1 //===-- X86WinEHState - Insert EH state updates for win32 exceptions ------===//
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 // All functions using an MSVC EH personality use an explicitly updated state
10 // number stored in an exception registration stack object. The registration
11 // object is linked into a thread-local chain of registrations stored at fs:00.
12 // This pass adds the registration object and EH state updates.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #include "X86.h"
17 #include "llvm/ADT/PostOrderIterator.h"
18 #include "llvm/Analysis/CFG.h"
19 #include "llvm/Analysis/EHPersonalities.h"
20 #include "llvm/CodeGen/MachineModuleInfo.h"
21 #include "llvm/CodeGen/WinEHFuncInfo.h"
22 #include "llvm/IR/CallSite.h"
23 #include "llvm/IR/Function.h"
24 #include "llvm/IR/IRBuilder.h"
25 #include "llvm/IR/Instructions.h"
26 #include "llvm/IR/Intrinsics.h"
27 #include "llvm/IR/IntrinsicsX86.h"
28 #include "llvm/IR/Module.h"
29 #include "llvm/Pass.h"
30 #include "llvm/Support/Debug.h"
31 #include <deque>
32 
33 using namespace llvm;
34 
35 #define DEBUG_TYPE "winehstate"
36 
37 namespace {
38 const int OverdefinedState = INT_MIN;
39 
40 class WinEHStatePass : public FunctionPass {
41 public:
42   static char ID; // Pass identification, replacement for typeid.
43 
44   WinEHStatePass() : FunctionPass(ID) { }
45 
46   bool runOnFunction(Function &Fn) override;
47 
48   bool doInitialization(Module &M) override;
49 
50   bool doFinalization(Module &M) override;
51 
52   void getAnalysisUsage(AnalysisUsage &AU) const override;
53 
54   StringRef getPassName() const override {
55     return "Windows 32-bit x86 EH state insertion";
56   }
57 
58 private:
59   void emitExceptionRegistrationRecord(Function *F);
60 
61   void linkExceptionRegistration(IRBuilder<> &Builder, Function *Handler);
62   void unlinkExceptionRegistration(IRBuilder<> &Builder);
63   void addStateStores(Function &F, WinEHFuncInfo &FuncInfo);
64   void insertStateNumberStore(Instruction *IP, int State);
65 
66   Value *emitEHLSDA(IRBuilder<> &Builder, Function *F);
67 
68   Function *generateLSDAInEAXThunk(Function *ParentFunc);
69 
70   bool isStateStoreNeeded(EHPersonality Personality, CallSite CS);
71   void rewriteSetJmpCallSite(IRBuilder<> &Builder, Function &F, CallSite CS,
72                              Value *State);
73   int getBaseStateForBB(DenseMap<BasicBlock *, ColorVector> &BlockColors,
74                         WinEHFuncInfo &FuncInfo, BasicBlock *BB);
75   int getStateForCallSite(DenseMap<BasicBlock *, ColorVector> &BlockColors,
76                           WinEHFuncInfo &FuncInfo, CallSite CS);
77 
78   // Module-level type getters.
79   Type *getEHLinkRegistrationType();
80   Type *getSEHRegistrationType();
81   Type *getCXXEHRegistrationType();
82 
83   // Per-module data.
84   Module *TheModule = nullptr;
85   StructType *EHLinkRegistrationTy = nullptr;
86   StructType *CXXEHRegistrationTy = nullptr;
87   StructType *SEHRegistrationTy = nullptr;
88   FunctionCallee SetJmp3 = nullptr;
89   FunctionCallee CxxLongjmpUnwind = nullptr;
90 
91   // Per-function state
92   EHPersonality Personality = EHPersonality::Unknown;
93   Function *PersonalityFn = nullptr;
94   bool UseStackGuard = false;
95   int ParentBaseState = 0;
96   FunctionCallee SehLongjmpUnwind = nullptr;
97   Constant *Cookie = nullptr;
98 
99   /// The stack allocation containing all EH data, including the link in the
100   /// fs:00 chain and the current state.
101   AllocaInst *RegNode = nullptr;
102 
103   // The allocation containing the EH security guard.
104   AllocaInst *EHGuardNode = nullptr;
105 
106   /// The index of the state field of RegNode.
107   int StateFieldIndex = ~0U;
108 
109   /// The linked list node subobject inside of RegNode.
