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/Casting.h" 21 #include "llvm/Support/Compiler.h" 22 #include "llvm/Support/Debug.h" 23 #include "llvm/Support/ErrorHandling.h" 24 #include "llvm/Support/raw_ostream.h" 25 #include <cassert> 26 #include <cstdint> 27 28 using namespace llvm; 29 30 #define DEBUG_TYPE "mcexpr" 31 32 namespace { 33 namespace stats { 34 35 STATISTIC(MCExprEvaluate, "Number of MCExpr evaluations"); 36 37 } // end namespace stats 38 } // end anonymous namespace 39 40 void MCExpr::print(raw_ostream &OS, const MCAsmInfo *MAI, bool InParens) const { 41 switch (getKind()) { 42 case MCExpr::Target: 43 return cast<MCTargetExpr>(this)->printImpl(OS, MAI); 44 case MCExpr::Constant: 45 OS << cast<MCConstantExpr>(*this).getValue(); 46 return; 47 48 case MCExpr::SymbolRef: { 49 const MCSymbolRefExpr &SRE = cast<MCSymbolRefExpr>(*this); 50 const MCSymbol &Sym = SRE.getSymbol(); 51 // Parenthesize names that start with $ so that they don't look like 52 // absolute names. 53 bool UseParens = 54 !InParens && !Sym.getName().empty() && Sym.getName()[0] == '$'; 55 if (UseParens) { 56 OS << '('; 57 Sym.print(OS, MAI); 58 OS << ')'; 59 } else 60 Sym.print(OS, MAI); 61 62 if (SRE.getKind() != MCSymbolRefExpr::VK_None) 63 SRE.printVariantKind(OS); 64 65 return; 66 } 67 68 case MCExpr::Unary: { 69 const MCUnaryExpr &UE = cast<MCUnaryExpr>(*this); 70 switch (UE.getOpcode()) { 71 case MCUnaryExpr::LNot: OS << '!'; break; 72 case MCUnaryExpr::Minus: OS << '-'; break; 73 case MCUnaryExpr::Not: OS << '~'; break; 74 case MCUnaryExpr::Plus: OS << '+'; break; 75 } 76 UE.getSubExpr()->print(OS, MAI); 77 return; 78 } 79 80 case MCExpr::Binary: { 81 const MCBinaryExpr &BE = cast<MCBinaryExpr>(*this); 82 83 // Only print parens around the LHS if it is non-trivial. 84 if (isa<MCConstantExpr>(BE.getLHS()) || isa<MCSymbolRefExpr>(BE.getLHS())) { 85 BE.getLHS()->print(OS, MAI); 86 } else { 87 OS << '('; 88 BE.getLHS()->print(OS, MAI); 89 OS << ')'; 90 } 91 92 switch (BE.getOpcode()) { 93 case MCBinaryExpr::Add: 94 // Print "X-42" instead of "X+-42". 95 if (const MCConstantExpr *RHSC = dyn_cast<MCConstantExpr>(BE.getRHS())) { 96 if (RHSC->getValue() < 0) { 97 OS << RHSC->getValue(); 98 return; 99 } 100 } 101 102 OS << '+'; 103 break; 104 case MCBinaryExpr::AShr: OS << ">>"; break; 105 case MCBinaryExpr::And: OS << '&'; break; 106 case MCBinaryExpr::Div: OS << '/'; break; 107 case MCBinaryExpr::EQ: OS << "=="; break; 108 case MCBinaryExpr::GT: OS << '>'; break; 109 case MCBinaryExpr::GTE: OS << ">="; break; 110 case MCBinaryExpr::LAnd: OS << "&&"; break; 111 case MCBinaryExpr::LOr: OS << "||"; break; 112 case MCBinaryExpr::LShr: OS << ">>"; break; 113 case MCBinaryExpr::LT: OS << '<'; break; 114 case MCBinaryExpr::LTE: OS << "<="; break; 115 case MCBinaryExpr::Mod: OS << '%'; break; 116 case MCBinaryExpr::Mul: OS << '*'; break; 117 case MCBinaryExpr::NE: OS << "!="; break; 118 case MCBinaryExpr::Or: OS << '|'; break; 119 case MCBinaryExpr::Shl: OS << "<<"; break; 120 case MCBinaryExpr::Sub: OS << '-'; break; 121 case MCBinaryExpr::Xor: OS << '^'; break; 122 } 123 124 // Only print parens around the LHS if it is non-trivial. 