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comparison lib/Transforms/IPO/FunctionAttrs.cpp @ 0:95c75e76d11b LLVM3.4

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LLVM 3.4
author Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
date Thu, 12 Dec 2013 13:56:28 +0900
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children e4204d083e25
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-1:000000000000 0:95c75e76d11b
1 //===- FunctionAttrs.cpp - Pass which marks functions attributes ----------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements a simple interprocedural pass which walks the
11 // call-graph, looking for functions which do not access or only read
12 // non-local memory, and marking them readnone/readonly. It does the
13 // same with function arguments independently, marking them readonly/
14 // readnone/nocapture. Finally, well-known library call declarations
15 // are marked with all attributes that are consistent with the
16 // function's standard definition. This pass is implemented as a
17 // bottom-up traversal of the call-graph.
18 //
19 //===----------------------------------------------------------------------===//
20
21 #define DEBUG_TYPE "functionattrs"
22 #include "llvm/Transforms/IPO.h"
23 #include "llvm/ADT/SCCIterator.h"
24 #include "llvm/ADT/SetVector.h"
25 #include "llvm/ADT/SmallSet.h"
26 #include "llvm/ADT/Statistic.h"
27 #include "llvm/Analysis/AliasAnalysis.h"
28 #include "llvm/Analysis/CallGraph.h"
29 #include "llvm/Analysis/CallGraphSCCPass.h"
30 #include "llvm/Analysis/CaptureTracking.h"
31 #include "llvm/IR/GlobalVariable.h"
32 #include "llvm/IR/IntrinsicInst.h"
33 #include "llvm/IR/LLVMContext.h"
34 #include "llvm/Support/InstIterator.h"
35 #include "llvm/Target/TargetLibraryInfo.h"
36 using namespace llvm;
37
38 STATISTIC(NumReadNone, "Number of functions marked readnone");
39 STATISTIC(NumReadOnly, "Number of functions marked readonly");
40 STATISTIC(NumNoCapture, "Number of arguments marked nocapture");
41 STATISTIC(NumReadNoneArg, "Number of arguments marked readnone");
42 STATISTIC(NumReadOnlyArg, "Number of arguments marked readonly");
43 STATISTIC(NumNoAlias, "Number of function returns marked noalias");
44 STATISTIC(NumAnnotated, "Number of attributes added to library functions");
45
46 namespace {
47 struct FunctionAttrs : public CallGraphSCCPass {
48 static char ID; // Pass identification, replacement for typeid
49 FunctionAttrs() : CallGraphSCCPass(ID), AA(0) {
50 initializeFunctionAttrsPass(*PassRegistry::getPassRegistry());
51 }
52
53 // runOnSCC - Analyze the SCC, performing the transformation if possible.
54 bool runOnSCC(CallGraphSCC &SCC);
55
56 // AddReadAttrs - Deduce readonly/readnone attributes for the SCC.
57 bool AddReadAttrs(const CallGraphSCC &SCC);
58
59 // AddArgumentAttrs - Deduce nocapture attributes for the SCC.
60 bool AddArgumentAttrs(const CallGraphSCC &SCC);
61
62 // IsFunctionMallocLike - Does this function allocate new memory?
63 bool IsFunctionMallocLike(Function *F,
64 SmallPtrSet<Function*, 8> &) const;
65
66 // AddNoAliasAttrs - Deduce noalias attributes for the SCC.
67 bool AddNoAliasAttrs(const CallGraphSCC &SCC);
68
69 // Utility methods used by inferPrototypeAttributes to add attributes
70 // and maintain annotation statistics.
71
72 void setDoesNotAccessMemory(Function &F) {
73 if (!F.doesNotAccessMemory()) {
74 F.setDoesNotAccessMemory();
75 ++NumAnnotated;
76 }
77 }
78
79 void setOnlyReadsMemory(Function &F) {
80 if (!F.onlyReadsMemory()) {
81 F.setOnlyReadsMemory();
82 ++NumAnnotated;
83 }
84 }
85
86 void setDoesNotThrow(Function &F) {
87 if (!F.doesNotThrow()) {
88 F.setDoesNotThrow();
89 ++NumAnnotated;
90 }
91 }
92
93 void setDoesNotCapture(Function &F, unsigned n) {
94 if (!F.doesNotCapture(n)) {
95 F.setDoesNotCapture(n);
96 ++NumAnnotated;
97 }
98 }
99
100 void setOnlyReadsMemory(Function &F, unsigned n) {
101 if (!F.onlyReadsMemory(n)) {
102 F.setOnlyReadsMemory(n);
103 ++NumAnnotated;
104 }
105 }
106
107 void setDoesNotAlias(Function &F, unsigned n) {
108 if (!F.doesNotAlias(n)) {
109 F.setDoesNotAlias(n);
110 ++NumAnnotated;
111 }
112 }
113
114 // inferPrototypeAttributes - Analyze the name and prototype of the
115 // given function and set any applicable attributes. Returns true
116 // if any attributes were set and false otherwise.
117 bool inferPrototypeAttributes(Function &F);
118
119 // annotateLibraryCalls - Adds attributes to well-known standard library
120 // call declarations.
121 bool annotateLibraryCalls(const CallGraphSCC &SCC);
122
123 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
124 AU.setPreservesCFG();
125 AU.addRequired<AliasAnalysis>();
126 AU.addRequired<TargetLibraryInfo>();
127 CallGraphSCCPass::getAnalysisUsage(AU);
128 }
129
130 private:
131 AliasAnalysis *AA;
132 TargetLibraryInfo *TLI;
133 };
134 }
135
136 char FunctionAttrs::ID = 0;
137 INITIALIZE_PASS_BEGIN(FunctionAttrs, "functionattrs",
138 "Deduce function attributes", false, false)
139 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
140 INITIALIZE_PASS_DEPENDENCY(CallGraph)
141 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
142 INITIALIZE_PASS_END(FunctionAttrs, "functionattrs",
143 "Deduce function attributes", false, false)
144
145 Pass *llvm::createFunctionAttrsPass() { return new FunctionAttrs(); }
146
147
148 /// AddReadAttrs - Deduce readonly/readnone attributes for the SCC.
149 bool FunctionAttrs::AddReadAttrs(const CallGraphSCC &SCC) {
150 SmallPtrSet<Function*, 8> SCCNodes;
151
152 // Fill SCCNodes with the elements of the SCC. Used for quickly
153 // looking up whether a given CallGraphNode is in this SCC.
154 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I)
155 SCCNodes.insert((*I)->getFunction());
156
157 // Check if any of the functions in the SCC read or write memory. If they
158 // write memory then they can't be marked readnone or readonly.
159 bool ReadsMemory = false;
160 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
161 Function *F = (*I)->getFunction();
162
163 if (F == 0)
164 // External node - may write memory. Just give up.
165 return false;
166
167 AliasAnalysis::ModRefBehavior MRB = AA->getModRefBehavior(F);
168 if (MRB == AliasAnalysis::DoesNotAccessMemory)
169 // Already perfect!
170 continue;
171
172 // Definitions with weak linkage may be overridden at linktime with
173 // something that writes memory, so treat them like declarations.
174 if (F->isDeclaration() || F->mayBeOverridden()) {
175 if (!AliasAnalysis::onlyReadsMemory(MRB))
176 // May write memory. Just give up.
177 return false;
178
179 ReadsMemory = true;
180 continue;
181 }
182
183 // Scan the function body for instructions that may read or write memory.
184 for (inst_iterator II = inst_begin(F), E = inst_end(F); II != E; ++II) {
185 Instruction *I = &*II;
186
187 // Some instructions can be ignored even if they read or write memory.
188 // Detect these now, skipping to the next instruction if one is found.
189 CallSite CS(cast<Value>(I));
190 if (CS) {
191 // Ignore calls to functions in the same SCC.
192 if (CS.getCalledFunction() && SCCNodes.count(CS.getCalledFunction()))
193 continue;
194 AliasAnalysis::ModRefBehavior MRB = AA->getModRefBehavior(CS);
195 // If the call doesn't access arbitrary memory, we may be able to
196 // figure out something.
