1 //===-- PPCAsmBackend.cpp - PPC 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/PPCFixupKinds.h" 10 #include "MCTargetDesc/PPCMCAsmInfo.h" 11 #include "MCTargetDesc/PPCMCTargetDesc.h" 12 #include "llvm/BinaryFormat/ELF.h" 13 #include "llvm/BinaryFormat/MachO.h" 14 #include "llvm/MC/MCAsmBackend.h" 15 #include "llvm/MC/MCAssembler.h" 16 #include "llvm/MC/MCELFObjectWriter.h" 17 #include "llvm/MC/MCMachObjectWriter.h" 18 #include "llvm/MC/MCObjectWriter.h" 19 #include "llvm/MC/MCSubtargetInfo.h" 20 #include "llvm/MC/MCSymbolELF.h" 21 #include "llvm/MC/MCSymbolXCOFF.h" 22 #include "llvm/MC/MCValue.h" 23 #include "llvm/MC/TargetRegistry.h" 24 #include "llvm/Support/ErrorHandling.h" 25 using namespace llvm; 26 27 static uint64_t adjustFixupValue(unsigned Kind, uint64_t Value) { 28 switch (Kind) { 29 default: 30 llvm_unreachable("Unknown fixup kind!"); 31 case FK_Data_1: 32 case FK_Data_2: 33 case FK_Data_4: 34 case FK_Data_8: 35 case PPC::fixup_ppc_nofixup: 36 return Value; 37 case PPC::fixup_ppc_brcond14: 38 case PPC::fixup_ppc_brcond14abs: 39 return Value & 0xfffc; 40 case PPC::fixup_ppc_br24: 41 case PPC::fixup_ppc_br24abs: 42 case PPC::fixup_ppc_br24_notoc: 43 return Value & 0x3fffffc; 44 case PPC::fixup_ppc_half16: 45 return Value & 0xffff; 46 case PPC::fixup_ppc_half16ds: 47 case PPC::fixup_ppc_half16dq: 48 return Value & 0xfffc; 49 case PPC::fixup_ppc_pcrel34: 50 case PPC::fixup_ppc_imm34: 51 return Value & 0x3ffffffff; 52 } 53 } 54 55 static unsigned getFixupKindNumBytes(unsigned Kind) { 56 switch (Kind) { 57 default: 58 llvm_unreachable("Unknown fixup kind!"); 59 case FK_Data_1: 60 return 1; 61 case FK_Data_2: 62 case PPC::fixup_ppc_half16: 63 case PPC::fixup_ppc_half16ds: 64 case PPC::fixup_ppc_half16dq: 65 return 2; 66 case FK_Data_4: 67 case PPC::fixup_ppc_brcond14: 68 case PPC::fixup_ppc_brcond14abs: 69 case PPC::fixup_ppc_br24: 70 case PPC::fixup_ppc_br24abs: 71 case PPC::fixup_ppc_br24_notoc: 72 return 4; 73 case PPC::fixup_ppc_pcrel34: 74 case PPC::fixup_ppc_imm34: 75 case FK_Data_8: 76 return 8; 77 case PPC::fixup_ppc_nofixup: 78 return 0; 79 } 80 } 81 82 namespace { 83 84 class PPCAsmBackend : public MCAsmBackend { 85 protected: 86 Triple TT; 87 public: 88 PPCAsmBackend(const Target &T, const Triple &TT) 89 : MCAsmBackend(TT.isLittleEndian() ? llvm::endianness::little 90 : llvm::endianness::big), 91 TT(TT) {} 92 93 MCFixupKindInfo getFixupKindInfo(MCFixupKind Kind) const override; 94 95 void applyFixup(const MCFragment &, const MCFixup &Fixup, 96 const MCValue &Target, MutableArrayRef<char> Data, 97 uint64_t Value, bool IsResolved) override; 98 99 bool shouldForceRelocation(const MCFixup &Fixup, const MCValue &Target) { 100 // If there is a @ specifier, unless it is optimized out (e.g. constant @l), 101 // force a relocation. 102 if (Target.getSpecifier()) 103 return true; 104 MCFixupKind Kind = Fixup.getKind(); 105 switch ((unsigned)Kind) { 106 default: 107 return false; 108 case PPC::fixup_ppc_br24: 109 case PPC::fixup_ppc_br24abs: 110 case PPC::fixup_ppc_br24_notoc: 111 // If the target symbol has a local entry point we must not attempt 112 // to resolve the fixup directly. Emit a relocation and leave 113 // resolution of the final target address to the linker. 