1//==- CGObjCRuntime.cpp - Interface to Shared Objective-C Runtime Features ==//
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 abstract class defines the interface for Objective-C runtime-specific
10// code generation. It provides some concrete helper methods for functionality
11// shared between all (or most) of the Objective-C runtimes supported by clang.
12//
13//===----------------------------------------------------------------------===//
14
15#include "CGObjCRuntime.h"
16#include "Address.h"
17#include "CGCXXABI.h"
18#include "CGCleanup.h"
19#include "CGRecordLayout.h"
20#include "CodeGenFunction.h"
21#include "CodeGenModule.h"
22#include "clang/AST/RecordLayout.h"
23#include "clang/AST/StmtObjC.h"
24#include "clang/CodeGen/CGFunctionInfo.h"
25#include "clang/CodeGen/CodeGenABITypes.h"
26#include "llvm/IR/Instruction.h"
27#include "llvm/IR/Instructions.h"
28#include "llvm/Support/ErrorHandling.h"
29#include "llvm/Support/SaveAndRestore.h"
30
31using namespace clang;
32using namespace CodeGen;
33
34uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,
35 const ObjCInterfaceDecl *OID,
36 const ObjCIvarDecl *Ivar) {
37 return CGM.getContext().lookupFieldBitOffset(OID, Ivar) /
38 CGM.getContext().getCharWidth();
39}
40
41uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,
42 const ObjCImplementationDecl *OID,
43 const ObjCIvarDecl *Ivar) {
44 return CGM.getContext().lookupFieldBitOffset(OID: OID->getClassInterface(), Ivar) /
45 CGM.getContext().getCharWidth();
46}
47
48unsigned CGObjCRuntime::ComputeBitfieldBitOffset(
49 CodeGen::CodeGenModule &CGM,
50 const ObjCInterfaceDecl *ID,
51 const ObjCIvarDecl *Ivar) {
52 return CGM.getContext().lookupFieldBitOffset(OID: ID, Ivar);
53}
54
55LValue CGObjCRuntime::EmitValueForIvarAtOffset(CodeGen::CodeGenFunction &CGF,
56 const ObjCInterfaceDecl *OID,
57 llvm::Value *BaseValue,
58 const ObjCIvarDecl *Ivar,
59 unsigned CVRQualifiers,
60 llvm::Value *Offset) {
61 // Compute (type*) ( (char *) BaseValue + Offset)
62 QualType InterfaceTy{OID->getTypeForDecl(), 0};
63 QualType ObjectPtrTy =
64 CGF.CGM.getContext().getObjCObjectPointerType(OIT: InterfaceTy);
65 QualType IvarTy =
66 Ivar->getUsageType(objectType: ObjectPtrTy).withCVRQualifiers(CVR: CVRQualifiers);
67 llvm::Value *V = BaseValue;
68 V = CGF.Builder.CreateInBoundsGEP(Ty: CGF.Int8Ty, Ptr: V, IdxList: Offset, Name: "add.ptr");
69
70 if (!Ivar->isBitField()) {
71 LValue LV = CGF.MakeNaturalAlignRawAddrLValue(V, T: IvarTy);
72 return LV;
73 }
74
75 // We need to compute an access strategy for this bit-field. We are given the
76 // offset to the first byte in the bit-field, the sub-byte offset is taken
77 // from the original layout. We reuse the normal bit-field access strategy by
78 // treating this as an access to a struct where the bit-field is in byte 0,
79 // and adjust the containing type size as appropriate.
80 //
81 // FIXME: Note that currently we make a very conservative estimate of the
82 // alignment of the bit-field, because (a) it is not clear what guarantees the
83 // runtime makes us, and (b) we don't have a way to specify that the struct is
84 // at an alignment plus offset.
85 //
86 // Note, there is a subtle invariant here: we can only call this routine on
87 // non-synthesized ivars but we may be called for synthesized ivars. However,
88 // a synthesized ivar can never be a bit-field, so this is safe.