125 if (isa<MCConstantExpr>(BE.getRHS()) || isa<MCSymbolRefExpr>(BE.getRHS())) { 126 BE.getRHS()->print(OS, MAI); 127 } else { 128 OS << '('; 129 BE.getRHS()->print(OS, MAI); 130 OS << ')'; 131 } 132 return; 133 } 134 } 135 136 llvm_unreachable("Invalid expression kind!"); 137 } 138 139 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 140 LLVM_DUMP_METHOD void MCExpr::dump() const { 141 dbgs() << *this; 142 dbgs() << '\n'; 143 } 144 #endif 145 146 /* *** */ 147 148 const MCBinaryExpr *MCBinaryExpr::create(Opcode Opc, const MCExpr *LHS, 149 const MCExpr *RHS, MCContext &Ctx, 150 SMLoc Loc) { 151 return new (Ctx) MCBinaryExpr(Opc, LHS, RHS, Loc); 152 } 153 154 const MCUnaryExpr *MCUnaryExpr::create(Opcode Opc, const MCExpr *Expr, 155 MCContext &Ctx, SMLoc Loc) { 156 return new (Ctx) MCUnaryExpr(Opc, Expr, Loc); 157 } 158 159 const MCConstantExpr *MCConstantExpr::create(int64_t Value, MCContext &Ctx) { 160 return new (Ctx) MCConstantExpr(Value); 161 } 162 163 /* *** */ 164 165 MCSymbolRefExpr::MCSymbolRefExpr(const MCSymbol *Symbol, VariantKind Kind, 166 const MCAsmInfo *MAI, SMLoc Loc) 167 : MCExpr(MCExpr::SymbolRef, Loc), Kind(Kind), 168 UseParensForSymbolVariant(MAI->useParensForSymbolVariant()), 169 HasSubsectionsViaSymbols(MAI->hasSubsectionsViaSymbols()), 170 Symbol(Symbol) { 171 assert(Symbol); 172 } 173 174 const MCSymbolRefExpr *MCSymbolRefExpr::create(const MCSymbol *Sym, 175 VariantKind Kind, 176 MCContext &Ctx, SMLoc Loc) { 177 return new (Ctx) MCSymbolRefExpr(Sym, Kind, Ctx.getAsmInfo(), Loc); 178 } 179 180 const MCSymbolRefExpr *MCSymbolRefExpr::create(StringRef Name, VariantKind Kind, 181 MCContext &Ctx) { 182 return create(Ctx.getOrCreateSymbol(Name), Kind, Ctx); 183 } 184 185 StringRef MCSymbolRefExpr::getVariantKindName(VariantKind Kind) { 186 switch (Kind) { 187 case VK_Invalid: return "<<invalid>>"; 188 case VK_None: return "<<none>>"; 189 190 case VK_DTPOFF: return "DTPOFF"; 191 case VK_DTPREL: return "DTPREL"; 192 case VK_GOT: return "GOT"; 193 case VK_GOTOFF: return "GOTOFF"; 194 case VK_GOTREL: return "GOTREL"; 195 case VK_GOTPCREL: return "GOTPCREL"; 196 case VK_GOTTPOFF: return "GOTTPOFF"; 197 case VK_INDNTPOFF: return "INDNTPOFF"; 198 case VK_NTPOFF: return "NTPOFF"; 199 case VK_GOTNTPOFF: return "GOTNTPOFF"; 200 case VK_PLT: return "PLT"; 201 case VK_TLSGD: return "TLSGD"; 202 case VK_TLSLD: return "TLSLD"; 203 case VK_TLSLDM: return "TLSLDM"; 204 case VK_TPOFF: return "TPOFF"; 205 case VK_TPREL: return "TPREL"; 206 case VK_TLSCALL: return "tlscall"; 207 case VK_TLSDESC: return "tlsdesc"; 208 case VK_TLVP: return "TLVP"; 209 case VK_TLVPPAGE: return "TLVPPAGE"; 210 case VK_TLVPPAGEOFF: return "TLVPPAGEOFF"; 211 case VK_PAGE: return "PAGE"; 212 case VK_PAGEOFF: return "PAGEOFF"; 213 case VK_GOTPAGE: return "GOTPAGE"; 214 case VK_GOTPAGEOFF: return "GOTPAGEOFF"; 215 case VK_SECREL: return "SECREL32"; 216 case VK_SIZE: return "SIZE"; 217 case VK_WEAKREF: return "WEAKREF"; 218 case VK_X86_ABS8: return "ABS8"; 219 case VK_ARM_NONE: return "none"; 220 case VK_ARM_GOT_PREL: return "GOT_PREL"; 221 case VK_ARM_TARGET1: return "target1"; 222 case VK_ARM_TARGET2: return "target2"; 223 case VK_ARM_PREL31: return "prel31"; 224 case VK_ARM_SBREL: return "sbrel"; 225 case VK_ARM_TLSLDO: return "tlsldo"; 226 case VK_ARM_TLSDESCSEQ: return "tlsdescseq"; 227 case VK_AVR_NONE: return "none"; 228 case VK_AVR_LO8: return "lo8"; 229 case VK_AVR_HI8: return "hi8"; 230 case VK_AVR_HLO8: return "hlo8"; 231 case VK_AVR_DIFF8: return "diff8"; 232 case VK_AVR_DIFF16: return "diff16"; 233 case VK_AVR_DIFF32: return "diff32"; 234 case VK_PPC_LO: return "l"; 235 case VK_PPC_HI: return "h"; 236 case VK_PPC_HA: return "ha"; 237 case VK_PPC_HIGHER: return "higher"; 238 case VK_PPC_HIGHERA: return "highera"; 239 case VK_PPC_HIGHEST: return "highest"; 240 