lib/Target/X86/X86WinEHState.cpp

   1 //===-- X86WinEHState - Insert EH state updates for win32 exceptions ------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // All functions using an MSVC EH personality use an explicitly updated state
  11 // number stored in an exception registration stack object. The registration
  12 // object is linked into a thread-local chain of registrations stored at fs:00.
  13 // This pass adds the registration object and EH state updates.
  14 //
  15 //===----------------------------------------------------------------------===//
  16
  17 #include "X86.h"
  18 #include "llvm/ADT/PostOrderIterator.h"
  19 #include "llvm/Analysis/CFG.h"
  20 #include "llvm/Analysis/EHPersonalities.h"
  21 #include "llvm/CodeGen/MachineModuleInfo.h"
  22 #include "llvm/CodeGen/WinEHFuncInfo.h"
  23 #include "llvm/IR/CallSite.h"
  24 #include "llvm/IR/Function.h"
  25 #include "llvm/IR/IRBuilder.h"
  26 #include "llvm/IR/Instructions.h"
  27 #include "llvm/IR/IntrinsicInst.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 llvm {
  38 void initializeWinEHStatePassPass(PassRegistry &);
  39 }
  40
  41 namespace {
  42 const int OverdefinedState = INT_MIN;
  43
  44 class WinEHStatePass : public FunctionPass {
  45 public:
  46   static char ID; // Pass identification, replacement for typeid.
  47
  48   WinEHStatePass() : FunctionPass(ID) {
  49     initializeWinEHStatePassPass(*PassRegistry::getPassRegistry());
  50   }
  51
  52   bool runOnFunction(Function &Fn) override;
  53
  54   bool doInitialization(Module &M) override;
  55
  56   bool doFinalization(Module &M) override;
  57
  58   void getAnalysisUsage(AnalysisUsage &AU) const override;
  59
  60   StringRef getPassName() const override {
  61     return "Windows 32-bit x86 EH state insertion";
  62   }
  63
  64 private:
  65   void emitExceptionRegistrationRecord(Function *F);
  66
  67   void linkExceptionRegistration(IRBuilder<> &Builder, Function *Handler);
  68   void unlinkExceptionRegistration(IRBuilder<> &Builder);
  69   void addStateStores(Function &F, WinEHFuncInfo &FuncInfo);
  70   void insertStateNumberStore(Instruction *IP, int State);
  71
  72   Value *emitEHLSDA(IRBuilder<> &Builder, Function *F);
  73
  74   Function *generateLSDAInEAXThunk(Function *ParentFunc);
  75
  76   bool isStateStoreNeeded(EHPersonality Personality, CallSite CS);
  77   void rewriteSetJmpCallSite(IRBuilder<> &Builder, Function &F, CallSite CS,
  78                              Value *State);
  79   int getBaseStateForBB(DenseMap<BasicBlock *, ColorVector> &BlockColors,
  80                         WinEHFuncInfo &FuncInfo, BasicBlock *BB);
  81   int getStateForCallSite(DenseMap<BasicBlock *, ColorVector> &BlockColors,
  82                           WinEHFuncInfo &FuncInfo, CallSite CS);
  83
  84   // Module-level type getters.
  85   Type *getEHLinkRegistrationType();
  86   Type *getSEHRegistrationType();
  87   Type *getCXXEHRegistrationType();
  88
  89   // Per-module data.
  90   Module *TheModule = nullptr;
  91   StructType *EHLinkRegistrationTy = nullptr;
  92   StructType *CXXEHRegistrationTy = nullptr;
  93   StructType *SEHRegistrationTy = nullptr;
  94   Constant *SetJmp3 = nullptr;
  95   Constant *CxxLongjmpUnwind = nullptr;
  96
  97   // Per-function state
  98   EHPersonality Personality = EHPersonality::Unknown;
  99   Function *PersonalityFn = nullptr;
 100   bool UseStackGuard = false;
 101   int ParentBaseState;
 102   Constant *SehLongjmpUnwind = nullptr;
 103   Constant *Cookie = nullptr;
 104
 105   /// The stack allocation containing all EH data, including the link in the
 106   /// fs:00 chain and the current state.
 107   AllocaInst *RegNode = nullptr;
 108
 109   // The allocation containing the EH security guard.
 110   AllocaInst *EHGuardNode = nullptr;
 111
 112   /// The index of the state field of RegNode.
 113   int StateFieldIndex = ~0U;
 114
 115   /// The linked list node subobject inside of RegNode.
