//==- CGObjCRuntime.cpp - Interface to Shared Objective-C Runtime Features ==//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// This abstract class defines the interface for Objective-C runtime-specific

// code generation.  It provides some concrete helper methods for functionality

// shared between all (or most) of the Objective-C runtimes supported by clang.

//

//===----------------------------------------------------------------------===//

#include "CGObjCRuntime.h"

#include "CGCXXABI.h"

#include "CGCleanup.h"

#include "CGRecordLayout.h"

#include "CodeGenFunction.h"

#include "CodeGenModule.h"

#include "clang/AST/RecordLayout.h"

#include "clang/AST/StmtObjC.h"

#include "clang/CodeGen/CGFunctionInfo.h"

#include "clang/CodeGen/CodeGenABITypes.h"

#include "llvm/IR/Instruction.h"

#include "llvm/Support/SaveAndRestore.h"

using namespace clang;

using namespace CodeGen;

uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,

                                              const ObjCInterfaceDecl *OID,

                                              const ObjCIvarDecl *Ivar) {

  return CGM.getContext().lookupFieldBitOffset(OID, nullptr, Ivar) /

         CGM.getContext().getCharWidth();

}

uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,

                                              const ObjCImplementationDecl *OID,

                                              const ObjCIvarDecl *Ivar) {

  return CGM.getContext().lookupFieldBitOffset(OID->getClassInterface(), OID,

                                               Ivar) /

         CGM.getContext().getCharWidth();

}

unsigned CGObjCRuntime::ComputeBitfieldBitOffset(

    CodeGen::CodeGenModule &CGM,

    const ObjCInterfaceDecl *ID,

    const ObjCIvarDecl *Ivar) {

  return CGM.getContext().lookupFieldBitOffset(ID, ID->getImplementation(),

                                               Ivar);

}

LValue CGObjCRuntime::EmitValueForIvarAtOffset(CodeGen::CodeGenFunction &CGF,

                                               const ObjCInterfaceDecl *OID,

                                               llvm::Value *BaseValue,

                                               const ObjCIvarDecl *Ivar,

                                               unsigned CVRQualifiers,

                                               llvm::Value *Offset) {

  // Compute (type*) ( (char *) BaseValue + Offset)

  QualType InterfaceTy{OID->getTypeForDecl(), 0};

  QualType ObjectPtrTy =

      CGF.CGM.getContext().getObjCObjectPointerType(InterfaceTy);

  QualType IvarTy =

      Ivar->getUsageType(ObjectPtrTy).withCVRQualifiers(CVRQualifiers);

  llvm::Value *V = BaseValue;

  V = CGF.Builder.CreateInBoundsGEP(CGF.Int8Ty, V, Offset, "add.ptr");

  if (!Ivar->isBitField()) {

    LValue LV = CGF.MakeNaturalAlignAddrLValue(V, IvarTy);

    return LV;

  }

  // We need to compute an access strategy for this bit-field. We are given the

  // offset to the first byte in the bit-field, the sub-byte offset is taken

  // from the original layout. We reuse the normal bit-field access strategy by

  // treating this as an access to a struct where the bit-field is in byte 0,

  // and adjust the containing type size as appropriate.

  //

  // FIXME: Note that currently we make a very conservative estimate of the

  // alignment of the bit-field, because (a) it is not clear what guarantees the

  // runtime makes us, and (b) we don't have a way to specify that the struct is

  // at an alignment plus offset.

  //

  // Note, there is a subtle invariant here: we can only call this routine on

  // non-synthesized ivars but we may be called for synthesized ivars.  However,

  // a synthesized ivar can never be a bit-field, so this is safe.

  uint64_t FieldBitOffset =

      CGF.CGM.getContext().lookupFieldBitOffset(OID, nullptr, Ivar);

  uint64_t BitOffset = FieldBitOffset % CGF.CGM.getContext().getCharWidth();

  uint64_t AlignmentBits = CGF.CGM.getTarget().getCharAlign();

  uint64_t BitFieldSize = Ivar->getBitWidthValue(CGF.getContext());

  CharUnits StorageSize = CGF.CGM.getContext().toCharUnitsFromBits(

      llvm::alignTo(BitOffset + BitFieldSize, AlignmentBits));

  CharUnits Alignment = CGF.CGM.getContext().toCharUnitsFromBits(AlignmentBits);

  // Allocate a new CGBitFieldInfo object to describe this access.