89 uint64_t FieldBitOffset =
90 CGF.CGM.getContext().lookupFieldBitOffset(OID, Ivar);
91 uint64_t BitOffset = FieldBitOffset % CGF.CGM.getContext().getCharWidth();
92 uint64_t AlignmentBits = CGF.CGM.getTarget().getCharAlign();
93 uint64_t BitFieldSize = Ivar->getBitWidthValue();
94 CharUnits StorageSize = CGF.CGM.getContext().toCharUnitsFromBits(
95 BitSize: llvm::alignTo(Value: BitOffset + BitFieldSize, Align: AlignmentBits));
96 CharUnits Alignment = CGF.CGM.getContext().toCharUnitsFromBits(BitSize: AlignmentBits);
97
98 // Allocate a new CGBitFieldInfo object to describe this access.
99 //
100 // FIXME: This is incredibly wasteful, these should be uniqued or part of some
101 // layout object. However, this is blocked on other cleanups to the
102 // Objective-C code, so for now we just live with allocating a bunch of these
103 // objects.
104 CGBitFieldInfo *Info = new (CGF.CGM.getContext()) CGBitFieldInfo(
105 CGBitFieldInfo::MakeInfo(Types&: CGF.CGM.getTypes(), FD: Ivar, Offset: BitOffset, Size: BitFieldSize,
106 StorageSize: CGF.CGM.getContext().toBits(CharSize: StorageSize),
107 StorageOffset: CharUnits::fromQuantity(Quantity: 0)));
108
109 Address Addr =
110 Address(V, llvm::Type::getIntNTy(C&: CGF.getLLVMContext(), N: Info->StorageSize),
111 Alignment);
112
113 return LValue::MakeBitfield(Addr, Info: *Info, type: IvarTy,
114 BaseInfo: LValueBaseInfo(AlignmentSource::Decl),
115 TBAAInfo: TBAAAccessInfo());
116}
117
118namespace {
119 struct CatchHandler {
120 const VarDecl *Variable;
121 const Stmt *Body;
122 llvm::BasicBlock *Block;
123 llvm::Constant *TypeInfo;
124 /// Flags used to differentiate cleanups and catchalls in Windows SEH
125 unsigned Flags;
126 };
127
128 struct CallObjCEndCatch final : EHScopeStack::Cleanup {
129 CallObjCEndCatch(bool MightThrow, llvm::FunctionCallee Fn)
130 : MightThrow(MightThrow), Fn(Fn) {}
131 bool MightThrow;
132 llvm::FunctionCallee Fn;
133
134 void Emit(CodeGenFunction &CGF, Flags flags) override {
135 if (MightThrow)
136 CGF.EmitRuntimeCallOrInvoke(callee: Fn);
137 else
138 CGF.EmitNounwindRuntimeCall(callee: Fn);
139 }
140 };
141}
142
143void CGObjCRuntime::EmitTryCatchStmt(CodeGenFunction &CGF,
144 const ObjCAtTryStmt &S,
145 llvm::FunctionCallee beginCatchFn,
146 llvm::FunctionCallee endCatchFn,
147 llvm::FunctionCallee exceptionRethrowFn) {
148 // Jump destination for falling out of catch bodies.
149 CodeGenFunction::JumpDest Cont;
150 if (S.getNumCatchStmts())
151 Cont = CGF.getJumpDestInCurrentScope(Name: "eh.cont");
152
153 bool useFunclets = EHPersonality::get(CGF).usesFuncletPads();
154 bool IsWasm = EHPersonality::get(CGF).isWasmPersonality();
155 bool IsMSVC = EHPersonality::get(CGF).isMSVCPersonality();
156
157 CodeGenFunction::FinallyInfo FinallyInfo;
158 if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt()) {
159 if (!useFunclets) {
160 // The finally statement is executed as a cleanup for the normal and
161 // exceptional control flow out of a try-catch block. This is all
162 // implemented in FinallyInfo. Here we enter a new EHCatchScope.
