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 MCAsmInfo *MAI, bool InParens) const { 34 switch (getKind()) { 35 case MCExpr::Target: 36 return cast<MCTargetExpr>(this)->printImpl(OS, MAI); 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 = 47 !InParens && Sym.getName().size() && Sym.getName()[0] == '$'; 48 if (UseParens) { 49 OS << '('; 50 Sym.print(OS, MAI); 51 OS << ')'; 52 } else 53 Sym.print(OS, MAI); 54 55 if (SRE.getKind() != MCSymbolRefExpr::VK_None) 56 SRE.printVariantKind(OS); 57 58 return; 59 } 60 61 case MCExpr::Unary: { 62 const MCUnaryExpr &UE = cast<MCUnaryExpr>(*this); 63 switch (UE.getOpcode()) { 64 case MCUnaryExpr::LNot: OS << '!'; break; 65 case MCUnaryExpr::Minus: OS << '-'; break; 66 case MCUnaryExpr::Not: OS << '~'; break; 67 case MCUnaryExpr::Plus: OS << '+'; break; 68 } 69 UE.getSubExpr()->print(OS, MAI); 70 return; 71 } 72 73 case MCExpr::Binary: { 74 const MCBinaryExpr &BE = cast<MCBinaryExpr>(*this); 75 76 // Only print parens around the LHS if it is non-trivial. 77 if (isa<MCConstantExpr>(BE.getLHS()) || isa<MCSymbolRefExpr>(BE.getLHS())) { 78 BE.getLHS()->print(OS, MAI); 79 } else { 80 OS << '('; 81 BE.getLHS()->print(OS, MAI); 82 OS << ')'; 83 } 84 85 switch (BE.getOpcode()) { 86 case MCBinaryExpr::Add: 87 // Print "X-42" instead of "X+-42". 88 if (const MCConstantExpr *RHSC = dyn_cast<MCConstantExpr>(BE.getRHS())) { 89 if (RHSC->getValue() < 0) { 90 OS << RHSC->getValue(); 91 return; 92 } 93 } 94 95 OS << '+'; 96 break; 97 case MCBinaryExpr::AShr: OS << ">>"; break; 98 case MCBinaryExpr::And: OS << '&'; break; 99 case MCBinaryExpr::Div: OS << '/'; break; 100 case MCBinaryExpr::EQ: OS << "=="; break; 101 case MCBinaryExpr::GT: OS << '>'; break; 102 case MCBinaryExpr::GTE: OS << ">="; break; 103 case MCBinaryExpr::LAnd: OS << "&&"; break; 104 case MCBinaryExpr::LOr: OS << "||"; break; 105 case MCBinaryExpr::LShr: OS << ">>"; break; 106 case MCBinaryExpr::LT: OS << '<'; break; 107 case MCBinaryExpr::LTE: OS << "<="; break; 108 case MCBinaryExpr::Mod: OS << '%'; break; 109 case MCBinaryExpr::Mul: OS << '*'; break; 110 case MCBinaryExpr::NE: OS << "!="; break; 111 case MCBinaryExpr::Or: OS << '|'; break; 112 case MCBinaryExpr::Shl: OS << "<<"; break; 113 case MCBinaryExpr::Sub: OS << '-'; break; 114 case MCBinaryExpr::Xor: OS << '^'; break; 115 } 116 117 // Only print parens around the LHS if it is non-trivial. 118 if (isa<MCConstantExpr>(BE.getRHS()) || isa<MCSymbolRefExpr>(BE.getRHS())) { 119 BE.getRHS()->print(OS, MAI); 120 } else { 121 OS << '('; 122 BE.getRHS()->print(OS, MAI); 123 OS << ')'; 124 } 125 return; 126 } 127 } 128 129 llvm_unreachable("Invalid expression kind!"); 130 } 131 132 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 133 LLVM_DUMP_METHOD void MCExpr::dump() const { 134 dbgs() << *this; 135 dbgs() << '\n'; 136 } 137 #endif 138 139 /* *** */ 140 141 const MCBinaryExpr *MCBinaryExpr::create(Opcode Opc, const MCExpr *LHS, 142 const MCExpr *RHS, MCContext &Ctx) { 143 return new (Ctx) MCBinaryExpr(Opc, LHS, RHS); 144 } 145 146 const MCUnaryExpr *MCUnaryExpr::create(Opcode Opc, const MCExpr *Expr, 147 MCContext &Ctx) { 148 return new (Ctx) MCUnaryExpr(Opc, Expr); 149 } 150 151 const MCConstantExpr *MCConstantExpr::create(int64_t Value, MCContext &Ctx) { 152 return new (Ctx) MCConstantExpr(Value); 153 } 154 155 /* *** */ 156 157 MCSymbolRefExpr::MCSymbolRefExpr(const MCSymbol *Symbol, VariantKind Kind, 158 const MCAsmInfo *MAI) 159 : MCExpr(MCExpr::SymbolRef), Kind(Kind), 160 UseParensForSymbolVariant(MAI->useParensForSymbolVariant()), 161 HasSubsectionsViaSymbols(MAI->hasSubsectionsViaSymbols()), 162 Symbol(Symbol) { 163 assert(Symbol); 164 } 165 166 const MCSymbolRefExpr *MCSymbolRefExpr::create(const MCSymbol *Sym, 167 VariantKind Kind, 168 MCContext &Ctx) { 169 return new (Ctx) MCSymbolRefExpr(Sym, Kind, Ctx.getAsmInfo()); 170 } 171 172 const MCSymbolRefExpr *MCSymbolRefExpr::create(StringRef Name, VariantKind Kind, 173 MCContext &Ctx) { 174 return create(Ctx.getOrCreateSymbol(Name), Kind, Ctx); 175 } 176 177 StringRef MCSymbolRefExpr::getVariantKindName(VariantKind Kind) { 178 switch (Kind) { 179 case VK_Invalid: return "<<invalid>>"; 180 case VK_None: return "<<none>>"; 181 182 case VK_DTPOFF: return "DTPOFF"; 183 case VK_DTPREL: return "DTPREL"; 184 case VK_GOT: return "GOT"; 185 case VK_GOTOFF: return "GOTOFF"; 186 case VK_GOTREL: return "GOTREL"; 187 case VK_GOTPCREL: return "GOTPCREL"; 188 case VK_GOTTPOFF: return "GOTTPOFF"; 189 case VK_INDNTPOFF: return "INDNTPOFF"; 190 case VK_NTPOFF: return "NTPOFF"; 191 case VK_GOTNTPOFF: return "GOTNTPOFF"; 192 case VK_PLT: return "PLT"; 193 case VK_TLSGD: return "TLSGD"; 194 case VK_TLSLD: return "TLSLD"; 195 case VK_TLSLDM: return "TLSLDM"; 196 case VK_TPOFF: return "TPOFF"; 197 case VK_TPREL: return "TPREL"; 198 case VK_TLSCALL: return "tlscall"; 199 case VK_TLSDESC: return "tlsdesc"; 200 case VK_TLVP: return "TLVP"; 201 case VK_TLVPPAGE: return "TLVPPAGE"; 202 case VK_TLVPPAGEOFF: return "TLVPPAGEOFF"; 203 case VK_PAGE: return "PAGE"; 204 case VK_PAGEOFF: return "PAGEOFF"; 205 case VK_GOTPAGE: return "GOTPAGE"; 206 case VK_GOTPAGEOFF: return "GOTPAGEOFF"; 207 case VK_SECREL: return "SECREL32"; 208 case VK_SIZE: return "SIZE"; 209 case VK_WEAKREF: return "WEAKREF"; 210 case VK_ARM_NONE: return "none"; 211 case VK_ARM_GOT_PREL: return "GOT_PREL"; 212 case VK_ARM_TARGET1: return "target1"; 213 case VK_ARM_TARGET2: return "target2"; 214 case VK_ARM_PREL31: return "prel31"; 215 case VK_ARM_SBREL: return "sbrel"; 216 case VK_ARM_TLSLDO: return "tlsldo"; 217 case VK_ARM_TLSDESCSEQ: return "tlsdescseq"; 218 case VK_PPC_LO: return "l"; 219 case VK_PPC_HI: return "h"; 220 case VK_PPC_HA: return "ha"; 221 case VK_PPC_HIGHER: return "higher"; 222 case VK_PPC_HIGHERA: return "highera"; 223 case VK_PPC_HIGHEST: return "highest"; 224 case VK_PPC_HIGHESTA: return "highesta"; 225 case VK_PPC_GOT_LO: return "got@l"; 226 case VK_PPC_GOT_HI: return "got@h"; 227 case VK_PPC_GOT_HA: return "got@ha"; 228 case VK_PPC_TOCBASE: return "tocbase"; 229 case VK_PPC_TOC: return "toc"; 230 case VK_PPC_TOC_LO: return "toc@l"; 