 116   Value *Link = nullptr;
 117 };
 118 }
 119
 120 FunctionPass *llvm::createX86WinEHStatePass() { return new WinEHStatePass(); }
 121
 122 char WinEHStatePass::ID = 0;
 123
 124 INITIALIZE_PASS(WinEHStatePass, "x86-winehstate",
 125                 "Insert stores for EH state numbers", false, false)
 126
 127 bool WinEHStatePass::doInitialization(Module &M) {
 128   TheModule = &M;
 129   return false;
 130 }
 131
 132 bool WinEHStatePass::doFinalization(Module &M) {
 133   assert(TheModule == &M);
 134   TheModule = nullptr;
 135   EHLinkRegistrationTy = nullptr;
 136   CXXEHRegistrationTy = nullptr;
 137   SEHRegistrationTy = nullptr;
 138   SetJmp3 = nullptr;
 139   CxxLongjmpUnwind = nullptr;
 140   SehLongjmpUnwind = nullptr;
 141   Cookie = nullptr;
 142   return false;
 143 }
 144
 145 void WinEHStatePass::getAnalysisUsage(AnalysisUsage &AU) const {
 146   // This pass should only insert a stack allocation, memory accesses, and
 147   // localrecovers.
 148   AU.setPreservesCFG();
 149 }
 150
 151 bool WinEHStatePass::runOnFunction(Function &F) {
 152   // Don't insert state stores or exception handler thunks for
 153   // available_externally functions. The handler needs to reference the LSDA,
 154   // which will not be emitted in this case.
 155   if (F.hasAvailableExternallyLinkage())
 156     return false;
 157
 158   // Check the personality. Do nothing if this personality doesn't use funclets.
 159   if (!F.hasPersonalityFn())
 160     return false;
 161   PersonalityFn =
 162       dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts());
 163   if (!PersonalityFn)
 164     return false;
 165   Personality = classifyEHPersonality(PersonalityFn);
 166   if (!isFuncletEHPersonality(Personality))
 167     return false;
 168
 169   // Skip this function if there are no EH pads and we aren't using IR-level
 170   // outlining.
 171   bool HasPads = false;
 172   for (BasicBlock &BB : F) {
 173     if (BB.isEHPad()) {
 174       HasPads = true;
 175       break;
 176     }
 177   }
 178   if (!HasPads)
 179     return false;
 180
 181   Type *Int8PtrType = Type::getInt8PtrTy(TheModule->getContext());
 182   SetJmp3 = TheModule->getOrInsertFunction(
 183       "_setjmp3", FunctionType::get(
 184                       Type::getInt32Ty(TheModule->getContext()),
 185                       {Int8PtrType, Type::getInt32Ty(TheModule->getContext())},
 186                       /*isVarArg=*/true));
 187
 188   // Disable frame pointer elimination in this function.
 189   // FIXME: Do the nested handlers need to keep the parent ebp in ebp, or can we
 190   // use an arbitrary register?
 191   F.addFnAttr("no-frame-pointer-elim", "true");
 192
 193   emitExceptionRegistrationRecord(&F);
 194
 195   // The state numbers calculated here in IR must agree with what we calculate
 196   // later on for the MachineFunction. In particular, if an IR pass deletes an
 197   // unreachable EH pad after this point before machine CFG construction, we
 198   // will be in trouble. If this assumption is ever broken, we should turn the
 199   // numbers into an immutable analysis pass.
 200   WinEHFuncInfo FuncInfo;
 201   addStateStores(F, FuncInfo);
 202
 203   // Reset per-function state.
 204   PersonalityFn = nullptr;
 205   Personality = EHPersonality::Unknown;
 206   UseStackGuard = false;
 207   RegNode = nullptr;
 208   EHGuardNode = nullptr;
 209
 210   return true;
 211 }
 212
 213 /// Get the common EH registration subobject:
 214 ///   typedef _EXCEPTION_DISPOSITION (*PEXCEPTION_ROUTINE)(
 215 ///       _EXCEPTION_RECORD *, void *, _CONTEXT *, void *);
 216 ///   struct EHRegistrationNode {
 217 ///     EHRegistrationNode *Next;
 218 ///     PEXCEPTION_ROUTINE Handler;
 219 ///   };
 220 Type *WinEHStatePass::getEHLinkRegistrationType() {
 221   if (EHLinkRegistrationTy)
 222     return EHLinkRegistrationTy;
