LLVM  8.0.0svn
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/IR/PassTimingInfo.h"
24 #include "llvm/Support/Debug.h"
25 #include "llvm/Support/Timer.h"
27 using namespace llvm;
28 
29 #define DEBUG_TYPE "loop-pass-manager"
30 
31 namespace {
32 
33 /// PrintLoopPass - Print a Function corresponding to a Loop.
34 ///
35 class PrintLoopPassWrapper : public LoopPass {
36  raw_ostream &OS;
37  std::string Banner;
38 
39 public:
40  static char ID;
41  PrintLoopPassWrapper() : LoopPass(ID), OS(dbgs()) {}
42  PrintLoopPassWrapper(raw_ostream &OS, const std::string &Banner)
43  : LoopPass(ID), OS(OS), Banner(Banner) {}
44 
45  void getAnalysisUsage(AnalysisUsage &AU) const override {
46  AU.setPreservesAll();
47  }
48 
49  bool runOnLoop(Loop *L, LPPassManager &) override {
50  auto BBI = llvm::find_if(L->blocks(), [](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) {
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) {
114  LP->deleteAnalysisValue(V, L);
115  }
116 }
117 
118 /// Invoke deleteAnalysisLoop hook for all passes.
120  for (unsigned Index = 0; Index < getNumContainedPasses(); ++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 
144  assert((&L == CurrentLoop || CurrentLoop->contains(&L)) &&
145  "Must not delete loop outside the current loop tree!");
146  // If this loop appears elsewhere within the queue, we also need to remove it
147  // there. However, we have to be careful to not remove the back of the queue
148  // as that is assumed to match the current loop.
149  assert(LQ.back() == CurrentLoop && "Loop queue back isn't the current loop!");
150  LQ.erase(std::remove(LQ.begin(), LQ.end(), &L), LQ.end());
151 
152  if (&L == CurrentLoop) {
153  CurrentLoopDeleted = true;
154  // Add this loop back onto the back of the queue to preserve our invariants.
155  LQ.push_back(&L);
156  }
157 }
158 
159 /// run - Execute all of the passes scheduled for execution. Keep track of
160 /// whether any of the passes modifies the function, and if so, return true.
162  auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
163  LI = &LIWP.getLoopInfo();
164  Module &M = *F.getParent();
165 #if 0
166  DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
167 #endif
168  bool Changed = false;
169 
170  // Collect inherited analysis from Module level pass manager.
172 
173  // Populate the loop queue in reverse program order. There is no clear need to
174  // process sibling loops in either forward or reverse order. There may be some
175  // advantage in deleting uses in a later loop before optimizing the
176  // definitions in an earlier loop. If we find a clear reason to process in
177  // forward order, then a forward variant of LoopPassManager should be created.
178  //
179  // Note that LoopInfo::iterator visits loops in reverse program
180  // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
181  // reverses the order a third time by popping from the back.
182  for (Loop *L : reverse(*LI))
183  addLoopIntoQueue(L, LQ);
184 
185  if (LQ.empty()) // No loops, skip calling finalizers
186  return false;
187 
188  // Initialization
189  for (Loop *L : LQ) {
190  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
192  Changed |= P->doInitialization(L, *this);
193  }
194  }
195 
196  // Walk Loops
197  unsigned InstrCount, FunctionSize = 0;
198  StringMap<std::pair<unsigned, unsigned>> FunctionToInstrCount;
199  bool EmitICRemark = M.shouldEmitInstrCountChangedRemark();
200  // Collect the initial size of the module and the function we're looking at.
201  if (EmitICRemark) {
202  InstrCount = initSizeRemarkInfo(M, FunctionToInstrCount);
203  FunctionSize = F.getInstructionCount();
204  }
205  while (!LQ.empty()) {
206  CurrentLoopDeleted = false;
207  CurrentLoop = LQ.back();
208 
209  // Run all passes on the current Loop.
210  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
212 
214  CurrentLoop->getHeader()->getName());
215  dumpRequiredSet(P);
216 
218 
219  {
220  PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
221  TimeRegion PassTimer(getPassTimer(P));
222  Changed |= P->runOnLoop(CurrentLoop, *this);
223  if (EmitICRemark) {
224  unsigned NewSize = F.getInstructionCount();
225  // Update the size of the function, emit a remark, and update the
226  // size of the module.