231 case VK_PPC_TOC_HI: return "toc@h"; 232 case VK_PPC_TOC_HA: return "toc@ha"; 233 case VK_PPC_DTPMOD: return "dtpmod"; 234 case VK_PPC_TPREL_LO: return "tprel@l"; 235 case VK_PPC_TPREL_HI: return "tprel@h"; 236 case VK_PPC_TPREL_HA: return "tprel@ha"; 237 case VK_PPC_TPREL_HIGHER: return "tprel@higher"; 238 case VK_PPC_TPREL_HIGHERA: return "tprel@highera"; 239 case VK_PPC_TPREL_HIGHEST: return "tprel@highest"; 240 case VK_PPC_TPREL_HIGHESTA: return "tprel@highesta"; 241 case VK_PPC_DTPREL_LO: return "dtprel@l"; 242 case VK_PPC_DTPREL_HI: return "dtprel@h"; 243 case VK_PPC_DTPREL_HA: return "dtprel@ha"; 244 case VK_PPC_DTPREL_HIGHER: return "dtprel@higher"; 245 case VK_PPC_DTPREL_HIGHERA: return "dtprel@highera"; 246 case VK_PPC_DTPREL_HIGHEST: return "dtprel@highest"; 247 case VK_PPC_DTPREL_HIGHESTA: return "dtprel@highesta"; 248 case VK_PPC_GOT_TPREL: return "got@tprel"; 249 case VK_PPC_GOT_TPREL_LO: return "got@tprel@l"; 250 case VK_PPC_GOT_TPREL_HI: return "got@tprel@h"; 251 case VK_PPC_GOT_TPREL_HA: return "got@tprel@ha"; 252 case VK_PPC_GOT_DTPREL: return "got@dtprel"; 253 case VK_PPC_GOT_DTPREL_LO: return "got@dtprel@l"; 254 case VK_PPC_GOT_DTPREL_HI: return "got@dtprel@h"; 255 case VK_PPC_GOT_DTPREL_HA: return "got@dtprel@ha"; 256 case VK_PPC_TLS: return "tls"; 257 case VK_PPC_GOT_TLSGD: return "got@tlsgd"; 258 case VK_PPC_GOT_TLSGD_LO: return "got@tlsgd@l"; 259 case VK_PPC_GOT_TLSGD_HI: return "got@tlsgd@h"; 260 case VK_PPC_GOT_TLSGD_HA: return "got@tlsgd@ha"; 261 case VK_PPC_TLSGD: return "tlsgd"; 262 case VK_PPC_GOT_TLSLD: return "got@tlsld"; 263 case VK_PPC_GOT_TLSLD_LO: return "got@tlsld@l"; 264 case VK_PPC_GOT_TLSLD_HI: return "got@tlsld@h"; 265 case VK_PPC_GOT_TLSLD_HA: return "got@tlsld@ha"; 266 case VK_PPC_TLSLD: return "tlsld"; 267 case VK_PPC_LOCAL: return "local"; 268 case VK_COFF_IMGREL32: return "IMGREL"; 269 case VK_Hexagon_PCREL: return "PCREL"; 270 case VK_Hexagon_LO16: return "LO16"; 271 case VK_Hexagon_HI16: return "HI16"; 272 case VK_Hexagon_GPREL: return "GPREL"; 273 case VK_Hexagon_GD_GOT: return "GDGOT"; 274 case VK_Hexagon_LD_GOT: return "LDGOT"; 275 case VK_Hexagon_GD_PLT: return "GDPLT"; 276 case VK_Hexagon_LD_PLT: return "LDPLT"; 277 case VK_Hexagon_IE: return "IE"; 278 case VK_Hexagon_IE_GOT: return "IEGOT"; 279 case VK_WebAssembly_FUNCTION: return "FUNCTION"; 280 } 281 llvm_unreachable("Invalid variant kind"); 282 } 283 284 MCSymbolRefExpr::VariantKind 285 MCSymbolRefExpr::getVariantKindForName(StringRef Name) { 286 return StringSwitch<VariantKind>(Name.lower()) 287 .Case("dtprel", VK_DTPREL) 288 .Case("dtpoff", VK_DTPOFF) 289 .Case("got", VK_GOT) 290 .Case("gotoff", VK_GOTOFF) 291 .Case("gotrel", VK_GOTREL) 292 .Case("gotpcrel", VK_GOTPCREL) 293 .Case("gottpoff", VK_GOTTPOFF) 294 .Case("indntpoff", VK_INDNTPOFF) 295 .Case("ntpoff", VK_NTPOFF) 296 .Case("gotntpoff", VK_GOTNTPOFF) 297 .Case("plt", VK_PLT) 298 .Case("tlscall", VK_TLSCALL) 299 .Case("tlsdesc", VK_TLSDESC) 300 .Case("tlsgd", VK_TLSGD) 301 .Case("tlsld", VK_TLSLD) 302 .Case("tlsldm", VK_TLSLDM) 303 .Case("tpoff", VK_TPOFF) 304 .Case("tprel", VK_TPREL) 305 .Case("tlvp", VK_TLVP) 306 .Case("tlvppage", VK_TLVPPAGE) 307 .Case("tlvppageoff", VK_TLVPPAGEOFF) 308 .Case("page", VK_PAGE) 309 .Case("pageoff", VK_PAGEOFF) 310 .Case("gotpage", VK_GOTPAGE) 311 .Case("gotpageoff", VK_GOTPAGEOFF) 312 .Case("imgrel", VK_COFF_IMGREL32) 313 .Case("secrel32", VK_SECREL) 314 .Case("size", VK_SIZE) 315 .Case("l", VK_PPC_LO) 316 .Case("h", VK_PPC_HI) 317 .Case("ha", VK_PPC_HA) 318 .Case("higher", VK_PPC_HIGHER) 319 .Case("highera", VK_PPC_HIGHERA) 320 .Case("highest", VK_PPC_HIGHEST) 321 .Case("highesta", VK_PPC_HIGHESTA) 322 .Case("got@l", VK_PPC_GOT_LO) 323 .Case("got@h", VK_PPC_GOT_HI) 324 .Case("got@ha", VK_PPC_GOT_HA) 325 .Case("local", VK_PPC_LOCAL) 326 .Case("tocbase", VK_PPC_TOCBASE) 327 .Case("toc", VK_PPC_TOC) 328 .Case("toc@l", VK_PPC_TOC_LO) 329 .Case("toc@h", VK_PPC_TOC_HI) 330 .Case("toc@ha", VK_PPC_TOC_HA) 331 .Case("tls", VK_PPC_TLS) 332 .Case("dtpmod", VK_PPC_DTPMOD) 333 .Case("tprel@l", VK_PPC_TPREL_LO) 334 .Case("tprel@h", VK_PPC_TPREL_HI) 335 .Case("tprel@ha", VK_PPC_TPREL_HA) 336 .Case("tprel@higher", VK_PPC_TPREL_HIGHER) 337 .Case("tprel@highera", VK_PPC_TPREL_HIGHERA) 338 .Case("tprel@highest", VK_PPC_TPREL_HIGHEST) 339 .Case("tprel@highesta", VK_PPC_TPREL_HIGHESTA) 340 .Case("dtprel@l", VK_PPC_DTPREL_LO) 341 .Case("dtprel@h", VK_PPC_DTPREL_HI) 342 .Case("dtprel@ha", VK_PPC_DTPREL_HA) 343 .Case("dtprel@higher", VK_PPC_DTPREL_HIGHER) 344 .Case("dtprel@highera", VK_PPC_DTPREL_HIGHERA) 345 .Case("dtprel@highest", VK_PPC_DTPREL_HIGHEST) 346 .Case("dtprel@highesta", VK_PPC_DTPREL_HIGHESTA) 347 .Case("got@tprel", VK_PPC_GOT_TPREL) 348 .Case("got@tprel@l", VK_PPC_GOT_TPREL_LO) 349 .Case("got@tprel@h", VK_PPC_GOT_TPREL_HI) 350 .Case("got@tprel@ha", VK_PPC_GOT_TPREL_HA) 351 .Case("got@dtprel", VK_PPC_GOT_DTPREL) 352 .Case("got@dtprel@l", VK_PPC_GOT_DTPREL_LO) 353 .Case("got@dtprel@h", VK_PPC_GOT_DTPREL_HI) 354 .Case("got@dtprel@ha", VK_PPC_GOT_DTPREL_HA) 355 .Case("got@tlsgd", VK_PPC_GOT_TLSGD) 356 .Case("got@tlsgd@l", VK_PPC_GOT_TLSGD_LO) 357 .Case("got@tlsgd@h", VK_PPC_GOT_TLSGD_HI) 358 .Case("got@tlsgd@ha", VK_PPC_GOT_TLSGD_HA) 359 .Case("got@tlsld", VK_PPC_GOT_TLSLD) 360 .Case("got@tlsld@l", VK_PPC_GOT_TLSLD_LO) 361 .Case("got@tlsld@h", VK_PPC_GOT_TLSLD_HI) 362 .Case("got@tlsld@ha", VK_PPC_GOT_TLSLD_HA) 363 .Case("gdgot", VK_Hexagon_GD_GOT) 364 .Case("gdplt", VK_Hexagon_GD_PLT) 365 .Case("iegot", VK_Hexagon_IE_GOT) 366 .Case("ie", VK_Hexagon_IE) 367 .Case("ldgot", VK_Hexagon_LD_GOT) 368 .Case("ldplt", VK_Hexagon_LD_PLT) 369 .Case("pcrel", VK_Hexagon_PCREL) 370 .Case("none", VK_ARM_NONE) 371 .Case("got_prel", VK_ARM_GOT_PREL) 372 .Case("target1", VK_ARM_TARGET1) 373 .Case("target2", VK_ARM_TARGET2) 374 .Case("prel31", VK_ARM_PREL31) 375 .Case("sbrel", VK_ARM_SBREL) 376 .Case("tlsldo", VK_ARM_TLSLDO) 377 .Default(VK_Invalid); 378 } 379 380 void MCSymbolRefExpr::printVariantKind(raw_ostream &OS) const { 381 if (UseParensForSymbolVariant) 382 OS << '(' << MCSymbolRefExpr::getVariantKindName(getKind()) << ')'; 