 223   LLVMContext &Context = TheModule->getContext();
 224   EHLinkRegistrationTy = StructType::create(Context, "EHRegistrationNode");
 225   Type *FieldTys[] = {
 226       EHLinkRegistrationTy->getPointerTo(0), // EHRegistrationNode *Next
 227       Type::getInt8PtrTy(Context) // EXCEPTION_DISPOSITION (*Handler)(...)
 228   };
 229   EHLinkRegistrationTy->setBody(FieldTys, false);
 230   return EHLinkRegistrationTy;
 231 }
 232
 233 /// The __CxxFrameHandler3 registration node:
 234 ///   struct CXXExceptionRegistration {
 235 ///     void *SavedESP;
 236 ///     EHRegistrationNode SubRecord;
 237 ///     int32_t TryLevel;
 238 ///   };
 239 Type *WinEHStatePass::getCXXEHRegistrationType() {
 240   if (CXXEHRegistrationTy)
 241     return CXXEHRegistrationTy;
 242   LLVMContext &Context = TheModule->getContext();
 243   Type *FieldTys[] = {
 244       Type::getInt8PtrTy(Context), // void *SavedESP
 245       getEHLinkRegistrationType(), // EHRegistrationNode SubRecord
 246       Type::getInt32Ty(Context)    // int32_t TryLevel
 247   };
 248   CXXEHRegistrationTy =
 249       StructType::create(FieldTys, "CXXExceptionRegistration");
 250   return CXXEHRegistrationTy;
 251 }
 252
 253 /// The _except_handler3/4 registration node:
 254 ///   struct EH4ExceptionRegistration {
 255 ///     void *SavedESP;
 256 ///     _EXCEPTION_POINTERS *ExceptionPointers;
 257 ///     EHRegistrationNode SubRecord;
 258 ///     int32_t EncodedScopeTable;
 259 ///     int32_t TryLevel;
 260 ///   };
 261 Type *WinEHStatePass::getSEHRegistrationType() {
 262   if (SEHRegistrationTy)
 263     return SEHRegistrationTy;
 264   LLVMContext &Context = TheModule->getContext();
 265   Type *FieldTys[] = {
 266       Type::getInt8PtrTy(Context), // void *SavedESP
 267       Type::getInt8PtrTy(Context), // void *ExceptionPointers
 268       getEHLinkRegistrationType(), // EHRegistrationNode SubRecord
 269       Type::getInt32Ty(Context),   // int32_t EncodedScopeTable
 270       Type::getInt32Ty(Context)    // int32_t TryLevel
 271   };
 272   SEHRegistrationTy = StructType::create(FieldTys, "SEHExceptionRegistration");
 273   return SEHRegistrationTy;
 274 }
 275
 276 // Emit an exception registration record. These are stack allocations with the
 277 // common subobject of two pointers: the previous registration record (the old
 278 // fs:00) and the personality function for the current frame. The data before
 279 // and after that is personality function specific.
 280 void WinEHStatePass::emitExceptionRegistrationRecord(Function *F) {
 281   assert(Personality == EHPersonality::MSVC_CXX ||
 282          Personality == EHPersonality::MSVC_X86SEH);
 283
 284   // Struct type of RegNode. Used for GEPing.
 285   Type *RegNodeTy;
 286
 287   IRBuilder<> Builder(&F->getEntryBlock(), F->getEntryBlock().begin());
 288   Type *Int8PtrType = Builder.getInt8PtrTy();
 289   Type *Int32Ty = Builder.getInt32Ty();
 290   Type *VoidTy = Builder.getVoidTy();
 291
 292   if (Personality == EHPersonality::MSVC_CXX) {
 293     RegNodeTy = getCXXEHRegistrationType();
 294     RegNode = Builder.CreateAlloca(RegNodeTy);
 295     // SavedESP = llvm.stacksave()
 296     Value *SP = Builder.CreateCall(
 297         Intrinsic::getDeclaration(TheModule, Intrinsic::stacksave), {});
 298     Builder.CreateStore(SP, Builder.CreateStructGEP(RegNodeTy, RegNode, 0));
 299     // TryLevel = -1
 300     StateFieldIndex = 2;
 301     ParentBaseState = -1;
 302     insertStateNumberStore(&*Builder.GetInsertPoint(), ParentBaseState);
 303     // Handler = __ehhandler$F
 304     Function *Trampoline = generateLSDAInEAXThunk(F);
 305     Link = Builder.CreateStructGEP(RegNodeTy, RegNode, 1);
 306     linkExceptionRegistration(Builder, Trampoline);
 307
 308     CxxLongjmpUnwind = TheModule->getOrInsertFunction(
 309         "__CxxLongjmpUnwind",
 310         FunctionType::get(VoidTy, Int8PtrType, /*isVarArg=*/false));
 311     cast<Function>(CxxLongjmpUnwind->stripPointerCasts())
 312         ->setCallingConv(CallingConv::X86_StdCall);
 313   } else if (Personality == EHPersonality::MSVC_X86SEH) {
 314     // If _except_handler4 is in use, some additional guard checks and prologue
 315     // stuff is required.
 316     StringRef PersonalityName = PersonalityFn->getName();
 317     UseStackGuard = (PersonalityName == "_except_handler4");
 318
 319     // Allocate local structures.