case VK_PPC_HIGHESTA: return "highesta"; 241 case VK_PPC_GOT_LO: return "got@l"; 242 case VK_PPC_GOT_HI: return "got@h"; 243 case VK_PPC_GOT_HA: return "got@ha"; 244 case VK_PPC_TOCBASE: return "tocbase"; 245 case VK_PPC_TOC: return "toc"; 246 case VK_PPC_TOC_LO: return "toc@l"; 247 case VK_PPC_TOC_HI: return "toc@h"; 248 case VK_PPC_TOC_HA: return "toc@ha"; 249 case VK_PPC_DTPMOD: return "dtpmod"; 250 case VK_PPC_TPREL_LO: return "tprel@l"; 251 case VK_PPC_TPREL_HI: return "tprel@h"; 252 case VK_PPC_TPREL_HA: return "tprel@ha"; 253 case VK_PPC_TPREL_HIGHER: return "tprel@higher"; 254 case VK_PPC_TPREL_HIGHERA: return "tprel@highera"; 255 case VK_PPC_TPREL_HIGHEST: return "tprel@highest"; 256 case VK_PPC_TPREL_HIGHESTA: return "tprel@highesta"; 257 case VK_PPC_DTPREL_LO: return "dtprel@l"; 258 case VK_PPC_DTPREL_HI: return "dtprel@h"; 259 case VK_PPC_DTPREL_HA: return "dtprel@ha"; 260 case VK_PPC_DTPREL_HIGHER: return "dtprel@higher"; 261 case VK_PPC_DTPREL_HIGHERA: return "dtprel@highera"; 262 case VK_PPC_DTPREL_HIGHEST: return "dtprel@highest"; 263 case VK_PPC_DTPREL_HIGHESTA: return "dtprel@highesta"; 264 case VK_PPC_GOT_TPREL: return "got@tprel"; 265 case VK_PPC_GOT_TPREL_LO: return "got@tprel@l"; 266 case VK_PPC_GOT_TPREL_HI: return "got@tprel@h"; 267 case VK_PPC_GOT_TPREL_HA: return "got@tprel@ha"; 268 case VK_PPC_GOT_DTPREL: return "got@dtprel"; 269 case VK_PPC_GOT_DTPREL_LO: return "got@dtprel@l"; 270 case VK_PPC_GOT_DTPREL_HI: return "got@dtprel@h"; 271 case VK_PPC_GOT_DTPREL_HA: return "got@dtprel@ha"; 272 case VK_PPC_TLS: return "tls"; 273 case VK_PPC_GOT_TLSGD: return "got@tlsgd"; 274 case VK_PPC_GOT_TLSGD_LO: return "got@tlsgd@l"; 275 case VK_PPC_GOT_TLSGD_HI: return "got@tlsgd@h"; 276 case VK_PPC_GOT_TLSGD_HA: return "got@tlsgd@ha"; 277 case VK_PPC_TLSGD: return "tlsgd"; 278 case VK_PPC_GOT_TLSLD: return "got@tlsld"; 279 case VK_PPC_GOT_TLSLD_LO: return "got@tlsld@l"; 280 case VK_PPC_GOT_TLSLD_HI: return "got@tlsld@h"; 281 case VK_PPC_GOT_TLSLD_HA: return "got@tlsld@ha"; 282 case VK_PPC_TLSLD: return "tlsld"; 283 case VK_PPC_LOCAL: return "local"; 284 case VK_COFF_IMGREL32: return "IMGREL"; 285 case VK_Hexagon_PCREL: return "PCREL"; 286 case VK_Hexagon_LO16: return "LO16"; 287 case VK_Hexagon_HI16: return "HI16"; 288 case VK_Hexagon_GPREL: return "GPREL"; 289 case VK_Hexagon_GD_GOT: return "GDGOT"; 290 case VK_Hexagon_LD_GOT: return "LDGOT"; 291 case VK_Hexagon_GD_PLT: return "GDPLT"; 292 case VK_Hexagon_LD_PLT: return "LDPLT"; 293 case VK_Hexagon_IE: return "IE"; 294 case VK_Hexagon_IE_GOT: return "IEGOT"; 295 case VK_WebAssembly_FUNCTION: return "FUNCTION"; 296 case VK_WebAssembly_TYPEINDEX: return "TYPEINDEX"; 297 case VK_AMDGPU_GOTPCREL32_LO: return "gotpcrel32@lo"; 298 case VK_AMDGPU_GOTPCREL32_HI: return "gotpcrel32@hi"; 299 case VK_AMDGPU_REL32_LO: return "rel32@lo"; 300 case VK_AMDGPU_REL32_HI: return "rel32@hi"; 301 } 302 llvm_unreachable("Invalid variant kind"); 303 } 304 305 MCSymbolRefExpr::VariantKind 306 MCSymbolRefExpr::getVariantKindForName(StringRef Name) { 307 return StringSwitch<VariantKind>(Name.lower()) 308 .Case("dtprel", VK_DTPREL) 309 .Case("dtpoff", VK_DTPOFF) 310 .Case("got", VK_GOT) 311 .Case("gotoff", VK_GOTOFF) 312 .Case("gotrel", VK_GOTREL) 313 .Case("gotpcrel", VK_GOTPCREL) 314 .Case("gottpoff", VK_GOTTPOFF) 315 .Case("indntpoff", VK_INDNTPOFF) 316 .Case("ntpoff", VK_NTPOFF) 317 .Case("gotntpoff", VK_GOTNTPOFF) 318 .Case("plt", VK_PLT) 319 .Case("tlscall", VK_TLSCALL) 320 .Case("tlsdesc", VK_TLSDESC) 