1 //===- BasicAliasAnalysis.cpp - Local Alias Analysis Impl -----------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the default implementation of the Alias Analysis interface
11 // that simply implements a few identities (two different globals cannot alias,
12 // etc), but otherwise does no analysis.
14 // FIXME: This could be extended for a very simple form of mod/ref information.
15 // If a pointer is locally allocated (either malloc or alloca) and never passed
16 // into a call or stored to memory, then we know that calls will not mod/ref the
17 // memory. This can be important for tailcallelim, and can support CSE of loads
18 // and dead store elimination across calls. This is particularly important for
19 // stack allocated arrays.
21 //===----------------------------------------------------------------------===//
23 #include "llvm/Analysis/AliasAnalysis.h"
24 #include "llvm/Constants.h"
25 #include "llvm/DerivedTypes.h"
26 #include "llvm/Function.h"
27 #include "llvm/GlobalVariable.h"
28 #include "llvm/iOther.h"
29 #include "llvm/iMemory.h"
30 #include "llvm/Pass.h"
31 #include "llvm/Target/TargetData.h"
32 #include "llvm/Support/GetElementPtrTypeIterator.h"
35 // Make sure that anything that uses AliasAnalysis pulls in this file...
36 void llvm::BasicAAStub() {}
39 struct BasicAliasAnalysis : public ImmutablePass, public AliasAnalysis {
41 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
42 AliasAnalysis::getAnalysisUsage(AU);
45 virtual void initializePass();
47 AliasResult alias(const Value *V1, unsigned V1Size,
48 const Value *V2, unsigned V2Size);
50 ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);
52 /// pointsToConstantMemory - Chase pointers until we find a (constant
54 bool pointsToConstantMemory(const Value *P);
56 virtual bool doesNotAccessMemory(Function *F);
57 virtual bool onlyReadsMemory(Function *F);
60 // CheckGEPInstructions - Check two GEP instructions with known
61 // must-aliasing base pointers. This checks to see if the index expressions
62 // preclude the pointers from aliasing...
64 CheckGEPInstructions(const Type* BasePtr1Ty, std::vector<Value*> &GEP1Ops,
66 const Type *BasePtr2Ty, std::vector<Value*> &GEP2Ops,
70 // Register this pass...
71 RegisterOpt<BasicAliasAnalysis>
72 X("basicaa", "Basic Alias Analysis (default AA impl)");
74 // Declare that we implement the AliasAnalysis interface
75 RegisterAnalysisGroup<AliasAnalysis, BasicAliasAnalysis, true> Y;
76 } // End of anonymous namespace
78 void BasicAliasAnalysis::initializePass() {
79 InitializeAliasAnalysis(this);
82 // hasUniqueAddress - Return true if the specified value points to something
83 // with a unique, discernable, address.
84 static inline bool hasUniqueAddress(const Value *V) {
85 return isa<GlobalValue>(V) || isa<AllocationInst>(V);
88 // getUnderlyingObject - This traverses the use chain to figure out what object
89 // the specified value points to. If the value points to, or is derived from, a
90 // unique object or an argument, return it.
91 static const Value *getUnderlyingObject(const Value *V) {
92 if (!isa<PointerType>(V->getType())) return 0;
94 // If we are at some type of object... return it.
95 if (hasUniqueAddress(V) || isa<Argument>(V)) return V;
97 // Traverse through different addressing mechanisms...
