1//===-- MBlazeAsmBackend.cpp - MBlaze Assembler Backend -------------------===//
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/MBlazeMCTargetDesc.h"
11#include "llvm/MC/MCAsmBackend.h"
12#include "llvm/MC/MCAssembler.h"
13#include "llvm/MC/MCAsmLayout.h"
14#include "llvm/MC/MCELFObjectWriter.h"
15#include "llvm/MC/MCELFSymbolFlags.h"
16#include "llvm/MC/MCExpr.h"
17#include "llvm/MC/MCObjectWriter.h"
18#include "llvm/MC/MCSectionELF.h"
19#include "llvm/MC/MCSectionMachO.h"
20#include "llvm/MC/MCValue.h"
21#include "llvm/ADT/Twine.h"
22#include "llvm/Support/ELF.h"
23#include "llvm/Support/ErrorHandling.h"
24#include "llvm/Support/TargetRegistry.h"
25#include "llvm/Support/raw_ostream.h"
26using namespace llvm;
27
28static unsigned getFixupKindSize(unsigned Kind) {
29  switch (Kind) {
30  default: llvm_unreachable("invalid fixup kind!");
31  case FK_Data_1: return 1;
32  case FK_PCRel_2:
33  case FK_Data_2: return 2;
34  case FK_PCRel_4:
35  case FK_Data_4: return 4;
36  case FK_Data_8: return 8;
37  }
38}
39
40
41namespace {
42
43class MBlazeAsmBackend : public MCAsmBackend {
44public:
45  MBlazeAsmBackend(const Target &T)
46    : MCAsmBackend() {
47  }
48
49  unsigned getNumFixupKinds() const {
50    return 2;
51  }
52
53  bool mayNeedRelaxation(const MCInst &Inst) const;
54
55  bool fixupNeedsRelaxation(const MCFixup &Fixup,
56                            uint64_t Value,
57                            const MCInstFragment *DF,
58                            const MCAsmLayout &Layout) const;
59
60  void relaxInstruction(const MCInst &Inst, MCInst &Res) const;
61
62  bool writeNopData(uint64_t Count, MCObjectWriter *OW) const;
63
64  unsigned getPointerSize() const {
65    return 4;
66  }
67};
68
69static unsigned getRelaxedOpcode(unsigned Op) {
70    switch (Op) {
71    default:            return Op;
72    case MBlaze::ADDIK: return MBlaze::ADDIK32;
73    case MBlaze::ORI:   return MBlaze::ORI32;
74    case MBlaze::BRLID: return MBlaze::BRLID32;
75    }
76}
77
78bool MBlazeAsmBackend::mayNeedRelaxation(const MCInst &Inst) const {
79  if (getRelaxedOpcode(Inst.getOpcode()) == Inst.getOpcode())
80    return false;
81
82  bool hasExprOrImm = false;
83  for (unsigned i = 0; i < Inst.getNumOperands(); ++i)
84    hasExprOrImm |= Inst.getOperand(i).isExpr();
85
86  return hasExprOrImm;
87}
88
89bool MBlazeAsmBackend::fixupNeedsRelaxation(const MCFixup &Fixup,
90                                            uint64_t Value,
91                                            const MCInstFragment *DF,
92                                            const MCAsmLayout &Layout) const {
93  // FIXME: Is this right? It's what the "generic" code was doing before,
94  // but is X86 specific. Is it actually true for MBlaze also, or was it
95  // just close enough to not be a big deal?
96  //
97  // Relax if the value is too big for a (signed) i8.
98  return int64_t(Value) != int64_t(int8_t(Value));
99}
100
101void MBlazeAsmBackend::relaxInstruction(const MCInst &Inst, MCInst &Res) const {
102  Res = Inst;
103  Res.setOpcode(getRelaxedOpcode(Inst.getOpcode()));
104}
105
106bool MBlazeAsmBackend::writeNopData(uint64_t Count, MCObjectWriter *OW) const {
107  if ((Count % 4) != 0)
108    return false;
109
110  for (uint64_t i = 0; i < Count; i += 4)
111      OW->Write32(0x00000000);
112
113  return true;
114}
115} // end anonymous namespace
116
117namespace {
118class ELFMBlazeAsmBackend : public MBlazeAsmBackend {
119public:
120  uint8_t OSABI;
121  ELFMBlazeAsmBackend(const Target &T, uint8_t _OSABI)
122    : MBlazeAsmBackend(T), OSABI(_OSABI) { }
123
124  void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
125                  uint64_t Value) const;
126
127  MCObjectWriter *createObjectWriter(raw_ostream &OS) const {
128    return createMBlazeELFObjectWriter(OS, OSABI);
129  }
130};
131
132void ELFMBlazeAsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
133                                     unsigned DataSize, uint64_t Value) const {
134  unsigned Size = getFixupKindSize(Fixup.getKind());
135
136  assert(Fixup.getOffset() + Size <= DataSize &&
137         "Invalid fixup offset!");
138
139  char *data = Data + Fixup.getOffset();
140  switch (Size) {
141  default: llvm_unreachable("Cannot fixup unknown value.");
142  case 1:  llvm_unreachable("Cannot fixup 1 byte value.");
143  case 8:  llvm_unreachable("Cannot fixup 8 byte value.");
144
145  case 4:
146    *(data+7) = uint8_t(Value);
147    *(data+6) = uint8_t(Value >> 8);
148    *(data+3) = uint8_t(Value >> 16);
149    *(data+2) = uint8_t(Value >> 24);
150    break;
151
152  case 2:
153    *(data+3) = uint8_t(Value >> 0);
154    *(data+2) = uint8_t(Value >> 8);
155  }
156}
157} // end anonymous namespace
158
159MCAsmBackend *llvm::createMBlazeAsmBackend(const Target &T, StringRef TT) {
160  Triple TheTriple(TT);
161
162  if (TheTriple.isOSDarwin())
163    assert(0 && "Mac not supported on MBlaze");
164
165  if (TheTriple.isOSWindows())
166    assert(0 && "Windows not supported on MBlaze");
167
168  uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TheTriple.getOS());
169  return new ELFMBlazeAsmBackend(T, OSABI);
170}
171