LoopPass.cpp revision 5ee99979065d75605d150d7e567e4351024aae8f 
1//===- LoopPass.cpp - Loop Pass and Loop Pass Manager ---------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by Devang Patel and is distributed under
6// the University of Illinois Open Source License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements LoopPass and LPPassManager. All loop optimization
11// and transformation passes are derived from LoopPass. LPPassManager is
12// responsible for managing LoopPasses.
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/Analysis/LoopPass.h"
17#include "llvm/Analysis/ScalarEvolutionExpander.h"
18using namespace llvm;
19
20//===----------------------------------------------------------------------===//
21// LPPassManager
22//
23/// LPPassManager manages FPPassManagers and CalLGraphSCCPasses.
24
25LPPassManager::LPPassManager(int Depth) : PMDataManager(Depth) {
26  skipThisLoop = false;
27  redoThisLoop = false;
28  LI = NULL;
29  CurrentLoop = NULL;
30}
31
32/// Delete loop from the loop queue and loop hierarcy (LoopInfo).
33void LPPassManager::deleteLoopFromQueue(Loop *L) {
34
35  if (Loop *ParentLoop = L->getParentLoop()) { // Not a top-level loop.
36    // Reparent all of the blocks in this loop.  Since BBLoop had a parent,
37    // they are now all in it.
38    for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
39         I != E; ++I)
40      if (LI->getLoopFor(*I) == L)    // Don't change blocks in subloops.
41        LI->changeLoopFor(*I, ParentLoop);
42
43    // Remove the loop from its parent loop.
44    for (Loop::iterator I = ParentLoop->begin(), E = ParentLoop->end();;
45         ++I) {
46      assert(I != E && "Couldn't find loop");
47      if (*I == L) {
48        ParentLoop->removeChildLoop(I);
49        break;
50      }
51    }
52
53    // Move all subloops into the parent loop.
54    while (L->begin() != L->end())
55      ParentLoop->addChildLoop(L->removeChildLoop(L->end()-1));
56  } else {
57    // Reparent all of the blocks in this loop.  Since BBLoop had no parent,
58    // they no longer in a loop at all.
59
60    for (unsigned i = 0; i != L->getBlocks().size(); ++i) {
61      // Don't change blocks in subloops.
62      if (LI->getLoopFor(L->getBlocks()[i]) == L) {
63        LI->removeBlock(L->getBlocks()[i]);
64        --i;
65      }
66    }
67
68    // Remove the loop from the top-level LoopInfo object.
69    for (LoopInfo::iterator I = LI->begin(), E = LI->end();; ++I) {
70      assert(I != E && "Couldn't find loop");
71      if (*I == L) {
72        LI->removeLoop(I);
73        break;
74      }
75    }
76
77    // Move all of the subloops to the top-level.
78    while (L->begin() != L->end())
79      LI->addTopLevelLoop(L->removeChildLoop(L->end()-1));
80  }
81
82  delete L;
83
84  // If L is current loop then skip rest of the passes and let
85  // runOnFunction remove L from LQ. Otherwise, remove L from LQ now
86  // and continue applying other passes on CurrentLoop.
87  if (CurrentLoop == L) {
88    skipThisLoop = true;
89    return;
90  }
91
92  for (std::deque<Loop *>::iterator I = LQ.begin(),
93         E = LQ.end(); I != E; ++I) {
94    if (*I == L) {
95      LQ.erase(I);
96      break;
97    }
98  }
99}
100
101// Inset loop into loop nest (LoopInfo) and loop queue (LQ).
102void LPPassManager::insertLoop(Loop *L, Loop *ParentLoop) {
103
104  assert (CurrentLoop != L && "Cannot insert CurrentLoop");
105
106  // Insert into loop nest
107  if (ParentLoop)
108    ParentLoop->addChildLoop(L);
109  else
110    LI->addTopLevelLoop(L);
111
112  // Insert L into loop queue
113  if (L == CurrentLoop)
114    redoLoop(L);
115  else if (!ParentLoop)
116    // This is top level loop.
117    LQ.push_front(L);
118  else {
119    // Insert L after ParentLoop
120    for (std::deque<Loop *>::iterator I = LQ.begin(),
121           E = LQ.end(); I != E; ++I) {
122      if (*I == ParentLoop) {
123        // deque does not support insert after.
124        ++I;
125        LQ.insert(I, 1, L);
126        break;
127      }
128    }
129  }
130}
131
132// Reoptimize this loop. LPPassManager will re-insert this loop into the
133// queue. This allows LoopPass to change loop nest for the loop. This
134// utility may send LPPassManager into infinite loops so use caution.
135void LPPassManager::redoLoop(Loop *L) {
136  assert (CurrentLoop == L && "Can redo only CurrentLoop");
137  redoThisLoop = true;
138}
139
140// Recurse through all subloops and all loops  into LQ.
141static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
142  LQ.push_back(L);
143  for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
144    addLoopIntoQueue(*I, LQ);
145}
146
147/// Pass Manager itself does not invalidate any analysis info.
