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 LLVM_DUMP_METHOD void MCExpr::dump() const { 133 dbgs() << *this; 134 dbgs() << '\n'; 135 } 136 137 /* *** */ 138 139 const MCBinaryExpr *MCBinaryExpr::create(Opcode Opc, const MCExpr *LHS, 140 const MCExpr *RHS, MCContext &Ctx) { 141 return new (Ctx) MCBinaryExpr(Opc, LHS, RHS); 142 } 143 144 const MCUnaryExpr *MCUnaryExpr::create(Opcode Opc, const MCExpr *Expr, 145 MCContext &Ctx) { 146 return new (Ctx) MCUnaryExpr(Opc, Expr); 147 } 148 149 const MCConstantExpr *MCConstantExpr::create(int64_t Value, MCContext &Ctx) { 150 return new (Ctx) MCConstantExpr(Value); 151 } 152 153 /* *** */ 154 155 MCSymbolRefExpr::MCSymbolRefExpr(const MCSymbol *Symbol, VariantKind Kind, 156 const MCAsmInfo *MAI) 157 : MCExpr(MCExpr::SymbolRef), Kind(Kind), 158 UseParensForSymbolVariant(MAI->useParensForSymbolVariant()), 159 HasSubsectionsViaSymbols(MAI->hasSubsectionsViaSymbols()), 160 Symbol(Symbol) { 161 assert(Symbol); 162 } 163 164 const MCSymbolRefExpr *MCSymbolRefExpr::create(const MCSymbol *Sym, 165 VariantKind Kind, 166 MCContext &Ctx) { 167 return new (Ctx) MCSymbolRefExpr(Sym, Kind, Ctx.getAsmInfo()); 168 } 169 170 const MCSymbolRefExpr *MCSymbolRefExpr::create(StringRef Name, VariantKind Kind, 171 MCContext &Ctx) { 172 return create(Ctx.getOrCreateSymbol(Name), Kind, Ctx); 173 } 174 175 StringRef MCSymbolRefExpr::getVariantKindName(VariantKind Kind) { 176 switch (Kind) { 177 case VK_Invalid: return "<<invalid>>"; 178 case VK_None: return "<<none>>"; 179 180 case VK_DTPOFF: return "DTPOFF"; 181 case VK_DTPREL: return "DTPREL"; 182 case VK_GOT: return "GOT"; 183 case VK_GOTOFF: return "GOTOFF"; 184 case VK_GOTREL: return "GOTREL"; 185 case VK_GOTPCREL: return "GOTPCREL"; 186 case VK_GOTTPOFF: return "GOTTPOFF"; 187 case VK_INDNTPOFF: return "INDNTPOFF"; 188 case VK_NTPOFF: return "NTPOFF"; 189 case VK_GOTNTPOFF: return "GOTNTPOFF"; 190 case VK_PLT: return "PLT"; 191 case VK_TLSGD: return "TLSGD"; 192 case VK_TLSLD: return "TLSLD"; 193 case VK_TLSLDM: return "TLSLDM"; 194 case VK_TPOFF: return "TPOFF"; 195 case VK_TPREL: return "TPREL"; 196 case VK_TLSCALL: return "tlscall"; 197 case VK_TLSDESC: return "tlsdesc"; 198 case VK_TLVP: return "TLVP"; 199 case VK_TLVPPAGE: return "TLVPPAGE"; 200 case VK_TLVPPAGEOFF: return "TLVPPAGEOFF"; 201 case VK_PAGE: return "PAGE"; 202 case VK_PAGEOFF: return "PAGEOFF"; 203 case VK_GOTPAGE: return "GOTPAGE"; 204 case VK_GOTPAGEOFF: return "GOTPAGEOFF"; 205 case VK_SECREL: return "SECREL32"; 206 case VK_SIZE: return "SIZE"; 207 case VK_WEAKREF: return "WEAKREF"; 208 case VK_ARM_NONE: return "none"; 209 case VK_ARM_GOT_PREL: return "GOT_PREL"; 210 case VK_ARM_TARGET1: return "target1"; 211 case VK_ARM_TARGET2: return "target2"; 212 case VK_ARM_PREL31: return "prel31"; 213 case VK_ARM_SBREL: return "sbrel"; 214 case VK_ARM_TLSLDO: return "tlsldo"; 215 case VK_ARM_TLSDESCSEQ: return "tlsdescseq"; 216 case VK_PPC_LO: return "l"; 217 case VK_PPC_HI: