llvm-6502/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
2010-03-14 19:56:39 +00:00

467 lines
16 KiB
C++

//===--- ScheduleDAGSDNodes.cpp - Implement the ScheduleDAGSDNodes 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.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "pre-RA-sched"
#include "SDNodeDbgValue.h"
#include "ScheduleDAGSDNodes.h"
#include "InstrEmitter.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtarget.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
STATISTIC(LoadsClustered, "Number of loads clustered together");
ScheduleDAGSDNodes::ScheduleDAGSDNodes(MachineFunction &mf)
: ScheduleDAG(mf) {
}
/// Run - perform scheduling.
///
void ScheduleDAGSDNodes::Run(SelectionDAG *dag, MachineBasicBlock *bb,
MachineBasicBlock::iterator insertPos) {
DAG = dag;
ScheduleDAG::Run(bb, insertPos);
}
SUnit *ScheduleDAGSDNodes::Clone(SUnit *Old) {
SUnit *SU = NewSUnit(Old->getNode());
SU->OrigNode = Old->OrigNode;
SU->Latency = Old->Latency;
SU->isTwoAddress = Old->isTwoAddress;
SU->isCommutable = Old->isCommutable;
SU->hasPhysRegDefs = Old->hasPhysRegDefs;
SU->hasPhysRegClobbers = Old->hasPhysRegClobbers;
Old->isCloned = true;
return SU;
}
/// CheckForPhysRegDependency - Check if the dependency between def and use of
/// a specified operand is a physical register dependency. If so, returns the
/// register and the cost of copying the register.
static void CheckForPhysRegDependency(SDNode *Def, SDNode *User, unsigned Op,
const TargetRegisterInfo *TRI,
const TargetInstrInfo *TII,
unsigned &PhysReg, int &Cost) {
if (Op != 2 || User->getOpcode() != ISD::CopyToReg)
return;
unsigned Reg = cast<RegisterSDNode>(User->getOperand(1))->getReg();
if (TargetRegisterInfo::isVirtualRegister(Reg))
return;
unsigned ResNo = User->getOperand(2).getResNo();
if (Def->isMachineOpcode()) {
const TargetInstrDesc &II = TII->get(Def->getMachineOpcode());
if (ResNo >= II.getNumDefs() &&
II.ImplicitDefs[ResNo - II.getNumDefs()] == Reg) {
PhysReg = Reg;
const TargetRegisterClass *RC =
TRI->getPhysicalRegisterRegClass(Reg, Def->getValueType(ResNo));
Cost = RC->getCopyCost();
}
}
}
static void AddFlags(SDNode *N, SDValue Flag, bool AddFlag,
SelectionDAG *DAG) {
SmallVector<EVT, 4> VTs;
for (unsigned i = 0, e = N->getNumValues(); i != e; ++i)
VTs.push_back(N->getValueType(i));
if (AddFlag)
VTs.push_back(MVT::Flag);
SmallVector<SDValue, 4> Ops;
for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i)
Ops.push_back(N->getOperand(i));
if (Flag.getNode())
Ops.push_back(Flag);
SDVTList VTList = DAG->getVTList(&VTs[0], VTs.size());
DAG->MorphNodeTo(N, N->getOpcode(), VTList, &Ops[0], Ops.size());
}
/// ClusterNeighboringLoads - Force nearby loads together by "flagging" them.
/// This function finds loads of the same base and different offsets. If the
/// offsets are not far apart (target specific), it add MVT::Flag inputs and
/// outputs to ensure they are scheduled together and in order. This
/// optimization may benefit some targets by improving cache locality.
void ScheduleDAGSDNodes::ClusterNeighboringLoads() {
SmallPtrSet<SDNode*, 16> Visited;
SmallVector<int64_t, 4> Offsets;
DenseMap<long long, SDNode*> O2SMap; // Map from offset to SDNode.
for (SelectionDAG::allnodes_iterator NI = DAG->allnodes_begin(),
E = DAG->allnodes_end(); NI != E; ++NI) {
SDNode *Node = &*NI;
if (!Node || !Node->isMachineOpcode())
continue;
unsigned Opc = Node->getMachineOpcode();
const TargetInstrDesc &TID = TII->get(Opc);
if (!TID.mayLoad())
continue;
SDNode *Chain = 0;
unsigned NumOps = Node->getNumOperands();
if (Node->getOperand(NumOps-1).getValueType() == MVT::Other)
Chain = Node->getOperand(NumOps-1).getNode();
if (!Chain)
continue;
// Look for other loads of the same chain. Find loads that are loading from
// the same base pointer and different offsets.