227  if (NewSize != FunctionSize) {
228  int64_t Delta = static_cast<int64_t>(NewSize) -
229  static_cast<int64_t>(FunctionSize);
230  emitInstrCountChangedRemark(P, M, Delta, InstrCount,
231  FunctionToInstrCount, &F);
232  InstrCount = static_cast<int64_t>(InstrCount) + Delta;
233  FunctionSize = NewSize;
234  }
235  }
236  }
237 
238  if (Changed)
240  CurrentLoopDeleted ? "<deleted loop>"
241  : CurrentLoop->getName());
242  dumpPreservedSet(P);
243 
244  if (CurrentLoopDeleted) {
245  // Notify passes that the loop is being deleted.
246  deleteSimpleAnalysisLoop(CurrentLoop);
247  } else {
248  // Manually check that this loop is still healthy. This is done
249  // instead of relying on LoopInfo::verifyLoop since LoopInfo
250  // is a function pass and it's really expensive to verify every
251  // loop in the function every time. That level of checking can be
252  // enabled with the -verify-loop-info option.
253  {
254  TimeRegion PassTimer(getPassTimer(&LIWP));
255  CurrentLoop->verifyLoop();
256  }
257  // Here we apply same reasoning as in the above case. Only difference
258  // is that LPPassManager might run passes which do not require LCSSA
259  // form (LoopPassPrinter for example). We should skip verification for
260  // such passes.
261  // FIXME: Loop-sink currently break LCSSA. Fix it and reenable the
262  // verification!
263 #if 0
265  assert(CurrentLoop->isRecursivelyLCSSAForm(*DT, *LI));
266 #endif
267 
268  // Then call the regular verifyAnalysis functions.
270 
271  F.getContext().yield();
272  }
273 
277  CurrentLoopDeleted ? "<deleted>"
278  : CurrentLoop->getHeader()->getName(),
279  ON_LOOP_MSG);
280 
281  if (CurrentLoopDeleted)
282  // Do not run other passes on this loop.
283  break;
284  }
285 
286  // If the loop was deleted, release all the loop passes. This frees up
287  // some memory, and avoids trouble with the pass manager trying to call
288  // verifyAnalysis on them.
289  if (CurrentLoopDeleted) {
290  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
292  freePass(P, "<deleted>", ON_LOOP_MSG);
293  }
294  }
295 
296  // Pop the loop from queue after running all passes.
297  LQ.pop_back();
298  }
299 
300  // Finalization
301  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
303  Changed |= P->doFinalization();
304  }
305 
306  return Changed;
307 }
308 
309 /// Print passes managed by this manager
311  errs().indent(Offset*2) << "Loop Pass Manager\n";
312  for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
314  P->dumpPassStructure(Offset + 1);
315  dumpLastUses(P, Offset+1);
316  }
317 }
318 
319 
320 //===----------------------------------------------------------------------===//
321 // LoopPass
322 
324  const std::string &Banner) const {
325  return new PrintLoopPassWrapper(O, Banner);
326 }
327 
328 // Check if this pass is suitable for the current LPPassManager, if
329 // available. This pass P is not suitable for a LPPassManager if P
330 // is not preserving higher level analysis info used by other
331 // LPPassManager passes. In such case, pop LPPassManager from the
332 // stack. This will force assignPassManager() to create new
333 // LPPassManger as expected.
335 
336  // Find LPPassManager
337  while (!PMS.empty() &&
339  PMS.pop();
340 
341  // If this pass is destroying high level information that is used
342  // by other passes that are managed by LPM then do not insert
343  // this pass in current LPM. Use new LPPassManager.
344  if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
345  !PMS.top()->preserveHigherLevelAnalysis(this))
346  PMS.pop();
347 }
348 
349 /// Assign pass manager to manage this pass.
351  PassManagerType PreferredType) {
352  // Find LPPassManager
353  while (!PMS.empty() &&
355  PMS.pop();
356 
357  LPPassManager *LPPM;
359  LPPM = (LPPassManager*)PMS.top();
360  else {
361  // Create new Loop Pass Manager if it does not exist.
362  assert (!PMS.empty() && "Unable to create Loop Pass Manager");
363  PMDataManager *PMD = PMS.top();
364 
365  // [1] Create new Loop Pass Manager
366  LPPM = new LPPassManager();
367  LPPM->populateInheritedAnalysis(PMS);
368 
369  // [2] Set up new manager's top level manager
370  PMTopLevelManager *TPM = PMD->getTopLevelManager();
371  TPM->addIndirectPassManager(LPPM);
372 
373  // [3] Assign manager to manage this new manager. This may create
374  // and push new managers into PMS
375  Pass *P = LPPM->getAsPass();
376  TPM->schedulePass(P);
377 
378  // [4] Push new manager into PMS
379  PMS.push(LPPM);
380  }
381 
382  LPPM->add(this);
383 }
384 
385 bool LoopPass::skipLoop(const Loop *L) const {
386  const Function *F = L->getHeader()->getParent();
387  if (!F)
388  return false;
389  // Check the opt bisect limit.
