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/CodeGen/MachineModuleInfo.h"
20#include "llvm/CodeGen/WinEHFuncInfo.h"
21#include "llvm/IR/CFG.h"
22#include "llvm/IR/EHPersonalities.h"
23#include "llvm/IR/Function.h"
24#include "llvm/IR/IRBuilder.h"
25#include "llvm/IR/Instructions.h"
26#include "llvm/IR/IntrinsicInst.h"
27#include "llvm/IR/Intrinsics.h"
28#include "llvm/IR/IntrinsicsX86.h"
29#include "llvm/IR/Module.h"
30#include "llvm/Pass.h"
31#include "llvm/Support/Debug.h"
32#include <deque>
33
34using namespace llvm;
35
36#define DEBUG_TYPE "winehstate"
37
38namespace {
39const int OverdefinedState = INT_MIN;
40
41class WinEHStatePass : public FunctionPass {
42public:
43 static char ID; // Pass identification, replacement for typeid.
44
45 WinEHStatePass() : FunctionPass(ID) {}
46
47 bool runOnFunction(Function &Fn) override;
48
49 bool doInitialization(Module &M) override;
50
51 bool doFinalization(Module &M) override;
52
53 void getAnalysisUsage(AnalysisUsage &AU) const override;
54
55 StringRef getPassName() const override {
56 return "Windows 32-bit x86 EH state insertion";
57 }
58
59private:
60 void emitExceptionRegistrationRecord(Function *F);
61
62 void linkExceptionRegistration(IRBuilder<> &Builder, Function *Handler);
63 void unlinkExceptionRegistration(IRBuilder<> &Builder);
64 void addStateStores(Function &F, WinEHFuncInfo &FuncInfo);
65 void insertStateNumberStore(Instruction *IP, int State);
66
67 Value *emitEHLSDA(IRBuilder<> &Builder, Function *F);
68
69 Function *generateLSDAInEAXThunk(Function *ParentFunc);
70
71 bool isStateStoreNeeded(EHPersonality Personality, CallBase &Call);
72 void rewriteSetJmpCall(IRBuilder<> &Builder, Function &F, CallBase &Call,
73 Value *State);
74 int getBaseStateForBB(DenseMap<BasicBlock *, ColorVector> &BlockColors,
75 WinEHFuncInfo &FuncInfo, BasicBlock *BB);
76 int getStateForCall(DenseMap<BasicBlock *, ColorVector> &BlockColors,
77 WinEHFuncInfo &FuncInfo, CallBase &Call);
78
79 void updateEspForInAllocas(Function &F);
80
81 // Module-level type getters.
82 Type *getEHLinkRegistrationType();
83 Type *getSEHRegistrationType();
84 Type *getCXXEHRegistrationType();
85
86 // Per-module data.
87 Module *TheModule = nullptr;
88 StructType *EHLinkRegistrationTy = nullptr;
89 StructType *CXXEHRegistrationTy = nullptr;
90 StructType *SEHRegistrationTy = nullptr;
91 FunctionCallee SetJmp3 = nullptr;
92 FunctionCallee CxxLongjmpUnwind = nullptr;
93
94 // Per-function state
95 EHPersonality Personality = EHPersonality::Unknown;
96 Function *PersonalityFn = nullptr;
97 bool UseStackGuard = false;
98 int ParentBaseState = 0;
99 FunctionCallee SehLongjmpUnwind = nullptr;
100 Constant *Cookie = nullptr;
101
102 /// The stack allocation containing all EH data, including the link in the
103 /// fs:00 chain and the current state.
104 AllocaInst *RegNode = nullptr;
105
106 // Struct type of RegNode. Used for GEPing.
107 Type *RegNodeTy = 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} // namespace
119
120FunctionPass *llvm::createX86WinEHStatePass() { return new WinEHStatePass(); }
121
122char WinEHStatePass::ID = 0;
123
124INITIALIZE_PASS(WinEHStatePass, "x86-winehstate",
125 "Insert stores for EH state numbers", false, false)
126
127bool WinEHStatePass::doInitialization(Module &M) {
128 TheModule = &M;
129 return false;
130}
131
132bool 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
145void WinEHStatePass::getAnalysisUsage(AnalysisUsage &AU) const {
146 // This pass should only insert a stack allocation, memory accesses, and
147 // localrecovers.
148 AU.setPreservesCFG();
149}
150
151bool 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 = dyn_cast<Function>(Val: F.getPersonalityFn()->stripPointerCasts());
162 if (!PersonalityFn)
163 return false;
164 Personality = classifyEHPersonality(Pers: PersonalityFn);
165 if (!isFuncletEHPersonality(Pers: Personality))
166 return false;
167
168 // Skip this function if there are no EH pads and we aren't using IR-level
169 // outlining.
