Mangle.cpp

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//===--- Mangle.cpp - Mangle C++ Names --------------------------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Implements generic name mangling support for blocks and Objective-C.
//
//===----------------------------------------------------------------------===//
#include "clang/AST/Attr.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/Mangle.h"
#include "clang/Basic/ABI.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/TargetInfo.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"

using namespace clang;

// FIXME: For blocks we currently mimic GCC's mangling scheme, which leaves
// much to be desired. Come up with a better mangling scheme.

static void mangleFunctionBlock(MangleContext &Context,
                                StringRef Outer,
                                const BlockDecl *BD,
                                raw_ostream &Out) {
  unsigned discriminator = Context.getBlockId(BD, true);
  if (discriminator == 0)
    Out << "__" << Outer << "_block_invoke";
  else
    Out << "__" << Outer << "_block_invoke_" << discriminator+1;
}

void MangleContext::anchor() { }

enum CCMangling {
  CCM_Other,
  CCM_Fast,
  CCM_RegCall,
  CCM_Vector,
  CCM_Std
};

static bool isExternC(const NamedDecl *ND) {
  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND))
    return FD->isExternC();
  return cast<VarDecl>(ND)->isExternC();
}

static CCMangling getCallingConvMangling(const ASTContext &Context,
                                         const NamedDecl *ND) {
  const TargetInfo &TI = Context.getTargetInfo();
  const llvm::Triple &Triple = TI.getTriple();
  if (!Triple.isOSWindows() ||
      !(Triple.getArch() == llvm::Triple::x86 ||
        Triple.getArch() == llvm::Triple::x86_64))
    return CCM_Other;

  if (Context.getLangOpts().CPlusPlus && !isExternC(ND) &&
      TI.getCXXABI() == TargetCXXABI::Microsoft)
    return CCM_Other;

  const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND);
  if (!FD)
    return CCM_Other;
  QualType T = FD->getType();

  const FunctionType *FT = T->castAs<FunctionType>();

  CallingConv CC = FT->getCallConv();
  switch (CC) {
  default:
    return CCM_Other;
  case CC_X86FastCall:
    return CCM_Fast;
  case CC_X86StdCall:
    return CCM_Std;
  case CC_X86VectorCall:
    return CCM_Vector;
  }
}

bool MangleContext::shouldMangleDeclName(const NamedDecl *D) {
  const ASTContext &ASTContext = getASTContext();

  CCMangling CC = getCallingConvMangling(ASTContext, D);
  if (CC != CCM_Other)
    return true;

  // If the declaration has an owning module for linkage purposes that needs to
  // be mangled, we must mangle its name.
  if (!D->hasExternalFormalLinkage() && D->getOwningModuleForLinkage())
    return true;

  // In C, functions with no attributes never need to be mangled. Fastpath them.
  if (!getASTContext().getLangOpts().CPlusPlus && !D->hasAttrs())
    return false;

  // Any decl can be declared with __asm("foo") on it, and this takes precedence
  // over all other naming in the .o file.
  if (D->hasAttr<AsmLabelAttr>())
    return true;

  return shouldMangleCXXName(D);
}

void MangleContext::mangleName(const NamedDecl *D, raw_ostream &Out) {
  // Any decl can be declared with __asm("foo") on it, and this takes precedence
  // over all other naming in the .o file.
  if (const AsmLabelAttr *ALA = D->getAttr<AsmLabelAttr>()) {
    // If we have an asm name, then we use it as the mangling.

    // Adding the prefix can cause problems when one file has a "foo" and
    // another has a "\01foo". That is known to happen on ELF with the
    // tricks normally used for producing aliases (PR9177). Fortunately the
    // llvm mangler on ELF is a nop, so we can just avoid adding the \01
    // marker.  We also avoid adding the marker if this is an alias for an
    // LLVM intrinsic.
    char GlobalPrefix =
        getASTContext().getTargetInfo().getDataLayout().getGlobalPrefix();
    if (GlobalPrefix && !ALA->getLabel().startswith("llvm."))
      Out << '\01'; // LLVM IR Marker for __asm("foo")

    Out << ALA->getLabel();
    return;
  }

  const ASTContext &ASTContext = getASTContext();
  CCMangling CC = getCallingConvMangling(ASTContext, D);
  bool MCXX = shouldMangleCXXName(D);
  const TargetInfo &TI = Context.getTargetInfo();
  if (CC == CCM_Other || (MCXX && TI.getCXXABI() == TargetCXXABI::Microsoft)) {
    if (const ObjCMethodDecl *OMD = dyn_cast<ObjCMethodDecl>(D))
      mangleObjCMethodName(OMD, Out);
    else
      mangleCXXName(D, Out);
    return;
  }