98 if (const Instruction *I = dyn_cast<Instruction>(V)) {
99 if (isa<CastInst>(I) || isa<GetElementPtrInst>(I))
100 return getUnderlyingObject(I->getOperand(0));
101 } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
102 if (CE->getOpcode() == Instruction::Cast ||
103 CE->getOpcode() == Instruction::GetElementPtr)
104 return getUnderlyingObject(CE->getOperand(0));
105 } else if (const ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(V)) {
106 return CPR->getValue();
111 static const User *isGEP(const Value *V) {
112 if (isa<GetElementPtrInst>(V) ||
113 (isa<ConstantExpr>(V) &&
114 cast<ConstantExpr>(V)->getOpcode() == Instruction::GetElementPtr))
115 return cast<User>(V);
119 static const Value *GetGEPOperands(const Value *V, std::vector<Value*> &GEPOps){
120 assert(GEPOps.empty() && "Expect empty list to populate!");
121 GEPOps.insert(GEPOps.end(), cast<User>(V)->op_begin()+1,
122 cast<User>(V)->op_end());
124 // Accumulate all of the chained indexes into the operand array
125 V = cast<User>(V)->getOperand(0);
127 while (const User *G = isGEP(V)) {
128 if (!isa<Constant>(GEPOps[0]) ||
129 !cast<Constant>(GEPOps[0])->isNullValue())
130 break; // Don't handle folding arbitrary pointer offsets yet...
131 GEPOps.erase(GEPOps.begin()); // Drop the zero index
132 GEPOps.insert(GEPOps.begin(), G->op_begin()+1, G->op_end());
133 V = G->getOperand(0);
138 /// pointsToConstantMemory - Chase pointers until we find a (constant
140 bool BasicAliasAnalysis::pointsToConstantMemory(const Value *P) {
141 if (const Value *V = getUnderlyingObject(P))
142 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
143 return GV->isConstant();
147 static bool AddressMightEscape(const Value *V) {
148 for (Value::use_const_iterator UI = V->use_begin(), E = V->use_end();
150 const Instruction *I = cast<Instruction>(*UI);
151 switch (I->getOpcode()) {
152 case Instruction::Load: break;
153 case Instruction::Store:
154 if (I->getOperand(0) == V)
155 return true; // Escapes if the pointer is stored.
157 case Instruction::GetElementPtr:
158 if (AddressMightEscape(I)) return true;
160 case Instruction::Cast:
161 if (!isa<PointerType>(I->getType()))
163 if (AddressMightEscape(I)) return true;
172 // getModRefInfo - Check to see if the specified callsite can clobber the
173 // specified memory object. Since we only look at local properties of this
174 // function, we really can't say much about this query. We do, however, use
175 // simple "address taken" analysis on local objects.
177 AliasAnalysis::ModRefResult
178 BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
179 if (!isa<Constant>(P) && !isa<GlobalValue>(P))
180 if (const AllocationInst *AI =
181 dyn_cast_or_null<AllocationInst>(getUnderlyingObject(P))) {
182 // Okay, the pointer is to a stack allocated object. If we can prove that
183 // the pointer never "escapes", then we know the call cannot clobber it,
184 // because it simply can't get its address.
185 if (!AddressMightEscape(AI))
189 // The AliasAnalysis base class has some smarts, lets use them.
190 return AliasAnalysis::getModRefInfo(CS, P, Size);
193 // alias - Provide a bunch of ad-hoc rules to disambiguate in common cases, such
194 // as array references. Note that this function is heavily tail recursive.
195 // Hopefully we have a smart C++ compiler. :)
197 AliasAnalysis::AliasResult
198 BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
199 const Value *V2, unsigned V2Size) {
200 // Strip off any constant expression casts if they exist
201 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V1))
202 if (CE->getOpcode() == Instruction::Cast)
203 V1 = CE->getOperand(0);
204 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V2))
205 if (CE->getOpcode() == Instruction::Cast)
206 V2 = CE->getOperand(0);
208 // Strip off constant pointer refs if they exist
209 if (const ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(V1))
210 V1 = CPR->getValue();
211 if (const ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(V2))
212 V2 = CPR->getValue();
214 // Are we checking for alias of the same value?
215 if (V1 == V2) return MustAlias;
217 if ((!isa<PointerType>(V1->getType()) || !isa<PointerType>(V2->getType())) &&
218 V1->getType() != Type::LongTy && V2->getType() != Type::LongTy)
219 return NoAlias; // Scalars cannot alias each other
221 // Strip off cast instructions...
222 if (const Instruction *I = dyn_cast<CastInst>(V1))
223 return alias(I->getOperand(0), V1Size, V2, V2Size);
224 if (const Instruction *I = dyn_cast<CastInst>(V2))
225 return alias(V1, V1Size, I->getOperand(0), V2Size);
227 // Figure out what objects these things are pointing to if we can...