321 .Case("tlsgd", VK_TLSGD) 322 .Case("tlsld", VK_TLSLD) 323 .Case("tlsldm", VK_TLSLDM) 324 .Case("tpoff", VK_TPOFF) 325 .Case("tprel", VK_TPREL) 326 .Case("tlvp", VK_TLVP) 327 .Case("tlvppage", VK_TLVPPAGE) 328 .Case("tlvppageoff", VK_TLVPPAGEOFF) 329 .Case("page", VK_PAGE) 330 .Case("pageoff", VK_PAGEOFF) 331 .Case("gotpage", VK_GOTPAGE) 332 .Case("gotpageoff", VK_GOTPAGEOFF) 333 .Case("imgrel", VK_COFF_IMGREL32) 334 .Case("secrel32", VK_SECREL) 335 .Case("size", VK_SIZE) 336 .Case("abs8", VK_X86_ABS8) 337 .Case("l", VK_PPC_LO) 338 .Case("h", VK_PPC_HI) 339 .Case("ha", VK_PPC_HA) 340 .Case("higher", VK_PPC_HIGHER) 341 .Case("highera", VK_PPC_HIGHERA) 342 .Case("highest", VK_PPC_HIGHEST) 343 .Case("highesta", VK_PPC_HIGHESTA) 344 .Case("got@l", VK_PPC_GOT_LO) 345 .Case("got@h", VK_PPC_GOT_HI) 346 .Case("got@ha", VK_PPC_GOT_HA) 347 .Case("local", VK_PPC_LOCAL) 348 .Case("tocbase", VK_PPC_TOCBASE) 349 .Case("toc", VK_PPC_TOC) 350 .Case("toc@l", VK_PPC_TOC_LO) 351 .Case("toc@h", VK_PPC_TOC_HI) 352 .Case("toc@ha", VK_PPC_TOC_HA) 353 .Case("tls", VK_PPC_TLS) 354 .Case("dtpmod", VK_PPC_DTPMOD) 355 .Case("tprel@l", VK_PPC_TPREL_LO) 356 .Case("tprel@h", VK_PPC_TPREL_HI) 357 .Case("tprel@ha", VK_PPC_TPREL_HA) 358 .Case("tprel@higher", VK_PPC_TPREL_HIGHER) 359 .Case("tprel@highera", VK_PPC_TPREL_HIGHERA) 360 .Case("tprel@highest", VK_PPC_TPREL_HIGHEST) 361 .Case("tprel@highesta", VK_PPC_TPREL_HIGHESTA) 362 .Case("dtprel@l", VK_PPC_DTPREL_LO) 363 .Case("dtprel@h", VK_PPC_DTPREL_HI) 364 .Case("dtprel@ha", VK_PPC_DTPREL_HA) 365 .Case("dtprel@higher", VK_PPC_DTPREL_HIGHER) 366 .Case("dtprel@highera", VK_PPC_DTPREL_HIGHERA) 367 .Case("dtprel@highest", VK_PPC_DTPREL_HIGHEST) 368 .Case("dtprel@highesta", VK_PPC_DTPREL_HIGHESTA) 369 .Case("got@tprel", VK_PPC_GOT_TPREL) 370 .Case("got@tprel@l", VK_PPC_GOT_TPREL_LO) 371 .Case("got@tprel@h", VK_PPC_GOT_TPREL_HI) 372 .Case("got@tprel@ha", VK_PPC_GOT_TPREL_HA) 373 .Case("got@dtprel", VK_PPC_GOT_DTPREL) 374 .Case("got@dtprel@l", VK_PPC_GOT_DTPREL_LO) 375 .Case("got@dtprel@h", VK_PPC_GOT_DTPREL_HI) 376 .Case("got@dtprel@ha", VK_PPC_GOT_DTPREL_HA) 377 .Case("got@tlsgd", VK_PPC_GOT_TLSGD) 378 .Case("got@tlsgd@l", VK_PPC_GOT_TLSGD_LO) 379 .Case("got@tlsgd@h", VK_PPC_GOT_TLSGD_HI) 380 .Case("got@tlsgd@ha", VK_PPC_GOT_TLSGD_HA) 381 .Case("got@tlsld", VK_PPC_GOT_TLSLD) 382 .Case("got@tlsld@l", VK_PPC_GOT_TLSLD_LO) 383 .Case("got@tlsld@h", VK_PPC_GOT_TLSLD_HI) 384 .Case("got@tlsld@ha", VK_PPC_GOT_TLSLD_HA) 385 .Case("gdgot", VK_Hexagon_GD_GOT) 386 .Case("gdplt", VK_Hexagon_GD_PLT) 387 .Case("iegot", VK_Hexagon_IE_GOT) 388 .Case("ie", VK_Hexagon_IE) 389 .Case("ldgot", VK_Hexagon_LD_GOT) 390 .Case("ldplt", VK_Hexagon_LD_PLT) 391 .Case("pcrel", VK_Hexagon_PCREL) 392 .Case("none", VK_ARM_NONE) 393 .Case("got_prel", VK_ARM_GOT_PREL) 394 .Case("target1", VK_ARM_TARGET1) 395 .Case("target2", VK_ARM_TARGET2) 396 .Case("prel31", VK_ARM_PREL31) 397 .Case("sbrel", VK_ARM_SBREL) 398 .Case("tlsldo", VK_ARM_TLSLDO) 399 .Case("lo8", VK_AVR_LO8) 400 .Case("hi8", VK_AVR_HI8) 401 .Case("hlo8", VK_AVR_HLO8) 402 .Case("gotpcrel32@lo", VK_AMDGPU_GOTPCREL32_LO) 403 .Case("gotpcrel32@hi", VK_AMDGPU_GOTPCREL32_HI) 404 .Case("rel32@lo", VK_AMDGPU_REL32_LO) 405 .Case("rel32@hi", VK_AMDGPU_REL32_HI) 406 .Default(VK_Invalid); 407 } 408 409 void MCSymbolRefExpr::printVariantKind(raw_ostream &OS) const { 410 if (UseParensForSymbolVariant) 411 OS << '(' << MCSymbolRefExpr::getVariantKindName(getKind()) << ')'; 412 else 413 OS << '@' << MCSymbolRefExpr::getVariantKindName(getKind()); 414 } 415 416 /* *** */ 417 418 void MCTargetExpr::anchor() {} 419 420 /* *** */ 421 422 bool MCExpr::evaluateAsAbsolute(int64_t &Res) const { 423 return evaluateAsAbsolute(Res, nullptr, nullptr, nullptr); 424 } 425 426 bool MCExpr::evaluateAsAbsolute(int64_t &Res, 427 const MCAsmLayout &Layout) const { 428 return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr); 429 } 430 431 bool MCExpr::evaluateAsAbsolute(int64_t &Res, 432 const MCAsmLayout &Layout, 433 const SectionAddrMap &Addrs) const { 434 return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, &Addrs); 435 } 436 437 bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const { 438 return evaluateAsAbsolute(Res, &Asm, nullptr, nullptr); 439 } 440 441 bool MCExpr::evaluateKnownAbsolute(int64_t &Res, 442 const MCAsmLayout &Layout) const { 443 return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr, 444 true); 445 } 446 447 bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm, 448 const MCAsmLayout *Layout, 449 const SectionAddrMap *Addrs) const { 450 // FIXME: The use if InSet = Addrs is a hack. Setting InSet causes us 451 // absolutize differences across sections and that is what the MachO writer 452 // uses Addrs for. 453 return evaluateAsAbsolute(Res, Asm, Layout, Addrs, Addrs); 454 } 455 456 bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm, 457 const MCAsmLayout *Layout, 458 const SectionAddrMap *Addrs, bool InSet) const { 459 MCValue Value; 460 461 // Fast path constants. 462 if (const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(this)) { 463 Res = CE->getValue(); 464 return true; 465 } 466 467 bool IsRelocatable = 468 evaluateAsRelocatableImpl(Value, Asm, Layout, nullptr, Addrs, InSet); 469 470 // Record the current value. 471 Res = Value.getConstant(); 472 473 return IsRelocatable && Value.isAbsolute(); 474 } 475 476 /// \brief Helper method for \see EvaluateSymbolAdd(). 477 static void AttemptToFoldSymbolOffsetDifference( 478 const MCAssembler *Asm, const MCAsmLayout *Layout, 479 const SectionAddrMap *Addrs, bool InSet, const MCSymbolRefExpr *&A, 480 const MCSymbolRefExpr *&B, int64_t &Addend) { 481 if (!A || !B) 482 return; 483 484 const MCSymbol &SA = A->getSymbol(); 485 const MCSymbol &SB = B->getSymbol(); 486 487 if (SA.isUndefined() || SB.isUndefined()) 488 return; 489 490 if (!Asm->getWriter().isSymbolRefDifferenceFullyResolved(*Asm, A, B, InSet)) 491 return; 492 493 if (SA.getFragment() == SB.getFragment() && !SA.isVariable() && 494 !SB.isVariable()) { 495 Addend += (SA.getOffset() - SB.getOffset()); 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 return; 506 } 507 508 if (!Layout) 509 return; 510 511 const MCSection &SecA = *SA.getFragment()->getParent(); 512 const MCSection &SecB = *SB.getFragment()->getParent(); 513 514 if ((&SecA != &SecB) && !Addrs) 515 return; 516 517 // Eagerly evaluate. 518 Addend += Layout->getSymbolOffset(A->getSymbol()) - 519 Layout->getSymbolOffset(B->getSymbol()); 520 if (Addrs && (&SecA != &SecB)) 521 Addend += (Addrs->lookup(&SecA) - Addrs->lookup(&SecB)); 522 523 // Pointers to Thumb symbols need to have their low-bit set to allow 524 // for interworking. 525 if (Asm->isThumbFunc(&SA)) 526 Addend |= 1; 527 528 // Clear the symbol expr pointers to indicate we have folded these 529 // operands. 530 A = B = nullptr; 531 } 532 533 /// \brief Evaluate the result of an add between (conceptually) two MCValues. 