  //

  // FIXME: This is incredibly wasteful, these should be uniqued or part of some

  // layout object. However, this is blocked on other cleanups to the

  // Objective-C code, so for now we just live with allocating a bunch of these

  // objects.

  CGBitFieldInfo *Info = new (CGF.CGM.getContext()) CGBitFieldInfo(

    CGBitFieldInfo::MakeInfo(CGF.CGM.getTypes(), Ivar, BitOffset, BitFieldSize,

                             CGF.CGM.getContext().toBits(StorageSize),

                             CharUnits::fromQuantity(0)));

  Address Addr =

      Address(V, llvm::Type::getIntNTy(CGF.getLLVMContext(), Info->StorageSize),

              Alignment);

  return LValue::MakeBitfield(Addr, *Info, IvarTy,

                              LValueBaseInfo(AlignmentSource::Decl),

                              TBAAAccessInfo());

}

namespace {

  struct CatchHandler {

    const VarDecl *Variable;

    const Stmt *Body;

    llvm::BasicBlock *Block;

    llvm::Constant *TypeInfo;

    /// Flags used to differentiate cleanups and catchalls in Windows SEH

    unsigned Flags;

  };

  struct CallObjCEndCatch final : EHScopeStack::Cleanup {

    CallObjCEndCatch(bool MightThrow, llvm::FunctionCallee Fn)

        : MightThrow(MightThrow), Fn(Fn) {}

    bool MightThrow;

    llvm::FunctionCallee Fn;

    void Emit(CodeGenFunction &CGF, Flags flags) override {

      if (MightThrow)

        CGF.EmitRuntimeCallOrInvoke(Fn);

      else

        CGF.EmitNounwindRuntimeCall(Fn);

    }

  };

}

void CGObjCRuntime::EmitTryCatchStmt(CodeGenFunction &CGF,

                                     const ObjCAtTryStmt &S,

                                     llvm::FunctionCallee beginCatchFn,

                                     llvm::FunctionCallee endCatchFn,

                                     llvm::FunctionCallee exceptionRethrowFn) {

  // Jump destination for falling out of catch bodies.

  CodeGenFunction::JumpDest Cont;

  if (S.getNumCatchStmts())

    Cont = CGF.getJumpDestInCurrentScope("eh.cont");

  bool useFunclets = EHPersonality::get(CGF).usesFuncletPads();

  CodeGenFunction::FinallyInfo FinallyInfo;

  if (!useFunclets)

    if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt())

      FinallyInfo.enter(CGF, Finally->getFinallyBody(),

                        beginCatchFn, endCatchFn, exceptionRethrowFn);

  SmallVector<CatchHandler, 8> Handlers;

  // Enter the catch, if there is one.

  if (S.getNumCatchStmts()) {

    for (const ObjCAtCatchStmt *CatchStmt : S.catch_stmts()) {

      const VarDecl *CatchDecl = CatchStmt->getCatchParamDecl();

      Handlers.push_back(CatchHandler());

      CatchHandler &Handler = Handlers.back();

      Handler.Variable = CatchDecl;

      Handler.Body = CatchStmt->getCatchBody();

      Handler.Block = CGF.createBasicBlock("catch");

      Handler.Flags = 0;

      // @catch(...) always matches.

      if (!CatchDecl) {

        auto catchAll = getCatchAllTypeInfo();

        Handler.TypeInfo = catchAll.RTTI;

        Handler.Flags = catchAll.Flags;

