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() {
63 CurrentLoop = nullptr;
66 /// Delete loop from the loop queue and loop hierarchy (LoopInfo).
67 void LPPassManager::deleteLoopFromQueue(Loop *L) {
71 // Notify passes that the loop is being deleted.
72 deleteSimpleAnalysisLoop(L);
74 // If L is current loop then skip rest of the passes and let
75 // runOnFunction remove L from LQ. Otherwise, remove L from LQ now
76 // and continue applying other passes on CurrentLoop.
85 for (std::deque<Loop *>::iterator I = LQ.begin(),
86 E = LQ.end(); I != E; ++I) {
94 // Inset loop into loop nest (LoopInfo) and loop queue (LQ).
95 Loop &LPPassManager::addLoop(Loop *ParentLoop) {
96 // Create a new loop. LI will take ownership.
99 // Insert into the loop nest and the loop queue.
101 // This is the top level loop.
102 LI->addTopLevelLoop(L);
107 ParentLoop->addChildLoop(L);
108 // Insert L into the loop queue after the parent loop.
109 for (auto I = LQ.begin(), E = LQ.end(); I != E; ++I) {
110 if (*I == L->getParentLoop()) {
111 // deque does not support insert after.
120 /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
122 void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From,
123 BasicBlock *To, Loop *L) {
124 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
125 LoopPass *LP = getContainedPass(Index);
126 LP->cloneBasicBlockAnalysis(From, To, L);
130 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
131 void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
132 if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
133 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;
135 Instruction &I = *BI;
136 deleteSimpleAnalysisValue(&I, L);
139 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
140 LoopPass *LP = getContainedPass(Index);
141 LP->deleteAnalysisValue(V, L);
145 /// Invoke deleteAnalysisLoop hook for all passes.
146 void LPPassManager::deleteSimpleAnalysisLoop(Loop *L) {
147 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
148 LoopPass *LP = getContainedPass(Index);
149 LP->deleteAnalysisLoop(L);
154 // Recurse through all subloops and all loops into LQ.
155 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
157 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I)
158 addLoopIntoQueue(*I, LQ);
161 /// Pass Manager itself does not invalidate any analysis info.
162 void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const {
163 // LPPassManager needs LoopInfo. In the long term LoopInfo class will
164 // become part of LPPassManager.
165 Info.addRequired<LoopInfoWrapperPass>();
166 Info.setPreservesAll();
169 /// run - Execute all of the passes scheduled for execution. Keep track of
170 /// whether any of the passes modifies the function, and if so, return true.
171 bool LPPassManager::runOnFunction(Function &F) {
172 auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
173 LI = &LIWP.getLoopInfo();
174 bool Changed = false;
176 // Collect inherited analysis from Module level pass manager.
177 populateInheritedAnalysis(TPM->activeStack);
179 // Populate the loop queue in reverse program order. There is no clear need to
180 // process sibling loops in either forward or reverse order. There may be some
181 // advantage in deleting uses in a later loop before optimizing the
182 // definitions in an earlier loop. If we find a clear reason to process in
183 // forward order, then a forward variant of LoopPassManager should be created.
185 // Note that LoopInfo::iterator visits loops in reverse program
186 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
187 // reverses the order a third time by popping from the back.
188 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
189 addLoopIntoQueue(*I, LQ);
191 if (LQ.empty()) // No loops, skip calling finalizers
195 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end();
198 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
199 LoopPass *P = getContainedPass(Index);
200 Changed |= P->doInitialization(L, *this);
205 while (!LQ.empty()) {
207 CurrentLoop = LQ.back();
208 skipThisLoop = false;
210 // Run all passes on the current Loop.
211 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
212 LoopPass *P = getContainedPass(Index);
214 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
215 CurrentLoop->getHeader()->getName());
218 initializeAnalysisImpl(P);
221 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
222 TimeRegion PassTimer(getPassTimer(P));
224 Changed |= P->runOnLoop(CurrentLoop, *this);
228 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG,
229 skipThisLoop ? "<deleted>" :
230 CurrentLoop->getHeader()->getName());
234 // Manually check that this loop is still healthy. This is done
235 // instead of relying on LoopInfo::verifyLoop since LoopInfo
236 // is a function pass and it's really expensive to verify every
237 // loop in the function every time. That level of checking can be
238 // enabled with the -verify-loop-info option.