163 FinallyInfo.enter(CGF, Finally: Finally->getFinallyBody(), beginCatchFn,
164 endCatchFn, rethrowFn: exceptionRethrowFn);
165 } else if (IsWasm) {
166 CGF.ErrorUnsupported(S: Finally,
167 Type: "@finally is not implemented for WebAssembly");
168 } else if (IsMSVC) {
169 CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);
170 if (!CGF.CurSEHParent)
171 CGF.CurSEHParent = cast<NamedDecl>(Val: CGF.CurFuncDecl);
172 const Stmt *FinallyBlock = Finally->getFinallyBody();
173 HelperCGF.startOutlinedSEHHelper(ParentCGF&: CGF, /*isFilter*/ IsFilter: false, OutlinedStmt: FinallyBlock);
174 HelperCGF.EmitStmt(S: FinallyBlock);
175 HelperCGF.FinishFunction(EndLoc: FinallyBlock->getEndLoc());
176
177 llvm::Function *FinallyFunc = HelperCGF.CurFn;
178 CGF.pushSEHCleanup(kind: NormalAndEHCleanup, FinallyFunc);
179 }
180 }
181
182 SmallVector<CatchHandler, 8> Handlers;
183
184 // Enter the catch, if there is one.
185 if (S.getNumCatchStmts()) {
186 for (const ObjCAtCatchStmt *CatchStmt : S.catch_stmts()) {
187 const VarDecl *CatchDecl = CatchStmt->getCatchParamDecl();
188
189 Handlers.push_back(Elt: CatchHandler());
190 CatchHandler &Handler = Handlers.back();
191 Handler.Variable = CatchDecl;
192 Handler.Body = CatchStmt->getCatchBody();
193 Handler.Block = CGF.createBasicBlock(name: "catch");
194 Handler.Flags = 0;
195
196 // @catch(...) always matches.
197 if (!CatchDecl) {
198 auto catchAll = getCatchAllTypeInfo();
199 Handler.TypeInfo = catchAll.RTTI;
200 Handler.Flags = catchAll.Flags;
201 // Don't consider any other catches.
202 break;
203 }
204
205 Handler.TypeInfo = GetEHType(T: CatchDecl->getType());
206 }
207
208 // Create a new catch scope
209 EHCatchScope *Catch = CGF.EHStack.pushCatch(NumHandlers: Handlers.size());
210 for (unsigned I = 0, E = Handlers.size(); I != E; ++I)
211 Catch->setHandler(I, Type: { .RTTI: Handlers[I].TypeInfo, .Flags: Handlers[I].Flags }, Block: Handlers[I].Block);
212 }
213
214 // Emit the try body.
215 CGF.EmitStmt(S: S.getTryBody());
216
217 // Leave the try.
218 llvm::BasicBlock *DispatchBlock = nullptr;
219 if (S.getNumCatchStmts()) {
220 EHCatchScope &CatchScope = cast<EHCatchScope>(Val&: *CGF.EHStack.begin());
221 if (CatchScope.hasEHBranches())
222 DispatchBlock = CatchScope.getCachedEHDispatchBlock();
223 CGF.popCatchScope();
224 }
225
226 // We save the old funclet pad here before we traverse each catch handler.
227 SaveAndRestore RestoreCurrentFuncletPad(CGF.CurrentFuncletPad);
228 llvm::BasicBlock *WasmCatchStartBlock = nullptr;
229 llvm::CatchPadInst *CPI = nullptr;
230 if (DispatchBlock && IsWasm) {
231 auto *CatchSwitch =
232 cast<llvm::CatchSwitchInst>(Val: DispatchBlock->getFirstNonPHIIt());
233 WasmCatchStartBlock = CatchSwitch->hasUnwindDest()
234 ? CatchSwitch->getSuccessor(Idx: 1)
235 : CatchSwitch->getSuccessor(Idx: 0);
236 CPI = cast<llvm::CatchPadInst>(Val: WasmCatchStartBlock->getFirstNonPHIIt());
237 CGF.CurrentFuncletPad = CPI;
238 }
239
240 // Remember where we were.
241 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();
242
243 // Emit the handlers. If there is no catch-all handler, we need to emit a
244 // fallthrough block in WASM. We therefore need to know if we have a
245 // catch-all handler in this catch scope.
