1 //===-- RegisterPressure.cpp - Dynamic Register Pressure ------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the RegisterPressure class which can be used to track
11 // MachineInstr level register pressure.
13 //===----------------------------------------------------------------------===//
15 #include "RegisterClassInfo.h"
16 #include "RegisterPressure.h"
17 #include "llvm/CodeGen/LiveInterval.h"
18 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
19 #include "llvm/CodeGen/MachineRegisterInfo.h"
20 #include "llvm/Target/TargetMachine.h"
24 /// Increase register pressure for each set impacted by this register class.
25 static void increaseSetPressure(std::vector<unsigned> &CurrSetPressure,
26 std::vector<unsigned> &MaxSetPressure,
27 const TargetRegisterClass *RC,
28 const TargetRegisterInfo *TRI) {
29 unsigned Weight = TRI->getRegClassWeight(RC).RegWeight;
30 for (const int *PSet = TRI->getRegClassPressureSets(RC);
31 *PSet != -1; ++PSet) {
32 CurrSetPressure[*PSet] += Weight;
33 if (&CurrSetPressure != &MaxSetPressure
34 && CurrSetPressure[*PSet] > MaxSetPressure[*PSet]) {
35 MaxSetPressure[*PSet] = CurrSetPressure[*PSet];
40 /// Decrease register pressure for each set impacted by this register class.
41 static void decreaseSetPressure(std::vector<unsigned> &CurrSetPressure,
42 const TargetRegisterClass *RC,
43 const TargetRegisterInfo *TRI) {
44 unsigned Weight = TRI->getRegClassWeight(RC).RegWeight;
45 for (const int *PSet = TRI->getRegClassPressureSets(RC);
46 *PSet != -1; ++PSet) {
47 assert(CurrSetPressure[*PSet] >= Weight && "register pressure underflow");
48 CurrSetPressure[*PSet] -= Weight;
52 /// Directly increase pressure only within this RegisterPressure result.
53 void RegisterPressure::increase(const TargetRegisterClass *RC,
54 const TargetRegisterInfo *TRI) {
55 increaseSetPressure(MaxSetPressure, MaxSetPressure, RC, TRI);
58 /// Directly decrease pressure only within this RegisterPressure result.
59 void RegisterPressure::decrease(const TargetRegisterClass *RC,
60 const TargetRegisterInfo *TRI) {
61 decreaseSetPressure(MaxSetPressure, RC, TRI);
64 /// Increase the current pressure as impacted by these physical registers and
65 /// bump the high water mark if needed.
66 void RegPressureTracker::increasePhysRegPressure(ArrayRef<unsigned> Regs) {
67 for (unsigned I = 0, E = Regs.size(); I != E; ++I)
68 increaseSetPressure(CurrSetPressure, P.MaxSetPressure,
69 TRI->getMinimalPhysRegClass(Regs[I]), TRI);
72 /// Simply decrease the current pressure as impacted by these physcial
74 void RegPressureTracker::decreasePhysRegPressure(ArrayRef<unsigned> Regs) {
75 for (unsigned I = 0, E = Regs.size(); I != E; ++I)
76 decreaseSetPressure(CurrSetPressure, TRI->getMinimalPhysRegClass(Regs[I]),
80 /// Increase the current pressure as impacted by these virtual registers and
81 /// bump the high water mark if needed.
82 void RegPressureTracker::increaseVirtRegPressure(ArrayRef<unsigned> Regs) {
83 for (unsigned I = 0, E = Regs.size(); I != E; ++I)
84 increaseSetPressure(CurrSetPressure, P.MaxSetPressure,
85 MRI->getRegClass(Regs[I]), TRI);
88 /// Simply decrease the current pressure as impacted by these virtual registers.
89 void RegPressureTracker::decreaseVirtRegPressure(ArrayRef<unsigned> Regs) {
90 for (unsigned I = 0, E = Regs.size(); I != E; ++I)
91 decreaseSetPressure(CurrSetPressure, MRI->getRegClass(Regs[I]), TRI);
94 /// Clear the result so it can be used for another round of pressure tracking.
95 void IntervalPressure::reset() {
96 TopIdx = BottomIdx = SlotIndex();
97 MaxSetPressure.clear();
102 /// Clear the result so it can be used for another round of pressure tracking.