114 if (const auto *A = Target.getAddSym()) { 115 if (const auto *S = dyn_cast<MCSymbolELF>(A)) { 116 // The "other" values are stored in the last 6 bits of the second 117 // byte. The traditional defines for STO values assume the full byte 118 // and thus the shift to pack it. 119 unsigned Other = S->getOther() << 2; 120 if ((Other & ELF::STO_PPC64_LOCAL_MASK) != 0) 121 return true; 122 } else if (const auto *S = dyn_cast<MCSymbolXCOFF>(A)) { 123 return !Target.isAbsolute() && S->isExternal() && 124 S->getStorageClass() == XCOFF::C_WEAKEXT; 125 } 126 } 127 return false; 128 } 129 } 130 131 bool writeNopData(raw_ostream &OS, uint64_t Count, 132 const MCSubtargetInfo *STI) const override { 133 uint64_t NumNops = Count / 4; 134 for (uint64_t i = 0; i != NumNops; ++i) 135 support::endian::write<uint32_t>(OS, 0x60000000, Endian); 136 137 OS.write_zeros(Count % 4); 138 139 return true; 140 } 141 }; 142 } // end anonymous namespace 143 144 MCFixupKindInfo PPCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const { 145 // clang-format off 146 const static MCFixupKindInfo InfosBE[PPC::NumTargetFixupKinds] = { 147 // name offset bits flags 148 {"fixup_ppc_br24", 6, 24, 0}, 149 {"fixup_ppc_br24_notoc", 6, 24, 0}, 150 {"fixup_ppc_brcond14", 16, 14, 0}, 151 {"fixup_ppc_br24abs", 6, 24, 0}, 152 {"fixup_ppc_brcond14abs", 16, 14, 0}, 153 {"fixup_ppc_half16", 0, 16, 0}, 154 {"fixup_ppc_half16ds", 0, 14, 0}, 155 {"fixup_ppc_pcrel34", 0, 34, 0}, 156 {"fixup_ppc_imm34", 0, 34, 0}, 157 {"fixup_ppc_nofixup", 0, 0, 0}}; 158 const static MCFixupKindInfo InfosLE[PPC::NumTargetFixupKinds] = { 159 // name offset bits flags 160 {"fixup_ppc_br24", 2, 24, 0}, 161 {"fixup_ppc_br24_notoc", 2, 24, 0}, 162 {"fixup_ppc_brcond14", 2, 14, 0}, 163 {"fixup_ppc_br24abs", 2, 24, 0}, 164 {"fixup_ppc_brcond14abs", 2, 14, 0}, 165 {"fixup_ppc_half16", 0, 16, 0}, 166 {"fixup_ppc_half16ds", 2, 14, 0}, 167 {"fixup_ppc_pcrel34", 0, 34, 0}, 168 {"fixup_ppc_imm34", 0, 34, 0}, 169 {"fixup_ppc_nofixup", 0, 0, 0}}; 170 // clang-format on 171 172 // Fixup kinds from .reloc directive are like R_PPC_NONE/R_PPC64_NONE. They 173 // do not require any extra processing. 174 if (mc::isRelocation(Kind)) 175 return {}; 176 177 if (Kind < FirstTargetFixupKind) 178 return MCAsmBackend::getFixupKindInfo(Kind); 179 180 assert(Kind - FirstTargetFixupKind < PPC::NumTargetFixupKinds && 181 "Invalid kind!"); 182 return (Endian == llvm::endianness::little 183 ? InfosLE 184 : InfosBE)[Kind - FirstTargetFixupKind]; 185 } 186 187 void PPCAsmBackend::applyFixup(const MCFragment &F, const MCFixup &Fixup, 188 const MCValue &TargetVal, 189 MutableArrayRef<char> Data, uint64_t Value, 190 bool IsResolved) { 191 // In PPC64 ELFv1, .quad .TOC.@tocbase in the .opd section is expected to 192 // reference the null symbol. 193 auto Target = TargetVal; 194 if (Target.getSpecifier() == PPC::S_TOCBASE) 195 Target.setAddSym(nullptr); 196 if (IsResolved && shouldForceRelocation(Fixup, Target)) 197 IsResolved = false; 198 if (!IsResolved) 199 Asm->getWriter().recordRelocation(F, Fixup, Target, Value); 200 201 MCFixupKind Kind = Fixup.getKind(); 202 if (mc::isRelocation(Kind)) 203 return; 204 Value = adjustFixupValue(Kind, Value); 205 if (!Value) 206 return; // Doesn't change encoding. 