1 //===-- LiveIntervalAnalysis.h - Live Interval Analysis ---------*- C++ -*-===//
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 LiveInterval analysis pass. Given some numbering of
11 // each the machine instructions (in this implemention depth-first order) an
12 // interval [i, j) is said to be a live interval for register v if there is no
13 // instruction with number j' > j such that v is live at j' and there is no
14 // instruction with number i' < i such that v is live at i'. In this
15 // implementation intervals can have holes, i.e. an interval might look like
16 // [1,20), [50,65), [1000,1001).
18 //===----------------------------------------------------------------------===//
20 #ifndef LLVM_CODEGEN_LIVEINTERVALANALYSIS_H
21 #define LLVM_CODEGEN_LIVEINTERVALANALYSIS_H
23 #include "llvm/ADT/IndexedMap.h"
24 #include "llvm/ADT/SmallVector.h"
25 #include "llvm/CodeGen/LiveInterval.h"
26 #include "llvm/CodeGen/MachineBasicBlock.h"
27 #include "llvm/CodeGen/MachineFunctionPass.h"
28 #include "llvm/CodeGen/SlotIndexes.h"
29 #include "llvm/Support/Allocator.h"
30 #include "llvm/Target/TargetRegisterInfo.h"
41 class MachineDominatorTree;
42 class MachineLoopInfo;
43 class TargetRegisterInfo;
44 class MachineRegisterInfo;
45 class TargetInstrInfo;
46 class TargetRegisterClass;
48 class MachineBlockFrequencyInfo;
50 class LiveIntervals : public MachineFunctionPass {
52 MachineRegisterInfo* MRI;
53 const TargetRegisterInfo* TRI;
54 const TargetInstrInfo* TII;
57 MachineDominatorTree *DomTree;
58 LiveRangeCalc *LRCalc;
60 /// Special pool allocator for VNInfo's (LiveInterval val#).
62 VNInfo::Allocator VNInfoAllocator;
64 /// Live interval pointers for all the virtual registers.
65 IndexedMap<LiveInterval*, VirtReg2IndexFunctor> VirtRegIntervals;
67 /// RegMaskSlots - Sorted list of instructions with register mask operands.
68 /// Always use the 'r' slot, RegMasks are normal clobbers, not early
70 SmallVector<SlotIndex, 8> RegMaskSlots;
72 /// RegMaskBits - This vector is parallel to RegMaskSlots, it holds a
73 /// pointer to the corresponding register mask. This pointer can be
76 /// MI = Indexes->getInstructionFromIndex(RegMaskSlot[N]);
77 /// unsigned OpNum = findRegMaskOperand(MI);
78 /// RegMaskBits[N] = MI->getOperand(OpNum).getRegMask();
80 /// This is kept in a separate vector partly because some standard
81 /// libraries don't support lower_bound() with mixed objects, partly to
82 /// improve locality when searching in RegMaskSlots.
83 /// Also see the comment in LiveInterval::find().
84 SmallVector<const uint32_t*, 8> RegMaskBits;
86 /// For each basic block number, keep (begin, size) pairs indexing into the
87 /// RegMaskSlots and RegMaskBits arrays.
88 /// Note that basic block numbers may not be layout contiguous, that's why
89 /// we can't just keep track of the first register mask in each basic
91 SmallVector<std::pair<unsigned, unsigned>, 8> RegMaskBlocks;
93 /// Keeps a live range set for each register unit to track fixed physreg
95 SmallVector<LiveRange*, 0> RegUnitRanges;
98 static char ID; // Pass identification, replacement for typeid
100 virtual ~LiveIntervals();
102 // Calculate the spill weight to assign to a single instruction.
103 static float getSpillWeight(bool isDef, bool isUse,
104 const MachineBlockFrequencyInfo *MBFI,
105 const MachineInstr *Instr);
107 LiveInterval &getInterval(unsigned Reg) {
108 if (hasInterval(Reg))
109 return *VirtRegIntervals[Reg];
111 return createAndComputeVirtRegInterval(Reg);
114 const LiveInterval &getInterval(unsigned Reg) const {
115 return const_cast<LiveIntervals*>(this)->getInterval(Reg);
118 bool hasInterval(unsigned Reg) const {
119 return VirtRegIntervals.inBounds(Reg) && VirtRegIntervals[Reg];
122 // Interval creation.