return "h"; 218 case VK_PPC_HA: return "ha"; 219 case VK_PPC_HIGHER: return "higher"; 220 case VK_PPC_HIGHERA: return "highera"; 221 case VK_PPC_HIGHEST: return "highest"; 222 case VK_PPC_HIGHESTA: return "highesta"; 223 case VK_PPC_GOT_LO: return "got@l"; 224 case VK_PPC_GOT_HI: return "got@h"; 225 case VK_PPC_GOT_HA: return "got@ha"; 226 case VK_PPC_TOCBASE: return "tocbase"; 227 case VK_PPC_TOC: return "toc"; 228 case VK_PPC_TOC_LO: return "toc@l"; 229 case VK_PPC_TOC_HI: return "toc@h"; 230 case VK_PPC_TOC_HA: return "toc@ha"; 231 case VK_PPC_DTPMOD: return "dtpmod"; 232 case VK_PPC_TPREL_LO: return "tprel@l"; 233 case VK_PPC_TPREL_HI: return "tprel@h"; 234 case VK_PPC_TPREL_HA: return "tprel@ha"; 235 case VK_PPC_TPREL_HIGHER: return "tprel@higher"; 236 case VK_PPC_TPREL_HIGHERA: return "tprel@highera"; 237 case VK_PPC_TPREL_HIGHEST: return "tprel@highest"; 238 case VK_PPC_TPREL_HIGHESTA: return "tprel@highesta"; 239 case VK_PPC_DTPREL_LO: return "dtprel@l"; 240 case VK_PPC_DTPREL_HI: return "dtprel@h"; 241 case VK_PPC_DTPREL_HA: return "dtprel@ha"; 242 case VK_PPC_DTPREL_HIGHER: return "dtprel@higher"; 243 case VK_PPC_DTPREL_HIGHERA: return "dtprel@highera"; 244 case VK_PPC_DTPREL_HIGHEST: return "dtprel@highest"; 245 case VK_PPC_DTPREL_HIGHESTA: return "dtprel@highesta"; 246 case VK_PPC_GOT_TPREL: return "got@tprel"; 247 case VK_PPC_GOT_TPREL_LO: return "got@tprel@l"; 248 case VK_PPC_GOT_TPREL_HI: return "got@tprel@h"; 249 case VK_PPC_GOT_TPREL_HA: return "got@tprel@ha"; 250 case VK_PPC_GOT_DTPREL: return "got@dtprel"; 251 case VK_PPC_GOT_DTPREL_LO: return "got@dtprel@l"; 252 case VK_PPC_GOT_DTPREL_HI: return "got@dtprel@h"; 253 case VK_PPC_GOT_DTPREL_HA: return "got@dtprel@ha"; 254 case VK_PPC_TLS: return "tls"; 255 case VK_PPC_GOT_TLSGD: return "got@tlsgd"; 256 case VK_PPC_GOT_TLSGD_LO: return "got@tlsgd@l"; 257 case VK_PPC_GOT_TLSGD_HI: return "got@tlsgd@h"; 258 case VK_PPC_GOT_TLSGD_HA: return "got@tlsgd@ha"; 259 case VK_PPC_TLSGD: return "tlsgd"; 260 case VK_PPC_GOT_TLSLD: return "got@tlsld"; 261 case VK_PPC_GOT_TLSLD_LO: return "got@tlsld@l"; 262 case VK_PPC_GOT_TLSLD_HI: return "got@tlsld@h"; 263 case VK_PPC_GOT_TLSLD_HA: return "got@tlsld@ha"; 264 case VK_PPC_TLSLD: return "tlsld"; 265 case VK_PPC_LOCAL: return "local"; 266 case VK_COFF_IMGREL32: return "IMGREL"; 267 case VK_Hexagon_PCREL: return "PCREL"; 268 case VK_Hexagon_LO16: return "LO16"; 269 case VK_Hexagon_HI16: return "HI16"; 270 case VK_Hexagon_GPREL: return "GPREL"; 271 case VK_Hexagon_GD_GOT: return "GDGOT"; 272 case VK_Hexagon_LD_GOT: return "LDGOT"; 273 case VK_Hexagon_GD_PLT: return "GDPLT"; 274 case VK_Hexagon_LD_PLT: return "LDPLT"; 275 case VK_Hexagon_IE: return "IE"; 276 case VK_Hexagon_IE_GOT: return "IEGOT"; 277 case VK_WebAssembly_FUNCTION: return "FUNCTION"; 278 case VK_AMDGPU_GOTPCREL32_LO: return "gotpcrel32@lo"; 279 case VK_AMDGPU_GOTPCREL32_HI: return "gotpcrel32@hi"; 280 case VK_AMDGPU_REL32_LO: return "rel32@lo"; 281 