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();
48 assert((*b) != nullptr && "Expecting non-null block");
55 char PrintLoopPass::ID = 0;
58 //===----------------------------------------------------------------------===//
62 char LPPassManager::ID = 0;
64 LPPassManager::LPPassManager()
65 : FunctionPass(ID), PMDataManager() {
69 CurrentLoop = nullptr;
72 /// Delete loop from the loop queue and loop hierarchy (LoopInfo).
73 void LPPassManager::deleteLoopFromQueue(Loop *L) {
77 // If L is current loop then skip rest of the passes and let
78 // runOnFunction remove L from LQ. Otherwise, remove L from LQ now
79 // and continue applying other passes on CurrentLoop.
88 for (std::deque<Loop *>::iterator I = LQ.begin(),
89 E = LQ.end(); I != E; ++I) {
97 // Inset loop into loop nest (LoopInfo) and loop queue (LQ).
98 void LPPassManager::insertLoop(Loop *L, Loop *ParentLoop) {
100 assert (CurrentLoop != L && "Cannot insert CurrentLoop");
102 // Insert into loop nest
104 ParentLoop->addChildLoop(L);
106 LI->addTopLevelLoop(L);
108 insertLoopIntoQueue(L);
111 void LPPassManager::insertLoopIntoQueue(Loop *L) {
112 // Insert L into loop queue
113 if (L == CurrentLoop)
115 else if (!L->getParentLoop())
116 // This is top level loop.
119 // Insert L after the parent loop.
120 for (std::deque<Loop *>::iterator I = LQ.begin(),
121 E = LQ.end(); I != E; ++I) {
122 if (*I == L->getParentLoop()) {
123 // deque does not support insert after.
132 // Reoptimize this loop. LPPassManager will re-insert this loop into the
133 // queue. This allows LoopPass to change loop nest for the loop. This
134 // utility may send LPPassManager into infinite loops so use caution.
135 void LPPassManager::redoLoop(Loop *L) {
136 assert (CurrentLoop == L && "Can redo only CurrentLoop");
140 /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
142 void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From,
143 BasicBlock *To, Loop *L) {
144 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
145 LoopPass *LP = getContainedPass(Index);
146 LP->cloneBasicBlockAnalysis(From, To, L);
150 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
151 void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
152 if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
153 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;
155 Instruction &I = *BI;
156 deleteSimpleAnalysisValue(&I, L);
159 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
160 LoopPass *LP = getContainedPass(Index);
161 LP->deleteAnalysisValue(V, L);
166 // Recurse through all subloops and all loops into LQ.
167 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
169 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I)
170 addLoopIntoQueue(*I, LQ);
173 /// Pass Manager itself does not invalidate any analysis info.
174 void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const {
175 // LPPassManager needs LoopInfo. In the long term LoopInfo class will
176 // become part of LPPassManager.
177 Info.addRequired<LoopInfo>();
178 Info.setPreservesAll();
181 /// run - Execute all of the passes scheduled for execution. Keep track of
182 /// whether any of the passes modifies the function, and if so, return true.
183 bool LPPassManager::runOnFunction(Function &F) {
184 LI = &getAnalysis<LoopInfo>();
185 bool Changed = false;
187 // Collect inherited analysis from Module level pass manager.
188 populateInheritedAnalysis(TPM->activeStack);
190 // Populate the loop queue in reverse program order. There is no clear need to
191 // process sibling loops in either forward or reverse order. There may be some
192 // advantage in deleting uses in a later loop before optimizing the
193 // definitions in an earlier loop. If we find a clear reason to process in
194 // forward order, then a forward variant of LoopPassManager should be created.
196 // Note that LoopInfo::iterator visits loops in reverse program
197 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
198 // reverses the order a third time by popping from the back.
199 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
200 addLoopIntoQueue(*I, LQ);
202 if (LQ.empty()) // No loops, skip calling finalizers
206 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end();
209 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
210 LoopPass *P = getContainedPass(Index);
211 Changed |= P->doInitialization(L, *this);
216 while (!LQ.empty()) {
218 CurrentLoop = LQ.back();
219 skipThisLoop = false;
220 redoThisLoop = false;
222 // Run all passes on the current Loop.
