1 //===--- CGException.cpp - Emit LLVM Code for C++ exceptions ----*- C++ -*-===//
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 // This contains code dealing with C++ exception related code generation.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "CGCXXABI.h"
14 #include "CGCleanup.h"
15 #include "CGObjCRuntime.h"
16 #include "CodeGenFunction.h"
17 #include "ConstantEmitter.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/DiagnosticSema.h"
24 #include "clang/Basic/TargetBuiltins.h"
25 #include "llvm/IR/IntrinsicInst.h"
26 #include "llvm/IR/Intrinsics.h"
27 #include "llvm/IR/IntrinsicsWebAssembly.h"
28 #include "llvm/Support/SaveAndRestore.h"
29
30 using namespace clang;
31 using namespace CodeGen;
32
getFreeExceptionFn(CodeGenModule & CGM)33 static llvm::FunctionCallee getFreeExceptionFn(CodeGenModule &CGM) {
34 // void __cxa_free_exception(void *thrown_exception);
35
36 llvm::FunctionType *FTy =
37 llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*isVarArg=*/false);
38
39 return CGM.CreateRuntimeFunction(FTy, "__cxa_free_exception");
40 }
41
getSehTryBeginFn(CodeGenModule & CGM)42 static llvm::FunctionCallee getSehTryBeginFn(CodeGenModule &CGM) {
43 llvm::FunctionType *FTy =
44 llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);
45 return CGM.CreateRuntimeFunction(FTy, "llvm.seh.try.begin");
46 }
47
getSehTryEndFn(CodeGenModule & CGM)48 static llvm::FunctionCallee getSehTryEndFn(CodeGenModule &CGM) {
49 llvm::FunctionType *FTy =
50 llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);
51 return CGM.CreateRuntimeFunction(FTy, "llvm.seh.try.end");
52 }
53
getUnexpectedFn(CodeGenModule & CGM)54 static llvm::FunctionCallee getUnexpectedFn(CodeGenModule &CGM) {
55 // void __cxa_call_unexpected(void *thrown_exception);
56
57 llvm::FunctionType *FTy =
58 llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*isVarArg=*/false);
59
60 return CGM.CreateRuntimeFunction(FTy, "__cxa_call_unexpected");
61 }
62
getTerminateFn()63 llvm::FunctionCallee CodeGenModule::getTerminateFn() {
64 // void __terminate();
65
66 llvm::FunctionType *FTy =
67 llvm::FunctionType::get(VoidTy, /*isVarArg=*/false);
68
69 StringRef name;
70
71 // In C++, use std::terminate().
72 if (getLangOpts().CPlusPlus &&
73 getTarget().getCXXABI().isItaniumFamily()) {
74 name = "_ZSt9terminatev";
75 } else if (getLangOpts().CPlusPlus &&
76 getTarget().getCXXABI().isMicrosoft()) {
77 if (getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2015))
78 name = "__std_terminate";
79 else
80 name = "?terminate@@YAXXZ";
81 } else if (getLangOpts().ObjC &&
82 getLangOpts().ObjCRuntime.hasTerminate())
83 name = "objc_terminate";
84 else
85 name = "abort";
86 return CreateRuntimeFunction(FTy, name);
87 }
88
getCatchallRethrowFn(CodeGenModule & CGM,StringRef Name)89 static llvm::FunctionCallee getCatchallRethrowFn(CodeGenModule &CGM,
90 StringRef Name) {
91 llvm::FunctionType *FTy =
92 llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*isVarArg=*/false);
93
94 return CGM.CreateRuntimeFunction(FTy, Name);
95 }
96
97 const EHPersonality EHPersonality::GNU_C = { "__gcc_personality_v0", nullptr };
98 const EHPersonality
99 EHPersonality::GNU_C_SJLJ = { "__gcc_personality_sj0", nullptr };
100 const EHPersonality
101 EHPersonality::GNU_C_SEH = { "__gcc_personality_seh0", nullptr };
102 const EHPersonality
103 EHPersonality::NeXT_ObjC = { "__objc_personality_v0", nullptr };
104 const EHPersonality
105 EHPersonality::GNU_CPlusPlus = { "__gxx_personality_v0", nullptr };
106 const EHPersonality
107 EHPersonality::GNU_CPlusPlus_SJLJ = { "__gxx_personality_sj0", nullptr };
108 const EHPersonality
109 EHPersonality::GNU_CPlusPlus_SEH = { "__gxx_personality_seh0", nullptr };
110 const EHPersonality
111 EHPersonality::GNU_ObjC = {"__gnu_objc_personality_v0", "objc_exception_throw"};
112 const EHPersonality
113 EHPersonality::GNU_ObjC_SJLJ = {"__gnu_objc_personality_sj0", "objc_exception_throw"};
114 const EHPersonality
115 EHPersonality::GNU_ObjC_SEH = {"__gnu_objc_personality_seh0", "objc_exception_throw"};
116 const EHPersonality
117 EHPersonality::GNU_ObjCXX = { "__gnustep_objcxx_personality_v0", nullptr };
118 const EHPersonality
119 EHPersonality::GNUstep_ObjC = { "__gnustep_objc_personality_v0", nullptr };
120 const EHPersonality
121 EHPersonality::MSVC_except_handler = { "_except_handler3", nullptr };
122 const EHPersonality
123 EHPersonality::MSVC_C_specific_handler = { "__C_specific_handler", nullptr };
124 const EHPersonality
125 EHPersonality::MSVC_CxxFrameHandler3 = { "__CxxFrameHandler3", nullptr };
126 const EHPersonality
127 EHPersonality::GNU_Wasm_CPlusPlus = { "__gxx_wasm_personality_v0", nullptr };
128 const EHPersonality EHPersonality::XL_CPlusPlus = {"__xlcxx_personality_v1",
129 nullptr};
130
getCPersonality(const TargetInfo & Target,const LangOptions & L)131 static const EHPersonality &getCPersonality(const TargetInfo &Target,
132 const LangOptions &L) {
133 const llvm::Triple &T = Target.getTriple();
134 if (T.isWindowsMSVCEnvironment())
135 return EHPersonality::MSVC_CxxFrameHandler3;
136 if (L.hasSjLjExceptions())
137 return EHPersonality::GNU_C_SJLJ;
138 if (L.hasDWARFExceptions())
139 return EHPersonality::GNU_C;
140 if (L.hasSEHExceptions())
141 return EHPersonality::GNU_C_SEH;
142 return EHPersonality::GNU_C;
143 }
144
getObjCPersonality(const TargetInfo & Target,const LangOptions & L)145 static const EHPersonality &getObjCPersonality(const TargetInfo &Target,
146 const LangOptions &L) {
147 const llvm::Triple &T = Target.getTriple();
148 if (T.isWindowsMSVCEnvironment())
149 return EHPersonality::MSVC_CxxFrameHandler3;
150
151 switch (L.ObjCRuntime.getKind()) {
152 case ObjCRuntime::FragileMacOSX:
153 return getCPersonality(Target, L);
154 case ObjCRuntime::MacOSX:
155 case ObjCRuntime::iOS:
156 case ObjCRuntime::WatchOS:
157 return EHPersonality::NeXT_ObjC;
158 case ObjCRuntime::GNUstep:
159 if (L.ObjCRuntime.getVersion() >= VersionTuple(1, 7))
160 return EHPersonality::GNUstep_ObjC;
161 LLVM_FALLTHROUGH;
162 case ObjCRuntime::GCC:
163 case ObjCRuntime::ObjFW:
164 if (L.hasSjLjExceptions())
165 return EHPersonality::GNU_ObjC_SJLJ;
166 if (L.hasSEHExceptions())
167 return EHPersonality::GNU_ObjC_SEH;
168 return EHPersonality::GNU_ObjC;
169 }
170 llvm_unreachable("bad runtime kind");
171 }
172
getCXXPersonality(const TargetInfo & Target,const LangOptions & L)173 static const EHPersonality &getCXXPersonality(const TargetInfo &Target,
174 const LangOptions &L) {
175 const llvm::Triple &T = Target.getTriple();
176 if (T.isWindowsMSVCEnvironment())
177 return EHPersonality::MSVC_CxxFrameHandler3;
178 if (T.isOSAIX())
179 return EHPersonality::XL_CPlusPlus;
180 if (L.hasSjLjExceptions())
181 return EHPersonality::GNU_CPlusPlus_SJLJ;
182 if (L.hasDWARFExceptions())
183 return EHPersonality::GNU_CPlusPlus;
184 if (L.hasSEHExceptions())
185 return EHPersonality::GNU_CPlusPlus_SEH;
186 if (L.hasWasmExceptions())
187 return EHPersonality::GNU_Wasm_CPlusPlus;
188 return EHPersonality::GNU_CPlusPlus;
189 }
190
191 /// Determines the personality function to use when both C++
192 /// and Objective-C exceptions are being caught.
getObjCXXPersonality(const TargetInfo & Target,const LangOptions & L)193 static const EHPersonality &getObjCXXPersonality(const TargetInfo &Target,
194 const LangOptions &L) {
195 if (Target.getTriple().isWindowsMSVCEnvironment())
196 return EHPersonality::MSVC_CxxFrameHandler3;
197
198 switch (L.ObjCRuntime.getKind()) {
199 // In the fragile ABI, just use C++ exception handling and hope
200 // they're not doing crazy exception mixing.
201 case ObjCRuntime::FragileMacOSX:
202 return getCXXPersonality(Target, L);
203
204 // The ObjC personality defers to the C++ personality for non-ObjC
205 // handlers. Unlike the C++ case, we use the same personality
206 // function on targets using (backend-driven) SJLJ EH.
207 case ObjCRuntime::MacOSX:
208 case ObjCRuntime::iOS:
209 case ObjCRuntime::WatchOS:
210 return getObjCPersonality(Target, L);
211
212 case ObjCRuntime::GNUstep:
213 return EHPersonality::GNU_ObjCXX;
214
215 // The GCC runtime's personality function inherently doesn't support
216 // mixed EH. Use the ObjC personality just to avoid returning null.
217 case ObjCRuntime::GCC:
218 case ObjCRuntime::ObjFW:
219 return getObjCPersonality(Target, L);
220 }
221 llvm_unreachable("bad runtime kind");
222 }
223
getSEHPersonalityMSVC(const llvm::Triple & T)224 static const EHPersonality &getSEHPersonalityMSVC(const llvm::Triple &T) {
225 if (T.getArch() == llvm::Triple::x86)
226 return EHPersonality::MSVC_except_handler;
227 return EHPersonality::MSVC_C_specific_handler;
228 }
229
get(CodeGenModule & CGM,const FunctionDecl * FD)230 const EHPersonality &EHPersonality::get(CodeGenModule &CGM,
231 const FunctionDecl *FD) {
232 const llvm::Triple &T = CGM.getTarget().getTriple();
233 const LangOptions &L = CGM.getLangOpts();
234 const TargetInfo &Target = CGM.getTarget();
235
236 // Functions using SEH get an SEH personality.
237 if (FD && FD->usesSEHTry())
238 return getSEHPersonalityMSVC(T);
239
240 if (L.ObjC)
241 return L.CPlusPlus ? getObjCXXPersonality(Target, L)
242 : getObjCPersonality(Target, L);
243 return L.CPlusPlus ? getCXXPersonality(Target, L)
244 : getCPersonality(Target, L);
245 }
246
get(CodeGenFunction & CGF)247 const EHPersonality &EHPersonality::get(CodeGenFunction &CGF) {
248 const auto *FD = CGF.CurCodeDecl;
249 // For outlined finallys and filters, use the SEH personality in case they
250 // contain more SEH. This mostly only affects finallys. Filters could
251 // hypothetically use gnu statement expressions to sneak in nested SEH.
252 FD = FD ? FD : CGF.CurSEHParent;
253 return get(CGF.CGM, dyn_cast_or_null<FunctionDecl>(FD));
254 }
255
getPersonalityFn(CodeGenModule & CGM,const EHPersonality & Personality)256 static llvm::FunctionCallee getPersonalityFn(CodeGenModule &CGM,
257 const EHPersonality &Personality) {
258 return CGM.CreateRuntimeFunction(llvm::FunctionType::get(CGM.Int32Ty, true),
259 Personality.PersonalityFn,
260 llvm::AttributeList(), /*Local=*/true);
261 }
262
getOpaquePersonalityFn(CodeGenModule & CGM,const EHPersonality & Personality)263 static llvm::Constant *getOpaquePersonalityFn(CodeGenModule &CGM,
264 const EHPersonality &Personality) {
265 llvm::FunctionCallee Fn = getPersonalityFn(CGM, Personality);
266 llvm::PointerType* Int8PtrTy = llvm::PointerType::get(
267 llvm::Type::getInt8Ty(CGM.getLLVMContext()),
268 CGM.getDataLayout().getProgramAddressSpace());
269
270 return llvm::ConstantExpr::getBitCast(cast<llvm::Constant>(Fn.getCallee()),
271 Int8PtrTy);
272 }
273
274 /// Check whether a landingpad instruction only uses C++ features.
LandingPadHasOnlyCXXUses(llvm::LandingPadInst * LPI)275 static bool LandingPadHasOnlyCXXUses(llvm::LandingPadInst *LPI) {
276 for (unsigned I = 0, E = LPI->getNumClauses(); I != E; ++I) {
277 // Look for something that would've been returned by the ObjC
278 // runtime's GetEHType() method.
279 llvm::Value *Val = LPI->getClause(I)->stripPointerCasts();
280 if (LPI->isCatch(I)) {
281 // Check if the catch value has the ObjC prefix.
282 if (llvm::GlobalVariable *GV = dyn_cast<llvm::GlobalVariable>(Val))
283 // ObjC EH selector entries are always global variables with
284 // names starting like this.
285 if (GV->getName().startswith("OBJC_EHTYPE"))
286 return false;
287 } else {
288 // Check if any of the filter values have the ObjC prefix.
