CGObjCRuntime.cpp revision 263508 
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/Support/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, 0, 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, 0, 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                             Alignment.getQuantity()));
138
139  V = CGF.Builder.CreateBitCast(V,
140                                llvm::Type::getIntNPtrTy(CGF.getLLVMContext(),
141                                                         Info->StorageSize));
142  return LValue::MakeBitfield(V, *Info,
143                              IvarTy.withCVRQualifiers(CVRQualifiers),
144                              Alignment);
145}
146
147namespace {
148  struct CatchHandler {
149    const VarDecl *Variable;
150    const Stmt *Body;
151    llvm::BasicBlock *Block;
152    llvm::Value *TypeInfo;
153  };
154
155  struct CallObjCEndCatch : EHScopeStack::Cleanup {
156    CallObjCEndCatch(bool MightThrow, llvm::Value *Fn) :
157      MightThrow(MightThrow), Fn(Fn) {}
158    bool MightThrow;
159    llvm::Value *Fn;
160
161    void Emit(CodeGenFunction &CGF, Flags flags) {
162      if (!MightThrow) {
163        CGF.Builder.CreateCall(Fn)->setDoesNotThrow();
164        return;
165      }
166
167      CGF.EmitRuntimeCallOrInvoke(Fn);
168    }
169  };
170}
171
172
173void CGObjCRuntime::EmitTryCatchStmt(CodeGenFunction &CGF,
174                                     const ObjCAtTryStmt &S,
175                                     llvm::Constant *beginCatchFn,
176                                     llvm::Constant *endCatchFn,
177                                     llvm::Constant *exceptionRethrowFn) {
178  // Jump destination for falling out of catch bodies.
179  CodeGenFunction::JumpDest Cont;
180  if (S.getNumCatchStmts())
181    Cont = CGF.getJumpDestInCurrentScope("eh.cont");
182
183  CodeGenFunction::FinallyInfo FinallyInfo;
184  if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt())
185    FinallyInfo.enter(CGF, Finally->getFinallyBody(),
186                      beginCatchFn, endCatchFn, exceptionRethrowFn);
187
188  SmallVector<CatchHandler, 8> Handlers;
189
190  // Enter the catch, if there is one.
191  if (S.getNumCatchStmts()) {
192    for (unsigned I = 0, N = S.getNumCatchStmts(); I != N; ++I) {
193      const ObjCAtCatchStmt *CatchStmt = S.getCatchStmt(I);
194      const VarDecl *CatchDecl = CatchStmt->getCatchParamDecl();
195
196      Handlers.push_back(CatchHandler());
197      CatchHandler &Handler = Handlers.back();
198      Handler.Variable = CatchDecl;
199      Handler.Body = CatchStmt->getCatchBody();
200      Handler.Block = CGF.createBasicBlock("catch");
201
202      // @catch(...) always matches.
203      if (!CatchDecl) {
204        Handler.TypeInfo = 0; // catch-all
205        // Don't consider any other catches.
206        break;
207      }
208
209      Handler.TypeInfo = GetEHType(CatchDecl->getType());
210    }
211
212    EHCatchScope *Catch = CGF.EHStack.pushCatch(Handlers.size());
213    for (unsigned I = 0, E = Handlers.size(); I != E; ++I)
214      Catch->setHandler(I, Handlers[I].TypeInfo, Handlers[I].Block);
215  }
216
217  // Emit the try body.
218  CGF.EmitStmt(S.getTryBody());
219
220  // Leave the try.
221  if (S.getNumCatchStmts())
222    CGF.popCatchScope();
223
224  // Remember where we were.
225  CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();
226
227  // Emit the handlers.
228  for (unsigned I = 0, E = Handlers.size(); I != E; ++I) {
229    CatchHandler &Handler = Handlers[I];
230
231    CGF.EmitBlock(Handler.Block);
232    llvm::Value *RawExn = CGF.getExceptionFromSlot();
233
234    // Enter the catch.
235    llvm::Value *Exn = RawExn;
236    if (beginCatchFn) {
237      Exn = CGF.Builder.CreateCall(beginCatchFn, RawExn, "exn.adjusted");
238      cast<llvm::CallInst>(Exn)->setDoesNotThrow();
239    }
240
241    CodeGenFunction::LexicalScope cleanups(CGF, Handler.Body->getSourceRange());
242
243    if (endCatchFn) {
244      // Add a cleanup to leave the catch.
245      bool EndCatchMightThrow = (Handler.Variable == 0);
246
247      CGF.EHStack.pushCleanup<CallObjCEndCatch>(NormalAndEHCleanup,
248                                                EndCatchMightThrow,
249                                                endCatchFn);
250    }
251
252    // Bind the catch parameter if it exists.
