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/LoopAnalysisManager.h"
18 #include "llvm/IR/Dominators.h"
19 #include "llvm/IR/IRPrintingPasses.h"
20 #include "llvm/IR/LLVMContext.h"
21 #include "llvm/IR/OptBisect.h"
22 #include "llvm/IR/PassManager.h"
23 #include "llvm/Support/Debug.h"
24 #include "llvm/Support/Timer.h"
25 #include "llvm/Support/raw_ostream.h"
28 #define DEBUG_TYPE "loop-pass-manager"
32 /// PrintLoopPass - Print a Function corresponding to a Loop.
34 class PrintLoopPassWrapper : public LoopPass {
40 PrintLoopPassWrapper() : LoopPass(ID), OS(dbgs()) {}
41 PrintLoopPassWrapper(raw_ostream &OS, const std::string &Banner)
42 : LoopPass(ID), OS(OS), Banner(Banner) {}
44 void getAnalysisUsage(AnalysisUsage &AU) const override {
48 bool runOnLoop(Loop *L, LPPassManager &) override {
49 auto BBI = find_if(L->blocks().begin(), L->blocks().end(),
50 [](BasicBlock *BB) { return BB; });
51 if (BBI != L->blocks().end() &&
52 isFunctionInPrintList((*BBI)->getParent()->getName())) {
53 printLoop(*L, OS, Banner);
58 StringRef getPassName() const override { return "Print Loop IR"; }
61 char PrintLoopPassWrapper::ID = 0;
64 //===----------------------------------------------------------------------===//
68 char LPPassManager::ID = 0;
70 LPPassManager::LPPassManager()
71 : FunctionPass(ID), PMDataManager() {
73 CurrentLoop = nullptr;
76 // Insert loop into loop nest (LoopInfo) and loop queue (LQ).
77 void LPPassManager::addLoop(Loop &L) {
78 if (!L.getParentLoop()) {
79 // This is the top level loop.
84 // Insert L into the loop queue after the parent loop.
85 for (auto I = LQ.begin(), E = LQ.end(); I != E; ++I) {
86 if (*I == L.getParentLoop()) {
87 // deque does not support insert after.
95 /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
97 void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From,
98 BasicBlock *To, Loop *L) {
99 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
100 LoopPass *LP = getContainedPass(Index);
101 LP->cloneBasicBlockAnalysis(From, To, L);
105 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
106 void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
107 if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
108 for (Instruction &I : *BB) {
109 deleteSimpleAnalysisValue(&I, L);
112 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
113 LoopPass *LP = getContainedPass(Index);
114 LP->deleteAnalysisValue(V, L);
118 /// Invoke deleteAnalysisLoop hook for all passes.
119 void LPPassManager::deleteSimpleAnalysisLoop(Loop *L) {
120 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
121 LoopPass *LP = getContainedPass(Index);
122 LP->deleteAnalysisLoop(L);
127 // Recurse through all subloops and all loops into LQ.
128 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
130 for (Loop *I : reverse(*L))
131 addLoopIntoQueue(I, LQ);
134 /// Pass Manager itself does not invalidate any analysis info.
135 void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const {
136 // LPPassManager needs LoopInfo. In the long term LoopInfo class will
137 // become part of LPPassManager.
138 Info.addRequired<LoopInfoWrapperPass>();
139 Info.addRequired<DominatorTreeWrapperPass>();
140 Info.setPreservesAll();
143 /// run - Execute all of the passes scheduled for execution. Keep track of
144 /// whether any of the passes modifies the function, and if so, return true.
145 bool LPPassManager::runOnFunction(Function &F) {
146 auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
147 LI = &LIWP.getLoopInfo();
148 DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
149 bool Changed = false;
151 // Collect inherited analysis from Module level pass manager.
152 populateInheritedAnalysis(TPM->activeStack);
154 // Populate the loop queue in reverse program order. There is no clear need to
155 // process sibling loops in either forward or reverse order. There may be some
156 // advantage in deleting uses in a later loop before optimizing the
157 // definitions in an earlier loop. If we find a clear reason to process in
158 // forward order, then a forward variant of LoopPassManager should be created.
160 // Note that LoopInfo::iterator visits loops in reverse program
161 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
162 // reverses the order a third time by popping from the back.
163 for (Loop *L : reverse(*LI))
164 addLoopIntoQueue(L, LQ);
166 if (LQ.empty()) // No loops, skip calling finalizers
171 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
172 LoopPass *P = getContainedPass(Index);
173 Changed |= P->doInitialization(L, *this);
178 while (!LQ.empty()) {
179 bool LoopWasDeleted = false;
180 CurrentLoop = LQ.back();
182 // Run all passes on the current Loop.
183 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
184 LoopPass *P = getContainedPass(Index);
186 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
187 CurrentLoop->getHeader()->getName());
190 initializeAnalysisImpl(P);
193 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
194 TimeRegion PassTimer(getPassTimer(P));
196 Changed |= P->runOnLoop(CurrentLoop, *this);
198 LoopWasDeleted = CurrentLoop->isInvalid();
201 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG,
202 LoopWasDeleted ? "<deleted>"
203 : CurrentLoop->getHeader()->getName());
206 if (LoopWasDeleted) {
207 // Notify passes that the loop is being deleted.
