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, 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->getClassInterface(), 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(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(InterfaceTy);
64  QualType IvarTy =
65      Ivar->getUsageType(ObjectPtrTy).withCVRQualifiers(CVRQualifiers);
66  llvm::Type *LTy = CGF.CGM.getTypes().ConvertTypeForMem(IvarTy);
67  llvm::Value *V = CGF.Builder.CreateBitCast(BaseValue, CGF.Int8PtrTy);
68  V = CGF.Builder.CreateInBoundsGEP(CGF.Int8Ty, V, Offset, "add.ptr");
69
70  if (!Ivar->isBitField()) {
71    V = CGF.Builder.CreateBitCast(V, llvm::PointerType::getUnqual(LTy));
72    LValue LV = CGF.MakeNaturalAlignAddrLValue(V, IvarTy);
73    return LV;
74  }
75
76  // We need to compute an access strategy for this bit-field. We are given the
77  // offset to the first byte in the bit-field, the sub-byte offset is taken
78  // from the original layout. We reuse the normal bit-field access strategy by
79  // treating this as an access to a struct where the bit-field is in byte 0,
80  // and adjust the containing type size as appropriate.
81  //
82  // FIXME: Note that currently we make a very conservative estimate of the
83  // alignment of the bit-field, because (a) it is not clear what guarantees the
84  // runtime makes us, and (b) we don't have a way to specify that the struct is
85  // at an alignment plus offset.
86  //
87  // Note, there is a subtle invariant here: we can only call this routine on
88  // non-synthesized ivars but we may be called for synthesized ivars.  However,
89  // a synthesized ivar can never be a bit-field, so this is safe.
90  uint64_t FieldBitOffset =
91      CGF.CGM.getContext().lookupFieldBitOffset(OID, nullptr, Ivar);
92  uint64_t BitOffset = FieldBitOffset % CGF.CGM.getContext().getCharWidth();
93  uint64_t AlignmentBits = CGF.CGM.getTarget().getCharAlign();
94  uint64_t BitFieldSize = Ivar->getBitWidthValue(CGF.getContext());
95  CharUnits StorageSize = CGF.CGM.getContext().toCharUnitsFromBits(
96      llvm::alignTo(BitOffset + BitFieldSize, AlignmentBits));
97  CharUnits Alignment = CGF.CGM.getContext().toCharUnitsFromBits(AlignmentBits);
98
99  // Allocate a new CGBitFieldInfo object to describe this access.
100  //
101  // FIXME: This is incredibly wasteful, these should be uniqued or part of some
102  // layout object. However, this is blocked on other cleanups to the
103  // Objective-C code, so for now we just live with allocating a bunch of these
104  // objects.
105  CGBitFieldInfo *Info = new (CGF.CGM.getContext()) CGBitFieldInfo(
106    CGBitFieldInfo::MakeInfo(CGF.CGM.getTypes(), Ivar, BitOffset, BitFieldSize,
107                             CGF.CGM.getContext().toBits(StorageSize),
108                             CharUnits::fromQuantity(0)));
109
110  Address Addr = Address(V, CGF.Int8Ty, Alignment);
111  Addr = CGF.Builder.CreateElementBitCast(Addr,
112                                   llvm::Type::getIntNTy(CGF.getLLVMContext(),
113                                                         Info->StorageSize));
114  return LValue::MakeBitfield(Addr, *Info, IvarTy,
115                              LValueBaseInfo(AlignmentSource::Decl),
116                              TBAAAccessInfo());
117}
118
119namespace {
120  struct CatchHandler {
121    const VarDecl *Variable;
122    const Stmt *Body;
123    llvm::BasicBlock *Block;
124    llvm::Constant *TypeInfo;
125    /// Flags used to differentiate cleanups and catchalls in Windows SEH
126    unsigned Flags;
127  };
128
129  struct CallObjCEndCatch final : EHScopeStack::Cleanup {
130    CallObjCEndCatch(bool MightThrow, llvm::FunctionCallee Fn)
131        : MightThrow(MightThrow), Fn(Fn) {}
132    bool MightThrow;
133    llvm::FunctionCallee Fn;
134
135    void Emit(CodeGenFunction &CGF, Flags flags) override {
136      if (MightThrow)
137        CGF.EmitRuntimeCallOrInvoke(Fn);
138      else
139        CGF.EmitNounwindRuntimeCall(Fn);
140    }
141  };
142}
143
144void CGObjCRuntime::EmitTryCatchStmt(CodeGenFunction &CGF,
145                                     const ObjCAtTryStmt &S,
146                                     llvm::FunctionCallee beginCatchFn,
147                                     llvm::FunctionCallee endCatchFn,
148                                     llvm::FunctionCallee exceptionRethrowFn) {
149  // Jump destination for falling out of catch bodies.
