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 #define DEBUG_TYPE "mcexpr" 11 #include "llvm/MC/MCExpr.h" 12 #include "llvm/ADT/Statistic.h" 13 #include "llvm/ADT/StringSwitch.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 namespace { 26 namespace stats { 27 STATISTIC(MCExprEvaluate, "Number of MCExpr evaluations"); 28 } 29 } 30 31 void MCExpr::print(raw_ostream &OS) const { 32 switch (getKind()) { 33 case MCExpr::Target: 34 return cast<MCTargetExpr>(this)->PrintImpl(OS); 35 case MCExpr::Constant: 36 OS << cast<MCConstantExpr>(*this).getValue(); 37 return; 38 39 case MCExpr::SymbolRef: { 40 const MCSymbolRefExpr &SRE = cast<MCSymbolRefExpr>(*this); 41 const MCSymbol &Sym = SRE.getSymbol(); 42 // Parenthesize names that start with $ so that they don't look like 43 // absolute names. 44 bool UseParens = Sym.getName()[0] == '$'; 45 46 if (SRE.getKind() == MCSymbolRefExpr::VK_PPC_DARWIN_HA16 || 47 SRE.getKind() == MCSymbolRefExpr::VK_PPC_DARWIN_LO16) { 48 OS << MCSymbolRefExpr::getVariantKindName(SRE.getKind()); 49 UseParens = true; 50 } 51 52 if (UseParens) 53 OS << '(' << Sym << ')'; 54 else 55 OS << Sym; 56 57 if (SRE.getKind() == MCSymbolRefExpr::VK_ARM_NONE || 58 SRE.getKind() == MCSymbolRefExpr::VK_ARM_PLT || 59 SRE.getKind() == MCSymbolRefExpr::VK_ARM_TLSGD || 60 SRE.getKind() == MCSymbolRefExpr::VK_ARM_GOT || 61 SRE.getKind() == MCSymbolRefExpr::VK_ARM_GOTOFF || 62 SRE.getKind() == MCSymbolRefExpr::VK_ARM_TPOFF || 63 SRE.getKind() == MCSymbolRefExpr::VK_ARM_GOTTPOFF || 64 SRE.getKind() == MCSymbolRefExpr::VK_ARM_TARGET1 || 65 SRE.getKind() == MCSymbolRefExpr::VK_ARM_TARGET2 || 66 SRE.getKind() == MCSymbolRefExpr::VK_ARM_PREL31) 67 OS << MCSymbolRefExpr::getVariantKindName(SRE.getKind()); 68 else if (SRE.getKind() != MCSymbolRefExpr::VK_None && 69 SRE.getKind() != MCSymbolRefExpr::VK_PPC_DARWIN_HA16 && 70 SRE.getKind() != MCSymbolRefExpr::VK_PPC_DARWIN_LO16) 71 OS << '@' << MCSymbolRefExpr::getVariantKindName(SRE.getKind()); 72 73 return; 74 } 75 76 case MCExpr::Unary: { 77 const MCUnaryExpr &UE = cast<MCUnaryExpr>(*this); 78 switch (UE.getOpcode()) { 79 case MCUnaryExpr::LNot: OS << '!'; break; 80 case MCUnaryExpr::Minus: OS << '-'; break; 81 case MCUnaryExpr::Not: OS << '~'; break; 82 case MCUnaryExpr::Plus: OS << '+'; break; 83 } 84 OS << *UE.getSubExpr(); 85 return; 86 } 87 88 case MCExpr::Binary: { 89 const MCBinaryExpr &BE = cast<MCBinaryExpr>(*this); 90 91 // Only print parens around the LHS if it is non-trivial. 92 if (isa<MCConstantExpr>(BE.getLHS()) || isa<MCSymbolRefExpr>(BE.getLHS())) { 93 OS << *BE.getLHS(); 94 } else { 95 OS << '(' << *BE.getLHS() << ')'; 96 } 97 98 switch (BE.getOpcode()) { 99 case MCBinaryExpr::Add: 100 // Print "X-42" instead of "X+-42". 