return -1;
return (it->second - FirstCycle) / InitiationInterval;
}
/// Return the cycle for a scheduled instruction. This function normalizes
/// the first cycle to be 0.
unsigned cycleScheduled(SUnit *SU) const {
std::map<SUnit *, int>::const_iterator it = InstrToCycle.find(SU);
assert(it != InstrToCycle.end() && "Instruction hasn't been scheduled.");
return (it->second - FirstCycle) % InitiationInterval;
}
/// Return the maximum stage count needed for this schedule.
unsigned getMaxStageCount() {
return (LastCycle - FirstCycle) / InitiationInterval;
}
/// Return the max. number of stages/iterations that can occur between a
/// register definition and its uses.
unsigned getStagesForReg(int Reg, unsigned CurStage) {
std::pair<unsigned, bool> Stages = RegToStageDiff[Reg];
if (CurStage > getMaxStageCount() && Stages.first == 0 && Stages.second)
return 1;
return Stages.first;
}
/// The number of stages for a Phi is a little different than other
/// instructions. The minimum value computed in RegToStageDiff is 1
/// because we assume the Phi is needed for at least 1 iteration.
/// This is not the case if the loop value is scheduled prior to the
/// Phi in the same stage. This function returns the number of stages
/// or iterations needed between the Phi definition and any uses.
unsigned getStagesForPhi(int Reg) {
std::pair<unsigned, bool> Stages = RegToStageDiff[Reg];
if (Stages.second)
return Stages.first;
return Stages.first - 1;
}
/// Return the instructions that are scheduled at the specified cycle.
std::deque<SUnit *> &getInstructions(int cycle) {
return ScheduledInstrs[cycle];
}
bool isValidSchedule(SwingSchedulerDAG *SSD);
void finalizeSchedule(SwingSchedulerDAG *SSD);
bool orderDependence(SwingSchedulerDAG *SSD, SUnit *SU,
std::deque<SUnit *> &Insts);
bool isLoopCarried(SwingSchedulerDAG *SSD, MachineInstr &Phi);
bool isLoopCarriedDefOfUse(SwingSchedulerDAG *SSD, MachineInstr *Inst,
MachineOperand &MO);
void print(raw_ostream &os) const;
void dump() const;
};
} // end anonymous namespace
unsigned SwingSchedulerDAG::Circuits::MaxPaths = 5;
char MachinePipeliner::ID = 0;
#ifndef NDEBUG
int MachinePipeliner::NumTries = 0;
#endif
char &llvm::MachinePipelinerID = MachinePipeliner::ID;
INITIALIZE_PASS_BEGIN(MachinePipeliner, DEBUG_TYPE,
"Modulo Software Pipelining", false, false)
INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
INITIALIZE_PASS_END(MachinePipeliner, DEBUG_TYPE,
"Modulo Software Pipelining", false, false)
/// The "main" function for implementing Swing Modulo Scheduling.
bool MachinePipeliner::runOnMachineFunction(MachineFunction &mf) {
if (skipFunction(*mf.getFunction()))
return false;
if (!EnableSWP)
return false;
if (mf.getFunction()->getAttributes().hasAttribute(
AttributeList::FunctionIndex, Attribute::OptimizeForSize) &&
!EnableSWPOptSize.getPosition())
return false;
MF = &mf;
MLI = &getAnalysis<MachineLoopInfo>();
MDT = &getAnalysis<MachineDominatorTree>();
TII = MF->getSubtarget().getInstrInfo();
RegClassInfo.runOnMachineFunction(*MF);
for (auto &L : *MLI)
scheduleLoop(*L);
return false;
}
/// Attempt to perform the SMS algorithm on the specified loop. This function is
/// the main entry point for the algorithm. The function identifies candidate
/// loops, calculates the minimum initiation interval, and attempts to schedule
/// the loop.
bool MachinePipeliner::scheduleLoop(MachineLoop &L) {
bool Changed = false;
for (auto &InnerLoop : L)
Changed |= scheduleLoop(*InnerLoop);
#ifndef NDEBUG
// Stop trying after reaching the limit (if any).
int Limit = SwpLoopLimit;
if (Limit >= 0) {
if (NumTries >= SwpLoopLimit)
return Changed;
NumTries++;
}
#endif
if (!canPipelineLoop(L))
return Changed;
++NumTrytoPipeline;
Changed = swingModuloScheduler(L);
return Changed;
}
/// Return true if the loop can be software pipelined. The algorithm is
/// restricted to loops with a single basic block. Make sure that the
/// branch in the loop can be analyzed.
bool MachinePipeliner::canPipelineLoop(MachineLoop &L) {
if (L.getNumBlocks() != 1)
return false;
// Check if the branch can't be understood because we can't do pipelining
// if that's the case.
LI.TBB = nullptr;
LI.FBB = nullptr;
LI.BrCond.clear();
if (TII->analyzeBranch(*L.getHeader(), LI.TBB, LI.FBB, LI.BrCond))
return false;
LI.LoopInductionVar = nullptr;
LI.LoopCompare = nullptr;
if (TII->analyzeLoop(L, LI.LoopInductionVar, LI.LoopCompare))
return false;
if (!L.getLoopPreheader())
return false;
// If any of the Phis contain subregs, then we can't pipeline
// because we don't know how to maintain subreg information in the
// VMap structure.
MachineBasicBlock *MBB = L.getHeader();
for (MachineBasicBlock::iterator BBI = MBB->instr_begin(),
BBE = MBB->getFirstNonPHI();
BBI != BBE; ++BBI)
for (unsigned i = 1; i != BBI->getNumOperands(); i += 2)
if (BBI->getOperand(i).getSubReg() != 0)
return false;
return true;
}
/// The SMS algorithm consists of the following main steps:
/// 1. Computation and analysis of the dependence graph.
/// 2. Ordering of the nodes (instructions).
/// 3. Attempt to Schedule the loop.
bool MachinePipeliner::swingModuloScheduler(MachineLoop &L) {
assert(L.getBlocks().size() == 1 && "SMS works on single blocks only.");
SwingSchedulerDAG SMS(*this, L, getAnalysis<LiveIntervals>(), RegClassInfo);
MachineBasicBlock *MBB = L.getHeader();
// The kernel should not include any terminator instructions. These
// will be added back later.
SMS.startBlock(MBB);
// Compute the number of 'real' instructions in the basic block by
// ignoring terminators.
unsigned size = MBB->size();
for (MachineBasicBlock::iterator I = MBB->getFirstTerminator(),
E = MBB->instr_end();
I != E; ++I, --size)
;
SMS.enterRegion(MBB, MBB->begin(), MBB->getFirstTerminator(), size);
SMS.schedule();
SMS.exitRegion();
SMS.finishBlock();
return SMS.hasNewSchedule();
}
/// We override the schedule function in ScheduleDAGInstrs to implement the
/// scheduling part of the Swing Modulo Scheduling algorithm.
void SwingSchedulerDAG::schedule() {
AliasAnalysis *AA = &Pass.getAnalysis<AAResultsWrapperPass>().getAAResults();
buildSchedGraph(AA);
addLoopCarriedDependences(AA);
updatePhiDependences();
Topo.InitDAGTopologicalSorting();
postprocessDAG();
changeDependences();
DEBUG({
for (unsigned su = 0, e = SUnits.size(); su != e; ++su)
SUnits[su].dumpAll(this);
});
NodeSetType NodeSets;
findCircuits(NodeSets);
// Calculate the MII.
unsigned ResMII = calculateResMII();
unsigned RecMII = calculateRecMII(NodeSets);
fuseRecs(NodeSets);
// This flag is used for testing and can cause correctness problems.
if (SwpIgnoreRecMII)
RecMII = 0;
MII = std::max(ResMII, RecMII);
DEBUG(dbgs() << "MII = " << MII << " (rec=" << RecMII << ", res=" << ResMII
<< ")\n");
// Can't schedule a loop without a valid MII.
if (MII == 0)
return;
// Don't pipeline large loops.
if (SwpMaxMii != -1 && (int)MII > SwpMaxMii)
return;
computeNodeFunctions(NodeSets);
registerPressureFilter(NodeSets);
colocateNodeSets(NodeSets);
checkNodeSets(NodeSets);
DEBUG({
for (auto &I : NodeSets) {
dbgs() << " Rec NodeSet ";
I.dump();
}
});
std::sort(NodeSets.begin(), NodeSets.end(), std::greater<NodeSet>());
groupRemainingNodes(NodeSets);
removeDuplicateNodes(NodeSets);
DEBUG({
for (auto &I : NodeSets) {
dbgs() << " NodeSet ";
I.dump();
}
});
computeNodeOrder(NodeSets);
SMSchedule Schedule(Pass.MF);
Scheduled = schedulePipeline(Schedule);
if (!Scheduled)
return;
unsigned numStages = Schedule.getMaxStageCount();
// No need to generate pipeline if there are no overlapped iterations.
if (numStages == 0)
return;
// Check that the maximum stage count is less than user-defined limit.
if (SwpMaxStages > -1 && (int)numStages > SwpMaxStages)
return;
generatePipelinedLoop(Schedule);
++NumPipelined;
}
/// Clean up after the software pipeliner runs.
void SwingSchedulerDAG::finishBlock() {
for (MachineInstr *I : NewMIs)
MF.DeleteMachineInstr(I);
NewMIs.clear();
// Call the superclass.
ScheduleDAGInstrs::finishBlock();
}
/// Return the register values for the operands of a Phi instruction.
/// This function assume the instruction is a Phi.
static void getPhiRegs(MachineInstr &Phi, MachineBasicBlock *Loop,
unsigned &InitVal, unsigned &LoopVal) {
assert(Phi.isPHI() && "Expecting a Phi.");
InitVal = 0;
LoopVal = 0;
for (unsigned i = 1, e = Phi.getNumOperands(); i != e; i += 2)
if (Phi.getOperand(i + 1).getMBB() != Loop)
InitVal = Phi.getOperand(i).getReg();
else
LoopVal = Phi.getOperand(i).getReg();
assert(InitVal != 0 && LoopVal != 0 && "Unexpected Phi structure.");
}
/// Return the Phi register value that comes from the incoming block.
static unsigned getInitPhiReg(MachineInstr &Phi, MachineBasicBlock *LoopBB) {
for (unsigned i = 1, e = Phi.getNumOperands(); i != e; i += 2)
if (Phi.getOperand(i + 1).getMBB() != LoopBB)
return Phi.getOperand(i).getReg();
return 0;
}
/// Return the Phi register value that comes the the loop block.
static unsigned getLoopPhiReg(MachineInstr &Phi, MachineBasicBlock *LoopBB) {
for (unsigned i = 1, e = Phi.getNumOperands(); i != e; i += 2)
if (Phi.getOperand(i + 1).getMBB() == LoopBB)
return Phi.getOperand(i).getReg();
return 0;
}
/// Return true if SUb can be reached from SUa following the chain edges.
static bool isSuccOrder(SUnit *SUa, SUnit *SUb) {
SmallPtrSet<SUnit *, 8> Visited;
SmallVector<SUnit *, 8> Worklist;
Worklist.push_back(SUa);
while (!Worklist.empty()) {
const SUnit *SU = Worklist.pop_back_val();
for (auto &SI : SU->Succs) {
SUnit *SuccSU = SI.getSUnit();
if (SI.getKind() == SDep::Order) {
if (Visited.count(SuccSU))
continue;
if (SuccSU == SUb)
return true;
Worklist.push_back(SuccSU);
Visited.insert(SuccSU);
}
}
}
return false;
}
/// Return true if the instruction causes a chain between memory
/// references before and after it.
static bool isDependenceBarrier(MachineInstr &MI, AliasAnalysis *AA) {
return MI.isCall() || MI.hasUnmodeledSideEffects() ||
(MI.hasOrderedMemoryRef() &&
(!MI.mayLoad() || !MI.isDereferenceableInvariantLoad(AA)));
}
/// Return the underlying objects for the memory references of an instruction.
/// This function calls the code in ValueTracking, but first checks that the
/// instruction has a memory operand.
static void getUnderlyingObjects(MachineInstr *MI,
SmallVectorImpl<Value *> &Objs,
const DataLayout &DL) {
if (!MI->hasOneMemOperand())
return;
MachineMemOperand *MM = *MI->memoperands_begin();
if (!MM->getValue())
return;
GetUnderlyingObjects(const_cast<Value *>(MM->getValue()), Objs, DL);
}
/// Add a chain edge between a load and store if the store can be an
/// alias of the load on a subsequent iteration, i.e., a loop carried
/// dependence. This code is very similar to the code in ScheduleDAGInstrs
/// but that code doesn't create loop carried dependences.
void SwingSchedulerDAG::addLoopCarriedDependences(AliasAnalysis *AA) {
MapVector<Value *, SmallVector<SUnit *, 4>> PendingLoads;
for (auto &SU : SUnits) {
MachineInstr &MI = *SU.getInstr();
if (isDependenceBarrier(MI, AA))
PendingLoads.clear();
else if (MI.mayLoad()) {
SmallVector<Value *, 4> Objs;
getUnderlyingObjects(&MI, Objs, MF.getDataLayout());
for (auto V : Objs) {
SmallVector<SUnit *, 4> &SUs = PendingLoads[V];
SUs.push_back(&SU);
}
} else if (MI.mayStore()) {
SmallVector<Value *, 4> Objs;
getUnderlyingObjects(&MI, Objs, MF.getDataLayout());
for (auto V : Objs) {
MapVector<Value *, SmallVector<SUnit *, 4>>::iterator I =
PendingLoads.find(V);
if (I == PendingLoads.end())
continue;
for (auto Load : I->second) {
if (isSuccOrder(Load, &SU))
continue;
MachineInstr &LdMI = *Load->getInstr();
// First, perform the cheaper check that compares the base register.
// If they are the same and the load offset is less than the store
// offset, then mark the dependence as loop carried potentially.
unsigned BaseReg1, BaseReg2;
int64_t Offset1, Offset2;
if (!TII->getMemOpBaseRegImmOfs(LdMI, BaseReg1, Offset1, TRI) ||
!TII->getMemOpBaseRegImmOfs(MI, BaseReg2, Offset2, TRI)) {
SU.addPred(SDep(Load, SDep::Barrier));
continue;
}
if (BaseReg1 == BaseReg2 && (int)Offset1 < (int)Offset2) {
assert(TII->areMemAccessesTriviallyDisjoint(LdMI, MI, AA) &&
"What happened to the chain edge?");
SU.addPred(SDep(Load, SDep::Barrier));
continue;
}
// Second, the more expensive check that uses alias analysis on the
// base registers. If they alias, and the load offset is less than
// the store offset, the mark the dependence as loop carried.
if (!AA) {
SU.addPred(SDep(Load, SDep::Barrier));
continue;
}
MachineMemOperand *MMO1 = *LdMI.memoperands_begin();
MachineMemOperand *MMO2 = *MI.memoperands_begin();
if (!MMO1->getValue() || !MMO2->getValue()) {
SU.addPred(SDep(Load, SDep::Barrier));
continue;
}
if (MMO1->getValue() == MMO2->getValue() &&
MMO1->getOffset() <= MMO2->getOffset()) {
SU.addPred(SDep(Load, SDep::Barrier));
continue;
}
AliasResult AAResult = AA->alias(
MemoryLocation(MMO1->getValue(), MemoryLocation::UnknownSize,
MMO1->getAAInfo()),
MemoryLocation(MMO2->getValue(), MemoryLocation::UnknownSize,
MMO2->getAAInfo()));
if (AAResult != NoAlias)
SU.addPred(SDep(Load, SDep::Barrier));
}
}
}
}
}
/// Update the phi dependences to the DAG because ScheduleDAGInstrs no longer
/// processes dependences for PHIs. This function adds true dependences
/// from a PHI to a use, and a loop carried dependence from the use to the
/// PHI. The loop carried dependence is represented as an anti dependence
/// edge. This function also removes chain dependences between unrelated
/// PHIs.
void SwingSchedulerDAG::updatePhiDependences() {
SmallVector<SDep, 4> RemoveDeps;
const TargetSubtargetInfo &ST = MF.getSubtarget<TargetSubtargetInfo>();
// Iterate over each DAG node.
for (SUnit &I : SUnits) {
RemoveDeps.clear();
// Set to true if the instruction has an operand defined by a Phi.
unsigned HasPhiUse = 0;
unsigned HasPhiDef = 0;
MachineInstr *MI = I.getInstr();
// Iterate over each operand, and we process the definitions.
for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
MOE = MI->operands_end();
MOI != MOE; ++MOI) {
if (!MOI->isReg())
continue;
unsigned Reg = MOI->getReg();
if (MOI->isDef()) {
// If the register is used by a Phi, then create an anti dependence.
for (MachineRegisterInfo::use_instr_iterator
UI = MRI.use_instr_begin(Reg),
UE = MRI.use_instr_end();
UI != UE; ++UI) {
MachineInstr *UseMI = &*UI;
SUnit *SU = getSUnit(UseMI);
if (SU != nullptr && UseMI->isPHI()) {
if (!MI->isPHI()) {
SDep Dep(SU, SDep::Anti, Reg);
I.addPred(Dep);
} else {
HasPhiDef = Reg;
// Add a chain edge to a dependent Phi that isn't an existing
// predecessor.
if (SU->NodeNum < I.NodeNum && !I.isPred(SU))
I.addPred(SDep(SU, SDep::Barrier));
}
}
}
} else if (MOI->isUse()) {
// If the register is defined by a Phi, then create a true dependence.
