LLVM  7.0.0svn
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/Dominators.h"
20 #include "llvm/IR/LLVMContext.h"
21 #include "llvm/IR/OptBisect.h"
22 #include "llvm/IR/PassManager.h"
23 #include "llvm/Support/Debug.h"
24 #include "llvm/Support/Timer.h"
26 using namespace llvm;
27 
28 #define DEBUG_TYPE "loop-pass-manager"
29 
30 namespace {
31 
32 /// PrintLoopPass - Print a Function corresponding to a Loop.
33 ///
34 class PrintLoopPassWrapper : public LoopPass {
35  raw_ostream &OS;
36  std::string Banner;
37 
38 public:
39  static char ID;
40  PrintLoopPassWrapper() : LoopPass(ID), OS(dbgs()) {}
41  PrintLoopPassWrapper(raw_ostream &OS, const std::string &Banner)
42  : LoopPass(ID), OS(OS), Banner(Banner) {}
43 
44  void getAnalysisUsage(AnalysisUsage &AU) const override {
45  AU.setPreservesAll();
46  }
47 
48  bool runOnLoop(Loop *L, LPPassManager &) override {
49  auto BBI = llvm::find_if(L->blocks(), [](BasicBlock *BB) { return BB; });
50  if (BBI != L->blocks().end() &&
51  isFunctionInPrintList((*BBI)->getParent()->getName())) {
52  printLoop(*L, OS, Banner);
53  }
54  return false;
55  }
56 
57  StringRef getPassName() const override { return "Print Loop IR"; }
58 };
59 
61 }
62 
63 //===----------------------------------------------------------------------===//
64 // LPPassManager
65 //
66 
67 char LPPassManager::ID = 0;
68 
71  LI = nullptr;
72  CurrentLoop = nullptr;
73 }
74 
75 // Insert loop into loop nest (LoopInfo) and loop queue (LQ).
77  if (!L.getParentLoop()) {
78  // This is the top level loop.
79  LQ.push_front(&L);
80  return;
81  }
82 
83  // Insert L into the loop queue after the parent loop.
84  for (auto I = LQ.begin(), E = LQ.end(); I != E; ++I) {
85  if (*I == L.getParentLoop()) {
86  // deque does not support insert after.
87  ++I;
88  LQ.insert(I, 1, &L);
89  return;
90  }
91  }
92 }
93 
94 /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
95 /// all loop passes.
97  BasicBlock *To, Loop *L) {
98  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
100  LP->cloneBasicBlockAnalysis(From, To, L);
101  }
102 }
103 
104 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
106  if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
107  for (Instruction &I : *BB) {
109  }
110  }
111  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
113  LP->deleteAnalysisValue(V, L);
114  }
115 }
116 
117 /// Invoke deleteAnalysisLoop hook for all passes.
119  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
121  LP->deleteAnalysisLoop(L);
122  }
123 }
124 
125 
126 // Recurse through all subloops and all loops into LQ.
127 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
128  LQ.push_back(L);
129  for (Loop *I : reverse(*L))
130  addLoopIntoQueue(I, LQ);
131 }
132 
133 /// Pass Manager itself does not invalidate any analysis info.
135  // LPPassManager needs LoopInfo. In the long term LoopInfo class will
136  // become part of LPPassManager.
139  Info.setPreservesAll();
140 }
141 
143  assert((&L == CurrentLoop || CurrentLoop->contains(&L)) &&
144  "Must not delete loop outside the current loop tree!");
145  if (&L == CurrentLoop)
146  CurrentLoopDeleted = true;
147 }
148 
149 /// run - Execute all of the passes scheduled for execution. Keep track of
150 /// whether any of the passes modifies the function, and if so, return true.
152  auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
153  LI = &LIWP.getLoopInfo();
154 #if 0
155  DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
156 #endif
157  bool Changed = false;
158 
159  // Collect inherited analysis from Module level pass manager.
161 
162  // Populate the loop queue in reverse program order. There is no clear need to
163  // process sibling loops in either forward or reverse order. There may be some
164  // advantage in deleting uses in a later loop before optimizing the
165  // definitions in an earlier loop. If we find a clear reason to process in
166  // forward order, then a forward variant of LoopPassManager should be created.
167  //
168  // Note that LoopInfo::iterator visits loops in reverse program
169  // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
170  // reverses the order a third time by popping from the back.
