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(llvm::endianness::little), OSABI(OSABI) {}
38 ~MSP430AsmBackend() override = default;
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 fixupNeedsRelaxationAdvanced(const MCAssembler &Asm,
51 const MCFixup &Fixup, bool Resolved,
52 uint64_t Value,
53 const MCRelaxableFragment *DF,
54 const bool WasForced) const override {
55 return false;
56 }
57
58 unsigned getNumFixupKinds() const override {
59 return MSP430::NumTargetFixupKinds;
60 }
61
62 const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override {
63 const static MCFixupKindInfo Infos[MSP430::NumTargetFixupKinds] = {
64 // This table must be in the same order of enum in MSP430FixupKinds.h.
65 //
66 // name offset bits flags
67 {.Name: "fixup_32", .TargetOffset: 0, .TargetSize: 32, .Flags: 0},
68 {.Name: "fixup_10_pcrel", .TargetOffset: 0, .TargetSize: 10, .Flags: MCFixupKindInfo::FKF_IsPCRel},
69 {.Name: "fixup_16", .TargetOffset: 0, .TargetSize: 16, .Flags: 0},
70 {.Name: "fixup_16_pcrel", .TargetOffset: 0, .TargetSize: 16, .Flags: MCFixupKindInfo::FKF_IsPCRel},
71 {.Name: "fixup_16_byte", .TargetOffset: 0, .TargetSize: 16, .Flags: 0},
72 {.Name: "fixup_16_pcrel_byte", .TargetOffset: 0, .TargetSize: 16, .Flags: MCFixupKindInfo::FKF_IsPCRel},
73 {.Name: "fixup_2x_pcrel", .TargetOffset: 0, .TargetSize: 10, .Flags: MCFixupKindInfo::FKF_IsPCRel},
74 {.Name: "fixup_rl_pcrel", .TargetOffset: 0, .TargetSize: 16, .Flags: MCFixupKindInfo::FKF_IsPCRel},
75 {.Name: "fixup_8", .TargetOffset: 0, .TargetSize: 8, .Flags: 0},
76 {.Name: "fixup_sym_diff", .TargetOffset: 0, .TargetSize: 32, .Flags: 0},
77 };
78 static_assert((std::size(Infos)) == MSP430::NumTargetFixupKinds,
79 "Not all fixup kinds added to Infos array");
80
81 if (Kind < FirstTargetFixupKind)
82 return MCAsmBackend::getFixupKindInfo(Kind);
83
84 return Infos[Kind - FirstTargetFixupKind];
85 }
86
87 bool writeNopData(raw_ostream &OS, uint64_t Count,
88 const MCSubtargetInfo *STI) const override;
89};
90
91uint64_t MSP430AsmBackend::adjustFixupValue(const MCFixup &Fixup,
92 uint64_t Value,
93 MCContext &Ctx) const {
94 unsigned Kind = Fixup.getKind();
95 switch (Kind) {
96 case MSP430::fixup_10_pcrel: {
97 if (Value & 0x1)
98 Ctx.reportError(L: Fixup.getLoc(), Msg: "fixup value must be 2-byte aligned");
99
100 // Offset is signed
101 int16_t Offset = Value;
102 // Jumps are in words
103 Offset >>= 1;
104 // PC points to the next instruction so decrement by one
105 --Offset;
106
107 if (Offset < -512 || Offset > 511)
108 Ctx.reportError(L: Fixup.getLoc(), Msg: "fixup value out of range");
109
110 // Mask 10 bits
111 Offset &= 0x3ff;
112
113 return Offset;
114 }
115 default:
116 return Value;
117 }
118}
119
120void MSP430AsmBackend::applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
121 const MCValue &Target,
122 MutableArrayRef<char> Data,
123 uint64_t Value, bool IsResolved,
124 const MCSubtargetInfo *STI) const {
125 Value = adjustFixupValue(Fixup, Value, Ctx&: Asm.getContext());
126 MCFixupKindInfo Info = getFixupKindInfo(Kind: Fixup.getKind());
127 if (!Value)
128 return; // Doesn't change encoding.
129
130 // Shift the value into position.
131 Value <<= Info.TargetOffset;
132
133 unsigned Offset = Fixup.getOffset();
134 unsigned NumBytes = alignTo(Value: Info.TargetSize + Info.TargetOffset, Align: 8) / 8;
135
136 assert(Offset + NumBytes <= Data.size() && "Invalid fixup offset!");
137
138 // For each byte of the fragment that the fixup touches, mask in the
139 // bits from the fixup value.
140 for (unsigned i = 0; i != NumBytes; ++i) {
141 Data[Offset + i] |= uint8_t((Value >> (i * 8)) & 0xff);
142 }
143}
144
145bool MSP430AsmBackend::writeNopData(raw_ostream &OS, uint64_t Count,
146 const MCSubtargetInfo *STI) const {
147 if ((Count % 2) != 0)
148 return false;
149
150 // The canonical nop on MSP430 is mov #0, r3
151 uint64_t NopCount = Count / 2;
152 while (NopCount--)
153 OS.write(Ptr: "\x03\x43", Size: 2);
154
155 return true;
156}
157
158} // end anonymous namespace
159
160MCAsmBackend *llvm::createMSP430MCAsmBackend(const Target &T,
161 const MCSubtargetInfo &STI,
162 const MCRegisterInfo &MRI,
163 const MCTargetOptions &Options) {
164 return new MSP430AsmBackend(STI, ELF::ELFOSABI_STANDALONE);
165}
166