llvm/lib/Target/X86/X86WinEHState.cpp

   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/CFG.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, CallBase &Call);
  71   void rewriteSetJmpCall(IRBuilder<> &Builder, Function &F, CallBase &Call,
  72                          Value *State);
  73   int getBaseStateForBB(DenseMap<BasicBlock *, ColorVector> &BlockColors,
  74                         WinEHFuncInfo &FuncInfo, BasicBlock *BB);
  75   int getStateForCall(DenseMap<BasicBlock *, ColorVector> &BlockColors,
  76                       WinEHFuncInfo &FuncInfo, CallBase &Call);
  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 } // namespace
 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::rewriteSetJmpCall(IRBuilder<> &Builder, Function &F,
 459                                        CallBase &Call, Value *State) {
 460   // Don't rewrite calls with a weird number of arguments.
 461   if (Call.getNumArgOperands() != 2)
 462     return;
 463
 464   SmallVector<OperandBundleDef, 1> OpBundles;
 465   Call.getOperandBundlesAsDefs(OpBundles);
 466
 467   SmallVector<Value *, 3> OptionalArgs;
 468   if (Personality == EHPersonality::MSVC_CXX) {
 469     OptionalArgs.push_back(CxxLongjmpUnwind.getCallee());
 470     OptionalArgs.push_back(State);
 471     OptionalArgs.push_back(emitEHLSDA(Builder, &F));
 472   } else if (Personality == EHPersonality::MSVC_X86SEH) {
 473     OptionalArgs.push_back(SehLongjmpUnwind.getCallee());
 474     OptionalArgs.push_back(State);
 475     if (UseStackGuard)
 476       OptionalArgs.push_back(Cookie);
 477   } else {
 478     llvm_unreachable("unhandled personality!");
 479   }
 480
 481   SmallVector<Value *, 5> Args;
 482   Args.push_back(
 483       Builder.CreateBitCast(Call.getArgOperand(0), Builder.getInt8PtrTy()));
 484   Args.push_back(Builder.getInt32(OptionalArgs.size()));
 485   Args.append(OptionalArgs.begin(), OptionalArgs.end());
 486
 487   CallBase *NewCall;
 488   if (auto *CI = dyn_cast<CallInst>(&Call)) {
 489     CallInst *NewCI = Builder.CreateCall(SetJmp3, Args, OpBundles);
 490     NewCI->setTailCallKind(CI->getTailCallKind());
 491     NewCall = NewCI;
 492   } else {
 493     auto *II = cast<InvokeInst>(&Call);
 494     NewCall = Builder.CreateInvoke(
 495         SetJmp3, II->getNormalDest(), II->getUnwindDest(), Args, OpBundles);
 496   }
 497   NewCall->setCallingConv(Call.getCallingConv());
 498   NewCall->setAttributes(Call.getAttributes());
 499   NewCall->setDebugLoc(Call.getDebugLoc());
 500
 501   NewCall->takeName(&Call);
 502   Call.replaceAllUsesWith(NewCall);
 503   Call.eraseFromParent();
 504 }
 505
 506 // Figure out what state we should assign calls in this block.
 507 int WinEHStatePass::getBaseStateForBB(
 508     DenseMap<BasicBlock *, ColorVector> &BlockColors, WinEHFuncInfo &FuncInfo,
 509     BasicBlock *BB) {
 510   int BaseState = ParentBaseState;
 511   auto &BBColors = BlockColors[BB];
 512
 513   assert(BBColors.size() == 1 && "multi-color BB not removed by preparation");
 514   BasicBlock *FuncletEntryBB = BBColors.front();
 515   if (auto *FuncletPad =
 516           dyn_cast<FuncletPadInst>(FuncletEntryBB->getFirstNonPHI())) {
 517     auto BaseStateI = FuncInfo.FuncletBaseStateMap.find(FuncletPad);
 518     if (BaseStateI != FuncInfo.FuncletBaseStateMap.end())
 519       BaseState = BaseStateI->second;
 520   }
 521
 522   return BaseState;
 523 }
 524
 525 // Calculate the state a call-site is in.