110   Value *Link = nullptr;
111 };
112 }
113 
114 FunctionPass *llvm::createX86WinEHStatePass() { return new WinEHStatePass(); }
115 
116 char WinEHStatePass::ID = 0;
117 
118 INITIALIZE_PASS(WinEHStatePass, "x86-winehstate",
119                 "Insert stores for EH state numbers", false, false)
120 
121 bool WinEHStatePass::doInitialization(Module &M) {
122   TheModule = &M;
123   return false;
124 }
125 
126 bool WinEHStatePass::doFinalization(Module &M) {
127   assert(TheModule == &M);
128   TheModule = nullptr;
129   EHLinkRegistrationTy = nullptr;
130   CXXEHRegistrationTy = nullptr;
131   SEHRegistrationTy = nullptr;
132   SetJmp3 = nullptr;
133   CxxLongjmpUnwind = nullptr;
134   SehLongjmpUnwind = nullptr;
135   Cookie = nullptr;
136   return false;
137 }
138 
139 void WinEHStatePass::getAnalysisUsage(AnalysisUsage &AU) const {
140   // This pass should only insert a stack allocation, memory accesses, and
141   // localrecovers.
142   AU.setPreservesCFG();
143 }
144 
145 bool WinEHStatePass::runOnFunction(Function &F) {
146   // Don't insert state stores or exception handler thunks for
147   // available_externally functions. The handler needs to reference the LSDA,
148   // which will not be emitted in this case.
149   if (F.hasAvailableExternallyLinkage())
150     return false;
151 
152   // Check the personality. Do nothing if this personality doesn't use funclets.
153   if (!F.hasPersonalityFn())
154     return false;
155   PersonalityFn =
156       dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts());
157   if (!PersonalityFn)
158     return false;
159   Personality = classifyEHPersonality(PersonalityFn);
160   if (!isFuncletEHPersonality(Personality))
161     return false;
162 
163   // Skip this function if there are no EH pads and we aren't using IR-level
164   // outlining.
165   bool HasPads = false;
166   for (BasicBlock &BB : F) {
167     if (BB.isEHPad()) {
168       HasPads = true;
169       break;
170     }
171   }
172   if (!HasPads)
173     return false;
174 
175   Type *Int8PtrType = Type::getInt8PtrTy(TheModule->getContext());
176   SetJmp3 = TheModule->getOrInsertFunction(
177       "_setjmp3", FunctionType::get(
178                       Type::getInt32Ty(TheModule->getContext()),
179                       {Int8PtrType, Type::getInt32Ty(TheModule->getContext())},
180                       /*isVarArg=*/true));
181 
182   emitExceptionRegistrationRecord(&F);
183 
184   // The state numbers calculated here in IR must agree with what we calculate
185   // later on for the MachineFunction. In particular, if an IR pass deletes an
186   // unreachable EH pad after this point before machine CFG construction, we
187   // will be in trouble. If this assumption is ever broken, we should turn the
188   // numbers into an immutable analysis pass.
189   WinEHFuncInfo FuncInfo;
190   addStateStores(F, FuncInfo);
191 
192   // Reset per-function state.
193   PersonalityFn = nullptr;
194   Personality = EHPersonality::Unknown;
195   UseStackGuard = false;
196   RegNode = nullptr;
197   EHGuardNode = nullptr;
198 
199   return true;
200 }
201 
202 /// Get the common EH registration subobject:
203 ///   typedef _EXCEPTION_DISPOSITION (*PEXCEPTION_ROUTINE)(
204 ///       _EXCEPTION_RECORD *, void *, _CONTEXT *, void *);
205 ///   struct EHRegistrationNode {
206 ///     EHRegistrationNode *Next;
207 ///     PEXCEPTION_ROUTINE Handler;
208 ///   };
209 Type *WinEHStatePass::getEHLinkRegistrationType() {
210   if (EHLinkRegistrationTy)
211     return EHLinkRegistrationTy;