103 void RegionPressure::reset() {
104 TopPos = BottomPos = MachineBasicBlock::const_iterator();
105 MaxSetPressure.clear();
110 /// If the current top is not less than or equal to the next index, open it.
111 /// We happen to need the SlotIndex for the next top for pressure update.
112 void IntervalPressure::openTop(SlotIndex NextTop) {
113 if (TopIdx <= NextTop)
115 TopIdx = SlotIndex();
119 /// If the current top is the previous instruction (before receding), open it.
120 void RegionPressure::openTop(MachineBasicBlock::const_iterator PrevTop) {
121 if (TopPos != PrevTop)
123 TopPos = MachineBasicBlock::const_iterator();
127 /// If the current bottom is not greater than the previous index, open it.
128 void IntervalPressure::openBottom(SlotIndex PrevBottom) {
129 if (BottomIdx > PrevBottom)
131 BottomIdx = SlotIndex();
135 /// If the current bottom is the previous instr (before advancing), open it.
136 void RegionPressure::openBottom(MachineBasicBlock::const_iterator PrevBottom) {
137 if (BottomPos != PrevBottom)
139 BottomPos = MachineBasicBlock::const_iterator();
143 /// Setup the RegPressureTracker.
145 /// TODO: Add support for pressure without LiveIntervals.
146 void RegPressureTracker::init(const MachineFunction *mf,
147 const RegisterClassInfo *rci,
148 const LiveIntervals *lis,
149 const MachineBasicBlock *mbb,
150 MachineBasicBlock::const_iterator pos)
153 TRI = MF->getTarget().getRegisterInfo();
155 MRI = &MF->getRegInfo();
158 if (RequireIntervals) {
159 assert(lis && "IntervalPressure requires LiveIntervals");
164 while (CurrPos != MBB->end() && CurrPos->isDebugValue())
167 CurrSetPressure.assign(TRI->getNumRegPressureSets(), 0);
169 if (RequireIntervals)
170 static_cast<IntervalPressure&>(P).reset();
172 static_cast<RegionPressure&>(P).reset();
173 P.MaxSetPressure = CurrSetPressure;
175 LivePhysRegs.clear();
176 LivePhysRegs.setUniverse(TRI->getNumRegs());
177 LiveVirtRegs.clear();
178 LiveVirtRegs.setUniverse(MRI->getNumVirtRegs());
181 /// Does this pressure result have a valid top position and live ins.
182 bool RegPressureTracker::isTopClosed() const {
183 if (RequireIntervals)
184 return static_cast<IntervalPressure&>(P).TopIdx.isValid();
185 return (static_cast<RegionPressure&>(P).TopPos ==
186 MachineBasicBlock::const_iterator());
189 /// Does this pressure result have a valid bottom position and live outs.
190 bool RegPressureTracker::isBottomClosed() const {
191 if (RequireIntervals)
192 return static_cast<IntervalPressure&>(P).BottomIdx.isValid();
193 return (static_cast<RegionPressure&>(P).BottomPos ==
194 MachineBasicBlock::const_iterator());
197 /// Set the boundary for the top of the region and summarize live ins.
198 void RegPressureTracker::closeTop() {
199 if (RequireIntervals)
200 static_cast<IntervalPressure&>(P).TopIdx =
201 LIS->getInstructionIndex(CurrPos).getRegSlot();
203 static_cast<RegionPressure&>(P).TopPos = CurrPos;
205 assert(P.LiveInRegs.empty() && "inconsistent max pressure result");
206 P.LiveInRegs.reserve(LivePhysRegs.size() + LiveVirtRegs.size());
207 P.LiveInRegs.append(LivePhysRegs.begin(), LivePhysRegs.end());
208 for (SparseSet<unsigned>::const_iterator I =
209 LiveVirtRegs.begin(), E = LiveVirtRegs.end(); I != E; ++I)
210 P.LiveInRegs.push_back(*I);
211 std::sort(P.LiveInRegs.begin(), P.LiveInRegs.end());
212 P.LiveInRegs.erase(std::unique(P.LiveInRegs.begin(), P.LiveInRegs.end()),
216 /// Set the boundary for the bottom of the region and summarize live outs.