 320     RegNodeTy = getSEHRegistrationType();
 321     RegNode = Builder.CreateAlloca(RegNodeTy);
 322     if (UseStackGuard)
 323       EHGuardNode = Builder.CreateAlloca(Int32Ty);
 324
 325     // SavedESP = llvm.stacksave()
 326     Value *SP = Builder.CreateCall(
 327         Intrinsic::getDeclaration(TheModule, Intrinsic::stacksave), {});
 328     Builder.CreateStore(SP, Builder.CreateStructGEP(RegNodeTy, RegNode, 0));
 329     // TryLevel = -2 / -1
 330     StateFieldIndex = 4;
 331     ParentBaseState = UseStackGuard ? -2 : -1;
 332     insertStateNumberStore(&*Builder.GetInsertPoint(), ParentBaseState);
 333     // ScopeTable = llvm.x86.seh.lsda(F)
 334     Value *LSDA = emitEHLSDA(Builder, F);
 335     LSDA = Builder.CreatePtrToInt(LSDA, Int32Ty);
 336     // If using _except_handler4, xor the address of the table with
 337     // __security_cookie.
 338     if (UseStackGuard) {
 339       Cookie = TheModule->getOrInsertGlobal("__security_cookie", Int32Ty);
 340       Value *Val = Builder.CreateLoad(Int32Ty, Cookie, "cookie");
 341       LSDA = Builder.CreateXor(LSDA, Val);
 342     }
 343     Builder.CreateStore(LSDA, Builder.CreateStructGEP(RegNodeTy, RegNode, 3));
 344
 345     // If using _except_handler4, the EHGuard contains: FramePtr xor Cookie.
 346     if (UseStackGuard) {
 347       Value *Val = Builder.CreateLoad(Int32Ty, Cookie);
 348       Value *FrameAddr = Builder.CreateCall(
 349           Intrinsic::getDeclaration(TheModule, Intrinsic::frameaddress),
 350           Builder.getInt32(0), "frameaddr");
 351       Value *FrameAddrI32 = Builder.CreatePtrToInt(FrameAddr, Int32Ty);
 352       FrameAddrI32 = Builder.CreateXor(FrameAddrI32, Val);
 353       Builder.CreateStore(FrameAddrI32, EHGuardNode);
 354     }
 355
 356     // Register the exception handler.
 357     Link = Builder.CreateStructGEP(RegNodeTy, RegNode, 2);
 358     linkExceptionRegistration(Builder, PersonalityFn);
 359
 360     SehLongjmpUnwind = TheModule->getOrInsertFunction(
 361         UseStackGuard ? "_seh_longjmp_unwind4" : "_seh_longjmp_unwind",
 362         FunctionType::get(Type::getVoidTy(TheModule->getContext()), Int8PtrType,
 363                           /*isVarArg=*/false));
 364     cast<Function>(SehLongjmpUnwind->stripPointerCasts())
 365         ->setCallingConv(CallingConv::X86_StdCall);
 366   } else {
 367     llvm_unreachable("unexpected personality function");
 368   }
 369
 370   // Insert an unlink before all returns.
 371   for (BasicBlock &BB : *F) {
 372     TerminatorInst *T = BB.getTerminator();
 373     if (!isa<ReturnInst>(T))
 374       continue;
 375     Builder.SetInsertPoint(T);
 376     unlinkExceptionRegistration(Builder);
 377   }
 378 }
 379
 380 Value *WinEHStatePass::emitEHLSDA(IRBuilder<> &Builder, Function *F) {
 381   Value *FI8 = Builder.CreateBitCast(F, Type::getInt8PtrTy(F->getContext()));
 382   return Builder.CreateCall(
 383       Intrinsic::getDeclaration(TheModule, Intrinsic::x86_seh_lsda), FI8);
 384 }
 385
 386 /// Generate a thunk that puts the LSDA of ParentFunc in EAX and then calls
 387 /// PersonalityFn, forwarding the parameters passed to PEXCEPTION_ROUTINE:
 388 ///   typedef _EXCEPTION_DISPOSITION (*PEXCEPTION_ROUTINE)(
 389 ///       _EXCEPTION_RECORD *, void *, _CONTEXT *, void *);
 390 /// We essentially want this code:
 391 ///   movl $lsda, %eax
 392 ///   jmpl ___CxxFrameHandler3
 393 Function *WinEHStatePass::generateLSDAInEAXThunk(Function *ParentFunc) {
 394   LLVMContext &Context = ParentFunc->getContext();
 395   Type *Int32Ty = Type::getInt32Ty(Context);
 396   Type *Int8PtrType = Type::getInt8PtrTy(Context);
 397   Type *ArgTys[5] = {Int8PtrType, Int8PtrType, Int8PtrType, Int8PtrType,
 398                      Int8PtrType};
 399   FunctionType *TrampolineTy =
 400       FunctionType::get(Int32Ty, makeArrayRef(&ArgTys[0], 4),
 401                         /*isVarArg=*/false);
 402   FunctionType *TargetFuncTy =
 403       FunctionType::get(Int32Ty, makeArrayRef(&ArgTys[0], 5),
 404                         /*isVarArg=*/false);
 405   Function *Trampoline =
 406       Function::Create(TrampolineTy, GlobalValue::InternalLinkage,
 407                        Twine("__ehhandler$") + GlobalValue::dropLLVMManglingEscape(
 408                                                    ParentFunc->getName()),
 409                        TheModule);
 410   if (auto *C = ParentFunc->getComdat())
 411     Trampoline->setComdat(C);
 412   BasicBlock *EntryBB = BasicBlock::Create(Context, "entry", Trampoline);
 413   IRBuilder<> Builder(EntryBB);
 414   Value *LSDA = emitEHLSDA(Builder, ParentFunc);
 415   Value *CastPersonality =
 416       Builder.CreateBitCast(PersonalityFn, TargetFuncTy->getPointerTo());
 417   auto AI = Trampoline->arg_begin();
 418   Value *Args[5] = {LSDA, &*AI++, &*AI++, &*AI++, &*AI++};
 419   CallInst *Call = Builder.CreateCall(CastPersonality, Args);
 420   // Can't use musttail due to prototype mismatch, but we can use tail.