case VK_AMDGPU_REL32_HI: return "rel32@hi"; 282 } 283 llvm_unreachable("Invalid variant kind"); 284 } 285 286 MCSymbolRefExpr::VariantKind 287 MCSymbolRefExpr::getVariantKindForName(StringRef Name) { 288 return StringSwitch<VariantKind>(Name.lower()) 289 .Case("dtprel", VK_DTPREL) 290 .Case("dtpoff", VK_DTPOFF) 291 .Case("got", VK_GOT) 292 .Case("gotoff", VK_GOTOFF) 293 .Case("gotrel", VK_GOTREL) 294 .Case("gotpcrel", VK_GOTPCREL) 295 .Case("gottpoff", VK_GOTTPOFF) 296 .Case("indntpoff", VK_INDNTPOFF) 297 .Case("ntpoff", VK_NTPOFF) 298 .Case("gotntpoff", VK_GOTNTPOFF) 299 .Case("plt", VK_PLT) 300 .Case("tlscall", VK_TLSCALL) 301 .Case("tlsdesc", VK_TLSDESC) 302 .Case("tlsgd", VK_TLSGD) 303 .Case("tlsld", VK_TLSLD) 304 .Case("tlsldm", VK_TLSLDM) 305 .Case("tpoff", VK_TPOFF) 306 .Case("tprel", VK_TPREL) 307 .Case("tlvp", VK_TLVP) 308 .Case("tlvppage", VK_TLVPPAGE) 309 .Case("tlvppageoff", VK_TLVPPAGEOFF) 310 .Case("page", VK_PAGE) 311 .Case("pageoff", VK_PAGEOFF) 312 .Case("gotpage", VK_GOTPAGE) 313 .Case("gotpageoff", VK_GOTPAGEOFF) 314 .Case("imgrel", VK_COFF_IMGREL32) 315 .Case("secrel32", VK_SECREL) 316 .Case("size", VK_SIZE) 317 .Case("l", VK_PPC_LO) 318 .Case("h", VK_PPC_HI) 319 .Case("ha", VK_PPC_HA) 320 .Case("higher", VK_PPC_HIGHER) 321 .Case("highera", VK_PPC_HIGHERA) 322 .Case("highest", VK_PPC_HIGHEST) 323 .Case("highesta", VK_PPC_HIGHESTA) 324 .Case("got@l", VK_PPC_GOT_LO) 325 .Case("got@h", VK_PPC_GOT_HI) 326 .Case("got@ha", VK_PPC_GOT_HA) 327 .Case("local", VK_PPC_LOCAL) 328 .Case("tocbase", VK_PPC_TOCBASE) 329 .Case("toc", VK_PPC_TOC) 330 .Case("toc@l", VK_PPC_TOC_LO) 331 .Case("toc@h", VK_PPC_TOC_HI) 332 .Case("toc@ha", VK_PPC_TOC_HA) 333 .Case("tls", VK_PPC_TLS) 334 .Case("dtpmod", VK_PPC_DTPMOD) 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@l", VK_PPC_DTPREL_LO) 343 .Case("dtprel@h", VK_PPC_DTPREL_HI) 344 .Case("dtprel@ha", VK_PPC_DTPREL_HA) 345 .Case("dtprel@higher", VK_PPC_DTPREL_HIGHER) 346 .Case("dtprel@highera", VK_PPC_DTPREL_HIGHERA) 347 .Case("dtprel@highest", VK_PPC_DTPREL_HIGHEST) 348 .Case("dtprel@highesta", VK_PPC_DTPREL_HIGHESTA) 349 .Case("got@tprel", VK_PPC_GOT_TPREL) 350 .Case("got@tprel@l", VK_PPC_GOT_TPREL_LO) 351 .Case("got@tprel@h", VK_PPC_GOT_TPREL_HI) 352 .Case("got@tprel@ha", VK_PPC_GOT_TPREL_HA) 353 .Case("got@dtprel", VK_PPC_GOT_DTPREL) 354 .Case("got@dtprel@l", VK_PPC_GOT_DTPREL_LO) 355 .Case("got@dtprel@h", VK_PPC_GOT_DTPREL_HI) 356 .Case("got@dtprel@ha", VK_PPC_GOT_DTPREL_HA) 357 .Case("got@tlsgd", VK_PPC_GOT_TLSGD) 358 .Case("got@tlsgd@l", VK_PPC_GOT_TLSGD_LO) 359 .Case("got@tlsgd@h", VK_PPC_GOT_TLSGD_HI) 360 .Case("got@tlsgd@ha", VK_PPC_GOT_TLSGD_HA) 361 .Case("got@tlsld", VK_PPC_GOT_TLSLD) 362 .Case("got@tlsld@l", VK_PPC_GOT_TLSLD_LO) 363 .Case("got@tlsld@h", VK_PPC_GOT_TLSLD_HI) 364 .Case("got@tlsld@ha", VK_PPC_GOT_TLSLD_HA) 365 .Case("gdgot", VK_Hexagon_GD_GOT) 366 .Case("gdplt", VK_Hexagon_GD_PLT) 367 .Case("iegot", VK_Hexagon_IE_GOT) 368 .Case("ie", VK_Hexagon_IE) 