1 //===--- ScheduleDAGSDNodes.cpp - Implement the ScheduleDAGSDNodes class --===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This implements the ScheduleDAG class, which is a base class used by
10 // scheduling implementation classes.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "ScheduleDAGSDNodes.h"
15 #include "InstrEmitter.h"
16 #include "SDNodeDbgValue.h"
17 #include "llvm/ADT/DenseMap.h"
18 #include "llvm/ADT/SmallPtrSet.h"
19 #include "llvm/ADT/SmallSet.h"
20 #include "llvm/ADT/SmallVector.h"
21 #include "llvm/ADT/Statistic.h"
22 #include "llvm/CodeGen/MachineInstrBuilder.h"
23 #include "llvm/CodeGen/MachineRegisterInfo.h"
24 #include "llvm/CodeGen/SelectionDAG.h"
25 #include "llvm/CodeGen/TargetInstrInfo.h"
26 #include "llvm/CodeGen/TargetLowering.h"
27 #include "llvm/CodeGen/TargetRegisterInfo.h"
28 #include "llvm/CodeGen/TargetSubtargetInfo.h"
29 #include "llvm/Config/llvm-config.h"
30 #include "llvm/IR/MemoryModelRelaxationAnnotations.h"
31 #include "llvm/MC/MCInstrItineraries.h"
32 #include "llvm/Support/CommandLine.h"
33 #include "llvm/Support/Debug.h"
34 #include "llvm/Support/raw_ostream.h"
35 #include "llvm/Target/TargetMachine.h"
36 using namespace llvm;
37
38 #define DEBUG_TYPE "pre-RA-sched"
39
40 STATISTIC(LoadsClustered, "Number of loads clustered together");
41
42 // This allows the latency-based scheduler to notice high latency instructions
43 // without a target itinerary. The choice of number here has more to do with
44 // balancing scheduler heuristics than with the actual machine latency.
45 static cl::opt<int> HighLatencyCycles(
46 "sched-high-latency-cycles", cl::Hidden, cl::init(10),
47 cl::desc("Roughly estimate the number of cycles that 'long latency'"
48 "instructions take for targets with no itinerary"));
49
ScheduleDAGSDNodes(MachineFunction & mf)50 ScheduleDAGSDNodes::ScheduleDAGSDNodes(MachineFunction &mf)
51 : ScheduleDAG(mf), InstrItins(mf.getSubtarget().getInstrItineraryData()) {}
52
53 /// Run - perform scheduling.
54 ///
Run(SelectionDAG * dag,MachineBasicBlock * bb)55 void ScheduleDAGSDNodes::Run(SelectionDAG *dag, MachineBasicBlock *bb) {
56 BB = bb;
57 DAG = dag;
58
59 // Clear the scheduler's SUnit DAG.
60 ScheduleDAG::clearDAG();
61 Sequence.clear();
62
63 // Invoke the target's selection of scheduler.
64 Schedule();
65 }
66
67 /// NewSUnit - Creates a new SUnit and return a ptr to it.
68 ///
newSUnit(SDNode * N)69 SUnit *ScheduleDAGSDNodes::newSUnit(SDNode *N) {
70 #ifndef NDEBUG
71 const SUnit *Addr = nullptr;
72 if (!SUnits.empty())
73 Addr = &SUnits[0];
74 #endif
75 SUnits.emplace_back(N, (unsigned)SUnits.size());
76 assert((Addr == nullptr || Addr == &SUnits[0]) &&
77 "SUnits std::vector reallocated on the fly!");
78 SUnits.back().OrigNode = &SUnits.back();
79 SUnit *SU = &SUnits.back();
80 const TargetLowering &TLI = DAG->getTargetLoweringInfo();
81 if (!N ||
82 (N->isMachineOpcode() &&
83 N->getMachineOpcode() == TargetOpcode::IMPLICIT_DEF))
84 SU->SchedulingPref = Sched::None;
85 else
86 SU->SchedulingPref = TLI.getSchedulingPreference(N);
87 return SU;
88 }
89
Clone(SUnit * Old)90 SUnit *ScheduleDAGSDNodes::Clone(SUnit *Old) {
91 SUnit *SU = newSUnit(Old->getNode());
92 SU->OrigNode = Old->OrigNode;
93 SU->Latency = Old->Latency;
94 SU->isVRegCycle = Old->isVRegCycle;
95 SU->isCall = Old->isCall;
96 SU->isCallOp = Old->isCallOp;
97 SU->isTwoAddress = Old->isTwoAddress;
98 SU->isCommutable = Old->isCommutable;
99 SU->hasPhysRegDefs = Old->hasPhysRegDefs;
100 SU->hasPhysRegClobbers = Old->hasPhysRegClobbers;
101 SU->isScheduleHigh = Old->isScheduleHigh;
102 SU->isScheduleLow = Old->isScheduleLow;
103 SU->SchedulingPref = Old->SchedulingPref;
104 Old->isCloned = true;
105 return SU;
106 }
107
108 /// CheckForPhysRegDependency - Check if the dependency between def and use of
109 /// a specified operand is a physical register dependency. If so, returns the
110 /// register and the cost of copying the register.
CheckForPhysRegDependency(SDNode * Def,SDNode * User,unsigned Op,const TargetRegisterInfo * TRI,const TargetInstrInfo * TII,const TargetLowering & TLI,unsigned & PhysReg,int & Cost)111 static void CheckForPhysRegDependency(SDNode *Def, SDNode *User, unsigned Op,
112 const TargetRegisterInfo *TRI,
113 const TargetInstrInfo *TII,
114 const TargetLowering &TLI,
115 unsigned &PhysReg, int &Cost) {
116 if (Op != 2 || User->getOpcode() != ISD::CopyToReg)
117 return;
118
119 unsigned Reg = cast<RegisterSDNode>(User->getOperand(1))->getReg();
120 if (TLI.checkForPhysRegDependency(Def, User, Op, TRI, TII, PhysReg, Cost))
121 return;
122
123 if (Register::isVirtualRegister(Reg))
124 return;
125
126 unsigned ResNo = User->getOperand(2).getResNo();
127 if (Def->getOpcode() == ISD::CopyFromReg &&
128 cast<RegisterSDNode>(Def->getOperand(1))->getReg() == Reg) {
129 PhysReg = Reg;
130 } else if (Def->isMachineOpcode()) {
131 const MCInstrDesc &II = TII->get(Def->getMachineOpcode());
132 if (ResNo >= II.getNumDefs() && II.hasImplicitDefOfPhysReg(Reg))
133 PhysReg = Reg;
134 }
135
136 if (PhysReg != 0) {
137 const TargetRegisterClass *RC =
138 TRI->getMinimalPhysRegClass(Reg, Def->getSimpleValueType(ResNo));
139 Cost = RC->getCopyCost();
140 }
141 }
142
143 // Helper for AddGlue to clone node operands.
