1 //===-- ARMAsmBackend.cpp - ARM Assembler Backend -------------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #include "MCTargetDesc/ARMMCTargetDesc.h" 11 #include "MCTargetDesc/ARMAddressingModes.h" 12 #include "MCTargetDesc/ARMBaseInfo.h" 13 #include "MCTargetDesc/ARMFixupKinds.h" 14 #include "llvm/ADT/StringSwitch.h" 15 #include "llvm/MC/MCAsmBackend.h" 16 #include "llvm/MC/MCAssembler.h" 17 #include "llvm/MC/MCContext.h" 18 #include "llvm/MC/MCDirectives.h" 19 #include "llvm/MC/MCELFObjectWriter.h" 20 #include "llvm/MC/MCExpr.h" 21 #include "llvm/MC/MCFixupKindInfo.h" 22 #include "llvm/MC/MCMachObjectWriter.h" 23 #include "llvm/MC/MCObjectWriter.h" 24 #include "llvm/MC/MCSectionELF.h" 25 #include "llvm/MC/MCSectionMachO.h" 26 #include "llvm/MC/MCSubtargetInfo.h" 27 #include "llvm/MC/MCValue.h" 28 #include "llvm/Object/MachOFormat.h" 29 #include "llvm/Support/ELF.h" 30 #include "llvm/Support/ErrorHandling.h" 31 #include "llvm/Support/raw_ostream.h" 32 using namespace llvm; 33 34 namespace { 35 class ARMELFObjectWriter : public MCELFObjectTargetWriter { 36 public: 37 ARMELFObjectWriter(uint8_t OSABI) 38 : MCELFObjectTargetWriter(/*Is64Bit*/ false, OSABI, ELF::EM_ARM, 39 /*HasRelocationAddend*/ false) {} 40 }; 41 42 class ARMAsmBackend : public MCAsmBackend { 43 const MCSubtargetInfo* STI; 44 bool isThumbMode; // Currently emitting Thumb code. 45 public: 46 ARMAsmBackend(const Target &T, const StringRef TT) 47 : MCAsmBackend(), STI(ARM_MC::createARMMCSubtargetInfo(TT, "", "")), 48 isThumbMode(TT.startswith("thumb")) {} 49 50 ~ARMAsmBackend() { 51 delete STI; 52 } 53 54 unsigned getNumFixupKinds() const { return ARM::NumTargetFixupKinds; } 55 56 bool hasNOP() const { 57 return (STI->getFeatureBits() & ARM::HasV6T2Ops) != 0; 58 } 59 60 const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const { 61 const static MCFixupKindInfo Infos[ARM::NumTargetFixupKinds] = { 62 // This table *must* be in the order that the fixup_* kinds are defined in 63 // ARMFixupKinds.h. 64 // 65 // Name Offset (bits) Size (bits) Flags 66 { "fixup_arm_ldst_pcrel_12", 0, 32, MCFixupKindInfo::FKF_IsPCRel }, 67 { "fixup_t2_ldst_pcrel_12", 0, 32, MCFixupKindInfo::FKF_IsPCRel | 68 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits}, 69 { "fixup_arm_pcrel_10_unscaled", 0, 32, MCFixupKindInfo::FKF_IsPCRel }, 70 { "fixup_arm_pcrel_10", 0, 32, MCFixupKindInfo::FKF_IsPCRel }, 71 { "fixup_t2_pcrel_10", 0, 32, MCFixupKindInfo::FKF_IsPCRel | 72 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits}, 73 { "fixup_thumb_adr_pcrel_10",0, 8, MCFixupKindInfo::FKF_IsPCRel | 74 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits}, 75 { "fixup_arm_adr_pcrel_12", 0, 32, MCFixupKindInfo::FKF_IsPCRel }, 76 { "fixup_t2_adr_pcrel_12", 0, 32, MCFixupKindInfo::FKF_IsPCRel | 77 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits}, 78 { "fixup_arm_condbranch", 0, 24, MCFixupKindInfo::FKF_IsPCRel }, 79 { "fixup_arm_uncondbranch", 0, 24, MCFixupKindInfo::FKF_IsPCRel }, 80 { "fixup_t2_condbranch", 0, 32, MCFixupKindInfo::FKF_IsPCRel }, 81 { "fixup_t2_uncondbranch", 0, 