1//===-- InterferenceCache.h - Caching per-block interference ---*- 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// InterferenceCache remembers per-block interference in LiveIntervalUnions.
11//
12//===----------------------------------------------------------------------===//
13
14#define DEBUG_TYPE "regalloc"
15#include "InterferenceCache.h"
16#include "llvm/Target/TargetRegisterInfo.h"
17#include "llvm/Support/ErrorHandling.h"
18
19using namespace llvm;
20
21// Static member used for null interference cursors.
22InterferenceCache::BlockInterference InterferenceCache::Cursor::NoInterference;
23
24void InterferenceCache::init(MachineFunction *mf,
25                             LiveIntervalUnion *liuarray,
26                             SlotIndexes *indexes,
27                             const TargetRegisterInfo *tri) {
28  MF = mf;
29  LIUArray = liuarray;
30  TRI = tri;
31  PhysRegEntries.assign(TRI->getNumRegs(), 0);
32  for (unsigned i = 0; i != CacheEntries; ++i)
33    Entries[i].clear(mf, indexes);
34}
35
36InterferenceCache::Entry *InterferenceCache::get(unsigned PhysReg) {
37  unsigned E = PhysRegEntries[PhysReg];
38  if (E < CacheEntries && Entries[E].getPhysReg() == PhysReg) {
39    if (!Entries[E].valid(LIUArray, TRI))
40      Entries[E].revalidate();
41    return &Entries[E];
42  }
43  // No valid entry exists, pick the next round-robin entry.
44  E = RoundRobin;
45  if (++RoundRobin == CacheEntries)
46    RoundRobin = 0;
47  for (unsigned i = 0; i != CacheEntries; ++i) {
48    // Skip entries that are in use.
49    if (Entries[E].hasRefs()) {
50      if (++E == CacheEntries)
51        E = 0;
52      continue;
53    }
54    Entries[E].reset(PhysReg, LIUArray, TRI, MF);
55    PhysRegEntries[PhysReg] = E;
56    return &Entries[E];
57  }
58  llvm_unreachable("Ran out of interference cache entries.");
59}
60
61/// revalidate - LIU contents have changed, update tags.
62void InterferenceCache::Entry::revalidate() {
63  // Invalidate all block entries.
64  ++Tag;
65  // Invalidate all iterators.
66  PrevPos = SlotIndex();
67  for (unsigned i = 0, e = Aliases.size(); i != e; ++i)
68    Aliases[i].second = Aliases[i].first->getTag();
69}
70
71void InterferenceCache::Entry::reset(unsigned physReg,
72                                     LiveIntervalUnion *LIUArray,
73                                     const TargetRegisterInfo *TRI,
74                                     const MachineFunction *MF) {
75  assert(!hasRefs() && "Cannot reset cache entry with references");
76  // LIU's changed, invalidate cache.
77  ++Tag;
78  PhysReg = physReg;
79  Blocks.resize(MF->getNumBlockIDs());
80  Aliases.clear();
81  for (const unsigned *AS = TRI->getOverlaps(PhysReg); *AS; ++AS) {
82    LiveIntervalUnion *LIU = LIUArray + *AS;
83    Aliases.push_back(std::make_pair(LIU, LIU->getTag()));
84  }
85
86  // Reset iterators.
87  PrevPos = SlotIndex();
88  unsigned e = Aliases.size();
89  Iters.resize(e);
90  for (unsigned i = 0; i != e; ++i)
91    Iters[i].setMap(Aliases[i].first->getMap());
92}
93
94bool InterferenceCache::Entry::valid(LiveIntervalUnion *LIUArray,
95                                     const TargetRegisterInfo *TRI) {
96  unsigned i = 0, e = Aliases.size();
97  for (const unsigned *AS = TRI->getOverlaps(PhysReg); *AS; ++AS, ++i) {
98    LiveIntervalUnion *LIU = LIUArray + *AS;
99    if (i == e ||  Aliases[i].first != LIU)
100      return false;
101    if (LIU->changedSince(Aliases[i].second))
102      return false;
103  }
104  return i == e;
105}
106
107void InterferenceCache::Entry::update(unsigned MBBNum) {
108  SlotIndex Start, Stop;
109  tie(Start, Stop) = Indexes->getMBBRange(MBBNum);
110
111  // Use advanceTo only when possible.
112  if (PrevPos != Start) {
113    if (!PrevPos.isValid() || Start < PrevPos)
114      for (unsigned i = 0, e = Iters.size(); i != e; ++i)
115        Iters[i].find(Start);
116    else
117      for (unsigned i = 0, e = Iters.size(); i != e; ++i)
118        Iters[i].advanceTo(Start);
119    PrevPos = Start;
120  }
121
122  MachineFunction::const_iterator MFI = MF->getBlockNumbered(MBBNum);
123  BlockInterference *BI = &Blocks[MBBNum];
124  for (;;) {
125    BI->Tag = Tag;
126    BI->First = BI->Last = SlotIndex();
127
128    // Check for first interference.
129    for (unsigned i = 0, e = Iters.size(); i != e; ++i) {
130      Iter &I = Iters[i];
131      if (!I.valid())
132        continue;
133      SlotIndex StartI = I.start();
134      if (StartI >= Stop)
135        continue;
136      if (!BI->First.isValid() || StartI < BI->First)
137        BI->First = StartI;
138    }
139
140    PrevPos = Stop;
141    if (BI->First.isValid())
142      break;
143
144    // No interference in this block? Go ahead and precompute the next block.
145    if (++MFI == MF->end())
146      return;
147    MBBNum = MFI->getNumber();
148    BI = &Blocks[MBBNum];
149    if (BI->Tag == Tag)
150      return;
151    tie(Start, Stop) = Indexes->getMBBRange(MBBNum);
152  }
153
154  // Check for last interference in block.
155  for (unsigned i = 0, e = Iters.size(); i != e; ++i) {
156    Iter &I = Iters[i];
157    if (!I.valid() || I.start() >= Stop)
158      continue;
159    I.advanceTo(Stop);
160    bool Backup = !I.valid() || I.start() >= Stop;
161    if (Backup)
162      --I;
163    SlotIndex StopI = I.stop();
164    if (!BI->Last.isValid() || StopI > BI->Last)
165      BI->Last = StopI;
166    if (Backup)
167      ++I;
168  }
169}
170