CloneNodeWithValues(SDNode * N,SelectionDAG * DAG,ArrayRef<EVT> VTs,SDValue ExtraOper=SDValue ())144 static void CloneNodeWithValues(SDNode *N, SelectionDAG *DAG, ArrayRef<EVT> VTs,
145 SDValue ExtraOper = SDValue()) {
146 SmallVector<SDValue, 8> Ops(N->op_begin(), N->op_end());
147 if (ExtraOper.getNode())
148 Ops.push_back(ExtraOper);
149
150 SDVTList VTList = DAG->getVTList(VTs);
151 MachineSDNode *MN = dyn_cast<MachineSDNode>(N);
152
153 // Store memory references.
154 SmallVector<MachineMemOperand *, 2> MMOs;
155 if (MN)
156 MMOs.assign(MN->memoperands_begin(), MN->memoperands_end());
157
158 DAG->MorphNodeTo(N, N->getOpcode(), VTList, Ops);
159
160 // Reset the memory references
161 if (MN)
162 DAG->setNodeMemRefs(MN, MMOs);
163 }
164
AddGlue(SDNode * N,SDValue Glue,bool AddGlue,SelectionDAG * DAG)165 static bool AddGlue(SDNode *N, SDValue Glue, bool AddGlue, SelectionDAG *DAG) {
166 SDNode *GlueDestNode = Glue.getNode();
167
168 // Don't add glue from a node to itself.
169 if (GlueDestNode == N) return false;
170
171 // Don't add a glue operand to something that already uses glue.
172 if (GlueDestNode &&
173 N->getOperand(N->getNumOperands()-1).getValueType() == MVT::Glue) {
174 return false;
175 }
176 // Don't add glue to something that already has a glue value.
177 if (N->getValueType(N->getNumValues() - 1) == MVT::Glue) return false;
178
179 SmallVector<EVT, 4> VTs(N->values());
180 if (AddGlue)
181 VTs.push_back(MVT::Glue);
182
183 CloneNodeWithValues(N, DAG, VTs, Glue);
184
185 return true;
186 }
187
188 // Cleanup after unsuccessful AddGlue. Use the standard method of morphing the
189 // node even though simply shrinking the value list is sufficient.
RemoveUnusedGlue(SDNode * N,SelectionDAG * DAG)190 static void RemoveUnusedGlue(SDNode *N, SelectionDAG *DAG) {
191 assert((N->getValueType(N->getNumValues() - 1) == MVT::Glue &&
192 !N->hasAnyUseOfValue(N->getNumValues() - 1)) &&
193 "expected an unused glue value");
194
195 CloneNodeWithValues(N, DAG,
196 ArrayRef(N->value_begin(), N->getNumValues() - 1));
197 }
198
199 /// ClusterNeighboringLoads - Force nearby loads together by "gluing" them.
200 /// This function finds loads of the same base and different offsets. If the
201 /// offsets are not far apart (target specific), it add MVT::Glue inputs and
202 /// outputs to ensure they are scheduled together and in order. This
203 /// optimization may benefit some targets by improving cache locality.
ClusterNeighboringLoads(SDNode * Node)204 void ScheduleDAGSDNodes::ClusterNeighboringLoads(SDNode *Node) {
205 SDValue Chain;
206 unsigned NumOps = Node->getNumOperands();
207 if (Node->getOperand(NumOps-1).getValueType() == MVT::Other)
208 Chain = Node->getOperand(NumOps-1);
209 if (!Chain)
210 return;
211
212 // Skip any load instruction that has a tied input. There may be an additional
213 // dependency requiring a different order than by increasing offsets, and the
214 // added glue may introduce a cycle.
215 auto hasTiedInput = [this](const SDNode *N) {
216 const MCInstrDesc &MCID = TII->get(N->getMachineOpcode());
217 for (unsigned I = 0; I != MCID.getNumOperands(); ++I) {
218 if (MCID.getOperandConstraint(I, MCOI::TIED_TO) != -1)
219 return true;
220 }
221
222 return false;
223 };
224
225 // Look for other loads of the same chain. Find loads that are loading from
226 // the same base pointer and different offsets.
227 SmallPtrSet<SDNode*, 16> Visited;
228 SmallVector<int64_t, 4> Offsets;
229 DenseMap<long long, SDNode*> O2SMap; // Map from offset to SDNode.
230 bool Cluster = false;
231 SDNode *Base = Node;
232
233 if (hasTiedInput(Base))
234 return;
235
236 // This algorithm requires a reasonably low use count before finding a match
237 // to avoid uselessly blowing up compile time in large blocks.
238 unsigned UseCount = 0;
239 for (SDNode::use_iterator I = Chain->use_begin(), E = Chain->use_end();
240 I != E && UseCount < 100; ++I, ++UseCount) {
241 if (I.getUse().getResNo() != Chain.getResNo())
242 continue;
243
244 SDNode *User = *I;
245 if (User == Node || !Visited.insert(User).second)
246 continue;
247 int64_t Offset1, Offset2;
248 if (!TII->areLoadsFromSameBasePtr(Base, User, Offset1, Offset2) ||
249 Offset1 == Offset2 ||
250 hasTiedInput(User)) {
251 // FIXME: Should be ok if they addresses are identical. But earlier
252 // optimizations really should have eliminated one of the loads.
253 continue;
254 }
255 if (O2SMap.insert(std::make_pair(Offset1, Base)).second)
256 Offsets.push_back(Offset1);
257 O2SMap.insert(std::make_pair(Offset2, User));
258 Offsets.push_back(Offset2);
259 if (Offset2 < Offset1)
260 Base = User;
261 Cluster = true;
262 // Reset UseCount to allow more matches.
263 UseCount = 0;
264 }
265
266 if (!Cluster)
267 return;
268
269 // Sort them in increasing order.