217 void RegPressureTracker::closeBottom() {
218 if (RequireIntervals)
219 if (CurrPos == MBB->end())
220 static_cast<IntervalPressure&>(P).BottomIdx = LIS->getMBBEndIdx(MBB);
222 static_cast<IntervalPressure&>(P).BottomIdx =
223 LIS->getInstructionIndex(CurrPos).getRegSlot();
225 static_cast<RegionPressure&>(P).BottomPos = CurrPos;
227 assert(P.LiveOutRegs.empty() && "inconsistent max pressure result");
228 P.LiveOutRegs.reserve(LivePhysRegs.size() + LiveVirtRegs.size());
229 P.LiveOutRegs.append(LivePhysRegs.begin(), LivePhysRegs.end());
230 for (SparseSet<unsigned>::const_iterator I =
231 LiveVirtRegs.begin(), E = LiveVirtRegs.end(); I != E; ++I)
232 P.LiveOutRegs.push_back(*I);
233 std::sort(P.LiveOutRegs.begin(), P.LiveOutRegs.end());
234 P.LiveOutRegs.erase(std::unique(P.LiveOutRegs.begin(), P.LiveOutRegs.end()),
235 P.LiveOutRegs.end());
238 /// Finalize the region boundaries and record live ins and live outs.
239 void RegPressureTracker::closeRegion() {
240 if (!isTopClosed() && !isBottomClosed()) {
241 assert(LivePhysRegs.empty() && LiveVirtRegs.empty() &&
242 "no region boundary");
245 if (!isBottomClosed())
247 else if (!isTopClosed())
249 // If both top and bottom are closed, do nothing.
252 /// Return true if Reg aliases a register in Regs SparseSet.
253 static bool hasRegAlias(unsigned Reg, SparseSet<unsigned> &Regs,
254 const TargetRegisterInfo *TRI) {
255 assert(!TargetRegisterInfo::isVirtualRegister(Reg) && "only for physregs");
256 for (const uint16_t *Alias = TRI->getOverlaps(Reg); *Alias; ++Alias) {
257 if (Regs.count(*Alias))
263 /// Return true if Reg aliases a register in unsorted Regs SmallVector.
264 /// This is only valid for physical registers.
265 static SmallVectorImpl<unsigned>::iterator
266 findRegAlias(unsigned Reg, SmallVectorImpl<unsigned> &Regs,
267 const TargetRegisterInfo *TRI) {
268 for (const uint16_t *Alias = TRI->getOverlaps(Reg); *Alias; ++Alias) {
269 SmallVectorImpl<unsigned>::iterator I =
270 std::find(Regs.begin(), Regs.end(), *Alias);
277 /// Return true if Reg can be inserted into Regs SmallVector. For virtual
278 /// register, do a linear search. For physical registers check for aliases.
279 static SmallVectorImpl<unsigned>::iterator
280 findReg(unsigned Reg, bool isVReg, SmallVectorImpl<unsigned> &Regs,
281 const TargetRegisterInfo *TRI) {
283 return std::find(Regs.begin(), Regs.end(), Reg);
284 return findRegAlias(Reg, Regs, TRI);
287 /// Collect this instruction's unique uses and defs into SmallVectors for
288 /// processing defs and uses in order.
289 template<bool isVReg>
290 struct RegisterOperands {
291 SmallVector<unsigned, 8> Uses;
292 SmallVector<unsigned, 8> Defs;
293 SmallVector<unsigned, 8> DeadDefs;
295 /// Push this operand's register onto the correct vector.
296 void collect(const MachineOperand &MO, const TargetRegisterInfo *TRI) {
298 if (findReg(MO.getReg(), isVReg, Uses, TRI) == Uses.end())
299 Uses.push_back(MO.getReg());
303 if (findReg(MO.getReg(), isVReg, DeadDefs, TRI) == DeadDefs.end())
304 DeadDefs.push_back(MO.getReg());
307 if (findReg(MO.getReg(), isVReg, Defs, TRI) == Defs.end())
308 Defs.push_back(MO.getReg());
313 typedef RegisterOperands<false> PhysRegOperands;
314 typedef RegisterOperands<true> VirtRegOperands;
316 /// Collect physical and virtual register operands.
