LLVM 19.0.0git
LoopPass.cpp
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1//===- LoopPass.cpp - Loop Pass and Loop Pass Manager ---------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements LoopPass and LPPassManager. All loop optimization
10// and transformation passes are derived from LoopPass. LPPassManager is
11// responsible for managing LoopPasses.
12//
13//===----------------------------------------------------------------------===//
14
17#include "llvm/IR/Dominators.h"
18#include "llvm/IR/LLVMContext.h"
19#include "llvm/IR/OptBisect.h"
21#include "llvm/IR/PrintPasses.h"
23#include "llvm/Support/Debug.h"
25#include "llvm/Support/Timer.h"
27using namespace llvm;
28
29#define DEBUG_TYPE "loop-pass-manager"
30
31namespace {
32
33/// PrintLoopPass - Print a Function corresponding to a Loop.
34///
35class PrintLoopPassWrapper : public LoopPass {
37 std::string Banner;
38
39public:
40 static char ID;
41 PrintLoopPassWrapper() : LoopPass(ID), OS(dbgs()) {}
42 PrintLoopPassWrapper(raw_ostream &OS, const std::string &Banner)
43 : LoopPass(ID), OS(OS), Banner(Banner) {}
44
45 void getAnalysisUsage(AnalysisUsage &AU) const override {
46 AU.setPreservesAll();
47 }
48
49 bool runOnLoop(Loop *L, LPPassManager &) override {
50 auto BBI = llvm::find_if(L->blocks(), [](BasicBlock *BB) { return BB; });
51 if (BBI != L->blocks().end() &&
52 isFunctionInPrintList((*BBI)->getParent()->getName())) {
53 printLoop(*L, OS, Banner);
54 }
55 return false;
56 }
57
58 StringRef getPassName() const override { return "Print Loop IR"; }
59};
60
61char PrintLoopPassWrapper::ID = 0;
62}
63
64//===----------------------------------------------------------------------===//
65// LPPassManager
66//
67
68char LPPassManager::ID = 0;
69
71 LI = nullptr;
72 CurrentLoop = nullptr;
73}
74
75// Insert loop into loop nest (LoopInfo) and loop queue (LQ).
77 if (L.isOutermost()) {
78 // This is the top level loop.
79 LQ.push_front(&L);
80 return;
81 }
82
83 // Insert L into the loop queue after the parent loop.
84 for (auto I = LQ.begin(), E = LQ.end(); I != E; ++I) {
85 if (*I == L.getParentLoop()) {
86 // deque does not support insert after.
87 ++I;
88 LQ.insert(I, 1, &L);
89 return;
90 }
91 }
92}
93
94// Recurse through all subloops and all loops into LQ.
95static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
96 LQ.push_back(L);
97 for (Loop *I : reverse(*L))
99}
100
101/// Pass Manager itself does not invalidate any analysis info.
103 // LPPassManager needs LoopInfo. In the long term LoopInfo class will
104 // become part of LPPassManager.
105 Info.addRequired<LoopInfoWrapperPass>();
106 Info.addRequired<DominatorTreeWrapperPass>();
107 Info.setPreservesAll();
108}
109
111 assert((&L == CurrentLoop || CurrentLoop->contains(&L)) &&
112 "Must not delete loop outside the current loop tree!");
113 // If this loop appears elsewhere within the queue, we also need to remove it
114 // there. However, we have to be careful to not remove the back of the queue
115 // as that is assumed to match the current loop.
116 assert(LQ.back() == CurrentLoop && "Loop queue back isn't the current loop!");
117 llvm::erase(LQ, &L);
118
119 if (&L == CurrentLoop) {
120 CurrentLoopDeleted = true;
121 // Add this loop back onto the back of the queue to preserve our invariants.
122 LQ.push_back(&L);
123 }
124}
125
126/// run - Execute all of the passes scheduled for execution. Keep track of
127/// whether any of the passes modifies the function, and if so, return true.
129 auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
130 LI = &LIWP.getLoopInfo();
131 Module &M = *F.getParent();
132#if 0
133 DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
134#endif
135 bool Changed = false;
136
137 // Collect inherited analysis from Module level pass manager.
