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 "CGCXXABI.h"
17#include "CGCleanup.h"
18#include "CGRecordLayout.h"
19#include "CodeGenFunction.h"
20#include "CodeGenModule.h"
21#include "clang/AST/RecordLayout.h"
22#include "clang/AST/StmtObjC.h"
23#include "clang/CodeGen/CGFunctionInfo.h"
24#include "clang/CodeGen/CodeGenABITypes.h"
25#include "llvm/IR/Instruction.h"
26#include "llvm/Support/SaveAndRestore.h"
27
28using namespace clang;
29using namespace CodeGen;
30
31uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,
32 const ObjCInterfaceDecl *OID,
33 const ObjCIvarDecl *Ivar) {
34 return CGM.getContext().lookupFieldBitOffset(OID, Ivar) /
35 CGM.getContext().getCharWidth();
36}
37
38uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,
39 const ObjCImplementationDecl *OID,
40 const ObjCIvarDecl *Ivar) {
41 return CGM.getContext().lookupFieldBitOffset(OID: OID->getClassInterface(), Ivar) /
42 CGM.getContext().getCharWidth();
43}
44
45unsigned CGObjCRuntime::ComputeBitfieldBitOffset(
46 CodeGen::CodeGenModule &CGM,
47 const ObjCInterfaceDecl *ID,
48 const ObjCIvarDecl *Ivar) {
49 return CGM.getContext().lookupFieldBitOffset(OID: ID, Ivar);
50}
51
52LValue CGObjCRuntime::EmitValueForIvarAtOffset(CodeGen::CodeGenFunction &CGF,
53 const ObjCInterfaceDecl *OID,
54 llvm::Value *BaseValue,
55 const ObjCIvarDecl *Ivar,
56 unsigned CVRQualifiers,
57 llvm::Value *Offset) {
58 // Compute (type*) ( (char *) BaseValue + Offset)
59 QualType InterfaceTy{OID->getTypeForDecl(), 0};
60 QualType ObjectPtrTy =
61 CGF.CGM.getContext().getObjCObjectPointerType(OIT: InterfaceTy);
62 QualType IvarTy =
63 Ivar->getUsageType(objectType: ObjectPtrTy).withCVRQualifiers(CVR: CVRQualifiers);
64 llvm::Value *V = BaseValue;
65 V = CGF.Builder.CreateInBoundsGEP(Ty: CGF.Int8Ty, Ptr: V, IdxList: Offset, Name: "add.ptr");
66
67 if (!Ivar->isBitField()) {
68 LValue LV = CGF.MakeNaturalAlignRawAddrLValue(V, T: IvarTy);
69 return LV;
70 }
71
72 // We need to compute an access strategy for this bit-field. We are given the
73 // offset to the first byte in the bit-field, the sub-byte offset is taken
74 // from the original layout. We reuse the normal bit-field access strategy by
75 // treating this as an access to a struct where the bit-field is in byte 0,
76 // and adjust the containing type size as appropriate.
77 //
78 // FIXME: Note that currently we make a very conservative estimate of the
79 // alignment of the bit-field, because (a) it is not clear what guarantees the
80 // runtime makes us, and (b) we don't have a way to specify that the struct is
81 // at an alignment plus offset.
82 //
83 // Note, there is a subtle invariant here: we can only call this routine on
84 // non-synthesized ivars but we may be called for synthesized ivars. However,
85 // a synthesized ivar can never be a bit-field, so this is safe.
86 uint64_t FieldBitOffset =
87 CGF.CGM.getContext().lookupFieldBitOffset(OID, Ivar);
88 uint64_t BitOffset = FieldBitOffset % CGF.CGM.getContext().getCharWidth();
89 uint64_t AlignmentBits = CGF.CGM.getTarget().getCharAlign();
90 uint64_t BitFieldSize = Ivar->getBitWidthValue();
91 CharUnits StorageSize = CGF.CGM.getContext().toCharUnitsFromBits(
92 BitSize: llvm::alignTo(Value: BitOffset + BitFieldSize, Align: AlignmentBits));
93 CharUnits Alignment = CGF.CGM.getContext().toCharUnitsFromBits(BitSize: AlignmentBits);
94
95 // Allocate a new CGBitFieldInfo object to describe this access.