369 .Case("ldgot", VK_Hexagon_LD_GOT) 370 .Case("ldplt", VK_Hexagon_LD_PLT) 371 .Case("pcrel", VK_Hexagon_PCREL) 372 .Case("none", VK_ARM_NONE) 373 .Case("got_prel", VK_ARM_GOT_PREL) 374 .Case("target1", VK_ARM_TARGET1) 375 .Case("target2", VK_ARM_TARGET2) 376 .Case("prel31", VK_ARM_PREL31) 377 .Case("sbrel", VK_ARM_SBREL) 378 .Case("tlsldo", VK_ARM_TLSLDO) 379 .Case("gotpcrel32@lo", VK_AMDGPU_GOTPCREL32_LO) 380 .Case("gotpcrel32@hi", VK_AMDGPU_GOTPCREL32_HI) 381 .Case("rel32@lo", VK_AMDGPU_REL32_LO) 382 .Case("rel32@hi", VK_AMDGPU_REL32_HI) 383 .Default(VK_Invalid); 384 } 385 386 void MCSymbolRefExpr::printVariantKind(raw_ostream &OS) const { 387 if (UseParensForSymbolVariant) 388 OS << '(' << MCSymbolRefExpr::getVariantKindName(getKind()) << ')'; 389 else 390 OS << '@' << MCSymbolRefExpr::getVariantKindName(getKind()); 391 } 392 393 /* *** */ 394 395 void MCTargetExpr::anchor() {} 396 397 /* *** */ 398 399 bool MCExpr::evaluateAsAbsolute(int64_t &Res) const { 400 return evaluateAsAbsolute(Res, nullptr, nullptr, nullptr); 401 } 402 403 bool MCExpr::evaluateAsAbsolute(int64_t &Res, 404 const MCAsmLayout &Layout) const { 405 return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr); 406 } 407 408 bool MCExpr::evaluateAsAbsolute(int64_t &Res, 409 const MCAsmLayout &Layout, 410 const SectionAddrMap &Addrs) const { 411 return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, &Addrs); 412 } 413 414 bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const { 415 return evaluateAsAbsolute(Res, &Asm, nullptr, nullptr); 416 } 417 418 bool MCExpr::evaluateKnownAbsolute(int64_t &Res, 419 const MCAsmLayout &Layout) const { 420 return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr, 421 true); 422 } 423 424 bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm, 425 const MCAsmLayout *Layout, 426 const SectionAddrMap *Addrs) const { 427 // FIXME: The use if InSet = Addrs is a hack. Setting InSet causes us 428 // absolutize differences across sections and that is what the MachO writer 429 // uses Addrs for. 430 return evaluateAsAbsolute(Res, Asm, Layout, Addrs, Addrs); 431 } 432 433 bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm, 434 const MCAsmLayout *Layout, 435 const SectionAddrMap *Addrs, bool InSet) const { 436 MCValue Value; 437 438 // Fast path constants. 439 if (const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(this)) { 440 Res = CE->getValue(); 441 return true; 442 } 443 444 bool IsRelocatable = 445 evaluateAsRelocatableImpl(Value, Asm, Layout, nullptr, Addrs, InSet); 446 447 // Record the current value. 448 Res = Value.getConstant(); 449 450 return IsRelocatable && Value.isAbsolute(); 451 } 452 453 /// \brief Helper method for \see EvaluateSymbolAdd(). 