MachineInstr *DefMI = MRI.getUniqueVRegDef(Reg);
if (DefMI == nullptr)
continue;
SUnit *SU = getSUnit(DefMI);
if (SU != nullptr && DefMI->isPHI()) {
if (!MI->isPHI()) {
SDep Dep(SU, SDep::Data, Reg);
Dep.setLatency(0);
ST.adjustSchedDependency(SU, &I, Dep);
I.addPred(Dep);
} else {
HasPhiUse = Reg;
// Add a chain edge to a dependent Phi that isn't an existing
// predecessor.
if (SU->NodeNum < I.NodeNum && !I.isPred(SU))
I.addPred(SDep(SU, SDep::Barrier));
}
}
}
}
// Remove order dependences from an unrelated Phi.
if (!SwpPruneDeps)
continue;
for (auto &PI : I.Preds) {
MachineInstr *PMI = PI.getSUnit()->getInstr();
if (PMI->isPHI() && PI.getKind() == SDep::Order) {
if (I.getInstr()->isPHI()) {
if (PMI->getOperand(0).getReg() == HasPhiUse)
continue;
if (getLoopPhiReg(*PMI, PMI->getParent()) == HasPhiDef)
continue;
}
RemoveDeps.push_back(PI);
}
}
for (int i = 0, e = RemoveDeps.size(); i != e; ++i)
I.removePred(RemoveDeps[i]);
}
}
/// Iterate over each DAG node and see if we can change any dependences
/// in order to reduce the recurrence MII.
void SwingSchedulerDAG::changeDependences() {
// See if an instruction can use a value from the previous iteration.
// If so, we update the base and offset of the instruction and change
// the dependences.
for (SUnit &I : SUnits) {
unsigned BasePos = 0, OffsetPos = 0, NewBase = 0;
int64_t NewOffset = 0;
if (!canUseLastOffsetValue(I.getInstr(), BasePos, OffsetPos, NewBase,
NewOffset))
continue;
// Get the MI and SUnit for the instruction that defines the original base.
unsigned OrigBase = I.getInstr()->getOperand(BasePos).getReg();
MachineInstr *DefMI = MRI.getUniqueVRegDef(OrigBase);
if (!DefMI)
continue;
SUnit *DefSU = getSUnit(DefMI);
if (!DefSU)
continue;
// Get the MI and SUnit for the instruction that defins the new base.
MachineInstr *LastMI = MRI.getUniqueVRegDef(NewBase);
if (!LastMI)
continue;
SUnit *LastSU = getSUnit(LastMI);
if (!LastSU)
continue;
if (Topo.IsReachable(&I, LastSU))
continue;
// Remove the dependence. The value now depends on a prior iteration.
SmallVector<SDep, 4> Deps;
for (SUnit::pred_iterator P = I.Preds.begin(), E = I.Preds.end(); P != E;
++P)
if (P->getSUnit() == DefSU)
Deps.push_back(*P);
for (int i = 0, e = Deps.size(); i != e; i++) {
Topo.RemovePred(&I, Deps[i].getSUnit());
I.removePred(Deps[i]);
}
// Remove the chain dependence between the instructions.
Deps.clear();
for (auto &P : LastSU->Preds)
if (P.getSUnit() == &I && P.getKind() == SDep::Order)
Deps.push_back(P);
for (int i = 0, e = Deps.size(); i != e; i++) {
Topo.RemovePred(LastSU, Deps[i].getSUnit());
LastSU->removePred(Deps[i]);
}
// Add a dependence between the new instruction and the instruction
// that defines the new base.
SDep Dep(&I, SDep::Anti, NewBase);
LastSU->addPred(Dep);
// Remember the base and offset information so that we can update the
// instruction during code generation.
InstrChanges[&I] = std::make_pair(NewBase, NewOffset);
}
}
namespace {
// FuncUnitSorter - Comparison operator used to sort instructions by
// the number of functional unit choices.
struct FuncUnitSorter {
const InstrItineraryData *InstrItins;
DenseMap<unsigned, unsigned> Resources;
// Compute the number of functional unit alternatives needed
// at each stage, and take the minimum value. We prioritize the
// instructions by the least number of choices first.
unsigned minFuncUnits(const MachineInstr *Inst, unsigned &F) const {
unsigned schedClass = Inst->getDesc().getSchedClass();
unsigned min = UINT_MAX;
for (const InstrStage *IS = InstrItins->beginStage(schedClass),
*IE = InstrItins->endStage(schedClass);
IS != IE; ++IS) {
unsigned funcUnits = IS->getUnits();
unsigned numAlternatives = countPopulation(funcUnits);
if (numAlternatives < min) {
min = numAlternatives;
F = funcUnits;
}
}
return min;
}
// Compute the critical resources needed by the instruction. This
// function records the functional units needed by instructions that
// must use only one functional unit. We use this as a tie breaker
// for computing the resource MII. The instrutions that require
// the same, highly used, functional unit have high priority.
void calcCriticalResources(MachineInstr &MI) {
unsigned SchedClass = MI.getDesc().getSchedClass();
for (const InstrStage *IS = InstrItins->beginStage(SchedClass),
*IE = InstrItins->endStage(SchedClass);
IS != IE; ++IS) {
unsigned FuncUnits = IS->getUnits();
if (countPopulation(FuncUnits) == 1)
Resources[FuncUnits]++;
}
}
FuncUnitSorter(const InstrItineraryData *IID) : InstrItins(IID) {}
/// Return true if IS1 has less priority than IS2.
bool operator()(const MachineInstr *IS1, const MachineInstr *IS2) const {
unsigned F1 = 0, F2 = 0;
unsigned MFUs1 = minFuncUnits(IS1, F1);
unsigned MFUs2 = minFuncUnits(IS2, F2);
if (MFUs1 == 1 && MFUs2 == 1)
return Resources.lookup(F1) < Resources.lookup(F2);
return MFUs1 > MFUs2;
}
};
} // end anonymous namespace
/// Calculate the resource constrained minimum initiation interval for the
/// specified loop. We use the DFA to model the resources needed for
/// each instruction, and we ignore dependences. A different DFA is created
/// for each cycle that is required. When adding a new instruction, we attempt
/// to add it to each existing DFA, until a legal space is found. If the
/// instruction cannot be reserved in an existing DFA, we create a new one.
unsigned SwingSchedulerDAG::calculateResMII() {
SmallVector<DFAPacketizer *, 8> Resources;
MachineBasicBlock *MBB = Loop.getHeader();
Resources.push_back(TII->CreateTargetScheduleState(MF.getSubtarget()));
// Sort the instructions by the number of available choices for scheduling,
// least to most. Use the number of critical resources as the tie breaker.
FuncUnitSorter FUS =
FuncUnitSorter(MF.getSubtarget().getInstrItineraryData());
for (MachineBasicBlock::iterator I = MBB->getFirstNonPHI(),
E = MBB->getFirstTerminator();
I != E; ++I)
FUS.calcCriticalResources(*I);
PriorityQueue<MachineInstr *, std::vector<MachineInstr *>, FuncUnitSorter>
FuncUnitOrder(FUS);
for (MachineBasicBlock::iterator I = MBB->getFirstNonPHI(),
E = MBB->getFirstTerminator();
I != E; ++I)
FuncUnitOrder.push(&*I);
while (!FuncUnitOrder.empty()) {
MachineInstr *MI = FuncUnitOrder.top();
FuncUnitOrder.pop();
if (TII->isZeroCost(MI->getOpcode()))
continue;
// Attempt to reserve the instruction in an existing DFA. At least one
// DFA is needed for each cycle.
unsigned NumCycles = getSUnit(MI)->Latency;
unsigned ReservedCycles = 0;
SmallVectorImpl<DFAPacketizer *>::iterator RI = Resources.begin();
SmallVectorImpl<DFAPacketizer *>::iterator RE = Resources.end();
for (unsigned C = 0; C < NumCycles; ++C)
while (RI != RE) {
if ((*RI++)->canReserveResources(*MI)) {
++ReservedCycles;
break;
}
}
// Start reserving resources using existing DFAs.
for (unsigned C = 0; C < ReservedCycles; ++C) {
--RI;
(*RI)->reserveResources(*MI);
}
// Add new DFAs, if needed, to reserve resources.
for (unsigned C = ReservedCycles; C < NumCycles; ++C) {
DFAPacketizer *NewResource =
TII->CreateTargetScheduleState(MF.getSubtarget());
assert(NewResource->canReserveResources(*MI) && "Reserve error.");
NewResource->reserveResources(*MI);
Resources.push_back(NewResource);
}
}
int Resmii = Resources.size();
// Delete the memory for each of the DFAs that were created earlier.
for (DFAPacketizer *RI : Resources) {
DFAPacketizer *D = RI;
delete D;
}
Resources.clear();
return Resmii;
}
/// Calculate the recurrence-constrainted minimum initiation interval.
/// Iterate over each circuit. Compute the delay(c) and distance(c)
/// for each circuit. The II needs to satisfy the inequality
/// delay(c) - II*distance(c) <= 0. For each circuit, choose the smallest
/// II that satistifies the inequality, and the RecMII is the maximum
/// of those values.
unsigned SwingSchedulerDAG::calculateRecMII(NodeSetType &NodeSets) {
unsigned RecMII = 0;
for (NodeSet &Nodes : NodeSets) {
if (Nodes.size() == 0)
continue;
unsigned Delay = Nodes.size() - 1;
unsigned Distance = 1;
// ii = ceil(delay / distance)
unsigned CurMII = (Delay + Distance - 1) / Distance;
Nodes.setRecMII(CurMII);
if (CurMII > RecMII)
RecMII = CurMII;
}
return RecMII;
}
/// Swap all the anti dependences in the DAG. That means it is no longer a DAG,
/// but we do this to find the circuits, and then change them back.
static void swapAntiDependences(std::vector<SUnit> &SUnits) {
SmallVector<std::pair<SUnit *, SDep>, 8> DepsAdded;
for (unsigned i = 0, e = SUnits.size(); i != e; ++i) {
SUnit *SU = &SUnits[i];
for (SUnit::pred_iterator IP = SU->Preds.begin(), EP = SU->Preds.end();
IP != EP; ++IP) {
if (IP->getKind() != SDep::Anti)
continue;
DepsAdded.push_back(std::make_pair(SU, *IP));
}
}
for (SmallVector<std::pair<SUnit *, SDep>, 8>::iterator I = DepsAdded.begin(),
E = DepsAdded.end();
I != E; ++I) {
// Remove this anti dependency and add one in the reverse direction.
SUnit *SU = I->first;
SDep &D = I->second;
SUnit *TargetSU = D.getSUnit();
unsigned Reg = D.getReg();
unsigned Lat = D.getLatency();
SU->removePred(D);
SDep Dep(SU, SDep::Anti, Reg);
Dep.setLatency(Lat);
TargetSU->addPred(Dep);
}
}
/// Create the adjacency structure of the nodes in the graph.
void SwingSchedulerDAG::Circuits::createAdjacencyStructure(
SwingSchedulerDAG *DAG) {
BitVector Added(SUnits.size());
for (int i = 0, e = SUnits.size(); i != e; ++i) {
Added.reset();
// Add any successor to the adjacency matrix and exclude duplicates.
for (auto &SI : SUnits[i].Succs) {
// Do not process a boundary node and a back-edge is processed only
// if it goes to a Phi.
if (SI.getSUnit()->isBoundaryNode() ||
(SI.getKind() == SDep::Anti && !SI.getSUnit()->getInstr()->isPHI()))
continue;
int N = SI.getSUnit()->NodeNum;
if (!Added.test(N)) {
AdjK[i].push_back(N);
Added.set(N);
}
}
// A chain edge between a store and a load is treated as a back-edge in the
// adjacency matrix.
for (auto &PI : SUnits[i].Preds) {
if (!SUnits[i].getInstr()->mayStore() ||
!DAG->isLoopCarriedOrder(&SUnits[i], PI, false))
continue;
if (PI.getKind() == SDep::Order && PI.getSUnit()->getInstr()->mayLoad()) {
int N = PI.getSUnit()->NodeNum;
if (!Added.test(N)) {
AdjK[i].push_back(N);
Added.set(N);
}
}
}
}
}
/// Identify an elementary circuit in the dependence graph starting at the
/// specified node.
bool SwingSchedulerDAG::Circuits::circuit(int V, int S, NodeSetType &NodeSets,
bool HasBackedge) {
SUnit *SV = &SUnits[V];
bool F = false;
Stack.insert(SV);
Blocked.set(V);
for (auto W : AdjK[V]) {
if (NumPaths > MaxPaths)
break;
if (W < S)
continue;
if (W == S) {
if (!HasBackedge)
NodeSets.push_back(NodeSet(Stack.begin(), Stack.end()));
F = true;
++NumPaths;
break;
} else if (!Blocked.test(W)) {
if (circuit(W, S, NodeSets, W < V ? true : HasBackedge))
F = true;
}
}
if (F)
unblock(V);
else {
for (auto W : AdjK[V]) {
if (W < S)
continue;
if (B[W].count(SV) == 0)
B[W].insert(SV);
}
}
Stack.pop_back();
return F;
}
/// Unblock a node in the circuit finding algorithm.
void SwingSchedulerDAG::Circuits::unblock(int U) {
Blocked.reset(U);
SmallPtrSet<SUnit *, 4> &BU = B[U];
while (!BU.empty()) {
SmallPtrSet<SUnit *, 4>::iterator SI = BU.begin();
assert(SI != BU.end() && "Invalid B set.");
SUnit *W = *SI;
BU.erase(W);
if (Blocked.test(W->NodeNum))
unblock(W->NodeNum);
}
}
/// Identify all the elementary circuits in the dependence graph using
/// Johnson's circuit algorithm.
void SwingSchedulerDAG::findCircuits(NodeSetType &NodeSets) {
// Swap all the anti dependences in the DAG. That means it is no longer a DAG,
// but we do this to find the circuits, and then change them back.
swapAntiDependences(SUnits);
Circuits Cir(SUnits);
// Create the adjacency structure.
Cir.createAdjacencyStructure(this);
for (int i = 0, e = SUnits.size(); i != e; ++i) {
Cir.reset();
Cir.circuit(i, i, NodeSets);
}
// Change the dependences back so that we've created a DAG again.
swapAntiDependences(SUnits);
}
/// Return true for DAG nodes that we ignore when computing the cost functions.
/// We ignore the back-edge recurrence in order to avoid unbounded recurison
/// in the calculation of the ASAP, ALAP, etc functions.
static bool ignoreDependence(const SDep &D, bool isPred) {
if (D.isArtificial())
return true;
return D.getKind() == SDep::Anti && isPred;
}
/// Compute several functions need to order the nodes for scheduling.
/// ASAP - Earliest time to schedule a node.
/// ALAP - Latest time to schedule a node.
/// MOV - Mobility function, difference between ALAP and ASAP.
/// D - Depth of each node.