 526 int WinEHStatePass::getStateForCall(
 527     DenseMap<BasicBlock *, ColorVector> &BlockColors, WinEHFuncInfo &FuncInfo,
 528     CallBase &Call) {
 529   if (auto *II = dyn_cast<InvokeInst>(&Call)) {
 530     // Look up the state number of the EH pad this unwinds to.
 531     assert(FuncInfo.InvokeStateMap.count(II) && "invoke has no state!");
 532     return FuncInfo.InvokeStateMap[II];
 533   }
 534   // Possibly throwing call instructions have no actions to take after
 535   // an unwind. Ensure they are in the -1 state.
 536   return getBaseStateForBB(BlockColors, FuncInfo, Call.getParent());
 537 }
 538
 539 // Calculate the intersection of all the FinalStates for a BasicBlock's
 540 // predecessors.
 541 static int getPredState(DenseMap<BasicBlock *, int> &FinalStates, Function &F,
 542                         int ParentBaseState, BasicBlock *BB) {
 543   // The entry block has no predecessors but we know that the prologue always
 544   // sets us up with a fixed state.
 545   if (&F.getEntryBlock() == BB)
 546     return ParentBaseState;
 547
 548   // This is an EH Pad, conservatively report this basic block as overdefined.
 549   if (BB->isEHPad())
 550     return OverdefinedState;
 551
 552   int CommonState = OverdefinedState;
 553   for (BasicBlock *PredBB : predecessors(BB)) {
 554     // We didn't manage to get a state for one of these predecessors,
 555     // conservatively report this basic block as overdefined.
 556     auto PredEndState = FinalStates.find(PredBB);
 557     if (PredEndState == FinalStates.end())
 558       return OverdefinedState;
 559
 560     // This code is reachable via exceptional control flow,
 561     // conservatively report this basic block as overdefined.
 562     if (isa<CatchReturnInst>(PredBB->getTerminator()))
 563       return OverdefinedState;
 564
 565     int PredState = PredEndState->second;
 566     assert(PredState != OverdefinedState &&
 567            "overdefined BBs shouldn't be in FinalStates");
 568     if (CommonState == OverdefinedState)
 569       CommonState = PredState;
 570
 571     // At least two predecessors have different FinalStates,
 572     // conservatively report this basic block as overdefined.
 573     if (CommonState != PredState)
 574       return OverdefinedState;
 575   }
 576
 577   return CommonState;
 578 }
 579
 580 // Calculate the intersection of all the InitialStates for a BasicBlock's
 581 // successors.
 582 static int getSuccState(DenseMap<BasicBlock *, int> &InitialStates, Function &F,
 583                         int ParentBaseState, BasicBlock *BB) {
 584   // This block rejoins normal control flow,
 585   // conservatively report this basic block as overdefined.
 586   if (isa<CatchReturnInst>(BB->getTerminator()))
 587     return OverdefinedState;
 588
 589   int CommonState = OverdefinedState;
 590   for (BasicBlock *SuccBB : successors(BB)) {
 591     // We didn't manage to get a state for one of these predecessors,
 592     // conservatively report this basic block as overdefined.
 593     auto SuccStartState = InitialStates.find(SuccBB);
 594     if (SuccStartState == InitialStates.end())
 595       return OverdefinedState;
 596
 597     // This is an EH Pad, conservatively report this basic block as overdefined.
 598     if (SuccBB->isEHPad())
 599       return OverdefinedState;
 600
 601     int SuccState = SuccStartState->second;
 602     assert(SuccState != OverdefinedState &&
 603            "overdefined BBs shouldn't be in FinalStates");
 604     if (CommonState == OverdefinedState)
 605       CommonState = SuccState;
 606
 607     // At least two successors have different InitialStates,
 608     // conservatively report this basic block as overdefined.
 609     if (CommonState != SuccState)
 610       return OverdefinedState;
 611   }
 612
 613   return CommonState;
 614 }
 615
 616 bool WinEHStatePass::isStateStoreNeeded(EHPersonality Personality,
 617                                         CallBase &Call) {
 618   // If the function touches memory, it needs a state store.