170 bool HasPads = false;
171 for (BasicBlock &BB : F) {
172 if (BB.isEHPad()) {
173 HasPads = true;
174 break;
175 }
176 }
177 if (!HasPads)
178 return false;
179
180 Type *Int8PtrType = PointerType::getUnqual(C&: TheModule->getContext());
181 SetJmp3 = TheModule->getOrInsertFunction(
182 Name: "_setjmp3", T: FunctionType::get(
183 Result: Type::getInt32Ty(C&: TheModule->getContext()),
184 Params: {Int8PtrType, Type::getInt32Ty(C&: TheModule->getContext())},
185 /*isVarArg=*/true));
186
187 emitExceptionRegistrationRecord(F: &F);
188
189 // The state numbers calculated here in IR must agree with what we calculate
190 // later on for the MachineFunction. In particular, if an IR pass deletes an
191 // unreachable EH pad after this point before machine CFG construction, we
192 // will be in trouble. If this assumption is ever broken, we should turn the
193 // numbers into an immutable analysis pass.
194 WinEHFuncInfo FuncInfo;
195 addStateStores(F, FuncInfo);
196 updateEspForInAllocas(F);
197
198 // Reset per-function state.
199 PersonalityFn = nullptr;
200 Personality = EHPersonality::Unknown;
201 UseStackGuard = false;
202 RegNodeTy = nullptr;
203 RegNode = nullptr;
204 EHGuardNode = nullptr;
205
206 return true;
207}
208
209/// Get the common EH registration subobject:
210/// typedef _EXCEPTION_DISPOSITION (*PEXCEPTION_ROUTINE)(
211/// _EXCEPTION_RECORD *, void *, _CONTEXT *, void *);
212/// struct EHRegistrationNode {
213/// EHRegistrationNode *Next;
214/// PEXCEPTION_ROUTINE Handler;
215/// };
216Type *WinEHStatePass::getEHLinkRegistrationType() {
217 if (EHLinkRegistrationTy)
218 return EHLinkRegistrationTy;
219 LLVMContext &Context = TheModule->getContext();
220 Type *FieldTys[] = {
221 PointerType::getUnqual(C&: Context), // EHRegistrationNode *Next
222 PointerType::getUnqual(C&: Context) // EXCEPTION_DISPOSITION (*Handler)(...)
223 };
224 EHLinkRegistrationTy = StructType::create(Elements: FieldTys, Name: "EHRegistrationNode");
225 return EHLinkRegistrationTy;
226}
227
228/// The __CxxFrameHandler3 registration node:
229/// struct CXXExceptionRegistration {
230/// void *SavedESP;
231/// EHRegistrationNode SubRecord;
232/// int32_t TryLevel;
233/// };
234Type *WinEHStatePass::getCXXEHRegistrationType() {
235 if (CXXEHRegistrationTy)
236 return CXXEHRegistrationTy;
237 LLVMContext &Context = TheModule->getContext();
238 Type *FieldTys[] = {
239 PointerType::getUnqual(C&: Context), // void *SavedESP
240 getEHLinkRegistrationType(), // EHRegistrationNode SubRecord
241 Type::getInt32Ty(C&: Context) // int32_t TryLevel
242 };
243 CXXEHRegistrationTy =
244 StructType::create(Elements: FieldTys, Name: "CXXExceptionRegistration");
245 return CXXEHRegistrationTy;
246}
247
248/// The _except_handler3/4 registration node:
249/// struct EH4ExceptionRegistration {
250/// void *SavedESP;
251/// _EXCEPTION_POINTERS *ExceptionPointers;
252/// EHRegistrationNode SubRecord;
253/// int32_t EncodedScopeTable;
254/// int32_t TryLevel;
255/// };
256Type *WinEHStatePass::getSEHRegistrationType() {
257 if (SEHRegistrationTy)
258 return SEHRegistrationTy;
259 LLVMContext &Context = TheModule->getContext();
260 Type *FieldTys[] = {
261 PointerType::getUnqual(C&: Context), // void *SavedESP
262 PointerType::getUnqual(C&: Context), // void *ExceptionPointers
263 getEHLinkRegistrationType(), // EHRegistrationNode SubRecord
264 Type::getInt32Ty(C&: Context), // int32_t EncodedScopeTable
265 Type::getInt32Ty(C&: Context) // int32_t TryLevel
266 };
267 SEHRegistrationTy = StructType::create(Elements: FieldTys, Name: "SEHExceptionRegistration");
268 return SEHRegistrationTy;
269}
270
271// Emit an exception registration record. These are stack allocations with the
272// common subobject of two pointers: the previous registration record (the old
273// fs:00) and the personality function for the current frame. The data before
274// and after that is personality function specific.
