34Pass *llvm::createIVUsersPass() {
35 return new IVUsers();
36}
37
38/// containsAddRecFromDifferentLoop - Determine whether expression S involves a
39/// subexpression that is an AddRec from a loop other than L. An outer loop
40/// of L is OK, but not an inner loop nor a disjoint loop.
41static bool containsAddRecFromDifferentLoop(const SCEV *S, Loop *L) {
42 // This is very common, put it first.
43 if (isa<SCEVConstant>(S))
44 return false;
45 if (const SCEVCommutativeExpr *AE = dyn_cast<SCEVCommutativeExpr>(S)) {
46 for (unsigned int i=0; i< AE->getNumOperands(); i++)
47 if (containsAddRecFromDifferentLoop(AE->getOperand(i), L))
48 return true;
49 return false;
50 }
51 if (const SCEVAddRecExpr *AE = dyn_cast<SCEVAddRecExpr>(S)) {
52 if (const Loop *newLoop = AE->getLoop()) {
53 if (newLoop == L)
54 return false;
55 // if newLoop is an outer loop of L, this is OK.
56 if (!LoopInfo::isNotAlreadyContainedIn(L, newLoop))
57 return false;
58 }
59 return true;
60 }
61 if (const SCEVUDivExpr *DE = dyn_cast<SCEVUDivExpr>(S))
62 return containsAddRecFromDifferentLoop(DE->getLHS(), L) ||
63 containsAddRecFromDifferentLoop(DE->getRHS(), L);
64#if 0
65 // SCEVSDivExpr has been backed out temporarily, but will be back; we'll
66 // need this when it is.
67 if (const SCEVSDivExpr *DE = dyn_cast<SCEVSDivExpr>(S))
68 return containsAddRecFromDifferentLoop(DE->getLHS(), L) ||
69 containsAddRecFromDifferentLoop(DE->getRHS(), L);
70#endif
71 if (const SCEVCastExpr *CE = dyn_cast<SCEVCastExpr>(S))
72 return containsAddRecFromDifferentLoop(CE->getOperand(), L);
73 return false;
74}
75
76/// getSCEVStartAndStride - Compute the start and stride of this expression,
77/// returning false if the expression is not a start/stride pair, or true if it
78/// is. The stride must be a loop invariant expression, but the start may be
79/// a mix of loop invariant and loop variant expressions. The start cannot,
80/// however, contain an AddRec from a different loop, unless that loop is an
81/// outer loop of the current loop.
82static bool getSCEVStartAndStride(const SCEV *&SH, Loop *L, Loop *UseLoop,
83 const SCEV *&Start, const SCEV *&Stride,
84 ScalarEvolution *SE, DominatorTree *DT) {
85 const SCEV *TheAddRec = Start; // Initialize to zero.
86
87 // If the outer level is an AddExpr, the operands are all start values except
88 // for a nested AddRecExpr.
89 if (const SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(SH)) {
90 for (unsigned i = 0, e = AE->getNumOperands(); i != e; ++i)
91 if (const SCEVAddRecExpr *AddRec =
92 dyn_cast<SCEVAddRecExpr>(AE->getOperand(i))) {
93 if (AddRec->getLoop() == L)
94 TheAddRec = SE->getAddExpr(AddRec, TheAddRec);
95 else
96 return false; // Nested IV of some sort?
97 } else {
98 Start = SE->getAddExpr(Start, AE->getOperand(i));
99 }
100 } else if (isa<SCEVAddRecExpr>(SH)) {
101 TheAddRec = SH;
102 } else {
103 return false; // not analyzable.
104 }
105
106 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(TheAddRec);
107 if (!AddRec || AddRec->getLoop() != L) return false;
108
109 // Use getSCEVAtScope to attempt to simplify other loops out of
110 // the picture.
111 const SCEV *AddRecStart = AddRec->getStart();
112 AddRecStart = SE->getSCEVAtScope(AddRecStart, UseLoop);
113 const SCEV *AddRecStride = AddRec->getStepRecurrence(*SE);
114
115 // FIXME: If Start contains an SCEVAddRecExpr from a different loop, other
116 // than an outer loop of the current loop, reject it. LSR has no concept of
117 // operating on more than one loop at a time so don't confuse it with such
118 // expressions.
