LLVM  6.0.0svn
LoopPass.cpp
Go to the documentation of this file.
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 = find_if(L->blocks().begin(), L->blocks().end(),
50  [](BasicBlock *BB) { return BB; });
51  if (BBI != L->blocks().end() &&
52  isFunctionInPrintList((*BBI)->getParent()->getName())) {
53  printLoop(*L, OS, Banner);
54  }
55  return false;
56  }
57 
58  StringRef getPassName() const override { return "Print Loop IR"; }
59 };
60 
62 }
63 
64 //===----------------------------------------------------------------------===//
65 // LPPassManager
66 //
67 
68 char LPPassManager::ID = 0;
69 
72  LI = nullptr;
73  CurrentLoop = nullptr;
74 }
75 
76 // Insert loop into loop nest (LoopInfo) and loop queue (LQ).
78  if (!L.getParentLoop()) {
79  // This is the top level loop.
80  LQ.push_front(&L);
81  return;
82  }
83 
84  // Insert L into the loop queue after the parent loop.
85  for (auto I = LQ.begin(), E = LQ.end(); I != E; ++I) {
86  if (*I == L.getParentLoop()) {
87  // deque does not support insert after.
88  ++I;
89  LQ.insert(I, 1, &L);
90  return;
91  }
92  }
93 }
94 
95 /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
96 /// all loop passes.
98  BasicBlock *To, Loop *L) {
99  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
100  LoopPass *LP = getContainedPass(Index);
101  LP->cloneBasicBlockAnalysis(From, To, L);
102  }
103 }
104 
105 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
107  if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
108  for (Instruction &I : *BB) {
110  }
111  }
112  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
113  LoopPass *LP = getContainedPass(Index);
114  LP->deleteAnalysisValue(V, L);
115  }
116 }
117 
118 /// Invoke deleteAnalysisLoop hook for all passes.
120  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
121  LoopPass *LP = getContainedPass(Index);
122  LP->deleteAnalysisLoop(L);
123  }
124 }
125 
126 
127 // Recurse through all subloops and all loops into LQ.
128 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
129  LQ.push_back(L);
130  for (Loop *I : reverse(*L))
131  addLoopIntoQueue(I, LQ);
132 }
133 
134 /// Pass Manager itself does not invalidate any analysis info.
136  // LPPassManager needs LoopInfo. In the long term LoopInfo class will
137  // become part of LPPassManager.
140  Info.setPreservesAll();
141 }
142 
143 /// run - Execute all of the passes scheduled for execution. Keep track of
144 /// whether any of the passes modifies the function, and if so, return true.
146  auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
147  LI = &LIWP.getLoopInfo();
148  DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
149  bool Changed = false;
150 
151  // Collect inherited analysis from Module level pass manager.
153 
154  // Populate the loop queue in reverse program order. There is no clear need to
155  // process sibling loops in either forward or reverse order. There may be some
156  // advantage in deleting uses in a later loop before optimizing the
157  // definitions in an earlier loop. If we find a clear reason to process in
158  // forward order, then a forward variant of LoopPassManager should be created.
159  //
160  // Note that LoopInfo::iterator visits loops in reverse program
161  // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
162  // reverses the order a third time by popping from the back.
163  for (Loop *L : reverse(*LI))
164  addLoopIntoQueue(L, LQ);
165 
166  if (LQ.empty()) // No loops, skip calling finalizers
167  return false;
168 
169  // Initialization
170  for (Loop *L : LQ) {
171  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
172  LoopPass *P = getContainedPass(Index);
173  Changed |= P->doInitialization(L, *this);
174  }
175  }
176 
177  // Walk Loops
178  while (!LQ.empty()) {
179  bool LoopWasDeleted = false;
180  CurrentLoop = LQ.back();
181 
182  // Run all passes on the current Loop.
183  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
184  LoopPass *P = getContainedPass(Index);
185 
187  CurrentLoop->getHeader()->getName());
188  dumpRequiredSet(P);
189 
191 
192  {
193  PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
194  TimeRegion PassTimer(getPassTimer(P));
195 
196  Changed |= P->runOnLoop(CurrentLoop, *this);
197  }
198  LoopWasDeleted = CurrentLoop->isInvalid();
199 
200  if (Changed)
201  dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG, CurrentLoop->getName());
202  dumpPreservedSet(P);
203 
204  if (LoopWasDeleted) {
205  // Notify passes that the loop is being deleted.
206  deleteSimpleAnalysisLoop(CurrentLoop);
207  } else {
208  // Manually check that this loop is still healthy. This is done
209  // instead of relying on LoopInfo::verifyLoop since LoopInfo
210  // is a function pass and it's really expensive to verify every
211  // loop in the function every time. That level of checking can be
212  // enabled with the -verify-loop-info option.
213  {
214  TimeRegion PassTimer(getPassTimer(&LIWP));
215  CurrentLoop->verifyLoop();
216  }
217  // Here we apply same reasoning as in the above case. Only difference
218  // is that LPPassManager might run passes which do not require LCSSA
219  // form (LoopPassPrinter for example). We should skip verification for
220  // such passes.
222  CurrentLoop->isRecursivelyLCSSAForm(*DT, *LI);
223 
224  // Then call the regular verifyAnalysis functions.
226 
227  F.getContext().yield();
228  }
229 
232  removeDeadPasses(P, LoopWasDeleted ? "<deleted>"
233  : CurrentLoop->getHeader()->getName(),
234  ON_LOOP_MSG);
235 
236  if (LoopWasDeleted)
237  // Do not run other passes on this loop.
