Line data Source code
1 : //===- LoopPass.cpp - Loop Pass and Loop Pass Manager ---------------------===//
2 : //
3 : // The LLVM Compiler Infrastructure
4 : //
5 : // This file is distributed under the University of Illinois Open Source
6 : // License. See LICENSE.TXT for details.
7 : //
8 : //===----------------------------------------------------------------------===//
9 : //
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.
13 : //
14 : //===----------------------------------------------------------------------===//
15 :
16 : #include "llvm/Analysis/LoopPass.h"
17 : #include "llvm/Analysis/LoopAnalysisManager.h"
18 : #include "llvm/IR/Dominators.h"
19 : #include "llvm/IR/IRPrintingPasses.h"
20 : #include "llvm/IR/LLVMContext.h"
21 : #include "llvm/IR/OptBisect.h"
22 : #include "llvm/IR/PassManager.h"
23 : #include "llvm/IR/PassTimingInfo.h"
24 : #include "llvm/Support/Debug.h"
25 : #include "llvm/Support/Timer.h"
26 : #include "llvm/Support/raw_ostream.h"
27 : using namespace llvm;
28 :
29 : #define DEBUG_TYPE "loop-pass-manager"
30 :
31 : namespace {
32 :
33 : /// PrintLoopPass - Print a Function corresponding to a Loop.
34 : ///
35 : class PrintLoopPassWrapper : public LoopPass {
36 : raw_ostream &OS;
37 : std::string Banner;
38 :
39 : public:
40 : static char ID;
41 : PrintLoopPassWrapper() : LoopPass(ID), OS(dbgs()) {}
42 : PrintLoopPassWrapper(raw_ostream &OS, const std::string &Banner)
43 38 : : LoopPass(ID), OS(OS), Banner(Banner) {}
44 :
45 19 : void getAnalysisUsage(AnalysisUsage &AU) const override {
46 : AU.setPreservesAll();
47 19 : }
48 :
49 6 : bool runOnLoop(Loop *L, LPPassManager &) override {
50 : auto BBI = llvm::find_if(L->blocks(), [](BasicBlock *BB) { return BB; });
51 12 : if (BBI != L->blocks().end() &&
52 6 : isFunctionInPrintList((*BBI)->getParent()->getName())) {
53 4 : printLoop(*L, OS, Banner);
54 : }
55 6 : return false;
56 : }
57 :
58 0 : StringRef getPassName() const override { return "Print Loop IR"; }
59 : };
60 :
61 : char PrintLoopPassWrapper::ID = 0;
62 : }
63 :
64 : //===----------------------------------------------------------------------===//
65 : // LPPassManager
66 : //
67 :
68 : char LPPassManager::ID = 0;
69 :
70 37036 : LPPassManager::LPPassManager()
71 37036 : : FunctionPass(ID), PMDataManager() {
72 37036 : LI = nullptr;
73 37036 : CurrentLoop = nullptr;
74 37036 : }
75 :
76 : // Insert loop into loop nest (LoopInfo) and loop queue (LQ).
77 326 : void LPPassManager::addLoop(Loop &L) {
78 326 : if (!L.getParentLoop()) {
79 : // This is the top level loop.
80 243 : LQ.push_front(&L);
81 243 : return;
82 : }
83 :
84 : // Insert L into the loop queue after the parent loop.
85 116 : for (auto I = LQ.begin(), E = LQ.end(); I != E; ++I) {
86 116 : if (*I == L.getParentLoop()) {
87 : // deque does not support insert after.
88 : ++I;
89 166 : LQ.insert(I, 1, &L);
90 : return;
91 : }
92 : }
93 : }
94 :
95 : /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
96 : /// all loop passes.
97 725 : void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From,
98 : BasicBlock *To, Loop *L) {
99 1497 : for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
100 : LoopPass *LP = getContainedPass(Index);
101 772 : LP->cloneBasicBlockAnalysis(From, To, L);
102 : }
103 725 : }
104 :
105 : /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
106 259 : void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
107 : if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
108 0 : for (Instruction &I : *BB) {
109 0 : deleteSimpleAnalysisValue(&I, L);
110 : }
111 : }
112 536 : for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
113 : LoopPass *LP = getContainedPass(Index);
114 277 : LP->deleteAnalysisValue(V, L);
115 : }
116 259 : }
117 :
118 : /// Invoke deleteAnalysisLoop hook for all passes.
