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