383 else 384 OS << '@' << MCSymbolRefExpr::getVariantKindName(getKind()); 385 } 386 387 /* *** */ 388 389 void MCTargetExpr::anchor() {} 390 391 /* *** */ 392 393 bool MCExpr::evaluateAsAbsolute(int64_t &Res) const { 394 return evaluateAsAbsolute(Res, nullptr, nullptr, nullptr); 395 } 396 397 bool MCExpr::evaluateAsAbsolute(int64_t &Res, 398 const MCAsmLayout &Layout) const { 399 return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr); 400 } 401 402 bool MCExpr::evaluateAsAbsolute(int64_t &Res, 403 const MCAsmLayout &Layout, 404 const SectionAddrMap &Addrs) const { 405 return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, &Addrs); 406 } 407 408 bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const { 409 return evaluateAsAbsolute(Res, &Asm, nullptr, nullptr); 410 } 411 412 bool MCExpr::evaluateKnownAbsolute(int64_t &Res, 413 const MCAsmLayout &Layout) const { 414 return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr, 415 true); 416 } 417 418 bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm, 419 const MCAsmLayout *Layout, 420 const SectionAddrMap *Addrs) const { 421 // FIXME: The use if InSet = Addrs is a hack. Setting InSet causes us 422 // absolutize differences across sections and that is what the MachO writer 423 // uses Addrs for. 424 return evaluateAsAbsolute(Res, Asm, Layout, Addrs, Addrs); 425 } 426 427 bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm, 428 const MCAsmLayout *Layout, 429 const SectionAddrMap *Addrs, bool InSet) const { 430 MCValue Value; 431 432 // Fast path constants. 433 if (const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(this)) { 434 Res = CE->getValue(); 435 return true; 436 } 437 438 bool IsRelocatable = 439 evaluateAsRelocatableImpl(Value, Asm, Layout, nullptr, Addrs, InSet); 440 441 // Record the current value. 442 Res = Value.getConstant(); 443 444 return IsRelocatable && Value.isAbsolute(); 445 } 446 447 /// \brief Helper method for \see EvaluateSymbolAdd(). 448 static void AttemptToFoldSymbolOffsetDifference( 449 const MCAssembler *Asm, const MCAsmLayout *Layout, 450 const SectionAddrMap *Addrs, bool InSet, const MCSymbolRefExpr *&A, 451 const MCSymbolRefExpr *&B, int64_t &Addend) { 452 if (!A || !B) 453 return; 454 455 const MCSymbol &SA = A->getSymbol(); 456 const MCSymbol &SB = B->getSymbol(); 457 458 if (SA.isUndefined() || SB.isUndefined()) 459 return; 460 461 if (!Asm->getWriter().isSymbolRefDifferenceFullyResolved(*Asm, A, B, InSet)) 462 return; 463 464 if (SA.getFragment() == SB.getFragment() && !SA.isVariable() && 465 !SB.isVariable()) { 466 Addend += (SA.getOffset() - SB.getOffset()); 467 468 // Pointers to Thumb symbols need to have their low-bit set to allow 469 // for interworking. 470 if (Asm->isThumbFunc(&SA)) 471 Addend |= 1; 472 473 // Clear the symbol expr pointers to indicate we have folded these 474 // operands. 475 A = B = nullptr; 476 return; 477 } 478 479 if (!Layout) 480 return; 481 482 const MCSection &SecA = *SA.getFragment()->getParent(); 483 const MCSection &SecB = *SB.getFragment()->getParent(); 484 485 if ((&SecA != &SecB) && !Addrs) 486 return; 487 488 // Eagerly evaluate. 