454 static void AttemptToFoldSymbolOffsetDifference( 455 const MCAssembler *Asm, const MCAsmLayout *Layout, 456 const SectionAddrMap *Addrs, bool InSet, const MCSymbolRefExpr *&A, 457 const MCSymbolRefExpr *&B, int64_t &Addend) { 458 if (!A || !B) 459 return; 460 461 const MCSymbol &SA = A->getSymbol(); 462 const MCSymbol &SB = B->getSymbol(); 463 464 if (SA.isUndefined() || SB.isUndefined()) 465 return; 466 467 if (!Asm->getWriter().isSymbolRefDifferenceFullyResolved(*Asm, A, B, InSet)) 468 return; 469 470 if (SA.getFragment() == SB.getFragment() && !SA.isVariable() && 471 !SB.isVariable()) { 472 Addend += (SA.getOffset() - SB.getOffset()); 473 474 // Pointers to Thumb symbols need to have their low-bit set to allow 475 // for interworking. 476 if (Asm->isThumbFunc(&SA)) 477 Addend |= 1; 478 479 // Clear the symbol expr pointers to indicate we have folded these 480 // operands. 481 A = B = nullptr; 482 return; 483 } 484 485 if (!Layout) 486 return; 487 488 const MCSection &SecA = *SA.getFragment()->getParent(); 489 const MCSection &SecB = *SB.getFragment()->getParent(); 490 491 if ((&SecA != &SecB) && !Addrs) 492 return; 493 494 // Eagerly evaluate. 495 Addend += Layout->getSymbolOffset(A->getSymbol()) - 496 Layout->getSymbolOffset(B->getSymbol()); 497 if (Addrs && (&SecA != &SecB)) 498 Addend += (Addrs->lookup(&SecA) - Addrs->lookup(&SecB)); 499 500 // Pointers to Thumb symbols need to have their low-bit set to allow 501 // for interworking. 502 if (Asm->isThumbFunc(&SA)) 503 Addend |= 1; 504 505 // Clear the symbol expr pointers to indicate we have folded these 506 // operands. 507 A = B = nullptr; 508 } 509 510 /// \brief Evaluate the result of an add between (conceptually) two MCValues. 511 /// 512 /// This routine conceptually attempts to construct an MCValue: 513 /// Result = (Result_A - Result_B + Result_Cst) 514 /// from two MCValue's LHS and RHS where 515 /// Result = LHS + RHS 516 /// and 517 /// Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst). 518 /// 519 /// This routine attempts to aggresively fold the operands such that the result 520 /// is representable in an MCValue, but may not always succeed. 521 /// 522 /// \returns True on success, false if the result is not representable in an 523 /// MCValue. 524 525 /// NOTE: It is really important to have both the Asm and Layout arguments. 526 /// They might look redundant, but this function can be used before layout 527 /// is done (see the object streamer for example) and having the Asm argument 528 /// lets us avoid relaxations early. 529 static bool 530 EvaluateSymbolicAdd(const MCAssembler *Asm, const MCAsmLayout *Layout, 531 const SectionAddrMap *Addrs, bool InSet, const MCValue &LHS, 532 const MCSymbolRefExpr *RHS_A, const MCSymbolRefExpr *RHS_B, 533 int64_t RHS_Cst, MCValue &Res) { 534 // FIXME: This routine (and other evaluation parts) are *incredibly* sloppy 535 // about dealing with modifiers. This will ultimately bite us, one day. 536 const MCSymbolRefExpr *LHS_A = LHS.getSymA(); 537 const MCSymbolRefExpr *LHS_B = LHS.getSymB(); 538 int64_t LHS_Cst = LHS.getConstant(); 539 540 // Fold the result constant immediately. 