LLVM 20.0.0git
LoopPass.cpp
Go to the documentation of this file.
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/Module.h"
20#include "llvm/IR/OptBisect.h"
22#include "llvm/IR/PrintPasses.h"
24#include "llvm/Support/Debug.h"
26#include "llvm/Support/Timer.h"
28using namespace llvm;
29
30#define DEBUG_TYPE "loop-pass-manager"
31
32namespace {
33
34/// PrintLoopPass - Print a Function corresponding to a Loop.
35///
36class PrintLoopPassWrapper : public LoopPass {
38 std::string Banner;
39
40public:
41 static char ID;
42 PrintLoopPassWrapper() : LoopPass(ID), OS(dbgs()) {}
43 PrintLoopPassWrapper(raw_ostream &OS, const std::string &Banner)
44 : LoopPass(ID), OS(OS), Banner(Banner) {}
45
46 void getAnalysisUsage(AnalysisUsage &AU) const override {
47 AU.setPreservesAll();
48 }
49
50 bool runOnLoop(Loop *L, LPPassManager &) override {
51 auto BBI = llvm::find_if(L->blocks(), [](BasicBlock *BB) { return BB; });
52 if (BBI != L->blocks().end() &&
53 isFunctionInPrintList((*BBI)->getParent()->getName())) {
54 printLoop(*L, OS, Banner);
55 }
56 return false;
57 }
58
59 StringRef getPassName() const override { return "Print Loop IR"; }
60};
61
62char PrintLoopPassWrapper::ID = 0;
63} // namespace
64
65//===----------------------------------------------------------------------===//
66// LPPassManager
67//
68
69char LPPassManager::ID = 0;
70
72 LI = nullptr;
73 CurrentLoop = nullptr;
74}
75
76// Insert loop into loop nest (LoopInfo) and loop queue (LQ).
78 if (L.isOutermost()) {
79 // This is the top level loop.
80 LQ.push_front(&L);
81 return;
82 }
83
84 // Insert L into the loop queue after the parent loop.
85 for (auto I = LQ.begin(), E = LQ.end(); I != E; ++I) {
86 if (*I == L.getParentLoop()) {
87 // deque does not support insert after.
88 ++I;
89 LQ.insert(I, 1, &L);
90 return;
91 }
92 }
93}
94
95// Recurse through all subloops and all loops into LQ.
96static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
97 LQ.push_back(L);
98 for (Loop *I : reverse(*L))
100}
101
102/// Pass Manager itself does not invalidate any analysis info.
104 // LPPassManager needs LoopInfo. In the long term LoopInfo class will
105 // become part of LPPassManager.
106 Info.addRequired<LoopInfoWrapperPass>();
107 Info.addRequired<DominatorTreeWrapperPass>();
108 Info.setPreservesAll();
109}
110
112 assert((&L == CurrentLoop || CurrentLoop->contains(&L)) &&
113 "Must not delete loop outside the current loop tree!");
114 // If this loop appears elsewhere within the queue, we also need to remove it
115 // there. However, we have to be careful to not remove the back of the queue
116 // as that is assumed to match the current loop.
117 assert(LQ.back() == CurrentLoop && "Loop queue back isn't the current loop!");
118 llvm::erase(LQ, &L);
119
120 if (&L == CurrentLoop) {
121 CurrentLoopDeleted = true;
122 // Add this loop back onto the back of the queue to preserve our invariants.
123 LQ.push_back(&L);
124 }
125}
126
127/// run - Execute all of the passes scheduled for execution. Keep track of
128/// whether any of the passes modifies the function, and if so, return true.
130 auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
131 LI = &LIWP.getLoopInfo();
132 Module &M = *F.getParent();
133#if 0
134 DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
135#endif
136 bool Changed = false;
137
138 // Collect inherited analysis from Module level pass manager.
140
141 // Populate the loop queue in reverse program order. There is no clear need to
142 // process sibling loops in either forward or reverse order. There may be some
143 // advantage in deleting uses in a later loop before optimizing the
144 // definitions in an earlier loop. If we find a clear reason to process in
145 // forward order, then a forward variant of LoopPassManager should be created.
146 //
147 // Note that LoopInfo::iterator visits loops in reverse program
148 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
149 // reverses the order a third time by popping from the back.