96 //
97 // FIXME: This is incredibly wasteful, these should be uniqued or part of some
98 // layout object. However, this is blocked on other cleanups to the
99 // Objective-C code, so for now we just live with allocating a bunch of these
100 // objects.
101 CGBitFieldInfo *Info = new (CGF.CGM.getContext()) CGBitFieldInfo(
102 CGBitFieldInfo::MakeInfo(Types&: CGF.CGM.getTypes(), FD: Ivar, Offset: BitOffset, Size: BitFieldSize,
103 StorageSize: CGF.CGM.getContext().toBits(CharSize: StorageSize),
104 StorageOffset: CharUnits::fromQuantity(Quantity: 0)));
105
106 Address Addr =
107 Address(V, llvm::Type::getIntNTy(C&: CGF.getLLVMContext(), N: Info->StorageSize),
108 Alignment);
109
110 return LValue::MakeBitfield(Addr, Info: *Info, type: IvarTy,
111 BaseInfo: LValueBaseInfo(AlignmentSource::Decl),
112 TBAAInfo: TBAAAccessInfo());
113}
114
115namespace {
116 struct CatchHandler {
117 const VarDecl *Variable;
118 const Stmt *Body;
119 llvm::BasicBlock *Block;
120 llvm::Constant *TypeInfo;
121 /// Flags used to differentiate cleanups and catchalls in Windows SEH
122 unsigned Flags;
123 };
124
125 struct CallObjCEndCatch final : EHScopeStack::Cleanup {
126 CallObjCEndCatch(bool MightThrow, llvm::FunctionCallee Fn)
127 : MightThrow(MightThrow), Fn(Fn) {}
128 bool MightThrow;
129 llvm::FunctionCallee Fn;
130
131 void Emit(CodeGenFunction &CGF, Flags flags) override {
132 if (MightThrow)
133 CGF.EmitRuntimeCallOrInvoke(callee: Fn);
134 else
135 CGF.EmitNounwindRuntimeCall(callee: Fn);
136 }
137 };
138}
139
140void CGObjCRuntime::EmitTryCatchStmt(CodeGenFunction &CGF,
141 const ObjCAtTryStmt &S,
142 llvm::FunctionCallee beginCatchFn,
143 llvm::FunctionCallee endCatchFn,
144 llvm::FunctionCallee exceptionRethrowFn) {
145 // Jump destination for falling out of catch bodies.
146 CodeGenFunction::JumpDest Cont;
147 if (S.getNumCatchStmts())
148 Cont = CGF.getJumpDestInCurrentScope(Name: "eh.cont");
149
150 bool useFunclets = EHPersonality::get(CGF).usesFuncletPads();
151
152 CodeGenFunction::FinallyInfo FinallyInfo;
153 if (!useFunclets)
154 if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt())
155 FinallyInfo.enter(CGF, Finally: Finally->getFinallyBody(),
156 beginCatchFn, endCatchFn, rethrowFn: exceptionRethrowFn);
157
158 SmallVector<CatchHandler, 8> Handlers;
159
160
161 // Enter the catch, if there is one.
162 if (S.getNumCatchStmts()) {
163 for (const ObjCAtCatchStmt *CatchStmt : S.catch_stmts()) {
164 const VarDecl *CatchDecl = CatchStmt->getCatchParamDecl();
165
166 Handlers.push_back(Elt: CatchHandler());
167 CatchHandler &Handler = Handlers.back();
168 Handler.Variable = CatchDecl;
169 Handler.Body = CatchStmt->getCatchBody();
170 Handler.Block = CGF.createBasicBlock(name: "catch");
171 Handler.Flags = 0;
172
173 // @catch(...) always matches.
174 if (!CatchDecl) {
175 auto catchAll = getCatchAllTypeInfo();
176 Handler.TypeInfo = catchAll.RTTI;
177 Handler.Flags = catchAll.Flags;
178 // Don't consider any other catches.
179 break;
180 }
181
182 Handler.TypeInfo = GetEHType(T: CatchDecl->getType());
183 }
184
185 EHCatchScope *Catch = CGF.EHStack.pushCatch(NumHandlers: Handlers.size());
186 for (unsigned I = 0, E = Handlers.size(); I != E; ++I)
187 Catch->setHandler(I, Type: { .RTTI: Handlers[I].TypeInfo, .Flags: Handlers[I].Flags }, Block: Handlers[I].Block);
188 }
189
190 if (useFunclets)
191 if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt()) {
192 CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);
193 if (!CGF.CurSEHParent)
194 CGF.CurSEHParent = cast<NamedDecl>(Val: CGF.CurFuncDecl);
195 // Outline the finally block.