240 TimeRegion PassTimer(getPassTimer(&LIWP));
241 CurrentLoop->verifyLoop();
244 // Then call the regular verifyAnalysis functions.
245 verifyPreservedAnalysis(P);
247 F.getContext().yield();
250 removeNotPreservedAnalysis(P);
251 recordAvailableAnalysis(P);
253 skipThisLoop ? "<deleted>" :
254 CurrentLoop->getHeader()->getName(),
258 // Do not run other passes on this loop.
262 // If the loop was deleted, release all the loop passes. This frees up
263 // some memory, and avoids trouble with the pass manager trying to call
264 // verifyAnalysis on them.
266 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
267 Pass *P = getContainedPass(Index);
268 freePass(P, "<deleted>", ON_LOOP_MSG);
271 // Pop the loop from queue after running all passes.
276 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
277 LoopPass *P = getContainedPass(Index);
278 Changed |= P->doFinalization();
284 /// Print passes managed by this manager
285 void LPPassManager::dumpPassStructure(unsigned Offset) {
286 errs().indent(Offset*2) << "Loop Pass Manager\n";
287 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
288 Pass *P = getContainedPass(Index);
289 P->dumpPassStructure(Offset + 1);
290 dumpLastUses(P, Offset+1);
295 //===----------------------------------------------------------------------===//
298 Pass *LoopPass::createPrinterPass(raw_ostream &O,
299 const std::string &Banner) const {
300 return new PrintLoopPassWrapper(O, Banner);
303 // Check if this pass is suitable for the current LPPassManager, if
304 // available. This pass P is not suitable for a LPPassManager if P
305 // is not preserving higher level analysis info used by other
306 // LPPassManager passes. In such case, pop LPPassManager from the
307 // stack. This will force assignPassManager() to create new
308 // LPPassManger as expected.
309 void LoopPass::preparePassManager(PMStack &PMS) {
311 // Find LPPassManager
312 while (!PMS.empty() &&
313 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
316 // If this pass is destroying high level information that is used
317 // by other passes that are managed by LPM then do not insert
318 // this pass in current LPM. Use new LPPassManager.
319 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
320 !PMS.top()->preserveHigherLevelAnalysis(this))
324 /// Assign pass manager to manage this pass.
325 void LoopPass::assignPassManager(PMStack &PMS,
326 PassManagerType PreferredType) {
327 // Find LPPassManager
328 while (!PMS.empty() &&
329 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
333 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
334 LPPM = (LPPassManager*)PMS.top();
336 // Create new Loop Pass Manager if it does not exist.
337 assert (!PMS.empty() && "Unable to create Loop Pass Manager");
338 PMDataManager *PMD = PMS.top();
340 // [1] Create new Loop Pass Manager
341 LPPM = new LPPassManager();
342 LPPM->populateInheritedAnalysis(PMS);
344 // [2] Set up new manager's top level manager
345 PMTopLevelManager *TPM = PMD->getTopLevelManager();
346 TPM->addIndirectPassManager(LPPM);
348 // [3] Assign manager to manage this new manager. This may create
349 // and push new managers into PMS
350 Pass *P = LPPM->getAsPass();
351 TPM->schedulePass(P);
353 // [4] Push new manager into PMS
360 // Containing function has Attribute::OptimizeNone and transformation
361 // passes should skip it.
362 bool LoopPass::skipOptnoneFunction(const Loop *L) const {
363 const Function *F = L->getHeader()->getParent();
364 if (F && F->hasFnAttribute(Attribute::OptimizeNone)) {
365 // FIXME: Report this to dbgs() only once per function.
366 DEBUG(dbgs() << "Skipping pass '" << getPassName()
367 << "' in function " << F->getName() << "\n");
368 // FIXME: Delete loop from pass manager's queue?