LLVM API Documentation

LiveInterval.h

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00001 //===-- llvm/CodeGen/LiveInterval.h - Interval representation ---*- C++ -*-===//
00002 //
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file was developed by the LLVM research group and is distributed under
00006 // the University of Illinois Open Source License. See LICENSE.TXT for details.
00007 //
00008 //===----------------------------------------------------------------------===//
00009 //
00010 // This file implements the LiveRange and LiveInterval classes.  Given some
00011 // numbering of each the machine instructions an interval [i, j) is said to be a
00012 // live interval for register v if there is no instruction with number j' > j
00013 // such that v is live at j' and there is no instruction with number i' < i such
00014 // that v is live at i'. In this implementation intervals can have holes,
00015 // i.e. an interval might look like [1,20), [50,65), [1000,1001).  Each
00016 // individual range is represented as an instance of LiveRange, and the whole
00017 // interval is represented as an instance of LiveInterval.
00018 //
00019 //===----------------------------------------------------------------------===//
00020 
00021 #ifndef LLVM_CODEGEN_LIVEINTERVAL_H
00022 #define LLVM_CODEGEN_LIVEINTERVAL_H
00023 
00024 #include <iosfwd>
00025 #include <vector>
00026 #include <cassert>
00027 
00028 namespace llvm {
00029   class MRegisterInfo;
00030 
00031   /// LiveRange structure - This represents a simple register range in the
00032   /// program, with an inclusive start point and an exclusive end point.
00033   /// These ranges are rendered as [start,end).
00034   struct LiveRange {
00035     unsigned start;  // Start point of the interval (inclusive)
00036     unsigned end;    // End point of the interval (exclusive)
00037     unsigned ValId;  // identifier for the value contained in this interval.
00038 
00039     LiveRange(unsigned S, unsigned E, unsigned V) : start(S), end(E), ValId(V) {
00040       assert(S < E && "Cannot create empty or backwards range");
00041     }
00042 
00043     /// contains - Return true if the index is covered by this range.
00044     ///
00045     bool contains(unsigned I) const {
00046       return start <= I && I < end;
00047     }
00048 
00049     bool operator<(const LiveRange &LR) const {
00050       return start < LR.start || (start == LR.start && end < LR.end);
00051     }
00052     bool operator==(const LiveRange &LR) const {
00053       return start == LR.start && end == LR.end;
00054     }
00055 
00056     void dump() const;
00057 
00058   private:
00059     LiveRange(); // DO NOT IMPLEMENT
00060   };
00061   std::ostream& operator<<(std::ostream& os, const LiveRange &LR);
00062 
00063   inline bool operator<(unsigned V, const LiveRange &LR) {
00064     return V < LR.start;
00065   }
00066 
00067   inline bool operator<(const LiveRange &LR, unsigned V) {
00068     return LR.start < V;
00069   }
00070 
00071   /// LiveInterval - This class represents some number of live ranges for a
00072   /// register or value.  This class also contains a bit of register allocator
00073   /// state.
00074   struct LiveInterval {
00075     typedef std::vector<LiveRange> Ranges;
00076     unsigned reg;        // the register of this interval
00077     float weight;        // weight of this interval
00078     Ranges ranges;       // the ranges in which this register is live
00079 
00080     LiveInterval(unsigned Reg, float Weight)
00081       : reg(Reg), weight(Weight), NumValues(0) {
00082     }
00083 
00084     typedef Ranges::iterator iterator;
00085     iterator begin() { return ranges.begin(); }
00086     iterator end()   { return ranges.end(); }
00087 
00088     typedef Ranges::const_iterator const_iterator;
00089     const_iterator begin() const { return ranges.begin(); }
00090     const_iterator end() const  { return ranges.end(); }
00091 
00092 
00093     /// advanceTo - Advance the specified iterator to point to the LiveRange
00094     /// containing the specified position, or end() if the position is past the
00095     /// end of the interval.  If no LiveRange contains this position, but the
00096     /// position is in a hole, this method returns an iterator pointing the the
00097     /// LiveRange immediately after the hole.