171  for (Loop *L : reverse(*LI))
172  addLoopIntoQueue(L, LQ);
173 
174  if (LQ.empty()) // No loops, skip calling finalizers
175  return false;
176 
177  // Initialization
178  for (Loop *L : LQ) {
179  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
181  Changed |= P->doInitialization(L, *this);
182  }
183  }
184 
185  // Walk Loops
186  while (!LQ.empty()) {
187  CurrentLoopDeleted = false;
188  CurrentLoop = LQ.back();
189 
190  // Run all passes on the current Loop.
191  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
193 
195  CurrentLoop->getHeader()->getName());
196  dumpRequiredSet(P);
197 
199 
200  {
201  PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
202  TimeRegion PassTimer(getPassTimer(P));
203 
204  Changed |= P->runOnLoop(CurrentLoop, *this);
205  }
206 
207  if (Changed)
209  CurrentLoopDeleted ? "<deleted loop>"
210  : CurrentLoop->getName());
211  dumpPreservedSet(P);
212 
213  if (CurrentLoopDeleted) {
214  // Notify passes that the loop is being deleted.
215  deleteSimpleAnalysisLoop(CurrentLoop);
216  } else {
217  // Manually check that this loop is still healthy. This is done
218  // instead of relying on LoopInfo::verifyLoop since LoopInfo
219  // is a function pass and it's really expensive to verify every
220  // loop in the function every time. That level of checking can be
221  // enabled with the -verify-loop-info option.
222  {
223  TimeRegion PassTimer(getPassTimer(&LIWP));
224  CurrentLoop->verifyLoop();
225  }
226  // Here we apply same reasoning as in the above case. Only difference
227  // is that LPPassManager might run passes which do not require LCSSA
228  // form (LoopPassPrinter for example). We should skip verification for
229  // such passes.
230  // FIXME: Loop-sink currently break LCSSA. Fix it and reenable the
231  // verification!
232 #if 0
234  assert(CurrentLoop->isRecursivelyLCSSAForm(*DT, *LI));
235 #endif
236 
237  // Then call the regular verifyAnalysis functions.
239 
240  F.getContext().yield();
241  }
242 
246  CurrentLoopDeleted ? "<deleted>"
247  : CurrentLoop->getHeader()->getName(),
248  ON_LOOP_MSG);
249 
250  if (CurrentLoopDeleted)
251  // Do not run other passes on this loop.
252  break;
253  }
254 
255  // If the loop was deleted, release all the loop passes. This frees up
256  // some memory, and avoids trouble with the pass manager trying to call
257  // verifyAnalysis on them.
258  if (CurrentLoopDeleted) {
259  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
261  freePass(P, "<deleted>", ON_LOOP_MSG);
262  }
263  }
264 
265  // Pop the loop from queue after running all passes.
266  LQ.pop_back();
267  }
268 
269  // Finalization
270  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
272  Changed |= P->doFinalization();
273  }
274 
275  return Changed;
276 }
277 
278 /// Print passes managed by this manager
280  errs().indent(Offset*2) << "Loop Pass Manager\n";
281  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
283  P->dumpPassStructure(Offset + 1);
284  dumpLastUses(P, Offset+1);
285  }
286 }
287 
288 
289 //===----------------------------------------------------------------------===//
290 // LoopPass
291 
293  const std::string &Banner) const {
294  return new PrintLoopPassWrapper(O, Banner);
295 }
296 
297 // Check if this pass is suitable for the current LPPassManager, if
298 // available. This pass P is not suitable for a LPPassManager if P
299 // is not preserving higher level analysis info used by other
300 // LPPassManager passes. In such case, pop LPPassManager from the
301 // stack. This will force assignPassManager() to create new
302 // LPPassManger as expected.
304 
305  // Find LPPassManager
306  while (!PMS.empty() &&
308  PMS.pop();
309 
310  // If this pass is destroying high level information that is used
311  // by other passes that are managed by LPM then do not insert
312  // this pass in current LPM. Use new LPPassManager.
313  if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
314  !PMS.top()->preserveHigherLevelAnalysis(this))
315  PMS.pop();
316 }
317 
318 /// Assign pass manager to manage this pass.
