1 //===- StackSafetyAnalysis.cpp - Stack memory safety analysis -------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 //===----------------------------------------------------------------------===//
10 
11 #include "llvm/Analysis/StackSafetyAnalysis.h"
12 #include "llvm/ADT/APInt.h"
13 #include "llvm/ADT/SmallPtrSet.h"
14 #include "llvm/ADT/SmallVector.h"
15 #include "llvm/ADT/Statistic.h"
16 #include "llvm/Analysis/ModuleSummaryAnalysis.h"
17 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
18 #include "llvm/Analysis/StackLifetime.h"
19 #include "llvm/IR/ConstantRange.h"
20 #include "llvm/IR/DerivedTypes.h"
21 #include "llvm/IR/GlobalValue.h"
22 #include "llvm/IR/InstIterator.h"
23 #include "llvm/IR/Instructions.h"
24 #include "llvm/IR/IntrinsicInst.h"
25 #include "llvm/IR/ModuleSummaryIndex.h"
26 #include "llvm/InitializePasses.h"
27 #include "llvm/Support/Casting.h"
28 #include "llvm/Support/CommandLine.h"
29 #include "llvm/Support/FormatVariadic.h"
30 #include "llvm/Support/raw_ostream.h"
31 #include <algorithm>
32 #include <memory>
33 
34 using namespace llvm;
35 
36 #define DEBUG_TYPE "stack-safety"
37 
38 STATISTIC(NumAllocaStackSafe, "Number of safe allocas");
39 STATISTIC(NumAllocaTotal, "Number of total allocas");
40 
41 STATISTIC(NumCombinedCalleeLookupTotal,
42           "Number of total callee lookups on combined index.");
43 STATISTIC(NumCombinedCalleeLookupFailed,
44           "Number of failed callee lookups on combined index.");
45 STATISTIC(NumModuleCalleeLookupTotal,
46           "Number of total callee lookups on module index.");
47 STATISTIC(NumModuleCalleeLookupFailed,
48           "Number of failed callee lookups on module index.");
49 STATISTIC(NumCombinedParamAccessesBefore,
50           "Number of total param accesses before generateParamAccessSummary.");
51 STATISTIC(NumCombinedParamAccessesAfter,
52           "Number of total param accesses after generateParamAccessSummary.");
53 STATISTIC(NumCombinedDataFlowNodes,
54           "Number of total nodes in combined index for dataflow processing.");
55 STATISTIC(NumIndexCalleeUnhandled, "Number of index callee which are unhandled.");
56 STATISTIC(NumIndexCalleeMultipleWeak, "Number of index callee non-unique weak.");
57 STATISTIC(NumIndexCalleeMultipleExternal, "Number of index callee non-unique external.");
58 
59 
60 static cl::opt<int> StackSafetyMaxIterations("stack-safety-max-iterations",
61                                              cl::init(20), cl::Hidden);
62 
63 static cl::opt<bool> StackSafetyPrint("stack-safety-print", cl::init(false),
64                                       cl::Hidden);
65 
66 static cl::opt<bool> StackSafetyRun("stack-safety-run", cl::init(false),
67                                     cl::Hidden);
68 
69 namespace {
70 
71 // Check if we should bailout for such ranges.
72 bool isUnsafe(const ConstantRange &R) {
73   return R.isEmptySet() || R.isFullSet() || R.isUpperSignWrapped();
74 }
75 
76 ConstantRange addOverflowNever(const ConstantRange &L, const ConstantRange &R) {
77   assert(!L.isSignWrappedSet());
78   assert(!R.isSignWrappedSet());
79   if (L.signedAddMayOverflow(R) !=
80       ConstantRange::OverflowResult::NeverOverflows)
81     return ConstantRange::getFull(L.getBitWidth());
82   ConstantRange Result = L.add(R);
83   assert(!Result.isSignWrappedSet());
84   return Result;
85 }
86 
87 ConstantRange unionNoWrap(const ConstantRange &L, const ConstantRange &R) {
88   assert(!L.isSignWrappedSet());
89   assert(!R.isSignWrappedSet());
90   auto Result = L.unionWith(R);
91   // Two non-wrapped sets can produce wrapped.
92   if (Result.isSignWrappedSet())
93     Result = ConstantRange::getFull(Result.getBitWidth());
94   return Result;
95 }
96 
97 /// Describes use of address in as a function call argument.
98 template <typename CalleeTy> struct CallInfo {
99   /// Function being called.
100   const CalleeTy *Callee = nullptr;
101   /// Index of argument which pass address.
102   size_t ParamNo = 0;
103 
104   CallInfo(const CalleeTy *Callee, size_t ParamNo)
105       : Callee(Callee), ParamNo(ParamNo) {}
106 
107   struct Less {
108     bool operator()(const CallInfo &L, const CallInfo &R) const {
109       return std::tie(L.ParamNo, L.Callee) < std::tie(R.ParamNo, R.Callee);
110     }
111   };
112 };
113 
114 /// Describe uses of address (alloca or parameter) inside of the function.
115 template <typename CalleeTy> struct UseInfo {
116   // Access range if the address (alloca or parameters).
117   // It is allowed to be empty-set when there are no known accesses.
118   ConstantRange Range;
119 
120   // List of calls which pass address as an argument.
