LiveIntervalAnalysis.h revision 84bc5427d6883f73cfeae3da640acd011d35c006 
1//===-- LiveIntervalAnalysis.h - Live Interval Analysis ---------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
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' abd 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).
17//
18//===----------------------------------------------------------------------===//
19
20#ifndef LLVM_CODEGEN_LIVEINTERVAL_ANALYSIS_H
21#define LLVM_CODEGEN_LIVEINTERVAL_ANALYSIS_H
22
23#include "llvm/CodeGen/MachineFunctionPass.h"
24#include "llvm/CodeGen/LiveInterval.h"
25#include "llvm/ADT/BitVector.h"
26#include "llvm/ADT/DenseMap.h"
27#include "llvm/ADT/SmallPtrSet.h"
28#include "llvm/ADT/SmallVector.h"
29#include "llvm/Support/Allocator.h"
30#include <cmath>
31
32namespace llvm {
33
34  class LiveVariables;
35  class MachineLoopInfo;
36  class MRegisterInfo;
37  class MachineRegisterInfo;
38  class TargetInstrInfo;
39  class TargetRegisterClass;
40  class VirtRegMap;
41  typedef std::pair<unsigned, MachineBasicBlock*> IdxMBBPair;
42
43  class LiveIntervals : public MachineFunctionPass {
44    MachineFunction* mf_;
45    const TargetMachine* tm_;
46    const MRegisterInfo* mri_;
47    const TargetInstrInfo* tii_;
48    LiveVariables* lv_;
49
50    /// Special pool allocator for VNInfo's (LiveInterval val#).
51    ///
52    BumpPtrAllocator VNInfoAllocator;
53
54    /// MBB2IdxMap - The indexes of the first and last instructions in the
55    /// specified basic block.
56    std::vector<std::pair<unsigned, unsigned> > MBB2IdxMap;
57
58    /// Idx2MBBMap - Sorted list of pairs of index of first instruction
59    /// and MBB id.
60    std::vector<IdxMBBPair> Idx2MBBMap;
61
62    typedef std::map<MachineInstr*, unsigned> Mi2IndexMap;
63    Mi2IndexMap mi2iMap_;
64
65    typedef std::vector<MachineInstr*> Index2MiMap;
66    Index2MiMap i2miMap_;
67
68    typedef std::map<unsigned, LiveInterval> Reg2IntervalMap;
69    Reg2IntervalMap r2iMap_;
70
71    BitVector allocatableRegs_;
72
73    std::vector<MachineInstr*> ClonedMIs;
74
75  public:
76    static char ID; // Pass identification, replacement for typeid
77    LiveIntervals() : MachineFunctionPass((intptr_t)&ID) {}
78
79    struct InstrSlots {
80      enum {
81        LOAD  = 0,
82        USE   = 1,
83        DEF   = 2,
84        STORE = 3,
85        NUM   = 4
86      };
87    };
88
89    static unsigned getBaseIndex(unsigned index) {
90      return index - (index % InstrSlots::NUM);
91    }
92    static unsigned getBoundaryIndex(unsigned index) {
93      return getBaseIndex(index + InstrSlots::NUM - 1);
94    }
95    static unsigned getLoadIndex(unsigned index) {
96      return getBaseIndex(index) + InstrSlots::LOAD;
97    }
98    static unsigned getUseIndex(unsigned index) {
99      return getBaseIndex(index) + InstrSlots::USE;
100    }
101    static unsigned getDefIndex(unsigned index) {
102      return getBaseIndex(index) + InstrSlots::DEF;
103    }
104    static unsigned getStoreIndex(unsigned index) {
105      return getBaseIndex(index) + InstrSlots::STORE;
106    }
107
108    static float getSpillWeight(bool isDef, bool isUse, unsigned loopDepth) {
109      return (isDef + isUse) * powf(10.0F, (float)loopDepth);
110    }
111
112    typedef Reg2IntervalMap::iterator iterator;
113    typedef Reg2IntervalMap::const_iterator const_iterator;
114    const_iterator begin() const { return r2iMap_.begin(); }
115    const_iterator end() const { return r2iMap_.end(); }
116    iterator begin() { return r2iMap_.begin(); }
117    iterator end() { return r2iMap_.end(); }
118    unsigned getNumIntervals() const { return r2iMap_.size(); }
119
120    LiveInterval &getInterval(unsigned reg) {
121      Reg2IntervalMap::iterator I = r2iMap_.find(reg);
122      assert(I != r2iMap_.end() && "Interval does not exist for register");
123      return I->second;
124    }
125
126    const LiveInterval &getInterval(unsigned reg) const {
127      Reg2IntervalMap::const_iterator I = r2iMap_.find(reg);
128      assert(I != r2iMap_.end() && "Interval does not exist for register");
129      return I->second;
130    }
131
132    bool hasInterval(unsigned reg) const {
133      return r2iMap_.count(reg);
134    }
135
136    /// getMBBStartIdx - Return the base index of the first instruction in the
137    /// specified MachineBasicBlock.