212   LLVMContext &Context = TheModule->getContext();
213   EHLinkRegistrationTy = StructType::create(Context, "EHRegistrationNode");
214   Type *FieldTys[] = {
215       EHLinkRegistrationTy->getPointerTo(0), // EHRegistrationNode *Next
216       Type::getInt8PtrTy(Context) // EXCEPTION_DISPOSITION (*Handler)(...)
217   };
218   EHLinkRegistrationTy->setBody(FieldTys, false);
219   return EHLinkRegistrationTy;
220 }
221 
222 /// The __CxxFrameHandler3 registration node:
223 ///   struct CXXExceptionRegistration {
224 ///     void *SavedESP;
225 ///     EHRegistrationNode SubRecord;
226 ///     int32_t TryLevel;
227 ///   };
228 Type *WinEHStatePass::getCXXEHRegistrationType() {
229   if (CXXEHRegistrationTy)
230     return CXXEHRegistrationTy;
231   LLVMContext &Context = TheModule->getContext();
232   Type *FieldTys[] = {
233       Type::getInt8PtrTy(Context), // void *SavedESP
234       getEHLinkRegistrationType(), // EHRegistrationNode SubRecord
235       Type::getInt32Ty(Context)    // int32_t TryLevel
236   };
237   CXXEHRegistrationTy =
238       StructType::create(FieldTys, "CXXExceptionRegistration");
239   return CXXEHRegistrationTy;
240 }
241 
242 /// The _except_handler3/4 registration node:
243 ///   struct EH4ExceptionRegistration {
244 ///     void *SavedESP;
245 ///     _EXCEPTION_POINTERS *ExceptionPointers;
246 ///     EHRegistrationNode SubRecord;
247 ///     int32_t EncodedScopeTable;
248 ///     int32_t TryLevel;
249 ///   };
250 Type *WinEHStatePass::getSEHRegistrationType() {
251   if (SEHRegistrationTy)
252     return SEHRegistrationTy;
253   LLVMContext &Context = TheModule->getContext();
254   Type *FieldTys[] = {
255       Type::getInt8PtrTy(Context), // void *SavedESP
256       Type::getInt8PtrTy(Context), // void *ExceptionPointers
257       getEHLinkRegistrationType(), // EHRegistrationNode SubRecord
258       Type::getInt32Ty(Context),   // int32_t EncodedScopeTable
259       Type::getInt32Ty(Context)    // int32_t TryLevel
260   };
261   SEHRegistrationTy = StructType::create(FieldTys, "SEHExceptionRegistration");
262   return SEHRegistrationTy;
263 }
264 
265 // Emit an exception registration record. These are stack allocations with the
266 // common subobject of two pointers: the previous registration record (the old
267 // fs:00) and the personality function for the current frame. The data before
268 // and after that is personality function specific.
269 void WinEHStatePass::emitExceptionRegistrationRecord(Function *F) {
270   assert(Personality == EHPersonality::MSVC_CXX ||
271          Personality == EHPersonality::MSVC_X86SEH);
272 
273   // Struct type of RegNode. Used for GEPing.
274   Type *RegNodeTy;
275 
276   IRBuilder<> Builder(&F->getEntryBlock(), F->getEntryBlock().begin());
277   Type *Int8PtrType = Builder.getInt8PtrTy();
278   Type *Int32Ty = Builder.getInt32Ty();
279   Type *VoidTy = Builder.getVoidTy();
280 
281   if (Personality == EHPersonality::MSVC_CXX) {
282     RegNodeTy = getCXXEHRegistrationType();
283     RegNode = Builder.CreateAlloca(RegNodeTy);
284     // SavedESP = llvm.stacksave()
285     Value *SP = Builder.CreateCall(
286         Intrinsic::getDeclaration(TheModule, Intrinsic::stacksave), {});
287     Builder.CreateStore(SP, Builder.CreateStructGEP(RegNodeTy, RegNode, 0));
288     // TryLevel = -1
289     StateFieldIndex = 2;
290     ParentBaseState = -1;
291     insertStateNumberStore(&*Builder.GetInsertPoint(), ParentBaseState);
292     // Handler = __ehhandler$F
293     Function *Trampoline = generateLSDAInEAXThunk(F);
294     Link = Builder.CreateStructGEP(RegNodeTy, RegNode, 1);
295     linkExceptionRegistration(Builder, Trampoline);
296 
297     CxxLongjmpUnwind = TheModule->getOrInsertFunction(
298         "__CxxLongjmpUnwind",
299         FunctionType::get(VoidTy, Int8PtrType, /*isVarArg=*/false));
300     cast<Function>(CxxLongjmpUnwind.getCallee()->stripPointerCasts())
301         ->setCallingConv(CallingConv::X86_StdCall);
302   } else if (Personality == EHPersonality::MSVC_X86SEH) {
303     // If _except_handler4 is in use, some additional guard checks and prologue
304     // stuff is required.
305     StringRef PersonalityName = PersonalityFn->getName();
306     UseStackGuard = (PersonalityName == "_except_handler4");
307 
308     // Allocate local structures.