123 LiveInterval &createEmptyInterval(unsigned Reg) {
124 assert(!hasInterval(Reg) && "Interval already exists!");
125 VirtRegIntervals.grow(Reg);
126 VirtRegIntervals[Reg] = createInterval(Reg);
127 return *VirtRegIntervals[Reg];
130 LiveInterval &createAndComputeVirtRegInterval(unsigned Reg) {
131 LiveInterval &LI = createEmptyInterval(Reg);
132 computeVirtRegInterval(LI);
137 void removeInterval(unsigned Reg) {
138 delete VirtRegIntervals[Reg];
139 VirtRegIntervals[Reg] = nullptr;
142 /// Given a register and an instruction, adds a live segment from that
143 /// instruction to the end of its MBB.
144 LiveInterval::Segment addSegmentToEndOfBlock(unsigned reg,
145 MachineInstr* startInst);
147 /// shrinkToUses - After removing some uses of a register, shrink its live
148 /// range to just the remaining uses. This method does not compute reaching
149 /// defs for new uses, and it doesn't remove dead defs.
150 /// Dead PHIDef values are marked as unused.
151 /// New dead machine instructions are added to the dead vector.
152 /// Return true if the interval may have been separated into multiple
153 /// connected components.
154 bool shrinkToUses(LiveInterval *li,
155 SmallVectorImpl<MachineInstr*> *dead = nullptr);
157 /// Specialized version of
158 /// shrinkToUses(LiveInterval *li, SmallVectorImpl<MachineInstr*> *dead)
159 /// that works on a subregister live range and only looks at uses matching
160 /// the lane mask of the subregister range.
161 void shrinkToUses(LiveInterval::SubRange &SR, unsigned Reg);
163 /// extendToIndices - Extend the live range of LI to reach all points in
164 /// Indices. The points in the Indices array must be jointly dominated by
165 /// existing defs in LI. PHI-defs are added as needed to maintain SSA form.
167 /// If a SlotIndex in Indices is the end index of a basic block, LI will be
168 /// extended to be live out of the basic block.
170 /// See also LiveRangeCalc::extend().
171 void extendToIndices(LiveRange &LR, ArrayRef<SlotIndex> Indices);
174 /// If @p LR has a live value at @p Kill, prune its live range by removing
175 /// any liveness reachable from Kill. Add live range end points to
176 /// EndPoints such that extendToIndices(LI, EndPoints) will reconstruct the
177 /// value's live range.
179 /// Calling pruneValue() and extendToIndices() can be used to reconstruct
180 /// SSA form after adding defs to a virtual register.
181 void pruneValue(LiveRange &LR, SlotIndex Kill,
182 SmallVectorImpl<SlotIndex> *EndPoints);
184 SlotIndexes *getSlotIndexes() const {
188 AliasAnalysis *getAliasAnalysis() const {
192 /// isNotInMIMap - returns true if the specified machine instr has been
193 /// removed or was never entered in the map.
194 bool isNotInMIMap(const MachineInstr* Instr) const {
195 return !Indexes->hasIndex(Instr);
198 /// Returns the base index of the given instruction.
199 SlotIndex getInstructionIndex(const MachineInstr *instr) const {
200 return Indexes->getInstructionIndex(instr);
203 /// Returns the instruction associated with the given index.
204 MachineInstr* getInstructionFromIndex(SlotIndex index) const {
205 return Indexes->getInstructionFromIndex(index);
208 /// Return the first index in the given basic block.
209 SlotIndex getMBBStartIdx(const MachineBasicBlock *mbb) const {
210 return Indexes->getMBBStartIdx(mbb);
213 /// Return the last index in the given basic block.
