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/Support/Debug.h"
20 #include "llvm/Support/Timer.h"
23 #define DEBUG_TYPE "loop-pass-manager"
27 /// PrintLoopPass - Print a Function corresponding to a Loop.
29 class PrintLoopPass : public LoopPass {
32 raw_ostream &Out; // raw_ostream to print on.
36 PrintLoopPass(const std::string &B, raw_ostream &o)
37 : LoopPass(ID), Banner(B), Out(o) {}
39 void getAnalysisUsage(AnalysisUsage &AU) const override {
43 bool runOnLoop(Loop *L, LPPassManager &) override {
45 for (Loop::block_iterator b = L->block_begin(), be = L->block_end();
51 Out << "Printing <null> block";
57 char PrintLoopPass::ID = 0;
60 //===----------------------------------------------------------------------===//
64 char LPPassManager::ID = 0;
66 LPPassManager::LPPassManager()
67 : FunctionPass(ID), PMDataManager() {
71 CurrentLoop = nullptr;
74 /// Delete loop from the loop queue and loop hierarchy (LoopInfo).
75 void LPPassManager::deleteLoopFromQueue(Loop *L) {
79 // Notify passes that the loop is being deleted.
80 deleteSimpleAnalysisLoop(L);
82 // If L is current loop then skip rest of the passes and let
83 // runOnFunction remove L from LQ. Otherwise, remove L from LQ now
84 // and continue applying other passes on CurrentLoop.
93 for (std::deque<Loop *>::iterator I = LQ.begin(),
94 E = LQ.end(); I != E; ++I) {
102 // Inset loop into loop nest (LoopInfo) and loop queue (LQ).
103 void LPPassManager::insertLoop(Loop *L, Loop *ParentLoop) {
105 assert (CurrentLoop != L && "Cannot insert CurrentLoop");
107 // Insert into loop nest
109 ParentLoop->addChildLoop(L);
111 LI->addTopLevelLoop(L);
113 insertLoopIntoQueue(L);
116 void LPPassManager::insertLoopIntoQueue(Loop *L) {
117 // Insert L into loop queue
118 if (L == CurrentLoop)
120 else if (!L->getParentLoop())
121 // This is top level loop.
124 // Insert L after the parent loop.
125 for (std::deque<Loop *>::iterator I = LQ.begin(),
126 E = LQ.end(); I != E; ++I) {
127 if (*I == L->getParentLoop()) {
128 // deque does not support insert after.
137 // Reoptimize this loop. LPPassManager will re-insert this loop into the
138 // queue. This allows LoopPass to change loop nest for the loop. This
139 // utility may send LPPassManager into infinite loops so use caution.
140 void LPPassManager::redoLoop(Loop *L) {
141 assert (CurrentLoop == L && "Can redo only CurrentLoop");
145 /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
147 void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From,
148 BasicBlock *To, Loop *L) {
149 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
150 LoopPass *LP = getContainedPass(Index);
151 LP->cloneBasicBlockAnalysis(From, To, L);
155 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
156 void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
157 if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
158 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;
160 Instruction &I = *BI;
161 deleteSimpleAnalysisValue(&I, L);
164 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
165 LoopPass *LP = getContainedPass(Index);
166 LP->deleteAnalysisValue(V, L);
170 /// Invoke deleteAnalysisLoop hook for all passes.
171 void LPPassManager::deleteSimpleAnalysisLoop(Loop *L) {
172 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
173 LoopPass *LP = getContainedPass(Index);
174 LP->deleteAnalysisLoop(L);
179 // Recurse through all subloops and all loops into LQ.
180 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
182 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I)
183 addLoopIntoQueue(*I, LQ);
186 /// Pass Manager itself does not invalidate any analysis info.
187 void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const {
188 // LPPassManager needs LoopInfo. In the long term LoopInfo class will
189 // become part of LPPassManager.
190 Info.addRequired<LoopInfoWrapperPass>();
191 Info.setPreservesAll();
194 /// run - Execute all of the passes scheduled for execution. Keep track of
195 /// whether any of the passes modifies the function, and if so, return true.
196 bool LPPassManager::runOnFunction(Function &F) {
197 auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
198 LI = &LIWP.getLoopInfo();
199 bool Changed = false;
201 // Collect inherited analysis from Module level pass manager.
202 populateInheritedAnalysis(TPM->activeStack);
204 // Populate the loop queue in reverse program order. There is no clear need to
205 // process sibling loops in either forward or reverse order. There may be some
206 // advantage in deleting uses in a later loop before optimizing the
207 // definitions in an earlier loop. If we find a clear reason to process in
208 // forward order, then a forward variant of LoopPassManager should be created.
210 // Note that LoopInfo::iterator visits loops in reverse program
211 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
212 // reverses the order a third time by popping from the back.