32, MCFixupKindInfo::FKF_IsPCRel }, 82 { "fixup_arm_thumb_br", 0, 16, MCFixupKindInfo::FKF_IsPCRel }, 83 { "fixup_arm_uncondbl", 0, 24, MCFixupKindInfo::FKF_IsPCRel }, 84 { "fixup_arm_condbl", 0, 24, MCFixupKindInfo::FKF_IsPCRel }, 85 { "fixup_arm_blx", 0, 24, MCFixupKindInfo::FKF_IsPCRel }, 86 { "fixup_arm_thumb_bl", 0, 32, MCFixupKindInfo::FKF_IsPCRel }, 87 { "fixup_arm_thumb_blx", 0, 32, MCFixupKindInfo::FKF_IsPCRel }, 88 { "fixup_arm_thumb_cb", 0, 16, MCFixupKindInfo::FKF_IsPCRel }, 89 { "fixup_arm_thumb_cp", 0, 8, MCFixupKindInfo::FKF_IsPCRel | 90 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits}, 91 { "fixup_arm_thumb_bcc", 0, 8, MCFixupKindInfo::FKF_IsPCRel }, 92 // movw / movt: 16-bits immediate but scattered into two chunks 0 - 12, 16 - 19. 93 { "fixup_arm_movt_hi16", 0, 20, 0 }, 94 { "fixup_arm_movw_lo16", 0, 20, 0 }, 95 { "fixup_t2_movt_hi16", 0, 20, 0 }, 96 { "fixup_t2_movw_lo16", 0, 20, 0 }, 97 { "fixup_arm_movt_hi16_pcrel", 0, 20, MCFixupKindInfo::FKF_IsPCRel }, 98 { "fixup_arm_movw_lo16_pcrel", 0, 20, MCFixupKindInfo::FKF_IsPCRel }, 99 { "fixup_t2_movt_hi16_pcrel", 0, 20, MCFixupKindInfo::FKF_IsPCRel }, 100 { "fixup_t2_movw_lo16_pcrel", 0, 20, MCFixupKindInfo::FKF_IsPCRel }, 101 }; 102 103 if (Kind < FirstTargetFixupKind) 104 return MCAsmBackend::getFixupKindInfo(Kind); 105 106 assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() && 107 "Invalid kind!"); 108 return Infos[Kind - FirstTargetFixupKind]; 109 } 110 111 /// processFixupValue - Target hook to process the literal value of a fixup 112 /// if necessary. 113 void processFixupValue(const MCAssembler &Asm, const MCAsmLayout &Layout, 114 const MCFixup &Fixup, const MCFragment *DF, 115 MCValue &Target, uint64_t &Value, 116 bool &IsResolved); 117 118 119 void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize, 120 uint64_t Value) const; 121 122 bool mayNeedRelaxation(const MCInst &Inst) const; 123 124 bool fixupNeedsRelaxation(const MCFixup &Fixup, 125 uint64_t Value, 126 const MCRelaxableFragment *DF, 127 const MCAsmLayout &Layout) const; 128 129 void relaxInstruction(const MCInst &Inst, MCInst &Res) const; 130 131 bool writeNopData(uint64_t Count, MCObjectWriter *OW) const; 132 133 void handleAssemblerFlag(MCAssemblerFlag Flag) { 134 switch (Flag) { 135 default: break; 136 case MCAF_Code16: 137 setIsThumb(true); 138 break; 139 case MCAF_Code32: 140 setIsThumb(false); 141 break; 142 } 143 } 144 145 unsigned getPointerSize() const { return 4; } 146 bool isThumb() const { return isThumbMode; } 147 void setIsThumb(bool it) { isThumbMode = it; } 148 }; 149 } // end anonymous namespace 150 151 static unsigned getRelaxedOpcode(unsigned Op) { 152 switch (Op) { 153 default: return Op; 154 case ARM::tBcc: return ARM::t2Bcc; 155 case ARM::tLDRpciASM: return ARM::t2LDRpci; 156 case ARM::tADR: return ARM::t2ADR; 157 case ARM::tB: return ARM::t2B; 158 } 159 } 160 161 bool ARMAsmBackend::mayNeedRelaxation(const MCInst &Inst) const { 162 if (getRelaxedOpcode(Inst.getOpcode()) != Inst.getOpcode()) 163 return true; 164 return false; 165 } 166 167 bool ARMAsmBackend::fixupNeedsRelaxation(const MCFixup &Fixup, 168 uint64_t Value, 169 const MCRelaxableFragment *DF, 170 const MCAsmLayout &Layout) const { 171 switch ((unsigned)Fixup.getKind()) { 172 case ARM::fixup_arm_thumb_br: { 173 // Relaxing tB to t2B. tB has a signed 12-bit displacement with the 174 // low bit being an implied zero. There's an implied +4 offset for the 175 // branch, so we adjust the other way here to determine what's 176 // encodable. 