317 static void collectOperands(const MachineInstr *MI,
318 PhysRegOperands &PhysRegOpers,
319 VirtRegOperands &VirtRegOpers,
320 const TargetRegisterInfo *TRI,
321 const RegisterClassInfo *RCI) {
322 for(ConstMIBundleOperands OperI(MI); OperI.isValid(); ++OperI) {
323 const MachineOperand &MO = *OperI;
324 if (!MO.isReg() || !MO.getReg())
327 if (TargetRegisterInfo::isVirtualRegister(MO.getReg()))
328 VirtRegOpers.collect(MO, TRI);
329 else if (RCI->isAllocatable(MO.getReg()))
330 PhysRegOpers.collect(MO, TRI);
332 // Remove redundant physreg dead defs.
333 for (unsigned i = PhysRegOpers.DeadDefs.size(); i > 0; --i) {
334 unsigned Reg = PhysRegOpers.DeadDefs[i-1];
335 if (findRegAlias(Reg, PhysRegOpers.Defs, TRI) != PhysRegOpers.Defs.end())
336 PhysRegOpers.DeadDefs.erase(&PhysRegOpers.DeadDefs[i-1]);
340 /// Add PhysReg to the live in set and increase max pressure.
341 void RegPressureTracker::discoverPhysLiveIn(unsigned Reg) {
342 assert(!LivePhysRegs.count(Reg) && "avoid bumping max pressure twice");
343 if (findRegAlias(Reg, P.LiveInRegs, TRI) == P.LiveInRegs.end())
346 // At live in discovery, unconditionally increase the high water mark.
347 P.LiveInRegs.push_back(Reg);
348 P.increase(TRI->getMinimalPhysRegClass(Reg), TRI);
351 /// Add PhysReg to the live out set and increase max pressure.
352 void RegPressureTracker::discoverPhysLiveOut(unsigned Reg) {
353 assert(!LivePhysRegs.count(Reg) && "avoid bumping max pressure twice");
354 if (findRegAlias(Reg, P.LiveOutRegs, TRI) == P.LiveOutRegs.end())
357 // At live out discovery, unconditionally increase the high water mark.
358 P.LiveOutRegs.push_back(Reg);
359 P.increase(TRI->getMinimalPhysRegClass(Reg), TRI);
362 /// Add VirtReg to the live in set and increase max pressure.
363 void RegPressureTracker::discoverVirtLiveIn(unsigned Reg) {
364 assert(!LiveVirtRegs.count(Reg) && "avoid bumping max pressure twice");
365 if (std::find(P.LiveInRegs.begin(), P.LiveInRegs.end(), Reg) !=
369 // At live in discovery, unconditionally increase the high water mark.
370 P.LiveInRegs.push_back(Reg);
371 P.increase(MRI->getRegClass(Reg), TRI);
374 /// Add VirtReg to the live out set and increase max pressure.
375 void RegPressureTracker::discoverVirtLiveOut(unsigned Reg) {
376 assert(!LiveVirtRegs.count(Reg) && "avoid bumping max pressure twice");
377 if (std::find(P.LiveOutRegs.begin(), P.LiveOutRegs.end(), Reg) !=
381 // At live out discovery, unconditionally increase the high water mark.
382 P.LiveOutRegs.push_back(Reg);
383 P.increase(MRI->getRegClass(Reg), TRI);
386 /// Recede across the previous instruction.
387 bool RegPressureTracker::recede() {
388 // Check for the top of the analyzable region.
389 if (CurrPos == MBB->begin()) {
393 if (!isBottomClosed())
396 // Open the top of the region using block iterators.
397 if (!RequireIntervals && isTopClosed())
398 static_cast<RegionPressure&>(P).openTop(CurrPos);
400 // Find the previous instruction.
403 while (CurrPos != MBB->begin() && CurrPos->isDebugValue());
405 if (CurrPos->isDebugValue()) {
410 if (RequireIntervals)
411 SlotIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
413 // Open the top of the region using slot indexes.
414 if (RequireIntervals && isTopClosed())
415 static_cast<IntervalPressure&>(P).openTop(SlotIdx);
417 PhysRegOperands PhysRegOpers;
418 VirtRegOperands VirtRegOpers;
419 collectOperands(CurrPos, PhysRegOpers, VirtRegOpers, TRI, RCI);
421 // Boost pressure for all dead defs together.
