1//==- CGObjCRuntime.cpp - Interface to Shared Objective-C Runtime Features ==//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This abstract class defines the interface for Objective-C runtime-specific
11// code generation.  It provides some concrete helper methods for functionality
12// shared between all (or most) of the Objective-C runtimes supported by clang.
13//
14//===----------------------------------------------------------------------===//
15
16#include "CGObjCRuntime.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 "llvm/IR/CallSite.h"
25
26using namespace clang;
27using namespace CodeGen;
28
29static uint64_t LookupFieldBitOffset(CodeGen::CodeGenModule &CGM,
30                                     const ObjCInterfaceDecl *OID,
31                                     const ObjCImplementationDecl *ID,
32                                     const ObjCIvarDecl *Ivar) {
33  const ObjCInterfaceDecl *Container = Ivar->getContainingInterface();
34
35  // FIXME: We should eliminate the need to have ObjCImplementationDecl passed
36  // in here; it should never be necessary because that should be the lexical
37  // decl context for the ivar.
38
39  // If we know have an implementation (and the ivar is in it) then
40  // look up in the implementation layout.
41  const ASTRecordLayout *RL;
42  if (ID && declaresSameEntity(ID->getClassInterface(), Container))
43    RL = &CGM.getContext().getASTObjCImplementationLayout(ID);
44  else
45    RL = &CGM.getContext().getASTObjCInterfaceLayout(Container);
46
47  // Compute field index.
48  //
49  // FIXME: The index here is closely tied to how ASTContext::getObjCLayout is
50  // implemented. This should be fixed to get the information from the layout
51  // directly.
52  unsigned Index = 0;
53
54  for (const ObjCIvarDecl *IVD = Container->all_declared_ivar_begin();
55       IVD; IVD = IVD->getNextIvar()) {
56    if (Ivar == IVD)
57      break;
58    ++Index;
59  }
60  assert(Index < RL->getFieldCount() && "Ivar is not inside record layout!");
61
62  return RL->getFieldOffset(Index);
63}
64
65uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,
66                                              const ObjCInterfaceDecl *OID,
67                                              const ObjCIvarDecl *Ivar) {
68  return LookupFieldBitOffset(CGM, OID, nullptr, Ivar) /
69    CGM.getContext().getCharWidth();
70}
71
72uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,
73                                              const ObjCImplementationDecl *OID,
74                                              const ObjCIvarDecl *Ivar) {
75  return LookupFieldBitOffset(CGM, OID->getClassInterface(), OID, Ivar) /
76    CGM.getContext().getCharWidth();
77}
78
79unsigned CGObjCRuntime::ComputeBitfieldBitOffset(
80    CodeGen::CodeGenModule &CGM,
81    const ObjCInterfaceDecl *ID,
82    const ObjCIvarDecl *Ivar) {
83  return LookupFieldBitOffset(CGM, ID, ID->getImplementation(), Ivar);
84}
85
86LValue CGObjCRuntime::EmitValueForIvarAtOffset(CodeGen::CodeGenFunction &CGF,
87                                               const ObjCInterfaceDecl *OID,
88                                               llvm::Value *BaseValue,
89                                               const ObjCIvarDecl *Ivar,
90                                               unsigned CVRQualifiers,
91                                               llvm::Value *Offset) {
92  // Compute (type*) ( (char *) BaseValue + Offset)
93  QualType IvarTy = Ivar->getType();
94  llvm::Type *LTy = CGF.CGM.getTypes().ConvertTypeForMem(IvarTy);
95  llvm::Value *V = CGF.Builder.CreateBitCast(BaseValue, CGF.Int8PtrTy);
96  V = CGF.Builder.CreateInBoundsGEP(V, Offset, "add.ptr");
97
98  if (!Ivar->isBitField()) {
99    V = CGF.Builder.CreateBitCast(V, llvm::PointerType::getUnqual(LTy));
100    LValue LV = CGF.MakeNaturalAlignAddrLValue(V, IvarTy);
101    LV.getQuals().addCVRQualifiers(CVRQualifiers);
102    return LV;
103  }
104
105  // We need to compute an access strategy for this bit-field. We are given the
106  // offset to the first byte in the bit-field, the sub-byte offset is taken
107  // from the original layout. We reuse the normal bit-field access strategy by
108  // treating this as an access to a struct where the bit-field is in byte 0,
109  // and adjust the containing type size as appropriate.
