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//===--- CGDecl.cpp - Emit LLVM Code for declarations ---------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This contains code dealing with C++ code generation.
//
//===----------------------------------------------------------------------===//
// We might split this into multiple files if it gets too unwieldy
#include "CGCXXABI.h"
#include "CodeGenFunction.h"
#include "CodeGenModule.h"
#include "Mangle.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/RecordLayout.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/StmtCXX.h"
#include "clang/Frontend/CodeGenOptions.h"
#include "llvm/ADT/StringExtras.h"
using namespace clang;
using namespace CodeGen;
/// Determines whether the given function has a trivial body that does
/// not require any specific codegen.
static bool HasTrivialBody(const FunctionDecl *FD) {
Stmt *S = FD->getBody();
if (!S)
return true;
if (isa<CompoundStmt>(S) && cast<CompoundStmt>(S)->body_empty())
return true;
return false;
}
/// Try to emit a base destructor as an alias to its primary
/// base-class destructor.
bool CodeGenModule::TryEmitBaseDestructorAsAlias(const CXXDestructorDecl *D) {
if (!getCodeGenOpts().CXXCtorDtorAliases)
return true;
// If the destructor doesn't have a trivial body, we have to emit it
// separately.
if (!HasTrivialBody(D))
return true;
const CXXRecordDecl *Class = D->getParent();
// If we need to manipulate a VTT parameter, give up.
if (Class->getNumVBases()) {
// Extra Credit: passing extra parameters is perfectly safe
// in many calling conventions, so only bail out if the ctor's
// calling convention is nonstandard.
return true;
}
// If any fields have a non-trivial destructor, we have to emit it
// separately.
for (CXXRecordDecl::field_iterator I = Class->field_begin(),
E = Class->field_end(); I != E; ++I)
if (const RecordType *RT = (*I)->getType()->getAs<RecordType>())
if (!cast<CXXRecordDecl>(RT->getDecl())->hasTrivialDestructor())
return true;
// Try to find a unique base class with a non-trivial destructor.
const CXXRecordDecl *UniqueBase = 0;
for (CXXRecordDecl::base_class_const_iterator I = Class->bases_begin(),
E = Class->bases_end(); I != E; ++I) {
// We're in the base destructor, so skip virtual bases.
if (I->isVirtual()) continue;
// Skip base classes with trivial destructors.
const CXXRecordDecl *Base
= cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
if (Base->hasTrivialDestructor()) continue;
// If we've already found a base class with a non-trivial
// destructor, give up.
if (UniqueBase) return true;
UniqueBase = Base;
}
// If we didn't find any bases with a non-trivial destructor, then
// the base destructor is actually effectively trivial, which can
// happen if it was needlessly user-defined or if there are virtual
// bases with non-trivial destructors.
if (!UniqueBase)
return true;
/// If we don't have a definition for the destructor yet, don't
/// emit. We can't emit aliases to declarations; that's just not
/// how aliases work.
const CXXDestructorDecl *BaseD = UniqueBase->getDestructor();
if (!BaseD->isImplicit() && !BaseD->getBody())
return true;
// If the base is at a non-zero offset, give up.
const ASTRecordLayout &ClassLayout = Context.getASTRecordLayout(Class);
if (ClassLayout.getBaseClassOffset(UniqueBase) != 0)
return true;
return TryEmitDefinitionAsAlias(GlobalDecl(D, Dtor_Base),
GlobalDecl(BaseD, Dtor_Base));
}
/// Try to emit a definition as a global alias for another definition.
bool CodeGenModule::TryEmitDefinitionAsAlias(GlobalDecl AliasDecl,
GlobalDecl TargetDecl) {
if (!getCodeGenOpts().CXXCtorDtorAliases)
return true;
// The alias will use the linkage of the referrent. If we can't
// support aliases with that linkage, fail.
llvm::GlobalValue::LinkageTypes Linkage
= getFunctionLinkage(cast<FunctionDecl>(AliasDecl.getDecl()));
switch (Linkage) {
// We can definitely emit aliases to definitions with external linkage.
case llvm::GlobalValue::ExternalLinkage:
case llvm::GlobalValue::ExternalWeakLinkage:
break;
// Same with local linkage.
case llvm::GlobalValue::InternalLinkage:
case llvm::GlobalValue::PrivateLinkage:
case llvm::GlobalValue::LinkerPrivateLinkage:
break;
// We should try to support linkonce linkages.
case llvm::GlobalValue::LinkOnceAnyLinkage:
case llvm::GlobalValue::LinkOnceODRLinkage:
return true;
// Other linkages will probably never be supported.