196 const Stmt *FinallyBlock = Finally->getFinallyBody();
197 HelperCGF.startOutlinedSEHHelper(ParentCGF&: CGF, /*isFilter*/IsFilter: false, OutlinedStmt: FinallyBlock);
198
199 // Emit the original filter expression, convert to i32, and return.
200 HelperCGF.EmitStmt(S: FinallyBlock);
201
202 HelperCGF.FinishFunction(EndLoc: FinallyBlock->getEndLoc());
203
204 llvm::Function *FinallyFunc = HelperCGF.CurFn;
205
206
207 // Push a cleanup for __finally blocks.
208 CGF.pushSEHCleanup(kind: NormalAndEHCleanup, FinallyFunc);
209 }
210
211
212 // Emit the try body.
213 CGF.EmitStmt(S: S.getTryBody());
214
215 // Leave the try.
216 if (S.getNumCatchStmts())
217 CGF.popCatchScope();
218
219 // Remember where we were.
220 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();
221
222 // Emit the handlers.
223 for (CatchHandler &Handler : Handlers) {
224 CGF.EmitBlock(BB: Handler.Block);
225
226 CodeGenFunction::LexicalScope Cleanups(CGF, Handler.Body->getSourceRange());
227 SaveAndRestore RevertAfterScope(CGF.CurrentFuncletPad);
228 if (useFunclets) {
229 llvm::BasicBlock::iterator CPICandidate =
230 Handler.Block->getFirstNonPHIIt();
231 if (CPICandidate != Handler.Block->end()) {
232 if (auto *CPI = dyn_cast_or_null<llvm::CatchPadInst>(Val&: CPICandidate)) {
233 CGF.CurrentFuncletPad = CPI;
234 CPI->setOperand(i_nocapture: 2, Val_nocapture: CGF.getExceptionSlot().emitRawPointer(CGF));
235 CGF.EHStack.pushCleanup<CatchRetScope>(Kind: NormalCleanup, A: CPI);
236 }
237 }
238 }
239
240 llvm::Value *RawExn = CGF.getExceptionFromSlot();
241
242 // Enter the catch.
243 llvm::Value *Exn = RawExn;
244 if (beginCatchFn)
245 Exn = CGF.EmitNounwindRuntimeCall(callee: beginCatchFn, args: RawExn, name: "exn.adjusted");
246
247 if (endCatchFn) {
248 // Add a cleanup to leave the catch.
249 bool EndCatchMightThrow = (Handler.Variable == nullptr);
250
251 CGF.EHStack.pushCleanup<CallObjCEndCatch>(Kind: NormalAndEHCleanup,
252 A: EndCatchMightThrow,
253 A: endCatchFn);
254 }
255
256 // Bind the catch parameter if it exists.
257 if (const VarDecl *CatchParam = Handler.Variable) {
258 llvm::Type *CatchType = CGF.ConvertType(T: CatchParam->getType());
259 llvm::Value *CastExn = CGF.Builder.CreateBitCast(V: Exn, DestTy: CatchType);
260
261 CGF.EmitAutoVarDecl(D: *CatchParam);
262 EmitInitOfCatchParam(CGF, exn: CastExn, paramDecl: CatchParam);
263 }
264
265 CGF.ObjCEHValueStack.push_back(Elt: Exn);
266 CGF.EmitStmt(S: Handler.Body);
267 CGF.ObjCEHValueStack.pop_back();
268
269 // Leave any cleanups associated with the catch.
270 Cleanups.ForceCleanup();
271
272 CGF.EmitBranchThroughCleanup(Dest: Cont);
273 }
274
275 // Go back to the try-statement fallthrough.
276 CGF.Builder.restoreIP(IP: SavedIP);
277
278 // Pop out of the finally.
