1 //===--- CGException.cpp - Emit LLVM Code for C++ exceptions ----*- C++ -*-===//
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 // This contains code dealing with C++ exception related code generation.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "CodeGenFunction.h"
15 #include "CGCXXABI.h"
16 #include "CGCleanup.h"
17 #include "CGObjCRuntime.h"
18 #include "TargetInfo.h"
19 #include "clang/AST/Mangle.h"
20 #include "clang/AST/StmtCXX.h"
21 #include "clang/AST/StmtObjC.h"
22 #include "clang/AST/StmtVisitor.h"
23 #include "clang/Basic/TargetBuiltins.h"
24 #include "llvm/IR/CallSite.h"
25 #include "llvm/IR/Intrinsics.h"
26 #include "llvm/IR/IntrinsicInst.h"
27 #include "llvm/Support/SaveAndRestore.h"
28
29 using namespace clang;
30 using namespace CodeGen;
31
getFreeExceptionFn(CodeGenModule & CGM)32 static llvm::Constant *getFreeExceptionFn(CodeGenModule &CGM) {
33 // void __cxa_free_exception(void *thrown_exception);
34
35 llvm::FunctionType *FTy =
36 llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false);
37
38 return CGM.CreateRuntimeFunction(FTy, "__cxa_free_exception");
39 }
40
getUnexpectedFn(CodeGenModule & CGM)41 static llvm::Constant *getUnexpectedFn(CodeGenModule &CGM) {
42 // void __cxa_call_unexpected(void *thrown_exception);
43
44 llvm::FunctionType *FTy =
45 llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false);
46
47 return CGM.CreateRuntimeFunction(FTy, "__cxa_call_unexpected");
48 }
49
getTerminateFn()50 llvm::Constant *CodeGenModule::getTerminateFn() {
51 // void __terminate();
52
53 llvm::FunctionType *FTy =
54 llvm::FunctionType::get(VoidTy, /*IsVarArgs=*/false);
55
56 StringRef name;
57
58 // In C++, use std::terminate().
59 if (getLangOpts().CPlusPlus &&
60 getTarget().getCXXABI().isItaniumFamily()) {
61 name = "_ZSt9terminatev";
62 } else if (getLangOpts().CPlusPlus &&
63 getTarget().getCXXABI().isMicrosoft()) {
64 if (getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2015))
65 name = "__std_terminate";
66 else
67 name = "\01?terminate@@YAXXZ";
68 } else if (getLangOpts().ObjC1 &&
69 getLangOpts().ObjCRuntime.hasTerminate())
70 name = "objc_terminate";
71 else
72 name = "abort";
73 return CreateRuntimeFunction(FTy, name);
74 }
75
getCatchallRethrowFn(CodeGenModule & CGM,StringRef Name)76 static llvm::Constant *getCatchallRethrowFn(CodeGenModule &CGM,
77 StringRef Name) {
78 llvm::FunctionType *FTy =
79 llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false);
80
81 return CGM.CreateRuntimeFunction(FTy, Name);
82 }
83
84 const EHPersonality EHPersonality::GNU_C = { "__gcc_personality_v0", nullptr };
85 const EHPersonality
86 EHPersonality::GNU_C_SJLJ = { "__gcc_personality_sj0", nullptr };
87 const EHPersonality
88 EHPersonality::GNU_C_SEH = { "__gcc_personality_seh0", nullptr };
89 const EHPersonality
90 EHPersonality::NeXT_ObjC = { "__objc_personality_v0", nullptr };
91 const EHPersonality
92 EHPersonality::GNU_CPlusPlus = { "__gxx_personality_v0", nullptr };
93 const EHPersonality
94 EHPersonality::GNU_CPlusPlus_SJLJ = { "__gxx_personality_sj0", nullptr };
95 const EHPersonality
96 EHPersonality::GNU_CPlusPlus_SEH = { "__gxx_personality_seh0", nullptr };
97 const EHPersonality
98 EHPersonality::GNU_ObjC = {"__gnu_objc_personality_v0", "objc_exception_throw"};
99 const EHPersonality
100 EHPersonality::GNU_ObjCXX = { "__gnustep_objcxx_personality_v0", nullptr };
101 const EHPersonality
102 EHPersonality::GNUstep_ObjC = { "__gnustep_objc_personality_v0", nullptr };
103 const EHPersonality
104 EHPersonality::MSVC_except_handler = { "_except_handler3", nullptr };
105 const EHPersonality
106 EHPersonality::MSVC_C_specific_handler = { "__C_specific_handler", nullptr };
107 const EHPersonality
108 EHPersonality::MSVC_CxxFrameHandler3 = { "__CxxFrameHandler3", nullptr };
109
110 /// On Win64, use libgcc's SEH personality function. We fall back to dwarf on
111 /// other platforms, unless the user asked for SjLj exceptions.
useLibGCCSEHPersonality(const llvm::Triple & T)112 static bool useLibGCCSEHPersonality(const llvm::Triple &T) {
113 return T.isOSWindows() && T.getArch() == llvm::Triple::x86_64;
114 }
115
getCPersonality(const llvm::Triple & T,const LangOptions & L)116 static const EHPersonality &getCPersonality(const llvm::Triple &T,
117 const LangOptions &L) {
118 if (L.SjLjExceptions)
119 return EHPersonality::GNU_C_SJLJ;
120 else if (useLibGCCSEHPersonality(T))
121 return EHPersonality::GNU_C_SEH;
122 return EHPersonality::GNU_C;
123 }
124
getObjCPersonality(const llvm::Triple & T,const LangOptions & L)125 static const EHPersonality &getObjCPersonality(const llvm::Triple &T,
126 const LangOptions &L) {
127 switch (L.ObjCRuntime.getKind()) {
128 case ObjCRuntime::FragileMacOSX:
129 return getCPersonality(T, L);
130 case ObjCRuntime::MacOSX:
131 case ObjCRuntime::iOS:
132 case ObjCRuntime::WatchOS:
133 return EHPersonality::NeXT_ObjC;
134 case ObjCRuntime::GNUstep:
135 if (L.ObjCRuntime.getVersion() >= VersionTuple(1, 7))
136 return EHPersonality::GNUstep_ObjC;
137 // fallthrough
138 case ObjCRuntime::GCC:
139 case ObjCRuntime::ObjFW:
140 return EHPersonality::GNU_ObjC;
141 }
142 llvm_unreachable("bad runtime kind");
143 }
144
getCXXPersonality(const llvm::Triple & T,const LangOptions & L)145 static const EHPersonality &getCXXPersonality(const llvm::Triple &T,
146 const LangOptions &L) {
147 if (L.SjLjExceptions)
148 return EHPersonality::GNU_CPlusPlus_SJLJ;
149 else if (useLibGCCSEHPersonality(T))
150 return EHPersonality::GNU_CPlusPlus_SEH;
151 return EHPersonality::GNU_CPlusPlus;
152 }
153
154 /// Determines the personality function to use when both C++
155 /// and Objective-C exceptions are being caught.
getObjCXXPersonality(const llvm::Triple & T,const LangOptions & L)156 static const EHPersonality &getObjCXXPersonality(const llvm::Triple &T,
157 const LangOptions &L) {
158 switch (L.ObjCRuntime.getKind()) {
159 // The ObjC personality defers to the C++ personality for non-ObjC
160 // handlers. Unlike the C++ case, we use the same personality
161 // function on targets using (backend-driven) SJLJ EH.
162 case ObjCRuntime::MacOSX:
163 case ObjCRuntime::iOS:
164 case ObjCRuntime::WatchOS:
165 return EHPersonality::NeXT_ObjC;
166
167 // In the fragile ABI, just use C++ exception handling and hope
168 // they're not doing crazy exception mixing.
169 case ObjCRuntime::FragileMacOSX:
170 return getCXXPersonality(T, L);
171
172 // The GCC runtime's personality function inherently doesn't support
173 // mixed EH. Use the C++ personality just to avoid returning null.
174 case ObjCRuntime::GCC:
175 case ObjCRuntime::ObjFW: // XXX: this will change soon
176 return EHPersonality::GNU_ObjC;
177 case ObjCRuntime::GNUstep:
178 return EHPersonality::GNU_ObjCXX;
179 }
180 llvm_unreachable("bad runtime kind");
181 }
182
getSEHPersonalityMSVC(const llvm::Triple & T)183 static const EHPersonality &getSEHPersonalityMSVC(const llvm::Triple &T) {
184 if (T.getArch() == llvm::Triple::x86)
185 return EHPersonality::MSVC_except_handler;
186 return EHPersonality::MSVC_C_specific_handler;
187 }
188
get(CodeGenModule & CGM,const FunctionDecl * FD)189 const EHPersonality &EHPersonality::get(CodeGenModule &CGM,
190 const FunctionDecl *FD) {
191 const llvm::Triple &T = CGM.getTarget().getTriple();
192 const LangOptions &L = CGM.getLangOpts();
193
194 // Functions using SEH get an SEH personality.
195 if (FD && FD->usesSEHTry())
196 return getSEHPersonalityMSVC(T);
197
198 // Try to pick a personality function that is compatible with MSVC if we're
199 // not compiling Obj-C. Obj-C users better have an Obj-C runtime that supports
200 // the GCC-style personality function.
201 if (T.isWindowsMSVCEnvironment() && !L.ObjC1) {
202 if (L.SjLjExceptions)
203 return EHPersonality::GNU_CPlusPlus_SJLJ;
204 else
205 return EHPersonality::MSVC_CxxFrameHandler3;
206 }
207
208 if (L.CPlusPlus && L.ObjC1)
209 return getObjCXXPersonality(T, L);
210 else if (L.CPlusPlus)
211 return getCXXPersonality(T, L);
212 else if (L.ObjC1)
213 return getObjCPersonality(T, L);
214 else
215 return getCPersonality(T, L);
216 }
217
get(CodeGenFunction & CGF)218 const EHPersonality &EHPersonality::get(CodeGenFunction &CGF) {
219 return get(CGF.CGM, dyn_cast_or_null<FunctionDecl>(CGF.CurCodeDecl));
220 }
221
getPersonalityFn(CodeGenModule & CGM,const EHPersonality & Personality)222 static llvm::Constant *getPersonalityFn(CodeGenModule &CGM,
223 const EHPersonality &Personality) {
224 llvm::Constant *Fn =
225 CGM.CreateRuntimeFunction(llvm::FunctionType::get(CGM.Int32Ty, true),
226 Personality.PersonalityFn);
227 return Fn;
228 }
229
getOpaquePersonalityFn(CodeGenModule & CGM,const EHPersonality & Personality)230 static llvm::Constant *getOpaquePersonalityFn(CodeGenModule &CGM,
231 const EHPersonality &Personality) {
232 llvm::Constant *Fn = getPersonalityFn(CGM, Personality);
233 return llvm::ConstantExpr::getBitCast(Fn, CGM.Int8PtrTy);
234 }
235
236 /// Check whether a landingpad instruction only uses C++ features.
LandingPadHasOnlyCXXUses(llvm::LandingPadInst * LPI)237 static bool LandingPadHasOnlyCXXUses(llvm::LandingPadInst *LPI) {
238 for (unsigned I = 0, E = LPI->getNumClauses(); I != E; ++I) {
239 // Look for something that would've been returned by the ObjC
240 // runtime's GetEHType() method.