121   // Value is offset range of address from base address (alloca or calling
122   // function argument). Range should never set to empty-set, that is an invalid
123   // access range that can cause empty-set to be propagated with
124   // ConstantRange::add
125   using CallsTy = std::map<CallInfo<CalleeTy>, ConstantRange,
126                            typename CallInfo<CalleeTy>::Less>;
127   CallsTy Calls;
128 
129   UseInfo(unsigned PointerSize) : Range{PointerSize, false} {}
130 
131   void updateRange(const ConstantRange &R) { Range = unionNoWrap(Range, R); }
132   void addRange(const Instruction *I, const ConstantRange &R) {
133     updateRange(R);
134   }
135 };
136 
137 template <typename CalleeTy>
138 raw_ostream &operator<<(raw_ostream &OS, const UseInfo<CalleeTy> &U) {
139   OS << U.Range;
140   for (auto &Call : U.Calls)
141     OS << ", "
142        << "@" << Call.first.Callee->getName() << "(arg" << Call.first.ParamNo
143        << ", " << Call.second << ")";
144   return OS;
145 }
146 
147 /// Calculate the allocation size of a given alloca. Returns empty range
148 // in case of confution.
149 ConstantRange getStaticAllocaSizeRange(const AllocaInst &AI) {
150   const DataLayout &DL = AI.getModule()->getDataLayout();
151   TypeSize TS = DL.getTypeAllocSize(AI.getAllocatedType());
152   unsigned PointerSize = DL.getMaxPointerSizeInBits();
153   // Fallback to empty range for alloca size.
154   ConstantRange R = ConstantRange::getEmpty(PointerSize);
155   if (TS.isScalable())
156     return R;
157   APInt APSize(PointerSize, TS.getFixedSize(), true);
158   if (APSize.isNonPositive())
159     return R;
160   if (AI.isArrayAllocation()) {
161     const auto *C = dyn_cast<ConstantInt>(AI.getArraySize());
162     if (!C)
163       return R;
164     bool Overflow = false;
165     APInt Mul = C->getValue();
166     if (Mul.isNonPositive())
167       return R;
168     Mul = Mul.sextOrTrunc(PointerSize);
169     APSize = APSize.smul_ov(Mul, Overflow);
170     if (Overflow)
171       return R;
172   }
173   R = ConstantRange(APInt::getZero(PointerSize), APSize);
174   assert(!isUnsafe(R));
175   return R;
176 }
177 
178 template <typename CalleeTy> struct FunctionInfo {
179   std::map<const AllocaInst *, UseInfo<CalleeTy>> Allocas;
180   std::map<uint32_t, UseInfo<CalleeTy>> Params;
181   // TODO: describe return value as depending on one or more of its arguments.
182 
183   // StackSafetyDataFlowAnalysis counter stored here for faster access.
184   int UpdateCount = 0;
185 
186   void print(raw_ostream &O, StringRef Name, const Function *F) const {
187     // TODO: Consider different printout format after
188     // StackSafetyDataFlowAnalysis. Calls and parameters are irrelevant then.
189     O << "  @" << Name << ((F && F->isDSOLocal()) ? "" : " dso_preemptable")
190       << ((F && F->isInterposable()) ? " interposable" : "") << "\n";
191 
192     O << "    args uses:\n";
193     for (auto &KV : Params) {
194       O << "      ";
195       if (F)
196         O << F->getArg(KV.first)->getName();
197       else
198         O << formatv("arg{0}", KV.first);
199       O << "[]: " << KV.second << "\n";
200     }
201 
202     O << "    allocas uses:\n";
203     if (F) {
204       for (auto &I : instructions(F)) {
205         if (const AllocaInst *AI = dyn_cast<AllocaInst>(&I)) {
206           auto &AS = Allocas.find(AI)->second;
207           O << "      " << AI->getName() << "["
208             << getStaticAllocaSizeRange(*AI).getUpper() << "]: " << AS << "\n";
209         }
210       }
211     } else {
212       assert(Allocas.empty());
213     }
214   }
215 };
216 
217 using GVToSSI = std::map<const GlobalValue *, FunctionInfo<GlobalValue>>;
218 
219 } // namespace
220 
221 struct StackSafetyInfo::InfoTy {
222   FunctionInfo<GlobalValue> Info;
223 };
224 
225 struct StackSafetyGlobalInfo::InfoTy {
226   GVToSSI Info;
227   SmallPtrSet<const AllocaInst *, 8> SafeAllocas;
228 };
229 
230 namespace {
231 
232 class StackSafetyLocalAnalysis {
233   Function &F;
234   const DataLayout &DL;
235   ScalarEvolution &SE;
236   unsigned PointerSize = 0;
237 
238   const ConstantRange UnknownRange;
239 
240   ConstantRange offsetFrom(Value *Addr, Value *Base);
241   ConstantRange getAccessRange(Value *Addr, Value *Base,
242                                const ConstantRange &SizeRange);
243   ConstantRange getAccessRange(Value *Addr, Value *Base, TypeSize Size);
244   ConstantRange getMemIntrinsicAccessRange(const MemIntrinsic *MI, const Use &U,
245                                            Value *Base);
246 
247   void analyzeAllUses(Value *Ptr, UseInfo<GlobalValue> &AS,
248                       const StackLifetime &SL);
249 
250 public:
251   StackSafetyLocalAnalysis(Function &F, ScalarEvolution &SE)
252       : F(F), DL(F.getParent()->getDataLayout()), SE(SE),
253         PointerSize(DL.getPointerSizeInBits()),
254         UnknownRange(PointerSize, true) {}
255 
256   // Run the transformation on the associated function.
257   FunctionInfo<GlobalValue> run();
258 };
259 
260 ConstantRange StackSafetyLocalAnalysis::offsetFrom(Value *Addr, Value *Base) {
261   if (!SE.isSCEVable(Addr->getType()) || !SE.isSCEVable(Base->getType()))
262     return UnknownRange;
263 
264   auto *PtrTy = IntegerType::getInt8PtrTy(SE.getContext());
265   const SCEV *AddrExp = SE.getTruncateOrZeroExtend(SE.getSCEV(Addr), PtrTy);
266   const SCEV *BaseExp = SE.getTruncateOrZeroExtend(SE.getSCEV(Base), PtrTy);
267   const SCEV *Diff = SE.getMinusSCEV(AddrExp, BaseExp);
268   if (isa<SCEVCouldNotCompute>(Diff))
269     return UnknownRange;
270 
271   ConstantRange Offset = SE.getSignedRange(Diff);
272   if (isUnsafe(Offset))
273     return UnknownRange;
274   return Offset.sextOrTrunc(PointerSize);
275 }
276 
277 ConstantRange
278 StackSafetyLocalAnalysis::getAccessRange(Value *Addr, Value *Base,
279                                          const ConstantRange &SizeRange) {
280   // Zero-size loads and stores do not access memory.
