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"
22 #define DEBUG_TYPE "loop-pass-manager"
26 /// PrintLoopPass - Print a Function corresponding to a Loop.
28 class PrintLoopPass : public LoopPass {
31 raw_ostream &Out; // raw_ostream to print on.
35 PrintLoopPass(const std::string &B, raw_ostream &o)
36 : LoopPass(ID), Banner(B), Out(o) {}
38 void getAnalysisUsage(AnalysisUsage &AU) const override {
42 bool runOnLoop(Loop *L, LPPassManager &) override {
44 for (Loop::block_iterator b = L->block_begin(), be = L->block_end();
53 char PrintLoopPass::ID = 0;
56 //===----------------------------------------------------------------------===//
60 char LPPassManager::ID = 0;
62 LPPassManager::LPPassManager()
63 : FunctionPass(ID), PMDataManager() {
67 CurrentLoop = nullptr;
70 /// Delete loop from the loop queue and loop hierarchy (LoopInfo).
71 void LPPassManager::deleteLoopFromQueue(Loop *L) {
75 // If L is current loop then skip rest of the passes and let
76 // runOnFunction remove L from LQ. Otherwise, remove L from LQ now
77 // and continue applying other passes on CurrentLoop.
86 for (std::deque<Loop *>::iterator I = LQ.begin(),
87 E = LQ.end(); I != E; ++I) {
95 // Inset loop into loop nest (LoopInfo) and loop queue (LQ).
96 void LPPassManager::insertLoop(Loop *L, Loop *ParentLoop) {
98 assert (CurrentLoop != L && "Cannot insert CurrentLoop");
100 // Insert into loop nest
102 ParentLoop->addChildLoop(L);
104 LI->addTopLevelLoop(L);
106 insertLoopIntoQueue(L);
109 void LPPassManager::insertLoopIntoQueue(Loop *L) {
110 // Insert L into loop queue
111 if (L == CurrentLoop)
113 else if (!L->getParentLoop())
114 // This is top level loop.
117 // Insert L after the parent loop.
118 for (std::deque<Loop *>::iterator I = LQ.begin(),
119 E = LQ.end(); I != E; ++I) {
120 if (*I == L->getParentLoop()) {
121 // deque does not support insert after.
130 // Reoptimize this loop. LPPassManager will re-insert this loop into the
131 // queue. This allows LoopPass to change loop nest for the loop. This
132 // utility may send LPPassManager into infinite loops so use caution.
133 void LPPassManager::redoLoop(Loop *L) {
134 assert (CurrentLoop == L && "Can redo only CurrentLoop");
138 /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
140 void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From,
141 BasicBlock *To, Loop *L) {
142 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
143 LoopPass *LP = getContainedPass(Index);
144 LP->cloneBasicBlockAnalysis(From, To, L);
148 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
149 void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
150 if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
151 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;
153 Instruction &I = *BI;
154 deleteSimpleAnalysisValue(&I, L);
157 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
158 LoopPass *LP = getContainedPass(Index);
159 LP->deleteAnalysisValue(V, L);
164 // Recurse through all subloops and all loops into LQ.
165 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
167 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I)
168 addLoopIntoQueue(*I, LQ);
171 /// Pass Manager itself does not invalidate any analysis info.
172 void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const {
173 // LPPassManager needs LoopInfo. In the long term LoopInfo class will
174 // become part of LPPassManager.
175 Info.addRequired<LoopInfo>();
176 Info.setPreservesAll();
179 /// run - Execute all of the passes scheduled for execution. Keep track of
180 /// whether any of the passes modifies the function, and if so, return true.
181 bool LPPassManager::runOnFunction(Function &F) {
182 LI = &getAnalysis<LoopInfo>();
183 bool Changed = false;
185 // Collect inherited analysis from Module level pass manager.
186 populateInheritedAnalysis(TPM->activeStack);
188 // Populate the loop queue in reverse program order. There is no clear need to
189 // process sibling loops in either forward or reverse order. There may be some
190 // advantage in deleting uses in a later loop before optimizing the
191 // definitions in an earlier loop. If we find a clear reason to process in
192 // forward order, then a forward variant of LoopPassManager should be created.
194 // Note that LoopInfo::iterator visits loops in reverse program
195 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
196 // reverses the order a third time by popping from the back.
197 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
198 addLoopIntoQueue(*I, LQ);
200 if (LQ.empty()) // No loops, skip calling finalizers
204 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end();
207 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
208 LoopPass *P = getContainedPass(Index);
209 Changed |= P->doInitialization(L, *this);
214 while (!LQ.empty()) {
216 CurrentLoop = LQ.back();
217 skipThisLoop = false;
218 redoThisLoop = false;
220 // Run all passes on the current Loop.