101 if (const MCConstantExpr *RHSC = dyn_cast<MCConstantExpr>(BE.getRHS())) { 102 if (RHSC->getValue() < 0) { 103 OS << RHSC->getValue(); 104 return; 105 } 106 } 107 108 OS << '+'; 109 break; 110 case MCBinaryExpr::And: OS << '&'; break; 111 case MCBinaryExpr::Div: OS << '/'; break; 112 case MCBinaryExpr::EQ: OS << "=="; break; 113 case MCBinaryExpr::GT: OS << '>'; break; 114 case MCBinaryExpr::GTE: OS << ">="; break; 115 case MCBinaryExpr::LAnd: OS << "&&"; break; 116 case MCBinaryExpr::LOr: OS << "||"; break; 117 case MCBinaryExpr::LT: OS << '<'; break; 118 case MCBinaryExpr::LTE: OS << "<="; break; 119 case MCBinaryExpr::Mod: OS << '%'; break; 120 case MCBinaryExpr::Mul: OS << '*'; break; 121 case MCBinaryExpr::NE: OS << "!="; break; 122 case MCBinaryExpr::Or: OS << '|'; break; 123 case MCBinaryExpr::Shl: OS << "<<"; break; 124 case MCBinaryExpr::Shr: OS << ">>"; break; 125 case MCBinaryExpr::Sub: OS << '-'; break; 126 case MCBinaryExpr::Xor: OS << '^'; break; 127 } 128 129 // Only print parens around the LHS if it is non-trivial. 130 if (isa<MCConstantExpr>(BE.getRHS()) || isa<MCSymbolRefExpr>(BE.getRHS())) { 131 OS << *BE.getRHS(); 132 } else { 133 OS << '(' << *BE.getRHS() << ')'; 134 } 135 return; 136 } 137 } 138 139 llvm_unreachable("Invalid expression kind!"); 140 } 141 142 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 143 void MCExpr::dump() const { 144 print(dbgs()); 145 dbgs() << '\n'; 146 } 147 #endif 148 149 /* *** */ 150 151 const MCBinaryExpr *MCBinaryExpr::Create(Opcode Opc, const MCExpr *LHS, 152 const MCExpr *RHS, MCContext &Ctx) { 153 return new (Ctx) MCBinaryExpr(Opc, LHS, RHS); 154 } 155 156 const MCUnaryExpr *MCUnaryExpr::Create(Opcode Opc, const MCExpr *Expr, 157 MCContext &Ctx) { 158 return new (Ctx) MCUnaryExpr(Opc, Expr); 159 } 160 161 const MCConstantExpr *MCConstantExpr::Create(int64_t Value, MCContext &Ctx) { 162 return new (Ctx) MCConstantExpr(Value); 163 } 164 165 /* *** */ 166 167 const MCSymbolRefExpr *MCSymbolRefExpr::Create(const MCSymbol *Sym, 168 VariantKind Kind, 169 MCContext &Ctx) { 170 return new (Ctx) MCSymbolRefExpr(Sym, Kind); 171 } 172 173 const MCSymbolRefExpr *MCSymbolRefExpr::Create(StringRef Name, VariantKind Kind, 174 MCContext &Ctx) { 175 return Create(Ctx.GetOrCreateSymbol(Name), Kind, Ctx); 176 } 177 178 StringRef MCSymbolRefExpr::getVariantKindName(VariantKind Kind) { 179 switch (Kind) { 180 case VK_Invalid: return "<<invalid>>"; 181 case VK_None: return "<<none>>"; 182 183 case VK_GOT: return "GOT"; 184 case VK_GOTOFF: return "GOTOFF"; 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_DTPOFF: return "DTPOFF"; 196 case VK_TLVP: return "TLVP"; 197 case VK_SECREL: return "SECREL32"; 198 case VK_ARM_NONE: return "(NONE)"; 199 case VK_ARM_PLT: return "(PLT)"; 200 case VK_ARM_GOT: return "(GOT)"; 201 case VK_ARM_GOTOFF: return "(GOTOFF)"; 202 case VK_ARM_TPOFF: return "(tpoff)"; 203 case VK_ARM_GOTTPOFF: return "(gottpoff)"; 204 case VK_ARM_TLSGD: return "(tlsgd)"; 205 case VK_ARM_TARGET1: return "(target1)"; 206 case VK_ARM_TARGET2: return "(target2)"; 207 case VK_ARM_PREL31: return "(prel31)"; 208 case VK_PPC_TOC: return "tocbase"; 209 case VK_PPC_TOC_ENTRY: return "toc"; 210 case VK_PPC_DARWIN_HA16: return "ha16"; 211 case VK_PPC_DARWIN_LO16: return "lo16"; 212 case VK_PPC_GAS_HA16: return "ha"; 