289 llvm::Constant *CVal = cast<llvm::Constant>(Val);
290 for (llvm::User::op_iterator
291 II = CVal->op_begin(), IE = CVal->op_end(); II != IE; ++II) {
292 if (llvm::GlobalVariable *GV =
293 cast<llvm::GlobalVariable>((*II)->stripPointerCasts()))
294 // ObjC EH selector entries are always global variables with
295 // names starting like this.
296 if (GV->getName().startswith("OBJC_EHTYPE"))
297 return false;
298 }
299 }
300 }
301 return true;
302 }
303
304 /// Check whether a personality function could reasonably be swapped
305 /// for a C++ personality function.
PersonalityHasOnlyCXXUses(llvm::Constant * Fn)306 static bool PersonalityHasOnlyCXXUses(llvm::Constant *Fn) {
307 for (llvm::User *U : Fn->users()) {
308 // Conditionally white-list bitcasts.
309 if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(U)) {
310 if (CE->getOpcode() != llvm::Instruction::BitCast) return false;
311 if (!PersonalityHasOnlyCXXUses(CE))
312 return false;
313 continue;
314 }
315
316 // Otherwise it must be a function.
317 llvm::Function *F = dyn_cast<llvm::Function>(U);
318 if (!F) return false;
319
320 for (auto BB = F->begin(), E = F->end(); BB != E; ++BB) {
321 if (BB->isLandingPad())
322 if (!LandingPadHasOnlyCXXUses(BB->getLandingPadInst()))
323 return false;
324 }
325 }
326
327 return true;
328 }
329
330 /// Try to use the C++ personality function in ObjC++. Not doing this
331 /// can cause some incompatibilities with gcc, which is more
332 /// aggressive about only using the ObjC++ personality in a function
333 /// when it really needs it.
SimplifyPersonality()334 void CodeGenModule::SimplifyPersonality() {
335 // If we're not in ObjC++ -fexceptions, there's nothing to do.
336 if (!LangOpts.CPlusPlus || !LangOpts.ObjC || !LangOpts.Exceptions)
337 return;
338
339 // Both the problem this endeavors to fix and the way the logic
340 // above works is specific to the NeXT runtime.
341 if (!LangOpts.ObjCRuntime.isNeXTFamily())
342 return;
343
344 const EHPersonality &ObjCXX = EHPersonality::get(*this, /*FD=*/nullptr);
345 const EHPersonality &CXX = getCXXPersonality(getTarget(), LangOpts);
346 if (&ObjCXX == &CXX)
347 return;
348
349 assert(std::strcmp(ObjCXX.PersonalityFn, CXX.PersonalityFn) != 0 &&
350 "Different EHPersonalities using the same personality function.");
351
352 llvm::Function *Fn = getModule().getFunction(ObjCXX.PersonalityFn);
353
354 // Nothing to do if it's unused.
355 if (!Fn || Fn->use_empty()) return;
356
357 // Can't do the optimization if it has non-C++ uses.
358 if (!PersonalityHasOnlyCXXUses(Fn)) return;
359
360 // Create the C++ personality function and kill off the old
361 // function.
362 llvm::FunctionCallee CXXFn = getPersonalityFn(*this, CXX);
363
364 // This can happen if the user is screwing with us.
365 if (Fn->getType() != CXXFn.getCallee()->getType())
366 return;
367
368 Fn->replaceAllUsesWith(CXXFn.getCallee());
369 Fn->eraseFromParent();
370 }
371
372 /// Returns the value to inject into a selector to indicate the
373 /// presence of a catch-all.
getCatchAllValue(CodeGenFunction & CGF)374 static llvm::Constant *getCatchAllValue(CodeGenFunction &CGF) {
375 // Possibly we should use @llvm.eh.catch.all.value here.
376 return llvm::ConstantPointerNull::get(CGF.Int8PtrTy);
377 }
378
379 namespace {
380 /// A cleanup to free the exception object if its initialization
381 /// throws.
382 struct FreeException final : EHScopeStack::Cleanup {
383 llvm::Value *exn;
FreeException__anon97e456f80111::FreeException384 FreeException(llvm::Value *exn) : exn(exn) {}
Emit__anon97e456f80111::FreeException385 void Emit(CodeGenFunction &CGF, Flags flags) override {
386 CGF.EmitNounwindRuntimeCall(getFreeExceptionFn(CGF.CGM), exn);
387 }
388 };
389 } // end anonymous namespace
390
391 // Emits an exception expression into the given location. This
392 // differs from EmitAnyExprToMem only in that, if a final copy-ctor
393 // call is required, an exception within that copy ctor causes
394 // std::terminate to be invoked.
EmitAnyExprToExn(const Expr * e,Address addr)395 void CodeGenFunction::EmitAnyExprToExn(const Expr *e, Address addr) {
396 // Make sure the exception object is cleaned up if there's an
397 // exception during initialization.
398 pushFullExprCleanup<FreeException>(EHCleanup, addr.getPointer());
399 EHScopeStack::stable_iterator cleanup = EHStack.stable_begin();
400
401 // __cxa_allocate_exception returns a void*; we need to cast this
402 // to the appropriate type for the object.
403 llvm::Type *ty = ConvertTypeForMem(e->getType())->getPointerTo();
404 Address typedAddr = Builder.CreateBitCast(addr, ty);
405
406 // FIXME: this isn't quite right! If there's a final unelided call
407 // to a copy constructor, then according to [except.terminate]p1 we
408 // must call std::terminate() if that constructor throws, because
409 // technically that copy occurs after the exception expression is
410 // evaluated but before the exception is caught. But the best way
411 // to handle that is to teach EmitAggExpr to do the final copy
412 // differently if it can't be elided.
413 EmitAnyExprToMem(e, typedAddr, e->getType().getQualifiers(),
414 /*IsInit*/ true);
415
416 // Deactivate the cleanup block.
417 DeactivateCleanupBlock(cleanup,
418 cast<llvm::Instruction>(typedAddr.getPointer()));
419 }
420
getExceptionSlot()421 Address CodeGenFunction::getExceptionSlot() {
422 if (!ExceptionSlot)
423 ExceptionSlot = CreateTempAlloca(Int8PtrTy, "exn.slot");
424 return Address(ExceptionSlot, getPointerAlign());
425 }
426
getEHSelectorSlot()427 Address CodeGenFunction::getEHSelectorSlot() {
428 if (!EHSelectorSlot)
429 EHSelectorSlot = CreateTempAlloca(Int32Ty, "ehselector.slot");
430 return Address(EHSelectorSlot, CharUnits::fromQuantity(4));
431 }
432
getExceptionFromSlot()433 llvm::Value *CodeGenFunction::getExceptionFromSlot() {
434 return Builder.CreateLoad(getExceptionSlot(), "exn");
435 }
436
getSelectorFromSlot()437 llvm::Value *CodeGenFunction::getSelectorFromSlot() {
438 return Builder.CreateLoad(getEHSelectorSlot(), "sel");
439 }
440
EmitCXXThrowExpr(const CXXThrowExpr * E,bool KeepInsertionPoint)441 void CodeGenFunction::EmitCXXThrowExpr(const CXXThrowExpr *E,
442 bool KeepInsertionPoint) {
443 if (const Expr *SubExpr = E->getSubExpr()) {
444 QualType ThrowType = SubExpr->getType();
445 if (ThrowType->isObjCObjectPointerType()) {
446 const Stmt *ThrowStmt = E->getSubExpr();
447 const ObjCAtThrowStmt S(E->getExprLoc(), const_cast<Stmt *>(ThrowStmt));
448 CGM.getObjCRuntime().EmitThrowStmt(*this, S, false);
449 } else {
450 CGM.getCXXABI().emitThrow(*this, E);
451 }
452 } else {
453 CGM.getCXXABI().emitRethrow(*this, /*isNoReturn=*/true);
454 }
455
456 // throw is an expression, and the expression emitters expect us
457 // to leave ourselves at a valid insertion point.
458 if (KeepInsertionPoint)
459 EmitBlock(createBasicBlock("throw.cont"));
460 }
461
EmitStartEHSpec(const Decl * D)462 void CodeGenFunction::EmitStartEHSpec(const Decl *D) {
463 if (!CGM.getLangOpts().CXXExceptions)
464 return;
465
466 const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D);
467 if (!FD) {
468 // Check if CapturedDecl is nothrow and create terminate scope for it.
469 if (const CapturedDecl* CD = dyn_cast_or_null<CapturedDecl>(D)) {
470 if (CD->isNothrow())
471 EHStack.pushTerminate();
472 }
473 return;
474 }
475 const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>();
476 if (!Proto)
477 return;
478
479 ExceptionSpecificationType EST = Proto->getExceptionSpecType();
480 if (isNoexceptExceptionSpec(EST) && Proto->canThrow() == CT_Cannot) {
481 // noexcept functions are simple terminate scopes.
482 if (!getLangOpts().EHAsynch) // -EHa: HW exception still can occur
483 EHStack.pushTerminate();
484 } else if (EST == EST_Dynamic || EST == EST_DynamicNone) {
485 // TODO: Revisit exception specifications for the MS ABI. There is a way to
486 // encode these in an object file but MSVC doesn't do anything with it.
487 if (getTarget().getCXXABI().isMicrosoft())
488 return;
489 // In Wasm EH we currently treat 'throw()' in the same way as 'noexcept'. In
490 // case of throw with types, we ignore it and print a warning for now.
491 // TODO Correctly handle exception specification in Wasm EH
492 if (CGM.getLangOpts().hasWasmExceptions()) {
493 if (EST == EST_DynamicNone)
494 EHStack.pushTerminate();
495 else
496 CGM.getDiags().Report(D->getLocation(),
497 diag::warn_wasm_dynamic_exception_spec_ignored)
498 << FD->getExceptionSpecSourceRange();
499 return;
500 }
501 // Currently Emscripten EH only handles 'throw()' but not 'throw' with
502 // types. 'throw()' handling will be done in JS glue code so we don't need
503 // to do anything in that case. Just print a warning message in case of
504 // throw with types.
505 // TODO Correctly handle exception specification in Emscripten EH
506 if (getTarget().getCXXABI() == TargetCXXABI::WebAssembly &&
507 CGM.getLangOpts().getExceptionHandling() ==
508 LangOptions::ExceptionHandlingKind::None &&
509 EST == EST_Dynamic)
510 CGM.getDiags().Report(D->getLocation(),
511 diag::warn_wasm_dynamic_exception_spec_ignored)
512 << FD->getExceptionSpecSourceRange();
513
514 unsigned NumExceptions = Proto->getNumExceptions();
515 EHFilterScope *Filter = EHStack.pushFilter(NumExceptions);
516
517 for (unsigned I = 0; I != NumExceptions; ++I) {
518 QualType Ty = Proto->getExceptionType(I);
519 QualType ExceptType = Ty.getNonReferenceType().getUnqualifiedType();
520 llvm::Value *EHType = CGM.GetAddrOfRTTIDescriptor(ExceptType,
521 /*ForEH=*/true);
522 Filter->setFilter(I, EHType);
523 }
524 }
525 }
526
527 /// Emit the dispatch block for a filter scope if necessary.
emitFilterDispatchBlock(CodeGenFunction & CGF,EHFilterScope & filterScope)528 static void emitFilterDispatchBlock(CodeGenFunction &CGF,
529 EHFilterScope &filterScope) {
530 llvm::BasicBlock *dispatchBlock = filterScope.getCachedEHDispatchBlock();
531 if (!dispatchBlock) return;
532 if (dispatchBlock->use_empty()) {
533 delete dispatchBlock;
534 return;
535 }
536
537 CGF.EmitBlockAfterUses(dispatchBlock);
538
539 // If this isn't a catch-all filter, we need to check whether we got
540 // here because the filter triggered.
541 if (filterScope.getNumFilters()) {
542 // Load the selector value.
543 llvm::Value *selector = CGF.getSelectorFromSlot();
544 llvm::BasicBlock *unexpectedBB = CGF.createBasicBlock("ehspec.unexpected");
545
546 llvm::Value *zero = CGF.Builder.getInt32(0);
547 llvm::Value *failsFilter =
548 CGF.Builder.CreateICmpSLT(selector, zero, "ehspec.fails");
549 CGF.Builder.CreateCondBr(failsFilter, unexpectedBB,
550 CGF.getEHResumeBlock(false));
551
552 CGF.EmitBlock(unexpectedBB);
553 }
554
555 // Call __cxa_call_unexpected. This doesn't need to be an invoke
556 // because __cxa_call_unexpected magically filters exceptions
557 // according to the last landing pad the exception was thrown
558 // into. Seriously.
559 llvm::Value *exn = CGF.getExceptionFromSlot();
560 CGF.EmitRuntimeCall(getUnexpectedFn(CGF.CGM), exn)
561 ->setDoesNotReturn();
562 CGF.Builder.CreateUnreachable();
563 }
564
EmitEndEHSpec(const Decl * D)565 void CodeGenFunction::EmitEndEHSpec(const Decl *D) {
566 if (!CGM.getLangOpts().CXXExceptions)
567 return;
568
569 const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D);
570 if (!FD) {
571 // Check if CapturedDecl is nothrow and pop terminate scope for it.
572 if (const CapturedDecl* CD = dyn_cast_or_null<CapturedDecl>(D)) {
573 if (CD->isNothrow() && !EHStack.empty())
574 EHStack.popTerminate();
575 }
576 return;
577 }
578 const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>();
579 if (!Proto)
580 return;
581
582 ExceptionSpecificationType EST = Proto->getExceptionSpecType();
583 if (isNoexceptExceptionSpec(EST) && Proto->canThrow() == CT_Cannot &&
584 !EHStack.empty() /* possible empty when under async exceptions */) {
585 EHStack.popTerminate();
586 } else if (EST == EST_Dynamic || EST == EST_DynamicNone) {
587 // TODO: Revisit exception specifications for the MS ABI. There is a way to
588 // encode these in an object file but MSVC doesn't do anything with it.
