//===-- ScheduleDAGSimple.cpp - Implement a trivial DAG scheduler ---------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by James M. Laskey and is distributed under the
// University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This implements a simple two pass scheduler. The first pass attempts to push
// backward any lengthy instructions and critical paths. The second pass packs
// instructions into semi-optimal time slots.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "pre-RA-sched"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/ScheduleDAG.h"
#include "llvm/CodeGen/SchedulerRegistry.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/CodeGen/SSARegMap.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Compiler.h"
#include <algorithm>
using namespace llvm;
namespace {
static RegisterScheduler
bfsDAGScheduler("none", " No scheduling: breadth first sequencing",
createBFS_DAGScheduler);
static RegisterScheduler
simpleDAGScheduler("simple",
" Simple two pass scheduling: minimize critical path "
"and maximize processor utilization",
createSimpleDAGScheduler);
static RegisterScheduler
noitinDAGScheduler("simple-noitin",
" Simple two pass scheduling: Same as simple "
"except using generic latency",
createNoItinsDAGScheduler);
class NodeInfo;
typedef NodeInfo *NodeInfoPtr;
typedef std::vector<NodeInfoPtr> NIVector;
typedef std::vector<NodeInfoPtr>::iterator NIIterator;
//===--------------------------------------------------------------------===//
///
/// Node group - This struct is used to manage flagged node groups.
///
class NodeGroup {
public:
NodeGroup *Next;
private:
NIVector Members; // Group member nodes
NodeInfo *Dominator; // Node with highest latency
unsigned Latency; // Total latency of the group
int Pending; // Number of visits pending before
// adding to order
public:
// Ctor.
NodeGroup() : Next(NULL), Dominator(NULL), Pending(0) {}
// Accessors
inline void setDominator(NodeInfo *D) { Dominator = D; }
inline NodeInfo *getTop() { return Members.front(); }
inline NodeInfo *getBottom() { return Members.back(); }
inline NodeInfo *getDominator() { return Dominator; }
inline void setLatency(unsigned L) { Latency = L; }
inline unsigned getLatency() { return Latency; }
inline int getPending() const { return Pending; }
inline void setPending(int P) { Pending = P; }
inline int addPending(int I) { return Pending += I; }
// Pass thru
inline bool group_empty() { return Members.empty(); }
inline NIIterator group_begin() { return Members.begin(); }
inline NIIterator group_end() { return Members.end(); }
inline void group_push_back(const NodeInfoPtr &NI) {
Members.push_back(NI);
}
inline NIIterator group_insert(NIIterator Pos, const NodeInfoPtr &NI) {
return Members.insert(Pos, NI);
}
inline void group_insert(NIIterator Pos, NIIterator First,
NIIterator Last) {
Members.insert(Pos, First, Last);
}
static void Add(NodeInfo *D, NodeInfo *U);
};
//===--------------------------------------------------------------------===//
///
/// NodeInfo - This struct tracks information used to schedule the a node.
///
class NodeInfo {
private:
int Pending; // Number of visits pending before
// adding to order
public:
SDNode *Node; // DAG node
InstrStage *StageBegin; // First stage in itinerary
InstrStage *StageEnd; // Last+1 stage in itinerary
unsigned Latency; // Total cycles to complete instr
bool IsCall : 1; // Is function call
bool IsLoad : 1; // Is memory load
bool IsStore : 1; // Is memory store
unsigned Slot; // Node's time slot
NodeGroup *Group; // Grouping information
#ifndef NDEBUG
unsigned Preorder; // Index before scheduling
#endif
// Ctor.
NodeInfo(SDNode *N = NULL)
: Pending(0)
, Node(N)
, StageBegin(NULL)
, StageEnd(NULL)
, Latency(0)
, IsCall(false)
, Slot(0)
, Group(NULL)
#ifndef NDEBUG
, Preorder(0)
#endif
{}
// Accessors
inline bool isInGroup() const {
assert(!Group || !Group->group_empty() && "Group with no members");
return Group != NULL;
}
inline bool isGroupDominator() const {
return isInGroup() && Group->getDominator() == this;
}
inline int getPending() const {
return Group ? Group->getPending() : Pending;
}
inline void setPending(int P) {
if (Group) Group->setPending(P);
else Pending = P;
}
inline int addPending(int I) {
if (Group) return Group->addPending(I);
else return Pending += I;
}
};
//===--------------------------------------------------------------------===//
///
/// NodeGroupIterator - Iterates over all the nodes indicated by the node
/// info. If the node is in a group then iterate over the members of the
/// group, otherwise just the node info.