default:
return true;
}
llvm::GlobalValue::LinkageTypes TargetLinkage
= getFunctionLinkage(cast<FunctionDecl>(TargetDecl.getDecl()));
if (llvm::GlobalValue::isWeakForLinker(TargetLinkage))
return true;
// Derive the type for the alias.
const llvm::PointerType *AliasType
= getTypes().GetFunctionType(AliasDecl)->getPointerTo();
// Find the referrent. Some aliases might require a bitcast, in
// which case the caller is responsible for ensuring the soundness
// of these semantics.
llvm::GlobalValue *Ref = cast<llvm::GlobalValue>(GetAddrOfGlobal(TargetDecl));
llvm::Constant *Aliasee = Ref;
if (Ref->getType() != AliasType)
Aliasee = llvm::ConstantExpr::getBitCast(Ref, AliasType);
// Create the alias with no name.
llvm::GlobalAlias *Alias =
new llvm::GlobalAlias(AliasType, Linkage, "", Aliasee, &getModule());
// Switch any previous uses to the alias.
llvm::StringRef MangledName = getMangledName(AliasDecl);
llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
if (Entry) {
assert(Entry->isDeclaration() && "definition already exists for alias");
assert(Entry->getType() == AliasType &&
"declaration exists with different type");
Alias->takeName(Entry);
Entry->replaceAllUsesWith(Alias);
Entry->eraseFromParent();
} else {
Alias->setName(MangledName);
}
// Finally, set up the alias with its proper name and attributes.
SetCommonAttributes(AliasDecl.getDecl(), Alias);
return false;
}
void CodeGenModule::EmitCXXConstructors(const CXXConstructorDecl *D) {
// The constructor used for constructing this as a complete class;
// constucts the virtual bases, then calls the base constructor.
EmitGlobal(GlobalDecl(D, Ctor_Complete));
// The constructor used for constructing this as a base class;
// ignores virtual bases.
EmitGlobal(GlobalDecl(D, Ctor_Base));
}
void CodeGenModule::EmitCXXConstructor(const CXXConstructorDecl *D,
CXXCtorType Type) {
// The complete constructor is equivalent to the base constructor
// for classes with no virtual bases. Try to emit it as an alias.
if (Type == Ctor_Complete &&
!D->getParent()->getNumVBases() &&
!TryEmitDefinitionAsAlias(GlobalDecl(D, Ctor_Complete),
GlobalDecl(D, Ctor_Base)))
return;
llvm::Function *Fn = cast<llvm::Function>(GetAddrOfCXXConstructor(D, Type));
setFunctionLinkage(D, Fn);
CodeGenFunction(*this).GenerateCode(GlobalDecl(D, Type), Fn);
SetFunctionDefinitionAttributes(D, Fn);
SetLLVMFunctionAttributesForDefinition(D, Fn);
}
llvm::GlobalValue *
CodeGenModule::GetAddrOfCXXConstructor(const CXXConstructorDecl *D,
CXXCtorType Type) {
GlobalDecl GD(D, Type);
llvm::StringRef Name = getMangledName(GD);
if (llvm::GlobalValue *V = GetGlobalValue(Name))
return V;
const FunctionProtoType *FPT = D->getType()->getAs<FunctionProtoType>();
const llvm::FunctionType *FTy =
getTypes().GetFunctionType(getTypes().getFunctionInfo(D, Type),
FPT->isVariadic());
return cast<llvm::Function>(GetOrCreateLLVMFunction(Name, FTy, GD));
}
void CodeGenModule::EmitCXXDestructors(const CXXDestructorDecl *D) {
// The destructor in a virtual table is always a 'deleting'
// destructor, which calls the complete destructor and then uses the
// appropriate operator delete.
if (D->isVirtual())
EmitGlobal(GlobalDecl(D, Dtor_Deleting));
// The destructor used for destructing this as a most-derived class;
// call the base destructor and then destructs any virtual bases.
EmitGlobal(GlobalDecl(D, Dtor_Complete));
// The destructor used for destructing this as a base class; ignores
// virtual bases.