270 llvm::sort(Offsets);
271
272 // Check if the loads are close enough.
273 SmallVector<SDNode*, 4> Loads;
274 unsigned NumLoads = 0;
275 int64_t BaseOff = Offsets[0];
276 SDNode *BaseLoad = O2SMap[BaseOff];
277 Loads.push_back(BaseLoad);
278 for (unsigned i = 1, e = Offsets.size(); i != e; ++i) {
279 int64_t Offset = Offsets[i];
280 SDNode *Load = O2SMap[Offset];
281 if (!TII->shouldScheduleLoadsNear(BaseLoad, Load, BaseOff, Offset,NumLoads))
282 break; // Stop right here. Ignore loads that are further away.
283 Loads.push_back(Load);
284 ++NumLoads;
285 }
286
287 if (NumLoads == 0)
288 return;
289
290 // Cluster loads by adding MVT::Glue outputs and inputs. This also
291 // ensure they are scheduled in order of increasing addresses.
292 SDNode *Lead = Loads[0];
293 SDValue InGlue;
294 if (AddGlue(Lead, InGlue, true, DAG))
295 InGlue = SDValue(Lead, Lead->getNumValues() - 1);
296 for (unsigned I = 1, E = Loads.size(); I != E; ++I) {
297 bool OutGlue = I < E - 1;
298 SDNode *Load = Loads[I];
299
300 // If AddGlue fails, we could leave an unsused glue value. This should not
301 // cause any
302 if (AddGlue(Load, InGlue, OutGlue, DAG)) {
303 if (OutGlue)
304 InGlue = SDValue(Load, Load->getNumValues() - 1);
305
306 ++LoadsClustered;
307 }
308 else if (!OutGlue && InGlue.getNode())
309 RemoveUnusedGlue(InGlue.getNode(), DAG);
310 }
311 }
312
313 /// ClusterNodes - Cluster certain nodes which should be scheduled together.
314 ///
ClusterNodes()315 void ScheduleDAGSDNodes::ClusterNodes() {
316 for (SDNode &NI : DAG->allnodes()) {
317 SDNode *Node = &NI;
318 if (!Node || !Node->isMachineOpcode())
319 continue;
320
321 unsigned Opc = Node->getMachineOpcode();
322 const MCInstrDesc &MCID = TII->get(Opc);
323 if (MCID.mayLoad())
324 // Cluster loads from "near" addresses into combined SUnits.
325 ClusterNeighboringLoads(Node);
326 }
327 }
328
BuildSchedUnits()329 void ScheduleDAGSDNodes::BuildSchedUnits() {
330 // During scheduling, the NodeId field of SDNode is used to map SDNodes
331 // to their associated SUnits by holding SUnits table indices. A value
332 // of -1 means the SDNode does not yet have an associated SUnit.
333 unsigned NumNodes = 0;
334 for (SDNode &NI : DAG->allnodes()) {
335 NI.setNodeId(-1);
336 ++NumNodes;
337 }
338
339 // Reserve entries in the vector for each of the SUnits we are creating. This
340 // ensure that reallocation of the vector won't happen, so SUnit*'s won't get
341 // invalidated.
342 // FIXME: Multiply by 2 because we may clone nodes during scheduling.
343 // This is a temporary workaround.
344 SUnits.reserve(NumNodes * 2);
345
346 // Add all nodes in depth first order.
347 SmallVector<SDNode*, 64> Worklist;
348 SmallPtrSet<SDNode*, 32> Visited;
349 Worklist.push_back(DAG->getRoot().getNode());
350 Visited.insert(DAG->getRoot().getNode());
351
352 SmallVector<SUnit*, 8> CallSUnits;
353 while (!Worklist.empty()) {
354 SDNode *NI = Worklist.pop_back_val();
355
356 // Add all operands to the worklist unless they've already been added.
357 for (const SDValue &Op : NI->op_values())
358 if (Visited.insert(Op.getNode()).second)
359 Worklist.push_back(Op.getNode());
360
361 if (isPassiveNode(NI)) // Leaf node, e.g. a TargetImmediate.
362 continue;
363
364 // If this node has already been processed, stop now.
365 if (NI->getNodeId() != -1) continue;
366
367 SUnit *NodeSUnit = newSUnit(NI);
368
369 // See if anything is glued to this node, if so, add them to glued
370 // nodes. Nodes can have at most one glue input and one glue output. Glue
371 // is required to be the last operand and result of a node.
372
373 // Scan up to find glued preds.
374 SDNode *N = NI;
375 while (N->getNumOperands() &&
376 N->getOperand(N->getNumOperands()-1).getValueType() == MVT::Glue) {
377 N = N->getOperand(N->getNumOperands()-1).getNode();
378 assert(N->getNodeId() == -1 && "Node already inserted!");
379 N->setNodeId(NodeSUnit->NodeNum);
380 if (N->isMachineOpcode() && TII->get(N->getMachineOpcode()).isCall())
381 NodeSUnit->isCall = true;
382 }
383
384 // Scan down to find any glued succs.
385 N = NI;
386 while (N->getValueType(N->getNumValues()-1) == MVT::Glue) {
387 SDValue GlueVal(N, N->getNumValues()-1);
388
389 // There are either zero or one users of the Glue result.
390 bool HasGlueUse = false;
391 for (SDNode *U : N->uses())
392 if (GlueVal.isOperandOf(U)) {
393 HasGlueUse = true;
394 assert(N->getNodeId() == -1 && "Node already inserted!");
395 N->setNodeId(NodeSUnit->NodeNum);
396 N = U;
397 if (N->isMachineOpcode() && TII->get(N->getMachineOpcode()).isCall())
398 NodeSUnit->isCall = true;
399 break;
400 }
401 if (!HasGlueUse) break;
402 }
403
404 if (NodeSUnit->isCall)
405 CallSUnits.push_back(NodeSUnit);
406
407 // Schedule zero-latency TokenFactor below any nodes that may increase the
408 // schedule height. Otherwise, ancestors of the TokenFactor may appear to
409 // have false stalls.
410 if (NI->getOpcode() == ISD::TokenFactor)
411 NodeSUnit->isScheduleLow = true;
412
413 // If there are glue operands involved, N is now the bottom-most node
414 // of the sequence of nodes that are glued together.
415 // Update the SUnit.