241 llvm::Value *Val = LPI->getClause(I)->stripPointerCasts();
242 if (LPI->isCatch(I)) {
243 // Check if the catch value has the ObjC prefix.
244 if (llvm::GlobalVariable *GV = dyn_cast<llvm::GlobalVariable>(Val))
245 // ObjC EH selector entries are always global variables with
246 // names starting like this.
247 if (GV->getName().startswith("OBJC_EHTYPE"))
248 return false;
249 } else {
250 // Check if any of the filter values have the ObjC prefix.
251 llvm::Constant *CVal = cast<llvm::Constant>(Val);
252 for (llvm::User::op_iterator
253 II = CVal->op_begin(), IE = CVal->op_end(); II != IE; ++II) {
254 if (llvm::GlobalVariable *GV =
255 cast<llvm::GlobalVariable>((*II)->stripPointerCasts()))
256 // ObjC EH selector entries are always global variables with
257 // names starting like this.
258 if (GV->getName().startswith("OBJC_EHTYPE"))
259 return false;
260 }
261 }
262 }
263 return true;
264 }
265
266 /// Check whether a personality function could reasonably be swapped
267 /// for a C++ personality function.
PersonalityHasOnlyCXXUses(llvm::Constant * Fn)268 static bool PersonalityHasOnlyCXXUses(llvm::Constant *Fn) {
269 for (llvm::User *U : Fn->users()) {
270 // Conditionally white-list bitcasts.
271 if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(U)) {
272 if (CE->getOpcode() != llvm::Instruction::BitCast) return false;
273 if (!PersonalityHasOnlyCXXUses(CE))
274 return false;
275 continue;
276 }
277
278 // Otherwise it must be a function.
279 llvm::Function *F = dyn_cast<llvm::Function>(U);
280 if (!F) return false;
281
282 for (auto BB = F->begin(), E = F->end(); BB != E; ++BB) {
283 if (BB->isLandingPad())
284 if (!LandingPadHasOnlyCXXUses(BB->getLandingPadInst()))
285 return false;
286 }
287 }
288
289 return true;
290 }
291
292 /// Try to use the C++ personality function in ObjC++. Not doing this
293 /// can cause some incompatibilities with gcc, which is more
294 /// aggressive about only using the ObjC++ personality in a function
295 /// when it really needs it.
SimplifyPersonality()296 void CodeGenModule::SimplifyPersonality() {
297 // If we're not in ObjC++ -fexceptions, there's nothing to do.
298 if (!LangOpts.CPlusPlus || !LangOpts.ObjC1 || !LangOpts.Exceptions)
299 return;
300
301 // Both the problem this endeavors to fix and the way the logic
302 // above works is specific to the NeXT runtime.
303 if (!LangOpts.ObjCRuntime.isNeXTFamily())
304 return;
305
306 const EHPersonality &ObjCXX = EHPersonality::get(*this, /*FD=*/nullptr);
307 const EHPersonality &CXX =
308 getCXXPersonality(getTarget().getTriple(), LangOpts);
309 if (&ObjCXX == &CXX)
310 return;
311
312 assert(std::strcmp(ObjCXX.PersonalityFn, CXX.PersonalityFn) != 0 &&
313 "Different EHPersonalities using the same personality function.");
314
315 llvm::Function *Fn = getModule().getFunction(ObjCXX.PersonalityFn);
316
317 // Nothing to do if it's unused.
318 if (!Fn || Fn->use_empty()) return;
319
320 // Can't do the optimization if it has non-C++ uses.
321 if (!PersonalityHasOnlyCXXUses(Fn)) return;
322
323 // Create the C++ personality function and kill off the old
324 // function.
325 llvm::Constant *CXXFn = getPersonalityFn(*this, CXX);
326
327 // This can happen if the user is screwing with us.
328 if (Fn->getType() != CXXFn->getType()) return;
329
330 Fn->replaceAllUsesWith(CXXFn);
331 Fn->eraseFromParent();
332 }
333
334 /// Returns the value to inject into a selector to indicate the
335 /// presence of a catch-all.
getCatchAllValue(CodeGenFunction & CGF)336 static llvm::Constant *getCatchAllValue(CodeGenFunction &CGF) {
337 // Possibly we should use @llvm.eh.catch.all.value here.
338 return llvm::ConstantPointerNull::get(CGF.Int8PtrTy);
339 }
340
341 namespace {
342 /// A cleanup to free the exception object if its initialization
343 /// throws.
344 struct FreeException final : EHScopeStack::Cleanup {
345 llvm::Value *exn;
FreeException__anonab2436450111::FreeException346 FreeException(llvm::Value *exn) : exn(exn) {}
Emit__anonab2436450111::FreeException347 void Emit(CodeGenFunction &CGF, Flags flags) override {
348 CGF.EmitNounwindRuntimeCall(getFreeExceptionFn(CGF.CGM), exn);
349 }
350 };
351 } // end anonymous namespace
352
353 // Emits an exception expression into the given location. This
354 // differs from EmitAnyExprToMem only in that, if a final copy-ctor
355 // call is required, an exception within that copy ctor causes
356 // std::terminate to be invoked.
EmitAnyExprToExn(const Expr * e,Address addr)357 void CodeGenFunction::EmitAnyExprToExn(const Expr *e, Address addr) {
358 // Make sure the exception object is cleaned up if there's an
359 // exception during initialization.
360 pushFullExprCleanup<FreeException>(EHCleanup, addr.getPointer());
361 EHScopeStack::stable_iterator cleanup = EHStack.stable_begin();
362
363 // __cxa_allocate_exception returns a void*; we need to cast this
364 // to the appropriate type for the object.
365 llvm::Type *ty = ConvertTypeForMem(e->getType())->getPointerTo();
366 Address typedAddr = Builder.CreateBitCast(addr, ty);
367
368 // FIXME: this isn't quite right! If there's a final unelided call
369 // to a copy constructor, then according to [except.terminate]p1 we
370 // must call std::terminate() if that constructor throws, because
371 // technically that copy occurs after the exception expression is
372 // evaluated but before the exception is caught. But the best way
373 // to handle that is to teach EmitAggExpr to do the final copy
374 // differently if it can't be elided.
375 EmitAnyExprToMem(e, typedAddr, e->getType().getQualifiers(),
376 /*IsInit*/ true);
377
378 // Deactivate the cleanup block.
379 DeactivateCleanupBlock(cleanup,
380 cast<llvm::Instruction>(typedAddr.getPointer()));
381 }
382
getExceptionSlot()383 Address CodeGenFunction::getExceptionSlot() {
384 if (!ExceptionSlot)
385 ExceptionSlot = CreateTempAlloca(Int8PtrTy, "exn.slot");
386 return Address(ExceptionSlot, getPointerAlign());
387 }
388
getEHSelectorSlot()389 Address CodeGenFunction::getEHSelectorSlot() {
390 if (!EHSelectorSlot)
391 EHSelectorSlot = CreateTempAlloca(Int32Ty, "ehselector.slot");
392 return Address(EHSelectorSlot, CharUnits::fromQuantity(4));
393 }
394
getExceptionFromSlot()395 llvm::Value *CodeGenFunction::getExceptionFromSlot() {
396 return Builder.CreateLoad(getExceptionSlot(), "exn");
397 }
398
getSelectorFromSlot()399 llvm::Value *CodeGenFunction::getSelectorFromSlot() {
400 return Builder.CreateLoad(getEHSelectorSlot(), "sel");
401 }
402
EmitCXXThrowExpr(const CXXThrowExpr * E,bool KeepInsertionPoint)403 void CodeGenFunction::EmitCXXThrowExpr(const CXXThrowExpr *E,
404 bool KeepInsertionPoint) {
405 if (const Expr *SubExpr = E->getSubExpr()) {
406 QualType ThrowType = SubExpr->getType();
407 if (ThrowType->isObjCObjectPointerType()) {
408 const Stmt *ThrowStmt = E->getSubExpr();
409 const ObjCAtThrowStmt S(E->getExprLoc(), const_cast<Stmt *>(ThrowStmt));
410 CGM.getObjCRuntime().EmitThrowStmt(*this, S, false);
411 } else {
412 CGM.getCXXABI().emitThrow(*this, E);
413 }
414 } else {
415 CGM.getCXXABI().emitRethrow(*this, /*isNoReturn=*/true);
416 }
417
418 // throw is an expression, and the expression emitters expect us
419 // to leave ourselves at a valid insertion point.
420 if (KeepInsertionPoint)
421 EmitBlock(createBasicBlock("throw.cont"));
422 }
423
EmitStartEHSpec(const Decl * D)424 void CodeGenFunction::EmitStartEHSpec(const Decl *D) {
425 if (!CGM.getLangOpts().CXXExceptions)
426 return;
427
428 const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D);
429 if (!FD) {
430 // Check if CapturedDecl is nothrow and create terminate scope for it.
431 if (const CapturedDecl* CD = dyn_cast_or_null<CapturedDecl>(D)) {
432 if (CD->isNothrow())
433 EHStack.pushTerminate();
434 }
435 return;
436 }
437 const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>();
438 if (!Proto)
439 return;
440
441 ExceptionSpecificationType EST = Proto->getExceptionSpecType();
442 if (isNoexceptExceptionSpec(EST)) {
443 if (Proto->getNoexceptSpec(getContext()) == FunctionProtoType::NR_Nothrow) {
444 // noexcept functions are simple terminate scopes.
445 EHStack.pushTerminate();
446 }
447 } else if (EST == EST_Dynamic || EST == EST_DynamicNone) {
448 // TODO: Revisit exception specifications for the MS ABI. There is a way to
449 // encode these in an object file but MSVC doesn't do anything with it.
450 if (getTarget().getCXXABI().isMicrosoft())
451 return;
452 unsigned NumExceptions = Proto->getNumExceptions();
453 EHFilterScope *Filter = EHStack.pushFilter(NumExceptions);
454
455 for (unsigned I = 0; I != NumExceptions; ++I) {
456 QualType Ty = Proto->getExceptionType(I);
457 QualType ExceptType = Ty.getNonReferenceType().getUnqualifiedType();
458 llvm::Value *EHType = CGM.GetAddrOfRTTIDescriptor(ExceptType,
459 /*ForEH=*/true);
460 Filter->setFilter(I, EHType);
461 }
462 }
463 }
464
465 /// Emit the dispatch block for a filter scope if necessary.
emitFilterDispatchBlock(CodeGenFunction & CGF,EHFilterScope & filterScope)466 static void emitFilterDispatchBlock(CodeGenFunction &CGF,
467 EHFilterScope &filterScope) {
468 llvm::BasicBlock *dispatchBlock = filterScope.getCachedEHDispatchBlock();
469 if (!dispatchBlock) return;
470 if (dispatchBlock->use_empty()) {
471 delete dispatchBlock;
472 return;
473 }
474
475 CGF.EmitBlockAfterUses(dispatchBlock);
476
477 // If this isn't a catch-all filter, we need to check whether we got
478 // here because the filter triggered.
479 if (filterScope.getNumFilters()) {
480 // Load the selector value.