197 if (AliasAnalysis::onlyAccessesArgPointees(MRB)) {
198 // If the call does access argument pointees, check each argument.
199 if (AliasAnalysis::doesAccessArgPointees(MRB))
200 // Check whether all pointer arguments point to local memory, and
201 // ignore calls that only access local memory.
202 for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
203 CI != CE; ++CI) {
204 Value *Arg = *CI;
205 if (Arg->getType()->isPointerTy()) {
206 AliasAnalysis::Location Loc(Arg,
207 AliasAnalysis::UnknownSize,
208 I->getMetadata(LLVMContext::MD_tbaa));
209 if (!AA->pointsToConstantMemory(Loc, /*OrLocal=*/true)) {
210 if (MRB & AliasAnalysis::Mod)
211 // Writes non-local memory. Give up.
212 return false;
213 if (MRB & AliasAnalysis::Ref)
214 // Ok, it reads non-local memory.
215 ReadsMemory = true;
216 }
217 }
218 }
219 continue;
220 }
221 // The call could access any memory. If that includes writes, give up.
222 if (MRB & AliasAnalysis::Mod)
223 return false;
224 // If it reads, note it.
225 if (MRB & AliasAnalysis::Ref)
226 ReadsMemory = true;
227 continue;
228 } else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
229 // Ignore non-volatile loads from local memory. (Atomic is okay here.)
230 if (!LI->isVolatile()) {
231 AliasAnalysis::Location Loc = AA->getLocation(LI);
232 if (AA->pointsToConstantMemory(Loc, /*OrLocal=*/true))
233 continue;
234 }
235 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
236 // Ignore non-volatile stores to local memory. (Atomic is okay here.)
237 if (!SI->isVolatile()) {
238 AliasAnalysis::Location Loc = AA->getLocation(SI);
239 if (AA->pointsToConstantMemory(Loc, /*OrLocal=*/true))
240 continue;
241 }
242 } else if (VAArgInst *VI = dyn_cast<VAArgInst>(I)) {
243 // Ignore vaargs on local memory.
244 AliasAnalysis::Location Loc = AA->getLocation(VI);
245 if (AA->pointsToConstantMemory(Loc, /*OrLocal=*/true))
246 continue;
247 }
248
249 // Any remaining instructions need to be taken seriously! Check if they
250 // read or write memory.
251 if (I->mayWriteToMemory())
252 // Writes memory. Just give up.
253 return false;
254
255 // If this instruction may read memory, remember that.
256 ReadsMemory |= I->mayReadFromMemory();
257 }
258 }
259
260 // Success! Functions in this SCC do not access memory, or only read memory.
261 // Give them the appropriate attribute.
262 bool MadeChange = false;
263 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
264 Function *F = (*I)->getFunction();
265
266 if (F->doesNotAccessMemory())
267 // Already perfect!
268 continue;
269
270 if (F->onlyReadsMemory() && ReadsMemory)
271 // No change.
272 continue;
273
274 MadeChange = true;
275
276 // Clear out any existing attributes.
277 AttrBuilder B;
278 B.addAttribute(Attribute::ReadOnly)
279 .addAttribute(Attribute::ReadNone);
280 F->removeAttributes(AttributeSet::FunctionIndex,
281 AttributeSet::get(F->getContext(),
282 AttributeSet::FunctionIndex, B));
283
284 // Add in the new attribute.
285 F->addAttribute(AttributeSet::FunctionIndex,
286 ReadsMemory ? Attribute::ReadOnly : Attribute::ReadNone);
287
288 if (ReadsMemory)
289 ++NumReadOnly;
290 else
291 ++NumReadNone;
292 }
293
294 return MadeChange;
295 }
296
297 namespace {
298 // For a given pointer Argument, this retains a list of Arguments of functions
299 // in the same SCC that the pointer data flows into. We use this to build an
300 // SCC of the arguments.
301 struct ArgumentGraphNode {
302 Argument *Definition;
303 SmallVector<ArgumentGraphNode*, 4> Uses;
304 };
305
306 class ArgumentGraph {
307 // We store pointers to ArgumentGraphNode objects, so it's important that
308 // that they not move around upon insert.
309 typedef std::map<Argument*, ArgumentGraphNode> ArgumentMapTy;
310
311 ArgumentMapTy ArgumentMap;
312
313 // There is no root node for the argument graph, in fact:
314 // void f(int *x, int *y) { if (...) f(x, y); }
315 // is an example where the graph is disconnected. The SCCIterator requires a
316 // single entry point, so we maintain a fake ("synthetic") root node that
317 // uses every node. Because the graph is directed and nothing points into
318 // the root, it will not participate in any SCCs (except for its own).
319 ArgumentGraphNode SyntheticRoot;
320
321 public:
322 ArgumentGraph() { SyntheticRoot.Definition = 0; }
323
324 typedef SmallVectorImpl<ArgumentGraphNode*>::iterator iterator;
325
326 iterator begin() { return SyntheticRoot.Uses.begin(); }
327 iterator end() { return SyntheticRoot.Uses.end(); }
328 ArgumentGraphNode *getEntryNode() { return &SyntheticRoot; }
329
330 ArgumentGraphNode *operator[](Argument *A) {
331 ArgumentGraphNode &Node = ArgumentMap[A];
332 Node.Definition = A;
333 SyntheticRoot.Uses.push_back(&Node);
334 return &Node;
335 }
336 };
337
338 // This tracker checks whether callees are in the SCC, and if so it does not
339 // consider that a capture, instead adding it to the "Uses" list and
340 // continuing with the analysis.
341 struct ArgumentUsesTracker : public CaptureTracker {
342 ArgumentUsesTracker(const SmallPtrSet<Function*, 8> &SCCNodes)
343 : Captured(false), SCCNodes(SCCNodes) {}
344
345 void tooManyUses() { Captured = true; }
346
347 bool captured(Use *U) {
348 CallSite CS(U->getUser());
349 if (!CS.getInstruction()) { Captured = true; return true; }
350
351 Function *F = CS.getCalledFunction();
352 if (!F || !SCCNodes.count(F)) { Captured = true; return true; }
353
354 bool Found = false;
355 Function::arg_iterator AI = F->arg_begin(), AE = F->arg_end();
356 for (CallSite::arg_iterator PI = CS.arg_begin(), PE = CS.arg_end();
357 PI != PE; ++PI, ++AI) {
358 if (AI == AE) {
359 assert(F->isVarArg() && "More params than args in non-varargs call");
360 Captured = true;
361 return true;
362 }
363 if (PI == U) {
364 Uses.push_back(AI);
365 Found = true;
366 break;
367 }
368 }
369 assert(Found && "Capturing call-site captured nothing?");
370 (void)Found;
371 return false;
372 }
373
374 bool Captured; // True only if certainly captured (used outside our SCC).
375 SmallVector<Argument*, 4> Uses; // Uses within our SCC.
376
377 const SmallPtrSet<Function*, 8> &SCCNodes;
378 };
379 }
380
381 namespace llvm {
382 template<> struct GraphTraits<ArgumentGraphNode*> {
383 typedef ArgumentGraphNode NodeType;
384 typedef SmallVectorImpl<ArgumentGraphNode*>::iterator ChildIteratorType;
385
386 static inline NodeType *getEntryNode(NodeType *A) { return A; }
387 static inline ChildIteratorType child_begin(NodeType *N) {
388 return N->Uses.begin();
389 }
390 static inline ChildIteratorType child_end(NodeType *N) {
391 return N->Uses.end();
392 }
393 };
394 template<> struct GraphTraits<ArgumentGraph*>
395 : public GraphTraits<ArgumentGraphNode*> {
396 static NodeType *getEntryNode(ArgumentGraph *AG) {
397 return AG->getEntryNode();
398 }
399 static ChildIteratorType nodes_begin(ArgumentGraph *AG) {
400 return AG->begin();
401 }
402 static ChildIteratorType nodes_end(ArgumentGraph *AG) {
403 return AG->end();
404 }
405 };
406 }
407
408 // Returns Attribute::None, Attribute::ReadOnly or Attribute::ReadNone.