        // Don't consider any other catches.

        break;

      }

      Handler.TypeInfo = GetEHType(CatchDecl->getType());

    }

    EHCatchScope *Catch = CGF.EHStack.pushCatch(Handlers.size());

    for (unsigned I = 0, E = Handlers.size(); I != E; ++I)

      Catch->setHandler(I, { Handlers[I].TypeInfo, Handlers[I].Flags }, Handlers[I].Block);

  }

  if (useFunclets)

    if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt()) {

        CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);

        if (!CGF.CurSEHParent)

            CGF.CurSEHParent = cast<NamedDecl>(CGF.CurFuncDecl);

        // Outline the finally block.

        const Stmt *FinallyBlock = Finally->getFinallyBody();

        HelperCGF.startOutlinedSEHHelper(CGF, /*isFilter*/false, FinallyBlock);

        // Emit the original filter expression, convert to i32, and return.

        HelperCGF.EmitStmt(FinallyBlock);

        HelperCGF.FinishFunction(FinallyBlock->getEndLoc());

        llvm::Function *FinallyFunc = HelperCGF.CurFn;

        // Push a cleanup for __finally blocks.

        CGF.pushSEHCleanup(NormalAndEHCleanup, FinallyFunc);

    }

  // Emit the try body.

  CGF.EmitStmt(S.getTryBody());

  // Leave the try.

  if (S.getNumCatchStmts())

    CGF.popCatchScope();

  // Remember where we were.

  CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();

  // Emit the handlers.

  for (unsigned I = 0, E = Handlers.size(); I != E; ++I) {

    CatchHandler &Handler = Handlers[I];

    CGF.EmitBlock(Handler.Block);

    CodeGenFunction::LexicalScope Cleanups(CGF, Handler.Body->getSourceRange());

    SaveAndRestore RevertAfterScope(CGF.CurrentFuncletPad);

    if (useFunclets) {

      llvm::Instruction *CPICandidate = Handler.Block->getFirstNonPHI();

      if (auto *CPI = dyn_cast_or_null<llvm::CatchPadInst>(CPICandidate)) {

        CGF.CurrentFuncletPad = CPI;

        CPI->setOperand(2, CGF.getExceptionSlot().getPointer());

        CGF.EHStack.pushCleanup<CatchRetScope>(NormalCleanup, CPI);

      }

    }

    llvm::Value *RawExn = CGF.getExceptionFromSlot();

    // Enter the catch.

    llvm::Value *Exn = RawExn;

    if (beginCatchFn)

      Exn = CGF.EmitNounwindRuntimeCall(beginCatchFn, RawExn, "exn.adjusted");

    if (endCatchFn) {

      // Add a cleanup to leave the catch.

      bool EndCatchMightThrow = (Handler.Variable == nullptr);

      CGF.EHStack.pushCleanup<CallObjCEndCatch>(NormalAndEHCleanup,

                                                EndCatchMightThrow,

                                                endCatchFn);

    }

    // Bind the catch parameter if it exists.

    if (const VarDecl *CatchParam = Handler.Variable) {

      llvm::Type *CatchType = CGF.ConvertType(CatchParam->getType());

      llvm::Value *CastExn = CGF.Builder.CreateBitCast(Exn, CatchType);

      CGF.EmitAutoVarDecl(*CatchParam);

      EmitInitOfCatchParam(CGF, CastExn, CatchParam);

    }

    CGF.ObjCEHValueStack.push_back(Exn);

    CGF.EmitStmt(Handler.Body);

    CGF.ObjCEHValueStack.pop_back();

    // Leave any cleanups associated with the catch.

    Cleanups.ForceCleanup();

    CGF.EmitBranchThroughCleanup(Cont);

  }

  // Go back to the try-statement fallthrough.

