1//===-- SystemZMCAsmBackend.cpp - SystemZ assembler backend ---------------===//
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 "MCTargetDesc/SystemZMCFixups.h"
10#include "MCTargetDesc/SystemZMCTargetDesc.h"
11#include "llvm/MC/MCAsmBackend.h"
12#include "llvm/MC/MCELFObjectWriter.h"
13#include "llvm/MC/MCFixupKindInfo.h"
14#include "llvm/MC/MCInst.h"
15#include "llvm/MC/MCObjectWriter.h"
16#include "llvm/MC/MCSubtargetInfo.h"
17
18using namespace llvm;
19
20// Value is a fully-resolved relocation value: Symbol + Addend [- Pivot].
21// Return the bits that should be installed in a relocation field for
22// fixup kind Kind.
23static uint64_t extractBitsForFixup(MCFixupKind Kind, uint64_t Value) {
24  if (Kind < FirstTargetFixupKind)
25    return Value;
26
27  switch (unsigned(Kind)) {
28  case SystemZ::FK_390_PC12DBL:
29  case SystemZ::FK_390_PC16DBL:
30  case SystemZ::FK_390_PC24DBL:
31  case SystemZ::FK_390_PC32DBL:
32    return (int64_t)Value / 2;
33
34  case SystemZ::FK_390_TLS_CALL:
35    return 0;
36  }
37
38  llvm_unreachable("Unknown fixup kind!");
39}
40
41namespace {
42class SystemZMCAsmBackend : public MCAsmBackend {
43  uint8_t OSABI;
44public:
45  SystemZMCAsmBackend(uint8_t osABI)
46      : MCAsmBackend(support::big), OSABI(osABI) {}
47
48  // Override MCAsmBackend
49  unsigned getNumFixupKinds() const override {
50    return SystemZ::NumTargetFixupKinds;
51  }
52  const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override;
53  void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
54                  const MCValue &Target, MutableArrayRef<char> Data,
55                  uint64_t Value, bool IsResolved,
56                  const MCSubtargetInfo *STI) const override;
57  bool mayNeedRelaxation(const MCInst &Inst,
58                         const MCSubtargetInfo &STI) const override {
59    return false;
60  }
61  bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
62                            const MCRelaxableFragment *Fragment,
63                            const MCAsmLayout &Layout) const override {
64    return false;
65  }
66  bool writeNopData(raw_ostream &OS, uint64_t Count) const override;
67  std::unique_ptr<MCObjectTargetWriter>
68  createObjectTargetWriter() const override {
69    return createSystemZObjectWriter(OSABI);
70  }
71};
72} // end anonymous namespace
73
74const MCFixupKindInfo &
75SystemZMCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
76  const static MCFixupKindInfo Infos[SystemZ::NumTargetFixupKinds] = {
77    { "FK_390_PC12DBL",  4, 12, MCFixupKindInfo::FKF_IsPCRel },
78    { "FK_390_PC16DBL",  0, 16, MCFixupKindInfo::FKF_IsPCRel },
79    { "FK_390_PC24DBL",  0, 24, MCFixupKindInfo::FKF_IsPCRel },
80    { "FK_390_PC32DBL",  0, 32, MCFixupKindInfo::FKF_IsPCRel },
81    { "FK_390_TLS_CALL", 0, 0, 0 }
82  };
83
84  if (Kind < FirstTargetFixupKind)
85    return MCAsmBackend::getFixupKindInfo(Kind);
86
87  assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
88         "Invalid kind!");
89  return Infos[Kind - FirstTargetFixupKind];
90}
91
92void SystemZMCAsmBackend::applyFixup(const MCAssembler &Asm,
93                                     const MCFixup &Fixup,
94                                     const MCValue &Target,
95                                     MutableArrayRef<char> Data, uint64_t Value,
96                                     bool IsResolved,
97                                     const MCSubtargetInfo *STI) const {
98  MCFixupKind Kind = Fixup.getKind();
99  unsigned Offset = Fixup.getOffset();
100  unsigned BitSize = getFixupKindInfo(Kind).TargetSize;
101  unsigned Size = (BitSize + 7) / 8;
102
103  assert(Offset + Size <= Data.size() && "Invalid fixup offset!");
104
105  // Big-endian insertion of Size bytes.
106  Value = extractBitsForFixup(Kind, Value);
107  if (BitSize < 64)
108    Value &= ((uint64_t)1 << BitSize) - 1;
109  unsigned ShiftValue = (Size * 8) - 8;
110  for (unsigned I = 0; I != Size; ++I) {
111    Data[Offset + I] |= uint8_t(Value >> ShiftValue);
112    ShiftValue -= 8;
113  }
114}
115
116bool SystemZMCAsmBackend::writeNopData(raw_ostream &OS, uint64_t Count) const {
117  for (uint64_t I = 0; I != Count; ++I)
118    OS << '\x7';
119  return true;
120}
121
122MCAsmBackend *llvm::createSystemZMCAsmBackend(const Target &T,
123                                              const MCSubtargetInfo &STI,
124                                              const MCRegisterInfo &MRI,
125                                              const MCTargetOptions &Options) {
126  uint8_t OSABI =
127      MCELFObjectTargetWriter::getOSABI(STI.getTargetTriple().getOS());
128  return new SystemZMCAsmBackend(OSABI);
129}
130