481 llvm::Value *selector = CGF.getSelectorFromSlot();
482 llvm::BasicBlock *unexpectedBB = CGF.createBasicBlock("ehspec.unexpected");
483
484 llvm::Value *zero = CGF.Builder.getInt32(0);
485 llvm::Value *failsFilter =
486 CGF.Builder.CreateICmpSLT(selector, zero, "ehspec.fails");
487 CGF.Builder.CreateCondBr(failsFilter, unexpectedBB,
488 CGF.getEHResumeBlock(false));
489
490 CGF.EmitBlock(unexpectedBB);
491 }
492
493 // Call __cxa_call_unexpected. This doesn't need to be an invoke
494 // because __cxa_call_unexpected magically filters exceptions
495 // according to the last landing pad the exception was thrown
496 // into. Seriously.
497 llvm::Value *exn = CGF.getExceptionFromSlot();
498 CGF.EmitRuntimeCall(getUnexpectedFn(CGF.CGM), exn)
499 ->setDoesNotReturn();
500 CGF.Builder.CreateUnreachable();
501 }
502
EmitEndEHSpec(const Decl * D)503 void CodeGenFunction::EmitEndEHSpec(const Decl *D) {
504 if (!CGM.getLangOpts().CXXExceptions)
505 return;
506
507 const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D);
508 if (!FD) {
509 // Check if CapturedDecl is nothrow and pop terminate scope for it.
510 if (const CapturedDecl* CD = dyn_cast_or_null<CapturedDecl>(D)) {
511 if (CD->isNothrow())
512 EHStack.popTerminate();
513 }
514 return;
515 }
516 const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>();
517 if (!Proto)
518 return;
519
520 ExceptionSpecificationType EST = Proto->getExceptionSpecType();
521 if (isNoexceptExceptionSpec(EST)) {
522 if (Proto->getNoexceptSpec(getContext()) == FunctionProtoType::NR_Nothrow) {
523 EHStack.popTerminate();
524 }
525 } else if (EST == EST_Dynamic || EST == EST_DynamicNone) {
526 // TODO: Revisit exception specifications for the MS ABI. There is a way to
527 // encode these in an object file but MSVC doesn't do anything with it.
528 if (getTarget().getCXXABI().isMicrosoft())
529 return;
530 EHFilterScope &filterScope = cast<EHFilterScope>(*EHStack.begin());
531 emitFilterDispatchBlock(*this, filterScope);
532 EHStack.popFilter();
533 }
534 }
535
EmitCXXTryStmt(const CXXTryStmt & S)536 void CodeGenFunction::EmitCXXTryStmt(const CXXTryStmt &S) {
537 EnterCXXTryStmt(S);
538 EmitStmt(S.getTryBlock());
539 ExitCXXTryStmt(S);
540 }
541
EnterCXXTryStmt(const CXXTryStmt & S,bool IsFnTryBlock)542 void CodeGenFunction::EnterCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) {
543 unsigned NumHandlers = S.getNumHandlers();
544 EHCatchScope *CatchScope = EHStack.pushCatch(NumHandlers);
545
546 for (unsigned I = 0; I != NumHandlers; ++I) {
547 const CXXCatchStmt *C = S.getHandler(I);
548
549 llvm::BasicBlock *Handler = createBasicBlock("catch");
550 if (C->getExceptionDecl()) {
551 // FIXME: Dropping the reference type on the type into makes it
552 // impossible to correctly implement catch-by-reference
553 // semantics for pointers. Unfortunately, this is what all
554 // existing compilers do, and it's not clear that the standard
555 // personality routine is capable of doing this right. See C++ DR 388:
556 // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#388
557 Qualifiers CaughtTypeQuals;
558 QualType CaughtType = CGM.getContext().getUnqualifiedArrayType(
559 C->getCaughtType().getNonReferenceType(), CaughtTypeQuals);
560
561 CatchTypeInfo TypeInfo{nullptr, 0};
562 if (CaughtType->isObjCObjectPointerType())
563 TypeInfo.RTTI = CGM.getObjCRuntime().GetEHType(CaughtType);
564 else
565 TypeInfo = CGM.getCXXABI().getAddrOfCXXCatchHandlerType(
566 CaughtType, C->getCaughtType());
567 CatchScope->setHandler(I, TypeInfo, Handler);
568 } else {
569 // No exception decl indicates '...', a catch-all.
570 CatchScope->setHandler(I, CGM.getCXXABI().getCatchAllTypeInfo(), Handler);
571 }
572 }
573 }
574
575 llvm::BasicBlock *
getEHDispatchBlock(EHScopeStack::stable_iterator si)576 CodeGenFunction::getEHDispatchBlock(EHScopeStack::stable_iterator si) {
577 if (EHPersonality::get(*this).usesFuncletPads())
578 return getMSVCDispatchBlock(si);
579
580 // The dispatch block for the end of the scope chain is a block that
581 // just resumes unwinding.
582 if (si == EHStack.stable_end())
583 return getEHResumeBlock(true);
584
585 // Otherwise, we should look at the actual scope.
586 EHScope &scope = *EHStack.find(si);
587
588 llvm::BasicBlock *dispatchBlock = scope.getCachedEHDispatchBlock();
589 if (!dispatchBlock) {
590 switch (scope.getKind()) {
591 case EHScope::Catch: {
592 // Apply a special case to a single catch-all.
593 EHCatchScope &catchScope = cast<EHCatchScope>(scope);
594 if (catchScope.getNumHandlers() == 1 &&
595 catchScope.getHandler(0).isCatchAll()) {
596 dispatchBlock = catchScope.getHandler(0).Block;
597
598 // Otherwise, make a dispatch block.
599 } else {
600 dispatchBlock = createBasicBlock("catch.dispatch");
601 }
602 break;
603 }
604
605 case EHScope::Cleanup:
606 dispatchBlock = createBasicBlock("ehcleanup");
607 break;
608
609 case EHScope::Filter:
610 dispatchBlock = createBasicBlock("filter.dispatch");
611 break;
612
613 case EHScope::Terminate:
614 dispatchBlock = getTerminateHandler();
615 break;
616
617 case EHScope::PadEnd:
618 llvm_unreachable("PadEnd unnecessary for Itanium!");
619 }
620 scope.setCachedEHDispatchBlock(dispatchBlock);
621 }
622 return dispatchBlock;
623 }
624
625 llvm::BasicBlock *
getMSVCDispatchBlock(EHScopeStack::stable_iterator SI)626 CodeGenFunction::getMSVCDispatchBlock(EHScopeStack::stable_iterator SI) {
627 // Returning nullptr indicates that the previous dispatch block should unwind
628 // to caller.
629 if (SI == EHStack.stable_end())
630 return nullptr;
631
632 // Otherwise, we should look at the actual scope.
633 EHScope &EHS = *EHStack.find(SI);
634
635 llvm::BasicBlock *DispatchBlock = EHS.getCachedEHDispatchBlock();
636 if (DispatchBlock)
637 return DispatchBlock;
638
639 if (EHS.getKind() == EHScope::Terminate)
640 DispatchBlock = getTerminateHandler();
641 else
642 DispatchBlock = createBasicBlock();
643 CGBuilderTy Builder(*this, DispatchBlock);
644
645 switch (EHS.getKind()) {
646 case EHScope::Catch:
647 DispatchBlock->setName("catch.dispatch");
648 break;
649
650 case EHScope::Cleanup:
651 DispatchBlock->setName("ehcleanup");
652 break;
653
654 case EHScope::Filter:
655 llvm_unreachable("exception specifications not handled yet!");
656
657 case EHScope::Terminate:
658 DispatchBlock->setName("terminate");
659 break;
660
661 case EHScope::PadEnd:
662 llvm_unreachable("PadEnd dispatch block missing!");
663 }
664 EHS.setCachedEHDispatchBlock(DispatchBlock);
665 return DispatchBlock;
666 }
667
668 /// Check whether this is a non-EH scope, i.e. a scope which doesn't
669 /// affect exception handling. Currently, the only non-EH scopes are
670 /// normal-only cleanup scopes.
isNonEHScope(const EHScope & S)671 static bool isNonEHScope(const EHScope &S) {
672 switch (S.getKind()) {
673 case EHScope::Cleanup:
674 return !cast<EHCleanupScope>(S).isEHCleanup();
675 case EHScope::Filter:
676 case EHScope::Catch:
677 case EHScope::Terminate:
678 case EHScope::PadEnd:
679 return false;
680 }
681
682 llvm_unreachable("Invalid EHScope Kind!");
683 }
684
getInvokeDestImpl()685 llvm::BasicBlock *CodeGenFunction::getInvokeDestImpl() {
686 assert(EHStack.requiresLandingPad());
687 assert(!EHStack.empty());
688
689 // If exceptions are disabled, there are usually no landingpads. However, when
690 // SEH is enabled, functions using SEH still get landingpads.
691 const LangOptions &LO = CGM.getLangOpts();
692 if (!LO.Exceptions) {
693 if (!LO.Borland && !LO.MicrosoftExt)
694 return nullptr;
695 if (!currentFunctionUsesSEHTry())
696 return nullptr;
697 }
698
699 // Check the innermost scope for a cached landing pad. If this is
700 // a non-EH cleanup, we'll check enclosing scopes in EmitLandingPad.
701 llvm::BasicBlock *LP = EHStack.begin()->getCachedLandingPad();
702 if (LP) return LP;
703
704 const EHPersonality &Personality = EHPersonality::get(*this);
705
706 if (!CurFn->hasPersonalityFn())
707 CurFn->setPersonalityFn(getOpaquePersonalityFn(CGM, Personality));
708
709 if (Personality.usesFuncletPads()) {
710 // We don't need separate landing pads in the funclet model.
711 LP = getEHDispatchBlock(EHStack.getInnermostEHScope());
712 } else {
713 // Build the landing pad for this scope.
714 LP = EmitLandingPad();
715 }
716
717 assert(LP);
718
719 // Cache the landing pad on the innermost scope. If this is a
720 // non-EH scope, cache the landing pad on the enclosing scope, too.
721 for (EHScopeStack::iterator ir = EHStack.begin(); true; ++ir) {
722 ir->setCachedLandingPad(LP);
723 if (!isNonEHScope(*ir)) break;
724 }
725
726 return LP;
727 }
728
EmitLandingPad()729 llvm::BasicBlock *CodeGenFunction::EmitLandingPad() {
730 assert(EHStack.requiresLandingPad());
731
732 EHScope &innermostEHScope = *EHStack.find(EHStack.getInnermostEHScope());
733 switch (innermostEHScope.getKind()) {
734 case EHScope::Terminate:
735 return getTerminateLandingPad();
736
737 case EHScope::PadEnd:
738 llvm_unreachable("PadEnd unnecessary for Itanium!");
739
740 case EHScope::Catch:
741 case EHScope::Cleanup:
742 case EHScope::Filter:
743 if (llvm::BasicBlock *lpad = innermostEHScope.getCachedLandingPad())
744 return lpad;
745 }
746
747 // Save the current IR generation state.
748 CGBuilderTy::InsertPoint savedIP = Builder.saveAndClearIP();
749 auto DL = ApplyDebugLocation::CreateDefaultArtificial(*this, CurEHLocation);
750
751 // Create and configure the landing pad.
