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 // Inset loop into loop nest (LoopInfo) and loop queue (LQ).
66 Loop &LPPassManager::addLoop(Loop *ParentLoop) {
67 // Create a new loop. LI will take ownership.
70 // Insert into the loop nest and the loop queue.
72 // This is the top level loop.
73 LI->addTopLevelLoop(L);
78 ParentLoop->addChildLoop(L);
79 // Insert L into the loop queue after the parent loop.
80 for (auto I = LQ.begin(), E = LQ.end(); I != E; ++I) {
81 if (*I == L->getParentLoop()) {
82 // deque does not support insert after.
91 /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
93 void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From,
94 BasicBlock *To, Loop *L) {
95 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
96 LoopPass *LP = getContainedPass(Index);
97 LP->cloneBasicBlockAnalysis(From, To, L);
101 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
102 void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
103 if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
104 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;
106 Instruction &I = *BI;
107 deleteSimpleAnalysisValue(&I, L);
110 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
111 LoopPass *LP = getContainedPass(Index);
112 LP->deleteAnalysisValue(V, L);
116 /// Invoke deleteAnalysisLoop hook for all passes.
117 void LPPassManager::deleteSimpleAnalysisLoop(Loop *L) {
118 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
119 LoopPass *LP = getContainedPass(Index);
120 LP->deleteAnalysisLoop(L);
125 // Recurse through all subloops and all loops into LQ.
126 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
128 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I)
129 addLoopIntoQueue(*I, LQ);
132 /// Pass Manager itself does not invalidate any analysis info.
133 void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const {
134 // LPPassManager needs LoopInfo. In the long term LoopInfo class will
135 // become part of LPPassManager.
136 Info.addRequired<LoopInfoWrapperPass>();
137 Info.setPreservesAll();
140 /// run - Execute all of the passes scheduled for execution. Keep track of
141 /// whether any of the passes modifies the function, and if so, return true.
142 bool LPPassManager::runOnFunction(Function &F) {
143 auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
144 LI = &LIWP.getLoopInfo();
145 bool Changed = false;
147 // Collect inherited analysis from Module level pass manager.
148 populateInheritedAnalysis(TPM->activeStack);
150 // Populate the loop queue in reverse program order. There is no clear need to
151 // process sibling loops in either forward or reverse order. There may be some
152 // advantage in deleting uses in a later loop before optimizing the
153 // definitions in an earlier loop. If we find a clear reason to process in
154 // forward order, then a forward variant of LoopPassManager should be created.
156 // Note that LoopInfo::iterator visits loops in reverse program
157 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
158 // reverses the order a third time by popping from the back.
159 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
160 addLoopIntoQueue(*I, LQ);
162 if (LQ.empty()) // No loops, skip calling finalizers
166 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end();
169 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
170 LoopPass *P = getContainedPass(Index);
171 Changed |= P->doInitialization(L, *this);
176 while (!LQ.empty()) {
178 CurrentLoop = LQ.back();
179 // Run all passes on the current Loop.
180 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
181 LoopPass *P = getContainedPass(Index);
183 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
184 CurrentLoop->getHeader()->getName());
187 initializeAnalysisImpl(P);
190 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
191 TimeRegion PassTimer(getPassTimer(P));
193 Changed |= P->runOnLoop(CurrentLoop, *this);
197 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG,
198 CurrentLoop->isUnloop()
200 : CurrentLoop->getHeader()->getName());
203 if (CurrentLoop->isUnloop()) {
204 // Notify passes that the loop is being deleted.
205 deleteSimpleAnalysisLoop(CurrentLoop);
207 // Manually check that this loop is still healthy. This is done
208 // instead of relying on LoopInfo::verifyLoop since LoopInfo
209 // is a function pass and it's really expensive to verify every
210 // loop in the function every time. That level of checking can be
211 // enabled with the -verify-loop-info option.
