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_WEAKREF: return "WEAKREF"; 196 case VK_ARM_NONE: return "none"; 197 case VK_ARM_TARGET1: return "target1"; 198 case VK_ARM_TARGET2: return "target2"; 199 case VK_ARM_PREL31: return "prel31"; 200 case VK_ARM_SBREL: return "sbrel"; 201 case VK_ARM_TLSLDO: return "tlsldo"; 202 case VK_ARM_TLSCALL: return "tlscall"; 203 case VK_ARM_TLSDESC: return "tlsdesc"; 204 case VK_ARM_TLSDESCSEQ: return "tlsdescseq"; 205 case VK_PPC_LO: return "l"; 206 case VK_PPC_HI: return "h"; 207 case VK_PPC_HA: return "ha"; 208 case VK_PPC_HIGHER: return "higher"; 209 case VK_PPC_HIGHERA: return "highera"; 210 case VK_PPC_HIGHEST: return "highest"; 211 case VK_PPC_HIGHESTA: return "highesta"; 212 case VK_PPC_GOT_LO: return "got@l"; 213 case VK_PPC_GOT_HI: return "got@h"; 214 case VK_PPC_GOT_HA: return "got@ha"; 215 case VK_PPC_TOCBASE: return "tocbase"; 216 case VK_PPC_TOC: return "toc"; 217 case VK_PPC_TOC_LO: return "toc@l"; 218 case VK_PPC_TOC_HI: return "toc@h"; 219 case VK_PPC_TOC_HA: return "toc@ha"; 220 case VK_PPC_DTPMOD: return "dtpmod"; 221 case VK_PPC_TPREL: return "tprel"; 222 case VK_PPC_TPREL_LO: return "tprel@l"; 223 case VK_PPC_TPREL_HI: return "tprel@h"; 224 case VK_PPC_TPREL_HA: return "tprel@ha"; 225 case VK_PPC_TPREL_HIGHER: return "tprel@higher"; 226 case VK_PPC_TPREL_HIGHERA: return "tprel@highera"; 227 case VK_PPC_TPREL_HIGHEST: return "tprel@highest"; 228 case VK_PPC_TPREL_HIGHESTA: return "tprel@highesta"; 229 case VK_PPC_DTPREL: return "dtprel"; 230 case VK_PPC_DTPREL_LO: return "dtprel@l"; 231 case VK_PPC_DTPREL_HI: return "dtprel@h"; 232 case VK_PPC_DTPREL_HA: return "dtprel@ha"; 233 case VK_PPC_DTPREL_HIGHER: return "dtprel@higher"; 234 case VK_PPC_DTPREL_HIGHERA: return "dtprel@highera"; 235 case VK_PPC_DTPREL_HIGHEST: return "dtprel@highest"; 236 case VK_PPC_DTPREL_HIGHESTA: return "dtprel@highesta"; 237 case VK_PPC_GOT_TPREL: return "got@tprel"; 238 case VK_PPC_GOT_TPREL_LO: return "got@tprel@l"; 239 case VK_PPC_GOT_TPREL_HI: return "got@tprel@h"; 240 case VK_PPC_GOT_TPREL_HA: return "got@tprel@ha"; 241 case VK_PPC_GOT_DTPREL: return "got@dtprel"; 242 case VK_PPC_GOT_DTPREL_LO: return "got@dtprel@l"; 243 case VK_PPC_GOT_DTPREL_HI: return "got@dtprel@h"; 244 case VK_PPC_GOT_DTPREL_HA: return "got@dtprel@ha"; 245 case VK_PPC_TLS: return "tls"; 246 case VK_PPC_GOT_TLSGD: return "got@tlsgd"; 247 case VK_PPC_GOT_TLSGD_LO: return "got@tlsgd@l"; 248 case VK_PPC_GOT_TLSGD_HI: return "got@tlsgd@h"; 249 case VK_PPC_GOT_TLSGD_HA: return "got@tlsgd@ha"; 250 case VK_PPC_TLSGD: return "tlsgd"; 251 case VK_PPC_GOT_TLSLD: return "got@tlsld"; 252 case VK_PPC_GOT_TLSLD_LO: return "got@tlsld@l"; 253 case VK_PPC_GOT_TLSLD_HI: return "got@tlsld@h"; 254 case VK_PPC_GOT_TLSLD_HA: return "got@tlsld@ha"; 255 case VK_PPC_TLSLD: return "tlsld"; 256 case VK_PPC_LOCAL: return "local"; 257 case VK_Mips_GPREL: return "GPREL"; 258 case VK_Mips_GOT_CALL: return "GOT_CALL"; 259 case VK_Mips_GOT16: return "GOT16"; 260 case VK_Mips_GOT: return "GOT"; 261 case VK_Mips_ABS_HI: return "ABS_HI"; 262 case VK_Mips_ABS_LO: return "ABS_LO"; 263 case VK_Mips_TLSGD: return "TLSGD"; 264 case VK_Mips_TLSLDM: return "TLSLDM"; 265 case VK_Mips_DTPREL_HI: return "DTPREL_HI"; 266 case VK_Mips_DTPREL_LO: return "DTPREL_LO"; 267 case VK_Mips_GOTTPREL: return "GOTTPREL"; 268 case VK_Mips_TPREL_HI: return "TPREL_HI"; 269 case VK_Mips_TPREL_LO: return "TPREL_LO"; 