214 SlotIndex getMBBEndIdx(const MachineBasicBlock *mbb) const {
215 return Indexes->getMBBEndIdx(mbb);
218 bool isLiveInToMBB(const LiveRange &LR,
219 const MachineBasicBlock *mbb) const {
220 return LR.liveAt(getMBBStartIdx(mbb));
223 bool isLiveOutOfMBB(const LiveRange &LR,
224 const MachineBasicBlock *mbb) const {
225 return LR.liveAt(getMBBEndIdx(mbb).getPrevSlot());
228 MachineBasicBlock* getMBBFromIndex(SlotIndex index) const {
229 return Indexes->getMBBFromIndex(index);
232 void insertMBBInMaps(MachineBasicBlock *MBB) {
233 Indexes->insertMBBInMaps(MBB);
234 assert(unsigned(MBB->getNumber()) == RegMaskBlocks.size() &&
235 "Blocks must be added in order.");
236 RegMaskBlocks.push_back(std::make_pair(RegMaskSlots.size(), 0));
239 SlotIndex InsertMachineInstrInMaps(MachineInstr *MI) {
240 return Indexes->insertMachineInstrInMaps(MI);
243 void InsertMachineInstrRangeInMaps(MachineBasicBlock::iterator B,
244 MachineBasicBlock::iterator E) {
245 for (MachineBasicBlock::iterator I = B; I != E; ++I)
246 Indexes->insertMachineInstrInMaps(I);
249 void RemoveMachineInstrFromMaps(MachineInstr *MI) {
250 Indexes->removeMachineInstrFromMaps(MI);
253 void ReplaceMachineInstrInMaps(MachineInstr *MI, MachineInstr *NewMI) {
254 Indexes->replaceMachineInstrInMaps(MI, NewMI);
257 bool findLiveInMBBs(SlotIndex Start, SlotIndex End,
258 SmallVectorImpl<MachineBasicBlock*> &MBBs) const {
259 return Indexes->findLiveInMBBs(Start, End, MBBs);
262 VNInfo::Allocator& getVNInfoAllocator() { return VNInfoAllocator; }
264 void getAnalysisUsage(AnalysisUsage &AU) const override;
265 void releaseMemory() override;
267 /// runOnMachineFunction - pass entry point
268 bool runOnMachineFunction(MachineFunction&) override;
270 /// print - Implement the dump method.
271 void print(raw_ostream &O, const Module* = nullptr) const override;
273 /// intervalIsInOneMBB - If LI is confined to a single basic block, return
274 /// a pointer to that block. If LI is live in to or out of any block,
276 MachineBasicBlock *intervalIsInOneMBB(const LiveInterval &LI) const;
278 /// Returns true if VNI is killed by any PHI-def values in LI.
279 /// This may conservatively return true to avoid expensive computations.
280 bool hasPHIKill(const LiveInterval &LI, const VNInfo *VNI) const;
282 /// addKillFlags - Add kill flags to any instruction that kills a virtual
284 void addKillFlags(const VirtRegMap*);
286 /// handleMove - call this method to notify LiveIntervals that
287 /// instruction 'mi' has been moved within a basic block. This will update
288 /// the live intervals for all operands of mi. Moves between basic blocks
289 /// are not supported.
291 /// \param UpdateFlags Update live intervals for nonallocatable physregs.
292 void handleMove(MachineInstr* MI, bool UpdateFlags = false);
294 /// moveIntoBundle - Update intervals for operands of MI so that they
295 /// begin/end on the SlotIndex for BundleStart.
297 /// \param UpdateFlags Update live intervals for nonallocatable physregs.
299 /// Requires MI and BundleStart to have SlotIndexes, and assumes
300 /// existing liveness is accurate. BundleStart should be the first
301 /// instruction in the Bundle.
302 void handleMoveIntoBundle(MachineInstr* MI, MachineInstr* BundleStart,
303 bool UpdateFlags = false);
305 /// repairIntervalsInRange - Update live intervals for instructions in a
306 /// range of iterators. It is intended for use after target hooks that may
307 /// insert or remove instructions, and is only efficient for a small number
310 /// OrigRegs is a vector of registers that were originally used by the
311 /// instructions in the range between the two iterators.
313 /// Currently, the only only changes that are supported are simple removal
314 /// and addition of uses.
315 void repairIntervalsInRange(MachineBasicBlock *MBB,
316 MachineBasicBlock::iterator Begin,
317 MachineBasicBlock::iterator End,
318 ArrayRef<unsigned> OrigRegs);
320 // Register mask functions.
322 // Machine instructions may use a register mask operand to indicate that a
323 // large number of registers are clobbered by the instruction. This is
324 // typically used for calls.
326 // For compile time performance reasons, these clobbers are not recorded in
327 // the live intervals for individual physical registers. Instead,
328 // LiveIntervalAnalysis maintains a sorted list of instructions with
329 // register mask operands.
331 /// getRegMaskSlots - Returns a sorted array of slot indices of all
332 /// instructions with register mask operands.