Visited.clear();
Offsets.clear();
O2SMap.clear();
bool Cluster = false;
SDNode *Base = Node;
int64_t BaseOffset;
for (SDNode::use_iterator I = Chain->use_begin(), E = Chain->use_end();
I != E; ++I) {
SDNode *User = *I;
if (User == Node || !Visited.insert(User))
continue;
int64_t Offset1, Offset2;
if (!TII->areLoadsFromSameBasePtr(Base, User, Offset1, Offset2) ||
Offset1 == Offset2)
// FIXME: Should be ok if they addresses are identical. But earlier
// optimizations really should have eliminated one of the loads.
continue;
if (O2SMap.insert(std::make_pair(Offset1, Base)).second)
Offsets.push_back(Offset1);
O2SMap.insert(std::make_pair(Offset2, User));
Offsets.push_back(Offset2);
if (Offset2 < Offset1) {
Base = User;
BaseOffset = Offset2;
} else {
BaseOffset = Offset1;
}
Cluster = true;
}
if (!Cluster)
continue;
// Sort them in increasing order.
std::sort(Offsets.begin(), Offsets.end());
// Check if the loads are close enough.
SmallVector<SDNode*, 4> Loads;
unsigned NumLoads = 0;
int64_t BaseOff = Offsets[0];
SDNode *BaseLoad = O2SMap[BaseOff];
Loads.push_back(BaseLoad);
for (unsigned i = 1, e = Offsets.size(); i != e; ++i) {
int64_t Offset = Offsets[i];
SDNode *Load = O2SMap[Offset];
if (!TII->shouldScheduleLoadsNear(BaseLoad, Load, BaseOff, Offset,
NumLoads))
break; // Stop right here. Ignore loads that are further away.
Loads.push_back(Load);
++NumLoads;
}
if (NumLoads == 0)
continue;
// Cluster loads by adding MVT::Flag outputs and inputs. This also
// ensure they are scheduled in order of increasing addresses.
SDNode *Lead = Loads[0];
AddFlags(Lead, SDValue(0,0), true, DAG);
SDValue InFlag = SDValue(Lead, Lead->getNumValues()-1);
for (unsigned i = 1, e = Loads.size(); i != e; ++i) {
bool OutFlag = i < e-1;
SDNode *Load = Loads[i];
AddFlags(Load, InFlag, OutFlag, DAG);
if (OutFlag)
InFlag = SDValue(Load, Load->getNumValues()-1);
++LoadsClustered;
}
}
}
void ScheduleDAGSDNodes::BuildSchedUnits() {
// During scheduling, the NodeId field of SDNode is used to map SDNodes
// to their associated SUnits by holding SUnits table indices. A value
// of -1 means the SDNode does not yet have an associated SUnit.
unsigned NumNodes = 0;
for (SelectionDAG::allnodes_iterator NI = DAG->allnodes_begin(),
E = DAG->allnodes_end(); NI != E; ++NI) {
NI->setNodeId(-1);
++NumNodes;
}
// Reserve entries in the vector for each of the SUnits we are creating. This
// ensure that reallocation of the vector won't happen, so SUnit*'s won't get
// invalidated.
// FIXME: Multiply by 2 because we may clone nodes during scheduling.
// This is a temporary workaround.
SUnits.reserve(NumNodes * 2);
// Check to see if the scheduler cares about latencies.
bool UnitLatencies = ForceUnitLatencies();
// Add all nodes in depth first order.
SmallVector<SDNode*, 64> Worklist;
SmallPtrSet<SDNode*, 64> Visited;
Worklist.push_back(DAG->getRoot().getNode());
Visited.insert(DAG->getRoot().getNode());
while (!Worklist.empty()) {
SDNode *NI = Worklist.pop_back_val();
// Add all operands to the worklist unless they've already been added.
for (unsigned i = 0, e = NI->getNumOperands(); i != e; ++i)
if (Visited.insert(NI->getOperand(i).getNode()))
Worklist.push_back(NI->getOperand(i).getNode());
if (isPassiveNode(NI)) // Leaf node, e.g. a TargetImmediate.
continue;
// If this node has already been processed, stop now.
if (NI->getNodeId() != -1) continue;
SUnit *NodeSUnit = NewSUnit(NI);
// See if anything is flagged to this node, if so, add them to flagged
// nodes. Nodes can have at most one flag input and one flag output. Flags
// are required to be the last operand and result of a node.