///
class NodeGroupIterator {
private:
NodeInfo *NI; // Node info
NIIterator NGI; // Node group iterator
NIIterator NGE; // Node group iterator end
bool iter_valid;
public:
// Ctor.
NodeGroupIterator(NodeInfo *N) : NI(N), iter_valid(false) {
// If the node is in a group then set up the group iterator. Otherwise
// the group iterators will trip first time out.
assert(N && "Bad node info");
if (N->isInGroup()) {
// get Group
NodeGroup *Group = NI->Group;
NGI = Group->group_begin();
NGE = Group->group_end();
// Prevent this node from being used (will be in members list
NI = NULL;
iter_valid = true;
}
}
/// next - Return the next node info, otherwise NULL.
///
NodeInfo *next() {
if (iter_valid) {
// If members list
if (NGI != NGE) return *NGI++;
}
// Use node as the result (may be NULL)
NodeInfo *Result = NI;
// Only use once
NI = NULL;
// Return node or NULL
return Result;
}
};
//===--------------------------------------------------------------------===//
//===--------------------------------------------------------------------===//
///
/// NodeGroupOpIterator - Iterates over all the operands of a node. If the
/// node is a member of a group, this iterates over all the operands of all
/// the members of the group.
///
class NodeGroupOpIterator {
private:
NodeInfo *NI; // Node containing operands
NodeGroupIterator GI; // Node group iterator
SDNode::op_iterator OI; // Operand iterator
SDNode::op_iterator OE; // Operand iterator end
/// CheckNode - Test if node has more operands. If not get the next node
/// skipping over nodes that have no operands.
void CheckNode() {
// Only if operands are exhausted first
while (OI == OE) {
// Get next node info
NodeInfo *NI = GI.next();
// Exit if nodes are exhausted
if (!NI) return;
// Get node itself
SDNode *Node = NI->Node;
// Set up the operand iterators
OI = Node->op_begin();
OE = Node->op_end();
}
}
public:
// Ctor.
NodeGroupOpIterator(NodeInfo *N)
: NI(N), GI(N), OI(SDNode::op_iterator()), OE(SDNode::op_iterator()) {}
/// isEnd - Returns true when not more operands are available.
///
inline bool isEnd() { CheckNode(); return OI == OE; }
/// next - Returns the next available operand.
///
inline SDOperand next() {
assert(OI != OE &&
"Not checking for end of NodeGroupOpIterator correctly");
return *OI++;
}
};
//===----------------------------------------------------------------------===//
///
/// BitsIterator - Provides iteration through individual bits in a bit vector.
///
template<class T>
class BitsIterator {
private:
T Bits; // Bits left to iterate through
public:
/// Ctor.
BitsIterator(T Initial) : Bits(Initial) {}
/// Next - Returns the next bit set or zero if exhausted.
inline T Next() {
// Get the rightmost bit set
T Result = Bits & -Bits;
// Remove from rest
Bits &= ~Result;
// Return single bit or zero
return Result;
}
};
//===----------------------------------------------------------------------===//
//===----------------------------------------------------------------------===//
///
/// ResourceTally - Manages the use of resources over time intervals. Each
/// item (slot) in the tally vector represents the resources used at a given
/// moment. A bit set to 1 indicates that a resource is in use, otherwise
/// available. An assumption is made that the tally is large enough to schedule
/// all current instructions (asserts otherwise.)
///
template<class T>
class ResourceTally {
private:
std::vector<T> Tally; // Resources used per slot
typedef typename std::vector<T>::iterator Iter;
// Tally iterator
/// SlotsAvailable - Returns true if all units are available.
///
bool SlotsAvailable(Iter Begin, unsigned N, unsigned ResourceSet,
unsigned &Resource) {
assert(N && "Must check availability with N != 0");
// Determine end of interval
Iter End = Begin + N;
assert(End <= Tally.end() && "Tally is not large enough for schedule");
// Iterate thru each resource
BitsIterator<T> Resources(ResourceSet & ~*Begin);
while (unsigned Res = Resources.Next()) {
// Check if resource is available for next N slots
Iter Interval = End;
do {
Interval--;
if (*Interval & Res) break;
} while (Interval != Begin);
// If available for N
if (Interval == Begin) {
// Success
Resource = Res;
return true;
}
}
// No luck
Resource = 0;
return false;
}
/// RetrySlot - Finds a good candidate slot to retry search.
