1 //===- LoopPass.cpp - Loop Pass and Loop Pass Manager ---------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.
14 //===----------------------------------------------------------------------===//
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"
27 #define DEBUG_TYPE "loop-pass-manager"
31 /// PrintLoopPass - Print a Function corresponding to a Loop.
33 class PrintLoopPassWrapper : public LoopPass {
38 PrintLoopPassWrapper() : LoopPass(ID) {}
39 PrintLoopPassWrapper(raw_ostream &OS, const std::string &Banner)
40 : LoopPass(ID), P(OS, Banner) {}
42 void getAnalysisUsage(AnalysisUsage &AU) const override {
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;
58 char PrintLoopPassWrapper::ID = 0;
61 //===----------------------------------------------------------------------===//
65 char LPPassManager::ID = 0;
67 LPPassManager::LPPassManager()
68 : FunctionPass(ID), PMDataManager() {
70 CurrentLoop = nullptr;
73 // Inset loop into loop nest (LoopInfo) and loop queue (LQ).
74 Loop &LPPassManager::addLoop(Loop *ParentLoop) {
75 // Create a new loop. LI will take ownership.
78 // Insert into the loop nest and the loop queue.
80 // This is the top level loop.
81 LI->addTopLevelLoop(L);
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.
99 /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
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);
109 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
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);
116 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
117 LoopPass *LP = getContainedPass(Index);
118 LP->deleteAnalysisValue(V, L);
122 /// Invoke deleteAnalysisLoop hook for all passes.
123 void LPPassManager::deleteSimpleAnalysisLoop(Loop *L) {
124 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
125 LoopPass *LP = getContainedPass(Index);
126 LP->deleteAnalysisLoop(L);
131 // Recurse through all subloops and all loops into LQ.
132 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
134 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I)
135 addLoopIntoQueue(*I, LQ);
138 /// Pass Manager itself does not invalidate any analysis info.
139 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();
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.
148 bool LPPassManager::runOnFunction(Function &F) {
149 auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
150 LI = &LIWP.getLoopInfo();
151 bool Changed = false;
153 // Collect inherited analysis from Module level pass manager.
154 populateInheritedAnalysis(TPM->activeStack);
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.
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);
168 if (LQ.empty()) // No loops, skip calling finalizers
172 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end();
175 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
176 LoopPass *P = getContainedPass(Index);
177 Changed |= P->doInitialization(L, *this);
182 while (!LQ.empty()) {
183 bool LoopWasDeleted = false;
184 CurrentLoop = LQ.back();
186 // Run all passes on the current Loop.
187 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
188 LoopPass *P = getContainedPass(Index);
190 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
191 CurrentLoop->getHeader()->getName());
194 initializeAnalysisImpl(P);
197 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
198 TimeRegion PassTimer(getPassTimer(P));
200 Changed |= P->runOnLoop(CurrentLoop, *this);
202 LoopWasDeleted = CurrentLoop->isInvalid();
205 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG,
206 LoopWasDeleted ? "<deleted>"
207 : CurrentLoop->getHeader()->getName());
210 if (LoopWasDeleted) {
211 // Notify passes that the loop is being deleted.
212 deleteSimpleAnalysisLoop(CurrentLoop);
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.
220 TimeRegion PassTimer(getPassTimer(&LIWP));
221 CurrentLoop->verifyLoop();
224 // Then call the regular verifyAnalysis functions.
225 verifyPreservedAnalysis(P);
227 F.getContext().yield();
230 removeNotPreservedAnalysis(P);
231 recordAvailableAnalysis(P);
232 removeDeadPasses(P, LoopWasDeleted ? "<deleted>"
233 : CurrentLoop->getHeader()->getName(),
237 // Do not run other passes on this loop.
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);
251 // Pop the loop from queue after running all passes.
256 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
257 LoopPass *P = getContainedPass(Index);
258 Changed |= P->doFinalization();
264 /// Print passes managed by this manager
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);
275 //===----------------------------------------------------------------------===//
278 Pass *LoopPass::createPrinterPass(raw_ostream &O,
279 const std::string &Banner) const {
280 return new PrintLoopPassWrapper(O, Banner);
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.
289 void LoopPass::preparePassManager(PMStack &PMS) {
291 // Find LPPassManager
292 while (!PMS.empty() &&
293 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
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))
304 /// Assign pass manager to manage this pass.
305 void LoopPass::assignPassManager(PMStack &PMS,
306 PassManagerType PreferredType) {
307 // Find LPPassManager
308 while (!PMS.empty() &&
309 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
313 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
314 LPPM = (LPPassManager*)PMS.top();
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();
320 // [1] Create new Loop Pass Manager
321 LPPM = new LPPassManager();
322 LPPM->populateInheritedAnalysis(PMS);
324 // [2] Set up new manager's top level manager
325 PMTopLevelManager *TPM = PMD->getTopLevelManager();
326 TPM->addIndirectPassManager(LPPM);
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);
333 // [4] Push new manager into PMS
340 bool LoopPass::skipLoop(const Loop *L) const {
341 const Function *F = L->getHeader()->getParent();
344 // Check the opt bisect limit.
345 LLVMContext &Context = F->getContext();
346 if (!Context.getOptBisect().shouldRunPass(this, *L))
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?