589 if (getTarget().getCXXABI().isMicrosoft())
590 return;
591 // In wasm we currently treat 'throw()' in the same way as 'noexcept'. In
592 // case of throw with types, we ignore it and print a warning for now.
593 // TODO Correctly handle exception specification in wasm
594 if (CGM.getLangOpts().hasWasmExceptions()) {
595 if (EST == EST_DynamicNone)
596 EHStack.popTerminate();
597 return;
598 }
599 EHFilterScope &filterScope = cast<EHFilterScope>(*EHStack.begin());
600 emitFilterDispatchBlock(*this, filterScope);
601 EHStack.popFilter();
602 }
603 }
604
EmitCXXTryStmt(const CXXTryStmt & S)605 void CodeGenFunction::EmitCXXTryStmt(const CXXTryStmt &S) {
606 EnterCXXTryStmt(S);
607 EmitStmt(S.getTryBlock());
608 ExitCXXTryStmt(S);
609 }
610
EnterCXXTryStmt(const CXXTryStmt & S,bool IsFnTryBlock)611 void CodeGenFunction::EnterCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) {
612 unsigned NumHandlers = S.getNumHandlers();
613 EHCatchScope *CatchScope = EHStack.pushCatch(NumHandlers);
614
615 for (unsigned I = 0; I != NumHandlers; ++I) {
616 const CXXCatchStmt *C = S.getHandler(I);
617
618 llvm::BasicBlock *Handler = createBasicBlock("catch");
619 if (C->getExceptionDecl()) {
620 // FIXME: Dropping the reference type on the type into makes it
621 // impossible to correctly implement catch-by-reference
622 // semantics for pointers. Unfortunately, this is what all
623 // existing compilers do, and it's not clear that the standard
624 // personality routine is capable of doing this right. See C++ DR 388:
625 // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#388
626 Qualifiers CaughtTypeQuals;
627 QualType CaughtType = CGM.getContext().getUnqualifiedArrayType(
628 C->getCaughtType().getNonReferenceType(), CaughtTypeQuals);
629
630 CatchTypeInfo TypeInfo{nullptr, 0};
631 if (CaughtType->isObjCObjectPointerType())
632 TypeInfo.RTTI = CGM.getObjCRuntime().GetEHType(CaughtType);
633 else
634 TypeInfo = CGM.getCXXABI().getAddrOfCXXCatchHandlerType(
635 CaughtType, C->getCaughtType());
636 CatchScope->setHandler(I, TypeInfo, Handler);
637 } else {
638 // No exception decl indicates '...', a catch-all.
639 CatchScope->setHandler(I, CGM.getCXXABI().getCatchAllTypeInfo(), Handler);
640 // Under async exceptions, catch(...) need to catch HW exception too
641 // Mark scope with SehTryBegin as a SEH __try scope
642 if (getLangOpts().EHAsynch)
643 EmitRuntimeCallOrInvoke(getSehTryBeginFn(CGM));
644 }
645 }
646 }
647
648 llvm::BasicBlock *
getEHDispatchBlock(EHScopeStack::stable_iterator si)649 CodeGenFunction::getEHDispatchBlock(EHScopeStack::stable_iterator si) {
650 if (EHPersonality::get(*this).usesFuncletPads())
651 return getFuncletEHDispatchBlock(si);
652
653 // The dispatch block for the end of the scope chain is a block that
654 // just resumes unwinding.
655 if (si == EHStack.stable_end())
656 return getEHResumeBlock(true);
657
658 // Otherwise, we should look at the actual scope.
659 EHScope &scope = *EHStack.find(si);
660
661 llvm::BasicBlock *dispatchBlock = scope.getCachedEHDispatchBlock();
662 if (!dispatchBlock) {
663 switch (scope.getKind()) {
664 case EHScope::Catch: {
665 // Apply a special case to a single catch-all.
666 EHCatchScope &catchScope = cast<EHCatchScope>(scope);
667 if (catchScope.getNumHandlers() == 1 &&
668 catchScope.getHandler(0).isCatchAll()) {
669 dispatchBlock = catchScope.getHandler(0).Block;
670
671 // Otherwise, make a dispatch block.
672 } else {
673 dispatchBlock = createBasicBlock("catch.dispatch");
674 }
675 break;
676 }
677
678 case EHScope::Cleanup:
679 dispatchBlock = createBasicBlock("ehcleanup");
680 break;
681
682 case EHScope::Filter:
683 dispatchBlock = createBasicBlock("filter.dispatch");
684 break;
685
686 case EHScope::Terminate:
687 dispatchBlock = getTerminateHandler();
688 break;
689 }
690 scope.setCachedEHDispatchBlock(dispatchBlock);
691 }
692 return dispatchBlock;
693 }
694
695 llvm::BasicBlock *
getFuncletEHDispatchBlock(EHScopeStack::stable_iterator SI)696 CodeGenFunction::getFuncletEHDispatchBlock(EHScopeStack::stable_iterator SI) {
697 // Returning nullptr indicates that the previous dispatch block should unwind
698 // to caller.
699 if (SI == EHStack.stable_end())
700 return nullptr;
701
702 // Otherwise, we should look at the actual scope.
703 EHScope &EHS = *EHStack.find(SI);
704
705 llvm::BasicBlock *DispatchBlock = EHS.getCachedEHDispatchBlock();
706 if (DispatchBlock)
707 return DispatchBlock;
708
709 if (EHS.getKind() == EHScope::Terminate)
710 DispatchBlock = getTerminateFunclet();
711 else
712 DispatchBlock = createBasicBlock();
713 CGBuilderTy Builder(*this, DispatchBlock);
714
715 switch (EHS.getKind()) {
716 case EHScope::Catch:
717 DispatchBlock->setName("catch.dispatch");
718 break;
719
720 case EHScope::Cleanup:
721 DispatchBlock->setName("ehcleanup");
722 break;
723
724 case EHScope::Filter:
725 llvm_unreachable("exception specifications not handled yet!");
726
727 case EHScope::Terminate:
728 DispatchBlock->setName("terminate");
729 break;
730 }
731 EHS.setCachedEHDispatchBlock(DispatchBlock);
732 return DispatchBlock;
733 }
734
735 /// Check whether this is a non-EH scope, i.e. a scope which doesn't
736 /// affect exception handling. Currently, the only non-EH scopes are
737 /// normal-only cleanup scopes.
isNonEHScope(const EHScope & S)738 static bool isNonEHScope(const EHScope &S) {
739 switch (S.getKind()) {
740 case EHScope::Cleanup:
741 return !cast<EHCleanupScope>(S).isEHCleanup();
742 case EHScope::Filter:
743 case EHScope::Catch:
744 case EHScope::Terminate:
745 return false;
746 }
747
748 llvm_unreachable("Invalid EHScope Kind!");
749 }
750
getInvokeDestImpl()751 llvm::BasicBlock *CodeGenFunction::getInvokeDestImpl() {
752 assert(EHStack.requiresLandingPad());
753 assert(!EHStack.empty());
754
755 // If exceptions are disabled/ignored and SEH is not in use, then there is no
756 // invoke destination. SEH "works" even if exceptions are off. In practice,
757 // this means that C++ destructors and other EH cleanups don't run, which is
758 // consistent with MSVC's behavior, except in the presence of -EHa
759 const LangOptions &LO = CGM.getLangOpts();
760 if (!LO.Exceptions || LO.IgnoreExceptions) {
761 if (!LO.Borland && !LO.MicrosoftExt)
762 return nullptr;
763 if (!currentFunctionUsesSEHTry())
764 return nullptr;
765 }
766
767 // CUDA device code doesn't have exceptions.
768 if (LO.CUDA && LO.CUDAIsDevice)
769 return nullptr;
770
771 // Check the innermost scope for a cached landing pad. If this is
772 // a non-EH cleanup, we'll check enclosing scopes in EmitLandingPad.
773 llvm::BasicBlock *LP = EHStack.begin()->getCachedLandingPad();
774 if (LP) return LP;
775
776 const EHPersonality &Personality = EHPersonality::get(*this);
777
778 if (!CurFn->hasPersonalityFn())
779 CurFn->setPersonalityFn(getOpaquePersonalityFn(CGM, Personality));
780
781 if (Personality.usesFuncletPads()) {
782 // We don't need separate landing pads in the funclet model.
783 LP = getEHDispatchBlock(EHStack.getInnermostEHScope());
784 } else {
785 // Build the landing pad for this scope.
786 LP = EmitLandingPad();
787 }
788
789 assert(LP);
790
791 // Cache the landing pad on the innermost scope. If this is a
792 // non-EH scope, cache the landing pad on the enclosing scope, too.
793 for (EHScopeStack::iterator ir = EHStack.begin(); true; ++ir) {
794 ir->setCachedLandingPad(LP);
795 if (!isNonEHScope(*ir)) break;
796 }
797
798 return LP;
799 }
800
EmitLandingPad()801 llvm::BasicBlock *CodeGenFunction::EmitLandingPad() {
802 assert(EHStack.requiresLandingPad());
803 assert(!CGM.getLangOpts().IgnoreExceptions &&
804 "LandingPad should not be emitted when -fignore-exceptions are in "
805 "effect.");
806 EHScope &innermostEHScope = *EHStack.find(EHStack.getInnermostEHScope());
807 switch (innermostEHScope.getKind()) {
808 case EHScope::Terminate:
809 return getTerminateLandingPad();
810
811 case EHScope::Catch:
812 case EHScope::Cleanup:
813 case EHScope::Filter:
814 if (llvm::BasicBlock *lpad = innermostEHScope.getCachedLandingPad())
815 return lpad;
816 }
817
818 // Save the current IR generation state.
819 CGBuilderTy::InsertPoint savedIP = Builder.saveAndClearIP();
820 auto DL = ApplyDebugLocation::CreateDefaultArtificial(*this, CurEHLocation);
821
822 // Create and configure the landing pad.
823 llvm::BasicBlock *lpad = createBasicBlock("lpad");
824 EmitBlock(lpad);
825
826 llvm::LandingPadInst *LPadInst =
827 Builder.CreateLandingPad(llvm::StructType::get(Int8PtrTy, Int32Ty), 0);
828
829 llvm::Value *LPadExn = Builder.CreateExtractValue(LPadInst, 0);
830 Builder.CreateStore(LPadExn, getExceptionSlot());
831 llvm::Value *LPadSel = Builder.CreateExtractValue(LPadInst, 1);
832 Builder.CreateStore(LPadSel, getEHSelectorSlot());
833
834 // Save the exception pointer. It's safe to use a single exception
835 // pointer per function because EH cleanups can never have nested
836 // try/catches.
837 // Build the landingpad instruction.
838
839 // Accumulate all the handlers in scope.
840 bool hasCatchAll = false;
841 bool hasCleanup = false;
842 bool hasFilter = false;
843 SmallVector<llvm::Value*, 4> filterTypes;
844 llvm::SmallPtrSet<llvm::Value*, 4> catchTypes;
845 for (EHScopeStack::iterator I = EHStack.begin(), E = EHStack.end(); I != E;
846 ++I) {
847
848 switch (I->getKind()) {
849 case EHScope::Cleanup:
850 // If we have a cleanup, remember that.
851 hasCleanup = (hasCleanup || cast<EHCleanupScope>(*I).isEHCleanup());
852 continue;
853
854 case EHScope::Filter: {
855 assert(I.next() == EHStack.end() && "EH filter is not end of EH stack");
856 assert(!hasCatchAll && "EH filter reached after catch-all");
857
858 // Filter scopes get added to the landingpad in weird ways.
859 EHFilterScope &filter = cast<EHFilterScope>(*I);
860 hasFilter = true;
861
862 // Add all the filter values.
863 for (unsigned i = 0, e = filter.getNumFilters(); i != e; ++i)
864 filterTypes.push_back(filter.getFilter(i));
865 goto done;
866 }
867
868 case EHScope::Terminate:
869 // Terminate scopes are basically catch-alls.
870 assert(!hasCatchAll);
871 hasCatchAll = true;
872 goto done;
873
874 case EHScope::Catch:
875 break;
876 }
877
878 EHCatchScope &catchScope = cast<EHCatchScope>(*I);
879 for (unsigned hi = 0, he = catchScope.getNumHandlers(); hi != he; ++hi) {
880 EHCatchScope::Handler handler = catchScope.getHandler(hi);
881 assert(handler.Type.Flags == 0 &&
882 "landingpads do not support catch handler flags");
883
884 // If this is a catch-all, register that and abort.
885 if (!handler.Type.RTTI) {
886 assert(!hasCatchAll);
887 hasCatchAll = true;
888 goto done;
889 }
890
891 // Check whether we already have a handler for this type.
892 if (catchTypes.insert(handler.Type.RTTI).second)
893 // If not, add it directly to the landingpad.
894 LPadInst->addClause(handler.Type.RTTI);
895 }
896 }
897
898 done:
899 // If we have a catch-all, add null to the landingpad.
900 assert(!(hasCatchAll && hasFilter));
901 if (hasCatchAll) {
902 LPadInst->addClause(getCatchAllValue(*this));
903
904 // If we have an EH filter, we need to add those handlers in the
905 // right place in the landingpad, which is to say, at the end.
906 } else if (hasFilter) {
907 // Create a filter expression: a constant array indicating which filter
908 // types there are. The personality routine only lands here if the filter
909 // doesn't match.
910 SmallVector<llvm::Constant*, 8> Filters;
911 llvm::ArrayType *AType =
912 llvm::ArrayType::get(!filterTypes.empty() ?
