Spiller.cpp revision d2bd8627d9bac9a1c4528ea19d76ac7740d52517 
1//===-- llvm/CodeGen/Spiller.cpp -  Spiller -------------------------------===//
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#define DEBUG_TYPE "spiller"
11
12#include "Spiller.h"
13#include "VirtRegMap.h"
14#include "llvm/CodeGen/LiveIntervalAnalysis.h"
15#include "llvm/CodeGen/LiveStackAnalysis.h"
16#include "llvm/CodeGen/MachineFunction.h"
17#include "llvm/CodeGen/MachineRegisterInfo.h"
18#include "llvm/CodeGen/MachineFrameInfo.h"
19#include "llvm/Target/TargetMachine.h"
20#include "llvm/Target/TargetInstrInfo.h"
21#include "llvm/Support/Debug.h"
22
23using namespace llvm;
24
25Spiller::~Spiller() {}
26
27namespace {
28
29/// Utility class for spillers.
30class SpillerBase : public Spiller {
31protected:
32
33  MachineFunction *mf;
34  LiveIntervals *lis;
35  LiveStacks *ls;
36  MachineFrameInfo *mfi;
37  MachineRegisterInfo *mri;
38  const TargetInstrInfo *tii;
39  VirtRegMap *vrm;
40
41  /// Construct a spiller base.
42  SpillerBase(MachineFunction *mf, LiveIntervals *lis, LiveStacks *ls,
43              VirtRegMap *vrm) :
44    mf(mf), lis(lis), ls(ls), vrm(vrm)
45  {
46    mfi = mf->getFrameInfo();
47    mri = &mf->getRegInfo();
48    tii = mf->getTarget().getInstrInfo();
49  }
50
51  /// Ensures there is space before the given machine instruction, returns the
52  /// instruction's new number.
53  unsigned makeSpaceBefore(MachineInstr *mi) {
54    if (!lis->hasGapBeforeInstr(lis->getInstructionIndex(mi))) {
55      lis->scaleNumbering(2);
56      ls->scaleNumbering(2);
57    }
58
59    unsigned miIdx = lis->getInstructionIndex(mi);
60
61    assert(lis->hasGapBeforeInstr(miIdx));
62
63    return miIdx;
64  }
65
66  /// Ensure there is space after the given machine instruction, returns the
67  /// instruction's new number.
68  unsigned makeSpaceAfter(MachineInstr *mi) {
69    if (!lis->hasGapAfterInstr(lis->getInstructionIndex(mi))) {
70      lis->scaleNumbering(2);
71      ls->scaleNumbering(2);
72    }
73
74    unsigned miIdx = lis->getInstructionIndex(mi);
75
76    assert(lis->hasGapAfterInstr(miIdx));
77
78    return miIdx;
79  }
80
81  /// Insert a store of the given vreg to the given stack slot immediately
82  /// after the given instruction. Returns the base index of the inserted
83  /// instruction. The caller is responsible for adding an appropriate
84  /// LiveInterval to the LiveIntervals analysis.
85  unsigned insertStoreAfter(MachineInstr *mi, unsigned ss,
86                          unsigned vreg,
87                          const TargetRegisterClass *trc) {
88
89    MachineBasicBlock::iterator nextInstItr(next(mi));
90
91    unsigned miIdx = makeSpaceAfter(mi);
92
93    tii->storeRegToStackSlot(*mi->getParent(), nextInstItr, vreg,
94                             true, ss, trc);
95    MachineBasicBlock::iterator storeInstItr(next(mi));
96    MachineInstr *storeInst = &*storeInstItr;
97    unsigned storeInstIdx = miIdx + LiveInterval::InstrSlots::NUM;
98
99    assert(lis->getInstructionFromIndex(storeInstIdx) == 0 &&
100           "Store inst index already in use.");
101
102    lis->InsertMachineInstrInMaps(storeInst, storeInstIdx);
103
104    return storeInstIdx;
105  }
106
107  /// Insert a store of the given vreg to the given stack slot immediately
108  /// before the given instructnion. Returns the base index of the inserted
109  /// Instruction.