275void WinEHStatePass::emitExceptionRegistrationRecord(Function *F) {
276 assert(Personality == EHPersonality::MSVC_CXX ||
277 Personality == EHPersonality::MSVC_X86SEH);
278
279 IRBuilder<> Builder(&F->getEntryBlock(), F->getEntryBlock().begin());
280 Type *Int8PtrType = Builder.getPtrTy();
281 Type *Int32Ty = Builder.getInt32Ty();
282 Type *VoidTy = Builder.getVoidTy();
283
284 if (Personality == EHPersonality::MSVC_CXX) {
285 RegNodeTy = getCXXEHRegistrationType();
286 RegNode = Builder.CreateAlloca(Ty: RegNodeTy);
287 // SavedESP = llvm.stacksave()
288 Value *SP = Builder.CreateStackSave();
289 Builder.CreateStore(Val: SP, Ptr: Builder.CreateStructGEP(Ty: RegNodeTy, Ptr: RegNode, Idx: 0));
290 // TryLevel = -1
291 StateFieldIndex = 2;
292 ParentBaseState = -1;
293 insertStateNumberStore(IP: &*Builder.GetInsertPoint(), State: ParentBaseState);
294 // Handler = __ehhandler$F
295 Function *Trampoline = generateLSDAInEAXThunk(ParentFunc: F);
296 Link = Builder.CreateStructGEP(Ty: RegNodeTy, Ptr: RegNode, Idx: 1);
297 linkExceptionRegistration(Builder, Handler: Trampoline);
298
299 CxxLongjmpUnwind = TheModule->getOrInsertFunction(
300 Name: "__CxxLongjmpUnwind",
301 T: FunctionType::get(Result: VoidTy, Params: Int8PtrType, /*isVarArg=*/false));
302 cast<Function>(Val: CxxLongjmpUnwind.getCallee()->stripPointerCasts())
303 ->setCallingConv(CallingConv::X86_StdCall);
304 } else if (Personality == EHPersonality::MSVC_X86SEH) {
305 // If _except_handler4 is in use, some additional guard checks and prologue
306 // stuff is required.
307 StringRef PersonalityName = PersonalityFn->getName();
308 UseStackGuard = (PersonalityName == "_except_handler4");
309
310 // Allocate local structures.
311 RegNodeTy = getSEHRegistrationType();
312 RegNode = Builder.CreateAlloca(Ty: RegNodeTy);
313 if (UseStackGuard)
314 EHGuardNode = Builder.CreateAlloca(Ty: Int32Ty);
315
316 // SavedESP = llvm.stacksave()
317 Value *SP = Builder.CreateStackSave();
318 Builder.CreateStore(Val: SP, Ptr: Builder.CreateStructGEP(Ty: RegNodeTy, Ptr: RegNode, Idx: 0));
319 // TryLevel = -2 / -1
320 StateFieldIndex = 4;
321 ParentBaseState = UseStackGuard ? -2 : -1;
322 insertStateNumberStore(IP: &*Builder.GetInsertPoint(), State: ParentBaseState);
323 // ScopeTable = llvm.x86.seh.lsda(F)
324 Value *LSDA = emitEHLSDA(Builder, F);
325 LSDA = Builder.CreatePtrToInt(V: LSDA, DestTy: Int32Ty);
326 // If using _except_handler4, xor the address of the table with
327 // __security_cookie.
328 if (UseStackGuard) {
329 Cookie = TheModule->getOrInsertGlobal(Name: "__security_cookie", Ty: Int32Ty);
330 Value *Val = Builder.CreateLoad(Ty: Int32Ty, Ptr: Cookie, Name: "cookie");
331 LSDA = Builder.CreateXor(LHS: LSDA, RHS: Val);
332 }
333 Builder.CreateStore(Val: LSDA, Ptr: Builder.CreateStructGEP(Ty: RegNodeTy, Ptr: RegNode, Idx: 3));
334
335 // If using _except_handler4, the EHGuard contains: FramePtr xor Cookie.