541 int64_t Result_Cst = LHS_Cst + RHS_Cst; 542 543 assert((!Layout || Asm) && 544 "Must have an assembler object if layout is given!"); 545 546 // If we have a layout, we can fold resolved differences. 547 if (Asm) { 548 // First, fold out any differences which are fully resolved. By 549 // reassociating terms in 550 // Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst). 551 // we have the four possible differences: 552 // (LHS_A - LHS_B), 553 // (LHS_A - RHS_B), 554 // (RHS_A - LHS_B), 555 // (RHS_A - RHS_B). 556 // Since we are attempting to be as aggressive as possible about folding, we 557 // attempt to evaluate each possible alternative. 558 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, LHS_B, 559 Result_Cst); 560 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, RHS_B, 561 Result_Cst); 562 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, LHS_B, 563 Result_Cst); 564 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, RHS_B, 565 Result_Cst); 566 } 567 568 // We can't represent the addition or subtraction of two symbols. 569 if ((LHS_A && RHS_A) || (LHS_B && RHS_B)) 570 return false; 571 572 // At this point, we have at most one additive symbol and one subtractive 573 // symbol -- find them. 574 const MCSymbolRefExpr *A = LHS_A ? LHS_A : RHS_A; 575 const MCSymbolRefExpr *B = LHS_B ? LHS_B : RHS_B; 576 577 Res = MCValue::get(A, B, Result_Cst); 578 return true; 579 } 580 581 bool MCExpr::evaluateAsRelocatable(MCValue &Res, 582 const MCAsmLayout *Layout, 583 const MCFixup *Fixup) const { 584 MCAssembler *Assembler = Layout ? &Layout->getAssembler() : nullptr; 585 return evaluateAsRelocatableImpl(Res, Assembler, Layout, Fixup, nullptr, 586 false); 587 } 588 589 bool MCExpr::evaluateAsValue(MCValue &Res, const MCAsmLayout &Layout) const { 590 MCAssembler *Assembler = &Layout.getAssembler(); 591 return evaluateAsRelocatableImpl(Res, Assembler, &Layout, nullptr, nullptr, 592 true); 593 } 594 595 static bool canExpand(const MCSymbol &Sym, bool InSet) { 596 const MCExpr *Expr = Sym.getVariableValue(); 597 const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr); 598 if (Inner) { 599 if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF) 600 return false; 601 } 602 603 if (InSet) 604 return true; 605 return !Sym.isInSection(); 606 } 607 608 bool MCExpr::evaluateAsRelocatableImpl(MCValue &Res, const MCAssembler *Asm, 609 const MCAsmLayout *Layout, 610 const MCFixup *Fixup, 611 const SectionAddrMap *Addrs, 612 bool InSet) const { 613 ++stats::MCExprEvaluate; 614 615 switch (getKind()) { 616 case Target: 617 return cast<MCTargetExpr>(this)->evaluateAsRelocatableImpl(Res, Layout, 618 Fixup); 619 620 case Constant: 621 Res = MCValue::get(cast<MCConstantExpr>(this)->getValue()); 622 return true; 623 624 case SymbolRef: { 625 const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this); 626 const MCSymbol &Sym = SRE->getSymbol(); 627 628 // Evaluate recursively if this is a variable. 