150 for (Loop *L : reverse(*LI))
151 addLoopIntoQueue(L, LQ);
152
153 if (LQ.empty()) // No loops, skip calling finalizers
154 return false;
155
156 // Initialization
157 for (Loop *L : LQ) {
158 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
159 LoopPass *P = getContainedPass(Index);
160 Changed |= P->doInitialization(L, *this);
161 }
162 }
163
164 // Walk Loops
165 unsigned InstrCount, FunctionSize = 0;
166 StringMap<std::pair<unsigned, unsigned>> FunctionToInstrCount;
167 bool EmitICRemark = M.shouldEmitInstrCountChangedRemark();
168 // Collect the initial size of the module and the function we're looking at.
169 if (EmitICRemark) {
170 InstrCount = initSizeRemarkInfo(M, FunctionToInstrCount);
171 FunctionSize = F.getInstructionCount();
172 }
173 while (!LQ.empty()) {
174 CurrentLoopDeleted = false;
175 CurrentLoop = LQ.back();
176
177 // Run all passes on the current Loop.
178 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
179 LoopPass *P = getContainedPass(Index);
180
181 llvm::TimeTraceScope LoopPassScope("RunLoopPass", P->getPassName());
182
184 CurrentLoop->getHeader()->getName());
186
188
189 bool LocalChanged = false;
190 {
191 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
192 TimeRegion PassTimer(getPassTimer(P));
193#ifdef EXPENSIVE_CHECKS
194 uint64_t RefHash = P->structuralHash(F);
195#endif
196 LocalChanged = P->runOnLoop(CurrentLoop, *this);
197
198#ifdef EXPENSIVE_CHECKS
199 if (!LocalChanged && (RefHash != P->structuralHash(F))) {
200 llvm::errs() << "Pass modifies its input and doesn't report it: "
201 << P->getPassName() << "\n";
202 llvm_unreachable("Pass modifies its input and doesn't report it");
203 }
204#endif
205
206 Changed |= LocalChanged;
207 if (EmitICRemark) {
208 unsigned NewSize = F.getInstructionCount();
209 // Update the size of the function, emit a remark, and update the
210 // size of the module.
211 if (NewSize != FunctionSize) {
212 int64_t Delta = static_cast<int64_t>(NewSize) -
213 static_cast<int64_t>(FunctionSize);
215 FunctionToInstrCount, &F);
216 InstrCount = static_cast<int64_t>(InstrCount) + Delta;
217 FunctionSize = NewSize;
218 }
219 }
220 }
221
222 if (LocalChanged)
224 CurrentLoopDeleted ? "<deleted loop>"
225 : CurrentLoop->getName());
227
228 if (!CurrentLoopDeleted) {
229 // Manually check that this loop is still healthy. This is done
230 // instead of relying on LoopInfo::verifyLoop since LoopInfo
231 // is a function pass and it's really expensive to verify every
232 // loop in the function every time. That level of checking can be
233 // enabled with the -verify-loop-info option.
234 {
235 TimeRegion PassTimer(getPassTimer(&LIWP));
236 CurrentLoop->verifyLoop();
237 }
238 // Here we apply same reasoning as in the above case. Only difference
239 // is that LPPassManager might run passes which do not require LCSSA
240 // form (LoopPassPrinter for example). We should skip verification for
241 // such passes.
242 // FIXME: Loop-sink currently break LCSSA. Fix it and reenable the
243 // verification!
244#if 0
246 assert(CurrentLoop->isRecursivelyLCSSAForm(*DT, *LI));
247#endif
248
249 // Then call the regular verifyAnalysis functions.
251
252 F.getContext().yield();
253 }
254
255 if (LocalChanged)
259 CurrentLoopDeleted ? "<deleted>"
260 : CurrentLoop->getHeader()->getName(),
262
263 if (CurrentLoopDeleted)
264 // Do not run other passes on this loop.
265 break;
266 }
267
268 // If the loop was deleted, release all the loop passes. This frees up
269 // some memory, and avoids trouble with the pass manager trying to call
270 // verifyAnalysis on them.
271 if (CurrentLoopDeleted) {
272 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
273 Pass *P = getContainedPass(Index);
274 freePass(P, "<deleted>", ON_LOOP_MSG);
275 }
276 }
277
278 // Pop the loop from queue after running all passes.
279 LQ.pop_back();
280 }
281
282 // Finalization
283 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
284 LoopPass *P = getContainedPass(Index);
285 Changed |= P->doFinalization();
286 }
287
288 return Changed;
289}
290
291/// Print passes managed by this manager
293 errs().indent(Offset*2) << "Loop Pass Manager\n";
294 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
295 Pass *P = getContainedPass(Index);
296 P->dumpPassStructure(Offset + 1);
298 }
299}
300
301
302//===----------------------------------------------------------------------===//
303// LoopPass
304
306 const std::string &Banner) const {
307 return new PrintLoopPassWrapper(O, Banner);
308}
309
310// Check if this pass is suitable for the current LPPassManager, if
311// available. This pass P is not suitable for a LPPassManager if P
312// is not preserving higher level analysis info used by other
313// LPPassManager passes. In such case, pop LPPassManager from the
314// stack. This will force assignPassManager() to create new
315// LPPassManger as expected.