/// H - Height of each node.
void SwingSchedulerDAG::computeNodeFunctions(NodeSetType &NodeSets) {
ScheduleInfo.resize(SUnits.size());
DEBUG({
for (ScheduleDAGTopologicalSort::const_iterator I = Topo.begin(),
E = Topo.end();
I != E; ++I) {
SUnit *SU = &SUnits[*I];
SU->dump(this);
}
});
int maxASAP = 0;
// Compute ASAP.
for (ScheduleDAGTopologicalSort::const_iterator I = Topo.begin(),
E = Topo.end();
I != E; ++I) {
int asap = 0;
SUnit *SU = &SUnits[*I];
for (SUnit::const_pred_iterator IP = SU->Preds.begin(),
EP = SU->Preds.end();
IP != EP; ++IP) {
if (ignoreDependence(*IP, true))
continue;
SUnit *pred = IP->getSUnit();
asap = std::max(asap, (int)(getASAP(pred) + getLatency(SU, *IP) -
getDistance(pred, SU, *IP) * MII));
}
maxASAP = std::max(maxASAP, asap);
ScheduleInfo[*I].ASAP = asap;
}
// Compute ALAP and MOV.
for (ScheduleDAGTopologicalSort::const_reverse_iterator I = Topo.rbegin(),
E = Topo.rend();
I != E; ++I) {
int alap = maxASAP;
SUnit *SU = &SUnits[*I];
for (SUnit::const_succ_iterator IS = SU->Succs.begin(),
ES = SU->Succs.end();
IS != ES; ++IS) {
if (ignoreDependence(*IS, true))
continue;
SUnit *succ = IS->getSUnit();
alap = std::min(alap, (int)(getALAP(succ) - getLatency(SU, *IS) +
getDistance(SU, succ, *IS) * MII));
}
ScheduleInfo[*I].ALAP = alap;
}
// After computing the node functions, compute the summary for each node set.
for (NodeSet &I : NodeSets)
I.computeNodeSetInfo(this);
DEBUG({
for (unsigned i = 0; i < SUnits.size(); i++) {
dbgs() << "\tNode " << i << ":\n";
dbgs() << "\t ASAP = " << getASAP(&SUnits[i]) << "\n";
dbgs() << "\t ALAP = " << getALAP(&SUnits[i]) << "\n";
dbgs() << "\t MOV = " << getMOV(&SUnits[i]) << "\n";
dbgs() << "\t D = " << getDepth(&SUnits[i]) << "\n";
dbgs() << "\t H = " << getHeight(&SUnits[i]) << "\n";
}
});
}
/// Compute the Pred_L(O) set, as defined in the paper. The set is defined
/// as the predecessors of the elements of NodeOrder that are not also in
/// NodeOrder.
static bool pred_L(SetVector<SUnit *> &NodeOrder,
SmallSetVector<SUnit *, 8> &Preds,
const NodeSet *S = nullptr) {
Preds.clear();
for (SetVector<SUnit *>::iterator I = NodeOrder.begin(), E = NodeOrder.end();
I != E; ++I) {
for (SUnit::pred_iterator PI = (*I)->Preds.begin(), PE = (*I)->Preds.end();
PI != PE; ++PI) {
if (S && S->count(PI->getSUnit()) == 0)
continue;
if (ignoreDependence(*PI, true))
continue;
if (NodeOrder.count(PI->getSUnit()) == 0)
Preds.insert(PI->getSUnit());
}
// Back-edges are predecessors with an anti-dependence.
for (SUnit::const_succ_iterator IS = (*I)->Succs.begin(),
ES = (*I)->Succs.end();
IS != ES; ++IS) {
if (IS->getKind() != SDep::Anti)
continue;
if (S && S->count(IS->getSUnit()) == 0)
continue;
if (NodeOrder.count(IS->getSUnit()) == 0)
Preds.insert(IS->getSUnit());
}
}
return Preds.size() > 0;
}
/// Compute the Succ_L(O) set, as defined in the paper. The set is defined
/// as the successors of the elements of NodeOrder that are not also in
/// NodeOrder.
static bool succ_L(SetVector<SUnit *> &NodeOrder,
SmallSetVector<SUnit *, 8> &Succs,
const NodeSet *S = nullptr) {
Succs.clear();
for (SetVector<SUnit *>::iterator I = NodeOrder.begin(), E = NodeOrder.end();
I != E; ++I) {
for (SUnit::succ_iterator SI = (*I)->Succs.begin(), SE = (*I)->Succs.end();
SI != SE; ++SI) {
if (S && S->count(SI->getSUnit()) == 0)
continue;
if (ignoreDependence(*SI, false))
continue;
if (NodeOrder.count(SI->getSUnit()) == 0)
Succs.insert(SI->getSUnit());
}
for (SUnit::const_pred_iterator PI = (*I)->Preds.begin(),
PE = (*I)->Preds.end();
PI != PE; ++PI) {
if (PI->getKind() != SDep::Anti)
continue;
if (S && S->count(PI->getSUnit()) == 0)
continue;
if (NodeOrder.count(PI->getSUnit()) == 0)
Succs.insert(PI->getSUnit());
}
}
return Succs.size() > 0;
}
/// Return true if there is a path from the specified node to any of the nodes
/// in DestNodes. Keep track and return the nodes in any path.
static bool computePath(SUnit *Cur, SetVector<SUnit *> &Path,
SetVector<SUnit *> &DestNodes,
SetVector<SUnit *> &Exclude,
SmallPtrSet<SUnit *, 8> &Visited) {
if (Cur->isBoundaryNode())
return false;
if (Exclude.count(Cur) != 0)
return false;
if (DestNodes.count(Cur) != 0)
return true;
if (!Visited.insert(Cur).second)
return Path.count(Cur) != 0;
bool FoundPath = false;
for (auto &SI : Cur->Succs)
FoundPath |= computePath(SI.getSUnit(), Path, DestNodes, Exclude, Visited);
for (auto &PI : Cur->Preds)
if (PI.getKind() == SDep::Anti)
FoundPath |=
computePath(PI.getSUnit(), Path, DestNodes, Exclude, Visited);
if (FoundPath)
Path.insert(Cur);
return FoundPath;
}
/// Return true if Set1 is a subset of Set2.
template <class S1Ty, class S2Ty> static bool isSubset(S1Ty &Set1, S2Ty &Set2) {
for (typename S1Ty::iterator I = Set1.begin(), E = Set1.end(); I != E; ++I)
if (Set2.count(*I) == 0)
return false;
return true;
}
/// Compute the live-out registers for the instructions in a node-set.
/// The live-out registers are those that are defined in the node-set,
/// but not used. Except for use operands of Phis.
static void computeLiveOuts(MachineFunction &MF, RegPressureTracker &RPTracker,
NodeSet &NS) {
const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
MachineRegisterInfo &MRI = MF.getRegInfo();
SmallVector<RegisterMaskPair, 8> LiveOutRegs;
SmallSet<unsigned, 4> Uses;
for (SUnit *SU : NS) {
const MachineInstr *MI = SU->getInstr();
if (MI->isPHI())
continue;
for (const MachineOperand &MO : MI->operands())
if (MO.isReg() && MO.isUse()) {
unsigned Reg = MO.getReg();
if (TargetRegisterInfo::isVirtualRegister(Reg))
Uses.insert(Reg);
else if (MRI.isAllocatable(Reg))
for (MCRegUnitIterator Units(Reg, TRI); Units.isValid(); ++Units)
Uses.insert(*Units);
}
}
for (SUnit *SU : NS)
for (const MachineOperand &MO : SU->getInstr()->operands())
if (MO.isReg() && MO.isDef() && !MO.isDead()) {
unsigned Reg = MO.getReg();
if (TargetRegisterInfo::isVirtualRegister(Reg)) {
if (!Uses.count(Reg))
LiveOutRegs.push_back(RegisterMaskPair(Reg,
LaneBitmask::getNone()));
} else if (MRI.isAllocatable(Reg)) {
for (MCRegUnitIterator Units(Reg, TRI); Units.isValid(); ++Units)
if (!Uses.count(*Units))
LiveOutRegs.push_back(RegisterMaskPair(*Units,
LaneBitmask::getNone()));
}
}
RPTracker.addLiveRegs(LiveOutRegs);
}
/// A heuristic to filter nodes in recurrent node-sets if the register
/// pressure of a set is too high.
void SwingSchedulerDAG::registerPressureFilter(NodeSetType &NodeSets) {
for (auto &NS : NodeSets) {
// Skip small node-sets since they won't cause register pressure problems.
if (NS.size() <= 2)
continue;
IntervalPressure RecRegPressure;
RegPressureTracker RecRPTracker(RecRegPressure);
RecRPTracker.init(&MF, &RegClassInfo, &LIS, BB, BB->end(), false, true);
computeLiveOuts(MF, RecRPTracker, NS);
RecRPTracker.closeBottom();
std::vector<SUnit *> SUnits(NS.begin(), NS.end());
std::sort(SUnits.begin(), SUnits.end(), [](const SUnit *A, const SUnit *B) {
return A->NodeNum > B->NodeNum;
});
for (auto &SU : SUnits) {
// Since we're computing the register pressure for a subset of the
// instructions in a block, we need to set the tracker for each
// instruction in the node-set. The tracker is set to the instruction
// just after the one we're interested in.
MachineBasicBlock::const_iterator CurInstI = SU->getInstr();
RecRPTracker.setPos(std::next(CurInstI));
RegPressureDelta RPDelta;
ArrayRef<PressureChange> CriticalPSets;
RecRPTracker.getMaxUpwardPressureDelta(SU->getInstr(), nullptr, RPDelta,
CriticalPSets,
RecRegPressure.MaxSetPressure);
if (RPDelta.Excess.isValid()) {
DEBUG(dbgs() << "Excess register pressure: SU(" << SU->NodeNum << ") "
<< TRI->getRegPressureSetName(RPDelta.Excess.getPSet())
<< ":" << RPDelta.Excess.getUnitInc());
NS.setExceedPressure(SU);
break;
}
RecRPTracker.recede();
}
}
}
/// A heuristic to colocate node sets that have the same set of
/// successors.
void SwingSchedulerDAG::colocateNodeSets(NodeSetType &NodeSets) {
unsigned Colocate = 0;
for (int i = 0, e = NodeSets.size(); i < e; ++i) {
NodeSet &N1 = NodeSets[i];
SmallSetVector<SUnit *, 8> S1;
if (N1.empty() || !succ_L(N1, S1))
continue;
for (int j = i + 1; j < e; ++j) {
NodeSet &N2 = NodeSets[j];
if (N1.compareRecMII(N2) != 0)
continue;
SmallSetVector<SUnit *, 8> S2;
if (N2.empty() || !succ_L(N2, S2))
continue;
if (isSubset(S1, S2) && S1.size() == S2.size()) {
N1.setColocate(++Colocate);
N2.setColocate(Colocate);
break;
}
}
}
}
/// Check if the existing node-sets are profitable. If not, then ignore the
/// recurrent node-sets, and attempt to schedule all nodes together. This is
/// a heuristic. If the MII is large and there is a non-recurrent node with
/// a large depth compared to the MII, then it's best to try and schedule
/// all instruction together instead of starting with the recurrent node-sets.
void SwingSchedulerDAG::checkNodeSets(NodeSetType &NodeSets) {
// Look for loops with a large MII.
if (MII <= 20)
return;
// Check if the node-set contains only a simple add recurrence.
for (auto &NS : NodeSets)
if (NS.size() > 2)
return;
// If the depth of any instruction is significantly larger than the MII, then
// ignore the recurrent node-sets and treat all instructions equally.
for (auto &SU : SUnits)
if (SU.getDepth() > MII * 1.5) {
NodeSets.clear();
DEBUG(dbgs() << "Clear recurrence node-sets\n");
return;
}
}
/// Add the nodes that do not belong to a recurrence set into groups
/// based upon connected componenets.
void SwingSchedulerDAG::groupRemainingNodes(NodeSetType &NodeSets) {
SetVector<SUnit *> NodesAdded;
SmallPtrSet<SUnit *, 8> Visited;
// Add the nodes that are on a path between the previous node sets and
// the current node set.
for (NodeSet &I : NodeSets) {
SmallSetVector<SUnit *, 8> N;
// Add the nodes from the current node set to the previous node set.
if (succ_L(I, N)) {
SetVector<SUnit *> Path;
for (SUnit *NI : N) {
Visited.clear();
computePath(NI, Path, NodesAdded, I, Visited);
}
if (Path.size() > 0)
I.insert(Path.begin(), Path.end());
}
// Add the nodes from the previous node set to the current node set.
N.clear();
if (succ_L(NodesAdded, N)) {
SetVector<SUnit *> Path;
for (SUnit *NI : N) {
Visited.clear();
computePath(NI, Path, I, NodesAdded, Visited);
}
if (Path.size() > 0)
I.insert(Path.begin(), Path.end());
}
NodesAdded.insert(I.begin(), I.end());
}
// Create a new node set with the connected nodes of any successor of a node
// in a recurrent set.
NodeSet NewSet;
SmallSetVector<SUnit *, 8> N;
if (succ_L(NodesAdded, N))
for (SUnit *I : N)
addConnectedNodes(I, NewSet, NodesAdded);
if (NewSet.size() > 0)
NodeSets.push_back(NewSet);
// Create a new node set with the connected nodes of any predecessor of a node
// in a recurrent set.
NewSet.clear();
if (pred_L(NodesAdded, N))
for (SUnit *I : N)
addConnectedNodes(I, NewSet, NodesAdded);
if (NewSet.size() > 0)
NodeSets.push_back(NewSet);
// Create new nodes sets with the connected nodes any any remaining node that
// has no predecessor.
for (unsigned i = 0; i < SUnits.size(); ++i) {
SUnit *SU = &SUnits[i];
if (NodesAdded.count(SU) == 0) {
NewSet.clear();
addConnectedNodes(SU, NewSet, NodesAdded);
if (NewSet.size() > 0)
NodeSets.push_back(NewSet);
}
}
}
/// Add the node to the set, and add all is its connected nodes to the set.
void SwingSchedulerDAG::addConnectedNodes(SUnit *SU, NodeSet &NewSet,
SetVector<SUnit *> &NodesAdded) {
NewSet.insert(SU);
NodesAdded.insert(SU);
for (auto &SI : SU->Succs) {
SUnit *Successor = SI.getSUnit();
if (!SI.isArtificial() && NodesAdded.count(Successor) == 0)
addConnectedNodes(Successor, NewSet, NodesAdded);
}
for (auto &PI : SU->Preds) {
SUnit *Predecessor = PI.getSUnit();
if (!PI.isArtificial() && NodesAdded.count(Predecessor) == 0)
addConnectedNodes(Predecessor, NewSet, NodesAdded);
}
}
/// Return true if Set1 contains elements in Set2. The elements in common
/// are returned in a different container.
static bool isIntersect(SmallSetVector<SUnit *, 8> &Set1, const NodeSet &Set2,
SmallSetVector<SUnit *, 8> &Result) {
Result.clear();
for (unsigned i = 0, e = Set1.size(); i != e; ++i) {
SUnit *SU = Set1[i];
if (Set2.count(SU) != 0)
Result.insert(SU);
}
return !Result.empty();
}
/// Merge the recurrence node sets that have the same initial node.
void SwingSchedulerDAG::fuseRecs(NodeSetType &NodeSets) {
for (NodeSetType::iterator I = NodeSets.begin(), E = NodeSets.end(); I != E;
++I) {
NodeSet &NI = *I;
for (NodeSetType::iterator J = I + 1; J != E;) {
NodeSet &NJ = *J;
if (NI.getNode(0)->NodeNum == NJ.getNode(0)->NodeNum) {
if (NJ.compareRecMII(NI) > 0)
NI.setRecMII(NJ.getRecMII());
for (NodeSet::iterator NII = J->begin(), ENI = J->end(); NII != ENI;
++NII)
I->insert(*NII);
NodeSets.erase(J);
E = NodeSets.end();
} else {
++J;
}
}
}
}
/// Remove nodes that have been scheduled in previous NodeSets.
void SwingSchedulerDAG::removeDuplicateNodes(NodeSetType &NodeSets) {
for (NodeSetType::iterator I = NodeSets.begin(), E = NodeSets.end(); I != E;
++I)
for (NodeSetType::iterator J = I + 1; J != E;) {
J->remove_if([&](SUnit *SUJ) { return I->count(SUJ); });
if (J->size() == 0) {
NodeSets.erase(J);
E = NodeSets.end();
} else {
++J;
}
}
}
/// Return true if Inst1 defines a value that is used in Inst2.
static bool hasDataDependence(SUnit *Inst1, SUnit *Inst2) {
for (auto &SI : Inst1->Succs)
if (SI.getSUnit() == Inst2 && SI.getKind() == SDep::Data)
return true;
return false;
}
/// Compute an ordered list of the dependence graph nodes, which
/// indicates the order that the nodes will be scheduled. This is a
/// two-level algorithm. First, a partial order is created, which
/// consists of a list of sets ordered from highest to lowest priority.
void SwingSchedulerDAG::computeNodeOrder(NodeSetType &NodeSets) {
SmallSetVector<SUnit *, 8> R;
NodeOrder.clear();
for (auto &Nodes : NodeSets) {
DEBUG(dbgs() << "NodeSet size " << Nodes.size() << "\n");
OrderKind Order;
SmallSetVector<SUnit *, 8> N;
if (pred_L(NodeOrder, N) && isSubset(N, Nodes)) {
R.insert(N.begin(), N.end());
Order = BottomUp;
DEBUG(dbgs() << " Bottom up (preds) ");
} else if (succ_L(NodeOrder, N) && isSubset(N, Nodes)) {
R.insert(N.begin(), N.end());
Order = TopDown;
DEBUG(dbgs() << " Top down (succs) ");
} else if (isIntersect(N, Nodes, R)) {
// If some of the successors are in the existing node-set, then use the
// top-down ordering.