177 // 178 // Relax if the value is too big for a (signed) i8. 179 int64_t Offset = int64_t(Value) - 4; 180 return Offset > 2046 || Offset < -2048; 181 } 182 case ARM::fixup_arm_thumb_bcc: { 183 // Relaxing tBcc to t2Bcc. tBcc has a signed 9-bit displacement with the 184 // low bit being an implied zero. There's an implied +4 offset for the 185 // branch, so we adjust the other way here to determine what's 186 // encodable. 187 // 188 // Relax if the value is too big for a (signed) i8. 189 int64_t Offset = int64_t(Value) - 4; 190 return Offset > 254 || Offset < -256; 191 } 192 case ARM::fixup_thumb_adr_pcrel_10: 193 case ARM::fixup_arm_thumb_cp: { 194 // If the immediate is negative, greater than 1020, or not a multiple 195 // of four, the wide version of the instruction must be used. 196 int64_t Offset = int64_t(Value) - 4; 197 return Offset > 1020 || Offset < 0 || Offset & 3; 198 } 199 } 200 llvm_unreachable("Unexpected fixup kind in fixupNeedsRelaxation()!"); 201 } 202 203 void ARMAsmBackend::relaxInstruction(const MCInst &Inst, MCInst &Res) const { 204 unsigned RelaxedOp = getRelaxedOpcode(Inst.getOpcode()); 205 206 // Sanity check w/ diagnostic if we get here w/ a bogus instruction. 207 if (RelaxedOp == Inst.getOpcode()) { 208 SmallString<256> Tmp; 209 raw_svector_ostream OS(Tmp); 210 Inst.dump_pretty(OS); 211 OS << "\n"; 212 report_fatal_error("unexpected instruction to relax: " + OS.str()); 213 } 214 215 // The instructions we're relaxing have (so far) the same operands. 216 // We just need to update to the proper opcode. 217 Res = Inst; 218 Res.setOpcode(RelaxedOp); 219 } 220 221 bool ARMAsmBackend::writeNopData(uint64_t Count, MCObjectWriter *OW) const { 222 const uint16_t Thumb1_16bitNopEncoding = 0x46c0; // using MOV r8,r8 223 const uint16_t Thumb2_16bitNopEncoding = 0xbf00; // NOP 224 const uint32_t ARMv4_NopEncoding = 0xe1a00000; // using MOV r0,r0 225 const uint32_t ARMv6T2_NopEncoding = 0xe320f000; // NOP 226 if (isThumb()) { 227 const uint16_t nopEncoding = hasNOP() ? Thumb2_16bitNopEncoding 228 : Thumb1_16bitNopEncoding; 229 uint64_t NumNops = Count / 2; 230 for (uint64_t i = 0; i != NumNops; ++i) 231 OW->Write16(nopEncoding); 232 if (Count & 1) 233 OW->Write8(0); 234 return true; 235 } 236 // ARM mode 237 const uint32_t nopEncoding = hasNOP() ? ARMv6T2_NopEncoding 238 : ARMv4_NopEncoding; 239 uint64_t NumNops = Count / 4; 240 for (uint64_t i = 0; i != NumNops; ++i) 241 OW->Write32(nopEncoding); 242 // FIXME: should this function return false when unable to write exactly 243 // 'Count' bytes with NOP encodings? 