270 case VK_Mips_GPOFF_HI: return "GPOFF_HI"; 271 case VK_Mips_GPOFF_LO: return "GPOFF_LO"; 272 case VK_Mips_GOT_DISP: return "GOT_DISP"; 273 case VK_Mips_GOT_PAGE: return "GOT_PAGE"; 274 case VK_Mips_GOT_OFST: return "GOT_OFST"; 275 case VK_Mips_HIGHER: return "HIGHER"; 276 case VK_Mips_HIGHEST: return "HIGHEST"; 277 case VK_Mips_GOT_HI16: return "GOT_HI16"; 278 case VK_Mips_GOT_LO16: return "GOT_LO16"; 279 case VK_Mips_CALL_HI16: return "CALL_HI16"; 280 case VK_Mips_CALL_LO16: return "CALL_LO16"; 281 case VK_Mips_PCREL_HI16: return "PCREL_HI16"; 282 case VK_Mips_PCREL_LO16: return "PCREL_LO16"; 283 case VK_COFF_IMGREL32: return "IMGREL"; 284 } 285 llvm_unreachable("Invalid variant kind"); 286 } 287 288 MCSymbolRefExpr::VariantKind 289 MCSymbolRefExpr::getVariantKindForName(StringRef Name) { 290 return StringSwitch<VariantKind>(Name.lower()) 291 .Case("got", VK_GOT) 292 .Case("gotoff", VK_GOTOFF) 293 .Case("gotpcrel", VK_GOTPCREL) 294 .Case("got_prel", 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("tlsgd", VK_TLSGD) 301 .Case("tlsld", VK_TLSLD) 302 .Case("tlsldm", VK_TLSLDM) 303 .Case("tpoff", VK_TPOFF) 304 .Case("dtpoff", VK_DTPOFF) 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("l", VK_PPC_LO) 315 .Case("h", VK_PPC_HI) 316 .Case("ha", VK_PPC_HA) 317 .Case("higher", VK_PPC_HIGHER) 318 .Case("highera", VK_PPC_HIGHERA) 319 .Case("highest", VK_PPC_HIGHEST) 320 .Case("highesta", VK_PPC_HIGHESTA) 321 .Case("got@l", VK_PPC_GOT_LO) 322 .Case("got@h", VK_PPC_GOT_HI) 323 .Case("got@ha", VK_PPC_GOT_HA) 324 .Case("local", VK_PPC_LOCAL) 325 .Case("tocbase", VK_PPC_TOCBASE) 326 .Case("toc", VK_PPC_TOC) 327 .Case("toc@l", VK_PPC_TOC_LO) 328 .Case("toc@h", VK_PPC_TOC_HI) 329 .Case("toc@ha", VK_PPC_TOC_HA) 330 .Case("tls", VK_PPC_TLS) 331 .Case("dtpmod", VK_PPC_DTPMOD) 332 .Case("tprel", VK_PPC_TPREL) 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", VK_PPC_DTPREL) 341 .Case("dtprel@l", VK_PPC_DTPREL_LO) 342 .Case("dtprel@h", VK_PPC_DTPREL_HI) 343 .Case("dtprel@ha", VK_PPC_DTPREL_HA) 344 .Case("dtprel@higher", VK_PPC_DTPREL_HIGHER) 345 .Case("dtprel@highera", VK_PPC_DTPREL_HIGHERA) 346 .Case("dtprel@highest", VK_PPC_DTPREL_HIGHEST) 347 .Case("dtprel@highesta", VK_PPC_DTPREL_HIGHESTA) 348 .Case("got@tprel", VK_PPC_GOT_TPREL) 349 .Case("got@tprel@l", VK_PPC_GOT_TPREL_LO) 350 .Case("got@tprel@h", VK_PPC_GOT_TPREL_HI) 351 .Case("got@tprel@ha", VK_PPC_GOT_TPREL_HA) 352 .Case("got@dtprel", VK_PPC_GOT_DTPREL) 353 .Case("got@dtprel@l", VK_PPC_GOT_DTPREL_LO) 354 .Case("got@dtprel@h", VK_PPC_GOT_DTPREL_HI) 355 .Case("got@dtprel@ha", VK_PPC_GOT_DTPREL_HA) 356 .Case("got@tlsgd", VK_PPC_GOT_TLSGD) 357 .Case("got@tlsgd@l", VK_PPC_GOT_TLSGD_LO) 358 .Case("got@tlsgd@h", VK_PPC_GOT_TLSGD_HI) 359 .Case("got@tlsgd@ha", VK_PPC_GOT_TLSGD_HA) 360 .Case("got@tlsld", VK_PPC_GOT_TLSLD) 361 .Case("got@tlsld@l", VK_PPC_GOT_TLSLD_LO) 362 .Case("got@tlsld@h", VK_PPC_GOT_TLSLD_HI) 363 .Case("got@tlsld@ha", VK_PPC_GOT_TLSLD_HA) 364 .Case("none", VK_ARM_NONE) 365 .Case("target1", VK_ARM_TARGET1) 366 .Case("target2", VK_ARM_TARGET2) 367 .Case("prel31", VK_ARM_PREL31) 368 .Case("sbrel", VK_ARM_SBREL) 369 .Case("tlsldo", VK_ARM_TLSLDO) 370 .Case("tlscall", VK_ARM_TLSCALL) 371 .Case("tlsdesc", VK_ARM_TLSDESC) 372 .Default(VK_Invalid); 373 } 374 375 void MCSymbolRefExpr::printVariantKind(raw_ostream &OS) const { 376 if (UseParensForSymbolVariant) 377 OS << '(' << MCSymbolRefExpr::getVariantKindName(getKind()) << ')'; 