489 Addend += Layout->getSymbolOffset(A->getSymbol()) - 490 Layout->getSymbolOffset(B->getSymbol()); 491 if (Addrs && (&SecA != &SecB)) 492 Addend += (Addrs->lookup(&SecA) - Addrs->lookup(&SecB)); 493 494 // Pointers to Thumb symbols need to have their low-bit set to allow 495 // for interworking. 496 if (Asm->isThumbFunc(&SA)) 497 Addend |= 1; 498 499 // Clear the symbol expr pointers to indicate we have folded these 500 // operands. 501 A = B = nullptr; 502 } 503 504 /// \brief Evaluate the result of an add between (conceptually) two MCValues. 505 /// 506 /// This routine conceptually attempts to construct an MCValue: 507 /// Result = (Result_A - Result_B + Result_Cst) 508 /// from two MCValue's LHS and RHS where 509 /// Result = LHS + RHS 510 /// and 511 /// Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst). 512 /// 513 /// This routine attempts to aggresively fold the operands such that the result 514 /// is representable in an MCValue, but may not always succeed. 515 /// 516 /// \returns True on success, false if the result is not representable in an 517 /// MCValue. 518 519 /// NOTE: It is really important to have both the Asm and Layout arguments. 520 /// They might look redundant, but this function can be used before layout 521 /// is done (see the object streamer for example) and having the Asm argument 522 /// lets us avoid relaxations early. 523 static bool 524 EvaluateSymbolicAdd(const MCAssembler *Asm, const MCAsmLayout *Layout, 525 const SectionAddrMap *Addrs, bool InSet, const MCValue &LHS, 526 const MCSymbolRefExpr *RHS_A, const MCSymbolRefExpr *RHS_B, 527 int64_t RHS_Cst, MCValue &Res) { 528 // FIXME: This routine (and other evaluation parts) are *incredibly* sloppy 529 // about dealing with modifiers. This will ultimately bite us, one day. 530 const MCSymbolRefExpr *LHS_A = LHS.getSymA(); 531 const MCSymbolRefExpr *LHS_B = LHS.getSymB(); 532 int64_t LHS_Cst = LHS.getConstant(); 533 534 // Fold the result constant immediately. 535 int64_t Result_Cst = LHS_Cst + RHS_Cst; 536 537 assert((!Layout || Asm) && 538 "Must have an assembler object if layout is given!"); 539 540 // If we have a layout, we can fold resolved differences. 541 if (Asm) { 542 // First, fold out any differences which are fully resolved. By 543 // reassociating terms in 544 // Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst). 545 // we have the four possible differences: 546 // (LHS_A - LHS_B), 547 // (LHS_A - RHS_B), 548 // (RHS_A - LHS_B), 549 // (RHS_A - RHS_B). 550 // Since we are attempting to be as aggressive as possible about folding, we 551 // attempt to evaluate each possible alternative. 552 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, LHS_B, 553 Result_Cst); 554 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, RHS_B, 555 Result_Cst); 556 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, LHS_B, 557 Result_Cst); 558 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, RHS_B, 559 Result_Cst); 560 } 561 562 // We can't represent the addition or subtraction of two symbols. 