244 switch (Count % 4) { 245 default: break; // No leftover bytes to write 246 case 1: OW->Write8(0); break; 247 case 2: OW->Write16(0); break; 248 case 3: OW->Write16(0); OW->Write8(0xa0); break; 249 } 250 251 return true; 252 } 253 254 static unsigned adjustFixupValue(const MCFixup &Fixup, uint64_t Value, 255 MCContext *Ctx = NULL) { 256 unsigned Kind = Fixup.getKind(); 257 switch (Kind) { 258 default: 259 llvm_unreachable("Unknown fixup kind!"); 260 case FK_Data_1: 261 case FK_Data_2: 262 case FK_Data_4: 263 return Value; 264 case ARM::fixup_arm_movt_hi16: 265 Value >>= 16; 266 // Fallthrough 267 case ARM::fixup_arm_movw_lo16: 268 case ARM::fixup_arm_movt_hi16_pcrel: 269 case ARM::fixup_arm_movw_lo16_pcrel: { 270 unsigned Hi4 = (Value & 0xF000) >> 12; 271 unsigned Lo12 = Value & 0x0FFF; 272 // inst{19-16} = Hi4; 273 // inst{11-0} = Lo12; 274 Value = (Hi4 << 16) | (Lo12); 275 return Value; 276 } 277 case ARM::fixup_t2_movt_hi16: 278 Value >>= 16; 279 // Fallthrough 280 case ARM::fixup_t2_movw_lo16: 281 case ARM::fixup_t2_movt_hi16_pcrel: //FIXME: Shouldn't this be shifted like 282 // the other hi16 fixup? 283 case ARM::fixup_t2_movw_lo16_pcrel: { 284 unsigned Hi4 = (Value & 0xF000) >> 12; 285 unsigned i = (Value & 0x800) >> 11; 286 unsigned Mid3 = (Value & 0x700) >> 8; 287 unsigned Lo8 = Value & 0x0FF; 288 // inst{19-16} = Hi4; 289 // inst{26} = i; 290 // inst{14-12} = Mid3; 291 // inst{7-0} = Lo8; 292 Value = (Hi4 << 16) | (i << 26) | (Mid3 << 12) | (Lo8); 293 uint64_t swapped = (Value & 0xFFFF0000) >> 16; 294 swapped |= (Value & 0x0000FFFF) << 16; 295 return swapped; 296 } 297 case ARM::fixup_arm_ldst_pcrel_12: 298 // ARM PC-relative values are offset by 8. 299 Value -= 4; 300 // FALLTHROUGH 301 case ARM::fixup_t2_ldst_pcrel_12: { 302 // Offset by 4, adjusted by two due to the half-word ordering of thumb. 303 Value -= 4; 304 bool isAdd = true; 305 if ((int64_t)Value < 0) { 306 Value = -Value; 307 isAdd = false; 308 } 309 if (Ctx && Value >= 4096) 310 Ctx->FatalError(Fixup.getLoc(), "out of range pc-relative fixup value"); 311 Value |= isAdd << 23; 312 313 // Same addressing mode as fixup_arm_pcrel_10, 314 // but with 16-bit halfwords swapped. 315 if (Kind == ARM::fixup_t2_ldst_pcrel_12) { 316 uint64_t swapped = (Value & 0xFFFF0000) >> 16; 317 swapped |= (Value & 0x0000FFFF) << 16; 318 return swapped; 319 } 320 321 return Value; 322 } 323 case ARM::fixup_thumb_adr_pcrel_10: 324 return ((Value - 4) >> 2) & 0xff; 325 case ARM::fixup_arm_adr_pcrel_12: { 326 // ARM PC-relative values are offset by 8. 327 Value -= 8; 328 unsigned opc = 4; // bits {24-21}. Default to add: 0b0100 329 if ((int64_t)Value < 0) { 330 Value = -Value; 331 opc = 2; // 0b0010 332 } 333 if (Ctx && ARM_AM::getSOImmVal(Value) == -1) 334 Ctx->FatalError(Fixup.getLoc(), "out of range pc-relative fixup value"); 335 // Encode the immediate and shift the opcode into place. 