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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/MangleNumberingContext.h"
     24 #include "clang/AST/RecordLayout.h"
     25 #include "clang/AST/Type.h"
     26 #include "clang/Basic/TargetInfo.h"
     27 
     28 using namespace clang;
     29 
     30 namespace {
     31 
     32 /// \brief Keeps track of the mangled names of lambda expressions and block
     33 /// literals within a particular context.
     34 class ItaniumNumberingContext : public MangleNumberingContext {
     35   llvm::DenseMap<IdentifierInfo*, unsigned> VarManglingNumbers;
     36   llvm::DenseMap<IdentifierInfo*, unsigned> TagManglingNumbers;
     37 
     38 public:
     39   /// Variable decls are numbered by identifier.
     40   unsigned getManglingNumber(const VarDecl *VD, unsigned) override {
     41     return ++VarManglingNumbers[VD->getIdentifier()];
     42   }
     43 
     44   unsigned getManglingNumber(const TagDecl *TD, unsigned) override {
     45     return ++TagManglingNumbers[TD->getIdentifier()];
     46   }
     47 };
     48 
     49 class ItaniumCXXABI : public CXXABI {
     50 protected:
     51   ASTContext &Context;
     52 public:
     53   ItaniumCXXABI(ASTContext &Ctx) : Context(Ctx) { }
     54 
     55   std::pair<uint64_t, unsigned>
     56   getMemberPointerWidthAndAlign(const MemberPointerType *MPT) const override {
     57     const TargetInfo &Target = Context.getTargetInfo();
     58     TargetInfo::IntType PtrDiff = Target.getPtrDiffType(0);
     59     uint64_t Width = Target.getTypeWidth(PtrDiff);
     60     unsigned Align = Target.getTypeAlign(PtrDiff);
     61     if (MPT->getPointeeType()->isFunctionType())
     62       Width = 2 * Width;
     63     return std::make_pair(Width, Align);
     64   }
     65 
     66   CallingConv getDefaultMethodCallConv(bool isVariadic) const override {
     67     const llvm::Triple &T = Context.getTargetInfo().getTriple();
     68     if (!isVariadic && T.isWindowsGNUEnvironment() &&
     69         T.getArch() == llvm::Triple::x86)
     70       return CC_X86ThisCall;
     71     return CC_C;
     72   }
     73 
     74   // We cheat and just check that the class has a vtable pointer, and that it's
     75   // only big enough to have a vtable pointer and nothing more (or less).
     76   bool isNearlyEmpty(const CXXRecordDecl *RD) const override {
     77 
     78     // Check that the class has a vtable pointer.
     79     if (!RD->isDynamicClass())
     80       return false;
     81 
     82     const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
     83     CharUnits PointerSize =
     84       Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
     85     return Layout.getNonVirtualSize() == PointerSize;
     86   }
     87 
     88   MangleNumberingContext *createMangleNumberingContext() const override {
     89     return new ItaniumNumberingContext();
     90   }
     91 };
     92 }
     93 
     94 CXXABI *clang::CreateItaniumCXXABI(ASTContext &Ctx) {
     95   return new ItaniumCXXABI(Ctx);
     96 }
     97