913 filterTypes[0]->getType() : Int8PtrTy,
914 filterTypes.size());
915
916 for (unsigned i = 0, e = filterTypes.size(); i != e; ++i)
917 Filters.push_back(cast<llvm::Constant>(filterTypes[i]));
918 llvm::Constant *FilterArray = llvm::ConstantArray::get(AType, Filters);
919 LPadInst->addClause(FilterArray);
920
921 // Also check whether we need a cleanup.
922 if (hasCleanup)
923 LPadInst->setCleanup(true);
924
925 // Otherwise, signal that we at least have cleanups.
926 } else if (hasCleanup) {
927 LPadInst->setCleanup(true);
928 }
929
930 assert((LPadInst->getNumClauses() > 0 || LPadInst->isCleanup()) &&
931 "landingpad instruction has no clauses!");
932
933 // Tell the backend how to generate the landing pad.
934 Builder.CreateBr(getEHDispatchBlock(EHStack.getInnermostEHScope()));
935
936 // Restore the old IR generation state.
937 Builder.restoreIP(savedIP);
938
939 return lpad;
940 }
941
emitCatchPadBlock(CodeGenFunction & CGF,EHCatchScope & CatchScope)942 static void emitCatchPadBlock(CodeGenFunction &CGF, EHCatchScope &CatchScope) {
943 llvm::BasicBlock *DispatchBlock = CatchScope.getCachedEHDispatchBlock();
944 assert(DispatchBlock);
945
946 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveIP();
947 CGF.EmitBlockAfterUses(DispatchBlock);
948
949 llvm::Value *ParentPad = CGF.CurrentFuncletPad;
950 if (!ParentPad)
951 ParentPad = llvm::ConstantTokenNone::get(CGF.getLLVMContext());
952 llvm::BasicBlock *UnwindBB =
953 CGF.getEHDispatchBlock(CatchScope.getEnclosingEHScope());
954
955 unsigned NumHandlers = CatchScope.getNumHandlers();
956 llvm::CatchSwitchInst *CatchSwitch =
957 CGF.Builder.CreateCatchSwitch(ParentPad, UnwindBB, NumHandlers);
958
959 // Test against each of the exception types we claim to catch.
960 for (unsigned I = 0; I < NumHandlers; ++I) {
961 const EHCatchScope::Handler &Handler = CatchScope.getHandler(I);
962
963 CatchTypeInfo TypeInfo = Handler.Type;
964 if (!TypeInfo.RTTI)
965 TypeInfo.RTTI = llvm::Constant::getNullValue(CGF.VoidPtrTy);
966
967 CGF.Builder.SetInsertPoint(Handler.Block);
968
969 if (EHPersonality::get(CGF).isMSVCXXPersonality()) {
970 CGF.Builder.CreateCatchPad(
971 CatchSwitch, {TypeInfo.RTTI, CGF.Builder.getInt32(TypeInfo.Flags),
972 llvm::Constant::getNullValue(CGF.VoidPtrTy)});
973 } else {
974 CGF.Builder.CreateCatchPad(CatchSwitch, {TypeInfo.RTTI});
975 }
976
977 CatchSwitch->addHandler(Handler.Block);
978 }
979 CGF.Builder.restoreIP(SavedIP);
980 }
981
982 // Wasm uses Windows-style EH instructions, but it merges all catch clauses into
983 // one big catchpad, within which we use Itanium's landingpad-style selector
984 // comparison instructions.
emitWasmCatchPadBlock(CodeGenFunction & CGF,EHCatchScope & CatchScope)985 static void emitWasmCatchPadBlock(CodeGenFunction &CGF,
986 EHCatchScope &CatchScope) {
987 llvm::BasicBlock *DispatchBlock = CatchScope.getCachedEHDispatchBlock();
988 assert(DispatchBlock);
989
990 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveIP();
991 CGF.EmitBlockAfterUses(DispatchBlock);
992
993 llvm::Value *ParentPad = CGF.CurrentFuncletPad;
994 if (!ParentPad)
995 ParentPad = llvm::ConstantTokenNone::get(CGF.getLLVMContext());
996 llvm::BasicBlock *UnwindBB =
997 CGF.getEHDispatchBlock(CatchScope.getEnclosingEHScope());
998
999 unsigned NumHandlers = CatchScope.getNumHandlers();
1000 llvm::CatchSwitchInst *CatchSwitch =
1001 CGF.Builder.CreateCatchSwitch(ParentPad, UnwindBB, NumHandlers);
1002
1003 // We don't use a landingpad instruction, so generate intrinsic calls to
1004 // provide exception and selector values.
1005 llvm::BasicBlock *WasmCatchStartBlock = CGF.createBasicBlock("catch.start");
1006 CatchSwitch->addHandler(WasmCatchStartBlock);
1007 CGF.EmitBlockAfterUses(WasmCatchStartBlock);
1008
1009 // Create a catchpad instruction.
1010 SmallVector<llvm::Value *, 4> CatchTypes;
1011 for (unsigned I = 0, E = NumHandlers; I < E; ++I) {
1012 const EHCatchScope::Handler &Handler = CatchScope.getHandler(I);
1013 CatchTypeInfo TypeInfo = Handler.Type;
1014 if (!TypeInfo.RTTI)
1015 TypeInfo.RTTI = llvm::Constant::getNullValue(CGF.VoidPtrTy);
1016 CatchTypes.push_back(TypeInfo.RTTI);
1017 }
1018 auto *CPI = CGF.Builder.CreateCatchPad(CatchSwitch, CatchTypes);
1019
1020 // Create calls to wasm.get.exception and wasm.get.ehselector intrinsics.
1021 // Before they are lowered appropriately later, they provide values for the
1022 // exception and selector.
1023 llvm::Function *GetExnFn =
1024 CGF.CGM.getIntrinsic(llvm::Intrinsic::wasm_get_exception);
1025 llvm::Function *GetSelectorFn =
1026 CGF.CGM.getIntrinsic(llvm::Intrinsic::wasm_get_ehselector);
1027 llvm::CallInst *Exn = CGF.Builder.CreateCall(GetExnFn, CPI);
1028 CGF.Builder.CreateStore(Exn, CGF.getExceptionSlot());
1029 llvm::CallInst *Selector = CGF.Builder.CreateCall(GetSelectorFn, CPI);
1030
1031 llvm::Function *TypeIDFn = CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_typeid_for);
1032
1033 // If there's only a single catch-all, branch directly to its handler.
1034 if (CatchScope.getNumHandlers() == 1 &&
1035 CatchScope.getHandler(0).isCatchAll()) {
1036 CGF.Builder.CreateBr(CatchScope.getHandler(0).Block);
1037 CGF.Builder.restoreIP(SavedIP);
1038 return;
1039 }
1040
1041 // Test against each of the exception types we claim to catch.
1042 for (unsigned I = 0, E = NumHandlers;; ++I) {
1043 assert(I < E && "ran off end of handlers!");
1044 const EHCatchScope::Handler &Handler = CatchScope.getHandler(I);
1045 CatchTypeInfo TypeInfo = Handler.Type;
1046 if (!TypeInfo.RTTI)
1047 TypeInfo.RTTI = llvm::Constant::getNullValue(CGF.VoidPtrTy);
1048
1049 // Figure out the next block.
1050 llvm::BasicBlock *NextBlock;
1051
1052 bool EmitNextBlock = false, NextIsEnd = false;
1053
1054 // If this is the last handler, we're at the end, and the next block is a
1055 // block that contains a call to the rethrow function, so we can unwind to
1056 // the enclosing EH scope. The call itself will be generated later.
1057 if (I + 1 == E) {
1058 NextBlock = CGF.createBasicBlock("rethrow");
1059 EmitNextBlock = true;
1060 NextIsEnd = true;
1061
1062 // If the next handler is a catch-all, we're at the end, and the
1063 // next block is that handler.
1064 } else if (CatchScope.getHandler(I + 1).isCatchAll()) {
1065 NextBlock = CatchScope.getHandler(I + 1).Block;
1066 NextIsEnd = true;
1067
1068 // Otherwise, we're not at the end and we need a new block.
1069 } else {
1070 NextBlock = CGF.createBasicBlock("catch.fallthrough");
1071 EmitNextBlock = true;
1072 }
1073
1074 // Figure out the catch type's index in the LSDA's type table.
1075 llvm::CallInst *TypeIndex = CGF.Builder.CreateCall(TypeIDFn, TypeInfo.RTTI);
1076 TypeIndex->setDoesNotThrow();
1077
1078 llvm::Value *MatchesTypeIndex =
1079 CGF.Builder.CreateICmpEQ(Selector, TypeIndex, "matches");
1080 CGF.Builder.CreateCondBr(MatchesTypeIndex, Handler.Block, NextBlock);
1081
1082 if (EmitNextBlock)
1083 CGF.EmitBlock(NextBlock);
1084 if (NextIsEnd)
1085 break;
1086 }
1087
1088 CGF.Builder.restoreIP(SavedIP);
1089 }
1090
1091 /// Emit the structure of the dispatch block for the given catch scope.
1092 /// It is an invariant that the dispatch block already exists.
emitCatchDispatchBlock(CodeGenFunction & CGF,EHCatchScope & catchScope)1093 static void emitCatchDispatchBlock(CodeGenFunction &CGF,
1094 EHCatchScope &catchScope) {
1095 if (EHPersonality::get(CGF).isWasmPersonality())
1096 return emitWasmCatchPadBlock(CGF, catchScope);
1097 if (EHPersonality::get(CGF).usesFuncletPads())
1098 return emitCatchPadBlock(CGF, catchScope);
1099
1100 llvm::BasicBlock *dispatchBlock = catchScope.getCachedEHDispatchBlock();
1101 assert(dispatchBlock);
1102
1103 // If there's only a single catch-all, getEHDispatchBlock returned
1104 // that catch-all as the dispatch block.
1105 if (catchScope.getNumHandlers() == 1 &&
1106 catchScope.getHandler(0).isCatchAll()) {
1107 assert(dispatchBlock == catchScope.getHandler(0).Block);
1108 return;
1109 }
1110
1111 CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveIP();
1112 CGF.EmitBlockAfterUses(dispatchBlock);
1113
1114 // Select the right handler.
1115 llvm::Function *llvm_eh_typeid_for =
1116 CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_typeid_for);
1117
1118 // Load the selector value.
1119 llvm::Value *selector = CGF.getSelectorFromSlot();
1120
1121 // Test against each of the exception types we claim to catch.
1122 for (unsigned i = 0, e = catchScope.getNumHandlers(); ; ++i) {
1123 assert(i < e && "ran off end of handlers!");
1124 const EHCatchScope::Handler &handler = catchScope.getHandler(i);
1125
1126 llvm::Value *typeValue = handler.Type.RTTI;
1127 assert(handler.Type.Flags == 0 &&
1128 "landingpads do not support catch handler flags");
1129 assert(typeValue && "fell into catch-all case!");
1130 typeValue = CGF.Builder.CreateBitCast(typeValue, CGF.Int8PtrTy);
1131
1132 // Figure out the next block.
1133 bool nextIsEnd;
1134 llvm::BasicBlock *nextBlock;
1135
1136 // If this is the last handler, we're at the end, and the next
1137 // block is the block for the enclosing EH scope.
1138 if (i + 1 == e) {
1139 nextBlock = CGF.getEHDispatchBlock(catchScope.getEnclosingEHScope());
1140 nextIsEnd = true;
1141
1142 // If the next handler is a catch-all, we're at the end, and the
1143 // next block is that handler.
1144 } else if (catchScope.getHandler(i+1).isCatchAll()) {
1145 nextBlock = catchScope.getHandler(i+1).Block;
1146 nextIsEnd = true;
1147
1148 // Otherwise, we're not at the end and we need a new block.
1149 } else {
1150 nextBlock = CGF.createBasicBlock("catch.fallthrough");
1151 nextIsEnd = false;
1152 }
1153
1154 // Figure out the catch type's index in the LSDA's type table.
1155 llvm::CallInst *typeIndex =
1156 CGF.Builder.CreateCall(llvm_eh_typeid_for, typeValue);
1157 typeIndex->setDoesNotThrow();
1158
1159 llvm::Value *matchesTypeIndex =
1160 CGF.Builder.CreateICmpEQ(selector, typeIndex, "matches");
1161 CGF.Builder.CreateCondBr(matchesTypeIndex, handler.Block, nextBlock);
1162
1163 // If the next handler is a catch-all, we're completely done.
1164 if (nextIsEnd) {
1165 CGF.Builder.restoreIP(savedIP);
1166 return;
1167 }
1168 // Otherwise we need to emit and continue at that block.
1169 CGF.EmitBlock(nextBlock);
1170 }
1171 }
1172
popCatchScope()1173 void CodeGenFunction::popCatchScope() {
1174 EHCatchScope &catchScope = cast<EHCatchScope>(*EHStack.begin());
1175 if (catchScope.hasEHBranches())
1176 emitCatchDispatchBlock(*this, catchScope);
1177 EHStack.popCatch();
1178 }
1179
ExitCXXTryStmt(const CXXTryStmt & S,bool IsFnTryBlock)1180 void CodeGenFunction::ExitCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) {
1181 unsigned NumHandlers = S.getNumHandlers();
1182 EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin());
1183 assert(CatchScope.getNumHandlers() == NumHandlers);
1184 llvm::BasicBlock *DispatchBlock = CatchScope.getCachedEHDispatchBlock();
1185
1186 // If the catch was not required, bail out now.
1187 if (!CatchScope.hasEHBranches()) {
1188 CatchScope.clearHandlerBlocks();
1189 EHStack.popCatch();
1190 return;
1191 }
1192
1193 // Emit the structure of the EH dispatch for this catch.
1194 emitCatchDispatchBlock(*this, CatchScope);
1195
1196 // Copy the handler blocks off before we pop the EH stack. Emitting
1197 // the handlers might scribble on this memory.
1198 SmallVector<EHCatchScope::Handler, 8> Handlers(
1199 CatchScope.begin(), CatchScope.begin() + NumHandlers);
1200
1201 EHStack.popCatch();
1202
1203 // The fall-through block.