416 NodeSUnit->setNode(N);
417 assert(N->getNodeId() == -1 && "Node already inserted!");
418 N->setNodeId(NodeSUnit->NodeNum);
419
420 // Compute NumRegDefsLeft. This must be done before AddSchedEdges.
421 InitNumRegDefsLeft(NodeSUnit);
422
423 // Assign the Latency field of NodeSUnit using target-provided information.
424 computeLatency(NodeSUnit);
425 }
426
427 // Find all call operands.
428 while (!CallSUnits.empty()) {
429 SUnit *SU = CallSUnits.pop_back_val();
430 for (const SDNode *SUNode = SU->getNode(); SUNode;
431 SUNode = SUNode->getGluedNode()) {
432 if (SUNode->getOpcode() != ISD::CopyToReg)
433 continue;
434 SDNode *SrcN = SUNode->getOperand(2).getNode();
435 if (isPassiveNode(SrcN)) continue; // Not scheduled.
436 SUnit *SrcSU = &SUnits[SrcN->getNodeId()];
437 SrcSU->isCallOp = true;
438 }
439 }
440 }
441
AddSchedEdges()442 void ScheduleDAGSDNodes::AddSchedEdges() {
443 const TargetSubtargetInfo &ST = MF.getSubtarget();
444
445 // Check to see if the scheduler cares about latencies.
446 bool UnitLatencies = forceUnitLatencies();
447
448 // Pass 2: add the preds, succs, etc.
449 for (SUnit &SU : SUnits) {
450 SDNode *MainNode = SU.getNode();
451
452 if (MainNode->isMachineOpcode()) {
453 unsigned Opc = MainNode->getMachineOpcode();
454 const MCInstrDesc &MCID = TII->get(Opc);
455 for (unsigned i = 0; i != MCID.getNumOperands(); ++i) {
456 if (MCID.getOperandConstraint(i, MCOI::TIED_TO) != -1) {
457 SU.isTwoAddress = true;
458 break;
459 }
460 }
461 if (MCID.isCommutable())
462 SU.isCommutable = true;
463 }
464
465 // Find all predecessors and successors of the group.
466 for (SDNode *N = SU.getNode(); N; N = N->getGluedNode()) {
467 if (N->isMachineOpcode() &&
468 !TII->get(N->getMachineOpcode()).implicit_defs().empty()) {
469 SU.hasPhysRegClobbers = true;
470 unsigned NumUsed = InstrEmitter::CountResults(N);
471 while (NumUsed != 0 && !N->hasAnyUseOfValue(NumUsed - 1))
472 --NumUsed; // Skip over unused values at the end.
473 if (NumUsed > TII->get(N->getMachineOpcode()).getNumDefs())
474 SU.hasPhysRegDefs = true;
475 }
476
477 for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) {
478 SDNode *OpN = N->getOperand(i).getNode();
479 unsigned DefIdx = N->getOperand(i).getResNo();
480 if (isPassiveNode(OpN)) continue; // Not scheduled.
481 SUnit *OpSU = &SUnits[OpN->getNodeId()];
482 assert(OpSU && "Node has no SUnit!");
483 if (OpSU == &SU)
484 continue; // In the same group.
485
486 EVT OpVT = N->getOperand(i).getValueType();
487 assert(OpVT != MVT::Glue && "Glued nodes should be in same sunit!");
488 bool isChain = OpVT == MVT::Other;
489
490 unsigned PhysReg = 0;
491 int Cost = 1;
492 // Determine if this is a physical register dependency.
493 const TargetLowering &TLI = DAG->getTargetLoweringInfo();
494 CheckForPhysRegDependency(OpN, N, i, TRI, TII, TLI, PhysReg, Cost);
495 assert((PhysReg == 0 || !isChain) &&
496 "Chain dependence via physreg data?");
497 // FIXME: See ScheduleDAGSDNodes::EmitCopyFromReg. For now, scheduler
498 // emits a copy from the physical register to a virtual register unless
499 // it requires a cross class copy (cost < 0). That means we are only
500 // treating "expensive to copy" register dependency as physical register
501 // dependency. This may change in the future though.
502 if (Cost >= 0 && !StressSched)
503 PhysReg = 0;
504
505 // If this is a ctrl dep, latency is 1.
506 unsigned OpLatency = isChain ? 1 : OpSU->Latency;
507 // Special-case TokenFactor chains as zero-latency.
508 if(isChain && OpN->getOpcode() == ISD::TokenFactor)
509 OpLatency = 0;
510
511 SDep Dep = isChain ? SDep(OpSU, SDep::Barrier)
512 : SDep(OpSU, SDep::Data, PhysReg);
513 Dep.setLatency(OpLatency);
514 if (!isChain && !UnitLatencies) {
515 computeOperandLatency(OpN, N, i, Dep);
516 ST.adjustSchedDependency(OpSU, DefIdx, &SU, i, Dep, nullptr);
517 }
518
519 if (!SU.addPred(Dep) && !Dep.isCtrl() && OpSU->NumRegDefsLeft > 1) {
520 // Multiple register uses are combined in the same SUnit. For example,
521 // we could have a set of glued nodes with all their defs consumed by
522 // another set of glued nodes. Register pressure tracking sees this as
523 // a single use, so to keep pressure balanced we reduce the defs.
524 //
525 // We can't tell (without more book-keeping) if this results from
526 // glued nodes or duplicate operands. As long as we don't reduce
527 // NumRegDefsLeft to zero, we handle the common cases well.
528 --OpSU->NumRegDefsLeft;
529 }
530 }
531 }
532 }
533 }
534
535 /// BuildSchedGraph - Build the SUnit graph from the selection dag that we
536 /// are input. This SUnit graph is similar to the SelectionDAG, but
537 /// excludes nodes that aren't interesting to scheduling, and represents
538 /// glued together nodes with a single SUnit.
BuildSchedGraph(AAResults * AA)539 void ScheduleDAGSDNodes::BuildSchedGraph(AAResults *AA) {
540 // Cluster certain nodes which should be scheduled together.
541 ClusterNodes();
542 // Populate the SUnits array.
543 BuildSchedUnits();
544 // Compute all the scheduling dependencies between nodes.
545 AddSchedEdges();
546 }
547
548 // Initialize NumNodeDefs for the current Node's opcode.