336 if (UseStackGuard) {
337 Value *Val = Builder.CreateLoad(Ty: Int32Ty, Ptr: Cookie);
338 Value *FrameAddr = Builder.CreateIntrinsic(
339 ID: Intrinsic::frameaddress,
340 Types: Builder.getPtrTy(AddrSpace: TheModule->getDataLayout().getAllocaAddrSpace()),
341 Args: Builder.getInt32(C: 0), /*FMFSource=*/nullptr, Name: "frameaddr");
342 Value *FrameAddrI32 = Builder.CreatePtrToInt(V: FrameAddr, DestTy: Int32Ty);
343 FrameAddrI32 = Builder.CreateXor(LHS: FrameAddrI32, RHS: Val);
344 Builder.CreateStore(Val: FrameAddrI32, Ptr: EHGuardNode);
345 }
346
347 // Register the exception handler.
348 Link = Builder.CreateStructGEP(Ty: RegNodeTy, Ptr: RegNode, Idx: 2);
349 linkExceptionRegistration(Builder, Handler: PersonalityFn);
350
351 SehLongjmpUnwind = TheModule->getOrInsertFunction(
352 Name: UseStackGuard ? "_seh_longjmp_unwind4" : "_seh_longjmp_unwind",
353 T: FunctionType::get(Result: Type::getVoidTy(C&: TheModule->getContext()), Params: Int8PtrType,
354 /*isVarArg=*/false));
355 cast<Function>(Val: SehLongjmpUnwind.getCallee()->stripPointerCasts())
356 ->setCallingConv(CallingConv::X86_StdCall);
357 } else {
358 llvm_unreachable("unexpected personality function");
359 }
360
361 // Insert an unlink before all returns.
362 for (BasicBlock &BB : *F) {
363 Instruction *T = BB.getTerminator();
364 if (!isa<ReturnInst>(Val: T))
365 continue;
366
367 // If there is a musttail call, that's the de-facto terminator.
368 if (CallInst *CI = BB.getTerminatingMustTailCall())
369 T = CI;
370
371 Builder.SetInsertPoint(T);
372 unlinkExceptionRegistration(Builder);
373 }
374}
375
376Value *WinEHStatePass::emitEHLSDA(IRBuilder<> &Builder, Function *F) {
377 return Builder.CreateIntrinsic(ID: Intrinsic::x86_seh_lsda, Args: F);
378}
379
380/// Generate a thunk that puts the LSDA of ParentFunc in EAX and then calls
381/// PersonalityFn, forwarding the parameters passed to PEXCEPTION_ROUTINE:
382/// typedef _EXCEPTION_DISPOSITION (*PEXCEPTION_ROUTINE)(
383/// _EXCEPTION_RECORD *, void *, _CONTEXT *, void *);
384/// We essentially want this code:
385/// movl $lsda, %eax
386/// jmpl ___CxxFrameHandler3
387Function *WinEHStatePass::generateLSDAInEAXThunk(Function *ParentFunc) {
388 LLVMContext &Context = ParentFunc->getContext();
389 Type *Int32Ty = Type::getInt32Ty(C&: Context);
390 Type *Int8PtrType = PointerType::getUnqual(C&: Context);
391 Type *ArgTys[5] = {Int8PtrType, Int8PtrType, Int8PtrType, Int8PtrType,
392 Int8PtrType};
393 FunctionType *TrampolineTy =
394 FunctionType::get(Result: Int32Ty, Params: ArrayRef(&ArgTys[0], 4),
395 /*isVarArg=*/false);
396 FunctionType *TargetFuncTy =
397 FunctionType::get(Result: Int32Ty, Params: ArrayRef(&ArgTys[0], 5),
398 /*isVarArg=*/false);
399 Function *Trampoline = Function::Create(
400 Ty: TrampolineTy, Linkage: GlobalValue::InternalLinkage,
401 N: Twine("__ehhandler$") +
402 GlobalValue::dropLLVMManglingEscape(Name: ParentFunc->getName()),
403 M: TheModule);
404 if (auto *C = ParentFunc->getComdat())
405 Trampoline->setComdat(C);
406 BasicBlock *EntryBB = BasicBlock::Create(Context, Name: "entry", Parent: Trampoline);
407 IRBuilder<> Builder(EntryBB);
408 Value *LSDA = emitEHLSDA(Builder, F: ParentFunc);
409 auto AI = Trampoline->arg_begin();
410 Value *Args[5] = {LSDA, &*AI++, &*AI++, &*AI++, &*AI++};
411 CallInst *Call = Builder.CreateCall(FTy: TargetFuncTy, Callee: PersonalityFn, 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(ArgNo: 0, Kind: Attribute::InReg);
416 Builder.CreateRet(V: Call);
417 return Trampoline;
418}
419
420void WinEHStatePass::linkExceptionRegistration(IRBuilder<> &Builder,
421 Function *Handler) {
422 // Emit the .safeseh directive for this function.