138    unsigned getMBBStartIdx(MachineBasicBlock *MBB) const {
139      return getMBBStartIdx(MBB->getNumber());
140    }
141    unsigned getMBBStartIdx(unsigned MBBNo) const {
142      assert(MBBNo < MBB2IdxMap.size() && "Invalid MBB number!");
143      return MBB2IdxMap[MBBNo].first;
144    }
145
146    /// getMBBEndIdx - Return the store index of the last instruction in the
147    /// specified MachineBasicBlock.
148    unsigned getMBBEndIdx(MachineBasicBlock *MBB) const {
149      return getMBBEndIdx(MBB->getNumber());
150    }
151    unsigned getMBBEndIdx(unsigned MBBNo) const {
152      assert(MBBNo < MBB2IdxMap.size() && "Invalid MBB number!");
153      return MBB2IdxMap[MBBNo].second;
154    }
155
156    /// getInstructionIndex - returns the base index of instr
157    unsigned getInstructionIndex(MachineInstr* instr) const {
158      Mi2IndexMap::const_iterator it = mi2iMap_.find(instr);
159      assert(it != mi2iMap_.end() && "Invalid instruction!");
160      return it->second;
161    }
162
163    /// getInstructionFromIndex - given an index in any slot of an
164    /// instruction return a pointer the instruction
165    MachineInstr* getInstructionFromIndex(unsigned index) const {
166      index /= InstrSlots::NUM; // convert index to vector index
167      assert(index < i2miMap_.size() &&
168             "index does not correspond to an instruction");
169      return i2miMap_[index];
170    }
171
172    /// conflictsWithPhysRegDef - Returns true if the specified register
173    /// is defined during the duration of the specified interval.
174    bool conflictsWithPhysRegDef(const LiveInterval &li, VirtRegMap &vrm,
175                                 unsigned reg);
176
177    /// findLiveInMBBs - Given a live range, if the value of the range
178    /// is live in any MBB returns true as well as the list of basic blocks
179    /// where the value is live in.
180    bool findLiveInMBBs(const LiveRange &LR,
181                        SmallVectorImpl<MachineBasicBlock*> &MBBs) const;
182
183    // Interval creation
184
185    LiveInterval &getOrCreateInterval(unsigned reg) {
186      Reg2IntervalMap::iterator I = r2iMap_.find(reg);
187      if (I == r2iMap_.end())
188        I = r2iMap_.insert(I, std::make_pair(reg, createInterval(reg)));
189      return I->second;
190    }
191
192    // Interval removal
193
194    void removeInterval(unsigned Reg) {
195      r2iMap_.erase(Reg);
196    }
197
198    /// isRemoved - returns true if the specified machine instr has been
199    /// removed.
200    bool isRemoved(MachineInstr* instr) const {
201      return !mi2iMap_.count(instr);
202    }
203
204    /// RemoveMachineInstrFromMaps - This marks the specified machine instr as
205    /// deleted.
206    void RemoveMachineInstrFromMaps(MachineInstr *MI) {
207      // remove index -> MachineInstr and
208      // MachineInstr -> index mappings
209      Mi2IndexMap::iterator mi2i = mi2iMap_.find(MI);
210      if (mi2i != mi2iMap_.end()) {
211        i2miMap_[mi2i->second/InstrSlots::NUM] = 0;
212        mi2iMap_.erase(mi2i);
213      }
214    }
215
216    BumpPtrAllocator& getVNInfoAllocator() { return VNInfoAllocator; }
217
218    virtual void getAnalysisUsage(AnalysisUsage &AU) const;
219    virtual void releaseMemory();
220
221    /// runOnMachineFunction - pass entry point
222    virtual bool runOnMachineFunction(MachineFunction&);
223
224    /// print - Implement the dump method.
225    virtual void print(std::ostream &O, const Module* = 0) const;
226    void print(std::ostream *O, const Module* M = 0) const {
227      if (O) print(*O, M);
228    }
229
230    /// addIntervalsForSpills - Create new intervals for spilled defs / uses of
231    /// the given interval.
232    std::vector<LiveInterval*>
233    addIntervalsForSpills(const LiveInterval& i,
234                          const MachineLoopInfo *loopInfo, VirtRegMap& vrm);
235
236    /// isReMaterializable - Returns true if every definition of MI of every
237    /// val# of the specified interval is re-materializable. Also returns true
238    /// by reference if all of the defs are load instructions.
239    bool isReMaterializable(const LiveInterval &li, bool &isLoad);
240
241  private:
242    /// computeIntervals - Compute live intervals.
243    void computeIntervals();
244
245    /// handleRegisterDef - update intervals for a register def
246    /// (calls handlePhysicalRegisterDef and
247    /// handleVirtualRegisterDef)
248    void handleRegisterDef(MachineBasicBlock *MBB,
249                           MachineBasicBlock::iterator MI, unsigned MIIdx,
250                           unsigned reg);
251
252    /// handleVirtualRegisterDef - update intervals for a virtual
253    /// register def
254    void handleVirtualRegisterDef(MachineBasicBlock *MBB,
255                                  MachineBasicBlock::iterator MI,
256                                  unsigned MIIdx,
257                                  LiveInterval& interval);
258
259    /// handlePhysicalRegisterDef - update intervals for a physical register
260    /// def.
