//===---- ScheduleDAG.cpp - Implement the ScheduleDAG class ---------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This implements the ScheduleDAG class, which is a base class used by
// scheduling implementation classes.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/ScheduleDAG.h"
#include "llvm/CodeGen/ScheduleHazardRecognizer.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
#include <climits>
using namespace llvm;
#define DEBUG_TYPE "pre-RA-sched"
#ifndef NDEBUG
static cl::opt<bool> StressSchedOpt(
"stress-sched", cl::Hidden, cl::init(false),
cl::desc("Stress test instruction scheduling"));
#endif
void SchedulingPriorityQueue::anchor() { }
ScheduleDAG::ScheduleDAG(MachineFunction &mf)
: TM(mf.getTarget()), TII(mf.getSubtarget().getInstrInfo()),
TRI(mf.getSubtarget().getRegisterInfo()), MF(mf),
MRI(mf.getRegInfo()), EntrySU(), ExitSU() {
#ifndef NDEBUG
StressSched = StressSchedOpt;
#endif
}
ScheduleDAG::~ScheduleDAG() {}
/// Clear the DAG state (e.g. between scheduling regions).
void ScheduleDAG::clearDAG() {
SUnits.clear();
EntrySU = SUnit();
ExitSU = SUnit();
}
/// getInstrDesc helper to handle SDNodes.
const MCInstrDesc *ScheduleDAG::getNodeDesc(const SDNode *Node) const {
if (!Node || !Node->isMachineOpcode()) return nullptr;
return &TII->get(Node->getMachineOpcode());
}
/// addPred - This adds the specified edge as a pred of the current node if
/// not already. It also adds the current node as a successor of the
/// specified node.
bool SUnit::addPred(const SDep &D, bool Required) {
// If this node already has this dependence, don't add a redundant one.
for (SmallVectorImpl<SDep>::iterator I = Preds.begin(), E = Preds.end();
I != E; ++I) {
// Zero-latency weak edges may be added purely for heuristic ordering. Don't
// add them if another kind of edge already exists.
if (!Required && I->getSUnit() == D.getSUnit())
return false;
if (I->overlaps(D)) {
// Extend the latency if needed. Equivalent to removePred(I) + addPred(D).
if (I->getLatency() < D.getLatency()) {
SUnit *PredSU = I->getSUnit();
// Find the corresponding successor in N.
SDep ForwardD = *I;
ForwardD.setSUnit(this);
for (SmallVectorImpl<SDep>::iterator II = PredSU->Succs.begin(),
EE = PredSU->Succs.end(); II != EE; ++II) {
if (*II == ForwardD) {
II->setLatency(D.getLatency());
break;
}
}
I->setLatency(D.getLatency());
}
return false;
}
}
// Now add a corresponding succ to N.
SDep P = D;
P.setSUnit(this);
SUnit *N = D.getSUnit();
// Update the bookkeeping.
if (D.getKind() == SDep::Data) {
assert(NumPreds < UINT_MAX && "NumPreds will overflow!");
assert(N->NumSuccs < UINT_MAX && "NumSuccs will overflow!");
++NumPreds;
++N->NumSuccs;
}
if (!N->isScheduled) {
if (D.isWeak()) {
++WeakPredsLeft;
}
else {
assert(NumPredsLeft < UINT_MAX && "NumPredsLeft will overflow!");
++NumPredsLeft;
}
}
if (!isScheduled) {
if (D.isWeak()) {
++N->WeakSuccsLeft;
}
else {
assert(N->NumSuccsLeft < UINT_MAX && "NumSuccsLeft will overflow!");
++N->NumSuccsLeft;
}
}
Preds.push_back(D);
N->Succs.push_back(P);
if (P.getLatency() != 0) {
this->setDepthDirty();
N->setHeightDirty();
}
return true;
}
/// removePred - This removes the specified edge as a pred of the current
/// node if it exists. It also removes the current node as a successor of
/// the specified node.
void SUnit::removePred(const SDep &D) {
// Find the matching predecessor.
for (SmallVectorImpl<SDep>::iterator I = Preds.begin(), E = Preds.end();
I != E; ++I)
if (*I == D) {
// Find the corresponding successor in N.
