1 //===- MCExpr.cpp - Assembly Level Expression Implementation --------------===// 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 "llvm/MC/MCExpr.h" 11 #include "llvm/ADT/Statistic.h" 12 #include "llvm/ADT/StringSwitch.h" 13 #include "llvm/MC/MCAsmInfo.h" 14 #include "llvm/MC/MCAsmLayout.h" 15 #include "llvm/MC/MCAssembler.h" 16 #include "llvm/MC/MCContext.h" 17 #include "llvm/MC/MCObjectWriter.h" 18 #include "llvm/MC/MCSymbol.h" 19 #include "llvm/MC/MCValue.h" 20 #include "llvm/Support/Debug.h" 21 #include "llvm/Support/ErrorHandling.h" 22 #include "llvm/Support/raw_ostream.h" 23 using namespace llvm; 24 25 #define DEBUG_TYPE "mcexpr" 26 27 namespace { 28 namespace stats { 29 STATISTIC(MCExprEvaluate, "Number of MCExpr evaluations"); 30 } 31 } 32 33 void MCExpr::print(raw_ostream &OS) const { 34 switch (getKind()) { 35 case MCExpr::Target: 36 return cast<MCTargetExpr>(this)->PrintImpl(OS); 37 case MCExpr::Constant: 38 OS << cast<MCConstantExpr>(*this).getValue(); 39 return; 40 41 case MCExpr::SymbolRef: { 42 const MCSymbolRefExpr &SRE = cast<MCSymbolRefExpr>(*this); 43 const MCSymbol &Sym = SRE.getSymbol(); 44 // Parenthesize names that start with $ so that they don't look like 45 // absolute names. 46 bool UseParens = Sym.getName()[0] == '$'; 47 if (UseParens) 48 OS << '(' << Sym << ')'; 49 else 50 OS << Sym; 51 52 if (SRE.getKind() != MCSymbolRefExpr::VK_None) 53 SRE.printVariantKind(OS); 54 55 return; 56 } 57 58 case MCExpr::Unary: { 59 const MCUnaryExpr &UE = cast<MCUnaryExpr>(*this); 60 switch (UE.getOpcode()) { 61 case MCUnaryExpr::LNot: OS << '!'; break; 62 case MCUnaryExpr::Minus: OS << '-'; break; 63 case MCUnaryExpr::Not: OS << '~'; break; 64 case MCUnaryExpr::Plus: OS << '+'; break; 65 } 66 OS << *UE.getSubExpr(); 67 return; 68 } 69 70 case MCExpr::Binary: { 71 const MCBinaryExpr &BE = cast<MCBinaryExpr>(*this); 72 73 // Only print parens around the LHS if it is non-trivial. 74 if (isa<MCConstantExpr>(BE.getLHS()) || isa<MCSymbolRefExpr>(BE.getLHS())) { 75 OS << *BE.getLHS(); 76 } else { 77 OS << '(' << *BE.getLHS() << ')'; 78 } 79 80 switch (BE.getOpcode()) { 81 case MCBinaryExpr::Add: 82 // Print "X-42" instead of "X+-42". 83 if (const MCConstantExpr *RHSC = dyn_cast<MCConstantExpr>(BE.getRHS())) { 84 if (RHSC->getValue() < 0) { 85 OS << RHSC->getValue(); 86 return; 87 } 88 } 89 90 OS << '+'; 91 break; 92 case MCBinaryExpr::And: OS << '&'; break; 93 case MCBinaryExpr::Div: OS << '/'; break; 94 case MCBinaryExpr::EQ: OS << "=="; break; 95 case MCBinaryExpr::GT: OS << '>'; break; 96 case MCBinaryExpr::GTE: OS << ">="; break; 97 case MCBinaryExpr::LAnd: OS << "&&"; break; 98 case MCBinaryExpr::LOr: OS << "||"; break; 99 case MCBinaryExpr::LT: OS << '<'; break; 100 case MCBinaryExpr::LTE: OS << "<="; break; 101 case MCBinaryExpr::Mod: OS << '%'; break; 102 case MCBinaryExpr::Mul: OS << '*'; break; 103 case MCBinaryExpr::NE: OS << "!="; break; 104 case MCBinaryExpr::Or: OS << '|'; break; 105 case MCBinaryExpr::Shl: OS << "<<"; break; 106 case MCBinaryExpr::Shr: OS << ">>"; break; 107 case MCBinaryExpr::Sub: OS << '-'; break; 108 case MCBinaryExpr::Xor: OS << '^'; break; 109 } 110 111 // Only print parens around the LHS if it is non-trivial. 