InitNodeNumDefs()549 void ScheduleDAGSDNodes::RegDefIter::InitNodeNumDefs() {
550 // Check for phys reg copy.
551 if (!Node)
552 return;
553
554 if (!Node->isMachineOpcode()) {
555 if (Node->getOpcode() == ISD::CopyFromReg)
556 NodeNumDefs = 1;
557 else
558 NodeNumDefs = 0;
559 return;
560 }
561 unsigned POpc = Node->getMachineOpcode();
562 if (POpc == TargetOpcode::IMPLICIT_DEF) {
563 // No register need be allocated for this.
564 NodeNumDefs = 0;
565 return;
566 }
567 if (POpc == TargetOpcode::PATCHPOINT &&
568 Node->getValueType(0) == MVT::Other) {
569 // PATCHPOINT is defined to have one result, but it might really have none
570 // if we're not using CallingConv::AnyReg. Don't mistake the chain for a
571 // real definition.
572 NodeNumDefs = 0;
573 return;
574 }
575 unsigned NRegDefs = SchedDAG->TII->get(Node->getMachineOpcode()).getNumDefs();
576 // Some instructions define regs that are not represented in the selection DAG
577 // (e.g. unused flags). See tMOVi8. Make sure we don't access past NumValues.
578 NodeNumDefs = std::min(Node->getNumValues(), NRegDefs);
579 DefIdx = 0;
580 }
581
582 // Construct a RegDefIter for this SUnit and find the first valid value.
RegDefIter(const SUnit * SU,const ScheduleDAGSDNodes * SD)583 ScheduleDAGSDNodes::RegDefIter::RegDefIter(const SUnit *SU,
584 const ScheduleDAGSDNodes *SD)
585 : SchedDAG(SD), Node(SU->getNode()) {
586 InitNodeNumDefs();
587 Advance();
588 }
589
590 // Advance to the next valid value defined by the SUnit.
Advance()591 void ScheduleDAGSDNodes::RegDefIter::Advance() {
592 for (;Node;) { // Visit all glued nodes.
593 for (;DefIdx < NodeNumDefs; ++DefIdx) {
594 if (!Node->hasAnyUseOfValue(DefIdx))
595 continue;
596 ValueType = Node->getSimpleValueType(DefIdx);
597 ++DefIdx;
598 return; // Found a normal regdef.
599 }
600 Node = Node->getGluedNode();
601 if (!Node) {
602 return; // No values left to visit.
603 }
604 InitNodeNumDefs();
605 }
606 }
607
InitNumRegDefsLeft(SUnit * SU)608 void ScheduleDAGSDNodes::InitNumRegDefsLeft(SUnit *SU) {
609 assert(SU->NumRegDefsLeft == 0 && "expect a new node");
610 for (RegDefIter I(SU, this); I.IsValid(); I.Advance()) {
611 assert(SU->NumRegDefsLeft < USHRT_MAX && "overflow is ok but unexpected");
612 ++SU->NumRegDefsLeft;
613 }
614 }
615
computeLatency(SUnit * SU)616 void ScheduleDAGSDNodes::computeLatency(SUnit *SU) {
617 SDNode *N = SU->getNode();
618
619 // TokenFactor operands are considered zero latency, and some schedulers
620 // (e.g. Top-Down list) may rely on the fact that operand latency is nonzero
621 // whenever node latency is nonzero.
622 if (N && N->getOpcode() == ISD::TokenFactor) {
623 SU->Latency = 0;
624 return;
625 }
626
627 // Check to see if the scheduler cares about latencies.
628 if (forceUnitLatencies()) {
629 SU->Latency = 1;
630 return;
631 }
632
633 if (!InstrItins || InstrItins->isEmpty()) {
634 if (N && N->isMachineOpcode() &&
635 TII->isHighLatencyDef(N->getMachineOpcode()))
636 SU->Latency = HighLatencyCycles;
637 else
638 SU->Latency = 1;
639 return;
640 }
641
642 // Compute the latency for the node. We use the sum of the latencies for
643 // all nodes glued together into this SUnit.
644 SU->Latency = 0;
645 for (SDNode *N = SU->getNode(); N; N = N->getGluedNode())
646 if (N->isMachineOpcode())
647 SU->Latency += TII->getInstrLatency(InstrItins, N);
648 }
649
computeOperandLatency(SDNode * Def,SDNode * Use,unsigned OpIdx,SDep & dep) const650 void ScheduleDAGSDNodes::computeOperandLatency(SDNode *Def, SDNode *Use,
651 unsigned OpIdx, SDep& dep) const{
652 // Check to see if the scheduler cares about latencies.
653 if (forceUnitLatencies())
654 return;
655
656 if (dep.getKind() != SDep::Data)
657 return;
658
659 unsigned DefIdx = Use->getOperand(OpIdx).getResNo();
660 if (Use->isMachineOpcode())
661 // Adjust the use operand index by num of defs.
662 OpIdx += TII->get(Use->getMachineOpcode()).getNumDefs();
663 std::optional<unsigned> Latency =
664 TII->getOperandLatency(InstrItins, Def, DefIdx, Use, OpIdx);
665 if (Latency > 1U && Use->getOpcode() == ISD::CopyToReg &&
666 !BB->succ_empty()) {
667 unsigned Reg = cast<RegisterSDNode>(Use->getOperand(1))->getReg();
668 if (Register::isVirtualRegister(Reg))
669 // This copy is a liveout value. It is likely coalesced, so reduce the
670 // latency so not to penalize the def.
671 // FIXME: need target specific adjustment here?