281   if (SizeRange.isEmptySet())
282     return ConstantRange::getEmpty(PointerSize);
283   assert(!isUnsafe(SizeRange));
284 
285   ConstantRange Offsets = offsetFrom(Addr, Base);
286   if (isUnsafe(Offsets))
287     return UnknownRange;
288 
289   Offsets = addOverflowNever(Offsets, SizeRange);
290   if (isUnsafe(Offsets))
291     return UnknownRange;
292   return Offsets;
293 }
294 
295 ConstantRange StackSafetyLocalAnalysis::getAccessRange(Value *Addr, Value *Base,
296                                                        TypeSize Size) {
297   if (Size.isScalable())
298     return UnknownRange;
299   APInt APSize(PointerSize, Size.getFixedSize(), true);
300   if (APSize.isNegative())
301     return UnknownRange;
302   return getAccessRange(Addr, Base,
303                         ConstantRange(APInt::getZero(PointerSize), APSize));
304 }
305 
306 ConstantRange StackSafetyLocalAnalysis::getMemIntrinsicAccessRange(
307     const MemIntrinsic *MI, const Use &U, Value *Base) {
308   if (const auto *MTI = dyn_cast<MemTransferInst>(MI)) {
309     if (MTI->getRawSource() != U && MTI->getRawDest() != U)
310       return ConstantRange::getEmpty(PointerSize);
311   } else {
312     if (MI->getRawDest() != U)
313       return ConstantRange::getEmpty(PointerSize);
314   }
315 
316   auto *CalculationTy = IntegerType::getIntNTy(SE.getContext(), PointerSize);
317   if (!SE.isSCEVable(MI->getLength()->getType()))
318     return UnknownRange;
319 
320   const SCEV *Expr =
321       SE.getTruncateOrZeroExtend(SE.getSCEV(MI->getLength()), CalculationTy);
322   ConstantRange Sizes = SE.getSignedRange(Expr);
323   if (Sizes.getUpper().isNegative() || isUnsafe(Sizes))
324     return UnknownRange;
325   Sizes = Sizes.sextOrTrunc(PointerSize);
326   ConstantRange SizeRange(APInt::getZero(PointerSize), Sizes.getUpper() - 1);
327   return getAccessRange(U, Base, SizeRange);
328 }
329 
330 /// The function analyzes all local uses of Ptr (alloca or argument) and
331 /// calculates local access range and all function calls where it was used.
332 void StackSafetyLocalAnalysis::analyzeAllUses(Value *Ptr,
333                                               UseInfo<GlobalValue> &US,
334                                               const StackLifetime &SL) {
335   SmallPtrSet<const Value *, 16> Visited;
336   SmallVector<const Value *, 8> WorkList;
337   WorkList.push_back(Ptr);
338   const AllocaInst *AI = dyn_cast<AllocaInst>(Ptr);
339 
340   // A DFS search through all uses of the alloca in bitcasts/PHI/GEPs/etc.
341   while (!WorkList.empty()) {
342     const Value *V = WorkList.pop_back_val();
343     for (const Use &UI : V->uses()) {
344       const auto *I = cast<Instruction>(UI.getUser());
345       if (!SL.isReachable(I))
346         continue;
347 
348       assert(V == UI.get());
349 
350       switch (I->getOpcode()) {
351       case Instruction::Load: {
352         if (AI && !SL.isAliveAfter(AI, I)) {
353           US.addRange(I, UnknownRange);
354           return;
355         }
356         US.addRange(I,
357                     getAccessRange(UI, Ptr, DL.getTypeStoreSize(I->getType())));
358         break;
359       }
360 
361       case Instruction::VAArg:
362         // "va-arg" from a pointer is safe.
363         break;
364       case Instruction::Store: {
365         if (V == I->getOperand(0)) {
366           // Stored the pointer - conservatively assume it may be unsafe.
367           US.addRange(I, UnknownRange);
368           return;
369         }
370         if (AI && !SL.isAliveAfter(AI, I)) {
371           US.addRange(I, UnknownRange);
372           return;
373         }
374         US.addRange(
375             I, getAccessRange(
376                    UI, Ptr, DL.getTypeStoreSize(I->getOperand(0)->getType())));
377         break;
378       }
379 
380       case Instruction::Ret:
381         // Information leak.
382         // FIXME: Process parameters correctly. This is a leak only if we return
383         // alloca.
384         US.addRange(I, UnknownRange);
385         return;
386 
387       case Instruction::Call:
388       case Instruction::Invoke: {
389         if (I->isLifetimeStartOrEnd())
390           break;
391 
392         if (AI && !SL.isAliveAfter(AI, I)) {
393           US.addRange(I, UnknownRange);
394           return;
395         }
396 
397         if (const MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I)) {
398           US.addRange(I, getMemIntrinsicAccessRange(MI, UI, Ptr));
399           break;
400         }
401 
402         const auto &CB = cast<CallBase>(*I);
403         if (!CB.isArgOperand(&UI)) {
404           US.addRange(I, UnknownRange);
405           return;
406         }
407 
408         unsigned ArgNo = CB.getArgOperandNo(&UI);
409         if (CB.isByValArgument(ArgNo)) {
410           US.addRange(I, getAccessRange(
411                              UI, Ptr,
412                              DL.getTypeStoreSize(CB.getParamByValType(ArgNo))));
413           break;
414         }
415 
416         // FIXME: consult devirt?