Iter RetrySlot(Iter Begin, unsigned N, unsigned ResourceSet) {
assert(N && "Must check availability with N != 0");
// Determine end of interval
Iter End = Begin + N;
assert(End <= Tally.end() && "Tally is not large enough for schedule");
while (Begin != End--) {
// Clear units in use
ResourceSet &= ~*End;
// If no units left then we should go no further
if (!ResourceSet) return End + 1;
}
// Made it all the way through
return Begin;
}
/// FindAndReserveStages - Return true if the stages can be completed. If
/// so mark as busy.
bool FindAndReserveStages(Iter Begin,
InstrStage *Stage, InstrStage *StageEnd) {
// If at last stage then we're done
if (Stage == StageEnd) return true;
// Get number of cycles for current stage
unsigned N = Stage->Cycles;
// Check to see if N slots are available, if not fail
unsigned Resource;
if (!SlotsAvailable(Begin, N, Stage->Units, Resource)) return false;
// Check to see if remaining stages are available, if not fail
if (!FindAndReserveStages(Begin + N, Stage + 1, StageEnd)) return false;
// Reserve resource
Reserve(Begin, N, Resource);
// Success
return true;
}
/// Reserve - Mark busy (set) the specified N slots.
void Reserve(Iter Begin, unsigned N, unsigned Resource) {
// Determine end of interval
Iter End = Begin + N;
assert(End <= Tally.end() && "Tally is not large enough for schedule");
// Set resource bit in each slot
for (; Begin < End; Begin++)
*Begin |= Resource;
}
/// FindSlots - Starting from Begin, locate consecutive slots where all stages
/// can be completed. Returns the address of first slot.
Iter FindSlots(Iter Begin, InstrStage *StageBegin, InstrStage *StageEnd) {
// Track position
Iter Cursor = Begin;
// Try all possible slots forward
while (true) {
// Try at cursor, if successful return position.
if (FindAndReserveStages(Cursor, StageBegin, StageEnd)) return Cursor;
// Locate a better position
Cursor = RetrySlot(Cursor + 1, StageBegin->Cycles, StageBegin->Units);
}
}
public:
/// Initialize - Resize and zero the tally to the specified number of time
/// slots.
inline void Initialize(unsigned N) {
Tally.assign(N, 0); // Initialize tally to all zeros.
}
// FindAndReserve - Locate an ideal slot for the specified stages and mark
// as busy.
unsigned FindAndReserve(unsigned Slot, InstrStage *StageBegin,
InstrStage *StageEnd) {
// Where to begin
Iter Begin = Tally.begin() + Slot;
// Find a free slot
Iter Where = FindSlots(Begin, StageBegin, StageEnd);
// Distance is slot number
unsigned Final = Where - Tally.begin();
return Final;
}
};
//===----------------------------------------------------------------------===//
///
/// ScheduleDAGSimple - Simple two pass scheduler.
///
class VISIBILITY_HIDDEN ScheduleDAGSimple : public ScheduleDAG {
private:
bool NoSched; // Just do a BFS schedule, nothing fancy
bool NoItins; // Don't use itineraries?
ResourceTally<unsigned> Tally; // Resource usage tally
unsigned NSlots; // Total latency
static const unsigned NotFound = ~0U; // Search marker
unsigned NodeCount; // Number of nodes in DAG
std::map<SDNode *, NodeInfo *> Map; // Map nodes to info
bool HasGroups; // True if there are any groups
NodeInfo *Info; // Info for nodes being scheduled
NIVector Ordering; // Emit ordering of nodes
NodeGroup *HeadNG, *TailNG; // Keep track of allocated NodeGroups
public:
// Ctor.
ScheduleDAGSimple(bool noSched, bool noItins, SelectionDAG &dag,
MachineBasicBlock *bb, const TargetMachine &tm)
: ScheduleDAG(dag, bb, tm), NoSched(noSched), NoItins(noItins), NSlots(0),
NodeCount(0), HasGroups(false), Info(NULL), HeadNG(NULL), TailNG(NULL) {
assert(&TII && "Target doesn't provide instr info?");
assert(&MRI && "Target doesn't provide register info?");
}
virtual ~ScheduleDAGSimple() {
if (Info)
delete[] Info;
NodeGroup *NG = HeadNG;
while (NG) {
NodeGroup *NextSU = NG->Next;
delete NG;
NG = NextSU;
}
}
void Schedule();
/// getNI - Returns the node info for the specified node.
