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 26 using namespace llvm; 27 28 namespace { 29 class MSP430AsmBackend : public MCAsmBackend { 30 uint8_t OSABI; 31 32 uint64_t adjustFixupValue(const MCFixup &Fixup, uint64_t Value, 33 MCContext &Ctx) const; 34 35 public: 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 {"fixup_32", 0, 32, 0}, 68 {"fixup_10_pcrel", 0, 10, MCFixupKindInfo::FKF_IsPCRel}, 69 {"fixup_16", 0, 16, 0}, 70 {"fixup_16_pcrel", 0, 16, MCFixupKindInfo::FKF_IsPCRel}, 71 {"fixup_16_byte", 0, 16, 0}, 72 {"fixup_16_pcrel_byte", 0, 16, MCFixupKindInfo::FKF_IsPCRel}, 73 {"fixup_2x_pcrel", 0, 10, MCFixupKindInfo::FKF_IsPCRel}, 74 {"fixup_rl_pcrel", 0, 16, MCFixupKindInfo::FKF_IsPCRel}, 75 {"fixup_8", 0, 8, 0}, 76 {"fixup_sym_diff", 0, 32, 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 91 uint64_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(Fixup.getLoc(), "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(Fixup.getLoc(), "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 } 119 120 void 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, Asm.getContext()); 126 MCFixupKindInfo Info = getFixupKindInfo(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(Info.TargetSize + Info.TargetOffset, 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 } 144 145 bool 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("\x03\x43", 2); 154 155 return true; 156 } 157 158 } // end anonymous namespace 159 160 MCAsmBackend *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