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, ID: nullptr, 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(), ID: OID,
42 Ivar) /
43 CGM.getContext().getCharWidth();
44}
45
46unsigned CGObjCRuntime::ComputeBitfieldBitOffset(
47 CodeGen::CodeGenModule &CGM,
48 const ObjCInterfaceDecl *ID,
49 const ObjCIvarDecl *Ivar) {
50 return CGM.getContext().lookupFieldBitOffset(OID: ID, ID: ID->getImplementation(),
51 Ivar);
52}
53
54LValue CGObjCRuntime::EmitValueForIvarAtOffset(CodeGen::CodeGenFunction &CGF,
55 const ObjCInterfaceDecl *OID,
56 llvm::Value *BaseValue,
57 const ObjCIvarDecl *Ivar,
58 unsigned CVRQualifiers,
59 llvm::Value *Offset) {
60 // Compute (type*) ( (char *) BaseValue + Offset)
61 QualType InterfaceTy{OID->getTypeForDecl(), 0};
62 QualType ObjectPtrTy =
63 CGF.CGM.getContext().getObjCObjectPointerType(OIT: InterfaceTy);
64 QualType IvarTy =
65 Ivar->getUsageType(objectType: ObjectPtrTy).withCVRQualifiers(CVR: CVRQualifiers);
66 llvm::Value *V = BaseValue;
67 V = CGF.Builder.CreateInBoundsGEP(Ty: CGF.Int8Ty, Ptr: V, IdxList: Offset, Name: "add.ptr");
68
69 if (!Ivar->isBitField()) {
70 LValue LV = CGF.MakeNaturalAlignAddrLValue(V, T: IvarTy);
71 return LV;
72 }
73
74 // We need to compute an access strategy for this bit-field. We are given the
75 // offset to the first byte in the bit-field, the sub-byte offset is taken
76 // from the original layout. We reuse the normal bit-field access strategy by
77 // treating this as an access to a struct where the bit-field is in byte 0,
78 // and adjust the containing type size as appropriate.
79 //
80 // FIXME: Note that currently we make a very conservative estimate of the
81 // alignment of the bit-field, because (a) it is not clear what guarantees the
82 // runtime makes us, and (b) we don't have a way to specify that the struct is
83 // at an alignment plus offset.
84 //
85 // Note, there is a subtle invariant here: we can only call this routine on
86 // non-synthesized ivars but we may be called for synthesized ivars. However,
87 // a synthesized ivar can never be a bit-field, so this is safe.
88 uint64_t FieldBitOffset =
89 CGF.CGM.getContext().lookupFieldBitOffset(OID, ID: nullptr, Ivar);
90 uint64_t BitOffset = FieldBitOffset % CGF.CGM.getContext().getCharWidth();
91 uint64_t AlignmentBits = CGF.CGM.getTarget().getCharAlign();
92 uint64_t BitFieldSize = Ivar->getBitWidthValue(CGF.getContext());
93 CharUnits StorageSize = CGF.CGM.getContext().toCharUnitsFromBits(
94 BitSize: llvm::alignTo(Value: BitOffset + BitFieldSize, Align: AlignmentBits));
95 CharUnits Alignment = CGF.CGM.getContext().toCharUnitsFromBits(BitSize: AlignmentBits);
96
97 // Allocate a new CGBitFieldInfo object to describe this access.
98 //
99 // FIXME: This is incredibly wasteful, these should be uniqued or part of some
100 // layout object. However, this is blocked on other cleanups to the
101 // Objective-C code, so for now we just live with allocating a bunch of these
102 // objects.