SDep P = D;
P.setSUnit(this);
SUnit *N = D.getSUnit();
SmallVectorImpl<SDep>::iterator Succ = std::find(N->Succs.begin(),
N->Succs.end(), P);
assert(Succ != N->Succs.end() && "Mismatching preds / succs lists!");
N->Succs.erase(Succ);
Preds.erase(I);
// Update the bookkeeping.
if (P.getKind() == SDep::Data) {
assert(NumPreds > 0 && "NumPreds will underflow!");
assert(N->NumSuccs > 0 && "NumSuccs will underflow!");
--NumPreds;
--N->NumSuccs;
}
if (!N->isScheduled) {
if (D.isWeak())
--WeakPredsLeft;
else {
assert(NumPredsLeft > 0 && "NumPredsLeft will underflow!");
--NumPredsLeft;
}
}
if (!isScheduled) {
if (D.isWeak())
--N->WeakSuccsLeft;
else {
assert(N->NumSuccsLeft > 0 && "NumSuccsLeft will underflow!");
--N->NumSuccsLeft;
}
}
if (P.getLatency() != 0) {
this->setDepthDirty();
N->setHeightDirty();
}
return;
}
}
void SUnit::setDepthDirty() {
if (!isDepthCurrent) return;
SmallVector<SUnit*, 8> WorkList;
WorkList.push_back(this);
do {
SUnit *SU = WorkList.pop_back_val();
SU->isDepthCurrent = false;
for (SUnit::const_succ_iterator I = SU->Succs.begin(),
E = SU->Succs.end(); I != E; ++I) {
SUnit *SuccSU = I->getSUnit();
if (SuccSU->isDepthCurrent)
WorkList.push_back(SuccSU);
}
} while (!WorkList.empty());
}
void SUnit::setHeightDirty() {
if (!isHeightCurrent) return;
SmallVector<SUnit*, 8> WorkList;
WorkList.push_back(this);
do {
SUnit *SU = WorkList.pop_back_val();
SU->isHeightCurrent = false;
for (SUnit::const_pred_iterator I = SU->Preds.begin(),
E = SU->Preds.end(); I != E; ++I) {
SUnit *PredSU = I->getSUnit();
if (PredSU->isHeightCurrent)
WorkList.push_back(PredSU);
}
} while (!WorkList.empty());
}
/// setDepthToAtLeast - Update this node's successors to reflect the
/// fact that this node's depth just increased.
///
void SUnit::setDepthToAtLeast(unsigned NewDepth) {
if (NewDepth <= getDepth())
return;
setDepthDirty();
Depth = NewDepth;
isDepthCurrent = true;
}
/// setHeightToAtLeast - Update this node's predecessors to reflect the
/// fact that this node's height just increased.
///
void SUnit::setHeightToAtLeast(unsigned NewHeight) {
if (NewHeight <= getHeight())
return;
setHeightDirty();
Height = NewHeight;
isHeightCurrent = true;
}
/// ComputeDepth - Calculate the maximal path from the node to the exit.
///
void SUnit::ComputeDepth() {
SmallVector<SUnit*, 8> WorkList;
WorkList.push_back(this);
do {
SUnit *Cur = WorkList.back();
bool Done = true;
unsigned MaxPredDepth = 0;
for (SUnit::const_pred_iterator I = Cur->Preds.begin(),
E = Cur->Preds.end(); I != E; ++I) {
SUnit *PredSU = I->getSUnit();
if (PredSU->isDepthCurrent)
MaxPredDepth = std::max(MaxPredDepth,
PredSU->Depth + I->getLatency());
else {
Done = false;
WorkList.push_back(PredSU);
}
}
if (Done) {
WorkList.pop_back();
if (MaxPredDepth != Cur->Depth) {
Cur->setDepthDirty();
Cur->Depth = MaxPredDepth;
}
Cur->isDepthCurrent = true;
}
} while (!WorkList.empty());
}
/// ComputeHeight - Calculate the maximal path from the node to the entry.