629 if (Sym.isVariable() && SRE->getKind() == MCSymbolRefExpr::VK_None && 630 canExpand(Sym, InSet)) { 631 bool IsMachO = SRE->hasSubsectionsViaSymbols(); 632 if (Sym.getVariableValue()->evaluateAsRelocatableImpl( 633 Res, Asm, Layout, Fixup, Addrs, InSet || IsMachO)) { 634 if (!IsMachO) 635 return true; 636 637 const MCSymbolRefExpr *A = Res.getSymA(); 638 const MCSymbolRefExpr *B = Res.getSymB(); 639 // FIXME: This is small hack. Given 640 // a = b + 4 641 // .long a 642 // the OS X assembler will completely drop the 4. We should probably 643 // include it in the relocation or produce an error if that is not 644 // possible. 645 if (!A && !B) 646 return true; 647 } 648 } 649 650 Res = MCValue::get(SRE, nullptr, 0); 651 return true; 652 } 653 654 case Unary: { 655 const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this); 656 MCValue Value; 657 658 if (!AUE->getSubExpr()->evaluateAsRelocatableImpl(Value, Asm, Layout, Fixup, 659 Addrs, InSet)) 660 return false; 661 662 switch (AUE->getOpcode()) { 663 case MCUnaryExpr::LNot: 664 if (!Value.isAbsolute()) 665 return false; 666 Res = MCValue::get(!Value.getConstant()); 667 break; 668 case MCUnaryExpr::Minus: 669 /// -(a - b + const) ==> (b - a - const) 670 if (Value.getSymA() && !Value.getSymB()) 671 return false; 672 673 // The cast avoids undefined behavior if the constant is INT64_MIN. 674 Res = MCValue::get(Value.getSymB(), Value.getSymA(), 675 -(uint64_t)Value.getConstant()); 676 break; 677 case MCUnaryExpr::Not: 678 if (!Value.isAbsolute()) 679 return false; 680 Res = MCValue::get(~Value.getConstant()); 681 break; 682 case MCUnaryExpr::Plus: 683 Res = Value; 684 break; 685 } 686 687 return true; 688 } 689 690 case Binary: { 691 const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this); 692 MCValue LHSValue, RHSValue; 693 694 if (!ABE->getLHS()->evaluateAsRelocatableImpl(LHSValue, Asm, Layout, Fixup, 695 Addrs, InSet) || 696 !ABE->getRHS()->evaluateAsRelocatableImpl(RHSValue, Asm, Layout, Fixup, 697 Addrs, InSet)) 698 return false; 699 700 // We only support a few operations on non-constant expressions, handle 701 // those first. 702 if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) { 703 switch (ABE->getOpcode()) { 704 default: 705 return false; 706 case MCBinaryExpr::Sub: 707 // Negate RHS and add. 708 // The cast avoids undefined behavior if the constant is INT64_MIN. 709 return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue, 710 RHSValue.getSymB(), RHSValue.getSymA(), 711 -(uint64_t)RHSValue.getConstant(), Res); 712 713 case MCBinaryExpr::Add: 714 return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue, 715 RHSValue.getSymA(), RHSValue.getSymB(), 716 RHSValue.getConstant(), Res); 717 } 718 } 719 720 // FIXME: We need target hooks for the evaluation. It may be limited in 721 // width, and gas defines the result of comparisons differently from 722 // Apple as. 723 int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant(); 724 int64_t Result = 0; 725 switch (ABE->getOpcode()) { 726 case MCBinaryExpr::AShr: Result = LHS >> RHS; break; 727 case MCBinaryExpr::Add: Result = LHS + RHS; break; 728 case MCBinaryExpr::And: Result = LHS & RHS; break; 729 case MCBinaryExpr::Div: 730 // Handle division by zero. gas just emits a warning and keeps going, 731 // we try to be stricter. 