309     RegNodeTy = getSEHRegistrationType();
310     RegNode = Builder.CreateAlloca(RegNodeTy);
311     if (UseStackGuard)
312       EHGuardNode = Builder.CreateAlloca(Int32Ty);
313 
314     // SavedESP = llvm.stacksave()
315     Value *SP = Builder.CreateCall(
316         Intrinsic::getDeclaration(TheModule, Intrinsic::stacksave), {});
317     Builder.CreateStore(SP, Builder.CreateStructGEP(RegNodeTy, RegNode, 0));
318     // TryLevel = -2 / -1
319     StateFieldIndex = 4;
320     ParentBaseState = UseStackGuard ? -2 : -1;
321     insertStateNumberStore(&*Builder.GetInsertPoint(), ParentBaseState);
322     // ScopeTable = llvm.x86.seh.lsda(F)
323     Value *LSDA = emitEHLSDA(Builder, F);
324     LSDA = Builder.CreatePtrToInt(LSDA, Int32Ty);
325     // If using _except_handler4, xor the address of the table with
326     // __security_cookie.
327     if (UseStackGuard) {
328       Cookie = TheModule->getOrInsertGlobal("__security_cookie", Int32Ty);
329       Value *Val = Builder.CreateLoad(Int32Ty, Cookie, "cookie");
330       LSDA = Builder.CreateXor(LSDA, Val);
331     }
332     Builder.CreateStore(LSDA, Builder.CreateStructGEP(RegNodeTy, RegNode, 3));
333 
334     // If using _except_handler4, the EHGuard contains: FramePtr xor Cookie.
335     if (UseStackGuard) {
336       Value *Val = Builder.CreateLoad(Int32Ty, Cookie);
337       Value *FrameAddr = Builder.CreateCall(
338           Intrinsic::getDeclaration(
339               TheModule, Intrinsic::frameaddress,
340               Builder.getInt8PtrTy(
341                   TheModule->getDataLayout().getAllocaAddrSpace())),
342           Builder.getInt32(0), "frameaddr");
343       Value *FrameAddrI32 = Builder.CreatePtrToInt(FrameAddr, Int32Ty);
344       FrameAddrI32 = Builder.CreateXor(FrameAddrI32, Val);
345       Builder.CreateStore(FrameAddrI32, EHGuardNode);
346     }
347 
348     // Register the exception handler.
349     Link = Builder.CreateStructGEP(RegNodeTy, RegNode, 2);
350     linkExceptionRegistration(Builder, PersonalityFn);
351 
352     SehLongjmpUnwind = TheModule->getOrInsertFunction(
353         UseStackGuard ? "_seh_longjmp_unwind4" : "_seh_longjmp_unwind",
354         FunctionType::get(Type::getVoidTy(TheModule->getContext()), Int8PtrType,
355                           /*isVarArg=*/false));
356     cast<Function>(SehLongjmpUnwind.getCallee()->stripPointerCasts())
357         ->setCallingConv(CallingConv::X86_StdCall);
358   } else {
359     llvm_unreachable("unexpected personality function");
360   }
361 
362   // Insert an unlink before all returns.
363   for (BasicBlock &BB : *F) {
364     Instruction *T = BB.getTerminator();
365     if (!isa<ReturnInst>(T))
366       continue;
367     Builder.SetInsertPoint(T);
368     unlinkExceptionRegistration(Builder);
369   }
370 }
371 
372 Value *WinEHStatePass::emitEHLSDA(IRBuilder<> &Builder, Function *F) {
373   Value *FI8 = Builder.CreateBitCast(F, Type::getInt8PtrTy(F->getContext()));
374   return Builder.CreateCall(
375       Intrinsic::getDeclaration(TheModule, Intrinsic::x86_seh_lsda), FI8);
376 }
377 
378 /// Generate a thunk that puts the LSDA of ParentFunc in EAX and then calls
379 /// PersonalityFn, forwarding the parameters passed to PEXCEPTION_ROUTINE:
380 ///   typedef _EXCEPTION_DISPOSITION (*PEXCEPTION_ROUTINE)(
381 ///       _EXCEPTION_RECORD *, void *, _CONTEXT *, void *);
382 /// We essentially want this code:
383 ///   movl $lsda, %eax
384 ///   jmpl ___CxxFrameHandler3
385 Function *WinEHStatePass::generateLSDAInEAXThunk(Function *ParentFunc) {
386   LLVMContext &Context = ParentFunc->getContext();
387   Type *Int32Ty = Type::getInt32Ty(Context);
388   Type *Int8PtrType = Type::getInt8PtrTy(Context);
389   Type *ArgTys[5] = {Int8PtrType, Int8PtrType, Int8PtrType, Int8PtrType,
390                      Int8PtrType};
391   FunctionType *TrampolineTy =
392       FunctionType::get(Int32Ty, makeArrayRef(&ArgTys[0], 4),
393                         /*isVarArg=*/false);
394   FunctionType *TargetFuncTy =
395       FunctionType::get(Int32Ty, makeArrayRef(&ArgTys[0], 5),
396                         /*isVarArg=*/false);
397   Function *Trampoline =
398       Function::Create(TrampolineTy, GlobalValue::InternalLinkage,
399                        Twine("__ehhandler$") + GlobalValue::dropLLVMManglingEscape(
400                                                    ParentFunc->getName()),
401                        TheModule);
402   if (auto *C = ParentFunc->getComdat())
403     Trampoline->setComdat(C);
404   BasicBlock *EntryBB = BasicBlock::Create(Context, "entry", Trampoline);
405   IRBuilder<> Builder(EntryBB);
406   Value *LSDA = emitEHLSDA(Builder, ParentFunc);
407   Value *CastPersonality =
408       Builder.CreateBitCast(PersonalityFn, TargetFuncTy->getPointerTo());
409   auto AI = Trampoline->arg_begin();
410   Value *Args[5] = {LSDA, &*AI++, &*AI++, &*AI++, &*AI++};
411   CallInst *Call = Builder.CreateCall(TargetFuncTy, CastPersonality, Args);
412   // Can't use musttail due to prototype mismatch, but we can use tail.