103 CGBitFieldInfo *Info = new (CGF.CGM.getContext()) CGBitFieldInfo(
104 CGBitFieldInfo::MakeInfo(CGF.CGM.getTypes(), Ivar, BitOffset, BitFieldSize,
105 CGF.CGM.getContext().toBits(CharSize: StorageSize),
106 CharUnits::fromQuantity(Quantity: 0)));
107
108 Address Addr =
109 Address(V, llvm::Type::getIntNTy(C&: CGF.getLLVMContext(), N: Info->StorageSize),
110 Alignment);
111
112 return LValue::MakeBitfield(Addr, Info: *Info, type: IvarTy,
113 BaseInfo: LValueBaseInfo(AlignmentSource::Decl),
114 TBAAInfo: TBAAAccessInfo());
115}
116
117namespace {
118 struct CatchHandler {
119 const VarDecl *Variable;
120 const Stmt *Body;
121 llvm::BasicBlock *Block;
122 llvm::Constant *TypeInfo;
123 /// Flags used to differentiate cleanups and catchalls in Windows SEH
124 unsigned Flags;
125 };
126
127 struct CallObjCEndCatch final : EHScopeStack::Cleanup {
128 CallObjCEndCatch(bool MightThrow, llvm::FunctionCallee Fn)
129 : MightThrow(MightThrow), Fn(Fn) {}
130 bool MightThrow;
131 llvm::FunctionCallee Fn;
132
133 void Emit(CodeGenFunction &CGF, Flags flags) override {
134 if (MightThrow)
135 CGF.EmitRuntimeCallOrInvoke(callee: Fn);
136 else
137 CGF.EmitNounwindRuntimeCall(callee: Fn);
138 }
139 };
140}
141
142void CGObjCRuntime::EmitTryCatchStmt(CodeGenFunction &CGF,
143 const ObjCAtTryStmt &S,
144 llvm::FunctionCallee beginCatchFn,
145 llvm::FunctionCallee endCatchFn,
146 llvm::FunctionCallee exceptionRethrowFn) {
147 // Jump destination for falling out of catch bodies.
148 CodeGenFunction::JumpDest Cont;
149 if (S.getNumCatchStmts())
150 Cont = CGF.getJumpDestInCurrentScope(Name: "eh.cont");
151
152 bool useFunclets = EHPersonality::get(CGF).usesFuncletPads();
153
154 CodeGenFunction::FinallyInfo FinallyInfo;
155 if (!useFunclets)
156 if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt())
157 FinallyInfo.enter(CGF, Finally: Finally->getFinallyBody(),
158 beginCatchFn, endCatchFn, rethrowFn: exceptionRethrowFn);
159
160 SmallVector<CatchHandler, 8> Handlers;
161
162
163 // Enter the catch, if there is one.
164 if (S.getNumCatchStmts()) {
165 for (const ObjCAtCatchStmt *CatchStmt : S.catch_stmts()) {
166 const VarDecl *CatchDecl = CatchStmt->getCatchParamDecl();
167
168 Handlers.push_back(CatchHandler());
169 CatchHandler &Handler = Handlers.back();
170 Handler.Variable = CatchDecl;
171 Handler.Body = CatchStmt->getCatchBody();
172 Handler.Block = CGF.createBasicBlock("catch");
173 Handler.Flags = 0;
174
175 // @catch(...) always matches.
176 if (!CatchDecl) {
177 auto catchAll = getCatchAllTypeInfo();
178 Handler.TypeInfo = catchAll.RTTI;
179 Handler.Flags = catchAll.Flags;
180 // Don't consider any other catches.
181 break;
182 }
183
184 Handler.TypeInfo = GetEHType(CatchDecl->getType());
185 }
186
187 EHCatchScope *Catch = CGF.EHStack.pushCatch(NumHandlers: Handlers.size());
188 for (unsigned I = 0, E = Handlers.size(); I != E; ++I)
189 Catch->setHandler(I, Type: { .RTTI: Handlers[I].TypeInfo, .Flags: Handlers[I].Flags }, Block: Handlers[I].Block);
190 }
191
192 if (useFunclets)
193 if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt()) {
194 CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);
195 if (!CGF.CurSEHParent)
196 CGF.CurSEHParent = cast<NamedDecl>(Val: CGF.CurFuncDecl);
197 // Outline the finally block.
198 const Stmt *FinallyBlock = Finally->getFinallyBody();
199 HelperCGF.startOutlinedSEHHelper(ParentCGF&: CGF, /*isFilter*/IsFilter: false, OutlinedStmt: FinallyBlock);
200
201 // Emit the original filter expression, convert to i32, and return.