119 935 : void LPPassManager::deleteSimpleAnalysisLoop(Loop *L) {
120 3276 : for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
121 : LoopPass *LP = getContainedPass(Index);
122 2341 : LP->deleteAnalysisLoop(L);
123 : }
124 935 : }
125 :
126 :
127 : // Recurse through all subloops and all loops into LQ.
128 40879 : static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
129 : LQ.push_back(L);
130 49243 : for (Loop *I : reverse(*L))
131 8364 : addLoopIntoQueue(I, LQ);
132 40879 : }
133 :
134 : /// Pass Manager itself does not invalidate any analysis info.
135 37036 : void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const {
136 : // LPPassManager needs LoopInfo. In the long term LoopInfo class will
137 : // become part of LPPassManager.
138 : Info.addRequired<LoopInfoWrapperPass>();
139 : Info.addRequired<DominatorTreeWrapperPass>();
140 : Info.setPreservesAll();
141 37036 : }
142 :
143 668 : void LPPassManager::markLoopAsDeleted(Loop &L) {
144 : assert((&L == CurrentLoop || CurrentLoop->contains(&L)) &&
145 : "Must not delete loop outside the current loop tree!");
146 : // If this loop appears elsewhere within the queue, we also need to remove it
147 : // there. However, we have to be careful to not remove the back of the queue
148 : // as that is assumed to match the current loop.
149 : assert(LQ.back() == CurrentLoop && "Loop queue back isn't the current loop!");
150 2004 : LQ.erase(std::remove(LQ.begin(), LQ.end(), &L), LQ.end());
151 :
152 668 : if (&L == CurrentLoop) {
153 668 : CurrentLoopDeleted = true;
154 : // Add this loop back onto the back of the queue to preserve our invariants.
155 1336 : LQ.push_back(&L);
156 : }
157 668 : }
158 :
159 : /// run - Execute all of the passes scheduled for execution. Keep track of
160 : /// whether any of the passes modifies the function, and if so, return true.
161 426094 : bool LPPassManager::runOnFunction(Function &F) {
162 426094 : auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
163 426094 : LI = &LIWP.getLoopInfo();
164 426094 : Module &M = *F.getParent();
165 : #if 0
166 : DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
167 : #endif
168 : bool Changed = false;
169 :
170 : // Collect inherited analysis from Module level pass manager.
171 426094 : populateInheritedAnalysis(TPM->activeStack);
172 :
173 : // Populate the loop queue in reverse program order. There is no clear need to
174 : // process sibling loops in either forward or reverse order. There may be some
175 : // advantage in deleting uses in a later loop before optimizing the
176 : // definitions in an earlier loop. If we find a clear reason to process in
177 : // forward order, then a forward variant of LoopPassManager should be created.
178 : //
179 : // Note that LoopInfo::iterator visits loops in reverse program
180 : // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
181 : // reverses the order a third time by popping from the back.
182 458609 : for (Loop *L : reverse(*LI))
183 32515 : addLoopIntoQueue(L, LQ);
184 :
185 426094 : if (LQ.empty()) // No loops, skip calling finalizers
186 : return false;
187 :
188 : // Initialization
189 64958 : for (Loop *L : LQ) {
190 114960 : for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
191 : LoopPass *P = getContainedPass(Index);
192 74081 : Changed |= P->doInitialization(L, *this);
193 : }
194 : }
195 :
196 : // Walk Loops
197 : unsigned InstrCount, FunctionSize = 0;
198 24079 : StringMap<std::pair<unsigned, unsigned>> FunctionToInstrCount;
199 24079 : bool EmitICRemark = M.shouldEmitInstrCountChangedRemark();
200 : // Collect the initial size of the module and the function we're looking at.