110  //
111  // FIXME: Note that currently we make a very conservative estimate of the
112  // alignment of the bit-field, because (a) it is not clear what guarantees the
113  // runtime makes us, and (b) we don't have a way to specify that the struct is
114  // at an alignment plus offset.
115  //
116  // Note, there is a subtle invariant here: we can only call this routine on
117  // non-synthesized ivars but we may be called for synthesized ivars.  However,
118  // a synthesized ivar can never be a bit-field, so this is safe.
119  uint64_t FieldBitOffset = LookupFieldBitOffset(CGF.CGM, OID, nullptr, Ivar);
120  uint64_t BitOffset = FieldBitOffset % CGF.CGM.getContext().getCharWidth();
121  uint64_t AlignmentBits = CGF.CGM.getTarget().getCharAlign();
122  uint64_t BitFieldSize = Ivar->getBitWidthValue(CGF.getContext());
123  CharUnits StorageSize =
124    CGF.CGM.getContext().toCharUnitsFromBits(
125      llvm::RoundUpToAlignment(BitOffset + BitFieldSize, AlignmentBits));
126  CharUnits Alignment = CGF.CGM.getContext().toCharUnitsFromBits(AlignmentBits);
127
128  // Allocate a new CGBitFieldInfo object to describe this access.
129  //
130  // FIXME: This is incredibly wasteful, these should be uniqued or part of some
131  // layout object. However, this is blocked on other cleanups to the
132  // Objective-C code, so for now we just live with allocating a bunch of these
133  // objects.
134  CGBitFieldInfo *Info = new (CGF.CGM.getContext()) CGBitFieldInfo(
135    CGBitFieldInfo::MakeInfo(CGF.CGM.getTypes(), Ivar, BitOffset, BitFieldSize,
136                             CGF.CGM.getContext().toBits(StorageSize),
137                             CharUnits::fromQuantity(0)));
138
139  Address Addr(V, Alignment);
140  Addr = CGF.Builder.CreateElementBitCast(Addr,
141                                   llvm::Type::getIntNTy(CGF.getLLVMContext(),
142                                                         Info->StorageSize));
143  return LValue::MakeBitfield(Addr, *Info,
144                              IvarTy.withCVRQualifiers(CVRQualifiers),
145                              AlignmentSource::Decl);
146}
147
148namespace {
149  struct CatchHandler {
150    const VarDecl *Variable;
151    const Stmt *Body;
152    llvm::BasicBlock *Block;
153    llvm::Constant *TypeInfo;
154  };
155
156  struct CallObjCEndCatch final : EHScopeStack::Cleanup {
157    CallObjCEndCatch(bool MightThrow, llvm::Value *Fn) :
158      MightThrow(MightThrow), Fn(Fn) {}
159    bool MightThrow;
160    llvm::Value *Fn;
161
162    void Emit(CodeGenFunction &CGF, Flags flags) override {
163      if (!MightThrow) {
164        CGF.Builder.CreateCall(Fn)->setDoesNotThrow();
165        return;
166      }
167
168      CGF.EmitRuntimeCallOrInvoke(Fn);
169    }
170  };
171}
172
173
174void CGObjCRuntime::EmitTryCatchStmt(CodeGenFunction &CGF,
175                                     const ObjCAtTryStmt &S,
176                                     llvm::Constant *beginCatchFn,
177                                     llvm::Constant *endCatchFn,
178                                     llvm::Constant *exceptionRethrowFn) {
179  // Jump destination for falling out of catch bodies.
180  CodeGenFunction::JumpDest Cont;
181  if (S.getNumCatchStmts())
182    Cont = CGF.getJumpDestInCurrentScope("eh.cont");
183
184  CodeGenFunction::FinallyInfo FinallyInfo;
185  if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt())
186    FinallyInfo.enter(CGF, Finally->getFinallyBody(),
187                      beginCatchFn, endCatchFn, exceptionRethrowFn);
188
189  SmallVector<CatchHandler, 8> Handlers;
190
191  // Enter the catch, if there is one.
