1 //===- FunctionAttrs.cpp - Pass which marks functions attributes ----------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.
19 //===----------------------------------------------------------------------===//
21 #include "llvm/Transforms/IPO.h"
22 #include "llvm/ADT/SCCIterator.h"
23 #include "llvm/ADT/SetVector.h"
24 #include "llvm/ADT/SmallSet.h"
25 #include "llvm/ADT/Statistic.h"
26 #include "llvm/Analysis/AliasAnalysis.h"
27 #include "llvm/Analysis/AssumptionCache.h"
28 #include "llvm/Analysis/BasicAliasAnalysis.h"
29 #include "llvm/Analysis/CallGraph.h"
30 #include "llvm/Analysis/CallGraphSCCPass.h"
31 #include "llvm/Analysis/CaptureTracking.h"
32 #include "llvm/Analysis/TargetLibraryInfo.h"
33 #include "llvm/Analysis/ValueTracking.h"
34 #include "llvm/IR/GlobalVariable.h"
35 #include "llvm/IR/InstIterator.h"
36 #include "llvm/IR/IntrinsicInst.h"
37 #include "llvm/IR/LLVMContext.h"
38 #include "llvm/Support/Debug.h"
39 #include "llvm/Support/raw_ostream.h"
40 #include "llvm/Analysis/TargetLibraryInfo.h"
43 #define DEBUG_TYPE "functionattrs"
45 STATISTIC(NumReadNone, "Number of functions marked readnone");
46 STATISTIC(NumReadOnly, "Number of functions marked readonly");
47 STATISTIC(NumNoCapture, "Number of arguments marked nocapture");
48 STATISTIC(NumReadNoneArg, "Number of arguments marked readnone");
49 STATISTIC(NumReadOnlyArg, "Number of arguments marked readonly");
50 STATISTIC(NumNoAlias, "Number of function returns marked noalias");
51 STATISTIC(NumNonNullReturn, "Number of function returns marked nonnull");
52 STATISTIC(NumAnnotated, "Number of attributes added to library functions");
55 typedef SmallSetVector<Function *, 8> SCCNodeSet;
59 struct FunctionAttrs : public CallGraphSCCPass {
60 static char ID; // Pass identification, replacement for typeid
61 FunctionAttrs() : CallGraphSCCPass(ID) {
62 initializeFunctionAttrsPass(*PassRegistry::getPassRegistry());
65 bool runOnSCC(CallGraphSCC &SCC) override;
67 void getAnalysisUsage(AnalysisUsage &AU) const override {
69 AU.addRequired<AssumptionCacheTracker>();
70 AU.addRequired<TargetLibraryInfoWrapperPass>();
71 CallGraphSCCPass::getAnalysisUsage(AU);
75 TargetLibraryInfo *TLI;
79 char FunctionAttrs::ID = 0;
80 INITIALIZE_PASS_BEGIN(FunctionAttrs, "functionattrs",
81 "Deduce function attributes", false, false)
82 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
83 INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
84 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
85 INITIALIZE_PASS_END(FunctionAttrs, "functionattrs",
86 "Deduce function attributes", false, false)
88 Pass *llvm::createFunctionAttrsPass() { return new FunctionAttrs(); }
91 /// The three kinds of memory access relevant to 'readonly' and
92 /// 'readnone' attributes.
93 enum MemoryAccessKind {
100 static MemoryAccessKind checkFunctionMemoryAccess(Function &F, AAResults &AAR,
101 const SCCNodeSet &SCCNodes) {
102 FunctionModRefBehavior MRB = AAR.getModRefBehavior(&F);
103 if (MRB == FMRB_DoesNotAccessMemory)
107 // Definitions with weak linkage may be overridden at linktime with
108 // something that writes memory, so treat them like declarations.
109 if (F.isDeclaration() || F.mayBeOverridden()) {
110 if (AliasAnalysis::onlyReadsMemory(MRB))
113 // Conservatively assume it writes to memory.
117 // Scan the function body for instructions that may read or write memory.
118 bool ReadsMemory = false;
119 for (inst_iterator II = inst_begin(F), E = inst_end(F); II != E; ++II) {
120 Instruction *I = &*II;
122 // Some instructions can be ignored even if they read or write memory.
123 // Detect these now, skipping to the next instruction if one is found.
124 CallSite CS(cast<Value>(I));
126 // Ignore calls to functions in the same SCC.
127 if (CS.getCalledFunction() && SCCNodes.count(CS.getCalledFunction()))
129 FunctionModRefBehavior MRB = AAR.getModRefBehavior(CS);
131 // If the call doesn't access memory, we're done.
132 if (!(MRB & MRI_ModRef))
135 if (!AliasAnalysis::onlyAccessesArgPointees(MRB)) {
136 // The call could access any memory. If that includes writes, give up.
139 // If it reads, note it.
145 // Check whether all pointer arguments point to local memory, and
146 // ignore calls that only access local memory.
147 for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
150 if (!Arg->getType()->isPointerTy())
154 I->getAAMetadata(AAInfo);
155 MemoryLocation Loc(Arg, MemoryLocation::UnknownSize, AAInfo);
157 // Skip accesses to local or constant memory as they don't impact the
158 // externally visible mod/ref behavior.
159 if (AAR.pointsToConstantMemory(Loc, /*OrLocal=*/true))
163 // Writes non-local memory. Give up.
166 // Ok, it reads non-local memory.
170 } else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
171 // Ignore non-volatile loads from local memory. (Atomic is okay here.)
172 if (!LI->isVolatile()) {
173 MemoryLocation Loc = MemoryLocation::get(LI);
174 if (AAR.pointsToConstantMemory(Loc, /*OrLocal=*/true))
177 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
178 // Ignore non-volatile stores to local memory. (Atomic is okay here.)
179 if (!SI->isVolatile()) {
180 MemoryLocation Loc = MemoryLocation::get(SI);
181 if (AAR.pointsToConstantMemory(Loc, /*OrLocal=*/true))
184 } else if (VAArgInst *VI = dyn_cast<VAArgInst>(I)) {
185 // Ignore vaargs on local memory.
186 MemoryLocation Loc = MemoryLocation::get(VI);
187 if (AAR.pointsToConstantMemory(Loc, /*OrLocal=*/true))
191 // Any remaining instructions need to be taken seriously! Check if they
192 // read or write memory.
193 if (I->mayWriteToMemory())
194 // Writes memory. Just give up.
197 // If this instruction may read memory, remember that.
198 ReadsMemory |= I->mayReadFromMemory();
201 return ReadsMemory ? MAK_ReadOnly : MAK_ReadNone;
204 /// Deduce readonly/readnone attributes for the SCC.
205 template <typename AARGetterT>
206 static bool addReadAttrs(const SCCNodeSet &SCCNodes, AARGetterT AARGetter) {
207 // Check if any of the functions in the SCC read or write memory. If they
208 // write memory then they can't be marked readnone or readonly.