317
318 // Find LPPassManager
319 while (!PMS.empty() &&
321 PMS.pop();
322
323 // If this pass is destroying high level information that is used
324 // by other passes that are managed by LPM then do not insert
325 // this pass in current LPM. Use new LPPassManager.
327 !PMS.top()->preserveHigherLevelAnalysis(this))
328 PMS.pop();
329}
330
331/// Assign pass manager to manage this pass.
333 PassManagerType PreferredType) {
334 // Find LPPassManager
335 while (!PMS.empty() &&
337 PMS.pop();
338
339 LPPassManager *LPPM;
341 LPPM = (LPPassManager*)PMS.top();
342 else {
343 // Create new Loop Pass Manager if it does not exist.
344 assert (!PMS.empty() && "Unable to create Loop Pass Manager");
345 PMDataManager *PMD = PMS.top();
346
347 // [1] Create new Loop Pass Manager
348 LPPM = new LPPassManager();
349 LPPM->populateInheritedAnalysis(PMS);
350
351 // [2] Set up new manager's top level manager
353 TPM->addIndirectPassManager(LPPM);
354
355 // [3] Assign manager to manage this new manager. This may create
356 // and push new managers into PMS
357 Pass *P = LPPM->getAsPass();
358 TPM->schedulePass(P);
359
360 // [4] Push new manager into PMS
361 PMS.push(LPPM);
362 }
363
364 LPPM->add(this);
365}
366
367static std::string getDescription(const Loop &L) {
368 return "loop";
369}
370
371bool LoopPass::skipLoop(const Loop *L) const {
372 const Function *F = L->getHeader()->getParent();
373 if (!F)
374 return false;
375 // Check the opt bisect limit.
376 OptPassGate &Gate = F->getContext().getOptPassGate();
377 if (Gate.isEnabled() &&
378 !Gate.shouldRunPass(this->getPassName(), getDescription(*L)))
379 return true;
380 // Check for the OptimizeNone attribute.
381 if (F->hasOptNone()) {
382 // FIXME: Report this to dbgs() only once per function.
383 LLVM_DEBUG(dbgs() << "Skipping pass '" << getPassName() << "' in function "
384 << F->getName() << "\n");
385 // FIXME: Delete loop from pass manager's queue?
386 return true;
387 }
388 return false;
389}
390
393}
394
396INITIALIZE_PASS(LCSSAVerificationPass, "lcssa-verification", "LCSSA Verifier",
397 false, false)
Analysis containing CSE Info
Definition: CSEInfo.cpp:27
static std::string getDescription(const CallGraphSCC &SCC)
static unsigned InstrCount
#define LLVM_DEBUG(...)
Definition: Debug.h:106
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang", "erlang-compatible garbage collector")
Module.h This file contains the declarations for the Module class.
static void addLoopIntoQueue(Loop *L, std::deque< Loop * > &LQ)
Definition: LoopPass.cpp:96
#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:61
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:317
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:310
static char ID
Definition: LoopPass.h:78
bool runOnFunction(Function &F) override
run - Execute all of the passes scheduled for execution.
Definition: LoopPass.cpp:129
Pass * getAsPass() override
Definition: LoopPass.h:92
void dumpPassStructure(unsigned Offset) override
Print passes managed by this manager.
Definition: LoopPass.cpp:292
void markLoopAsDeleted(Loop &L)
Definition: LoopPass.cpp:111
void addLoop(Loop &L)
Definition: LoopPass.cpp:77
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:103
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:316
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:305
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:332
bool skipLoop(const Loop *L) const
Optional passes call this function to check whether the pass should be skipped.
Definition: LoopPass.cpp:371
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:39
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:470
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:51
The TimeRegion class is used as a helper class to call the startTimer() and stopTimer() methods of th...
Definition: Timer.h:143
The TimeTraceScope is a helper class to call the begin and end functions of the time trace profiler.
Definition: TimeProfiler.h:180
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:480
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:2107
Timer * getPassTimer(Pass *)
Request the timer for this legacy-pass-manager's pass instance.
auto reverse(ContainerTy &&C)
Definition: STLExtras.h:420
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:1766
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:989