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 // If L is current loop then skip rest of the passes and let
80 // runOnFunction remove L from LQ. Otherwise, remove L from LQ now
81 // and continue applying other passes on CurrentLoop.
90 for (std::deque<Loop *>::iterator I = LQ.begin(),
91 E = LQ.end(); I != E; ++I) {
99 // Inset loop into loop nest (LoopInfo) and loop queue (LQ).
100 void LPPassManager::insertLoop(Loop *L, Loop *ParentLoop) {
102 assert (CurrentLoop != L && "Cannot insert CurrentLoop");
104 // Insert into loop nest
106 ParentLoop->addChildLoop(L);
108 LI->addTopLevelLoop(L);
110 insertLoopIntoQueue(L);
113 void LPPassManager::insertLoopIntoQueue(Loop *L) {
114 // Insert L into loop queue
115 if (L == CurrentLoop)
117 else if (!L->getParentLoop())
118 // This is top level loop.
121 // Insert L after the parent loop.
122 for (std::deque<Loop *>::iterator I = LQ.begin(),
123 E = LQ.end(); I != E; ++I) {
124 if (*I == L->getParentLoop()) {
125 // deque does not support insert after.
134 // Reoptimize this loop. LPPassManager will re-insert this loop into the
135 // queue. This allows LoopPass to change loop nest for the loop. This
136 // utility may send LPPassManager into infinite loops so use caution.
137 void LPPassManager::redoLoop(Loop *L) {
138 assert (CurrentLoop == L && "Can redo only CurrentLoop");
142 /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
144 void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From,
145 BasicBlock *To, Loop *L) {
146 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
147 LoopPass *LP = getContainedPass(Index);
148 LP->cloneBasicBlockAnalysis(From, To, L);
152 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
153 void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
154 if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
155 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;
157 Instruction &I = *BI;
158 deleteSimpleAnalysisValue(&I, L);
161 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
162 LoopPass *LP = getContainedPass(Index);
163 LP->deleteAnalysisValue(V, L);
168 // Recurse through all subloops and all loops into LQ.
169 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
171 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I)
172 addLoopIntoQueue(*I, LQ);
175 /// Pass Manager itself does not invalidate any analysis info.
176 void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const {
177 // LPPassManager needs LoopInfo. In the long term LoopInfo class will
178 // become part of LPPassManager.
179 Info.addRequired<LoopInfo>();
180 Info.setPreservesAll();
183 /// run - Execute all of the passes scheduled for execution. Keep track of
184 /// whether any of the passes modifies the function, and if so, return true.
185 bool LPPassManager::runOnFunction(Function &F) {
186 LI = &getAnalysis<LoopInfo>();
187 bool Changed = false;
189 // Collect inherited analysis from Module level pass manager.
190 populateInheritedAnalysis(TPM->activeStack);
192 // Populate the loop queue in reverse program order. There is no clear need to
193 // process sibling loops in either forward or reverse order. There may be some
194 // advantage in deleting uses in a later loop before optimizing the
195 // definitions in an earlier loop. If we find a clear reason to process in
196 // forward order, then a forward variant of LoopPassManager should be created.
198 // Note that LoopInfo::iterator visits loops in reverse program
199 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
200 // reverses the order a third time by popping from the back.
201 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
202 addLoopIntoQueue(*I, LQ);
204 if (LQ.empty()) // No loops, skip calling finalizers
208 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end();
211 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
212 LoopPass *P = getContainedPass(Index);
213 Changed |= P->doInitialization(L, *this);
218 while (!LQ.empty()) {
220 CurrentLoop = LQ.back();
221 skipThisLoop = false;
222 redoThisLoop = false;
224 // Run all passes on the current Loop.
225 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
226 LoopPass *P = getContainedPass(Index);
228 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
229 CurrentLoop->getHeader()->getName());
232 initializeAnalysisImpl(P);
235 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
236 TimeRegion PassTimer(getPassTimer(P));
238 Changed |= P->runOnLoop(CurrentLoop, *this);
242 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG,
243 skipThisLoop ? "<deleted>" :
244 CurrentLoop->getHeader()->getName());
248 // Manually check that this loop is still healthy. This is done
249 // instead of relying on LoopInfo::verifyLoop since LoopInfo
250 // is a function pass and it's really expensive to verify every
251 // loop in the function every time. That level of checking can be
252 // enabled with the -verify-loop-info option.