///
NodeInfo *getNI(SDNode *Node) { return Map[Node]; }
private:
static bool isDefiner(NodeInfo *A, NodeInfo *B);
void IncludeNode(NodeInfo *NI);
void VisitAll();
void GatherSchedulingInfo();
void FakeGroupDominators();
bool isStrongDependency(NodeInfo *A, NodeInfo *B);
bool isWeakDependency(NodeInfo *A, NodeInfo *B);
void ScheduleBackward();
void ScheduleForward();
void AddToGroup(NodeInfo *D, NodeInfo *U);
/// PrepareNodeInfo - Set up the basic minimum node info for scheduling.
///
void PrepareNodeInfo();
/// IdentifyGroups - Put flagged nodes into groups.
///
void IdentifyGroups();
/// print - Print ordering to specified output stream.
///
void print(std::ostream &O) const;
void print(std::ostream *O) const { if (O) print(*O); }
void dump(const char *tag) const;
virtual void dump() const;
/// EmitAll - Emit all nodes in schedule sorted order.
///
void EmitAll();
/// printNI - Print node info.
///
void printNI(std::ostream &O, NodeInfo *NI) const;
void printNI(std::ostream *O, NodeInfo *NI) const { if (O) printNI(*O, NI); }
/// printChanges - Hilight changes in order caused by scheduling.
///
void printChanges(unsigned Index) const;
};
//===----------------------------------------------------------------------===//
/// Special case itineraries.
///
enum {
CallLatency = 40, // To push calls back in time
RSInteger = 0xC0000000, // Two integer units
RSFloat = 0x30000000, // Two float units
RSLoadStore = 0x0C000000, // Two load store units
RSBranch = 0x02000000 // One branch unit
};
static InstrStage LoadStage = { 5, RSLoadStore };
static InstrStage StoreStage = { 2, RSLoadStore };
static InstrStage IntStage = { 2, RSInteger };
static InstrStage FloatStage = { 3, RSFloat };
//===----------------------------------------------------------------------===//
} // namespace
//===----------------------------------------------------------------------===//
/// PrepareNodeInfo - Set up the basic minimum node info for scheduling.
///
void ScheduleDAGSimple::PrepareNodeInfo() {
// Allocate node information
Info = new NodeInfo[NodeCount];
unsigned i = 0;
for (SelectionDAG::allnodes_iterator I = DAG.allnodes_begin(),
E = DAG.allnodes_end(); I != E; ++I, ++i) {
// Fast reference to node schedule info
NodeInfo* NI = &Info[i];
// Set up map
Map[I] = NI;
// Set node
NI->Node = I;
// Set pending visit count
NI->setPending(I->use_size());
}
}
/// IdentifyGroups - Put flagged nodes into groups.
///
void ScheduleDAGSimple::IdentifyGroups() {
for (unsigned i = 0, N = NodeCount; i < N; i++) {
NodeInfo* NI = &Info[i];
SDNode *Node = NI->Node;
// For each operand (in reverse to only look at flags)
for (unsigned N = Node->getNumOperands(); 0 < N--;) {
// Get operand
SDOperand Op = Node->getOperand(N);
// No more flags to walk
if (Op.getValueType() != MVT::Flag) break;
// Add to node group
AddToGroup(getNI(Op.Val), NI);
// Let everyone else know
HasGroups = true;
}
}
}
/// CountInternalUses - Returns the number of edges between the two nodes.
///
static unsigned CountInternalUses(NodeInfo *D, NodeInfo *U) {
unsigned N = 0;
for (unsigned M = U->Node->getNumOperands(); 0 < M--;) {
SDOperand Op = U->Node->getOperand(M);
if (Op.Val == D->Node) N++;
}
return N;
}
//===----------------------------------------------------------------------===//
/// Add - Adds a definer and user pair to a node group.