119 if (containsAddRecFromDifferentLoop(AddRecStart, L))
120 return false;
121
122 Start = SE->getAddExpr(Start, AddRecStart);
123
124 // If stride is an instruction, make sure it properly dominates the header.
125 // Otherwise we could end up with a use before def situation.
126 if (!isa<SCEVConstant>(AddRecStride)) {
127 BasicBlock *Header = L->getHeader();
128 if (!AddRecStride->properlyDominates(Header, DT))
129 return false;
130
131 DEBUG(errs() << "[" << L->getHeader()->getName()
132 << "] Variable stride: " << *AddRec << "\n");
133 }
134
135 Stride = AddRecStride;
136 return true;
137}
138
139/// IVUseShouldUsePostIncValue - We have discovered a "User" of an IV expression
140/// and now we need to decide whether the user should use the preinc or post-inc
141/// value. If this user should use the post-inc version of the IV, return true.
142///
143/// Choosing wrong here can break dominance properties (if we choose to use the
144/// post-inc value when we cannot) or it can end up adding extra live-ranges to
145/// the loop, resulting in reg-reg copies (if we use the pre-inc value when we
146/// should use the post-inc value).
147static bool IVUseShouldUsePostIncValue(Instruction *User, Instruction *IV,
148 Loop *L, LoopInfo *LI, DominatorTree *DT,
149 Pass *P) {
150 // If the user is in the loop, use the preinc value.
151 if (L->contains(User->getParent())) return false;
152
153 BasicBlock *LatchBlock = L->getLoopLatch();
154 if (!LatchBlock)
155 return false;
156
157 // Ok, the user is outside of the loop. If it is dominated by the latch
158 // block, use the post-inc value.
159 if (DT->dominates(LatchBlock, User->getParent()))
160 return true;
161
162 // There is one case we have to be careful of: PHI nodes. These little guys
163 // can live in blocks that are not dominated by the latch block, but (since
164 // their uses occur in the predecessor block, not the block the PHI lives in)
165 // should still use the post-inc value. Check for this case now.
166 PHINode *PN = dyn_cast<PHINode>(User);
167 if (!PN) return false; // not a phi, not dominated by latch block.
168
169 // Look at all of the uses of IV by the PHI node. If any use corresponds to
170 // a block that is not dominated by the latch block, give up and use the
171 // preincremented value.
172 unsigned NumUses = 0;
173 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
174 if (PN->getIncomingValue(i) == IV) {
175 ++NumUses;
176 if (!DT->dominates(LatchBlock, PN->getIncomingBlock(i)))
177 return false;
178 }
179
180 // Okay, all uses of IV by PN are in predecessor blocks that really are
181 // dominated by the latch block. Use the post-incremented value.
182 return true;
183}
184
185/// AddUsersIfInteresting - Inspect the specified instruction. If it is a
186/// reducible SCEV, recursively add its users to the IVUsesByStride set and
187/// return true. Otherwise, return false.
188bool IVUsers::AddUsersIfInteresting(Instruction *I) {
189 if (!SE->isSCEVable(I->getType()))
190 return false; // Void and FP expressions cannot be reduced.
191
192 // LSR is not APInt clean, do not touch integers bigger than 64-bits.
193 if (SE->getTypeSizeInBits(I->getType()) > 64)
194 return false;
195
196 if (!Processed.insert(I))
197 return true; // Instruction already handled.
198
199 // Get the symbolic expression for this instruction.
200 const SCEV *ISE = SE->getSCEV(I);
201 if (isa<SCEVCouldNotCompute>(ISE)) return false;
202
203 // Get the start and stride for this expression.
204 Loop *UseLoop = LI->getLoopFor(I->getParent());
205 const SCEV *Start = SE->getIntegerSCEV(0, ISE->getType());
206 const SCEV *Stride = Start;
207
208 if (!getSCEVStartAndStride(ISE, L, UseLoop, Start, Stride, SE, DT))
209 return false; // Non-reducible symbolic expression, bail out.
210
| 39Pass *llvm::createIVUsersPass() {
40 return new IVUsers();
41}
42
43/// containsAddRecFromDifferentLoop - Determine whether expression S involves a
44/// subexpression that is an AddRec from a loop other than L. An outer loop
45/// of L is OK, but not an inner loop nor a disjoint loop.
46static bool containsAddRecFromDifferentLoop(const SCEV *S, Loop *L) {
47 // This is very common, put it first.