336 return ARM_AM::getSOImmVal(Value) | (opc << 21); 337 } 338 339 case ARM::fixup_t2_adr_pcrel_12: { 340 Value -= 4; 341 unsigned opc = 0; 342 if ((int64_t)Value < 0) { 343 Value = -Value; 344 opc = 5; 345 } 346 347 uint32_t out = (opc << 21); 348 out |= (Value & 0x800) << 15; 349 out |= (Value & 0x700) << 4; 350 out |= (Value & 0x0FF); 351 352 uint64_t swapped = (out & 0xFFFF0000) >> 16; 353 swapped |= (out & 0x0000FFFF) << 16; 354 return swapped; 355 } 356 357 case ARM::fixup_arm_condbranch: 358 case ARM::fixup_arm_uncondbranch: 359 case ARM::fixup_arm_uncondbl: 360 case ARM::fixup_arm_condbl: 361 case ARM::fixup_arm_blx: 362 // These values don't encode the low two bits since they're always zero. 363 // Offset by 8 just as above. 364 return 0xffffff & ((Value - 8) >> 2); 365 case ARM::fixup_t2_uncondbranch: { 366 Value = Value - 4; 367 Value >>= 1; // Low bit is not encoded. 368 369 uint32_t out = 0; 370 bool I = Value & 0x800000; 371 bool J1 = Value & 0x400000; 372 bool J2 = Value & 0x200000; 373 J1 ^= I; 374 J2 ^= I; 375 376 out |= I << 26; // S bit 377 out |= !J1 << 13; // J1 bit 378 out |= !J2 << 11; // J2 bit 379 out |= (Value & 0x1FF800) << 5; // imm6 field 380 out |= (Value & 0x0007FF); // imm11 field 381 382 uint64_t swapped = (out & 0xFFFF0000) >> 16; 383 swapped |= (out & 0x0000FFFF) << 16; 384 return swapped; 385 } 386 case ARM::fixup_t2_condbranch: { 387 Value = Value - 4; 388 Value >>= 1; // Low bit is not encoded. 389 390 uint64_t out = 0; 391 out |= (Value & 0x80000) << 7; // S bit 392 out |= (Value & 0x40000) >> 7; // J2 bit 393 out |= (Value & 0x20000) >> 4; // J1 bit 394 out |= (Value & 0x1F800) << 5; // imm6 field 395 out |= (Value & 0x007FF); // imm11 field 396 397 uint32_t swapped = (out & 0xFFFF0000) >> 16; 398 swapped |= (out & 0x0000FFFF) << 16; 399 return swapped; 400 } 401 case ARM::fixup_arm_thumb_bl: { 402 // The value doesn't encode the low bit (always zero) and is offset by 403 // four. The 32-bit immediate value is encoded as 404 // imm32 = SignExtend(S:I1:I2:imm10:imm11:0) 405 // where I1 = NOT(J1 ^ S) and I2 = NOT(J2 ^ S). 406 // The value is encoded into disjoint bit positions in the destination 407 // opcode. x = unchanged, I = immediate value bit, S = sign extension bit, 408 // J = either J1 or J2 bit 409 // 410 // BL: xxxxxSIIIIIIIIII xxJxJIIIIIIIIIII 411 // 412 // Note that the halfwords are stored high first, low second; so we need 413 // to transpose the fixup value here to map properly. 414 uint32_t offset = (Value - 4) >> 1; 415 uint32_t signBit = (offset & 0x800000) >> 23; 416 uint32_t I1Bit = (offset & 0x400000) >> 22; 417 uint32_t J1Bit = (I1Bit ^ 0x1) ^ signBit; 418 uint32_t I2Bit = (offset & 0x200000) >> 21; 419 uint32_t J2Bit = (I2Bit ^ 0x1) ^ signBit; 420 uint32_t imm10Bits = (offset & 0x1FF800) >> 11; 421 uint32_t imm11Bits = (offset & 0x000007FF); 422 423 uint32_t Binary = 0; 424 uint32_t firstHalf = (((uint16_t)signBit << 10) | (uint16_t)imm10Bits); 425 uint32_t secondHalf = (((uint16_t)J1Bit << 13) | ((uint16_t)J2Bit << 11) | 426 (uint16_t)imm11Bits); 427 Binary |= secondHalf << 16; 428 Binary |= firstHalf; 429 return Binary; 430 431 } 432 case ARM::fixup_arm_thumb_blx: { 433 // The value doesn't encode the low two bits (always zero) and is offset by 434 // four (see fixup_arm_thumb_cp). The 32-bit immediate value is encoded as 435 // imm32 = SignExtend(S:I1:I2:imm10H:imm10L:00) 436 // where I1 = NOT(J1 ^ S) and I2 = NOT(J2 ^ S). 