///
void ScheduleDAGSimple::AddToGroup(NodeInfo *D, NodeInfo *U) {
// Get current groups
NodeGroup *DGroup = D->Group;
NodeGroup *UGroup = U->Group;
// If both are members of groups
if (DGroup && UGroup) {
// There may have been another edge connecting
if (DGroup == UGroup) return;
// Add the pending users count
DGroup->addPending(UGroup->getPending());
// For each member of the users group
NodeGroupIterator UNGI(U);
while (NodeInfo *UNI = UNGI.next() ) {
// Change the group
UNI->Group = DGroup;
// For each member of the definers group
NodeGroupIterator DNGI(D);
while (NodeInfo *DNI = DNGI.next() ) {
// Remove internal edges
DGroup->addPending(-CountInternalUses(DNI, UNI));
}
}
// Merge the two lists
DGroup->group_insert(DGroup->group_end(),
UGroup->group_begin(), UGroup->group_end());
} else if (DGroup) {
// Make user member of definers group
U->Group = DGroup;
// Add users uses to definers group pending
DGroup->addPending(U->Node->use_size());
// For each member of the definers group
NodeGroupIterator DNGI(D);
while (NodeInfo *DNI = DNGI.next() ) {
// Remove internal edges
DGroup->addPending(-CountInternalUses(DNI, U));
}
DGroup->group_push_back(U);
} else if (UGroup) {
// Make definer member of users group
D->Group = UGroup;
// Add definers uses to users group pending
UGroup->addPending(D->Node->use_size());
// For each member of the users group
NodeGroupIterator UNGI(U);
while (NodeInfo *UNI = UNGI.next() ) {
// Remove internal edges
UGroup->addPending(-CountInternalUses(D, UNI));
}
UGroup->group_insert(UGroup->group_begin(), D);
} else {
D->Group = U->Group = DGroup = new NodeGroup();
DGroup->addPending(D->Node->use_size() + U->Node->use_size() -
CountInternalUses(D, U));
DGroup->group_push_back(D);
DGroup->group_push_back(U);
if (HeadNG == NULL)
HeadNG = DGroup;
if (TailNG != NULL)
TailNG->Next = DGroup;
TailNG = DGroup;
}
}
/// print - Print ordering to specified output stream.
///
void ScheduleDAGSimple::print(std::ostream &O) const {
#ifndef NDEBUG
O << "Ordering\n";
for (unsigned i = 0, N = Ordering.size(); i < N; i++) {
NodeInfo *NI = Ordering[i];
printNI(O, NI);
O << "\n";
if (NI->isGroupDominator()) {
NodeGroup *Group = NI->Group;
for (NIIterator NII = Group->group_begin(), E = Group->group_end();
NII != E; NII++) {
O << " ";
printNI(O, *NII);
O << "\n";
}
}
}
#endif
}
void ScheduleDAGSimple::dump(const char *tag) const {
cerr << tag; dump();
}
void ScheduleDAGSimple::dump() const {
print(cerr);
}
/// EmitAll - Emit all nodes in schedule sorted order.
///
void ScheduleDAGSimple::EmitAll() {
// If this is the first basic block in the function, and if it has live ins
// that need to be copied into vregs, emit the copies into the top of the
// block before emitting the code for the block.
MachineFunction &MF = DAG.getMachineFunction();
if (&MF.front() == BB && MF.livein_begin() != MF.livein_end()) {
for (MachineFunction::livein_iterator LI = MF.livein_begin(),
E = MF.livein_end(); LI != E; ++LI)
if (LI->second)
MRI->copyRegToReg(*MF.begin(), MF.begin()->end(), LI->second,
LI->first, RegMap->getRegClass(LI->second));
}
DenseMap<SDOperand, unsigned> VRBaseMap;
// For each node in the ordering
for (unsigned i = 0, N = Ordering.size(); i < N; i++) {
// Get the scheduling info
NodeInfo *NI = Ordering[i];
if (NI->isInGroup()) {
NodeGroupIterator NGI(Ordering[i]);
while (NodeInfo *NI = NGI.next()) EmitNode(NI->Node, VRBaseMap);
} else {
EmitNode(NI->Node, VRBaseMap);
}
}
}
/// isFlagDefiner - Returns true if the node defines a flag result.
static bool isFlagDefiner(SDNode *A) {
unsigned N = A->getNumValues();
return N && A->getValueType(N - 1) == MVT::Flag;
}
/// isFlagUser - Returns true if the node uses a flag result.
///
static bool isFlagUser(SDNode *A) {
unsigned N = A->getNumOperands();
return N && A->getOperand(N - 1).getValueType() == MVT::Flag;
}
/// printNI - Print node info.
///
void ScheduleDAGSimple::printNI(std::ostream &O, NodeInfo *NI) const {
#ifndef NDEBUG
SDNode *Node = NI->Node;
O << " "
<< std::hex << Node << std::dec
<< ", Lat=" << NI->Latency
<< ", Slot=" << NI->Slot
<< ", ARITY=(" << Node->getNumOperands() << ","
<< Node->getNumValues() << ")"
<< " " << Node->getOperationName(&DAG);
if (isFlagDefiner(Node)) O << "<#";
if (isFlagUser(Node)) O << ">#";
#endif
}
/// printChanges - Hilight changes in order caused by scheduling.