Order = TopDown;
DEBUG(dbgs() << " Top down (intersect) ");
} else if (NodeSets.size() == 1) {
for (auto &N : Nodes)
if (N->Succs.size() == 0)
R.insert(N);
Order = BottomUp;
DEBUG(dbgs() << " Bottom up (all) ");
} else {
// Find the node with the highest ASAP.
SUnit *maxASAP = nullptr;
for (SUnit *SU : Nodes) {
if (maxASAP == nullptr || getASAP(SU) >= getASAP(maxASAP))
maxASAP = SU;
}
R.insert(maxASAP);
Order = BottomUp;
DEBUG(dbgs() << " Bottom up (default) ");
}
while (!R.empty()) {
if (Order == TopDown) {
// Choose the node with the maximum height. If more than one, choose
// the node with the lowest MOV. If still more than one, check if there
// is a dependence between the instructions.
while (!R.empty()) {
SUnit *maxHeight = nullptr;
for (SUnit *I : R) {
if (maxHeight == nullptr || getHeight(I) > getHeight(maxHeight))
maxHeight = I;
else if (getHeight(I) == getHeight(maxHeight) &&
getMOV(I) < getMOV(maxHeight) &&
!hasDataDependence(maxHeight, I))
maxHeight = I;
else if (hasDataDependence(I, maxHeight))
maxHeight = I;
}
NodeOrder.insert(maxHeight);
DEBUG(dbgs() << maxHeight->NodeNum << " ");
R.remove(maxHeight);
for (const auto &I : maxHeight->Succs) {
if (Nodes.count(I.getSUnit()) == 0)
continue;
if (NodeOrder.count(I.getSUnit()) != 0)
continue;
if (ignoreDependence(I, false))
continue;
R.insert(I.getSUnit());
}
// Back-edges are predecessors with an anti-dependence.
for (const auto &I : maxHeight->Preds) {
if (I.getKind() != SDep::Anti)
continue;
if (Nodes.count(I.getSUnit()) == 0)
continue;
if (NodeOrder.count(I.getSUnit()) != 0)
continue;
R.insert(I.getSUnit());
}
}
Order = BottomUp;
DEBUG(dbgs() << "\n Switching order to bottom up ");
SmallSetVector<SUnit *, 8> N;
if (pred_L(NodeOrder, N, &Nodes))
R.insert(N.begin(), N.end());
} else {
// Choose the node with the maximum depth. If more than one, choose
// the node with the lowest MOV. If there is still more than one, check
// for a dependence between the instructions.
while (!R.empty()) {
SUnit *maxDepth = nullptr;
for (SUnit *I : R) {
if (maxDepth == nullptr || getDepth(I) > getDepth(maxDepth))
maxDepth = I;
else if (getDepth(I) == getDepth(maxDepth) &&
getMOV(I) < getMOV(maxDepth) &&
!hasDataDependence(I, maxDepth))
maxDepth = I;
else if (hasDataDependence(maxDepth, I))
maxDepth = I;
}
NodeOrder.insert(maxDepth);
DEBUG(dbgs() << maxDepth->NodeNum << " ");
R.remove(maxDepth);
if (Nodes.isExceedSU(maxDepth)) {
Order = TopDown;
R.clear();
R.insert(Nodes.getNode(0));
break;
}
for (const auto &I : maxDepth->Preds) {
if (Nodes.count(I.getSUnit()) == 0)
continue;
if (NodeOrder.count(I.getSUnit()) != 0)
continue;
if (I.getKind() == SDep::Anti)
continue;
R.insert(I.getSUnit());
}
// Back-edges are predecessors with an anti-dependence.
for (const auto &I : maxDepth->Succs) {
if (I.getKind() != SDep::Anti)
continue;
if (Nodes.count(I.getSUnit()) == 0)
continue;
if (NodeOrder.count(I.getSUnit()) != 0)
continue;
R.insert(I.getSUnit());
}
}
Order = TopDown;
DEBUG(dbgs() << "\n Switching order to top down ");
SmallSetVector<SUnit *, 8> N;
if (succ_L(NodeOrder, N, &Nodes))
R.insert(N.begin(), N.end());
}
}
DEBUG(dbgs() << "\nDone with Nodeset\n");
}
DEBUG({
dbgs() << "Node order: ";
for (SUnit *I : NodeOrder)
dbgs() << " " << I->NodeNum << " ";
dbgs() << "\n";
});
}
/// Process the nodes in the computed order and create the pipelined schedule
/// of the instructions, if possible. Return true if a schedule is found.
bool SwingSchedulerDAG::schedulePipeline(SMSchedule &Schedule) {
if (NodeOrder.size() == 0)
return false;
bool scheduleFound = false;
// Keep increasing II until a valid schedule is found.
for (unsigned II = MII; II < MII + 10 && !scheduleFound; ++II) {
Schedule.reset();
Schedule.setInitiationInterval(II);
DEBUG(dbgs() << "Try to schedule with " << II << "\n");
SetVector<SUnit *>::iterator NI = NodeOrder.begin();
SetVector<SUnit *>::iterator NE = NodeOrder.end();
do {
SUnit *SU = *NI;
// Compute the schedule time for the instruction, which is based
// upon the scheduled time for any predecessors/successors.
int EarlyStart = INT_MIN;
int LateStart = INT_MAX;
// These values are set when the size of the schedule window is limited
// due to chain dependences.
int SchedEnd = INT_MAX;
int SchedStart = INT_MIN;
Schedule.computeStart(SU, &EarlyStart, &LateStart, &SchedEnd, &SchedStart,
II, this);
DEBUG({
dbgs() << "Inst (" << SU->NodeNum << ") ";
SU->getInstr()->dump();
dbgs() << "\n";
});
DEBUG({
dbgs() << "\tes: " << EarlyStart << " ls: " << LateStart
<< " me: " << SchedEnd << " ms: " << SchedStart << "\n";
});
if (EarlyStart > LateStart || SchedEnd < EarlyStart ||
SchedStart > LateStart)
scheduleFound = false;
else if (EarlyStart != INT_MIN && LateStart == INT_MAX) {
SchedEnd = std::min(SchedEnd, EarlyStart + (int)II - 1);
scheduleFound = Schedule.insert(SU, EarlyStart, SchedEnd, II);
} else if (EarlyStart == INT_MIN && LateStart != INT_MAX) {
SchedStart = std::max(SchedStart, LateStart - (int)II + 1);
scheduleFound = Schedule.insert(SU, LateStart, SchedStart, II);
} else if (EarlyStart != INT_MIN && LateStart != INT_MAX) {
SchedEnd =
std::min(SchedEnd, std::min(LateStart, EarlyStart + (int)II - 1));
// When scheduling a Phi it is better to start at the late cycle and go
// backwards. The default order may insert the Phi too far away from
// its first dependence.
if (SU->getInstr()->isPHI())
scheduleFound = Schedule.insert(SU, SchedEnd, EarlyStart, II);
else
scheduleFound = Schedule.insert(SU, EarlyStart, SchedEnd, II);
} else {
int FirstCycle = Schedule.getFirstCycle();
scheduleFound = Schedule.insert(SU, FirstCycle + getASAP(SU),
FirstCycle + getASAP(SU) + II - 1, II);
}
// Even if we find a schedule, make sure the schedule doesn't exceed the
// allowable number of stages. We keep trying if this happens.
if (scheduleFound)
if (SwpMaxStages > -1 &&
Schedule.getMaxStageCount() > (unsigned)SwpMaxStages)
scheduleFound = false;
DEBUG({
if (!scheduleFound)
dbgs() << "\tCan't schedule\n";
});
} while (++NI != NE && scheduleFound);
// If a schedule is found, check if it is a valid schedule too.
if (scheduleFound)
scheduleFound = Schedule.isValidSchedule(this);
}
DEBUG(dbgs() << "Schedule Found? " << scheduleFound << "\n");
if (scheduleFound)
Schedule.finalizeSchedule(this);
else
Schedule.reset();
return scheduleFound && Schedule.getMaxStageCount() > 0;
}
/// Given a schedule for the loop, generate a new version of the loop,
/// and replace the old version. This function generates a prolog
/// that contains the initial iterations in the pipeline, and kernel
/// loop, and the epilogue that contains the code for the final
/// iterations.
void SwingSchedulerDAG::generatePipelinedLoop(SMSchedule &Schedule) {
// Create a new basic block for the kernel and add it to the CFG.
MachineBasicBlock *KernelBB = MF.CreateMachineBasicBlock(BB->getBasicBlock());
unsigned MaxStageCount = Schedule.getMaxStageCount();
// Remember the registers that are used in different stages. The index is
// the iteration, or stage, that the instruction is scheduled in. This is
// a map between register names in the orignal block and the names created
// in each stage of the pipelined loop.
ValueMapTy *VRMap = new ValueMapTy[(MaxStageCount + 1) * 2];
InstrMapTy InstrMap;
SmallVector<MachineBasicBlock *, 4> PrologBBs;
// Generate the prolog instructions that set up the pipeline.
generateProlog(Schedule, MaxStageCount, KernelBB, VRMap, PrologBBs);
MF.insert(BB->getIterator(), KernelBB);
// Rearrange the instructions to generate the new, pipelined loop,
// and update register names as needed.
for (int Cycle = Schedule.getFirstCycle(),
LastCycle = Schedule.getFinalCycle();
Cycle <= LastCycle; ++Cycle) {
std::deque<SUnit *> &CycleInstrs = Schedule.getInstructions(Cycle);
// This inner loop schedules each instruction in the cycle.
for (SUnit *CI : CycleInstrs) {
if (CI->getInstr()->isPHI())
continue;
unsigned StageNum = Schedule.stageScheduled(getSUnit(CI->getInstr()));
MachineInstr *NewMI = cloneInstr(CI->getInstr(), MaxStageCount, StageNum);
updateInstruction(NewMI, false, MaxStageCount, StageNum, Schedule, VRMap);
KernelBB->push_back(NewMI);
InstrMap[NewMI] = CI->getInstr();
}
}
// Copy any terminator instructions to the new kernel, and update
// names as needed.
for (MachineBasicBlock::iterator I = BB->getFirstTerminator(),
E = BB->instr_end();
I != E; ++I) {
MachineInstr *NewMI = MF.CloneMachineInstr(&*I);
updateInstruction(NewMI, false, MaxStageCount, 0, Schedule, VRMap);
KernelBB->push_back(NewMI);
InstrMap[NewMI] = &*I;
}
KernelBB->transferSuccessors(BB);
KernelBB->replaceSuccessor(BB, KernelBB);
generateExistingPhis(KernelBB, PrologBBs.back(), KernelBB, KernelBB, Schedule,
VRMap, InstrMap, MaxStageCount, MaxStageCount, false);
generatePhis(KernelBB, PrologBBs.back(), KernelBB, KernelBB, Schedule, VRMap,
InstrMap, MaxStageCount, MaxStageCount, false);
DEBUG(dbgs() << "New block\n"; KernelBB->dump(););
SmallVector<MachineBasicBlock *, 4> EpilogBBs;
// Generate the epilog instructions to complete the pipeline.
generateEpilog(Schedule, MaxStageCount, KernelBB, VRMap, EpilogBBs,
PrologBBs);
// We need this step because the register allocation doesn't handle some
// situations well, so we insert copies to help out.
splitLifetimes(KernelBB, EpilogBBs, Schedule);
// Remove dead instructions due to loop induction variables.
removeDeadInstructions(KernelBB, EpilogBBs);
// Add branches between prolog and epilog blocks.
addBranches(PrologBBs, KernelBB, EpilogBBs, Schedule, VRMap);
// Remove the original loop since it's no longer referenced.
BB->clear();
BB->eraseFromParent();
delete[] VRMap;
}
/// Generate the pipeline prolog code.
void SwingSchedulerDAG::generateProlog(SMSchedule &Schedule, unsigned LastStage,
MachineBasicBlock *KernelBB,
ValueMapTy *VRMap,
MBBVectorTy &PrologBBs) {
MachineBasicBlock *PreheaderBB = MLI->getLoopFor(BB)->getLoopPreheader();
assert(PreheaderBB != NULL &&
"Need to add code to handle loops w/o preheader");
MachineBasicBlock *PredBB = PreheaderBB;
InstrMapTy InstrMap;
// Generate a basic block for each stage, not including the last stage,
// which will be generated in the kernel. Each basic block may contain
// instructions from multiple stages/iterations.
for (unsigned i = 0; i < LastStage; ++i) {
// Create and insert the prolog basic block prior to the original loop
// basic block. The original loop is removed later.
MachineBasicBlock *NewBB = MF.CreateMachineBasicBlock(BB->getBasicBlock());
PrologBBs.push_back(NewBB);
MF.insert(BB->getIterator(), NewBB);
NewBB->transferSuccessors(PredBB);
PredBB->addSuccessor(NewBB);
PredBB = NewBB;
// Generate instructions for each appropriate stage. Process instructions
// in original program order.
for (int StageNum = i; StageNum >= 0; --StageNum) {
for (MachineBasicBlock::iterator BBI = BB->instr_begin(),
BBE = BB->getFirstTerminator();
BBI != BBE; ++BBI) {
if (Schedule.isScheduledAtStage(getSUnit(&*BBI), (unsigned)StageNum)) {
if (BBI->isPHI())
continue;
MachineInstr *NewMI =
cloneAndChangeInstr(&*BBI, i, (unsigned)StageNum, Schedule);
updateInstruction(NewMI, false, i, (unsigned)StageNum, Schedule,
VRMap);
NewBB->push_back(NewMI);
InstrMap[NewMI] = &*BBI;
}
}
}
rewritePhiValues(NewBB, i, Schedule, VRMap, InstrMap);
DEBUG({
dbgs() << "prolog:\n";
NewBB->dump();
});
}
PredBB->replaceSuccessor(BB, KernelBB);
// Check if we need to remove the branch from the preheader to the original
// loop, and replace it with a branch to the new loop.
unsigned numBranches = TII->removeBranch(*PreheaderBB);
if (numBranches) {
SmallVector<MachineOperand, 0> Cond;
TII->insertBranch(*PreheaderBB, PrologBBs[0], nullptr, Cond, DebugLoc());
}
}
/// Generate the pipeline epilog code. The epilog code finishes the iterations
/// that were started in either the prolog or the kernel. We create a basic
/// block for each stage that needs to complete.
void SwingSchedulerDAG::generateEpilog(SMSchedule &Schedule, unsigned LastStage,
MachineBasicBlock *KernelBB,
ValueMapTy *VRMap,
MBBVectorTy &EpilogBBs,
MBBVectorTy &PrologBBs) {
// We need to change the branch from the kernel to the first epilog block, so
// this call to analyze branch uses the kernel rather than the original BB.
MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
SmallVector<MachineOperand, 4> Cond;
bool checkBranch = TII->analyzeBranch(*KernelBB, TBB, FBB, Cond);
assert(!checkBranch && "generateEpilog must be able to analyze the branch");
if (checkBranch)
return;
MachineBasicBlock::succ_iterator LoopExitI = KernelBB->succ_begin();
if (*LoopExitI == KernelBB)
++LoopExitI;
assert(LoopExitI != KernelBB->succ_end() && "Expecting a successor");
MachineBasicBlock *LoopExitBB = *LoopExitI;
MachineBasicBlock *PredBB = KernelBB;
MachineBasicBlock *EpilogStart = LoopExitBB;
InstrMapTy InstrMap;
// Generate a basic block for each stage, not including the last stage,
// which was generated for the kernel. Each basic block may contain
// instructions from multiple stages/iterations.
int EpilogStage = LastStage + 1;
for (unsigned i = LastStage; i >= 1; --i, ++EpilogStage) {
MachineBasicBlock *NewBB = MF.CreateMachineBasicBlock();
EpilogBBs.push_back(NewBB);
MF.insert(BB->getIterator(), NewBB);
PredBB->replaceSuccessor(LoopExitBB, NewBB);
NewBB->addSuccessor(LoopExitBB);
if (EpilogStart == LoopExitBB)
EpilogStart = NewBB;
// Add instructions to the epilog depending on the current block.