238  break;
239  }
240 
241  // If the loop was deleted, release all the loop passes. This frees up
242  // some memory, and avoids trouble with the pass manager trying to call
243  // verifyAnalysis on them.
244  if (LoopWasDeleted) {
245  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
246  Pass *P = getContainedPass(Index);
247  freePass(P, "<deleted>", ON_LOOP_MSG);
248  }
249  }
250 
251  // Pop the loop from queue after running all passes.
252  LQ.pop_back();
253  }
254 
255  // Finalization
256  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
257  LoopPass *P = getContainedPass(Index);
258  Changed |= P->doFinalization();
259  }
260 
261  return Changed;
262 }
263 
264 /// Print passes managed by this manager
266  errs().indent(Offset*2) << "Loop Pass Manager\n";
267  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
268  Pass *P = getContainedPass(Index);
269  P->dumpPassStructure(Offset + 1);
270  dumpLastUses(P, Offset+1);
271  }
272 }
273 
274 
275 //===----------------------------------------------------------------------===//
276 // LoopPass
277 
279  const std::string &Banner) const {
280  return new PrintLoopPassWrapper(O, Banner);
281 }
282 
283 // Check if this pass is suitable for the current LPPassManager, if
284 // available. This pass P is not suitable for a LPPassManager if P
285 // is not preserving higher level analysis info used by other
286 // LPPassManager passes. In such case, pop LPPassManager from the
287 // stack. This will force assignPassManager() to create new
288 // LPPassManger as expected.
290 
291  // Find LPPassManager
292  while (!PMS.empty() &&
294  PMS.pop();
295 
296  // If this pass is destroying high level information that is used
297  // by other passes that are managed by LPM then do not insert
298  // this pass in current LPM. Use new LPPassManager.
299  if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
300  !PMS.top()->preserveHigherLevelAnalysis(this))
301  PMS.pop();
302 }
303 
304 /// Assign pass manager to manage this pass.
306  PassManagerType PreferredType) {
307  // Find LPPassManager
308  while (!PMS.empty() &&
310  PMS.pop();
311 
312  LPPassManager *LPPM;
314  LPPM = (LPPassManager*)PMS.top();
315  else {
316  // Create new Loop Pass Manager if it does not exist.
317  assert (!PMS.empty() && "Unable to create Loop Pass Manager");
318  PMDataManager *PMD = PMS.top();
319 
320  // [1] Create new Loop Pass Manager
321  LPPM = new LPPassManager();
322  LPPM->populateInheritedAnalysis(PMS);
323 
324  // [2] Set up new manager's top level manager
325  PMTopLevelManager *TPM = PMD->getTopLevelManager();
326  TPM->addIndirectPassManager(LPPM);
327 
328  // [3] Assign manager to manage this new manager. This may create
329  // and push new managers into PMS
330  Pass *P = LPPM->getAsPass();
331  TPM->schedulePass(P);
332 
333  // [4] Push new manager into PMS
334  PMS.push(LPPM);
335  }
336 
337  LPPM->add(this);
338 }
339 
340 bool LoopPass::skipLoop(const Loop *L) const {
341  const Function *F = L->getHeader()->getParent();
342  if (!F)
343  return false;
344  // Check the opt bisect limit.
346  if (!Context.getOptBisect().shouldRunPass(this, *L))
347  return true;
348  // Check for the OptimizeNone attribute.
349  if (F->hasFnAttribute(Attribute::OptimizeNone)) {
350  // FIXME: Report this to dbgs() only once per function.
351  DEBUG(dbgs() << "Skipping pass '" << getPassName()
352  << "' in function " << F->getName() << "\n");
353  // FIXME: Delete loop from pass manager's queue?
354  return true;
355  }
356  return false;
357 }
358 
360 INITIALIZE_PASS(LCSSAVerificationPass, "lcssa-verification", "LCSSA Verifier",
361  false, false)
362 
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:262
void assignPassManager(PMStack &PMS, PassManagerType PMT) override
Assign pass manager to manage this pass.
Definition: LoopPass.cpp:305
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
bool isInvalid() const
Return true if this loop is no longer valid.
Definition: LoopInfo.h:176
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:128
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:119
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:107
auto reverse(ContainerTy &&C, typename std::enable_if< has_rbegin< ContainerTy >::value >::type *=nullptr) -> decltype(make_range(C.rbegin(), C.rend()))
Definition: STLExtras.h:248
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:278
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:140
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:135
Represent the analysis usage information of a pass.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:285
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:340
void deleteSimpleAnalysisValue(Value *V, Loop *L)
deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes that implement simple anal...
Definition: LoopPass.cpp:106
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.
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:265
void preparePassManager(PMStack &PMS) override
Check if available pass managers are suitable for this pass or not.
Definition: LoopPass.cpp:289
virtual bool runOnLoop(Loop *L, LPPassManager &LPM)=0
LoopT * getParentLoop() const
Definition: LoopInfo.h:108
StringRef getName() const
Definition: LoopInfo.h:536
void cloneBasicBlockSimpleAnalysis(BasicBlock *From, BasicBlock *To, Loop *L)
SimpleAnalysis - Provides simple interface to update analysis info maintained by various passes...
Definition: LoopPass.cpp:97
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:404
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:218
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:77
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:145
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:896
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:267
This header defines various interfaces for pass management in LLVM.
auto find_if(R &&Range, UnaryPredicate P) -> decltype(std::begin(Range))
Provide wrappers to std::find_if which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:844
iterator_range< block_iterator > blocks() const
Definition: LoopInfo.h:163
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:702
void dumpPreservedSet(const Pass *P) const