PPCTargetObjectFile.cpp

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//===-- PPCTargetObjectFile.cpp - PPC Object Info -------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
 
#include "PPCTargetObjectFile.h"
#include "MCTargetDesc/PPCMCAsmInfo.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
 
using namespace llvm;
 
void PPC64LinuxTargetObjectFile::initialize(MCContext &Ctx,
                                            const TargetMachine &TM,
                                            const Module &M) {
  TargetLoweringObjectFileELF::initialize(Ctx, TM, M);
}
 
MCSection *PPC64LinuxTargetObjectFile::SelectSectionForGlobal(
    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
  // Here override ReadOnlySection to DataRelROSection for PPC64 SVR4 ABI
  // when we have a constant that contains global relocations.  This is
  // necessary because of this ABI's handling of pointers to functions in
  // a shared library.  The address of a function is actually the address
  // of a function descriptor, which resides in the .opd section.  Generated
  // code uses the descriptor directly rather than going via the GOT as some
  // other ABIs do, which means that initialized function pointers must
  // reference the descriptor.  The linker must convert copy relocs of
  // pointers to functions in shared libraries into dynamic relocations,
  // because of an ordering problem with initialization of copy relocs and
  // PLT entries.  The dynamic relocation will be initialized by the dynamic
  // linker, so we must use DataRelROSection instead of ReadOnlySection.
  // For more information, see the description of ELIMINATE_COPY_RELOCS in
  // GNU ld.
  if (Kind.isReadOnly()) {
    const auto *GVar = dyn_cast<GlobalVariable>(GO);
 
    if (GVar && GVar->isConstant() &&
        GVar->getInitializer()->needsDynamicRelocation())
      Kind = SectionKind::getReadOnlyWithRel();
  }
 
  return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, Kind, TM);
}
 
const MCExpr *PPC64LinuxTargetObjectFile::
getDebugThreadLocalSymbol(const MCSymbol *Sym) const {
  const MCExpr *Expr =
      MCSymbolRefExpr::create(Sym, PPC::S_DTPREL, getContext());
  return MCBinaryExpr::createAdd(Expr,
                                 MCConstantExpr::create(0x8000, getContext()),
                                 getContext());
}