LiveInterval.h revision bae74d9192f04d8185c7b4580565d56cc4ef53f2
1//===-- llvm/CodeGen/LiveInterval.h - Interval representation ---*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by the LLVM research group and is distributed under 6// the University of Illinois Open Source License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements the LiveRange and LiveInterval classes. Given some 11// numbering of each the machine instructions an interval [i, j) is said to be a 12// live interval for register v if there is no instruction with number j' > j 13// such that v is live at j' and there is no instruction with number i' < i such 14// that v is live at i'. In this implementation intervals can have holes, 15// i.e. an interval might look like [1,20), [50,65), [1000,1001). Each 16// individual range is represented as an instance of LiveRange, and the whole 17// interval is represented as an instance of LiveInterval. 18// 19//===----------------------------------------------------------------------===// 20 21#ifndef LLVM_CODEGEN_LIVEINTERVAL_H 22#define LLVM_CODEGEN_LIVEINTERVAL_H 23 24#include <iosfwd> 25#include <vector> 26#include <cassert> 27 28namespace llvm { 29 /// LiveRange structure - This represents a simple register range in the 30 /// program, with an inclusive start point and an exclusive end point. 31 /// These ranges are rendered as [start,end). 32 struct LiveRange { 33 unsigned start; // Start point of the interval (inclusive) 34 unsigned end; // End point of the interval (exclusive) 35 unsigned ValId; // identifier for the value contained in this interval. 36 37 LiveRange(unsigned S, unsigned E, unsigned V) : start(S), end(E), ValId(V) { 38 assert(S < E && "Cannot create empty or backwards range"); 39 } 40 41 /// contains - Return true if the index is covered by this range. 42 /// 43 bool contains(unsigned I) const { 44 return start <= I && I < end; 45 } 46 47 bool operator<(const LiveRange &LR) const { 48 return start < LR.start || (start == LR.start && end < LR.end); 49 } 50 bool operator==(const LiveRange &LR) const { 51 return start == LR.start && end == LR.end; 52 } 53 54 void dump() const; 55 56 private: 57 LiveRange(); // DO NOT IMPLEMENT 58 }; 59 std::ostream& operator<<(std::ostream& os, const LiveRange &LR); 60 61 inline bool operator<(unsigned V, const LiveRange &LR) { 62 return V < LR.start; 63 } 64 65 66 /// LiveInterval - This class represents some number of live ranges for a 67 /// register or value. This class also contains a bit of register allocator 68 /// state. 69 struct LiveInterval { 70 typedef std::vector<LiveRange> Ranges; 71 unsigned reg; // the register of this interval 72 float weight; // weight of this interval 73 Ranges ranges; // the ranges in which this register is live 74 75 LiveInterval(unsigned Reg, float Weight) 76 : reg(Reg), weight(Weight), NumValues(0) { 77 } 78 79 typedef Ranges::iterator iterator; 80 iterator begin() { return ranges.begin(); } 81 iterator end() { return ranges.end(); } 82 83 typedef Ranges::const_iterator const_iterator; 84 const_iterator begin() const { return ranges.begin(); } 85 const_iterator end() const { return ranges.end(); } 86 87 88 /// advanceTo - Advance the specified iterator to point to the LiveRange 89 /// containing the specified position, or end() if the position is past the 90 /// end of the interval. If no LiveRange contains this position, but the 91 /// position is in a hole, this method returns an iterator pointing the the 92 /// LiveRange immediately after the hold. 93 iterator advanceTo(iterator I, unsigned Pos) { 94 if (Pos >= endNumber()) 95 return end(); 96 while (I->end <= Pos) ++I; 97 return I; 98 } 99 100 void swap(LiveInterval& other) { 101 std::swap(reg, other.reg); 102 std::swap(weight, other.weight); 103 ranges.swap(other.ranges); 104 std::swap(NumValues, other.NumValues); 105 } 106 107 bool containsOneValue() const { return NumValues == 1; } 108 109 unsigned getNextValue() { 110 return NumValues++; 111 } 112 113 bool empty() const { return ranges.empty(); } 114 115 /// beginNumber - Return the lowest numbered slot covered by interval. 116 unsigned beginNumber() const { 117 assert(!empty() && "empty interval for register"); 118 return ranges.front().start; 119 } 120 121 /// endNumber - return the maximum point of the interval of the whole, 122 /// exclusive. 123 unsigned endNumber() const { 124 assert(!empty() && "empty interval for register"); 125 return ranges.back().end; 126 } 127 128 bool expiredAt(unsigned index) const { 129 return index >= endNumber(); 130 } 131 132 bool liveAt(unsigned index) const; 133 134 /// getLiveRangeContaining - Return the live range that contains the 135 /// specified index, or null if there is none. 136 const LiveRange *getLiveRangeContaining(unsigned Idx) const; 137 138 139 /// joinable - Two intervals are joinable if the either don't overlap at all 140 /// or if the destination of the copy is a single assignment value, and it 141 /// only overlaps with one value in the source interval. 142 bool joinable(const LiveInterval& other, unsigned CopyIdx) const; 143 144 145 /// overlaps - Return true if the intersection of the two live intervals is 146 /// not empty. 147 bool overlaps(const LiveInterval& other) const { 148 return overlapsFrom(other, other.begin()); 149 } 150 151 /// overlapsFrom - Return true if the intersection of the two live intervals 152 /// is not empty. The specified iterator is a hint that we can begin 153 /// scanning the Other interval starting at I. 154 bool overlapsFrom(const LiveInterval& other, const_iterator I) const; 155 156 /// addRange - Add the specified LiveRange to this interval, merging 157 /// intervals as appropriate. This returns an iterator to the inserted live 158 /// range (which may have grown since it was inserted. 159 void addRange(LiveRange LR) { 160 addRangeFrom(LR, ranges.begin()); 161 } 162 163 /// join - Join two live intervals (this, and other) together. This 164 /// operation is the result of a copy instruction in the source program, 165 /// that occurs at index 'CopyIdx' that copies from 'other' to 'this'. This 166 /// destroys 'other'. 167 void join(LiveInterval& other, unsigned CopyIdx); 168 169 170 /// removeRange - Remove the specified range from this interval. Note that 171 /// the range must already be in this interval in its entirety. 172 void removeRange(unsigned Start, unsigned End); 173 174 bool operator<(const LiveInterval& other) const { 175 return beginNumber() < other.beginNumber(); 176 } 177 178 void dump() const; 179 180 private: 181 unsigned NumValues; // the number of distinct values in this interval. 182 Ranges::iterator addRangeFrom(LiveRange LR, Ranges::iterator From); 183 void extendIntervalEndTo(Ranges::iterator I, unsigned NewEnd); 184 Ranges::iterator extendIntervalStartTo(Ranges::iterator I, unsigned NewStr); 185 LiveInterval& operator=(const LiveInterval& rhs); // DO NOT IMPLEMENT 186 }; 187 188 std::ostream& operator<<(std::ostream& os, const LiveInterval& li); 189} 190 191#endif 192