 421   Call->setTailCall(true);
 422   // Set inreg so we pass it in EAX.
 423   Call->addParamAttr(0, Attribute::InReg);
 424   Builder.CreateRet(Call);
 425   return Trampoline;
 426 }
 427
 428 void WinEHStatePass::linkExceptionRegistration(IRBuilder<> &Builder,
 429                                                Function *Handler) {
 430   // Emit the .safeseh directive for this function.
 431   Handler->addFnAttr("safeseh");
 432
 433   Type *LinkTy = getEHLinkRegistrationType();
 434   // Handler = Handler
 435   Value *HandlerI8 = Builder.CreateBitCast(Handler, Builder.getInt8PtrTy());
 436   Builder.CreateStore(HandlerI8, Builder.CreateStructGEP(LinkTy, Link, 1));
 437   // Next = [fs:00]
 438   Constant *FSZero =
 439       Constant::getNullValue(LinkTy->getPointerTo()->getPointerTo(257));
 440   Value *Next = Builder.CreateLoad(FSZero);
 441   Builder.CreateStore(Next, Builder.CreateStructGEP(LinkTy, Link, 0));
 442   // [fs:00] = Link
 443   Builder.CreateStore(Link, FSZero);
 444 }
 445
 446 void WinEHStatePass::unlinkExceptionRegistration(IRBuilder<> &Builder) {
 447   // Clone Link into the current BB for better address mode folding.
 448   if (auto *GEP = dyn_cast<GetElementPtrInst>(Link)) {
 449     GEP = cast<GetElementPtrInst>(GEP->clone());
 450     Builder.Insert(GEP);
 451     Link = GEP;
 452   }
 453   Type *LinkTy = getEHLinkRegistrationType();
 454   // [fs:00] = Link->Next
 455   Value *Next =
 456       Builder.CreateLoad(Builder.CreateStructGEP(LinkTy, Link, 0));
 457   Constant *FSZero =
 458       Constant::getNullValue(LinkTy->getPointerTo()->getPointerTo(257));
 459   Builder.CreateStore(Next, FSZero);
 460 }
 461
 462 // Calls to setjmp(p) are lowered to _setjmp3(p, 0) by the frontend.
 463 // The idea behind _setjmp3 is that it takes an optional number of personality
 464 // specific parameters to indicate how to restore the personality-specific frame
 465 // state when longjmp is initiated.  Typically, the current TryLevel is saved.
 466 void WinEHStatePass::rewriteSetJmpCallSite(IRBuilder<> &Builder, Function &F,
 467                                            CallSite CS, Value *State) {
 468   // Don't rewrite calls with a weird number of arguments.