752 llvm::BasicBlock *lpad = createBasicBlock("lpad");
753 EmitBlock(lpad);
754
755 llvm::LandingPadInst *LPadInst = Builder.CreateLandingPad(
756 llvm::StructType::get(Int8PtrTy, Int32Ty, nullptr), 0);
757
758 llvm::Value *LPadExn = Builder.CreateExtractValue(LPadInst, 0);
759 Builder.CreateStore(LPadExn, getExceptionSlot());
760 llvm::Value *LPadSel = Builder.CreateExtractValue(LPadInst, 1);
761 Builder.CreateStore(LPadSel, getEHSelectorSlot());
762
763 // Save the exception pointer. It's safe to use a single exception
764 // pointer per function because EH cleanups can never have nested
765 // try/catches.
766 // Build the landingpad instruction.
767
768 // Accumulate all the handlers in scope.
769 bool hasCatchAll = false;
770 bool hasCleanup = false;
771 bool hasFilter = false;
772 SmallVector<llvm::Value*, 4> filterTypes;
773 llvm::SmallPtrSet<llvm::Value*, 4> catchTypes;
774 for (EHScopeStack::iterator I = EHStack.begin(), E = EHStack.end(); I != E;
775 ++I) {
776
777 switch (I->getKind()) {
778 case EHScope::Cleanup:
779 // If we have a cleanup, remember that.
780 hasCleanup = (hasCleanup || cast<EHCleanupScope>(*I).isEHCleanup());
781 continue;
782
783 case EHScope::Filter: {
784 assert(I.next() == EHStack.end() && "EH filter is not end of EH stack");
785 assert(!hasCatchAll && "EH filter reached after catch-all");
786
787 // Filter scopes get added to the landingpad in weird ways.
788 EHFilterScope &filter = cast<EHFilterScope>(*I);
789 hasFilter = true;
790
791 // Add all the filter values.
792 for (unsigned i = 0, e = filter.getNumFilters(); i != e; ++i)
793 filterTypes.push_back(filter.getFilter(i));
794 goto done;
795 }
796
797 case EHScope::Terminate:
798 // Terminate scopes are basically catch-alls.
799 assert(!hasCatchAll);
800 hasCatchAll = true;
801 goto done;
802
803 case EHScope::Catch:
804 break;
805
806 case EHScope::PadEnd:
807 llvm_unreachable("PadEnd unnecessary for Itanium!");
808 }
809
810 EHCatchScope &catchScope = cast<EHCatchScope>(*I);
811 for (unsigned hi = 0, he = catchScope.getNumHandlers(); hi != he; ++hi) {
812 EHCatchScope::Handler handler = catchScope.getHandler(hi);
813 assert(handler.Type.Flags == 0 &&
814 "landingpads do not support catch handler flags");
815
816 // If this is a catch-all, register that and abort.
817 if (!handler.Type.RTTI) {
818 assert(!hasCatchAll);
819 hasCatchAll = true;
820 goto done;
821 }
822
823 // Check whether we already have a handler for this type.
824 if (catchTypes.insert(handler.Type.RTTI).second)
825 // If not, add it directly to the landingpad.
826 LPadInst->addClause(handler.Type.RTTI);
827 }
828 }
829
830 done:
831 // If we have a catch-all, add null to the landingpad.
832 assert(!(hasCatchAll && hasFilter));
833 if (hasCatchAll) {
834 LPadInst->addClause(getCatchAllValue(*this));
835
836 // If we have an EH filter, we need to add those handlers in the
837 // right place in the landingpad, which is to say, at the end.
838 } else if (hasFilter) {
839 // Create a filter expression: a constant array indicating which filter
840 // types there are. The personality routine only lands here if the filter
841 // doesn't match.
842 SmallVector<llvm::Constant*, 8> Filters;
843 llvm::ArrayType *AType =
844 llvm::ArrayType::get(!filterTypes.empty() ?
845 filterTypes[0]->getType() : Int8PtrTy,
846 filterTypes.size());
847
848 for (unsigned i = 0, e = filterTypes.size(); i != e; ++i)
849 Filters.push_back(cast<llvm::Constant>(filterTypes[i]));
850 llvm::Constant *FilterArray = llvm::ConstantArray::get(AType, Filters);
851 LPadInst->addClause(FilterArray);
852
853 // Also check whether we need a cleanup.
854 if (hasCleanup)
855 LPadInst->setCleanup(true);
856
857 // Otherwise, signal that we at least have cleanups.
858 } else if (hasCleanup) {
859 LPadInst->setCleanup(true);
860 }
861
862 assert((LPadInst->getNumClauses() > 0 || LPadInst->isCleanup()) &&
863 "landingpad instruction has no clauses!");
864
865 // Tell the backend how to generate the landing pad.
866 Builder.CreateBr(getEHDispatchBlock(EHStack.getInnermostEHScope()));
867
868 // Restore the old IR generation state.
869 Builder.restoreIP(savedIP);
870
871 return lpad;
872 }
873
emitCatchPadBlock(CodeGenFunction & CGF,EHCatchScope & CatchScope)874 static void emitCatchPadBlock(CodeGenFunction &CGF, EHCatchScope &CatchScope) {
875 llvm::BasicBlock *DispatchBlock = CatchScope.getCachedEHDispatchBlock();
876 assert(DispatchBlock);
877
878 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveIP();
879 CGF.EmitBlockAfterUses(DispatchBlock);
880
881 llvm::Value *ParentPad = CGF.CurrentFuncletPad;
882 if (!ParentPad)
883 ParentPad = llvm::ConstantTokenNone::get(CGF.getLLVMContext());
884 llvm::BasicBlock *UnwindBB =
885 CGF.getEHDispatchBlock(CatchScope.getEnclosingEHScope());
886
887 unsigned NumHandlers = CatchScope.getNumHandlers();
888 llvm::CatchSwitchInst *CatchSwitch =
889 CGF.Builder.CreateCatchSwitch(ParentPad, UnwindBB, NumHandlers);
890
891 // Test against each of the exception types we claim to catch.
892 for (unsigned I = 0; I < NumHandlers; ++I) {
893 const EHCatchScope::Handler &Handler = CatchScope.getHandler(I);
894
895 CatchTypeInfo TypeInfo = Handler.Type;
896 if (!TypeInfo.RTTI)
897 TypeInfo.RTTI = llvm::Constant::getNullValue(CGF.VoidPtrTy);
898
899 CGF.Builder.SetInsertPoint(Handler.Block);
900
901 if (EHPersonality::get(CGF).isMSVCXXPersonality()) {
902 CGF.Builder.CreateCatchPad(
903 CatchSwitch, {TypeInfo.RTTI, CGF.Builder.getInt32(TypeInfo.Flags),
904 llvm::Constant::getNullValue(CGF.VoidPtrTy)});
905 } else {
906 CGF.Builder.CreateCatchPad(CatchSwitch, {TypeInfo.RTTI});
907 }
908
909 CatchSwitch->addHandler(Handler.Block);
910 }
911 CGF.Builder.restoreIP(SavedIP);
912 }
913
914 /// Emit the structure of the dispatch block for the given catch scope.
915 /// It is an invariant that the dispatch block already exists.
emitCatchDispatchBlock(CodeGenFunction & CGF,EHCatchScope & catchScope)916 static void emitCatchDispatchBlock(CodeGenFunction &CGF,
917 EHCatchScope &catchScope) {
918 if (EHPersonality::get(CGF).usesFuncletPads())
919 return emitCatchPadBlock(CGF, catchScope);
920
921 llvm::BasicBlock *dispatchBlock = catchScope.getCachedEHDispatchBlock();
922 assert(dispatchBlock);
923
924 // If there's only a single catch-all, getEHDispatchBlock returned
925 // that catch-all as the dispatch block.
926 if (catchScope.getNumHandlers() == 1 &&
927 catchScope.getHandler(0).isCatchAll()) {
928 assert(dispatchBlock == catchScope.getHandler(0).Block);
929 return;
930 }
931
932 CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveIP();
933 CGF.EmitBlockAfterUses(dispatchBlock);
934
935 // Select the right handler.
936 llvm::Value *llvm_eh_typeid_for =
937 CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_typeid_for);
938
939 // Load the selector value.
940 llvm::Value *selector = CGF.getSelectorFromSlot();
941
942 // Test against each of the exception types we claim to catch.
943 for (unsigned i = 0, e = catchScope.getNumHandlers(); ; ++i) {
944 assert(i < e && "ran off end of handlers!");
945 const EHCatchScope::Handler &handler = catchScope.getHandler(i);
946
947 llvm::Value *typeValue = handler.Type.RTTI;
948 assert(handler.Type.Flags == 0 &&
949 "landingpads do not support catch handler flags");
950 assert(typeValue && "fell into catch-all case!");
951 typeValue = CGF.Builder.CreateBitCast(typeValue, CGF.Int8PtrTy);
952
953 // Figure out the next block.
954 bool nextIsEnd;
955 llvm::BasicBlock *nextBlock;
956
957 // If this is the last handler, we're at the end, and the next
958 // block is the block for the enclosing EH scope.
959 if (i + 1 == e) {
960 nextBlock = CGF.getEHDispatchBlock(catchScope.getEnclosingEHScope());
961 nextIsEnd = true;
962
963 // If the next handler is a catch-all, we're at the end, and the
964 // next block is that handler.
965 } else if (catchScope.getHandler(i+1).isCatchAll()) {
966 nextBlock = catchScope.getHandler(i+1).Block;
967 nextIsEnd = true;
968
969 // Otherwise, we're not at the end and we need a new block.
970 } else {
971 nextBlock = CGF.createBasicBlock("catch.fallthrough");
972 nextIsEnd = false;
973 }
974
975 // Figure out the catch type's index in the LSDA's type table.
976 llvm::CallInst *typeIndex =
977 CGF.Builder.CreateCall(llvm_eh_typeid_for, typeValue);
978 typeIndex->setDoesNotThrow();
979
980 llvm::Value *matchesTypeIndex =
981 CGF.Builder.CreateICmpEQ(selector, typeIndex, "matches");
982 CGF.Builder.CreateCondBr(matchesTypeIndex, handler.Block, nextBlock);
983
984 // If the next handler is a catch-all, we're completely done.
985 if (nextIsEnd) {
986 CGF.Builder.restoreIP(savedIP);
987 return;
988 }
989 // Otherwise we need to emit and continue at that block.
990 CGF.EmitBlock(nextBlock);
991 }
992 }
993
popCatchScope()994 void CodeGenFunction::popCatchScope() {
995 EHCatchScope &catchScope = cast<EHCatchScope>(*EHStack.begin());
996 if (catchScope.hasEHBranches())
997 emitCatchDispatchBlock(*this, catchScope);
998 EHStack.popCatch();
999 }
1000
ExitCXXTryStmt(const CXXTryStmt & S,bool IsFnTryBlock)1001 void CodeGenFunction::ExitCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) {
1002 unsigned NumHandlers = S.getNumHandlers();
1003 EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin());
1004 assert(CatchScope.getNumHandlers() == NumHandlers);
1005
1006 // If the catch was not required, bail out now.
1007 if (!CatchScope.hasEHBranches()) {
1008 CatchScope.clearHandlerBlocks();
1009 EHStack.popCatch();
1010 return;
1011 }
1012
1013 // Emit the structure of the EH dispatch for this catch.