391  if (!Context.getOptPassGate().shouldRunPass(this, *L))
392  return true;
393  // Check for the OptimizeNone attribute.
394  if (F->hasFnAttribute(Attribute::OptimizeNone)) {
395  // FIXME: Report this to dbgs() only once per function.
396  LLVM_DEBUG(dbgs() << "Skipping pass '" << getPassName() << "' in function "
397  << F->getName() << "\n");
398  // FIXME: Delete loop from pass manager's queue?
399  return true;
400  }
401  return false;
402 }
403 
405 INITIALIZE_PASS(LCSSAVerificationPass, "lcssa-verification", "LCSSA Verifier",
406  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
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:68
void dumpLastUses(Pass *P, unsigned Offset) const
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:64
std::error_code remove(const Twine &path, bool IgnoreNonExisting=true)
Remove path.
unsigned getInstructionCount() const
Returns the number of non-debug IR instructions in this function.
Definition: Function.cpp:198
bool isRecursivelyLCSSAForm(DominatorTree &DT, const LoopInfo &LI) const
Return true if this Loop and all inner subloops are in LCSSA form.
Definition: LoopInfo.cpp:184
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:321
void assignPassManager(PMStack &PMS, PassManagerType PMT) override
Assign pass manager to manage this pass.
Definition: LoopPass.cpp:350
F(f)
void yield()
Calls the yield callback (if applicable).
static unsigned InstrCount
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:63
PMTopLevelManager manages LastUser info and collects common APIs used by top level pass managers...
Timer * getPassTimer(Pass *)
Request the timer for this legacy-pass-manager&#39;s pass instance.
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:141
virtual bool shouldRunPass(const Pass *P, const Module &U)
Definition: OptBisect.h:36
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)
This header defines classes/functions to handle pass execution timing information with interfaces for...
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:251
OptPassGate & getOptPassGate() const
Access the object which can disable optional passes and individual optimizations at compile time...
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:323
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:145
virtual bool doInitialization(Loop *L, LPPassManager &LPM)
Definition: LoopPass.h:46
#define P(N)
LLVM Basic Block Representation.
Definition: BasicBlock.h:58
This is an important class for using LLVM in a threaded context.
Definition: LLVMContext.h:69
virtual bool doFinalization()
Definition: LoopPass.h:52
bool shouldEmitInstrCountChangedRemark()
Return true if size-info optimization remark is enabled, false otherwise.
Definition: Module.h:262
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
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:1070
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:385
void deleteSimpleAnalysisValue(Value *V, Loop *L)
deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes that implement simple anal...
Definition: LoopPass.cpp:106
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
BlockVerifier::State From
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.
unsigned initSizeRemarkInfo(Module &M, StringMap< std::pair< unsigned, unsigned >> &FunctionToInstrCount)
Set the initial size of the module if the user has specified that they want remarks for size...
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:143
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:133
StringMap - This is an unconventional map that is specialized for handling keys that are "strings"...
Definition: StringMap.h:220
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:310
void preparePassManager(PMStack &PMS) override
Check if available pass managers are suitable for this pass or not.
Definition: LoopPass.cpp:334
virtual bool runOnLoop(Loop *L, LPPassManager &LPM)=0
LoopT * getParentLoop() const
Definition: LoopInfo.h:101
StringRef getName() const
Definition: LoopInfo.h:583
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:459
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:107
#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
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:566
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:161
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:46
The legacy pass manager&#39;s analysis pass to compute loop information.
Definition: LoopInfo.h:964
void verifyLoop() const
Verify loop structure.
Definition: LoopInfoImpl.h:295
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.
#define LLVM_DEBUG(X)
Definition: Debug.h:123
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:660
void dumpPreservedSet(const Pass *P) const
void emitInstrCountChangedRemark(Pass *P, Module &M, int64_t Delta, unsigned CountBefore, StringMap< std::pair< unsigned, unsigned >> &FunctionToInstrCount, Function *F=nullptr)
Emit a remark signifying that the number of IR instructions in the module changed.