254 TimeRegion PassTimer(getPassTimer(LI));
255 CurrentLoop->verifyLoop();
258 // Then call the regular verifyAnalysis functions.
259 verifyPreservedAnalysis(P);
261 F.getContext().yield();
264 removeNotPreservedAnalysis(P);
265 recordAvailableAnalysis(P);
267 skipThisLoop ? "<deleted>" :
268 CurrentLoop->getHeader()->getName(),
272 // Do not run other passes on this loop.
276 // If the loop was deleted, release all the loop passes. This frees up
277 // some memory, and avoids trouble with the pass manager trying to call
278 // verifyAnalysis on them.
280 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
281 Pass *P = getContainedPass(Index);
282 freePass(P, "<deleted>", ON_LOOP_MSG);
285 // Pop the loop from queue after running all passes.
289 LQ.push_back(CurrentLoop);
293 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
294 LoopPass *P = getContainedPass(Index);
295 Changed |= P->doFinalization();
301 /// Print passes managed by this manager
302 void LPPassManager::dumpPassStructure(unsigned Offset) {
303 errs().indent(Offset*2) << "Loop Pass Manager\n";
304 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
305 Pass *P = getContainedPass(Index);
306 P->dumpPassStructure(Offset + 1);
307 dumpLastUses(P, Offset+1);
312 //===----------------------------------------------------------------------===//
315 Pass *LoopPass::createPrinterPass(raw_ostream &O,
316 const std::string &Banner) const {
317 return new PrintLoopPass(Banner, O);
320 // Check if this pass is suitable for the current LPPassManager, if
321 // available. This pass P is not suitable for a LPPassManager if P
322 // is not preserving higher level analysis info used by other
323 // LPPassManager passes. In such case, pop LPPassManager from the
324 // stack. This will force assignPassManager() to create new
325 // LPPassManger as expected.
326 void LoopPass::preparePassManager(PMStack &PMS) {
328 // Find LPPassManager
329 while (!PMS.empty() &&
330 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
333 // If this pass is destroying high level information that is used
334 // by other passes that are managed by LPM then do not insert
335 // this pass in current LPM. Use new LPPassManager.
336 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
337 !PMS.top()->preserveHigherLevelAnalysis(this))
341 /// Assign pass manager to manage this pass.
342 void LoopPass::assignPassManager(PMStack &PMS,
343 PassManagerType PreferredType) {
344 // Find LPPassManager
345 while (!PMS.empty() &&
346 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
350 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
351 LPPM = (LPPassManager*)PMS.top();
353 // Create new Loop Pass Manager if it does not exist.
354 assert (!PMS.empty() && "Unable to create Loop Pass Manager");
355 PMDataManager *PMD = PMS.top();
357 // [1] Create new Loop Pass Manager
358 LPPM = new LPPassManager();
359 LPPM->populateInheritedAnalysis(PMS);
361 // [2] Set up new manager's top level manager
362 PMTopLevelManager *TPM = PMD->getTopLevelManager();
363 TPM->addIndirectPassManager(LPPM);
365 // [3] Assign manager to manage this new manager. This may create
366 // and push new managers into PMS
367 Pass *P = LPPM->getAsPass();
368 TPM->schedulePass(P);
370 // [4] Push new manager into PMS
377 // Containing function has Attribute::OptimizeNone and transformation
378 // passes should skip it.
379 bool LoopPass::skipOptnoneFunction(const Loop *L) const {
380 const Function *F = L->getHeader()->getParent();
381 if (F && F->hasFnAttribute(Attribute::OptimizeNone)) {
382 // FIXME: Report this to dbgs() only once per function.
383 DEBUG(dbgs() << "Skipping pass '" << getPassName()
384 << "' in function " << F->getName() << "\n");
385 // FIXME: Delete loop from pass manager's queue?