LLVM  3.7.0
LiveIntervalUnion.cpp
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1 //===-- LiveIntervalUnion.cpp - Live interval union data structure --------===//
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 represents a coalesced set of live intervals. This may be
11 // used during coalescing to represent a congruence class, or during register
12 // allocation to model liveness of a physical register.
13 //
14 //===----------------------------------------------------------------------===//
15 
18 #include "llvm/Support/Debug.h"
21 #include <algorithm>
22 
23 using namespace llvm;
24 
25 #define DEBUG_TYPE "regalloc"
26 
27 
28 // Merge a LiveInterval's segments. Guarantee no overlaps.
29 void LiveIntervalUnion::unify(LiveInterval &VirtReg, const LiveRange &Range) {
30  if (Range.empty())
31  return;
32  ++Tag;
33 
34  // Insert each of the virtual register's live segments into the map.
35  LiveRange::const_iterator RegPos = Range.begin();
36  LiveRange::const_iterator RegEnd = Range.end();
37  SegmentIter SegPos = Segments.find(RegPos->start);
38 
39  while (SegPos.valid()) {
40  SegPos.insert(RegPos->start, RegPos->end, &VirtReg);
41  if (++RegPos == RegEnd)
42  return;
43  SegPos.advanceTo(RegPos->start);
44  }
45 
46  // We have reached the end of Segments, so it is no longer necessary to search
47  // for the insertion position.
48  // It is faster to insert the end first.
49  --RegEnd;
50  SegPos.insert(RegEnd->start, RegEnd->end, &VirtReg);
51  for (; RegPos != RegEnd; ++RegPos, ++SegPos)
52  SegPos.insert(RegPos->start, RegPos->end, &VirtReg);
53 }
54 
55 // Remove a live virtual register's segments from this union.
56 void LiveIntervalUnion::extract(LiveInterval &VirtReg, const LiveRange &Range) {
57  if (Range.empty())
58  return;
59  ++Tag;
60 
61  // Remove each of the virtual register's live segments from the map.
62  LiveRange::const_iterator RegPos = Range.begin();
63  LiveRange::const_iterator RegEnd = Range.end();
64  SegmentIter SegPos = Segments.find(RegPos->start);
65 
66  for (;;) {
67  assert(SegPos.value() == &VirtReg && "Inconsistent LiveInterval");
68  SegPos.erase();
69  if (!SegPos.valid())
70  return;
71 
72  // Skip all segments that may have been coalesced.
73  RegPos = Range.advanceTo(RegPos, SegPos.start());
74  if (RegPos == RegEnd)
75  return;
76 
77  SegPos.advanceTo(RegPos->start);
78  }
79 }
80 
81 void
83  if (empty()) {
84  OS << " empty\n";
85  return;
86  }
87  for (LiveSegments::const_iterator SI = Segments.begin(); SI.valid(); ++SI) {
88  OS << " [" << SI.start() << ' ' << SI.stop() << "):"
89  << PrintReg(SI.value()->reg, TRI);
90  }
91  OS << '\n';
92 }
93 
94 #ifndef NDEBUG
95 // Verify the live intervals in this union and add them to the visited set.
97  for (SegmentIter SI = Segments.begin(); SI.valid(); ++SI)
98  VisitedVRegs.set(SI.value()->reg);
99 }
100 #endif //!NDEBUG
101 
102 // Scan the vector of interfering virtual registers in this union. Assume it's
103 // quite small.
106  std::find(InterferingVRegs.begin(), InterferingVRegs.end(), VirtReg);
107  return I != InterferingVRegs.end();
108 }
109 
110 // Collect virtual registers in this union that interfere with this
111 // query's live virtual register.
112 //
113 // The query state is one of:
114 //
115 // 1. CheckedFirstInterference == false: Iterators are uninitialized.
116 // 2. SeenAllInterferences == true: InterferingVRegs complete, iterators unused.
117 // 3. Iterators left at the last seen intersection.
118 //
120 collectInterferingVRegs(unsigned MaxInterferingRegs) {
121  // Fast path return if we already have the desired information.
122  if (SeenAllInterferences || InterferingVRegs.size() >= MaxInterferingRegs)
123  return InterferingVRegs.size();
124 
125  // Set up iterators on the first call.
126  if (!CheckedFirstInterference) {
127  CheckedFirstInterference = true;
128 
129  // Quickly skip interference check for empty sets.
130  if (VirtReg->empty() || LiveUnion->empty()) {
131  SeenAllInterferences = true;
132  return 0;
133  }
134 
135  // In most cases, the union will start before VirtReg.