///
void ScheduleDAGSimple::printChanges(unsigned Index) const {
#ifndef NDEBUG
// Get the ordered node count
unsigned N = Ordering.size();
// Determine if any changes
unsigned i = 0;
for (; i < N; i++) {
NodeInfo *NI = Ordering[i];
if (NI->Preorder != i) break;
}
if (i < N) {
cerr << Index << ". New Ordering\n";
for (i = 0; i < N; i++) {
NodeInfo *NI = Ordering[i];
cerr << " " << NI->Preorder << ". ";
printNI(cerr, NI);
cerr << "\n";
if (NI->isGroupDominator()) {
NodeGroup *Group = NI->Group;
for (NIIterator NII = Group->group_begin(), E = Group->group_end();
NII != E; NII++) {
cerr << " ";
printNI(cerr, *NII);
cerr << "\n";
}
}
}
} else {
cerr << Index << ". No Changes\n";
}
#endif
}
//===----------------------------------------------------------------------===//
/// isDefiner - Return true if node A is a definer for B.
///
bool ScheduleDAGSimple::isDefiner(NodeInfo *A, NodeInfo *B) {
// While there are A nodes
NodeGroupIterator NII(A);
while (NodeInfo *NI = NII.next()) {
// Extract node
SDNode *Node = NI->Node;
// While there operands in nodes of B
NodeGroupOpIterator NGOI(B);
while (!NGOI.isEnd()) {
SDOperand Op = NGOI.next();
// If node from A defines a node in B
if (Node == Op.Val) return true;
}
}
return false;
}
/// IncludeNode - Add node to NodeInfo vector.
///
void ScheduleDAGSimple::IncludeNode(NodeInfo *NI) {
// Get node
SDNode *Node = NI->Node;
// Ignore entry node
if (Node->getOpcode() == ISD::EntryToken) return;
// Check current count for node
int Count = NI->getPending();
// If the node is already in list
if (Count < 0) return;
// Decrement count to indicate a visit
Count--;
// If count has gone to zero then add node to list
if (!Count) {
// Add node
if (NI->isInGroup()) {
Ordering.push_back(NI->Group->getDominator());
} else {
Ordering.push_back(NI);
}
// indicate node has been added
Count--;
}
// Mark as visited with new count
NI->setPending(Count);
}
/// GatherSchedulingInfo - Get latency and resource information about each node.
///
void ScheduleDAGSimple::GatherSchedulingInfo() {
// Get instruction itineraries for the target
const InstrItineraryData &InstrItins = TM.getInstrItineraryData();
// For each node
for (unsigned i = 0, N = NodeCount; i < N; i++) {
// Get node info
NodeInfo* NI = &Info[i];
SDNode *Node = NI->Node;
// If there are itineraries and it is a machine instruction
if (InstrItins.isEmpty() || NoItins) {
// If machine opcode
if (Node->isTargetOpcode()) {
// Get return type to guess which processing unit
MVT::ValueType VT = Node->getValueType(0);
// Get machine opcode
MachineOpCode TOpc = Node->getTargetOpcode();
NI->IsCall = TII->isCall(TOpc);
NI->IsLoad = TII->isLoad(TOpc);
NI->IsStore = TII->isStore(TOpc);
if (TII->isLoad(TOpc)) NI->StageBegin = &LoadStage;
else if (TII->isStore(TOpc)) NI->StageBegin = &StoreStage;
else if (MVT::isInteger(VT)) NI->StageBegin = &IntStage;
else if (MVT::isFloatingPoint(VT)) NI->StageBegin = &FloatStage;
if (NI->StageBegin) NI->StageEnd = NI->StageBegin + 1;
}
} else if (Node->isTargetOpcode()) {
// get machine opcode
MachineOpCode TOpc = Node->getTargetOpcode();
// Check to see if it is a call
NI->IsCall = TII->isCall(TOpc);
// Get itinerary stages for instruction
unsigned II = TII->getSchedClass(TOpc);
NI->StageBegin = InstrItins.begin(II);
NI->StageEnd = InstrItins.end(II);
}
// One slot for the instruction itself
NI->Latency = 1;
// Add long latency for a call to push it back in time
if (NI->IsCall) NI->Latency += CallLatency;
// Sum up all the latencies
for (InstrStage *Stage = NI->StageBegin, *E = NI->StageEnd;
Stage != E; Stage++) {
NI->Latency += Stage->Cycles;
}
// Sum up all the latencies for max tally size
NSlots += NI->Latency;
}
// Unify metrics if in a group
if (HasGroups) {
for (unsigned i = 0, N = NodeCount; i < N; i++) {
NodeInfo* NI = &Info[i];
if (NI->isInGroup()) {
NodeGroup *Group = NI->Group;
if (!Group->getDominator()) {
NIIterator NGI = Group->group_begin(), NGE = Group->group_end();
NodeInfo *Dominator = *NGI;
unsigned Latency = 0;
for (NGI++; NGI != NGE; NGI++) {
NodeInfo* NGNI = *NGI;
Latency += NGNI->Latency;
if (Dominator->Latency < NGNI->Latency) Dominator = NGNI;
}
Dominator->Latency = Latency;
Group->setDominator(Dominator);
}
}
}
}
}
/// VisitAll - Visit each node breadth-wise to produce an initial ordering.