48 if (isa<SCEVConstant>(S))
49 return false;
50 if (const SCEVCommutativeExpr *AE = dyn_cast<SCEVCommutativeExpr>(S)) {
51 for (unsigned int i=0; i< AE->getNumOperands(); i++)
52 if (containsAddRecFromDifferentLoop(AE->getOperand(i), L))
53 return true;
54 return false;
55 }
56 if (const SCEVAddRecExpr *AE = dyn_cast<SCEVAddRecExpr>(S)) {
57 if (const Loop *newLoop = AE->getLoop()) {
58 if (newLoop == L)
59 return false;
60 // if newLoop is an outer loop of L, this is OK.
61 if (!LoopInfo::isNotAlreadyContainedIn(L, newLoop))
62 return false;
63 }
64 return true;
65 }
66 if (const SCEVUDivExpr *DE = dyn_cast<SCEVUDivExpr>(S))
67 return containsAddRecFromDifferentLoop(DE->getLHS(), L) ||
68 containsAddRecFromDifferentLoop(DE->getRHS(), L);
69#if 0
70 // SCEVSDivExpr has been backed out temporarily, but will be back; we'll
71 // need this when it is.
72 if (const SCEVSDivExpr *DE = dyn_cast<SCEVSDivExpr>(S))
73 return containsAddRecFromDifferentLoop(DE->getLHS(), L) ||
74 containsAddRecFromDifferentLoop(DE->getRHS(), L);
75#endif
76 if (const SCEVCastExpr *CE = dyn_cast<SCEVCastExpr>(S))
77 return containsAddRecFromDifferentLoop(CE->getOperand(), L);
78 return false;
79}
80
81/// getSCEVStartAndStride - Compute the start and stride of this expression,
82/// returning false if the expression is not a start/stride pair, or true if it
83/// is. The stride must be a loop invariant expression, but the start may be
84/// a mix of loop invariant and loop variant expressions. The start cannot,
85/// however, contain an AddRec from a different loop, unless that loop is an
86/// outer loop of the current loop.
87static bool getSCEVStartAndStride(const SCEV *&SH, Loop *L, Loop *UseLoop,
88 const SCEV *&Start, const SCEV *&Stride,
89 ScalarEvolution *SE, DominatorTree *DT) {
90 const SCEV *TheAddRec = Start; // Initialize to zero.
91
92 // If the outer level is an AddExpr, the operands are all start values except
93 // for a nested AddRecExpr.
94 if (const SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(SH)) {
95 for (unsigned i = 0, e = AE->getNumOperands(); i != e; ++i)
96 if (const SCEVAddRecExpr *AddRec =
97 dyn_cast<SCEVAddRecExpr>(AE->getOperand(i))) {
98 if (AddRec->getLoop() == L)
99 TheAddRec = SE->getAddExpr(AddRec, TheAddRec);
100 else
101 return false; // Nested IV of some sort?
102 } else {
103 Start = SE->getAddExpr(Start, AE->getOperand(i));
104 }
105 } else if (isa<SCEVAddRecExpr>(SH)) {
106 TheAddRec = SH;
107 } else {
108 return false; // not analyzable.
109 }
110
111 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(TheAddRec);
112 if (!AddRec || AddRec->getLoop() != L) return false;
113
114 // Use getSCEVAtScope to attempt to simplify other loops out of
115 // the picture.
116 const SCEV *AddRecStart = AddRec->getStart();
117 AddRecStart = SE->getSCEVAtScope(AddRecStart, UseLoop);
118 const SCEV *AddRecStride = AddRec->getStepRecurrence(*SE);
119
120 // FIXME: If Start contains an SCEVAddRecExpr from a different loop, other
121 // than an outer loop of the current loop, reject it. LSR has no concept of
122 // operating on more than one loop at a time so don't confuse it with such
123 // expressions.
124 if (containsAddRecFromDifferentLoop(AddRecStart, L))
125 return false;
126
127 Start = SE->getAddExpr(Start, AddRecStart);
128
129 // If stride is an instruction, make sure it properly dominates the header.
130 // Otherwise we could end up with a use before def situation.