413   Call->setTailCall(true);
414   // Set inreg so we pass it in EAX.
415   Call->addParamAttr(0, Attribute::InReg);
416   Builder.CreateRet(Call);
417   return Trampoline;
418 }
419 
420 void WinEHStatePass::linkExceptionRegistration(IRBuilder<> &Builder,
421                                                Function *Handler) {
422   // Emit the .safeseh directive for this function.
423   Handler->addFnAttr("safeseh");
424 
425   Type *LinkTy = getEHLinkRegistrationType();
426   // Handler = Handler
427   Value *HandlerI8 = Builder.CreateBitCast(Handler, Builder.getInt8PtrTy());
428   Builder.CreateStore(HandlerI8, Builder.CreateStructGEP(LinkTy, Link, 1));
429   // Next = [fs:00]
430   Constant *FSZero =
431       Constant::getNullValue(LinkTy->getPointerTo()->getPointerTo(257));
432   Value *Next = Builder.CreateLoad(LinkTy->getPointerTo(), FSZero);
433   Builder.CreateStore(Next, Builder.CreateStructGEP(LinkTy, Link, 0));
434   // [fs:00] = Link
435   Builder.CreateStore(Link, FSZero);
436 }
437 
438 void WinEHStatePass::unlinkExceptionRegistration(IRBuilder<> &Builder) {
439   // Clone Link into the current BB for better address mode folding.
440   if (auto *GEP = dyn_cast<GetElementPtrInst>(Link)) {
441     GEP = cast<GetElementPtrInst>(GEP->clone());
442     Builder.Insert(GEP);
443     Link = GEP;
444   }
445   Type *LinkTy = getEHLinkRegistrationType();
446   // [fs:00] = Link->Next
447   Value *Next = Builder.CreateLoad(LinkTy->getPointerTo(),
448                                    Builder.CreateStructGEP(LinkTy, Link, 0));
449   Constant *FSZero =
450       Constant::getNullValue(LinkTy->getPointerTo()->getPointerTo(257));
451   Builder.CreateStore(Next, FSZero);
452 }
453 
454 // Calls to setjmp(p) are lowered to _setjmp3(p, 0) by the frontend.
455 // The idea behind _setjmp3 is that it takes an optional number of personality
456 // specific parameters to indicate how to restore the personality-specific frame
457 // state when longjmp is initiated.  Typically, the current TryLevel is saved.
458 void WinEHStatePass::rewriteSetJmpCallSite(IRBuilder<> &Builder, Function &F,
459                                            CallSite CS, Value *State) {
460   // Don't rewrite calls with a weird number of arguments.
