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/Support/Debug.h"
19 #include "llvm/Support/Timer.h"
24 /// PrintLoopPass - Print a Function corresponding to a Loop.
26 class PrintLoopPass : public LoopPass {
29 raw_ostream &Out; // raw_ostream to print on.
33 PrintLoopPass(const std::string &B, raw_ostream &o)
34 : LoopPass(ID), Banner(B), Out(o) {}
36 void getAnalysisUsage(AnalysisUsage &AU) const override {
40 bool runOnLoop(Loop *L, LPPassManager &) override {
42 for (Loop::block_iterator b = L->block_begin(), be = L->block_end();
51 char PrintLoopPass::ID = 0;
54 //===----------------------------------------------------------------------===//
58 char LPPassManager::ID = 0;
60 LPPassManager::LPPassManager()
61 : FunctionPass(ID), PMDataManager() {
65 CurrentLoop = nullptr;
68 /// Delete loop from the loop queue and loop hierarchy (LoopInfo).
69 void LPPassManager::deleteLoopFromQueue(Loop *L) {
73 // If L is current loop then skip rest of the passes and let
74 // runOnFunction remove L from LQ. Otherwise, remove L from LQ now
75 // and continue applying other passes on CurrentLoop.
84 for (std::deque<Loop *>::iterator I = LQ.begin(),
85 E = LQ.end(); I != E; ++I) {
93 // Inset loop into loop nest (LoopInfo) and loop queue (LQ).
94 void LPPassManager::insertLoop(Loop *L, Loop *ParentLoop) {
96 assert (CurrentLoop != L && "Cannot insert CurrentLoop");
98 // Insert into loop nest
100 ParentLoop->addChildLoop(L);
102 LI->addTopLevelLoop(L);
104 insertLoopIntoQueue(L);
107 void LPPassManager::insertLoopIntoQueue(Loop *L) {
108 // Insert L into loop queue
109 if (L == CurrentLoop)
111 else if (!L->getParentLoop())
112 // This is top level loop.
115 // Insert L after the parent loop.
116 for (std::deque<Loop *>::iterator I = LQ.begin(),
117 E = LQ.end(); I != E; ++I) {
118 if (*I == L->getParentLoop()) {
119 // deque does not support insert after.
128 // Reoptimize this loop. LPPassManager will re-insert this loop into the
129 // queue. This allows LoopPass to change loop nest for the loop. This
130 // utility may send LPPassManager into infinite loops so use caution.
131 void LPPassManager::redoLoop(Loop *L) {
132 assert (CurrentLoop == L && "Can redo only CurrentLoop");
136 /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
138 void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From,
139 BasicBlock *To, Loop *L) {
140 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
141 LoopPass *LP = getContainedPass(Index);
142 LP->cloneBasicBlockAnalysis(From, To, L);
146 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
147 void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
148 if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
149 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;
151 Instruction &I = *BI;
152 deleteSimpleAnalysisValue(&I, L);
155 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
156 LoopPass *LP = getContainedPass(Index);
157 LP->deleteAnalysisValue(V, L);
162 // Recurse through all subloops and all loops into LQ.
163 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
165 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I)
166 addLoopIntoQueue(*I, LQ);
169 /// Pass Manager itself does not invalidate any analysis info.
170 void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const {
171 // LPPassManager needs LoopInfo. In the long term LoopInfo class will
172 // become part of LPPassManager.
173 Info.addRequired<LoopInfo>();
174 Info.setPreservesAll();
177 /// run - Execute all of the passes scheduled for execution. Keep track of
178 /// whether any of the passes modifies the function, and if so, return true.
179 bool LPPassManager::runOnFunction(Function &F) {
180 LI = &getAnalysis<LoopInfo>();
181 bool Changed = false;
183 // Collect inherited analysis from Module level pass manager.
184 populateInheritedAnalysis(TPM->activeStack);
186 // Populate the loop queue in reverse program order. There is no clear need to
187 // process sibling loops in either forward or reverse order. There may be some
188 // advantage in deleting uses in a later loop before optimizing the
189 // definitions in an earlier loop. If we find a clear reason to process in
190 // forward order, then a forward variant of LoopPassManager should be created.
192 // Note that LoopInfo::iterator visits loops in reverse program
193 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
194 // reverses the order a third time by popping from the back.
195 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
196 addLoopIntoQueue(*I, LQ);
198 if (LQ.empty()) // No loops, skip calling finalizers
202 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end();
205 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
206 LoopPass *P = getContainedPass(Index);
207 Changed |= P->doInitialization(L, *this);
212 while (!LQ.empty()) {
214 CurrentLoop = LQ.back();
215 skipThisLoop = false;
216 redoThisLoop = false;
218 // Run all passes on the current Loop.