150  CodeGenFunction::JumpDest Cont;
151  if (S.getNumCatchStmts())
152    Cont = CGF.getJumpDestInCurrentScope("eh.cont");
153
154  bool useFunclets = EHPersonality::get(CGF).usesFuncletPads();
155
156  CodeGenFunction::FinallyInfo FinallyInfo;
157  if (!useFunclets)
158    if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt())
159      FinallyInfo.enter(CGF, Finally->getFinallyBody(),
160                        beginCatchFn, endCatchFn, exceptionRethrowFn);
161
162  SmallVector<CatchHandler, 8> Handlers;
163
164
165  // Enter the catch, if there is one.
166  if (S.getNumCatchStmts()) {
167    for (const ObjCAtCatchStmt *CatchStmt : S.catch_stmts()) {
168      const VarDecl *CatchDecl = CatchStmt->getCatchParamDecl();
169
170      Handlers.push_back(CatchHandler());
171      CatchHandler &Handler = Handlers.back();
172      Handler.Variable = CatchDecl;
173      Handler.Body = CatchStmt->getCatchBody();
174      Handler.Block = CGF.createBasicBlock("catch");
175      Handler.Flags = 0;
176
177      // @catch(...) always matches.
178      if (!CatchDecl) {
179        auto catchAll = getCatchAllTypeInfo();
180        Handler.TypeInfo = catchAll.RTTI;
181        Handler.Flags = catchAll.Flags;
182        // Don't consider any other catches.
183        break;
184      }
185
186      Handler.TypeInfo = GetEHType(CatchDecl->getType());
187    }
188
189    EHCatchScope *Catch = CGF.EHStack.pushCatch(Handlers.size());
190    for (unsigned I = 0, E = Handlers.size(); I != E; ++I)
191      Catch->setHandler(I, { Handlers[I].TypeInfo, Handlers[I].Flags }, Handlers[I].Block);
192  }
193
194  if (useFunclets)
195    if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt()) {
196        CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);
197        if (!CGF.CurSEHParent)
198            CGF.CurSEHParent = cast<NamedDecl>(CGF.CurFuncDecl);
199        // Outline the finally block.
200        const Stmt *FinallyBlock = Finally->getFinallyBody();
201        HelperCGF.startOutlinedSEHHelper(CGF, /*isFilter*/false, FinallyBlock);
202
203        // Emit the original filter expression, convert to i32, and return.
204        HelperCGF.EmitStmt(FinallyBlock);
205
206        HelperCGF.FinishFunction(FinallyBlock->getEndLoc());
207
208        llvm::Function *FinallyFunc = HelperCGF.CurFn;
209
210
211        // Push a cleanup for __finally blocks.
212        CGF.pushSEHCleanup(NormalAndEHCleanup, FinallyFunc);
213    }
214
215
216  // Emit the try body.
217  CGF.EmitStmt(S.getTryBody());
218
219  // Leave the try.
220  if (S.getNumCatchStmts())
221    CGF.popCatchScope();
222
223  // Remember where we were.
224  CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();
225
226  // Emit the handlers.
227  for (unsigned I = 0, E = Handlers.size(); I != E; ++I) {
228    CatchHandler &Handler = Handlers[I];
229
230    CGF.EmitBlock(Handler.Block);
231
232    CodeGenFunction::LexicalScope Cleanups(CGF, Handler.Body->getSourceRange());
233    SaveAndRestore RevertAfterScope(CGF.CurrentFuncletPad);
234    if (useFunclets) {
235      llvm::Instruction *CPICandidate = Handler.Block->getFirstNonPHI();
236      if (auto *CPI = dyn_cast_or_null<llvm::CatchPadInst>(CPICandidate)) {
237        CGF.CurrentFuncletPad = CPI;
238        CPI->setOperand(2, CGF.getExceptionSlot().getPointer());
239        CGF.EHStack.pushCleanup<CatchRetScope>(NormalCleanup, CPI);
240      }
241    }
242
243    llvm::Value *RawExn = CGF.getExceptionFromSlot();
244
245    // Enter the catch.
246    llvm::Value *Exn = RawExn;
247    if (beginCatchFn)
248      Exn = CGF.EmitNounwindRuntimeCall(beginCatchFn, RawExn, "exn.adjusted");
249
250    if (endCatchFn) {
251      // Add a cleanup to leave the catch.
252      bool EndCatchMightThrow = (Handler.Variable == nullptr);
253
254      CGF.EHStack.pushCleanup<CallObjCEndCatch>(NormalAndEHCleanup,
255                                                EndCatchMightThrow,
256                                                endCatchFn);
257    }
258
259    // Bind the catch parameter if it exists.