1014 emitCatchDispatchBlock(*this, CatchScope);
1015
1016 // Copy the handler blocks off before we pop the EH stack. Emitting
1017 // the handlers might scribble on this memory.
1018 SmallVector<EHCatchScope::Handler, 8> Handlers(
1019 CatchScope.begin(), CatchScope.begin() + NumHandlers);
1020
1021 EHStack.popCatch();
1022
1023 // The fall-through block.
1024 llvm::BasicBlock *ContBB = createBasicBlock("try.cont");
1025
1026 // We just emitted the body of the try; jump to the continue block.
1027 if (HaveInsertPoint())
1028 Builder.CreateBr(ContBB);
1029
1030 // Determine if we need an implicit rethrow for all these catch handlers;
1031 // see the comment below.
1032 bool doImplicitRethrow = false;
1033 if (IsFnTryBlock)
1034 doImplicitRethrow = isa<CXXDestructorDecl>(CurCodeDecl) ||
1035 isa<CXXConstructorDecl>(CurCodeDecl);
1036
1037 // Perversely, we emit the handlers backwards precisely because we
1038 // want them to appear in source order. In all of these cases, the
1039 // catch block will have exactly one predecessor, which will be a
1040 // particular block in the catch dispatch. However, in the case of
1041 // a catch-all, one of the dispatch blocks will branch to two
1042 // different handlers, and EmitBlockAfterUses will cause the second
1043 // handler to be moved before the first.
1044 for (unsigned I = NumHandlers; I != 0; --I) {
1045 llvm::BasicBlock *CatchBlock = Handlers[I-1].Block;
1046 EmitBlockAfterUses(CatchBlock);
1047
1048 // Catch the exception if this isn't a catch-all.
1049 const CXXCatchStmt *C = S.getHandler(I-1);
1050
1051 // Enter a cleanup scope, including the catch variable and the
1052 // end-catch.
1053 RunCleanupsScope CatchScope(*this);
1054
1055 // Initialize the catch variable and set up the cleanups.
1056 SaveAndRestore<llvm::Instruction *> RestoreCurrentFuncletPad(
1057 CurrentFuncletPad);
1058 CGM.getCXXABI().emitBeginCatch(*this, C);
1059
1060 // Emit the PGO counter increment.
1061 incrementProfileCounter(C);
1062
1063 // Perform the body of the catch.
1064 EmitStmt(C->getHandlerBlock());
1065
1066 // [except.handle]p11:
1067 // The currently handled exception is rethrown if control
1068 // reaches the end of a handler of the function-try-block of a
1069 // constructor or destructor.
1070
1071 // It is important that we only do this on fallthrough and not on
1072 // return. Note that it's illegal to put a return in a
1073 // constructor function-try-block's catch handler (p14), so this
1074 // really only applies to destructors.
1075 if (doImplicitRethrow && HaveInsertPoint()) {
1076 CGM.getCXXABI().emitRethrow(*this, /*isNoReturn*/false);
1077 Builder.CreateUnreachable();
1078 Builder.ClearInsertionPoint();
1079 }
1080
1081 // Fall out through the catch cleanups.
1082 CatchScope.ForceCleanup();
1083
1084 // Branch out of the try.
1085 if (HaveInsertPoint())
1086 Builder.CreateBr(ContBB);
1087 }
1088
1089 EmitBlock(ContBB);
1090 incrementProfileCounter(&S);
1091 }
1092
1093 namespace {
1094 struct CallEndCatchForFinally final : EHScopeStack::Cleanup {
1095 llvm::Value *ForEHVar;
1096 llvm::Value *EndCatchFn;
CallEndCatchForFinally__anonab2436450211::CallEndCatchForFinally1097 CallEndCatchForFinally(llvm::Value *ForEHVar, llvm::Value *EndCatchFn)
1098 : ForEHVar(ForEHVar), EndCatchFn(EndCatchFn) {}
1099
Emit__anonab2436450211::CallEndCatchForFinally1100 void Emit(CodeGenFunction &CGF, Flags flags) override {
1101 llvm::BasicBlock *EndCatchBB = CGF.createBasicBlock("finally.endcatch");
1102 llvm::BasicBlock *CleanupContBB =
1103 CGF.createBasicBlock("finally.cleanup.cont");
1104
1105 llvm::Value *ShouldEndCatch =
1106 CGF.Builder.CreateFlagLoad(ForEHVar, "finally.endcatch");
1107 CGF.Builder.CreateCondBr(ShouldEndCatch, EndCatchBB, CleanupContBB);
1108 CGF.EmitBlock(EndCatchBB);
1109 CGF.EmitRuntimeCallOrInvoke(EndCatchFn); // catch-all, so might throw
1110 CGF.EmitBlock(CleanupContBB);
1111 }
1112 };
1113
1114 struct PerformFinally final : EHScopeStack::Cleanup {
1115 const Stmt *Body;
1116 llvm::Value *ForEHVar;
1117 llvm::Value *EndCatchFn;
1118 llvm::Value *RethrowFn;
1119 llvm::Value *SavedExnVar;
1120
PerformFinally__anonab2436450211::PerformFinally1121 PerformFinally(const Stmt *Body, llvm::Value *ForEHVar,
1122 llvm::Value *EndCatchFn,
1123 llvm::Value *RethrowFn, llvm::Value *SavedExnVar)
1124 : Body(Body), ForEHVar(ForEHVar), EndCatchFn(EndCatchFn),
1125 RethrowFn(RethrowFn), SavedExnVar(SavedExnVar) {}
1126
Emit__anonab2436450211::PerformFinally1127 void Emit(CodeGenFunction &CGF, Flags flags) override {
1128 // Enter a cleanup to call the end-catch function if one was provided.
1129 if (EndCatchFn)
1130 CGF.EHStack.pushCleanup<CallEndCatchForFinally>(NormalAndEHCleanup,
1131 ForEHVar, EndCatchFn);
1132
1133 // Save the current cleanup destination in case there are
1134 // cleanups in the finally block.
1135 llvm::Value *SavedCleanupDest =
1136 CGF.Builder.CreateLoad(CGF.getNormalCleanupDestSlot(),
1137 "cleanup.dest.saved");
1138
1139 // Emit the finally block.
1140 CGF.EmitStmt(Body);
1141
1142 // If the end of the finally is reachable, check whether this was
1143 // for EH. If so, rethrow.
1144 if (CGF.HaveInsertPoint()) {
1145 llvm::BasicBlock *RethrowBB = CGF.createBasicBlock("finally.rethrow");
1146 llvm::BasicBlock *ContBB = CGF.createBasicBlock("finally.cont");
1147
1148 llvm::Value *ShouldRethrow =
1149 CGF.Builder.CreateFlagLoad(ForEHVar, "finally.shouldthrow");
1150 CGF.Builder.CreateCondBr(ShouldRethrow, RethrowBB, ContBB);
1151
1152 CGF.EmitBlock(RethrowBB);
1153 if (SavedExnVar) {
1154 CGF.EmitRuntimeCallOrInvoke(RethrowFn,
1155 CGF.Builder.CreateAlignedLoad(SavedExnVar, CGF.getPointerAlign()));
1156 } else {
1157 CGF.EmitRuntimeCallOrInvoke(RethrowFn);
1158 }
1159 CGF.Builder.CreateUnreachable();
1160
1161 CGF.EmitBlock(ContBB);
1162
1163 // Restore the cleanup destination.
1164 CGF.Builder.CreateStore(SavedCleanupDest,
1165 CGF.getNormalCleanupDestSlot());
1166 }
1167
1168 // Leave the end-catch cleanup. As an optimization, pretend that
1169 // the fallthrough path was inaccessible; we've dynamically proven
1170 // that we're not in the EH case along that path.
1171 if (EndCatchFn) {
1172 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();
1173 CGF.PopCleanupBlock();
1174 CGF.Builder.restoreIP(SavedIP);
1175 }
1176
1177 // Now make sure we actually have an insertion point or the
1178 // cleanup gods will hate us.
1179 CGF.EnsureInsertPoint();
1180 }
1181 };
1182 } // end anonymous namespace
1183
1184 /// Enters a finally block for an implementation using zero-cost
1185 /// exceptions. This is mostly general, but hard-codes some
1186 /// language/ABI-specific behavior in the catch-all sections.
enter(CodeGenFunction & CGF,const Stmt * body,llvm::Constant * beginCatchFn,llvm::Constant * endCatchFn,llvm::Constant * rethrowFn)1187 void CodeGenFunction::FinallyInfo::enter(CodeGenFunction &CGF,
1188 const Stmt *body,
1189 llvm::Constant *beginCatchFn,
1190 llvm::Constant *endCatchFn,
1191 llvm::Constant *rethrowFn) {
1192 assert((beginCatchFn != nullptr) == (endCatchFn != nullptr) &&
1193 "begin/end catch functions not paired");
1194 assert(rethrowFn && "rethrow function is required");
1195
1196 BeginCatchFn = beginCatchFn;
1197
1198 // The rethrow function has one of the following two types:
1199 // void (*)()
1200 // void (*)(void*)
1201 // In the latter case we need to pass it the exception object.
1202 // But we can't use the exception slot because the @finally might
1203 // have a landing pad (which would overwrite the exception slot).
1204 llvm::FunctionType *rethrowFnTy =
1205 cast<llvm::FunctionType>(
1206 cast<llvm::PointerType>(rethrowFn->getType())->getElementType());
1207 SavedExnVar = nullptr;
1208 if (rethrowFnTy->getNumParams())
1209 SavedExnVar = CGF.CreateTempAlloca(CGF.Int8PtrTy, "finally.exn");
1210
1211 // A finally block is a statement which must be executed on any edge
1212 // out of a given scope. Unlike a cleanup, the finally block may
1213 // contain arbitrary control flow leading out of itself. In
1214 // addition, finally blocks should always be executed, even if there
1215 // are no catch handlers higher on the stack. Therefore, we
1216 // surround the protected scope with a combination of a normal
1217 // cleanup (to catch attempts to break out of the block via normal
1218 // control flow) and an EH catch-all (semantically "outside" any try
1219 // statement to which the finally block might have been attached).
1220 // The finally block itself is generated in the context of a cleanup
1221 // which conditionally leaves the catch-all.
1222
1223 // Jump destination for performing the finally block on an exception
1224 // edge. We'll never actually reach this block, so unreachable is
1225 // fine.
1226 RethrowDest = CGF.getJumpDestInCurrentScope(CGF.getUnreachableBlock());
1227
1228 // Whether the finally block is being executed for EH purposes.
1229 ForEHVar = CGF.CreateTempAlloca(CGF.Builder.getInt1Ty(), "finally.for-eh");
1230 CGF.Builder.CreateFlagStore(false, ForEHVar);
1231
1232 // Enter a normal cleanup which will perform the @finally block.
1233 CGF.EHStack.pushCleanup<PerformFinally>(NormalCleanup, body,
1234 ForEHVar, endCatchFn,
1235 rethrowFn, SavedExnVar);
1236
1237 // Enter a catch-all scope.
1238 llvm::BasicBlock *catchBB = CGF.createBasicBlock("finally.catchall");
1239 EHCatchScope *catchScope = CGF.EHStack.pushCatch(1);
1240 catchScope->setCatchAllHandler(0, catchBB);
1241 }
1242
exit(CodeGenFunction & CGF)1243 void CodeGenFunction::FinallyInfo::exit(CodeGenFunction &CGF) {
1244 // Leave the finally catch-all.