// Process instructions in original program order.
for (unsigned StageNum = i; StageNum <= LastStage; ++StageNum) {
for (auto &BBI : *BB) {
if (BBI.isPHI())
continue;
MachineInstr *In = &BBI;
if (Schedule.isScheduledAtStage(getSUnit(In), StageNum)) {
MachineInstr *NewMI = cloneInstr(In, EpilogStage - LastStage, 0);
updateInstruction(NewMI, i == 1, EpilogStage, 0, Schedule, VRMap);
NewBB->push_back(NewMI);
InstrMap[NewMI] = In;
}
}
}
generateExistingPhis(NewBB, PrologBBs[i - 1], PredBB, KernelBB, Schedule,
VRMap, InstrMap, LastStage, EpilogStage, i == 1);
generatePhis(NewBB, PrologBBs[i - 1], PredBB, KernelBB, Schedule, VRMap,
InstrMap, LastStage, EpilogStage, i == 1);
PredBB = NewBB;
DEBUG({
dbgs() << "epilog:\n";
NewBB->dump();
});
}
// Fix any Phi nodes in the loop exit block.
for (MachineInstr &MI : *LoopExitBB) {
if (!MI.isPHI())
break;
for (unsigned i = 2, e = MI.getNumOperands() + 1; i != e; i += 2) {
MachineOperand &MO = MI.getOperand(i);
if (MO.getMBB() == BB)
MO.setMBB(PredBB);
}
}
// Create a branch to the new epilog from the kernel.
// Remove the original branch and add a new branch to the epilog.
TII->removeBranch(*KernelBB);
TII->insertBranch(*KernelBB, KernelBB, EpilogStart, Cond, DebugLoc());
// Add a branch to the loop exit.
if (EpilogBBs.size() > 0) {
MachineBasicBlock *LastEpilogBB = EpilogBBs.back();
SmallVector<MachineOperand, 4> Cond1;
TII->insertBranch(*LastEpilogBB, LoopExitBB, nullptr, Cond1, DebugLoc());
}
}
/// Replace all uses of FromReg that appear outside the specified
/// basic block with ToReg.
static void replaceRegUsesAfterLoop(unsigned FromReg, unsigned ToReg,
MachineBasicBlock *MBB,
MachineRegisterInfo &MRI,
LiveIntervals &LIS) {
for (MachineRegisterInfo::use_iterator I = MRI.use_begin(FromReg),
E = MRI.use_end();
I != E;) {
MachineOperand &O = *I;
++I;
if (O.getParent()->getParent() != MBB)
O.setReg(ToReg);
}
if (!LIS.hasInterval(ToReg))
LIS.createEmptyInterval(ToReg);
}
/// Return true if the register has a use that occurs outside the
/// specified loop.
static bool hasUseAfterLoop(unsigned Reg, MachineBasicBlock *BB,
MachineRegisterInfo &MRI) {
for (MachineRegisterInfo::use_iterator I = MRI.use_begin(Reg),
E = MRI.use_end();
I != E; ++I)
if (I->getParent()->getParent() != BB)
return true;
return false;
}
/// Generate Phis for the specific block in the generated pipelined code.
/// This function looks at the Phis from the original code to guide the
/// creation of new Phis.
void SwingSchedulerDAG::generateExistingPhis(
MachineBasicBlock *NewBB, MachineBasicBlock *BB1, MachineBasicBlock *BB2,
MachineBasicBlock *KernelBB, SMSchedule &Schedule, ValueMapTy *VRMap,
InstrMapTy &InstrMap, unsigned LastStageNum, unsigned CurStageNum,
bool IsLast) {
// Compute the stage number for the initial value of the Phi, which
// comes from the prolog. The prolog to use depends on to which kernel/
// epilog that we're adding the Phi.
unsigned PrologStage = 0;
unsigned PrevStage = 0;
bool InKernel = (LastStageNum == CurStageNum);
if (InKernel) {
PrologStage = LastStageNum - 1;
PrevStage = CurStageNum;
} else {
PrologStage = LastStageNum - (CurStageNum - LastStageNum);
PrevStage = LastStageNum + (CurStageNum - LastStageNum) - 1;
}
for (MachineBasicBlock::iterator BBI = BB->instr_begin(),
BBE = BB->getFirstNonPHI();
BBI != BBE; ++BBI) {
unsigned Def = BBI->getOperand(0).getReg();
unsigned InitVal = 0;
unsigned LoopVal = 0;
getPhiRegs(*BBI, BB, InitVal, LoopVal);
unsigned PhiOp1 = 0;
// The Phi value from the loop body typically is defined in the loop, but
// not always. So, we need to check if the value is defined in the loop.
unsigned PhiOp2 = LoopVal;
if (VRMap[LastStageNum].count(LoopVal))
PhiOp2 = VRMap[LastStageNum][LoopVal];
int StageScheduled = Schedule.stageScheduled(getSUnit(&*BBI));
int LoopValStage =
Schedule.stageScheduled(getSUnit(MRI.getVRegDef(LoopVal)));
unsigned NumStages = Schedule.getStagesForReg(Def, CurStageNum);
if (NumStages == 0) {
// We don't need to generate a Phi anymore, but we need to rename any uses
// of the Phi value.
unsigned NewReg = VRMap[PrevStage][LoopVal];
rewriteScheduledInstr(NewBB, Schedule, InstrMap, CurStageNum, 0, &*BBI,
Def, NewReg);
if (VRMap[CurStageNum].count(LoopVal))
VRMap[CurStageNum][Def] = VRMap[CurStageNum][LoopVal];
}
// Adjust the number of Phis needed depending on the number of prologs left,
// and the distance from where the Phi is first scheduled.
unsigned NumPhis = NumStages;
if (!InKernel && (int)PrologStage < LoopValStage)
// The NumPhis is the maximum number of new Phis needed during the steady
// state. If the Phi has not been scheduled in current prolog, then we
// need to generate less Phis.
NumPhis = std::max((int)NumPhis - (int)(LoopValStage - PrologStage), 1);
// The number of Phis cannot exceed the number of prolog stages. Each
// stage can potentially define two values.
NumPhis = std::min(NumPhis, PrologStage + 2);
unsigned NewReg = 0;
unsigned AccessStage = (LoopValStage != -1) ? LoopValStage : StageScheduled;
// In the epilog, we may need to look back one stage to get the correct
// Phi name because the epilog and prolog blocks execute the same stage.
// The correct name is from the previous block only when the Phi has
// been completely scheduled prior to the epilog, and Phi value is not
// needed in multiple stages.
int StageDiff = 0;
if (!InKernel && StageScheduled >= LoopValStage && AccessStage == 0 &&
NumPhis == 1)
StageDiff = 1;
// Adjust the computations below when the phi and the loop definition
// are scheduled in different stages.
if (InKernel && LoopValStage != -1 && StageScheduled > LoopValStage)
StageDiff = StageScheduled - LoopValStage;
for (unsigned np = 0; np < NumPhis; ++np) {
// If the Phi hasn't been scheduled, then use the initial Phi operand
// value. Otherwise, use the scheduled version of the instruction. This
// is a little complicated when a Phi references another Phi.
if (np > PrologStage || StageScheduled >= (int)LastStageNum)
PhiOp1 = InitVal;
// Check if the Phi has already been scheduled in a prolog stage.
else if (PrologStage >= AccessStage + StageDiff + np &&
VRMap[PrologStage - StageDiff - np].count(LoopVal) != 0)
PhiOp1 = VRMap[PrologStage - StageDiff - np][LoopVal];
// Check if the Phi has already been scheduled, but the loop intruction
// is either another Phi, or doesn't occur in the loop.
else if (PrologStage >= AccessStage + StageDiff + np) {
// If the Phi references another Phi, we need to examine the other
// Phi to get the correct value.
PhiOp1 = LoopVal;
MachineInstr *InstOp1 = MRI.getVRegDef(PhiOp1);
int Indirects = 1;
while (InstOp1 && InstOp1->isPHI() && InstOp1->getParent() == BB) {
int PhiStage = Schedule.stageScheduled(getSUnit(InstOp1));
if ((int)(PrologStage - StageDiff - np) < PhiStage + Indirects)
PhiOp1 = getInitPhiReg(*InstOp1, BB);
else
PhiOp1 = getLoopPhiReg(*InstOp1, BB);
InstOp1 = MRI.getVRegDef(PhiOp1);
int PhiOpStage = Schedule.stageScheduled(getSUnit(InstOp1));
int StageAdj = (PhiOpStage != -1 ? PhiStage - PhiOpStage : 0);
if (PhiOpStage != -1 && PrologStage - StageAdj >= Indirects + np &&
VRMap[PrologStage - StageAdj - Indirects - np].count(PhiOp1)) {
PhiOp1 = VRMap[PrologStage - StageAdj - Indirects - np][PhiOp1];
break;
}
++Indirects;
}
} else
PhiOp1 = InitVal;
// If this references a generated Phi in the kernel, get the Phi operand
// from the incoming block.
if (MachineInstr *InstOp1 = MRI.getVRegDef(PhiOp1))
if (InstOp1->isPHI() && InstOp1->getParent() == KernelBB)
PhiOp1 = getInitPhiReg(*InstOp1, KernelBB);
MachineInstr *PhiInst = MRI.getVRegDef(LoopVal);
bool LoopDefIsPhi = PhiInst && PhiInst->isPHI();
// In the epilog, a map lookup is needed to get the value from the kernel,
// or previous epilog block. How is does this depends on if the
// instruction is scheduled in the previous block.
if (!InKernel) {
int StageDiffAdj = 0;
if (LoopValStage != -1 && StageScheduled > LoopValStage)
StageDiffAdj = StageScheduled - LoopValStage;
// Use the loop value defined in the kernel, unless the kernel
// contains the last definition of the Phi.
if (np == 0 && PrevStage == LastStageNum &&
(StageScheduled != 0 || LoopValStage != 0) &&
VRMap[PrevStage - StageDiffAdj].count(LoopVal))
PhiOp2 = VRMap[PrevStage - StageDiffAdj][LoopVal];
// Use the value defined by the Phi. We add one because we switch
// from looking at the loop value to the Phi definition.
else if (np > 0 && PrevStage == LastStageNum &&
VRMap[PrevStage - np + 1].count(Def))
PhiOp2 = VRMap[PrevStage - np + 1][Def];
// Use the loop value defined in the kernel.
else if ((unsigned)LoopValStage + StageDiffAdj > PrologStage + 1 &&
VRMap[PrevStage - StageDiffAdj - np].count(LoopVal))
PhiOp2 = VRMap[PrevStage - StageDiffAdj - np][LoopVal];
// Use the value defined by the Phi, unless we're generating the first
// epilog and the Phi refers to a Phi in a different stage.
else if (VRMap[PrevStage - np].count(Def) &&
(!LoopDefIsPhi || PrevStage != LastStageNum))
PhiOp2 = VRMap[PrevStage - np][Def];
}
// Check if we can reuse an existing Phi. This occurs when a Phi
// references another Phi, and the other Phi is scheduled in an
// earlier stage. We can try to reuse an existing Phi up until the last
// stage of the current Phi.
if (LoopDefIsPhi && (int)PrologStage >= StageScheduled) {
int LVNumStages = Schedule.getStagesForPhi(LoopVal);
int StageDiff = (StageScheduled - LoopValStage);
LVNumStages -= StageDiff;
if (LVNumStages > (int)np) {
NewReg = PhiOp2;
unsigned ReuseStage = CurStageNum;
if (Schedule.isLoopCarried(this, *PhiInst))
ReuseStage -= LVNumStages;
// Check if the Phi to reuse has been generated yet. If not, then
// there is nothing to reuse.
if (VRMap[ReuseStage].count(LoopVal)) {
NewReg = VRMap[ReuseStage][LoopVal];
rewriteScheduledInstr(NewBB, Schedule, InstrMap, CurStageNum, np,
&*BBI, Def, NewReg);
// Update the map with the new Phi name.
VRMap[CurStageNum - np][Def] = NewReg;
PhiOp2 = NewReg;
if (VRMap[LastStageNum - np - 1].count(LoopVal))
PhiOp2 = VRMap[LastStageNum - np - 1][LoopVal];
if (IsLast && np == NumPhis - 1)
replaceRegUsesAfterLoop(Def, NewReg, BB, MRI, LIS);
continue;
}
} else if (InKernel && StageDiff > 0 &&
VRMap[CurStageNum - StageDiff - np].count(LoopVal))
PhiOp2 = VRMap[CurStageNum - StageDiff - np][LoopVal];
}
const TargetRegisterClass *RC = MRI.getRegClass(Def);
NewReg = MRI.createVirtualRegister(RC);
MachineInstrBuilder NewPhi =
BuildMI(*NewBB, NewBB->getFirstNonPHI(), DebugLoc(),
TII->get(TargetOpcode::PHI), NewReg);
NewPhi.addReg(PhiOp1).addMBB(BB1);
NewPhi.addReg(PhiOp2).addMBB(BB2);
if (np == 0)
InstrMap[NewPhi] = &*BBI;
// We define the Phis after creating the new pipelined code, so
// we need to rename the Phi values in scheduled instructions.
unsigned PrevReg = 0;
if (InKernel && VRMap[PrevStage - np].count(LoopVal))
PrevReg = VRMap[PrevStage - np][LoopVal];
rewriteScheduledInstr(NewBB, Schedule, InstrMap, CurStageNum, np, &*BBI,
Def, NewReg, PrevReg);
// If the Phi has been scheduled, use the new name for rewriting.
if (VRMap[CurStageNum - np].count(Def)) {
unsigned R = VRMap[CurStageNum - np][Def];
rewriteScheduledInstr(NewBB, Schedule, InstrMap, CurStageNum, np, &*BBI,
R, NewReg);
}
// Check if we need to rename any uses that occurs after the loop. The
// register to replace depends on whether the Phi is scheduled in the
// epilog.
if (IsLast && np == NumPhis - 1)
replaceRegUsesAfterLoop(Def, NewReg, BB, MRI, LIS);
// In the kernel, a dependent Phi uses the value from this Phi.
if (InKernel)
PhiOp2 = NewReg;
// Update the map with the new Phi name.
VRMap[CurStageNum - np][Def] = NewReg;
}
while (NumPhis++ < NumStages) {
rewriteScheduledInstr(NewBB, Schedule, InstrMap, CurStageNum, NumPhis,
&*BBI, Def, NewReg, 0);
}
// Check if we need to rename a Phi that has been eliminated due to
// scheduling.
if (NumStages == 0 && IsLast && VRMap[CurStageNum].count(LoopVal))
replaceRegUsesAfterLoop(Def, VRMap[CurStageNum][LoopVal], BB, MRI, LIS);
}
}
/// Generate Phis for the specified block in the generated pipelined code.