378 else 379 OS << '@' << MCSymbolRefExpr::getVariantKindName(getKind()); 380 } 381 382 /* *** */ 383 384 void MCTargetExpr::anchor() {} 385 386 /* *** */ 387 388 bool MCExpr::EvaluateAsAbsolute(int64_t &Res) const { 389 return EvaluateAsAbsolute(Res, nullptr, nullptr, nullptr); 390 } 391 392 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, 393 const MCAsmLayout &Layout) const { 394 return EvaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr); 395 } 396 397 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, 398 const MCAsmLayout &Layout, 399 const SectionAddrMap &Addrs) const { 400 return EvaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, &Addrs); 401 } 402 403 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const { 404 return EvaluateAsAbsolute(Res, &Asm, nullptr, nullptr); 405 } 406 407 int64_t MCExpr::evaluateKnownAbsolute(const MCAsmLayout &Layout) const { 408 int64_t Res; 409 bool Abs = 410 evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr, true); 411 (void)Abs; 412 assert(Abs && "Not actually absolute"); 413 return Res; 414 } 415 416 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm, 417 const MCAsmLayout *Layout, 418 const SectionAddrMap *Addrs) const { 419 // FIXME: The use if InSet = Addrs is a hack. Setting InSet causes us 420 // absolutize differences across sections and that is what the MachO writer 421 // uses Addrs for. 422 return evaluateAsAbsolute(Res, Asm, Layout, Addrs, Addrs); 423 } 424 425 bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm, 426 const MCAsmLayout *Layout, 427 const SectionAddrMap *Addrs, bool InSet) const { 428 MCValue Value; 429 430 // Fast path constants. 431 if (const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(this)) { 432 Res = CE->getValue(); 433 return true; 434 } 435 436 bool IsRelocatable = EvaluateAsRelocatableImpl( 437 Value, Asm, Layout, nullptr, Addrs, InSet, /*ForceVarExpansion*/ false); 438 439 // Record the current value. 440 Res = Value.getConstant(); 441 442 return IsRelocatable && Value.isAbsolute(); 443 } 444 445 /// \brief Helper method for \see EvaluateSymbolAdd(). 446 static void AttemptToFoldSymbolOffsetDifference(const MCAssembler *Asm, 447 const MCAsmLayout *Layout, 448 const SectionAddrMap *Addrs, 449 bool InSet, 450 const MCSymbolRefExpr *&A, 451 const MCSymbolRefExpr *&B, 452 int64_t &Addend) { 453 if (!A || !B) 454 return; 455 456 const MCSymbol &SA = A->getSymbol(); 457 const MCSymbol &SB = B->getSymbol(); 458 459 if (SA.isUndefined() || SB.isUndefined()) 460 return; 461 462 if (!Asm->getWriter().IsSymbolRefDifferenceFullyResolved(*Asm, A, B, InSet)) 463 return; 464 465 const MCSymbolData &AD = Asm->getSymbolData(SA); 466 const MCSymbolData &BD = Asm->getSymbolData(SB); 467 468 if (AD.getFragment() == BD.getFragment()) { 469 Addend += (AD.getOffset() - BD.getOffset()); 470 471 // Pointers to Thumb symbols need to have their low-bit set to allow 472 // for interworking. 473 if (Asm->isThumbFunc(&SA)) 474 Addend |= 1; 475 476 // Clear the symbol expr pointers to indicate we have folded these 477 // operands. 478 A = B = nullptr; 479 return; 480 } 481 482 if (!Layout) 483 return; 484 485 const MCSectionData &SecA = *AD.getFragment()->getParent(); 486 const MCSectionData &SecB = *BD.getFragment()->getParent(); 487 488 if ((&SecA != &SecB) && !Addrs) 489 return; 490 491 // Eagerly evaluate. 