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/Analysis/LoopPassManager.h"
18 #include "llvm/IR/IRPrintingPasses.h"
19 #include "llvm/IR/LLVMContext.h"
20 #include "llvm/IR/OptBisect.h"
21 #include "llvm/IR/PassManager.h"
22 #include "llvm/Support/Debug.h"
23 #include "llvm/Support/Timer.h"
24 #include "llvm/Support/raw_ostream.h"
25 using namespace llvm;
26
27 #define DEBUG_TYPE "loop-pass-manager"
28
29 namespace {
30
31 /// PrintLoopPass - Print a Function corresponding to a Loop.
32 ///
33 class PrintLoopPassWrapper : public LoopPass {
34 PrintLoopPass P;
35
36 public:
37 static char ID;
PrintLoopPassWrapper()38 PrintLoopPassWrapper() : LoopPass(ID) {}
PrintLoopPassWrapper(raw_ostream & OS,const std::string & Banner)39 PrintLoopPassWrapper(raw_ostream &OS, const std::string &Banner)
40 : LoopPass(ID), P(OS, Banner) {}
41
getAnalysisUsage(AnalysisUsage & AU) const42 void getAnalysisUsage(AnalysisUsage &AU) const override {
43 AU.setPreservesAll();
44 }
45
runOnLoop(Loop * L,LPPassManager &)46 bool runOnLoop(Loop *L, LPPassManager &) override {
47 auto BBI = find_if(L->blocks().begin(), L->blocks().end(),
48 [](BasicBlock *BB) { return BB; });
49 if (BBI != L->blocks().end() &&
50 isFunctionInPrintList((*BBI)->getParent()->getName())) {
51 AnalysisManager<Loop> DummyLAM;
52 P.run(*L, DummyLAM);
53 }
54 return false;
55 }
56 };
57
58 char PrintLoopPassWrapper::ID = 0;
59 }
60
61 //===----------------------------------------------------------------------===//
62 // LPPassManager
63 //
64
65 char LPPassManager::ID = 0;
66
LPPassManager()67 LPPassManager::LPPassManager()
68 : FunctionPass(ID), PMDataManager() {
69 LI = nullptr;
70 CurrentLoop = nullptr;
71 }
72
73 // Inset loop into loop nest (LoopInfo) and loop queue (LQ).
addLoop(Loop * ParentLoop)74 Loop &LPPassManager::addLoop(Loop *ParentLoop) {
75 // Create a new loop. LI will take ownership.
76 Loop *L = new Loop();
77
78 // Insert into the loop nest and the loop queue.
79 if (!ParentLoop) {
80 // This is the top level loop.
81 LI->addTopLevelLoop(L);
82 LQ.push_front(L);
83 return *L;
84 }
85
86 ParentLoop->addChildLoop(L);
87 // Insert L into the loop queue after the parent loop.
88 for (auto I = LQ.begin(), E = LQ.end(); I != E; ++I) {
89 if (*I == L->getParentLoop()) {
90 // deque does not support insert after.
91 ++I;
92 LQ.insert(I, 1, L);
93 break;
94 }
95 }
96 return *L;
97 }
98
99 /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
100 /// all loop passes.
cloneBasicBlockSimpleAnalysis(BasicBlock * From,BasicBlock * To,Loop * L)101 void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From,
102 BasicBlock *To, Loop *L) {
103 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
104 LoopPass *LP = getContainedPass(Index);
105 LP->cloneBasicBlockAnalysis(From, To, L);
106 }
107 }
108
109 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
deleteSimpleAnalysisValue(Value * V,Loop * L)110 void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
111 if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
112 for (Instruction &I : *BB) {
113 deleteSimpleAnalysisValue(&I, L);
114 }
115 }
116 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
117 LoopPass *LP = getContainedPass(Index);
118 LP->deleteAnalysisValue(V, L);
119 }
120 }
121
122 /// Invoke deleteAnalysisLoop hook for all passes.
deleteSimpleAnalysisLoop(Loop * L)123 void LPPassManager::deleteSimpleAnalysisLoop(Loop *L) {
124 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
125 LoopPass *LP = getContainedPass(Index);
126 LP->deleteAnalysisLoop(L);
127 }
128 }
129
130
131 // Recurse through all subloops and all loops into LQ.
addLoopIntoQueue(Loop * L,std::deque<Loop * > & LQ)132 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
133 LQ.push_back(L);
134 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I)
135 addLoopIntoQueue(*I, LQ);
136 }
137
138 /// Pass Manager itself does not invalidate any analysis info.
getAnalysisUsage(AnalysisUsage & Info) const139 void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const {
140 // LPPassManager needs LoopInfo. In the long term LoopInfo class will
141 // become part of LPPassManager.