// Scan up to find flagged preds.
SDNode *N = NI;
while (N->getNumOperands() &&
N->getOperand(N->getNumOperands()-1).getValueType() == MVT::Flag) {
N = N->getOperand(N->getNumOperands()-1).getNode();
assert(N->getNodeId() == -1 && "Node already inserted!");
N->setNodeId(NodeSUnit->NodeNum);
}
// Scan down to find any flagged succs.
N = NI;
while (N->getValueType(N->getNumValues()-1) == MVT::Flag) {
SDValue FlagVal(N, N->getNumValues()-1);
// There are either zero or one users of the Flag result.
bool HasFlagUse = false;
for (SDNode::use_iterator UI = N->use_begin(), E = N->use_end();
UI != E; ++UI)
if (FlagVal.isOperandOf(*UI)) {
HasFlagUse = true;
assert(N->getNodeId() == -1 && "Node already inserted!");
N->setNodeId(NodeSUnit->NodeNum);
N = *UI;
break;
}
if (!HasFlagUse) break;
}
// If there are flag operands involved, N is now the bottom-most node
// of the sequence of nodes that are flagged together.
// Update the SUnit.
NodeSUnit->setNode(N);
assert(N->getNodeId() == -1 && "Node already inserted!");
N->setNodeId(NodeSUnit->NodeNum);
// Assign the Latency field of NodeSUnit using target-provided information.
if (UnitLatencies)
NodeSUnit->Latency = 1;
else
ComputeLatency(NodeSUnit);
}
}
void ScheduleDAGSDNodes::AddSchedEdges() {
const TargetSubtarget &ST = TM.getSubtarget<TargetSubtarget>();
// Check to see if the scheduler cares about latencies.
bool UnitLatencies = ForceUnitLatencies();
// Pass 2: add the preds, succs, etc.
for (unsigned su = 0, e = SUnits.size(); su != e; ++su) {
SUnit *SU = &SUnits[su];
SDNode *MainNode = SU->getNode();
if (MainNode->isMachineOpcode()) {
unsigned Opc = MainNode->getMachineOpcode();
const TargetInstrDesc &TID = TII->get(Opc);
for (unsigned i = 0; i != TID.getNumOperands(); ++i) {
if (TID.getOperandConstraint(i, TOI::TIED_TO) != -1) {
SU->isTwoAddress = true;
break;
}
}
if (TID.isCommutable())
SU->isCommutable = true;
}
// Find all predecessors and successors of the group.
for (SDNode *N = SU->getNode(); N; N = N->getFlaggedNode()) {
if (N->isMachineOpcode() &&
TII->get(N->getMachineOpcode()).getImplicitDefs()) {
SU->hasPhysRegClobbers = true;
unsigned NumUsed = InstrEmitter::CountResults(N);
while (NumUsed != 0 && !N->hasAnyUseOfValue(NumUsed - 1))
--NumUsed; // Skip over unused values at the end.
if (NumUsed > TII->get(N->getMachineOpcode()).getNumDefs())
SU->hasPhysRegDefs = true;
}
for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) {
SDNode *OpN = N->getOperand(i).getNode();
if (isPassiveNode(OpN)) continue; // Not scheduled.
SUnit *OpSU = &SUnits[OpN->getNodeId()];
assert(OpSU && "Node has no SUnit!");
if (OpSU == SU) continue; // In the same group.
EVT OpVT = N->getOperand(i).getValueType();
assert(OpVT != MVT::Flag && "Flagged nodes should be in same sunit!");
bool isChain = OpVT == MVT::Other;
unsigned PhysReg = 0;
int Cost = 1;
// Determine if this is a physical register dependency.