409 static Attribute::AttrKind
410 determinePointerReadAttrs(Argument *A,
411 const SmallPtrSet<Argument*, 8> &SCCNodes) {
412
413 SmallVector<Use*, 32> Worklist;
414 SmallSet<Use*, 32> Visited;
415 int Count = 0;
416
417 bool IsRead = false;
418 // We don't need to track IsWritten. If A is written to, return immediately.
419
420 for (Value::use_iterator UI = A->use_begin(), UE = A->use_end();
421 UI != UE; ++UI) {
422 if (Count++ >= 20)
423 return Attribute::None;
424
425 Use *U = &UI.getUse();
426 Visited.insert(U);
427 Worklist.push_back(U);
428 }
429
430 while (!Worklist.empty()) {
431 Use *U = Worklist.pop_back_val();
432 Instruction *I = cast<Instruction>(U->getUser());
433 Value *V = U->get();
434
435 switch (I->getOpcode()) {
436 case Instruction::BitCast:
437 case Instruction::GetElementPtr:
438 case Instruction::PHI:
439 case Instruction::Select:
440 // The original value is not read/written via this if the new value isn't.
441 for (Instruction::use_iterator UI = I->use_begin(), UE = I->use_end();
442 UI != UE; ++UI) {
443 Use *U = &UI.getUse();
444 if (Visited.insert(U))
445 Worklist.push_back(U);
446 }
447 break;
448
449 case Instruction::Call:
450 case Instruction::Invoke: {
451 CallSite CS(I);
452 if (CS.doesNotAccessMemory())
453 continue;
454
455 Function *F = CS.getCalledFunction();
456 if (!F) {
457 if (CS.onlyReadsMemory()) {
458 IsRead = true;
459 continue;
460 }
461 return Attribute::None;
462 }
463
464 Function::arg_iterator AI = F->arg_begin(), AE = F->arg_end();
465 CallSite::arg_iterator B = CS.arg_begin(), E = CS.arg_end();
466 for (CallSite::arg_iterator A = B; A != E; ++A, ++AI) {
467 if (A->get() == V) {
468 if (AI == AE) {
469 assert(F->isVarArg() &&
470 "More params than args in non-varargs call.");
471 return Attribute::None;
472 }
473 if (SCCNodes.count(AI))
474 continue;
475 if (!CS.onlyReadsMemory() && !CS.onlyReadsMemory(A - B))
476 return Attribute::None;
477 if (!CS.doesNotAccessMemory(A - B))
478 IsRead = true;
479 }
480 }
481 break;
482 }
483
484 case Instruction::Load:
485 IsRead = true;
486 break;
487
488 case Instruction::ICmp:
489 case Instruction::Ret:
490 break;
491
492 default:
493 return Attribute::None;
494 }
495 }
496
497 return IsRead ? Attribute::ReadOnly : Attribute::ReadNone;
498 }
499
500 /// AddArgumentAttrs - Deduce nocapture attributes for the SCC.
501 bool FunctionAttrs::AddArgumentAttrs(const CallGraphSCC &SCC) {
502 bool Changed = false;
503
504 SmallPtrSet<Function*, 8> SCCNodes;
505
506 // Fill SCCNodes with the elements of the SCC. Used for quickly
507 // looking up whether a given CallGraphNode is in this SCC.
508 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
509 Function *F = (*I)->getFunction();
510 if (F && !F->isDeclaration() && !F->mayBeOverridden())
511 SCCNodes.insert(F);
512 }
513
514 ArgumentGraph AG;
515
516 AttrBuilder B;
517 B.addAttribute(Attribute::NoCapture);
518
519 // Check each function in turn, determining which pointer arguments are not
520 // captured.
521 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
522 Function *F = (*I)->getFunction();
523
524 if (F == 0)
525 // External node - only a problem for arguments that we pass to it.
526 continue;
527
528 // Definitions with weak linkage may be overridden at linktime with
529 // something that captures pointers, so treat them like declarations.
530 if (F->isDeclaration() || F->mayBeOverridden())
531 continue;
532
533 // Functions that are readonly (or readnone) and nounwind and don't return
534 // a value can't capture arguments. Don't analyze them.
535 if (F->onlyReadsMemory() && F->doesNotThrow() &&
536 F->getReturnType()->isVoidTy()) {
537 for (Function::arg_iterator A = F->arg_begin(), E = F->arg_end();
538 A != E; ++A) {
539 if (A->getType()->isPointerTy() && !A->hasNoCaptureAttr()) {
540 A->addAttr(AttributeSet::get(F->getContext(), A->getArgNo() + 1, B));
541 ++NumNoCapture;
542 Changed = true;
543 }
544 }
545 continue;
546 }
547
548 for (Function::arg_iterator A = F->arg_begin(), E = F->arg_end();
549 A != E; ++A) {
550 if (!A->getType()->isPointerTy()) continue;
551 bool HasNonLocalUses = false;
552 if (!A->hasNoCaptureAttr()) {
553 ArgumentUsesTracker Tracker(SCCNodes);
554 PointerMayBeCaptured(A, &Tracker);
555 if (!Tracker.Captured) {
556 if (Tracker.Uses.empty()) {
557 // If it's trivially not captured, mark it nocapture now.
558 A->addAttr(AttributeSet::get(F->getContext(), A->getArgNo()+1, B));
559 ++NumNoCapture;
560 Changed = true;
561 } else {
562 // If it's not trivially captured and not trivially not captured,
563 // then it must be calling into another function in our SCC. Save
564 // its particulars for Argument-SCC analysis later.
565 ArgumentGraphNode *Node = AG[A];
566 for (SmallVectorImpl<Argument*>::iterator UI = Tracker.Uses.begin(),
567 UE = Tracker.Uses.end(); UI != UE; ++UI) {
568 Node->Uses.push_back(AG[*UI]);
569 if (*UI != A)
570 HasNonLocalUses = true;
571 }
572 }
573 }
574 // Otherwise, it's captured. Don't bother doing SCC analysis on it.
575 }
576 if (!HasNonLocalUses && !A->onlyReadsMemory()) {
577 // Can we determine that it's readonly/readnone without doing an SCC?
578 // Note that we don't allow any calls at all here, or else our result
579 // will be dependent on the iteration order through the functions in the
580 // SCC.
581 SmallPtrSet<Argument*, 8> Self;
582 Self.insert(A);
583 Attribute::AttrKind R = determinePointerReadAttrs(A, Self);
584 if (R != Attribute::None) {
585 AttrBuilder B;
586 B.addAttribute(R);
587 A->addAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, B));
588 Changed = true;
589 R == Attribute::ReadOnly ? ++NumReadOnlyArg : ++NumReadNoneArg;
590 }
591 }
592 }
593 }
594
595 // The graph we've collected is partial because we stopped scanning for
596 // argument uses once we solved the argument trivially. These partial nodes
597 // show up as ArgumentGraphNode objects with an empty Uses list, and for
598 // these nodes the final decision about whether they capture has already been
599 // made. If the definition doesn't have a 'nocapture' attribute by now, it
600 // captures.
601
602 for (scc_iterator<ArgumentGraph*> I = scc_begin(&AG), E = scc_end(&AG);
603 I != E; ++I) {
604 std::vector<ArgumentGraphNode*> &ArgumentSCC = *I;
605 if (ArgumentSCC.size() == 1) {
606 if (!ArgumentSCC[0]->Definition) continue; // synthetic root node
607
608 // eg. "void f(int* x) { if (...) f(x); }"
609 if (ArgumentSCC[0]->Uses.size() == 1 &&
610 ArgumentSCC[0]->Uses[0] == ArgumentSCC[0]) {
611 Argument *A = ArgumentSCC[0]->Definition;
612 A->addAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, B));
613 ++NumNoCapture;
614 Changed = true;
615 }
616 continue;
617 }
618
619 bool SCCCaptured = false;
620 for (std::vector<ArgumentGraphNode*>::iterator I = ArgumentSCC.begin(),
621 E = ArgumentSCC.end(); I != E && !SCCCaptured; ++I) {
622 ArgumentGraphNode *Node = *I;
623 if (Node->Uses.empty()) {
624 if (!Node->Definition->hasNoCaptureAttr())
625 SCCCaptured = true;
626 }
627 }
628 if (SCCCaptured) continue;
629
630 SmallPtrSet<Argument*, 8> ArgumentSCCNodes;
631 // Fill ArgumentSCCNodes with the elements of the ArgumentSCC. Used for
632 // quickly looking up whether a given Argument is in this ArgumentSCC.