672 Latency = *Latency - 1;
673 }
674 if (Latency)
675 dep.setLatency(*Latency);
676 }
677
dumpNode(const SUnit & SU) const678 void ScheduleDAGSDNodes::dumpNode(const SUnit &SU) const {
679 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
680 dumpNodeName(SU);
681 dbgs() << ": ";
682
683 if (!SU.getNode()) {
684 dbgs() << "PHYS REG COPY\n";
685 return;
686 }
687
688 SU.getNode()->dump(DAG);
689 dbgs() << "\n";
690 SmallVector<SDNode *, 4> GluedNodes;
691 for (SDNode *N = SU.getNode()->getGluedNode(); N; N = N->getGluedNode())
692 GluedNodes.push_back(N);
693 while (!GluedNodes.empty()) {
694 dbgs() << " ";
695 GluedNodes.back()->dump(DAG);
696 dbgs() << "\n";
697 GluedNodes.pop_back();
698 }
699 #endif
700 }
701
dump() const702 void ScheduleDAGSDNodes::dump() const {
703 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
704 if (EntrySU.getNode() != nullptr)
705 dumpNodeAll(EntrySU);
706 for (const SUnit &SU : SUnits)
707 dumpNodeAll(SU);
708 if (ExitSU.getNode() != nullptr)
709 dumpNodeAll(ExitSU);
710 #endif
711 }
712
713 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
dumpSchedule() const714 void ScheduleDAGSDNodes::dumpSchedule() const {
715 for (const SUnit *SU : Sequence) {
716 if (SU)
717 dumpNode(*SU);
718 else
719 dbgs() << "**** NOOP ****\n";
720 }
721 }
722 #endif
723
724 #ifndef NDEBUG
725 /// VerifyScheduledSequence - Verify that all SUnits were scheduled and that
726 /// their state is consistent with the nodes listed in Sequence.
727 ///
VerifyScheduledSequence(bool isBottomUp)728 void ScheduleDAGSDNodes::VerifyScheduledSequence(bool isBottomUp) {
729 unsigned ScheduledNodes = ScheduleDAG::VerifyScheduledDAG(isBottomUp);
730 unsigned Noops = llvm::count(Sequence, nullptr);
731 assert(Sequence.size() - Noops == ScheduledNodes &&
732 "The number of nodes scheduled doesn't match the expected number!");
733 }
734 #endif // NDEBUG
735
736 /// ProcessSDDbgValues - Process SDDbgValues associated with this node.
737 static void
ProcessSDDbgValues(SDNode * N,SelectionDAG * DAG,InstrEmitter & Emitter,SmallVectorImpl<std::pair<unsigned,MachineInstr * >> & Orders,DenseMap<SDValue,Register> & VRBaseMap,unsigned Order)738 ProcessSDDbgValues(SDNode *N, SelectionDAG *DAG, InstrEmitter &Emitter,
739 SmallVectorImpl<std::pair<unsigned, MachineInstr*> > &Orders,
740 DenseMap<SDValue, Register> &VRBaseMap, unsigned Order) {
741 if (!N->getHasDebugValue())
742 return;
743
744 /// Returns true if \p DV has any VReg operand locations which don't exist in
745 /// VRBaseMap.
746 auto HasUnknownVReg = [&VRBaseMap](SDDbgValue *DV) {
747 for (const SDDbgOperand &L : DV->getLocationOps()) {
748 if (L.getKind() == SDDbgOperand::SDNODE &&
749 VRBaseMap.count({L.getSDNode(), L.getResNo()}) == 0)
750 return true;
751 }
752 return false;
753 };
754
755 // Opportunistically insert immediate dbg_value uses, i.e. those with the same
756 // source order number as N.
757 MachineBasicBlock *BB = Emitter.getBlock();
758 MachineBasicBlock::iterator InsertPos = Emitter.getInsertPos();
759 for (auto *DV : DAG->GetDbgValues(N)) {
760 if (DV->isEmitted())
761 continue;
762 unsigned DVOrder = DV->getOrder();
763 if (Order != 0 && DVOrder != Order)
764 continue;
765 // If DV has any VReg location operands which haven't been mapped then
766 // either that node is no longer available or we just haven't visited the
767 // node yet. In the former case we should emit an undef dbg_value, but we
768 // can do it later. And for the latter we'll want to wait until all
769 // dependent nodes have been visited.
770 if (!DV->isInvalidated() && HasUnknownVReg(DV))
771 continue;
772 MachineInstr *DbgMI = Emitter.EmitDbgValue(DV, VRBaseMap);
773 if (!DbgMI)
774 continue;
775 Orders.push_back({DVOrder, DbgMI});
776 BB->insert(InsertPos, DbgMI);
777 }
778 }
779
780 // ProcessSourceNode - Process nodes with source order numbers. These are added
781 // to a vector which EmitSchedule uses to determine how to insert dbg_value
782 // instructions in the right order.
783 static void
ProcessSourceNode(SDNode * N,SelectionDAG * DAG,InstrEmitter & Emitter,DenseMap<SDValue,Register> & VRBaseMap,SmallVectorImpl<std::pair<unsigned,MachineInstr * >> & Orders,SmallSet<Register,8> & Seen,MachineInstr * NewInsn)784 ProcessSourceNode(SDNode *N, SelectionDAG *DAG, InstrEmitter &Emitter,
785 DenseMap<SDValue, Register> &VRBaseMap,
786 SmallVectorImpl<std::pair<unsigned, MachineInstr *>> &Orders,
787 SmallSet<Register, 8> &Seen, MachineInstr *NewInsn) {
788 unsigned Order = N->getIROrder();
789 if (!Order || Seen.count(Order)) {
790 // Process any valid SDDbgValues even if node does not have any order
791 // assigned.
792 ProcessSDDbgValues(N, DAG, Emitter, Orders, VRBaseMap, 0);
793 return;
794 }
795
796 // If a new instruction was generated for this Order number, record it.
797 // Otherwise, leave this order number unseen: we will either find later
798 // instructions for it, or leave it unseen if there were no instructions at
799 // all.
800 if (NewInsn) {
801 Seen.insert(Order);
802 Orders.push_back({Order, NewInsn});
803 }
804
805 // Even if no instruction was generated, a Value may have become defined via
806 // earlier nodes. Try to process them now.
807 ProcessSDDbgValues(N, DAG, Emitter, Orders, VRBaseMap, Order);
808 }
809
810 void ScheduleDAGSDNodes::
EmitPhysRegCopy(SUnit * SU,DenseMap<SUnit *,Register> & VRBaseMap,MachineBasicBlock::iterator InsertPos)811 EmitPhysRegCopy(SUnit *SU, DenseMap<SUnit*, Register> &VRBaseMap,
812 MachineBasicBlock::iterator InsertPos) {
813 for (const SDep &Pred : SU->Preds) {
814 if (Pred.isCtrl())
815 continue; // ignore chain preds
816 if (Pred.getSUnit()->CopyDstRC) {
817 // Copy to physical register.
818 DenseMap<SUnit *, Register>::iterator VRI =
819 VRBaseMap.find(Pred.getSUnit());
820 assert(VRI != VRBaseMap.end() && "Node emitted out of order - late");
821 // Find the destination physical register.