192  if (S.getNumCatchStmts()) {
193    for (unsigned I = 0, N = S.getNumCatchStmts(); I != N; ++I) {
194      const ObjCAtCatchStmt *CatchStmt = S.getCatchStmt(I);
195      const VarDecl *CatchDecl = CatchStmt->getCatchParamDecl();
196
197      Handlers.push_back(CatchHandler());
198      CatchHandler &Handler = Handlers.back();
199      Handler.Variable = CatchDecl;
200      Handler.Body = CatchStmt->getCatchBody();
201      Handler.Block = CGF.createBasicBlock("catch");
202
203      // @catch(...) always matches.
204      if (!CatchDecl) {
205        Handler.TypeInfo = nullptr; // catch-all
206        // Don't consider any other catches.
207        break;
208      }
209
210      Handler.TypeInfo = GetEHType(CatchDecl->getType());
211    }
212
213    EHCatchScope *Catch = CGF.EHStack.pushCatch(Handlers.size());
214    for (unsigned I = 0, E = Handlers.size(); I != E; ++I)
215      Catch->setHandler(I, Handlers[I].TypeInfo, Handlers[I].Block);
216  }
217
218  // Emit the try body.
219  CGF.EmitStmt(S.getTryBody());
220
221  // Leave the try.
222  if (S.getNumCatchStmts())
223    CGF.popCatchScope();
224
225  // Remember where we were.
226  CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();
227
228  // Emit the handlers.
229  for (unsigned I = 0, E = Handlers.size(); I != E; ++I) {
230    CatchHandler &Handler = Handlers[I];
231
232    CGF.EmitBlock(Handler.Block);
233    llvm::Value *RawExn = CGF.getExceptionFromSlot();
234
235    // Enter the catch.
236    llvm::Value *Exn = RawExn;
237    if (beginCatchFn) {
238      Exn = CGF.Builder.CreateCall(beginCatchFn, RawExn, "exn.adjusted");
239      cast<llvm::CallInst>(Exn)->setDoesNotThrow();
240    }
241
242    CodeGenFunction::LexicalScope cleanups(CGF, Handler.Body->getSourceRange());
243
244    if (endCatchFn) {
245      // Add a cleanup to leave the catch.
246      bool EndCatchMightThrow = (Handler.Variable == nullptr);
247
248      CGF.EHStack.pushCleanup<CallObjCEndCatch>(NormalAndEHCleanup,
249                                                EndCatchMightThrow,
250                                                endCatchFn);
251    }
252
253    // Bind the catch parameter if it exists.
254    if (const VarDecl *CatchParam = Handler.Variable) {
255      llvm::Type *CatchType = CGF.ConvertType(CatchParam->getType());
256      llvm::Value *CastExn = CGF.Builder.CreateBitCast(Exn, CatchType);
257
258      CGF.EmitAutoVarDecl(*CatchParam);
259      EmitInitOfCatchParam(CGF, CastExn, CatchParam);
260    }
261
262    CGF.ObjCEHValueStack.push_back(Exn);
263    CGF.EmitStmt(Handler.Body);
264    CGF.ObjCEHValueStack.pop_back();
265
266    // Leave any cleanups associated with the catch.
267    cleanups.ForceCleanup();
268
269    CGF.EmitBranchThroughCleanup(Cont);
270  }
271
272  // Go back to the try-statement fallthrough.
273  CGF.Builder.restoreIP(SavedIP);
274
275  // Pop out of the finally.