1204 llvm::BasicBlock *ContBB = createBasicBlock("try.cont");
1205
1206 // We just emitted the body of the try; jump to the continue block.
1207 if (HaveInsertPoint())
1208 Builder.CreateBr(ContBB);
1209
1210 // Determine if we need an implicit rethrow for all these catch handlers;
1211 // see the comment below.
1212 bool doImplicitRethrow = false;
1213 if (IsFnTryBlock)
1214 doImplicitRethrow = isa<CXXDestructorDecl>(CurCodeDecl) ||
1215 isa<CXXConstructorDecl>(CurCodeDecl);
1216
1217 // Wasm uses Windows-style EH instructions, but merges all catch clauses into
1218 // one big catchpad. So we save the old funclet pad here before we traverse
1219 // each catch handler.
1220 SaveAndRestore<llvm::Instruction *> RestoreCurrentFuncletPad(
1221 CurrentFuncletPad);
1222 llvm::BasicBlock *WasmCatchStartBlock = nullptr;
1223 if (EHPersonality::get(*this).isWasmPersonality()) {
1224 auto *CatchSwitch =
1225 cast<llvm::CatchSwitchInst>(DispatchBlock->getFirstNonPHI());
1226 WasmCatchStartBlock = CatchSwitch->hasUnwindDest()
1227 ? CatchSwitch->getSuccessor(1)
1228 : CatchSwitch->getSuccessor(0);
1229 auto *CPI = cast<llvm::CatchPadInst>(WasmCatchStartBlock->getFirstNonPHI());
1230 CurrentFuncletPad = CPI;
1231 }
1232
1233 // Perversely, we emit the handlers backwards precisely because we
1234 // want them to appear in source order. In all of these cases, the
1235 // catch block will have exactly one predecessor, which will be a
1236 // particular block in the catch dispatch. However, in the case of
1237 // a catch-all, one of the dispatch blocks will branch to two
1238 // different handlers, and EmitBlockAfterUses will cause the second
1239 // handler to be moved before the first.
1240 bool HasCatchAll = false;
1241 for (unsigned I = NumHandlers; I != 0; --I) {
1242 HasCatchAll |= Handlers[I - 1].isCatchAll();
1243 llvm::BasicBlock *CatchBlock = Handlers[I-1].Block;
1244 EmitBlockAfterUses(CatchBlock);
1245
1246 // Catch the exception if this isn't a catch-all.
1247 const CXXCatchStmt *C = S.getHandler(I-1);
1248
1249 // Enter a cleanup scope, including the catch variable and the
1250 // end-catch.
1251 RunCleanupsScope CatchScope(*this);
1252
1253 // Initialize the catch variable and set up the cleanups.
1254 SaveAndRestore<llvm::Instruction *> RestoreCurrentFuncletPad(
1255 CurrentFuncletPad);
1256 CGM.getCXXABI().emitBeginCatch(*this, C);
1257
1258 // Emit the PGO counter increment.
1259 incrementProfileCounter(C);
1260
1261 // Perform the body of the catch.
1262 EmitStmt(C->getHandlerBlock());
1263
1264 // [except.handle]p11:
1265 // The currently handled exception is rethrown if control
1266 // reaches the end of a handler of the function-try-block of a
1267 // constructor or destructor.
1268
1269 // It is important that we only do this on fallthrough and not on
1270 // return. Note that it's illegal to put a return in a
1271 // constructor function-try-block's catch handler (p14), so this
1272 // really only applies to destructors.
1273 if (doImplicitRethrow && HaveInsertPoint()) {
1274 CGM.getCXXABI().emitRethrow(*this, /*isNoReturn*/false);
1275 Builder.CreateUnreachable();
1276 Builder.ClearInsertionPoint();
1277 }
1278
1279 // Fall out through the catch cleanups.
1280 CatchScope.ForceCleanup();
1281
1282 // Branch out of the try.
1283 if (HaveInsertPoint())
1284 Builder.CreateBr(ContBB);
1285 }
1286
1287 // Because in wasm we merge all catch clauses into one big catchpad, in case
1288 // none of the types in catch handlers matches after we test against each of
1289 // them, we should unwind to the next EH enclosing scope. We generate a call
1290 // to rethrow function here to do that.
1291 if (EHPersonality::get(*this).isWasmPersonality() && !HasCatchAll) {
1292 assert(WasmCatchStartBlock);
1293 // Navigate for the "rethrow" block we created in emitWasmCatchPadBlock().
1294 // Wasm uses landingpad-style conditional branches to compare selectors, so
1295 // we follow the false destination for each of the cond branches to reach
1296 // the rethrow block.
1297 llvm::BasicBlock *RethrowBlock = WasmCatchStartBlock;
1298 while (llvm::Instruction *TI = RethrowBlock->getTerminator()) {
1299 auto *BI = cast<llvm::BranchInst>(TI);
1300 assert(BI->isConditional());
1301 RethrowBlock = BI->getSuccessor(1);
1302 }
1303 assert(RethrowBlock != WasmCatchStartBlock && RethrowBlock->empty());
1304 Builder.SetInsertPoint(RethrowBlock);
1305 llvm::Function *RethrowInCatchFn =
1306 CGM.getIntrinsic(llvm::Intrinsic::wasm_rethrow);
1307 EmitNoreturnRuntimeCallOrInvoke(RethrowInCatchFn, {});
1308 }
1309
1310 EmitBlock(ContBB);
1311 incrementProfileCounter(&S);
1312 }
1313
1314 namespace {
1315 struct CallEndCatchForFinally final : EHScopeStack::Cleanup {
1316 llvm::Value *ForEHVar;
1317 llvm::FunctionCallee EndCatchFn;
CallEndCatchForFinally__anon97e456f80211::CallEndCatchForFinally1318 CallEndCatchForFinally(llvm::Value *ForEHVar,
1319 llvm::FunctionCallee EndCatchFn)
1320 : ForEHVar(ForEHVar), EndCatchFn(EndCatchFn) {}
1321
Emit__anon97e456f80211::CallEndCatchForFinally1322 void Emit(CodeGenFunction &CGF, Flags flags) override {
1323 llvm::BasicBlock *EndCatchBB = CGF.createBasicBlock("finally.endcatch");
1324 llvm::BasicBlock *CleanupContBB =
1325 CGF.createBasicBlock("finally.cleanup.cont");
1326
1327 llvm::Value *ShouldEndCatch =
1328 CGF.Builder.CreateFlagLoad(ForEHVar, "finally.endcatch");
1329 CGF.Builder.CreateCondBr(ShouldEndCatch, EndCatchBB, CleanupContBB);
1330 CGF.EmitBlock(EndCatchBB);
1331 CGF.EmitRuntimeCallOrInvoke(EndCatchFn); // catch-all, so might throw
1332 CGF.EmitBlock(CleanupContBB);
1333 }
1334 };
1335
1336 struct PerformFinally final : EHScopeStack::Cleanup {
1337 const Stmt *Body;
1338 llvm::Value *ForEHVar;
1339 llvm::FunctionCallee EndCatchFn;
1340 llvm::FunctionCallee RethrowFn;
1341 llvm::Value *SavedExnVar;
1342
PerformFinally__anon97e456f80211::PerformFinally1343 PerformFinally(const Stmt *Body, llvm::Value *ForEHVar,
1344 llvm::FunctionCallee EndCatchFn,
1345 llvm::FunctionCallee RethrowFn, llvm::Value *SavedExnVar)
1346 : Body(Body), ForEHVar(ForEHVar), EndCatchFn(EndCatchFn),
1347 RethrowFn(RethrowFn), SavedExnVar(SavedExnVar) {}
1348
Emit__anon97e456f80211::PerformFinally1349 void Emit(CodeGenFunction &CGF, Flags flags) override {
1350 // Enter a cleanup to call the end-catch function if one was provided.
1351 if (EndCatchFn)
1352 CGF.EHStack.pushCleanup<CallEndCatchForFinally>(NormalAndEHCleanup,
1353 ForEHVar, EndCatchFn);
1354
1355 // Save the current cleanup destination in case there are
1356 // cleanups in the finally block.
1357 llvm::Value *SavedCleanupDest =
1358 CGF.Builder.CreateLoad(CGF.getNormalCleanupDestSlot(),
1359 "cleanup.dest.saved");
1360
1361 // Emit the finally block.
1362 CGF.EmitStmt(Body);
1363
1364 // If the end of the finally is reachable, check whether this was
1365 // for EH. If so, rethrow.
1366 if (CGF.HaveInsertPoint()) {
1367 llvm::BasicBlock *RethrowBB = CGF.createBasicBlock("finally.rethrow");
1368 llvm::BasicBlock *ContBB = CGF.createBasicBlock("finally.cont");
1369
1370 llvm::Value *ShouldRethrow =
1371 CGF.Builder.CreateFlagLoad(ForEHVar, "finally.shouldthrow");
1372 CGF.Builder.CreateCondBr(ShouldRethrow, RethrowBB, ContBB);
1373
1374 CGF.EmitBlock(RethrowBB);
1375 if (SavedExnVar) {
1376 CGF.EmitRuntimeCallOrInvoke(RethrowFn,
1377 CGF.Builder.CreateAlignedLoad(CGF.Int8PtrTy, SavedExnVar,
1378 CGF.getPointerAlign()));
1379 } else {
1380 CGF.EmitRuntimeCallOrInvoke(RethrowFn);
1381 }
1382 CGF.Builder.CreateUnreachable();
1383
1384 CGF.EmitBlock(ContBB);
1385
1386 // Restore the cleanup destination.
1387 CGF.Builder.CreateStore(SavedCleanupDest,
1388 CGF.getNormalCleanupDestSlot());
1389 }
1390
1391 // Leave the end-catch cleanup. As an optimization, pretend that
1392 // the fallthrough path was inaccessible; we've dynamically proven
1393 // that we're not in the EH case along that path.
1394 if (EndCatchFn) {
1395 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();
1396 CGF.PopCleanupBlock();
1397 CGF.Builder.restoreIP(SavedIP);
1398 }
1399
1400 // Now make sure we actually have an insertion point or the
1401 // cleanup gods will hate us.
1402 CGF.EnsureInsertPoint();
1403 }
1404 };
1405 } // end anonymous namespace
1406
1407 /// Enters a finally block for an implementation using zero-cost
1408 /// exceptions. This is mostly general, but hard-codes some
1409 /// language/ABI-specific behavior in the catch-all sections.
enter(CodeGenFunction & CGF,const Stmt * body,llvm::FunctionCallee beginCatchFn,llvm::FunctionCallee endCatchFn,llvm::FunctionCallee rethrowFn)1410 void CodeGenFunction::FinallyInfo::enter(CodeGenFunction &CGF, const Stmt *body,
1411 llvm::FunctionCallee beginCatchFn,
1412 llvm::FunctionCallee endCatchFn,
1413 llvm::FunctionCallee rethrowFn) {
1414 assert((!!beginCatchFn) == (!!endCatchFn) &&
1415 "begin/end catch functions not paired");
1416 assert(rethrowFn && "rethrow function is required");
1417
1418 BeginCatchFn = beginCatchFn;
1419
1420 // The rethrow function has one of the following two types:
1421 // void (*)()
1422 // void (*)(void*)
1423 // In the latter case we need to pass it the exception object.
1424 // But we can't use the exception slot because the @finally might
1425 // have a landing pad (which would overwrite the exception slot).
1426 llvm::FunctionType *rethrowFnTy = rethrowFn.getFunctionType();
1427 SavedExnVar = nullptr;
1428 if (rethrowFnTy->getNumParams())
1429 SavedExnVar = CGF.CreateTempAlloca(CGF.Int8PtrTy, "finally.exn");
1430
1431 // A finally block is a statement which must be executed on any edge
1432 // out of a given scope. Unlike a cleanup, the finally block may
1433 // contain arbitrary control flow leading out of itself. In
1434 // addition, finally blocks should always be executed, even if there
1435 // are no catch handlers higher on the stack. Therefore, we
1436 // surround the protected scope with a combination of a normal
1437 // cleanup (to catch attempts to break out of the block via normal
1438 // control flow) and an EH catch-all (semantically "outside" any try
1439 // statement to which the finally block might have been attached).
1440 // The finally block itself is generated in the context of a cleanup
1441 // which conditionally leaves the catch-all.
1442
1443 // Jump destination for performing the finally block on an exception
1444 // edge. We'll never actually reach this block, so unreachable is
1445 // fine.
1446 RethrowDest = CGF.getJumpDestInCurrentScope(CGF.getUnreachableBlock());
1447
1448 // Whether the finally block is being executed for EH purposes.
1449 ForEHVar = CGF.CreateTempAlloca(CGF.Builder.getInt1Ty(), "finally.for-eh");
1450 CGF.Builder.CreateFlagStore(false, ForEHVar);
1451
1452 // Enter a normal cleanup which will perform the @finally block.
1453 CGF.EHStack.pushCleanup<PerformFinally>(NormalCleanup, body,
1454 ForEHVar, endCatchFn,
1455 rethrowFn, SavedExnVar);
1456
1457 // Enter a catch-all scope.
1458 llvm::BasicBlock *catchBB = CGF.createBasicBlock("finally.catchall");
1459 EHCatchScope *catchScope = CGF.EHStack.pushCatch(1);
1460 catchScope->setCatchAllHandler(0, catchBB);
1461 }
1462
exit(CodeGenFunction & CGF)1463 void CodeGenFunction::FinallyInfo::exit(CodeGenFunction &CGF) {
1464 // Leave the finally catch-all.
1465 EHCatchScope &catchScope = cast<EHCatchScope>(*CGF.EHStack.begin());
1466 llvm::BasicBlock *catchBB = catchScope.getHandler(0).Block;
1467
1468 CGF.popCatchScope();
1469
1470 // If there are any references to the catch-all block, emit it.