417         // Do not follow aliases, otherwise we could inadvertently follow
418         // dso_preemptable aliases or aliases with interposable linkage.
419         const GlobalValue *Callee =
420             dyn_cast<GlobalValue>(CB.getCalledOperand()->stripPointerCasts());
421         if (!Callee) {
422           US.addRange(I, UnknownRange);
423           return;
424         }
425 
426         assert(isa<Function>(Callee) || isa<GlobalAlias>(Callee));
427         ConstantRange Offsets = offsetFrom(UI, Ptr);
428         auto Insert =
429             US.Calls.emplace(CallInfo<GlobalValue>(Callee, ArgNo), Offsets);
430         if (!Insert.second)
431           Insert.first->second = Insert.first->second.unionWith(Offsets);
432         break;
433       }
434 
435       default:
436         if (Visited.insert(I).second)
437           WorkList.push_back(cast<const Instruction>(I));
438       }
439     }
440   }
441 }
442 
443 FunctionInfo<GlobalValue> StackSafetyLocalAnalysis::run() {
444   FunctionInfo<GlobalValue> Info;
445   assert(!F.isDeclaration() &&
446          "Can't run StackSafety on a function declaration");
447 
448   LLVM_DEBUG(dbgs() << "[StackSafety] " << F.getName() << "\n");
449 
450   SmallVector<AllocaInst *, 64> Allocas;
451   for (auto &I : instructions(F))
452     if (auto *AI = dyn_cast<AllocaInst>(&I))
453       Allocas.push_back(AI);
454   StackLifetime SL(F, Allocas, StackLifetime::LivenessType::Must);
455   SL.run();
456 
457   for (auto *AI : Allocas) {
458     auto &UI = Info.Allocas.emplace(AI, PointerSize).first->second;
459     analyzeAllUses(AI, UI, SL);
460   }
461 
462   for (Argument &A : F.args()) {
463     // Non pointers and bypass arguments are not going to be used in any global
464     // processing.
465     if (A.getType()->isPointerTy() && !A.hasByValAttr()) {
466       auto &UI = Info.Params.emplace(A.getArgNo(), PointerSize).first->second;
467       analyzeAllUses(&A, UI, SL);
468     }
469   }
470 
471   LLVM_DEBUG(Info.print(dbgs(), F.getName(), &F));
472   LLVM_DEBUG(dbgs() << "\n[StackSafety] done\n");
473   return Info;
474 }
475 
476 template <typename CalleeTy> class StackSafetyDataFlowAnalysis {
477   using FunctionMap = std::map<const CalleeTy *, FunctionInfo<CalleeTy>>;
478 
479   FunctionMap Functions;
480   const ConstantRange UnknownRange;
481 
482   // Callee-to-Caller multimap.
483   DenseMap<const CalleeTy *, SmallVector<const CalleeTy *, 4>> Callers;
484   SetVector<const CalleeTy *> WorkList;
485 
486   bool updateOneUse(UseInfo<CalleeTy> &US, bool UpdateToFullSet);
487   void updateOneNode(const CalleeTy *Callee, FunctionInfo<CalleeTy> &FS);
488   void updateOneNode(const CalleeTy *Callee) {
489     updateOneNode(Callee, Functions.find(Callee)->second);
490   }
491   void updateAllNodes() {
492     for (auto &F : Functions)
493       updateOneNode(F.first, F.second);
494   }
495   void runDataFlow();
496 #ifndef NDEBUG
497   void verifyFixedPoint();
498 #endif
499 
500 public:
501   StackSafetyDataFlowAnalysis(uint32_t PointerBitWidth, FunctionMap Functions)
502       : Functions(std::move(Functions)),
503         UnknownRange(ConstantRange::getFull(PointerBitWidth)) {}
504 
505   const FunctionMap &run();
506 
507   ConstantRange getArgumentAccessRange(const CalleeTy *Callee, unsigned ParamNo,
508                                        const ConstantRange &Offsets) const;
509 };
510 
511 template <typename CalleeTy>
512 ConstantRange StackSafetyDataFlowAnalysis<CalleeTy>::getArgumentAccessRange(
513     const CalleeTy *Callee, unsigned ParamNo,
514     const ConstantRange &Offsets) const {
515   auto FnIt = Functions.find(Callee);
516   // Unknown callee (outside of LTO domain or an indirect call).
517   if (FnIt == Functions.end())
518     return UnknownRange;
519   auto &FS = FnIt->second;
520   auto ParamIt = FS.Params.find(ParamNo);
521   if (ParamIt == FS.Params.end())
522     return UnknownRange;
523   auto &Access = ParamIt->second.Range;
524   if (Access.isEmptySet())
525     return Access;
526   if (Access.isFullSet())
527     return UnknownRange;
528   return addOverflowNever(Access, Offsets);
529 }
530 
531 template <typename CalleeTy>
532 bool StackSafetyDataFlowAnalysis<CalleeTy>::updateOneUse(UseInfo<CalleeTy> &US,
533                                                          bool UpdateToFullSet) {
534   bool Changed = false;
535   for (auto &KV : US.Calls) {
536     assert(!KV.second.isEmptySet() &&
537            "Param range can't be empty-set, invalid offset range");
538 
539     ConstantRange CalleeRange =
540         getArgumentAccessRange(KV.first.Callee, KV.first.ParamNo, KV.second);
541     if (!US.Range.contains(CalleeRange)) {
542       Changed = true;
543       if (UpdateToFullSet)
544         US.Range = UnknownRange;
545       else
546         US.updateRange(CalleeRange);
547     }
548   }
549   return Changed;
550 }
551 
552 template <typename CalleeTy>
553 void StackSafetyDataFlowAnalysis<CalleeTy>::updateOneNode(
554     const CalleeTy *Callee, FunctionInfo<CalleeTy> &FS) {
555   bool UpdateToFullSet = FS.UpdateCount > StackSafetyMaxIterations;
556   bool Changed = false;
557   for (auto &KV : FS.Params)
558     Changed |= updateOneUse(KV.second, UpdateToFullSet);
559 
560   if (Changed) {
561     LLVM_DEBUG(dbgs() << "=== update [" << FS.UpdateCount
562                       << (UpdateToFullSet ? ", full-set" : "") << "] " << &FS
563                       << "\n");
564     // Callers of this function may need updating.