534 /// 535 /// This routine conceptually attempts to construct an MCValue: 536 /// Result = (Result_A - Result_B + Result_Cst) 537 /// from two MCValue's LHS and RHS where 538 /// Result = LHS + RHS 539 /// and 540 /// Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst). 541 /// 542 /// This routine attempts to aggresively fold the operands such that the result 543 /// is representable in an MCValue, but may not always succeed. 544 /// 545 /// \returns True on success, false if the result is not representable in an 546 /// MCValue. 547 548 /// NOTE: It is really important to have both the Asm and Layout arguments. 549 /// They might look redundant, but this function can be used before layout 550 /// is done (see the object streamer for example) and having the Asm argument 551 /// lets us avoid relaxations early. 552 static bool 553 EvaluateSymbolicAdd(const MCAssembler *Asm, const MCAsmLayout *Layout, 554 const SectionAddrMap *Addrs, bool InSet, const MCValue &LHS, 555 const MCSymbolRefExpr *RHS_A, const MCSymbolRefExpr *RHS_B, 556 int64_t RHS_Cst, MCValue &Res) { 557 // FIXME: This routine (and other evaluation parts) are *incredibly* sloppy 558 // about dealing with modifiers. This will ultimately bite us, one day. 559 const MCSymbolRefExpr *LHS_A = LHS.getSymA(); 560 const MCSymbolRefExpr *LHS_B = LHS.getSymB(); 561 int64_t LHS_Cst = LHS.getConstant(); 562 563 // Fold the result constant immediately. 564 int64_t Result_Cst = LHS_Cst + RHS_Cst; 565 566 assert((!Layout || Asm) && 567 "Must have an assembler object if layout is given!"); 568 569 // If we have a layout, we can fold resolved differences. 570 if (Asm) { 571 // First, fold out any differences which are fully resolved. By 572 // reassociating terms in 573 // Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst). 574 // we have the four possible differences: 575 // (LHS_A - LHS_B), 576 // (LHS_A - RHS_B), 577 // (RHS_A - LHS_B), 578 // (RHS_A - RHS_B). 579 // Since we are attempting to be as aggressive as possible about folding, we 580 // attempt to evaluate each possible alternative. 581 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, LHS_B, 582 Result_Cst); 583 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, RHS_B, 584 Result_Cst); 585 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, LHS_B, 586 Result_Cst); 587 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, RHS_B, 588 Result_Cst); 589 } 590 591 // We can't represent the addition or subtraction of two symbols. 592 if ((LHS_A && RHS_A) || (LHS_B && RHS_B)) 593 return false; 594 595 // At this point, we have at most one additive symbol and one subtractive 596 // symbol -- find them. 597 const MCSymbolRefExpr *A = LHS_A ? LHS_A : RHS_A; 598 const MCSymbolRefExpr *B = LHS_B ? LHS_B : RHS_B; 599 600 Res = MCValue::get(A, B, Result_Cst); 601 return true; 602 } 603 604 bool MCExpr::evaluateAsRelocatable(MCValue &Res, 605 const MCAsmLayout *Layout, 606 const MCFixup *Fixup) const { 607 MCAssembler *Assembler = Layout ? &Layout->getAssembler() : nullptr; 608 return evaluateAsRelocatableImpl(Res, Assembler, Layout, Fixup, nullptr, 609 false); 610 } 611 612 bool MCExpr::evaluateAsValue(MCValue &Res, const MCAsmLayout &Layout) const { 613 MCAssembler *Assembler = &Layout.getAssembler(); 614 return evaluateAsRelocatableImpl(Res, Assembler, &Layout, nullptr, nullptr, 615 true); 616 } 617 618 static bool canExpand(const MCSymbol &Sym, bool InSet) { 619 const MCExpr *Expr = Sym.getVariableValue(); 620 const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr); 