1//===- LoopPass.cpp - Loop Pass and Loop Pass Manager ---------------------===//
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// 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/Assembly/PrintModulePass.h"
18#include "llvm/Support/Debug.h"
19#include "llvm/Support/Timer.h"
20using namespace llvm;
21
22namespace {
23
24/// PrintLoopPass - Print a Function corresponding to a Loop.
25///
26class PrintLoopPass : public LoopPass {
27private:
28  std::string Banner;
29  raw_ostream &Out;       // raw_ostream to print on.
30
31public:
32  static char ID;
33  PrintLoopPass(const std::string &B, raw_ostream &o)
34      : LoopPass(ID), Banner(B), Out(o) {}
35
36  virtual void getAnalysisUsage(AnalysisUsage &AU) const {
37    AU.setPreservesAll();
38  }
39
40  bool runOnLoop(Loop *L, LPPassManager &) {
41    Out << Banner;
42    for (Loop::block_iterator b = L->block_begin(), be = L->block_end();
43         b != be;
44         ++b) {
45      (*b)->print(Out);
46    }
47    return false;
48  }
49};
50
51char PrintLoopPass::ID = 0;
52}
53
54//===----------------------------------------------------------------------===//
55// LPPassManager
56//
57
58char LPPassManager::ID = 0;
59
60LPPassManager::LPPassManager()
61  : FunctionPass(ID), PMDataManager() {
62  skipThisLoop = false;
63  redoThisLoop = false;
64  LI = NULL;
65  CurrentLoop = NULL;
66}
67
68/// Delete loop from the loop queue and loop hierarchy (LoopInfo).
69void LPPassManager::deleteLoopFromQueue(Loop *L) {
70
71  LI->updateUnloop(L);
72
73  // If L is current loop then skip rest of the passes and let
74  // runOnFunction remove L from LQ. Otherwise, remove L from LQ now
75  // and continue applying other passes on CurrentLoop.
76  if (CurrentLoop == L)
77    skipThisLoop = true;
78
79  delete L;
80
81  if (skipThisLoop)
82    return;
83
84  for (std::deque<Loop *>::iterator I = LQ.begin(),
85         E = LQ.end(); I != E; ++I) {
86    if (*I == L) {
87      LQ.erase(I);
88      break;
89    }
90  }
91}
92
93// Inset loop into loop nest (LoopInfo) and loop queue (LQ).
94void LPPassManager::insertLoop(Loop *L, Loop *ParentLoop) {
95
96  assert (CurrentLoop != L && "Cannot insert CurrentLoop");
97
98  // Insert into loop nest
99  if (ParentLoop)
100    ParentLoop->addChildLoop(L);
101  else
102    LI->addTopLevelLoop(L);
103
104  insertLoopIntoQueue(L);
105}
106
107void LPPassManager::insertLoopIntoQueue(Loop *L) {
108  // Insert L into loop queue
109  if (L == CurrentLoop)
110    redoLoop(L);
111  else if (!L->getParentLoop())
112    // This is top level loop.
113    LQ.push_front(L);
114  else {
115    // Insert L after the parent loop.
116    for (std::deque<Loop *>::iterator I = LQ.begin(),
117           E = LQ.end(); I != E; ++I) {
118      if (*I == L->getParentLoop()) {
119        // deque does not support insert after.
120        ++I;
121        LQ.insert(I, 1, L);
122        break;
123      }
124    }
125  }
126}
127
128// Reoptimize this loop. LPPassManager will re-insert this loop into the
129// queue. This allows LoopPass to change loop nest for the loop. This
130// utility may send LPPassManager into infinite loops so use caution.
131void LPPassManager::redoLoop(Loop *L) {
132  assert (CurrentLoop == L && "Can redo only CurrentLoop");
133  redoThisLoop = true;
134}
135
136/// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
137/// all loop passes.
138void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From,
139                                                  BasicBlock *To, Loop *L) {
140  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
141    LoopPass *LP = getContainedPass(Index);
142    LP->cloneBasicBlockAnalysis(From, To, L);
143  }
144}
145
146/// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
147void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
148  if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
149    for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;
150         ++BI) {
151      Instruction &I = *BI;
152      deleteSimpleAnalysisValue(&I, L);
153    }
154  }
155  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
156    LoopPass *LP = getContainedPass(Index);
157    LP->deleteAnalysisValue(V, L);
158  }
159}
160
161
162// Recurse through all subloops and all loops  into LQ.
163static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
164  LQ.push_back(L);
165  for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I)
166    addLoopIntoQueue(*I, LQ);
167}
168
169/// Pass Manager itself does not invalidate any analysis info.
170void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const {
171  // LPPassManager needs LoopInfo. In the long term LoopInfo class will
172  // become part of LPPassManager.
173  Info.addRequired<LoopInfo>();
174  Info.setPreservesAll();
175}
176
177/// run - Execute all of the passes scheduled for execution.  Keep track of
178/// whether any of the passes modifies the function, and if so, return true.
179bool LPPassManager::runOnFunction(Function &F) {
180  LI = &getAnalysis<LoopInfo>();
181  bool Changed = false;
182
183  // Collect inherited analysis from Module level pass manager.
184  populateInheritedAnalysis(TPM->activeStack);
185
186  // Populate the loop queue in reverse program order. There is no clear need to
187  // process sibling loops in either forward or reverse order. There may be some
188  // advantage in deleting uses in a later loop before optimizing the
189  // definitions in an earlier loop. If we find a clear reason to process in
190  // forward order, then a forward variant of LoopPassManager should be created.