/// Note that the ordering in the Nodes vector is reversed.
void ScheduleDAGSimple::VisitAll() {
// Add first element to list
NodeInfo *NI = getNI(DAG.getRoot().Val);
if (NI->isInGroup()) {
Ordering.push_back(NI->Group->getDominator());
} else {
Ordering.push_back(NI);
}
// Iterate through all nodes that have been added
for (unsigned i = 0; i < Ordering.size(); i++) { // note: size() varies
// Visit all operands
NodeGroupOpIterator NGI(Ordering[i]);
while (!NGI.isEnd()) {
// Get next operand
SDOperand Op = NGI.next();
// Get node
SDNode *Node = Op.Val;
// Ignore passive nodes
if (isPassiveNode(Node)) continue;
// Check out node
IncludeNode(getNI(Node));
}
}
// Add entry node last (IncludeNode filters entry nodes)
if (DAG.getEntryNode().Val != DAG.getRoot().Val)
Ordering.push_back(getNI(DAG.getEntryNode().Val));
// Reverse the order
std::reverse(Ordering.begin(), Ordering.end());
}
/// FakeGroupDominators - Set dominators for non-scheduling.
///
void ScheduleDAGSimple::FakeGroupDominators() {
for (unsigned i = 0, N = NodeCount; i < N; i++) {
NodeInfo* NI = &Info[i];
if (NI->isInGroup()) {
NodeGroup *Group = NI->Group;
if (!Group->getDominator()) {
Group->setDominator(NI);
}
}
}
}
/// isStrongDependency - Return true if node A has results used by node B.
/// I.E., B must wait for latency of A.
bool ScheduleDAGSimple::isStrongDependency(NodeInfo *A, NodeInfo *B) {
// If A defines for B then it's a strong dependency or
// if a load follows a store (may be dependent but why take a chance.)
return isDefiner(A, B) || (A->IsStore && B->IsLoad);
}
/// isWeakDependency Return true if node A produces a result that will
/// conflict with operands of B. It is assumed that we have called
/// isStrongDependency prior.
bool ScheduleDAGSimple::isWeakDependency(NodeInfo *A, NodeInfo *B) {
// TODO check for conflicting real registers and aliases
#if 0 // FIXME - Since we are in SSA form and not checking register aliasing
return A->Node->getOpcode() == ISD::EntryToken || isStrongDependency(B, A);
#else
return A->Node->getOpcode() == ISD::EntryToken;
#endif
}
/// ScheduleBackward - Schedule instructions so that any long latency
/// instructions and the critical path get pushed back in time. Time is run in
/// reverse to allow code reuse of the Tally and eliminate the overhead of
/// biasing every slot indices against NSlots.
void ScheduleDAGSimple::ScheduleBackward() {
// Size and clear the resource tally
Tally.Initialize(NSlots);
// Get number of nodes to schedule
unsigned N = Ordering.size();
// For each node being scheduled
for (unsigned i = N; 0 < i--;) {
NodeInfo *NI = Ordering[i];
// Track insertion
unsigned Slot = NotFound;
// Compare against those previously scheduled nodes
unsigned j = i + 1;
for (; j < N; j++) {
// Get following instruction
NodeInfo *Other = Ordering[j];
// Check dependency against previously inserted nodes
if (isStrongDependency(NI, Other)) {
Slot = Other->Slot + Other->Latency;
break;
} else if (isWeakDependency(NI, Other)) {
Slot = Other->Slot;
break;
}
}
// If independent of others (or first entry)
if (Slot == NotFound) Slot = 0;
#if 0 // FIXME - measure later
// Find a slot where the needed resources are available
if (NI->StageBegin != NI->StageEnd)
Slot = Tally.FindAndReserve(Slot, NI->StageBegin, NI->StageEnd);
#endif
// Set node slot
NI->Slot = Slot;
// Insert sort based on slot
j = i + 1;
for (; j < N; j++) {
// Get following instruction
NodeInfo *Other = Ordering[j];
// Should we look further (remember slots are in reverse time)
if (Slot >= Other->Slot) break;
// Shuffle other into ordering
Ordering[j - 1] = Other;
}
// Insert node in proper slot
if (j != i + 1) Ordering[j - 1] = NI;
}
}
/// ScheduleForward - Schedule instructions to maximize packing.