/// These are new Phis needed because the definition is scheduled after the
/// use in the pipelened sequence.
void SwingSchedulerDAG::generatePhis(
MachineBasicBlock *NewBB, MachineBasicBlock *BB1, MachineBasicBlock *BB2,
MachineBasicBlock *KernelBB, SMSchedule &Schedule, ValueMapTy *VRMap,
InstrMapTy &InstrMap, unsigned LastStageNum, unsigned CurStageNum,
bool IsLast) {
// Compute the stage number that contains the initial Phi value, and
// the Phi from the previous stage.
unsigned PrologStage = 0;
unsigned PrevStage = 0;
unsigned StageDiff = CurStageNum - LastStageNum;
bool InKernel = (StageDiff == 0);
if (InKernel) {
PrologStage = LastStageNum - 1;
PrevStage = CurStageNum;
} else {
PrologStage = LastStageNum - StageDiff;
PrevStage = LastStageNum + StageDiff - 1;
}
for (MachineBasicBlock::iterator BBI = BB->getFirstNonPHI(),
BBE = BB->instr_end();
BBI != BBE; ++BBI) {
for (unsigned i = 0, e = BBI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = BBI->getOperand(i);
if (!MO.isReg() || !MO.isDef() ||
!TargetRegisterInfo::isVirtualRegister(MO.getReg()))
continue;
int StageScheduled = Schedule.stageScheduled(getSUnit(&*BBI));
assert(StageScheduled != -1 && "Expecting scheduled instruction.");
unsigned Def = MO.getReg();
unsigned NumPhis = Schedule.getStagesForReg(Def, CurStageNum);
// An instruction scheduled in stage 0 and is used after the loop
// requires a phi in the epilog for the last definition from either
// the kernel or prolog.
if (!InKernel && NumPhis == 0 && StageScheduled == 0 &&
hasUseAfterLoop(Def, BB, MRI))
NumPhis = 1;
if (!InKernel && (unsigned)StageScheduled > PrologStage)
continue;
unsigned PhiOp2 = VRMap[PrevStage][Def];
if (MachineInstr *InstOp2 = MRI.getVRegDef(PhiOp2))
if (InstOp2->isPHI() && InstOp2->getParent() == NewBB)
PhiOp2 = getLoopPhiReg(*InstOp2, BB2);
// The number of Phis can't exceed the number of prolog stages. The
// prolog stage number is zero based.
if (NumPhis > PrologStage + 1 - StageScheduled)
NumPhis = PrologStage + 1 - StageScheduled;
for (unsigned np = 0; np < NumPhis; ++np) {
unsigned PhiOp1 = VRMap[PrologStage][Def];
if (np <= PrologStage)
PhiOp1 = VRMap[PrologStage - np][Def];
if (MachineInstr *InstOp1 = MRI.getVRegDef(PhiOp1)) {
if (InstOp1->isPHI() && InstOp1->getParent() == KernelBB)
PhiOp1 = getInitPhiReg(*InstOp1, KernelBB);
if (InstOp1->isPHI() && InstOp1->getParent() == NewBB)
PhiOp1 = getInitPhiReg(*InstOp1, NewBB);
}
if (!InKernel)
PhiOp2 = VRMap[PrevStage - np][Def];
const TargetRegisterClass *RC = MRI.getRegClass(Def);
unsigned NewReg = MRI.createVirtualRegister(RC);
MachineInstrBuilder NewPhi =
BuildMI(*NewBB, NewBB->getFirstNonPHI(), DebugLoc(),
TII->get(TargetOpcode::PHI), NewReg);
NewPhi.addReg(PhiOp1).addMBB(BB1);
NewPhi.addReg(PhiOp2).addMBB(BB2);
if (np == 0)
InstrMap[NewPhi] = &*BBI;
// Rewrite uses and update the map. The actions depend upon whether
// we generating code for the kernel or epilog blocks.
if (InKernel) {
rewriteScheduledInstr(NewBB, Schedule, InstrMap, CurStageNum, np,
&*BBI, PhiOp1, NewReg);
rewriteScheduledInstr(NewBB, Schedule, InstrMap, CurStageNum, np,
&*BBI, PhiOp2, NewReg);
PhiOp2 = NewReg;
VRMap[PrevStage - np - 1][Def] = NewReg;
} else {
VRMap[CurStageNum - np][Def] = NewReg;
if (np == NumPhis - 1)
rewriteScheduledInstr(NewBB, Schedule, InstrMap, CurStageNum, np,
&*BBI, Def, NewReg);
}
if (IsLast && np == NumPhis - 1)
replaceRegUsesAfterLoop(Def, NewReg, BB, MRI, LIS);
}
}
}
}
/// Remove instructions that generate values with no uses.
/// Typically, these are induction variable operations that generate values
/// used in the loop itself. A dead instruction has a definition with
/// no uses, or uses that occur in the original loop only.
void SwingSchedulerDAG::removeDeadInstructions(MachineBasicBlock *KernelBB,
MBBVectorTy &EpilogBBs) {
// For each epilog block, check that the value defined by each instruction
// is used. If not, delete it.
for (MBBVectorTy::reverse_iterator MBB = EpilogBBs.rbegin(),
MBE = EpilogBBs.rend();
MBB != MBE; ++MBB)
for (MachineBasicBlock::reverse_instr_iterator MI = (*MBB)->instr_rbegin(),
ME = (*MBB)->instr_rend();
MI != ME;) {
// From DeadMachineInstructionElem. Don't delete inline assembly.
if (MI->isInlineAsm()) {
++MI;
continue;
}
bool SawStore = false;
// Check if it's safe to remove the instruction due to side effects.
// We can, and want to, remove Phis here.
if (!MI->isSafeToMove(nullptr, SawStore) && !MI->isPHI()) {
++MI;
continue;
}
bool used = true;
for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
MOE = MI->operands_end();
MOI != MOE; ++MOI) {
if (!MOI->isReg() || !MOI->isDef())
continue;
unsigned reg = MOI->getReg();
unsigned realUses = 0;
for (MachineRegisterInfo::use_iterator UI = MRI.use_begin(reg),
EI = MRI.use_end();
UI != EI; ++UI) {
// Check if there are any uses that occur only in the original
// loop. If so, that's not a real use.
if (UI->getParent()->getParent() != BB) {
realUses++;
used = true;
break;
}
}
if (realUses > 0)
break;
used = false;
}
if (!used) {
MI++->eraseFromParent();
continue;
}
++MI;
}
// In the kernel block, check if we can remove a Phi that generates a value
// used in an instruction removed in the epilog block.
for (MachineBasicBlock::iterator BBI = KernelBB->instr_begin(),
BBE = KernelBB->getFirstNonPHI();
BBI != BBE;) {
MachineInstr *MI = &*BBI;
++BBI;
unsigned reg = MI->getOperand(0).getReg();
if (MRI.use_begin(reg) == MRI.use_end()) {
MI->eraseFromParent();
}
}
}
/// For loop carried definitions, we split the lifetime of a virtual register
/// that has uses past the definition in the next iteration. A copy with a new
/// virtual register is inserted before the definition, which helps with
/// generating a better register assignment.
///
/// v1 = phi(a, v2) v1 = phi(a, v2)
/// v2 = phi(b, v3) v2 = phi(b, v3)
/// v3 = .. v4 = copy v1
/// .. = V1 v3 = ..
/// .. = v4
void SwingSchedulerDAG::splitLifetimes(MachineBasicBlock *KernelBB,
MBBVectorTy &EpilogBBs,
SMSchedule &Schedule) {
const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
for (MachineBasicBlock::iterator BBI = KernelBB->instr_begin(),
BBF = KernelBB->getFirstNonPHI();
BBI != BBF; ++BBI) {
unsigned Def = BBI->getOperand(0).getReg();
// Check for any Phi definition that used as an operand of another Phi
// in the same block.
for (MachineRegisterInfo::use_instr_iterator I = MRI.use_instr_begin(Def),
E = MRI.use_instr_end();
I != E; ++I) {
if (I->isPHI() && I->getParent() == KernelBB) {
// Get the loop carried definition.
unsigned LCDef = getLoopPhiReg(*BBI, KernelBB);
if (!LCDef)
continue;
MachineInstr *MI = MRI.getVRegDef(LCDef);
if (!MI || MI->getParent() != KernelBB || MI->isPHI())
continue;
// Search through the rest of the block looking for uses of the Phi
// definition. If one occurs, then split the lifetime.
unsigned SplitReg = 0;
for (auto &BBJ : make_range(MachineBasicBlock::instr_iterator(MI),
KernelBB->instr_end()))
if (BBJ.readsRegister(Def)) {
// We split the lifetime when we find the first use.
if (SplitReg == 0) {
SplitReg = MRI.createVirtualRegister(MRI.getRegClass(Def));
BuildMI(*KernelBB, MI, MI->getDebugLoc(),
TII->get(TargetOpcode::COPY), SplitReg)
.addReg(Def);
}
BBJ.substituteRegister(Def, SplitReg, 0, *TRI);
}
if (!SplitReg)
continue;
// Search through each of the epilog blocks for any uses to be renamed.
for (auto &Epilog : EpilogBBs)
for (auto &I : *Epilog)
if (I.readsRegister(Def))
I.substituteRegister(Def, SplitReg, 0, *TRI);
break;
}
}
}
}
/// Remove the incoming block from the Phis in a basic block.
static void removePhis(MachineBasicBlock *BB, MachineBasicBlock *Incoming) {
for (MachineInstr &MI : *BB) {
if (!MI.isPHI())
break;
for (unsigned i = 1, e = MI.getNumOperands(); i != e; i += 2)
if (MI.getOperand(i + 1).getMBB() == Incoming) {
MI.RemoveOperand(i + 1);
MI.RemoveOperand(i);
break;
}
}
}
/// Create branches from each prolog basic block to the appropriate epilog
/// block. These edges are needed if the loop ends before reaching the
/// kernel.
void SwingSchedulerDAG::addBranches(MBBVectorTy &PrologBBs,
MachineBasicBlock *KernelBB,
MBBVectorTy &EpilogBBs,
SMSchedule &Schedule, ValueMapTy *VRMap) {
assert(PrologBBs.size() == EpilogBBs.size() && "Prolog/Epilog mismatch");
MachineInstr *IndVar = Pass.LI.LoopInductionVar;
MachineInstr *Cmp = Pass.LI.LoopCompare;
MachineBasicBlock *LastPro = KernelBB;
MachineBasicBlock *LastEpi = KernelBB;
// Start from the blocks connected to the kernel and work "out"
// to the first prolog and the last epilog blocks.
SmallVector<MachineInstr *, 4> PrevInsts;
unsigned MaxIter = PrologBBs.size() - 1;
unsigned LC = UINT_MAX;
unsigned LCMin = UINT_MAX;
for (unsigned i = 0, j = MaxIter; i <= MaxIter; ++i, --j) {
// Add branches to the prolog that go to the corresponding
// epilog, and the fall-thru prolog/kernel block.
MachineBasicBlock *Prolog = PrologBBs[j];
MachineBasicBlock *Epilog = EpilogBBs[i];
// We've executed one iteration, so decrement the loop count and check for
// the loop end.
SmallVector<MachineOperand, 4> Cond;
// Check if the LOOP0 has already been removed. If so, then there is no need
// to reduce the trip count.
if (LC != 0)
LC = TII->reduceLoopCount(*Prolog, IndVar, *Cmp, Cond, PrevInsts, j,
MaxIter);
// Record the value of the first trip count, which is used to determine if
// branches and blocks can be removed for constant trip counts.
if (LCMin == UINT_MAX)
LCMin = LC;
unsigned numAdded = 0;
if (TargetRegisterInfo::isVirtualRegister(LC)) {
Prolog->addSuccessor(Epilog);
numAdded = TII->insertBranch(*Prolog, Epilog, LastPro, Cond, DebugLoc());
} else if (j >= LCMin) {
Prolog->addSuccessor(Epilog);
Prolog->removeSuccessor(LastPro);
LastEpi->removeSuccessor(Epilog);
numAdded = TII->insertBranch(*Prolog, Epilog, nullptr, Cond, DebugLoc());
removePhis(Epilog, LastEpi);
// Remove the blocks that are no longer referenced.
if (LastPro != LastEpi) {
LastEpi->clear();
LastEpi->eraseFromParent();
}
LastPro->clear();
LastPro->eraseFromParent();
} else {
numAdded = TII->insertBranch(*Prolog, LastPro, nullptr, Cond, DebugLoc());
removePhis(Epilog, Prolog);
}
LastPro = Prolog;
LastEpi = Epilog;
for (MachineBasicBlock::reverse_instr_iterator I = Prolog->instr_rbegin(),
E = Prolog->instr_rend();
I != E && numAdded > 0; ++I, --numAdded)
updateInstruction(&*I, false, j, 0, Schedule, VRMap);
}
}
/// Return true if we can compute the amount the instruction changes
/// during each iteration. Set Delta to the amount of the change.
bool SwingSchedulerDAG::computeDelta(MachineInstr &MI, unsigned &Delta) {
const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
unsigned BaseReg;
int64_t Offset;
if (!TII->getMemOpBaseRegImmOfs(MI, BaseReg, Offset, TRI))
return false;
MachineRegisterInfo &MRI = MF.getRegInfo();
// Check if there is a Phi. If so, get the definition in the loop.
MachineInstr *BaseDef = MRI.getVRegDef(BaseReg);
if (BaseDef && BaseDef->isPHI()) {
BaseReg = getLoopPhiReg(*BaseDef, MI.getParent());
BaseDef = MRI.getVRegDef(BaseReg);
}
if (!BaseDef)
return false;
int D = 0;
if (!TII->getIncrementValue(*BaseDef, D) && D >= 0)
return false;
Delta = D;
return true;
}
/// Update the memory operand with a new offset when the pipeliner
/// generates a new copy of the instruction that refers to a
/// different memory location.
void SwingSchedulerDAG::updateMemOperands(MachineInstr &NewMI,
MachineInstr &OldMI, unsigned Num) {
if (Num == 0)
return;
// If the instruction has memory operands, then adjust the offset
// when the instruction appears in different stages.
unsigned NumRefs = NewMI.memoperands_end() - NewMI.memoperands_begin();
if (NumRefs == 0)
return;
MachineInstr::mmo_iterator NewMemRefs = MF.allocateMemRefsArray(NumRefs);
unsigned Refs = 0;
for (MachineMemOperand *MMO : NewMI.memoperands()) {
if (MMO->isVolatile() || (MMO->isInvariant() && MMO->isDereferenceable()) ||
(!MMO->getValue())) {
NewMemRefs[Refs++] = MMO;
continue;
}
unsigned Delta;
if (computeDelta(OldMI, Delta)) {
int64_t AdjOffset = Delta * Num;
NewMemRefs[Refs++] =
MF.getMachineMemOperand(MMO, AdjOffset, MMO->getSize());
} else
NewMemRefs[Refs++] = MF.getMachineMemOperand(MMO, 0, UINT64_MAX);
}
NewMI.setMemRefs(NewMemRefs, NewMemRefs + NumRefs);
}
/// Clone the instruction for the new pipelined loop and update the
/// memory operands, if needed.
MachineInstr *SwingSchedulerDAG::cloneInstr(MachineInstr *OldMI,
unsigned CurStageNum,
unsigned InstStageNum) {
MachineInstr *NewMI = MF.CloneMachineInstr(OldMI);
// Check for tied operands in inline asm instructions. This should be handled
// elsewhere, but I'm not sure of the best solution.
if (OldMI->isInlineAsm())
for (unsigned i = 0, e = OldMI->getNumOperands(); i != e; ++i) {
const auto &MO = OldMI->getOperand(i);
if (MO.isReg() && MO.isUse())
break;
unsigned UseIdx;
if (OldMI->isRegTiedToUseOperand(i, &UseIdx))
NewMI->tieOperands(i, UseIdx);
}
updateMemOperands(*NewMI, *OldMI, CurStageNum - InstStageNum);
return NewMI;
}
/// Clone the instruction for the new pipelined loop. If needed, this
/// function updates the instruction using the values saved in the
/// InstrChanges structure.
MachineInstr *SwingSchedulerDAG::cloneAndChangeInstr(MachineInstr *OldMI,
unsigned CurStageNum,
unsigned InstStageNum,
SMSchedule &Schedule) {
MachineInstr *NewMI = MF.CloneMachineInstr(OldMI);
DenseMap<SUnit *, std::pair<unsigned, int64_t>>::iterator It =
InstrChanges.find(getSUnit(OldMI));
if (It != InstrChanges.end()) {
std::pair<unsigned, int64_t> RegAndOffset = It->second;
unsigned BasePos, OffsetPos;
if (!TII->getBaseAndOffsetPosition(*OldMI, BasePos, OffsetPos))
return nullptr;
int64_t NewOffset = OldMI->getOperand(OffsetPos).getImm();
MachineInstr *LoopDef = findDefInLoop(RegAndOffset.first);
if (Schedule.stageScheduled(getSUnit(LoopDef)) > (signed)InstStageNum)
NewOffset += RegAndOffset.second * (CurStageNum - InstStageNum);
NewMI->getOperand(OffsetPos).setImm(NewOffset);
}
updateMemOperands(*NewMI, *OldMI, CurStageNum - InstStageNum);
return NewMI;
}
/// Update the machine instruction with new virtual registers. This
/// function may change the defintions and/or uses.
void SwingSchedulerDAG::updateInstruction(MachineInstr *NewMI, bool LastDef,
unsigned CurStageNum,
unsigned InstrStageNum,
SMSchedule &Schedule,
ValueMapTy *VRMap) {
for (unsigned i = 0, e = NewMI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = NewMI->getOperand(i);
if (!MO.isReg() || !TargetRegisterInfo::isVirtualRegister(MO.getReg()))
continue;
unsigned reg = MO.getReg();
if (MO.isDef()) {
// Create a new virtual register for the definition.
const TargetRegisterClass *RC = MRI.getRegClass(reg);
unsigned NewReg = MRI.createVirtualRegister(RC);
MO.setReg(NewReg);
VRMap[CurStageNum][reg] = NewReg;
if (LastDef)
replaceRegUsesAfterLoop(reg, NewReg, BB, MRI, LIS);
} else if (MO.isUse()) {
MachineInstr *Def = MRI.getVRegDef(reg);
// Compute the stage that contains the last definition for instruction.
int DefStageNum = Schedule.stageScheduled(getSUnit(Def));
unsigned StageNum = CurStageNum;
if (DefStageNum != -1 && (int)InstrStageNum > DefStageNum) {
// Compute the difference in stages between the defintion and the use.
unsigned StageDiff = (InstrStageNum - DefStageNum);
// Make an adjustment to get the last definition.
