1//===-- SystemZMCObjectWriter.cpp - SystemZ ELF writer --------------------===//
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 "MCTargetDesc/SystemZMCTargetDesc.h"
11#include "MCTargetDesc/SystemZMCFixups.h"
12#include "llvm/MC/MCELFObjectWriter.h"
13#include "llvm/MC/MCExpr.h"
14#include "llvm/MC/MCValue.h"
15
16using namespace llvm;
17
18namespace {
19class SystemZObjectWriter : public MCELFObjectTargetWriter {
20public:
21  SystemZObjectWriter(uint8_t OSABI);
22
23  virtual ~SystemZObjectWriter();
24
25protected:
26  // Override MCELFObjectTargetWriter.
27  virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
28                                bool IsPCRel, bool IsRelocWithSymbol,
29                                int64_t Addend) const LLVM_OVERRIDE;
30  virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
31                                         const MCValue &Target,
32                                         const MCFragment &F,
33                                         const MCFixup &Fixup,
34                                         bool IsPCRel) const LLVM_OVERRIDE;
35};
36} // end anonymouse namespace
37
38SystemZObjectWriter::SystemZObjectWriter(uint8_t OSABI)
39  : MCELFObjectTargetWriter(/*Is64Bit=*/true, OSABI, ELF::EM_S390,
40                            /*HasRelocationAddend=*/ true) {}
41
42SystemZObjectWriter::~SystemZObjectWriter() {
43}
44
45// Return the relocation type for an absolute value of MCFixupKind Kind.
46static unsigned getAbsoluteReloc(unsigned Kind) {
47  switch (Kind) {
48  case FK_Data_1: return ELF::R_390_8;
49  case FK_Data_2: return ELF::R_390_16;
50  case FK_Data_4: return ELF::R_390_32;
51  case FK_Data_8: return ELF::R_390_64;
52  }
53  llvm_unreachable("Unsupported absolute address");
54}
55
56// Return the relocation type for a PC-relative value of MCFixupKind Kind.
57static unsigned getPCRelReloc(unsigned Kind) {
58  switch (Kind) {
59  case FK_Data_2:                return ELF::R_390_PC16;
60  case FK_Data_4:                return ELF::R_390_PC32;
61  case FK_Data_8:                return ELF::R_390_PC64;
62  case SystemZ::FK_390_PC16DBL:  return ELF::R_390_PC16DBL;
63  case SystemZ::FK_390_PC32DBL:  return ELF::R_390_PC32DBL;
64  case SystemZ::FK_390_PLT16DBL: return ELF::R_390_PLT16DBL;
65  case SystemZ::FK_390_PLT32DBL: return ELF::R_390_PLT32DBL;
66  }
67  llvm_unreachable("Unsupported PC-relative address");
68}
69
70// Return the R_390_TLS_LE* relocation type for MCFixupKind Kind.
71static unsigned getTLSLEReloc(unsigned Kind) {
72  switch (Kind) {
73  case FK_Data_4: return ELF::R_390_TLS_LE32;
74  case FK_Data_8: return ELF::R_390_TLS_LE64;
75  }
76  llvm_unreachable("Unsupported absolute address");
77}
78
79// Return the PLT relocation counterpart of MCFixupKind Kind.
80static unsigned getPLTReloc(unsigned Kind) {
81  switch (Kind) {
82  case SystemZ::FK_390_PC16DBL: return ELF::R_390_PLT16DBL;
83  case SystemZ::FK_390_PC32DBL: return ELF::R_390_PLT32DBL;
84  }
85  llvm_unreachable("Unsupported absolute address");
86}
87
88unsigned SystemZObjectWriter::GetRelocType(const MCValue &Target,
89                                           const MCFixup &Fixup,
90                                           bool IsPCRel,
91                                           bool IsRelocWithSymbol,
92                                           int64_t Addend) const {
93  MCSymbolRefExpr::VariantKind Modifier = (Target.isAbsolute() ?
94                                           MCSymbolRefExpr::VK_None :
95                                           Target.getSymA()->getKind());
96  unsigned Kind = Fixup.getKind();
97  switch (Modifier) {
98  case MCSymbolRefExpr::VK_None:
99    if (IsPCRel)
100      return getPCRelReloc(Kind);
101    return getAbsoluteReloc(Kind);
102
103  case MCSymbolRefExpr::VK_NTPOFF:
104    assert(!IsPCRel && "NTPOFF shouldn't be PC-relative");
105    return getTLSLEReloc(Kind);
106
107  case MCSymbolRefExpr::VK_GOT:
108    if (IsPCRel && Kind == SystemZ::FK_390_PC32DBL)
109      return ELF::R_390_GOTENT;
110    llvm_unreachable("Only PC-relative GOT accesses are supported for now");
111
112  case MCSymbolRefExpr::VK_PLT:
113    assert(IsPCRel && "@PLT shouldt be PC-relative");
114    return getPLTReloc(Kind);
115
116  default:
117    llvm_unreachable("Modifier not supported");
118  }
119}
120
121const MCSymbol *SystemZObjectWriter::ExplicitRelSym(const MCAssembler &Asm,
122                                                    const MCValue &Target,
123                                                    const MCFragment &F,
124                                                    const MCFixup &Fixup,
125                                                    bool IsPCRel) const {
126  // The addend in a PC-relative R_390_* relocation is always applied to
127  // the PC-relative part of the address.  If some kind of indirection
128  // is applied to the symbol first, we can't use an addend there too.
129  if (!Target.isAbsolute() &&
130      Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None &&
131      IsPCRel)
132    return &Target.getSymA()->getSymbol().AliasedSymbol();
133  return NULL;
134}
135
136MCObjectWriter *llvm::createSystemZObjectWriter(raw_ostream &OS,
137                                                uint8_t OSABI) {
138  MCELFObjectTargetWriter *MOTW = new SystemZObjectWriter(OSABI);
139  return createELFObjectWriter(MOTW, OS, /*IsLittleEndian=*/false);
140}
141