732 // FIXME: Currently the caller of this function has no way to understand 733 // we're bailing out because of 'division by zero'. Therefore, it will 734 // emit a 'expected relocatable expression' error. It would be nice to 735 // change this code to emit a better diagnostic. 736 if (RHS == 0) 737 return false; 738 Result = LHS / RHS; 739 break; 740 case MCBinaryExpr::EQ: Result = LHS == RHS; break; 741 case MCBinaryExpr::GT: Result = LHS > RHS; break; 742 case MCBinaryExpr::GTE: Result = LHS >= RHS; break; 743 case MCBinaryExpr::LAnd: Result = LHS && RHS; break; 744 case MCBinaryExpr::LOr: Result = LHS || RHS; break; 745 case MCBinaryExpr::LShr: Result = uint64_t(LHS) >> uint64_t(RHS); break; 746 case MCBinaryExpr::LT: Result = LHS < RHS; break; 747 case MCBinaryExpr::LTE: Result = LHS <= RHS; break; 748 case MCBinaryExpr::Mod: Result = LHS % RHS; break; 749 case MCBinaryExpr::Mul: Result = LHS * RHS; break; 750 case MCBinaryExpr::NE: Result = LHS != RHS; break; 751 case MCBinaryExpr::Or: Result = LHS | RHS; break; 752 case MCBinaryExpr::Shl: Result = uint64_t(LHS) << uint64_t(RHS); break; 753 case MCBinaryExpr::Sub: Result = LHS - RHS; break; 754 case MCBinaryExpr::Xor: Result = LHS ^ RHS; break; 755 } 756 757 Res = MCValue::get(Result); 758 return true; 759 } 760 } 761 762 llvm_unreachable("Invalid assembly expression kind!"); 763 } 764 765 MCFragment *MCExpr::findAssociatedFragment() const { 766 switch (getKind()) { 767 case Target: 768 // We never look through target specific expressions. 769 return cast<MCTargetExpr>(this)->findAssociatedFragment(); 770 771 case Constant: 772 return MCSymbol::AbsolutePseudoFragment; 773 774 case SymbolRef: { 775 const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this); 776 const MCSymbol &Sym = SRE->getSymbol(); 777 return Sym.getFragment(); 778 } 779 780 case Unary: 781 return cast<MCUnaryExpr>(this)->getSubExpr()->findAssociatedFragment(); 782 783 case Binary: { 784 const MCBinaryExpr *BE = cast<MCBinaryExpr>(this); 785 MCFragment *LHS_F = BE->getLHS()->findAssociatedFragment(); 786 MCFragment *RHS_F = BE->getRHS()->findAssociatedFragment(); 787 788 // If either is absolute, return the other. 789 if (LHS_F == MCSymbol::AbsolutePseudoFragment) 790 return RHS_F; 791 if (RHS_F == MCSymbol::AbsolutePseudoFragment) 792 return LHS_F; 793 794 // Not always correct, but probably the best we can do without more context. 795 if (BE->getOpcode() == MCBinaryExpr::Sub) 796 return MCSymbol::AbsolutePseudoFragment; 797 798 // Otherwise, return the first non-null fragment. 799 return LHS_F ? LHS_F : RHS_F; 800 } 801 } 802 803 llvm_unreachable("Invalid assembly expression kind!"); 804 } 805