228 const Value *O1 = getUnderlyingObject(V1);
229 const Value *O2 = getUnderlyingObject(V2);
231 // Pointing at a discernible object?
233 if (isa<Argument>(O1)) {
234 // Incoming argument cannot alias locally allocated object!
235 if (isa<AllocationInst>(O2)) return NoAlias;
236 // Otherwise, nothing is known...
237 } else if (isa<Argument>(O2)) {
238 // Incoming argument cannot alias locally allocated object!
239 if (isa<AllocationInst>(O1)) return NoAlias;
240 // Otherwise, nothing is known...
242 // If they are two different objects, we know that we have no alias...
243 if (O1 != O2) return NoAlias;
246 // If they are the same object, they we can look at the indexes. If they
247 // index off of the object is the same for both pointers, they must alias.
248 // If they are provably different, they must not alias. Otherwise, we can't
250 } else if (O1 && !isa<Argument>(O1) && isa<ConstantPointerNull>(V2)) {
251 return NoAlias; // Unique values don't alias null
252 } else if (O2 && !isa<Argument>(O2) && isa<ConstantPointerNull>(V1)) {
253 return NoAlias; // Unique values don't alias null
256 // If we have two gep instructions with must-alias'ing base pointers, figure
257 // out if the indexes to the GEP tell us anything about the derived pointer.
258 // Note that we also handle chains of getelementptr instructions as well as
259 // constant expression getelementptrs here.
261 if (isGEP(V1) && isGEP(V2)) {
262 // Drill down into the first non-gep value, to test for must-aliasing of
263 // the base pointers.
264 const Value *BasePtr1 = V1, *BasePtr2 = V2;
266 BasePtr1 = cast<User>(BasePtr1)->getOperand(0);
267 } while (isGEP(BasePtr1) &&
268 cast<User>(BasePtr1)->getOperand(1) ==
269 Constant::getNullValue(cast<User>(BasePtr1)->getOperand(1)->getType()));
271 BasePtr2 = cast<User>(BasePtr2)->getOperand(0);
272 } while (isGEP(BasePtr2) &&
273 cast<User>(BasePtr2)->getOperand(1) ==
274 Constant::getNullValue(cast<User>(BasePtr2)->getOperand(1)->getType()));
276 // Do the base pointers alias?
277 AliasResult BaseAlias = alias(BasePtr1, V1Size, BasePtr2, V2Size);
278 if (BaseAlias == NoAlias) return NoAlias;
279 if (BaseAlias == MustAlias) {
280 // If the base pointers alias each other exactly, check to see if we can
281 // figure out anything about the resultant pointers, to try to prove
284 // Collect all of the chained GEP operands together into one simple place
285 std::vector<Value*> GEP1Ops, GEP2Ops;
286 BasePtr1 = GetGEPOperands(V1, GEP1Ops);
287 BasePtr2 = GetGEPOperands(V2, GEP2Ops);
290 CheckGEPInstructions(BasePtr1->getType(), GEP1Ops, V1Size,
291 BasePtr2->getType(), GEP2Ops, V2Size);
292 if (GAlias != MayAlias)
297 // Check to see if these two pointers are related by a getelementptr
298 // instruction. If one pointer is a GEP with a non-zero index of the other
299 // pointer, we know they cannot alias.
303 std::swap(V1Size, V2Size);
306 if (V1Size != ~0U && V2Size != ~0U)
307 if (const User *GEP = isGEP(V1)) {
308 std::vector<Value*> GEPOperands;
309 const Value *BasePtr = GetGEPOperands(V1, GEPOperands);
311 AliasResult R = alias(BasePtr, V1Size, V2, V2Size);
312 if (R == MustAlias) {
313 // If there is at least one non-zero constant index, we know they cannot
315 bool ConstantFound = false;
316 bool AllZerosFound = true;
317 for (unsigned i = 0, e = GEPOperands.size(); i != e; ++i)
318 if (const Constant *C = dyn_cast<Constant>(GEPOperands[i])) {
319 if (!C->isNullValue()) {
320 ConstantFound = true;
321 AllZerosFound = false;
325 AllZerosFound = false;
328 // If we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2 must aliases
329 // the ptr, the end result is a must alias also.
