1 //===-- LiveIntervalUnion.h - Live interval union data struct --*- 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 // LiveIntervalUnion is a union of live segments across multiple live virtual
11 // registers. This may be used during coalescing to represent a congruence
12 // class, or during register allocation to model liveness of a physical
13 // register.
14 //
15 //===----------------------------------------------------------------------===//
16
17 #ifndef LLVM_CODEGEN_LIVEINTERVALUNION_H
18 #define LLVM_CODEGEN_LIVEINTERVALUNION_H
19
20 #include "llvm/ADT/IntervalMap.h"
21 #include "llvm/CodeGen/LiveInterval.h"
22
23 namespace llvm {
24
25 class TargetRegisterInfo;
26
27 #ifndef NDEBUG
28 // forward declaration
29 template <unsigned Element> class SparseBitVector;
30 typedef SparseBitVector<128> LiveVirtRegBitSet;
31 #endif
32
33 /// Compare a live virtual register segment to a LiveIntervalUnion segment.
34 inline bool
overlap(const LiveInterval::Segment & VRSeg,const IntervalMap<SlotIndex,LiveInterval * >::const_iterator & LUSeg)35 overlap(const LiveInterval::Segment &VRSeg,
36 const IntervalMap<SlotIndex, LiveInterval*>::const_iterator &LUSeg) {
37 return VRSeg.start < LUSeg.stop() && LUSeg.start() < VRSeg.end;
38 }
39
40 /// Union of live intervals that are strong candidates for coalescing into a
41 /// single register (either physical or virtual depending on the context). We
42 /// expect the constituent live intervals to be disjoint, although we may
43 /// eventually make exceptions to handle value-based interference.
44 class LiveIntervalUnion {
45 // A set of live virtual register segments that supports fast insertion,
46 // intersection, and removal.
47 // Mapping SlotIndex intervals to virtual register numbers.
48 typedef IntervalMap<SlotIndex, LiveInterval*> LiveSegments;
49
50 public:
51 // SegmentIter can advance to the next segment ordered by starting position
52 // which may belong to a different live virtual register. We also must be able
53 // to reach the current segment's containing virtual register.
54 typedef LiveSegments::iterator SegmentIter;
55
56 // LiveIntervalUnions share an external allocator.
57 typedef LiveSegments::Allocator Allocator;
58
59 class Query;
60
61 private:
62 unsigned Tag; // unique tag for current contents.
63 LiveSegments Segments; // union of virtual reg segments
64
65 public:
LiveIntervalUnion(Allocator & a)66 explicit LiveIntervalUnion(Allocator &a) : Tag(0), Segments(a) {}
67
68 // Iterate over all segments in the union of live virtual registers ordered
69 // by their starting position.
begin()70 SegmentIter begin() { return Segments.begin(); }
end()71 SegmentIter end() { return Segments.end(); }
find(SlotIndex x)72 SegmentIter find(SlotIndex x) { return Segments.find(x); }
empty()73 bool empty() const { return Segments.empty(); }
startIndex()74 SlotIndex startIndex() const { return Segments.start(); }
75
76 // Provide public access to the underlying map to allow overlap iteration.
77 typedef LiveSegments Map;
getMap()78 const Map &getMap() { return Segments; }
79
80 /// getTag - Return an opaque tag representing the current state of the union.
getTag()81 unsigned getTag() const { return Tag; }
82
83 /// changedSince - Return true if the union change since getTag returned tag.
changedSince(unsigned tag)84 bool changedSince(unsigned tag) const { return tag != Tag; }
85
86 // Add a live virtual register to this union and merge its segments.
87 void unify(LiveInterval &VirtReg);
88
89 // Remove a live virtual register's segments from this union.
90 void extract(LiveInterval &VirtReg);
91
92 // Remove all inserted virtual registers.
clear()93 void clear() { Segments.clear(); ++Tag; }
94
95 // Print union, using TRI to translate register names
96 void print(raw_ostream &OS, const TargetRegisterInfo *TRI) const;
97
98 #ifndef NDEBUG
99 // Verify the live intervals in this union and add them to the visited set.