112 if (isa<MCConstantExpr>(BE.getRHS()) || isa<MCSymbolRefExpr>(BE.getRHS())) { 113 OS << *BE.getRHS(); 114 } else { 115 OS << '(' << *BE.getRHS() << ')'; 116 } 117 return; 118 } 119 } 120 121 llvm_unreachable("Invalid expression kind!"); 122 } 123 124 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 125 void MCExpr::dump() const { 126 print(dbgs()); 127 dbgs() << '\n'; 128 } 129 #endif 130 131 /* *** */ 132 133 const MCBinaryExpr *MCBinaryExpr::Create(Opcode Opc, const MCExpr *LHS, 134 const MCExpr *RHS, MCContext &Ctx) { 135 return new (Ctx) MCBinaryExpr(Opc, LHS, RHS); 136 } 137 138 const MCUnaryExpr *MCUnaryExpr::Create(Opcode Opc, const MCExpr *Expr, 139 MCContext &Ctx) { 140 return new (Ctx) MCUnaryExpr(Opc, Expr); 141 } 142 143 const MCConstantExpr *MCConstantExpr::Create(int64_t Value, MCContext &Ctx) { 144 return new (Ctx) MCConstantExpr(Value); 145 } 146 147 /* *** */ 148 149 MCSymbolRefExpr::MCSymbolRefExpr(const MCSymbol *Symbol, VariantKind Kind, 150 const MCAsmInfo *MAI) 151 : MCExpr(MCExpr::SymbolRef), Kind(Kind), 152 UseParensForSymbolVariant(MAI->useParensForSymbolVariant()), 153 HasSubsectionsViaSymbols(MAI->hasSubsectionsViaSymbols()), 154 Symbol(Symbol) { 155 assert(Symbol); 156 } 157 158 const MCSymbolRefExpr *MCSymbolRefExpr::Create(const MCSymbol *Sym, 159 VariantKind Kind, 160 MCContext &Ctx) { 161 return new (Ctx) MCSymbolRefExpr(Sym, Kind, Ctx.getAsmInfo()); 162 } 163 164 const MCSymbolRefExpr *MCSymbolRefExpr::Create(StringRef Name, VariantKind Kind, 165 MCContext &Ctx) { 166 return Create(Ctx.GetOrCreateSymbol(Name), Kind, Ctx); 167 } 168 169 StringRef MCSymbolRefExpr::getVariantKindName(VariantKind Kind) { 170 switch (Kind) { 171 case VK_Invalid: return "<<invalid>>"; 172 case VK_None: return "<<none>>"; 173 174 case VK_GOT: return "GOT"; 175 case VK_GOTOFF: return "GOTOFF"; 176 case VK_GOTPCREL: return "GOTPCREL"; 177 case VK_GOTTPOFF: return "GOTTPOFF"; 178 case VK_INDNTPOFF: return "INDNTPOFF"; 179 case VK_NTPOFF: return "NTPOFF"; 180 case VK_GOTNTPOFF: return "GOTNTPOFF"; 181 case VK_PLT: return "PLT"; 182 case VK_TLSGD: return "TLSGD"; 183 case VK_TLSLD: return "TLSLD"; 184 case VK_TLSLDM: return "TLSLDM"; 185 case VK_TPOFF: return "TPOFF"; 186 case VK_DTPOFF: return "DTPOFF"; 187 case VK_TLVP: return "TLVP"; 188 case VK_TLVPPAGE: return "TLVPPAGE"; 189 case VK_TLVPPAGEOFF: return "TLVPPAGEOFF"; 190 case VK_PAGE: return "PAGE"; 191 case VK_PAGEOFF: return "PAGEOFF"; 192 case VK_GOTPAGE: return "GOTPAGE"; 193 case VK_GOTPAGEOFF: return "GOTPAGEOFF"; 194 case VK_SECREL: return "SECREL32"; 195 case VK_SIZE: return "SIZE"; 196 case VK_WEAKREF: return "WEAKREF"; 197 case VK_ARM_NONE: return "none"; 198 case VK_ARM_TARGET1: return "target1"; 199 case VK_ARM_TARGET2: return "target2"; 200 case VK_ARM_PREL31: return "prel31"; 201 case VK_ARM_SBREL: return "sbrel"; 202 case VK_ARM_TLSLDO: return "tlsldo"; 203 case VK_ARM_TLSCALL: return "tlscall"; 204 case VK_ARM_TLSDESC: return "tlsdesc"; 205 case VK_ARM_TLSDESCSEQ: return "tlsdescseq"; 206 case VK_PPC_LO: return "l"; 207 case VK_PPC_HI: return "h"; 208 case VK_PPC_HA: return "ha"; 209 case VK_PPC_HIGHER: return "higher"; 210 case VK_PPC_HIGHERA: return "highera"; 211 case VK_PPC_HIGHEST: return "highest"; 212 case VK_PPC_HIGHESTA: return "highesta"; 213 case VK_PPC_GOT_LO: return "got@l"; 214 case VK_PPC_GOT_HI: return "got@h"; 215 case VK_PPC_GOT_HA: return "got@ha"; 216 case VK_PPC_TOCBASE: return "tocbase"; 217 case VK_PPC_TOC: return "toc"; 218 case VK_PPC_TOC_LO: return "toc@l"; 219 case