822 Register Reg;
823 for (const SDep &Succ : SU->Succs) {
824 if (Succ.isCtrl())
825 continue; // ignore chain preds
826 if (Succ.getReg()) {
827 Reg = Succ.getReg();
828 break;
829 }
830 }
831 BuildMI(*BB, InsertPos, DebugLoc(), TII->get(TargetOpcode::COPY), Reg)
832 .addReg(VRI->second);
833 } else {
834 // Copy from physical register.
835 assert(Pred.getReg() && "Unknown physical register!");
836 Register VRBase = MRI.createVirtualRegister(SU->CopyDstRC);
837 bool isNew = VRBaseMap.insert(std::make_pair(SU, VRBase)).second;
838 (void)isNew; // Silence compiler warning.
839 assert(isNew && "Node emitted out of order - early");
840 BuildMI(*BB, InsertPos, DebugLoc(), TII->get(TargetOpcode::COPY), VRBase)
841 .addReg(Pred.getReg());
842 }
843 break;
844 }
845 }
846
847 /// EmitSchedule - Emit the machine code in scheduled order. Return the new
848 /// InsertPos and MachineBasicBlock that contains this insertion
849 /// point. ScheduleDAGSDNodes holds a BB pointer for convenience, but this does
850 /// not necessarily refer to returned BB. The emitter may split blocks.
851 MachineBasicBlock *ScheduleDAGSDNodes::
EmitSchedule(MachineBasicBlock::iterator & InsertPos)852 EmitSchedule(MachineBasicBlock::iterator &InsertPos) {
853 InstrEmitter Emitter(DAG->getTarget(), BB, InsertPos);
854 DenseMap<SDValue, Register> VRBaseMap;
855 DenseMap<SUnit*, Register> CopyVRBaseMap;
856 SmallVector<std::pair<unsigned, MachineInstr*>, 32> Orders;
857 SmallSet<Register, 8> Seen;
858 bool HasDbg = DAG->hasDebugValues();
859
860 // Emit a node, and determine where its first instruction is for debuginfo.
861 // Zero, one, or multiple instructions can be created when emitting a node.
862 auto EmitNode =
863 [&](SDNode *Node, bool IsClone, bool IsCloned,
864 DenseMap<SDValue, Register> &VRBaseMap) -> MachineInstr * {
865 // Fetch instruction prior to this, or end() if nonexistant.
866 auto GetPrevInsn = [&](MachineBasicBlock::iterator I) {
867 if (I == BB->begin())
868 return BB->end();
869 else
870 return std::prev(Emitter.getInsertPos());
871 };
872
873 MachineBasicBlock::iterator Before = GetPrevInsn(Emitter.getInsertPos());
874 Emitter.EmitNode(Node, IsClone, IsCloned, VRBaseMap);
875 MachineBasicBlock::iterator After = GetPrevInsn(Emitter.getInsertPos());
876
877 // If the iterator did not change, no instructions were inserted.
878 if (Before == After)
879 return nullptr;
880
881 MachineInstr *MI;
882 if (Before == BB->end()) {
883 // There were no prior instructions; the new ones must start at the
884 // beginning of the block.
885 MI = &Emitter.getBlock()->instr_front();
886 } else {
887 // Return first instruction after the pre-existing instructions.
888 MI = &*std::next(Before);
889 }
890
891 if (MI->isCandidateForCallSiteEntry() &&
892 DAG->getTarget().Options.EmitCallSiteInfo) {
893 MF.addCallSiteInfo(MI, DAG->getCallSiteInfo(Node));
894 }
895
896 if (DAG->getNoMergeSiteInfo(Node)) {
897 MI->setFlag(MachineInstr::MIFlag::NoMerge);
898 }
899
900 if (MDNode *MD = DAG->getPCSections(Node))
901 MI->setPCSections(MF, MD);
902
903 // Set MMRAs on _all_ added instructions.
904 if (MDNode *MMRA = DAG->getMMRAMetadata(Node)) {
905 for (MachineBasicBlock::iterator It = MI->getIterator(),
906 End = std::next(After);
907 It != End; ++It)
908 It->setMMRAMetadata(MF, MMRA);
909 }
910
911 return MI;
912 };
913
914 // If this is the first BB, emit byval parameter dbg_value's.
915 if (HasDbg && BB->getParent()->begin() == MachineFunction::iterator(BB)) {
916 SDDbgInfo::DbgIterator PDI = DAG->ByvalParmDbgBegin();
917 SDDbgInfo::DbgIterator PDE = DAG->ByvalParmDbgEnd();
918 for (; PDI != PDE; ++PDI) {
919 MachineInstr *DbgMI= Emitter.EmitDbgValue(*PDI, VRBaseMap);
920 if (DbgMI) {
921 BB->insert(InsertPos, DbgMI);
922 // We re-emit the dbg_value closer to its use, too, after instructions
923 // are emitted to the BB.
924 (*PDI)->clearIsEmitted();
925 }
926 }
927 }
928
929 for (SUnit *SU : Sequence) {
930 if (!SU) {
931 // Null SUnit* is a noop.
932 TII->insertNoop(*Emitter.getBlock(), InsertPos);
933 continue;
934 }
935
936 // For pre-regalloc scheduling, create instructions corresponding to the
937 // SDNode and any glued SDNodes and append them to the block.
938 if (!SU->getNode()) {
939 // Emit a copy.
940 EmitPhysRegCopy(SU, CopyVRBaseMap, InsertPos);
941 continue;
942 }
943
944 SmallVector<SDNode *, 4> GluedNodes;
945 for (SDNode *N = SU->getNode()->getGluedNode(); N; N = N->getGluedNode())
946 GluedNodes.push_back(N);
947 while (!GluedNodes.empty()) {
948 SDNode *N = GluedNodes.back();
949 auto NewInsn = EmitNode(N, SU->OrigNode != SU, SU->isCloned, VRBaseMap);
950 // Remember the source order of the inserted instruction.
951 if (HasDbg)
952 ProcessSourceNode(N, DAG, Emitter, VRBaseMap, Orders, Seen, NewInsn);
953
954 if (MDNode *MD = DAG->getHeapAllocSite(N))
955 if (NewInsn && NewInsn->isCall())
956 NewInsn->setHeapAllocMarker(MF, MD);
957
958 GluedNodes.pop_back();
959 }
960 auto NewInsn =
961 EmitNode(SU->getNode(), SU->OrigNode != SU, SU->isCloned, VRBaseMap);
962 // Remember the source order of the inserted instruction.