422 increasePhysRegPressure(PhysRegOpers.DeadDefs);
423 increaseVirtRegPressure(VirtRegOpers.DeadDefs);
424 decreasePhysRegPressure(PhysRegOpers.DeadDefs);
425 decreaseVirtRegPressure(VirtRegOpers.DeadDefs);
427 // Kill liveness at live defs.
428 // TODO: consider earlyclobbers?
429 for (unsigned i = 0, e = PhysRegOpers.Defs.size(); i < e; ++i) {
430 unsigned Reg = PhysRegOpers.Defs[i];
431 if (LivePhysRegs.erase(Reg))
432 decreasePhysRegPressure(Reg);
434 discoverPhysLiveOut(Reg);
436 for (unsigned i = 0, e = VirtRegOpers.Defs.size(); i < e; ++i) {
437 unsigned Reg = VirtRegOpers.Defs[i];
438 if (LiveVirtRegs.erase(Reg))
439 decreaseVirtRegPressure(Reg);
441 discoverVirtLiveOut(Reg);
444 // Generate liveness for uses.
445 for (unsigned i = 0, e = PhysRegOpers.Uses.size(); i < e; ++i) {
446 unsigned Reg = PhysRegOpers.Uses[i];
447 if (!hasRegAlias(Reg, LivePhysRegs, TRI)) {
448 increasePhysRegPressure(Reg);
449 LivePhysRegs.insert(Reg);
452 for (unsigned i = 0, e = VirtRegOpers.Uses.size(); i < e; ++i) {
453 unsigned Reg = VirtRegOpers.Uses[i];
454 if (!LiveVirtRegs.count(Reg)) {
455 // Adjust liveouts if LiveIntervals are available.
456 if (RequireIntervals) {
457 const LiveInterval *LI = &LIS->getInterval(Reg);
458 if (!LI->killedAt(SlotIdx))
459 discoverVirtLiveOut(Reg);
461 increaseVirtRegPressure(Reg);
462 LiveVirtRegs.insert(Reg);
468 /// Advance across the current instruction.
469 bool RegPressureTracker::advance() {
470 // Check for the bottom of the analyzable region.
471 if (CurrPos == MBB->end()) {
479 if (RequireIntervals)
480 SlotIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
482 // Open the bottom of the region using slot indexes.
483 if (isBottomClosed()) {
484 if (RequireIntervals)
485 static_cast<IntervalPressure&>(P).openBottom(SlotIdx);
487 static_cast<RegionPressure&>(P).openBottom(CurrPos);
490 PhysRegOperands PhysRegOpers;
491 VirtRegOperands VirtRegOpers;
492 collectOperands(CurrPos, PhysRegOpers, VirtRegOpers, TRI, RCI);
494 // Kill liveness at last uses.
495 for (unsigned i = 0, e = PhysRegOpers.Uses.size(); i < e; ++i) {
496 unsigned Reg = PhysRegOpers.Uses[i];
497 if (!hasRegAlias(Reg, LivePhysRegs, TRI))
498 discoverPhysLiveIn(Reg);
500 // Allocatable physregs are always single-use before regalloc.
501 decreasePhysRegPressure(Reg);
502 LivePhysRegs.erase(Reg);
505 for (unsigned i = 0, e = VirtRegOpers.Uses.size(); i < e; ++i) {
506 unsigned Reg = VirtRegOpers.Uses[i];
507 if (RequireIntervals) {
508 const LiveInterval *LI = &LIS->getInterval(Reg);
509 if (LI->killedAt(SlotIdx)) {
510 if (LiveVirtRegs.erase(Reg))
511 decreaseVirtRegPressure(Reg);
513 discoverVirtLiveIn(Reg);
516 else if (!LiveVirtRegs.count(Reg)) {
517 discoverVirtLiveIn(Reg);
518 increaseVirtRegPressure(Reg);
522 // Generate liveness for defs.