  Out << '\01';
  if (CC == CCM_Std)
    Out << '_';
  else if (CC == CCM_Fast)
    Out << '@';
  else if (CC == CCM_RegCall)
    Out << "__regcall3__";

  if (!MCXX)
    Out << D->getIdentifier()->getName();
  else if (const ObjCMethodDecl *OMD = dyn_cast<ObjCMethodDecl>(D))
    mangleObjCMethodName(OMD, Out);
  else
    mangleCXXName(D, Out);

  const FunctionDecl *FD = cast<FunctionDecl>(D);
  const FunctionType *FT = FD->getType()->castAs<FunctionType>();
  const FunctionProtoType *Proto = dyn_cast<FunctionProtoType>(FT);
  if (CC == CCM_Vector)
    Out << '@';
  Out << '@';
  if (!Proto) {
    Out << '0';
    return;
  }
  assert(!Proto->isVariadic());
  unsigned ArgWords = 0;
  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD))
    if (!MD->isStatic())
      ++ArgWords;
  for (const auto &AT : Proto->param_types())
    // Size should be aligned to pointer size.
    ArgWords +=
        llvm::alignTo(ASTContext.getTypeSize(AT), TI.getPointerWidth(0)) /
        TI.getPointerWidth(0);
  Out << ((TI.getPointerWidth(0) / 8) * ArgWords);
}

void MangleContext::mangleGlobalBlock(const BlockDecl *BD,
                                      const NamedDecl *ID,
                                      raw_ostream &Out) {
  unsigned discriminator = getBlockId(BD, false);
  if (ID) {
    if (shouldMangleDeclName(ID))
      mangleName(ID, Out);
    else {
      Out << ID->getIdentifier()->getName();
    }
  }
  if (discriminator == 0)
    Out << "_block_invoke";
  else
    Out << "_block_invoke_" << discriminator+1;
}

void MangleContext::mangleCtorBlock(const CXXConstructorDecl *CD,
                                    CXXCtorType CT, const BlockDecl *BD,
                                    raw_ostream &ResStream) {
  SmallString<64> Buffer;
  llvm::raw_svector_ostream Out(Buffer);
  mangleCXXCtor(CD, CT, Out);
  mangleFunctionBlock(*this, Buffer, BD, ResStream);
}

void MangleContext::mangleDtorBlock(const CXXDestructorDecl *DD,
                                    CXXDtorType DT, const BlockDecl *BD,
                                    raw_ostream &ResStream) {
  SmallString<64> Buffer;
  llvm::raw_svector_ostream Out(Buffer);
  mangleCXXDtor(DD, DT, Out);
  mangleFunctionBlock(*this, Buffer, BD, ResStream);
}

void MangleContext::mangleBlock(const DeclContext *DC, const BlockDecl *BD,
                                raw_ostream &Out) {
  assert(!isa<CXXConstructorDecl>(DC) && !isa<CXXDestructorDecl>(DC));

  SmallString<64> Buffer;
  llvm::raw_svector_ostream Stream(Buffer);
  if (const ObjCMethodDecl *Method = dyn_cast<ObjCMethodDecl>(DC)) {
    mangleObjCMethodName(Method, Stream);
  } else {
    assert((isa<NamedDecl>(DC) || isa<BlockDecl>(DC)) &&
           "expected a NamedDecl or BlockDecl");
    if (isa<BlockDecl>(DC))
      for (; DC && isa<BlockDecl>(DC); DC = DC->getParent())
        (void) getBlockId(cast<BlockDecl>(DC), true);
    assert((isa<TranslationUnitDecl>(DC) || isa<NamedDecl>(DC)) &&
           "expected a TranslationUnitDecl or a NamedDecl");
    if (const auto *CD = dyn_cast<CXXConstructorDecl>(DC))
      mangleCtorBlock(CD, /*CT*/ Ctor_Complete, BD, Out);
    else if (const auto *DD = dyn_cast<CXXDestructorDecl>(DC))
      mangleDtorBlock(DD, /*DT*/ Dtor_Complete, BD, Out);
    else if (auto ND = dyn_cast<NamedDecl>(DC)) {
      if (!shouldMangleDeclName(ND) && ND->getIdentifier())
        Stream << ND->getIdentifier()->getName();
      else {
        // FIXME: We were doing a mangleUnqualifiedName() before, but that's
        // a private member of a class that will soon itself be private to the
        // Itanium C++ ABI object. What should we do now? Right now, I'm just
        // calling the mangleName() method on the MangleContext; is there a
        // better way?
        mangleName(ND, Stream);
      }
    }
  }
  mangleFunctionBlock(*this, Buffer, BD, Out);
}

void MangleContext::mangleObjCMethodNameWithoutSize(const ObjCMethodDecl *MD,
                                                    raw_ostream &OS) {
  const ObjCContainerDecl *CD =
  dyn_cast<ObjCContainerDecl>(MD->getDeclContext());
  assert (CD && "Missing container decl in GetNameForMethod");
  OS << (MD->isInstanceMethod() ? '-' : '+') << '[';
  if (const ObjCCategoryImplDecl *CID = dyn_cast<ObjCCategoryImplDecl>(CD)) {
    OS << CID->getClassInterface()->getName();
    OS << '(' << *CID << ')';
  } else {
    OS << CD->getName();
  }
  OS << ' ';
  MD->getSelector().print(OS);
  OS << ']';
}

void MangleContext::mangleObjCMethodName(const ObjCMethodDecl *MD,
                                         raw_ostream &Out) {
  SmallString<64> Name;
  llvm::raw_svector_ostream OS(Name);

  mangleObjCMethodNameWithoutSize(MD, OS);
  Out << OS.str().size() << OS.str();
}