621 if (Inner) { 622 if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF) 623 return false; 624 } 625 626 if (InSet) 627 return true; 628 return !Sym.isInSection(); 629 } 630 631 bool MCExpr::evaluateAsRelocatableImpl(MCValue &Res, const MCAssembler *Asm, 632 const MCAsmLayout *Layout, 633 const MCFixup *Fixup, 634 const SectionAddrMap *Addrs, 635 bool InSet) const { 636 ++stats::MCExprEvaluate; 637 638 switch (getKind()) { 639 case Target: 640 return cast<MCTargetExpr>(this)->evaluateAsRelocatableImpl(Res, Layout, 641 Fixup); 642 643 case Constant: 644 Res = MCValue::get(cast<MCConstantExpr>(this)->getValue()); 645 return true; 646 647 case SymbolRef: { 648 const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this); 649 const MCSymbol &Sym = SRE->getSymbol(); 650 651 // Evaluate recursively if this is a variable. 652 if (Sym.isVariable() && SRE->getKind() == MCSymbolRefExpr::VK_None && 653 canExpand(Sym, InSet)) { 654 bool IsMachO = SRE->hasSubsectionsViaSymbols(); 655 if (Sym.getVariableValue()->evaluateAsRelocatableImpl( 656 Res, Asm, Layout, Fixup, Addrs, InSet || IsMachO)) { 657 if (!IsMachO) 658 return true; 659 660 const MCSymbolRefExpr *A = Res.getSymA(); 661 const MCSymbolRefExpr *B = Res.getSymB(); 662 // FIXME: This is small hack. Given 663 // a = b + 4 664 // .long a 665 // the OS X assembler will completely drop the 4. We should probably 666 // include it in the relocation or produce an error if that is not 667 // possible. 668 // Allow constant expressions. 669 if (!A && !B) 670 return true; 671 // Allows aliases with zero offset. 672 if (Res.getConstant() == 0 && (!A || !B)) 673 return true; 674 } 675 } 676 677 Res = MCValue::get(SRE, nullptr, 0); 678 return true; 679 } 680 681 case Unary: { 682 const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this); 683 MCValue Value; 684 685 if (!AUE->getSubExpr()->evaluateAsRelocatableImpl(Value, Asm, Layout, Fixup, 686 Addrs, InSet)) 687 return false; 688 689 switch (AUE->getOpcode()) { 690 case MCUnaryExpr::LNot: 691 if (!Value.isAbsolute()) 692 return false; 693 Res = MCValue::get(!Value.getConstant()); 694 break; 695 case MCUnaryExpr::Minus: 696 /// -(a - b + const) ==> (b - a - const) 697 if (Value.getSymA() && !Value.getSymB()) 698 return false; 699 700 // The cast avoids undefined behavior if the constant is INT64_MIN. 701 Res = MCValue::get(Value.getSymB(), Value.getSymA(), 702 -(uint64_t)Value.getConstant()); 703 break; 704 case MCUnaryExpr::Not: 705 if (!Value.isAbsolute()) 706 return false; 707 Res = MCValue::get(~Value.getConstant()); 708 break; 709 case MCUnaryExpr::Plus: 710 Res = Value; 711 break; 712 } 713 714 return true; 715 } 716 717 case Binary: { 718 const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this); 719 MCValue LHSValue, RHSValue; 720 721 if (!ABE->getLHS()->evaluateAsRelocatableImpl(LHSValue, Asm, Layout, Fixup, 722 Addrs, InSet) || 723 !ABE->getRHS()->evaluateAsRelocatableImpl(RHSValue, Asm, Layout, Fixup, 724 Addrs, InSet)) 725 return false; 726 727 // We only support a few operations on non-constant expressions, handle 728 // those first. 