202 HelperCGF.EmitStmt(S: FinallyBlock);
203
204 HelperCGF.FinishFunction(EndLoc: FinallyBlock->getEndLoc());
205
206 llvm::Function *FinallyFunc = HelperCGF.CurFn;
207
208
209 // Push a cleanup for __finally blocks.
210 CGF.pushSEHCleanup(kind: NormalAndEHCleanup, FinallyFunc);
211 }
212
213
214 // Emit the try body.
215 CGF.EmitStmt(S: S.getTryBody());
216
217 // Leave the try.
218 if (S.getNumCatchStmts())
219 CGF.popCatchScope();
220
221 // Remember where we were.
222 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();
223
224 // Emit the handlers.
225 for (unsigned I = 0, E = Handlers.size(); I != E; ++I) {
226 CatchHandler &Handler = Handlers[I];
227
228 CGF.EmitBlock(BB: Handler.Block);
229
230 CodeGenFunction::LexicalScope Cleanups(CGF, Handler.Body->getSourceRange());
231 SaveAndRestore RevertAfterScope(CGF.CurrentFuncletPad);
232 if (useFunclets) {
233 llvm::Instruction *CPICandidate = Handler.Block->getFirstNonPHI();
234 if (auto *CPI = dyn_cast_or_null<llvm::CatchPadInst>(Val: CPICandidate)) {
235 CGF.CurrentFuncletPad = CPI;
236 CPI->setOperand(i_nocapture: 2, Val_nocapture: CGF.getExceptionSlot().getPointer());
237 CGF.EHStack.pushCleanup<CatchRetScope>(Kind: NormalCleanup, A: CPI);
238 }
239 }
240
241 llvm::Value *RawExn = CGF.getExceptionFromSlot();
242
243 // Enter the catch.
244 llvm::Value *Exn = RawExn;
245 if (beginCatchFn)
246 Exn = CGF.EmitNounwindRuntimeCall(callee: beginCatchFn, args: RawExn, name: "exn.adjusted");
247
248 if (endCatchFn) {
249 // Add a cleanup to leave the catch.
250 bool EndCatchMightThrow = (Handler.Variable == nullptr);
251
252 CGF.EHStack.pushCleanup<CallObjCEndCatch>(Kind: NormalAndEHCleanup,
253 A: EndCatchMightThrow,
254 A: endCatchFn);
255 }
256
257 // Bind the catch parameter if it exists.
258 if (const VarDecl *CatchParam = Handler.Variable) {
259 llvm::Type *CatchType = CGF.ConvertType(CatchParam->getType());
260 llvm::Value *CastExn = CGF.Builder.CreateBitCast(V: Exn, DestTy: CatchType);
261
262 CGF.EmitAutoVarDecl(D: *CatchParam);
263 EmitInitOfCatchParam(CGF, exn: CastExn, paramDecl: CatchParam);
264 }
265
266 CGF.ObjCEHValueStack.push_back(Elt: Exn);
267 CGF.EmitStmt(S: Handler.Body);
268 CGF.ObjCEHValueStack.pop_back();
269
270 // Leave any cleanups associated with the catch.
271 Cleanups.ForceCleanup();
272
273 CGF.EmitBranchThroughCleanup(Dest: Cont);
274 }
275
276 // Go back to the try-statement fallthrough.
277 CGF.Builder.restoreIP(IP: SavedIP);
278
279 // Pop out of the finally.