633 for (std::vector<ArgumentGraphNode*>::iterator I = ArgumentSCC.begin(),
634 E = ArgumentSCC.end(); I != E; ++I) {
635 ArgumentSCCNodes.insert((*I)->Definition);
636 }
637
638 for (std::vector<ArgumentGraphNode*>::iterator I = ArgumentSCC.begin(),
639 E = ArgumentSCC.end(); I != E && !SCCCaptured; ++I) {
640 ArgumentGraphNode *N = *I;
641 for (SmallVectorImpl<ArgumentGraphNode*>::iterator UI = N->Uses.begin(),
642 UE = N->Uses.end(); UI != UE; ++UI) {
643 Argument *A = (*UI)->Definition;
644 if (A->hasNoCaptureAttr() || ArgumentSCCNodes.count(A))
645 continue;
646 SCCCaptured = true;
647 break;
648 }
649 }
650 if (SCCCaptured) continue;
651
652 for (unsigned i = 0, e = ArgumentSCC.size(); i != e; ++i) {
653 Argument *A = ArgumentSCC[i]->Definition;
654 A->addAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, B));
655 ++NumNoCapture;
656 Changed = true;
657 }
658
659 // We also want to compute readonly/readnone. With a small number of false
660 // negatives, we can assume that any pointer which is captured isn't going
661 // to be provably readonly or readnone, since by definition we can't
662 // analyze all uses of a captured pointer.
663 //
664 // The false negatives happen when the pointer is captured by a function
665 // that promises readonly/readnone behaviour on the pointer, then the
666 // pointer's lifetime ends before anything that writes to arbitrary memory.
667 // Also, a readonly/readnone pointer may be returned, but returning a
668 // pointer is capturing it.
669
670 Attribute::AttrKind ReadAttr = Attribute::ReadNone;
671 for (unsigned i = 0, e = ArgumentSCC.size(); i != e; ++i) {
672 Argument *A = ArgumentSCC[i]->Definition;
673 Attribute::AttrKind K = determinePointerReadAttrs(A, ArgumentSCCNodes);
674 if (K == Attribute::ReadNone)
675 continue;
676 if (K == Attribute::ReadOnly) {
677 ReadAttr = Attribute::ReadOnly;
678 continue;
679 }
680 ReadAttr = K;
681 break;
682 }
683
684 if (ReadAttr != Attribute::None) {
685 AttrBuilder B;
686 B.addAttribute(ReadAttr);
687 for (unsigned i = 0, e = ArgumentSCC.size(); i != e; ++i) {
688 Argument *A = ArgumentSCC[i]->Definition;
689 A->addAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, B));
690 ReadAttr == Attribute::ReadOnly ? ++NumReadOnlyArg : ++NumReadNoneArg;
691 Changed = true;
692 }
693 }
694 }
695
696 return Changed;
697 }
698
699 /// IsFunctionMallocLike - A function is malloc-like if it returns either null
700 /// or a pointer that doesn't alias any other pointer visible to the caller.
701 bool FunctionAttrs::IsFunctionMallocLike(Function *F,
702 SmallPtrSet<Function*, 8> &SCCNodes) const {
703 SmallSetVector<Value *, 8> FlowsToReturn;
704 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I)
705 if (ReturnInst *Ret = dyn_cast<ReturnInst>(I->getTerminator()))
706 FlowsToReturn.insert(Ret->getReturnValue());
707
708 for (unsigned i = 0; i != FlowsToReturn.size(); ++i) {
709 Value *RetVal = FlowsToReturn[i];
710
711 if (Constant *C = dyn_cast<Constant>(RetVal)) {
712 if (!C->isNullValue() && !isa<UndefValue>(C))
713 return false;
714
715 continue;
716 }
717
718 if (isa<Argument>(RetVal))
719 return false;
720
721 if (Instruction *RVI = dyn_cast<Instruction>(RetVal))
722 switch (RVI->getOpcode()) {
723 // Extend the analysis by looking upwards.
724 case Instruction::BitCast:
725 case Instruction::GetElementPtr:
726 FlowsToReturn.insert(RVI->getOperand(0));
727 continue;
728 case Instruction::Select: {
729 SelectInst *SI = cast<SelectInst>(RVI);
730 FlowsToReturn.insert(SI->getTrueValue());
731 FlowsToReturn.insert(SI->getFalseValue());
732 continue;
733 }
734 case Instruction::PHI: {
735 PHINode *PN = cast<PHINode>(RVI);
736 for (int i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
737 FlowsToReturn.insert(PN->getIncomingValue(i));
738 continue;
739 }
740
741 // Check whether the pointer came from an allocation.
742 case Instruction::Alloca:
743 break;
744 case Instruction::Call:
745 case Instruction::Invoke: {
746 CallSite CS(RVI);
747 if (CS.paramHasAttr(0, Attribute::NoAlias))
748 break;
749 if (CS.getCalledFunction() &&
750 SCCNodes.count(CS.getCalledFunction()))
751 break;
752 } // fall-through
753 default:
754 return false; // Did not come from an allocation.
755 }
756
757 if (PointerMayBeCaptured(RetVal, false, /*StoreCaptures=*/false))
758 return false;
759 }
760
761 return true;
762 }
763
764 /// AddNoAliasAttrs - Deduce noalias attributes for the SCC.
765 bool FunctionAttrs::AddNoAliasAttrs(const CallGraphSCC &SCC) {
766 SmallPtrSet<Function*, 8> SCCNodes;
767
768 // Fill SCCNodes with the elements of the SCC. Used for quickly
769 // looking up whether a given CallGraphNode is in this SCC.
770 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I)
771 SCCNodes.insert((*I)->getFunction());
772
773 // Check each function in turn, determining which functions return noalias
774 // pointers.
775 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
776 Function *F = (*I)->getFunction();
777
778 if (F == 0)
779 // External node - skip it;
780 return false;
781
782 // Already noalias.
783 if (F->doesNotAlias(0))
784 continue;
785
786 // Definitions with weak linkage may be overridden at linktime, so
787 // treat them like declarations.
788 if (F->isDeclaration() || F->mayBeOverridden())
789 return false;
790
791 // We annotate noalias return values, which are only applicable to
792 // pointer types.
793 if (!F->getReturnType()->isPointerTy())
794 continue;
795
796 if (!IsFunctionMallocLike(F, SCCNodes))
797 return false;
798 }
799
800 bool MadeChange = false;
801 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
802 Function *F = (*I)->getFunction();
803 if (F->doesNotAlias(0) || !F->getReturnType()->isPointerTy())
804 continue;
805
806 F->setDoesNotAlias(0);
807 ++NumNoAlias;
808 MadeChange = true;
809 }
810
811 return MadeChange;
812 }
813
814 /// inferPrototypeAttributes - Analyze the name and prototype of the
815 /// given function and set any applicable attributes. Returns true
816 /// if any attributes were set and false otherwise.