139
140 // Populate the loop queue in reverse program order. There is no clear need to
141 // process sibling loops in either forward or reverse order. There may be some
142 // advantage in deleting uses in a later loop before optimizing the
143 // definitions in an earlier loop. If we find a clear reason to process in
144 // forward order, then a forward variant of LoopPassManager should be created.
145 //
146 // Note that LoopInfo::iterator visits loops in reverse program
147 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
148 // reverses the order a third time by popping from the back.
149 for (Loop *L : reverse(*LI))
150 addLoopIntoQueue(L, LQ);
151
152 if (LQ.empty()) // No loops, skip calling finalizers
153 return false;
154
155 // Initialization
156 for (Loop *L : LQ) {
157 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
159 Changed |= P->doInitialization(L, *this);
160 }
161 }
162
163 // Walk Loops
164 unsigned InstrCount, FunctionSize = 0;
165 StringMap<std::pair<unsigned, unsigned>> FunctionToInstrCount;
166 bool EmitICRemark = M.shouldEmitInstrCountChangedRemark();
167 // Collect the initial size of the module and the function we're looking at.
168 if (EmitICRemark) {
169 InstrCount = initSizeRemarkInfo(M, FunctionToInstrCount);
170 FunctionSize = F.getInstructionCount();
171 }
172 while (!LQ.empty()) {
173 CurrentLoopDeleted = false;
174 CurrentLoop = LQ.back();
175
176 // Run all passes on the current Loop.
177 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
179
180 llvm::TimeTraceScope LoopPassScope("RunLoopPass", P->getPassName());
181
183 CurrentLoop->getHeader()->getName());
185
187
188 bool LocalChanged = false;
189 {
190 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
191 TimeRegion PassTimer(getPassTimer(P));
192#ifdef EXPENSIVE_CHECKS
193 uint64_t RefHash = P->structuralHash(F);
194#endif
195 LocalChanged = P->runOnLoop(CurrentLoop, *this);
196
197#ifdef EXPENSIVE_CHECKS
198 if (!LocalChanged && (RefHash != P->structuralHash(F))) {
199 llvm::errs() << "Pass modifies its input and doesn't report it: "
200 << P->getPassName() << "\n";
201 llvm_unreachable("Pass modifies its input and doesn't report it");
202 }
203#endif
204
205 Changed |= LocalChanged;
206 if (EmitICRemark) {
207 unsigned NewSize = F.getInstructionCount();
208 // Update the size of the function, emit a remark, and update the
209 // size of the module.
210 if (NewSize != FunctionSize) {
211 int64_t Delta = static_cast<int64_t>(NewSize) -
212 static_cast<int64_t>(FunctionSize);
214 FunctionToInstrCount, &F);
215 InstrCount = static_cast<int64_t>(InstrCount) + Delta;
216 FunctionSize = NewSize;
217 }
218 }
219 }
220
221 if (LocalChanged)
223 CurrentLoopDeleted ? "<deleted loop>"
224 : CurrentLoop->getName());
226
227 if (!CurrentLoopDeleted) {
228 // Manually check that this loop is still healthy. This is done
229 // instead of relying on LoopInfo::verifyLoop since LoopInfo
230 // is a function pass and it's really expensive to verify every
231 // loop in the function every time. That level of checking can be
232 // enabled with the -verify-loop-info option.
233 {
234 TimeRegion PassTimer(getPassTimer(&LIWP));
235 CurrentLoop->verifyLoop();
236 }
237 // Here we apply same reasoning as in the above case. Only difference
238 // is that LPPassManager might run passes which do not require LCSSA
239 // form (LoopPassPrinter for example). We should skip verification for
240 // such passes.
241 // FIXME: Loop-sink currently break LCSSA. Fix it and reenable the
242 // verification!
243#if 0
245 assert(CurrentLoop->isRecursivelyLCSSAForm(*DT, *LI));
246#endif
247
248 // Then call the regular verifyAnalysis functions.