131 if (!isa<SCEVConstant>(AddRecStride)) {
132 BasicBlock *Header = L->getHeader();
133 if (!AddRecStride->properlyDominates(Header, DT))
134 return false;
135
136 DEBUG(errs() << "[" << L->getHeader()->getName()
137 << "] Variable stride: " << *AddRec << "\n");
138 }
139
140 Stride = AddRecStride;
141 return true;
142}
143
144/// IVUseShouldUsePostIncValue - We have discovered a "User" of an IV expression
145/// and now we need to decide whether the user should use the preinc or post-inc
146/// value. If this user should use the post-inc version of the IV, return true.
147///
148/// Choosing wrong here can break dominance properties (if we choose to use the
149/// post-inc value when we cannot) or it can end up adding extra live-ranges to
150/// the loop, resulting in reg-reg copies (if we use the pre-inc value when we
151/// should use the post-inc value).
152static bool IVUseShouldUsePostIncValue(Instruction *User, Instruction *IV,
153 Loop *L, LoopInfo *LI, DominatorTree *DT,
154 Pass *P) {
155 // If the user is in the loop, use the preinc value.
156 if (L->contains(User->getParent())) return false;
157
158 BasicBlock *LatchBlock = L->getLoopLatch();
159 if (!LatchBlock)
160 return false;
161
162 // Ok, the user is outside of the loop. If it is dominated by the latch
163 // block, use the post-inc value.
164 if (DT->dominates(LatchBlock, User->getParent()))
165 return true;
166
167 // There is one case we have to be careful of: PHI nodes. These little guys
168 // can live in blocks that are not dominated by the latch block, but (since
169 // their uses occur in the predecessor block, not the block the PHI lives in)
170 // should still use the post-inc value. Check for this case now.
171 PHINode *PN = dyn_cast<PHINode>(User);
172 if (!PN) return false; // not a phi, not dominated by latch block.
173
174 // Look at all of the uses of IV by the PHI node. If any use corresponds to
175 // a block that is not dominated by the latch block, give up and use the
176 // preincremented value.
177 unsigned NumUses = 0;
178 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
179 if (PN->getIncomingValue(i) == IV) {
180 ++NumUses;
181 if (!DT->dominates(LatchBlock, PN->getIncomingBlock(i)))
182 return false;
183 }
184
185 // Okay, all uses of IV by PN are in predecessor blocks that really are
186 // dominated by the latch block. Use the post-incremented value.
187 return true;
188}
189
190/// AddUsersIfInteresting - Inspect the specified instruction. If it is a
191/// reducible SCEV, recursively add its users to the IVUsesByStride set and
192/// return true. Otherwise, return false.
193bool IVUsers::AddUsersIfInteresting(Instruction *I) {
194 if (!SE->isSCEVable(I->getType()))
195 return false; // Void and FP expressions cannot be reduced.
196
197 // LSR is not APInt clean, do not touch integers bigger than 64-bits.
198 if (SE->getTypeSizeInBits(I->getType()) > 64)
199 return false;
200
201 if (!Processed.insert(I))
202 return true; // Instruction already handled.
203
204 // Get the symbolic expression for this instruction.
205 const SCEV *ISE = SE->getSCEV(I);
206 if (isa<SCEVCouldNotCompute>(ISE)) return false;
207
208 // Get the start and stride for this expression.
209 Loop *UseLoop = LI->getLoopFor(I->getParent());
210 const SCEV *Start = SE->getIntegerSCEV(0, ISE->getType());
211 const SCEV *Stride = Start;
212
213 if (!getSCEVStartAndStride(ISE, L, UseLoop, Start, Stride, SE, DT))
214 return false; // Non-reducible symbolic expression, bail out.
215
|
211 SmallPtrSet<Instruction *, 4> UniqueUsers;
212 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
213 UI != E; ++UI) {
214 Instruction *User = cast<Instruction>(*UI);
215 if (!UniqueUsers.insert(User))
216 continue;
217
218 // Do not infinitely recurse on PHI nodes.
219 if (isa<PHINode>(User) && Processed.count(User))
220 continue;
221
222 // Descend recursively, but not into PHI nodes outside the current loop.
223 // It's important to see the entire expression outside the loop to get
224 // choices that depend on addressing mode use right, although we won't
225 // consider references ouside the loop in all cases.
226 // If User is already in Processed, we don't want to recurse into it again,
227 // but do want to record a second reference in the same instruction.