191  for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
192    addLoopIntoQueue(*I, LQ);
193
194  if (LQ.empty()) // No loops, skip calling finalizers
195    return false;
196
197  // Initialization
198  for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end();
199       I != E; ++I) {
200    Loop *L = *I;
201    for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
202      LoopPass *P = getContainedPass(Index);
203      Changed |= P->doInitialization(L, *this);
204    }
205  }
206
207  // Walk Loops
208  while (!LQ.empty()) {
209
210    CurrentLoop  = LQ.back();
211    skipThisLoop = false;
212    redoThisLoop = false;
213
214    // Run all passes on the current Loop.
215    for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
216      LoopPass *P = getContainedPass(Index);
217
218      dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
219                   CurrentLoop->getHeader()->getName());
220      dumpRequiredSet(P);
221
222      initializeAnalysisImpl(P);
223
224      {
225        PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
226        TimeRegion PassTimer(getPassTimer(P));
227
228        Changed |= P->runOnLoop(CurrentLoop, *this);
229      }
230
231      if (Changed)
232        dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG,
233                     skipThisLoop ? "<deleted>" :
234                                    CurrentLoop->getHeader()->getName());
235      dumpPreservedSet(P);
236
237      if (!skipThisLoop) {
238        // Manually check that this loop is still healthy. This is done
239        // instead of relying on LoopInfo::verifyLoop since LoopInfo
240        // is a function pass and it's really expensive to verify every
241        // loop in the function every time. That level of checking can be
242        // enabled with the -verify-loop-info option.
243        {
244          TimeRegion PassTimer(getPassTimer(LI));
245          CurrentLoop->verifyLoop();
246        }
247
248        // Then call the regular verifyAnalysis functions.
249        verifyPreservedAnalysis(P);
250      }
251
252      removeNotPreservedAnalysis(P);
253      recordAvailableAnalysis(P);
254      removeDeadPasses(P,
255                       skipThisLoop ? "<deleted>" :
256                                      CurrentLoop->getHeader()->getName(),
257                       ON_LOOP_MSG);
258
259      if (skipThisLoop)
260        // Do not run other passes on this loop.
261        break;
262    }
263
264    // If the loop was deleted, release all the loop passes. This frees up
265    // some memory, and avoids trouble with the pass manager trying to call
266    // verifyAnalysis on them.
267    if (skipThisLoop)
268      for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
269        Pass *P = getContainedPass(Index);
270        freePass(P, "<deleted>", ON_LOOP_MSG);
271      }
272
273    // Pop the loop from queue after running all passes.
274    LQ.pop_back();
275
276    if (redoThisLoop)
277      LQ.push_back(CurrentLoop);
278  }
279
280  // Finalization
281  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
282    LoopPass *P = getContainedPass(Index);
283    Changed |= P->doFinalization();
284  }
285
286  return Changed;
287}
288
289/// Print passes managed by this manager
290void LPPassManager::dumpPassStructure(unsigned Offset) {
291  errs().indent(Offset*2) << "Loop Pass Manager\n";
292  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
293    Pass *P = getContainedPass(Index);
294    P->dumpPassStructure(Offset + 1);
295    dumpLastUses(P, Offset+1);
296  }
297}
298
299
300//===----------------------------------------------------------------------===//
301// LoopPass
302
303Pass *LoopPass::createPrinterPass(raw_ostream &O,
304                                  const std::string &Banner) const {
305  return new PrintLoopPass(Banner, O);
306}
307
308// Check if this pass is suitable for the current LPPassManager, if
309// available. This pass P is not suitable for a LPPassManager if P
310// is not preserving higher level analysis info used by other
311// LPPassManager passes. In such case, pop LPPassManager from the
312// stack. This will force assignPassManager() to create new
313// LPPassManger as expected.
314void LoopPass::preparePassManager(PMStack &PMS) {
315
316  // Find LPPassManager
317  while (!PMS.empty() &&
318         PMS.top()->getPassManagerType() > PMT_LoopPassManager)
319    PMS.pop();
320
321  // If this pass is destroying high level information that is used
322  // by other passes that are managed by LPM then do not insert
323  // this pass in current LPM. Use new LPPassManager.
324  if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
325      !PMS.top()->preserveHigherLevelAnalysis(this))
326    PMS.pop();
327}
328
329/// Assign pass manager to manage this pass.
330void LoopPass::assignPassManager(PMStack &PMS,
331                                 PassManagerType PreferredType) {
332  // Find LPPassManager
333  while (!PMS.empty() &&
334         PMS.top()->getPassManagerType() > PMT_LoopPassManager)
335    PMS.pop();
336
337  LPPassManager *LPPM;
338  if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
339    LPPM = (LPPassManager*)PMS.top();
340  else {
341    // Create new Loop Pass Manager if it does not exist.
342    assert (!PMS.empty() && "Unable to create Loop Pass Manager");
343    PMDataManager *PMD = PMS.top();
344
345    // [1] Create new Loop Pass Manager
346    LPPM = new LPPassManager();
347    LPPM->populateInheritedAnalysis(PMS);
348
349    // [2] Set up new manager's top level manager
350    PMTopLevelManager *TPM = PMD->getTopLevelManager();
351    TPM->addIndirectPassManager(LPPM);
352
353    // [3] Assign manager to manage this new manager. This may create
354    // and push new managers into PMS
355    Pass *P = LPPM->getAsPass();
356    TPM->schedulePass(P);
357
358    // [4] Push new manager into PMS
359    PMS.push(LPPM);
360  }
361
362  LPPM->add(this);
363}
364