423 Handler->addFnAttr(Kind: "safeseh");
424
425 LLVMContext &C = Builder.getContext();
426 Type *LinkTy = getEHLinkRegistrationType();
427 // Handler = Handler
428 Builder.CreateStore(Val: Handler, Ptr: Builder.CreateStructGEP(Ty: LinkTy, Ptr: Link, Idx: 1));
429 // Next = [fs:00]
430 Constant *FSZero = Constant::getNullValue(Ty: PointerType::get(C, AddressSpace: X86AS::FS));
431 Value *Next = Builder.CreateLoad(Ty: PointerType::getUnqual(C), Ptr: FSZero);
432 Builder.CreateStore(Val: Next, Ptr: Builder.CreateStructGEP(Ty: LinkTy, Ptr: Link, Idx: 0));
433 // [fs:00] = Link
434 Builder.CreateStore(Val: Link, Ptr: FSZero);
435}
436
437void WinEHStatePass::unlinkExceptionRegistration(IRBuilder<> &Builder) {
438 // Clone Link into the current BB for better address mode folding.
439 if (auto *GEP = dyn_cast<GetElementPtrInst>(Val: Link)) {
440 GEP = cast<GetElementPtrInst>(Val: GEP->clone());
441 Builder.Insert(I: GEP);
442 Link = GEP;
443 }
444
445 LLVMContext &C = Builder.getContext();
446 Type *LinkTy = getEHLinkRegistrationType();
447 // [fs:00] = Link->Next
448 Value *Next = Builder.CreateLoad(Ty: PointerType::getUnqual(C),
449 Ptr: Builder.CreateStructGEP(Ty: LinkTy, Ptr: Link, Idx: 0));
450 Constant *FSZero = Constant::getNullValue(Ty: PointerType::get(C, AddressSpace: X86AS::FS));
451 Builder.CreateStore(Val: Next, Ptr: 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.
458void 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.arg_size() != 2)
462 return;
463
464 SmallVector<OperandBundleDef, 1> OpBundles;
465 Call.getOperandBundlesAsDefs(Defs&: OpBundles);
466
467 SmallVector<Value *, 3> OptionalArgs;
468 if (Personality == EHPersonality::MSVC_CXX) {
469 OptionalArgs.push_back(Elt: CxxLongjmpUnwind.getCallee());
470 OptionalArgs.push_back(Elt: State);
471 OptionalArgs.push_back(Elt: emitEHLSDA(Builder, F: &F));
472 } else if (Personality == EHPersonality::MSVC_X86SEH) {
473 OptionalArgs.push_back(Elt: SehLongjmpUnwind.getCallee());
474 OptionalArgs.push_back(Elt: State);
475 if (UseStackGuard)
476 OptionalArgs.push_back(Elt: Cookie);
477 } else {
478 llvm_unreachable("unhandled personality!");
479 }
480
481 SmallVector<Value *, 5> Args;
482 Args.push_back(
483 Elt: Builder.CreateBitCast(V: Call.getArgOperand(i: 0), DestTy: Builder.getPtrTy()));
484 Args.push_back(Elt: Builder.getInt32(C: OptionalArgs.size()));
485 Args.append(in_start: OptionalArgs.begin(), in_end: OptionalArgs.end());
486
487 CallBase *NewCall;
488 if (auto *CI = dyn_cast<CallInst>(Val: &Call)) {
489 CallInst *NewCI = Builder.CreateCall(Callee: SetJmp3, Args, OpBundles);
490 NewCI->setTailCallKind(CI->getTailCallKind());
491 NewCall = NewCI;
492 } else {
493 auto *II = cast<InvokeInst>(Val: &Call);
494 NewCall = Builder.CreateInvoke(Callee: SetJmp3, NormalDest: II->getNormalDest(),
495 UnwindDest: II->getUnwindDest(), Args, OpBundles);
496 }
497 NewCall->setCallingConv(Call.getCallingConv());
498 NewCall->setAttributes(Call.getAttributes());
499 NewCall->setDebugLoc(Call.getDebugLoc());
500
501 NewCall->takeName(V: &Call);
502 Call.replaceAllUsesWith(V: NewCall);
503 Call.eraseFromParent();
504}
505
506// Figure out what state we should assign calls in this block.