437 // The value is encoded into disjoint bit positions in the destination 438 // opcode. x = unchanged, I = immediate value bit, S = sign extension bit, 439 // J = either J1 or J2 bit, 0 = zero. 440 // 441 // BLX: xxxxxSIIIIIIIIII xxJxJIIIIIIIIII0 442 // 443 // Note that the halfwords are stored high first, low second; so we need 444 // to transpose the fixup value here to map properly. 445 uint32_t offset = (Value - 2) >> 2; 446 uint32_t signBit = (offset & 0x400000) >> 22; 447 uint32_t I1Bit = (offset & 0x200000) >> 21; 448 uint32_t J1Bit = (I1Bit ^ 0x1) ^ signBit; 449 uint32_t I2Bit = (offset & 0x100000) >> 20; 450 uint32_t J2Bit = (I2Bit ^ 0x1) ^ signBit; 451 uint32_t imm10HBits = (offset & 0xFFC00) >> 10; 452 uint32_t imm10LBits = (offset & 0x3FF); 453 454 uint32_t Binary = 0; 455 uint32_t firstHalf = (((uint16_t)signBit << 10) | (uint16_t)imm10HBits); 456 uint32_t secondHalf = (((uint16_t)J1Bit << 13) | ((uint16_t)J2Bit << 11) | 457 ((uint16_t)imm10LBits) << 1); 458 Binary |= secondHalf << 16; 459 Binary |= firstHalf; 460 return Binary; 461 } 462 case ARM::fixup_arm_thumb_cp: 463 // Offset by 4, and don't encode the low two bits. Two bytes of that 464 // 'off by 4' is implicitly handled by the half-word ordering of the 465 // Thumb encoding, so we only need to adjust by 2 here. 466 return ((Value - 2) >> 2) & 0xff; 467 case ARM::fixup_arm_thumb_cb: { 468 // Offset by 4 and don't encode the lower bit, which is always 0. 469 uint32_t Binary = (Value - 4) >> 1; 470 return ((Binary & 0x20) << 4) | ((Binary & 0x1f) << 3); 471 } 472 case ARM::fixup_arm_thumb_br: 473 // Offset by 4 and don't encode the lower bit, which is always 0. 474 return ((Value - 4) >> 1) & 0x7ff; 475 case ARM::fixup_arm_thumb_bcc: 476 // Offset by 4 and don't encode the lower bit, which is always 0. 477 return ((Value - 4) >> 1) & 0xff; 478 case ARM::fixup_arm_pcrel_10_unscaled: { 479 Value = Value - 8; // ARM fixups offset by an additional word and don't 480 // need to adjust for the half-word ordering. 481 bool isAdd = true; 482 if ((int64_t)Value < 0) { 483 Value = -Value; 484 isAdd = false; 485 } 486 // The value has the low 4 bits encoded in [3:0] and the high 4 in [11:8]. 487 if (Ctx && Value >= 256) 488 Ctx->FatalError(Fixup.getLoc(), "out of range pc-relative fixup value"); 489 Value = (Value & 0xf) | ((Value & 0xf0) << 4); 490 return Value | (isAdd << 23); 491 } 492 case ARM::fixup_arm_pcrel_10: 493 Value = Value - 4; // ARM fixups offset by an additional word and don't 494 // need to adjust for the half-word ordering. 495 // Fall through. 496 case ARM::fixup_t2_pcrel_10: { 497 // Offset by 4, adjusted by two due to the half-word ordering of thumb. 498 Value = Value - 4; 499 bool isAdd = true; 500 if ((int64_t)Value < 0) { 501 Value = -Value; 502 isAdd = false; 503 } 504 // These values don't encode the low two bits since they're always zero. 505 Value >>= 2; 506 if (Ctx && Value >= 256) 507 Ctx->FatalError(Fixup.getLoc(), "out of range pc-relative fixup value"); 508 Value |= isAdd << 23; 509 510 // Same addressing mode as fixup_arm_pcrel_10, but with 16-bit halfwords 511 // swapped. 