207 208 unsigned Offset = Fixup.getOffset(); 209 unsigned NumBytes = getFixupKindNumBytes(Kind); 210 211 // For each byte of the fragment that the fixup touches, mask in the bits 212 // from the fixup value. The Value has been "split up" into the appropriate 213 // bitfields above. 214 for (unsigned i = 0; i != NumBytes; ++i) { 215 unsigned Idx = Endian == llvm::endianness::little ? i : (NumBytes - 1 - i); 216 Data[Offset + i] |= uint8_t((Value >> (Idx * 8)) & 0xff); 217 } 218 } 219 220 // FIXME: This should be in a separate file. 221 namespace { 222 223 class ELFPPCAsmBackend : public PPCAsmBackend { 224 public: 225 ELFPPCAsmBackend(const Target &T, const Triple &TT) : PPCAsmBackend(T, TT) {} 226 227 std::unique_ptr<MCObjectTargetWriter> 228 createObjectTargetWriter() const override { 229 uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TT.getOS()); 230 bool Is64 = TT.isPPC64(); 231 return createPPCELFObjectWriter(Is64, OSABI); 232 } 233 234 std::optional<MCFixupKind> getFixupKind(StringRef Name) const override; 235 }; 236 237 class XCOFFPPCAsmBackend : public PPCAsmBackend { 238 public: 239 XCOFFPPCAsmBackend(const Target &T, const Triple &TT) 240 : PPCAsmBackend(T, TT) {} 241 242 std::unique_ptr<MCObjectTargetWriter> 243 createObjectTargetWriter() const override { 244 return createPPCXCOFFObjectWriter(TT.isArch64Bit()); 245 } 246 247 std::optional<MCFixupKind> getFixupKind(StringRef Name) const override; 248 }; 249 250 } // end anonymous namespace 251 252 std::optional<MCFixupKind> 253 ELFPPCAsmBackend::getFixupKind(StringRef Name) const { 254 if (TT.isOSBinFormatELF()) { 255 unsigned Type; 256 if (TT.isPPC64()) { 257 Type = llvm::StringSwitch<unsigned>(Name) 258 #define ELF_RELOC(X, Y) .Case(#X, Y) 259 #include "llvm/BinaryFormat/ELFRelocs/PowerPC64.def" 260 #undef ELF_RELOC 261 .Case("BFD_RELOC_NONE", ELF::R_PPC64_NONE) 262 .Case("BFD_RELOC_16", ELF::R_PPC64_ADDR16) 263 .Case("BFD_RELOC_32", ELF::R_PPC64_ADDR32) 264 .Case("BFD_RELOC_64", ELF::R_PPC64_ADDR64) 265 .Default(-1u); 266 } else { 267 Type = llvm::StringSwitch<unsigned>(Name) 268 #define ELF_RELOC(X, Y) .Case(#X, Y) 269 #include "llvm/BinaryFormat/ELFRelocs/PowerPC.def" 270 #undef ELF_RELOC 271 .Case("BFD_RELOC_NONE", ELF::R_PPC_NONE) 272 .Case("BFD_RELOC_16", ELF::R_PPC_ADDR16) 273 .Case("BFD_RELOC_32", ELF::R_PPC_ADDR32) 274 .Default(-1u); 275 } 276 if (Type != -1u) 277 return static_cast<MCFixupKind>(FirstLiteralRelocationKind + Type); 278 } 279 return std::nullopt; 280 } 281 282 std::optional<MCFixupKind> 283 XCOFFPPCAsmBackend::getFixupKind(StringRef Name) const { 284 return StringSwitch<std::optional<MCFixupKind>>(Name) 285 .Case("R_REF", PPC::fixup_ppc_nofixup) 286 .Default(std::nullopt); 287 } 288 289 MCAsmBackend *llvm::createPPCAsmBackend(const Target &T, 290 const MCSubtargetInfo &STI, 291 const MCRegisterInfo &MRI, 292 const MCTargetOptions &Options) { 293 const Triple &TT = STI.getTargetTriple(); 294 if (TT.isOSBinFormatXCOFF()) 295 return new XCOFFPPCAsmBackend(T, TT); 296 297 return new ELFPPCAsmBackend(T, TT); 298 } 299