228 bool AddUserToIVUsers = false;
229 if (LI->getLoopFor(User->getParent()) != L) {
230 if (isa<PHINode>(User) || Processed.count(User) ||
231 !AddUsersIfInteresting(User)) {
232 DEBUG(errs() << "FOUND USER in other loop: " << *User << '\n'
233 << " OF SCEV: " << *ISE << '\n');
234 AddUserToIVUsers = true;
235 }
236 } else if (Processed.count(User) ||
237 !AddUsersIfInteresting(User)) {
238 DEBUG(errs() << "FOUND USER: " << *User << '\n'
239 << " OF SCEV: " << *ISE << '\n');
240 AddUserToIVUsers = true;
241 }
242
243 if (AddUserToIVUsers) {
244 IVUsersOfOneStride *StrideUses = IVUsesByStride[Stride];
245 if (!StrideUses) { // First occurrence of this stride?
246 StrideOrder.push_back(Stride);
247 StrideUses = new IVUsersOfOneStride(Stride);
248 IVUses.push_back(StrideUses);
249 IVUsesByStride[Stride] = StrideUses;
250 }
251
252 // Okay, we found a user that we cannot reduce. Analyze the instruction
253 // and decide what to do with it. If we are a use inside of the loop, use
254 // the value before incrementation, otherwise use it after incrementation.
255 if (IVUseShouldUsePostIncValue(User, I, L, LI, DT, this)) {
256 // The value used will be incremented by the stride more than we are
257 // expecting, so subtract this off.
258 const SCEV *NewStart = SE->getMinusSCEV(Start, Stride);
259 StrideUses->addUser(NewStart, User, I);
260 StrideUses->Users.back().setIsUseOfPostIncrementedValue(true);
261 DEBUG(errs() << " USING POSTINC SCEV, START=" << *NewStart<< "\n");
262 } else {
263 StrideUses->addUser(Start, User, I);
264 }
265 }
266 }
267 return true;
268}
269
270void IVUsers::AddUser(const SCEV *Stride, const SCEV *Offset,
271 Instruction *User, Value *Operand) {
272 IVUsersOfOneStride *StrideUses = IVUsesByStride[Stride];
273 if (!StrideUses) { // First occurrence of this stride?
274 StrideOrder.push_back(Stride);
275 StrideUses = new IVUsersOfOneStride(Stride);
276 IVUses.push_back(StrideUses);
277 IVUsesByStride[Stride] = StrideUses;
278 }
279 IVUsesByStride[Stride]->addUser(Offset, User, Operand);
280}
281
282IVUsers::IVUsers()
283 : LoopPass(&ID) {
284}
285
286void IVUsers::getAnalysisUsage(AnalysisUsage &AU) const {
287 AU.addRequired<LoopInfo>();
288 AU.addRequired<DominatorTree>();
289 AU.addRequired<ScalarEvolution>();
290 AU.setPreservesAll();
291}
292
293bool IVUsers::runOnLoop(Loop *l, LPPassManager &LPM) {
294
295 L = l;
296 LI = &getAnalysis<LoopInfo>();
297 DT = &getAnalysis<DominatorTree>();
298 SE = &getAnalysis<ScalarEvolution>();
299
300 // Find all uses of induction variables in this loop, and categorize
301 // them by stride. Start by finding all of the PHI nodes in the header for
302 // this loop. If they are induction variables, inspect their uses.
303 for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ++I)
304 AddUsersIfInteresting(I);
305
306 return false;
307}
308
309/// getReplacementExpr - Return a SCEV expression which computes the
310/// value of the OperandValToReplace of the given IVStrideUse.
311const SCEV *IVUsers::getReplacementExpr(const IVStrideUse &U) const {
312 // Start with zero.
313 const SCEV *RetVal = SE->getIntegerSCEV(0, U.getParent()->Stride->getType());
314 // Create the basic add recurrence.
315 RetVal = SE->getAddRecExpr(RetVal, U.getParent()->Stride, L);
316 // Add the offset in a separate step, because it may be loop-variant.
317 RetVal = SE->getAddExpr(RetVal, U.getOffset());
318 // For uses of post-incremented values, add an extra stride to compute
319 // the actual replacement value.
320 if (U.isUseOfPostIncrementedValue())
321 RetVal = SE->getAddExpr(RetVal, U.getParent()->Stride);
322 // Evaluate the expression out of the loop, if possible.