333 ArrayRef<SlotIndex> getRegMaskSlots() const { return RegMaskSlots; }
335 /// getRegMaskSlotsInBlock - Returns a sorted array of slot indices of all
336 /// instructions with register mask operands in the basic block numbered
338 ArrayRef<SlotIndex> getRegMaskSlotsInBlock(unsigned MBBNum) const {
339 std::pair<unsigned, unsigned> P = RegMaskBlocks[MBBNum];
340 return getRegMaskSlots().slice(P.first, P.second);
343 /// getRegMaskBits() - Returns an array of register mask pointers
344 /// corresponding to getRegMaskSlots().
345 ArrayRef<const uint32_t*> getRegMaskBits() const { return RegMaskBits; }
347 /// getRegMaskBitsInBlock - Returns an array of mask pointers corresponding
348 /// to getRegMaskSlotsInBlock(MBBNum).
349 ArrayRef<const uint32_t*> getRegMaskBitsInBlock(unsigned MBBNum) const {
350 std::pair<unsigned, unsigned> P = RegMaskBlocks[MBBNum];
351 return getRegMaskBits().slice(P.first, P.second);
354 /// checkRegMaskInterference - Test if LI is live across any register mask
355 /// instructions, and compute a bit mask of physical registers that are not
356 /// clobbered by any of them.
358 /// Returns false if LI doesn't cross any register mask instructions. In
359 /// that case, the bit vector is not filled in.
360 bool checkRegMaskInterference(LiveInterval &LI,
361 BitVector &UsableRegs);
363 // Register unit functions.
365 // Fixed interference occurs when MachineInstrs use physregs directly
366 // instead of virtual registers. This typically happens when passing
367 // arguments to a function call, or when instructions require operands in
370 // Each physreg has one or more register units, see MCRegisterInfo. We
371 // track liveness per register unit to handle aliasing registers more
374 /// getRegUnit - Return the live range for Unit.
375 /// It will be computed if it doesn't exist.
376 LiveRange &getRegUnit(unsigned Unit) {
377 LiveRange *LR = RegUnitRanges[Unit];
379 // Compute missing ranges on demand.
380 RegUnitRanges[Unit] = LR = new LiveRange();
381 computeRegUnitRange(*LR, Unit);
386 /// getCachedRegUnit - Return the live range for Unit if it has already
387 /// been computed, or NULL if it hasn't been computed yet.
388 LiveRange *getCachedRegUnit(unsigned Unit) {
389 return RegUnitRanges[Unit];
392 const LiveRange *getCachedRegUnit(unsigned Unit) const {
393 return RegUnitRanges[Unit];
396 /// Remove value numbers and related live segments starting at position
397 /// @p Pos that are part of any liverange of physical register @p Reg or one
398 /// of its subregisters.
399 void removePhysRegDefAt(unsigned Reg, SlotIndex Pos);
402 /// Compute live intervals for all virtual registers.
403 void computeVirtRegs();
405 /// Compute RegMaskSlots and RegMaskBits.
406 void computeRegMasks();
408 /// Walk the values in @p LI and check for dead values:
409 /// - Dead PHIDef values are marked as unused.
410 /// - Dead operands are marked as such.
411 /// - Completely dead machine instructions are added to the @p dead vector
412 /// if it is not nullptr.
413 /// Returns true if any PHI value numbers have been removed which may
414 /// have separated the interval into multiple connected components.
415 bool computeDeadValues(LiveInterval &LI,
416 SmallVectorImpl<MachineInstr*> *dead);
418 static LiveInterval* createInterval(unsigned Reg);
420 void printInstrs(raw_ostream &O) const;
421 void dumpInstrs() const;
423 void computeLiveInRegUnits();
424 void computeRegUnitRange(LiveRange&, unsigned Unit);
425 void computeVirtRegInterval(LiveInterval&);
428 /// Helper function for repairIntervalsInRange(), walks backwards and
429 /// creates/modifies live segments in @p LR to match the operands found.
430 /// Only full operands or operands with subregisters matching @p LaneMask
432 void repairOldRegInRange(MachineBasicBlock::iterator Begin,
433 MachineBasicBlock::iterator End,
434 const SlotIndex endIdx, LiveRange &LR,
435 unsigned Reg, unsigned LaneMask = ~0u);
439 } // End llvm namespace