817 bool FunctionAttrs::inferPrototypeAttributes(Function &F) {
818 FunctionType *FTy = F.getFunctionType();
819 LibFunc::Func TheLibFunc;
820 if (!(TLI->getLibFunc(F.getName(), TheLibFunc) && TLI->has(TheLibFunc)))
821 return false;
822
823 switch (TheLibFunc) {
824 case LibFunc::strlen:
825 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
826 return false;
827 setOnlyReadsMemory(F);
828 setDoesNotThrow(F);
829 setDoesNotCapture(F, 1);
830 break;
831 case LibFunc::strchr:
832 case LibFunc::strrchr:
833 if (FTy->getNumParams() != 2 ||
834 !FTy->getParamType(0)->isPointerTy() ||
835 !FTy->getParamType(1)->isIntegerTy())
836 return false;
837 setOnlyReadsMemory(F);
838 setDoesNotThrow(F);
839 break;
840 case LibFunc::strtol:
841 case LibFunc::strtod:
842 case LibFunc::strtof:
843 case LibFunc::strtoul:
844 case LibFunc::strtoll:
845 case LibFunc::strtold:
846 case LibFunc::strtoull:
847 if (FTy->getNumParams() < 2 ||
848 !FTy->getParamType(1)->isPointerTy())
849 return false;
850 setDoesNotThrow(F);
851 setDoesNotCapture(F, 2);
852 setOnlyReadsMemory(F, 1);
853 break;
854 case LibFunc::strcpy:
855 case LibFunc::stpcpy:
856 case LibFunc::strcat:
857 case LibFunc::strncat:
858 case LibFunc::strncpy:
859 case LibFunc::stpncpy:
860 if (FTy->getNumParams() < 2 ||
861 !FTy->getParamType(1)->isPointerTy())
862 return false;
863 setDoesNotThrow(F);
864 setDoesNotCapture(F, 2);
865 setOnlyReadsMemory(F, 2);
866 break;
867 case LibFunc::strxfrm:
868 if (FTy->getNumParams() != 3 ||
869 !FTy->getParamType(0)->isPointerTy() ||
870 !FTy->getParamType(1)->isPointerTy())
871 return false;
872 setDoesNotThrow(F);
873 setDoesNotCapture(F, 1);
874 setDoesNotCapture(F, 2);
875 setOnlyReadsMemory(F, 2);
876 break;
877 case LibFunc::strcmp: //0,1
878 case LibFunc::strspn: // 0,1
879 case LibFunc::strncmp: // 0,1
880 case LibFunc::strcspn: //0,1
881 case LibFunc::strcoll: //0,1
882 case LibFunc::strcasecmp: // 0,1
883 case LibFunc::strncasecmp: //
884 if (FTy->getNumParams() < 2 ||
885 !FTy->getParamType(0)->isPointerTy() ||
886 !FTy->getParamType(1)->isPointerTy())
887 return false;
888 setOnlyReadsMemory(F);
889 setDoesNotThrow(F);
890 setDoesNotCapture(F, 1);
891 setDoesNotCapture(F, 2);
892 break;
893 case LibFunc::strstr:
894 case LibFunc::strpbrk:
895 if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
896 return false;
897 setOnlyReadsMemory(F);
898 setDoesNotThrow(F);
899 setDoesNotCapture(F, 2);
900 break;
901 case LibFunc::strtok:
902 case LibFunc::strtok_r:
903 if (FTy->getNumParams() < 2 || !FTy->getParamType(1)->isPointerTy())
904 return false;
905 setDoesNotThrow(F);
906 setDoesNotCapture(F, 2);
907 setOnlyReadsMemory(F, 2);
908 break;
909 case LibFunc::scanf:
910 if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy())
911 return false;
912 setDoesNotThrow(F);
913 setDoesNotCapture(F, 1);
914 setOnlyReadsMemory(F, 1);
915 break;
916 case LibFunc::setbuf:
917 case LibFunc::setvbuf:
918 if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy())
919 return false;
920 setDoesNotThrow(F);
921 setDoesNotCapture(F, 1);
922 break;
923 case LibFunc::strdup:
924 case LibFunc::strndup:
925 if (FTy->getNumParams() < 1 || !FTy->getReturnType()->isPointerTy() ||
926 !FTy->getParamType(0)->isPointerTy())
927 return false;
928 setDoesNotThrow(F);
929 setDoesNotAlias(F, 0);
930 setDoesNotCapture(F, 1);
931 setOnlyReadsMemory(F, 1);
932 break;
933 case LibFunc::stat:
934 case LibFunc::statvfs:
935 if (FTy->getNumParams() < 2 ||
936 !FTy->getParamType(0)->isPointerTy() ||
937 !FTy->getParamType(1)->isPointerTy())
938 return false;
939 setDoesNotThrow(F);
940 setDoesNotCapture(F, 1);
941 setDoesNotCapture(F, 2);
942 setOnlyReadsMemory(F, 1);
943 break;
944 case LibFunc::sscanf:
945 if (FTy->getNumParams() < 2 ||
946 !FTy->getParamType(0)->isPointerTy() ||
947 !FTy->getParamType(1)->isPointerTy())
948 return false;
949 setDoesNotThrow(F);
950 setDoesNotCapture(F, 1);
951 setDoesNotCapture(F, 2);
952 setOnlyReadsMemory(F, 1);
953 setOnlyReadsMemory(F, 2);
954 break;
955 case LibFunc::sprintf:
956 if (FTy->getNumParams() < 2 ||
957 !FTy->getParamType(0)->isPointerTy() ||
958 !FTy->getParamType(1)->isPointerTy())
959 return false;
960 setDoesNotThrow(F);
961 setDoesNotCapture(F, 1);
962 setDoesNotCapture(F, 2);
963 setOnlyReadsMemory(F, 2);
964 break;
965 case LibFunc::snprintf:
966 if (FTy->getNumParams() != 3 ||
967 !FTy->getParamType(0)->isPointerTy() ||
968 !FTy->getParamType(2)->isPointerTy())
969 return false;
970 setDoesNotThrow(F);
971 setDoesNotCapture(F, 1);
972 setDoesNotCapture(F, 3);
973 setOnlyReadsMemory(F, 3);
974 break;
975 case LibFunc::setitimer:
976 if (FTy->getNumParams() != 3 ||
977 !FTy->getParamType(1)->isPointerTy() ||
978 !FTy->getParamType(2)->isPointerTy())
979 return false;
980 setDoesNotThrow(F);
981 setDoesNotCapture(F, 2);
982 setDoesNotCapture(F, 3);
983 setOnlyReadsMemory(F, 2);
984 break;
985 case LibFunc::system:
986 if (FTy->getNumParams() != 1 ||
987 !FTy->getParamType(0)->isPointerTy())
988 return false;
989 // May throw; "system" is a valid pthread cancellation point.
990 setDoesNotCapture(F, 1);
991 setOnlyReadsMemory(F, 1);
992 break;
993 case LibFunc::malloc:
994 if (FTy->getNumParams() != 1 ||
995 !FTy->getReturnType()->isPointerTy())
996 return false;
997 setDoesNotThrow(F);
998 setDoesNotAlias(F, 0);
999 break;
1000 case LibFunc::memcmp:
1001 if (FTy->getNumParams() != 3 ||
1002 !FTy->getParamType(0)->isPointerTy() ||
1003 !FTy->getParamType(1)->isPointerTy())
1004 return false;
1005 setOnlyReadsMemory(F);
1006 setDoesNotThrow(F);
1007 setDoesNotCapture(F, 1);
1008 setDoesNotCapture(F, 2);
1009 break;
1010 case LibFunc::memchr:
1011 case LibFunc::memrchr:
1012 if (FTy->getNumParams() != 3)
1013 return false;
1014 setOnlyReadsMemory(F);
1015 setDoesNotThrow(F);
1016 break;
1017 case LibFunc::modf:
1018 case LibFunc::modff:
1019 case LibFunc::modfl:
1020 if (FTy->getNumParams() < 2 ||
1021 !FTy->getParamType(1)->isPointerTy())
1022 return false;
1023 setDoesNotThrow(F);
1024 setDoesNotCapture(F, 2);
1025 break;
1026 case LibFunc::memcpy:
1027 case LibFunc::memccpy:
1028 case LibFunc::memmove:
1029 if (FTy->getNumParams() < 2 ||
1030 !FTy->getParamType(1)->isPointerTy())
1031 return false;
1032 setDoesNotThrow(F);
1033 setDoesNotCapture(F, 2);
1034 setOnlyReadsMemory(F, 2);
1035 break;
1036 case LibFunc::memalign:
1037 if (!FTy->getReturnType()->isPointerTy())
1038 return false;
1039 setDoesNotAlias(F, 0);
1040 break;
1041 case LibFunc::mkdir:
1042 if (FTy->getNumParams() == 0 ||
1043 !FTy->getParamType(0)->isPointerTy())
1044 return false;
1045 setDoesNotThrow(F);
1046 setDoesNotCapture(F, 1);
1047 setOnlyReadsMemory(F, 1);
1048 break;
1049 case LibFunc::mktime:
1050 if (FTy->getNumParams() == 0 ||
1051 !FTy->getParamType(0)->isPointerTy())
1052 return false;
1053 setDoesNotThrow(F);
1054 setDoesNotCapture(F, 1);
1055 break;
1056 case LibFunc::realloc:
1057 if (FTy->getNumParams() != 2 ||
1058 !FTy->getParamType(0)->isPointerTy() ||
1059 !FTy->getReturnType()->isPointerTy())
1060 return false;
1061 setDoesNotThrow(F);
1062 setDoesNotAlias(F, 0);
1063 setDoesNotCapture(F, 1);
1064 break;
1065 case LibFunc::read:
1066 if (FTy->getNumParams() != 3 ||
1067 !FTy->getParamType(1)->isPointerTy())
1068 return false;
1069 // May throw; "read" is a valid pthread cancellation point.