209 bool ReadsMemory = false;
210 for (Function *F : SCCNodes) {
211 // Call the callable parameter to look up AA results for this function.
212 AAResults &AAR = AARGetter(*F);
214 switch (checkFunctionMemoryAccess(*F, AAR, SCCNodes)) {
226 // Success! Functions in this SCC do not access memory, or only read memory.
227 // Give them the appropriate attribute.
228 bool MadeChange = false;
229 for (Function *F : SCCNodes) {
230 if (F->doesNotAccessMemory())
234 if (F->onlyReadsMemory() && ReadsMemory)
240 // Clear out any existing attributes.
242 B.addAttribute(Attribute::ReadOnly).addAttribute(Attribute::ReadNone);
244 AttributeSet::FunctionIndex,
245 AttributeSet::get(F->getContext(), AttributeSet::FunctionIndex, B));
247 // Add in the new attribute.
248 F->addAttribute(AttributeSet::FunctionIndex,
249 ReadsMemory ? Attribute::ReadOnly : Attribute::ReadNone);
261 /// For a given pointer Argument, this retains a list of Arguments of functions
262 /// in the same SCC that the pointer data flows into. We use this to build an
263 /// SCC of the arguments.
264 struct ArgumentGraphNode {
265 Argument *Definition;
266 SmallVector<ArgumentGraphNode *, 4> Uses;
269 class ArgumentGraph {
270 // We store pointers to ArgumentGraphNode objects, so it's important that
271 // that they not move around upon insert.
272 typedef std::map<Argument *, ArgumentGraphNode> ArgumentMapTy;
274 ArgumentMapTy ArgumentMap;
276 // There is no root node for the argument graph, in fact:
277 // void f(int *x, int *y) { if (...) f(x, y); }
278 // is an example where the graph is disconnected. The SCCIterator requires a
279 // single entry point, so we maintain a fake ("synthetic") root node that
280 // uses every node. Because the graph is directed and nothing points into
281 // the root, it will not participate in any SCCs (except for its own).
282 ArgumentGraphNode SyntheticRoot;
285 ArgumentGraph() { SyntheticRoot.Definition = nullptr; }
287 typedef SmallVectorImpl<ArgumentGraphNode *>::iterator iterator;
289 iterator begin() { return SyntheticRoot.Uses.begin(); }
290 iterator end() { return SyntheticRoot.Uses.end(); }
291 ArgumentGraphNode *getEntryNode() { return &SyntheticRoot; }
293 ArgumentGraphNode *operator[](Argument *A) {
294 ArgumentGraphNode &Node = ArgumentMap[A];
296 SyntheticRoot.Uses.push_back(&Node);
301 /// This tracker checks whether callees are in the SCC, and if so it does not
302 /// consider that a capture, instead adding it to the "Uses" list and
303 /// continuing with the analysis.
304 struct ArgumentUsesTracker : public CaptureTracker {
305 ArgumentUsesTracker(const SCCNodeSet &SCCNodes)
306 : Captured(false), SCCNodes(SCCNodes) {}
308 void tooManyUses() override { Captured = true; }
310 bool captured(const Use *U) override {
311 CallSite CS(U->getUser());
312 if (!CS.getInstruction()) {
317 Function *F = CS.getCalledFunction();
318 if (!F || F->isDeclaration() || F->mayBeOverridden() ||
319 !SCCNodes.count(F)) {
324 // Note: the callee and the two successor blocks *follow* the argument
325 // operands. This means there is no need to adjust UseIndex to account for
329 std::distance(const_cast<const Use *>(CS.arg_begin()), U);
331 assert(UseIndex < CS.data_operands_size() &&
332 "Indirect function calls should have been filtered above!");
334 if (UseIndex >= CS.getNumArgOperands()) {
335 // Data operand, but not a argument operand -- must be a bundle operand
336 assert(CS.hasOperandBundles() && "Must be!");
338 // CaptureTracking told us that we're being captured by an operand bundle
339 // use. In this case it does not matter if the callee is within our SCC
340 // or not -- we've been captured in some unknown way, and we have to be
346 if (UseIndex >= F->arg_size()) {
347 assert(F->isVarArg() && "More params than args in non-varargs call");
352 Uses.push_back(&*std::next(F->arg_begin(), UseIndex));
356 bool Captured; // True only if certainly captured (used outside our SCC).
357 SmallVector<Argument *, 4> Uses; // Uses within our SCC.
359 const SCCNodeSet &SCCNodes;
364 template <> struct GraphTraits<ArgumentGraphNode *> {
365 typedef ArgumentGraphNode NodeType;
366 typedef SmallVectorImpl<ArgumentGraphNode *>::iterator ChildIteratorType;
368 static inline NodeType *getEntryNode(NodeType *A) { return A; }
369 static inline ChildIteratorType child_begin(NodeType *N) {
370 return N->Uses.begin();
372 static inline ChildIteratorType child_end(NodeType *N) {
373 return N->Uses.end();
377 struct GraphTraits<ArgumentGraph *> : public GraphTraits<ArgumentGraphNode *> {
378 static NodeType *getEntryNode(ArgumentGraph *AG) {
379 return AG->getEntryNode();
381 static ChildIteratorType nodes_begin(ArgumentGraph *AG) {
384 static ChildIteratorType nodes_end(ArgumentGraph *AG) { return AG->end(); }
388 /// Returns Attribute::None, Attribute::ReadOnly or Attribute::ReadNone.
389 static Attribute::AttrKind
390 determinePointerReadAttrs(Argument *A,
391 const SmallPtrSet<Argument *, 8> &SCCNodes) {
393 SmallVector<Use *, 32> Worklist;
394 SmallSet<Use *, 32> Visited;
396 // inalloca arguments are always clobbered by the call.
397 if (A->hasInAllocaAttr())
398 return Attribute::None;
401 // We don't need to track IsWritten. If A is written to, return immediately.
403 for (Use &U : A->uses()) {
405 Worklist.push_back(&U);
408 while (!Worklist.empty()) {
409 Use *U = Worklist.pop_back_val();
410 Instruction *I = cast<Instruction>(U->getUser());
412 switch (I->getOpcode()) {
413 case Instruction::BitCast:
414 case Instruction::GetElementPtr:
415 case Instruction::PHI:
416 case Instruction::Select:
417 case Instruction::AddrSpaceCast:
418 // The original value is not read/written via this if the new value isn't.
