1 //===-- llvm/CodeGen/LiveInterval.h - Interval representation ---*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
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.
8 //===----------------------------------------------------------------------===//
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.
19 //===----------------------------------------------------------------------===//
21 #ifndef LLVM_CODEGEN_LIVEINTERVAL_H
22 #define LLVM_CODEGEN_LIVEINTERVAL_H
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).
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.
37 LiveRange(unsigned S, unsigned E, unsigned V) : start(S), end(E), ValId(V) {
38 assert(S < E && "Cannot create empty or backwards range");
41 /// contains - Return true if the index is covered by this range.
43 bool contains(unsigned I) const {
44 return start <= I && I < end;
47 bool operator<(const LiveRange &LR) const {
48 return start < LR.start || (start == LR.start && end < LR.end);
50 bool operator==(const LiveRange &LR) const {
51 return start == LR.start && end == LR.end;
57 LiveRange(); // DO NOT IMPLEMENT
59 std::ostream& operator<<(std::ostream& os, const LiveRange &LR);
61 inline bool operator<(unsigned V, const LiveRange &LR) {
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
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
75 LiveInterval(unsigned Reg, float Weight)
76 : reg(Reg), weight(Weight), NumValues(0) {
79 typedef Ranges::iterator iterator;
80 iterator begin() { return ranges.begin(); }
81 iterator end() { return ranges.end(); }
83 typedef Ranges::const_iterator const_iterator;
84 const_iterator begin() const { return ranges.begin(); }
85 const_iterator end() const { return ranges.end(); }
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 hole.
93 iterator advanceTo(iterator I, unsigned Pos) {
94 if (Pos >= endNumber())
96 while (I->end <= Pos) ++I;
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);
107 bool containsOneValue() const { return NumValues == 1; }
109 unsigned getNextValue() {
113 bool empty() const { return ranges.empty(); }
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;
121 /// endNumber - return the maximum point of the interval of the whole,
123 unsigned endNumber() const {
124 assert(!empty() && "empty interval for register");
125 return ranges.back().end;
128 bool expiredAt(unsigned index) const {
129 return index >= endNumber();
132 bool liveAt(unsigned index) const;
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;
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;
145 /// overlaps - Return true if the intersection of the two live intervals is
147 bool overlaps(const LiveInterval& other) const {
148 return overlapsFrom(other, other.begin());
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;
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());
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);
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);
174 bool operator<(const LiveInterval& other) const {
175 return beginNumber() < other.beginNumber();
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
188 std::ostream& operator<<(std::ostream& os, const LiveInterval& li);