///
void SUnit::ComputeHeight() {
SmallVector<SUnit*, 8> WorkList;
WorkList.push_back(this);
do {
SUnit *Cur = WorkList.back();
bool Done = true;
unsigned MaxSuccHeight = 0;
for (SUnit::const_succ_iterator I = Cur->Succs.begin(),
E = Cur->Succs.end(); I != E; ++I) {
SUnit *SuccSU = I->getSUnit();
if (SuccSU->isHeightCurrent)
MaxSuccHeight = std::max(MaxSuccHeight,
SuccSU->Height + I->getLatency());
else {
Done = false;
WorkList.push_back(SuccSU);
}
}
if (Done) {
WorkList.pop_back();
if (MaxSuccHeight != Cur->Height) {
Cur->setHeightDirty();
Cur->Height = MaxSuccHeight;
}
Cur->isHeightCurrent = true;
}
} while (!WorkList.empty());
}
void SUnit::biasCriticalPath() {
if (NumPreds < 2)
return;
SUnit::pred_iterator BestI = Preds.begin();
unsigned MaxDepth = BestI->getSUnit()->getDepth();
for (SUnit::pred_iterator I = std::next(BestI), E = Preds.end(); I != E;
++I) {
if (I->getKind() == SDep::Data && I->getSUnit()->getDepth() > MaxDepth)
BestI = I;
}
if (BestI != Preds.begin())
std::swap(*Preds.begin(), *BestI);
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
/// SUnit - Scheduling unit. It's an wrapper around either a single SDNode or
/// a group of nodes flagged together.
void SUnit::dump(const ScheduleDAG *G) const {
dbgs() << "SU(" << NodeNum << "): ";
G->dumpNode(this);
}
void SUnit::dumpAll(const ScheduleDAG *G) const {
dump(G);
dbgs() << " # preds left : " << NumPredsLeft << "\n";
dbgs() << " # succs left : " << NumSuccsLeft << "\n";
if (WeakPredsLeft)
dbgs() << " # weak preds left : " << WeakPredsLeft << "\n";
if (WeakSuccsLeft)
dbgs() << " # weak succs left : " << WeakSuccsLeft << "\n";
dbgs() << " # rdefs left : " << NumRegDefsLeft << "\n";
dbgs() << " Latency : " << Latency << "\n";
dbgs() << " Depth : " << getDepth() << "\n";
dbgs() << " Height : " << getHeight() << "\n";
if (Preds.size() != 0) {
dbgs() << " Predecessors:\n";
for (SUnit::const_succ_iterator I = Preds.begin(), E = Preds.end();
I != E; ++I) {
dbgs() << " ";
switch (I->getKind()) {
case SDep::Data: dbgs() << "val "; break;
case SDep::Anti: dbgs() << "anti"; break;
case SDep::Output: dbgs() << "out "; break;
case SDep::Order: dbgs() << "ch "; break;
}
dbgs() << "SU(" << I->getSUnit()->NodeNum << ")";
if (I->isArtificial())
dbgs() << " *";
dbgs() << ": Latency=" << I->getLatency();
if (I->isAssignedRegDep())
dbgs() << " Reg=" << PrintReg(I->getReg(), G->TRI);
dbgs() << "\n";
}
}
if (Succs.size() != 0) {
dbgs() << " Successors:\n";
for (SUnit::const_succ_iterator I = Succs.begin(), E = Succs.end();
I != E; ++I) {
dbgs() << " ";
switch (I->getKind()) {
case SDep::Data: dbgs() << "val "; break;
case SDep::Anti: dbgs() << "anti"; break;
case SDep::Output: dbgs() << "out "; break;
case SDep::Order: dbgs() << "ch "; break;
}
dbgs() << "SU(" << I->getSUnit()->NodeNum << ")";
if (I->isArtificial())
dbgs() << " *";
dbgs() << ": Latency=" << I->getLatency();
if (I->isAssignedRegDep())
dbgs() << " Reg=" << PrintReg(I->getReg(), G->TRI);
dbgs() << "\n";
}
}
}
#endif
#ifndef NDEBUG
/// VerifyScheduledDAG - Verify that all SUnits were scheduled and that
/// their state is consistent. Return the number of scheduled nodes.