280 if (!useFunclets && S.getFinallyStmt())
281 FinallyInfo.exit(CGF);
282
283 if (Cont.isValid())
284 CGF.EmitBlock(BB: Cont.getBlock());
285}
286
287void CGObjCRuntime::EmitInitOfCatchParam(CodeGenFunction &CGF,
288 llvm::Value *exn,
289 const VarDecl *paramDecl) {
290
291 Address paramAddr = CGF.GetAddrOfLocalVar(VD: paramDecl);
292
293 switch (paramDecl->getType().getQualifiers().getObjCLifetime()) {
294 case Qualifiers::OCL_Strong:
295 exn = CGF.EmitARCRetainNonBlock(value: exn);
296 [[fallthrough]];
297
298 case Qualifiers::OCL_None:
299 case Qualifiers::OCL_ExplicitNone:
300 case Qualifiers::OCL_Autoreleasing:
301 CGF.Builder.CreateStore(Val: exn, Addr: paramAddr);
302 return;
303
304 case Qualifiers::OCL_Weak:
305 CGF.EmitARCInitWeak(addr: paramAddr, value: exn);
306 return;
307 }
308 llvm_unreachable("invalid ownership qualifier");
309}
310
311namespace {
312 struct CallSyncExit final : EHScopeStack::Cleanup {
313 llvm::FunctionCallee SyncExitFn;
314 llvm::Value *SyncArg;
315 CallSyncExit(llvm::FunctionCallee SyncExitFn, llvm::Value *SyncArg)
316 : SyncExitFn(SyncExitFn), SyncArg(SyncArg) {}
317
318 void Emit(CodeGenFunction &CGF, Flags flags) override {
319 CGF.EmitNounwindRuntimeCall(callee: SyncExitFn, args: SyncArg);
320 }
321 };
322}
323
324void CGObjCRuntime::EmitAtSynchronizedStmt(CodeGenFunction &CGF,
325 const ObjCAtSynchronizedStmt &S,
326 llvm::FunctionCallee syncEnterFn,
327 llvm::FunctionCallee syncExitFn) {
328 CodeGenFunction::RunCleanupsScope cleanups(CGF);
329
330 // Evaluate the lock operand. This is guaranteed to dominate the
331 // ARC release and lock-release cleanups.
332 const Expr *lockExpr = S.getSynchExpr();
333 llvm::Value *lock;
334 if (CGF.getLangOpts().ObjCAutoRefCount) {
335 lock = CGF.EmitARCRetainScalarExpr(expr: lockExpr);
336 lock = CGF.EmitObjCConsumeObject(T: lockExpr->getType(), Ptr: lock);
337 } else {
338 lock = CGF.EmitScalarExpr(E: lockExpr);
339 }
340 lock = CGF.Builder.CreateBitCast(V: lock, DestTy: CGF.VoidPtrTy);
341
342 // Acquire the lock.
343 CGF.Builder.CreateCall(Callee: syncEnterFn, Args: lock)->setDoesNotThrow();
344
345 // Register an all-paths cleanup to release the lock.
346 CGF.EHStack.pushCleanup<CallSyncExit>(Kind: NormalAndEHCleanup, A: syncExitFn, A: lock);
347
348 // Emit the body of the statement.
349 CGF.EmitStmt(S.getSynchBody());
350}
351
352/// Compute the pointer-to-function type to which a message send
353/// should be casted in order to correctly call the given method
354/// with the given arguments.
355///
356/// \param method - may be null
357/// \param resultType - the result type to use if there's no method
358/// \param callArgs - the actual arguments, including implicit ones
359CGObjCRuntime::MessageSendInfo
360CGObjCRuntime::getMessageSendInfo(const ObjCMethodDecl *method,
361 QualType resultType,
362 CallArgList &callArgs) {
363 unsigned ProgramAS = CGM.getDataLayout().getProgramAddressSpace();
364
365 llvm::PointerType *signatureType =
366 llvm::PointerType::get(C&: CGM.getLLVMContext(), AddressSpace: ProgramAS);
367
368 // If there's a method, use information from that.
369 if (method) {
370 const CGFunctionInfo &signature =
371 CGM.getTypes().arrangeObjCMessageSendSignature(MD: method, receiverType: callArgs[0].Ty);
372
373 const CGFunctionInfo &signatureForCall =
374 CGM.getTypes().arrangeCall(declFI: signature, args: callArgs);
375
376 return MessageSendInfo(signatureForCall, signatureType);
377 }
378
379 // There's no method; just use a default CC.
