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/IR/IRPrintingPasses.h"
18 #include "llvm/IR/LLVMContext.h"
19 #include "llvm/IR/PassManager.h"
20 #include "llvm/Support/Debug.h"
21 #include "llvm/Support/Timer.h"
22 #include "llvm/Support/raw_ostream.h"
25 #define DEBUG_TYPE "loop-pass-manager"
29 /// PrintLoopPass - Print a Function corresponding to a Loop.
31 class PrintLoopPassWrapper : public LoopPass {
36 PrintLoopPassWrapper() : LoopPass(ID) {}
37 PrintLoopPassWrapper(raw_ostream &OS, const std::string &Banner)
38 : LoopPass(ID), P(OS, Banner) {}
40 void getAnalysisUsage(AnalysisUsage &AU) const override {
44 bool runOnLoop(Loop *L, LPPassManager &) override {
50 char PrintLoopPassWrapper::ID = 0;
53 //===----------------------------------------------------------------------===//
57 char LPPassManager::ID = 0;
59 LPPassManager::LPPassManager()
60 : FunctionPass(ID), PMDataManager() {
62 CurrentLoop = nullptr;
65 /// Delete loop from the loop queue and loop hierarchy (LoopInfo).
66 void LPPassManager::deleteLoopFromQueue(Loop *L) {
67 assert(CurrentLoop == L && "deleting a loop that is not being operated on");
71 // Inset loop into loop nest (LoopInfo) and loop queue (LQ).
72 Loop &LPPassManager::addLoop(Loop *ParentLoop) {
73 // Create a new loop. LI will take ownership.
76 // Insert into the loop nest and the loop queue.
78 // This is the top level loop.
79 LI->addTopLevelLoop(L);
84 ParentLoop->addChildLoop(L);
85 // Insert L into the loop queue after the parent loop.
86 for (auto I = LQ.begin(), E = LQ.end(); I != E; ++I) {
87 if (*I == L->getParentLoop()) {
88 // deque does not support insert after.
97 /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
99 void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From,
100 BasicBlock *To, Loop *L) {
101 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
102 LoopPass *LP = getContainedPass(Index);
103 LP->cloneBasicBlockAnalysis(From, To, L);
107 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
108 void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
109 if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
110 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;
112 Instruction &I = *BI;
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()) {
184 CurrentLoop = LQ.back();
185 // Run all passes on the current Loop.
186 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
187 LoopPass *P = getContainedPass(Index);
189 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
190 CurrentLoop->getHeader()->getName());
193 initializeAnalysisImpl(P);
196 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
197 TimeRegion PassTimer(getPassTimer(P));
199 Changed |= P->runOnLoop(CurrentLoop, *this);
203 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG,
204 CurrentLoop->isUnloop()
206 : CurrentLoop->getHeader()->getName());
209 if (CurrentLoop->isUnloop()) {
210 // Notify passes that the loop is being deleted.
211 deleteSimpleAnalysisLoop(CurrentLoop);
213 // Manually check that this loop is still healthy. This is done
214 // instead of relying on LoopInfo::verifyLoop since LoopInfo
215 // is a function pass and it's really expensive to verify every
216 // loop in the function every time. That level of checking can be
217 // enabled with the -verify-loop-info option.
219 TimeRegion PassTimer(getPassTimer(&LIWP));
220 CurrentLoop->verifyLoop();
223 // Then call the regular verifyAnalysis functions.
224 verifyPreservedAnalysis(P);
226 F.getContext().yield();
229 removeNotPreservedAnalysis(P);
230 recordAvailableAnalysis(P);
231 removeDeadPasses(P, CurrentLoop->isUnloop()
233 : CurrentLoop->getHeader()->getName(),
236 if (CurrentLoop->isUnloop())
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 (CurrentLoop->isUnloop()) {
245 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
246 Pass *P = getContainedPass(Index);
247 freePass(P, "<deleted>", ON_LOOP_MSG);
252 // Pop the loop from queue after running all passes.
257 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
258 LoopPass *P = getContainedPass(Index);
259 Changed |= P->doFinalization();
265 /// Print passes managed by this manager
266 void LPPassManager::dumpPassStructure(unsigned Offset) {
267 errs().indent(Offset*2) << "Loop Pass Manager\n";
268 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
269 Pass *P = getContainedPass(Index);
270 P->dumpPassStructure(Offset + 1);
271 dumpLastUses(P, Offset+1);
276 //===----------------------------------------------------------------------===//
279 Pass *LoopPass::createPrinterPass(raw_ostream &O,
280 const std::string &Banner) const {
281 return new PrintLoopPassWrapper(O, Banner);
284 // Check if this pass is suitable for the current LPPassManager, if
285 // available. This pass P is not suitable for a LPPassManager if P
286 // is not preserving higher level analysis info used by other
287 // LPPassManager passes. In such case, pop LPPassManager from the
288 // stack. This will force assignPassManager() to create new
289 // LPPassManger as expected.
290 void LoopPass::preparePassManager(PMStack &PMS) {
292 // Find LPPassManager
293 while (!PMS.empty() &&
294 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
297 // If this pass is destroying high level information that is used
298 // by other passes that are managed by LPM then do not insert
299 // this pass in current LPM. Use new LPPassManager.
300 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
301 !PMS.top()->preserveHigherLevelAnalysis(this))
305 /// Assign pass manager to manage this pass.
306 void LoopPass::assignPassManager(PMStack &PMS,
307 PassManagerType PreferredType) {
308 // Find LPPassManager
309 while (!PMS.empty() &&
310 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
314 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
315 LPPM = (LPPassManager*)PMS.top();
317 // Create new Loop Pass Manager if it does not exist.
318 assert (!PMS.empty() && "Unable to create Loop Pass Manager");
319 PMDataManager *PMD = PMS.top();
321 // [1] Create new Loop Pass Manager
322 LPPM = new LPPassManager();
323 LPPM->populateInheritedAnalysis(PMS);
325 // [2] Set up new manager's top level manager
326 PMTopLevelManager *TPM = PMD->getTopLevelManager();
327 TPM->addIndirectPassManager(LPPM);
329 // [3] Assign manager to manage this new manager. This may create
330 // and push new managers into PMS
331 Pass *P = LPPM->getAsPass();
332 TPM->schedulePass(P);
334 // [4] Push new manager into PMS
341 // Containing function has Attribute::OptimizeNone and transformation
342 // passes should skip it.
343 bool LoopPass::skipOptnoneFunction(const Loop *L) const {
344 const Function *F = L->getHeader()->getParent();
345 if (F && F->hasFnAttribute(Attribute::OptimizeNone)) {
346 // FIXME: Report this to dbgs() only once per function.
347 DEBUG(dbgs() << "Skipping pass '" << getPassName()
348 << "' in function " << F->getName() << "\n");
349 // FIXME: Delete loop from pass manager's queue?