///
unsigned ScheduleDAG::VerifyScheduledDAG(bool isBottomUp) {
bool AnyNotSched = false;
unsigned DeadNodes = 0;
for (unsigned i = 0, e = SUnits.size(); i != e; ++i) {
if (!SUnits[i].isScheduled) {
if (SUnits[i].NumPreds == 0 && SUnits[i].NumSuccs == 0) {
++DeadNodes;
continue;
}
if (!AnyNotSched)
dbgs() << "*** Scheduling failed! ***\n";
SUnits[i].dump(this);
dbgs() << "has not been scheduled!\n";
AnyNotSched = true;
}
if (SUnits[i].isScheduled &&
(isBottomUp ? SUnits[i].getHeight() : SUnits[i].getDepth()) >
unsigned(INT_MAX)) {
if (!AnyNotSched)
dbgs() << "*** Scheduling failed! ***\n";
SUnits[i].dump(this);
dbgs() << "has an unexpected "
<< (isBottomUp ? "Height" : "Depth") << " value!\n";
AnyNotSched = true;
}
if (isBottomUp) {
if (SUnits[i].NumSuccsLeft != 0) {
if (!AnyNotSched)
dbgs() << "*** Scheduling failed! ***\n";
SUnits[i].dump(this);
dbgs() << "has successors left!\n";
AnyNotSched = true;
}
} else {
if (SUnits[i].NumPredsLeft != 0) {
if (!AnyNotSched)
dbgs() << "*** Scheduling failed! ***\n";
SUnits[i].dump(this);
dbgs() << "has predecessors left!\n";
AnyNotSched = true;
}
}
}
assert(!AnyNotSched);
return SUnits.size() - DeadNodes;
}
#endif
/// InitDAGTopologicalSorting - create the initial topological
/// ordering from the DAG to be scheduled.
///
/// The idea of the algorithm is taken from
/// "Online algorithms for managing the topological order of
/// a directed acyclic graph" by David J. Pearce and Paul H.J. Kelly
/// This is the MNR algorithm, which was first introduced by
/// A. Marchetti-Spaccamela, U. Nanni and H. Rohnert in
/// "Maintaining a topological order under edge insertions".
///
/// Short description of the algorithm:
///
/// Topological ordering, ord, of a DAG maps each node to a topological
/// index so that for all edges X->Y it is the case that ord(X) < ord(Y).
///
/// This means that if there is a path from the node X to the node Z,
/// then ord(X) < ord(Z).
///
/// This property can be used to check for reachability of nodes:
/// if Z is reachable from X, then an insertion of the edge Z->X would
/// create a cycle.
///
/// The algorithm first computes a topological ordering for the DAG by
/// initializing the Index2Node and Node2Index arrays and then tries to keep
/// the ordering up-to-date after edge insertions by reordering the DAG.
///
/// On insertion of the edge X->Y, the algorithm first marks by calling DFS
/// the nodes reachable from Y, and then shifts them using Shift to lie
/// immediately after X in Index2Node.
void ScheduleDAGTopologicalSort::InitDAGTopologicalSorting() {
unsigned DAGSize = SUnits.size();
std::vector<SUnit*> WorkList;
WorkList.reserve(DAGSize);
Index2Node.resize(DAGSize);
Node2Index.resize(DAGSize);
// Initialize the data structures.
if (ExitSU)
WorkList.push_back(ExitSU);
for (unsigned i = 0, e = DAGSize; i != e; ++i) {
SUnit *SU = &SUnits[i];
int NodeNum = SU->NodeNum;
unsigned Degree = SU->Succs.size();
// Temporarily use the Node2Index array as scratch space for degree counts.
Node2Index[NodeNum] = Degree;
// Is it a node without dependencies?
if (Degree == 0) {
assert(SU->Succs.empty() && "SUnit should have no successors");
// Collect leaf nodes.
WorkList.push_back(SU);
}
}
int Id = DAGSize;
while (!WorkList.empty()) {
SUnit *SU = WorkList.back();
WorkList.pop_back();
if (SU->NodeNum < DAGSize)
Allocate(SU->NodeNum, --Id);
for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
I != E; ++I) {
SUnit *SU = I->getSUnit();
if (SU->NodeNum < DAGSize && !--Node2Index[SU->NodeNum])
// If all dependencies of the node are processed already,
// then the node can be computed now.
WorkList.push_back(SU);
}
}
Visited.resize(DAGSize);
#ifndef NDEBUG
// Check correctness of the ordering
for (unsigned i = 0, e = DAGSize; i != e; ++i) {
SUnit *SU = &SUnits[i];
for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
I != E; ++I) {
assert(Node2Index[SU->NodeNum] > Node2Index[I->getSUnit()->NodeNum] &&
"Wrong topological sorting");
}
}
#endif
}
/// AddPred - Updates the topological ordering to accommodate an edge
/// to be added from SUnit X to SUnit Y.
void ScheduleDAGTopologicalSort::AddPred(SUnit *Y, SUnit *X) {
int UpperBound, LowerBound;
LowerBound = Node2Index[Y->NodeNum];
UpperBound = Node2Index[X->NodeNum];
bool HasLoop = false;
// Is Ord(X) < Ord(Y) ?
if (LowerBound < UpperBound) {
// Update the topological order.