279 if (!useFunclets && S.getFinallyStmt())
280 FinallyInfo.exit(CGF);
281
282 if (Cont.isValid())
283 CGF.EmitBlock(BB: Cont.getBlock());
284}
285
286void CGObjCRuntime::EmitInitOfCatchParam(CodeGenFunction &CGF,
287 llvm::Value *exn,
288 const VarDecl *paramDecl) {
289
290 Address paramAddr = CGF.GetAddrOfLocalVar(VD: paramDecl);
291
292 switch (paramDecl->getType().getQualifiers().getObjCLifetime()) {
293 case Qualifiers::OCL_Strong:
294 exn = CGF.EmitARCRetainNonBlock(value: exn);
295 [[fallthrough]];
296
297 case Qualifiers::OCL_None:
298 case Qualifiers::OCL_ExplicitNone:
299 case Qualifiers::OCL_Autoreleasing:
300 CGF.Builder.CreateStore(Val: exn, Addr: paramAddr);
301 return;
302
303 case Qualifiers::OCL_Weak:
304 CGF.EmitARCInitWeak(addr: paramAddr, value: exn);
305 return;
306 }
307 llvm_unreachable("invalid ownership qualifier");
308}
309
310namespace {
311 struct CallSyncExit final : EHScopeStack::Cleanup {
312 llvm::FunctionCallee SyncExitFn;
313 llvm::Value *SyncArg;
314 CallSyncExit(llvm::FunctionCallee SyncExitFn, llvm::Value *SyncArg)
315 : SyncExitFn(SyncExitFn), SyncArg(SyncArg) {}
316
317 void Emit(CodeGenFunction &CGF, Flags flags) override {
318 CGF.EmitNounwindRuntimeCall(callee: SyncExitFn, args: SyncArg);
319 }
320 };
321}
322
323void CGObjCRuntime::EmitAtSynchronizedStmt(CodeGenFunction &CGF,
324 const ObjCAtSynchronizedStmt &S,
325 llvm::FunctionCallee syncEnterFn,
326 llvm::FunctionCallee syncExitFn) {
327 CodeGenFunction::RunCleanupsScope cleanups(CGF);
328
329 // Evaluate the lock operand. This is guaranteed to dominate the
330 // ARC release and lock-release cleanups.
331 const Expr *lockExpr = S.getSynchExpr();
332 llvm::Value *lock;
333 if (CGF.getLangOpts().ObjCAutoRefCount) {
334 lock = CGF.EmitARCRetainScalarExpr(expr: lockExpr);
335 lock = CGF.EmitObjCConsumeObject(T: lockExpr->getType(), Ptr: lock);
336 } else {
337 lock = CGF.EmitScalarExpr(E: lockExpr);
338 }
339 lock = CGF.Builder.CreateBitCast(V: lock, DestTy: CGF.VoidPtrTy);
340
341 // Acquire the lock.
342 CGF.Builder.CreateCall(Callee: syncEnterFn, Args: lock)->setDoesNotThrow();
343
344 // Register an all-paths cleanup to release the lock.
345 CGF.EHStack.pushCleanup<CallSyncExit>(Kind: NormalAndEHCleanup, A: syncExitFn, A: lock);
346
347 // Emit the body of the statement.
348 CGF.EmitStmt(S: S.getSynchBody());
349}
350
351/// Compute the pointer-to-function type to which a message send
352/// should be casted in order to correctly call the given method
353/// with the given arguments.
354///
355/// \param method - may be null
356/// \param resultType - the result type to use if there's no method
357/// \param callArgs - the actual arguments, including implicit ones
358CGObjCRuntime::MessageSendInfo
359CGObjCRuntime::getMessageSendInfo(const ObjCMethodDecl *method,
360 QualType resultType,
361 CallArgList &callArgs) {
362 unsigned ProgramAS = CGM.getDataLayout().getProgramAddressSpace();
363
364 llvm::PointerType *signatureType =
365 llvm::PointerType::get(C&: CGM.getLLVMContext(), AddressSpace: ProgramAS);
366
367 // If there's a method, use information from that.
368 if (method) {
369 const CGFunctionInfo &signature =
370 CGM.getTypes().arrangeObjCMessageSendSignature(MD: method, receiverType: callArgs[0].Ty);
371
372 const CGFunctionInfo &signatureForCall =
373 CGM.getTypes().arrangeCall(declFI: signature, args: callArgs);
374
375 return MessageSendInfo(signatureForCall, signatureType);
376 }
377
378 // There's no method; just use a default CC.