419 for (Use &UU : I->uses())
420 if (Visited.insert(&UU).second)
421 Worklist.push_back(&UU);
424 case Instruction::Call:
425 case Instruction::Invoke: {
426 bool Captures = true;
428 if (I->getType()->isVoidTy())
431 auto AddUsersToWorklistIfCapturing = [&] {
433 for (Use &UU : I->uses())
434 if (Visited.insert(&UU).second)
435 Worklist.push_back(&UU);
439 if (CS.doesNotAccessMemory()) {
440 AddUsersToWorklistIfCapturing();
444 Function *F = CS.getCalledFunction();
446 if (CS.onlyReadsMemory()) {
448 AddUsersToWorklistIfCapturing();
451 return Attribute::None;
454 // Note: the callee and the two successor blocks *follow* the argument
455 // operands. This means there is no need to adjust UseIndex to account
458 unsigned UseIndex = std::distance(CS.arg_begin(), U);
460 // U cannot be the callee operand use: since we're exploring the
461 // transitive uses of an Argument, having such a use be a callee would
462 // imply the CallSite is an indirect call or invoke; and we'd take the
464 assert(UseIndex < CS.data_operands_size() &&
465 "Data operand use expected!");
467 bool IsOperandBundleUse = UseIndex >= CS.getNumArgOperands();
469 if (UseIndex >= F->arg_size() && !IsOperandBundleUse) {
470 assert(F->isVarArg() && "More params than args in non-varargs call");
471 return Attribute::None;
474 Captures &= !CS.doesNotCapture(UseIndex);
476 // Since the optimizer (by design) cannot see the data flow corresponding
477 // to a operand bundle use, these cannot participate in the optimistic SCC
478 // analysis. Instead, we model the operand bundle uses as arguments in
479 // call to a function external to the SCC.
480 if (!SCCNodes.count(std::next(F->arg_begin(), UseIndex)) ||
481 IsOperandBundleUse) {
483 // The accessors used on CallSite here do the right thing for calls and
484 // invokes with operand bundles.
486 if (!CS.onlyReadsMemory() && !CS.onlyReadsMemory(UseIndex))
487 return Attribute::None;
488 if (!CS.doesNotAccessMemory(UseIndex))
492 AddUsersToWorklistIfCapturing();
496 case Instruction::Load:
500 case Instruction::ICmp:
501 case Instruction::Ret:
505 return Attribute::None;
509 return IsRead ? Attribute::ReadOnly : Attribute::ReadNone;
512 /// Deduce nocapture attributes for the SCC.
513 static bool addArgumentAttrs(const SCCNodeSet &SCCNodes) {
514 bool Changed = false;
519 B.addAttribute(Attribute::NoCapture);
521 // Check each function in turn, determining which pointer arguments are not
523 for (Function *F : SCCNodes) {
524 // Definitions with weak linkage may be overridden at linktime with
525 // something that captures pointers, so treat them like declarations.
526 if (F->isDeclaration() || F->mayBeOverridden())
529 // Functions that are readonly (or readnone) and nounwind and don't return
530 // a value can't capture arguments. Don't analyze them.
531 if (F->onlyReadsMemory() && F->doesNotThrow() &&
532 F->getReturnType()->isVoidTy()) {
533 for (Function::arg_iterator A = F->arg_begin(), E = F->arg_end(); A != E;
535 if (A->getType()->isPointerTy() && !A->hasNoCaptureAttr()) {
536 A->addAttr(AttributeSet::get(F->getContext(), A->getArgNo() + 1, B));
544 for (Function::arg_iterator A = F->arg_begin(), E = F->arg_end(); A != E;
546 if (!A->getType()->isPointerTy())
548 bool HasNonLocalUses = false;
549 if (!A->hasNoCaptureAttr()) {
550 ArgumentUsesTracker Tracker(SCCNodes);
551 PointerMayBeCaptured(&*A, &Tracker);
552 if (!Tracker.Captured) {
553 if (Tracker.Uses.empty()) {
554 // If it's trivially not captured, mark it nocapture now.
556 AttributeSet::get(F->getContext(), A->getArgNo() + 1, B));
560 // If it's not trivially captured and not trivially not captured,
561 // then it must be calling into another function in our SCC. Save
562 // its particulars for Argument-SCC analysis later.
563 ArgumentGraphNode *Node = AG[&*A];
564 for (SmallVectorImpl<Argument *>::iterator
565 UI = Tracker.Uses.begin(),
566 UE = Tracker.Uses.end();
568 Node->Uses.push_back(AG[*UI]);
570 HasNonLocalUses = true;
574 // Otherwise, it's captured. Don't bother doing SCC analysis on it.
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
581 SmallPtrSet<Argument *, 8> Self;
583 Attribute::AttrKind R = determinePointerReadAttrs(&*A, Self);
584 if (R != Attribute::None) {
587 A->addAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, B));
589 R == Attribute::ReadOnly ? ++NumReadOnlyArg : ++NumReadNoneArg;
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
602 for (scc_iterator<ArgumentGraph *> I = scc_begin(&AG); !I.isAtEnd(); ++I) {
603 const std::vector<ArgumentGraphNode *> &ArgumentSCC = *I;
604 if (ArgumentSCC.size() == 1) {
605 if (!ArgumentSCC[0]->Definition)
606 continue; // synthetic root node
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));
619 bool SCCCaptured = false;
620 for (auto I = ArgumentSCC.begin(), E = ArgumentSCC.end();
621 I != E && !SCCCaptured; ++I) {
622 ArgumentGraphNode *Node = *I;
623 if (Node->Uses.empty()) {
624 if (!Node->Definition->hasNoCaptureAttr())
631 SmallPtrSet<Argument *, 8> ArgumentSCCNodes;
632 // Fill ArgumentSCCNodes with the elements of the ArgumentSCC. Used for
633 // quickly looking up whether a given Argument is in this ArgumentSCC.
634 for (auto I = ArgumentSCC.begin(), E = ArgumentSCC.end(); I != E; ++I) {
635 ArgumentSCCNodes.insert((*I)->Definition);
638 for (auto I = ArgumentSCC.begin(), E = ArgumentSCC.end();
639 I != E && !SCCCaptured; ++I) {
640 ArgumentGraphNode *N = *I;
641 for (SmallVectorImpl<ArgumentGraphNode *>::iterator UI = N->Uses.begin(),
644 Argument *A = (*UI)->Definition;
645 if (A->hasNoCaptureAttr() || ArgumentSCCNodes.count(A))
654 for (unsigned i = 0, e = ArgumentSCC.size(); i != e; ++i) {
655 Argument *A = ArgumentSCC[i]->Definition;
656 A->addAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, B));
661 // We also want to compute readonly/readnone. With a small number of false
662 // negatives, we can assume that any pointer which is captured isn't going
663 // to be provably readonly or readnone, since by definition we can't
664 // analyze all uses of a captured pointer.
666 // The false negatives happen when the pointer is captured by a function
667 // that promises readonly/readnone behaviour on the pointer, then the
668 // pointer's lifetime ends before anything that writes to arbitrary memory.