VK_PPC_TOC_HI: return "toc@h"; 220 case VK_PPC_TOC_HA: return "toc@ha"; 221 case VK_PPC_DTPMOD: return "dtpmod"; 222 case VK_PPC_TPREL: return "tprel"; 223 case VK_PPC_TPREL_LO: return "tprel@l"; 224 case VK_PPC_TPREL_HI: return "tprel@h"; 225 case VK_PPC_TPREL_HA: return "tprel@ha"; 226 case VK_PPC_TPREL_HIGHER: return "tprel@higher"; 227 case VK_PPC_TPREL_HIGHERA: return "tprel@highera"; 228 case VK_PPC_TPREL_HIGHEST: return "tprel@highest"; 229 case VK_PPC_TPREL_HIGHESTA: return "tprel@highesta"; 230 case VK_PPC_DTPREL: return "dtprel"; 231 case VK_PPC_DTPREL_LO: return "dtprel@l"; 232 case VK_PPC_DTPREL_HI: return "dtprel@h"; 233 case VK_PPC_DTPREL_HA: return "dtprel@ha"; 234 case VK_PPC_DTPREL_HIGHER: return "dtprel@higher"; 235 case VK_PPC_DTPREL_HIGHERA: return "dtprel@highera"; 236 case VK_PPC_DTPREL_HIGHEST: return "dtprel@highest"; 237 case VK_PPC_DTPREL_HIGHESTA: return "dtprel@highesta"; 238 case VK_PPC_GOT_TPREL: return "got@tprel"; 239 case VK_PPC_GOT_TPREL_LO: return "got@tprel@l"; 240 case VK_PPC_GOT_TPREL_HI: return "got@tprel@h"; 241 case VK_PPC_GOT_TPREL_HA: return "got@tprel@ha"; 242 case VK_PPC_GOT_DTPREL: return "got@dtprel"; 243 case VK_PPC_GOT_DTPREL_LO: return "got@dtprel@l"; 244 case VK_PPC_GOT_DTPREL_HI: return "got@dtprel@h"; 245 case VK_PPC_GOT_DTPREL_HA: return "got@dtprel@ha"; 246 case VK_PPC_TLS: return "tls"; 247 case VK_PPC_GOT_TLSGD: return "got@tlsgd"; 248 case VK_PPC_GOT_TLSGD_LO: return "got@tlsgd@l"; 249 case VK_PPC_GOT_TLSGD_HI: return "got@tlsgd@h"; 250 case VK_PPC_GOT_TLSGD_HA: return "got@tlsgd@ha"; 251 case VK_PPC_TLSGD: return "tlsgd"; 252 case VK_PPC_GOT_TLSLD: return "got@tlsld"; 253 case VK_PPC_GOT_TLSLD_LO: return "got@tlsld@l"; 254 case VK_PPC_GOT_TLSLD_HI: return "got@tlsld@h"; 255 case VK_PPC_GOT_TLSLD_HA: return "got@tlsld@ha"; 256 case VK_PPC_TLSLD: return "tlsld"; 257 case VK_PPC_LOCAL: return "local"; 258 case VK_Mips_GPREL: return "GPREL"; 259 case VK_Mips_GOT_CALL: return "GOT_CALL"; 260 case VK_Mips_GOT16: return "GOT16"; 261 case VK_Mips_GOT: return "GOT"; 262 case VK_Mips_ABS_HI: return "ABS_HI"; 263 case VK_Mips_ABS_LO: return "ABS_LO"; 264 case VK_Mips_TLSGD: return "TLSGD"; 265 case VK_Mips_TLSLDM: return "TLSLDM"; 266 case VK_Mips_DTPREL_HI: return "DTPREL_HI"; 267 case VK_Mips_DTPREL_LO: return "DTPREL_LO"; 268 case VK_Mips_GOTTPREL: return "GOTTPREL"; 269 case VK_Mips_TPREL_HI: return "TPREL_HI"; 270 case VK_Mips_TPREL_LO: return "TPREL_LO"; 271 case VK_Mips_GPOFF_HI: return "GPOFF_HI"; 272 case VK_Mips_GPOFF_LO: return "GPOFF_LO"; 273 case VK_Mips_GOT_DISP: return "GOT_DISP"; 274 case VK_Mips_GOT_PAGE: return "GOT_PAGE"; 275 case VK_Mips_GOT_OFST: return "GOT_OFST"; 276 case VK_Mips_HIGHER: return "HIGHER"; 277 case VK_Mips_HIGHEST: return "HIGHEST"; 278 case VK_Mips_GOT_HI16: return "GOT_HI16"; 279 case VK_Mips_GOT_LO16: return "GOT_LO16"; 280 case VK_Mips_CALL_HI16: return "CALL_HI16"; 281 case VK_Mips_CALL_LO16: return "CALL_LO16"; 282 case VK_Mips_PCREL_HI16: return "PCREL_HI16"; 283 case VK_Mips_PCREL_LO16: return "PCREL_LO16"; 284 case VK_COFF_IMGREL32: return "IMGREL"; 285 } 286 llvm_unreachable("Invalid variant kind"); 287 } 288 289 MCSymbolRefExpr::VariantKind 290 MCSymbolRefExpr::getVariantKindForName(StringRef Name) { 291 return StringSwitch<VariantKind>(Name.lower()) 292 .Case("got", VK_GOT) 293 .Case("gotoff", VK_GOTOFF) 294 .Case("gotpcrel", VK_GOTPCREL) 