523 for (unsigned i = 0, e = PhysRegOpers.Defs.size(); i < e; ++i) {
524 unsigned Reg = PhysRegOpers.Defs[i];
525 if (!hasRegAlias(Reg, LivePhysRegs, TRI)) {
526 increasePhysRegPressure(Reg);
527 LivePhysRegs.insert(Reg);
530 for (unsigned i = 0, e = VirtRegOpers.Defs.size(); i < e; ++i) {
531 unsigned Reg = VirtRegOpers.Defs[i];
532 if (LiveVirtRegs.insert(Reg).second)
533 increaseVirtRegPressure(Reg);
536 // Boost pressure for all dead defs together.
537 increasePhysRegPressure(PhysRegOpers.DeadDefs);
538 increaseVirtRegPressure(VirtRegOpers.DeadDefs);
539 decreasePhysRegPressure(PhysRegOpers.DeadDefs);
540 decreaseVirtRegPressure(VirtRegOpers.DeadDefs);
542 // Find the next instruction.
545 while (CurrPos != MBB->end() && CurrPos->isDebugValue());
549 // Find the max change in excess pressure across all sets.
550 static int computeMaxPressureDelta(ArrayRef<unsigned> OldPressureVec,
551 ArrayRef<unsigned> NewPressureVec,
553 const TargetRegisterInfo *TRI) {
555 for (unsigned i = 0, e = OldPressureVec.size(); i < e; ++i) {
556 unsigned POld = OldPressureVec[i];
557 unsigned PNew = NewPressureVec[i];
558 int PDiff = (int)PNew - (int)POld;
559 if (!PDiff) // No change in this set in the common case.
561 // Only consider change beyond the limit.
562 unsigned Limit = TRI->getRegPressureSetLimit(i);
565 PDiff = 0; // Under the limit
567 PDiff = PNew - Limit; // Just exceeded limit.
569 else if (Limit > PNew)
570 PDiff = Limit - POld; // Just obeyed limit.
572 if (std::abs(PDiff) > std::abs(ExcessUnits)) {
580 /// Consider the pressure increase caused by traversing this instruction
581 /// bottom-up. Find the pressure set with the most change beyond its pressure
582 /// limit based on the tracker's current pressure, and return the change in
583 /// number of register units of that pressure set introduced by this
586 /// This assumes that the current LiveOut set is sufficient.
588 /// FIXME: This is expensive for an on-the-fly query. We need to cache the
589 /// result per-SUnit with enough information to adjust for the current
590 /// scheduling position. But this works as a proof of concept.
591 void RegPressureTracker::
592 getMaxUpwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta) {
593 // Account for register pressure similar to RegPressureTracker::recede().
594 PhysRegOperands PhysRegOpers;
595 VirtRegOperands VirtRegOpers;
596 collectOperands(MI, PhysRegOpers, VirtRegOpers, TRI, RCI);
598 // Snapshot Pressure.
599 std::vector<unsigned> SavedPressure = CurrSetPressure;
600 std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
602 // Boost max pressure for all dead defs together.
603 // Since CurrSetPressure and MaxSetPressure
604 increasePhysRegPressure(PhysRegOpers.DeadDefs);
605 increaseVirtRegPressure(VirtRegOpers.DeadDefs);
606 decreasePhysRegPressure(PhysRegOpers.DeadDefs);
607 decreaseVirtRegPressure(VirtRegOpers.DeadDefs);
609 // Kill liveness at live defs.
610 // TODO: consider earlyclobbers?
611 for (unsigned i = 0; i < PhysRegOpers.Defs.size(); ++i) {
612 unsigned Reg = PhysRegOpers.Defs[i];
613 if (LivePhysRegs.erase(Reg))
614 decreasePhysRegPressure(Reg);
616 discoverPhysLiveOut(Reg);
618 for (unsigned i = 0; i < VirtRegOpers.Defs.size(); ++i) {
619 unsigned Reg = VirtRegOpers.Defs[i];
620 if (LiveVirtRegs.erase(Reg))
621 decreaseVirtRegPressure(Reg);
623 discoverVirtLiveOut(Reg);
626 // Generate liveness for uses.