669 // Also, a readonly/readnone pointer may be returned, but returning a
670 // pointer is capturing it.
672 Attribute::AttrKind ReadAttr = Attribute::ReadNone;
673 for (unsigned i = 0, e = ArgumentSCC.size(); i != e; ++i) {
674 Argument *A = ArgumentSCC[i]->Definition;
675 Attribute::AttrKind K = determinePointerReadAttrs(A, ArgumentSCCNodes);
676 if (K == Attribute::ReadNone)
678 if (K == Attribute::ReadOnly) {
679 ReadAttr = Attribute::ReadOnly;
686 if (ReadAttr != Attribute::None) {
688 B.addAttribute(ReadAttr);
689 R.addAttribute(Attribute::ReadOnly).addAttribute(Attribute::ReadNone);
690 for (unsigned i = 0, e = ArgumentSCC.size(); i != e; ++i) {
691 Argument *A = ArgumentSCC[i]->Definition;
692 // Clear out existing readonly/readnone attributes
693 A->removeAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, R));
694 A->addAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, B));
695 ReadAttr == Attribute::ReadOnly ? ++NumReadOnlyArg : ++NumReadNoneArg;
704 /// Tests whether a function is "malloc-like".
706 /// A function is "malloc-like" if it returns either null or a pointer that
707 /// doesn't alias any other pointer visible to the caller.
708 static bool isFunctionMallocLike(Function *F, const SCCNodeSet &SCCNodes) {
709 SmallSetVector<Value *, 8> FlowsToReturn;
710 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I)
711 if (ReturnInst *Ret = dyn_cast<ReturnInst>(I->getTerminator()))
712 FlowsToReturn.insert(Ret->getReturnValue());
714 for (unsigned i = 0; i != FlowsToReturn.size(); ++i) {
715 Value *RetVal = FlowsToReturn[i];
717 if (Constant *C = dyn_cast<Constant>(RetVal)) {
718 if (!C->isNullValue() && !isa<UndefValue>(C))
724 if (isa<Argument>(RetVal))
727 if (Instruction *RVI = dyn_cast<Instruction>(RetVal))
728 switch (RVI->getOpcode()) {
729 // Extend the analysis by looking upwards.
730 case Instruction::BitCast:
731 case Instruction::GetElementPtr:
732 case Instruction::AddrSpaceCast:
733 FlowsToReturn.insert(RVI->getOperand(0));
735 case Instruction::Select: {
736 SelectInst *SI = cast<SelectInst>(RVI);
737 FlowsToReturn.insert(SI->getTrueValue());
738 FlowsToReturn.insert(SI->getFalseValue());
741 case Instruction::PHI: {
742 PHINode *PN = cast<PHINode>(RVI);
743 for (Value *IncValue : PN->incoming_values())
744 FlowsToReturn.insert(IncValue);
748 // Check whether the pointer came from an allocation.
749 case Instruction::Alloca:
751 case Instruction::Call:
752 case Instruction::Invoke: {
754 if (CS.paramHasAttr(0, Attribute::NoAlias))
756 if (CS.getCalledFunction() && SCCNodes.count(CS.getCalledFunction()))
760 return false; // Did not come from an allocation.
763 if (PointerMayBeCaptured(RetVal, false, /*StoreCaptures=*/false))
770 /// Deduce noalias attributes for the SCC.
771 static bool addNoAliasAttrs(const SCCNodeSet &SCCNodes) {
772 // Check each function in turn, determining which functions return noalias
774 for (Function *F : SCCNodes) {
776 if (F->doesNotAlias(0))
779 // Definitions with weak linkage may be overridden at linktime, so
780 // treat them like declarations.
781 if (F->isDeclaration() || F->mayBeOverridden())
784 // We annotate noalias return values, which are only applicable to
786 if (!F->getReturnType()->isPointerTy())
789 if (!isFunctionMallocLike(F, SCCNodes))
793 bool MadeChange = false;
794 for (Function *F : SCCNodes) {
795 if (F->doesNotAlias(0) || !F->getReturnType()->isPointerTy())
798 F->setDoesNotAlias(0);
806 /// Tests whether this function is known to not return null.
808 /// Requires that the function returns a pointer.
810 /// Returns true if it believes the function will not return a null, and sets
811 /// \p Speculative based on whether the returned conclusion is a speculative
812 /// conclusion due to SCC calls.
813 static bool isReturnNonNull(Function *F, const SCCNodeSet &SCCNodes,
814 const TargetLibraryInfo &TLI, bool &Speculative) {
815 assert(F->getReturnType()->isPointerTy() &&
816 "nonnull only meaningful on pointer types");
819 SmallSetVector<Value *, 8> FlowsToReturn;
820 for (BasicBlock &BB : *F)
821 if (auto *Ret = dyn_cast<ReturnInst>(BB.getTerminator()))
822 FlowsToReturn.insert(Ret->getReturnValue());
824 for (unsigned i = 0; i != FlowsToReturn.size(); ++i) {
825 Value *RetVal = FlowsToReturn[i];
827 // If this value is locally known to be non-null, we're good
828 if (isKnownNonNull(RetVal, &TLI))
831 // Otherwise, we need to look upwards since we can't make any local
833 Instruction *RVI = dyn_cast<Instruction>(RetVal);
836 switch (RVI->getOpcode()) {
837 // Extend the analysis by looking upwards.
838 case Instruction::BitCast:
839 case Instruction::GetElementPtr:
840 case Instruction::AddrSpaceCast:
841 FlowsToReturn.insert(RVI->getOperand(0));
843 case Instruction::Select: {
844 SelectInst *SI = cast<SelectInst>(RVI);
845 FlowsToReturn.insert(SI->getTrueValue());
846 FlowsToReturn.insert(SI->getFalseValue());
849 case Instruction::PHI: {
850 PHINode *PN = cast<PHINode>(RVI);
851 for (int i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
852 FlowsToReturn.insert(PN->getIncomingValue(i));
855 case Instruction::Call:
856 case Instruction::Invoke: {
858 Function *Callee = CS.getCalledFunction();
859 // A call to a node within the SCC is assumed to return null until
861 if (Callee && SCCNodes.count(Callee)) {
868 return false; // Unknown source, may be null
870 llvm_unreachable("should have either continued or returned");
876 /// Deduce nonnull attributes for the SCC.
877 static bool addNonNullAttrs(const SCCNodeSet &SCCNodes,
878 const TargetLibraryInfo &TLI) {
879 // Speculative that all functions in the SCC return only nonnull
880 // pointers. We may refute this as we analyze functions.
881 bool SCCReturnsNonNull = true;
883 bool MadeChange = false;
885 // Check each function in turn, determining which functions return nonnull
887 for (Function *F : SCCNodes) {
889 if (F->getAttributes().hasAttribute(AttributeSet::ReturnIndex,
893 // Definitions with weak linkage may be overridden at linktime, so
894 // treat them like declarations.