461   if (CS.getNumArgOperands() != 2)
462     return;
463 
464   Instruction *Inst = CS.getInstruction();
465 
466   SmallVector<OperandBundleDef, 1> OpBundles;
467   CS.getOperandBundlesAsDefs(OpBundles);
468 
469   SmallVector<Value *, 3> OptionalArgs;
470   if (Personality == EHPersonality::MSVC_CXX) {
471     OptionalArgs.push_back(CxxLongjmpUnwind.getCallee());
472     OptionalArgs.push_back(State);
473     OptionalArgs.push_back(emitEHLSDA(Builder, &F));
474   } else if (Personality == EHPersonality::MSVC_X86SEH) {
475     OptionalArgs.push_back(SehLongjmpUnwind.getCallee());
476     OptionalArgs.push_back(State);
477     if (UseStackGuard)
478       OptionalArgs.push_back(Cookie);
479   } else {
480     llvm_unreachable("unhandled personality!");
481   }
482 
483   SmallVector<Value *, 5> Args;
484   Args.push_back(
485       Builder.CreateBitCast(CS.getArgOperand(0), Builder.getInt8PtrTy()));
486   Args.push_back(Builder.getInt32(OptionalArgs.size()));
487   Args.append(OptionalArgs.begin(), OptionalArgs.end());
488 
489   CallSite NewCS;
490   if (CS.isCall()) {
491     auto *CI = cast<CallInst>(Inst);
492     CallInst *NewCI = Builder.CreateCall(SetJmp3, Args, OpBundles);
493     NewCI->setTailCallKind(CI->getTailCallKind());
494     NewCS = NewCI;
495   } else {
496     auto *II = cast<InvokeInst>(Inst);
497     NewCS = Builder.CreateInvoke(
498         SetJmp3, II->getNormalDest(), II->getUnwindDest(), Args, OpBundles);
499   }
500   NewCS.setCallingConv(CS.getCallingConv());
501   NewCS.setAttributes(CS.getAttributes());
502   NewCS->setDebugLoc(CS->getDebugLoc());
503 
504   Instruction *NewInst = NewCS.getInstruction();
505   NewInst->takeName(Inst);
506   Inst->replaceAllUsesWith(NewInst);
507   Inst->eraseFromParent();
508 }
509 
510 // Figure out what state we should assign calls in this block.
511 int WinEHStatePass::getBaseStateForBB(
512     DenseMap<BasicBlock *, ColorVector> &BlockColors, WinEHFuncInfo &FuncInfo,
513     BasicBlock *BB) {
514   int BaseState = ParentBaseState;
515   auto &BBColors = BlockColors[BB];
516 
517   assert(BBColors.size() == 1 && "multi-color BB not removed by preparation");
518   BasicBlock *FuncletEntryBB = BBColors.front();
519   if (auto *FuncletPad =
520           dyn_cast<FuncletPadInst>(FuncletEntryBB->getFirstNonPHI())) {
521     auto BaseStateI = FuncInfo.FuncletBaseStateMap.find(FuncletPad);
522     if (BaseStateI != FuncInfo.FuncletBaseStateMap.end())
523       BaseState = BaseStateI->second;
524   }
525 
526   return BaseState;
527 }
528 
529 // Calculate the state a call-site is in.
530 int WinEHStatePass::getStateForCallSite(
531     DenseMap<BasicBlock *, ColorVector> &BlockColors, WinEHFuncInfo &FuncInfo,
532     CallSite CS) {
533   if (auto *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
534     // Look up the state number of the EH pad this unwinds to.
535     assert(FuncInfo.InvokeStateMap.count(II) && "invoke has no state!");
536     return FuncInfo.InvokeStateMap[II];
537   }
538   // Possibly throwing call instructions have no actions to take after
539   // an unwind. Ensure they are in the -1 state.
540   return getBaseStateForBB(BlockColors, FuncInfo, CS.getParent());
541 }
542 
543 // Calculate the intersection of all the FinalStates for a BasicBlock's
544 // predecessors.
545 static int getPredState(DenseMap<BasicBlock *, int> &FinalStates, Function &F,
546                         int ParentBaseState, BasicBlock *BB) {
547   // The entry block has no predecessors but we know that the prologue always
548   // sets us up with a fixed state.
549   if (&F.getEntryBlock() == BB)
550     return ParentBaseState;
551 
552   // This is an EH Pad, conservatively report this basic block as overdefined.
553   if (BB->isEHPad())
554     return OverdefinedState;
555 
556   int CommonState = OverdefinedState;
557   for (BasicBlock *PredBB : predecessors(BB)) {
558     // We didn't manage to get a state for one of these predecessors,
559     // conservatively report this basic block as overdefined.
560     auto PredEndState = FinalStates.find(PredBB);
561     if (PredEndState == FinalStates.end())
562       return OverdefinedState;
563 
564     // This code is reachable via exceptional control flow,
565     // conservatively report this basic block as overdefined.
566     if (isa<CatchReturnInst>(PredBB->getTerminator()))
567       return OverdefinedState;
568 
569     int PredState = PredEndState->second;
570     assert(PredState != OverdefinedState &&
571            "overdefined BBs shouldn't be in FinalStates");
572     if (CommonState == OverdefinedState)
573       CommonState = PredState;
574 
575     // At least two predecessors have different FinalStates,
576     // conservatively report this basic block as overdefined.