627 for (unsigned i = 0, e = PhysRegOpers.Uses.size(); i < e; ++i) {
628 unsigned Reg = PhysRegOpers.Uses[i];
629 if (!hasRegAlias(Reg, LivePhysRegs, TRI)) {
630 increasePhysRegPressure(Reg);
631 LivePhysRegs.insert(Reg);
634 for (unsigned i = 0, e = VirtRegOpers.Uses.size(); i < e; ++i) {
635 unsigned Reg = VirtRegOpers.Uses[i];
636 if (!LiveVirtRegs.count(Reg)) {
637 increaseVirtRegPressure(Reg);
641 computeMaxPressureDelta(SavedPressure, CurrSetPressure,
642 Delta.ExcessSetID, TRI);
643 Delta.MaxUnitIncrease =
644 computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure,
645 Delta.MaxSetID, TRI);
646 assert(Delta.MaxUnitIncrease >= 0 && "cannot increase max pressure");
648 // Restore the tracker's state.
649 P.MaxSetPressure.swap(SavedMaxPressure);
650 CurrSetPressure.swap(SavedPressure);
653 /// Helper to find a vreg use between two indices [PriorUseIdx, NextUseIdx).
654 static bool findUseBetween(unsigned Reg,
655 SlotIndex PriorUseIdx, SlotIndex NextUseIdx,
656 const MachineRegisterInfo *MRI,
657 const LiveIntervals *LIS) {
658 for (MachineRegisterInfo::use_nodbg_iterator
659 UI = MRI->use_nodbg_begin(Reg), UE = MRI->use_nodbg_end();
660 UI != UE; UI.skipInstruction()) {
661 const MachineInstr* MI = &*UI;
662 SlotIndex InstSlot = LIS->getInstructionIndex(MI).getRegSlot();
663 if (InstSlot >= PriorUseIdx && InstSlot < NextUseIdx)
669 /// Consider the pressure increase caused by traversing this instruction
670 /// top-down. Find the register class with the most change in its pressure limit
671 /// based on the tracker's current pressure, and return the number of excess
672 /// register units of that pressure set introduced by this instruction.
674 /// This assumes that the current LiveIn set is sufficient.
675 void RegPressureTracker::
676 getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta) {
677 // Account for register pressure similar to RegPressureTracker::recede().
678 PhysRegOperands PhysRegOpers;
679 VirtRegOperands VirtRegOpers;
680 collectOperands(MI, PhysRegOpers, VirtRegOpers, TRI, RCI);
682 // Snapshot Pressure.
683 std::vector<unsigned> SavedPressure = CurrSetPressure;
684 std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
686 // Kill liveness at last uses. Assume allocatable physregs are single-use
687 // rather than checking LiveIntervals.
688 decreasePhysRegPressure(PhysRegOpers.Uses);
689 if (RequireIntervals) {
690 SlotIndex SlotIdx = LIS->getInstructionIndex(MI).getRegSlot();
691 for (unsigned i = 0, e = VirtRegOpers.Uses.size(); i < e; ++i) {
692 unsigned Reg = VirtRegOpers.Uses[i];
693 const LiveInterval *LI = &LIS->getInterval(Reg);
694 // FIXME: allow the caller to pass in the list of vreg uses that remain to
695 // be top-scheduled to avoid searching uses at each query.
696 SlotIndex CurrIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
697 if (LI->killedAt(SlotIdx)
698 && !findUseBetween(Reg, CurrIdx, SlotIdx, MRI, LIS)) {
699 decreaseVirtRegPressure(Reg);
704 // Generate liveness for defs.
705 increasePhysRegPressure(PhysRegOpers.Defs);
706 increaseVirtRegPressure(VirtRegOpers.Defs);
708 // Boost pressure for all dead defs together.
709 increasePhysRegPressure(PhysRegOpers.DeadDefs);
710 increaseVirtRegPressure(VirtRegOpers.DeadDefs);
711 decreasePhysRegPressure(PhysRegOpers.DeadDefs);
712 decreaseVirtRegPressure(VirtRegOpers.DeadDefs);
715 computeMaxPressureDelta(SavedPressure, CurrSetPressure,
716 Delta.ExcessSetID, TRI);
717 Delta.MaxUnitIncrease =
718 computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure,
719 Delta.MaxSetID, TRI);
721 // Restore the tracker's state.
722 P.MaxSetPressure.swap(SavedMaxPressure);
723 CurrSetPressure.swap(SavedPressure);