895 if (F->isDeclaration() || F->mayBeOverridden())
898 // We annotate nonnull return values, which are only applicable to
900 if (!F->getReturnType()->isPointerTy())
903 bool Speculative = false;
904 if (isReturnNonNull(F, SCCNodes, TLI, Speculative)) {
906 // Mark the function eagerly since we may discover a function
907 // which prevents us from speculating about the entire SCC
908 DEBUG(dbgs() << "Eagerly marking " << F->getName() << " as nonnull\n");
909 F->addAttribute(AttributeSet::ReturnIndex, Attribute::NonNull);
915 // At least one function returns something which could be null, can't
916 // speculate any more.
917 SCCReturnsNonNull = false;
920 if (SCCReturnsNonNull) {
921 for (Function *F : SCCNodes) {
922 if (F->getAttributes().hasAttribute(AttributeSet::ReturnIndex,
923 Attribute::NonNull) ||
924 !F->getReturnType()->isPointerTy())
927 DEBUG(dbgs() << "SCC marking " << F->getName() << " as nonnull\n");
928 F->addAttribute(AttributeSet::ReturnIndex, Attribute::NonNull);
937 static void setDoesNotAccessMemory(Function &F) {
938 if (!F.doesNotAccessMemory()) {
939 F.setDoesNotAccessMemory();
944 static void setOnlyReadsMemory(Function &F) {
945 if (!F.onlyReadsMemory()) {
946 F.setOnlyReadsMemory();
951 static void setDoesNotThrow(Function &F) {
952 if (!F.doesNotThrow()) {
958 static void setDoesNotCapture(Function &F, unsigned n) {
959 if (!F.doesNotCapture(n)) {
960 F.setDoesNotCapture(n);
965 static void setOnlyReadsMemory(Function &F, unsigned n) {
966 if (!F.onlyReadsMemory(n)) {
967 F.setOnlyReadsMemory(n);
972 static void setDoesNotAlias(Function &F, unsigned n) {
973 if (!F.doesNotAlias(n)) {
974 F.setDoesNotAlias(n);
979 /// Analyze the name and prototype of the given function and set any applicable
982 /// Returns true if any attributes were set and false otherwise.
983 static bool inferPrototypeAttributes(Function &F, const TargetLibraryInfo &TLI) {
984 if (F.hasFnAttribute(Attribute::OptimizeNone))
987 FunctionType *FTy = F.getFunctionType();
988 LibFunc::Func TheLibFunc;
989 if (!(TLI.getLibFunc(F.getName(), TheLibFunc) && TLI.has(TheLibFunc)))
992 switch (TheLibFunc) {
993 case LibFunc::strlen:
994 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
996 setOnlyReadsMemory(F);
998 setDoesNotCapture(F, 1);
1000 case LibFunc::strchr:
1001 case LibFunc::strrchr:
1002 if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy() ||
1003 !FTy->getParamType(1)->isIntegerTy())
1005 setOnlyReadsMemory(F);
1008 case LibFunc::strtol:
1009 case LibFunc::strtod:
1010 case LibFunc::strtof:
1011 case LibFunc::strtoul:
1012 case LibFunc::strtoll:
1013 case LibFunc::strtold:
1014 case LibFunc::strtoull:
1015 if (FTy->getNumParams() < 2 || !FTy->getParamType(1)->isPointerTy())
1018 setDoesNotCapture(F, 2);
1019 setOnlyReadsMemory(F, 1);
1021 case LibFunc::strcpy:
1022 case LibFunc::stpcpy:
1023 case LibFunc::strcat:
1024 case LibFunc::strncat:
1025 case LibFunc::strncpy:
1026 case LibFunc::stpncpy:
1027 if (FTy->getNumParams() < 2 || !FTy->getParamType(1)->isPointerTy())
1030 setDoesNotCapture(F, 2);
1031 setOnlyReadsMemory(F, 2);
1033 case LibFunc::strxfrm:
1034 if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy() ||
1035 !FTy->getParamType(1)->isPointerTy())
1038 setDoesNotCapture(F, 1);
1039 setDoesNotCapture(F, 2);
1040 setOnlyReadsMemory(F, 2);
1042 case LibFunc::strcmp: // 0,1
1043 case LibFunc::strspn: // 0,1
1044 case LibFunc::strncmp: // 0,1
1045 case LibFunc::strcspn: // 0,1
1046 case LibFunc::strcoll: // 0,1
1047 case LibFunc::strcasecmp: // 0,1
1048 case LibFunc::strncasecmp: //
1049 if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
1050 !FTy->getParamType(1)->isPointerTy())
1052 setOnlyReadsMemory(F);
1054 setDoesNotCapture(F, 1);
1055 setDoesNotCapture(F, 2);
1057 case LibFunc::strstr:
1058 case LibFunc::strpbrk:
1059 if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
1061 setOnlyReadsMemory(F);
1063 setDoesNotCapture(F, 2);
1065 case LibFunc::strtok:
1066 case LibFunc::strtok_r:
1067 if (FTy->getNumParams() < 2 || !FTy->getParamType(1)->isPointerTy())
1070 setDoesNotCapture(F, 2);
1071 setOnlyReadsMemory(F, 2);
1073 case LibFunc::scanf:
1074 if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy())
1077 setDoesNotCapture(F, 1);
1078 setOnlyReadsMemory(F, 1);
1080 case LibFunc::setbuf:
1081 case LibFunc::setvbuf:
1082 if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy())
1085 setDoesNotCapture(F, 1);
1087 case LibFunc::strdup:
1088 case LibFunc::strndup:
1089 if (FTy->getNumParams() < 1 || !FTy->getReturnType()->isPointerTy() ||
1090 !FTy->getParamType(0)->isPointerTy())
1093 setDoesNotAlias(F, 0);
1094 setDoesNotCapture(F, 1);
1095 setOnlyReadsMemory(F, 1);
1098 case LibFunc::statvfs:
1099 if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
1100 !FTy->getParamType(1)->isPointerTy())
1103 setDoesNotCapture(F, 1);
1104 setDoesNotCapture(F, 2);
1105 setOnlyReadsMemory(F, 1);
1107 case LibFunc::sscanf:
1108 if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
1109 !FTy->getParamType(1)->isPointerTy())
1112 setDoesNotCapture(F, 1);
1113 setDoesNotCapture(F, 2);
1114 setOnlyReadsMemory(F, 1);
1115 setOnlyReadsMemory(F, 2);
1117 case LibFunc::sprintf:
1118 if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
1119 !FTy->getParamType(1)->isPointerTy())
1122 setDoesNotCapture(F, 1);
1123 setDoesNotCapture(F, 2);
1124 setOnlyReadsMemory(F, 2);
1126 case LibFunc::snprintf:
1127 if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy() ||
1128 !FTy->getParamType(2)->isPointerTy())
1131 setDoesNotCapture(F, 1);
1132 setDoesNotCapture(F, 3);
1133 setOnlyReadsMemory(F, 3);
1135 case LibFunc::setitimer:
1136 if (FTy->getNumParams() != 3 || !FTy->getParamType(1)->isPointerTy() ||
1137 !FTy->getParamType(2)->isPointerTy())
1140 setDoesNotCapture(F, 2);
1141 setDoesNotCapture(F, 3);
1142 setOnlyReadsMemory(F, 2);
1144 case LibFunc::system:
1145 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1147 // May throw; "system" is a valid pthread cancellation point.
