MBlazeAsmBackend.cpp revision 370b78d795154899a22ca2b4674e890661ff1d59 
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: assert(0 && "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 {
42class MBlazeELFObjectWriter : public MCELFObjectTargetWriter {
43public:
44  MBlazeELFObjectWriter(Triple::OSType OSType)
45    : MCELFObjectTargetWriter(/*is64Bit*/ false, OSType, ELF::EM_MBLAZE,
46                              /*HasRelocationAddend*/ true) {}
47};
48
49class MBlazeAsmBackend : public MCAsmBackend {
50public:
51  MBlazeAsmBackend(const Target &T)
52    : MCAsmBackend() {
53  }
54
55  unsigned getNumFixupKinds() const {
56    return 2;
57  }
58
59  bool MayNeedRelaxation(const MCInst &Inst) const;
60
61  bool fixupNeedsRelaxation(const MCFixup &Fixup,
62                            uint64_t Value,
63                            const MCInstFragment *DF,
64                            const MCAsmLayout &Layout) const;
65
66  void RelaxInstruction(const MCInst &Inst, MCInst &Res) const;
67
68  bool WriteNopData(uint64_t Count, MCObjectWriter *OW) const;
69
70  unsigned getPointerSize() const {
71    return 4;
72  }
73};
74
75static unsigned getRelaxedOpcode(unsigned Op) {
76    switch (Op) {
77    default:            return Op;
78    case MBlaze::ADDIK: return MBlaze::ADDIK32;
79    case MBlaze::ORI:   return MBlaze::ORI32;
80    case MBlaze::BRLID: return MBlaze::BRLID32;
81    }
82}
83
84bool MBlazeAsmBackend::MayNeedRelaxation(const MCInst &Inst) const {
85  if (getRelaxedOpcode(Inst.getOpcode()) == Inst.getOpcode())
86    return false;
87
88  bool hasExprOrImm = false;
89  for (unsigned i = 0; i < Inst.getNumOperands(); ++i)
90    hasExprOrImm |= Inst.getOperand(i).isExpr();
91
92  return hasExprOrImm;
93}
94
95bool MBlazeAsmBackend::fixupNeedsRelaxation(const MCFixup &Fixup,
96                                            uint64_t Value,
97                                            const MCInstFragment *DF,
98                                            const MCAsmLayout &Layout) const {
99  // FIXME: Is this right? It's what the "generic" code was doing before,
100  // but is X86 specific. Is it actually true for MBlaze also, or was it
101  // just close enough to not be a big deal?
102  //
103  // Relax if the value is too big for a (signed) i8.
104  return int64_t(Value) != int64_t(int8_t(Value));
105}
106
107void MBlazeAsmBackend::RelaxInstruction(const MCInst &Inst, MCInst &Res) const {
108  Res = Inst;
109  Res.setOpcode(getRelaxedOpcode(Inst.getOpcode()));
110}
111
112bool MBlazeAsmBackend::WriteNopData(uint64_t Count, MCObjectWriter *OW) const {
113  if ((Count % 4) != 0)
114    return false;
115
116  for (uint64_t i = 0; i < Count; i += 4)
117      OW->Write32(0x00000000);
118
119  return true;
120}
121} // end anonymous namespace
122
123namespace {
124class ELFMBlazeAsmBackend : public MBlazeAsmBackend {
125public:
126  Triple::OSType OSType;
127  ELFMBlazeAsmBackend(const Target &T, Triple::OSType _OSType)
128    : MBlazeAsmBackend(T), OSType(_OSType) { }
129
130  void ApplyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
131                  uint64_t Value) const;
132
133  MCObjectWriter *createObjectWriter(raw_ostream &OS) const {
134    return createELFObjectWriter(new MBlazeELFObjectWriter(OSType), OS,
135                                 /*IsLittleEndian*/ false);
136  }
137};
138
139void ELFMBlazeAsmBackend::ApplyFixup(const MCFixup &Fixup, char *Data,
140                                     unsigned DataSize, uint64_t Value) const {
141  unsigned Size = getFixupKindSize(Fixup.getKind());
142
143  assert(Fixup.getOffset() + Size <= DataSize &&
144         "Invalid fixup offset!");
145
146  char *data = Data + Fixup.getOffset();
147  switch (Size) {
148  default: llvm_unreachable("Cannot fixup unknown value.");
149  case 1:  llvm_unreachable("Cannot fixup 1 byte value.");
150  case 8:  llvm_unreachable("Cannot fixup 8 byte value.");
151
152  case 4:
153    *(data+7) = uint8_t(Value);
154    *(data+6) = uint8_t(Value >> 8);
155    *(data+3) = uint8_t(Value >> 16);
156    *(data+2) = uint8_t(Value >> 24);
157    break;
158
159  case 2:
160    *(data+3) = uint8_t(Value >> 0);
161    *(data+2) = uint8_t(Value >> 8);
162  }
163}
164} // end anonymous namespace
165
166MCAsmBackend *llvm::createMBlazeAsmBackend(const Target &T, StringRef TT) {
167  Triple TheTriple(TT);
168
169  if (TheTriple.isOSDarwin())
170    assert(0 && "Mac not supported on MBlaze");
171
172  if (TheTriple.isOSWindows())
173    assert(0 && "Windows not supported on MBlaze");
174
175  return new ELFMBlazeAsmBackend(T, TheTriple.getOS());
176}
177