110  unsigned insertStoreBefore(MachineInstr *mi, unsigned ss,
111                            unsigned vreg,
112                            const TargetRegisterClass *trc) {
113    unsigned miIdx = makeSpaceBefore(mi);
114
115    tii->storeRegToStackSlot(*mi->getParent(), mi, vreg, true, ss, trc);
116    MachineBasicBlock::iterator storeInstItr(prior(mi));
117    MachineInstr *storeInst = &*storeInstItr;
118    unsigned storeInstIdx = miIdx - LiveInterval::InstrSlots::NUM;
119
120    assert(lis->getInstructionFromIndex(storeInstIdx) == 0 &&
121           "Store inst index already in use.");
122
123    lis->InsertMachineInstrInMaps(storeInst, storeInstIdx);
124
125    return storeInstIdx;
126  }
127
128  void insertStoreAfterInstOnInterval(LiveInterval *li,
129                                      MachineInstr *mi, unsigned ss,
130                                      unsigned vreg,
131                                      const TargetRegisterClass *trc) {
132
133    unsigned storeInstIdx = insertStoreAfter(mi, ss, vreg, trc);
134    unsigned start = lis->getDefIndex(lis->getInstructionIndex(mi)),
135             end = lis->getUseIndex(storeInstIdx);
136
137    VNInfo *vni =
138      li->getNextValue(storeInstIdx, 0, true, lis->getVNInfoAllocator());
139    li->addKill(vni, storeInstIdx, false);
140    DOUT << "    Inserting store range: [" << start << ", " << end << ")\n";
141    LiveRange lr(start, end, vni);
142
143    li->addRange(lr);
144  }
145
146  /// Insert a load of the given vreg from the given stack slot immediately
147  /// after the given instruction. Returns the base index of the inserted
148  /// instruction. The caller is responsibel for adding/removing an appropriate
149  /// range vreg's LiveInterval.
150  unsigned insertLoadAfter(MachineInstr *mi, unsigned ss,
151                          unsigned vreg,
152                          const TargetRegisterClass *trc) {
153
154    MachineBasicBlock::iterator nextInstItr(next(mi));
155
156    unsigned miIdx = makeSpaceAfter(mi);
157
158    tii->loadRegFromStackSlot(*mi->getParent(), nextInstItr, vreg, ss, trc);
159    MachineBasicBlock::iterator loadInstItr(next(mi));
160    MachineInstr *loadInst = &*loadInstItr;
161    unsigned loadInstIdx = miIdx + LiveInterval::InstrSlots::NUM;
162
163    assert(lis->getInstructionFromIndex(loadInstIdx) == 0 &&
164           "Store inst index already in use.");
165
166    lis->InsertMachineInstrInMaps(loadInst, loadInstIdx);
167
168    return loadInstIdx;
169  }
170
171  /// Insert a load of the given vreg from the given stack slot immediately
172  /// before the given instruction. Returns the base index of the inserted
173  /// instruction. The caller is responsible for adding an appropriate
174  /// LiveInterval to the LiveIntervals analysis.
175  unsigned insertLoadBefore(MachineInstr *mi, unsigned ss,
176                            unsigned vreg,
177                            const TargetRegisterClass *trc) {
178    unsigned miIdx = makeSpaceBefore(mi);
179
180    tii->loadRegFromStackSlot(*mi->getParent(), mi, vreg, ss, trc);
181    MachineBasicBlock::iterator loadInstItr(prior(mi));
182    MachineInstr *loadInst = &*loadInstItr;
183    unsigned loadInstIdx = miIdx - LiveInterval::InstrSlots::NUM;
184
185    assert(lis->getInstructionFromIndex(loadInstIdx) == 0 &&
186           "Load inst index already in use.");
187
188    lis->InsertMachineInstrInMaps(loadInst, loadInstIdx);
189
190    return loadInstIdx;
191  }
192
193  void insertLoadBeforeInstOnInterval(LiveInterval *li,
194                                      MachineInstr *mi, unsigned ss,
195                                      unsigned vreg,
196                                      const TargetRegisterClass *trc) {
197
198    unsigned loadInstIdx = insertLoadBefore(mi, ss, vreg, trc);
199    unsigned start = lis->getDefIndex(loadInstIdx),
200             end = lis->getUseIndex(lis->getInstructionIndex(mi));
201
202    VNInfo *vni =
203      li->getNextValue(loadInstIdx, 0, true, lis->getVNInfoAllocator());
204    li->addKill(vni, lis->getInstructionIndex(mi), false);
205    DOUT << "    Intserting load range: [" << start << ", " << end << ")\n";
206    LiveRange lr(start, end, vni);
207
208    li->addRange(lr);
209  }
210
211
212
213  /// Add spill ranges for every use/def of the live interval, inserting loads
214  /// immediately before each use, and stores after each def. No folding is
215  /// attempted.
