LLVM  3.7.0
LoopPass.cpp
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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"
18 #include "llvm/IR/LLVMContext.h"
19 #include "llvm/Support/Debug.h"
20 #include "llvm/Support/Timer.h"
22 using namespace llvm;
23 
24 #define DEBUG_TYPE "loop-pass-manager"
25 
26 namespace {
27 
28 /// PrintLoopPass - Print a Function corresponding to a Loop.
29 ///
30 class PrintLoopPass : public LoopPass {
31 private:
32  std::string Banner;
33  raw_ostream &Out; // raw_ostream to print on.
34 
35 public:
36  static char ID;
37  PrintLoopPass(const std::string &B, raw_ostream &o)
38  : LoopPass(ID), Banner(B), Out(o) {}
39 
40  void getAnalysisUsage(AnalysisUsage &AU) const override {
41  AU.setPreservesAll();
42  }
43 
44  bool runOnLoop(Loop *L, LPPassManager &) override {
45  Out << Banner;
46  for (Loop::block_iterator b = L->block_begin(), be = L->block_end();
47  b != be;
48  ++b) {
49  if (*b)
50  (*b)->print(Out);
51  else
52  Out << "Printing <null> block";
53  }
54  return false;
55  }
56 };
57 
58 char PrintLoopPass::ID = 0;
59 }
60 
61 //===----------------------------------------------------------------------===//
62 // LPPassManager
63 //
64 
65 char LPPassManager::ID = 0;
66 
69  skipThisLoop = false;
70  redoThisLoop = false;
71  LI = nullptr;
72  CurrentLoop = nullptr;
73 }
74 
75 /// Delete loop from the loop queue and loop hierarchy (LoopInfo).
77 
78  LI->updateUnloop(L);
79 
80  // Notify passes that the loop is being deleted.
82 
83  // If L is current loop then skip rest of the passes and let
84  // runOnFunction remove L from LQ. Otherwise, remove L from LQ now
85  // and continue applying other passes on CurrentLoop.
86  if (CurrentLoop == L)
87  skipThisLoop = true;
88 
89  delete L;
90 
91  if (skipThisLoop)
92  return;
93 
94  for (std::deque<Loop *>::iterator I = LQ.begin(),
95  E = LQ.end(); I != E; ++I) {
96  if (*I == L) {
97  LQ.erase(I);
98  break;
99  }
100  }
101 }
102 
103 // Inset loop into loop nest (LoopInfo) and loop queue (LQ).
104 void LPPassManager::insertLoop(Loop *L, Loop *ParentLoop) {
105 
106  assert (CurrentLoop != L && "Cannot insert CurrentLoop");
107 
108  // Insert into loop nest
109  if (ParentLoop)
110  ParentLoop->addChildLoop(L);
111  else
112  LI->addTopLevelLoop(L);
113 
115 }
116 
118  // Insert L into loop queue
119  if (L == CurrentLoop)
120  redoLoop(L);
121  else if (!L->getParentLoop())
122  // This is top level loop.
123  LQ.push_front(L);
124  else {
125  // Insert L after the parent loop.
126  for (std::deque<Loop *>::iterator I = LQ.begin(),
127  E = LQ.end(); I != E; ++I) {
128  if (*I == L->getParentLoop()) {
129  // deque does not support insert after.
130  ++I;
131  LQ.insert(I, 1, L);
132  break;
133  }
134  }
135  }
136 }
137 
138 // Reoptimize this loop. LPPassManager will re-insert this loop into the
139 // queue. This allows LoopPass to change loop nest for the loop. This
140 // utility may send LPPassManager into infinite loops so use caution.
142  assert (CurrentLoop == L && "Can redo only CurrentLoop");
143  redoThisLoop = true;
144 }
145 
146 /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
147 /// all loop passes.