213 TimeRegion PassTimer(getPassTimer(&LIWP));
214 CurrentLoop->verifyLoop();
217 // Then call the regular verifyAnalysis functions.
218 verifyPreservedAnalysis(P);
220 F.getContext().yield();
223 removeNotPreservedAnalysis(P);
224 recordAvailableAnalysis(P);
225 removeDeadPasses(P, CurrentLoop->isUnloop()
227 : CurrentLoop->getHeader()->getName(),
230 if (CurrentLoop->isUnloop())
231 // Do not run other passes on this loop.
235 // If the loop was deleted, release all the loop passes. This frees up
236 // some memory, and avoids trouble with the pass manager trying to call
237 // verifyAnalysis on them.
238 if (CurrentLoop->isUnloop()) {
239 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
240 Pass *P = getContainedPass(Index);
241 freePass(P, "<deleted>", ON_LOOP_MSG);
246 // Pop the loop from queue after running all passes.
251 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
252 LoopPass *P = getContainedPass(Index);
253 Changed |= P->doFinalization();
259 /// Print passes managed by this manager
260 void LPPassManager::dumpPassStructure(unsigned Offset) {
261 errs().indent(Offset*2) << "Loop Pass Manager\n";
262 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
263 Pass *P = getContainedPass(Index);
264 P->dumpPassStructure(Offset + 1);
265 dumpLastUses(P, Offset+1);
270 //===----------------------------------------------------------------------===//
273 Pass *LoopPass::createPrinterPass(raw_ostream &O,
274 const std::string &Banner) const {
275 return new PrintLoopPassWrapper(O, Banner);
278 // Check if this pass is suitable for the current LPPassManager, if
279 // available. This pass P is not suitable for a LPPassManager if P
280 // is not preserving higher level analysis info used by other
281 // LPPassManager passes. In such case, pop LPPassManager from the
282 // stack. This will force assignPassManager() to create new
283 // LPPassManger as expected.
284 void LoopPass::preparePassManager(PMStack &PMS) {
286 // Find LPPassManager
287 while (!PMS.empty() &&
288 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
291 // If this pass is destroying high level information that is used
292 // by other passes that are managed by LPM then do not insert
293 // this pass in current LPM. Use new LPPassManager.
294 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
295 !PMS.top()->preserveHigherLevelAnalysis(this))
299 /// Assign pass manager to manage this pass.
300 void LoopPass::assignPassManager(PMStack &PMS,
301 PassManagerType PreferredType) {
302 // Find LPPassManager
303 while (!PMS.empty() &&
304 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
308 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
309 LPPM = (LPPassManager*)PMS.top();
311 // Create new Loop Pass Manager if it does not exist.
312 assert (!PMS.empty() && "Unable to create Loop Pass Manager");
313 PMDataManager *PMD = PMS.top();
315 // [1] Create new Loop Pass Manager
316 LPPM = new LPPassManager();
317 LPPM->populateInheritedAnalysis(PMS);
319 // [2] Set up new manager's top level manager
320 PMTopLevelManager *TPM = PMD->getTopLevelManager();
321 TPM->addIndirectPassManager(LPPM);
323 // [3] Assign manager to manage this new manager. This may create
324 // and push new managers into PMS
325 Pass *P = LPPM->getAsPass();
326 TPM->schedulePass(P);
328 // [4] Push new manager into PMS
335 // Containing function has Attribute::OptimizeNone and transformation
336 // passes should skip it.
337 bool LoopPass::skipOptnoneFunction(const Loop *L) const {
338 const Function *F = L->getHeader()->getParent();
339 if (F && F->hasFnAttribute(Attribute::OptimizeNone)) {
340 // FIXME: Report this to dbgs() only once per function.
341 DEBUG(dbgs() << "Skipping pass '" << getPassName()
342 << "' in function " << F->getName() << "\n");
343 // FIXME: Delete loop from pass manager's queue?