1148 setDoesNotCapture(F, 1);
1149 setOnlyReadsMemory(F, 1);
1151 case LibFunc::malloc:
1152 if (FTy->getNumParams() != 1 || !FTy->getReturnType()->isPointerTy())
1155 setDoesNotAlias(F, 0);
1157 case LibFunc::memcmp:
1158 if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy() ||
1159 !FTy->getParamType(1)->isPointerTy())
1161 setOnlyReadsMemory(F);
1163 setDoesNotCapture(F, 1);
1164 setDoesNotCapture(F, 2);
1166 case LibFunc::memchr:
1167 case LibFunc::memrchr:
1168 if (FTy->getNumParams() != 3)
1170 setOnlyReadsMemory(F);
1174 case LibFunc::modff:
1175 case LibFunc::modfl:
1176 if (FTy->getNumParams() < 2 || !FTy->getParamType(1)->isPointerTy())
1179 setDoesNotCapture(F, 2);
1181 case LibFunc::memcpy:
1182 case LibFunc::memccpy:
1183 case LibFunc::memmove:
1184 if (FTy->getNumParams() < 2 || !FTy->getParamType(1)->isPointerTy())
1187 setDoesNotCapture(F, 2);
1188 setOnlyReadsMemory(F, 2);
1190 case LibFunc::memalign:
1191 if (!FTy->getReturnType()->isPointerTy())
1193 setDoesNotAlias(F, 0);
1195 case LibFunc::mkdir:
1196 if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
1199 setDoesNotCapture(F, 1);
1200 setOnlyReadsMemory(F, 1);
1202 case LibFunc::mktime:
1203 if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
1206 setDoesNotCapture(F, 1);
1208 case LibFunc::realloc:
1209 if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy() ||
1210 !FTy->getReturnType()->isPointerTy())
1213 setDoesNotAlias(F, 0);
1214 setDoesNotCapture(F, 1);
1217 if (FTy->getNumParams() != 3 || !FTy->getParamType(1)->isPointerTy())
1219 // May throw; "read" is a valid pthread cancellation point.
1220 setDoesNotCapture(F, 2);
1222 case LibFunc::rewind:
1223 if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy())
1226 setDoesNotCapture(F, 1);
1228 case LibFunc::rmdir:
1229 case LibFunc::remove:
1230 case LibFunc::realpath:
1231 if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy())
1234 setDoesNotCapture(F, 1);
1235 setOnlyReadsMemory(F, 1);
1237 case LibFunc::rename:
1238 if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
1239 !FTy->getParamType(1)->isPointerTy())
1242 setDoesNotCapture(F, 1);
1243 setDoesNotCapture(F, 2);
1244 setOnlyReadsMemory(F, 1);
1245 setOnlyReadsMemory(F, 2);
1247 case LibFunc::readlink:
1248 if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
1249 !FTy->getParamType(1)->isPointerTy())
1252 setDoesNotCapture(F, 1);
1253 setDoesNotCapture(F, 2);
1254 setOnlyReadsMemory(F, 1);
1256 case LibFunc::write:
1257 if (FTy->getNumParams() != 3 || !FTy->getParamType(1)->isPointerTy())
1259 // May throw; "write" is a valid pthread cancellation point.
1260 setDoesNotCapture(F, 2);
1261 setOnlyReadsMemory(F, 2);
1263 case LibFunc::bcopy:
1264 if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy() ||
1265 !FTy->getParamType(1)->isPointerTy())
1268 setDoesNotCapture(F, 1);
1269 setDoesNotCapture(F, 2);
1270 setOnlyReadsMemory(F, 1);
1273 if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy() ||
1274 !FTy->getParamType(1)->isPointerTy())
1277 setOnlyReadsMemory(F);
1278 setDoesNotCapture(F, 1);
1279 setDoesNotCapture(F, 2);
1281 case LibFunc::bzero:
1282 if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy())
1285 setDoesNotCapture(F, 1);
1287 case LibFunc::calloc:
1288 if (FTy->getNumParams() != 2 || !FTy->getReturnType()->isPointerTy())
1291 setDoesNotAlias(F, 0);
1293 case LibFunc::chmod:
1294 case LibFunc::chown:
1295 if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
1298 setDoesNotCapture(F, 1);
1299 setOnlyReadsMemory(F, 1);
1301 case LibFunc::ctermid:
1302 case LibFunc::clearerr:
1303 case LibFunc::closedir:
1304 if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
1307 setDoesNotCapture(F, 1);
1312 case LibFunc::atoll:
1313 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1316 setOnlyReadsMemory(F);
1317 setDoesNotCapture(F, 1);
1319 case LibFunc::access:
1320 if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy())
1323 setDoesNotCapture(F, 1);
1324 setOnlyReadsMemory(F, 1);
1326 case LibFunc::fopen:
1327 if (FTy->getNumParams() != 2 || !FTy->getReturnType()->isPointerTy() ||
1328 !FTy->getParamType(0)->isPointerTy() ||
1329 !FTy->getParamType(1)->isPointerTy())
1332 setDoesNotAlias(F, 0);
1333 setDoesNotCapture(F, 1);
1334 setDoesNotCapture(F, 2);
1335 setOnlyReadsMemory(F, 1);
1336 setOnlyReadsMemory(F, 2);
1338 case LibFunc::fdopen:
1339 if (FTy->getNumParams() != 2 || !FTy->getReturnType()->isPointerTy() ||
1340 !FTy->getParamType(1)->isPointerTy())
1343 setDoesNotAlias(F, 0);
1344 setDoesNotCapture(F, 2);
1345 setOnlyReadsMemory(F, 2);
1349 case LibFunc::fseek:
1350 case LibFunc::ftell:
1351 case LibFunc::fgetc:
1352 case LibFunc::fseeko:
1353 case LibFunc::ftello:
1354 case LibFunc::fileno:
1355 case LibFunc::fflush:
1356 case LibFunc::fclose:
1357 case LibFunc::fsetpos:
1358 case LibFunc::flockfile:
1359 case LibFunc::funlockfile:
1360 case LibFunc::ftrylockfile:
1361 if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
1364 setDoesNotCapture(F, 1);
1366 case LibFunc::ferror:
1367 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1370 setDoesNotCapture(F, 1);
1371 setOnlyReadsMemory(F);
1373 case LibFunc::fputc:
1374 case LibFunc::fstat:
1375 case LibFunc::frexp:
1376 case LibFunc::frexpf:
1377 case LibFunc::frexpl:
1378 case LibFunc::fstatvfs:
1379 if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
1382 setDoesNotCapture(F, 2);