334 if (V2Size <= 1 && V1Size <= 1) // Just pointer check?
337 // Otherwise we have to check to see that the distance is more than
338 // the size of the argument... build an index vector that is equal to
339 // the arguments provided, except substitute 0's for any variable
340 // indexes we find...
341 for (unsigned i = 0; i != GEPOperands.size(); ++i)
342 if (!isa<Constant>(GEPOperands[i]) ||
343 isa<ConstantExpr>(GEPOperands[i]))
344 GEPOperands[i] =Constant::getNullValue(GEPOperands[i]->getType());
345 int64_t Offset = getTargetData().getIndexedOffset(BasePtr->getType(),
347 if (Offset >= (int64_t)V2Size || Offset <= -(int64_t)V1Size)
356 /// CheckGEPInstructions - Check two GEP instructions with known must-aliasing
357 /// base pointers. This checks to see if the index expressions preclude the
358 /// pointers from aliasing...
359 AliasAnalysis::AliasResult BasicAliasAnalysis::
360 CheckGEPInstructions(const Type* BasePtr1Ty, std::vector<Value*> &GEP1Ops,
362 const Type *BasePtr2Ty, std::vector<Value*> &GEP2Ops,
364 // We currently can't handle the case when the base pointers have different
365 // primitive types. Since this is uncommon anyway, we are happy being
366 // extremely conservative.
367 if (BasePtr1Ty != BasePtr2Ty)
370 const Type *GEPPointerTy = BasePtr1Ty;
372 // Find the (possibly empty) initial sequence of equal values... which are not
373 // necessarily constants.
374 unsigned NumGEP1Operands = GEP1Ops.size(), NumGEP2Operands = GEP2Ops.size();
375 unsigned MinOperands = std::min(NumGEP1Operands, NumGEP2Operands);
376 unsigned MaxOperands = std::max(NumGEP1Operands, NumGEP2Operands);
377 unsigned UnequalOper = 0;
378 while (UnequalOper != MinOperands &&
379 GEP1Ops[UnequalOper] == GEP2Ops[UnequalOper]) {
380 // Advance through the type as we go...
382 if (const CompositeType *CT = dyn_cast<CompositeType>(BasePtr1Ty))
383 BasePtr1Ty = CT->getTypeAtIndex(GEP1Ops[UnequalOper-1]);
385 // If all operands equal each other, then the derived pointers must
386 // alias each other...
388 assert(UnequalOper == NumGEP1Operands && UnequalOper == NumGEP2Operands &&
389 "Ran out of type nesting, but not out of operands?");
394 // If we have seen all constant operands, and run out of indexes on one of the
395 // getelementptrs, check to see if the tail of the leftover one is all zeros.
396 // If so, return mustalias.
397 if (UnequalOper == MinOperands) {
398 if (GEP1Ops.size() < GEP2Ops.size()) std::swap(GEP1Ops, GEP2Ops);
400 bool AllAreZeros = true;
401 for (unsigned i = UnequalOper; i != MaxOperands; ++i)
402 if (!isa<Constant>(GEP1Ops[i]) ||
403 !cast<Constant>(GEP1Ops[i])->isNullValue()) {
407 if (AllAreZeros) return MustAlias;
411 // So now we know that the indexes derived from the base pointers,
412 // which are known to alias, are different. We can still determine a
413 // no-alias result if there are differing constant pairs in the index
414 // chain. For example:
415 // A[i][0] != A[j][1] iff (&A[0][1]-&A[0][0] >= std::max(G1S, G2S))
417 unsigned SizeMax = std::max(G1S, G2S);
418 if (SizeMax == ~0U) return MayAlias; // Avoid frivolous work...
420 // Scan for the first operand that is constant and unequal in the
421 // two getelemenptrs...