577     if (CommonState != PredState)
578       return OverdefinedState;
579   }
580 
581   return CommonState;
582 }
583 
584 // Calculate the intersection of all the InitialStates for a BasicBlock's
585 // successors.
586 static int getSuccState(DenseMap<BasicBlock *, int> &InitialStates, Function &F,
587                         int ParentBaseState, BasicBlock *BB) {
588   // This block rejoins normal control flow,
589   // conservatively report this basic block as overdefined.
590   if (isa<CatchReturnInst>(BB->getTerminator()))
591     return OverdefinedState;
592 
593   int CommonState = OverdefinedState;
594   for (BasicBlock *SuccBB : successors(BB)) {
595     // We didn't manage to get a state for one of these predecessors,
596     // conservatively report this basic block as overdefined.
597     auto SuccStartState = InitialStates.find(SuccBB);
598     if (SuccStartState == InitialStates.end())
599       return OverdefinedState;
600 
601     // This is an EH Pad, conservatively report this basic block as overdefined.
602     if (SuccBB->isEHPad())
603       return OverdefinedState;
604 
605     int SuccState = SuccStartState->second;
606     assert(SuccState != OverdefinedState &&
607            "overdefined BBs shouldn't be in FinalStates");
608     if (CommonState == OverdefinedState)
609       CommonState = SuccState;
610 
611     // At least two successors have different InitialStates,
612     // conservatively report this basic block as overdefined.
613     if (CommonState != SuccState)
614       return OverdefinedState;
615   }
616 
617   return CommonState;
618 }
619 
620 bool WinEHStatePass::isStateStoreNeeded(EHPersonality Personality,
621                                         CallSite CS) {
622   if (!CS)
623     return false;
624 
625   // If the function touches memory, it needs a state store.
626   if (isAsynchronousEHPersonality(Personality))
627     return !CS.doesNotAccessMemory();
628 
629   // If the function throws, it needs a state store.
630   return !CS.doesNotThrow();
631 }
632 
633 void WinEHStatePass::addStateStores(Function &F, WinEHFuncInfo &FuncInfo) {
634   // Mark the registration node. The backend needs to know which alloca it is so
635   // that it can recover the original frame pointer.
636   IRBuilder<> Builder(RegNode->getNextNode());
637   Value *RegNodeI8 = Builder.CreateBitCast(RegNode, Builder.getInt8PtrTy());
638   Builder.CreateCall(
639       Intrinsic::getDeclaration(TheModule, Intrinsic::x86_seh_ehregnode),
640       {RegNodeI8});
641 
642   if (EHGuardNode) {
643     IRBuilder<> Builder(EHGuardNode->getNextNode());
644     Value *EHGuardNodeI8 =
645         Builder.CreateBitCast(EHGuardNode, Builder.getInt8PtrTy());
646     Builder.CreateCall(
647         Intrinsic::getDeclaration(TheModule, Intrinsic::x86_seh_ehguard),
648         {EHGuardNodeI8});
649   }
650 
651   // Calculate state numbers.
652   if (isAsynchronousEHPersonality(Personality))
653     calculateSEHStateNumbers(&F, FuncInfo);
654   else
655     calculateWinCXXEHStateNumbers(&F, FuncInfo);
656 
657   // Iterate all the instructions and emit state number stores.
658   DenseMap<BasicBlock *, ColorVector> BlockColors = colorEHFunclets(F);
659   ReversePostOrderTraversal<Function *> RPOT(&F);
660 
661   // InitialStates yields the state of the first call-site for a BasicBlock.
662   DenseMap<BasicBlock *, int> InitialStates;
663   // FinalStates yields the state of the last call-site for a BasicBlock.
664   DenseMap<BasicBlock *, int> FinalStates;
665   // Worklist used to revisit BasicBlocks with indeterminate
666   // Initial/Final-States.
667   std::deque<BasicBlock *> Worklist;
668   // Fill in InitialStates and FinalStates for BasicBlocks with call-sites.
669   for (BasicBlock *BB : RPOT) {
670     int InitialState = OverdefinedState;
671     int FinalState;
672     if (&F.getEntryBlock() == BB)
673       InitialState = FinalState = ParentBaseState;
674     for (Instruction &I : *BB) {
675       CallSite CS(&I);
676       if (!isStateStoreNeeded(Personality, CS))
677         continue;
678 
679       int State = getStateForCallSite(BlockColors, FuncInfo, CS);
680       if (InitialState == OverdefinedState)
681         InitialState = State;
682       FinalState = State;
683     }
684     // No call-sites in this basic block? That's OK, we will come back to these
685     // in a later pass.