  CGF.Builder.restoreIP(SavedIP);

  // Pop out of the finally.

  if (!useFunclets && S.getFinallyStmt())

    FinallyInfo.exit(CGF);

  if (Cont.isValid())

    CGF.EmitBlock(Cont.getBlock());

}

void CGObjCRuntime::EmitInitOfCatchParam(CodeGenFunction &CGF,

                                         llvm::Value *exn,

                                         const VarDecl *paramDecl) {

  Address paramAddr = CGF.GetAddrOfLocalVar(paramDecl);

  switch (paramDecl->getType().getQualifiers().getObjCLifetime()) {

  case Qualifiers::OCL_Strong:

    exn = CGF.EmitARCRetainNonBlock(exn);

    [[fallthrough]];

  case Qualifiers::OCL_None:

  case Qualifiers::OCL_ExplicitNone:

  case Qualifiers::OCL_Autoreleasing:

    CGF.Builder.CreateStore(exn, paramAddr);

    return;

  case Qualifiers::OCL_Weak:

    CGF.EmitARCInitWeak(paramAddr, exn);

    return;

  }

  llvm_unreachable("invalid ownership qualifier");

}

namespace {

  struct CallSyncExit final : EHScopeStack::Cleanup {

    llvm::FunctionCallee SyncExitFn;

    llvm::Value *SyncArg;

    CallSyncExit(llvm::FunctionCallee SyncExitFn, llvm::Value *SyncArg)

        : SyncExitFn(SyncExitFn), SyncArg(SyncArg) {}

    void Emit(CodeGenFunction &CGF, Flags flags) override {

      CGF.EmitNounwindRuntimeCall(SyncExitFn, SyncArg);

    }

  };

}

void CGObjCRuntime::EmitAtSynchronizedStmt(CodeGenFunction &CGF,

                                           const ObjCAtSynchronizedStmt &S,

                                           llvm::FunctionCallee syncEnterFn,

                                           llvm::FunctionCallee syncExitFn) {

  CodeGenFunction::RunCleanupsScope cleanups(CGF);

  // Evaluate the lock operand.  This is guaranteed to dominate the

  // ARC release and lock-release cleanups.

  const Expr *lockExpr = S.getSynchExpr();

  llvm::Value *lock;

  if (CGF.getLangOpts().ObjCAutoRefCount) {

    lock = CGF.EmitARCRetainScalarExpr(lockExpr);

    lock = CGF.EmitObjCConsumeObject(lockExpr->getType(), lock);

  } else {

    lock = CGF.EmitScalarExpr(lockExpr);

  }

  lock = CGF.Builder.CreateBitCast(lock, CGF.VoidPtrTy);

  // Acquire the lock.

  CGF.Builder.CreateCall(syncEnterFn, lock)->setDoesNotThrow();

  // Register an all-paths cleanup to release the lock.

  CGF.EHStack.pushCleanup<CallSyncExit>(NormalAndEHCleanup, syncExitFn, lock);

  // Emit the body of the statement.

  CGF.EmitStmt(S.getSynchBody());

}

/// Compute the pointer-to-function type to which a message send

/// should be casted in order to correctly call the given method

/// with the given arguments.

///

/// \param method - may be null

/// \param resultType - the result type to use if there's no method

/// \param callArgs - the actual arguments, including implicit ones

CGObjCRuntime::MessageSendInfo

CGObjCRuntime::getMessageSendInfo(const ObjCMethodDecl *method,

                                  QualType resultType,

                                  CallArgList &callArgs) {

  unsigned ProgramAS = CGM.getDataLayout().getProgramAddressSpace();

  llvm::PointerType *signatureType =

      llvm::PointerType::get(CGM.getLLVMContext(), ProgramAS);

  // If there's a method, use information from that.

  if (method) {

    const CGFunctionInfo &signature =

      CGM.getTypes().arrangeObjCMessageSendSignature(method, callArgs[0].Ty);

    const CGFunctionInfo &signatureForCall =

      CGM.getTypes().arrangeCall(signature, callArgs);

    return MessageSendInfo(signatureForCall, signatureType);