201 24079 : if (EmitICRemark) {
202 1 : InstrCount = initSizeRemarkInfo(M, FunctionToInstrCount);
203 1 : FunctionSize = F.getInstructionCount();
204 : }
205 65283 : while (!LQ.empty()) {
206 41204 : CurrentLoopDeleted = false;
207 41204 : CurrentLoop = LQ.back();
208 :
209 : // Run all passes on the current Loop.
210 114754 : for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
211 : LoopPass *P = getContainedPass(Index);
212 :
213 74218 : dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
214 74218 : CurrentLoop->getHeader()->getName());
215 74218 : dumpRequiredSet(P);
216 :
217 74218 : initializeAnalysisImpl(P);
218 :
219 : {
220 148436 : PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
221 74218 : TimeRegion PassTimer(getPassTimer(P));
222 74218 : Changed |= P->runOnLoop(CurrentLoop, *this);
223 74218 : if (EmitICRemark) {
224 1 : unsigned NewSize = F.getInstructionCount();
225 : // Update the size of the function, emit a remark, and update the
226 : // size of the module.
227 1 : if (NewSize != FunctionSize) {
228 2 : int64_t Delta = static_cast<int64_t>(NewSize) -
229 1 : static_cast<int64_t>(FunctionSize);
230 1 : emitInstrCountChangedRemark(P, M, Delta, InstrCount,
231 : FunctionToInstrCount, &F);
232 1 : InstrCount = static_cast<int64_t>(InstrCount) + Delta;
233 : FunctionSize = NewSize;
234 : }
235 : }
236 : }
237 :
238 74218 : if (Changed)
239 25464 : dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG,
240 25464 : CurrentLoopDeleted ? "<deleted loop>"
241 24796 : : CurrentLoop->getName());
242 74218 : dumpPreservedSet(P);
243 :
244 74218 : if (CurrentLoopDeleted) {
245 : // Notify passes that the loop is being deleted.
246 668 : deleteSimpleAnalysisLoop(CurrentLoop);
247 : } else {
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.
253 : {
254 73550 : TimeRegion PassTimer(getPassTimer(&LIWP));
255 73550 : CurrentLoop->verifyLoop();
256 : }
257 : // Here we apply same reasoning as in the above case. Only difference
258 : // is that LPPassManager might run passes which do not require LCSSA
259 : // form (LoopPassPrinter for example). We should skip verification for
260 : // such passes.
261 : // FIXME: Loop-sink currently break LCSSA. Fix it and reenable the
262 : // verification!
263 : #if 0
264 : if (mustPreserveAnalysisID(LCSSAVerificationPass::ID))
265 : assert(CurrentLoop->isRecursivelyLCSSAForm(*DT, *LI));
266 : #endif
267 :
268 : // Then call the regular verifyAnalysis functions.
269 73550 : verifyPreservedAnalysis(P);
270 :
271 73550 : F.getContext().yield();
272 : }
273 :
274 74218 : removeNotPreservedAnalysis(P);
275 74218 : recordAvailableAnalysis(P);
276 74218 : removeDeadPasses(P,
277 74218 : CurrentLoopDeleted ? "<deleted>"
278 147100 : : CurrentLoop->getHeader()->getName(),
279 : ON_LOOP_MSG);
280 :
281 74218 : if (CurrentLoopDeleted)
282 : // Do not run other passes on this loop.
283 : break;
284 : }
285 :
286 : // If the loop was deleted, release all the loop passes. This frees up
287 : // some memory, and avoids trouble with the pass manager trying to call
288 : // verifyAnalysis on them.
289 41204 : if (CurrentLoopDeleted) {
290 2731 : for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
291 : Pass *P = getContainedPass(Index);
292 4126 : freePass(P, "<deleted>", ON_LOOP_MSG);
293 : }
294 : }
295 :
296 : // Pop the loop from queue after running all passes.