565     for (auto &CallerID : Callers[Callee])
566       WorkList.insert(CallerID);
567 
568     ++FS.UpdateCount;
569   }
570 }
571 
572 template <typename CalleeTy>
573 void StackSafetyDataFlowAnalysis<CalleeTy>::runDataFlow() {
574   SmallVector<const CalleeTy *, 16> Callees;
575   for (auto &F : Functions) {
576     Callees.clear();
577     auto &FS = F.second;
578     for (auto &KV : FS.Params)
579       for (auto &CS : KV.second.Calls)
580         Callees.push_back(CS.first.Callee);
581 
582     llvm::sort(Callees);
583     Callees.erase(std::unique(Callees.begin(), Callees.end()), Callees.end());
584 
585     for (auto &Callee : Callees)
586       Callers[Callee].push_back(F.first);
587   }
588 
589   updateAllNodes();
590 
591   while (!WorkList.empty()) {
592     const CalleeTy *Callee = WorkList.back();
593     WorkList.pop_back();
594     updateOneNode(Callee);
595   }
596 }
597 
598 #ifndef NDEBUG
599 template <typename CalleeTy>
600 void StackSafetyDataFlowAnalysis<CalleeTy>::verifyFixedPoint() {
601   WorkList.clear();
602   updateAllNodes();
603   assert(WorkList.empty());
604 }
605 #endif
606 
607 template <typename CalleeTy>
608 const typename StackSafetyDataFlowAnalysis<CalleeTy>::FunctionMap &
609 StackSafetyDataFlowAnalysis<CalleeTy>::run() {
610   runDataFlow();
611   LLVM_DEBUG(verifyFixedPoint());
612   return Functions;
613 }
614 
615 FunctionSummary *findCalleeFunctionSummary(ValueInfo VI, StringRef ModuleId) {
616   if (!VI)
617     return nullptr;
618   auto SummaryList = VI.getSummaryList();
619   GlobalValueSummary* S = nullptr;
620   for (const auto& GVS : SummaryList) {
621     if (!GVS->isLive())
622       continue;
623     if (const AliasSummary *AS = dyn_cast<AliasSummary>(GVS.get()))
624       if (!AS->hasAliasee())
625         continue;
626     if (!isa<FunctionSummary>(GVS->getBaseObject()))
627       continue;
628     if (GlobalValue::isLocalLinkage(GVS->linkage())) {
629       if (GVS->modulePath() == ModuleId) {
630         S = GVS.get();
631         break;
632       }
633     } else if (GlobalValue::isExternalLinkage(GVS->linkage())) {
634       if (S) {
635         ++NumIndexCalleeMultipleExternal;
636         return nullptr;
637       }
638       S = GVS.get();
639     } else if (GlobalValue::isWeakLinkage(GVS->linkage())) {
640       if (S) {
641         ++NumIndexCalleeMultipleWeak;
642         return nullptr;
643       }
644       S = GVS.get();
645     } else if (GlobalValue::isAvailableExternallyLinkage(GVS->linkage()) ||
646                GlobalValue::isLinkOnceLinkage(GVS->linkage())) {
647       if (SummaryList.size() == 1)
648         S = GVS.get();
649       // According thinLTOResolvePrevailingGUID these are unlikely prevailing.
650     } else {
651       ++NumIndexCalleeUnhandled;
652     }
653   };
654   while (S) {
655     if (!S->isLive() || !S->isDSOLocal())
656       return nullptr;
657     if (FunctionSummary *FS = dyn_cast<FunctionSummary>(S))
658       return FS;
659     AliasSummary *AS = dyn_cast<AliasSummary>(S);
660     if (!AS || !AS->hasAliasee())
661       return nullptr;
662     S = AS->getBaseObject();
663     if (S == AS)
664       return nullptr;
665   }
666   return nullptr;
667 }
668 
669 const Function *findCalleeInModule(const GlobalValue *GV) {
670   while (GV) {
671     if (GV->isDeclaration() || GV->isInterposable() || !GV->isDSOLocal())
672       return nullptr;
673     if (const Function *F = dyn_cast<Function>(GV))
674       return F;
675     const GlobalAlias *A = dyn_cast<GlobalAlias>(GV);
676     if (!A)
677       return nullptr;
678     GV = A->getBaseObject();
679     if (GV == A)
680       return nullptr;
681   }
682   return nullptr;
683 }
684 
685 const ConstantRange *findParamAccess(const FunctionSummary &FS,
686                                      uint32_t ParamNo) {
687   assert(FS.isLive());
688   assert(FS.isDSOLocal());
689   for (auto &PS : FS.paramAccesses())
690     if (ParamNo == PS.ParamNo)
691       return &PS.Use;
692   return nullptr;
693 }
694 
695 void resolveAllCalls(UseInfo<GlobalValue> &Use,
696                      const ModuleSummaryIndex *Index) {
697   ConstantRange FullSet(Use.Range.getBitWidth(), true);
698   // Move Use.Calls to a temp storage and repopulate - don't use std::move as it
699   // leaves Use.Calls in an undefined state.