149  BasicBlock *To, Loop *L) {
150  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
151  LoopPass *LP = getContainedPass(Index);
152  LP->cloneBasicBlockAnalysis(From, To, L);
153  }
154 }
155 
156 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
158  if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
159  for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;
160  ++BI) {
161  Instruction &I = *BI;
163  }
164  }
165  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
166  LoopPass *LP = getContainedPass(Index);
167  LP->deleteAnalysisValue(V, L);
168  }
169 }
170 
171 /// Invoke deleteAnalysisLoop hook for all passes.
173  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
174  LoopPass *LP = getContainedPass(Index);
175  LP->deleteAnalysisLoop(L);
176  }
177 }
178 
179 
180 // Recurse through all subloops and all loops into LQ.
181 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
182  LQ.push_back(L);
183  for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I)
184  addLoopIntoQueue(*I, LQ);
185 }
186 
187 /// Pass Manager itself does not invalidate any analysis info.
189  // LPPassManager needs LoopInfo. In the long term LoopInfo class will
190  // become part of LPPassManager.
192  Info.setPreservesAll();
193 }
194 
195 /// run - Execute all of the passes scheduled for execution. Keep track of
196 /// whether any of the passes modifies the function, and if so, return true.
198  auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
199  LI = &LIWP.getLoopInfo();
200  bool Changed = false;
201 
202  // Collect inherited analysis from Module level pass manager.
204 
205  // Populate the loop queue in reverse program order. There is no clear need to
206  // process sibling loops in either forward or reverse order. There may be some
207  // advantage in deleting uses in a later loop before optimizing the
208  // definitions in an earlier loop. If we find a clear reason to process in
209  // forward order, then a forward variant of LoopPassManager should be created.
210  //
211  // Note that LoopInfo::iterator visits loops in reverse program
212  // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
213  // reverses the order a third time by popping from the back.
214  for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
215  addLoopIntoQueue(*I, LQ);
216 
217  if (LQ.empty()) // No loops, skip calling finalizers
218  return false;
219 
220  // Initialization
221  for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end();
222  I != E; ++I) {
223  Loop *L = *I;
224  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
225  LoopPass *P = getContainedPass(Index);
226  Changed |= P->doInitialization(L, *this);
227  }
228  }
229 
230  // Walk Loops
231  while (!LQ.empty()) {
232 
233  CurrentLoop = LQ.back();
234  skipThisLoop = false;
235  redoThisLoop = false;
236 
237  // Run all passes on the current Loop.
238  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
239  LoopPass *P = getContainedPass(Index);
240 
242  CurrentLoop->getHeader()->getName());
243  dumpRequiredSet(P);
244 
246 
247  {
248  PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
249  TimeRegion PassTimer(getPassTimer(P));
250 
251  Changed |= P->runOnLoop(CurrentLoop, *this);
252  }
253 
254  if (Changed)
256  skipThisLoop ? "<deleted>" :
257  CurrentLoop->getHeader()->getName());
258  dumpPreservedSet(P);
259 
260  if (!skipThisLoop) {
261  // Manually check that this loop is still healthy. This is done
262  // instead of relying on LoopInfo::verifyLoop since LoopInfo
263  // is a function pass and it's really expensive to verify every
264  // loop in the function every time. That level of checking can be
265  // enabled with the -verify-loop-info option.
266  {
267  TimeRegion PassTimer(getPassTimer(&LIWP));
268  CurrentLoop->verifyLoop();
269  }
270 
271  // Then call the regular verifyAnalysis functions.
273 
274  F.getContext().yield();
275  }
276 
280  skipThisLoop ? "<deleted>" :
281  CurrentLoop->getHeader()->getName(),
282  ON_LOOP_MSG);
283 
284  if (skipThisLoop)
285  // Do not run other passes on this loop.
286  break;
287  }
288 
289  // If the loop was deleted, release all the loop passes. This frees up
290  // some memory, and avoids trouble with the pass manager trying to call
291  // verifyAnalysis on them.