StageNum -= StageDiff;
}
if (VRMap[StageNum].count(reg))
MO.setReg(VRMap[StageNum][reg]);
}
}
}
/// Return the instruction in the loop that defines the register.
/// If the definition is a Phi, then follow the Phi operand to
/// the instruction in the loop.
MachineInstr *SwingSchedulerDAG::findDefInLoop(unsigned Reg) {
SmallPtrSet<MachineInstr *, 8> Visited;
MachineInstr *Def = MRI.getVRegDef(Reg);
while (Def->isPHI()) {
if (!Visited.insert(Def).second)
break;
for (unsigned i = 1, e = Def->getNumOperands(); i < e; i += 2)
if (Def->getOperand(i + 1).getMBB() == BB) {
Def = MRI.getVRegDef(Def->getOperand(i).getReg());
break;
}
}
return Def;
}
/// Return the new name for the value from the previous stage.
unsigned SwingSchedulerDAG::getPrevMapVal(unsigned StageNum, unsigned PhiStage,
unsigned LoopVal, unsigned LoopStage,
ValueMapTy *VRMap,
MachineBasicBlock *BB) {
unsigned PrevVal = 0;
if (StageNum > PhiStage) {
MachineInstr *LoopInst = MRI.getVRegDef(LoopVal);
if (PhiStage == LoopStage && VRMap[StageNum - 1].count(LoopVal))
// The name is defined in the previous stage.
PrevVal = VRMap[StageNum - 1][LoopVal];
else if (VRMap[StageNum].count(LoopVal))
// The previous name is defined in the current stage when the instruction
// order is swapped.
PrevVal = VRMap[StageNum][LoopVal];
else if (!LoopInst->isPHI() || LoopInst->getParent() != BB)
// The loop value hasn't yet been scheduled.
PrevVal = LoopVal;
else if (StageNum == PhiStage + 1)
// The loop value is another phi, which has not been scheduled.
PrevVal = getInitPhiReg(*LoopInst, BB);
else if (StageNum > PhiStage + 1 && LoopInst->getParent() == BB)
// The loop value is another phi, which has been scheduled.
PrevVal =
getPrevMapVal(StageNum - 1, PhiStage, getLoopPhiReg(*LoopInst, BB),
LoopStage, VRMap, BB);
}
return PrevVal;
}
/// Rewrite the Phi values in the specified block to use the mappings
/// from the initial operand. Once the Phi is scheduled, we switch
/// to using the loop value instead of the Phi value, so those names
/// do not need to be rewritten.
void SwingSchedulerDAG::rewritePhiValues(MachineBasicBlock *NewBB,
unsigned StageNum,
SMSchedule &Schedule,
ValueMapTy *VRMap,
InstrMapTy &InstrMap) {
for (MachineBasicBlock::iterator BBI = BB->instr_begin(),
BBE = BB->getFirstNonPHI();
BBI != BBE; ++BBI) {
unsigned InitVal = 0;
unsigned LoopVal = 0;
getPhiRegs(*BBI, BB, InitVal, LoopVal);
unsigned PhiDef = BBI->getOperand(0).getReg();
unsigned PhiStage =
(unsigned)Schedule.stageScheduled(getSUnit(MRI.getVRegDef(PhiDef)));
unsigned LoopStage =
(unsigned)Schedule.stageScheduled(getSUnit(MRI.getVRegDef(LoopVal)));
unsigned NumPhis = Schedule.getStagesForPhi(PhiDef);
if (NumPhis > StageNum)
NumPhis = StageNum;
for (unsigned np = 0; np <= NumPhis; ++np) {
unsigned NewVal =
getPrevMapVal(StageNum - np, PhiStage, LoopVal, LoopStage, VRMap, BB);
if (!NewVal)
NewVal = InitVal;
rewriteScheduledInstr(NewBB, Schedule, InstrMap, StageNum - np, np, &*BBI,
PhiDef, NewVal);
}
}
}
/// Rewrite a previously scheduled instruction to use the register value
/// from the new instruction. Make sure the instruction occurs in the
/// basic block, and we don't change the uses in the new instruction.
void SwingSchedulerDAG::rewriteScheduledInstr(
MachineBasicBlock *BB, SMSchedule &Schedule, InstrMapTy &InstrMap,
unsigned CurStageNum, unsigned PhiNum, MachineInstr *Phi, unsigned OldReg,
unsigned NewReg, unsigned PrevReg) {
bool InProlog = (CurStageNum < Schedule.getMaxStageCount());
int StagePhi = Schedule.stageScheduled(getSUnit(Phi)) + PhiNum;
// Rewrite uses that have been scheduled already to use the new
// Phi register.
for (MachineRegisterInfo::use_iterator UI = MRI.use_begin(OldReg),
EI = MRI.use_end();
UI != EI;) {
MachineOperand &UseOp = *UI;
MachineInstr *UseMI = UseOp.getParent();
++UI;
if (UseMI->getParent() != BB)
continue;
if (UseMI->isPHI()) {
if (!Phi->isPHI() && UseMI->getOperand(0).getReg() == NewReg)
continue;
if (getLoopPhiReg(*UseMI, BB) != OldReg)
continue;
}
InstrMapTy::iterator OrigInstr = InstrMap.find(UseMI);
assert(OrigInstr != InstrMap.end() && "Instruction not scheduled.");
SUnit *OrigMISU = getSUnit(OrigInstr->second);
int StageSched = Schedule.stageScheduled(OrigMISU);
int CycleSched = Schedule.cycleScheduled(OrigMISU);
unsigned ReplaceReg = 0;
// This is the stage for the scheduled instruction.
if (StagePhi == StageSched && Phi->isPHI()) {
int CyclePhi = Schedule.cycleScheduled(getSUnit(Phi));
if (PrevReg && InProlog)
ReplaceReg = PrevReg;
else if (PrevReg && !Schedule.isLoopCarried(this, *Phi) &&
(CyclePhi <= CycleSched || OrigMISU->getInstr()->isPHI()))
ReplaceReg = PrevReg;
else
ReplaceReg = NewReg;
}
// The scheduled instruction occurs before the scheduled Phi, and the
// Phi is not loop carried.
if (!InProlog && StagePhi + 1 == StageSched &&
!Schedule.isLoopCarried(this, *Phi))
ReplaceReg = NewReg;
if (StagePhi > StageSched && Phi->isPHI())
ReplaceReg = NewReg;
if (!InProlog && !Phi->isPHI() && StagePhi < StageSched)
ReplaceReg = NewReg;
if (ReplaceReg) {
MRI.constrainRegClass(ReplaceReg, MRI.getRegClass(OldReg));
UseOp.setReg(ReplaceReg);
}
}
}
/// Check if we can change the instruction to use an offset value from the
/// previous iteration. If so, return true and set the base and offset values
/// so that we can rewrite the load, if necessary.
/// v1 = Phi(v0, v3)
/// v2 = load v1, 0
/// v3 = post_store v1, 4, x
/// This function enables the load to be rewritten as v2 = load v3, 4.
bool SwingSchedulerDAG::canUseLastOffsetValue(MachineInstr *MI,
unsigned &BasePos,
unsigned &OffsetPos,
unsigned &NewBase,
int64_t &Offset) {
// Get the load instruction.
if (TII->isPostIncrement(*MI))
return false;
unsigned BasePosLd, OffsetPosLd;
if (!TII->getBaseAndOffsetPosition(*MI, BasePosLd, OffsetPosLd))
return false;
unsigned BaseReg = MI->getOperand(BasePosLd).getReg();
// Look for the Phi instruction.
MachineRegisterInfo &MRI = MI->getParent()->getParent()->getRegInfo();
MachineInstr *Phi = MRI.getVRegDef(BaseReg);
if (!Phi || !Phi->isPHI())
return false;
// Get the register defined in the loop block.
unsigned PrevReg = getLoopPhiReg(*Phi, MI->getParent());
if (!PrevReg)
return false;
// Check for the post-increment load/store instruction.
MachineInstr *PrevDef = MRI.getVRegDef(PrevReg);
if (!PrevDef || PrevDef == MI)
return false;
if (!TII->isPostIncrement(*PrevDef))
return false;
unsigned BasePos1 = 0, OffsetPos1 = 0;
if (!TII->getBaseAndOffsetPosition(*PrevDef, BasePos1, OffsetPos1))
return false;
// Make sure offset values are both positive or both negative.
int64_t LoadOffset = MI->getOperand(OffsetPosLd).getImm();
int64_t StoreOffset = PrevDef->getOperand(OffsetPos1).getImm();
if ((LoadOffset >= 0) != (StoreOffset >= 0))
return false;
// Set the return value once we determine that we return true.
BasePos = BasePosLd;
OffsetPos = OffsetPosLd;
NewBase = PrevReg;
Offset = StoreOffset;
return true;
}
/// Apply changes to the instruction if needed. The changes are need
/// to improve the scheduling and depend up on the final schedule.
MachineInstr *SwingSchedulerDAG::applyInstrChange(MachineInstr *MI,
SMSchedule &Schedule,
bool UpdateDAG) {
SUnit *SU = getSUnit(MI);
DenseMap<SUnit *, std::pair<unsigned, int64_t>>::iterator It =
InstrChanges.find(SU);
if (It != InstrChanges.end()) {
std::pair<unsigned, int64_t> RegAndOffset = It->second;
unsigned BasePos, OffsetPos;
if (!TII->getBaseAndOffsetPosition(*MI, BasePos, OffsetPos))
return nullptr;
unsigned BaseReg = MI->getOperand(BasePos).getReg();
MachineInstr *LoopDef = findDefInLoop(BaseReg);
int DefStageNum = Schedule.stageScheduled(getSUnit(LoopDef));
int DefCycleNum = Schedule.cycleScheduled(getSUnit(LoopDef));
int BaseStageNum = Schedule.stageScheduled(SU);
int BaseCycleNum = Schedule.cycleScheduled(SU);
if (BaseStageNum < DefStageNum) {
MachineInstr *NewMI = MF.CloneMachineInstr(MI);
int OffsetDiff = DefStageNum - BaseStageNum;
if (DefCycleNum < BaseCycleNum) {
NewMI->getOperand(BasePos).setReg(RegAndOffset.first);
if (OffsetDiff > 0)
--OffsetDiff;
}
int64_t NewOffset =
MI->getOperand(OffsetPos).getImm() + RegAndOffset.second * OffsetDiff;
NewMI->getOperand(OffsetPos).setImm(NewOffset);
if (UpdateDAG) {
SU->setInstr(NewMI);
MISUnitMap[NewMI] = SU;
}
NewMIs.insert(NewMI);
return NewMI;
}
}
return nullptr;
}
/// Return true for an order dependence that is loop carried potentially.
/// An order dependence is loop carried if the destination defines a value
/// that may be used by the source in a subsequent iteration.
bool SwingSchedulerDAG::isLoopCarriedOrder(SUnit *Source, const SDep &Dep,
bool isSucc) {
if (!isOrder(Source, Dep) || Dep.isArtificial())
return false;
if (!SwpPruneLoopCarried)
return true;
MachineInstr *SI = Source->getInstr();
MachineInstr *DI = Dep.getSUnit()->getInstr();
if (!isSucc)
std::swap(SI, DI);
assert(SI != nullptr && DI != nullptr && "Expecting SUnit with an MI.");
// Assume ordered loads and stores may have a loop carried dependence.
if (SI->hasUnmodeledSideEffects() || DI->hasUnmodeledSideEffects() ||
SI->hasOrderedMemoryRef() || DI->hasOrderedMemoryRef())
return true;
// Only chain dependences between a load and store can be loop carried.
if (!DI->mayStore() || !SI->mayLoad())
return false;
unsigned DeltaS, DeltaD;
if (!computeDelta(*SI, DeltaS) || !computeDelta(*DI, DeltaD))
return true;
unsigned BaseRegS, BaseRegD;
int64_t OffsetS, OffsetD;
const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
if (!TII->getMemOpBaseRegImmOfs(*SI, BaseRegS, OffsetS, TRI) ||
!TII->getMemOpBaseRegImmOfs(*DI, BaseRegD, OffsetD, TRI))
return true;
if (BaseRegS != BaseRegD)
return true;
uint64_t AccessSizeS = (*SI->memoperands_begin())->getSize();
uint64_t AccessSizeD = (*DI->memoperands_begin())->getSize();
// This is the main test, which checks the offset values and the loop
// increment value to determine if the accesses may be loop carried.
if (OffsetS >= OffsetD)
return OffsetS + AccessSizeS > DeltaS;
else
return OffsetD + AccessSizeD > DeltaD;
return true;
}
void SwingSchedulerDAG::postprocessDAG() {
for (auto &M : Mutations)
M->apply(this);
}
/// Try to schedule the node at the specified StartCycle and continue
/// until the node is schedule or the EndCycle is reached. This function
/// returns true if the node is scheduled. This routine may search either
/// forward or backward for a place to insert the instruction based upon
/// the relative values of StartCycle and EndCycle.
bool SMSchedule::insert(SUnit *SU, int StartCycle, int EndCycle, int II) {
bool forward = true;
if (StartCycle > EndCycle)
forward = false;
// The terminating condition depends on the direction.
int termCycle = forward ? EndCycle + 1 : EndCycle - 1;
for (int curCycle = StartCycle; curCycle != termCycle;
forward ? ++curCycle : --curCycle) {
// Add the already scheduled instructions at the specified cycle to the DFA.
Resources->clearResources();
for (int checkCycle = FirstCycle + ((curCycle - FirstCycle) % II);
checkCycle <= LastCycle; checkCycle += II) {
std::deque<SUnit *> &cycleInstrs = ScheduledInstrs[checkCycle];
for (std::deque<SUnit *>::iterator I = cycleInstrs.begin(),
E = cycleInstrs.end();
I != E; ++I) {
if (ST.getInstrInfo()->isZeroCost((*I)->getInstr()->getOpcode()))
continue;
assert(Resources->canReserveResources(*(*I)->getInstr()) &&
"These instructions have already been scheduled.");
Resources->reserveResources(*(*I)->getInstr());
}
}
if (ST.getInstrInfo()->isZeroCost(SU->getInstr()->getOpcode()) ||
Resources->canReserveResources(*SU->getInstr())) {
DEBUG({
dbgs() << "\tinsert at cycle " << curCycle << " ";
SU->getInstr()->dump();
});
ScheduledInstrs[curCycle].push_back(SU);
InstrToCycle.insert(std::make_pair(SU, curCycle));
if (curCycle > LastCycle)
LastCycle = curCycle;
if (curCycle < FirstCycle)
FirstCycle = curCycle;
return true;
}
DEBUG({
dbgs() << "\tfailed to insert at cycle " << curCycle << " ";
SU->getInstr()->dump();
});
}
return false;
}
// Return the cycle of the earliest scheduled instruction in the chain.
int SMSchedule::earliestCycleInChain(const SDep &Dep) {
SmallPtrSet<SUnit *, 8> Visited;
SmallVector<SDep, 8> Worklist;
Worklist.push_back(Dep);
int EarlyCycle = INT_MAX;
while (!Worklist.empty()) {
const SDep &Cur = Worklist.pop_back_val();
SUnit *PrevSU = Cur.getSUnit();
if (Visited.count(PrevSU))
continue;
std::map<SUnit *, int>::const_iterator it = InstrToCycle.find(PrevSU);
if (it == InstrToCycle.end())
continue;
EarlyCycle = std::min(EarlyCycle, it->second);
for (const auto &PI : PrevSU->Preds)
if (SwingSchedulerDAG::isOrder(PrevSU, PI))
Worklist.push_back(PI);
Visited.insert(PrevSU);
}
return EarlyCycle;
}
// Return the cycle of the latest scheduled instruction in the chain.
int SMSchedule::latestCycleInChain(const SDep &Dep) {
SmallPtrSet<SUnit *, 8> Visited;
SmallVector<SDep, 8> Worklist;
Worklist.push_back(Dep);
int LateCycle = INT_MIN;
while (!Worklist.empty()) {
const SDep &Cur = Worklist.pop_back_val();
SUnit *SuccSU = Cur.getSUnit();
if (Visited.count(SuccSU))
continue;
std::map<SUnit *, int>::const_iterator it = InstrToCycle.find(SuccSU);
if (it == InstrToCycle.end())
continue;
LateCycle = std::max(LateCycle, it->second);
for (const auto &SI : SuccSU->Succs)
if (SwingSchedulerDAG::isOrder(SuccSU, SI))
Worklist.push_back(SI);
Visited.insert(SuccSU);
}
return LateCycle;
}
/// If an instruction has a use that spans multiple iterations, then
/// return true. These instructions are characterized by having a back-ege
/// to a Phi, which contains a reference to another Phi.
