LiveIntervalUnion.h revision 263508 
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
23namespace llvm {
24
25class TargetRegisterInfo;
26
27#ifndef NDEBUG
28// forward declaration
29template <unsigned Element> class SparseBitVector;
30typedef SparseBitVector<128> LiveVirtRegBitSet;
31#endif
32
33/// Compare a live virtual register segment to a LiveIntervalUnion segment.
34inline bool
35overlap(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.
44class 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
50public:
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
61private:
62  unsigned Tag;           // unique tag for current contents.
63  LiveSegments Segments;  // union of virtual reg segments
64
65public:
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.
70  SegmentIter begin() { return Segments.begin(); }
71  SegmentIter end() { return Segments.end(); }
72  SegmentIter find(SlotIndex x) { return Segments.find(x); }
73  bool empty() const { return Segments.empty(); }
74  SlotIndex startIndex() const { return Segments.start(); }
75
76  // Provide public access to the underlying map to allow overlap iteration.
77  typedef LiveSegments Map;
78  const Map &getMap() { return Segments; }
79
80  /// getTag - Return an opaque tag representing the current state of the union.
81  unsigned getTag() const { return Tag; }
82
83  /// changedSince - Return true if the union change since getTag returned 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.
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:
117    Query(): LiveUnion(), VirtReg(), Tag(0), UserTag(0) {}
118
119    Query(LiveInterval *VReg, LiveIntervalUnion *LIU):
120      LiveUnion(LIU), VirtReg(VReg), CheckedFirstInterference(false),
121      SeenAllInterferences(false), SeenUnspillableVReg(false)
122    {}
123
124    void clear() {
125      LiveUnion = NULL;
126      VirtReg = NULL;
127      InterferingVRegs.clear();
128      CheckedFirstInterference = false;
129      SeenAllInterferences = false;
130      SeenUnspillableVReg = false;
131      Tag = 0;
132      UserTag = 0;
133    }
134
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
149    LiveInterval &virtReg() const {
150      assert(VirtReg && "uninitialized");
151      return *VirtReg;
152    }
153
154    // Does this live virtual register interfere with the union?
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?
165    bool seenAllInterferences() const { return SeenAllInterferences; }
166
167    // Did collectInterferingVRegs encounter an unspillable vreg?
168    bool seenUnspillableVReg() const { return SeenUnspillableVReg; }
169
170    // Vector generated by collectInterferingVRegs.
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:
185    Array() : Size(0), LIUs(0) {}
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
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