Visited.reset();
DFS(Y, UpperBound, HasLoop);
assert(!HasLoop && "Inserted edge creates a loop!");
// Recompute topological indexes.
Shift(Visited, LowerBound, UpperBound);
}
}
/// RemovePred - Updates the topological ordering to accommodate an
/// an edge to be removed from the specified node N from the predecessors
/// of the current node M.
void ScheduleDAGTopologicalSort::RemovePred(SUnit *M, SUnit *N) {
// InitDAGTopologicalSorting();
}
/// DFS - Make a DFS traversal to mark all nodes reachable from SU and mark
/// all nodes affected by the edge insertion. These nodes will later get new
/// topological indexes by means of the Shift method.
void ScheduleDAGTopologicalSort::DFS(const SUnit *SU, int UpperBound,
bool &HasLoop) {
std::vector<const SUnit*> WorkList;
WorkList.reserve(SUnits.size());
WorkList.push_back(SU);
do {
SU = WorkList.back();
WorkList.pop_back();
Visited.set(SU->NodeNum);
for (int I = SU->Succs.size()-1; I >= 0; --I) {
unsigned s = SU->Succs[I].getSUnit()->NodeNum;
// Edges to non-SUnits are allowed but ignored (e.g. ExitSU).
if (s >= Node2Index.size())
continue;
if (Node2Index[s] == UpperBound) {
HasLoop = true;
return;
}
// Visit successors if not already and in affected region.
if (!Visited.test(s) && Node2Index[s] < UpperBound) {
WorkList.push_back(SU->Succs[I].getSUnit());
}
}
} while (!WorkList.empty());
}
/// Shift - Renumber the nodes so that the topological ordering is
/// preserved.
void ScheduleDAGTopologicalSort::Shift(BitVector& Visited, int LowerBound,
int UpperBound) {
std::vector<int> L;
int shift = 0;
int i;
for (i = LowerBound; i <= UpperBound; ++i) {
// w is node at topological index i.
int w = Index2Node[i];
if (Visited.test(w)) {
// Unmark.
Visited.reset(w);
L.push_back(w);
shift = shift + 1;
} else {
Allocate(w, i - shift);
}
}
for (unsigned j = 0; j < L.size(); ++j) {
Allocate(L[j], i - shift);
i = i + 1;
}
}
/// WillCreateCycle - Returns true if adding an edge to TargetSU from SU will
/// create a cycle. If so, it is not safe to call AddPred(TargetSU, SU).
bool ScheduleDAGTopologicalSort::WillCreateCycle(SUnit *TargetSU, SUnit *SU) {
// Is SU reachable from TargetSU via successor edges?
if (IsReachable(SU, TargetSU))
return true;
for (SUnit::pred_iterator
I = TargetSU->Preds.begin(), E = TargetSU->Preds.end(); I != E; ++I)
if (I->isAssignedRegDep() &&
IsReachable(SU, I->getSUnit()))
return true;
return false;
}
/// IsReachable - Checks if SU is reachable from TargetSU.
bool ScheduleDAGTopologicalSort::IsReachable(const SUnit *SU,
const SUnit *TargetSU) {
// If insertion of the edge SU->TargetSU would create a cycle
// then there is a path from TargetSU to SU.
int UpperBound, LowerBound;
LowerBound = Node2Index[TargetSU->NodeNum];
UpperBound = Node2Index[SU->NodeNum];
bool HasLoop = false;
// Is Ord(TargetSU) < Ord(SU) ?
if (LowerBound < UpperBound) {
Visited.reset();
// There may be a path from TargetSU to SU. Check for it.
DFS(TargetSU, UpperBound, HasLoop);
}
return HasLoop;
}
/// Allocate - assign the topological index to the node n.
void ScheduleDAGTopologicalSort::Allocate(int n, int index) {
Node2Index[n] = index;
Index2Node[index] = n;
}
ScheduleDAGTopologicalSort::
ScheduleDAGTopologicalSort(std::vector<SUnit> &sunits, SUnit *exitsu)
: SUnits(sunits), ExitSU(exitsu) {}
ScheduleHazardRecognizer::~ScheduleHazardRecognizer() {}