1070 setDoesNotCapture(F, 2);
1071 break;
1072 case LibFunc::rewind:
1073 if (FTy->getNumParams() < 1 ||
1074 !FTy->getParamType(0)->isPointerTy())
1075 return false;
1076 setDoesNotThrow(F);
1077 setDoesNotCapture(F, 1);
1078 break;
1079 case LibFunc::rmdir:
1080 case LibFunc::remove:
1081 case LibFunc::realpath:
1082 if (FTy->getNumParams() < 1 ||
1083 !FTy->getParamType(0)->isPointerTy())
1084 return false;
1085 setDoesNotThrow(F);
1086 setDoesNotCapture(F, 1);
1087 setOnlyReadsMemory(F, 1);
1088 break;
1089 case LibFunc::rename:
1090 if (FTy->getNumParams() < 2 ||
1091 !FTy->getParamType(0)->isPointerTy() ||
1092 !FTy->getParamType(1)->isPointerTy())
1093 return false;
1094 setDoesNotThrow(F);
1095 setDoesNotCapture(F, 1);
1096 setDoesNotCapture(F, 2);
1097 setOnlyReadsMemory(F, 1);
1098 setOnlyReadsMemory(F, 2);
1099 break;
1100 case LibFunc::readlink:
1101 if (FTy->getNumParams() < 2 ||
1102 !FTy->getParamType(0)->isPointerTy() ||
1103 !FTy->getParamType(1)->isPointerTy())
1104 return false;
1105 setDoesNotThrow(F);
1106 setDoesNotCapture(F, 1);
1107 setDoesNotCapture(F, 2);
1108 setOnlyReadsMemory(F, 1);
1109 break;
1110 case LibFunc::write:
1111 if (FTy->getNumParams() != 3 || !FTy->getParamType(1)->isPointerTy())
1112 return false;
1113 // May throw; "write" is a valid pthread cancellation point.
1114 setDoesNotCapture(F, 2);
1115 setOnlyReadsMemory(F, 2);
1116 break;
1117 case LibFunc::bcopy:
1118 if (FTy->getNumParams() != 3 ||
1119 !FTy->getParamType(0)->isPointerTy() ||
1120 !FTy->getParamType(1)->isPointerTy())
1121 return false;
1122 setDoesNotThrow(F);
1123 setDoesNotCapture(F, 1);
1124 setDoesNotCapture(F, 2);
1125 setOnlyReadsMemory(F, 1);
1126 break;
1127 case LibFunc::bcmp:
1128 if (FTy->getNumParams() != 3 ||
1129 !FTy->getParamType(0)->isPointerTy() ||
1130 !FTy->getParamType(1)->isPointerTy())
1131 return false;
1132 setDoesNotThrow(F);
1133 setOnlyReadsMemory(F);
1134 setDoesNotCapture(F, 1);
1135 setDoesNotCapture(F, 2);
1136 break;
1137 case LibFunc::bzero:
1138 if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy())
1139 return false;
1140 setDoesNotThrow(F);
1141 setDoesNotCapture(F, 1);
1142 break;
1143 case LibFunc::calloc:
1144 if (FTy->getNumParams() != 2 ||
1145 !FTy->getReturnType()->isPointerTy())
1146 return false;
1147 setDoesNotThrow(F);
1148 setDoesNotAlias(F, 0);
1149 break;
1150 case LibFunc::chmod:
1151 case LibFunc::chown:
1152 if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
1153 return false;
1154 setDoesNotThrow(F);
1155 setDoesNotCapture(F, 1);
1156 setOnlyReadsMemory(F, 1);
1157 break;
1158 case LibFunc::ctermid:
1159 case LibFunc::clearerr:
1160 case LibFunc::closedir:
1161 if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
1162 return false;
1163 setDoesNotThrow(F);
1164 setDoesNotCapture(F, 1);
1165 break;
1166 case LibFunc::atoi:
1167 case LibFunc::atol:
1168 case LibFunc::atof:
1169 case LibFunc::atoll:
1170 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1171 return false;
1172 setDoesNotThrow(F);
1173 setOnlyReadsMemory(F);
1174 setDoesNotCapture(F, 1);
1175 break;
1176 case LibFunc::access:
1177 if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy())
1178 return false;
1179 setDoesNotThrow(F);
1180 setDoesNotCapture(F, 1);
1181 setOnlyReadsMemory(F, 1);
1182 break;
1183 case LibFunc::fopen:
1184 if (FTy->getNumParams() != 2 ||
1185 !FTy->getReturnType()->isPointerTy() ||
1186 !FTy->getParamType(0)->isPointerTy() ||
1187 !FTy->getParamType(1)->isPointerTy())
1188 return false;
1189 setDoesNotThrow(F);
1190 setDoesNotAlias(F, 0);
1191 setDoesNotCapture(F, 1);
1192 setDoesNotCapture(F, 2);
1193 setOnlyReadsMemory(F, 1);
1194 setOnlyReadsMemory(F, 2);
1195 break;
1196 case LibFunc::fdopen:
1197 if (FTy->getNumParams() != 2 ||
1198 !FTy->getReturnType()->isPointerTy() ||
1199 !FTy->getParamType(1)->isPointerTy())
1200 return false;
1201 setDoesNotThrow(F);
1202 setDoesNotAlias(F, 0);
1203 setDoesNotCapture(F, 2);
1204 setOnlyReadsMemory(F, 2);
1205 break;
1206 case LibFunc::feof:
1207 case LibFunc::free:
1208 case LibFunc::fseek:
1209 case LibFunc::ftell:
1210 case LibFunc::fgetc:
1211 case LibFunc::fseeko:
1212 case LibFunc::ftello:
1213 case LibFunc::fileno:
1214 case LibFunc::fflush:
1215 case LibFunc::fclose:
1216 case LibFunc::fsetpos:
1217 case LibFunc::flockfile:
1218 case LibFunc::funlockfile:
1219 case LibFunc::ftrylockfile:
1220 if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
1221 return false;
1222 setDoesNotThrow(F);
1223 setDoesNotCapture(F, 1);
1224 break;
1225 case LibFunc::ferror:
1226 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1227 return false;
1228 setDoesNotThrow(F);
1229 setDoesNotCapture(F, 1);
1230 setOnlyReadsMemory(F);
1231 break;
1232 case LibFunc::fputc:
1233 case LibFunc::fstat:
1234 case LibFunc::frexp:
1235 case LibFunc::frexpf:
1236 case LibFunc::frexpl:
1237 case LibFunc::fstatvfs:
1238 if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
1239 return false;
1240 setDoesNotThrow(F);
1241 setDoesNotCapture(F, 2);
1242 break;
1243 case LibFunc::fgets:
1244 if (FTy->getNumParams() != 3 ||
1245 !FTy->getParamType(0)->isPointerTy() ||
1246 !FTy->getParamType(2)->isPointerTy())
1247 return false;
1248 setDoesNotThrow(F);
1249 setDoesNotCapture(F, 3);
1250 break;
1251 case LibFunc::fread:
1252 if (FTy->getNumParams() != 4 ||
1253 !FTy->getParamType(0)->isPointerTy() ||
1254 !FTy->getParamType(3)->isPointerTy())
1255 return false;
1256 setDoesNotThrow(F);
1257 setDoesNotCapture(F, 1);
1258 setDoesNotCapture(F, 4);
1259 break;
1260 case LibFunc::fwrite:
1261 if (FTy->getNumParams() != 4 ||
1262 !FTy->getParamType(0)->isPointerTy() ||
1263 !FTy->getParamType(3)->isPointerTy())
1264 return false;
1265 setDoesNotThrow(F);
1266 setDoesNotCapture(F, 1);
1267 setDoesNotCapture(F, 4);
1268 break;
1269 case LibFunc::fputs:
1270 if (FTy->getNumParams() < 2 ||
1271 !FTy->getParamType(0)->isPointerTy() ||
1272 !FTy->getParamType(1)->isPointerTy())
1273 return false;
1274 setDoesNotThrow(F);
1275 setDoesNotCapture(F, 1);
1276 setDoesNotCapture(F, 2);
1277 setOnlyReadsMemory(F, 1);
1278 break;
1279 case LibFunc::fscanf:
1280 case LibFunc::fprintf:
1281 if (FTy->getNumParams() < 2 ||
1282 !FTy->getParamType(0)->isPointerTy() ||
1283 !FTy->getParamType(1)->isPointerTy())
1284 return false;
1285 setDoesNotThrow(F);
1286 setDoesNotCapture(F, 1);
1287 setDoesNotCapture(F, 2);
1288 setOnlyReadsMemory(F, 2);
1289 break;
1290 case LibFunc::fgetpos:
1291 if (FTy->getNumParams() < 2 ||
1292 !FTy->getParamType(0)->isPointerTy() ||
1293 !FTy->getParamType(1)->isPointerTy())
1294 return false;
1295 setDoesNotThrow(F);
1296 setDoesNotCapture(F, 1);
1297 setDoesNotCapture(F, 2);
1298 break;
1299 case LibFunc::getc:
1300 case LibFunc::getlogin_r:
1301 case LibFunc::getc_unlocked:
1302 if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
1303 return false;
1304 setDoesNotThrow(F);
1305 setDoesNotCapture(F, 1);
1306 break;
1307 case LibFunc::getenv:
1308 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1309 return false;
1310 setDoesNotThrow(F);
1311 setOnlyReadsMemory(F);
1312 setDoesNotCapture(F, 1);
1313 break;
1314 case LibFunc::gets:
1315 case LibFunc::getchar:
1316 setDoesNotThrow(F);
1317 break;
1318 case LibFunc::getitimer:
1319 if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
1320 return false;
1321 setDoesNotThrow(F);
1322 setDoesNotCapture(F, 2);
1323 break;
1324 case LibFunc::getpwnam:
1325 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1326 return false;
1327 setDoesNotThrow(F);
1328 setDoesNotCapture(F, 1);
1329 setOnlyReadsMemory(F, 1);
1330 break;
1331 case LibFunc::ungetc:
1332 if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
1333 return false;
1334 setDoesNotThrow(F);
1335 setDoesNotCapture(F, 2);
1336 break;
1337 case LibFunc::uname:
1338 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1339 return false;
1340 setDoesNotThrow(F);
1341 setDoesNotCapture(F, 1);
1342 break;
1343 case LibFunc::unlink:
1344 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1345 return false;
1346 setDoesNotThrow(F);
1347 setDoesNotCapture(F, 1);
1348 setOnlyReadsMemory(F, 1);
1349 break;
1350 case LibFunc::unsetenv:
1351 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1352 return false;
1353 setDoesNotThrow(F);
1354 setDoesNotCapture(F, 1);
1355 setOnlyReadsMemory(F, 1);
1356 break;
1357 case LibFunc::utime:
1358 case LibFunc::utimes:
1359 if (FTy->getNumParams() != 2 ||
1360 !FTy->getParamType(0)->isPointerTy() ||
1361 !FTy->getParamType(1)->isPointerTy())
1362 return false;
1363 setDoesNotThrow(F);
1364 setDoesNotCapture(F, 1);
1365 setDoesNotCapture(F, 2);
1366 setOnlyReadsMemory(F, 1);
1367 setOnlyReadsMemory(F, 2);
1368 break;
1369 case LibFunc::putc:
1370 if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
1371 return false;
1372 setDoesNotThrow(F);
1373 setDoesNotCapture(F, 2);
1374 break;
1375 case LibFunc::puts:
1376 case LibFunc::printf:
1377 case LibFunc::perror:
1378 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1379 return false;
1380 setDoesNotThrow(F);
1381 setDoesNotCapture(F, 1);
1382 setOnlyReadsMemory(F, 1);
1383 break;
1384 case LibFunc::pread:
1385 if (FTy->getNumParams() != 4 || !FTy->getParamType(1)->isPointerTy())
1386 return false;
1387 // May throw; "pread" is a valid pthread cancellation point.
1388 setDoesNotCapture(F, 2);
1389 break;
1390 case LibFunc::pwrite:
1391 if (FTy->getNumParams() != 4 || !FTy->getParamType(1)->isPointerTy())
1392 return false;
1393 // May throw; "pwrite" is a valid pthread cancellation point.
1394 setDoesNotCapture(F, 2);
1395 setOnlyReadsMemory(F, 2);
1396 break;
1397 case LibFunc::putchar:
1398 setDoesNotThrow(F);
1399 break;
1400 case LibFunc::popen:
1401 if (FTy->getNumParams() != 2 ||
1402 !FTy->getReturnType()->isPointerTy() ||
1403 !FTy->getParamType(0)->isPointerTy() ||
1404 !FTy->getParamType(1)->isPointerTy())
1405 return false;
1406 setDoesNotThrow(F);
1407 setDoesNotAlias(F, 0);
1408 setDoesNotCapture(F, 1);
1409 setDoesNotCapture(F, 2);
1410 setOnlyReadsMemory(F, 1);
1411 setOnlyReadsMemory(F, 2);
1412 break;
1413 case LibFunc::pclose:
1414 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1415 return false;
1416 setDoesNotThrow(F);
1417 setDoesNotCapture(F, 1);
1418 break;
1419 case LibFunc::vscanf:
1420 if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
1421 return false;
1422 setDoesNotThrow(F);
1423 setDoesNotCapture(F, 1);
1424 setOnlyReadsMemory(F, 1);
1425 break;
1426 case LibFunc::vsscanf:
1427 if (FTy->getNumParams() != 3 ||
1428 !FTy->getParamType(1)->isPointerTy() ||
1429 !FTy->getParamType(2)->isPointerTy())
1430 return false;
1431 setDoesNotThrow(F);
1432 setDoesNotCapture(F, 1);
1433 setDoesNotCapture(F, 2);
1434 setOnlyReadsMemory(F, 1);
1435 setOnlyReadsMemory(F, 2);
1436 break;
1437 case LibFunc::vfscanf:
1438 if (FTy->getNumParams() != 3 ||
1439 !FTy->getParamType(1)->isPointerTy() ||
1440 !FTy->getParamType(2)->isPointerTy())
1441 return false;
1442 setDoesNotThrow(F);
1443 setDoesNotCapture(F, 1);
1444 setDoesNotCapture(F, 2);
1445 setOnlyReadsMemory(F, 2);
1446 break;
1447 case LibFunc::valloc:
1448 if (!FTy->getReturnType()->isPointerTy())
1449 return false;
1450 setDoesNotThrow(F);
1451 setDoesNotAlias(F, 0);
1452 break;
1453 case LibFunc::vprintf:
1454 if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy())
1455 return false;
1456 setDoesNotThrow(F);
1457 setDoesNotCapture(F, 1);
1458 setOnlyReadsMemory(F, 1);
1459 break;
1460 case LibFunc::vfprintf:
1461 case LibFunc::vsprintf:
1462 if (FTy->getNumParams() != 3 ||
1463 !FTy->getParamType(0)->isPointerTy() ||
1464 !FTy->getParamType(1)->isPointerTy())
1465 return false;
1466 setDoesNotThrow(F);
1467 setDoesNotCapture(F, 1);
1468 setDoesNotCapture(F, 2);
1469 setOnlyReadsMemory(F, 2);
1470 break;
1471 case LibFunc::vsnprintf:
1472 if (FTy->getNumParams() != 4 ||
1473 !FTy->getParamType(0)->isPointerTy() ||
1474 !FTy->getParamType(2)->isPointerTy())
1475 return false;
1476 setDoesNotThrow(F);
1477 setDoesNotCapture(F, 1);
1478 setDoesNotCapture(F, 3);
1479 setOnlyReadsMemory(F, 3);
1480 break;
1481 case LibFunc::open:
1482 if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy())
1483 return false;
1484 // May throw; "open" is a valid pthread cancellation point.