EmitGlobal(GlobalDecl(D, Dtor_Base));
}
void CodeGenModule::EmitCXXDestructor(const CXXDestructorDecl *D,
CXXDtorType Type) {
// The complete destructor is equivalent to the base destructor for
// classes with no virtual bases, so try to emit it as an alias.
if (Type == Dtor_Complete &&
!D->getParent()->getNumVBases() &&
!TryEmitDefinitionAsAlias(GlobalDecl(D, Dtor_Complete),
GlobalDecl(D, Dtor_Base)))
return;
// The base destructor is equivalent to the base destructor of its
// base class if there is exactly one non-virtual base class with a
// non-trivial destructor, there are no fields with a non-trivial
// destructor, and the body of the destructor is trivial.
if (Type == Dtor_Base && !TryEmitBaseDestructorAsAlias(D))
return;
llvm::Function *Fn = cast<llvm::Function>(GetAddrOfCXXDestructor(D, Type));
setFunctionLinkage(D, Fn);
CodeGenFunction(*this).GenerateCode(GlobalDecl(D, Type), Fn);
SetFunctionDefinitionAttributes(D, Fn);
SetLLVMFunctionAttributesForDefinition(D, Fn);
}
llvm::GlobalValue *
CodeGenModule::GetAddrOfCXXDestructor(const CXXDestructorDecl *D,
CXXDtorType Type) {
GlobalDecl GD(D, Type);
llvm::StringRef Name = getMangledName(GD);
if (llvm::GlobalValue *V = GetGlobalValue(Name))
return V;
const llvm::FunctionType *FTy =
getTypes().GetFunctionType(getTypes().getFunctionInfo(D, Type), false);
return cast<llvm::Function>(GetOrCreateLLVMFunction(Name, FTy, GD));
}
llvm::Constant *
CodeGenModule::GetCXXMemberFunctionPointerValue(const CXXMethodDecl *MD) {
assert(MD->isInstance() && "Member function must not be static!");
MD = MD->getCanonicalDecl();
const llvm::Type *PtrDiffTy = Types.ConvertType(Context.getPointerDiffType());
// Get the function pointer (or index if this is a virtual function).
if (MD->isVirtual()) {
uint64_t Index = VTables.getMethodVTableIndex(MD);
// FIXME: We shouldn't use / 8 here.
uint64_t PointerWidthInBytes = Context.Target.getPointerWidth(0) / 8;
// Itanium C++ ABI 2.3:
// For a non-virtual function, this field is a simple function pointer.
// For a virtual function, it is 1 plus the virtual table offset
// (in bytes) of the function, represented as a ptrdiff_t.
return llvm::ConstantInt::get(PtrDiffTy, (Index * PointerWidthInBytes) + 1);
}
const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
const llvm::Type *Ty;
// Check whether the function has a computable LLVM signature.
if (!CodeGenTypes::VerifyFuncTypeComplete(FPT)) {
// The function has a computable LLVM signature; use the correct type.
Ty = Types.GetFunctionType(Types.getFunctionInfo(MD), FPT->isVariadic());
} else {
// Use an arbitrary non-function type to tell GetAddrOfFunction that the
// function type is incomplete.
Ty = PtrDiffTy;
}
llvm::Constant *FuncPtr = GetAddrOfFunction(MD, Ty);
return llvm::ConstantExpr::getPtrToInt(FuncPtr, PtrDiffTy);
}
static llvm::Value *BuildVirtualCall(CodeGenFunction &CGF, uint64_t VTableIndex,
llvm::Value *This, const llvm::Type *Ty) {
Ty = Ty->getPointerTo()->getPointerTo()->getPointerTo();
llvm::Value *VTable = CGF.Builder.CreateBitCast(This, Ty);
VTable = CGF.Builder.CreateLoad(VTable);
llvm::Value *VFuncPtr =
CGF.Builder.CreateConstInBoundsGEP1_64(VTable, VTableIndex, "vfn");
return CGF.Builder.CreateLoad(VFuncPtr);
}
llvm::Value *
CodeGenFunction::BuildVirtualCall(const CXXMethodDecl *MD, llvm::Value *This,
const llvm::Type *Ty) {
MD = MD->getCanonicalDecl();
uint64_t VTableIndex = CGM.getVTables().getMethodVTableIndex(MD);
return ::BuildVirtualCall(*this, VTableIndex, This, Ty);
}
llvm::Value *
CodeGenFunction::BuildVirtualCall(const CXXDestructorDecl *DD, CXXDtorType Type,
llvm::Value *&This, const llvm::Type *Ty) {
DD = cast<CXXDestructorDecl>(DD->getCanonicalDecl());
uint64_t VTableIndex =
CGM.getVTables().getMethodVTableIndex(GlobalDecl(DD, Type));
return ::BuildVirtualCall(*this, VTableIndex, This, Ty);
}
CXXABI::~CXXABI() {}