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 18 #include "CGRecordLayout.h" 19 #include "CodeGenModule.h" 20 #include "CodeGenFunction.h" 21 #include "CGCleanup.h" 22 23 #include "clang/AST/RecordLayout.h" 24 #include "clang/AST/StmtObjC.h" 25 26 #include "llvm/Support/CallSite.h" 27 28 using namespace clang; 29 using namespace CodeGen; 30 31 static uint64_t LookupFieldBitOffset(CodeGen::CodeGenModule &CGM, 32 const ObjCInterfaceDecl *OID, 33 const ObjCImplementationDecl *ID, 34 const ObjCIvarDecl *Ivar) { 35 const ObjCInterfaceDecl *Container = Ivar->getContainingInterface(); 36 37 // FIXME: We should eliminate the need to have ObjCImplementationDecl passed 38 // in here; it should never be necessary because that should be the lexical 39 // decl context for the ivar. 40 41 // If we know have an implementation (and the ivar is in it) then 42 // look up in the implementation layout. 43 const ASTRecordLayout *RL; 44 if (ID && ID->getClassInterface() == Container) 45 RL = &CGM.getContext().getASTObjCImplementationLayout(ID); 46 else 47 RL = &CGM.getContext().getASTObjCInterfaceLayout(Container); 48 49 // Compute field index. 50 // 51 // FIXME: The index here is closely tied to how ASTContext::getObjCLayout is 52 // implemented. This should be fixed to get the information from the layout 53 // directly. 54 unsigned Index = 0; 55 56 for (const ObjCIvarDecl *IVD = Container->all_declared_ivar_begin(); 57 IVD; IVD = IVD->getNextIvar()) { 58 if (Ivar == IVD) 59 break; 60 ++Index; 61 } 62 assert(Index < RL->getFieldCount() && "Ivar is not inside record layout!"); 63 64 return RL->getFieldOffset(Index); 65 } 66 67 uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM, 68 const ObjCInterfaceDecl *OID, 69 const ObjCIvarDecl *Ivar) { 70 return LookupFieldBitOffset(CGM, OID, 0, Ivar) / 71 CGM.getContext().getCharWidth(); 72 } 73 74 uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM, 75 const ObjCImplementationDecl *OID, 76 const ObjCIvarDecl *Ivar) { 77 return LookupFieldBitOffset(CGM, OID->getClassInterface(), OID, Ivar) / 78 CGM.getContext().getCharWidth(); 79 } 80 81 LValue CGObjCRuntime::EmitValueForIvarAtOffset(CodeGen::CodeGenFunction &CGF, 82 const ObjCInterfaceDecl *OID, 83 llvm::Value *BaseValue, 84 const ObjCIvarDecl *Ivar, 85 unsigned CVRQualifiers, 86 llvm::Value *Offset) { 87 // Compute (type*) ( (char *) BaseValue + Offset) 88 llvm::Type *I8Ptr = llvm::Type::getInt8PtrTy(CGF.getLLVMContext()); 89 QualType IvarTy = Ivar->getType(); 90 llvm::Type *LTy = CGF.CGM.getTypes().ConvertTypeForMem(IvarTy); 91 llvm::Value *V = CGF.Builder.CreateBitCast(BaseValue, I8Ptr); 92 V = CGF.Builder.CreateInBoundsGEP(V, Offset, "add.ptr"); 93 V = CGF.Builder.CreateBitCast(V, llvm::PointerType::getUnqual(LTy)); 94 95 if (!Ivar->isBitField()) { 96 LValue LV = CGF.MakeAddrLValue(V, IvarTy); 97 LV.getQuals().addCVRQualifiers(CVRQualifiers); 98 return LV; 99 } 100 101 // We need to compute an access strategy for this bit-field. We are given the 102 // offset to the first byte in the bit-field, the sub-byte offset is taken 103 // from the original layout. We reuse the normal bit-field access strategy by 104 // treating this as an access to a struct where the bit-field is in byte 0, 105 // and adjust the containing type size as appropriate. 106 // 107 // FIXME: Note that currently we make a very conservative estimate of the 108 // alignment of the bit-field, because (a) it is not clear what guarantees the 109 // runtime makes us, and (b) we don't have a way to specify that the struct is 110 // at an alignment plus offset. 