686     if (InitialState == OverdefinedState) {
687       Worklist.push_back(BB);
688       continue;
689     }
690     LLVM_DEBUG(dbgs() << "X86WinEHState: " << BB->getName()
691                       << " InitialState=" << InitialState << '\n');
692     LLVM_DEBUG(dbgs() << "X86WinEHState: " << BB->getName()
693                       << " FinalState=" << FinalState << '\n');
694     InitialStates.insert({BB, InitialState});
695     FinalStates.insert({BB, FinalState});
696   }
697 
698   // Try to fill-in InitialStates and FinalStates which have no call-sites.
699   while (!Worklist.empty()) {
700     BasicBlock *BB = Worklist.front();
701     Worklist.pop_front();
702     // This BasicBlock has already been figured out, nothing more we can do.
703     if (InitialStates.count(BB) != 0)
704       continue;
705 
706     int PredState = getPredState(FinalStates, F, ParentBaseState, BB);
707     if (PredState == OverdefinedState)
708       continue;
709 
710     // We successfully inferred this BasicBlock's state via it's predecessors;
711     // enqueue it's successors to see if we can infer their states.
712     InitialStates.insert({BB, PredState});
713     FinalStates.insert({BB, PredState});
714     for (BasicBlock *SuccBB : successors(BB))
715       Worklist.push_back(SuccBB);
716   }
717 
718   // Try to hoist stores from successors.
719   for (BasicBlock *BB : RPOT) {
720     int SuccState = getSuccState(InitialStates, F, ParentBaseState, BB);
721     if (SuccState == OverdefinedState)
722       continue;
723 
724     // Update our FinalState to reflect the common InitialState of our
725     // successors.
726     FinalStates.insert({BB, SuccState});
727   }
728 
729   // Finally, insert state stores before call-sites which transition us to a new
730   // state.
731   for (BasicBlock *BB : RPOT) {
732     auto &BBColors = BlockColors[BB];
733     BasicBlock *FuncletEntryBB = BBColors.front();
734     if (isa<CleanupPadInst>(FuncletEntryBB->getFirstNonPHI()))
735       continue;
736 
737     int PrevState = getPredState(FinalStates, F, ParentBaseState, BB);
738     LLVM_DEBUG(dbgs() << "X86WinEHState: " << BB->getName()
739                       << " PrevState=" << PrevState << '\n');
740 
741     for (Instruction &I : *BB) {
742       CallSite CS(&I);
743       if (!isStateStoreNeeded(Personality, CS))
744         continue;
745 
746       int State = getStateForCallSite(BlockColors, FuncInfo, CS);
747       if (State != PrevState)
748         insertStateNumberStore(&I, State);
749       PrevState = State;
750     }
751 
752     // We might have hoisted a state store into this block, emit it now.
753     auto EndState = FinalStates.find(BB);
754     if (EndState != FinalStates.end())
755       if (EndState->second != PrevState)
756         insertStateNumberStore(BB->getTerminator(), EndState->second);
757   }
758 
759   SmallVector<CallSite, 1> SetJmp3CallSites;
760   for (BasicBlock *BB : RPOT) {
761     for (Instruction &I : *BB) {
762       CallSite CS(&I);
763       if (!CS)
764         continue;
765       if (CS.getCalledValue()->stripPointerCasts() !=
766           SetJmp3.getCallee()->stripPointerCasts())
767         continue;
768 
769       SetJmp3CallSites.push_back(CS);
770     }
771   }
772 
773   for (CallSite CS : SetJmp3CallSites) {
774     auto &BBColors = BlockColors[CS->getParent()];
775     BasicBlock *FuncletEntryBB = BBColors.front();
776     bool InCleanup = isa<CleanupPadInst>(FuncletEntryBB->getFirstNonPHI());
777 
778     IRBuilder<> Builder(CS.getInstruction());
779     Value *State;
780     if (InCleanup) {
781       Value *StateField = Builder.CreateStructGEP(RegNode->getAllocatedType(),
782                                                   RegNode, StateFieldIndex);
783       State = Builder.CreateLoad(Builder.getInt32Ty(), StateField);
784     } else {
785       State = Builder.getInt32(getStateForCallSite(BlockColors, FuncInfo, CS));
786     }
787     rewriteSetJmpCallSite(Builder, F, CS, State);
788   }
789 }
790 
791 void WinEHStatePass::insertStateNumberStore(Instruction *IP, int State) {
792   IRBuilder<> Builder(IP);
793   Value *StateField = Builder.CreateStructGEP(RegNode->getAllocatedType(),
794                                               RegNode, StateFieldIndex);
795   Builder.CreateStore(Builder.getInt32(State), StateField);
796 }
797