512 if (Kind == ARM::fixup_t2_pcrel_10) { 513 uint32_t swapped = (Value & 0xFFFF0000) >> 16; 514 swapped |= (Value & 0x0000FFFF) << 16; 515 return swapped; 516 } 517 518 return Value; 519 } 520 } 521 } 522 523 void ARMAsmBackend::processFixupValue(const MCAssembler &Asm, 524 const MCAsmLayout &Layout, 525 const MCFixup &Fixup, 526 const MCFragment *DF, 527 MCValue &Target, uint64_t &Value, 528 bool &IsResolved) { 529 const MCSymbolRefExpr *A = Target.getSymA(); 530 // Some fixups to thumb function symbols need the low bit (thumb bit) 531 // twiddled. 532 if ((unsigned)Fixup.getKind() != ARM::fixup_arm_ldst_pcrel_12 && 533 (unsigned)Fixup.getKind() != ARM::fixup_t2_ldst_pcrel_12 && 534 (unsigned)Fixup.getKind() != ARM::fixup_arm_adr_pcrel_12 && 535 (unsigned)Fixup.getKind() != ARM::fixup_thumb_adr_pcrel_10 && 536 (unsigned)Fixup.getKind() != ARM::fixup_t2_adr_pcrel_12 && 537 (unsigned)Fixup.getKind() != ARM::fixup_arm_thumb_cp) { 538 if (A) { 539 const MCSymbol &Sym = A->getSymbol().AliasedSymbol(); 540 if (Asm.isThumbFunc(&Sym)) 541 Value |= 1; 542 } 543 } 544 // We must always generate a relocation for BL/BLX instructions if we have 545 // a symbol to reference, as the linker relies on knowing the destination 546 // symbol's thumb-ness to get interworking right. 547 if (A && ((unsigned)Fixup.getKind() == ARM::fixup_arm_thumb_blx || 548 (unsigned)Fixup.getKind() == ARM::fixup_arm_thumb_bl || 549 (unsigned)Fixup.getKind() == ARM::fixup_arm_blx || 550 (unsigned)Fixup.getKind() == ARM::fixup_arm_uncondbl || 551 (unsigned)Fixup.getKind() == ARM::fixup_arm_condbl)) 552 IsResolved = false; 553 554 // Try to get the encoded value for the fixup as-if we're mapping it into 555 // the instruction. This allows adjustFixupValue() to issue a diagnostic 556 // if the value aren't invalid. 557 (void)adjustFixupValue(Fixup, Value, &Asm.getContext()); 558 } 559 560 /// getFixupKindNumBytes - The number of bytes the fixup may change. 561 static unsigned getFixupKindNumBytes(unsigned Kind) { 562 switch (Kind) { 563 default: 564 llvm_unreachable("Unknown fixup kind!"); 565 566 case FK_Data_1: 567 case ARM::fixup_arm_thumb_bcc: 568 case ARM::fixup_arm_thumb_cp: 569 case ARM::fixup_thumb_adr_pcrel_10: 570 return 1; 571 572 case FK_Data_2: 573 case ARM::fixup_arm_thumb_br: 574 case ARM::fixup_arm_thumb_cb: 575 return 2; 576 577 case ARM::fixup_arm_pcrel_10_unscaled: 578 case ARM::fixup_arm_ldst_pcrel_12: 579 case ARM::fixup_arm_pcrel_10: 580 case ARM::fixup_arm_adr_pcrel_12: 581 case ARM::fixup_arm_uncondbl: 582 case ARM::fixup_arm_condbl: 583 case ARM::fixup_arm_blx: 584 case ARM::fixup_arm_condbranch: 585 case ARM::fixup_arm_uncondbranch: 586 return 3; 587 588 case FK_Data_4: 589 case ARM::fixup_t2_ldst_pcrel_12: 590 case ARM::fixup_t2_condbranch: 591 case ARM::fixup_t2_uncondbranch: 592 case ARM::fixup_t2_pcrel_10: 593 case ARM::fixup_t2_adr_pcrel_12: 594 case ARM::fixup_arm_thumb_bl: 595 case ARM::fixup_arm_thumb_blx: 596 case ARM::fixup_arm_movt_hi16: 597 case ARM::fixup_arm_movw_lo16: 598 case ARM::fixup_arm_movt_hi16_pcrel: 599 case