1471 if (catchBB->use_empty()) {
1472 delete catchBB;
1473 } else {
1474 CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveAndClearIP();
1475 CGF.EmitBlock(catchBB);
1476
1477 llvm::Value *exn = nullptr;
1478
1479 // If there's a begin-catch function, call it.
1480 if (BeginCatchFn) {
1481 exn = CGF.getExceptionFromSlot();
1482 CGF.EmitNounwindRuntimeCall(BeginCatchFn, exn);
1483 }
1484
1485 // If we need to remember the exception pointer to rethrow later, do so.
1486 if (SavedExnVar) {
1487 if (!exn) exn = CGF.getExceptionFromSlot();
1488 CGF.Builder.CreateAlignedStore(exn, SavedExnVar, CGF.getPointerAlign());
1489 }
1490
1491 // Tell the cleanups in the finally block that we're do this for EH.
1492 CGF.Builder.CreateFlagStore(true, ForEHVar);
1493
1494 // Thread a jump through the finally cleanup.
1495 CGF.EmitBranchThroughCleanup(RethrowDest);
1496
1497 CGF.Builder.restoreIP(savedIP);
1498 }
1499
1500 // Finally, leave the @finally cleanup.
1501 CGF.PopCleanupBlock();
1502 }
1503
getTerminateLandingPad()1504 llvm::BasicBlock *CodeGenFunction::getTerminateLandingPad() {
1505 if (TerminateLandingPad)
1506 return TerminateLandingPad;
1507
1508 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
1509
1510 // This will get inserted at the end of the function.
1511 TerminateLandingPad = createBasicBlock("terminate.lpad");
1512 Builder.SetInsertPoint(TerminateLandingPad);
1513
1514 // Tell the backend that this is a landing pad.
1515 const EHPersonality &Personality = EHPersonality::get(*this);
1516
1517 if (!CurFn->hasPersonalityFn())
1518 CurFn->setPersonalityFn(getOpaquePersonalityFn(CGM, Personality));
1519
1520 llvm::LandingPadInst *LPadInst =
1521 Builder.CreateLandingPad(llvm::StructType::get(Int8PtrTy, Int32Ty), 0);
1522 LPadInst->addClause(getCatchAllValue(*this));
1523
1524 llvm::Value *Exn = nullptr;
1525 if (getLangOpts().CPlusPlus)
1526 Exn = Builder.CreateExtractValue(LPadInst, 0);
1527 llvm::CallInst *terminateCall =
1528 CGM.getCXXABI().emitTerminateForUnexpectedException(*this, Exn);
1529 terminateCall->setDoesNotReturn();
1530 Builder.CreateUnreachable();
1531
1532 // Restore the saved insertion state.
1533 Builder.restoreIP(SavedIP);
1534
1535 return TerminateLandingPad;
1536 }
1537
getTerminateHandler()1538 llvm::BasicBlock *CodeGenFunction::getTerminateHandler() {
1539 if (TerminateHandler)
1540 return TerminateHandler;
1541
1542 // Set up the terminate handler. This block is inserted at the very
1543 // end of the function by FinishFunction.
1544 TerminateHandler = createBasicBlock("terminate.handler");
1545 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
1546 Builder.SetInsertPoint(TerminateHandler);
1547
1548 llvm::Value *Exn = nullptr;
1549 if (getLangOpts().CPlusPlus)
1550 Exn = getExceptionFromSlot();
1551 llvm::CallInst *terminateCall =
1552 CGM.getCXXABI().emitTerminateForUnexpectedException(*this, Exn);
1553 terminateCall->setDoesNotReturn();
1554 Builder.CreateUnreachable();
1555
1556 // Restore the saved insertion state.
1557 Builder.restoreIP(SavedIP);
1558
1559 return TerminateHandler;
1560 }
1561
getTerminateFunclet()1562 llvm::BasicBlock *CodeGenFunction::getTerminateFunclet() {
1563 assert(EHPersonality::get(*this).usesFuncletPads() &&
1564 "use getTerminateLandingPad for non-funclet EH");
1565
1566 llvm::BasicBlock *&TerminateFunclet = TerminateFunclets[CurrentFuncletPad];
1567 if (TerminateFunclet)
1568 return TerminateFunclet;
1569
1570 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
1571
1572 // Set up the terminate handler. This block is inserted at the very
1573 // end of the function by FinishFunction.
1574 TerminateFunclet = createBasicBlock("terminate.handler");
1575 Builder.SetInsertPoint(TerminateFunclet);
1576
1577 // Create the cleanuppad using the current parent pad as its token. Use 'none'
1578 // if this is a top-level terminate scope, which is the common case.
1579 SaveAndRestore<llvm::Instruction *> RestoreCurrentFuncletPad(
1580 CurrentFuncletPad);
1581 llvm::Value *ParentPad = CurrentFuncletPad;
1582 if (!ParentPad)
1583 ParentPad = llvm::ConstantTokenNone::get(CGM.getLLVMContext());
1584 CurrentFuncletPad = Builder.CreateCleanupPad(ParentPad);
1585
1586 // Emit the __std_terminate call.
1587 llvm::CallInst *terminateCall =
1588 CGM.getCXXABI().emitTerminateForUnexpectedException(*this, nullptr);
1589 terminateCall->setDoesNotReturn();
1590 Builder.CreateUnreachable();
1591
1592 // Restore the saved insertion state.
1593 Builder.restoreIP(SavedIP);
1594
1595 return TerminateFunclet;
1596 }
1597
getEHResumeBlock(bool isCleanup)1598 llvm::BasicBlock *CodeGenFunction::getEHResumeBlock(bool isCleanup) {
1599 if (EHResumeBlock) return EHResumeBlock;
1600
1601 CGBuilderTy::InsertPoint SavedIP = Builder.saveIP();
1602
1603 // We emit a jump to a notional label at the outermost unwind state.
1604 EHResumeBlock = createBasicBlock("eh.resume");
1605 Builder.SetInsertPoint(EHResumeBlock);
1606
1607 const EHPersonality &Personality = EHPersonality::get(*this);
1608
1609 // This can always be a call because we necessarily didn't find
1610 // anything on the EH stack which needs our help.
1611 const char *RethrowName = Personality.CatchallRethrowFn;
1612 if (RethrowName != nullptr && !isCleanup) {
1613 EmitRuntimeCall(getCatchallRethrowFn(CGM, RethrowName),
1614 getExceptionFromSlot())->setDoesNotReturn();
1615 Builder.CreateUnreachable();
1616 Builder.restoreIP(SavedIP);
1617 return EHResumeBlock;
1618 }
1619
1620 // Recreate the landingpad's return value for the 'resume' instruction.
1621 llvm::Value *Exn = getExceptionFromSlot();
1622 llvm::Value *Sel = getSelectorFromSlot();
1623
1624 llvm::Type *LPadType = llvm::StructType::get(Exn->getType(), Sel->getType());
1625 llvm::Value *LPadVal = llvm::UndefValue::get(LPadType);
1626 LPadVal = Builder.CreateInsertValue(LPadVal, Exn, 0, "lpad.val");
1627 LPadVal = Builder.CreateInsertValue(LPadVal, Sel, 1, "lpad.val");
1628
1629 Builder.CreateResume(LPadVal);
1630 Builder.restoreIP(SavedIP);
1631 return EHResumeBlock;
1632 }
1633
EmitSEHTryStmt(const SEHTryStmt & S)1634 void CodeGenFunction::EmitSEHTryStmt(const SEHTryStmt &S) {
1635 EnterSEHTryStmt(S);
1636 {
1637 JumpDest TryExit = getJumpDestInCurrentScope("__try.__leave");
1638
1639 SEHTryEpilogueStack.push_back(&TryExit);
1640
1641 llvm::BasicBlock *TryBB = nullptr;
1642 // IsEHa: emit an invoke to _seh_try_begin() runtime for -EHa
1643 if (getLangOpts().EHAsynch) {
1644 EmitRuntimeCallOrInvoke(getSehTryBeginFn(CGM));
1645 if (SEHTryEpilogueStack.size() == 1) // outermost only
1646 TryBB = Builder.GetInsertBlock();
1647 }
1648
1649 EmitStmt(S.getTryBlock());
1650
1651 // Volatilize all blocks in Try, till current insert point
1652 if (TryBB) {
1653 llvm::SmallPtrSet<llvm::BasicBlock *, 10> Visited;
1654 VolatilizeTryBlocks(TryBB, Visited);
1655 }
1656
1657 SEHTryEpilogueStack.pop_back();
1658
1659 if (!TryExit.getBlock()->use_empty())
1660 EmitBlock(TryExit.getBlock(), /*IsFinished=*/true);
1661 else
1662 delete TryExit.getBlock();
1663 }
1664 ExitSEHTryStmt(S);
1665 }
1666
1667 // Recursively walk through blocks in a _try
1668 // and make all memory instructions volatile
VolatilizeTryBlocks(llvm::BasicBlock * BB,llvm::SmallPtrSet<llvm::BasicBlock *,10> & V)1669 void CodeGenFunction::VolatilizeTryBlocks(
1670 llvm::BasicBlock *BB, llvm::SmallPtrSet<llvm::BasicBlock *, 10> &V) {
1671 if (BB == SEHTryEpilogueStack.back()->getBlock() /* end of Try */ ||
1672 !V.insert(BB).second /* already visited */ ||
1673 !BB->getParent() /* not emitted */ || BB->empty())
1674 return;
1675
1676 if (!BB->isEHPad()) {
1677 for (llvm::BasicBlock::iterator J = BB->begin(), JE = BB->end(); J != JE;
1678 ++J) {
1679 if (auto LI = dyn_cast<llvm::LoadInst>(J)) {
1680 LI->setVolatile(true);
1681 } else if (auto SI = dyn_cast<llvm::StoreInst>(J)) {
1682 SI->setVolatile(true);
1683 } else if (auto* MCI = dyn_cast<llvm::MemIntrinsic>(J)) {
1684 MCI->setVolatile(llvm::ConstantInt::get(Builder.getInt1Ty(), 1));
1685 }
1686 }
1687 }
1688 const llvm::Instruction *TI = BB->getTerminator();
1689 if (TI) {
1690 unsigned N = TI->getNumSuccessors();
1691 for (unsigned I = 0; I < N; I++)
1692 VolatilizeTryBlocks(TI->getSuccessor(I), V);
1693 }
1694 }
1695
1696 namespace {
1697 struct PerformSEHFinally final : EHScopeStack::Cleanup {
1698 llvm::Function *OutlinedFinally;
PerformSEHFinally__anon97e456f80311::PerformSEHFinally1699 PerformSEHFinally(llvm::Function *OutlinedFinally)
1700 : OutlinedFinally(OutlinedFinally) {}
1701
Emit__anon97e456f80311::PerformSEHFinally1702 void Emit(CodeGenFunction &CGF, Flags F) override {
1703 ASTContext &Context = CGF.getContext();
1704 CodeGenModule &CGM = CGF.CGM;
1705
1706 CallArgList Args;
1707
1708 // Compute the two argument values.
1709 QualType ArgTys[2] = {Context.UnsignedCharTy, Context.VoidPtrTy};
1710 llvm::Value *FP = nullptr;
1711 // If CFG.IsOutlinedSEHHelper is true, then we are within a finally block.
1712 if (CGF.IsOutlinedSEHHelper) {
1713 FP = &CGF.CurFn->arg_begin()[1];
1714 } else {
1715 llvm::Function *LocalAddrFn =
1716 CGM.getIntrinsic(llvm::Intrinsic::localaddress);
1717 FP = CGF.Builder.CreateCall(LocalAddrFn);
1718 }
1719
1720 llvm::Value *IsForEH =
1721 llvm::ConstantInt::get(CGF.ConvertType(ArgTys[0]), F.isForEHCleanup());
1722
1723 // Except _leave and fall-through at the end, all other exits in a _try
1724 // (return/goto/continue/break) are considered as abnormal terminations
1725 // since _leave/fall-through is always Indexed 0,
1726 // just use NormalCleanupDestSlot (>= 1 for goto/return/..),
1727 // as 1st Arg to indicate abnormal termination
1728 if (!F.isForEHCleanup() && F.hasExitSwitch()) {
1729 Address Addr = CGF.getNormalCleanupDestSlot();
1730 llvm::Value *Load = CGF.Builder.CreateLoad(Addr, "cleanup.dest");
1731 llvm::Value *Zero = llvm::Constant::getNullValue(CGM.Int32Ty);
1732 IsForEH = CGF.Builder.CreateICmpNE(Load, Zero);
1733 }
1734
1735 Args.add(RValue::get(IsForEH), ArgTys[0]);
1736 Args.add(RValue::get(FP), ArgTys[1]);
1737
1738 // Arrange a two-arg function info and type.
1739 const CGFunctionInfo &FnInfo =
1740 CGM.getTypes().arrangeBuiltinFunctionCall(Context.VoidTy, Args);
1741
1742 auto Callee = CGCallee::forDirect(OutlinedFinally);
1743 CGF.EmitCall(FnInfo, Callee, ReturnValueSlot(), Args);
1744 }
1745 };
1746 } // end anonymous namespace
1747
1748 namespace {
1749 /// Find all local variable captures in the statement.
1750 struct CaptureFinder : ConstStmtVisitor<CaptureFinder> {
1751 CodeGenFunction &ParentCGF;
1752 const VarDecl *ParentThis;
1753 llvm::SmallSetVector<const VarDecl *, 4> Captures;
1754 Address SEHCodeSlot = Address::invalid();
CaptureFinder__anon97e456f80411::CaptureFinder1755 CaptureFinder(CodeGenFunction &ParentCGF, const VarDecl *ParentThis)
1756 : ParentCGF(ParentCGF), ParentThis(ParentThis) {}
1757
1758 // Return true if we need to do any capturing work.
foundCaptures__anon97e456f80411::CaptureFinder1759 bool foundCaptures() {
1760 return !Captures.empty() || SEHCodeSlot.isValid();
1761 }
1762
Visit__anon97e456f80411::CaptureFinder1763 void Visit(const Stmt *S) {
1764 // See if this is a capture, then recurse.
