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