ARM::fixup_arm_movw_lo16_pcrel: 600 case ARM::fixup_t2_movt_hi16: 601 case ARM::fixup_t2_movw_lo16: 602 case ARM::fixup_t2_movt_hi16_pcrel: 603 case ARM::fixup_t2_movw_lo16_pcrel: 604 return 4; 605 } 606 } 607 608 void ARMAsmBackend::applyFixup(const MCFixup &Fixup, char *Data, 609 unsigned DataSize, uint64_t Value) const { 610 unsigned NumBytes = getFixupKindNumBytes(Fixup.getKind()); 611 Value = adjustFixupValue(Fixup, Value); 612 if (!Value) return; // Doesn't change encoding. 613 614 unsigned Offset = Fixup.getOffset(); 615 assert(Offset + NumBytes <= DataSize && "Invalid fixup offset!"); 616 617 // For each byte of the fragment that the fixup touches, mask in the bits from 618 // the fixup value. The Value has been "split up" into the appropriate 619 // bitfields above. 620 for (unsigned i = 0; i != NumBytes; ++i) 621 Data[Offset + i] |= uint8_t((Value >> (i * 8)) & 0xff); 622 } 623 624 namespace { 625 626 // FIXME: This should be in a separate file. 627 // ELF is an ELF of course... 628 class ELFARMAsmBackend : public ARMAsmBackend { 629 public: 630 uint8_t OSABI; 631 ELFARMAsmBackend(const Target &T, const StringRef TT, 632 uint8_t _OSABI) 633 : ARMAsmBackend(T, TT), OSABI(_OSABI) { } 634 635 MCObjectWriter *createObjectWriter(raw_ostream &OS) const { 636 return createARMELFObjectWriter(OS, OSABI); 637 } 638 }; 639 640 // FIXME: This should be in a separate file. 641 class DarwinARMAsmBackend : public ARMAsmBackend { 642 public: 643 const object::mach::CPUSubtypeARM Subtype; 644 DarwinARMAsmBackend(const Target &T, const StringRef TT, 645 object::mach::CPUSubtypeARM st) 646 : ARMAsmBackend(T, TT), Subtype(st) { 647 HasDataInCodeSupport = true; 648 } 649 650 MCObjectWriter *createObjectWriter(raw_ostream &OS) const { 651 return createARMMachObjectWriter(OS, /*Is64Bit=*/false, 652 object::mach::CTM_ARM, 653 Subtype); 654 } 655 656 virtual bool doesSectionRequireSymbols(const MCSection &Section) const { 657 return false; 658 } 659 }; 660 661 } // end anonymous namespace 662 663 MCAsmBackend *llvm::createARMAsmBackend(const Target &T, StringRef TT, StringRef CPU) { 664 Triple TheTriple(TT); 665 666 if (TheTriple.isOSDarwin()) { 667 object::mach::CPUSubtypeARM CS = 668 StringSwitch<object::mach::CPUSubtypeARM>(TheTriple.getArchName()) 669 .Cases("armv4t", "thumbv4t", object::mach::CSARM_V4T) 670 .Cases("armv5e", "thumbv5e",object::mach::CSARM_V5TEJ) 671 .Cases("armv6", "thumbv6", object::mach::CSARM_V6) 672 .Cases("armv6m", "thumbv6m", object::mach::CSARM_V6M) 673 .Cases("armv7em", "thumbv7em", object::mach::CSARM_V7EM) 674 .Cases("armv7f", "thumbv7f", object::mach::CSARM_V7F) 675 .Cases("armv7k", "thumbv7k", object::mach::CSARM_V7K) 676 .Cases("armv7m", "thumbv7m", object::mach::CSARM_V7M) 677 .Cases("armv7s", "thumbv7s", object::mach::CSARM_V7S) 678 .Default(object::mach::CSARM_V7); 679 680 return new DarwinARMAsmBackend(T, TT, CS); 681 } 682 683 if (TheTriple.isOSWindows()) 684 assert(0 && "Windows not supported on ARM"); 685 686 uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(Triple(TT).getOS()); 687 return new ELFARMAsmBackend(T, TT, OSABI); 688 } 689