320  PassManagerType PreferredType) {
321  // Find LPPassManager
322  while (!PMS.empty() &&
324  PMS.pop();
325 
326  LPPassManager *LPPM;
328  LPPM = (LPPassManager*)PMS.top();
329  else {
330  // Create new Loop Pass Manager if it does not exist.
331  assert (!PMS.empty() && "Unable to create Loop Pass Manager");
332  PMDataManager *PMD = PMS.top();
333 
334  // [1] Create new Loop Pass Manager
335  LPPM = new LPPassManager();
336  LPPM->populateInheritedAnalysis(PMS);
337 
338  // [2] Set up new manager's top level manager
339  PMTopLevelManager *TPM = PMD->getTopLevelManager();
340  TPM->addIndirectPassManager(LPPM);
341 
342  // [3] Assign manager to manage this new manager. This may create
343  // and push new managers into PMS
344  Pass *P = LPPM->getAsPass();
345  TPM->schedulePass(P);
346 
347  // [4] Push new manager into PMS
348  PMS.push(LPPM);
349  }
350 
351  LPPM->add(this);
352 }
353 
354 bool LoopPass::skipLoop(const Loop *L) const {
355  const Function *F = L->getHeader()->getParent();
356  if (!F)
357  return false;
358  // Check the opt bisect limit.
360  if (!Context.getOptBisect().shouldRunPass(this, *L))
361  return true;
362  // Check for the OptimizeNone attribute.
363  if (F->hasFnAttribute(Attribute::OptimizeNone)) {
364  // FIXME: Report this to dbgs() only once per function.
365  DEBUG(dbgs() << "Skipping pass '" << getPassName()
366  << "' in function " << F->getName() << "\n");
367  // FIXME: Delete loop from pass manager's queue?
368  return true;
369  }
370  return false;
371 }
372 
374 INITIALIZE_PASS(LCSSAVerificationPass, "lcssa-verification", "LCSSA Verifier",
375  false, false)
PMTopLevelManager * TPM
Pass interface - Implemented by all &#39;passes&#39;.
Definition: Pass.h:81
bool preserveHigherLevelAnalysis(Pass *P)
PassManagerType
Different types of internal pass managers.
Definition: Pass.h:54
bool shouldRunPass(const Pass *P, const UnitT &U)
Checks the bisect limit to determine if the specified pass should run.
Definition: OptBisect.cpp:104
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang", "erlang-compatible garbage collector")
raw_ostream & errs()
This returns a reference to a raw_ostream for standard error.
LLVMContext & Context
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
virtual void dumpPassStructure(unsigned Offset=0)
Definition: Pass.cpp:67
void dumpLastUses(Pass *P, unsigned Offset) const
bool isRecursivelyLCSSAForm(DominatorTree &DT, const LoopInfo &LI) const
Return true if this Loop and all inner subloops are in LCSSA form.
Definition: LoopInfo.cpp:182
virtual void deleteAnalysisLoop(Loop *L)
Delete analysis info associated with Loop L.
Definition: LoopPass.h:88
raw_ostream & indent(unsigned NumSpaces)
indent - Insert &#39;NumSpaces&#39; spaces.
StringRef getPassName() const override
getPassName - Return a nice clean name for a pass.
Definition: LoopPass.h:110
bool hasFnAttribute(Attribute::AttrKind Kind) const
Return true if the function has the attribute.
Definition: Function.h:302
void assignPassManager(PMStack &PMS, PassManagerType PMT) override
Assign pass manager to manage this pass.
Definition: LoopPass.cpp:319
F(f)
void yield()
Calls the yield callback (if applicable).
void dumpPassInfo(Pass *P, enum PassDebuggingString S1, enum PassDebuggingString S2, StringRef Msg)
bool mustPreserveAnalysisID(char &AID) const
mustPreserveAnalysisID - This method serves the same function as getAnalysisIfAvailable, but works if you just have an AnalysisID.
Definition: Pass.cpp:62
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.
static void addLoopIntoQueue(Loop *L, std::deque< Loop *> &LQ)
Definition: LoopPass.cpp:127
The TimeRegion class is used as a helper class to call the startTimer() and stopTimer() methods of th...
Definition: Timer.h:140
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:118
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...