111 // 112 // Note, there is a subtle invariant here: we can only call this routine on 113 // non-synthesized ivars but we may be called for synthesized ivars. However, 114 // a synthesized ivar can never be a bit-field, so this is safe. 115 const ASTRecordLayout &RL = 116 CGF.CGM.getContext().getASTObjCInterfaceLayout(OID); 117 uint64_t TypeSizeInBits = CGF.CGM.getContext().toBits(RL.getSize()); 118 uint64_t FieldBitOffset = LookupFieldBitOffset(CGF.CGM, OID, 0, Ivar); 119 uint64_t BitOffset = FieldBitOffset % CGF.CGM.getContext().getCharWidth(); 120 uint64_t ContainingTypeAlign = CGF.CGM.getContext().getTargetInfo().getCharAlign(); 121 uint64_t ContainingTypeSize = TypeSizeInBits - (FieldBitOffset - BitOffset); 122 uint64_t BitFieldSize = Ivar->getBitWidthValue(CGF.getContext()); 123 124 // Allocate a new CGBitFieldInfo object to describe this access. 125 // 126 // FIXME: This is incredibly wasteful, these should be uniqued or part of some 127 // layout object. However, this is blocked on other cleanups to the 128 // Objective-C code, so for now we just live with allocating a bunch of these 129 // objects. 130 CGBitFieldInfo *Info = new (CGF.CGM.getContext()) CGBitFieldInfo( 131 CGBitFieldInfo::MakeInfo(CGF.CGM.getTypes(), Ivar, BitOffset, BitFieldSize, 132 ContainingTypeSize, ContainingTypeAlign)); 133 134 return LValue::MakeBitfield(V, *Info, 135 IvarTy.withCVRQualifiers(CVRQualifiers)); 136 } 137 138 namespace { 139 struct CatchHandler { 140 const VarDecl *Variable; 141 const Stmt *Body; 142 llvm::BasicBlock *Block; 143 llvm::Value *TypeInfo; 144 }; 145 146 struct CallObjCEndCatch : EHScopeStack::Cleanup { 147 CallObjCEndCatch(bool MightThrow, llvm::Value *Fn) : 148 MightThrow(MightThrow), Fn(Fn) {} 149 bool MightThrow; 150 llvm::Value *Fn; 151 152 void Emit(CodeGenFunction &CGF, Flags flags) { 153 if (!MightThrow) { 154 CGF.Builder.CreateCall(Fn)->setDoesNotThrow(); 155 return; 156 } 157 158 CGF.EmitCallOrInvoke(Fn); 159 } 160 }; 161 } 162 163 164 void CGObjCRuntime::EmitTryCatchStmt(CodeGenFunction &CGF, 165 const ObjCAtTryStmt &S, 166 llvm::Constant *beginCatchFn, 167 llvm::Constant *endCatchFn, 168 llvm::Constant *exceptionRethrowFn) { 169 // Jump destination for falling out of catch bodies. 170 CodeGenFunction::JumpDest Cont; 171 if (S.getNumCatchStmts()) 172 Cont = CGF.getJumpDestInCurrentScope("eh.cont"); 173 174 CodeGenFunction::FinallyInfo FinallyInfo; 175 if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt()) 176 FinallyInfo.enter(CGF, Finally->getFinallyBody(), 177 beginCatchFn, endCatchFn, exceptionRethrowFn); 178 179 SmallVector<CatchHandler, 8> Handlers; 180 181 // Enter the catch, if there is one. 182 if (S.getNumCatchStmts()) { 183 for (unsigned I = 0, N = S.getNumCatchStmts(); I != N; ++I) { 184 const ObjCAtCatchStmt *CatchStmt = S.getCatchStmt(I); 185 const VarDecl *CatchDecl = CatchStmt->getCatchParamDecl(); 186 187 Handlers.push_back(CatchHandler()); 188 CatchHandler &Handler = Handlers.back(); 189 Handler.Variable = CatchDecl; 190 Handler.Body = CatchStmt->getCatchBody(); 191 Handler.Block = CGF.createBasicBlock("catch"); 192 193 // @catch(...) always matches. 194 if (!CatchDecl) { 195 Handler.TypeInfo = 0; // catch-all 196 // Don't consider any other catches. 