295 .Case("got_prel", VK_GOTPCREL) 296 .Case("gottpoff", VK_GOTTPOFF) 297 .Case("indntpoff", VK_INDNTPOFF) 298 .Case("ntpoff", VK_NTPOFF) 299 .Case("gotntpoff", VK_GOTNTPOFF) 300 .Case("plt", VK_PLT) 301 .Case("tlsgd", VK_TLSGD) 302 .Case("tlsld", VK_TLSLD) 303 .Case("tlsldm", VK_TLSLDM) 304 .Case("tpoff", VK_TPOFF) 305 .Case("dtpoff", VK_DTPOFF) 306 .Case("tlvp", VK_TLVP) 307 .Case("tlvppage", VK_TLVPPAGE) 308 .Case("tlvppageoff", VK_TLVPPAGEOFF) 309 .Case("page", VK_PAGE) 310 .Case("pageoff", VK_PAGEOFF) 311 .Case("gotpage", VK_GOTPAGE) 312 .Case("gotpageoff", VK_GOTPAGEOFF) 313 .Case("imgrel", VK_COFF_IMGREL32) 314 .Case("secrel32", VK_SECREL) 315 .Case("size", VK_SIZE) 316 .Case("l", VK_PPC_LO) 317 .Case("h", VK_PPC_HI) 318 .Case("ha", VK_PPC_HA) 319 .Case("higher", VK_PPC_HIGHER) 320 .Case("highera", VK_PPC_HIGHERA) 321 .Case("highest", VK_PPC_HIGHEST) 322 .Case("highesta", VK_PPC_HIGHESTA) 323 .Case("got@l", VK_PPC_GOT_LO) 324 .Case("got@h", VK_PPC_GOT_HI) 325 .Case("got@ha", VK_PPC_GOT_HA) 326 .Case("local", VK_PPC_LOCAL) 327 .Case("tocbase", VK_PPC_TOCBASE) 328 .Case("toc", VK_PPC_TOC) 329 .Case("toc@l", VK_PPC_TOC_LO) 330 .Case("toc@h", VK_PPC_TOC_HI) 331 .Case("toc@ha", VK_PPC_TOC_HA) 332 .Case("tls", VK_PPC_TLS) 333 .Case("dtpmod", VK_PPC_DTPMOD) 334 .Case("tprel", VK_PPC_TPREL) 335 .Case("tprel@l", VK_PPC_TPREL_LO) 336 .Case("tprel@h", VK_PPC_TPREL_HI) 337 .Case("tprel@ha", VK_PPC_TPREL_HA) 338 .Case("tprel@higher", VK_PPC_TPREL_HIGHER) 339 .Case("tprel@highera", VK_PPC_TPREL_HIGHERA) 340 .Case("tprel@highest", VK_PPC_TPREL_HIGHEST) 341 .Case("tprel@highesta", VK_PPC_TPREL_HIGHESTA) 342 .Case("dtprel", VK_PPC_DTPREL) 343 .Case("dtprel@l", VK_PPC_DTPREL_LO) 344 .Case("dtprel@h", VK_PPC_DTPREL_HI) 345 .Case("dtprel@ha", VK_PPC_DTPREL_HA) 346 .Case("dtprel@higher", VK_PPC_DTPREL_HIGHER) 347 .Case("dtprel@highera", VK_PPC_DTPREL_HIGHERA) 348 .Case("dtprel@highest", VK_PPC_DTPREL_HIGHEST) 349 .Case("dtprel@highesta", VK_PPC_DTPREL_HIGHESTA) 350 .Case("got@tprel", VK_PPC_GOT_TPREL) 351 .Case("got@tprel@l", VK_PPC_GOT_TPREL_LO) 352 .Case("got@tprel@h", VK_PPC_GOT_TPREL_HI) 353 .Case("got@tprel@ha", VK_PPC_GOT_TPREL_HA) 354 .Case("got@dtprel", VK_PPC_GOT_DTPREL) 355 .Case("got@dtprel@l", VK_PPC_GOT_DTPREL_LO) 356 .Case("got@dtprel@h", VK_PPC_GOT_DTPREL_HI) 357 .Case("got@dtprel@ha", VK_PPC_GOT_DTPREL_HA) 358 .Case("got@tlsgd", VK_PPC_GOT_TLSGD) 359 .Case("got@tlsgd@l", VK_PPC_GOT_TLSGD_LO) 360 .Case("got@tlsgd@h", VK_PPC_GOT_TLSGD_HI) 361 .Case("got@tlsgd@ha", VK_PPC_GOT_TLSGD_HA) 362 .Case("got@tlsld", VK_PPC_GOT_TLSLD) 363 .Case("got@tlsld@l", VK_PPC_GOT_TLSLD_LO) 364 .Case("got@tlsld@h", VK_PPC_GOT_TLSLD_HI) 365 .Case("got@tlsld@ha", VK_PPC_GOT_TLSLD_HA) 366 .Case("none", VK_ARM_NONE) 367 .Case("target1", VK_ARM_TARGET1) 368 .Case("target2", VK_ARM_TARGET2) 369 .Case("prel31", VK_ARM_PREL31) 370 .Case("sbrel", VK_ARM_SBREL) 371 .Case("tlsldo", VK_ARM_TLSLDO) 372 .Case("tlscall", VK_ARM_TLSCALL) 373 .Case("tlsdesc", VK_ARM_TLSDESC) 374 .Default(VK_Invalid); 375 } 376 377 void MCSymbolRefExpr::printVariantKind(raw_ostream &OS) const { 378 if (UseParensForSymbolVariant) 379 OS << '(' << MCSymbolRefExpr::getVariantKindName(getKind()) << ')'; 380 else 381 OS << '@' << MCSymbolRefExpr::getVariantKindName(getKind()); 382 } 383 384 /* *** */ 385 386 void MCTargetExpr::anchor() {} 387 388 /* *** */ 389 390 