///
void ScheduleDAGSimple::ScheduleForward() {
// Size and clear the resource tally
Tally.Initialize(NSlots);
// Get number of nodes to schedule
unsigned N = Ordering.size();
// For each node being scheduled
for (unsigned i = 0; i < N; i++) {
NodeInfo *NI = Ordering[i];
// Track insertion
unsigned Slot = NotFound;
// Compare against those previously scheduled nodes
unsigned j = i;
for (; 0 < j--;) {
// Get following instruction
NodeInfo *Other = Ordering[j];
// Check dependency against previously inserted nodes
if (isStrongDependency(Other, NI)) {
Slot = Other->Slot + Other->Latency;
break;
} else if (Other->IsCall || isWeakDependency(Other, NI)) {
Slot = Other->Slot;
break;
}
}
// If independent of others (or first entry)
if (Slot == NotFound) Slot = 0;
// Find a slot where the needed resources are available
if (NI->StageBegin != NI->StageEnd)
Slot = Tally.FindAndReserve(Slot, NI->StageBegin, NI->StageEnd);
// Set node slot
NI->Slot = Slot;
// Insert sort based on slot
j = i;
for (; 0 < j--;) {
// Get prior instruction
NodeInfo *Other = Ordering[j];
// Should we look further
if (Slot >= Other->Slot) break;
// Shuffle other into ordering
Ordering[j + 1] = Other;
}
// Insert node in proper slot
if (j != i) Ordering[j + 1] = NI;
}
}
/// Schedule - Order nodes according to selected style.
///
void ScheduleDAGSimple::Schedule() {
// Number the nodes
NodeCount = std::distance(DAG.allnodes_begin(), DAG.allnodes_end());
// Set up minimum info for scheduling
PrepareNodeInfo();
// Construct node groups for flagged nodes
IdentifyGroups();
// Test to see if scheduling should occur
bool ShouldSchedule = NodeCount > 3 && !NoSched;
// Don't waste time if is only entry and return
if (ShouldSchedule) {
// Get latency and resource requirements
GatherSchedulingInfo();
} else if (HasGroups) {
// Make sure all the groups have dominators
FakeGroupDominators();
}
// Breadth first walk of DAG
VisitAll();
#ifndef NDEBUG
static unsigned Count = 0;
Count++;
for (unsigned i = 0, N = Ordering.size(); i < N; i++) {
NodeInfo *NI = Ordering[i];
NI->Preorder = i;
}
#endif
// Don't waste time if is only entry and return
if (ShouldSchedule) {
// Push back long instructions and critical path
ScheduleBackward();
// Pack instructions to maximize resource utilization
ScheduleForward();
}
DEBUG(printChanges(Count));
// Emit in scheduled order
EmitAll();
}
/// createSimpleDAGScheduler - This creates a simple two pass instruction
/// scheduler using instruction itinerary.
llvm::ScheduleDAG* llvm::createSimpleDAGScheduler(SelectionDAGISel *IS,
SelectionDAG *DAG,
MachineBasicBlock *BB) {
return new ScheduleDAGSimple(false, false, *DAG, BB, DAG->getTarget());
}
/// createNoItinsDAGScheduler - This creates a simple two pass instruction
/// scheduler without using instruction itinerary.
llvm::ScheduleDAG* llvm::createNoItinsDAGScheduler(SelectionDAGISel *IS,
SelectionDAG *DAG,
MachineBasicBlock *BB) {
return new ScheduleDAGSimple(false, true, *DAG, BB, DAG->getTarget());
}
/// createBFS_DAGScheduler - This creates a simple breadth first instruction
/// scheduler.
llvm::ScheduleDAG* llvm::createBFS_DAGScheduler(SelectionDAGISel *IS,
SelectionDAG *DAG,
MachineBasicBlock *BB) {
return new ScheduleDAGSimple(true, false, *DAG, BB, DAG->getTarget());
}
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