250
251 F.getContext().yield();
252 }
253
254 if (LocalChanged)
258 CurrentLoopDeleted ? "<deleted>"
259 : CurrentLoop->getHeader()->getName(),
261
262 if (CurrentLoopDeleted)
263 // Do not run other passes on this loop.
264 break;
265 }
266
267 // If the loop was deleted, release all the loop passes. This frees up
268 // some memory, and avoids trouble with the pass manager trying to call
269 // verifyAnalysis on them.
270 if (CurrentLoopDeleted) {
271 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
273 freePass(P, "<deleted>", ON_LOOP_MSG);
274 }
275 }
276
277 // Pop the loop from queue after running all passes.
278 LQ.pop_back();
279 }
280
281 // Finalization
282 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
284 Changed |= P->doFinalization();
285 }
286
287 return Changed;
288}
289
290/// Print passes managed by this manager
292 errs().indent(Offset*2) << "Loop Pass Manager\n";
293 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
295 P->dumpPassStructure(Offset + 1);
297 }
298}
299
300
301//===----------------------------------------------------------------------===//
302// LoopPass
303
305 const std::string &Banner) const {
306 return new PrintLoopPassWrapper(O, Banner);
307}
308
309// Check if this pass is suitable for the current LPPassManager, if
310// available. This pass P is not suitable for a LPPassManager if P
311// is not preserving higher level analysis info used by other
312// LPPassManager passes. In such case, pop LPPassManager from the
313// stack. This will force assignPassManager() to create new
314// LPPassManger as expected.
316
317 // Find LPPassManager
318 while (!PMS.empty() &&
320 PMS.pop();
321
322 // If this pass is destroying high level information that is used
323 // by other passes that are managed by LPM then do not insert
324 // this pass in current LPM. Use new LPPassManager.
326 !PMS.top()->preserveHigherLevelAnalysis(this))
327 PMS.pop();
328}
329
330/// Assign pass manager to manage this pass.
332 PassManagerType PreferredType) {
333 // Find LPPassManager
334 while (!PMS.empty() &&
336 PMS.pop();
337
338 LPPassManager *LPPM;
340 LPPM = (LPPassManager*)PMS.top();
341 else {
342 // Create new Loop Pass Manager if it does not exist.
343 assert (!PMS.empty() && "Unable to create Loop Pass Manager");
344 PMDataManager *PMD = PMS.top();
345
346 // [1] Create new Loop Pass Manager
347 LPPM = new LPPassManager();
348 LPPM->populateInheritedAnalysis(PMS);
349
350 // [2] Set up new manager's top level manager
352 TPM->addIndirectPassManager(LPPM);
353
354 // [3] Assign manager to manage this new manager. This may create
355 // and push new managers into PMS
356 Pass *P = LPPM->getAsPass();
357 TPM->schedulePass(P);
358
359 // [4] Push new manager into PMS
360 PMS.push(LPPM);
361 }
362
363 LPPM->add(this);
364}
365
366static std::string getDescription(const Loop &L) {
367 return "loop";
368}
369
370bool LoopPass::skipLoop(const Loop *L) const {
371 const Function *F = L->getHeader()->getParent();
372 if (!F)
373 return false;
374 // Check the opt bisect limit.
375 OptPassGate &Gate = F->getContext().getOptPassGate();
376 if (Gate.isEnabled() &&
377 !Gate.shouldRunPass(this->getPassName(), getDescription(*L)))
378 return true;
379 // Check for the OptimizeNone attribute.
380 if (F->hasOptNone()) {
381 // FIXME: Report this to dbgs() only once per function.
382 LLVM_DEBUG(dbgs() << "Skipping pass '" << getPassName() << "' in function "
383 << F->getName() << "\n");
384 // FIXME: Delete loop from pass manager's queue?
385 return true;
386 }
387 return false;
388}
389
392}
393
395INITIALIZE_PASS(LCSSAVerificationPass, "lcssa-verification", "LCSSA Verifier",
396 false, false)
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
Analysis containing CSE Info
Definition: CSEInfo.cpp:27
static std::string getDescription(const CallGraphSCC &SCC)
static unsigned InstrCount
#define LLVM_DEBUG(X)
Definition: Debug.h:101
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang", "erlang-compatible garbage collector")
static void addLoopIntoQueue(Loop *L, std::deque< Loop * > &LQ)
Definition: LoopPass.cpp:95
#define F(x, y, z)
Definition: MD5.cpp:55
#define I(x, y, z)
Definition: MD5.cpp:58
This file declares the interface for bisecting optimizations.