BlockT * getHeader() const
Definition: LoopInfo.h:100
auto reverse(ContainerTy &&C, typename std::enable_if< has_rbegin< ContainerTy >::value >::type *=nullptr) -> decltype(make_range(C.rbegin(), C.rend()))
Definition: STLExtras.h:233
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:292
void add(Pass *P, bool ProcessAnalysis=true)
Add pass P into the PassVector.
This header provides classes for managing per-loop analyses.
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:142
virtual bool doInitialization(Loop *L, LPPassManager &LPM)
Definition: LoopPass.h:46
#define P(N)
LLVM Basic Block Representation.
Definition: BasicBlock.h:59
This is an important class for using LLVM in a threaded context.
Definition: LLVMContext.h:69
virtual bool doFinalization()
Definition: LoopPass.h:52
void addIndirectPassManager(PMDataManager *Manager)
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
virtual PassManagerType getPassManagerType() const
void getAnalysisUsage(AnalysisUsage &Info) const override
Pass Manager itself does not invalidate any analysis info.
Definition: LoopPass.cpp:134
Represent the analysis usage information of a pass.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:285
auto find_if(R &&Range, UnaryPredicate P) -> decltype(adl_begin(Range))
Provide wrappers to std::find_if which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:842
LLVMContext & getContext() const
getContext - Return a reference to the LLVMContext associated with this function. ...
Definition: Function.cpp:194
static char ID
Definition: LoopPass.h:99
#define INITIALIZE_PASS(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:34
bool skipLoop(const Loop *L) const
Optional passes call this function to check whether the pass should be skipped.
Definition: LoopPass.cpp:354
void deleteSimpleAnalysisValue(Value *V, Loop *L)
deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes that implement simple anal...
Definition: LoopPass.cpp:105
bool contains(const LoopT *L) const
Return true if the specified loop is contained within in this loop.
Definition: LoopInfo.h:110
LPPassManager.
Definition: Pass.h:59
void recordAvailableAnalysis(Pass *P)
Augment AvailableAnalysis by adding analysis made available by pass P.
void dumpRequiredSet(const Pass *P) const
void removeNotPreservedAnalysis(Pass *P)
Remove Analysis that is not preserved by the pass.
void removeDeadPasses(Pass *P, StringRef Msg, enum PassDebuggingString)
Remove dead passes used by P.
This file declares the interface for bisecting optimizations.
void markLoopAsDeleted(Loop &L)
Definition: LoopPass.cpp:142
bool isFunctionInPrintList(StringRef FunctionName)
isFunctionInPrintList - returns true if a function should be printed via
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
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:279
void preparePassManager(PMStack &PMS) override
Check if available pass managers are suitable for this pass or not.
Definition: LoopPass.cpp:303
virtual bool runOnLoop(Loop *L, LPPassManager &LPM)=0
LoopT * getParentLoop() const
Definition: LoopInfo.h:101
StringRef getName() const
Definition: LoopInfo.h:577
void cloneBasicBlockSimpleAnalysis(BasicBlock *From, BasicBlock *To, Loop *L)
SimpleAnalysis - Provides simple interface to update analysis info maintained by various passes...
Definition: LoopPass.cpp:96
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:439
OptBisect & getOptBisect()
Access the object which manages optimization bisection for failure analysis.
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:224
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:108
#define I(x, y, z)
Definition: MD5.cpp:58
void addLoop(Loop &L)
Definition: LoopPass.cpp:76
LoopPass * getContainedPass(unsigned N)
Definition: LoopPass.h:118
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
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
PMDataManager * top() const
LLVM Value Representation.
Definition: Value.h:73
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:151
unsigned getNumContainedPasses() const
bool empty() const
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:44
#define DEBUG(X)
Definition: Debug.h:118
The legacy pass manager&#39;s analysis pass to compute loop information.
Definition: LoopInfo.h:958
void verifyLoop() const
Verify loop structure.
Definition: LoopInfoImpl.h:227
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
Pass * getAsPass() override
Definition: LoopPass.h:113
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:260
This header defines various interfaces for pass management in LLVM.
iterator_range< block_iterator > blocks() const
Definition: LoopInfo.h:156
void printLoop(Loop &L, raw_ostream &OS, const std::string &Banner="")
Function to print a loop&#39;s contents as LLVM&#39;s text IR assembly.
Definition: LoopInfo.cpp:733
void dumpPreservedSet(const Pass *P) const