1245 EHCatchScope &catchScope = cast<EHCatchScope>(*CGF.EHStack.begin());
1246 llvm::BasicBlock *catchBB = catchScope.getHandler(0).Block;
1247
1248 CGF.popCatchScope();
1249
1250 // If there are any references to the catch-all block, emit it.
1251 if (catchBB->use_empty()) {
1252 delete catchBB;
1253 } else {
1254 CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveAndClearIP();
1255 CGF.EmitBlock(catchBB);
1256
1257 llvm::Value *exn = nullptr;
1258
1259 // If there's a begin-catch function, call it.
1260 if (BeginCatchFn) {
1261 exn = CGF.getExceptionFromSlot();
1262 CGF.EmitNounwindRuntimeCall(BeginCatchFn, exn);
1263 }
1264
1265 // If we need to remember the exception pointer to rethrow later, do so.
1266 if (SavedExnVar) {
1267 if (!exn) exn = CGF.getExceptionFromSlot();
1268 CGF.Builder.CreateAlignedStore(exn, SavedExnVar, CGF.getPointerAlign());
1269 }
1270
1271 // Tell the cleanups in the finally block that we're do this for EH.
1272 CGF.Builder.CreateFlagStore(true, ForEHVar);
1273
1274 // Thread a jump through the finally cleanup.
1275 CGF.EmitBranchThroughCleanup(RethrowDest);
1276
1277 CGF.Builder.restoreIP(savedIP);
1278 }
1279
1280 // Finally, leave the @finally cleanup.
1281 CGF.PopCleanupBlock();
1282 }
1283
getTerminateLandingPad()1284 llvm::BasicBlock *CodeGenFunction::getTerminateLandingPad() {
1285 if (TerminateLandingPad)
1286 return TerminateLandingPad;
1287
1288 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
1289
1290 // This will get inserted at the end of the function.
1291 TerminateLandingPad = createBasicBlock("terminate.lpad");
1292 Builder.SetInsertPoint(TerminateLandingPad);
1293
1294 // Tell the backend that this is a landing pad.
1295 const EHPersonality &Personality = EHPersonality::get(*this);
1296
1297 if (!CurFn->hasPersonalityFn())
1298 CurFn->setPersonalityFn(getOpaquePersonalityFn(CGM, Personality));
1299
1300 llvm::LandingPadInst *LPadInst = Builder.CreateLandingPad(
1301 llvm::StructType::get(Int8PtrTy, Int32Ty, nullptr), 0);
1302 LPadInst->addClause(getCatchAllValue(*this));
1303
1304 llvm::Value *Exn = nullptr;
1305 if (getLangOpts().CPlusPlus)
1306 Exn = Builder.CreateExtractValue(LPadInst, 0);
1307 llvm::CallInst *terminateCall =
1308 CGM.getCXXABI().emitTerminateForUnexpectedException(*this, Exn);
1309 terminateCall->setDoesNotReturn();
1310 Builder.CreateUnreachable();
1311
1312 // Restore the saved insertion state.
1313 Builder.restoreIP(SavedIP);
1314
1315 return TerminateLandingPad;
1316 }
1317
getTerminateHandler()1318 llvm::BasicBlock *CodeGenFunction::getTerminateHandler() {
1319 if (TerminateHandler)
1320 return TerminateHandler;
1321
1322 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
1323
1324 // Set up the terminate handler. This block is inserted at the very
1325 // end of the function by FinishFunction.
1326 TerminateHandler = createBasicBlock("terminate.handler");
1327 Builder.SetInsertPoint(TerminateHandler);
1328 llvm::Value *Exn = nullptr;
1329 if (EHPersonality::get(*this).usesFuncletPads()) {
1330 llvm::Value *ParentPad = CurrentFuncletPad;
1331 if (!ParentPad)
1332 ParentPad = llvm::ConstantTokenNone::get(CGM.getLLVMContext());
1333 Builder.CreateCleanupPad(ParentPad);
1334 } else {
1335 if (getLangOpts().CPlusPlus)
1336 Exn = getExceptionFromSlot();
1337 }
1338 llvm::CallInst *terminateCall =
1339 CGM.getCXXABI().emitTerminateForUnexpectedException(*this, Exn);
1340 terminateCall->setDoesNotReturn();
1341 Builder.CreateUnreachable();
1342
1343 // Restore the saved insertion state.
1344 Builder.restoreIP(SavedIP);
1345
1346 return TerminateHandler;
1347 }
1348
getEHResumeBlock(bool isCleanup)1349 llvm::BasicBlock *CodeGenFunction::getEHResumeBlock(bool isCleanup) {
1350 if (EHResumeBlock) return EHResumeBlock;
1351
1352 CGBuilderTy::InsertPoint SavedIP = Builder.saveIP();
1353
1354 // We emit a jump to a notional label at the outermost unwind state.
1355 EHResumeBlock = createBasicBlock("eh.resume");
1356 Builder.SetInsertPoint(EHResumeBlock);
1357
1358 const EHPersonality &Personality = EHPersonality::get(*this);
1359
1360 // This can always be a call because we necessarily didn't find
1361 // anything on the EH stack which needs our help.
1362 const char *RethrowName = Personality.CatchallRethrowFn;
1363 if (RethrowName != nullptr && !isCleanup) {
1364 EmitRuntimeCall(getCatchallRethrowFn(CGM, RethrowName),
1365 getExceptionFromSlot())->setDoesNotReturn();
1366 Builder.CreateUnreachable();
1367 Builder.restoreIP(SavedIP);
1368 return EHResumeBlock;
1369 }
1370
1371 // Recreate the landingpad's return value for the 'resume' instruction.
1372 llvm::Value *Exn = getExceptionFromSlot();
1373 llvm::Value *Sel = getSelectorFromSlot();
1374
1375 llvm::Type *LPadType = llvm::StructType::get(Exn->getType(),
1376 Sel->getType(), nullptr);
1377 llvm::Value *LPadVal = llvm::UndefValue::get(LPadType);
1378 LPadVal = Builder.CreateInsertValue(LPadVal, Exn, 0, "lpad.val");
1379 LPadVal = Builder.CreateInsertValue(LPadVal, Sel, 1, "lpad.val");
1380
1381 Builder.CreateResume(LPadVal);
1382 Builder.restoreIP(SavedIP);
1383 return EHResumeBlock;
1384 }
1385
EmitSEHTryStmt(const SEHTryStmt & S)1386 void CodeGenFunction::EmitSEHTryStmt(const SEHTryStmt &S) {
1387 EnterSEHTryStmt(S);
1388 {
1389 JumpDest TryExit = getJumpDestInCurrentScope("__try.__leave");
1390
1391 SEHTryEpilogueStack.push_back(&TryExit);
1392 EmitStmt(S.getTryBlock());
1393 SEHTryEpilogueStack.pop_back();
1394
1395 if (!TryExit.getBlock()->use_empty())
1396 EmitBlock(TryExit.getBlock(), /*IsFinished=*/true);
1397 else
1398 delete TryExit.getBlock();
1399 }
1400 ExitSEHTryStmt(S);
1401 }
1402
1403 namespace {
1404 struct PerformSEHFinally final : EHScopeStack::Cleanup {
1405 llvm::Function *OutlinedFinally;
PerformSEHFinally__anonab2436450311::PerformSEHFinally1406 PerformSEHFinally(llvm::Function *OutlinedFinally)
1407 : OutlinedFinally(OutlinedFinally) {}
1408
Emit__anonab2436450311::PerformSEHFinally1409 void Emit(CodeGenFunction &CGF, Flags F) override {
1410 ASTContext &Context = CGF.getContext();
1411 CodeGenModule &CGM = CGF.CGM;
1412
1413 CallArgList Args;
1414
1415 // Compute the two argument values.
1416 QualType ArgTys[2] = {Context.UnsignedCharTy, Context.VoidPtrTy};
1417 llvm::Value *LocalAddrFn = CGM.getIntrinsic(llvm::Intrinsic::localaddress);
1418 llvm::Value *FP = CGF.Builder.CreateCall(LocalAddrFn);
1419 llvm::Value *IsForEH =
1420 llvm::ConstantInt::get(CGF.ConvertType(ArgTys[0]), F.isForEHCleanup());
1421 Args.add(RValue::get(IsForEH), ArgTys[0]);
1422 Args.add(RValue::get(FP), ArgTys[1]);
1423
1424 // Arrange a two-arg function info and type.
1425 FunctionProtoType::ExtProtoInfo EPI;
1426 const auto *FPT = cast<FunctionProtoType>(
1427 Context.getFunctionType(Context.VoidTy, ArgTys, EPI));
1428 const CGFunctionInfo &FnInfo =
1429 CGM.getTypes().arrangeFreeFunctionCall(Args, FPT,
1430 /*chainCall=*/false);
1431
1432 CGF.EmitCall(FnInfo, OutlinedFinally, ReturnValueSlot(), Args);
1433 }
1434 };
1435 } // end anonymous namespace
1436
1437 namespace {
1438 /// Find all local variable captures in the statement.
1439 struct CaptureFinder : ConstStmtVisitor<CaptureFinder> {
1440 CodeGenFunction &ParentCGF;
1441 const VarDecl *ParentThis;
1442 llvm::SmallSetVector<const VarDecl *, 4> Captures;
1443 Address SEHCodeSlot = Address::invalid();
CaptureFinder__anonab2436450411::CaptureFinder1444 CaptureFinder(CodeGenFunction &ParentCGF, const VarDecl *ParentThis)
1445 : ParentCGF(ParentCGF), ParentThis(ParentThis) {}
1446
1447 // Return true if we need to do any capturing work.
foundCaptures__anonab2436450411::CaptureFinder1448 bool foundCaptures() {
1449 return !Captures.empty() || SEHCodeSlot.isValid();
1450 }
1451
Visit__anonab2436450411::CaptureFinder1452 void Visit(const Stmt *S) {
1453 // See if this is a capture, then recurse.
1454 ConstStmtVisitor<CaptureFinder>::Visit(S);
1455 for (const Stmt *Child : S->children())
1456 if (Child)
1457 Visit(Child);
1458 }
1459
VisitDeclRefExpr__anonab2436450411::CaptureFinder1460 void VisitDeclRefExpr(const DeclRefExpr *E) {
1461 // If this is already a capture, just make sure we capture 'this'.
1462 if (E->refersToEnclosingVariableOrCapture()) {
1463 Captures.insert(ParentThis);
1464 return;
1465 }
1466
1467 const auto *D = dyn_cast<VarDecl>(E->getDecl());
1468 if (D && D->isLocalVarDeclOrParm() && D->hasLocalStorage())
1469 Captures.insert(D);
1470 }
1471
VisitCXXThisExpr__anonab2436450411::CaptureFinder1472 void VisitCXXThisExpr(const CXXThisExpr *E) {
1473 Captures.insert(ParentThis);
1474 }
1475
VisitCallExpr__anonab2436450411::CaptureFinder1476 void VisitCallExpr(const CallExpr *E) {
1477 // We only need to add parent frame allocations for these builtins in x86.