246 bool HasCatchAll = false;
247 for (CatchHandler &Handler : Handlers) {
248 HasCatchAll |= Handler.TypeInfo == nullptr;
249 CGF.EmitBlock(BB: Handler.Block);
250
251 CodeGenFunction::LexicalScope Cleanups(CGF, Handler.Body->getSourceRange());
252 SaveAndRestore RevertAfterScope(CGF.CurrentFuncletPad);
253 if (IsMSVC) {
254 llvm::BasicBlock::iterator CPICandidate =
255 Handler.Block->getFirstNonPHIIt();
256 if (CPICandidate != Handler.Block->end()) {
257 if ((CPI = dyn_cast_or_null<llvm::CatchPadInst>(Val&: CPICandidate))) {
258 CGF.CurrentFuncletPad = CPI;
259 CPI->setOperand(i_nocapture: 2, Val_nocapture: CGF.getExceptionSlot().emitRawPointer(CGF));
260 }
261 }
262 }
263
264 if (CPI) {
265 // A catchpad requires a matching catchret instruction. We emit this in
266 // form of a cleanup.
267 CGF.EHStack.pushCleanup<CatchRetScope>(Kind: NormalCleanup, A: CPI);
268 }
269
270 llvm::Value *RawExn = CGF.getExceptionFromSlot();
271
272 // Enter the catch.
273 llvm::Value *Exn = RawExn;
274 if (beginCatchFn)
275 Exn = CGF.EmitNounwindRuntimeCall(callee: beginCatchFn, args: RawExn, name: "exn.adjusted");
276
277 if (endCatchFn) {
278 // Add a cleanup to leave the catch.
279 bool EndCatchMightThrow = (Handler.Variable == nullptr);
280
281 CGF.EHStack.pushCleanup<CallObjCEndCatch>(Kind: NormalAndEHCleanup,
282 A: EndCatchMightThrow,
283 A: endCatchFn);
284 }
285
286 // Bind the catch parameter if it exists.
287 if (const VarDecl *CatchParam = Handler.Variable) {
288 llvm::Type *CatchType = CGF.ConvertType(T: CatchParam->getType());
289 llvm::Value *CastExn = CGF.Builder.CreateBitCast(V: Exn, DestTy: CatchType);
290
291 CGF.EmitAutoVarDecl(D: *CatchParam);
292 EmitInitOfCatchParam(CGF, exn: CastExn, paramDecl: CatchParam);
293 }
294
295 // The body of the handler might have more try-catch blocks, so we need to
296 // save the current exception before emitting the body.
297 CGF.ObjCEHValueStack.push_back(Elt: Exn);
298 CGF.EmitStmt(S: Handler.Body);
299 CGF.ObjCEHValueStack.pop_back();
300
301 // Leave any cleanups associated with the catch.
302 Cleanups.ForceCleanup();
303
304 CGF.EmitBranchThroughCleanup(Dest: Cont);
305 }
306
307 if (IsWasm && !HasCatchAll && WasmCatchStartBlock) {
308 CGF.WasmEmitFallthroughRethrow(WasmCatchStartBlock);
309 }
310
311 // Go back to the try-statement fallthrough.
312 CGF.Builder.restoreIP(IP: SavedIP);
313
314 // Pop out of the finally.