729 if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) { 730 switch (ABE->getOpcode()) { 731 default: 732 return false; 733 case MCBinaryExpr::Sub: 734 // Negate RHS and add. 735 // The cast avoids undefined behavior if the constant is INT64_MIN. 736 return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue, 737 RHSValue.getSymB(), RHSValue.getSymA(), 738 -(uint64_t)RHSValue.getConstant(), Res); 739 740 case MCBinaryExpr::Add: 741 return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue, 742 RHSValue.getSymA(), RHSValue.getSymB(), 743 RHSValue.getConstant(), Res); 744 } 745 } 746 747 // FIXME: We need target hooks for the evaluation. It may be limited in 748 // width, and gas defines the result of comparisons differently from 749 // Apple as. 750 int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant(); 751 int64_t Result = 0; 752 switch (ABE->getOpcode()) { 753 case MCBinaryExpr::AShr: Result = LHS >> RHS; break; 754 case MCBinaryExpr::Add: Result = LHS + RHS; break; 755 case MCBinaryExpr::And: Result = LHS & RHS; break; 756 case MCBinaryExpr::Div: 757 // Handle division by zero. gas just emits a warning and keeps going, 758 // we try to be stricter. 759 // FIXME: Currently the caller of this function has no way to understand 760 // we're bailing out because of 'division by zero'. Therefore, it will 761 // emit a 'expected relocatable expression' error. It would be nice to 762 // change this code to emit a better diagnostic. 763 if (RHS == 0) 764 return false; 765 Result = LHS / RHS; 766 break; 767 case MCBinaryExpr::EQ: Result = LHS == RHS; break; 768 case MCBinaryExpr::GT: Result = LHS > RHS; break; 769 case MCBinaryExpr::GTE: Result = LHS >= RHS; break; 770 case MCBinaryExpr::LAnd: Result = LHS && RHS; break; 771 case MCBinaryExpr::LOr: Result = LHS || RHS; break; 772 case MCBinaryExpr::LShr: Result = uint64_t(LHS) >> uint64_t(RHS); break; 773 case MCBinaryExpr::LT: Result = LHS < RHS; break; 774 case MCBinaryExpr::LTE: Result = LHS <= RHS; break; 775 case MCBinaryExpr::Mod: Result = LHS % RHS; break; 776 case MCBinaryExpr::Mul: Result = LHS * RHS; break; 777 case MCBinaryExpr::NE: Result = LHS != RHS; break; 778 case MCBinaryExpr::Or: Result = LHS | RHS; break; 779 case MCBinaryExpr::Shl: Result = uint64_t(LHS) << uint64_t(RHS); break; 780 case MCBinaryExpr::Sub: Result = LHS - RHS; break; 781 case MCBinaryExpr::Xor: Result = LHS ^ RHS; break; 782 } 783 784 Res = MCValue::get(Result); 785 return true; 786 } 787 } 788 789 llvm_unreachable("Invalid assembly expression kind!"); 790 } 791 792 MCFragment *MCExpr::findAssociatedFragment() const { 793 switch (getKind()) { 794 case Target: 795 // We never look through target specific expressions. 796 return cast<MCTargetExpr>(this)->findAssociatedFragment(); 797 798 case Constant: 799 return MCSymbol::AbsolutePseudoFragment; 800 801 case SymbolRef: { 802 const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this); 803 const MCSymbol &Sym = SRE->getSymbol(); 804 return Sym.getFragment(); 805 } 806 807 case Unary: 808 return cast<MCUnaryExpr>(this)->getSubExpr()->findAssociatedFragment(); 809 810 case Binary: { 811 const MCBinaryExpr *BE = cast<MCBinaryExpr>(this); 812 MCFragment *LHS_F = BE->getLHS()->findAssociatedFragment(); 813 MCFragment *RHS_F = BE->getRHS()->findAssociatedFragment(); 814 815 // If either is absolute, return the other. 816 if (LHS_F == MCSymbol::AbsolutePseudoFragment) 817 return RHS_F; 818 if (RHS_F == MCSymbol::AbsolutePseudoFragment) 819 return LHS_F; 820 821 // Not always correct, but probably the best we can do without more context. 822 if (BE->getOpcode() == MCBinaryExpr::Sub) 823 return MCSymbol::AbsolutePseudoFragment; 824 825 // Otherwise, return the first non-null fragment. 826 return LHS_F ? LHS_F : RHS_F; 827 } 828 } 829 830 llvm_unreachable("Invalid assembly expression kind!"); 831 } 832