323 if (!L->contains(U.getUser()->getParent())) {
324 const SCEV *ExitVal = SE->getSCEVAtScope(RetVal, L->getParentLoop());
325 if (ExitVal->isLoopInvariant(L))
326 RetVal = ExitVal;
327 }
328 return RetVal;
329}
330
331void IVUsers::print(raw_ostream &OS, const Module *M) const {
332 OS << "IV Users for loop ";
333 WriteAsOperand(OS, L->getHeader(), false);
334 if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
335 OS << " with backedge-taken count "
336 << *SE->getBackedgeTakenCount(L);
337 }
338 OS << ":\n";
339
340 for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e; ++Stride) {
341 std::map<const SCEV *, IVUsersOfOneStride*>::const_iterator SI =
342 IVUsesByStride.find(StrideOrder[Stride]);
343 assert(SI != IVUsesByStride.end() && "Stride doesn't exist!");
344 OS << " Stride " << *SI->first->getType() << " " << *SI->first << ":\n";
345
346 for (ilist<IVStrideUse>::const_iterator UI = SI->second->Users.begin(),
347 E = SI->second->Users.end(); UI != E; ++UI) {
348 OS << " ";
349 WriteAsOperand(OS, UI->getOperandValToReplace(), false);
350 OS << " = ";
351 OS << *getReplacementExpr(*UI);
352 if (UI->isUseOfPostIncrementedValue())
353 OS << " (post-inc)";
354 OS << " in ";
355 UI->getUser()->print(OS);
356 OS << '\n';
357 }
358 }
359}
360
361void IVUsers::dump() const {
362 print(errs());
363}
364
365void IVUsers::releaseMemory() {
366 IVUsesByStride.clear();
367 StrideOrder.clear();
368 Processed.clear();
369}
370
371void IVStrideUse::deleted() {
372 // Remove this user from the list.
373 Parent->Users.erase(this);
374 // this now dangles!
375}
| 221 SmallPtrSet<Instruction *, 4> UniqueUsers;
222 for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
223 UI != E; ++UI) {
224 Instruction *User = cast<Instruction>(*UI);
225 if (!UniqueUsers.insert(User))
226 continue;
227
228 // Do not infinitely recurse on PHI nodes.
229 if (isa<PHINode>(User) && Processed.count(User))
230 continue;
231
232 // Descend recursively, but not into PHI nodes outside the current loop.
233 // It's important to see the entire expression outside the loop to get
234 // choices that depend on addressing mode use right, although we won't
235 // consider references ouside the loop in all cases.
236 // If User is already in Processed, we don't want to recurse into it again,
237 // but do want to record a second reference in the same instruction.
238 bool AddUserToIVUsers = false;
239 if (LI->getLoopFor(User->getParent()) != L) {
240 if (isa<PHINode>(User) || Processed.count(User) ||
241 !AddUsersIfInteresting(User)) {
242 DEBUG(errs() << "FOUND USER in other loop: " << *User << '\n'
243 << " OF SCEV: " << *ISE << '\n');
244 AddUserToIVUsers = true;
245 }
246 } else if (Processed.count(User) ||
247 !AddUsersIfInteresting(User)) {
248 DEBUG(errs() << "FOUND USER: " << *User << '\n'
249 << " OF SCEV: " << *ISE << '\n');
250 AddUserToIVUsers = true;
251 }
252
253 if (AddUserToIVUsers) {
254 IVUsersOfOneStride *StrideUses = IVUsesByStride[Stride];
255 if (!StrideUses) { // First occurrence of this stride?
256 StrideOrder.push_back(Stride);
257 StrideUses = new IVUsersOfOneStride(Stride);
258 IVUses.push_back(StrideUses);
259 IVUsesByStride[Stride] = StrideUses;
260 }
261
262 // Okay, we found a user that we cannot reduce. Analyze the instruction
263 // and decide what to do with it. If we are a use inside of the loop, use
264 // the value before incrementation, otherwise use it after incrementation.
265 if (IVUseShouldUsePostIncValue(User, I, L, LI, DT, this)) {
266 // The value used will be incremented by the stride more than we are
267 // expecting, so subtract this off.
268 const SCEV *NewStart = SE->getMinusSCEV(Start, Stride);
269 StrideUses->addUser(NewStart, User, I);
270 StrideUses->Users.back().setIsUseOfPostIncrementedValue(true);
271 DEBUG(errs() << " USING POSTINC SCEV, START=" << *NewStart<< "\n");
272 } else {
273 StrideUses->addUser(Start, User, I);
274 }
275 }
276 }
277 return true;
278}
279
280void IVUsers::AddUser(const SCEV *Stride, const SCEV *Offset,
281 Instruction *User, Value *Operand) {
282 IVUsersOfOneStride *StrideUses = IVUsesByStride[Stride];
283 if (!StrideUses) { // First occurrence of this stride?