1384 case LibFunc::fgets:
1385 if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy() ||
1386 !FTy->getParamType(2)->isPointerTy())
1389 setDoesNotCapture(F, 3);
1391 case LibFunc::fread:
1392 if (FTy->getNumParams() != 4 || !FTy->getParamType(0)->isPointerTy() ||
1393 !FTy->getParamType(3)->isPointerTy())
1396 setDoesNotCapture(F, 1);
1397 setDoesNotCapture(F, 4);
1399 case LibFunc::fwrite:
1400 if (FTy->getNumParams() != 4 || !FTy->getParamType(0)->isPointerTy() ||
1401 !FTy->getParamType(3)->isPointerTy())
1404 setDoesNotCapture(F, 1);
1405 setDoesNotCapture(F, 4);
1407 case LibFunc::fputs:
1408 if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
1409 !FTy->getParamType(1)->isPointerTy())
1412 setDoesNotCapture(F, 1);
1413 setDoesNotCapture(F, 2);
1414 setOnlyReadsMemory(F, 1);
1416 case LibFunc::fscanf:
1417 case LibFunc::fprintf:
1418 if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
1419 !FTy->getParamType(1)->isPointerTy())
1422 setDoesNotCapture(F, 1);
1423 setDoesNotCapture(F, 2);
1424 setOnlyReadsMemory(F, 2);
1426 case LibFunc::fgetpos:
1427 if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy() ||
1428 !FTy->getParamType(1)->isPointerTy())
1431 setDoesNotCapture(F, 1);
1432 setDoesNotCapture(F, 2);
1435 case LibFunc::getlogin_r:
1436 case LibFunc::getc_unlocked:
1437 if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
1440 setDoesNotCapture(F, 1);
1442 case LibFunc::getenv:
1443 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1446 setOnlyReadsMemory(F);
1447 setDoesNotCapture(F, 1);
1450 case LibFunc::getchar:
1453 case LibFunc::getitimer:
1454 if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
1457 setDoesNotCapture(F, 2);
1459 case LibFunc::getpwnam:
1460 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1463 setDoesNotCapture(F, 1);
1464 setOnlyReadsMemory(F, 1);
1466 case LibFunc::ungetc:
1467 if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
1470 setDoesNotCapture(F, 2);
1472 case LibFunc::uname:
1473 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1476 setDoesNotCapture(F, 1);
1478 case LibFunc::unlink:
1479 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1482 setDoesNotCapture(F, 1);
1483 setOnlyReadsMemory(F, 1);
1485 case LibFunc::unsetenv:
1486 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1489 setDoesNotCapture(F, 1);
1490 setOnlyReadsMemory(F, 1);
1492 case LibFunc::utime:
1493 case LibFunc::utimes:
1494 if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy() ||
1495 !FTy->getParamType(1)->isPointerTy())
1498 setDoesNotCapture(F, 1);
1499 setDoesNotCapture(F, 2);
1500 setOnlyReadsMemory(F, 1);
1501 setOnlyReadsMemory(F, 2);
1504 if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
1507 setDoesNotCapture(F, 2);
1510 case LibFunc::printf:
1511 case LibFunc::perror:
1512 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1515 setDoesNotCapture(F, 1);
1516 setOnlyReadsMemory(F, 1);
1518 case LibFunc::pread:
1519 if (FTy->getNumParams() != 4 || !FTy->getParamType(1)->isPointerTy())
1521 // May throw; "pread" is a valid pthread cancellation point.
1522 setDoesNotCapture(F, 2);
1524 case LibFunc::pwrite:
1525 if (FTy->getNumParams() != 4 || !FTy->getParamType(1)->isPointerTy())
1527 // May throw; "pwrite" is a valid pthread cancellation point.
1528 setDoesNotCapture(F, 2);
1529 setOnlyReadsMemory(F, 2);
1531 case LibFunc::putchar:
1534 case LibFunc::popen:
1535 if (FTy->getNumParams() != 2 || !FTy->getReturnType()->isPointerTy() ||
1536 !FTy->getParamType(0)->isPointerTy() ||
1537 !FTy->getParamType(1)->isPointerTy())
1540 setDoesNotAlias(F, 0);
1541 setDoesNotCapture(F, 1);
1542 setDoesNotCapture(F, 2);
1543 setOnlyReadsMemory(F, 1);
1544 setOnlyReadsMemory(F, 2);
1546 case LibFunc::pclose:
1547 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1550 setDoesNotCapture(F, 1);
1552 case LibFunc::vscanf:
1553 if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
1556 setDoesNotCapture(F, 1);
1557 setOnlyReadsMemory(F, 1);
1559 case LibFunc::vsscanf:
1560 if (FTy->getNumParams() != 3 || !FTy->getParamType(1)->isPointerTy() ||
1561 !FTy->getParamType(2)->isPointerTy())
1564 setDoesNotCapture(F, 1);
1565 setDoesNotCapture(F, 2);
1566 setOnlyReadsMemory(F, 1);
1567 setOnlyReadsMemory(F, 2);
1569 case LibFunc::vfscanf:
1570 if (FTy->getNumParams() != 3 || !FTy->getParamType(1)->isPointerTy() ||
1571 !FTy->getParamType(2)->isPointerTy())
1574 setDoesNotCapture(F, 1);
1575 setDoesNotCapture(F, 2);
1576 setOnlyReadsMemory(F, 2);
1578 case LibFunc::valloc:
1579 if (!FTy->getReturnType()->isPointerTy())
1582 setDoesNotAlias(F, 0);
1584 case LibFunc::vprintf:
1585 if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy())
1588 setDoesNotCapture(F, 1);
1589 setOnlyReadsMemory(F, 1);
1591 case LibFunc::vfprintf:
1592 case LibFunc::vsprintf:
1593 if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy() ||
1594 !FTy->getParamType(1)->isPointerTy())
1597 setDoesNotCapture(F, 1);
1598 setDoesNotCapture(F, 2);
1599 setOnlyReadsMemory(F, 2);
1601 case LibFunc::vsnprintf:
1602 if (FTy->getNumParams() != 4 || !FTy->getParamType(0)->isPointerTy() ||
1603 !FTy->getParamType(2)->isPointerTy())
1606 setDoesNotCapture(F, 1);
1607 setDoesNotCapture(F, 3);
1608 setOnlyReadsMemory(F, 3);
1611 if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy())
1613 // May throw; "open" is a valid pthread cancellation point.