507int 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>(Val: FuncletEntryBB->getFirstNonPHIIt())) {
517 auto BaseStateI = FuncInfo.FuncletBaseStateMap.find(Val: FuncletPad);
518 if (BaseStateI != FuncInfo.FuncletBaseStateMap.end())
519 BaseState = BaseStateI->second;
520 }
521
522 return BaseState;
523}
524
525static bool isIntrinsic(const CallBase &Call, Intrinsic::ID ID) {
526 const Function *CF = Call.getCalledFunction();
527 return CF && CF->isIntrinsic() && CF->getIntrinsicID() == ID;
528}
529
530static bool isSehScopeEnd(const CallBase &Call) {
531 return isIntrinsic(Call, ID: Intrinsic::seh_scope_end);
532}
533
534static bool isSehScopeBegin(const CallBase &Call) {
535 return isIntrinsic(Call, ID: Intrinsic::seh_scope_begin);
536}
537
538// Calculate the state a call-site is in.
539int WinEHStatePass::getStateForCall(
540 DenseMap<BasicBlock *, ColorVector> &BlockColors, WinEHFuncInfo &FuncInfo,
541 CallBase &Call) {
542 if (auto *II = dyn_cast<InvokeInst>(Val: &Call)) {
543 if (isSehScopeEnd(Call: *II)) {
544 return getBaseStateForBB(BlockColors, FuncInfo, BB: II->getNormalDest());
545 }
546
547 // Look up the state number of the EH pad this unwinds to.
548 assert(FuncInfo.InvokeStateMap.count(II) && "invoke has no state!");
549 return FuncInfo.InvokeStateMap[II];
550 }
551 // Possibly throwing call instructions have no actions to take after
552 // an unwind. Ensure they are in the -1 state.
553 return getBaseStateForBB(BlockColors, FuncInfo, BB: Call.getParent());
554}
555
556// Calculate the intersection of all the FinalStates for a BasicBlock's
557// predecessors.
558static int getPredState(DenseMap<BasicBlock *, int> &FinalStates, Function &F,
559 int ParentBaseState, BasicBlock *BB) {
560 // The entry block has no predecessors but we know that the prologue always
561 // sets us up with a fixed state.
562 if (&F.getEntryBlock() == BB)
563 return ParentBaseState;
564
565 // This is an EH Pad, conservatively report this basic block as overdefined.
566 if (BB->isEHPad())
567 return OverdefinedState;
568
569 int CommonState = OverdefinedState;
570 for (BasicBlock *PredBB : predecessors(BB)) {
571 // We didn't manage to get a state for one of these predecessors,
572 // conservatively report this basic block as overdefined.
573 auto PredEndState = FinalStates.find(Val: PredBB);
574 if (PredEndState == FinalStates.end())
575 return OverdefinedState;
576
577 // This code is reachable via exceptional control flow,
578 // conservatively report this basic block as overdefined.
579 if (isa<CatchReturnInst>(Val: PredBB->getTerminator()))
580 return OverdefinedState;
581
582 int PredState = PredEndState->second;
583 assert(PredState != OverdefinedState &&
584 "overdefined BBs shouldn't be in FinalStates");
585 if (CommonState == OverdefinedState)
586 CommonState = PredState;
587
588 // At least two predecessors have different FinalStates,
589 // conservatively report this basic block as overdefined.
590 if (CommonState != PredState)
591 return OverdefinedState;
592 }
593
594 return CommonState;
595}
596
597// Calculate the intersection of all the InitialStates for a BasicBlock's
598// successors.
599static int getSuccState(DenseMap<BasicBlock *, int> &InitialStates, Function &F,
600 int ParentBaseState, BasicBlock *BB) {
601 // This block rejoins normal control flow,
602 // conservatively report this basic block as overdefined.
603 if (isa<CatchReturnInst>(Val: BB->getTerminator()))
604 return OverdefinedState;
605
606 int CommonState = OverdefinedState;
607 for (BasicBlock *SuccBB : successors(BB)) {
608 // We didn't manage to get a state for one of these predecessors,
609 // conservatively report this basic block as overdefined.
610 auto SuccStartState = InitialStates.find(Val: SuccBB);
611 if (SuccStartState == InitialStates.end())
612 return OverdefinedState;
613
614 // This is an EH Pad, conservatively report this basic block as overdefined.
615 if (SuccBB->isEHPad())
616 return OverdefinedState;
617
618 int SuccState = SuccStartState->second;
619 assert(SuccState != OverdefinedState &&
620 "overdefined BBs shouldn't be in FinalStates");
621 if (CommonState == OverdefinedState)
622 CommonState = SuccState;
623
624 // At least two successors have different InitialStates,
625 // conservatively report this basic block as overdefined.
626 if (CommonState != SuccState)
627 return OverdefinedState;
628 }
629
630 return CommonState;
631}
632
633bool WinEHStatePass::isStateStoreNeeded(EHPersonality Personality,
634 CallBase &Call) {
635 if (isSehScopeBegin(Call) || isSehScopeEnd(Call)) {
636 return true;
637 }
638
639 // If the function touches memory, it needs a state store.