422 unsigned FirstConstantOper = UnequalOper;
423 for (; FirstConstantOper != MinOperands; ++FirstConstantOper) {
424 const Value *G1Oper = GEP1Ops[FirstConstantOper];
425 const Value *G2Oper = GEP2Ops[FirstConstantOper];
427 if (G1Oper != G2Oper) // Found non-equal constant indexes...
428 if (Constant *G1OC = dyn_cast<Constant>(const_cast<Value*>(G1Oper)))
429 if (Constant *G2OC = dyn_cast<Constant>(const_cast<Value*>(G2Oper))) {
430 // Make sure they are comparable (ie, not constant expressions)...
431 // and make sure the GEP with the smaller leading constant is GEP1.
432 Constant *Compare = ConstantExpr::get(Instruction::SetGT, G1OC, G2OC);
433 if (ConstantBool *CV = dyn_cast<ConstantBool>(Compare)) {
434 if (CV->getValue()) // If they are comparable and G2 > G1
435 std::swap(GEP1Ops, GEP2Ops); // Make GEP1 < GEP2
439 BasePtr1Ty = cast<CompositeType>(BasePtr1Ty)->getTypeAtIndex(G1Oper);
442 // No shared constant operands, and we ran out of common operands. At this
443 // point, the GEP instructions have run through all of their operands, and we
444 // haven't found evidence that there are any deltas between the GEP's.
445 // However, one GEP may have more operands than the other. If this is the
446 // case, there may still be hope. This this now.
447 if (FirstConstantOper == MinOperands) {
448 // Make GEP1Ops be the longer one if there is a longer one.
449 if (GEP1Ops.size() < GEP2Ops.size())
450 std::swap(GEP1Ops, GEP2Ops);
452 // Is there anything to check?
453 if (GEP1Ops.size() > MinOperands) {
454 for (unsigned i = FirstConstantOper; i != MaxOperands; ++i)
455 if (isa<Constant>(GEP1Ops[i]) && !isa<ConstantExpr>(GEP1Ops[i]) &&
456 !cast<Constant>(GEP1Ops[i])->isNullValue()) {
457 // Yup, there's a constant in the tail. Set all variables to
458 // constants in the GEP instruction to make it suiteable for
459 // TargetData::getIndexedOffset.
460 for (i = 0; i != MaxOperands; ++i)
461 if (!isa<Constant>(GEP1Ops[i]) || isa<ConstantExpr>(GEP1Ops[i]))
462 GEP1Ops[i] = Constant::getNullValue(GEP1Ops[i]->getType());
463 // Okay, now get the offset. This is the relative offset for the full
465 const TargetData &TD = getTargetData();
466 int64_t Offset1 = TD.getIndexedOffset(GEPPointerTy, GEP1Ops);
468 // Now crop off any constants from the end...
469 GEP1Ops.resize(MinOperands);
470 int64_t Offset2 = TD.getIndexedOffset(GEPPointerTy, GEP1Ops);
472 // If the tail provided a bit enough offset, return noalias!
473 if ((uint64_t)(Offset2-Offset1) >= SizeMax)
478 // Couldn't find anything useful.
482 // If there are non-equal constants arguments, then we can figure
483 // out a minimum known delta between the two index expressions... at
484 // this point we know that the first constant index of GEP1 is less
485 // than the first constant index of GEP2.
487 // Advance BasePtr[12]Ty over this first differing constant operand.
488 BasePtr2Ty = cast<CompositeType>(BasePtr1Ty)->getTypeAtIndex(GEP2Ops[FirstConstantOper]);
489 BasePtr1Ty = cast<CompositeType>(BasePtr1Ty)->getTypeAtIndex(GEP1Ops[FirstConstantOper]);
491 // We are going to be using TargetData::getIndexedOffset to determine the
492 // offset that each of the GEP's is reaching. To do this, we have to convert
493 // all variable references to constant references. To do this, we convert the
494 // initial equal sequence of variables into constant zeros to start with.