 469   if (CS.getNumArgOperands() != 2)
 470     return;
 471
 472   Instruction *Inst = CS.getInstruction();
 473
 474   SmallVector<OperandBundleDef, 1> OpBundles;
 475   CS.getOperandBundlesAsDefs(OpBundles);
 476
 477   SmallVector<Value *, 3> OptionalArgs;
 478   if (Personality == EHPersonality::MSVC_CXX) {
 479     OptionalArgs.push_back(CxxLongjmpUnwind);
 480     OptionalArgs.push_back(State);
 481     OptionalArgs.push_back(emitEHLSDA(Builder, &F));
 482   } else if (Personality == EHPersonality::MSVC_X86SEH) {
 483     OptionalArgs.push_back(SehLongjmpUnwind);
 484     OptionalArgs.push_back(State);
 485     if (UseStackGuard)
 486       OptionalArgs.push_back(Cookie);
 487   } else {
 488     llvm_unreachable("unhandled personality!");
 489   }
 490
 491   SmallVector<Value *, 5> Args;
 492   Args.push_back(
 493       Builder.CreateBitCast(CS.getArgOperand(0), Builder.getInt8PtrTy()));
 494   Args.push_back(Builder.getInt32(OptionalArgs.size()));
 495   Args.append(OptionalArgs.begin(), OptionalArgs.end());
 496
 497   CallSite NewCS;
 498   if (CS.isCall()) {
 499     auto *CI = cast<CallInst>(Inst);
 500     CallInst *NewCI = Builder.CreateCall(SetJmp3, Args, OpBundles);
 501     NewCI->setTailCallKind(CI->getTailCallKind());
 502     NewCS = NewCI;
 503   } else {
 504     auto *II = cast<InvokeInst>(Inst);
 505     NewCS = Builder.CreateInvoke(
 506         SetJmp3, II->getNormalDest(), II->getUnwindDest(), Args, OpBundles);
 507   }
 508   NewCS.setCallingConv(CS.getCallingConv());
 509   NewCS.setAttributes(CS.getAttributes());
 510   NewCS->setDebugLoc(CS->getDebugLoc());
 511
 512   Instruction *NewInst = NewCS.getInstruction();
 513   NewInst->takeName(Inst);
 514   Inst->replaceAllUsesWith(NewInst);
 515   Inst->eraseFromParent();
 516 }
 517
 518 // Figure out what state we should assign calls in this block.
 519 int WinEHStatePass::getBaseStateForBB(
 520     DenseMap<BasicBlock *, ColorVector> &BlockColors, WinEHFuncInfo &FuncInfo,
 521     BasicBlock *BB) {
 522   int BaseState = ParentBaseState;
 523   auto &BBColors = BlockColors[BB];
 524
 525   assert(BBColors.size() == 1 && "multi-color BB not removed by preparation");
 526   BasicBlock *FuncletEntryBB = BBColors.front();
 527   if (auto *FuncletPad =
 528           dyn_cast<FuncletPadInst>(FuncletEntryBB->getFirstNonPHI())) {
 529     auto BaseStateI = FuncInfo.FuncletBaseStateMap.find(FuncletPad);
 530     if (BaseStateI != FuncInfo.FuncletBaseStateMap.end())
 531       BaseState = BaseStateI->second;
 532   }
 533
 534   return BaseState;
 535 }
 536
 537 // Calculate the state a call-site is in.
 538 int WinEHStatePass::getStateForCallSite(
 539     DenseMap<BasicBlock *, ColorVector> &BlockColors, WinEHFuncInfo &FuncInfo,
 540     CallSite CS) {
 541   if (auto *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
 542     // Look up the state number of the EH pad this unwinds to.
 543     assert(FuncInfo.InvokeStateMap.count(II) && "invoke has no state!");
 544     return FuncInfo.InvokeStateMap[II];
 545   }
 546   // Possibly throwing call instructions have no actions to take after
 547   // an unwind. Ensure they are in the -1 state.
 548   return getBaseStateForBB(BlockColors, FuncInfo, CS.getParent());
 549 }
 550
 551 // Calculate the intersection of all the FinalStates for a BasicBlock's
 552 // predecessors.
 553 static int getPredState(DenseMap<BasicBlock *, int> &FinalStates, Function &F,
 554                         int ParentBaseState, BasicBlock *BB) {
 555   // The entry block has no predecessors but we know that the prologue always
 556   // sets us up with a fixed state.
 557   if (&F.getEntryBlock() == BB)
 558     return ParentBaseState;
 559
 560   // This is an EH Pad, conservatively report this basic block as overdefined.
 561   if (BB->isEHPad())
 562     return OverdefinedState;
 563
 564   int CommonState = OverdefinedState;
 565   for (BasicBlock *PredBB : predecessors(BB)) {
 566     // We didn't manage to get a state for one of these predecessors,
 567     // conservatively report this basic block as overdefined.
 568     auto PredEndState = FinalStates.find(PredBB);
 569     if (PredEndState == FinalStates.end())
 570       return OverdefinedState;
 571
 572     // This code is reachable via exceptional control flow,
 573     // conservatively report this basic block as overdefined.
 574     if (isa<CatchReturnInst>(PredBB->getTerminator()))
 575       return OverdefinedState;
 576
 577     int PredState = PredEndState->second;
 578     assert(PredState != OverdefinedState &&
 579            "overdefined BBs shouldn't be in FinalStates");
 580     if (CommonState == OverdefinedState)
 581       CommonState = PredState;
 582
 583     // At least two predecessors have different FinalStates,
 584     // conservatively report this basic block as overdefined.