640 if (isAsynchronousEHPersonality(Pers: Personality))
641 return !Call.doesNotAccessMemory();
642
643 // If the function throws, it needs a state store.
644 return !Call.doesNotThrow();
645}
646
647void WinEHStatePass::addStateStores(Function &F, WinEHFuncInfo &FuncInfo) {
648 // Mark the registration node. The backend needs to know which alloca it is so
649 // that it can recover the original frame pointer.
650 IRBuilder<> Builder(RegNode->getNextNode());
651 Value *RegNodeI8 = Builder.CreateBitCast(V: RegNode, DestTy: Builder.getPtrTy());
652 Builder.CreateIntrinsic(ID: Intrinsic::x86_seh_ehregnode, Args: {RegNodeI8});
653
654 if (EHGuardNode) {
655 IRBuilder<> Builder(EHGuardNode->getNextNode());
656 Value *EHGuardNodeI8 =
657 Builder.CreateBitCast(V: EHGuardNode, DestTy: Builder.getPtrTy());
658 Builder.CreateIntrinsic(ID: Intrinsic::x86_seh_ehguard, Args: {EHGuardNodeI8});
659 }
660
661 // Calculate state numbers.
662 if (isAsynchronousEHPersonality(Pers: Personality))
663 calculateSEHStateNumbers(ParentFn: &F, FuncInfo);
664 else
665 calculateWinCXXEHStateNumbers(ParentFn: &F, FuncInfo);
666
667 // Iterate all the instructions and emit state number stores.
668 DenseMap<BasicBlock *, ColorVector> BlockColors = colorEHFunclets(F);
669 ReversePostOrderTraversal<Function *> RPOT(&F);
670
671 // InitialStates yields the state of the first call-site for a BasicBlock.
672 DenseMap<BasicBlock *, int> InitialStates;
673 // FinalStates yields the state of the last call-site for a BasicBlock.
674 DenseMap<BasicBlock *, int> FinalStates;
675 // Worklist used to revisit BasicBlocks with indeterminate
676 // Initial/Final-States.
677 std::deque<BasicBlock *> Worklist;
678 // Fill in InitialStates and FinalStates for BasicBlocks with call-sites.
679 for (BasicBlock *BB : RPOT) {
680 int InitialState = OverdefinedState;
681 int FinalState;
682 if (&F.getEntryBlock() == BB)
683 InitialState = FinalState = ParentBaseState;
684 for (Instruction &I : *BB) {
685 auto *Call = dyn_cast<CallBase>(Val: &I);
686 if (!Call || !isStateStoreNeeded(Personality, Call&: *Call))
687 continue;
688
689 int State = getStateForCall(BlockColors, FuncInfo, Call&: *Call);
690 if (InitialState == OverdefinedState)
691 InitialState = State;
692 FinalState = State;
693 }
694 // No call-sites in this basic block? That's OK, we will come back to these
695 // in a later pass.
696 if (InitialState == OverdefinedState) {
697 Worklist.push_back(x: BB);
698 continue;
699 }
700 LLVM_DEBUG(dbgs() << "X86WinEHState: " << BB->getName()
701 << " InitialState=" << InitialState << '\n');
702 LLVM_DEBUG(dbgs() << "X86WinEHState: " << BB->getName()
703 << " FinalState=" << FinalState << '\n');
704 InitialStates.insert(KV: {BB, InitialState});
705 FinalStates.insert(KV: {BB, FinalState});
706 }
707
708 // Try to fill-in InitialStates and FinalStates which have no call-sites.
709 while (!Worklist.empty()) {
710 BasicBlock *BB = Worklist.front();
711 Worklist.pop_front();
712 // This BasicBlock has already been figured out, nothing more we can do.
713 if (InitialStates.count(Val: BB) != 0)
714 continue;
715
716 int PredState = getPredState(FinalStates, F, ParentBaseState, BB);
717 if (PredState == OverdefinedState)
718 continue;
719
720 // We successfully inferred this BasicBlock's state via it's predecessors;
721 // enqueue it's successors to see if we can infer their states.
722 InitialStates.insert(KV: {BB, PredState});
723 FinalStates.insert(KV: {BB, PredState});
724 for (BasicBlock *SuccBB : successors(BB))
725 Worklist.push_back(x: SuccBB);
726 }
727
728 // Try to hoist stores from successors.
729 for (BasicBlock *BB : RPOT) {
730 int SuccState = getSuccState(InitialStates, F, ParentBaseState, BB);
731 if (SuccState == OverdefinedState)
732 continue;
733
734 // Update our FinalState to reflect the common InitialState of our
735 // successors.