216  std::vector<LiveInterval*> trivialSpillEverywhere(LiveInterval *li) {
217    DOUT << "Spilling everywhere " << *li << "\n";
218
219    assert(li->weight != HUGE_VALF &&
220           "Attempting to spill already spilled value.");
221
222    assert(!li->isStackSlot() &&
223           "Trying to spill a stack slot.");
224
225    DOUT << "Trivial spill everywhere of reg" << li->reg << "\n";
226
227    std::vector<LiveInterval*> added;
228
229    const TargetRegisterClass *trc = mri->getRegClass(li->reg);
230    unsigned ss = vrm->assignVirt2StackSlot(li->reg);
231
232    for (MachineRegisterInfo::reg_iterator
233         regItr = mri->reg_begin(li->reg); regItr != mri->reg_end();) {
234
235      MachineInstr *mi = &*regItr;
236
237      DOUT << "  Processing " << *mi;
238
239      do {
240        ++regItr;
241      } while (regItr != mri->reg_end() && (&*regItr == mi));
242
243      SmallVector<unsigned, 2> indices;
244      bool hasUse = false;
245      bool hasDef = false;
246
247      for (unsigned i = 0; i != mi->getNumOperands(); ++i) {
248        MachineOperand &op = mi->getOperand(i);
249
250        if (!op.isReg() || op.getReg() != li->reg)
251          continue;
252
253        hasUse |= mi->getOperand(i).isUse();
254        hasDef |= mi->getOperand(i).isDef();
255
256        indices.push_back(i);
257      }
258
259      unsigned newVReg = mri->createVirtualRegister(trc);
260      vrm->grow();
261      vrm->assignVirt2StackSlot(newVReg, ss);
262
263      LiveInterval *newLI = &lis->getOrCreateInterval(newVReg);
264      newLI->weight = HUGE_VALF;
265
266      for (unsigned i = 0; i < indices.size(); ++i) {
267        mi->getOperand(indices[i]).setReg(newVReg);
268
269        if (mi->getOperand(indices[i]).isUse()) {
270          mi->getOperand(indices[i]).setIsKill(true);
271        }
272      }
273
274      assert(hasUse || hasDef);
275
276      if (hasUse) {
277        insertLoadBeforeInstOnInterval(newLI, mi, ss, newVReg, trc);
278      }
279
280      if (hasDef) {
281        insertStoreAfterInstOnInterval(newLI, mi, ss, newVReg, trc);
282      }
283
284      added.push_back(newLI);
285    }
286
287    return added;
288  }
289
290};
291
292
293/// Spills any live range using the spill-everywhere method with no attempt at
294/// folding.
295class TrivialSpiller : public SpillerBase {
296public:
297
298  TrivialSpiller(MachineFunction *mf, LiveIntervals *lis, LiveStacks *ls,
299                 VirtRegMap *vrm) :
300    SpillerBase(mf, lis, ls, vrm) {}
301
302  std::vector<LiveInterval*> spill(LiveInterval *li) {
303    return trivialSpillEverywhere(li);
304  }
305
306  std::vector<LiveInterval*> intraBlockSplit(LiveInterval *li, VNInfo *valno)  {
307    std::vector<LiveInterval*> spillIntervals;
308
309    if (!valno->isDefAccurate() && !valno->isPHIDef()) {
310      // Early out for values which have no well defined def point.
311      return spillIntervals;
312    }
313
314    // Ok.. we should be able to proceed...
315    const TargetRegisterClass *trc = mri->getRegClass(li->reg);
316    unsigned ss = vrm->assignVirt2StackSlot(li->reg);
317    vrm->grow();
318    vrm->assignVirt2StackSlot(li->reg, ss);
319
320    MachineInstr *mi = 0;
321    unsigned storeIdx = 0;
322
323    if (valno->isDefAccurate()) {
324      // If we have an accurate def we can just grab an iterator to the instr
325      // after the def.
326      mi = lis->getInstructionFromIndex(valno->def);
327      storeIdx = insertStoreAfter(mi, ss, li->reg, trc) +
328        LiveInterval::InstrSlots::DEF;
329    } else {
330      // if we get here we have a PHI def.
331      mi = &lis->getMBBFromIndex(valno->def)->front();
332      storeIdx = insertStoreBefore(mi, ss, li->reg, trc) +
333        LiveInterval::InstrSlots::DEF;
334    }
335
336    MachineBasicBlock *defBlock = mi->getParent();
337    unsigned loadIdx = 0;
338
339    // Now we need to find the load...
340    MachineBasicBlock::iterator useItr(mi);
341    for (; !useItr->readsRegister(li->reg); ++useItr) {}
342
343    if (useItr != defBlock->end()) {
344      MachineInstr *loadInst = useItr;
345      loadIdx = insertLoadBefore(loadInst, ss, li->reg, trc) +
346        LiveInterval::InstrSlots::USE;
347    }
348    else {
349      MachineInstr *loadInst = &defBlock->back();
350      loadIdx = insertLoadAfter(loadInst, ss, li->reg, trc) +
351        LiveInterval::InstrSlots::USE;
352    }
353
354    li->removeRange(storeIdx, loadIdx, true);
355
356    return spillIntervals;
357  }
358
359};
360
361}
362
363llvm::Spiller* llvm::createSpiller(MachineFunction *mf, LiveIntervals *lis,
364                                   LiveStacks *ls, VirtRegMap *vrm) {
365  return new TrivialSpiller(mf, lis, ls, vrm);
366}
367