#define P(N)
#define INITIALIZE_PASS(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:38
This header defines classes/functions to handle pass execution timing information with interfaces for...
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
raw_pwrite_stream & OS
Represent the analysis usage information of a pass.
void setPreservesAll()
Set by analyses that do not transform their input at all.
LLVM Basic Block Representation.
Definition: BasicBlock.h:60
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:313
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree.
Definition: Dominators.h:162
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:311
static char ID
Definition: LoopPass.h:78
bool runOnFunction(Function &F) override
run - Execute all of the passes scheduled for execution.
Definition: LoopPass.cpp:128
Pass * getAsPass() override
Definition: LoopPass.h:92
void dumpPassStructure(unsigned Offset) override
Print passes managed by this manager.
Definition: LoopPass.cpp:291
void markLoopAsDeleted(Loop &L)
Definition: LoopPass.cpp:110
void addLoop(Loop &L)
Definition: LoopPass.cpp:76
LoopPass * getContainedPass(unsigned N)
Definition: LoopPass.h:97
void getAnalysisUsage(AnalysisUsage &Info) const override
Pass Manager itself does not invalidate any analysis info.
Definition: LoopPass.cpp:102
bool contains(const LoopT *L) const
Return true if the specified loop is contained within in this loop.
void verifyLoop() const
Verify loop structure.
BlockT * getHeader() const
The legacy pass manager's analysis pass to compute loop information.
Definition: LoopInfo.h:593
void preparePassManager(PMStack &PMS) override
Check if available pass managers are suitable for this pass or not.
Definition: LoopPass.cpp:315
Pass * createPrinterPass(raw_ostream &O, const std::string &Banner) const override
getPrinterPass - Get a pass to print the function corresponding to a Loop.
Definition: LoopPass.cpp:304
virtual bool runOnLoop(Loop *L, LPPassManager &LPM)=0
void assignPassManager(PMStack &PMS, PassManagerType PMT) override
Assign pass manager to manage this pass.
Definition: LoopPass.cpp:331
bool skipLoop(const Loop *L) const
Optional passes call this function to check whether the pass should be skipped.
Definition: LoopPass.cpp:370
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:44
StringRef getName() const
Definition: LoopInfo.h:388
bool isRecursivelyLCSSAForm(const DominatorTree &DT, const LoopInfo &LI, bool IgnoreTokens=true) const
Return true if this Loop and all inner subloops are in LCSSA form.
Definition: LoopInfo.cpp:469
A Module instance is used to store all the information related to an LLVM module.
Definition: Module.h:65
Extensions to this class implement mechanisms to disable passes and individual optimizations at compi...
Definition: OptBisect.h:24
virtual bool isEnabled() const
isEnabled() should return true before calling shouldRunPass().
Definition: OptBisect.h:36
virtual bool shouldRunPass(const StringRef PassName, StringRef IRDescription)
IRDescription is a textual description of the IR unit the pass is running over.
Definition: OptBisect.h:30
PMDataManager provides the common place to manage the analysis data used by pass managers.
void removeDeadPasses(Pass *P, StringRef Msg, enum PassDebuggingString)
Remove dead passes used by P.
void dumpLastUses(Pass *P, unsigned Offset) const
void recordAvailableAnalysis(Pass *P)
Augment AvailableAnalysis by adding analysis made available by pass P.