563 if ((LHS_A && RHS_A) || (LHS_B && RHS_B)) 564 return false; 565 566 // At this point, we have at most one additive symbol and one subtractive 567 // symbol -- find them. 568 const MCSymbolRefExpr *A = LHS_A ? LHS_A : RHS_A; 569 const MCSymbolRefExpr *B = LHS_B ? LHS_B : RHS_B; 570 571 Res = MCValue::get(A, B, Result_Cst); 572 return true; 573 } 574 575 bool MCExpr::evaluateAsRelocatable(MCValue &Res, 576 const MCAsmLayout *Layout, 577 const MCFixup *Fixup) const { 578 MCAssembler *Assembler = Layout ? &Layout->getAssembler() : nullptr; 579 return evaluateAsRelocatableImpl(Res, Assembler, Layout, Fixup, nullptr, 580 false); 581 } 582 583 bool MCExpr::evaluateAsValue(MCValue &Res, const MCAsmLayout &Layout) const { 584 MCAssembler *Assembler = &Layout.getAssembler(); 585 return evaluateAsRelocatableImpl(Res, Assembler, &Layout, nullptr, nullptr, 586 true); 587 } 588 589 static bool canExpand(const MCSymbol &Sym, bool InSet) { 590 const MCExpr *Expr = Sym.getVariableValue(); 591 const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr); 592 if (Inner) { 593 if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF) 594 return false; 595 } 596 597 if (InSet) 598 return true; 599 return !Sym.isInSection(); 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, 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; 666 667 // The cast avoids undefined behavior if the constant is INT64_MIN. 668 Res = MCValue::get(Value.getSymB(), Value.getSymA(), 669 -(uint64_t)Value.getConstant()); 670 break; 671 case MCUnaryExpr::Not: 672 if (!Value.isAbsolute()) 673 return false; 674 Res = MCValue::get(~Value.getConstant()); 675 break; 676 case MCUnaryExpr::Plus: 677 Res = Value; 678 break; 679 } 680 681 return true; 682 } 683 684 case Binary: { 685 const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this); 686 MCValue LHSValue, RHSValue; 687 688 if (!ABE->getLHS()->evaluateAsRelocatableImpl(LHSValue, Asm, Layout, Fixup, 689 Addrs, InSet) || 690 !ABE->getRHS()->evaluateAsRelocatableImpl(RHSValue, Asm, Layout, Fixup, 691 Addrs, InSet)) 692 return false; 693 694 // We only support a few operations on non-constant expressions, handle 695 // those first. 696 if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) { 697 switch (ABE->getOpcode()) { 698 default: 699 return false; 700 case MCBinaryExpr::Sub: 701 // Negate RHS and add. 702 // The cast avoids undefined behavior if the constant is INT64_MIN. 703 return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue, 704 RHSValue.getSymB(), RHSValue.getSymA(), 705 -(uint64_t)RHSValue.getConstant(), Res); 706 707 case MCBinaryExpr::Add: 708 return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue, 709 RHSValue.getSymA(), RHSValue.getSymB(), 710 RHSValue.getConstant(), Res); 711 } 712 } 713 714 // FIXME: We need target hooks for the evaluation. It may be limited in 715 // width, and gas defines the result of comparisons differently from 716 // Apple as. 717 int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant(); 718 int64_t Result = 0; 719 switch (ABE->getOpcode()) { 720 case MCBinaryExpr::AShr: Result = LHS >> RHS; break; 721 case MCBinaryExpr::Add: Result = LHS + RHS; break; 722 case MCBinaryExpr::And: Result = LHS & RHS; break; 723 case MCBinaryExpr::Div: 724 // Handle division by zero. gas just emits a warning and keeps going, 725 // we try to be stricter. 