260    if (const VarDecl *CatchParam = Handler.Variable) {
261      llvm::Type *CatchType = CGF.ConvertType(CatchParam->getType());
262      llvm::Value *CastExn = CGF.Builder.CreateBitCast(Exn, CatchType);
263
264      CGF.EmitAutoVarDecl(*CatchParam);
265      EmitInitOfCatchParam(CGF, CastExn, CatchParam);
266    }
267
268    CGF.ObjCEHValueStack.push_back(Exn);
269    CGF.EmitStmt(Handler.Body);
270    CGF.ObjCEHValueStack.pop_back();
271
272    // Leave any cleanups associated with the catch.
273    Cleanups.ForceCleanup();
274
275    CGF.EmitBranchThroughCleanup(Cont);
276  }
277
278  // Go back to the try-statement fallthrough.
279  CGF.Builder.restoreIP(SavedIP);
280
281  // Pop out of the finally.
282  if (!useFunclets && S.getFinallyStmt())
283    FinallyInfo.exit(CGF);
284
285  if (Cont.isValid())
286    CGF.EmitBlock(Cont.getBlock());
287}
288
289void CGObjCRuntime::EmitInitOfCatchParam(CodeGenFunction &CGF,
290                                         llvm::Value *exn,
291                                         const VarDecl *paramDecl) {
292
293  Address paramAddr = CGF.GetAddrOfLocalVar(paramDecl);
294
295  switch (paramDecl->getType().getQualifiers().getObjCLifetime()) {
296  case Qualifiers::OCL_Strong:
297    exn = CGF.EmitARCRetainNonBlock(exn);
298    [[fallthrough]];
299
300  case Qualifiers::OCL_None:
301  case Qualifiers::OCL_ExplicitNone:
302  case Qualifiers::OCL_Autoreleasing:
303    CGF.Builder.CreateStore(exn, paramAddr);
304    return;
305
306  case Qualifiers::OCL_Weak:
307    CGF.EmitARCInitWeak(paramAddr, exn);
308    return;
309  }
310  llvm_unreachable("invalid ownership qualifier");
311}
312
313namespace {
314  struct CallSyncExit final : EHScopeStack::Cleanup {
315    llvm::FunctionCallee SyncExitFn;
316    llvm::Value *SyncArg;
317    CallSyncExit(llvm::FunctionCallee SyncExitFn, llvm::Value *SyncArg)
318        : SyncExitFn(SyncExitFn), SyncArg(SyncArg) {}
319
320    void Emit(CodeGenFunction &CGF, Flags flags) override {
321      CGF.EmitNounwindRuntimeCall(SyncExitFn, SyncArg);
322    }
323  };
324}
325
326void CGObjCRuntime::EmitAtSynchronizedStmt(CodeGenFunction &CGF,
327                                           const ObjCAtSynchronizedStmt &S,
328                                           llvm::FunctionCallee syncEnterFn,
329                                           llvm::FunctionCallee syncExitFn) {
330  CodeGenFunction::RunCleanupsScope cleanups(CGF);
331
332  // Evaluate the lock operand.  This is guaranteed to dominate the
333  // ARC release and lock-release cleanups.
334  const Expr *lockExpr = S.getSynchExpr();
335  llvm::Value *lock;
336  if (CGF.getLangOpts().ObjCAutoRefCount) {
337    lock = CGF.EmitARCRetainScalarExpr(lockExpr);
338    lock = CGF.EmitObjCConsumeObject(lockExpr->getType(), lock);
339  } else {
340    lock = CGF.EmitScalarExpr(lockExpr);
341  }
342  lock = CGF.Builder.CreateBitCast(lock, CGF.VoidPtrTy);
343
344  // Acquire the lock.
345  CGF.Builder.CreateCall(syncEnterFn, lock)->setDoesNotThrow();
346
347  // Register an all-paths cleanup to release the lock.
348  CGF.EHStack.pushCleanup<CallSyncExit>(NormalAndEHCleanup, syncExitFn, lock);
349
350  // Emit the body of the statement.
351  CGF.EmitStmt(S.getSynchBody());
352}
353
354/// Compute the pointer-to-function type to which a message send
355/// should be casted in order to correctly call the given method
356/// with the given arguments.
357///
358/// \param method - may be null
359/// \param resultType - the result type to use if there's no method
360/// \param callArgs - the actual arguments, including implicit ones
361CGObjCRuntime::MessageSendInfo
362CGObjCRuntime::getMessageSendInfo(const ObjCMethodDecl *method,
363                                  QualType resultType,
364                                  CallArgList &callArgs) {
365  unsigned ProgramAS = CGM.getDataLayout().getProgramAddressSpace();
366
367  // If there's a method, use information from that.