208 deleteSimpleAnalysisLoop(CurrentLoop);
210 // Manually check that this loop is still healthy. This is done
211 // instead of relying on LoopInfo::verifyLoop since LoopInfo
212 // is a function pass and it's really expensive to verify every
213 // loop in the function every time. That level of checking can be
214 // enabled with the -verify-loop-info option.
216 TimeRegion PassTimer(getPassTimer(&LIWP));
217 CurrentLoop->verifyLoop();
219 // Here we apply same reasoning as in the above case. Only difference
220 // is that LPPassManager might run passes which do not require LCSSA
221 // form (LoopPassPrinter for example). We should skip verification for
223 if (mustPreserveAnalysisID(LCSSAVerificationPass::ID))
224 CurrentLoop->isRecursivelyLCSSAForm(*DT, *LI);
226 // Then call the regular verifyAnalysis functions.
227 verifyPreservedAnalysis(P);
229 F.getContext().yield();
232 removeNotPreservedAnalysis(P);
233 recordAvailableAnalysis(P);
234 removeDeadPasses(P, LoopWasDeleted ? "<deleted>"
235 : CurrentLoop->getHeader()->getName(),
239 // Do not run other passes on this loop.
243 // If the loop was deleted, release all the loop passes. This frees up
244 // some memory, and avoids trouble with the pass manager trying to call
245 // verifyAnalysis on them.
246 if (LoopWasDeleted) {
247 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
248 Pass *P = getContainedPass(Index);
249 freePass(P, "<deleted>", ON_LOOP_MSG);
253 // Pop the loop from queue after running all passes.
258 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
259 LoopPass *P = getContainedPass(Index);
260 Changed |= P->doFinalization();
266 /// Print passes managed by this manager
267 void LPPassManager::dumpPassStructure(unsigned Offset) {
268 errs().indent(Offset*2) << "Loop Pass Manager\n";
269 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
270 Pass *P = getContainedPass(Index);
271 P->dumpPassStructure(Offset + 1);
272 dumpLastUses(P, Offset+1);
277 //===----------------------------------------------------------------------===//
280 Pass *LoopPass::createPrinterPass(raw_ostream &O,
281 const std::string &Banner) const {
282 return new PrintLoopPassWrapper(O, Banner);
285 // Check if this pass is suitable for the current LPPassManager, if
286 // available. This pass P is not suitable for a LPPassManager if P
287 // is not preserving higher level analysis info used by other
288 // LPPassManager passes. In such case, pop LPPassManager from the
289 // stack. This will force assignPassManager() to create new
290 // LPPassManger as expected.
291 void LoopPass::preparePassManager(PMStack &PMS) {
293 // Find LPPassManager
294 while (!PMS.empty() &&
295 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
298 // If this pass is destroying high level information that is used
299 // by other passes that are managed by LPM then do not insert
300 // this pass in current LPM. Use new LPPassManager.
301 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
302 !PMS.top()->preserveHigherLevelAnalysis(this))
306 /// Assign pass manager to manage this pass.
307 void LoopPass::assignPassManager(PMStack &PMS,
308 PassManagerType PreferredType) {
309 // Find LPPassManager
310 while (!PMS.empty() &&
311 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
315 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
316 LPPM = (LPPassManager*)PMS.top();
318 // Create new Loop Pass Manager if it does not exist.
319 assert (!PMS.empty() && "Unable to create Loop Pass Manager");
320 PMDataManager *PMD = PMS.top();
322 // [1] Create new Loop Pass Manager
323 LPPM = new LPPassManager();
324 LPPM->populateInheritedAnalysis(PMS);
326 // [2] Set up new manager's top level manager
327 PMTopLevelManager *TPM = PMD->getTopLevelManager();
328 TPM->addIndirectPassManager(LPPM);
330 // [3] Assign manager to manage this new manager. This may create
331 // and push new managers into PMS
332 Pass *P = LPPM->getAsPass();
333 TPM->schedulePass(P);
335 // [4] Push new manager into PMS
342 bool LoopPass::skipLoop(const Loop *L) const {
343 const Function *F = L->getHeader()->getParent();
346 // Check the opt bisect limit.
347 LLVMContext &Context = F->getContext();
348 if (!Context.getOptBisect().shouldRunPass(this, *L))
350 // Check for the OptimizeNone attribute.
351 if (F->hasFnAttribute(Attribute::OptimizeNone)) {
352 // FIXME: Report this to dbgs() only once per function.
353 DEBUG(dbgs() << "Skipping pass '" << getPassName()
354 << "' in function " << F->getName() << "\n");
355 // FIXME: Delete loop from pass manager's queue?
361 char LCSSAVerificationPass::ID = 0;
362 INITIALIZE_PASS(LCSSAVerificationPass, "lcssa-verification", "LCSSA Verifier",