148void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const {
149  // LPPassManager needs LoopInfo. In the long term LoopInfo class will
150  // become part of LPPassManager.
151  Info.addRequired<LoopInfo>();
152  // Used by IndVar doInitialization.
153  Info.addRequired<ScalarEvolution>();
154  Info.setPreservesAll();
155}
156
157/// run - Execute all of the passes scheduled for execution.  Keep track of
158/// whether any of the passes modifies the function, and if so, return true.
159bool LPPassManager::runOnFunction(Function &F) {
160  LI = &getAnalysis<LoopInfo>();
161  bool Changed = false;
162
163  // Populate Loop Queue
164  for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
165    addLoopIntoQueue(*I, LQ);
166
167  // Initialization
168  for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end();
169       I != E; ++I) {
170    Loop *L = *I;
171    for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
172      Pass *P = getContainedPass(Index);
173      LoopPass *LP = dynamic_cast<LoopPass *>(P);
174      if (LP)
175        Changed |= LP->doInitialization(L, *this);
176    }
177  }
178
179  // Walk Loops
180  while (!LQ.empty()) {
181
182    CurrentLoop  = LQ.back();
183    skipThisLoop = false;
184    redoThisLoop = false;
185
186    // Run all passes on current SCC
187    for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
188
189      Pass *P = getContainedPass(Index);
190      AnalysisUsage AnUsage;
191      P->getAnalysisUsage(AnUsage);
192
193      dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG, "");
194      dumpAnalysisSetInfo("Required", P, AnUsage.getRequiredSet());
195
196      initializeAnalysisImpl(P);
197
198      StartPassTimer(P);
199      LoopPass *LP = dynamic_cast<LoopPass *>(P);
200      assert (LP && "Invalid LPPassManager member");
201      LP->runOnLoop(CurrentLoop, *this);
202      StopPassTimer(P);
203
204      if (Changed)
205        dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG, "");
206      dumpAnalysisSetInfo("Preserved", P, AnUsage.getPreservedSet());
207
208      removeNotPreservedAnalysis(P);
209      recordAvailableAnalysis(P);
210      removeDeadPasses(P, "", ON_LOOP_MSG);
211
212      if (skipThisLoop)
213        // Do not run other passes on this loop.
214        break;
215    }
216
217    // Pop the loop from queue after running all passes.
218    LQ.pop_back();
219
220    if (redoThisLoop)
221      LQ.push_back(CurrentLoop);
222  }
223
224  // Finalization
225  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
226    Pass *P = getContainedPass(Index);
227    LoopPass *LP = dynamic_cast <LoopPass *>(P);
228    if (LP)
229      Changed |= LP->doFinalization();
230  }
231
232  return Changed;
233}
234
235
236//===----------------------------------------------------------------------===//
237// LoopPass
238
239// Check if this pass is suitable for the current LPPassManager, if
240// available. This pass P is not suitable for a LPPassManager if P
241// is not preserving higher level analysis info used by other
242// LPPassManager passes. In such case, pop LPPassManager from the
243// stack. This will force assignPassManager() to create new
244// LPPassManger as expected.
245void LoopPass::preparePassManager(PMStack &PMS) {
246
247  // Find LPPassManager
248  while (!PMS.empty()) {
249    if (PMS.top()->getPassManagerType() > PMT_LoopPassManager)
250      PMS.pop();
251    else;
252    break;
253  }
254
255  LPPassManager *LPPM = dynamic_cast<LPPassManager *>(PMS.top());
256
257  // If this pass is destroying high level information that is used
258  // by other passes that are managed by LPM then do not insert
259  // this pass in current LPM. Use new LPPassManager.
260  if (LPPM && !LPPM->preserveHigherLevelAnalysis(this))
261    PMS.pop();
262}
263
264/// Assign pass manager to manage this pass.
265void LoopPass::assignPassManager(PMStack &PMS,
266                                 PassManagerType PreferredType) {
267  // Find LPPassManager
268  while (!PMS.empty()) {
269    if (PMS.top()->getPassManagerType() > PMT_LoopPassManager)
270      PMS.pop();
271    else;
272    break;
273  }
274
275  LPPassManager *LPPM = dynamic_cast<LPPassManager *>(PMS.top());
276
277  // Create new Loop Pass Manager if it does not exist.
278  if (!LPPM) {
279
280    assert (!PMS.empty() && "Unable to create Loop Pass Manager");
281    PMDataManager *PMD = PMS.top();
282
283    // [1] Create new Call Graph Pass Manager
284    LPPM = new LPPassManager(PMD->getDepth() + 1);
285    LPPM->populateInheritedAnalysis(PMS);
286
287    // [2] Set up new manager's top level manager
288    PMTopLevelManager *TPM = PMD->getTopLevelManager();
289    TPM->addIndirectPassManager(LPPM);
290
291    // [3] Assign manager to manage this new manager. This may create
292    // and push new managers into PMS
293    Pass *P = dynamic_cast<Pass *>(LPPM);
294    TPM->schedulePass(P);
295
296    // [4] Push new manager into PMS
297    PMS.push(LPPM);
298  }
299
300  LPPM->add(this);
301}
302
303