PPCTargetObjectFile.cpp revision 263508 
1//===-- PPCTargetObjectFile.cpp - PPC Object Info -------------------------===//
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#include "PPCTargetObjectFile.h"
11#include "llvm/MC/MCContext.h"
12#include "llvm/MC/MCExpr.h"
13#include "llvm/MC/MCSectionELF.h"
14#include "llvm/Target/Mangler.h"
15
16using namespace llvm;
17
18void
19PPC64LinuxTargetObjectFile::
20Initialize(MCContext &Ctx, const TargetMachine &TM) {
21  TargetLoweringObjectFileELF::Initialize(Ctx, TM);
22  InitializeELF(TM.Options.UseInitArray);
23}
24
25const MCSection * PPC64LinuxTargetObjectFile::
26SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
27                       Mangler *Mang, const TargetMachine &TM) const {
28
29  const MCSection *DefaultSection =
30    TargetLoweringObjectFileELF::SelectSectionForGlobal(GV, Kind, Mang, TM);
31
32  if (DefaultSection != ReadOnlySection)
33    return DefaultSection;
34
35  // Here override ReadOnlySection to DataRelROSection for PPC64 SVR4 ABI
36  // when we have a constant that contains global relocations.  This is
37  // necessary because of this ABI's handling of pointers to functions in
38  // a shared library.  The address of a function is actually the address
39  // of a function descriptor, which resides in the .opd section.  Generated
40  // code uses the descriptor directly rather than going via the GOT as some
41  // other ABIs do, which means that initialized function pointers must
42  // reference the descriptor.  The linker must convert copy relocs of
43  // pointers to functions in shared libraries into dynamic relocations,
44  // because of an ordering problem with initialization of copy relocs and
45  // PLT entries.  The dynamic relocation will be initialized by the dynamic
46  // linker, so we must use DataRelROSection instead of ReadOnlySection.
47  // For more information, see the description of ELIMINATE_COPY_RELOCS in
48  // GNU ld.
49  const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
50
51  if (GVar && GVar->isConstant() &&
52      (GVar->getInitializer()->getRelocationInfo() ==
53       Constant::GlobalRelocations))
54    return DataRelROSection;
55
56  return DefaultSection;
57}
58
59const MCExpr *PPC64LinuxTargetObjectFile::
60getDebugThreadLocalSymbol(const MCSymbol *Sym) const {
61  const MCExpr *Expr =
62    MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_PPC_DTPREL, getContext());
63  return MCBinaryExpr::CreateAdd(Expr,
64                                 MCConstantExpr::Create(0x8000, getContext()),
65                                 getContext());
66}
67
68