LLVM API Documentation
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 /// LiveRange structure - This represents a simple register range in the 00030 /// program, with an inclusive start point and an exclusive end point. 00031 /// These ranges are rendered as [start,end). 00032 struct LiveRange { 00033 unsigned start; // Start point of the interval (inclusive) 00034 unsigned end; // End point of the interval (exclusive) 00035 unsigned ValId; // identifier for the value contained in this interval. 00036 00037 LiveRange(unsigned S, unsigned E, unsigned V) : start(S), end(E), ValId(V) { 00038 assert(S < E && "Cannot create empty or backwards range"); 00039 } 00040 00041 /// contains - Return true if the index is covered by this range. 00042 /// 00043 bool contains(unsigned I) const { 00044 return start <= I && I < end; 00045 } 00046 00047 bool operator<(const LiveRange &LR) const { 00048 return start < LR.start || (start == LR.start && end < LR.end); 00049 } 00050 bool operator==(const LiveRange &LR) const { 00051 return start == LR.start && end == LR.end; 00052 } 00053 00054 void dump() const; 00055 00056 private: 00057 LiveRange(); // DO NOT IMPLEMENT 00058 }; 00059 std::ostream& operator<<(std::ostream& os, const LiveRange &LR); 00060 00061 inline bool operator<(unsigned V, const LiveRange &LR) { 00062 return V < LR.start; 00063 } 00064 00065 00066 /// LiveInterval - This class represents some number of live ranges for a 00067 /// register or value. This class also contains a bit of register allocator 00068 /// state. 00069 struct LiveInterval { 00070 typedef std::vector<LiveRange> Ranges; 00071 unsigned reg; // the register of this interval 00072 float weight; // weight of this interval 00073 Ranges ranges; // the ranges in which this register is live 00074 00075 LiveInterval(unsigned Reg, float Weight) 00076 : reg(Reg), weight(Weight), NumValues(0) { 00077 } 00078 00079 typedef Ranges::iterator iterator; 00080 iterator begin() { return ranges.begin(); } 00081 iterator end() { return ranges.end(); } 00082 00083 typedef Ranges::const_iterator const_iterator; 00084 const_iterator begin() const { return ranges.begin(); } 00085 const_iterator end() const { return ranges.end(); } 00086 00087 00088 /// advanceTo - Advance the specified iterator to point to the LiveRange 00089 /// containing the specified position, or end() if the position is past the 00090 /// end of the interval. If no LiveRange contains this position, but the 00091 /// position is in a hole, this method returns an iterator pointing the the 00092 /// LiveRange immediately after the hole. 00093 iterator advanceTo(iterator I, unsigned Pos) { 00094 if (Pos >= endNumber()) 00095 return end(); 00096 while (I->end <= Pos) ++I; 00097 return I; 00098 } 00099 00100 void swap(LiveInterval& other) { 00101 std::swap(reg, other.reg); 00102 std::swap(weight, other.weight); 00103 ranges.swap(other.ranges); 00104 std::swap(NumValues, other.NumValues); 00105 } 00106 00107 bool containsOneValue() const { return NumValues == 1; } 00108 00109 unsigned getNextValue() { 00110 return NumValues++; 00111 } 00112 00113 bool empty() const { return ranges.empty(); } 00114 00115 /// beginNumber - Return the lowest numbered slot covered by interval. 00116 unsigned beginNumber() const { 00117 assert(!empty() && "empty interval for register"); 00118 return ranges.front().start; 00119 } 00120 00121 /// endNumber - return the maximum point of the interval of the whole, 00122 /// exclusive. 00123 unsigned endNumber() const { 00124 assert(!empty() && "empty interval for register"); 00125 return ranges.back().end; 00126 } 00127 00128 bool expiredAt(unsigned index) const { 00129 return index >= endNumber(); 00130 } 00131 00132 bool liveAt(unsigned index) const; 00133 00134 /// getLiveRangeContaining - Return the live range that contains the 00135 /// specified index, or null if there is none. 00136 const LiveRange *getLiveRangeContaining(unsigned Idx) const; 00137 00138 00139 /// joinable - Two intervals are joinable if the either don't overlap at all 00140 /// or if the destination of the copy is a single assignment value, and it 00141 /// only overlaps with one value in the source interval. 00142 bool joinable(const LiveInterval& other, unsigned CopyIdx) const; 00143 00144 00145 /// overlaps - Return true if the intersection of the two live intervals is 00146 /// not empty. 00147 bool overlaps(const LiveInterval& other) const { 00148 return overlapsFrom(other, other.begin()); 00149 } 00150 00151 /// overlapsFrom - Return true if the intersection of the two live intervals 00152 /// is not empty. The specified iterator is a hint that we can begin 00153 /// scanning the Other interval starting at I. 00154 bool overlapsFrom(const LiveInterval& other, const_iterator I) const; 00155 00156 /// addRange - Add the specified LiveRange to this interval, merging 00157 /// intervals as appropriate. This returns an iterator to the inserted live 00158 /// range (which may have grown since it was inserted. 00159 void addRange(LiveRange LR) { 00160 addRangeFrom(LR, ranges.begin()); 00161 } 00162 00163 /// join - Join two live intervals (this, and other) together. This 00164 /// operation is the result of a copy instruction in the source program, 00165 /// that occurs at index 'CopyIdx' that copies from 'other' to 'this'. This 00166 /// destroys 'other'. 00167 void join(LiveInterval& other, unsigned CopyIdx); 00168 00169 00170 /// removeRange - Remove the specified range from this interval. Note that 00171 /// the range must already be in this interval in its entirety. 00172 void removeRange(unsigned Start, unsigned End); 00173 00174 bool operator<(const LiveInterval& other) const { 00175 return beginNumber() < other.beginNumber(); 00176 } 00177 00178 void dump() const; 00179 00180 private: 00181 unsigned NumValues; // the number of distinct values in this interval. 00182 Ranges::iterator addRangeFrom(LiveRange LR, Ranges::iterator From); 00183 void extendIntervalEndTo(Ranges::iterator I, unsigned NewEnd); 00184 Ranges::iterator extendIntervalStartTo(Ranges::iterator I, unsigned NewStr); 00185 LiveInterval& operator=(const LiveInterval& rhs); // DO NOT IMPLEMENT 00186 }; 00187 00188 std::ostream& operator<<(std::ostream& os, const LiveInterval& li); 00189 } 00190 00191 #endif