1614 setDoesNotCapture(F, 1);
1615 setOnlyReadsMemory(F, 1);
1617 case LibFunc::opendir:
1618 if (FTy->getNumParams() != 1 || !FTy->getReturnType()->isPointerTy() ||
1619 !FTy->getParamType(0)->isPointerTy())
1622 setDoesNotAlias(F, 0);
1623 setDoesNotCapture(F, 1);
1624 setOnlyReadsMemory(F, 1);
1626 case LibFunc::tmpfile:
1627 if (!FTy->getReturnType()->isPointerTy())
1630 setDoesNotAlias(F, 0);
1632 case LibFunc::times:
1633 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1636 setDoesNotCapture(F, 1);
1638 case LibFunc::htonl:
1639 case LibFunc::htons:
1640 case LibFunc::ntohl:
1641 case LibFunc::ntohs:
1643 setDoesNotAccessMemory(F);
1645 case LibFunc::lstat:
1646 if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy() ||
1647 !FTy->getParamType(1)->isPointerTy())
1650 setDoesNotCapture(F, 1);
1651 setDoesNotCapture(F, 2);
1652 setOnlyReadsMemory(F, 1);
1654 case LibFunc::lchown:
1655 if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy())
1658 setDoesNotCapture(F, 1);
1659 setOnlyReadsMemory(F, 1);
1661 case LibFunc::qsort:
1662 if (FTy->getNumParams() != 4 || !FTy->getParamType(3)->isPointerTy())
1664 // May throw; places call through function pointer.
1665 setDoesNotCapture(F, 4);
1667 case LibFunc::dunder_strdup:
1668 case LibFunc::dunder_strndup:
1669 if (FTy->getNumParams() < 1 || !FTy->getReturnType()->isPointerTy() ||
1670 !FTy->getParamType(0)->isPointerTy())
1673 setDoesNotAlias(F, 0);
1674 setDoesNotCapture(F, 1);
1675 setOnlyReadsMemory(F, 1);
1677 case LibFunc::dunder_strtok_r:
1678 if (FTy->getNumParams() != 3 || !FTy->getParamType(1)->isPointerTy())
1681 setDoesNotCapture(F, 2);
1682 setOnlyReadsMemory(F, 2);
1684 case LibFunc::under_IO_getc:
1685 if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
1688 setDoesNotCapture(F, 1);
1690 case LibFunc::under_IO_putc:
1691 if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
1694 setDoesNotCapture(F, 2);
1696 case LibFunc::dunder_isoc99_scanf:
1697 if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy())
1700 setDoesNotCapture(F, 1);
1701 setOnlyReadsMemory(F, 1);
1703 case LibFunc::stat64:
1704 case LibFunc::lstat64:
1705 case LibFunc::statvfs64:
1706 if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy() ||
1707 !FTy->getParamType(1)->isPointerTy())
1710 setDoesNotCapture(F, 1);
1711 setDoesNotCapture(F, 2);
1712 setOnlyReadsMemory(F, 1);
1714 case LibFunc::dunder_isoc99_sscanf:
1715 if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy() ||
1716 !FTy->getParamType(1)->isPointerTy())
1719 setDoesNotCapture(F, 1);
1720 setDoesNotCapture(F, 2);
1721 setOnlyReadsMemory(F, 1);
1722 setOnlyReadsMemory(F, 2);
1724 case LibFunc::fopen64:
1725 if (FTy->getNumParams() != 2 || !FTy->getReturnType()->isPointerTy() ||
1726 !FTy->getParamType(0)->isPointerTy() ||
1727 !FTy->getParamType(1)->isPointerTy())
1730 setDoesNotAlias(F, 0);
1731 setDoesNotCapture(F, 1);
1732 setDoesNotCapture(F, 2);
1733 setOnlyReadsMemory(F, 1);
1734 setOnlyReadsMemory(F, 2);
1736 case LibFunc::fseeko64:
1737 case LibFunc::ftello64:
1738 if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
1741 setDoesNotCapture(F, 1);
1743 case LibFunc::tmpfile64:
1744 if (!FTy->getReturnType()->isPointerTy())
1747 setDoesNotAlias(F, 0);
1749 case LibFunc::fstat64:
1750 case LibFunc::fstatvfs64:
1751 if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
1754 setDoesNotCapture(F, 2);
1756 case LibFunc::open64:
1757 if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy())
1759 // May throw; "open" is a valid pthread cancellation point.
1760 setDoesNotCapture(F, 1);
1761 setOnlyReadsMemory(F, 1);
1763 case LibFunc::gettimeofday:
1764 if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy() ||
1765 !FTy->getParamType(1)->isPointerTy())
1767 // Currently some platforms have the restrict keyword on the arguments to
1768 // gettimeofday. To be conservative, do not add noalias to gettimeofday's
1771 setDoesNotCapture(F, 1);
1772 setDoesNotCapture(F, 2);
1775 // Didn't mark any attributes.
1782 bool FunctionAttrs::runOnSCC(CallGraphSCC &SCC) {
1783 TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
1784 bool Changed = false;
1786 // We compute dedicated AA results for each function in the SCC as needed. We
1787 // use a lambda referencing external objects so that they live long enough to
1788 // be queried, but we re-use them each time.
1789 Optional<BasicAAResult> BAR;
1790 Optional<AAResults> AAR;
1791 auto AARGetter = [&](Function &F) -> AAResults & {
1792 BAR.emplace(createLegacyPMBasicAAResult(*this, F));
1793 AAR.emplace(createLegacyPMAAResults(*this, F, *BAR));
1797 // Fill SCCNodes with the elements of the SCC. Used for quickly looking up
1798 // whether a given CallGraphNode is in this SCC. Also track whether there are
1799 // any external or opt-none nodes that will prevent us from optimizing any
1801 SCCNodeSet SCCNodes;
1802 bool ExternalNode = false;
1803 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
1804 Function *F = (*I)->getFunction();
1805 if (!F || F->hasFnAttribute(Attribute::OptimizeNone)) {
1806 // External node or function we're trying not to optimize - we both avoid
1807 // transform them and avoid leveraging information they provide.
1808 ExternalNode = true;
1812 // When initially processing functions, also infer their prototype
1813 // attributes if they are declarations.
1814 if (F->isDeclaration())
1815 Changed |= inferPrototypeAttributes(*F, *TLI);
1820 Changed |= addReadAttrs(SCCNodes, AARGetter);
1821 Changed |= addArgumentAttrs(SCCNodes);
1823 // If we have no external nodes participating in the SCC, we can infer some
1824 // more precise attributes as well.
1825 if (!ExternalNode) {
1826 Changed |= addNoAliasAttrs(SCCNodes);
1827 Changed |= addNonNullAttrs(SCCNodes, *TLI);