100 void verify(LiveVirtRegBitSet& VisitedVRegs);
101 #endif
102
103 /// Query interferences between a single live virtual register and a live
104 /// interval union.
105 class Query {
106 LiveIntervalUnion *LiveUnion;
107 LiveInterval *VirtReg;
108 LiveInterval::iterator VirtRegI; // current position in VirtReg
109 SegmentIter LiveUnionI; // current position in LiveUnion
110 SmallVector<LiveInterval*,4> InterferingVRegs;
111 bool CheckedFirstInterference;
112 bool SeenAllInterferences;
113 bool SeenUnspillableVReg;
114 unsigned Tag, UserTag;
115
116 public:
Query()117 Query(): LiveUnion(), VirtReg(), Tag(0), UserTag(0) {}
118
Query(LiveInterval * VReg,LiveIntervalUnion * LIU)119 Query(LiveInterval *VReg, LiveIntervalUnion *LIU):
120 LiveUnion(LIU), VirtReg(VReg), CheckedFirstInterference(false),
121 SeenAllInterferences(false), SeenUnspillableVReg(false)
122 {}
123
clear()124 void clear() {
125 LiveUnion = nullptr;
126 VirtReg = nullptr;
127 InterferingVRegs.clear();
128 CheckedFirstInterference = false;
129 SeenAllInterferences = false;
130 SeenUnspillableVReg = false;
131 Tag = 0;
132 UserTag = 0;
133 }
134
init(unsigned UTag,LiveInterval * VReg,LiveIntervalUnion * LIU)135 void init(unsigned UTag, LiveInterval *VReg, LiveIntervalUnion *LIU) {
136 assert(VReg && LIU && "Invalid arguments");
137 if (UserTag == UTag && VirtReg == VReg &&
138 LiveUnion == LIU && !LIU->changedSince(Tag)) {
139 // Retain cached results, e.g. firstInterference.
140 return;
141 }
142 clear();
143 LiveUnion = LIU;
144 VirtReg = VReg;
145 Tag = LIU->getTag();
146 UserTag = UTag;
147 }
148
virtReg()149 LiveInterval &virtReg() const {
150 assert(VirtReg && "uninitialized");
151 return *VirtReg;
152 }
153
154 // Does this live virtual register interfere with the union?
checkInterference()155 bool checkInterference() { return collectInterferingVRegs(1); }
156
157 // Count the virtual registers in this union that interfere with this
158 // query's live virtual register, up to maxInterferingRegs.
159 unsigned collectInterferingVRegs(unsigned MaxInterferingRegs = UINT_MAX);
160
161 // Was this virtual register visited during collectInterferingVRegs?
162 bool isSeenInterference(LiveInterval *VReg) const;
163
164 // Did collectInterferingVRegs collect all interferences?
seenAllInterferences()165 bool seenAllInterferences() const { return SeenAllInterferences; }
166
167 // Did collectInterferingVRegs encounter an unspillable vreg?
seenUnspillableVReg()168 bool seenUnspillableVReg() const { return SeenUnspillableVReg; }
169
170 // Vector generated by collectInterferingVRegs.
interferingVRegs()171 const SmallVectorImpl<LiveInterval*> &interferingVRegs() const {
172 return InterferingVRegs;
173 }
174
175 private:
176 Query(const Query&) LLVM_DELETED_FUNCTION;
177 void operator=(const Query&) LLVM_DELETED_FUNCTION;
178 };
179
180 // Array of LiveIntervalUnions.
181 class Array {
182 unsigned Size;
183 LiveIntervalUnion *LIUs;
184 public:
Array()185 Array() : Size(0), LIUs(nullptr) {}
~Array()186 ~Array() { clear(); }
187
188 // Initialize the array to have Size entries.
189 // Reuse an existing allocation if the size matches.
190 void init(LiveIntervalUnion::Allocator&, unsigned Size);
191
size()192 unsigned size() const { return Size; }
193
194 void clear();
195
196 LiveIntervalUnion& operator[](unsigned idx) {
197 assert(idx < Size && "idx out of bounds");
198 return LIUs[idx];
199 }
200 };
201 };
202
203 } // end namespace llvm
204
205 #endif // !defined(LLVM_CODEGEN_LIVEINTERVALUNION_H)
206