221 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
222 LoopPass *P = getContainedPass(Index);
224 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
225 CurrentLoop->getHeader()->getName());
228 initializeAnalysisImpl(P);
231 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
232 TimeRegion PassTimer(getPassTimer(P));
234 Changed |= P->runOnLoop(CurrentLoop, *this);
238 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG,
239 skipThisLoop ? "<deleted>" :
240 CurrentLoop->getHeader()->getName());
244 // Manually check that this loop is still healthy. This is done
245 // instead of relying on LoopInfo::verifyLoop since LoopInfo
246 // is a function pass and it's really expensive to verify every
247 // loop in the function every time. That level of checking can be
248 // enabled with the -verify-loop-info option.
250 TimeRegion PassTimer(getPassTimer(LI));
251 CurrentLoop->verifyLoop();
254 // Then call the regular verifyAnalysis functions.
255 verifyPreservedAnalysis(P);
258 removeNotPreservedAnalysis(P);
259 recordAvailableAnalysis(P);
261 skipThisLoop ? "<deleted>" :
262 CurrentLoop->getHeader()->getName(),
266 // Do not run other passes on this loop.
270 // If the loop was deleted, release all the loop passes. This frees up
271 // some memory, and avoids trouble with the pass manager trying to call
272 // verifyAnalysis on them.
274 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
275 Pass *P = getContainedPass(Index);
276 freePass(P, "<deleted>", ON_LOOP_MSG);
279 // Pop the loop from queue after running all passes.
283 LQ.push_back(CurrentLoop);
287 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
288 LoopPass *P = getContainedPass(Index);
289 Changed |= P->doFinalization();
295 /// Print passes managed by this manager
296 void LPPassManager::dumpPassStructure(unsigned Offset) {
297 errs().indent(Offset*2) << "Loop Pass Manager\n";
298 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
299 Pass *P = getContainedPass(Index);
300 P->dumpPassStructure(Offset + 1);
301 dumpLastUses(P, Offset+1);
306 //===----------------------------------------------------------------------===//
309 Pass *LoopPass::createPrinterPass(raw_ostream &O,
310 const std::string &Banner) const {
311 return new PrintLoopPass(Banner, O);
314 // Check if this pass is suitable for the current LPPassManager, if
315 // available. This pass P is not suitable for a LPPassManager if P
316 // is not preserving higher level analysis info used by other
317 // LPPassManager passes. In such case, pop LPPassManager from the
318 // stack. This will force assignPassManager() to create new
319 // LPPassManger as expected.
320 void LoopPass::preparePassManager(PMStack &PMS) {
322 // Find LPPassManager
323 while (!PMS.empty() &&
324 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
327 // If this pass is destroying high level information that is used
328 // by other passes that are managed by LPM then do not insert
329 // this pass in current LPM. Use new LPPassManager.
330 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
331 !PMS.top()->preserveHigherLevelAnalysis(this))
335 /// Assign pass manager to manage this pass.
336 void LoopPass::assignPassManager(PMStack &PMS,
337 PassManagerType PreferredType) {
338 // Find LPPassManager
339 while (!PMS.empty() &&
340 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
344 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
345 LPPM = (LPPassManager*)PMS.top();
347 // Create new Loop Pass Manager if it does not exist.
348 assert (!PMS.empty() && "Unable to create Loop Pass Manager");
349 PMDataManager *PMD = PMS.top();
351 // [1] Create new Loop Pass Manager
352 LPPM = new LPPassManager();
353 LPPM->populateInheritedAnalysis(PMS);
355 // [2] Set up new manager's top level manager
356 PMTopLevelManager *TPM = PMD->getTopLevelManager();
357 TPM->addIndirectPassManager(LPPM);
359 // [3] Assign manager to manage this new manager. This may create
360 // and push new managers into PMS
361 Pass *P = LPPM->getAsPass();
362 TPM->schedulePass(P);
364 // [4] Push new manager into PMS
371 // Containing function has Attribute::OptimizeNone and transformation
372 // passes should skip it.
373 bool LoopPass::skipOptnoneFunction(const Loop *L) const {
374 const Function *F = L->getHeader()->getParent();
375 if (F && F->hasFnAttribute(Attribute::OptimizeNone)) {
376 // FIXME: Report this to dbgs() only once per function.
377 DEBUG(dbgs() << "Skipping pass '" << getPassName()
378 << "' in function " << F->getName() << "\n");
379 // FIXME: Delete loop from pass manager's queue?