00098     iterator advanceTo(iterator I, unsigned Pos) {
00099       if (Pos >= endNumber())
00100         return end();
00101       while (I->end <= Pos) ++I;
00102       return I;
00103     }
00104 
00105     void swap(LiveInterval& other) {
00106       std::swap(reg, other.reg);
00107       std::swap(weight, other.weight);
00108       ranges.swap(other.ranges);
00109       std::swap(NumValues, other.NumValues);
00110     }
00111 
00112     bool containsOneValue() const { return NumValues == 1; }
00113 
00114     unsigned getNextValue() {
00115       return NumValues++;
00116     }
00117 
00118     bool empty() const { return ranges.empty(); }
00119 
00120     /// beginNumber - Return the lowest numbered slot covered by interval.
00121     unsigned beginNumber() const {
00122       assert(!empty() && "empty interval for register");
00123       return ranges.front().start;
00124     }
00125 
00126     /// endNumber - return the maximum point of the interval of the whole,
00127     /// exclusive.
00128     unsigned endNumber() const {
00129       assert(!empty() && "empty interval for register");
00130       return ranges.back().end;
00131     }
00132 
00133     bool expiredAt(unsigned index) const {
00134       return index >= endNumber();
00135     }
00136 
00137     bool liveAt(unsigned index) const;
00138 
00139     /// getLiveRangeContaining - Return the live range that contains the
00140     /// specified index, or null if there is none.
00141     const LiveRange *getLiveRangeContaining(unsigned Idx) const;
00142 
00143 
00144     /// joinable - Two intervals are joinable if the either don't overlap at all
00145     /// or if the destination of the copy is a single assignment value, and it
00146     /// only overlaps with one value in the source interval.
00147     bool joinable(const LiveInterval& other, unsigned CopyIdx) const;
00148 
00149     /// getOverlapingRanges - Given another live interval which is defined as a
00150     /// copy from this one, return a list of all of the live ranges where the
00151     /// two overlap and have different value numbers.
00152     void getOverlapingRanges(const LiveInterval &Other, unsigned CopyIdx,
00153                              std::vector<LiveRange*> &Ranges);
00154 
00155     /// overlaps - Return true if the intersection of the two live intervals is
00156     /// not empty.
00157     bool overlaps(const LiveInterval& other) const {
00158       return overlapsFrom(other, other.begin());
00159     }
00160 
00161     /// overlapsFrom - Return true if the intersection of the two live intervals
00162     /// is not empty.  The specified iterator is a hint that we can begin
00163     /// scanning the Other interval starting at I.
00164     bool overlapsFrom(const LiveInterval& other, const_iterator I) const;
00165 
00166     /// addRange - Add the specified LiveRange to this interval, merging
00167     /// intervals as appropriate.  This returns an iterator to the inserted live
00168     /// range (which may have grown since it was inserted.
00169     void addRange(LiveRange LR) {
00170       addRangeFrom(LR, ranges.begin());
00171     }
00172 
00173     /// join - Join two live intervals (this, and other) together.  This
00174     /// operation is the result of a copy instruction in the source program,
00175     /// that occurs at index 'CopyIdx' that copies from 'other' to 'this'.  This
00176     /// destroys 'other'.
00177     void join(LiveInterval& other, unsigned CopyIdx);
00178 
00179 
00180     /// removeRange - Remove the specified range from this interval.  Note that
00181     /// the range must already be in this interval in its entirety.
00182     void removeRange(unsigned Start, unsigned End);
00183 
00184     bool operator<(const LiveInterval& other) const {
00185       return beginNumber() < other.beginNumber();
00186     }
00187 
00188     void print(std::ostream &OS, const MRegisterInfo *MRI = 0) const;
00189     void dump() const;
00190 
00191   private:
00192     unsigned NumValues;  // the number of distinct values in this interval.
00193     Ranges::iterator addRangeFrom(LiveRange LR, Ranges::iterator From);
00194     void extendIntervalEndTo(Ranges::iterator I, unsigned NewEnd);
00195     Ranges::iterator extendIntervalStartTo(Ranges::iterator I, unsigned NewStr);
00196     LiveInterval& operator=(const LiveInterval& rhs); // DO NOT IMPLEMENT
00197   };
00198 
00199   inline std::ostream &operator<<(std::ostream &OS, const LiveInterval &LI) {
00200     LI.print(OS);
00201     return OS;
00202   }
00203 }
00204 
00205 #endif