700   UseInfo<GlobalValue>::CallsTy TmpCalls;
701   std::swap(TmpCalls, Use.Calls);
702   for (const auto &C : TmpCalls) {
703     const Function *F = findCalleeInModule(C.first.Callee);
704     if (F) {
705       Use.Calls.emplace(CallInfo<GlobalValue>(F, C.first.ParamNo), C.second);
706       continue;
707     }
708 
709     if (!Index)
710       return Use.updateRange(FullSet);
711     FunctionSummary *FS =
712         findCalleeFunctionSummary(Index->getValueInfo(C.first.Callee->getGUID()),
713                                   C.first.Callee->getParent()->getModuleIdentifier());
714     ++NumModuleCalleeLookupTotal;
715     if (!FS) {
716       ++NumModuleCalleeLookupFailed;
717       return Use.updateRange(FullSet);
718     }
719     const ConstantRange *Found = findParamAccess(*FS, C.first.ParamNo);
720     if (!Found || Found->isFullSet())
721       return Use.updateRange(FullSet);
722     ConstantRange Access = Found->sextOrTrunc(Use.Range.getBitWidth());
723     if (!Access.isEmptySet())
724       Use.updateRange(addOverflowNever(Access, C.second));
725   }
726 }
727 
728 GVToSSI createGlobalStackSafetyInfo(
729     std::map<const GlobalValue *, FunctionInfo<GlobalValue>> Functions,
730     const ModuleSummaryIndex *Index) {
731   GVToSSI SSI;
732   if (Functions.empty())
733     return SSI;
734 
735   // FIXME: Simplify printing and remove copying here.
736   auto Copy = Functions;
737 
738   for (auto &FnKV : Copy)
739     for (auto &KV : FnKV.second.Params) {
740       resolveAllCalls(KV.second, Index);
741       if (KV.second.Range.isFullSet())
742         KV.second.Calls.clear();
743     }
744 
745   uint32_t PointerSize = Copy.begin()
746                              ->first->getParent()
747                              ->getDataLayout()
748                              .getMaxPointerSizeInBits();
749   StackSafetyDataFlowAnalysis<GlobalValue> SSDFA(PointerSize, std::move(Copy));
750 
751   for (auto &F : SSDFA.run()) {
752     auto FI = F.second;
753     auto &SrcF = Functions[F.first];
754     for (auto &KV : FI.Allocas) {
755       auto &A = KV.second;
756       resolveAllCalls(A, Index);
757       for (auto &C : A.Calls) {
758         A.updateRange(SSDFA.getArgumentAccessRange(C.first.Callee,
759                                                    C.first.ParamNo, C.second));
760       }
761       // FIXME: This is needed only to preserve calls in print() results.
762       A.Calls = SrcF.Allocas.find(KV.first)->second.Calls;
763     }
764     for (auto &KV : FI.Params) {
765       auto &P = KV.second;
766       P.Calls = SrcF.Params.find(KV.first)->second.Calls;
767     }
768     SSI[F.first] = std::move(FI);
769   }
770 
771   return SSI;
772 }
773 
774 } // end anonymous namespace
775 
776 StackSafetyInfo::StackSafetyInfo() = default;
777 
778 StackSafetyInfo::StackSafetyInfo(Function *F,
779                                  std::function<ScalarEvolution &()> GetSE)
780     : F(F), GetSE(GetSE) {}
781 
782 StackSafetyInfo::StackSafetyInfo(StackSafetyInfo &&) = default;
783 
784 StackSafetyInfo &StackSafetyInfo::operator=(StackSafetyInfo &&) = default;
785 
786 StackSafetyInfo::~StackSafetyInfo() = default;
787 
788 const StackSafetyInfo::InfoTy &StackSafetyInfo::getInfo() const {
789   if (!Info) {
790     StackSafetyLocalAnalysis SSLA(*F, GetSE());
791     Info.reset(new InfoTy{SSLA.run()});
792   }
793   return *Info;
794 }
795 
796 void StackSafetyInfo::print(raw_ostream &O) const {
797   getInfo().Info.print(O, F->getName(), dyn_cast<Function>(F));
798   O << "\n";
799 }
800 
801 const StackSafetyGlobalInfo::InfoTy &StackSafetyGlobalInfo::getInfo() const {
802   if (!Info) {
803     std::map<const GlobalValue *, FunctionInfo<GlobalValue>> Functions;
804     for (auto &F : M->functions()) {
805       if (!F.isDeclaration()) {
806         auto FI = GetSSI(F).getInfo().Info;
807         Functions.emplace(&F, std::move(FI));
808       }
809     }
810     Info.reset(new InfoTy{
811         createGlobalStackSafetyInfo(std::move(Functions), Index), {}});
812     for (auto &FnKV : Info->Info) {
813       for (auto &KV : FnKV.second.Allocas) {
814         ++NumAllocaTotal;
815         const AllocaInst *AI = KV.first;
816         if (getStaticAllocaSizeRange(*AI).contains(KV.second.Range)) {
817           Info->SafeAllocas.insert(AI);
818           ++NumAllocaStackSafe;
819         }
820       }
821     }
822     if (StackSafetyPrint)
823       print(errs());
824   }
825   return *Info;
826 }
827 
828 std::vector<FunctionSummary::ParamAccess>
829 StackSafetyInfo::getParamAccesses(ModuleSummaryIndex &Index) const {
830   // Implementation transforms internal representation of parameter information
831   // into FunctionSummary format.
832   std::vector<FunctionSummary::ParamAccess> ParamAccesses;
833   for (const auto &KV : getInfo().Info.Params) {
834     auto &PS = KV.second;
835     // Parameter accessed by any or unknown offset, represented as FullSet by
836     // StackSafety, is handled as the parameter for which we have no
837     // StackSafety info at all. So drop it to reduce summary size.
838     if (PS.Range.isFullSet())
839       continue;
840 
841     ParamAccesses.emplace_back(KV.first, PS.Range);
842     FunctionSummary::ParamAccess &Param = ParamAccesses.back();
843 
844     Param.Calls.reserve(PS.Calls.size());
845     for (auto &C : PS.Calls) {
846       // Parameter forwarded into another function by any or unknown offset
847       // will make ParamAccess::Range as FullSet anyway. So we can drop the
848       // entire parameter like we did above.