 619   if (isAsynchronousEHPersonality(Personality))
 620     return !Call.doesNotAccessMemory();
 621
 622   // If the function throws, it needs a state store.
 623   return !Call.doesNotThrow();
 624 }
 625
 626 void WinEHStatePass::addStateStores(Function &F, WinEHFuncInfo &FuncInfo) {
 627   // Mark the registration node. The backend needs to know which alloca it is so
 628   // that it can recover the original frame pointer.
 629   IRBuilder<> Builder(RegNode->getNextNode());
 630   Value *RegNodeI8 = Builder.CreateBitCast(RegNode, Builder.getInt8PtrTy());
 631   Builder.CreateCall(
 632       Intrinsic::getDeclaration(TheModule, Intrinsic::x86_seh_ehregnode),
 633       {RegNodeI8});
 634
 635   if (EHGuardNode) {
 636     IRBuilder<> Builder(EHGuardNode->getNextNode());
 637     Value *EHGuardNodeI8 =
 638         Builder.CreateBitCast(EHGuardNode, Builder.getInt8PtrTy());
 639     Builder.CreateCall(
 640         Intrinsic::getDeclaration(TheModule, Intrinsic::x86_seh_ehguard),
 641         {EHGuardNodeI8});
 642   }
 643
 644   // Calculate state numbers.
 645   if (isAsynchronousEHPersonality(Personality))
 646     calculateSEHStateNumbers(&F, FuncInfo);
 647   else
 648     calculateWinCXXEHStateNumbers(&F, FuncInfo);
 649
 650   // Iterate all the instructions and emit state number stores.
 651   DenseMap<BasicBlock *, ColorVector> BlockColors = colorEHFunclets(F);
 652   ReversePostOrderTraversal<Function *> RPOT(&F);
 653
 654   // InitialStates yields the state of the first call-site for a BasicBlock.
 655   DenseMap<BasicBlock *, int> InitialStates;
 656   // FinalStates yields the state of the last call-site for a BasicBlock.
 657   DenseMap<BasicBlock *, int> FinalStates;
 658   // Worklist used to revisit BasicBlocks with indeterminate
 659   // Initial/Final-States.
 660   std::deque<BasicBlock *> Worklist;
 661   // Fill in InitialStates and FinalStates for BasicBlocks with call-sites.
 662   for (BasicBlock *BB : RPOT) {
 663     int InitialState = OverdefinedState;
 664     int FinalState;
 665     if (&F.getEntryBlock() == BB)
 666       InitialState = FinalState = ParentBaseState;
 667     for (Instruction &I : *BB) {
 668       auto *Call = dyn_cast<CallBase>(&I);
 669       if (!Call || !isStateStoreNeeded(Personality, *Call))
 670         continue;
 671
 672       int State = getStateForCall(BlockColors, FuncInfo, *Call);
 673       if (InitialState == OverdefinedState)
 674         InitialState = State;
 675       FinalState = State;
 676     }
 677     // No call-sites in this basic block? That's OK, we will come back to these
 678     // in a later pass.
 679     if (InitialState == OverdefinedState) {
 680       Worklist.push_back(BB);
 681       continue;
 682     }
 683     LLVM_DEBUG(dbgs() << "X86WinEHState: " << BB->getName()
 684                       << " InitialState=" << InitialState << '\n');
 685     LLVM_DEBUG(dbgs() << "X86WinEHState: " << BB->getName()
 686                       << " FinalState=" << FinalState << '\n');
 687     InitialStates.insert({BB, InitialState});
 688     FinalStates.insert({BB, FinalState});
 689   }
 690
 691   // Try to fill-in InitialStates and FinalStates which have no call-sites.
 692   while (!Worklist.empty()) {
 693     BasicBlock *BB = Worklist.front();
 694     Worklist.pop_front();
 695     // This BasicBlock has already been figured out, nothing more we can do.