219 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
220 LoopPass *P = getContainedPass(Index);
222 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
223 CurrentLoop->getHeader()->getName());
226 initializeAnalysisImpl(P);
229 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
230 TimeRegion PassTimer(getPassTimer(P));
232 Changed |= P->runOnLoop(CurrentLoop, *this);
236 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG,
237 skipThisLoop ? "<deleted>" :
238 CurrentLoop->getHeader()->getName());
242 // Manually check that this loop is still healthy. This is done
243 // instead of relying on LoopInfo::verifyLoop since LoopInfo
244 // is a function pass and it's really expensive to verify every
245 // loop in the function every time. That level of checking can be
246 // enabled with the -verify-loop-info option.
248 TimeRegion PassTimer(getPassTimer(LI));
249 CurrentLoop->verifyLoop();
252 // Then call the regular verifyAnalysis functions.
253 verifyPreservedAnalysis(P);
256 removeNotPreservedAnalysis(P);
257 recordAvailableAnalysis(P);
259 skipThisLoop ? "<deleted>" :
260 CurrentLoop->getHeader()->getName(),
264 // Do not run other passes on this loop.
268 // If the loop was deleted, release all the loop passes. This frees up
269 // some memory, and avoids trouble with the pass manager trying to call
270 // verifyAnalysis on them.
272 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
273 Pass *P = getContainedPass(Index);
274 freePass(P, "<deleted>", ON_LOOP_MSG);
277 // Pop the loop from queue after running all passes.
281 LQ.push_back(CurrentLoop);
285 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
286 LoopPass *P = getContainedPass(Index);
287 Changed |= P->doFinalization();
293 /// Print passes managed by this manager
294 void LPPassManager::dumpPassStructure(unsigned Offset) {
295 errs().indent(Offset*2) << "Loop Pass Manager\n";
296 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
297 Pass *P = getContainedPass(Index);
298 P->dumpPassStructure(Offset + 1);
299 dumpLastUses(P, Offset+1);
304 //===----------------------------------------------------------------------===//
307 Pass *LoopPass::createPrinterPass(raw_ostream &O,
308 const std::string &Banner) const {
309 return new PrintLoopPass(Banner, O);
312 // Check if this pass is suitable for the current LPPassManager, if
313 // available. This pass P is not suitable for a LPPassManager if P
314 // is not preserving higher level analysis info used by other
315 // LPPassManager passes. In such case, pop LPPassManager from the
316 // stack. This will force assignPassManager() to create new
317 // LPPassManger as expected.
318 void LoopPass::preparePassManager(PMStack &PMS) {
320 // Find LPPassManager
321 while (!PMS.empty() &&
322 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
325 // If this pass is destroying high level information that is used
326 // by other passes that are managed by LPM then do not insert
327 // this pass in current LPM. Use new LPPassManager.
328 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
329 !PMS.top()->preserveHigherLevelAnalysis(this))
333 /// Assign pass manager to manage this pass.
334 void LoopPass::assignPassManager(PMStack &PMS,
335 PassManagerType PreferredType) {
336 // Find LPPassManager
337 while (!PMS.empty() &&
338 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
342 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
343 LPPM = (LPPassManager*)PMS.top();
345 // Create new Loop Pass Manager if it does not exist.
346 assert (!PMS.empty() && "Unable to create Loop Pass Manager");
347 PMDataManager *PMD = PMS.top();
349 // [1] Create new Loop Pass Manager
350 LPPM = new LPPassManager();
351 LPPM->populateInheritedAnalysis(PMS);
353 // [2] Set up new manager's top level manager
354 PMTopLevelManager *TPM = PMD->getTopLevelManager();
355 TPM->addIndirectPassManager(LPPM);
357 // [3] Assign manager to manage this new manager. This may create
358 // and push new managers into PMS
359 Pass *P = LPPM->getAsPass();
360 TPM->schedulePass(P);
362 // [4] Push new manager into PMS
369 // Containing function has Attribute::OptimizeNone and transformation
370 // passes should skip it.
371 bool LoopPass::skipOptnoneFunction(const Loop *L) const {
372 const Function *F = L->getHeader()->getParent();
373 if (F && F->hasFnAttribute(Attribute::OptimizeNone)) {
374 // FIXME: Report this to dbgs() only once per function.
375 DEBUG(dbgs() << "Skipping pass '" << getPassName()
376 << "' in function " << F->getName() << "\n");
377 // FIXME: Delete loop from pass manager's queue?