495 for (unsigned i = 0; i != FirstConstantOper; ++i) {
496 if (!isa<Constant>(GEP1Ops[i]) || isa<ConstantExpr>(GEP1Ops[i]) ||
497 !isa<Constant>(GEP2Ops[i]) || isa<ConstantExpr>(GEP2Ops[i])) {
498 GEP1Ops[i] = Constant::getNullValue(GEP1Ops[i]->getType());
499 GEP2Ops[i] = Constant::getNullValue(GEP2Ops[i]->getType());
503 // We know that GEP1Ops[FirstConstantOper] & GEP2Ops[FirstConstantOper] are ok
505 // Loop over the rest of the operands...
506 for (unsigned i = FirstConstantOper+1; i != MaxOperands; ++i) {
507 const Value *Op1 = i < GEP1Ops.size() ? GEP1Ops[i] : 0;
508 const Value *Op2 = i < GEP2Ops.size() ? GEP2Ops[i] : 0;
509 // If they are equal, use a zero index...
510 if (Op1 == Op2 && BasePtr1Ty == BasePtr2Ty) {
511 if (!isa<Constant>(Op1) || isa<ConstantExpr>(Op1))
512 GEP1Ops[i] = GEP2Ops[i] = Constant::getNullValue(Op1->getType());
513 // Otherwise, just keep the constants we have.
516 if (const ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
517 // If this is an array index, make sure the array element is in range.
518 if (const ArrayType *AT = dyn_cast<ArrayType>(BasePtr1Ty))
519 if (Op1C->getRawValue() >= AT->getNumElements())
520 return MayAlias; // Be conservative with out-of-range accesses
523 // GEP1 is known to produce a value less than GEP2. To be
524 // conservatively correct, we must assume the largest possible
525 // constant is used in this position. This cannot be the initial
526 // index to the GEP instructions (because we know we have at least one
527 // element before this one with the different constant arguments), so
528 // we know that the current index must be into either a struct or
529 // array. Because we know it's not constant, this cannot be a
530 // structure index. Because of this, we can calculate the maximum
533 if (const ArrayType *AT = dyn_cast<ArrayType>(BasePtr1Ty))
534 GEP1Ops[i] = ConstantSInt::get(Type::LongTy,AT->getNumElements()-1);
539 if (const ConstantInt *Op2C = dyn_cast<ConstantInt>(Op2)) {
540 // If this is an array index, make sure the array element is in range.
541 if (const ArrayType *AT = dyn_cast<ArrayType>(BasePtr1Ty))
542 if (Op2C->getRawValue() >= AT->getNumElements())
543 return MayAlias; // Be conservative with out-of-range accesses
544 } else { // Conservatively assume the minimum value for this index
545 GEP2Ops[i] = Constant::getNullValue(Op2->getType());
550 if (BasePtr1Ty && Op1) {
551 if (const CompositeType *CT = dyn_cast<CompositeType>(BasePtr1Ty))
552 BasePtr1Ty = CT->getTypeAtIndex(GEP1Ops[i]);
557 if (BasePtr2Ty && Op2) {
558 if (const CompositeType *CT = dyn_cast<CompositeType>(BasePtr2Ty))
559 BasePtr2Ty = CT->getTypeAtIndex(GEP2Ops[i]);
565 int64_t Offset1 = getTargetData().getIndexedOffset(GEPPointerTy, GEP1Ops);
566 int64_t Offset2 = getTargetData().getIndexedOffset(GEPPointerTy, GEP2Ops);
567 assert(Offset1 < Offset2 &&"There is at least one different constant here!");
569 if ((uint64_t)(Offset2-Offset1) >= SizeMax) {
570 //std::cerr << "Determined that these two GEP's don't alias ["
571 // << SizeMax << " bytes]: \n" << *GEP1 << *GEP2;
578 struct StringCompare {
579 bool operator()(const char *LHS, const char *RHS) {
580 return strcmp(LHS, RHS) < 0;
585 // Note that this list cannot contain libm functions (such as acos and sqrt)
586 // that set errno on a domain or other error.