1478 if (ParentCGF.getTarget().getTriple().getArch() != llvm::Triple::x86)
1479 return;
1480
1481 unsigned ID = E->getBuiltinCallee();
1482 switch (ID) {
1483 case Builtin::BI__exception_code:
1484 case Builtin::BI_exception_code:
1485 // This is the simple case where we are the outermost finally. All we
1486 // have to do here is make sure we escape this and recover it in the
1487 // outlined handler.
1488 if (!SEHCodeSlot.isValid())
1489 SEHCodeSlot = ParentCGF.SEHCodeSlotStack.back();
1490 break;
1491 }
1492 }
1493 };
1494 } // end anonymous namespace
1495
recoverAddrOfEscapedLocal(CodeGenFunction & ParentCGF,Address ParentVar,llvm::Value * ParentFP)1496 Address CodeGenFunction::recoverAddrOfEscapedLocal(CodeGenFunction &ParentCGF,
1497 Address ParentVar,
1498 llvm::Value *ParentFP) {
1499 llvm::CallInst *RecoverCall = nullptr;
1500 CGBuilderTy Builder(*this, AllocaInsertPt);
1501 if (auto *ParentAlloca = dyn_cast<llvm::AllocaInst>(ParentVar.getPointer())) {
1502 // Mark the variable escaped if nobody else referenced it and compute the
1503 // localescape index.
1504 auto InsertPair = ParentCGF.EscapedLocals.insert(
1505 std::make_pair(ParentAlloca, ParentCGF.EscapedLocals.size()));
1506 int FrameEscapeIdx = InsertPair.first->second;
1507 // call i8* @llvm.localrecover(i8* bitcast(@parentFn), i8* %fp, i32 N)
1508 llvm::Function *FrameRecoverFn = llvm::Intrinsic::getDeclaration(
1509 &CGM.getModule(), llvm::Intrinsic::localrecover);
1510 llvm::Constant *ParentI8Fn =
1511 llvm::ConstantExpr::getBitCast(ParentCGF.CurFn, Int8PtrTy);
1512 RecoverCall = Builder.CreateCall(
1513 FrameRecoverFn, {ParentI8Fn, ParentFP,
1514 llvm::ConstantInt::get(Int32Ty, FrameEscapeIdx)});
1515
1516 } else {
1517 // If the parent didn't have an alloca, we're doing some nested outlining.
1518 // Just clone the existing localrecover call, but tweak the FP argument to
1519 // use our FP value. All other arguments are constants.
1520 auto *ParentRecover =
1521 cast<llvm::IntrinsicInst>(ParentVar.getPointer()->stripPointerCasts());
1522 assert(ParentRecover->getIntrinsicID() == llvm::Intrinsic::localrecover &&
1523 "expected alloca or localrecover in parent LocalDeclMap");
1524 RecoverCall = cast<llvm::CallInst>(ParentRecover->clone());
1525 RecoverCall->setArgOperand(1, ParentFP);
1526 RecoverCall->insertBefore(AllocaInsertPt);
1527 }
1528
1529 // Bitcast the variable, rename it, and insert it in the local decl map.
1530 llvm::Value *ChildVar =
1531 Builder.CreateBitCast(RecoverCall, ParentVar.getType());
1532 ChildVar->setName(ParentVar.getName());
1533 return Address(ChildVar, ParentVar.getAlignment());
1534 }
1535
EmitCapturedLocals(CodeGenFunction & ParentCGF,const Stmt * OutlinedStmt,bool IsFilter)1536 void CodeGenFunction::EmitCapturedLocals(CodeGenFunction &ParentCGF,
1537 const Stmt *OutlinedStmt,
1538 bool IsFilter) {
1539 // Find all captures in the Stmt.
1540 CaptureFinder Finder(ParentCGF, ParentCGF.CXXABIThisDecl);
1541 Finder.Visit(OutlinedStmt);
1542
1543 // We can exit early on x86_64 when there are no captures. We just have to
1544 // save the exception code in filters so that __exception_code() works.
1545 if (!Finder.foundCaptures() &&
1546 CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) {
1547 if (IsFilter)
1548 EmitSEHExceptionCodeSave(ParentCGF, nullptr, nullptr);
1549 return;
1550 }
1551
1552 llvm::Value *EntryFP = nullptr;
1553 CGBuilderTy Builder(CGM, AllocaInsertPt);
1554 if (IsFilter && CGM.getTarget().getTriple().getArch() == llvm::Triple::x86) {
1555 // 32-bit SEH filters need to be careful about FP recovery. The end of the
1556 // EH registration is passed in as the EBP physical register. We can
1557 // recover that with llvm.frameaddress(1).
1558 EntryFP = Builder.CreateCall(
1559 CGM.getIntrinsic(llvm::Intrinsic::frameaddress), {Builder.getInt32(1)});
1560 } else {
1561 // Otherwise, for x64 and 32-bit finally functions, the parent FP is the
1562 // second parameter.
1563 auto AI = CurFn->arg_begin();
1564 ++AI;
1565 EntryFP = &*AI;
1566 }
1567
1568 llvm::Value *ParentFP = EntryFP;
1569 if (IsFilter) {
1570 // Given whatever FP the runtime provided us in EntryFP, recover the true
1571 // frame pointer of the parent function. We only need to do this in filters,
1572 // since finally funclets recover the parent FP for us.
1573 llvm::Function *RecoverFPIntrin =
1574 CGM.getIntrinsic(llvm::Intrinsic::x86_seh_recoverfp);
1575 llvm::Constant *ParentI8Fn =
1576 llvm::ConstantExpr::getBitCast(ParentCGF.CurFn, Int8PtrTy);
1577 ParentFP = Builder.CreateCall(RecoverFPIntrin, {ParentI8Fn, EntryFP});
1578 }
1579
1580 // Create llvm.localrecover calls for all captures.
1581 for (const VarDecl *VD : Finder.Captures) {
1582 if (isa<ImplicitParamDecl>(VD)) {
1583 CGM.ErrorUnsupported(VD, "'this' captured by SEH");
1584 CXXThisValue = llvm::UndefValue::get(ConvertTypeForMem(VD->getType()));
1585 continue;
1586 }
1587 if (VD->getType()->isVariablyModifiedType()) {
1588 CGM.ErrorUnsupported(VD, "VLA captured by SEH");
1589 continue;
1590 }
1591 assert((isa<ImplicitParamDecl>(VD) || VD->isLocalVarDeclOrParm()) &&
1592 "captured non-local variable");
1593
1594 // If this decl hasn't been declared yet, it will be declared in the
1595 // OutlinedStmt.
1596 auto I = ParentCGF.LocalDeclMap.find(VD);
1597 if (I == ParentCGF.LocalDeclMap.end())
1598 continue;
1599
1600 Address ParentVar = I->second;
1601 setAddrOfLocalVar(
1602 VD, recoverAddrOfEscapedLocal(ParentCGF, ParentVar, ParentFP));
1603 }
1604
1605 if (Finder.SEHCodeSlot.isValid()) {
1606 SEHCodeSlotStack.push_back(
1607 recoverAddrOfEscapedLocal(ParentCGF, Finder.SEHCodeSlot, ParentFP));
1608 }
1609
1610 if (IsFilter)
1611 EmitSEHExceptionCodeSave(ParentCGF, ParentFP, EntryFP);
1612 }
1613
1614 /// Arrange a function prototype that can be called by Windows exception
1615 /// handling personalities. On Win64, the prototype looks like:
1616 /// RetTy func(void *EHPtrs, void *ParentFP);
startOutlinedSEHHelper(CodeGenFunction & ParentCGF,bool IsFilter,const Stmt * OutlinedStmt)1617 void CodeGenFunction::startOutlinedSEHHelper(CodeGenFunction &ParentCGF,
1618 bool IsFilter,
1619 const Stmt *OutlinedStmt) {
1620 SourceLocation StartLoc = OutlinedStmt->getLocStart();
1621
1622 // Get the mangled function name.
1623 SmallString<128> Name;
1624 {
1625 llvm::raw_svector_ostream OS(Name);
1626 const Decl *ParentCodeDecl = ParentCGF.CurCodeDecl;
1627 const NamedDecl *Parent = dyn_cast_or_null<NamedDecl>(ParentCodeDecl);
1628 assert(Parent && "FIXME: handle unnamed decls (lambdas, blocks) with SEH");
1629 MangleContext &Mangler = CGM.getCXXABI().getMangleContext();
1630 if (IsFilter)
1631 Mangler.mangleSEHFilterExpression(Parent, OS);
1632 else
1633 Mangler.mangleSEHFinallyBlock(Parent, OS);
1634 }
1635
1636 FunctionArgList Args;
1637 if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86 || !IsFilter) {
1638 // All SEH finally functions take two parameters. Win64 filters take two
1639 // parameters. Win32 filters take no parameters.
1640 if (IsFilter) {
1641 Args.push_back(ImplicitParamDecl::Create(
1642 getContext(), nullptr, StartLoc,
1643 &getContext().Idents.get("exception_pointers"),
1644 getContext().VoidPtrTy));
1645 } else {
1646 Args.push_back(ImplicitParamDecl::Create(
1647 getContext(), nullptr, StartLoc,
1648 &getContext().Idents.get("abnormal_termination"),
1649 getContext().UnsignedCharTy));
1650 }
1651 Args.push_back(ImplicitParamDecl::Create(
1652 getContext(), nullptr, StartLoc,
1653 &getContext().Idents.get("frame_pointer"), getContext().VoidPtrTy));
1654 }
1655
1656 QualType RetTy = IsFilter ? getContext().LongTy : getContext().VoidTy;
1657
1658 llvm::Function *ParentFn = ParentCGF.CurFn;
1659 const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeFreeFunctionDeclaration(
1660 RetTy, Args, FunctionType::ExtInfo(), /*isVariadic=*/false);
1661
1662 llvm::FunctionType *FnTy = CGM.getTypes().GetFunctionType(FnInfo);
1663 llvm::Function *Fn = llvm::Function::Create(
1664 FnTy, llvm::GlobalValue::InternalLinkage, Name.str(), &CGM.getModule());
1665 // The filter is either in the same comdat as the function, or it's internal.
1666 if (llvm::Comdat *C = ParentFn->getComdat()) {
1667 Fn->setComdat(C);
1668 } else if (ParentFn->hasWeakLinkage() || ParentFn->hasLinkOnceLinkage()) {
1669 llvm::Comdat *C = CGM.getModule().getOrInsertComdat(ParentFn->getName());
1670 ParentFn->setComdat(C);
1671 Fn->setComdat(C);
1672 } else {
1673 Fn->setLinkage(llvm::GlobalValue::InternalLinkage);
1674 }
1675
1676 IsOutlinedSEHHelper = true;
1677
1678 StartFunction(GlobalDecl(), RetTy, Fn, FnInfo, Args,
1679 OutlinedStmt->getLocStart(), OutlinedStmt->getLocStart());
1680
1681 CGM.SetLLVMFunctionAttributes(nullptr, FnInfo, CurFn);
1682 EmitCapturedLocals(ParentCGF, OutlinedStmt, IsFilter);
1683 }
1684
1685 /// Create a stub filter function that will ultimately hold the code of the
1686 /// filter expression. The EH preparation passes in LLVM will outline the code
1687 /// from the main function body into this stub.