 585     if (CommonState != PredState)
 586       return OverdefinedState;
 587   }
 588
 589   return CommonState;
 590 }
 591
 592 // Calculate the intersection of all the InitialStates for a BasicBlock's
 593 // successors.
 594 static int getSuccState(DenseMap<BasicBlock *, int> &InitialStates, Function &F,
 595                         int ParentBaseState, BasicBlock *BB) {
 596   // This block rejoins normal control flow,
 597   // conservatively report this basic block as overdefined.
 598   if (isa<CatchReturnInst>(BB->getTerminator()))
 599     return OverdefinedState;
 600
 601   int CommonState = OverdefinedState;
 602   for (BasicBlock *SuccBB : successors(BB)) {
 603     // We didn't manage to get a state for one of these predecessors,
 604     // conservatively report this basic block as overdefined.
 605     auto SuccStartState = InitialStates.find(SuccBB);
 606     if (SuccStartState == InitialStates.end())
 607       return OverdefinedState;
 608
 609     // This is an EH Pad, conservatively report this basic block as overdefined.
 610     if (SuccBB->isEHPad())
 611       return OverdefinedState;
 612
 613     int SuccState = SuccStartState->second;
 614     assert(SuccState != OverdefinedState &&
 615            "overdefined BBs shouldn't be in FinalStates");
 616     if (CommonState == OverdefinedState)
 617       CommonState = SuccState;
 618
 619     // At least two successors have different InitialStates,
 620     // conservatively report this basic block as overdefined.
 621     if (CommonState != SuccState)
 622       return OverdefinedState;
 623   }
 624
 625   return CommonState;
 626 }
 627
 628 bool WinEHStatePass::isStateStoreNeeded(EHPersonality Personality,
 629                                         CallSite CS) {
 630   if (!CS)
 631     return false;
 632
 633   // If the function touches memory, it needs a state store.
 634   if (isAsynchronousEHPersonality(Personality))
 635     return !CS.doesNotAccessMemory();
 636
 637   // If the function throws, it needs a state store.
 638   return !CS.doesNotThrow();
 639 }
 640
 641 void WinEHStatePass::addStateStores(Function &F, WinEHFuncInfo &FuncInfo) {
 642   // Mark the registration node. The backend needs to know which alloca it is so
 643   // that it can recover the original frame pointer.
 644   IRBuilder<> Builder(RegNode->getNextNode());
 645   Value *RegNodeI8 = Builder.CreateBitCast(RegNode, Builder.getInt8PtrTy());
 646   Builder.CreateCall(
 647       Intrinsic::getDeclaration(TheModule, Intrinsic::x86_seh_ehregnode),
 648       {RegNodeI8});
 649
 650   if (EHGuardNode) {
 651     IRBuilder<> Builder(EHGuardNode->getNextNode());
 652     Value *EHGuardNodeI8 =
 653         Builder.CreateBitCast(EHGuardNode, Builder.getInt8PtrTy());
 654     Builder.CreateCall(
 655         Intrinsic::getDeclaration(TheModule, Intrinsic::x86_seh_ehguard),
 656         {EHGuardNodeI8});
 657   }
 658
 659   // Calculate state numbers.
 660   if (isAsynchronousEHPersonality(Personality))
 661     calculateSEHStateNumbers(&F, FuncInfo);
 662   else
 663     calculateWinCXXEHStateNumbers(&F, FuncInfo);
 664
 665   // Iterate all the instructions and emit state number stores.
 666   DenseMap<BasicBlock *, ColorVector> BlockColors = colorEHFunclets(F);
 667   ReversePostOrderTraversal<Function *> RPOT(&F);
 668
 669   // InitialStates yields the state of the first call-site for a BasicBlock.
 670   DenseMap<BasicBlock *, int> InitialStates;
 671   // FinalStates yields the state of the last call-site for a BasicBlock.
 672   DenseMap<BasicBlock *, int> FinalStates;
 673   // Worklist used to revisit BasicBlocks with indeterminate
 674   // Initial/Final-States.
 675   std::deque<BasicBlock *> Worklist;
 676   // Fill in InitialStates and FinalStates for BasicBlocks with call-sites.
 677   for (BasicBlock *BB : RPOT) {
 678     int InitialState = OverdefinedState;
 679     int FinalState;
 680     if (&F.getEntryBlock() == BB)
 681       InitialState = FinalState = ParentBaseState;
 682     for (Instruction &I : *BB) {
 683       CallSite CS(&I);
 684       if (!isStateStoreNeeded(Personality, CS))
 685         continue;
 686
 687       int State = getStateForCallSite(BlockColors, FuncInfo, CS);
 688       if (InitialState == OverdefinedState)
 689         InitialState = State;
 690       FinalState = State;
 691     }
 692     // No call-sites in this basic block? That's OK, we will come back to these
 693     // in a later pass.