292  if (skipThisLoop)
293  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
294  Pass *P = getContainedPass(Index);
295  freePass(P, "<deleted>", ON_LOOP_MSG);
296  }
297 
298  // Pop the loop from queue after running all passes.
299  LQ.pop_back();
300 
301  if (redoThisLoop)
302  LQ.push_back(CurrentLoop);
303  }
304 
305  // Finalization
306  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
307  LoopPass *P = getContainedPass(Index);
308  Changed |= P->doFinalization();
309  }
310 
311  return Changed;
312 }
313 
314 /// Print passes managed by this manager
315 void LPPassManager::dumpPassStructure(unsigned Offset) {
316  errs().indent(Offset*2) << "Loop Pass Manager\n";
317  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
318  Pass *P = getContainedPass(Index);
319  P->dumpPassStructure(Offset + 1);
320  dumpLastUses(P, Offset+1);
321  }
322 }
323 
324 
325 //===----------------------------------------------------------------------===//
326 // LoopPass
327 
329  const std::string &Banner) const {
330  return new PrintLoopPass(Banner, O);
331 }
332 
333 // Check if this pass is suitable for the current LPPassManager, if
334 // available. This pass P is not suitable for a LPPassManager if P
335 // is not preserving higher level analysis info used by other
336 // LPPassManager passes. In such case, pop LPPassManager from the
337 // stack. This will force assignPassManager() to create new
338 // LPPassManger as expected.
340 
341  // Find LPPassManager
342  while (!PMS.empty() &&
344  PMS.pop();
345 
346  // If this pass is destroying high level information that is used
347  // by other passes that are managed by LPM then do not insert
348  // this pass in current LPM. Use new LPPassManager.
349  if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
350  !PMS.top()->preserveHigherLevelAnalysis(this))
351  PMS.pop();
352 }
353 
354 /// Assign pass manager to manage this pass.
356  PassManagerType PreferredType) {
357  // Find LPPassManager
358  while (!PMS.empty() &&
360  PMS.pop();
361 
362  LPPassManager *LPPM;
364  LPPM = (LPPassManager*)PMS.top();
365  else {
366  // Create new Loop Pass Manager if it does not exist.
367  assert (!PMS.empty() && "Unable to create Loop Pass Manager");
368  PMDataManager *PMD = PMS.top();
369 
370  // [1] Create new Loop Pass Manager
371  LPPM = new LPPassManager();
372  LPPM->populateInheritedAnalysis(PMS);
373 
374  // [2] Set up new manager's top level manager
375  PMTopLevelManager *TPM = PMD->getTopLevelManager();
376  TPM->addIndirectPassManager(LPPM);
377 
378  // [3] Assign manager to manage this new manager. This may create
379  // and push new managers into PMS
380  Pass *P = LPPM->getAsPass();
381  TPM->schedulePass(P);
382 
383  // [4] Push new manager into PMS
384  PMS.push(LPPM);
385  }
386 
387  LPPM->add(this);
388 }
389 
390 // Containing function has Attribute::OptimizeNone and transformation
391 // passes should skip it.
392 bool LoopPass::skipOptnoneFunction(const Loop *L) const {
393  const Function *F = L->getHeader()->getParent();
395  // FIXME: Report this to dbgs() only once per function.
396  DEBUG(dbgs() << "Skipping pass '" << getPassName()
397  << "' in function " << F->getName() << "\n");
398  // FIXME: Delete loop from pass manager's queue?
399  return true;
400  }
401  return false;
402 }
PMTopLevelManager * TPM
Pass interface - Implemented by all 'passes'.
Definition: Pass.h:82
bool preserveHigherLevelAnalysis(Pass *P)
PassManagerType
Different types of internal pass managers.
Definition: Pass.h:55
raw_ostream & errs()
This returns a reference to a raw_ostream for standard error.
LLVMContext & getContext() const
getContext - Return a reference to the LLVMContext associated with this function. ...