PMTopLevelManager * getTopLevelManager()
unsigned initSizeRemarkInfo(Module &M, StringMap< std::pair< unsigned, unsigned > > &FunctionToInstrCount)
Set the initial size of the module if the user has specified that they want remarks for size.
void dumpRequiredSet(const Pass *P) const
void initializeAnalysisImpl(Pass *P)
All Required analyses should be available to the pass as it runs! Here we fill in the AnalysisImpls m...
void verifyPreservedAnalysis(Pass *P)
verifyPreservedAnalysis – Verify analysis presreved by pass P.
void freePass(Pass *P, StringRef Msg, enum PassDebuggingString)
Remove P.
bool preserveHigherLevelAnalysis(Pass *P)
unsigned getNumContainedPasses() const
virtual PassManagerType getPassManagerType() const
PMTopLevelManager * TPM
void emitInstrCountChangedRemark(Pass *P, Module &M, int64_t Delta, unsigned CountBefore, StringMap< std::pair< unsigned, unsigned > > &FunctionToInstrCount, Function *F=nullptr)
Emit a remark signifying that the number of IR instructions in the module changed.
void add(Pass *P, bool ProcessAnalysis=true)
Add pass P into the PassVector.
void populateInheritedAnalysis(PMStack &PMS)
void dumpPreservedSet(const Pass *P) const
void removeNotPreservedAnalysis(Pass *P)
Remove Analysis that is not preserved by the pass.
void dumpPassInfo(Pass *P, enum PassDebuggingString S1, enum PassDebuggingString S2, StringRef Msg)
PMStack - This class implements a stack data structure of PMDataManager pointers.
PMDataManager * top() const
bool empty() const
void push(PMDataManager *PM)
PMTopLevelManager manages LastUser info and collects common APIs used by top level pass managers.
void addIndirectPassManager(PMDataManager *Manager)
void schedulePass(Pass *P)
Schedule pass P for execution.
PassManagerPrettyStackEntry - This is used to print informative information about what pass is runnin...
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
Pass interface - Implemented by all 'passes'.
Definition: Pass.h:94
bool mustPreserveAnalysisID(char &AID) const
mustPreserveAnalysisID - This method serves the same function as getAnalysisIfAvailable,...
Definition: Pass.cpp:69
virtual void getAnalysisUsage(AnalysisUsage &) const
getAnalysisUsage - This function should be overriden by passes that need analysis information to do t...
Definition: Pass.cpp:98
virtual StringRef getPassName() const
getPassName - Return a nice clean name for a pass.
Definition: Pass.cpp:81
StringMap - This is an unconventional map that is specialized for handling keys that are "strings",...
Definition: StringMap.h:128
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
The TimeRegion class is used as a helper class to call the startTimer() and stopTimer() methods of th...
Definition: Timer.h:143
StringRef getName() const
Return a constant reference to the value's name.
Definition: Value.cpp:309
This class implements an extremely fast bulk output stream that can only output to a stream.
Definition: raw_ostream.h:52
raw_ostream & indent(unsigned NumSpaces)
indent - Insert 'NumSpaces' spaces.
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
unsigned ID
LLVM IR allows to use arbitrary numbers as calling convention identifiers.
Definition: CallingConv.h:24
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
void initializeLCSSAVerificationPassPass(PassRegistry &)
@ Offset
Definition: DWP.cpp:456
PassManagerType
Different types of internal pass managers.
Definition: Pass.h:55
@ PMT_LoopPassManager
LPPassManager.
Definition: Pass.h:60
void erase(Container &C, ValueType V)
Wrapper function to remove a value from a container:
Definition: STLExtras.h:2039
Timer * getPassTimer(Pass *)
Request the timer for this legacy-pass-manager's pass instance.
auto reverse(ContainerTy &&C)
Definition: STLExtras.h:428
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:163
bool isFunctionInPrintList(StringRef FunctionName)
@ MODIFICATION_MSG
raw_fd_ostream & errs()
This returns a reference to a raw_ostream for standard error.
auto find_if(R &&Range, UnaryPredicate P)
Provide wrappers to std::find_if which take ranges instead of having to pass begin/end explicitly.
Definition: STLExtras.h:1758
void printLoop(Loop &L, raw_ostream &OS, const std::string &Banner="")
Function to print a loop's contents as LLVM's text IR assembly.
Definition: LoopInfo.cpp:977
The TimeTraceScope is a helper class to call the begin and end functions of the time trace profiler.
Definition: TimeProfiler.h:134