 696     if (InitialStates.count(BB) != 0)
 697       continue;
 698
 699     int PredState = getPredState(FinalStates, F, ParentBaseState, BB);
 700     if (PredState == OverdefinedState)
 701       continue;
 702
 703     // We successfully inferred this BasicBlock's state via it's predecessors;
 704     // enqueue it's successors to see if we can infer their states.
 705     InitialStates.insert({BB, PredState});
 706     FinalStates.insert({BB, PredState});
 707     for (BasicBlock *SuccBB : successors(BB))
 708       Worklist.push_back(SuccBB);
 709   }
 710
 711   // Try to hoist stores from successors.
 712   for (BasicBlock *BB : RPOT) {
 713     int SuccState = getSuccState(InitialStates, F, ParentBaseState, BB);
 714     if (SuccState == OverdefinedState)
 715       continue;
 716
 717     // Update our FinalState to reflect the common InitialState of our
 718     // successors.
 719     FinalStates.insert({BB, SuccState});
 720   }
 721
 722   // Finally, insert state stores before call-sites which transition us to a new
 723   // state.
 724   for (BasicBlock *BB : RPOT) {
 725     auto &BBColors = BlockColors[BB];
 726     BasicBlock *FuncletEntryBB = BBColors.front();
 727     if (isa<CleanupPadInst>(FuncletEntryBB->getFirstNonPHI()))
 728       continue;
 729
 730     int PrevState = getPredState(FinalStates, F, ParentBaseState, BB);
 731     LLVM_DEBUG(dbgs() << "X86WinEHState: " << BB->getName()
 732                       << " PrevState=" << PrevState << '\n');
 733
 734     for (Instruction &I : *BB) {
 735       auto *Call = dyn_cast<CallBase>(&I);
 736       if (!Call || !isStateStoreNeeded(Personality, *Call))
 737         continue;
 738
 739       int State = getStateForCall(BlockColors, FuncInfo, *Call);
 740       if (State != PrevState)
 741         insertStateNumberStore(&I, State);
 742       PrevState = State;
 743     }
 744
 745     // We might have hoisted a state store into this block, emit it now.
 746     auto EndState = FinalStates.find(BB);
 747     if (EndState != FinalStates.end())
 748       if (EndState->second != PrevState)
 749         insertStateNumberStore(BB->getTerminator(), EndState->second);
 750   }
 751
 752   SmallVector<CallBase *, 1> SetJmp3Calls;
 753   for (BasicBlock *BB : RPOT) {
 754     for (Instruction &I : *BB) {
 755       auto *Call = dyn_cast<CallBase>(&I);
 756       if (!Call)
 757         continue;
 758       if (Call->getCalledOperand()->stripPointerCasts() !=
 759           SetJmp3.getCallee()->stripPointerCasts())
 760         continue;
 761
 762       SetJmp3Calls.push_back(Call);
 763     }
 764   }
 765
 766   for (CallBase *Call : SetJmp3Calls) {
 767     auto &BBColors = BlockColors[Call->getParent()];
 768     BasicBlock *FuncletEntryBB = BBColors.front();
 769     bool InCleanup = isa<CleanupPadInst>(FuncletEntryBB->getFirstNonPHI());
 770
 771     IRBuilder<> Builder(Call);
 772     Value *State;
 773     if (InCleanup) {
 774       Value *StateField = Builder.CreateStructGEP(RegNode->getAllocatedType(),
 775                                                   RegNode, StateFieldIndex);
 776       State = Builder.CreateLoad(Builder.getInt32Ty(), StateField);
 777     } else {
 778       State = Builder.getInt32(getStateForCall(BlockColors, FuncInfo, *Call));
 779     }
 780     rewriteSetJmpCall(Builder, F, *Call, State);
 781   }
 782 }
 783
 784 void WinEHStatePass::insertStateNumberStore(Instruction *IP, int State) {
 785   IRBuilder<> Builder(IP);
 786   Value *StateField = Builder.CreateStructGEP(RegNode->getAllocatedType(),
 787                                               RegNode, StateFieldIndex);
 788   Builder.CreateStore(Builder.getInt32(State), StateField);
 789 }