315 if (!useFunclets && S.getFinallyStmt())
316 FinallyInfo.exit(CGF);
317
318 if (Cont.isValid())
319 CGF.EmitBlock(BB: Cont.getBlock());
320}
321
322void CGObjCRuntime::EmitInitOfCatchParam(CodeGenFunction &CGF,
323 llvm::Value *exn,
324 const VarDecl *paramDecl) {
325
326 Address paramAddr = CGF.GetAddrOfLocalVar(VD: paramDecl);
327
328 switch (paramDecl->getType().getQualifiers().getObjCLifetime()) {
329 case Qualifiers::OCL_Strong:
330 exn = CGF.EmitARCRetainNonBlock(value: exn);
331 [[fallthrough]];
332
333 case Qualifiers::OCL_None:
334 case Qualifiers::OCL_ExplicitNone:
335 case Qualifiers::OCL_Autoreleasing:
336 CGF.Builder.CreateStore(Val: exn, Addr: paramAddr);
337 return;
338
339 case Qualifiers::OCL_Weak:
340 CGF.EmitARCInitWeak(addr: paramAddr, value: exn);
341 return;
342 }
343 llvm_unreachable("invalid ownership qualifier");
344}
345
346namespace {
347 struct CallSyncExit final : EHScopeStack::Cleanup {
348 llvm::FunctionCallee SyncExitFn;
349 llvm::Value *SyncArg;
350 CallSyncExit(llvm::FunctionCallee SyncExitFn, llvm::Value *SyncArg)
351 : SyncExitFn(SyncExitFn), SyncArg(SyncArg) {}
352
353 void Emit(CodeGenFunction &CGF, Flags flags) override {
354 CGF.EmitNounwindRuntimeCall(callee: SyncExitFn, args: SyncArg);
355 }
356 };
357}
358
359void CGObjCRuntime::EmitAtSynchronizedStmt(CodeGenFunction &CGF,
360 const ObjCAtSynchronizedStmt &S,
361 llvm::FunctionCallee syncEnterFn,
362 llvm::FunctionCallee syncExitFn) {
363 CodeGenFunction::RunCleanupsScope cleanups(CGF);
364
365 // Evaluate the lock operand. This is guaranteed to dominate the
366 // ARC release and lock-release cleanups.
367 const Expr *lockExpr = S.getSynchExpr();
368 llvm::Value *lock;
369 if (CGF.getLangOpts().ObjCAutoRefCount) {
370 lock = CGF.EmitARCRetainScalarExpr(expr: lockExpr);
371 lock = CGF.EmitObjCConsumeObject(T: lockExpr->getType(), Ptr: lock);
372 } else {
373 lock = CGF.EmitScalarExpr(E: lockExpr);
374 }
375 lock = CGF.Builder.CreateBitCast(V: lock, DestTy: CGF.VoidPtrTy);
376
377 // Acquire the lock.
378 CGF.Builder.CreateCall(Callee: syncEnterFn, Args: lock)->setDoesNotThrow();
379
380 // Register an all-paths cleanup to release the lock.
381 CGF.EHStack.pushCleanup<CallSyncExit>(Kind: NormalAndEHCleanup, A: syncExitFn, A: lock);
382
383 // Emit the body of the statement.
384 CGF.EmitStmt(S: S.getSynchBody());
385}
386
387/// Compute the pointer-to-function type to which a message send
388/// should be casted in order to correctly call the given method
389/// with the given arguments.
390///
391/// \param method - may be null
392/// \param resultType - the result type to use if there's no method
393/// \param callArgs - the actual arguments, including implicit ones
394CGObjCRuntime::MessageSendInfo
395CGObjCRuntime::getMessageSendInfo(const ObjCMethodDecl *method,
396 QualType resultType,
397 CallArgList &callArgs) {
398 unsigned ProgramAS = CGM.getDataLayout().getProgramAddressSpace();
399
400 llvm::PointerType *signatureType =
401 llvm::PointerType::get(C&: CGM.getLLVMContext(), AddressSpace: ProgramAS);
402
403 // FIXME: Pass the enclosing FunctionDecl so Objective-C message sends use
404 // the caller's target features when arranging their ABI.
405 // If there's a method, use information from that.
406 if (method) {
407 const CGFunctionInfo &signature =
408 CGM.getTypes().arrangeObjCMessageSendSignature(MD: method, receiverType: callArgs[0].Ty);
409
410 const CGFunctionInfo &signatureForCall =
411 CGM.getTypes().arrangeCall(declFI: signature, args: callArgs, /*ABIInfoFD=*/nullptr);
412
413 return MessageSendInfo(signatureForCall, signatureType);
414 }
415
416 // There's no method; just use a default CC.
417 const CGFunctionInfo &argsInfo =
418 CGM.getTypes().arrangeUnprototypedObjCMessageSend(returnType: resultType, args: callArgs);
419
420 return MessageSendInfo(argsInfo, signatureType);
421}
422
423bool CGObjCRuntime::canMessageReceiverBeNull(
424 CodeGenFunction &CGF, const ObjCMethodDecl *method, bool isSuper,
425 const ObjCInterfaceDecl *classReceiver, llvm::Value *receiver) {
426 // Super dispatch assumes that self is non-null; even the messenger
427 // doesn't have a null check internally.