136  VirtRegI = VirtReg->begin();
137  LiveUnionI.setMap(LiveUnion->getMap());
138  LiveUnionI.find(VirtRegI->start);
139  }
140 
141  LiveInterval::iterator VirtRegEnd = VirtReg->end();
142  LiveInterval *RecentReg = nullptr;
143  while (LiveUnionI.valid()) {
144  assert(VirtRegI != VirtRegEnd && "Reached end of VirtReg");
145 
146  // Check for overlapping interference.
147  while (VirtRegI->start < LiveUnionI.stop() &&
148  VirtRegI->end > LiveUnionI.start()) {
149  // This is an overlap, record the interfering register.
150  LiveInterval *VReg = LiveUnionI.value();
151  if (VReg != RecentReg && !isSeenInterference(VReg)) {
152  RecentReg = VReg;
153  InterferingVRegs.push_back(VReg);
154  if (InterferingVRegs.size() >= MaxInterferingRegs)
155  return InterferingVRegs.size();
156  }
157  // This LiveUnion segment is no longer interesting.
158  if (!(++LiveUnionI).valid()) {
159  SeenAllInterferences = true;
160  return InterferingVRegs.size();
161  }
162  }
163 
164  // The iterators are now not overlapping, LiveUnionI has been advanced
165  // beyond VirtRegI.
166  assert(VirtRegI->end <= LiveUnionI.start() && "Expected non-overlap");
167 
168  // Advance the iterator that ends first.
169  VirtRegI = VirtReg->advanceTo(VirtRegI, LiveUnionI.start());
170  if (VirtRegI == VirtRegEnd)
171  break;
172 
173  // Detect overlap, handle above.
174  if (VirtRegI->start < LiveUnionI.stop())
175  continue;
176 
177  // Still not overlapping. Catch up LiveUnionI.
178  LiveUnionI.advanceTo(VirtRegI->start);
179  }
180  SeenAllInterferences = true;
181  return InterferingVRegs.size();
182 }
183 
185  unsigned NSize) {
186  // Reuse existing allocation.
187  if (NSize == Size)
188  return;
189  clear();
190  Size = NSize;
191  LIUs = static_cast<LiveIntervalUnion*>(
192  malloc(sizeof(LiveIntervalUnion)*NSize));
193  for (unsigned i = 0; i != Size; ++i)
194  new(LIUs + i) LiveIntervalUnion(Alloc);
195 }
196 
198  if (!LIUs)
199  return;
200  for (unsigned i = 0; i != Size; ++i)
201  LIUs[i].~LiveIntervalUnion();
202  free(LIUs);
203  Size = 0;
204  LIUs = nullptr;
205 }
const_iterator begin() const
Definition: IntervalMap.h:1100
LiveIntervalUnion(Allocator &a)
void set(unsigned Idx)
LiveInterval - This class represents the liveness of a register, or stack slot.
Definition: LiveInterval.h:588
iterator advanceTo(iterator I, SlotIndex Pos)
advanceTo - Advance the specified iterator to point to the Segment containing the specified position...
Definition: LiveInterval.h:246
const_iterator find(KeyT x) const
find - Return an iterator pointing to the first interval ending at or after x, or end()...
Definition: IntervalMap.h:1126
size_t size() const
Definition: LiveInterval.h:280
bool empty() const
Definition: LiveInterval.h:353
This class represents the liveness of a register, stack slot, etc.
Definition: LiveInterval.h:153
iterator end()
Definition: LiveInterval.h:206
RecyclingAllocator - This class wraps an Allocator, adding the functionality of recycling deleted obj...
PrintReg - Helper class for printing registers on a raw_ostream.
Union of live intervals that are strong candidates for coalescing into a single register (either phys...
void print(raw_ostream &OS, const TargetRegisterInfo *TRI) const
bool isSeenInterference(LiveInterval *VReg) const
NDEBUG.
TargetRegisterInfo base class - We assume that the target defines a static array of TargetRegisterDes...
void unify(LiveInterval &VirtReg, const LiveRange &Range)
void init(LiveIntervalUnion::Allocator &, unsigned Size)
LiveSegments::iterator SegmentIter
void verify(LiveVirtRegBitSet &VisitedVRegs)
#define I(x, y, z)
Definition: MD5.cpp:54
unsigned collectInterferingVRegs(unsigned MaxInterferingRegs=UINT_MAX)
void extract(LiveInterval &VirtReg, const LiveRange &Range)
iterator begin()
Definition: LiveInterval.h:205
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:38