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<LoopInfo>();
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 LI = &getAnalysis<LoopInfo>();
198 bool Changed = false;
200 // Collect inherited analysis from Module level pass manager.
201 populateInheritedAnalysis(TPM->activeStack);
203 // Populate the loop queue in reverse program order. There is no clear need to
204 // process sibling loops in either forward or reverse order. There may be some
205 // advantage in deleting uses in a later loop before optimizing the
206 // definitions in an earlier loop. If we find a clear reason to process in
207 // forward order, then a forward variant of LoopPassManager should be created.
209 // Note that LoopInfo::iterator visits loops in reverse program
210 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
211 // reverses the order a third time by popping from the back.
212 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
213 addLoopIntoQueue(*I, LQ);
215 if (LQ.empty()) // No loops, skip calling finalizers
219 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end();
222 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
223 LoopPass *P = getContainedPass(Index);
224 Changed |= P->doInitialization(L, *this);
229 while (!LQ.empty()) {
231 CurrentLoop = LQ.back();
232 skipThisLoop = false;
233 redoThisLoop = false;
235 // Run all passes on the current Loop.
236 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
237 LoopPass *P = getContainedPass(Index);
239 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
240 CurrentLoop->getHeader()->getName());
243 initializeAnalysisImpl(P);
246 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
247 TimeRegion PassTimer(getPassTimer(P));
249 Changed |= P->runOnLoop(CurrentLoop, *this);
253 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG,
254 skipThisLoop ? "<deleted>" :
255 CurrentLoop->getHeader()->getName());
259 // Manually check that this loop is still healthy. This is done
260 // instead of relying on LoopInfo::verifyLoop since LoopInfo
261 // is a function pass and it's really expensive to verify every
262 // loop in the function every time. That level of checking can be
263 // enabled with the -verify-loop-info option.
265 TimeRegion PassTimer(getPassTimer(LI));
266 CurrentLoop->verifyLoop();
269 // Then call the regular verifyAnalysis functions.
270 verifyPreservedAnalysis(P);
272 F.getContext().yield();
275 removeNotPreservedAnalysis(P);
276 recordAvailableAnalysis(P);
278 skipThisLoop ? "<deleted>" :
279 CurrentLoop->getHeader()->getName(),
283 // Do not run other passes on this loop.
287 // If the loop was deleted, release all the loop passes. This frees up
288 // some memory, and avoids trouble with the pass manager trying to call
289 // verifyAnalysis on them.
291 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
292 Pass *P = getContainedPass(Index);
293 freePass(P, "<deleted>", ON_LOOP_MSG);
296 // Pop the loop from queue after running all passes.
300 LQ.push_back(CurrentLoop);
304 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
305 LoopPass *P = getContainedPass(Index);
306 Changed |= P->doFinalization();
312 /// Print passes managed by this manager
313 void LPPassManager::dumpPassStructure(unsigned Offset) {
314 errs().indent(Offset*2) << "Loop Pass Manager\n";
315 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
316 Pass *P = getContainedPass(Index);
317 P->dumpPassStructure(Offset + 1);
318 dumpLastUses(P, Offset+1);
323 //===----------------------------------------------------------------------===//
326 Pass *LoopPass::createPrinterPass(raw_ostream &O,
327 const std::string &Banner) const {
328 return new PrintLoopPass(Banner, O);
331 // Check if this pass is suitable for the current LPPassManager, if
332 // available. This pass P is not suitable for a LPPassManager if P
333 // is not preserving higher level analysis info used by other
334 // LPPassManager passes. In such case, pop LPPassManager from the
335 // stack. This will force assignPassManager() to create new
336 // LPPassManger as expected.
337 void LoopPass::preparePassManager(PMStack &PMS) {
339 // Find LPPassManager
340 while (!PMS.empty() &&
341 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
344 // If this pass is destroying high level information that is used
345 // by other passes that are managed by LPM then do not insert
346 // this pass in current LPM. Use new LPPassManager.
347 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
348 !PMS.top()->preserveHigherLevelAnalysis(this))
352 /// Assign pass manager to manage this pass.
353 void LoopPass::assignPassManager(PMStack &PMS,
354 PassManagerType PreferredType) {
355 // Find LPPassManager
356 while (!PMS.empty() &&
357 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
361 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
362 LPPM = (LPPassManager*)PMS.top();
364 // Create new Loop Pass Manager if it does not exist.
365 assert (!PMS.empty() && "Unable to create Loop Pass Manager");
366 PMDataManager *PMD = PMS.top();
368 // [1] Create new Loop Pass Manager
369 LPPM = new LPPassManager();
370 LPPM->populateInheritedAnalysis(PMS);
372 // [2] Set up new manager's top level manager
373 PMTopLevelManager *TPM = PMD->getTopLevelManager();
374 TPM->addIndirectPassManager(LPPM);
376 // [3] Assign manager to manage this new manager. This may create
377 // and push new managers into PMS
378 Pass *P = LPPM->getAsPass();
379 TPM->schedulePass(P);
381 // [4] Push new manager into PMS
388 // Containing function has Attribute::OptimizeNone and transformation
389 // passes should skip it.
390 bool LoopPass::skipOptnoneFunction(const Loop *L) const {
391 const Function *F = L->getHeader()->getParent();
392 if (F && F->hasFnAttribute(Attribute::OptimizeNone)) {
393 // FIXME: Report this to dbgs() only once per function.
394 DEBUG(dbgs() << "Skipping pass '" << getPassName()
395 << "' in function " << F->getName() << "\n");
396 // FIXME: Delete loop from pass manager's queue?