284 StrideOrder.push_back(Stride);
285 StrideUses = new IVUsersOfOneStride(Stride);
286 IVUses.push_back(StrideUses);
287 IVUsesByStride[Stride] = StrideUses;
288 }
289 IVUsesByStride[Stride]->addUser(Offset, User, Operand);
290}
291
292IVUsers::IVUsers()
293 : LoopPass(&ID) {
294}
295
296void IVUsers::getAnalysisUsage(AnalysisUsage &AU) const {
297 AU.addRequired<LoopInfo>();
298 AU.addRequired<DominatorTree>();
299 AU.addRequired<ScalarEvolution>();
300 AU.setPreservesAll();
301}
302
303bool IVUsers::runOnLoop(Loop *l, LPPassManager &LPM) {
304
305 L = l;
306 LI = &getAnalysis<LoopInfo>();
307 DT = &getAnalysis<DominatorTree>();
308 SE = &getAnalysis<ScalarEvolution>();
309
310 // Find all uses of induction variables in this loop, and categorize
311 // them by stride. Start by finding all of the PHI nodes in the header for
312 // this loop. If they are induction variables, inspect their uses.
313 for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ++I)
314 AddUsersIfInteresting(I);
315
316 return false;
317}
318
319/// getReplacementExpr - Return a SCEV expression which computes the
320/// value of the OperandValToReplace of the given IVStrideUse.
321const SCEV *IVUsers::getReplacementExpr(const IVStrideUse &U) const {
322 // Start with zero.
323 const SCEV *RetVal = SE->getIntegerSCEV(0, U.getParent()->Stride->getType());
324 // Create the basic add recurrence.
325 RetVal = SE->getAddRecExpr(RetVal, U.getParent()->Stride, L);
326 // Add the offset in a separate step, because it may be loop-variant.
327 RetVal = SE->getAddExpr(RetVal, U.getOffset());
328 // For uses of post-incremented values, add an extra stride to compute
329 // the actual replacement value.
330 if (U.isUseOfPostIncrementedValue())
331 RetVal = SE->getAddExpr(RetVal, U.getParent()->Stride);
332 // Evaluate the expression out of the loop, if possible.
333 if (!L->contains(U.getUser()->getParent())) {
334 const SCEV *ExitVal = SE->getSCEVAtScope(RetVal, L->getParentLoop());
335 if (ExitVal->isLoopInvariant(L))
336 RetVal = ExitVal;
337 }
338 return RetVal;
339}
340
341void IVUsers::print(raw_ostream &OS, const Module *M) const {
342 OS << "IV Users for loop ";
343 WriteAsOperand(OS, L->getHeader(), false);
344 if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
345 OS << " with backedge-taken count "
346 << *SE->getBackedgeTakenCount(L);
347 }
348 OS << ":\n";
349
350 for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e; ++Stride) {
351 std::map<const SCEV *, IVUsersOfOneStride*>::const_iterator SI =
352 IVUsesByStride.find(StrideOrder[Stride]);
353 assert(SI != IVUsesByStride.end() && "Stride doesn't exist!");
354 OS << " Stride " << *SI->first->getType() << " " << *SI->first << ":\n";
355
356 for (ilist<IVStrideUse>::const_iterator UI = SI->second->Users.begin(),
357 E = SI->second->Users.end(); UI != E; ++UI) {
358 OS << " ";
359 WriteAsOperand(OS, UI->getOperandValToReplace(), false);
360 OS << " = ";
361 OS << *getReplacementExpr(*UI);
362 if (UI->isUseOfPostIncrementedValue())
363 OS << " (post-inc)";
364 OS << " in ";
365 UI->getUser()->print(OS);
366 OS << '\n';
367 }
368 }
369}
370
371void IVUsers::dump() const {
372 print(errs());
373}
374
375void IVUsers::releaseMemory() {
376 IVUsesByStride.clear();
377 StrideOrder.clear();
378 Processed.clear();
379}
380
381void IVStrideUse::deleted() {
382 // Remove this user from the list.
383 Parent->Users.erase(this);
384 // this now dangles!
385}
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