587 static const char *DoesntAccessMemoryTable[] = {
588 "abs", "labs", "llabs", "imaxabs", "fabs", "fabsf", "fabsl",
589 "trunc", "truncf", "truncl", "ldexp",
591 "atan", "atanf", "atanl", "atan2", "atan2f", "atan2l",
593 "cos", "cosf", "cosl", "cosh", "coshf", "coshl",
594 "exp", "expf", "expl",
596 "sin", "sinf", "sinl", "sinh", "sinhf", "sinhl",
597 "tan", "tanf", "tanl", "tanh", "tanhf", "tanhl",
600 "isalnum", "isalpha", "iscntrl", "isdigit", "isgraph", "islower", "isprint"
601 "ispunct", "isspace", "isupper", "isxdigit", "tolower", "toupper",
604 "iswalnum", "iswalpha", "iswcntrl", "iswdigit", "iswgraph", "iswlower",
605 "iswprint", "iswpunct", "iswspace", "iswupper", "iswxdigit",
607 "iswctype", "towctrans", "towlower", "towupper",
611 "isinf", "isnan", "finite",
613 // C99 math functions
614 "copysign", "copysignf", "copysignd",
615 "nexttoward", "nexttowardf", "nexttowardd",
616 "nextafter", "nextafterf", "nextafterd",
619 "__fpclassify", "__fpclassifyf", "__fpclassifyl",
620 "__signbit", "__signbitf", "__signbitl",
623 static const unsigned DAMTableSize =
624 sizeof(DoesntAccessMemoryTable)/sizeof(DoesntAccessMemoryTable[0]);
626 /// doesNotAccessMemory - Return true if we know that the function does not
627 /// access memory at all. Since basicaa does no analysis, we can only do simple
628 /// things here. In particular, if we have an external function with the name
629 /// of a standard C library function, we are allowed to assume it will be
630 /// resolved by libc, so we can hardcode some entries in here.
631 bool BasicAliasAnalysis::doesNotAccessMemory(Function *F) {
632 if (!F->isExternal()) return false;
634 static bool Initialized = false;
636 // Sort the table the first time through.
637 std::sort(DoesntAccessMemoryTable, DoesntAccessMemoryTable+DAMTableSize,
642 const char **Ptr = std::lower_bound(DoesntAccessMemoryTable,
643 DoesntAccessMemoryTable+DAMTableSize,
644 F->getName().c_str(), StringCompare());
645 return Ptr != DoesntAccessMemoryTable+DAMTableSize && *Ptr == F->getName();
649 static const char *OnlyReadsMemoryTable[] = {
650 "atoi", "atol", "atof", "atoll", "atoq", "a64l",
651 "bcmp", "memcmp", "memchr", "memrchr", "wmemcmp", "wmemchr",
654 "strcmp", "strcasecmp", "strcoll", "strncmp", "strncasecmp",
655 "strchr", "strcspn", "strlen", "strpbrk", "strrchr", "strspn", "strstr",
659 "wcschr", "wcscmp", "wcscoll", "wcscspn", "wcslen", "wcsncmp", "wcspbrk",
660 "wcsrchr", "wcsspn", "wcsstr",
663 "alphasort", "alphasort64", "versionsort", "versionsort64",
666 "nan", "nanf", "nand",
669 static const unsigned ORMTableSize =
670 sizeof(OnlyReadsMemoryTable)/sizeof(OnlyReadsMemoryTable[0]);
672 bool BasicAliasAnalysis::onlyReadsMemory(Function *F) {
673 if (doesNotAccessMemory(F)) return true;
674 if (!F->isExternal()) return false;
676 static bool Initialized = false;
678 // Sort the table the first time through.
679 std::sort(OnlyReadsMemoryTable, OnlyReadsMemoryTable+ORMTableSize,
684 const char **Ptr = std::lower_bound(OnlyReadsMemoryTable,
685 OnlyReadsMemoryTable+ORMTableSize,
686 F->getName().c_str(), StringCompare());
687 return Ptr != OnlyReadsMemoryTable+ORMTableSize && *Ptr == F->getName();