492 Addend += (Layout->getSymbolOffset(&Asm->getSymbolData(A->getSymbol())) - 493 Layout->getSymbolOffset(&Asm->getSymbolData(B->getSymbol()))); 494 if (Addrs && (&SecA != &SecB)) 495 Addend += (Addrs->lookup(&SecA) - Addrs->lookup(&SecB)); 496 497 // Pointers to Thumb symbols need to have their low-bit set to allow 498 // for interworking. 499 if (Asm->isThumbFunc(&SA)) 500 Addend |= 1; 501 502 // Clear the symbol expr pointers to indicate we have folded these 503 // operands. 504 A = B = nullptr; 505 } 506 507 /// \brief Evaluate the result of an add between (conceptually) two MCValues. 508 /// 509 /// This routine conceptually attempts to construct an MCValue: 510 /// Result = (Result_A - Result_B + Result_Cst) 511 /// from two MCValue's LHS and RHS where 512 /// Result = LHS + RHS 513 /// and 514 /// Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst). 515 /// 516 /// This routine attempts to aggresively fold the operands such that the result 517 /// is representable in an MCValue, but may not always succeed. 518 /// 519 /// \returns True on success, false if the result is not representable in an 520 /// MCValue. 521 522 /// NOTE: It is really important to have both the Asm and Layout arguments. 523 /// They might look redundant, but this function can be used before layout 524 /// is done (see the object streamer for example) and having the Asm argument 525 /// lets us avoid relaxations early. 526 static bool EvaluateSymbolicAdd(const MCAssembler *Asm, 527 const MCAsmLayout *Layout, 528 const SectionAddrMap *Addrs, 529 bool InSet, 530 const MCValue &LHS,const MCSymbolRefExpr *RHS_A, 531 const MCSymbolRefExpr *RHS_B, int64_t RHS_Cst, 532 MCValue &Res) { 533 // FIXME: This routine (and other evaluation parts) are *incredibly* sloppy 534 // about dealing with modifiers. This will ultimately bite us, one day. 535 const MCSymbolRefExpr *LHS_A = LHS.getSymA(); 536 const MCSymbolRefExpr *LHS_B = LHS.getSymB(); 537 int64_t LHS_Cst = LHS.getConstant(); 538 539 // Fold the result constant immediately. 540 int64_t Result_Cst = LHS_Cst + RHS_Cst; 541 542 assert((!Layout || Asm) && 543 "Must have an assembler object if layout is given!"); 544 545 // If we have a layout, we can fold resolved differences. 546 if (Asm) { 547 // First, fold out any differences which are fully resolved. By 548 // reassociating terms in 549 // Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst). 550 // we have the four possible differences: 551 // (LHS_A - LHS_B), 552 // (LHS_A - RHS_B), 553 // (RHS_A - LHS_B), 554 // (RHS_A - RHS_B). 555 // Since we are attempting to be as aggressive as possible about folding, we 556 // attempt to evaluate each possible alternative. 557 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, LHS_B, 558 Result_Cst); 559 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, RHS_B, 560 Result_Cst); 561 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, LHS_B, 562 Result_Cst); 563 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, RHS_B, 564 Result_Cst); 565 } 566 567 // We can't represent the addition or subtraction of two symbols. 568 if ((LHS_A && RHS_A) || (LHS_B && RHS_B)) 569 return false; 570 571 // At this point, we have at most one additive symbol and one subtractive 572 // symbol -- find them. 573 const MCSymbolRefExpr *A = LHS_A ? LHS_A : RHS_A; 574 const MCSymbolRefExpr *B = LHS_B ? LHS_B : RHS_B; 575 576 // If we have a negated symbol, then we must have also have a non-negated 577 // symbol in order to encode the expression. 