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//===------- ItaniumCXXABI.cpp - Emit LLVM Code from ASTs for a Module ----===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This provides C++ code generation targetting the Itanium C++ ABI. The class
// in this file generates structures that follow the Itanium C++ ABI, which is
// documented at:
// http://www.codesourcery.com/public/cxx-abi/abi.html
// http://www.codesourcery.com/public/cxx-abi/abi-eh.html
//
// It also supports the closely-related ARM ABI, documented at:
// http://infocenter.arm.com/help/topic/com.arm.doc.ihi0041c/IHI0041C_cppabi.pdf
//
//===----------------------------------------------------------------------===//
#include "CGCXXABI.h"
#include "CodeGenFunction.h"
#include "CodeGenModule.h"
#include "Mangle.h"
#include <clang/AST/Type.h>
#include <llvm/Value.h>
using namespace clang;
using namespace CodeGen;
namespace {
class ItaniumCXXABI : public CodeGen::CGCXXABI {
protected:
CodeGenModule &CGM;
CodeGen::MangleContext MangleCtx;
public:
ItaniumCXXABI(CodeGen::CodeGenModule &CGM) :
CGM(CGM), MangleCtx(CGM.getContext(), CGM.getDiags()) { }
CodeGen::MangleContext &getMangleContext() {
return MangleCtx;
}
llvm::Value *EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
llvm::Value *&This,
llvm::Value *MemFnPtr,
const MemberPointerType *MPT);
};
class ARMCXXABI : public ItaniumCXXABI {
public:
ARMCXXABI(CodeGen::CodeGenModule &CGM) : ItaniumCXXABI(CGM) {}
};
}
CodeGen::CGCXXABI *CodeGen::CreateItaniumCXXABI(CodeGenModule &CGM) {
return new ItaniumCXXABI(CGM);
}
CodeGen::CGCXXABI *CodeGen::CreateARMCXXABI(CodeGenModule &CGM) {
return new ARMCXXABI(CGM);
}
llvm::Value *
ItaniumCXXABI::EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
llvm::Value *&This,
llvm::Value *MemFnPtr,
const MemberPointerType *MPT) {
CGBuilderTy &Builder = CGF.Builder;
const FunctionProtoType *FPT =
MPT->getPointeeType()->getAs<FunctionProtoType>();
const CXXRecordDecl *RD =
cast<CXXRecordDecl>(MPT->getClass()->getAs<RecordType>()->getDecl());
const llvm::FunctionType *FTy =
CGM.getTypes().GetFunctionType(CGM.getTypes().getFunctionInfo(RD, FPT),
FPT->isVariadic());
llvm::BasicBlock *FnVirtual = CGF.createBasicBlock("fn.virtual");
llvm::BasicBlock *FnNonVirtual = CGF.createBasicBlock("fn.nonvirtual");
llvm::BasicBlock *FnEnd = CGF.createBasicBlock("fn.end");
// Load the adjustment, which is in the second field.
llvm::Value *Adj = Builder.CreateStructGEP(MemFnPtr, 1);
Adj = Builder.CreateLoad(Adj, "mem.fn.adj");
// Apply the adjustment and cast back to the original struct type
// for consistency.
llvm::Value *Ptr = Builder.CreateBitCast(This, Builder.getInt8PtrTy(), "ptr");
Ptr = Builder.CreateInBoundsGEP(Ptr, Adj, "adj");
This = Builder.CreateBitCast(Ptr, This->getType(), "this");
// Load the function pointer.
llvm::Value *FnPtr = Builder.CreateStructGEP(MemFnPtr, 0, "mem.fn.ptr");
llvm::Value *FnAsInt = Builder.CreateLoad(FnPtr, "fn");
// If the LSB in the function pointer is 1, the function pointer points to
// a virtual function.
llvm::Constant *iptr_1 = llvm::ConstantInt::get(FnAsInt->getType(), 1);
llvm::Value *IsVirtual = Builder.CreateAnd(FnAsInt, iptr_1);
IsVirtual = Builder.CreateIsNotNull(IsVirtual);
Builder.CreateCondBr(IsVirtual, FnVirtual, FnNonVirtual);
// In the virtual path, the adjustment left 'This' pointing to the
// vtable of the correct base subobject. The "function pointer" is an
// offset within the vtable (+1 for the virtual flag).
CGF.EmitBlock(FnVirtual);
// Cast the adjusted this to a pointer to vtable pointer and load.
const llvm::Type *VTableTy = Builder.getInt8PtrTy();
llvm::Value *VTable = Builder.CreateBitCast(This, VTableTy->getPointerTo());
VTable = Builder.CreateLoad(VTable);
// Apply the offset.
llvm::Value *VTableOffset = Builder.CreateSub(FnAsInt, iptr_1);
VTable = Builder.CreateGEP(VTable, VTableOffset, "fn");
// Load the virtual function to call.
VTable = Builder.CreateBitCast(VTable, FTy->getPointerTo()->getPointerTo());
llvm::Value *VirtualFn = Builder.CreateLoad(VTable, "virtualfn");
CGF.EmitBranch(FnEnd);
// In the non-virtual path, the function pointer is actually a
// function pointer.
CGF.EmitBlock(FnNonVirtual);
llvm::Value *NonVirtualFn =
Builder.CreateIntToPtr(FnAsInt, FTy->getPointerTo());
// We're done.
CGF.EmitBlock(FnEnd);
llvm::PHINode *Callee = Builder.CreatePHI(FTy->getPointerTo());
Callee->reserveOperandSpace(2);
Callee->addIncoming(VirtualFn, FnVirtual);
Callee->addIncoming(NonVirtualFn, FnNonVirtual);
return Callee;
}
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