1765 ConstStmtVisitor<CaptureFinder>::Visit(S);
1766 for (const Stmt *Child : S->children())
1767 if (Child)
1768 Visit(Child);
1769 }
1770
VisitDeclRefExpr__anon97e456f80411::CaptureFinder1771 void VisitDeclRefExpr(const DeclRefExpr *E) {
1772 // If this is already a capture, just make sure we capture 'this'.
1773 if (E->refersToEnclosingVariableOrCapture())
1774 Captures.insert(ParentThis);
1775
1776 const auto *D = dyn_cast<VarDecl>(E->getDecl());
1777 if (D && D->isLocalVarDeclOrParm() && D->hasLocalStorage())
1778 Captures.insert(D);
1779 }
1780
VisitCXXThisExpr__anon97e456f80411::CaptureFinder1781 void VisitCXXThisExpr(const CXXThisExpr *E) {
1782 Captures.insert(ParentThis);
1783 }
1784
VisitCallExpr__anon97e456f80411::CaptureFinder1785 void VisitCallExpr(const CallExpr *E) {
1786 // We only need to add parent frame allocations for these builtins in x86.
1787 if (ParentCGF.getTarget().getTriple().getArch() != llvm::Triple::x86)
1788 return;
1789
1790 unsigned ID = E->getBuiltinCallee();
1791 switch (ID) {
1792 case Builtin::BI__exception_code:
1793 case Builtin::BI_exception_code:
1794 // This is the simple case where we are the outermost finally. All we
1795 // have to do here is make sure we escape this and recover it in the
1796 // outlined handler.
1797 if (!SEHCodeSlot.isValid())
1798 SEHCodeSlot = ParentCGF.SEHCodeSlotStack.back();
1799 break;
1800 }
1801 }
1802 };
1803 } // end anonymous namespace
1804
recoverAddrOfEscapedLocal(CodeGenFunction & ParentCGF,Address ParentVar,llvm::Value * ParentFP)1805 Address CodeGenFunction::recoverAddrOfEscapedLocal(CodeGenFunction &ParentCGF,
1806 Address ParentVar,
1807 llvm::Value *ParentFP) {
1808 llvm::CallInst *RecoverCall = nullptr;
1809 CGBuilderTy Builder(*this, AllocaInsertPt);
1810 if (auto *ParentAlloca = dyn_cast<llvm::AllocaInst>(ParentVar.getPointer())) {
1811 // Mark the variable escaped if nobody else referenced it and compute the
1812 // localescape index.
1813 auto InsertPair = ParentCGF.EscapedLocals.insert(
1814 std::make_pair(ParentAlloca, ParentCGF.EscapedLocals.size()));
1815 int FrameEscapeIdx = InsertPair.first->second;
1816 // call i8* @llvm.localrecover(i8* bitcast(@parentFn), i8* %fp, i32 N)
1817 llvm::Function *FrameRecoverFn = llvm::Intrinsic::getDeclaration(
1818 &CGM.getModule(), llvm::Intrinsic::localrecover);
1819 llvm::Constant *ParentI8Fn =
1820 llvm::ConstantExpr::getBitCast(ParentCGF.CurFn, Int8PtrTy);
1821 RecoverCall = Builder.CreateCall(
1822 FrameRecoverFn, {ParentI8Fn, ParentFP,
1823 llvm::ConstantInt::get(Int32Ty, FrameEscapeIdx)});
1824
1825 } else {
1826 // If the parent didn't have an alloca, we're doing some nested outlining.
1827 // Just clone the existing localrecover call, but tweak the FP argument to
1828 // use our FP value. All other arguments are constants.
1829 auto *ParentRecover =
1830 cast<llvm::IntrinsicInst>(ParentVar.getPointer()->stripPointerCasts());
1831 assert(ParentRecover->getIntrinsicID() == llvm::Intrinsic::localrecover &&
1832 "expected alloca or localrecover in parent LocalDeclMap");
1833 RecoverCall = cast<llvm::CallInst>(ParentRecover->clone());
1834 RecoverCall->setArgOperand(1, ParentFP);
1835 RecoverCall->insertBefore(AllocaInsertPt);
1836 }
1837
1838 // Bitcast the variable, rename it, and insert it in the local decl map.
1839 llvm::Value *ChildVar =
1840 Builder.CreateBitCast(RecoverCall, ParentVar.getType());
1841 ChildVar->setName(ParentVar.getName());
1842 return Address(ChildVar, ParentVar.getAlignment());
1843 }
1844
EmitCapturedLocals(CodeGenFunction & ParentCGF,const Stmt * OutlinedStmt,bool IsFilter)1845 void CodeGenFunction::EmitCapturedLocals(CodeGenFunction &ParentCGF,
1846 const Stmt *OutlinedStmt,
1847 bool IsFilter) {
1848 // Find all captures in the Stmt.
1849 CaptureFinder Finder(ParentCGF, ParentCGF.CXXABIThisDecl);
1850 Finder.Visit(OutlinedStmt);
1851
1852 // We can exit early on x86_64 when there are no captures. We just have to
1853 // save the exception code in filters so that __exception_code() works.
1854 if (!Finder.foundCaptures() &&
1855 CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) {
1856 if (IsFilter)
1857 EmitSEHExceptionCodeSave(ParentCGF, nullptr, nullptr);
1858 return;
1859 }
1860
1861 llvm::Value *EntryFP = nullptr;
1862 CGBuilderTy Builder(CGM, AllocaInsertPt);
1863 if (IsFilter && CGM.getTarget().getTriple().getArch() == llvm::Triple::x86) {
1864 // 32-bit SEH filters need to be careful about FP recovery. The end of the
1865 // EH registration is passed in as the EBP physical register. We can
1866 // recover that with llvm.frameaddress(1).
1867 EntryFP = Builder.CreateCall(
1868 CGM.getIntrinsic(llvm::Intrinsic::frameaddress, AllocaInt8PtrTy),
1869 {Builder.getInt32(1)});
1870 } else {
1871 // Otherwise, for x64 and 32-bit finally functions, the parent FP is the
1872 // second parameter.
1873 auto AI = CurFn->arg_begin();
1874 ++AI;
1875 EntryFP = &*AI;
1876 }
1877
1878 llvm::Value *ParentFP = EntryFP;
1879 if (IsFilter) {
1880 // Given whatever FP the runtime provided us in EntryFP, recover the true
1881 // frame pointer of the parent function. We only need to do this in filters,
1882 // since finally funclets recover the parent FP for us.
1883 llvm::Function *RecoverFPIntrin =
1884 CGM.getIntrinsic(llvm::Intrinsic::eh_recoverfp);
1885 llvm::Constant *ParentI8Fn =
1886 llvm::ConstantExpr::getBitCast(ParentCGF.CurFn, Int8PtrTy);
1887 ParentFP = Builder.CreateCall(RecoverFPIntrin, {ParentI8Fn, EntryFP});
1888
1889 // if the parent is a _finally, the passed-in ParentFP is the FP
1890 // of parent _finally, not Establisher's FP (FP of outermost function).
1891 // Establkisher FP is 2nd paramenter passed into parent _finally.
1892 // Fortunately, it's always saved in parent's frame. The following
1893 // code retrieves it, and escapes it so that spill instruction won't be
1894 // optimized away.
1895 if (ParentCGF.ParentCGF != nullptr) {
1896 // Locate and escape Parent's frame_pointer.addr alloca
1897 // Depending on target, should be 1st/2nd one in LocalDeclMap.
1898 // Let's just scan for ImplicitParamDecl with VoidPtrTy.
1899 llvm::AllocaInst *FramePtrAddrAlloca = nullptr;
1900 for (auto &I : ParentCGF.LocalDeclMap) {
1901 const VarDecl *D = cast<VarDecl>(I.first);
1902 if (isa<ImplicitParamDecl>(D) &&
1903 D->getType() == getContext().VoidPtrTy) {
1904 assert(D->getName().startswith("frame_pointer"));
1905 FramePtrAddrAlloca = cast<llvm::AllocaInst>(I.second.getPointer());
1906 break;
1907 }
1908 }
1909 assert(FramePtrAddrAlloca);
1910 auto InsertPair = ParentCGF.EscapedLocals.insert(
1911 std::make_pair(FramePtrAddrAlloca, ParentCGF.EscapedLocals.size()));
1912 int FrameEscapeIdx = InsertPair.first->second;
1913
1914 // an example of a filter's prolog::
1915 // %0 = call i8* @llvm.eh.recoverfp(bitcast(@"?fin$0@0@main@@"),..)
1916 // %1 = call i8* @llvm.localrecover(bitcast(@"?fin$0@0@main@@"),..)
1917 // %2 = bitcast i8* %1 to i8**
1918 // %3 = load i8*, i8* *%2, align 8
1919 // ==> %3 is the frame-pointer of outermost host function
1920 llvm::Function *FrameRecoverFn = llvm::Intrinsic::getDeclaration(
1921 &CGM.getModule(), llvm::Intrinsic::localrecover);
1922 llvm::Constant *ParentI8Fn =
1923 llvm::ConstantExpr::getBitCast(ParentCGF.CurFn, Int8PtrTy);
1924 ParentFP = Builder.CreateCall(
1925 FrameRecoverFn, {ParentI8Fn, ParentFP,
1926 llvm::ConstantInt::get(Int32Ty, FrameEscapeIdx)});
1927 ParentFP = Builder.CreateBitCast(ParentFP, CGM.VoidPtrPtrTy);
1928 ParentFP = Builder.CreateLoad(Address(ParentFP, getPointerAlign()));
1929 }
1930 }
1931
1932 // Create llvm.localrecover calls for all captures.
1933 for (const VarDecl *VD : Finder.Captures) {
1934 if (VD->getType()->isVariablyModifiedType()) {
1935 CGM.ErrorUnsupported(VD, "VLA captured by SEH");
1936 continue;
1937 }
1938 assert((isa<ImplicitParamDecl>(VD) || VD->isLocalVarDeclOrParm()) &&
1939 "captured non-local variable");
1940
1941 auto L = ParentCGF.LambdaCaptureFields.find(VD);
1942 if (L != ParentCGF.LambdaCaptureFields.end()) {
1943 LambdaCaptureFields[VD] = L->second;
1944 continue;
1945 }
1946
1947 // If this decl hasn't been declared yet, it will be declared in the
1948 // OutlinedStmt.
1949 auto I = ParentCGF.LocalDeclMap.find(VD);
1950 if (I == ParentCGF.LocalDeclMap.end())
1951 continue;
1952
1953 Address ParentVar = I->second;
1954 Address Recovered =
1955 recoverAddrOfEscapedLocal(ParentCGF, ParentVar, ParentFP);
1956 setAddrOfLocalVar(VD, Recovered);
1957
1958 if (isa<ImplicitParamDecl>(VD)) {
1959 CXXABIThisAlignment = ParentCGF.CXXABIThisAlignment;
1960 CXXThisAlignment = ParentCGF.CXXThisAlignment;
1961 CXXABIThisValue = Builder.CreateLoad(Recovered, "this");
1962 if (ParentCGF.LambdaThisCaptureField) {
1963 LambdaThisCaptureField = ParentCGF.LambdaThisCaptureField;
1964 // We are in a lambda function where "this" is captured so the
1965 // CXXThisValue need to be loaded from the lambda capture
1966 LValue ThisFieldLValue =
1967 EmitLValueForLambdaField(LambdaThisCaptureField);
1968 if (!LambdaThisCaptureField->getType()->isPointerType()) {
1969 CXXThisValue = ThisFieldLValue.getAddress(*this).getPointer();
1970 } else {
1971 CXXThisValue = EmitLoadOfLValue(ThisFieldLValue, SourceLocation())
1972 .getScalarVal();
1973 }
1974 } else {
1975 CXXThisValue = CXXABIThisValue;
1976 }
1977 }
1978 }
1979
1980 if (Finder.SEHCodeSlot.isValid()) {
1981 SEHCodeSlotStack.push_back(
1982 recoverAddrOfEscapedLocal(ParentCGF, Finder.SEHCodeSlot, ParentFP));
1983 }
1984
1985 if (IsFilter)
1986 EmitSEHExceptionCodeSave(ParentCGF, ParentFP, EntryFP);
1987 }
1988
1989 /// Arrange a function prototype that can be called by Windows exception
1990 /// handling personalities. On Win64, the prototype looks like:
1991 /// RetTy func(void *EHPtrs, void *ParentFP);
startOutlinedSEHHelper(CodeGenFunction & ParentCGF,bool IsFilter,const Stmt * OutlinedStmt)1992 void CodeGenFunction::startOutlinedSEHHelper(CodeGenFunction &ParentCGF,
1993 bool IsFilter,
1994 const Stmt *OutlinedStmt) {
1995 SourceLocation StartLoc = OutlinedStmt->getBeginLoc();
1996
1997 // Get the mangled function name.
1998 SmallString<128> Name;
1999 {
2000 llvm::raw_svector_ostream OS(Name);
2001 const NamedDecl *ParentSEHFn = ParentCGF.CurSEHParent;
2002 assert(ParentSEHFn && "No CurSEHParent!");
2003 MangleContext &Mangler = CGM.getCXXABI().getMangleContext();
2004 if (IsFilter)
2005 Mangler.mangleSEHFilterExpression(ParentSEHFn, OS);
2006 else
2007 Mangler.mangleSEHFinallyBlock(ParentSEHFn, OS);
2008 }
2009
2010 FunctionArgList Args;
2011 if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86 || !IsFilter) {
2012 // All SEH finally functions take two parameters. Win64 filters take two
2013 // parameters. Win32 filters take no parameters.