213 case VK_PPC_GAS_LO16: return "l"; 214 case VK_PPC_TPREL16_HA: return "tprel@ha"; 215 case VK_PPC_TPREL16_LO: return "tprel@l"; 216 case VK_PPC_DTPREL16_HA: return "dtprel@ha"; 217 case VK_PPC_DTPREL16_LO: return "dtprel@l"; 218 case VK_PPC_TOC16_HA: return "toc@ha"; 219 case VK_PPC_TOC16_LO: return "toc@l"; 220 case VK_PPC_GOT_TPREL16_HA: return "got@tprel@ha"; 221 case VK_PPC_GOT_TPREL16_LO: return "got@tprel@l"; 222 case VK_PPC_TLS: return "tls"; 223 case VK_PPC_GOT_TLSGD16_HA: return "got@tlsgd@ha"; 224 case VK_PPC_GOT_TLSGD16_LO: return "got@tlsgd@l"; 225 case VK_PPC_GOT_TLSLD16_HA: return "got@tlsld@ha"; 226 case VK_PPC_GOT_TLSLD16_LO: return "got@tlsld@l"; 227 case VK_PPC_TLSGD: return "tlsgd"; 228 case VK_PPC_TLSLD: return "tlsld"; 229 case VK_Mips_GPREL: return "GPREL"; 230 case VK_Mips_GOT_CALL: return "GOT_CALL"; 231 case VK_Mips_GOT16: return "GOT16"; 232 case VK_Mips_GOT: return "GOT"; 233 case VK_Mips_ABS_HI: return "ABS_HI"; 234 case VK_Mips_ABS_LO: return "ABS_LO"; 235 case VK_Mips_TLSGD: return "TLSGD"; 236 case VK_Mips_TLSLDM: return "TLSLDM"; 237 case VK_Mips_DTPREL_HI: return "DTPREL_HI"; 238 case VK_Mips_DTPREL_LO: return "DTPREL_LO"; 239 case VK_Mips_GOTTPREL: return "GOTTPREL"; 240 case VK_Mips_TPREL_HI: return "TPREL_HI"; 241 case VK_Mips_TPREL_LO: return "TPREL_LO"; 242 case VK_Mips_GPOFF_HI: return "GPOFF_HI"; 243 case VK_Mips_GPOFF_LO: return "GPOFF_LO"; 244 case VK_Mips_GOT_DISP: return "GOT_DISP"; 245 case VK_Mips_GOT_PAGE: return "GOT_PAGE"; 246 case VK_Mips_GOT_OFST: return "GOT_OFST"; 247 case VK_Mips_HIGHER: return "HIGHER"; 248 case VK_Mips_HIGHEST: return "HIGHEST"; 249 case VK_Mips_GOT_HI16: return "GOT_HI16"; 250 case VK_Mips_GOT_LO16: return "GOT_LO16"; 251 case VK_Mips_CALL_HI16: return "CALL_HI16"; 252 case VK_Mips_CALL_LO16: return "CALL_LO16"; 253 case VK_COFF_IMGREL32: return "IMGREL32"; 254 } 255 llvm_unreachable("Invalid variant kind"); 256 } 257 258 MCSymbolRefExpr::VariantKind 259 MCSymbolRefExpr::getVariantKindForName(StringRef Name) { 260 return StringSwitch<VariantKind>(Name) 261 .Case("GOT", VK_GOT) 262 .Case("got", VK_GOT) 263 .Case("GOTOFF", VK_GOTOFF) 264 .Case("gotoff", VK_GOTOFF) 265 .Case("GOTPCREL", VK_GOTPCREL) 266 .Case("gotpcrel", VK_GOTPCREL) 267 .Case("GOTTPOFF", VK_GOTTPOFF) 268 .Case("gottpoff", VK_GOTTPOFF) 269 .Case("INDNTPOFF", VK_INDNTPOFF) 270 .Case("indntpoff", VK_INDNTPOFF) 271 .Case("NTPOFF", VK_NTPOFF) 272 .Case("ntpoff", VK_NTPOFF) 273 .Case("GOTNTPOFF", VK_GOTNTPOFF) 274 .Case("gotntpoff", VK_GOTNTPOFF) 275 .Case("PLT", VK_PLT) 276 .Case("plt", VK_PLT) 277 .Case("TLSGD", VK_TLSGD) 278 .Case("tlsgd", VK_TLSGD) 279 .Case("TLSLD", VK_TLSLD) 280 .Case("tlsld", VK_TLSLD) 281 .Case("TLSLDM", VK_TLSLDM) 282 .Case("tlsldm", VK_TLSLDM) 283 .Case("TPOFF", VK_TPOFF) 284 .Case("tpoff", VK_TPOFF) 285 .Case("DTPOFF", VK_DTPOFF) 286 .Case("dtpoff", VK_DTPOFF) 287 .Case("TLVP", VK_TLVP) 288 .Case("tlvp", VK_TLVP) 289 .Case("IMGREL", VK_COFF_IMGREL32) 290 .Case("imgrel", VK_COFF_IMGREL32) 291 .Case("SECREL32", VK_SECREL) 