Definition: Function.cpp:223
void dumpLastUses(Pass *P, unsigned Offset) const
virtual void dumpPassStructure(unsigned Offset=0)
Definition: Pass.cpp:53
virtual void deleteAnalysisLoop(Loop *L)
Delete analysis info associated with Loop L.
Definition: LoopPass.h:88
raw_ostream & indent(unsigned NumSpaces)
indent - Insert 'NumSpaces' spaces.
std::vector< LoopT * >::const_reverse_iterator reverse_iterator
Definition: LoopInfo.h:530
virtual const char * getPassName() const
getPassName - Return a nice clean name for a pass.
Definition: Pass.cpp:61
void assignPassManager(PMStack &PMS, PassManagerType PMT) override
Assign pass manager to manage this pass.
Definition: LoopPass.cpp:355
void dumpRequiredSet(const Pass *P) const
LoopT * getParentLoop() const
Definition: LoopInfo.h:97
void updateUnloop(Loop *Unloop)
updateUnloop - Update LoopInfo after removing the last backedge from a loop–now the "unloop"...
Definition: LoopInfo.cpp:612
F(f)
void yield()
Calls the yield callback (if applicable).
void dumpPassInfo(Pass *P, enum PassDebuggingString S1, enum PassDebuggingString S2, StringRef Msg)
BlockT * getHeader() const
Definition: LoopInfo.h:96
virtual PassManagerType getPassManagerType() const
PMTopLevelManager manages LastUser info and collects common APIs used by top level pass managers...
Timer * getPassTimer(Pass *)
If TimingInfo is enabled then start pass timer.
StringRef getName() const
Return a constant reference to the value's name.
Definition: Value.cpp:188
The TimeRegion class is used as a helper class to call the startTimer() and stopTimer() methods of th...
Definition: Timer.h:126
void schedulePass(Pass *P)
Schedule pass P for execution.
AnalysisUsage & addRequired()
void freePass(Pass *P, StringRef Msg, enum PassDebuggingString)
Remove P.
void deleteSimpleAnalysisLoop(Loop *L)
Invoke deleteAnalysisLoop hook for all passes that implement simple analysis interface.
Definition: LoopPass.cpp:172
void verifyPreservedAnalysis(Pass *P)
verifyPreservedAnalysis – Verify analysis presreved by pass P.
void populateInheritedAnalysis(PMStack &PMS)
PMStack - This class implements a stack data structure of PMDataManager pointers. ...
void initializeAnalysisImpl(Pass *P)
All Required analyses should be available to the pass as it runs! Here we fill in the AnalysisImpls m...
PassManagerPrettyStackEntry - This is used to print informative information about what pass is runnin...
reverse_iterator rbegin() const
Definition: LoopInfo.h:133
Pass * createPrinterPass(raw_ostream &O, const std::string &Banner) const override
getPrinterPass - Get a pass to print the function corresponding to a Loop.
Definition: LoopPass.cpp:328
void add(Pass *P, bool ProcessAnalysis=true)
Add pass P into the PassVector.
void addChildLoop(LoopT *NewChild)
addChildLoop - Add the specified loop to be a child of this loop.
Definition: LoopInfo.h:265
unsigned getNumContainedPasses() const
void insertLoopIntoQueue(Loop *L)
Definition: LoopPass.cpp:117
void verifyLoop() const
verifyLoop - Verify loop structure
Definition: LoopInfoImpl.h:224
std::vector< LoopT * >::const_reverse_iterator reverse_iterator
Definition: LoopInfo.h:130
void redoLoop(Loop *L)
Definition: LoopPass.cpp:141
virtual bool doInitialization(Loop *L, LPPassManager &LPM)
Definition: LoopPass.h:46
#define P(N)
void insertLoop(Loop *L, Loop *ParentLoop)
Definition: LoopPass.cpp:104
void dumpPreservedSet(const Pass *P) const
LLVM Basic Block Representation.
