1//===-- MSP430AsmBackend.cpp - MSP430 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/MSP430FixupKinds.h"
10#include "MCTargetDesc/MSP430MCTargetDesc.h"
11#include "llvm/ADT/APInt.h"
12#include "llvm/MC/MCAsmBackend.h"
13#include "llvm/MC/MCAssembler.h"
14#include "llvm/MC/MCContext.h"
15#include "llvm/MC/MCDirectives.h"
16#include "llvm/MC/MCELFObjectWriter.h"
17#include "llvm/MC/MCExpr.h"
18#include "llvm/MC/MCFixupKindInfo.h"
19#include "llvm/MC/MCObjectWriter.h"
20#include "llvm/MC/MCSubtargetInfo.h"
21#include "llvm/MC/MCSymbol.h"
22#include "llvm/MC/MCTargetOptions.h"
23#include "llvm/Support/ErrorHandling.h"
24#include "llvm/Support/raw_ostream.h"
25
26using namespace llvm;
27
28namespace {
29class MSP430AsmBackend : public MCAsmBackend {
30  uint8_t OSABI;
31
32  uint64_t adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
33                            MCContext &Ctx) const;
34
35public:
36  MSP430AsmBackend(const MCSubtargetInfo &STI, uint8_t OSABI)
37      : MCAsmBackend(support::little), OSABI(OSABI) {}
38  ~MSP430AsmBackend() override {}
39
40  void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
41                  const MCValue &Target, MutableArrayRef<char> Data,
42                  uint64_t Value, bool IsResolved,
43                  const MCSubtargetInfo *STI) const override;
44
45  std::unique_ptr<MCObjectTargetWriter>
46  createObjectTargetWriter() const override {
47    return createMSP430ELFObjectWriter(OSABI);
48  }
49
50  bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
51                            const MCRelaxableFragment *DF,
52                            const MCAsmLayout &Layout) const override {
53    return false;
54  }
55
56  bool fixupNeedsRelaxationAdvanced(const MCFixup &Fixup, bool Resolved,
57                                    uint64_t Value,
58                                    const MCRelaxableFragment *DF,
59                                    const MCAsmLayout &Layout,
60                                    const bool WasForced) const override {
61    return false;
62  }
63
64  unsigned getNumFixupKinds() const override {
65    return MSP430::NumTargetFixupKinds;
66  }
67
68  const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override {
69    const static MCFixupKindInfo Infos[MSP430::NumTargetFixupKinds] = {
70      // This table must be in the same order of enum in MSP430FixupKinds.h.
71      //
72      // name            offset bits flags
73      {"fixup_32",            0, 32, 0},
74      {"fixup_10_pcrel",      0, 10, MCFixupKindInfo::FKF_IsPCRel},
75      {"fixup_16",            0, 16, 0},
76      {"fixup_16_pcrel",      0, 16, MCFixupKindInfo::FKF_IsPCRel},
77      {"fixup_16_byte",       0, 16, 0},
78      {"fixup_16_pcrel_byte", 0, 16, MCFixupKindInfo::FKF_IsPCRel},
79      {"fixup_2x_pcrel",      0, 10, MCFixupKindInfo::FKF_IsPCRel},
80      {"fixup_rl_pcrel",      0, 16, MCFixupKindInfo::FKF_IsPCRel},
81      {"fixup_8",             0,  8, 0},
82      {"fixup_sym_diff",      0, 32, 0},
83    };
84    static_assert((array_lengthof(Infos)) == MSP430::NumTargetFixupKinds,
85                  "Not all fixup kinds added to Infos array");
86
87    if (Kind < FirstTargetFixupKind)
88      return MCAsmBackend::getFixupKindInfo(Kind);
89
90    return Infos[Kind - FirstTargetFixupKind];
91  }
92
93  bool mayNeedRelaxation(const MCInst &Inst,
94                         const MCSubtargetInfo &STI) const override {
95    return false;
96  }
97
98  void relaxInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
99                        MCInst &Res) const override {}
100
101  bool writeNopData(raw_ostream &OS, uint64_t Count) const override;
102};
103
104uint64_t MSP430AsmBackend::adjustFixupValue(const MCFixup &Fixup,
105                                            uint64_t Value,
106                                            MCContext &Ctx) const {
107  unsigned Kind = Fixup.getKind();
108  switch (Kind) {
109  case MSP430::fixup_10_pcrel: {
110    if (Value & 0x1)
111      Ctx.reportError(Fixup.getLoc(), "fixup value must be 2-byte aligned");
112
113    // Offset is signed
114    int16_t Offset = Value;
115    // Jumps are in words
116    Offset >>= 1;
117    // PC points to the next instruction so decrement by one
118    --Offset;
119
120    if (Offset < -512 || Offset > 511)
121      Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
122
123    // Mask 10 bits
124    Offset &= 0x3ff;
125
126    return Offset;
127  }
128  default:
129    return Value;
130  }
131}
132
133void MSP430AsmBackend::applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
134                                  const MCValue &Target,
135                                  MutableArrayRef<char> Data,
136                                  uint64_t Value, bool IsResolved,
137                                  const MCSubtargetInfo *STI) const {
138  Value = adjustFixupValue(Fixup, Value, Asm.getContext());
139  MCFixupKindInfo Info = getFixupKindInfo(Fixup.getKind());
140  if (!Value)
141    return; // Doesn't change encoding.
142
143  // Shift the value into position.
144  Value <<= Info.TargetOffset;
145
146  unsigned Offset = Fixup.getOffset();
147  unsigned NumBytes = alignTo(Info.TargetSize + Info.TargetOffset, 8) / 8;
148
149  assert(Offset + NumBytes <= Data.size() && "Invalid fixup offset!");
150
151  // For each byte of the fragment that the fixup touches, mask in the
152  // bits from the fixup value.
153  for (unsigned i = 0; i != NumBytes; ++i) {
154    Data[Offset + i] |= uint8_t((Value >> (i * 8)) & 0xff);
155  }
156}
157
158bool MSP430AsmBackend::writeNopData(raw_ostream &OS, uint64_t Count) const {
159  if ((Count % 2) != 0)
160    return false;
161
162  // The canonical nop on MSP430 is mov #0, r3
163  uint64_t NopCount = Count / 2;
164  while (NopCount--)
165    OS.write("\x03\x43", 2);
166
167  return true;
168}
169
170} // end anonymous namespace
171
172MCAsmBackend *llvm::createMSP430MCAsmBackend(const Target &T,
173                                             const MCSubtargetInfo &STI,
174                                             const MCRegisterInfo &MRI,
175                                             const MCTargetOptions &Options) {
176  return new MSP430AsmBackend(STI, ELF::ELFOSABI_STANDALONE);
177}
178