297 41204 : LQ.pop_back();
298 : }
299 :
300 : // Finalization
301 67890 : for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
302 : LoopPass *P = getContainedPass(Index);
303 43811 : Changed |= P->doFinalization();
304 : }
305 :
306 : return Changed;
307 : }
308 :
309 : /// Print passes managed by this manager
310 64 : void LPPassManager::dumpPassStructure(unsigned Offset) {
311 64 : errs().indent(Offset*2) << "Loop Pass Manager\n";
312 176 : for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
313 : Pass *P = getContainedPass(Index);
314 112 : P->dumpPassStructure(Offset + 1);
315 112 : dumpLastUses(P, Offset+1);
316 : }
317 64 : }
318 :
319 :
320 : //===----------------------------------------------------------------------===//
321 : // LoopPass
322 :
323 19 : Pass *LoopPass::createPrinterPass(raw_ostream &O,
324 : const std::string &Banner) const {
325 19 : return new PrintLoopPassWrapper(O, Banner);
326 : }
327 :
328 : // Check if this pass is suitable for the current LPPassManager, if
329 : // available. This pass P is not suitable for a LPPassManager if P
330 : // is not preserving higher level analysis info used by other
331 : // LPPassManager passes. In such case, pop LPPassManager from the
332 : // stack. This will force assignPassManager() to create new
333 : // LPPassManger as expected.
334 64292 : void LoopPass::preparePassManager(PMStack &PMS) {
335 :
336 : // Find LPPassManager
337 64292 : while (!PMS.empty() &&
338 64292 : PMS.top()->getPassManagerType() > PMT_LoopPassManager)
339 0 : PMS.pop();
340 :
341 : // If this pass is destroying high level information that is used
342 : // by other passes that are managed by LPM then do not insert
343 : // this pass in current LPM. Use new LPPassManager.
344 71487 : if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
345 7195 : !PMS.top()->preserveHigherLevelAnalysis(this))
346 30 : PMS.pop();
347 64292 : }
348 :
349 : /// Assign pass manager to manage this pass.
350 64311 : void LoopPass::assignPassManager(PMStack &PMS,
351 : PassManagerType PreferredType) {
352 : // Find LPPassManager
353 64311 : while (!PMS.empty() &&
354 64311 : PMS.top()->getPassManagerType() > PMT_LoopPassManager)
355 0 : PMS.pop();
356 :
357 : LPPassManager *LPPM;
358 64311 : if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
359 27275 : LPPM = (LPPassManager*)PMS.top();
360 : else {
361 : // Create new Loop Pass Manager if it does not exist.
362 : assert (!PMS.empty() && "Unable to create Loop Pass Manager");
363 : PMDataManager *PMD = PMS.top();
364 :
365 : // [1] Create new Loop Pass Manager
366 37036 : LPPM = new LPPassManager();
367 : LPPM->populateInheritedAnalysis(PMS);
368 :
369 : // [2] Set up new manager's top level manager
370 37036 : PMTopLevelManager *TPM = PMD->getTopLevelManager();
371 37036 : TPM->addIndirectPassManager(LPPM);
372 :
373 : // [3] Assign manager to manage this new manager. This may create
374 : // and push new managers into PMS
375 37036 : Pass *P = LPPM->getAsPass();
376 37036 : TPM->schedulePass(P);
377 :
378 : // [4] Push new manager into PMS
379 37036 : PMS.push(LPPM);
380 : }
381 :
382 64311 : LPPM->add(this);
383 64311 : }
384 :
385 65266 : bool LoopPass::skipLoop(const Loop *L) const {
386 65266 : const Function *F = L->getHeader()->getParent();
387 65266 : if (!F)
388 : return false;
389 : // Check the opt bisect limit.
390 65266 : LLVMContext &Context = F->getContext();
391 65266 : if (!Context.getOptPassGate().shouldRunPass(this, *L))
392 : return true;
393 : // Check for the OptimizeNone attribute.
394 65109 : if (F->hasFnAttribute(Attribute::OptimizeNone)) {
395 : // FIXME: Report this to dbgs() only once per function.
396 : LLVM_DEBUG(dbgs() << "Skipping pass '" << getPassName() << "' in function "
397 : << F->getName() << "\n");
398 : // FIXME: Delete loop from pass manager's queue?
399 53 : return true;
400 : }
401 : return false;
402 : }
403 :
404 : char LCSSAVerificationPass::ID = 0;
405 195164 : INITIALIZE_PASS(LCSSAVerificationPass, "lcssa-verification", "LCSSA Verifier",
406 : false, false)
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