477 lines · cpp
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-exception6//7//===----------------------------------------------------------------------===//8//9// This abstract class defines the interface for Objective-C runtime-specific10// code generation. It provides some concrete helper methods for functionality11// 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, 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(), Ivar) /42 CGM.getContext().getCharWidth();43}44 45unsigned CGObjCRuntime::ComputeBitfieldBitOffset(46 CodeGen::CodeGenModule &CGM,47 const ObjCInterfaceDecl *ID,48 const ObjCIvarDecl *Ivar) {49 return CGM.getContext().lookupFieldBitOffset(ID, Ivar);50}51 52LValue CGObjCRuntime::EmitValueForIvarAtOffset(CodeGen::CodeGenFunction &CGF,53 const ObjCInterfaceDecl *OID,54 llvm::Value *BaseValue,55 const ObjCIvarDecl *Ivar,56 unsigned CVRQualifiers,57 llvm::Value *Offset) {58 // Compute (type*) ( (char *) BaseValue + Offset)59 QualType InterfaceTy{OID->getTypeForDecl(), 0};60 QualType ObjectPtrTy =61 CGF.CGM.getContext().getObjCObjectPointerType(InterfaceTy);62 QualType IvarTy =63 Ivar->getUsageType(ObjectPtrTy).withCVRQualifiers(CVRQualifiers);64 llvm::Value *V = BaseValue;65 V = CGF.Builder.CreateInBoundsGEP(CGF.Int8Ty, V, Offset, "add.ptr");66 67 if (!Ivar->isBitField()) {68 LValue LV = CGF.MakeNaturalAlignRawAddrLValue(V, IvarTy);69 return LV;70 }71 72 // We need to compute an access strategy for this bit-field. We are given the73 // offset to the first byte in the bit-field, the sub-byte offset is taken74 // from the original layout. We reuse the normal bit-field access strategy by75 // treating this as an access to a struct where the bit-field is in byte 0,76 // and adjust the containing type size as appropriate.77 //78 // FIXME: Note that currently we make a very conservative estimate of the79 // alignment of the bit-field, because (a) it is not clear what guarantees the80 // runtime makes us, and (b) we don't have a way to specify that the struct is81 // at an alignment plus offset.82 //83 // Note, there is a subtle invariant here: we can only call this routine on84 // non-synthesized ivars but we may be called for synthesized ivars. However,85 // a synthesized ivar can never be a bit-field, so this is safe.86 uint64_t FieldBitOffset =87 CGF.CGM.getContext().lookupFieldBitOffset(OID, Ivar);88 uint64_t BitOffset = FieldBitOffset % CGF.CGM.getContext().getCharWidth();89 uint64_t AlignmentBits = CGF.CGM.getTarget().getCharAlign();90 uint64_t BitFieldSize = Ivar->getBitWidthValue();91 CharUnits StorageSize = CGF.CGM.getContext().toCharUnitsFromBits(92 llvm::alignTo(BitOffset + BitFieldSize, AlignmentBits));93 CharUnits Alignment = CGF.CGM.getContext().toCharUnitsFromBits(AlignmentBits);94 95 // Allocate a new CGBitFieldInfo object to describe this access.96 //97 // FIXME: This is incredibly wasteful, these should be uniqued or part of some98 // layout object. However, this is blocked on other cleanups to the99 // Objective-C code, so for now we just live with allocating a bunch of these100 // objects.101 CGBitFieldInfo *Info = new (CGF.CGM.getContext()) CGBitFieldInfo(102 CGBitFieldInfo::MakeInfo(CGF.CGM.getTypes(), Ivar, BitOffset, BitFieldSize,103 CGF.CGM.getContext().toBits(StorageSize),104 CharUnits::fromQuantity(0)));105 106 Address Addr =107 Address(V, llvm::Type::getIntNTy(CGF.getLLVMContext(), Info->StorageSize),108 Alignment);109 110 return LValue::MakeBitfield(Addr, *Info, IvarTy,111 LValueBaseInfo(AlignmentSource::Decl),112 TBAAAccessInfo());113}114 115namespace {116 struct CatchHandler {117 const VarDecl *Variable;118 const Stmt *Body;119 llvm::BasicBlock *Block;120 llvm::Constant *TypeInfo;121 /// Flags used to differentiate cleanups