223 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
224 LoopPass *P = getContainedPass(Index);
226 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
227 CurrentLoop->getHeader()->getName());
230 initializeAnalysisImpl(P);
233 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
234 TimeRegion PassTimer(getPassTimer(P));
236 Changed |= P->runOnLoop(CurrentLoop, *this);
240 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG,
241 skipThisLoop ? "<deleted>" :
242 CurrentLoop->getHeader()->getName());
246 // Manually check that this loop is still healthy. This is done
247 // instead of relying on LoopInfo::verifyLoop since LoopInfo
248 // is a function pass and it's really expensive to verify every
249 // loop in the function every time. That level of checking can be
250 // enabled with the -verify-loop-info option.
252 TimeRegion PassTimer(getPassTimer(LI));
253 CurrentLoop->verifyLoop();
256 // Then call the regular verifyAnalysis functions.
257 verifyPreservedAnalysis(P);
259 F.getContext().yield();
262 removeNotPreservedAnalysis(P);
263 recordAvailableAnalysis(P);
265 skipThisLoop ? "<deleted>" :
266 CurrentLoop->getHeader()->getName(),
270 // Do not run other passes on this loop.
274 // If the loop was deleted, release all the loop passes. This frees up
275 // some memory, and avoids trouble with the pass manager trying to call
276 // verifyAnalysis on them.
278 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
279 Pass *P = getContainedPass(Index);
280 freePass(P, "<deleted>", ON_LOOP_MSG);
283 // Pop the loop from queue after running all passes.
287 LQ.push_back(CurrentLoop);
291 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
292 LoopPass *P = getContainedPass(Index);
293 Changed |= P->doFinalization();
299 /// Print passes managed by this manager
300 void LPPassManager::dumpPassStructure(unsigned Offset) {
301 errs().indent(Offset*2) << "Loop Pass Manager\n";
302 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
303 Pass *P = getContainedPass(Index);
304 P->dumpPassStructure(Offset + 1);
305 dumpLastUses(P, Offset+1);
310 //===----------------------------------------------------------------------===//
313 Pass *LoopPass::createPrinterPass(raw_ostream &O,
314 const std::string &Banner) const {
315 return new PrintLoopPass(Banner, O);
318 // Check if this pass is suitable for the current LPPassManager, if
319 // available. This pass P is not suitable for a LPPassManager if P
320 // is not preserving higher level analysis info used by other
321 // LPPassManager passes. In such case, pop LPPassManager from the
322 // stack. This will force assignPassManager() to create new
323 // LPPassManger as expected.
324 void LoopPass::preparePassManager(PMStack &PMS) {
326 // Find LPPassManager
327 while (!PMS.empty() &&
328 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
331 // If this pass is destroying high level information that is used
332 // by other passes that are managed by LPM then do not insert
333 // this pass in current LPM. Use new LPPassManager.
334 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
335 !PMS.top()->preserveHigherLevelAnalysis(this))
339 /// Assign pass manager to manage this pass.
340 void LoopPass::assignPassManager(PMStack &PMS,
341 PassManagerType PreferredType) {
342 // Find LPPassManager
343 while (!PMS.empty() &&
344 PMS.top()->getPassManagerType() > PMT_LoopPassManager)
348 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
349 LPPM = (LPPassManager*)PMS.top();
351 // Create new Loop Pass Manager if it does not exist.
352 assert (!PMS.empty() && "Unable to create Loop Pass Manager");
353 PMDataManager *PMD = PMS.top();
355 // [1] Create new Loop Pass Manager
356 LPPM = new LPPassManager();
357 LPPM->populateInheritedAnalysis(PMS);
359 // [2] Set up new manager's top level manager
360 PMTopLevelManager *TPM = PMD->getTopLevelManager();
361 TPM->addIndirectPassManager(LPPM);
363 // [3] Assign manager to manage this new manager. This may create
364 // and push new managers into PMS
365 Pass *P = LPPM->getAsPass();
366 TPM->schedulePass(P);
368 // [4] Push new manager into PMS
375 // Containing function has Attribute::OptimizeNone and transformation
376 // passes should skip it.
377 bool LoopPass::skipOptnoneFunction(const Loop *L) const {
378 const Function *F = L->getHeader()->getParent();
379 if (F && F->hasFnAttribute(Attribute::OptimizeNone)) {
380 // FIXME: Report this to dbgs() only once per function.
381 DEBUG(dbgs() << "Skipping pass '" << getPassName()
382 << "' in function " << F->getName() << "\n");
383 // FIXME: Delete loop from pass manager's queue?