2014 if (IsFilter) {
2015 Args.push_back(ImplicitParamDecl::Create(
2016 getContext(), /*DC=*/nullptr, StartLoc,
2017 &getContext().Idents.get("exception_pointers"),
2018 getContext().VoidPtrTy, ImplicitParamDecl::Other));
2019 } else {
2020 Args.push_back(ImplicitParamDecl::Create(
2021 getContext(), /*DC=*/nullptr, StartLoc,
2022 &getContext().Idents.get("abnormal_termination"),
2023 getContext().UnsignedCharTy, ImplicitParamDecl::Other));
2024 }
2025 Args.push_back(ImplicitParamDecl::Create(
2026 getContext(), /*DC=*/nullptr, StartLoc,
2027 &getContext().Idents.get("frame_pointer"), getContext().VoidPtrTy,
2028 ImplicitParamDecl::Other));
2029 }
2030
2031 QualType RetTy = IsFilter ? getContext().LongTy : getContext().VoidTy;
2032
2033 const CGFunctionInfo &FnInfo =
2034 CGM.getTypes().arrangeBuiltinFunctionDeclaration(RetTy, Args);
2035
2036 llvm::FunctionType *FnTy = CGM.getTypes().GetFunctionType(FnInfo);
2037 llvm::Function *Fn = llvm::Function::Create(
2038 FnTy, llvm::GlobalValue::InternalLinkage, Name.str(), &CGM.getModule());
2039
2040 IsOutlinedSEHHelper = true;
2041
2042 StartFunction(GlobalDecl(), RetTy, Fn, FnInfo, Args,
2043 OutlinedStmt->getBeginLoc(), OutlinedStmt->getBeginLoc());
2044 CurSEHParent = ParentCGF.CurSEHParent;
2045
2046 CGM.SetInternalFunctionAttributes(GlobalDecl(), CurFn, FnInfo);
2047 EmitCapturedLocals(ParentCGF, OutlinedStmt, IsFilter);
2048 }
2049
2050 /// Create a stub filter function that will ultimately hold the code of the
2051 /// filter expression. The EH preparation passes in LLVM will outline the code
2052 /// from the main function body into this stub.
2053 llvm::Function *
GenerateSEHFilterFunction(CodeGenFunction & ParentCGF,const SEHExceptStmt & Except)2054 CodeGenFunction::GenerateSEHFilterFunction(CodeGenFunction &ParentCGF,
2055 const SEHExceptStmt &Except) {
2056 const Expr *FilterExpr = Except.getFilterExpr();
2057 startOutlinedSEHHelper(ParentCGF, true, FilterExpr);
2058
2059 // Emit the original filter expression, convert to i32, and return.
2060 llvm::Value *R = EmitScalarExpr(FilterExpr);
2061 R = Builder.CreateIntCast(R, ConvertType(getContext().LongTy),
2062 FilterExpr->getType()->isSignedIntegerType());
2063 Builder.CreateStore(R, ReturnValue);
2064
2065 FinishFunction(FilterExpr->getEndLoc());
2066
2067 return CurFn;
2068 }
2069
2070 llvm::Function *
GenerateSEHFinallyFunction(CodeGenFunction & ParentCGF,const SEHFinallyStmt & Finally)2071 CodeGenFunction::GenerateSEHFinallyFunction(CodeGenFunction &ParentCGF,
2072 const SEHFinallyStmt &Finally) {
2073 const Stmt *FinallyBlock = Finally.getBlock();
2074 startOutlinedSEHHelper(ParentCGF, false, FinallyBlock);
2075
2076 // Emit the original filter expression, convert to i32, and return.
2077 EmitStmt(FinallyBlock);
2078
2079 FinishFunction(FinallyBlock->getEndLoc());
2080
2081 return CurFn;
2082 }
2083
EmitSEHExceptionCodeSave(CodeGenFunction & ParentCGF,llvm::Value * ParentFP,llvm::Value * EntryFP)2084 void CodeGenFunction::EmitSEHExceptionCodeSave(CodeGenFunction &ParentCGF,
2085 llvm::Value *ParentFP,
2086 llvm::Value *EntryFP) {
2087 // Get the pointer to the EXCEPTION_POINTERS struct. This is returned by the
2088 // __exception_info intrinsic.
2089 if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) {
2090 // On Win64, the info is passed as the first parameter to the filter.
2091 SEHInfo = &*CurFn->arg_begin();
2092 SEHCodeSlotStack.push_back(
2093 CreateMemTemp(getContext().IntTy, "__exception_code"));
2094 } else {
2095 // On Win32, the EBP on entry to the filter points to the end of an
2096 // exception registration object. It contains 6 32-bit fields, and the info
2097 // pointer is stored in the second field. So, GEP 20 bytes backwards and
2098 // load the pointer.
2099 SEHInfo = Builder.CreateConstInBoundsGEP1_32(Int8Ty, EntryFP, -20);
2100 SEHInfo = Builder.CreateBitCast(SEHInfo, Int8PtrTy->getPointerTo());
2101 SEHInfo = Builder.CreateAlignedLoad(Int8PtrTy, SEHInfo, getPointerAlign());
2102 SEHCodeSlotStack.push_back(recoverAddrOfEscapedLocal(
2103 ParentCGF, ParentCGF.SEHCodeSlotStack.back(), ParentFP));
2104 }
2105
2106 // Save the exception code in the exception slot to unify exception access in
2107 // the filter function and the landing pad.
2108 // struct EXCEPTION_POINTERS {
2109 // EXCEPTION_RECORD *ExceptionRecord;
2110 // CONTEXT *ContextRecord;
2111 // };
2112 // int exceptioncode = exception_pointers->ExceptionRecord->ExceptionCode;
2113 llvm::Type *RecordTy = CGM.Int32Ty->getPointerTo();
2114 llvm::Type *PtrsTy = llvm::StructType::get(RecordTy, CGM.VoidPtrTy);
2115 llvm::Value *Ptrs = Builder.CreateBitCast(SEHInfo, PtrsTy->getPointerTo());
2116 llvm::Value *Rec = Builder.CreateStructGEP(PtrsTy, Ptrs, 0);
2117 Rec = Builder.CreateAlignedLoad(RecordTy, Rec, getPointerAlign());
2118 llvm::Value *Code = Builder.CreateAlignedLoad(Int32Ty, Rec, getIntAlign());
2119 assert(!SEHCodeSlotStack.empty() && "emitting EH code outside of __except");
2120 Builder.CreateStore(Code, SEHCodeSlotStack.back());
2121 }
2122
EmitSEHExceptionInfo()2123 llvm::Value *CodeGenFunction::EmitSEHExceptionInfo() {
2124 // Sema should diagnose calling this builtin outside of a filter context, but
2125 // don't crash if we screw up.
2126 if (!SEHInfo)
2127 return llvm::UndefValue::get(Int8PtrTy);
2128 assert(SEHInfo->getType() == Int8PtrTy);
2129 return SEHInfo;
2130 }
2131
EmitSEHExceptionCode()2132 llvm::Value *CodeGenFunction::EmitSEHExceptionCode() {
2133 assert(!SEHCodeSlotStack.empty() && "emitting EH code outside of __except");
2134 return Builder.CreateLoad(SEHCodeSlotStack.back());
2135 }
2136
EmitSEHAbnormalTermination()2137 llvm::Value *CodeGenFunction::EmitSEHAbnormalTermination() {
2138 // Abnormal termination is just the first parameter to the outlined finally
2139 // helper.
2140 auto AI = CurFn->arg_begin();
2141 return Builder.CreateZExt(&*AI, Int32Ty);
2142 }
2143
pushSEHCleanup(CleanupKind Kind,llvm::Function * FinallyFunc)2144 void CodeGenFunction::pushSEHCleanup(CleanupKind Kind,
2145 llvm::Function *FinallyFunc) {
2146 EHStack.pushCleanup<PerformSEHFinally>(Kind, FinallyFunc);
2147 }
2148
EnterSEHTryStmt(const SEHTryStmt & S)2149 void CodeGenFunction::EnterSEHTryStmt(const SEHTryStmt &S) {
2150 CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);
2151 HelperCGF.ParentCGF = this;
2152 if (const SEHFinallyStmt *Finally = S.getFinallyHandler()) {
2153 // Outline the finally block.
2154 llvm::Function *FinallyFunc =
2155 HelperCGF.GenerateSEHFinallyFunction(*this, *Finally);
2156
2157 // Push a cleanup for __finally blocks.
2158 EHStack.pushCleanup<PerformSEHFinally>(NormalAndEHCleanup, FinallyFunc);
2159 return;
2160 }
2161
2162 // Otherwise, we must have an __except block.
2163 const SEHExceptStmt *Except = S.getExceptHandler();
2164 assert(Except);
2165 EHCatchScope *CatchScope = EHStack.pushCatch(1);
2166 SEHCodeSlotStack.push_back(
2167 CreateMemTemp(getContext().IntTy, "__exception_code"));
2168
2169 // If the filter is known to evaluate to 1, then we can use the clause
2170 // "catch i8* null". We can't do this on x86 because the filter has to save
2171 // the exception code.
2172 llvm::Constant *C =
2173 ConstantEmitter(*this).tryEmitAbstract(Except->getFilterExpr(),
2174 getContext().IntTy);
2175 if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86 && C &&
2176 C->isOneValue()) {
2177 CatchScope->setCatchAllHandler(0, createBasicBlock("__except"));
2178 return;
2179 }
2180
2181 // In general, we have to emit an outlined filter function. Use the function
2182 // in place of the RTTI typeinfo global that C++ EH uses.
2183 llvm::Function *FilterFunc =
2184 HelperCGF.GenerateSEHFilterFunction(*this, *Except);
2185 llvm::Constant *OpaqueFunc =
2186 llvm::ConstantExpr::getBitCast(FilterFunc, Int8PtrTy);
2187 CatchScope->setHandler(0, OpaqueFunc, createBasicBlock("__except.ret"));
2188 }
2189
ExitSEHTryStmt(const SEHTryStmt & S)2190 void CodeGenFunction::ExitSEHTryStmt(const SEHTryStmt &S) {
2191 // Just pop the cleanup if it's a __finally block.
2192 if (S.getFinallyHandler()) {
2193 PopCleanupBlock();
2194 return;
2195 }
2196
2197 // IsEHa: emit an invoke _seh_try_end() to mark end of FT flow
2198 if (getLangOpts().EHAsynch && Builder.GetInsertBlock()) {
2199 llvm::FunctionCallee SehTryEnd = getSehTryEndFn(CGM);
2200 EmitRuntimeCallOrInvoke(SehTryEnd);
2201 }
2202
2203 // Otherwise, we must have an __except block.
2204 const SEHExceptStmt *Except = S.getExceptHandler();
2205 assert(Except && "__try must have __finally xor __except");
2206 EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin());
2207
2208 // Don't emit the __except block if the __try block lacked invokes.
2209 // TODO: Model unwind edges from instructions, either with iload / istore or
2210 // a try body function.
2211 if (!CatchScope.hasEHBranches()) {
2212 CatchScope.clearHandlerBlocks();
2213 EHStack.popCatch();
2214 SEHCodeSlotStack.pop_back();
2215 return;
2216 }
2217
2218 // The fall-through block.
2219 llvm::BasicBlock *ContBB = createBasicBlock("__try.cont");
2220
2221 // We just emitted the body of the __try; jump to the continue block.
2222 if (HaveInsertPoint())
2223 Builder.CreateBr(ContBB);
2224
2225 // Check if our filter function returned true.
2226 emitCatchDispatchBlock(*this, CatchScope);
2227
2228 // Grab the block before we pop the handler.
2229 llvm::BasicBlock *CatchPadBB = CatchScope.getHandler(0).Block;
2230 EHStack.popCatch();
2231
2232 EmitBlockAfterUses(CatchPadBB);
2233
2234 // __except blocks don't get outlined into funclets, so immediately do a
2235 // catchret.
2236 llvm::CatchPadInst *CPI =
2237 cast<llvm::CatchPadInst>(CatchPadBB->getFirstNonPHI());
2238 llvm::BasicBlock *ExceptBB = createBasicBlock("__except");
2239 Builder.CreateCatchRet(CPI, ExceptBB);
2240 EmitBlock(ExceptBB);
2241
2242 // On Win64, the exception code is returned in EAX. Copy it into the slot.
2243 if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) {
2244 llvm::Function *SEHCodeIntrin =
2245 CGM.getIntrinsic(llvm::Intrinsic::eh_exceptioncode);
2246 llvm::Value *Code = Builder.CreateCall(SEHCodeIntrin, {CPI});
2247 Builder.CreateStore(Code, SEHCodeSlotStack.back());
2248 }
2249
2250 // Emit the __except body.
2251 EmitStmt(Except->getBlock());
2252
2253 // End the lifetime of the exception code.
2254 SEHCodeSlotStack.pop_back();
2255
2256 if (HaveInsertPoint())
2257 Builder.CreateBr(ContBB);
2258
2259 EmitBlock(ContBB);
2260 }
2261
EmitSEHLeaveStmt(const SEHLeaveStmt & S)2262 void CodeGenFunction::EmitSEHLeaveStmt(const SEHLeaveStmt &S) {
2263 // If this code is reachable then emit a stop point (if generating
2264 // debug info). We have to do this ourselves because we are on the
2265 // "simple" statement path.
2266 if (HaveInsertPoint())
2267 EmitStopPoint(&S);
2268
2269 // This must be a __leave from a __finally block, which we warn on and is UB.
2270 // Just emit unreachable.
2271 if (!isSEHTryScope()) {
2272 Builder.CreateUnreachable();
2273 Builder.ClearInsertionPoint();
2274 return;
2275 }
2276
2277 EmitBranchThroughCleanup(*SEHTryEpilogueStack.back());
2278 }
2279