197 break; 198 } 199 200 Handler.TypeInfo = GetEHType(CatchDecl->getType()); 201 } 202 203 EHCatchScope *Catch = CGF.EHStack.pushCatch(Handlers.size()); 204 for (unsigned I = 0, E = Handlers.size(); I != E; ++I) 205 Catch->setHandler(I, Handlers[I].TypeInfo, Handlers[I].Block); 206 } 207 208 // Emit the try body. 209 CGF.EmitStmt(S.getTryBody()); 210 211 // Leave the try. 212 if (S.getNumCatchStmts()) 213 CGF.popCatchScope(); 214 215 // Remember where we were. 216 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP(); 217 218 // Emit the handlers. 219 for (unsigned I = 0, E = Handlers.size(); I != E; ++I) { 220 CatchHandler &Handler = Handlers[I]; 221 222 CGF.EmitBlock(Handler.Block); 223 llvm::Value *RawExn = CGF.getExceptionFromSlot(); 224 225 // Enter the catch. 226 llvm::Value *Exn = RawExn; 227 if (beginCatchFn) { 228 Exn = CGF.Builder.CreateCall(beginCatchFn, RawExn, "exn.adjusted"); 229 cast<llvm::CallInst>(Exn)->setDoesNotThrow(); 230 } 231 232 CodeGenFunction::LexicalScope cleanups(CGF, Handler.Body->getSourceRange()); 233 234 if (endCatchFn) { 235 // Add a cleanup to leave the catch. 236 bool EndCatchMightThrow = (Handler.Variable == 0); 237 238 CGF.EHStack.pushCleanup<CallObjCEndCatch>(NormalAndEHCleanup, 239 EndCatchMightThrow, 240 endCatchFn); 241 } 242 243 // Bind the catch parameter if it exists. 244 if (const VarDecl *CatchParam = Handler.Variable) { 245 llvm::Type *CatchType = CGF.ConvertType(CatchParam->getType()); 246 llvm::Value *CastExn = CGF.Builder.CreateBitCast(Exn, CatchType); 247 248 CGF.EmitAutoVarDecl(*CatchParam); 249 CGF.Builder.CreateStore(CastExn, CGF.GetAddrOfLocalVar(CatchParam)); 250 } 251 252 CGF.ObjCEHValueStack.push_back(Exn); 253 CGF.EmitStmt(Handler.Body); 254 CGF.ObjCEHValueStack.pop_back(); 255 256 // Leave any cleanups associated with the catch. 257 cleanups.ForceCleanup(); 258 259 CGF.EmitBranchThroughCleanup(Cont); 260 } 261 262 // Go back to the try-statement fallthrough. 263 CGF.Builder.restoreIP(SavedIP); 264 265 // Pop out of the finally. 266 if (S.getFinallyStmt()) 267 FinallyInfo.exit(CGF); 268 269 if (Cont.isValid()) 270 CGF.EmitBlock(Cont.getBlock()); 271 } 272 273 namespace { 274 struct CallSyncExit : EHScopeStack::Cleanup { 275 llvm::Value *SyncExitFn; 276 llvm::Value *SyncArg; 277 CallSyncExit(llvm::Value *SyncExitFn, llvm::Value *SyncArg) 278 : SyncExitFn(SyncExitFn), SyncArg(SyncArg) {} 279 280 void Emit(CodeGenFunction &CGF, Flags flags) { 281 CGF.Builder.CreateCall(SyncExitFn, SyncArg)->setDoesNotThrow(); 282 } 283 }; 284 } 285 286 void CGObjCRuntime::EmitAtSynchronizedStmt(CodeGenFunction &CGF, 287 const ObjCAtSynchronizedStmt &S, 288 llvm::Function *syncEnterFn, 289 llvm::Function *syncExitFn) { 290 CodeGenFunction::RunCleanupsScope cleanups(CGF); 291 292 // Evaluate the lock operand. This is guaranteed to dominate the 293 // ARC release and lock-release cleanups. 294 const Expr *lockExpr = S.getSynchExpr(); 295 llvm::Value *lock; 296 if (CGF.getLangOptions().ObjCAutoRefCount) { 297 lock = CGF.EmitARCRetainScalarExpr(lockExpr); 298 lock = CGF.EmitObjCConsumeObject(lockExpr->getType(), lock); 299 } else { 300 lock = CGF.EmitScalarExpr(lockExpr); 301 } 302 lock = CGF.Builder.CreateBitCast(lock, CGF.VoidPtrTy); 303 304 // Acquire the lock. 305 CGF.Builder.CreateCall(syncEnterFn, lock)->setDoesNotThrow(); 306 307 // Register an all-paths cleanup to release the lock. 308 CGF.EHStack.pushCleanup<CallSyncExit>(NormalAndEHCleanup, syncExitFn, lock); 309 310 // Emit the body of the statement. 311 CGF.EmitStmt(S.getSynchBody()); 312 } 313