bool MCExpr::EvaluateAsAbsolute(int64_t &Res) const { 391 return EvaluateAsAbsolute(Res, nullptr, nullptr, nullptr); 392 } 393 394 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, 395 const MCAsmLayout &Layout) const { 396 return EvaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr); 397 } 398 399 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, 400 const MCAsmLayout &Layout, 401 const SectionAddrMap &Addrs) const { 402 return EvaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, &Addrs); 403 } 404 405 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const { 406 return EvaluateAsAbsolute(Res, &Asm, nullptr, nullptr); 407 } 408 409 bool MCExpr::evaluateKnownAbsolute(int64_t &Res, 410 const MCAsmLayout &Layout) const { 411 return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr, 412 true); 413 } 414 415 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm, 416 const MCAsmLayout *Layout, 417 const SectionAddrMap *Addrs) const { 418 // FIXME: The use if InSet = Addrs is a hack. Setting InSet causes us 419 // absolutize differences across sections and that is what the MachO writer 420 // uses Addrs for. 421 return evaluateAsAbsolute(Res, Asm, Layout, Addrs, Addrs); 422 } 423 424 bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm, 425 const MCAsmLayout *Layout, 426 const SectionAddrMap *Addrs, bool InSet) const { 427 MCValue Value; 428 429 // Fast path constants. 430 if (const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(this)) { 431 Res = CE->getValue(); 432 return true; 433 } 434 435 bool IsRelocatable = 436 EvaluateAsRelocatableImpl(Value, Asm, Layout, nullptr, Addrs, InSet); 437 438 // Record the current value. 439 Res = Value.getConstant(); 440 441 return IsRelocatable && Value.isAbsolute(); 442 } 443 444 /// \brief Helper method for \see EvaluateSymbolAdd(). 445 static void AttemptToFoldSymbolOffsetDifference( 446 const MCAssembler *Asm, const MCAsmLayout *Layout, 447 const SectionAddrMap *Addrs, bool InSet, const MCSymbolRefExpr *&A, 448 const MCSymbolRefExpr *&B, int64_t &Addend) { 449 if (!A || !B) 450 return; 451 452 const MCSymbol &SA = A->getSymbol(); 453 const MCSymbol &SB = B->getSymbol(); 454 455 if (SA.isUndefined() || SB.isUndefined()) 456 return; 457 458 if (!Asm->getWriter().IsSymbolRefDifferenceFullyResolved(*Asm, A, B, InSet)) 459 return; 460 461 const MCSymbolData &AD = Asm->getSymbolData(SA); 462 const MCSymbolData &BD = Asm->getSymbolData(SB); 463 464 if (AD.getFragment() == BD.getFragment()) { 465 Addend += (AD.getOffset() - BD.getOffset()); 466 467 // Pointers to Thumb symbols need to have their low-bit set to allow 468 // for interworking. 469 if (Asm->isThumbFunc(&SA)) 470 Addend |= 1; 471 472 // Clear the symbol expr pointers to indicate we have folded these 473 // operands. 474 A = B = nullptr; 475 return; 476 } 477 478 if (!Layout) 479 return; 480 481 const MCSectionData &SecA = *AD.getFragment()->getParent(); 482 const MCSectionData &SecB = *BD.getFragment()->getParent(); 483 484 if ((&SecA != &SecB) && !Addrs) 485 return; 486 487 // Eagerly evaluate. 488 Addend += (Layout->getSymbolOffset(&Asm->getSymbolData(A->getSymbol())) - 489 Layout->getSymbolOffset(&Asm->getSymbolData(B->getSymbol()))); 490 if (Addrs && (&SecA != &SecB)) 491 Addend += (Addrs->lookup(&SecA) - Addrs->lookup(&SecB)); 492 493 // Pointers to Thumb symbols need to have their low-bit set to allow 494 // for interworking. 