726 // FIXME: Currently the caller of this function has no way to understand 727 // we're bailing out because of 'division by zero'. Therefore, it will 728 // emit a 'expected relocatable expression' error. It would be nice to 729 // change this code to emit a better diagnostic. 730 if (RHS == 0) 731 return false; 732 Result = LHS / RHS; 733 break; 734 case MCBinaryExpr::EQ: Result = LHS == RHS; break; 735 case MCBinaryExpr::GT: Result = LHS > RHS; break; 736 case MCBinaryExpr::GTE: Result = LHS >= RHS; break; 737 case MCBinaryExpr::LAnd: Result = LHS && RHS; break; 738 case MCBinaryExpr::LOr: Result = LHS || RHS; break; 739 case MCBinaryExpr::LShr: Result = uint64_t(LHS) >> uint64_t(RHS); break; 740 case MCBinaryExpr::LT: Result = LHS < RHS; break; 741 case MCBinaryExpr::LTE: Result = LHS <= RHS; break; 742 case MCBinaryExpr::Mod: Result = LHS % RHS; break; 743 case MCBinaryExpr::Mul: Result = LHS * RHS; break; 744 case MCBinaryExpr::NE: Result = LHS != RHS; break; 745 case MCBinaryExpr::Or: Result = LHS | RHS; break; 746 case MCBinaryExpr::Shl: Result = uint64_t(LHS) << uint64_t(RHS); break; 747 case MCBinaryExpr::Sub: Result = LHS - RHS; break; 748 case MCBinaryExpr::Xor: Result = LHS ^ RHS; break; 749 } 750 751 Res = MCValue::get(Result); 752 return true; 753 } 754 } 755 756 llvm_unreachable("Invalid assembly expression kind!"); 757 } 758 759 MCFragment *MCExpr::findAssociatedFragment() const { 760 switch (getKind()) { 761 case Target: 762 // We never look through target specific expressions. 763 return cast<MCTargetExpr>(this)->findAssociatedFragment(); 764 765 case Constant: 766 return MCSymbol::AbsolutePseudoFragment; 767 768 case SymbolRef: { 769 const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this); 770 const MCSymbol &Sym = SRE->getSymbol(); 771 return Sym.getFragment(); 772 } 773 774 case Unary: 775 return cast<MCUnaryExpr>(this)->getSubExpr()->findAssociatedFragment(); 776 777 case Binary: { 778 const MCBinaryExpr *BE = cast<MCBinaryExpr>(this); 779 MCFragment *LHS_F = BE->getLHS()->findAssociatedFragment(); 780 MCFragment *RHS_F = BE->getRHS()->findAssociatedFragment(); 781 782 // If either is absolute, return the other. 783 if (LHS_F == MCSymbol::AbsolutePseudoFragment) 784 return RHS_F; 785 if (RHS_F == MCSymbol::AbsolutePseudoFragment) 786 return LHS_F; 787 788 // Not always correct, but probably the best we can do without more context. 789 if (BE->getOpcode() == MCBinaryExpr::Sub) 790 return MCSymbol::AbsolutePseudoFragment; 791 792 // Otherwise, return the first non-null fragment. 793 return LHS_F ? LHS_F : RHS_F; 794 } 795 } 796 797 llvm_unreachable("Invalid assembly expression kind!"); 798 } 799