253    if (const VarDecl *CatchParam = Handler.Variable) {
254      llvm::Type *CatchType = CGF.ConvertType(CatchParam->getType());
255      llvm::Value *CastExn = CGF.Builder.CreateBitCast(Exn, CatchType);
256
257      CGF.EmitAutoVarDecl(*CatchParam);
258
259      llvm::Value *CatchParamAddr = CGF.GetAddrOfLocalVar(CatchParam);
260
261      switch (CatchParam->getType().getQualifiers().getObjCLifetime()) {
262      case Qualifiers::OCL_Strong:
263        CastExn = CGF.EmitARCRetainNonBlock(CastExn);
264        // fallthrough
265
266      case Qualifiers::OCL_None:
267      case Qualifiers::OCL_ExplicitNone:
268      case Qualifiers::OCL_Autoreleasing:
269        CGF.Builder.CreateStore(CastExn, CatchParamAddr);
270        break;
271
272      case Qualifiers::OCL_Weak:
273        CGF.EmitARCInitWeak(CatchParamAddr, CastExn);
274        break;
275      }
276    }
277
278    CGF.ObjCEHValueStack.push_back(Exn);
279    CGF.EmitStmt(Handler.Body);
280    CGF.ObjCEHValueStack.pop_back();
281
282    // Leave any cleanups associated with the catch.
283    cleanups.ForceCleanup();
284
285    CGF.EmitBranchThroughCleanup(Cont);
286  }
287
288  // Go back to the try-statement fallthrough.
289  CGF.Builder.restoreIP(SavedIP);
290
291  // Pop out of the finally.
292  if (S.getFinallyStmt())
293    FinallyInfo.exit(CGF);
294
295  if (Cont.isValid())
296    CGF.EmitBlock(Cont.getBlock());
297}
298
299namespace {
300  struct CallSyncExit : EHScopeStack::Cleanup {
301    llvm::Value *SyncExitFn;
302    llvm::Value *SyncArg;
303    CallSyncExit(llvm::Value *SyncExitFn, llvm::Value *SyncArg)
304      : SyncExitFn(SyncExitFn), SyncArg(SyncArg) {}
305
306    void Emit(CodeGenFunction &CGF, Flags flags) {
307      CGF.Builder.CreateCall(SyncExitFn, SyncArg)->setDoesNotThrow();
308    }
309  };
310}
311
312void CGObjCRuntime::EmitAtSynchronizedStmt(CodeGenFunction &CGF,
313                                           const ObjCAtSynchronizedStmt &S,
314                                           llvm::Function *syncEnterFn,
315                                           llvm::Function *syncExitFn) {
316  CodeGenFunction::RunCleanupsScope cleanups(CGF);
317
318  // Evaluate the lock operand.  This is guaranteed to dominate the
319  // ARC release and lock-release cleanups.
320  const Expr *lockExpr = S.getSynchExpr();
321  llvm::Value *lock;
322  if (CGF.getLangOpts().ObjCAutoRefCount) {
323    lock = CGF.EmitARCRetainScalarExpr(lockExpr);
324    lock = CGF.EmitObjCConsumeObject(lockExpr->getType(), lock);
325  } else {
326    lock = CGF.EmitScalarExpr(lockExpr);
327  }
328  lock = CGF.Builder.CreateBitCast(lock, CGF.VoidPtrTy);
329
330  // Acquire the lock.
331  CGF.Builder.CreateCall(syncEnterFn, lock)->setDoesNotThrow();
332
333  // Register an all-paths cleanup to release the lock.
334  CGF.EHStack.pushCleanup<CallSyncExit>(NormalAndEHCleanup, syncExitFn, lock);
335
336  // Emit the body of the statement.
337  CGF.EmitStmt(S.getSynchBody());
338}
339
340/// Compute the pointer-to-function type to which a message send
341/// should be casted in order to correctly call the given method
342/// with the given arguments.
343///
344/// \param method - may be null
345/// \param resultType - the result type to use if there's no method
346/// \param callArgs - the actual arguments, including implicit ones
347CGObjCRuntime::MessageSendInfo
348CGObjCRuntime::getMessageSendInfo(const ObjCMethodDecl *method,
349                                  QualType resultType,
350                                  CallArgList &callArgs) {
351  // If there's a method, use information from that.
352  if (method) {
353    const CGFunctionInfo &signature =
354      CGM.getTypes().arrangeObjCMessageSendSignature(method, callArgs[0].Ty);
355
356    llvm::PointerType *signatureType =
357      CGM.getTypes().GetFunctionType(signature)->getPointerTo();
358
359    // If that's not variadic, there's no need to recompute the ABI
360    // arrangement.
361    if (!signature.isVariadic())
362      return MessageSendInfo(signature, signatureType);
363
364    // Otherwise, there is.
365    FunctionType::ExtInfo einfo = signature.getExtInfo();
366    const CGFunctionInfo &argsInfo =
367      CGM.getTypes().arrangeFreeFunctionCall(resultType, callArgs, einfo,
368                                             signature.getRequiredArgs());
369
370    return MessageSendInfo(argsInfo, signatureType);
371  }
372
373  // There's no method;  just use a default CC.
374  const CGFunctionInfo &argsInfo =
375    CGM.getTypes().arrangeFreeFunctionCall(resultType, callArgs,
376                                           FunctionType::ExtInfo(),
377                                           RequiredArgs::All);
378
379  // Derive the signature to call from that.
380  llvm::PointerType *signatureType =
381    CGM.getTypes().GetFunctionType(argsInfo)->getPointerTo();
382  return MessageSendInfo(argsInfo, signatureType);
383}
384