380 const CGFunctionInfo &argsInfo =
381 CGM.getTypes().arrangeUnprototypedObjCMessageSend(returnType: resultType, args: callArgs);
382
383 return MessageSendInfo(argsInfo, signatureType);
384}
385
386bool CGObjCRuntime::canMessageReceiverBeNull(CodeGenFunction &CGF,
387 const ObjCMethodDecl *method,
388 bool isSuper,
389 const ObjCInterfaceDecl *classReceiver,
390 llvm::Value *receiver) {
391 // Super dispatch assumes that self is non-null; even the messenger
392 // doesn't have a null check internally.
393 if (isSuper)
394 return false;
395
396 // If this is a direct dispatch of a class method, check whether the class,
397 // or anything in its hierarchy, was weak-linked.
398 if (classReceiver && method && method->isClassMethod())
399 return isWeakLinkedClass(cls: classReceiver);
400
401 // If we're emitting a method, and self is const (meaning just ARC, for now),
402 // and the receiver is a load of self, then self is a valid object.
403 if (auto curMethod =
404 dyn_cast_or_null<ObjCMethodDecl>(Val: CGF.CurCodeDecl)) {
405 auto self = curMethod->getSelfDecl();
406 if (self->getType().isConstQualified()) {
407 if (auto LI = dyn_cast<llvm::LoadInst>(Val: receiver->stripPointerCasts())) {
408 llvm::Value *selfAddr = CGF.GetAddrOfLocalVar(self).getPointer();
409 if (selfAddr == LI->getPointerOperand()) {
410 return false;
411 }
412 }
413 }
414 }
415
416 // Otherwise, assume it can be null.
417 return true;
418}
419
420bool CGObjCRuntime::isWeakLinkedClass(const ObjCInterfaceDecl *ID) {
421 do {
422 if (ID->isWeakImported())
423 return true;
424 } while ((ID = ID->getSuperClass()));
425
426 return false;
427}
428
429void CGObjCRuntime::destroyCalleeDestroyedArguments(CodeGenFunction &CGF,
430 const ObjCMethodDecl *method,
431 const CallArgList &callArgs) {
432 CallArgList::const_iterator I = callArgs.begin();
433 for (auto i = method->param_begin(), e = method->param_end();
434 i != e; ++i, ++I) {
435 const ParmVarDecl *param = (*i);
436 if (param->hasAttr<NSConsumedAttr>()) {
437 RValue RV = I->getRValue(CGF);
438 assert(RV.isScalar() &&
439 "NullReturnState::complete - arg not on object");
440 CGF.EmitARCRelease(value: RV.getScalarVal(), precise: ARCImpreciseLifetime);
441 } else {
442 QualType QT = param->getType();
443 auto *RT = QT->getAs<RecordType>();
444 if (RT && RT->getDecl()->isParamDestroyedInCallee()) {
445 RValue RV = I->getRValue(CGF);
446 QualType::DestructionKind DtorKind = QT.isDestructedType();
447 switch (DtorKind) {
448 case QualType::DK_cxx_destructor:
449 CGF.destroyCXXObject(CGF, RV.getAggregateAddress(), QT);
450 break;
451 case QualType::DK_nontrivial_c_struct:
452 CGF.destroyNonTrivialCStruct(CGF, RV.getAggregateAddress(), QT);
453 break;
454 default:
455 llvm_unreachable("unexpected dtor kind");
456 break;
457 }
458 }
459 }
460 }
461}
462
463llvm::Constant *
464clang::CodeGen::emitObjCProtocolObject(CodeGenModule &CGM,
465 const ObjCProtocolDecl *protocol) {
466 return CGM.getObjCRuntime().GetOrEmitProtocol(PD: protocol);
467}
468
469std::string CGObjCRuntime::getSymbolNameForMethod(const ObjCMethodDecl *OMD,
470 bool includeCategoryName) {
471 std::string buffer;
472 llvm::raw_string_ostream out(buffer);
473 CGM.getCXXABI().getMangleContext().mangleObjCMethodName(MD: OMD, OS&: out,
474 /*includePrefixByte=*/true,
475 includeCategoryNamespace: includeCategoryName);
476 return buffer;
477}
478

source code of clang/lib/CodeGen/CGObjCRuntime.cpp