379 const CGFunctionInfo &argsInfo =
380 CGM.getTypes().arrangeUnprototypedObjCMessageSend(returnType: resultType, args: callArgs);
381
382 return MessageSendInfo(argsInfo, signatureType);
383}
384
385bool CGObjCRuntime::canMessageReceiverBeNull(CodeGenFunction &CGF,
386 const ObjCMethodDecl *method,
387 bool isSuper,
388 const ObjCInterfaceDecl *classReceiver,
389 llvm::Value *receiver) {
390 // Super dispatch assumes that self is non-null; even the messenger
391 // doesn't have a null check internally.
392 if (isSuper)
393 return false;
394
395 // If this is a direct dispatch of a class method, check whether the class,
396 // or anything in its hierarchy, was weak-linked.
397 if (classReceiver && method && method->isClassMethod())
398 return isWeakLinkedClass(cls: classReceiver);
399
400 // If we're emitting a method, and self is const (meaning just ARC, for now),
401 // and the receiver is a load of self, then self is a valid object.
402 if (auto curMethod =
403 dyn_cast_or_null<ObjCMethodDecl>(Val: CGF.CurCodeDecl)) {
404 auto self = curMethod->getSelfDecl();
405 if (self->getType().isConstQualified()) {
406 if (auto LI = dyn_cast<llvm::LoadInst>(Val: receiver->stripPointerCasts())) {
407 llvm::Value *selfAddr = CGF.GetAddrOfLocalVar(VD: self).emitRawPointer(CGF);
408 if (selfAddr == LI->getPointerOperand()) {
409 return false;
410 }
411 }
412 }
413 }
414
415 // Otherwise, assume it can be null.
416 return true;
417}
418
419bool CGObjCRuntime::isWeakLinkedClass(const ObjCInterfaceDecl *ID) {
420 do {
421 if (ID->isWeakImported())
422 return true;
423 } while ((ID = ID->getSuperClass()));
424
425 return false;
426}
427
428void CGObjCRuntime::destroyCalleeDestroyedArguments(CodeGenFunction &CGF,
429 const ObjCMethodDecl *method,
430 const CallArgList &callArgs) {
431 CallArgList::const_iterator I = callArgs.begin();
432 for (auto i = method->param_begin(), e = method->param_end();
433 i != e; ++i, ++I) {
434 const ParmVarDecl *param = (*i);
435 if (param->hasAttr<NSConsumedAttr>()) {
436 RValue RV = I->getRValue(CGF);
437 assert(RV.isScalar() &&
438 "NullReturnState::complete - arg not on object");
439 CGF.EmitARCRelease(value: RV.getScalarVal(), precise: ARCImpreciseLifetime);
440 } else {
441 QualType QT = param->getType();
442 auto *RT = QT->getAs<RecordType>();
443 if (RT && RT->getDecl()->isParamDestroyedInCallee()) {
444 RValue RV = I->getRValue(CGF);
445 QualType::DestructionKind DtorKind = QT.isDestructedType();
446 switch (DtorKind) {
447 case QualType::DK_cxx_destructor:
448 CGF.destroyCXXObject(CGF, RV.getAggregateAddress(), QT);
449 break;
450 case QualType::DK_nontrivial_c_struct:
451 CGF.destroyNonTrivialCStruct(CGF, RV.getAggregateAddress(), QT);
452 break;
453 default:
454 llvm_unreachable("unexpected dtor kind");
455 break;
456 }
457 }
458 }
459 }
460}
461
462llvm::Constant *
463clang::CodeGen::emitObjCProtocolObject(CodeGenModule &CGM,
464 const ObjCProtocolDecl *protocol) {
465 return CGM.getObjCRuntime().GetOrEmitProtocol(PD: protocol);
466}
467
468std::string CGObjCRuntime::getSymbolNameForMethod(const ObjCMethodDecl *OMD,
469 bool includeCategoryName) {
470 std::string buffer;
471 llvm::raw_string_ostream out(buffer);
472 CGM.getCXXABI().getMangleContext().mangleObjCMethodName(MD: OMD, OS&: out,
473 /*includePrefixByte=*/true,
474 includeCategoryNamespace: includeCategoryName);
475 return buffer;
476}
477