1688 llvm::Function *
GenerateSEHFilterFunction(CodeGenFunction & ParentCGF,const SEHExceptStmt & Except)1689 CodeGenFunction::GenerateSEHFilterFunction(CodeGenFunction &ParentCGF,
1690 const SEHExceptStmt &Except) {
1691 const Expr *FilterExpr = Except.getFilterExpr();
1692 startOutlinedSEHHelper(ParentCGF, true, FilterExpr);
1693
1694 // Emit the original filter expression, convert to i32, and return.
1695 llvm::Value *R = EmitScalarExpr(FilterExpr);
1696 R = Builder.CreateIntCast(R, ConvertType(getContext().LongTy),
1697 FilterExpr->getType()->isSignedIntegerType());
1698 Builder.CreateStore(R, ReturnValue);
1699
1700 FinishFunction(FilterExpr->getLocEnd());
1701
1702 return CurFn;
1703 }
1704
1705 llvm::Function *
GenerateSEHFinallyFunction(CodeGenFunction & ParentCGF,const SEHFinallyStmt & Finally)1706 CodeGenFunction::GenerateSEHFinallyFunction(CodeGenFunction &ParentCGF,
1707 const SEHFinallyStmt &Finally) {
1708 const Stmt *FinallyBlock = Finally.getBlock();
1709 startOutlinedSEHHelper(ParentCGF, false, FinallyBlock);
1710
1711 // Mark finally block calls as nounwind and noinline to make LLVM's job a
1712 // little easier.
1713 // FIXME: Remove these restrictions in the future.
1714 CurFn->addFnAttr(llvm::Attribute::NoUnwind);
1715 CurFn->addFnAttr(llvm::Attribute::NoInline);
1716
1717 // Emit the original filter expression, convert to i32, and return.
1718 EmitStmt(FinallyBlock);
1719
1720 FinishFunction(FinallyBlock->getLocEnd());
1721
1722 return CurFn;
1723 }
1724
EmitSEHExceptionCodeSave(CodeGenFunction & ParentCGF,llvm::Value * ParentFP,llvm::Value * EntryFP)1725 void CodeGenFunction::EmitSEHExceptionCodeSave(CodeGenFunction &ParentCGF,
1726 llvm::Value *ParentFP,
1727 llvm::Value *EntryFP) {
1728 // Get the pointer to the EXCEPTION_POINTERS struct. This is returned by the
1729 // __exception_info intrinsic.
1730 if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) {
1731 // On Win64, the info is passed as the first parameter to the filter.
1732 SEHInfo = &*CurFn->arg_begin();
1733 SEHCodeSlotStack.push_back(
1734 CreateMemTemp(getContext().IntTy, "__exception_code"));
1735 } else {
1736 // On Win32, the EBP on entry to the filter points to the end of an
1737 // exception registration object. It contains 6 32-bit fields, and the info
1738 // pointer is stored in the second field. So, GEP 20 bytes backwards and
1739 // load the pointer.
1740 SEHInfo = Builder.CreateConstInBoundsGEP1_32(Int8Ty, EntryFP, -20);
1741 SEHInfo = Builder.CreateBitCast(SEHInfo, Int8PtrTy->getPointerTo());
1742 SEHInfo = Builder.CreateAlignedLoad(Int8PtrTy, SEHInfo, getPointerAlign());
1743 SEHCodeSlotStack.push_back(recoverAddrOfEscapedLocal(
1744 ParentCGF, ParentCGF.SEHCodeSlotStack.back(), ParentFP));
1745 }
1746
1747 // Save the exception code in the exception slot to unify exception access in
1748 // the filter function and the landing pad.
1749 // struct EXCEPTION_POINTERS {
1750 // EXCEPTION_RECORD *ExceptionRecord;
1751 // CONTEXT *ContextRecord;
1752 // };
1753 // int exceptioncode = exception_pointers->ExceptionRecord->ExceptionCode;
1754 llvm::Type *RecordTy = CGM.Int32Ty->getPointerTo();
1755 llvm::Type *PtrsTy = llvm::StructType::get(RecordTy, CGM.VoidPtrTy, nullptr);
1756 llvm::Value *Ptrs = Builder.CreateBitCast(SEHInfo, PtrsTy->getPointerTo());
1757 llvm::Value *Rec = Builder.CreateStructGEP(PtrsTy, Ptrs, 0);
1758 Rec = Builder.CreateAlignedLoad(Rec, getPointerAlign());
1759 llvm::Value *Code = Builder.CreateAlignedLoad(Rec, getIntAlign());
1760 assert(!SEHCodeSlotStack.empty() && "emitting EH code outside of __except");
1761 Builder.CreateStore(Code, SEHCodeSlotStack.back());
1762 }
1763
EmitSEHExceptionInfo()1764 llvm::Value *CodeGenFunction::EmitSEHExceptionInfo() {
1765 // Sema should diagnose calling this builtin outside of a filter context, but
1766 // don't crash if we screw up.
1767 if (!SEHInfo)
1768 return llvm::UndefValue::get(Int8PtrTy);
1769 assert(SEHInfo->getType() == Int8PtrTy);
1770 return SEHInfo;
1771 }
1772
EmitSEHExceptionCode()1773 llvm::Value *CodeGenFunction::EmitSEHExceptionCode() {
1774 assert(!SEHCodeSlotStack.empty() && "emitting EH code outside of __except");
1775 return Builder.CreateLoad(SEHCodeSlotStack.back());
1776 }
1777
EmitSEHAbnormalTermination()1778 llvm::Value *CodeGenFunction::EmitSEHAbnormalTermination() {
1779 // Abnormal termination is just the first parameter to the outlined finally
1780 // helper.
1781 auto AI = CurFn->arg_begin();
1782 return Builder.CreateZExt(&*AI, Int32Ty);
1783 }
1784
EnterSEHTryStmt(const SEHTryStmt & S)1785 void CodeGenFunction::EnterSEHTryStmt(const SEHTryStmt &S) {
1786 CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);
1787 if (const SEHFinallyStmt *Finally = S.getFinallyHandler()) {
1788 // Outline the finally block.
1789 llvm::Function *FinallyFunc =
1790 HelperCGF.GenerateSEHFinallyFunction(*this, *Finally);
1791
1792 // Push a cleanup for __finally blocks.
1793 EHStack.pushCleanup<PerformSEHFinally>(NormalAndEHCleanup, FinallyFunc);
1794 return;
1795 }
1796
1797 // Otherwise, we must have an __except block.
1798 const SEHExceptStmt *Except = S.getExceptHandler();
1799 assert(Except);
1800 EHCatchScope *CatchScope = EHStack.pushCatch(1);
1801 SEHCodeSlotStack.push_back(
1802 CreateMemTemp(getContext().IntTy, "__exception_code"));
1803
1804 // If the filter is known to evaluate to 1, then we can use the clause
1805 // "catch i8* null". We can't do this on x86 because the filter has to save
1806 // the exception code.
1807 llvm::Constant *C =
1808 CGM.EmitConstantExpr(Except->getFilterExpr(), getContext().IntTy, this);
1809 if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86 && C &&
1810 C->isOneValue()) {
1811 CatchScope->setCatchAllHandler(0, createBasicBlock("__except"));
1812 return;
1813 }
1814
1815 // In general, we have to emit an outlined filter function. Use the function
1816 // in place of the RTTI typeinfo global that C++ EH uses.
1817 llvm::Function *FilterFunc =
1818 HelperCGF.GenerateSEHFilterFunction(*this, *Except);
1819 llvm::Constant *OpaqueFunc =
1820 llvm::ConstantExpr::getBitCast(FilterFunc, Int8PtrTy);
1821 CatchScope->setHandler(0, OpaqueFunc, createBasicBlock("__except.ret"));
1822 }
1823
ExitSEHTryStmt(const SEHTryStmt & S)1824 void CodeGenFunction::ExitSEHTryStmt(const SEHTryStmt &S) {
1825 // Just pop the cleanup if it's a __finally block.
1826 if (S.getFinallyHandler()) {
1827 PopCleanupBlock();
1828 return;
1829 }
1830
1831 // Otherwise, we must have an __except block.
1832 const SEHExceptStmt *Except = S.getExceptHandler();
1833 assert(Except && "__try must have __finally xor __except");
1834 EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin());
1835
1836 // Don't emit the __except block if the __try block lacked invokes.
1837 // TODO: Model unwind edges from instructions, either with iload / istore or
1838 // a try body function.
1839 if (!CatchScope.hasEHBranches()) {
1840 CatchScope.clearHandlerBlocks();
1841 EHStack.popCatch();
1842 SEHCodeSlotStack.pop_back();
1843 return;
1844 }
1845
1846 // The fall-through block.
1847 llvm::BasicBlock *ContBB = createBasicBlock("__try.cont");
1848
1849 // We just emitted the body of the __try; jump to the continue block.
1850 if (HaveInsertPoint())
1851 Builder.CreateBr(ContBB);
1852
1853 // Check if our filter function returned true.
1854 emitCatchDispatchBlock(*this, CatchScope);
1855
1856 // Grab the block before we pop the handler.
1857 llvm::BasicBlock *CatchPadBB = CatchScope.getHandler(0).Block;
1858 EHStack.popCatch();
1859
1860 EmitBlockAfterUses(CatchPadBB);
1861
1862 // __except blocks don't get outlined into funclets, so immediately do a
1863 // catchret.
1864 llvm::CatchPadInst *CPI =
1865 cast<llvm::CatchPadInst>(CatchPadBB->getFirstNonPHI());
1866 llvm::BasicBlock *ExceptBB = createBasicBlock("__except");
1867 Builder.CreateCatchRet(CPI, ExceptBB);
1868 EmitBlock(ExceptBB);
1869
1870 // On Win64, the exception code is returned in EAX. Copy it into the slot.
1871 if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) {
1872 llvm::Function *SEHCodeIntrin =
1873 CGM.getIntrinsic(llvm::Intrinsic::eh_exceptioncode);
1874 llvm::Value *Code = Builder.CreateCall(SEHCodeIntrin, {CPI});
1875 Builder.CreateStore(Code, SEHCodeSlotStack.back());
1876 }
1877
1878 // Emit the __except body.
1879 EmitStmt(Except->getBlock());
1880
1881 // End the lifetime of the exception code.
1882 SEHCodeSlotStack.pop_back();
1883
1884 if (HaveInsertPoint())
1885 Builder.CreateBr(ContBB);
1886
1887 EmitBlock(ContBB);
1888 }
1889
EmitSEHLeaveStmt(const SEHLeaveStmt & S)1890 void CodeGenFunction::EmitSEHLeaveStmt(const SEHLeaveStmt &S) {
1891 // If this code is reachable then emit a stop point (if generating
1892 // debug info). We have to do this ourselves because we are on the
1893 // "simple" statement path.
1894 if (HaveInsertPoint())
1895 EmitStopPoint(&S);
1896
1897 // This must be a __leave from a __finally block, which we warn on and is UB.
1898 // Just emit unreachable.
1899 if (!isSEHTryScope()) {
1900 Builder.CreateUnreachable();
1901 Builder.ClearInsertionPoint();
1902 return;
1903 }
1904
1905 EmitBranchThroughCleanup(*SEHTryEpilogueStack.back());
1906 }
1907