368  if (method) {
369    const CGFunctionInfo &signature =
370      CGM.getTypes().arrangeObjCMessageSendSignature(method, callArgs[0].Ty);
371
372    llvm::PointerType *signatureType =
373      CGM.getTypes().GetFunctionType(signature)->getPointerTo(ProgramAS);
374
375    const CGFunctionInfo &signatureForCall =
376      CGM.getTypes().arrangeCall(signature, callArgs);
377
378    return MessageSendInfo(signatureForCall, signatureType);
379  }
380
381  // There's no method;  just use a default CC.
382  const CGFunctionInfo &argsInfo =
383    CGM.getTypes().arrangeUnprototypedObjCMessageSend(resultType, callArgs);
384
385  // Derive the signature to call from that.
386  llvm::PointerType *signatureType =
387    CGM.getTypes().GetFunctionType(argsInfo)->getPointerTo(ProgramAS);
388  return MessageSendInfo(argsInfo, signatureType);
389}
390
391bool CGObjCRuntime::canMessageReceiverBeNull(CodeGenFunction &CGF,
392                                             const ObjCMethodDecl *method,
393                                             bool isSuper,
394                                       const ObjCInterfaceDecl *classReceiver,
395                                             llvm::Value *receiver) {
396  // Super dispatch assumes that self is non-null; even the messenger
397  // doesn't have a null check internally.
398  if (isSuper)
399    return false;
400
401  // If this is a direct dispatch of a class method, check whether the class,
402  // or anything in its hierarchy, was weak-linked.
403  if (classReceiver && method && method->isClassMethod())
404    return isWeakLinkedClass(classReceiver);
405
406  // If we're emitting a method, and self is const (meaning just ARC, for now),
407  // and the receiver is a load of self, then self is a valid object.
408  if (auto curMethod =
409               dyn_cast_or_null<ObjCMethodDecl>(CGF.CurCodeDecl)) {
410    auto self = curMethod->getSelfDecl();
411    if (self->getType().isConstQualified()) {
412      if (auto LI = dyn_cast<llvm::LoadInst>(receiver->stripPointerCasts())) {
413        llvm::Value *selfAddr = CGF.GetAddrOfLocalVar(self).getPointer();
414        if (selfAddr == LI->getPointerOperand()) {
415          return false;
416        }
417      }
418    }
419  }
420
421  // Otherwise, assume it can be null.
422  return true;
423}
424
425bool CGObjCRuntime::isWeakLinkedClass(const ObjCInterfaceDecl *ID) {
426  do {
427    if (ID->isWeakImported())
428      return true;
429  } while ((ID = ID->getSuperClass()));
430
431  return false;
432}
433
434void CGObjCRuntime::destroyCalleeDestroyedArguments(CodeGenFunction &CGF,
435                                              const ObjCMethodDecl *method,
436                                              const CallArgList &callArgs) {
437  CallArgList::const_iterator I = callArgs.begin();
438  for (auto i = method->param_begin(), e = method->param_end();
439         i != e; ++i, ++I) {
440    const ParmVarDecl *param = (*i);
441    if (param->hasAttr<NSConsumedAttr>()) {
442      RValue RV = I->getRValue(CGF);
443      assert(RV.isScalar() &&
444             "NullReturnState::complete - arg not on object");
445      CGF.EmitARCRelease(RV.getScalarVal(), ARCImpreciseLifetime);
446    } else {
447      QualType QT = param->getType();
448      auto *RT = QT->getAs<RecordType>();
449      if (RT && RT->getDecl()->isParamDestroyedInCallee()) {
450        RValue RV = I->getRValue(CGF);
451        QualType::DestructionKind DtorKind = QT.isDestructedType();
452        switch (DtorKind) {
453        case QualType::DK_cxx_destructor:
454          CGF.destroyCXXObject(CGF, RV.getAggregateAddress(), QT);
455          break;
456        case QualType::DK_nontrivial_c_struct:
457          CGF.destroyNonTrivialCStruct(CGF, RV.getAggregateAddress(), QT);
458          break;
459        default:
460          llvm_unreachable("unexpected dtor kind");
461          break;
462        }
463      }
464    }
465  }
466}
467
468llvm::Constant *
469clang::CodeGen::emitObjCProtocolObject(CodeGenModule &CGM,
470                                       const ObjCProtocolDecl *protocol) {
471  return CGM.getObjCRuntime().GetOrEmitProtocol(protocol);
472}
473
474std::string CGObjCRuntime::getSymbolNameForMethod(const ObjCMethodDecl *OMD,
475                                                  bool includeCategoryName) {
476  std::string buffer;
477  llvm::raw_string_ostream out(buffer);
478  CGM.getCXXABI().getMangleContext().mangleObjCMethodName(OMD, out,
479                                       /*includePrefixByte=*/true,
480                                       includeCategoryName);
481  return buffer;
482}
483