  }

  // There's no method;  just use a default CC.

  const CGFunctionInfo &argsInfo =

    CGM.getTypes().arrangeUnprototypedObjCMessageSend(resultType, callArgs);

  return MessageSendInfo(argsInfo, signatureType);

}

bool CGObjCRuntime::canMessageReceiverBeNull(CodeGenFunction &CGF,

                                             const ObjCMethodDecl *method,

                                             bool isSuper,

                                       const ObjCInterfaceDecl *classReceiver,

                                             llvm::Value *receiver) {

  // Super dispatch assumes that self is non-null; even the messenger

  // doesn't have a null check internally.

  if (isSuper)

    return false;

  // If this is a direct dispatch of a class method, check whether the class,

  // or anything in its hierarchy, was weak-linked.

  if (classReceiver && method && method->isClassMethod())

    return isWeakLinkedClass(classReceiver);

  // If we're emitting a method, and self is const (meaning just ARC, for now),

  // and the receiver is a load of self, then self is a valid object.

  if (auto curMethod =

               dyn_cast_or_null<ObjCMethodDecl>(CGF.CurCodeDecl)) {

    auto self = curMethod->getSelfDecl();

    if (self->getType().isConstQualified()) {

      if (auto LI = dyn_cast<llvm::LoadInst>(receiver->stripPointerCasts())) {

        llvm::Value *selfAddr = CGF.GetAddrOfLocalVar(self).getPointer();

        if (selfAddr == LI->getPointerOperand()) {

          return false;

        }

      }

    }

  }

  // Otherwise, assume it can be null.

  return true;

}

bool CGObjCRuntime::isWeakLinkedClass(const ObjCInterfaceDecl *ID) {

  do {

    if (ID->isWeakImported())

      return true;

  } while ((ID = ID->getSuperClass()));

  return false;

}

void CGObjCRuntime::destroyCalleeDestroyedArguments(CodeGenFunction &CGF,

                                              const ObjCMethodDecl *method,

                                              const CallArgList &callArgs) {

  CallArgList::const_iterator I = callArgs.begin();

  for (auto i = method->param_begin(), e = method->param_end();

         i != e; ++i, ++I) {

    const ParmVarDecl *param = (*i);

    if (param->hasAttr<NSConsumedAttr>()) {

      RValue RV = I->getRValue(CGF);

      assert(RV.isScalar() &&

             "NullReturnState::complete - arg not on object");

      CGF.EmitARCRelease(RV.getScalarVal(), ARCImpreciseLifetime);

    } else {

      QualType QT = param->getType();

      auto *RT = QT->getAs<RecordType>();

      if (RT && RT->getDecl()->isParamDestroyedInCallee()) {

        RValue RV = I->getRValue(CGF);

        QualType::DestructionKind DtorKind = QT.isDestructedType();

        switch (DtorKind) {

        case QualType::DK_cxx_destructor:

          CGF.destroyCXXObject(CGF, RV.getAggregateAddress(), QT);

          break;

        case QualType::DK_nontrivial_c_struct:

          CGF.destroyNonTrivialCStruct(CGF, RV.getAggregateAddress(), QT);

          break;

        default:

          llvm_unreachable("unexpected dtor kind");

          break;

        }

      }

    }

  }

}

llvm::Constant *

clang::CodeGen::emitObjCProtocolObject(CodeGenModule &CGM,

                                       const ObjCProtocolDecl *protocol) {

  return CGM.getObjCRuntime().GetOrEmitProtocol(protocol);

}

std::string CGObjCRuntime::getSymbolNameForMethod(const ObjCMethodDecl *OMD,

                                                  bool includeCategoryName) {

  std::string buffer;

  llvm::raw_string_ostream out(buffer);

  CGM.getCXXABI().getMangleContext().mangleObjCMethodName(OMD, out,

                                       /*includePrefixByte=*/true,

                                       includeCategoryName);

  return buffer;

}