1485 setDoesNotCapture(F, 1);
1486 setOnlyReadsMemory(F, 1);
1487 break;
1488 case LibFunc::opendir:
1489 if (FTy->getNumParams() != 1 ||
1490 !FTy->getReturnType()->isPointerTy() ||
1491 !FTy->getParamType(0)->isPointerTy())
1492 return false;
1493 setDoesNotThrow(F);
1494 setDoesNotAlias(F, 0);
1495 setDoesNotCapture(F, 1);
1496 setOnlyReadsMemory(F, 1);
1497 break;
1498 case LibFunc::tmpfile:
1499 if (!FTy->getReturnType()->isPointerTy())
1500 return false;
1501 setDoesNotThrow(F);
1502 setDoesNotAlias(F, 0);
1503 break;
1504 case LibFunc::times:
1505 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1506 return false;
1507 setDoesNotThrow(F);
1508 setDoesNotCapture(F, 1);
1509 break;
1510 case LibFunc::htonl:
1511 case LibFunc::htons:
1512 case LibFunc::ntohl:
1513 case LibFunc::ntohs:
1514 setDoesNotThrow(F);
1515 setDoesNotAccessMemory(F);
1516 break;
1517 case LibFunc::lstat:
1518 if (FTy->getNumParams() != 2 ||
1519 !FTy->getParamType(0)->isPointerTy() ||
1520 !FTy->getParamType(1)->isPointerTy())
1521 return false;
1522 setDoesNotThrow(F);
1523 setDoesNotCapture(F, 1);
1524 setDoesNotCapture(F, 2);
1525 setOnlyReadsMemory(F, 1);
1526 break;
1527 case LibFunc::lchown:
1528 if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy())
1529 return false;
1530 setDoesNotThrow(F);
1531 setDoesNotCapture(F, 1);
1532 setOnlyReadsMemory(F, 1);
1533 break;
1534 case LibFunc::qsort:
1535 if (FTy->getNumParams() != 4 || !FTy->getParamType(3)->isPointerTy())
1536 return false;
1537 // May throw; places call through function pointer.
1538 setDoesNotCapture(F, 4);
1539 break;
1540 case LibFunc::dunder_strdup:
1541 case LibFunc::dunder_strndup:
1542 if (FTy->getNumParams() < 1 ||
1543 !FTy->getReturnType()->isPointerTy() ||
1544 !FTy->getParamType(0)->isPointerTy())
1545 return false;
1546 setDoesNotThrow(F);
1547 setDoesNotAlias(F, 0);
1548 setDoesNotCapture(F, 1);
1549 setOnlyReadsMemory(F, 1);
1550 break;
1551 case LibFunc::dunder_strtok_r:
1552 if (FTy->getNumParams() != 3 ||
1553 !FTy->getParamType(1)->isPointerTy())
1554 return false;
1555 setDoesNotThrow(F);
1556 setDoesNotCapture(F, 2);
1557 setOnlyReadsMemory(F, 2);
1558 break;
1559 case LibFunc::under_IO_getc:
1560 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1561 return false;
1562 setDoesNotThrow(F);
1563 setDoesNotCapture(F, 1);
1564 break;
1565 case LibFunc::under_IO_putc:
1566 if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
1567 return false;
1568 setDoesNotThrow(F);
1569 setDoesNotCapture(F, 2);
1570 break;
1571 case LibFunc::dunder_isoc99_scanf:
1572 if (FTy->getNumParams() < 1 ||
1573 !FTy->getParamType(0)->isPointerTy())
1574 return false;
1575 setDoesNotThrow(F);
1576 setDoesNotCapture(F, 1);
1577 setOnlyReadsMemory(F, 1);
1578 break;
1579 case LibFunc::stat64:
1580 case LibFunc::lstat64:
1581 case LibFunc::statvfs64:
1582 if (FTy->getNumParams() < 1 ||
1583 !FTy->getParamType(0)->isPointerTy() ||
1584 !FTy->getParamType(1)->isPointerTy())
1585 return false;
1586 setDoesNotThrow(F);
1587 setDoesNotCapture(F, 1);
1588 setDoesNotCapture(F, 2);
1589 setOnlyReadsMemory(F, 1);
1590 break;
1591 case LibFunc::dunder_isoc99_sscanf:
1592 if (FTy->getNumParams() < 1 ||
1593 !FTy->getParamType(0)->isPointerTy() ||
1594 !FTy->getParamType(1)->isPointerTy())
1595 return false;
1596 setDoesNotThrow(F);
1597 setDoesNotCapture(F, 1);
1598 setDoesNotCapture(F, 2);
1599 setOnlyReadsMemory(F, 1);
1600 setOnlyReadsMemory(F, 2);
1601 break;
1602 case LibFunc::fopen64:
1603 if (FTy->getNumParams() != 2 ||
1604 !FTy->getReturnType()->isPointerTy() ||
1605 !FTy->getParamType(0)->isPointerTy() ||
1606 !FTy->getParamType(1)->isPointerTy())
1607 return false;
1608 setDoesNotThrow(F);
1609 setDoesNotAlias(F, 0);
1610 setDoesNotCapture(F, 1);
1611 setDoesNotCapture(F, 2);
1612 setOnlyReadsMemory(F, 1);
1613 setOnlyReadsMemory(F, 2);
1614 break;
1615 case LibFunc::fseeko64:
1616 case LibFunc::ftello64:
1617 if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
1618 return false;
1619 setDoesNotThrow(F);
1620 setDoesNotCapture(F, 1);
1621 break;
1622 case LibFunc::tmpfile64:
1623 if (!FTy->getReturnType()->isPointerTy())
1624 return false;
1625 setDoesNotThrow(F);
1626 setDoesNotAlias(F, 0);
1627 break;
1628 case LibFunc::fstat64:
1629 case LibFunc::fstatvfs64:
1630 if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
1631 return false;
1632 setDoesNotThrow(F);
1633 setDoesNotCapture(F, 2);
1634 break;
1635 case LibFunc::open64:
1636 if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy())
1637 return false;
1638 // May throw; "open" is a valid pthread cancellation point.
1639 setDoesNotCapture(F, 1);
1640 setOnlyReadsMemory(F, 1);
1641 break;
1642 case LibFunc::gettimeofday:
1643 if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy() ||
1644 !FTy->getParamType(1)->isPointerTy())
1645 return false;
1646 // Currently some platforms have the restrict keyword on the arguments to
1647 // gettimeofday. To be conservative, do not add noalias to gettimeofday's
1648 // arguments.
1649 setDoesNotThrow(F);
1650 setDoesNotCapture(F, 1);
1651 setDoesNotCapture(F, 2);
1652 default:
1653 // Didn't mark any attributes.
1654 return false;
1655 }
1656
1657 return true;
1658 }
1659
1660 /// annotateLibraryCalls - Adds attributes to well-known standard library
1661 /// call declarations.
1662 bool FunctionAttrs::annotateLibraryCalls(const CallGraphSCC &SCC) {
1663 bool MadeChange = false;
1664
1665 // Check each function in turn annotating well-known library function
1666 // declarations with attributes.
1667 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
1668 Function *F = (*I)->getFunction();
1669
1670 if (F != 0 && F->isDeclaration())
1671 MadeChange |= inferPrototypeAttributes(*F);
1672 }
1673
1674 return MadeChange;
1675 }
1676
1677 bool FunctionAttrs::runOnSCC(CallGraphSCC &SCC) {
1678 AA = &getAnalysis<AliasAnalysis>();
1679 TLI = &getAnalysis<TargetLibraryInfo>();
1680
1681 bool Changed = annotateLibraryCalls(SCC);
1682 Changed |= AddReadAttrs(SCC);
1683 Changed |= AddArgumentAttrs(SCC);
1684 Changed |= AddNoAliasAttrs(SCC);
1685 return Changed;
1686 }