428 if (isSuper)
429 return false;
430
431 // If this is a direct dispatch of a class method, check whether the class,
432 // or anything in its hierarchy, was weak-linked.
433 if (classReceiver && method && method->isClassMethod())
434 return isWeakLinkedClass(cls: classReceiver);
435
436 // If we're emitting a method, and self is const (meaning just ARC, for now),
437 // and the receiver is a load of self, then self is a valid object.
438 if (auto curMethod = dyn_cast_or_null<ObjCMethodDecl>(Val: CGF.CurCodeDecl)) {
439 auto self = curMethod->getSelfDecl();
440 if (self->getType().isConstQualified()) {
441 if (auto LI = dyn_cast<llvm::LoadInst>(Val: receiver->stripPointerCasts())) {
442 llvm::Value *selfAddr = CGF.GetAddrOfLocalVar(VD: self).emitRawPointer(CGF);
443 if (selfAddr == LI->getPointerOperand()) {
444 return false;
445 }
446 }
447 }
448 }
449
450 // Otherwise, assume it can be null.
451 return true;
452}
453
454bool CGObjCRuntime::canClassObjectBeUnrealized(
455 const ObjCInterfaceDecl *CalleeClassDecl, CodeGenFunction &CGF) const {
456 // TODO
457 // Otherwise, assume it can be unrealized.
458 return true;
459}
460
461bool CGObjCRuntime::isWeakLinkedClass(const ObjCInterfaceDecl *ID) {
462 do {
463 if (ID->isWeakImported())
464 return true;
465 } while ((ID = ID->getSuperClass()));
466
467 return false;
468}
469
470void CGObjCRuntime::destroyCalleeDestroyedArguments(CodeGenFunction &CGF,
471 const ObjCMethodDecl *method,
472 const CallArgList &callArgs) {
473 CallArgList::const_iterator I = callArgs.begin();
474 for (auto i = method->param_begin(), e = method->param_end();
475 i != e; ++i, ++I) {
476 const ParmVarDecl *param = (*i);
477 if (param->hasAttr<NSConsumedAttr>()) {
478 RValue RV = I->getRValue(CGF);
479 assert(RV.isScalar() &&
480 "NullReturnState::complete - arg not on object");
481 CGF.EmitARCRelease(value: RV.getScalarVal(), precise: ARCImpreciseLifetime);
482 } else {
483 QualType QT = param->getType();
484 auto *RD = QT->getAsRecordDecl();
485 if (RD && RD->isParamDestroyedInCallee()) {
486 RValue RV = I->getRValue(CGF);
487 QualType::DestructionKind DtorKind = QT.isDestructedType();
488 switch (DtorKind) {
489 case QualType::DK_cxx_destructor:
490 CGF.destroyCXXObject(CGF, RV.getAggregateAddress(), QT);
491 break;
492 case QualType::DK_nontrivial_c_struct:
493 CGF.destroyNonTrivialCStruct(CGF, RV.getAggregateAddress(), QT);
494 break;
495 default:
496 llvm_unreachable("unexpected dtor kind");
497 break;
498 }
499 }
500 }
501 }
502}
503
504llvm::Constant *
505clang::CodeGen::emitObjCProtocolObject(CodeGenModule &CGM,
506 const ObjCProtocolDecl *protocol) {
507 return CGM.getObjCRuntime().GetOrEmitProtocol(PD: protocol);
508}
509
510std::string CGObjCRuntime::getSymbolNameForMethod(const ObjCMethodDecl *OMD,
511 bool includeCategoryName,
512 bool useDirectABI) {
513 std::string buffer;
514 llvm::raw_string_ostream out(buffer);
515 CGM.getCXXABI().getMangleContext().mangleObjCMethodName(
516 MD: OMD, OS&: out, /*includePrefixByte=*/true, includeCategoryNamespace: includeCategoryName, useDirectABI);
517 return buffer;
518}
519