276  if (S.getFinallyStmt())
277    FinallyInfo.exit(CGF);
278
279  if (Cont.isValid())
280    CGF.EmitBlock(Cont.getBlock());
281}
282
283void CGObjCRuntime::EmitInitOfCatchParam(CodeGenFunction &CGF,
284                                         llvm::Value *exn,
285                                         const VarDecl *paramDecl) {
286
287  Address paramAddr = CGF.GetAddrOfLocalVar(paramDecl);
288
289  switch (paramDecl->getType().getQualifiers().getObjCLifetime()) {
290  case Qualifiers::OCL_Strong:
291    exn = CGF.EmitARCRetainNonBlock(exn);
292    // fallthrough
293
294  case Qualifiers::OCL_None:
295  case Qualifiers::OCL_ExplicitNone:
296  case Qualifiers::OCL_Autoreleasing:
297    CGF.Builder.CreateStore(exn, paramAddr);
298    return;
299
300  case Qualifiers::OCL_Weak:
301    CGF.EmitARCInitWeak(paramAddr, exn);
302    return;
303  }
304  llvm_unreachable("invalid ownership qualifier");
305}
306
307namespace {
308  struct CallSyncExit final : EHScopeStack::Cleanup {
309    llvm::Value *SyncExitFn;
310    llvm::Value *SyncArg;
311    CallSyncExit(llvm::Value *SyncExitFn, llvm::Value *SyncArg)
312      : SyncExitFn(SyncExitFn), SyncArg(SyncArg) {}
313
314    void Emit(CodeGenFunction &CGF, Flags flags) override {
315      CGF.Builder.CreateCall(SyncExitFn, SyncArg)->setDoesNotThrow();
316    }
317  };
318}
319
320void CGObjCRuntime::EmitAtSynchronizedStmt(CodeGenFunction &CGF,
321                                           const ObjCAtSynchronizedStmt &S,
322                                           llvm::Function *syncEnterFn,
323                                           llvm::Function *syncExitFn) {
324  CodeGenFunction::RunCleanupsScope cleanups(CGF);
325
326  // Evaluate the lock operand.  This is guaranteed to dominate the
327  // ARC release and lock-release cleanups.
328  const Expr *lockExpr = S.getSynchExpr();
329  llvm::Value *lock;
330  if (CGF.getLangOpts().ObjCAutoRefCount) {
331    lock = CGF.EmitARCRetainScalarExpr(lockExpr);
332    lock = CGF.EmitObjCConsumeObject(lockExpr->getType(), lock);
333  } else {
334    lock = CGF.EmitScalarExpr(lockExpr);
335  }
336  lock = CGF.Builder.CreateBitCast(lock, CGF.VoidPtrTy);
337
338  // Acquire the lock.
339  CGF.Builder.CreateCall(syncEnterFn, lock)->setDoesNotThrow();
340
341  // Register an all-paths cleanup to release the lock.
342  CGF.EHStack.pushCleanup<CallSyncExit>(NormalAndEHCleanup, syncExitFn, lock);
343
344  // Emit the body of the statement.
345  CGF.EmitStmt(S.getSynchBody());
346}
347
348/// Compute the pointer-to-function type to which a message send
349/// should be casted in order to correctly call the given method
350/// with the given arguments.
351///
352/// \param method - may be null
353/// \param resultType - the result type to use if there's no method
354/// \param callArgs - the actual arguments, including implicit ones
355CGObjCRuntime::MessageSendInfo
356CGObjCRuntime::getMessageSendInfo(const ObjCMethodDecl *method,
357                                  QualType resultType,
358                                  CallArgList &callArgs) {
359  // If there's a method, use information from that.
360  if (method) {
361    const CGFunctionInfo &signature =
362      CGM.getTypes().arrangeObjCMessageSendSignature(method, callArgs[0].Ty);
363
364    llvm::PointerType *signatureType =
365      CGM.getTypes().GetFunctionType(signature)->getPointerTo();
366
367    // If that's not variadic, there's no need to recompute the ABI
368    // arrangement.
369    if (!signature.isVariadic())
370      return MessageSendInfo(signature, signatureType);
371
372    // Otherwise, there is.
373    FunctionType::ExtInfo einfo = signature.getExtInfo();
374    const CGFunctionInfo &argsInfo =
375      CGM.getTypes().arrangeFreeFunctionCall(resultType, callArgs, einfo,
376                                             signature.getRequiredArgs());
377
378    return MessageSendInfo(argsInfo, signatureType);
379  }
380
381  // There's no method;  just use a default CC.
382  const CGFunctionInfo &argsInfo =
383    CGM.getTypes().arrangeFreeFunctionCall(resultType, callArgs,
384                                           FunctionType::ExtInfo(),
385                                           RequiredArgs::All);
386
387  // Derive the signature to call from that.
388  llvm::PointerType *signatureType =
389    CGM.getTypes().GetFunctionType(argsInfo)->getPointerTo();
390  return MessageSendInfo(argsInfo, signatureType);
391}
392