and catchalls in Windows SEH122 unsigned Flags;123 };124 125 struct CallObjCEndCatch final : EHScopeStack::Cleanup {126 CallObjCEndCatch(bool MightThrow, llvm::FunctionCallee Fn)127 : MightThrow(MightThrow), Fn(Fn) {}128 bool MightThrow;129 llvm::FunctionCallee Fn;130 131 void Emit(CodeGenFunction &CGF, Flags flags) override {132 if (MightThrow)133 CGF.EmitRuntimeCallOrInvoke(Fn);134 else135 CGF.EmitNounwindRuntimeCall(Fn);136 }137 };138}139 140void CGObjCRuntime::EmitTryCatchStmt(CodeGenFunction &CGF,141 const ObjCAtTryStmt &S,142 llvm::FunctionCallee beginCatchFn,143 llvm::FunctionCallee endCatchFn,144 llvm::FunctionCallee exceptionRethrowFn) {145 // Jump destination for falling out of catch bodies.146 CodeGenFunction::JumpDest Cont;147 if (S.getNumCatchStmts())148 Cont = CGF.getJumpDestInCurrentScope("eh.cont");149 150 bool useFunclets = EHPersonality::get(CGF).usesFuncletPads();151 152 CodeGenFunction::FinallyInfo FinallyInfo;153 if (!useFunclets)154 if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt())155 FinallyInfo.enter(CGF, Finally->getFinallyBody(),156 beginCatchFn, endCatchFn, exceptionRethrowFn);157 158 SmallVector<CatchHandler, 8> Handlers;159 160 161 // Enter the catch, if there is one.162 if (S.getNumCatchStmts()) {163 for (const ObjCAtCatchStmt *CatchStmt : S.catch_stmts()) {164 const VarDecl *CatchDecl = CatchStmt->getCatchParamDecl();165 166 Handlers.push_back(CatchHandler());167 CatchHandler &Handler = Handlers.back();168 Handler.Variable = CatchDecl;169 Handler.Body = CatchStmt->getCatchBody();170 Handler.Block = CGF.createBasicBlock("catch");171 Handler.Flags = 0;172 173 // @catch(...) always matches.174 if (!CatchDecl) {175 auto catchAll = getCatchAllTypeInfo();176 Handler.TypeInfo = catchAll.RTTI;177 Handler.Flags = catchAll.Flags;178 // Don't consider any other catches.179 break;180 }181 182 Handler.TypeInfo = GetEHType(CatchDecl->getType());183 }184 185 EHCatchScope *Catch = CGF.EHStack.pushCatch(Handlers.size());186 for (unsigned I = 0, E = Handlers.size(); I != E; ++I)187 Catch->setHandler(I, { Handlers[I].TypeInfo, Handlers[I].Flags }, Handlers[I].Block);188 }189 190 if (useFunclets)191 if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt()) {192 CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);193 if (!CGF.CurSEHParent)194 CGF.CurSEHParent = cast<NamedDecl>(CGF.CurFuncDecl);195 // Outline the finally block.196 const Stmt *FinallyBlock = Finally->getFinallyBody();197 HelperCGF.startOutlinedSEHHelper(CGF, /*isFilter*/false, FinallyBlock);198 199 // Emit the original filter expression, convert to i32, and return.200 HelperCGF.EmitStmt(FinallyBlock);201 202 HelperCGF.FinishFunction(FinallyBlock->getEndLoc());203 204 llvm::Function *FinallyFunc = HelperCGF.CurFn;205 206 207 // Push a cleanup for __finally blocks.208 CGF.pushSEHCleanup(NormalAndEHCleanup, FinallyFunc);209 }210 211 212 // Emit the try body.213 CGF.EmitStmt(S.getTryBody());214 215 // Leave the try.216 if (S.getNumCatchStmts())217 CGF.popCatchScope();218 219 // Remember where we were.220 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();221 222 // Emit the handlers.223 for (CatchHandler &Handler : Handlers) {224 CGF.EmitBlock(Handler.Block);225 226 CodeGenFunction::LexicalScope Cleanups(CGF, Handler.Body->getSourceRange());227 SaveAndRestore RevertAfterScope(CGF.CurrentFuncletPad);228 if (useFunclets) {229 llvm::BasicBlock::iterator CPICandidate =230 Handler.Block->getFirstNonPHIIt();231 if (CPICandidate != Handler.Block->end()) {232 if (auto *CPI = dyn_cast_or_null<llvm::CatchPadInst>(CPICandidate)) {233 CGF.CurrentFuncletPad = CPI;234 CPI->setOperand(2, CGF.getExceptionSlot().emitRawPointer(CGF));235 CGF.EHStack.pushCleanup<CatchRetScope>(NormalCleanup, CPI);236 }237 }238 }239 240 llvm::Value *RawExn = CGF.getExceptionFromSlot();241 242 // Enter the catch.243 llvm::Value *Exn = RawExn;244 if (beginCatchFn)245 Exn = CGF.EmitNounwindRuntimeCall(beginCatchFn, RawExn, "exn.adjusted");246 247 if (endCatchFn) {248 // Add a cleanup to leave the catch.249 bool EndCatchMightThrow = (Handler.Variable == nullptr);250 251 CGF.EHStack.pushCleanup<CallObjCEndCatch>(NormalAndEHCleanup,252 EndCatchMightThrow,253 endCatchFn);254 }255 256 // Bind the catch parameter if it exists.257 if (const VarDecl *CatchParam = Handler.Variable) {258 llvm::Type *CatchType = CGF.ConvertType(CatchParam->getType());259 llvm::Value *CastExn = CGF.Builder.CreateBitCast(Exn, CatchType);260 261 CGF.EmitAutoVarDecl(*CatchParam);262 EmitInitOfCatchParam(CGF, CastExn, CatchParam);263 }264 265 CGF.ObjCEHValueStack.push_back(Exn);266 CGF.EmitStmt(Handler.Body);267 CGF.ObjCEHValueStack.pop_back();268 269 // Leave any cleanups associated with the catch.270 Cleanups.ForceCleanup();271 272 CGF.EmitBranchThroughCleanup(Cont);273 }274 275 // Go back to the try-statement fallthrough.276 CGF.Builder.restoreIP(SavedIP);277 278 // Pop out of the finally.279 if (!useFunclets && S.getFinallyStmt())280 FinallyInfo.exit(CGF);281 282 if (Cont.isValid())283 CGF.EmitBlock(Cont.getBlock());284}285 286void CGObjCRuntime::EmitInitOfCatchParam(CodeGenFunction &CGF,287 llvm::Value *exn,288 const VarDecl *paramDecl) {289 290 Address paramAddr = CGF.GetAddrOfLocalVar(paramDecl);291 292 switch (paramDecl->getType().getQualifiers().getObjCLifetime()) {293 case Qualifiers::OCL_Strong:294 exn = CGF.EmitARCRetainNonBlock(exn);295 [[fallthrough]];296 297 case Qualifiers::OCL_None:298 case Qualifiers::OCL_ExplicitNone:299 case Qualifiers::OCL_Autoreleasing:300 CGF.Builder.CreateStore(exn, paramAddr);301 return;302 303 case Qualifiers::OCL_Weak:304 CGF.EmitARCInitWeak(paramAddr, exn);305 return;306 }307 llvm_unreachable("invalid ownership qualifier");308}309 310namespace {311 struct CallSyncExit final : EHScopeStack::Cleanup {312 llvm::FunctionCallee SyncExitFn;313 llvm::Value *SyncArg;314 CallSyncExit(llvm::FunctionCallee SyncExitFn, llvm::Value *SyncArg)315 : SyncExitFn(SyncExitFn), SyncArg(SyncArg) {}316 317 void Emit(CodeGenFunction &CGF, Flags flags) override {318 CGF.EmitNounwindRuntimeCall(SyncExitFn, SyncArg);319 }320 };321}322 323void CGObjCRuntime::EmitAtSynchronizedStmt(CodeGenFunction &CGF,324 const ObjCAtSynchronizedStmt &S,325 llvm::FunctionCallee syncEnterFn,326 llvm::FunctionCallee syncExitFn) {327 CodeGenFunction::RunCleanupsScope cleanups(CGF);328 329 // Evaluate the lock operand. This is guaranteed to dominate the330 // ARC release and lock-release cleanups.331 const Expr *lockExpr = S.getSynchExpr();332 llvm::Value *lock;333 if (CGF.getLangOpts().ObjCAutoRefCount) {334 lock = CGF.EmitARCRetainScalarExpr(lockExpr);335 lock = CGF.EmitObjCConsumeObject(lockExpr->getType(), lock);336 } else {337 lock = CGF.EmitScalarExpr(lockExpr);338 }339 lock = CGF.Builder.CreateBitCast(lock, CGF.VoidPtrTy);340 341 // Acquire the lock.342 CGF.Builder.CreateCall(syncEnterFn, lock)->setDoesNotThrow();343 344 // Register an all-paths cleanup to release the lock.345 CGF.EHStack.pushCleanup<CallSyncExit>(NormalAndEHCleanup, syncExitFn, lock);346 347 // Emit the body of the statement.348 CGF.EmitStmt(S.getSynchBody());349}350 351/// Compute the pointer-to-function type to which a message send352/// should be casted in order to correctly call the given method353/// with the given arguments.354///355/// \param method - may be null356/// \param resultType - the result type to use if there's no method357/// \param callArgs - the actual arguments, including implicit ones358CGObjCRuntime::MessageSendInfo359CGObjCRuntime::getMessageSendInfo(const