849       // TODO(vitalybuka): Return already filtered parameters from getInfo().
850       if (C.second.isFullSet()) {
851         ParamAccesses.pop_back();
852         break;
853       }
854       Param.Calls.emplace_back(C.first.ParamNo,
855                                Index.getOrInsertValueInfo(C.first.Callee),
856                                C.second);
857     }
858   }
859   for (FunctionSummary::ParamAccess &Param : ParamAccesses) {
860     sort(Param.Calls, [](const FunctionSummary::ParamAccess::Call &L,
861                          const FunctionSummary::ParamAccess::Call &R) {
862       return std::tie(L.ParamNo, L.Callee) < std::tie(R.ParamNo, R.Callee);
863     });
864   }
865   return ParamAccesses;
866 }
867 
868 StackSafetyGlobalInfo::StackSafetyGlobalInfo() = default;
869 
870 StackSafetyGlobalInfo::StackSafetyGlobalInfo(
871     Module *M, std::function<const StackSafetyInfo &(Function &F)> GetSSI,
872     const ModuleSummaryIndex *Index)
873     : M(M), GetSSI(GetSSI), Index(Index) {
874   if (StackSafetyRun)
875     getInfo();
876 }
877 
878 StackSafetyGlobalInfo::StackSafetyGlobalInfo(StackSafetyGlobalInfo &&) =
879     default;
880 
881 StackSafetyGlobalInfo &
882 StackSafetyGlobalInfo::operator=(StackSafetyGlobalInfo &&) = default;
883 
884 StackSafetyGlobalInfo::~StackSafetyGlobalInfo() = default;
885 
886 bool StackSafetyGlobalInfo::isSafe(const AllocaInst &AI) const {
887   const auto &Info = getInfo();
888   return Info.SafeAllocas.count(&AI);
889 }
890 
891 void StackSafetyGlobalInfo::print(raw_ostream &O) const {
892   auto &SSI = getInfo().Info;
893   if (SSI.empty())
894     return;
895   const Module &M = *SSI.begin()->first->getParent();
896   for (auto &F : M.functions()) {
897     if (!F.isDeclaration()) {
898       SSI.find(&F)->second.print(O, F.getName(), &F);
899       O << "\n";
900       O << "\n";
901     }
902   }
903 }
904 
905 LLVM_DUMP_METHOD void StackSafetyGlobalInfo::dump() const { print(dbgs()); }
906 
907 AnalysisKey StackSafetyAnalysis::Key;
908 
909 StackSafetyInfo StackSafetyAnalysis::run(Function &F,
910                                          FunctionAnalysisManager &AM) {
911   return StackSafetyInfo(&F, [&AM, &F]() -> ScalarEvolution & {
912     return AM.getResult<ScalarEvolutionAnalysis>(F);
913   });
914 }
915 
916 PreservedAnalyses StackSafetyPrinterPass::run(Function &F,
917                                               FunctionAnalysisManager &AM) {
918   OS << "'Stack Safety Local Analysis' for function '" << F.getName() << "'\n";
919   AM.getResult<StackSafetyAnalysis>(F).print(OS);
920   return PreservedAnalyses::all();
921 }
922 
923 char StackSafetyInfoWrapperPass::ID = 0;
924 
925 StackSafetyInfoWrapperPass::StackSafetyInfoWrapperPass() : FunctionPass(ID) {
926   initializeStackSafetyInfoWrapperPassPass(*PassRegistry::getPassRegistry());
927 }
928 
929 void StackSafetyInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
930   AU.addRequiredTransitive<ScalarEvolutionWrapperPass>();
931   AU.setPreservesAll();
932 }
933 
934 void StackSafetyInfoWrapperPass::print(raw_ostream &O, const Module *M) const {
935   SSI.print(O);
936 }
937 
938 bool StackSafetyInfoWrapperPass::runOnFunction(Function &F) {
939   auto *SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
940   SSI = {&F, [SE]() -> ScalarEvolution & { return *SE; }};
941   return false;
942 }
943 
944 AnalysisKey StackSafetyGlobalAnalysis::Key;
945 
946 StackSafetyGlobalInfo
947 StackSafetyGlobalAnalysis::run(Module &M, ModuleAnalysisManager &AM) {
948   // FIXME: Lookup Module Summary.