142 Info.addRequired<LoopInfoWrapperPass>();
143 Info.setPreservesAll();
144 }
145
146 /// run - Execute all of the passes scheduled for execution. Keep track of
147 /// whether any of the passes modifies the function, and if so, return true.
runOnFunction(Function & F)148 bool LPPassManager::runOnFunction(Function &F) {
149 auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
150 LI = &LIWP.getLoopInfo();
151 bool Changed = false;
152
153 // Collect inherited analysis from Module level pass manager.
154 populateInheritedAnalysis(TPM->activeStack);
155
156 // Populate the loop queue in reverse program order. There is no clear need to
157 // process sibling loops in either forward or reverse order. There may be some
158 // advantage in deleting uses in a later loop before optimizing the
159 // definitions in an earlier loop. If we find a clear reason to process in
160 // forward order, then a forward variant of LoopPassManager should be created.
161 //
162 // Note that LoopInfo::iterator visits loops in reverse program
163 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
164 // reverses the order a third time by popping from the back.
165 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
166 addLoopIntoQueue(*I, LQ);
167
168 if (LQ.empty()) // No loops, skip calling finalizers
169 return false;
170
171 // Initialization
172 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end();
173 I != E; ++I) {
174 Loop *L = *I;
175 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
176 LoopPass *P = getContainedPass(Index);
177 Changed |= P->doInitialization(L, *this);
178 }
179 }
180
181 // Walk Loops
182 while (!LQ.empty()) {
183 bool LoopWasDeleted = false;
184 CurrentLoop = LQ.back();
185
186 // Run all passes on the current Loop.
187 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
188 LoopPass *P = getContainedPass(Index);
189
190 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
191 CurrentLoop->getHeader()->getName());
192 dumpRequiredSet(P);
193
194 initializeAnalysisImpl(P);
195
196 {
197 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
198 TimeRegion PassTimer(getPassTimer(P));
199
200 Changed |= P->runOnLoop(CurrentLoop, *this);
201 }
202 LoopWasDeleted = CurrentLoop->isInvalid();
203
204 if (Changed)
205 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG,
206 LoopWasDeleted ? "<deleted>"
207 : CurrentLoop->getHeader()->getName());
208 dumpPreservedSet(P);
209
210 if (LoopWasDeleted) {
211 // Notify passes that the loop is being deleted.
212 deleteSimpleAnalysisLoop(CurrentLoop);
213 } else {
214 // Manually check that this loop is still healthy. This is done
215 // instead of relying on LoopInfo::verifyLoop since LoopInfo
216 // is a function pass and it's really expensive to verify every
217 // loop in the function every time. That level of checking can be
218 // enabled with the -verify-loop-info option.
219 {
220 TimeRegion PassTimer(getPassTimer(&LIWP));
221 CurrentLoop->verifyLoop();
222 }
223
224 // Then call the regular verifyAnalysis functions.
225 verifyPreservedAnalysis(P);
226
227 F.getContext().yield();
228 }
229
230 removeNotPreservedAnalysis(P);
231 recordAvailableAnalysis(P);
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
dumpPassStructure(unsigned Offset)265 void LPPassManager::dumpPassStructure(unsigned Offset) {
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
createPrinterPass(raw_ostream & O,const std::string & Banner) const278 Pass *LoopPass::createPrinterPass(raw_ostream &O,
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.
preparePassManager(PMStack & PMS)289 void LoopPass::preparePassManager(PMStack &PMS) {
290
291 // Find LPPassManager
292 while (!PMS.empty() &&
293 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
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.
assignPassManager(PMStack & PMS,PassManagerType PreferredType)305 void LoopPass::assignPassManager(PMStack &PMS,
306 PassManagerType PreferredType) {
307 // Find LPPassManager
308 while (!PMS.empty() &&
309 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
310 PMS.pop();
311
312 LPPassManager *LPPM;
313 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
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
skipLoop(const Loop * L) const340 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.
345 LLVMContext &Context = F->getContext();
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