292 .Case("secrel32", VK_SECREL) 293 .Case("HA", VK_PPC_GAS_HA16) 294 .Case("ha", VK_PPC_GAS_HA16) 295 .Case("L", VK_PPC_GAS_LO16) 296 .Case("l", VK_PPC_GAS_LO16) 297 .Case("TOCBASE", VK_PPC_TOC) 298 .Case("tocbase", VK_PPC_TOC) 299 .Case("TOC", VK_PPC_TOC_ENTRY) 300 .Case("toc", VK_PPC_TOC_ENTRY) 301 .Case("TOC@HA", VK_PPC_TOC16_HA) 302 .Case("toc@ha", VK_PPC_TOC16_HA) 303 .Case("TOC@L", VK_PPC_TOC16_LO) 304 .Case("toc@l", VK_PPC_TOC16_LO) 305 .Case("TLS", VK_PPC_TLS) 306 .Case("tls", VK_PPC_TLS) 307 .Case("TPREL@HA", VK_PPC_TPREL16_HA) 308 .Case("tprel@ha", VK_PPC_TPREL16_HA) 309 .Case("TPREL@L", VK_PPC_TPREL16_LO) 310 .Case("tprel@l", VK_PPC_TPREL16_LO) 311 .Case("DTPREL@HA", VK_PPC_DTPREL16_HA) 312 .Case("dtprel@ha", VK_PPC_DTPREL16_HA) 313 .Case("DTPREL@L", VK_PPC_DTPREL16_LO) 314 .Case("dtprel@l", VK_PPC_DTPREL16_LO) 315 .Case("GOT@TPREL@HA", VK_PPC_GOT_TPREL16_HA) 316 .Case("got@tprel@ha", VK_PPC_GOT_TPREL16_HA) 317 .Case("GOT@TPREL@L", VK_PPC_GOT_TPREL16_LO) 318 .Case("got@tprel@l", VK_PPC_GOT_TPREL16_LO) 319 .Case("GOT@TLSGD@HA", VK_PPC_GOT_TLSGD16_HA) 320 .Case("got@tlsgd@ha", VK_PPC_GOT_TLSGD16_HA) 321 .Case("GOT@TLSGD@L", VK_PPC_GOT_TLSGD16_LO) 322 .Case("got@tlsgd@l", VK_PPC_GOT_TLSGD16_LO) 323 .Case("GOT@TLSLD@HA", VK_PPC_GOT_TLSLD16_HA) 324 .Case("got@tlsld@ha", VK_PPC_GOT_TLSLD16_HA) 325 .Case("GOT@TLSLD@L", VK_PPC_GOT_TLSLD16_LO) 326 .Case("got@tlsld@l", VK_PPC_GOT_TLSLD16_LO) 327 .Default(VK_Invalid); 328 } 329 330 /* *** */ 331 332 void MCTargetExpr::anchor() {} 333 334 /* *** */ 335 336 bool MCExpr::EvaluateAsAbsolute(int64_t &Res) const { 337 return EvaluateAsAbsolute(Res, 0, 0, 0); 338 } 339 340 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, 341 const MCAsmLayout &Layout) const { 342 return EvaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, 0); 343 } 344 345 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, 346 const MCAsmLayout &Layout, 347 const SectionAddrMap &Addrs) const { 348 return EvaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, &Addrs); 349 } 350 351 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const { 352 return EvaluateAsAbsolute(Res, &Asm, 0, 0); 353 } 354 355 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm, 356 const MCAsmLayout *Layout, 357 const SectionAddrMap *Addrs) const { 358 MCValue Value; 359 360 // Fast path constants. 361 if (const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(this)) { 362 Res = CE->getValue(); 363 return true; 364 } 365 366 // FIXME: The use if InSet = Addrs is a hack. Setting InSet causes us 367 // absolutize differences across sections and that is what the MachO writer 368 // uses Addrs for. 369 bool IsRelocatable = 370 EvaluateAsRelocatableImpl(Value, Asm, Layout, Addrs, /*InSet*/ Addrs); 371 372 // Record the current value. 373 Res = Value.getConstant(); 374 375 return IsRelocatable && Value.isAbsolute(); 376 } 377 378 /// \brief Helper method for \see EvaluateSymbolAdd(). 