261    void handlePhysicalRegisterDef(MachineBasicBlock* mbb,
262                                   MachineBasicBlock::iterator mi,
263                                   unsigned MIIdx,
264                                   LiveInterval &interval,
265                                   unsigned SrcReg);
266
267    /// handleLiveInRegister - Create interval for a livein register.
268    void handleLiveInRegister(MachineBasicBlock* mbb,
269                              unsigned MIIdx,
270                              LiveInterval &interval, bool isAlias = false);
271
272    /// isReMaterializable - Returns true if the definition MI of the specified
273    /// val# of the specified interval is re-materializable. Also returns true
274    /// by reference if the def is a load.
275    bool isReMaterializable(const LiveInterval &li, const VNInfo *ValNo,
276                            MachineInstr *MI, bool &isLoad);
277
278    /// tryFoldMemoryOperand - Attempts to fold either a spill / restore from
279    /// slot / to reg or any rematerialized load into ith operand of specified
280    /// MI. If it is successul, MI is updated with the newly created MI and
281    /// returns true.
282    bool tryFoldMemoryOperand(MachineInstr* &MI, VirtRegMap &vrm,
283                              MachineInstr *DefMI, unsigned InstrIdx,
284                              SmallVector<unsigned, 2> &Ops,
285                              bool isSS, int Slot, unsigned Reg);
286
287    /// canFoldMemoryOperand - Returns true if the specified load / store
288    /// folding is possible.
289    bool canFoldMemoryOperand(MachineInstr *MI,
290                              SmallVector<unsigned, 2> &Ops) const;
291
292    /// anyKillInMBBAfterIdx - Returns true if there is a kill of the specified
293    /// VNInfo that's after the specified index but is within the basic block.
294    bool anyKillInMBBAfterIdx(const LiveInterval &li, const VNInfo *VNI,
295                              MachineBasicBlock *MBB, unsigned Idx) const;
296
297    /// intervalIsInOneMBB - Returns true if the specified interval is entirely
298    /// within a single basic block.
299    bool intervalIsInOneMBB(const LiveInterval &li) const;
300
301    /// SRInfo - Spill / restore info.
302    struct SRInfo {
303      int index;
304      unsigned vreg;
305      bool canFold;
306      SRInfo(int i, unsigned vr, bool f) : index(i), vreg(vr), canFold(f) {};
307    };
308
309    bool alsoFoldARestore(int Id, int index, unsigned vr,
310                          BitVector &RestoreMBBs,
311                          std::map<unsigned,std::vector<SRInfo> >&RestoreIdxes);
312    void eraseRestoreInfo(int Id, int index, unsigned vr,
313                          BitVector &RestoreMBBs,
314                          std::map<unsigned,std::vector<SRInfo> >&RestoreIdxes);
315
316    /// rewriteInstructionForSpills, rewriteInstructionsForSpills - Helper
317    /// functions for addIntervalsForSpills to rewrite uses / defs for the given
318    /// live range.
319    bool rewriteInstructionForSpills(const LiveInterval &li, bool TrySplit,
320        unsigned id, unsigned index, unsigned end, MachineInstr *MI,
321        MachineInstr *OrigDefMI, MachineInstr *DefMI, unsigned Slot, int LdSlot,
322        bool isLoad, bool isLoadSS, bool DefIsReMat, bool CanDelete,
323        VirtRegMap &vrm, MachineRegisterInfo &RegMap,
324                                     const TargetRegisterClass* rc,
325        SmallVector<int, 4> &ReMatIds,
326        unsigned &NewVReg, bool &HasDef, bool &HasUse,
327        const MachineLoopInfo *loopInfo,
328        std::map<unsigned,unsigned> &MBBVRegsMap,
329        std::vector<LiveInterval*> &NewLIs);
330    void rewriteInstructionsForSpills(const LiveInterval &li, bool TrySplit,
331        LiveInterval::Ranges::const_iterator &I,
332        MachineInstr *OrigDefMI, MachineInstr *DefMI, unsigned Slot, int LdSlot,
333        bool isLoad, bool isLoadSS, bool DefIsReMat, bool CanDelete,
334        VirtRegMap &vrm, MachineRegisterInfo &RegMap,
335                                      const TargetRegisterClass* rc,
336        SmallVector<int, 4> &ReMatIds, const MachineLoopInfo *loopInfo,
337        BitVector &SpillMBBs,
338        std::map<unsigned,std::vector<SRInfo> > &SpillIdxes,
339        BitVector &RestoreMBBs,
340        std::map<unsigned,std::vector<SRInfo> > &RestoreIdxes,
341        std::map<unsigned,unsigned> &MBBVRegsMap,
342        std::vector<LiveInterval*> &NewLIs);
343
344    static LiveInterval createInterval(unsigned Reg);
345
346    void printRegName(unsigned reg) const;
347  };
348
349} // End llvm namespace
350
351#endif
352