578 if (B && !A) 579 return false; 580 581 Res = MCValue::get(A, B, Result_Cst); 582 return true; 583 } 584 585 bool MCExpr::EvaluateAsRelocatable(MCValue &Res, 586 const MCAsmLayout *Layout, 587 const MCFixup *Fixup) const { 588 MCAssembler *Assembler = Layout ? &Layout->getAssembler() : nullptr; 589 return EvaluateAsRelocatableImpl(Res, Assembler, Layout, Fixup, nullptr, 590 false, /*ForceVarExpansion*/ false); 591 } 592 593 bool MCExpr::EvaluateAsValue(MCValue &Res, const MCAsmLayout *Layout, 594 const MCFixup *Fixup) const { 595 MCAssembler *Assembler = Layout ? &Layout->getAssembler() : nullptr; 596 return EvaluateAsRelocatableImpl(Res, Assembler, Layout, Fixup, nullptr, 597 false, /*ForceVarExpansion*/ true); 598 } 599 600 bool MCExpr::EvaluateAsRelocatableImpl(MCValue &Res, const MCAssembler *Asm, 601 const MCAsmLayout *Layout, 602 const MCFixup *Fixup, 603 const SectionAddrMap *Addrs, bool InSet, 604 bool ForceVarExpansion) const { 605 ++stats::MCExprEvaluate; 606 607 switch (getKind()) { 608 case Target: 609 return cast<MCTargetExpr>(this)->EvaluateAsRelocatableImpl(Res, Layout, 610 Fixup); 611 612 case Constant: 613 Res = MCValue::get(cast<MCConstantExpr>(this)->getValue()); 614 return true; 615 616 case SymbolRef: { 617 const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this); 618 const MCSymbol &Sym = SRE->getSymbol(); 619 620 // Evaluate recursively if this is a variable. 621 if (Sym.isVariable() && SRE->getKind() == MCSymbolRefExpr::VK_None) { 622 if (Sym.getVariableValue()->EvaluateAsRelocatableImpl( 623 Res, Asm, Layout, Fixup, Addrs, true, ForceVarExpansion)) { 624 const MCSymbolRefExpr *A = Res.getSymA(); 625 const MCSymbolRefExpr *B = Res.getSymB(); 626 627 if (SRE->hasSubsectionsViaSymbols()) { 628 // FIXME: This is small hack. Given 629 // a = b + 4 630 // .long a 631 // the OS X assembler will completely drop the 4. We should probably 632 // include it in the relocation or produce an error if that is not 633 // possible. 634 if (!A && !B) 635 return true; 636 } else { 637 if (ForceVarExpansion) 638 return true; 639 bool IsSymbol = A && A->getSymbol().isDefined(); 640 if (!IsSymbol) 641 return true; 642 } 643 } 644 } 645 646 Res = MCValue::get(SRE, nullptr, 0); 647 return true; 648 } 649 650 case Unary: { 651 const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this); 652 MCValue Value; 653 654 if (!AUE->getSubExpr()->EvaluateAsRelocatableImpl(Value, Asm, Layout, 655 Fixup, Addrs, InSet, 656 ForceVarExpansion)) 657 return false; 658 659 switch (AUE->getOpcode()) { 660 case MCUnaryExpr::LNot: 661 if (!Value.isAbsolute()) 662 return false; 663 Res = MCValue::get(!Value.getConstant()); 664 break; 665 case MCUnaryExpr::Minus: 666 /// -(a - b + const) ==> (b - a - const) 667 if (Value.getSymA() && !Value.getSymB()) 668 return false; 669 Res = MCValue::get(Value.getSymB(), Value.getSymA(), 670 -Value.getConstant()); 671 break; 672 case MCUnaryExpr::Not: 673 if (!Value.isAbsolute()) 674 return false; 675 Res = MCValue::get(~Value.getConstant()); 676 break; 677 case MCUnaryExpr::Plus: 678 Res = Value; 679 break; 680 } 681 682 return true; 683 } 684 685 case Binary: { 686 const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this); 687 MCValue LHSValue, RHSValue; 688 689 if (!ABE->getLHS()->EvaluateAsRelocatableImpl(LHSValue, Asm, Layout, 690 Fixup, Addrs, InSet, 691 ForceVarExpansion) || 692 !ABE->getRHS()->EvaluateAsRelocatableImpl(RHSValue, Asm, Layout, 693 Fixup, Addrs, InSet, 694 ForceVarExpansion)) 695 return false; 696 697 // We only support a few operations on non-constant expressions, handle 698 // those first. 