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      1 //===------- ItaniumCXXABI.cpp - AST support for the Itanium C++ ABI ------===//
      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 provides C++ AST support targeting the Itanium C++ ABI, which is
     11 // documented at:
     12 //  http://www.codesourcery.com/public/cxx-abi/abi.html
     13 //  http://www.codesourcery.com/public/cxx-abi/abi-eh.html
     14 //
     15 // It also supports the closely-related ARM C++ ABI, documented at:
     16 // http://infocenter.arm.com/help/topic/com.arm.doc.ihi0041c/IHI0041C_cppabi.pdf
     17 //
     18 //===----------------------------------------------------------------------===//
     19 
     20 #include "CXXABI.h"
     21 #include "clang/AST/ASTContext.h"
     22 #include "clang/AST/DeclCXX.h"
     23 #include "clang/AST/RecordLayout.h"
     24 #include "clang/AST/Type.h"
     25 #include "clang/Basic/TargetInfo.h"
     26 
     27 using namespace clang;
     28 
     29 namespace {
     30 class ItaniumCXXABI : public CXXABI {
     31 protected:
     32   ASTContext &Context;
     33 public:
     34   ItaniumCXXABI(ASTContext &Ctx) : Context(Ctx) { }
     35 
     36   std::pair<uint64_t, unsigned>
     37   getMemberPointerWidthAndAlign(const MemberPointerType *MPT) const {
     38     const TargetInfo &Target = Context.getTargetInfo();
     39     TargetInfo::IntType PtrDiff = Target.getPtrDiffType(0);
     40     uint64_t Width = Target.getTypeWidth(PtrDiff);
     41     unsigned Align = Target.getTypeAlign(PtrDiff);
     42     if (MPT->getPointeeType()->isFunctionType())
     43       Width = 2 * Width;
     44     return std::make_pair(Width, Align);
     45   }
     46 
     47   CallingConv getDefaultMethodCallConv(bool isVariadic) const {
     48     return CC_C;
     49   }
     50 
     51   // We cheat and just check that the class has a vtable pointer, and that it's
     52   // only big enough to have a vtable pointer and nothing more (or less).
     53   bool isNearlyEmpty(const CXXRecordDecl *RD) const {
     54 
     55     // Check that the class has a vtable pointer.
     56     if (!RD->isDynamicClass())
     57       return false;
     58 
     59     const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
     60     CharUnits PointerSize =
     61       Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
     62     return Layout.getNonVirtualSize() == PointerSize;
     63   }
     64 };
     65 
     66 class ARMCXXABI : public ItaniumCXXABI {
     67 public:
     68   ARMCXXABI(ASTContext &Ctx) : ItaniumCXXABI(Ctx) { }
     69 };
     70 }
     71 
     72 CXXABI *clang::CreateItaniumCXXABI(ASTContext &Ctx) {
     73   return new ItaniumCXXABI(Ctx);
     74 }
     75 
     76 CXXABI *clang::CreateARMCXXABI(ASTContext &Ctx) {
     77   return new ARMCXXABI(Ctx);
     78 }
     79