CheckForPhysRegDependency(OpN, N, i, TRI, TII, PhysReg, Cost);
assert((PhysReg == 0 || !isChain) &&
"Chain dependence via physreg data?");
// FIXME: See ScheduleDAGSDNodes::EmitCopyFromReg. For now, scheduler
// emits a copy from the physical register to a virtual register unless
// it requires a cross class copy (cost < 0). That means we are only
// treating "expensive to copy" register dependency as physical register
// dependency. This may change in the future though.
if (Cost >= 0)
PhysReg = 0;
const SDep& dep = SDep(OpSU, isChain ? SDep::Order : SDep::Data,
OpSU->Latency, PhysReg);
if (!isChain && !UnitLatencies) {
ComputeOperandLatency(OpSU, SU, (SDep &)dep);
ST.adjustSchedDependency(OpSU, SU, (SDep &)dep);
}
SU->addPred(dep);
}
}
}
}
/// BuildSchedGraph - Build the SUnit graph from the selection dag that we
/// are input. This SUnit graph is similar to the SelectionDAG, but
/// excludes nodes that aren't interesting to scheduling, and represents
/// flagged together nodes with a single SUnit.
void ScheduleDAGSDNodes::BuildSchedGraph(AliasAnalysis *AA) {
// Cluster loads from "near" addresses into combined SUnits.
ClusterNeighboringLoads();
// Populate the SUnits array.
BuildSchedUnits();
// Compute all the scheduling dependencies between nodes.
AddSchedEdges();
}
void ScheduleDAGSDNodes::ComputeLatency(SUnit *SU) {
const InstrItineraryData &InstrItins = TM.getInstrItineraryData();
// Compute the latency for the node. We use the sum of the latencies for
// all nodes flagged together into this SUnit.
SU->Latency = 0;
for (SDNode *N = SU->getNode(); N; N = N->getFlaggedNode())
if (N->isMachineOpcode()) {
SU->Latency += InstrItins.
getStageLatency(TII->get(N->getMachineOpcode()).getSchedClass());
}
}
void ScheduleDAGSDNodes::dumpNode(const SUnit *SU) const {
if (!SU->getNode()) {
dbgs() << "PHYS REG COPY\n";
return;
}
SU->getNode()->dump(DAG);
dbgs() << "\n";
SmallVector<SDNode *, 4> FlaggedNodes;
for (SDNode *N = SU->getNode()->getFlaggedNode(); N; N = N->getFlaggedNode())
FlaggedNodes.push_back(N);
while (!FlaggedNodes.empty()) {
dbgs() << " ";
FlaggedNodes.back()->dump(DAG);
dbgs() << "\n";
FlaggedNodes.pop_back();
}
}
/// EmitSchedule - Emit the machine code in scheduled order.
MachineBasicBlock *ScheduleDAGSDNodes::
EmitSchedule(DenseMap<MachineBasicBlock*, MachineBasicBlock*> *EM) {
InstrEmitter Emitter(BB, InsertPos);
DenseMap<SDValue, unsigned> VRBaseMap;
DenseMap<SUnit*, unsigned> CopyVRBaseMap;
// For now, any constant debug info nodes go at the beginning.
for (SDDbgInfo::ConstDbgIterator I = DAG->DbgConstBegin(),
E = DAG->DbgConstEnd(); I!=E; I++) {
Emitter.EmitDbgValue(*I, EM);
delete *I;
}
for (unsigned i = 0, e = Sequence.size(); i != e; i++) {
SUnit *SU = Sequence[i];
if (!SU) {
// Null SUnit* is a noop.
EmitNoop();
continue;
}
// For pre-regalloc scheduling, create instructions corresponding to the
// SDNode and any flagged SDNodes and append them to the block.
if (!SU->getNode()) {
// Emit a copy.
EmitPhysRegCopy(SU, CopyVRBaseMap);
continue;
}
SmallVector<SDNode *, 4> FlaggedNodes;
for (SDNode *N = SU->getNode()->getFlaggedNode(); N;
N = N->getFlaggedNode())
FlaggedNodes.push_back(N);
while (!FlaggedNodes.empty()) {
Emitter.EmitNode(FlaggedNodes.back(), SU->OrigNode != SU, SU->isCloned,
VRBaseMap, EM);
if (FlaggedNodes.back()->getHasDebugValue())
if (SDDbgValue *sd = DAG->GetDbgInfo(FlaggedNodes.back())) {
Emitter.EmitDbgValue(FlaggedNodes.back(), VRBaseMap, sd);
delete sd;
}
FlaggedNodes.pop_back();
}
Emitter.EmitNode(SU->getNode(), SU->OrigNode != SU, SU->isCloned,
VRBaseMap, EM);
if (SU->getNode()->getHasDebugValue())
if (SDDbgValue *sd = DAG->GetDbgInfo(SU->getNode())) {
Emitter.EmitDbgValue(SU->getNode(), VRBaseMap, sd);
delete sd;
}
}
BB = Emitter.getBlock();
InsertPos = Emitter.getInsertPos();
return BB;
}