ObjCMethodDecl *method,360 QualType resultType,361 CallArgList &callArgs) {362 unsigned ProgramAS = CGM.getDataLayout().getProgramAddressSpace();363 364 llvm::PointerType *signatureType =365 llvm::PointerType::get(CGM.getLLVMContext(), ProgramAS);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 const CGFunctionInfo &signatureForCall =373 CGM.getTypes().arrangeCall(signature, callArgs);374 375 return MessageSendInfo(signatureForCall, signatureType);376 }377 378 // There's no method; just use a default CC.379 const CGFunctionInfo &argsInfo =380 CGM.getTypes().arrangeUnprototypedObjCMessageSend(resultType, callArgs);381 382 return MessageSendInfo(argsInfo, signatureType);383}384 385bool CGObjCRuntime::canMessageReceiverBeNull(CodeGenFunction &CGF,386 const ObjCMethodDecl *method,387 bool isSuper,388 const ObjCInterfaceDecl *classReceiver,389 llvm::Value *receiver) {390 // Super dispatch assumes that self is non-null; even the messenger391 // doesn't have a null check internally.392 if (isSuper)393 return false;394 395 // If this is a direct dispatch of a class method, check whether the class,396 // or anything in its hierarchy, was weak-linked.397 if (classReceiver && method && method->isClassMethod())398 return isWeakLinkedClass(classReceiver);399 400 // If we're emitting a method, and self is const (meaning just ARC, for now),401 // and the receiver is a load of self, then self is a valid object.402 if (auto curMethod =403 dyn_cast_or_null<ObjCMethodDecl>(CGF.CurCodeDecl)) {404 auto self = curMethod->getSelfDecl();405 if (self->getType().isConstQualified()) {406 if (auto LI = dyn_cast<llvm::LoadInst>(receiver->stripPointerCasts())) {407 llvm::Value *selfAddr = CGF.GetAddrOfLocalVar(self).emitRawPointer(CGF);408 if (selfAddr == LI->getPointerOperand()) {409 return false;410 }411 }412 }413 }414 415 // Otherwise, assume it can be null.416 return true;417}418 419bool CGObjCRuntime::isWeakLinkedClass(const ObjCInterfaceDecl *ID) {420 do {421 if (ID->isWeakImported())422 return true;423 } while ((ID = ID->getSuperClass()));424 425 return false;426}427 428void CGObjCRuntime::destroyCalleeDestroyedArguments(CodeGenFunction &CGF,429 const ObjCMethodDecl *method,430 const CallArgList &callArgs) {431 CallArgList::const_iterator I = callArgs.begin();432 for (auto i = method->param_begin(), e = method->param_end();433 i != e; ++i, ++I) {434 const ParmVarDecl *param = (*i);435 if (param->hasAttr<NSConsumedAttr>()) {436 RValue RV = I->getRValue(CGF);437 assert(RV.isScalar() &&438 "NullReturnState::complete - arg not on object");439 CGF.EmitARCRelease(RV.getScalarVal(), ARCImpreciseLifetime);440 } else {441 QualType QT = param->getType();442 auto *RD = QT->getAsRecordDecl();443 if (RD && RD->isParamDestroyedInCallee()) {444 RValue RV = I->getRValue(CGF);445 QualType::DestructionKind DtorKind = QT.isDestructedType();446 switch (DtorKind) {447 case QualType::DK_cxx_destructor:448 CGF.destroyCXXObject(CGF, RV.getAggregateAddress(), QT);449 break;450 case QualType::DK_nontrivial_c_struct:451 CGF.destroyNonTrivialCStruct(CGF, RV.getAggregateAddress(), QT);452 break;453 default:454 llvm_unreachable("unexpected dtor kind");455 break;456 }457 }458 }459 }460}461 462llvm::Constant *463clang::CodeGen::emitObjCProtocolObject(CodeGenModule &CGM,464 const ObjCProtocolDecl *protocol) {465 return CGM.getObjCRuntime().GetOrEmitProtocol(protocol);466}467 468std::string CGObjCRuntime::getSymbolNameForMethod(const ObjCMethodDecl *OMD,469 bool includeCategoryName) {470 std::string buffer;471 llvm::raw_string_ostream out(buffer);472 CGM.getCXXABI().getMangleContext().mangleObjCMethodName(OMD, out,473 /*includePrefixByte=*/true,474 includeCategoryName);475 return buffer;476}477