949   FunctionAnalysisManager &FAM =
950       AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
951   return {&M,
952           [&FAM](Function &F) -> const StackSafetyInfo & {
953             return FAM.getResult<StackSafetyAnalysis>(F);
954           },
955           nullptr};
956 }
957 
958 PreservedAnalyses StackSafetyGlobalPrinterPass::run(Module &M,
959                                                     ModuleAnalysisManager &AM) {
960   OS << "'Stack Safety Analysis' for module '" << M.getName() << "'\n";
961   AM.getResult<StackSafetyGlobalAnalysis>(M).print(OS);
962   return PreservedAnalyses::all();
963 }
964 
965 char StackSafetyGlobalInfoWrapperPass::ID = 0;
966 
967 StackSafetyGlobalInfoWrapperPass::StackSafetyGlobalInfoWrapperPass()
968     : ModulePass(ID) {
969   initializeStackSafetyGlobalInfoWrapperPassPass(
970       *PassRegistry::getPassRegistry());
971 }
972 
973 StackSafetyGlobalInfoWrapperPass::~StackSafetyGlobalInfoWrapperPass() = default;
974 
975 void StackSafetyGlobalInfoWrapperPass::print(raw_ostream &O,
976                                              const Module *M) const {
977   SSGI.print(O);
978 }
979 
980 void StackSafetyGlobalInfoWrapperPass::getAnalysisUsage(
981     AnalysisUsage &AU) const {
982   AU.setPreservesAll();
983   AU.addRequired<StackSafetyInfoWrapperPass>();
984 }
985 
986 bool StackSafetyGlobalInfoWrapperPass::runOnModule(Module &M) {
987   const ModuleSummaryIndex *ImportSummary = nullptr;
988   if (auto *IndexWrapperPass =
989           getAnalysisIfAvailable<ImmutableModuleSummaryIndexWrapperPass>())
990     ImportSummary = IndexWrapperPass->getIndex();
991 
992   SSGI = {&M,
993           [this](Function &F) -> const StackSafetyInfo & {
994             return getAnalysis<StackSafetyInfoWrapperPass>(F).getResult();
995           },
996           ImportSummary};
997   return false;
998 }
999 
1000 bool llvm::needsParamAccessSummary(const Module &M) {
1001   if (StackSafetyRun)
1002     return true;
1003   for (auto &F : M.functions())
1004     if (F.hasFnAttribute(Attribute::SanitizeMemTag))
1005       return true;
1006   return false;
1007 }
1008 
1009 void llvm::generateParamAccessSummary(ModuleSummaryIndex &Index) {
1010   if (!Index.hasParamAccess())
1011     return;
1012   const ConstantRange FullSet(FunctionSummary::ParamAccess::RangeWidth, true);
1013 
1014   auto CountParamAccesses = [&](auto &Stat) {
1015     if (!AreStatisticsEnabled())
1016       return;
1017     for (auto &GVS : Index)
1018       for (auto &GV : GVS.second.SummaryList)
1019         if (FunctionSummary *FS = dyn_cast<FunctionSummary>(GV.get()))
1020           Stat += FS->paramAccesses().size();
1021   };
1022 
1023   CountParamAccesses(NumCombinedParamAccessesBefore);
1024 
1025   std::map<const FunctionSummary *, FunctionInfo<FunctionSummary>> Functions;
1026 
1027   // Convert the ModuleSummaryIndex to a FunctionMap
1028   for (auto &GVS : Index) {
1029     for (auto &GV : GVS.second.SummaryList) {
1030       FunctionSummary *FS = dyn_cast<FunctionSummary>(GV.get());
1031       if (!FS || FS->paramAccesses().empty())
1032         continue;
1033       if (FS->isLive() && FS->isDSOLocal()) {
1034         FunctionInfo<FunctionSummary> FI;
1035         for (auto &PS : FS->paramAccesses()) {
1036           auto &US =
1037               FI.Params
1038                   .emplace(PS.ParamNo, FunctionSummary::ParamAccess::RangeWidth)
1039                   .first->second;
1040           US.Range = PS.Use;
1041           for (auto &Call : PS.Calls) {
1042             assert(!Call.Offsets.isFullSet());
1043             FunctionSummary *S =
1044                 findCalleeFunctionSummary(Call.Callee, FS->modulePath());
1045             ++NumCombinedCalleeLookupTotal;
1046             if (!S) {
1047               ++NumCombinedCalleeLookupFailed;
1048               US.Range = FullSet;
1049               US.Calls.clear();
1050               break;
1051             }
1052             US.Calls.emplace(CallInfo<FunctionSummary>(S, Call.ParamNo),
1053                              Call.Offsets);
1054           }
1055         }
1056         Functions.emplace(FS, std::move(FI));
1057       }
1058       // Reset data for all summaries. Alive and DSO local will be set back from
1059       // of data flow results below. Anything else will not be accessed
1060       // by ThinLTO backend, so we can save on bitcode size.
1061       FS->setParamAccesses({});
1062     }
1063   }
1064   NumCombinedDataFlowNodes += Functions.size();
1065   StackSafetyDataFlowAnalysis<FunctionSummary> SSDFA(
1066       FunctionSummary::ParamAccess::RangeWidth, std::move(Functions));
1067   for (auto &KV : SSDFA.run()) {
1068     std::vector<FunctionSummary::ParamAccess> NewParams;
1069     NewParams.reserve(KV.second.Params.size());
1070     for (auto &Param : KV.second.Params) {
1071       // It's not needed as FullSet is processed the same as a missing value.
1072       if (Param.second.Range.isFullSet())
1073         continue;
1074       NewParams.emplace_back();
1075       FunctionSummary::ParamAccess &New = NewParams.back();
1076       New.ParamNo = Param.first;
1077       New.Use = Param.second.Range; // Only range is needed.
1078     }
1079     const_cast<FunctionSummary *>(KV.first)->setParamAccesses(
1080         std::move(NewParams));
1081   }
1082 
1083   CountParamAccesses(NumCombinedParamAccessesAfter);
1084 }
1085 
1086 static const char LocalPassArg[] = "stack-safety-local";
1087 static const char LocalPassName[] = "Stack Safety Local Analysis";
1088 INITIALIZE_PASS_BEGIN(StackSafetyInfoWrapperPass, LocalPassArg, LocalPassName,
1089                       false, true)
1090 INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass)
1091 INITIALIZE_PASS_END(StackSafetyInfoWrapperPass, LocalPassArg, LocalPassName,
1092                     false, true)
1093 
1094 static const char GlobalPassName[] = "Stack Safety Analysis";
1095 INITIALIZE_PASS_BEGIN(StackSafetyGlobalInfoWrapperPass, DEBUG_TYPE,
1096                       GlobalPassName, false, true)
1097 INITIALIZE_PASS_DEPENDENCY(StackSafetyInfoWrapperPass)
1098 INITIALIZE_PASS_DEPENDENCY(ImmutableModuleSummaryIndexWrapperPass)
1099 INITIALIZE_PASS_END(StackSafetyGlobalInfoWrapperPass, DEBUG_TYPE,
1100                     GlobalPassName, false, true)
1101