 694     if (InitialState == OverdefinedState) {
 695       Worklist.push_back(BB);
 696       continue;
 697     }
 698     LLVM_DEBUG(dbgs() << "X86WinEHState: " << BB->getName()
 699                       << " InitialState=" << InitialState << '\n');
 700     LLVM_DEBUG(dbgs() << "X86WinEHState: " << BB->getName()
 701                       << " FinalState=" << FinalState << '\n');
 702     InitialStates.insert({BB, InitialState});
 703     FinalStates.insert({BB, FinalState});
 704   }
 705
 706   // Try to fill-in InitialStates and FinalStates which have no call-sites.
 707   while (!Worklist.empty()) {
 708     BasicBlock *BB = Worklist.front();
 709     Worklist.pop_front();
 710     // This BasicBlock has already been figured out, nothing more we can do.
 711     if (InitialStates.count(BB) != 0)
 712       continue;
 713
 714     int PredState = getPredState(FinalStates, F, ParentBaseState, BB);
 715     if (PredState == OverdefinedState)
 716       continue;
 717
 718     // We successfully inferred this BasicBlock's state via it's predecessors;
 719     // enqueue it's successors to see if we can infer their states.
 720     InitialStates.insert({BB, PredState});
 721     FinalStates.insert({BB, PredState});
 722     for (BasicBlock *SuccBB : successors(BB))
 723       Worklist.push_back(SuccBB);
 724   }
 725
 726   // Try to hoist stores from successors.
 727   for (BasicBlock *BB : RPOT) {
 728     int SuccState = getSuccState(InitialStates, F, ParentBaseState, BB);
 729     if (SuccState == OverdefinedState)
 730       continue;
 731
 732     // Update our FinalState to reflect the common InitialState of our
 733     // successors.
 734     FinalStates.insert({BB, SuccState});
 735   }
 736
 737   // Finally, insert state stores before call-sites which transition us to a new
 738   // state.
 739   for (BasicBlock *BB : RPOT) {
 740     auto &BBColors = BlockColors[BB];
 741     BasicBlock *FuncletEntryBB = BBColors.front();
 742     if (isa<CleanupPadInst>(FuncletEntryBB->getFirstNonPHI()))
 743       continue;
 744
 745     int PrevState = getPredState(FinalStates, F, ParentBaseState, BB);
 746     LLVM_DEBUG(dbgs() << "X86WinEHState: " << BB->getName()
 747                       << " PrevState=" << PrevState << '\n');
 748
 749     for (Instruction &I : *BB) {
 750       CallSite CS(&I);
 751       if (!isStateStoreNeeded(Personality, CS))
 752         continue;
 753
 754       int State = getStateForCallSite(BlockColors, FuncInfo, CS);
 755       if (State != PrevState)
 756         insertStateNumberStore(&I, State);
 757       PrevState = State;
 758     }
 759
 760     // We might have hoisted a state store into this block, emit it now.
 761     auto EndState = FinalStates.find(BB);
 762     if (EndState != FinalStates.end())
 763       if (EndState->second != PrevState)
 764         insertStateNumberStore(BB->getTerminator(), EndState->second);
 765   }
 766
 767   SmallVector<CallSite, 1> SetJmp3CallSites;
 768   for (BasicBlock *BB : RPOT) {
 769     for (Instruction &I : *BB) {
 770       CallSite CS(&I);
 771       if (!CS)
 772         continue;
 773       if (CS.getCalledValue()->stripPointerCasts() !=
 774           SetJmp3->stripPointerCasts())
 775         continue;
 776
 777       SetJmp3CallSites.push_back(CS);
 778     }
 779   }
 780
 781   for (CallSite CS : SetJmp3CallSites) {
 782     auto &BBColors = BlockColors[CS->getParent()];
 783     BasicBlock *FuncletEntryBB = BBColors.front();
 784     bool InCleanup = isa<CleanupPadInst>(FuncletEntryBB->getFirstNonPHI());
 785
 786     IRBuilder<> Builder(CS.getInstruction());
 787     Value *State;
 788     if (InCleanup) {
 789       Value *StateField =
 790           Builder.CreateStructGEP(nullptr, RegNode, StateFieldIndex);
 791       State = Builder.CreateLoad(StateField);
 792     } else {
 793       State = Builder.getInt32(getStateForCallSite(BlockColors, FuncInfo, CS));
 794     }
 795     rewriteSetJmpCallSite(Builder, F, CS, State);
 796   }
 797 }
 798
 799 void WinEHStatePass::insertStateNumberStore(Instruction *IP, int State) {
 800   IRBuilder<> Builder(IP);
 801   Value *StateField =
 802       Builder.CreateStructGEP(nullptr, RegNode, StateFieldIndex);
 803   Builder.CreateStore(Builder.getInt32(State), StateField);
 804 }