llvm/lib/Target/PowerPC/PPCTargetObjectFile.cpp

   1 //===-- PPCTargetObjectFile.cpp - PPC Object Info -------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "PPCTargetObjectFile.h"
  10 #include "llvm/IR/GlobalVariable.h"
  11 #include "llvm/IR/Mangler.h"
  12 #include "llvm/MC/MCContext.h"
  13 #include "llvm/MC/MCExpr.h"
  14 #include "llvm/MC/MCSectionELF.h"
  15
  16 using namespace llvm;
  17
  18 void
  19 PPC64LinuxTargetObjectFile::
  20 Initialize(MCContext &Ctx, const TargetMachine &TM) {
  21   TargetLoweringObjectFileELF::Initialize(Ctx, TM);
  22 }
  23
  24 MCSection *PPC64LinuxTargetObjectFile::SelectSectionForGlobal(
  25     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
  26   // Here override ReadOnlySection to DataRelROSection for PPC64 SVR4 ABI
  27   // when we have a constant that contains global relocations.  This is
  28   // necessary because of this ABI's handling of pointers to functions in
  29   // a shared library.  The address of a function is actually the address
  30   // of a function descriptor, which resides in the .opd section.  Generated
  31   // code uses the descriptor directly rather than going via the GOT as some
  32   // other ABIs do, which means that initialized function pointers must
  33   // reference the descriptor.  The linker must convert copy relocs of
  34   // pointers to functions in shared libraries into dynamic relocations,
  35   // because of an ordering problem with initialization of copy relocs and
  36   // PLT entries.  The dynamic relocation will be initialized by the dynamic
  37   // linker, so we must use DataRelROSection instead of ReadOnlySection.
  38   // For more information, see the description of ELIMINATE_COPY_RELOCS in
  39   // GNU ld.
  40   if (Kind.isReadOnly()) {
  41     const auto *GVar = dyn_cast<GlobalVariable>(GO);
  42
  43     if (GVar && GVar->isConstant() &&
  44         GVar->getInitializer()->needsDynamicRelocation())
  45       Kind = SectionKind::getReadOnlyWithRel();
  46   }
  47
  48   return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, Kind, TM);
  49 }
  50
  51 const MCExpr *PPC64LinuxTargetObjectFile::
  52 getDebugThreadLocalSymbol(const MCSymbol *Sym) const {
  53   const MCExpr *Expr =
  54     MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_DTPREL, getContext());
  55   return MCBinaryExpr::createAdd(Expr,
  56                                  MCConstantExpr::create(0x8000, getContext()),
  57                                  getContext());
  58 }
  59