Definition: BasicBlock.h:65
virtual bool doFinalization()
Definition: LoopPass.h:52
void addIndirectPassManager(PMDataManager *Manager)
void getAnalysisUsage(AnalysisUsage &Info) const override
Pass Manager itself does not invalidate any analysis info.
Definition: LoopPass.cpp:188
Represent the analysis usage information of a pass.
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang","erlang-compatible garbage collector")
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:294
static char ID
Definition: LoopPass.h:98
void deleteSimpleAnalysisValue(Value *V, Loop *L)
deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes that implement simple anal...
Definition: LoopPass.cpp:157
bool empty() const
LPPassManager.
Definition: Pass.h:60
void recordAvailableAnalysis(Pass *P)
Augment AvailableAnalysis by adding analysis made available by pass P.
reverse_iterator rend() const
Definition: LoopInfo.h:134
void removeNotPreservedAnalysis(Pass *P)
Remove Analysis that is not preserved by the pass.
void deleteLoopFromQueue(Loop *L)
Delete loop from the loop queue and loop hierarchy (LoopInfo).
Definition: LoopPass.cpp:76
void removeDeadPasses(Pass *P, StringRef Msg, enum PassDebuggingString)
Remove dead passes used by P.
bool skipOptnoneFunction(const Loop *L) const
skipOptnoneFunction - Containing function has Attribute::OptimizeNone and most transformation passes ...
Definition: LoopPass.cpp:392
void addTopLevelLoop(LoopT *New)
addTopLevelLoop - This adds the specified loop to the collection of top-level loops.
Definition: LoopInfo.h:597
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:123
PMDataManager * top() const
Function must not be optimized.
Definition: Attributes.h:98
void setPreservesAll()
Set by analyses that do not transform their input at all.
void dumpPassStructure(unsigned Offset) override
Print passes managed by this manager.
Definition: LoopPass.cpp:315
void preparePassManager(PMStack &PMS) override
Check if available pass managers are suitable for this pass or not.
Definition: LoopPass.cpp:339
std::vector< BlockT * >::const_iterator block_iterator
Definition: LoopInfo.h:140
virtual bool runOnLoop(Loop *L, LPPassManager &LPM)=0
block_iterator block_end() const
Definition: LoopInfo.h:142
bool hasFnAttribute(Attribute::AttrKind Kind) const
Return true if the function has the attribute.
Definition: Function.h:217
void cloneBasicBlockSimpleAnalysis(BasicBlock *From, BasicBlock *To, Loop *L)
SimpleAnalysis - Provides simple interface to update analysis info maintained by various passes...
Definition: LoopPass.cpp:148
#define I(x, y, z)
Definition: MD5.cpp:54
LoopPass * getContainedPass(unsigned N)
Definition: LoopPass.h:119
void push(PMDataManager *PM)
PMDataManager provides the common place to manage the analysis data used by pass managers.
This file defines passes to print out IR in various granularities.
virtual void cloneBasicBlockAnalysis(BasicBlock *F, BasicBlock *T, Loop *L)
SimpleAnalysis - Provides simple interface to update analysis info maintained by various passes...
Definition: LoopPass.h:80
LLVM Value Representation.
Definition: Value.h:69
virtual void deleteAnalysisValue(Value *V, Loop *L)
deleteAnalysisValue - Delete analysis info associated with value V.
Definition: LoopPass.h:83
bool runOnFunction(Function &F) override
run - Execute all of the passes scheduled for execution.
Definition: LoopPass.cpp:197
static void addLoopIntoQueue(Loop *L, std::deque< Loop * > &LQ)
Definition: LoopPass.cpp:181
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:38
#define DEBUG(X)
Definition: Debug.h:92
block_iterator block_begin() const
Definition: LoopInfo.h:141
The legacy pass manager's analysis pass to compute loop information.
Definition: LoopInfo.h:737
Pass * getAsPass() override
Definition: LoopPass.h:114