736 FinalStates.insert(KV: {BB, SuccState});
737 }
738
739 // Finally, insert state stores before call-sites which transition us to a new
740 // state.
741 for (BasicBlock *BB : RPOT) {
742 auto &BBColors = BlockColors[BB];
743 BasicBlock *FuncletEntryBB = BBColors.front();
744 if (isa<CleanupPadInst>(Val: FuncletEntryBB->getFirstNonPHIIt()))
745 continue;
746
747 int PrevState = getPredState(FinalStates, F, ParentBaseState, BB);
748 LLVM_DEBUG(dbgs() << "X86WinEHState: " << BB->getName()
749 << " PrevState=" << PrevState << '\n');
750
751 for (Instruction &I : *BB) {
752 auto *Call = dyn_cast<CallBase>(Val: &I);
753 if (!Call || !isStateStoreNeeded(Personality, Call&: *Call))
754 continue;
755
756 int State = getStateForCall(BlockColors, FuncInfo, Call&: *Call);
757 if (State != PrevState)
758 insertStateNumberStore(IP: &I, State);
759 PrevState = State;
760 }
761
762 // We might have hoisted a state store into this block, emit it now.
763 auto EndState = FinalStates.find(Val: BB);
764 if (EndState != FinalStates.end())
765 if (EndState->second != PrevState)
766 insertStateNumberStore(IP: BB->getTerminator(), State: EndState->second);
767 }
768
769 SmallVector<CallBase *, 1> SetJmp3Calls;
770 for (BasicBlock *BB : RPOT) {
771 for (Instruction &I : *BB) {
772 auto *Call = dyn_cast<CallBase>(Val: &I);
773 if (!Call)
774 continue;
775 if (Call->getCalledOperand()->stripPointerCasts() !=
776 SetJmp3.getCallee()->stripPointerCasts())
777 continue;
778
779 SetJmp3Calls.push_back(Elt: Call);
780 }
781 }
782
783 for (CallBase *Call : SetJmp3Calls) {
784 auto &BBColors = BlockColors[Call->getParent()];
785 BasicBlock *FuncletEntryBB = BBColors.front();
786 bool InCleanup = isa<CleanupPadInst>(Val: FuncletEntryBB->getFirstNonPHIIt());
787
788 IRBuilder<> Builder(Call);
789 Value *State;
790 if (InCleanup) {
791 Value *StateField = Builder.CreateStructGEP(Ty: RegNode->getAllocatedType(),
792 Ptr: RegNode, Idx: StateFieldIndex);
793 State = Builder.CreateLoad(Ty: Builder.getInt32Ty(), Ptr: StateField);
794 } else {
795 State = Builder.getInt32(C: getStateForCall(BlockColors, FuncInfo, Call&: *Call));
796 }
797 rewriteSetJmpCall(Builder, F, Call&: *Call, State);
798 }
799}
800
801void WinEHStatePass::insertStateNumberStore(Instruction *IP, int State) {
802 IRBuilder<> Builder(IP);
803 Value *StateField = Builder.CreateStructGEP(Ty: RegNode->getAllocatedType(),
804 Ptr: RegNode, Idx: StateFieldIndex);
805 Builder.CreateStore(Val: Builder.getInt32(C: State), Ptr: StateField);
806}
807
808void WinEHStatePass::updateEspForInAllocas(Function &F) {
809 for (BasicBlock &BB : F) {
810 for (Instruction &I : BB) {
811 if (auto *Alloca = dyn_cast<AllocaInst>(Val: &I)) {
812 if (Alloca->isStaticAlloca())
813 continue;
814 IRBuilder<> Builder(Alloca->getNextNonDebugInstruction());
815 // SavedESP = llvm.stacksave()
816 Value *SP = Builder.CreateStackSave();
817 Builder.CreateStore(Val: SP, Ptr: Builder.CreateStructGEP(Ty: RegNodeTy, Ptr: RegNode, Idx: 0));
818 }
819
820 if (auto *II = dyn_cast<IntrinsicInst>(Val: &I)) {
821 if (II->getIntrinsicID() != Intrinsic::stackrestore)
822 continue;
823 IRBuilder<> Builder(II->getNextNonDebugInstruction());
824 // SavedESP = llvm.stacksave()
825 Value *SP = Builder.CreateStackSave();
826 Builder.CreateStore(Val: SP, Ptr: Builder.CreateStructGEP(Ty: RegNodeTy, Ptr: RegNode, Idx: 0));
827 }
828 }
829 }
830}
831