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"
21 #include "llvm/Support/raw_ostream.h"
24 #define DEBUG_TYPE "loop-pass-manager"
28 /// PrintLoopPass - Print a Function corresponding to a Loop.
30 class PrintLoopPass : public LoopPass {
33 raw_ostream &Out; // raw_ostream to print on.
37 PrintLoopPass(const std::string &B, raw_ostream &o)
38 : LoopPass(ID), Banner(B), Out(o) {}
40 void getAnalysisUsage(AnalysisUsage &AU) const override {
44 bool runOnLoop(Loop *L, LPPassManager &) override {
46 for (Loop::block_iterator b = L->block_begin(), be = L->block_end();
52 Out << "Printing <null> block";
58 char PrintLoopPass::ID = 0;
61 //===----------------------------------------------------------------------===//
65 char LPPassManager::ID = 0;
67 LPPassManager::LPPassManager()
68 : 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 Loop &LPPassManager::addLoop(Loop *ParentLoop) {
104 // Create a new loop. LI will take ownership.
105 Loop *L = new Loop();
107 // Insert into the loop nest and the loop queue.
109 // This is the top level loop.
110 LI->addTopLevelLoop(L);
115 ParentLoop->addChildLoop(L);
116 // Insert L into the loop queue after the parent loop.
117 for (auto I = LQ.begin(), E = LQ.end(); I != E; ++I) {
118 if (*I == L->getParentLoop()) {
119 // deque does not support insert after.
128 /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
130 void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From,
131 BasicBlock *To, Loop *L) {
132 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
133 LoopPass *LP = getContainedPass(Index);
134 LP->cloneBasicBlockAnalysis(From, To, L);
138 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
139 void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
140 if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
141 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;
143 Instruction &I = *BI;
144 deleteSimpleAnalysisValue(&I, L);
147 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
148 LoopPass *LP = getContainedPass(Index);
149 LP->deleteAnalysisValue(V, L);
153 /// Invoke deleteAnalysisLoop hook for all passes.
154 void LPPassManager::deleteSimpleAnalysisLoop(Loop *L) {
155 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
156 LoopPass *LP = getContainedPass(Index);
157 LP->deleteAnalysisLoop(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<LoopInfoWrapperPass>();
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 auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
181 LI = &LIWP.getLoopInfo();
182 bool Changed = false;
184 // Collect inherited analysis from Module level pass manager.
185 populateInheritedAnalysis(TPM->activeStack);
187 // Populate the loop queue in reverse program order. There is no clear need to
188 // process sibling loops in either forward or reverse order. There may be some
189 // advantage in deleting uses in a later loop before optimizing the
190 // definitions in an earlier loop. If we find a clear reason to process in
191 // forward order, then a forward variant of LoopPassManager should be created.
193 // Note that LoopInfo::iterator visits loops in reverse program
194 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
195 // reverses the order a third time by popping from the back.
196 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
197 addLoopIntoQueue(*I, LQ);
199 if (LQ.empty()) // No loops, skip calling finalizers
203 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end();
206 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
207 LoopPass *P = getContainedPass(Index);
208 Changed |= P->doInitialization(L, *this);
213 while (!LQ.empty()) {
215 CurrentLoop = LQ.back();
216 skipThisLoop = 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(&LIWP));
249 CurrentLoop->verifyLoop();
252 // Then call the regular verifyAnalysis functions.
253 verifyPreservedAnalysis(P);
255 F.getContext().yield();
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.
284 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
285 LoopPass *P = getContainedPass(Index);
286 Changed |= P->doFinalization();
292 /// Print passes managed by this manager
293 void LPPassManager::dumpPassStructure(unsigned Offset) {
294 errs().indent(Offset*2) << "Loop Pass Manager\n";
295 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
296 Pass *P = getContainedPass(Index);
297 P->dumpPassStructure(Offset + 1);
298 dumpLastUses(P, Offset+1);
303 //===----------------------------------------------------------------------===//
306 Pass *LoopPass::createPrinterPass(raw_ostream &O,
307 const std::string &Banner) const {
308 return new PrintLoopPass(Banner, O);
311 // Check if this pass is suitable for the current LPPassManager, if
312 // available. This pass P is not suitable for a LPPassManager if P
313 // is not preserving higher level analysis info used by other
314 // LPPassManager passes. In such case, pop LPPassManager from the
315 // stack. This will force assignPassManager() to create new
316 // LPPassManger as expected.
317 void LoopPass::preparePassManager(PMStack &PMS) {
319 // Find LPPassManager
320 while (!PMS.empty() &&
321 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
324 // If this pass is destroying high level information that is used
325 // by other passes that are managed by LPM then do not insert
326 // this pass in current LPM. Use new LPPassManager.
327 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
328 !PMS.top()->preserveHigherLevelAnalysis(this))
332 /// Assign pass manager to manage this pass.
333 void LoopPass::assignPassManager(PMStack &PMS,
334 PassManagerType PreferredType) {
335 // Find LPPassManager
336 while (!PMS.empty() &&
337 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
341 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
342 LPPM = (LPPassManager*)PMS.top();
344 // Create new Loop Pass Manager if it does not exist.
345 assert (!PMS.empty() && "Unable to create Loop Pass Manager");
346 PMDataManager *PMD = PMS.top();
348 // [1] Create new Loop Pass Manager
349 LPPM = new LPPassManager();
350 LPPM->populateInheritedAnalysis(PMS);
352 // [2] Set up new manager's top level manager
353 PMTopLevelManager *TPM = PMD->getTopLevelManager();
354 TPM->addIndirectPassManager(LPPM);
356 // [3] Assign manager to manage this new manager. This may create
357 // and push new managers into PMS
358 Pass *P = LPPM->getAsPass();
359 TPM->schedulePass(P);
361 // [4] Push new manager into PMS
368 // Containing function has Attribute::OptimizeNone and transformation
369 // passes should skip it.
370 bool LoopPass::skipOptnoneFunction(const Loop *L) const {
371 const Function *F = L->getHeader()->getParent();
372 if (F && F->hasFnAttribute(Attribute::OptimizeNone)) {
373 // FIXME: Report this to dbgs() only once per function.
374 DEBUG(dbgs() << "Skipping pass '" << getPassName()
375 << "' in function " << F->getName() << "\n");
376 // FIXME: Delete loop from pass manager's queue?