495 if (Asm->isThumbFunc(&SA)) 496 Addend |= 1; 497 498 // Clear the symbol expr pointers to indicate we have folded these 499 // operands. 500 A = B = nullptr; 501 } 502 503 /// \brief Evaluate the result of an add between (conceptually) two MCValues. 504 /// 505 /// This routine conceptually attempts to construct an MCValue: 506 /// Result = (Result_A - Result_B + Result_Cst) 507 /// from two MCValue's LHS and RHS where 508 /// Result = LHS + RHS 509 /// and 510 /// Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst). 511 /// 512 /// This routine attempts to aggresively fold the operands such that the result 513 /// is representable in an MCValue, but may not always succeed. 514 /// 515 /// \returns True on success, false if the result is not representable in an 516 /// MCValue. 517 518 /// NOTE: It is really important to have both the Asm and Layout arguments. 519 /// They might look redundant, but this function can be used before layout 520 /// is done (see the object streamer for example) and having the Asm argument 521 /// lets us avoid relaxations early. 522 static bool 523 EvaluateSymbolicAdd(const MCAssembler *Asm, const MCAsmLayout *Layout, 524 const SectionAddrMap *Addrs, bool InSet, const MCValue &LHS, 525 const MCSymbolRefExpr *RHS_A, const MCSymbolRefExpr *RHS_B, 526 int64_t RHS_Cst, MCValue &Res) { 527 // FIXME: This routine (and other evaluation parts) are *incredibly* sloppy 528 // about dealing with modifiers. This will ultimately bite us, one day. 529 const MCSymbolRefExpr *LHS_A = LHS.getSymA(); 530 const MCSymbolRefExpr *LHS_B = LHS.getSymB(); 531 int64_t LHS_Cst = LHS.getConstant(); 532 533 // Fold the result constant immediately. 534 int64_t Result_Cst = LHS_Cst + RHS_Cst; 535 536 assert((!Layout || Asm) && 537 "Must have an assembler object if layout is given!"); 538 539 // If we have a layout, we can fold resolved differences. 540 if (Asm) { 541 // First, fold out any differences which are fully resolved. By 542 // reassociating terms in 543 // Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst). 544 // we have the four possible differences: 545 // (LHS_A - LHS_B), 546 // (LHS_A - RHS_B), 547 // (RHS_A - LHS_B), 548 // (RHS_A - RHS_B). 549 // Since we are attempting to be as aggressive as possible about folding, we 550 // attempt to evaluate each possible alternative. 551 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, LHS_B, 552 Result_Cst); 553 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, RHS_B, 554 Result_Cst); 555 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, LHS_B, 556 Result_Cst); 557 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, RHS_B, 558 Result_Cst); 559 } 560 561 // We can't represent the addition or subtraction of two symbols. 562 if ((LHS_A && RHS_A) || (LHS_B && RHS_B)) 563 return false; 564 565 // At this point, we have at most one additive symbol and one subtractive 566 // symbol -- find them. 567 const MCSymbolRefExpr *A = LHS_A ? LHS_A : RHS_A; 568 const MCSymbolRefExpr *B = LHS_B ? LHS_B : RHS_B; 569 570 // If we have a negated symbol, then we must have also have a non-negated 571 // symbol in order to encode the expression. 