213 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
214 addLoopIntoQueue(*I, LQ);
216 if (LQ.empty()) // No loops, skip calling finalizers
220 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end();
223 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
224 LoopPass *P = getContainedPass(Index);
225 Changed |= P->doInitialization(L, *this);
230 while (!LQ.empty()) {
232 CurrentLoop = LQ.back();
233 skipThisLoop = false;
234 redoThisLoop = false;
236 // Run all passes on the current Loop.
237 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
238 LoopPass *P = getContainedPass(Index);
240 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
241 CurrentLoop->getHeader()->getName());
244 initializeAnalysisImpl(P);
247 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
248 TimeRegion PassTimer(getPassTimer(P));
250 Changed |= P->runOnLoop(CurrentLoop, *this);
254 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG,
255 skipThisLoop ? "<deleted>" :
256 CurrentLoop->getHeader()->getName());
260 // Manually check that this loop is still healthy. This is done
261 // instead of relying on LoopInfo::verifyLoop since LoopInfo
262 // is a function pass and it's really expensive to verify every
263 // loop in the function every time. That level of checking can be
264 // enabled with the -verify-loop-info option.
266 TimeRegion PassTimer(getPassTimer(&LIWP));
267 CurrentLoop->verifyLoop();
270 // Then call the regular verifyAnalysis functions.
271 verifyPreservedAnalysis(P);
273 F.getContext().yield();
276 removeNotPreservedAnalysis(P);
277 recordAvailableAnalysis(P);
279 skipThisLoop ? "<deleted>" :
280 CurrentLoop->getHeader()->getName(),
284 // Do not run other passes on this loop.
288 // If the loop was deleted, release all the loop passes. This frees up
289 // some memory, and avoids trouble with the pass manager trying to call
290 // verifyAnalysis on them.
292 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
293 Pass *P = getContainedPass(Index);
294 freePass(P, "<deleted>", ON_LOOP_MSG);
297 // Pop the loop from queue after running all passes.
301 LQ.push_back(CurrentLoop);
305 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
306 LoopPass *P = getContainedPass(Index);
307 Changed |= P->doFinalization();
313 /// Print passes managed by this manager
314 void LPPassManager::dumpPassStructure(unsigned Offset) {
315 errs().indent(Offset*2) << "Loop Pass Manager\n";
316 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
317 Pass *P = getContainedPass(Index);
318 P->dumpPassStructure(Offset + 1);
319 dumpLastUses(P, Offset+1);
324 //===----------------------------------------------------------------------===//
327 Pass *LoopPass::createPrinterPass(raw_ostream &O,
328 const std::string &Banner) const {
329 return new PrintLoopPass(Banner, O);
332 // Check if this pass is suitable for the current LPPassManager, if
333 // available. This pass P is not suitable for a LPPassManager if P
334 // is not preserving higher level analysis info used by other
335 // LPPassManager passes. In such case, pop LPPassManager from the
336 // stack. This will force assignPassManager() to create new
337 // LPPassManger as expected.
338 void LoopPass::preparePassManager(PMStack &PMS) {
340 // Find LPPassManager
341 while (!PMS.empty() &&
342 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
345 // If this pass is destroying high level information that is used
346 // by other passes that are managed by LPM then do not insert
347 // this pass in current LPM. Use new LPPassManager.
348 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
349 !PMS.top()->preserveHigherLevelAnalysis(this))
353 /// Assign pass manager to manage this pass.
354 void LoopPass::assignPassManager(PMStack &PMS,
355 PassManagerType PreferredType) {
356 // Find LPPassManager
357 while (!PMS.empty() &&
358 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
362 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
363 LPPM = (LPPassManager*)PMS.top();
365 // Create new Loop Pass Manager if it does not exist.
366 assert (!PMS.empty() && "Unable to create Loop Pass Manager");
367 PMDataManager *PMD = PMS.top();
369 // [1] Create new Loop Pass Manager
370 LPPM = new LPPassManager();
371 LPPM->populateInheritedAnalysis(PMS);
373 // [2] Set up new manager's top level manager
374 PMTopLevelManager *TPM = PMD->getTopLevelManager();
375 TPM->addIndirectPassManager(LPPM);
377 // [3] Assign manager to manage this new manager. This may create
378 // and push new managers into PMS
379 Pass *P = LPPM->getAsPass();
380 TPM->schedulePass(P);
382 // [4] Push new manager into PMS
389 // Containing function has Attribute::OptimizeNone and transformation
390 // passes should skip it.
391 bool LoopPass::skipOptnoneFunction(const Loop *L) const {
392 const Function *F = L->getHeader()->getParent();
393 if (F && F->hasFnAttribute(Attribute::OptimizeNone)) {
394 // FIXME: Report this to dbgs() only once per function.
395 DEBUG(dbgs() << "Skipping pass '" << getPassName()
396 << "' in function " << F->getName() << "\n");
397 // FIXME: Delete loop from pass manager's queue?