963 if (HasDbg)
964 ProcessSourceNode(SU->getNode(), DAG, Emitter, VRBaseMap, Orders, Seen,
965 NewInsn);
966
967 if (MDNode *MD = DAG->getHeapAllocSite(SU->getNode())) {
968 if (NewInsn && NewInsn->isCall())
969 NewInsn->setHeapAllocMarker(MF, MD);
970 }
971 }
972
973 // Insert all the dbg_values which have not already been inserted in source
974 // order sequence.
975 if (HasDbg) {
976 MachineBasicBlock::iterator BBBegin = BB->getFirstNonPHI();
977
978 // Sort the source order instructions and use the order to insert debug
979 // values. Use stable_sort so that DBG_VALUEs are inserted in the same order
980 // regardless of the host's implementation fo std::sort.
981 llvm::stable_sort(Orders, less_first());
982 std::stable_sort(DAG->DbgBegin(), DAG->DbgEnd(),
983 [](const SDDbgValue *LHS, const SDDbgValue *RHS) {
984 return LHS->getOrder() < RHS->getOrder();
985 });
986
987 SDDbgInfo::DbgIterator DI = DAG->DbgBegin();
988 SDDbgInfo::DbgIterator DE = DAG->DbgEnd();
989 // Now emit the rest according to source order.
990 unsigned LastOrder = 0;
991 for (unsigned i = 0, e = Orders.size(); i != e && DI != DE; ++i) {
992 unsigned Order = Orders[i].first;
993 MachineInstr *MI = Orders[i].second;
994 // Insert all SDDbgValue's whose order(s) are before "Order".
995 assert(MI);
996 for (; DI != DE; ++DI) {
997 if ((*DI)->getOrder() < LastOrder || (*DI)->getOrder() >= Order)
998 break;
999 if ((*DI)->isEmitted())
1000 continue;
1001
1002 MachineInstr *DbgMI = Emitter.EmitDbgValue(*DI, VRBaseMap);
1003 if (DbgMI) {
1004 if (!LastOrder)
1005 // Insert to start of the BB (after PHIs).
1006 BB->insert(BBBegin, DbgMI);
1007 else {
1008 // Insert at the instruction, which may be in a different
1009 // block, if the block was split by a custom inserter.
1010 MachineBasicBlock::iterator Pos = MI;
1011 MI->getParent()->insert(Pos, DbgMI);
1012 }
1013 }
1014 }
1015 LastOrder = Order;
1016 }
1017 // Add trailing DbgValue's before the terminator. FIXME: May want to add
1018 // some of them before one or more conditional branches?
1019 SmallVector<MachineInstr*, 8> DbgMIs;
1020 for (; DI != DE; ++DI) {
1021 if ((*DI)->isEmitted())
1022 continue;
1023 assert((*DI)->getOrder() >= LastOrder &&
1024 "emitting DBG_VALUE out of order");
1025 if (MachineInstr *DbgMI = Emitter.EmitDbgValue(*DI, VRBaseMap))
1026 DbgMIs.push_back(DbgMI);
1027 }
1028
1029 MachineBasicBlock *InsertBB = Emitter.getBlock();
1030 MachineBasicBlock::iterator Pos = InsertBB->getFirstTerminator();
1031 InsertBB->insert(Pos, DbgMIs.begin(), DbgMIs.end());
1032
1033 SDDbgInfo::DbgLabelIterator DLI = DAG->DbgLabelBegin();
1034 SDDbgInfo::DbgLabelIterator DLE = DAG->DbgLabelEnd();
1035 // Now emit the rest according to source order.
1036 LastOrder = 0;
1037 for (const auto &InstrOrder : Orders) {
1038 unsigned Order = InstrOrder.first;
1039 MachineInstr *MI = InstrOrder.second;
1040 if (!MI)
1041 continue;
1042
1043 // Insert all SDDbgLabel's whose order(s) are before "Order".
1044 for (; DLI != DLE &&
1045 (*DLI)->getOrder() >= LastOrder && (*DLI)->getOrder() < Order;
1046 ++DLI) {
1047 MachineInstr *DbgMI = Emitter.EmitDbgLabel(*DLI);
1048 if (DbgMI) {
1049 if (!LastOrder)
1050 // Insert to start of the BB (after PHIs).
1051 BB->insert(BBBegin, DbgMI);
1052 else {
1053 // Insert at the instruction, which may be in a different
1054 // block, if the block was split by a custom inserter.
1055 MachineBasicBlock::iterator Pos = MI;
1056 MI->getParent()->insert(Pos, DbgMI);
1057 }
1058 }
1059 }
1060 if (DLI == DLE)
1061 break;
1062
1063 LastOrder = Order;
1064 }
1065 }
1066
1067 InsertPos = Emitter.getInsertPos();
1068 // In some cases, DBG_VALUEs might be inserted after the first terminator,
1069 // which results in an invalid MBB. If that happens, move the DBG_VALUEs
1070 // before the first terminator.
1071 MachineBasicBlock *InsertBB = Emitter.getBlock();
1072 auto FirstTerm = InsertBB->getFirstTerminator();
1073 if (FirstTerm != InsertBB->end()) {
1074 assert(!FirstTerm->isDebugValue() &&
1075 "first terminator cannot be a debug value");
1076 for (MachineInstr &MI : make_early_inc_range(
1077 make_range(std::next(FirstTerm), InsertBB->end()))) {
1078 // Only scan up to insertion point.
1079 if (&MI == InsertPos)
1080 break;
1081
1082 if (!MI.isDebugValue())
1083 continue;
1084
1085 // The DBG_VALUE was referencing a value produced by a terminator. By
1086 // moving the DBG_VALUE, the referenced value also needs invalidating.
1087 MI.getOperand(0).ChangeToRegister(0, false);
1088 MI.moveBefore(&*FirstTerm);
1089 }
1090 }
1091 return InsertBB;
1092 }
1093
1094 /// Return the basic block label.
getDAGName() const1095 std::string ScheduleDAGSDNodes::getDAGName() const {
1096 return "sunit-dag." + BB->getFullName();
1097 }
1098