572 if (B && !A) 573 return false; 574 575 Res = MCValue::get(A, B, Result_Cst); 576 return true; 577 } 578 579 bool MCExpr::EvaluateAsRelocatable(MCValue &Res, 580 const MCAsmLayout *Layout, 581 const MCFixup *Fixup) const { 582 MCAssembler *Assembler = Layout ? &Layout->getAssembler() : nullptr; 583 return EvaluateAsRelocatableImpl(Res, Assembler, Layout, Fixup, nullptr, 584 false); 585 } 586 587 bool MCExpr::evaluateAsValue(MCValue &Res, const MCAsmLayout &Layout) const { 588 MCAssembler *Assembler = &Layout.getAssembler(); 589 return EvaluateAsRelocatableImpl(Res, Assembler, &Layout, nullptr, nullptr, 590 true); 591 } 592 593 static bool canExpand(const MCSymbol &Sym, const MCAssembler *Asm, bool InSet) { 594 if (InSet) 595 return true; 596 if (!Asm) 597 return false; 598 const MCSymbolData &SD = Asm->getSymbolData(Sym); 599 return !Asm->getWriter().isWeak(SD); 600 } 601 602 bool MCExpr::EvaluateAsRelocatableImpl(MCValue &Res, const MCAssembler *Asm, 603 const MCAsmLayout *Layout, 604 const MCFixup *Fixup, 605 const SectionAddrMap *Addrs, 606 bool InSet) const { 607 ++stats::MCExprEvaluate; 608 609 switch (getKind()) { 610 case Target: 611 return cast<MCTargetExpr>(this)->EvaluateAsRelocatableImpl(Res, Layout, 612 Fixup); 613 614 case Constant: 615 Res = MCValue::get(cast<MCConstantExpr>(this)->getValue()); 616 return true; 617 618 case SymbolRef: { 619 const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this); 620 const MCSymbol &Sym = SRE->getSymbol(); 621 622 // Evaluate recursively if this is a variable. 623 if (Sym.isVariable() && SRE->getKind() == MCSymbolRefExpr::VK_None && 624 canExpand(Sym, Asm, InSet)) { 625 bool IsMachO = SRE->hasSubsectionsViaSymbols(); 626 if (Sym.getVariableValue()->EvaluateAsRelocatableImpl( 627 Res, Asm, Layout, Fixup, Addrs, InSet || IsMachO)) { 628 if (!IsMachO) 629 return true; 630 631 const MCSymbolRefExpr *A = Res.getSymA(); 632 const MCSymbolRefExpr *B = Res.getSymB(); 633 // FIXME: This is small hack. Given 634 // a = b + 4 635 // .long a 636 // the OS X assembler will completely drop the 4. We should probably 637 // include it in the relocation or produce an error if that is not 638 // possible. 639 if (!A && !B) 640 return true; 641 } 642 } 643 644 Res = MCValue::get(SRE, nullptr, 0); 645 return true; 646 } 647 648 case Unary: { 649 const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this); 650 MCValue Value; 651 652 if (!AUE->getSubExpr()->EvaluateAsRelocatableImpl(Value, Asm, Layout, Fixup, 653 Addrs, InSet)) 654 return false; 655 656 switch (AUE->getOpcode()) { 657 case MCUnaryExpr::LNot: 658 if (!Value.isAbsolute()) 659 return false; 660 Res = MCValue::get(!Value.getConstant()); 661 break; 662 case MCUnaryExpr::Minus: 663 /// -(a - b + const) ==> (b - a - const) 664 if (Value.getSymA() && !Value.getSymB()) 665 return false; 666 Res = MCValue::get(Value.getSymB(), Value.getSymA(), 667 -Value.getConstant()); 668 break; 669 case MCUnaryExpr::Not: 670 if (!Value.isAbsolute()) 671 return false; 672 Res = MCValue::get(~Value.getConstant()); 673 break; 674 case MCUnaryExpr::Plus: 675 Res = Value; 676 break; 677 } 678 679 return true; 680 } 681 682 case Binary: { 683 const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this); 684 MCValue LHSValue, RHSValue; 685 686 if (!ABE->getLHS()->EvaluateAsRelocatableImpl(LHSValue, Asm, Layout, Fixup, 687 Addrs, InSet) || 688 !ABE->getRHS()->EvaluateAsRelocatableImpl(RHSValue, Asm, Layout, Fixup, 689 Addrs, InSet)) 690 return false; 691 692 // We only support a few operations on non-constant expressions, handle 693 // those first. 