static SUnit *multipleIterations(SUnit *SU, SwingSchedulerDAG *DAG) {
for (auto &P : SU->Preds)
if (DAG->isBackedge(SU, P) && P.getSUnit()->getInstr()->isPHI())
for (auto &S : P.getSUnit()->Succs)
if (S.getKind() == SDep::Order && S.getSUnit()->getInstr()->isPHI())
return P.getSUnit();
return nullptr;
}
/// Compute the scheduling start slot for the instruction. The start slot
/// depends on any predecessor or successor nodes scheduled already.
void SMSchedule::computeStart(SUnit *SU, int *MaxEarlyStart, int *MinLateStart,
int *MinEnd, int *MaxStart, int II,
SwingSchedulerDAG *DAG) {
// Iterate over each instruction that has been scheduled already. The start
// slot computuation depends on whether the previously scheduled instruction
// is a predecessor or successor of the specified instruction.
for (int cycle = getFirstCycle(); cycle <= LastCycle; ++cycle) {
// Iterate over each instruction in the current cycle.
for (SUnit *I : getInstructions(cycle)) {
// Because we're processing a DAG for the dependences, we recognize
// the back-edge in recurrences by anti dependences.
for (unsigned i = 0, e = (unsigned)SU->Preds.size(); i != e; ++i) {
const SDep &Dep = SU->Preds[i];
if (Dep.getSUnit() == I) {
if (!DAG->isBackedge(SU, Dep)) {
int EarlyStart = cycle + DAG->getLatency(SU, Dep) -
DAG->getDistance(Dep.getSUnit(), SU, Dep) * II;
*MaxEarlyStart = std::max(*MaxEarlyStart, EarlyStart);
if (DAG->isLoopCarriedOrder(SU, Dep, false)) {
int End = earliestCycleInChain(Dep) + (II - 1);
*MinEnd = std::min(*MinEnd, End);
}
} else {
int LateStart = cycle - DAG->getLatency(SU, Dep) +
DAG->getDistance(SU, Dep.getSUnit(), Dep) * II;
*MinLateStart = std::min(*MinLateStart, LateStart);
}
}
// For instruction that requires multiple iterations, make sure that
// the dependent instruction is not scheduled past the definition.
SUnit *BE = multipleIterations(I, DAG);
if (BE && Dep.getSUnit() == BE && !SU->getInstr()->isPHI() &&
!SU->isPred(I))
*MinLateStart = std::min(*MinLateStart, cycle);
}
for (unsigned i = 0, e = (unsigned)SU->Succs.size(); i != e; ++i)
if (SU->Succs[i].getSUnit() == I) {
const SDep &Dep = SU->Succs[i];
if (!DAG->isBackedge(SU, Dep)) {
int LateStart = cycle - DAG->getLatency(SU, Dep) +
DAG->getDistance(SU, Dep.getSUnit(), Dep) * II;
*MinLateStart = std::min(*MinLateStart, LateStart);
if (DAG->isLoopCarriedOrder(SU, Dep)) {
int Start = latestCycleInChain(Dep) + 1 - II;
*MaxStart = std::max(*MaxStart, Start);
}
} else {
int EarlyStart = cycle + DAG->getLatency(SU, Dep) -
DAG->getDistance(Dep.getSUnit(), SU, Dep) * II;
*MaxEarlyStart = std::max(*MaxEarlyStart, EarlyStart);
}
}
}
}
}
/// Order the instructions within a cycle so that the definitions occur
/// before the uses. Returns true if the instruction is added to the start
/// of the list, or false if added to the end.
bool SMSchedule::orderDependence(SwingSchedulerDAG *SSD, SUnit *SU,
std::deque<SUnit *> &Insts) {
MachineInstr *MI = SU->getInstr();
bool OrderBeforeUse = false;
bool OrderAfterDef = false;
bool OrderBeforeDef = false;
unsigned MoveDef = 0;
unsigned MoveUse = 0;
int StageInst1 = stageScheduled(SU);
unsigned Pos = 0;
for (std::deque<SUnit *>::iterator I = Insts.begin(), E = Insts.end(); I != E;
++I, ++Pos) {
// Relative order of Phis does not matter.
if (MI->isPHI() && (*I)->getInstr()->isPHI())
continue;
for (unsigned i = 0, e = MI->getNumOperands(); i < e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !TargetRegisterInfo::isVirtualRegister(MO.getReg()))
continue;
unsigned Reg = MO.getReg();
unsigned BasePos, OffsetPos;
if (ST.getInstrInfo()->getBaseAndOffsetPosition(*MI, BasePos, OffsetPos))
if (MI->getOperand(BasePos).getReg() == Reg)
if (unsigned NewReg = SSD->getInstrBaseReg(SU))
Reg = NewReg;
bool Reads, Writes;
std::tie(Reads, Writes) =
(*I)->getInstr()->readsWritesVirtualRegister(Reg);
if (MO.isDef() && Reads && stageScheduled(*I) <= StageInst1) {
OrderBeforeUse = true;
MoveUse = Pos;
} else if (MO.isDef() && Reads && stageScheduled(*I) > StageInst1) {
// Add the instruction after the scheduled instruction.
OrderAfterDef = true;
MoveDef = Pos;
} else if (MO.isUse() && Writes && stageScheduled(*I) == StageInst1) {
if (cycleScheduled(*I) == cycleScheduled(SU) && !(*I)->isSucc(SU)) {
OrderBeforeUse = true;
MoveUse = Pos;
} else {
OrderAfterDef = true;
MoveDef = Pos;
}
} else if (MO.isUse() && Writes && stageScheduled(*I) > StageInst1) {
OrderBeforeUse = true;
MoveUse = Pos;
if (MoveUse != 0) {
OrderAfterDef = true;
MoveDef = Pos - 1;
}
} else if (MO.isUse() && Writes && stageScheduled(*I) < StageInst1) {
// Add the instruction before the scheduled instruction.
OrderBeforeUse = true;
MoveUse = Pos;
} else if (MO.isUse() && stageScheduled(*I) == StageInst1 &&
isLoopCarriedDefOfUse(SSD, (*I)->getInstr(), MO)) {
OrderBeforeDef = true;
MoveUse = Pos;
}
}
// Check for order dependences between instructions. Make sure the source
// is ordered before the destination.
for (auto &S : SU->Succs)
if (S.getKind() == SDep::Order) {
if (S.getSUnit() == *I && stageScheduled(*I) == StageInst1) {
OrderBeforeUse = true;
MoveUse = Pos;
}
} else if (TargetRegisterInfo::isPhysicalRegister(S.getReg())) {
if (cycleScheduled(SU) != cycleScheduled(S.getSUnit())) {
if (S.isAssignedRegDep()) {
OrderAfterDef = true;
MoveDef = Pos;
}
} else {
OrderBeforeUse = true;
MoveUse = Pos;
}
}
for (auto &P : SU->Preds)
if (P.getKind() == SDep::Order) {
if (P.getSUnit() == *I && stageScheduled(*I) == StageInst1) {
OrderAfterDef = true;
MoveDef = Pos;
}
} else if (TargetRegisterInfo::isPhysicalRegister(P.getReg())) {
if (cycleScheduled(SU) != cycleScheduled(P.getSUnit())) {
if (P.isAssignedRegDep()) {
OrderBeforeUse = true;
MoveUse = Pos;
}
} else {
OrderAfterDef = true;
MoveDef = Pos;
}
}
}
// A circular dependence.
if (OrderAfterDef && OrderBeforeUse && MoveUse == MoveDef)
OrderBeforeUse = false;
// OrderAfterDef takes precedences over OrderBeforeDef. The latter is due
// to a loop-carried dependence.
if (OrderBeforeDef)
OrderBeforeUse = !OrderAfterDef || (MoveUse > MoveDef);
// The uncommon case when the instruction order needs to be updated because
// there is both a use and def.
if (OrderBeforeUse && OrderAfterDef) {
SUnit *UseSU = Insts.at(MoveUse);
SUnit *DefSU = Insts.at(MoveDef);
if (MoveUse > MoveDef) {
Insts.erase(Insts.begin() + MoveUse);
Insts.erase(Insts.begin() + MoveDef);
} else {
Insts.erase(Insts.begin() + MoveDef);
Insts.erase(Insts.begin() + MoveUse);
}
if (orderDependence(SSD, UseSU, Insts)) {
Insts.push_front(SU);
orderDependence(SSD, DefSU, Insts);
return true;
}
Insts.pop_back();
Insts.push_back(SU);
Insts.push_back(UseSU);
orderDependence(SSD, DefSU, Insts);
return false;
}
// Put the new instruction first if there is a use in the list. Otherwise,
// put it at the end of the list.
if (OrderBeforeUse)
Insts.push_front(SU);
else
Insts.push_back(SU);
return OrderBeforeUse;
}
/// Return true if the scheduled Phi has a loop carried operand.
bool SMSchedule::isLoopCarried(SwingSchedulerDAG *SSD, MachineInstr &Phi) {
if (!Phi.isPHI())
return false;
assert(Phi.isPHI() && "Expecing a Phi.");
SUnit *DefSU = SSD->getSUnit(&Phi);
unsigned DefCycle = cycleScheduled(DefSU);
int DefStage = stageScheduled(DefSU);
unsigned InitVal = 0;
unsigned LoopVal = 0;
getPhiRegs(Phi, Phi.getParent(), InitVal, LoopVal);
SUnit *UseSU = SSD->getSUnit(MRI.getVRegDef(LoopVal));
if (!UseSU)
return true;
if (UseSU->getInstr()->isPHI())
return true;
unsigned LoopCycle = cycleScheduled(UseSU);
int LoopStage = stageScheduled(UseSU);
return (LoopCycle > DefCycle) || (LoopStage <= DefStage);
}
/// Return true if the instruction is a definition that is loop carried
/// and defines the use on the next iteration.
/// v1 = phi(v2, v3)
/// (Def) v3 = op v1
/// (MO) = v1
/// If MO appears before Def, then then v1 and v3 may get assigned to the same
/// register.
bool SMSchedule::isLoopCarriedDefOfUse(SwingSchedulerDAG *SSD,
MachineInstr *Def, MachineOperand &MO) {
if (!MO.isReg())
return false;
if (Def->isPHI())
return false;
MachineInstr *Phi = MRI.getVRegDef(MO.getReg());
if (!Phi || !Phi->isPHI() || Phi->getParent() != Def->getParent())
return false;
if (!isLoopCarried(SSD, *Phi))
return false;
unsigned LoopReg = getLoopPhiReg(*Phi, Phi->getParent());
for (unsigned i = 0, e = Def->getNumOperands(); i != e; ++i) {
MachineOperand &DMO = Def->getOperand(i);
if (!DMO.isReg() || !DMO.isDef())
continue;
if (DMO.getReg() == LoopReg)
return true;
}
return false;
}
// Check if the generated schedule is valid. This function checks if
// an instruction that uses a physical register is scheduled in a
// different stage than the definition. The pipeliner does not handle
// physical register values that may cross a basic block boundary.
bool SMSchedule::isValidSchedule(SwingSchedulerDAG *SSD) {
for (int i = 0, e = SSD->SUnits.size(); i < e; ++i) {
SUnit &SU = SSD->SUnits[i];
if (!SU.hasPhysRegDefs)
continue;
int StageDef = stageScheduled(&SU);
assert(StageDef != -1 && "Instruction should have been scheduled.");
for (auto &SI : SU.Succs)
if (SI.isAssignedRegDep())
if (ST.getRegisterInfo()->isPhysicalRegister(SI.getReg()))
if (stageScheduled(SI.getSUnit()) != StageDef)
return false;
}
return true;
}
/// After the schedule has been formed, call this function to combine
/// the instructions from the different stages/cycles. That is, this
/// function creates a schedule that represents a single iteration.
void SMSchedule::finalizeSchedule(SwingSchedulerDAG *SSD) {
// Move all instructions to the first stage from later stages.
for (int cycle = getFirstCycle(); cycle <= getFinalCycle(); ++cycle) {
for (int stage = 1, lastStage = getMaxStageCount(); stage <= lastStage;
++stage) {
std::deque<SUnit *> &cycleInstrs =
ScheduledInstrs[cycle + (stage * InitiationInterval)];
for (std::deque<SUnit *>::reverse_iterator I = cycleInstrs.rbegin(),
E = cycleInstrs.rend();
I != E; ++I)
ScheduledInstrs[cycle].push_front(*I);
}
}
// Iterate over the definitions in each instruction, and compute the
// stage difference for each use. Keep the maximum value.
for (auto &I : InstrToCycle) {
int DefStage = stageScheduled(I.first);
MachineInstr *MI = I.first->getInstr();
for (unsigned i = 0, e = MI->getNumOperands(); i < e; ++i) {
MachineOperand &Op = MI->getOperand(i);
if (!Op.isReg() || !Op.isDef())
continue;
unsigned Reg = Op.getReg();
unsigned MaxDiff = 0;
bool PhiIsSwapped = false;
for (MachineRegisterInfo::use_iterator UI = MRI.use_begin(Reg),
EI = MRI.use_end();
UI != EI; ++UI) {
MachineOperand &UseOp = *UI;
MachineInstr *UseMI = UseOp.getParent();
SUnit *SUnitUse = SSD->getSUnit(UseMI);
int UseStage = stageScheduled(SUnitUse);
unsigned Diff = 0;
if (UseStage != -1 && UseStage >= DefStage)
Diff = UseStage - DefStage;
if (MI->isPHI()) {
if (isLoopCarried(SSD, *MI))
++Diff;
else
PhiIsSwapped = true;
}
MaxDiff = std::max(Diff, MaxDiff);
}
RegToStageDiff[Reg] = std::make_pair(MaxDiff, PhiIsSwapped);
}
}
// Erase all the elements in the later stages. Only one iteration should
// remain in the scheduled list, and it contains all the instructions.
for (int cycle = getFinalCycle() + 1; cycle <= LastCycle; ++cycle)
ScheduledInstrs.erase(cycle);
// Change the registers in instruction as specified in the InstrChanges
// map. We need to use the new registers to create the correct order.
for (int i = 0, e = SSD->SUnits.size(); i != e; ++i) {
SUnit *SU = &SSD->SUnits[i];
SSD->applyInstrChange(SU->getInstr(), *this, true);
}
// Reorder the instructions in each cycle to fix and improve the
// generated code.
for (int Cycle = getFirstCycle(), E = getFinalCycle(); Cycle <= E; ++Cycle) {
std::deque<SUnit *> &cycleInstrs = ScheduledInstrs[Cycle];
std::deque<SUnit *> newOrderZC;
// Put the zero-cost, pseudo instructions at the start of the cycle.
for (unsigned i = 0, e = cycleInstrs.size(); i < e; ++i) {
SUnit *SU = cycleInstrs[i];
if (ST.getInstrInfo()->isZeroCost(SU->getInstr()->getOpcode()))
orderDependence(SSD, SU, newOrderZC);
}
std::deque<SUnit *> newOrderI;
// Then, add the regular instructions back.
for (unsigned i = 0, e = cycleInstrs.size(); i < e; ++i) {
SUnit *SU = cycleInstrs[i];
if (!ST.getInstrInfo()->isZeroCost(SU->getInstr()->getOpcode()))
orderDependence(SSD, SU, newOrderI);
}
// Replace the old order with the new order.
cycleInstrs.swap(newOrderZC);
cycleInstrs.insert(cycleInstrs.end(), newOrderI.begin(), newOrderI.end());
}
DEBUG(dump(););
}
/// Print the schedule information to the given output.
void SMSchedule::print(raw_ostream &os) const {
// Iterate over each cycle.
for (int cycle = getFirstCycle(); cycle <= getFinalCycle(); ++cycle) {
// Iterate over each instruction in the cycle.
const_sched_iterator cycleInstrs = ScheduledInstrs.find(cycle);
for (SUnit *CI : cycleInstrs->second) {
os << "cycle " << cycle << " (" << stageScheduled(CI) << ") ";
os << "(" << CI->NodeNum << ") ";
CI->getInstr()->print(os);
os << "\n";
}
}
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
/// Utility function used for debugging to print the schedule.
LLVM_DUMP_METHOD void SMSchedule::dump() const { print(dbgs()); }
#endif
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