699 if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) { 700 switch (ABE->getOpcode()) { 701 default: 702 return false; 703 case MCBinaryExpr::Sub: 704 // Negate RHS and add. 705 return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue, 706 RHSValue.getSymB(), RHSValue.getSymA(), 707 -RHSValue.getConstant(), 708 Res); 709 710 case MCBinaryExpr::Add: 711 return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue, 712 RHSValue.getSymA(), RHSValue.getSymB(), 713 RHSValue.getConstant(), 714 Res); 715 } 716 } 717 718 // FIXME: We need target hooks for the evaluation. It may be limited in 719 // width, and gas defines the result of comparisons and right shifts 720 // differently from Apple as. 721 int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant(); 722 int64_t Result = 0; 723 switch (ABE->getOpcode()) { 724 case MCBinaryExpr::Add: Result = LHS + RHS; break; 725 case MCBinaryExpr::And: Result = LHS & RHS; break; 726 case MCBinaryExpr::Div: Result = LHS / RHS; break; 727 case MCBinaryExpr::EQ: Result = LHS == RHS; break; 728 case MCBinaryExpr::GT: Result = LHS > RHS; break; 729 case MCBinaryExpr::GTE: Result = LHS >= RHS; break; 730 case MCBinaryExpr::LAnd: Result = LHS && RHS; break; 731 case MCBinaryExpr::LOr: Result = LHS || RHS; break; 732 case MCBinaryExpr::LT: Result = LHS < RHS; break; 733 case MCBinaryExpr::LTE: Result = LHS <= RHS; break; 734 case MCBinaryExpr::Mod: Result = LHS % RHS; break; 735 case MCBinaryExpr::Mul: Result = LHS * RHS; break; 736 case MCBinaryExpr::NE: Result = LHS != RHS; break; 737 case MCBinaryExpr::Or: Result = LHS | RHS; break; 738 case MCBinaryExpr::Shl: Result = LHS << RHS; break; 739 case MCBinaryExpr::Shr: Result = LHS >> RHS; break; 740 case MCBinaryExpr::Sub: Result = LHS - RHS; break; 741 case MCBinaryExpr::Xor: Result = LHS ^ RHS; break; 742 } 743 744 Res = MCValue::get(Result); 745 return true; 746 } 747 } 748 749 llvm_unreachable("Invalid assembly expression kind!"); 750 } 751 752 const MCSection *MCExpr::FindAssociatedSection() const { 753 switch (getKind()) { 754 case Target: 755 // We never look through target specific expressions. 756 return cast<MCTargetExpr>(this)->FindAssociatedSection(); 757 758 case Constant: 759 return MCSymbol::AbsolutePseudoSection; 760 761 case SymbolRef: { 762 const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this); 763 const MCSymbol &Sym = SRE->getSymbol(); 764 765 if (Sym.isDefined()) 766 return &Sym.getSection(); 767 768 return nullptr; 769 } 770 771 case Unary: 772 return cast<MCUnaryExpr>(this)->getSubExpr()->FindAssociatedSection(); 773 774 case Binary: { 775 const MCBinaryExpr *BE = cast<MCBinaryExpr>(this); 776 const MCSection *LHS_S = BE->getLHS()->FindAssociatedSection(); 777 const MCSection *RHS_S = BE->getRHS()->FindAssociatedSection(); 778 779 // If either section is absolute, return the other. 780 if (LHS_S == MCSymbol::AbsolutePseudoSection) 781 return RHS_S; 782 if (RHS_S == MCSymbol::AbsolutePseudoSection) 783 return LHS_S; 784 785 // Otherwise, return the first non-null section. 786 return LHS_S ? LHS_S : RHS_S; 787 } 788 } 789 790 llvm_unreachable("Invalid assembly expression kind!"); 791 } 792