694 if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) { 695 switch (ABE->getOpcode()) { 696 default: 697 return false; 698 case MCBinaryExpr::Sub: 699 // Negate RHS and add. 700 return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue, 701 RHSValue.getSymB(), RHSValue.getSymA(), 702 -RHSValue.getConstant(), Res); 703 704 case MCBinaryExpr::Add: 705 return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue, 706 RHSValue.getSymA(), RHSValue.getSymB(), 707 RHSValue.getConstant(), Res); 708 } 709 } 710 711 // FIXME: We need target hooks for the evaluation. It may be limited in 712 // width, and gas defines the result of comparisons and right shifts 713 // differently from Apple as. 714 int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant(); 715 int64_t Result = 0; 716 switch (ABE->getOpcode()) { 717 case MCBinaryExpr::Add: Result = LHS + RHS; break; 718 case MCBinaryExpr::And: Result = LHS & RHS; break; 719 case MCBinaryExpr::Div: Result = LHS / RHS; break; 720 case MCBinaryExpr::EQ: Result = LHS == RHS; break; 721 case MCBinaryExpr::GT: Result = LHS > RHS; break; 722 case MCBinaryExpr::GTE: Result = LHS >= RHS; break; 723 case MCBinaryExpr::LAnd: Result = LHS && RHS; break; 724 case MCBinaryExpr::LOr: Result = LHS || RHS; break; 725 case MCBinaryExpr::LT: Result = LHS < RHS; break; 726 case MCBinaryExpr::LTE: Result = LHS <= RHS; break; 727 case MCBinaryExpr::Mod: Result = LHS % RHS; break; 728 case MCBinaryExpr::Mul: Result = LHS * RHS; break; 729 case MCBinaryExpr::NE: Result = LHS != RHS; break; 730 case MCBinaryExpr::Or: Result = LHS | RHS; break; 731 case MCBinaryExpr::Shl: Result = LHS << RHS; break; 732 case MCBinaryExpr::Shr: Result = LHS >> RHS; break; 733 case MCBinaryExpr::Sub: Result = LHS - RHS; break; 734 case MCBinaryExpr::Xor: Result = LHS ^ RHS; break; 735 } 736 737 Res = MCValue::get(Result); 738 return true; 739 } 740 } 741 742 llvm_unreachable("Invalid assembly expression kind!"); 743 } 744 745 const MCSection *MCExpr::FindAssociatedSection() const { 746 switch (getKind()) { 747 case Target: 748 // We never look through target specific expressions. 749 return cast<MCTargetExpr>(this)->FindAssociatedSection(); 750 751 case Constant: 752 return MCSymbol::AbsolutePseudoSection; 753 754 case SymbolRef: { 755 const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this); 756 const MCSymbol &Sym = SRE->getSymbol(); 757 758 if (Sym.isDefined()) 759 return &Sym.getSection(); 760 761 return nullptr; 762 } 763 764 case Unary: 765 return cast<MCUnaryExpr>(this)->getSubExpr()->FindAssociatedSection(); 766 767 case Binary: { 768 const MCBinaryExpr *BE = cast<MCBinaryExpr>(this); 769 const MCSection *LHS_S = BE->getLHS()->FindAssociatedSection(); 770 const MCSection *RHS_S = BE->getRHS()->FindAssociatedSection(); 771 772 // If either section is absolute, return the other. 773 if (LHS_S == MCSymbol::AbsolutePseudoSection) 774 return RHS_S; 775 if (RHS_S == MCSymbol::AbsolutePseudoSection) 776 return LHS_S; 777 778 // Not always correct, but probably the best we can do without more context. 779 if (BE->getOpcode() == MCBinaryExpr::Sub) 780 return MCSymbol::AbsolutePseudoSection; 781 782 // Otherwise, return the first non-null section. 783 return LHS_S ? LHS_S : RHS_S; 784 } 785 } 786 787 llvm_unreachable("Invalid assembly expression kind!"); 788 } 789