379 static void AttemptToFoldSymbolOffsetDifference(const MCAssembler *Asm, 380 const MCAsmLayout *Layout, 381 const SectionAddrMap *Addrs, 382 bool InSet, 383 const MCSymbolRefExpr *&A, 384 const MCSymbolRefExpr *&B, 385 int64_t &Addend) { 386 if (!A || !B) 387 return; 388 389 const MCSymbol &SA = A->getSymbol(); 390 const MCSymbol &SB = B->getSymbol(); 391 392 if (SA.isUndefined() || SB.isUndefined()) 393 return; 394 395 if (!Asm->getWriter().IsSymbolRefDifferenceFullyResolved(*Asm, A, B, InSet)) 396 return; 397 398 MCSymbolData &AD = Asm->getSymbolData(SA); 399 MCSymbolData &BD = Asm->getSymbolData(SB); 400 401 if (AD.getFragment() == BD.getFragment()) { 402 Addend += (AD.getOffset() - BD.getOffset()); 403 404 // Pointers to Thumb symbols need to have their low-bit set to allow 405 // for interworking. 406 if (Asm->isThumbFunc(&SA)) 407 Addend |= 1; 408 409 // Clear the symbol expr pointers to indicate we have folded these 410 // operands. 411 A = B = 0; 412 return; 413 } 414 415 if (!Layout) 416 return; 417 418 const MCSectionData &SecA = *AD.getFragment()->getParent(); 419 const MCSectionData &SecB = *BD.getFragment()->getParent(); 420 421 if ((&SecA != &SecB) && !Addrs) 422 return; 423 424 // Eagerly evaluate. 425 Addend += (Layout->getSymbolOffset(&Asm->getSymbolData(A->getSymbol())) - 426 Layout->getSymbolOffset(&Asm->getSymbolData(B->getSymbol()))); 427 if (Addrs && (&SecA != &SecB)) 428 Addend += (Addrs->lookup(&SecA) - Addrs->lookup(&SecB)); 429 430 // Pointers to Thumb symbols need to have their low-bit set to allow 431 // for interworking. 432 if (Asm->isThumbFunc(&SA)) 433 Addend |= 1; 434 435 // Clear the symbol expr pointers to indicate we have folded these 436 // operands. 437 A = B = 0; 438 } 439 440 /// \brief Evaluate the result of an add between (conceptually) two MCValues. 441 /// 442 /// This routine conceptually attempts to construct an MCValue: 443 /// Result = (Result_A - Result_B + Result_Cst) 444 /// from two MCValue's LHS and RHS where 445 /// Result = LHS + RHS 446 /// and 447 /// Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst). 448 /// 449 /// This routine attempts to aggresively fold the operands such that the result 450 /// is representable in an MCValue, but may not always succeed. 451 /// 452 /// \returns True on success, false if the result is not representable in an 453 /// MCValue. 454 455 /// NOTE: It is really important to have both the Asm and Layout arguments. 456 /// They might look redundant, but this function can be used before layout 457 /// is done (see the object streamer for example) and having the Asm argument 458 /// lets us avoid relaxations early. 459 static bool EvaluateSymbolicAdd(const MCAssembler *Asm, 460 const MCAsmLayout *Layout, 461 const SectionAddrMap *Addrs, 462 bool InSet, 463 const MCValue &LHS,const MCSymbolRefExpr *RHS_A, 464 const MCSymbolRefExpr *RHS_B, int64_t RHS_Cst, 465 MCValue &Res) { 466 // FIXME: This routine (and other evaluation parts) are *incredibly* sloppy 467 // about dealing with modifiers. This will ultimately bite us, one day. 468 const MCSymbolRefExpr *LHS_A = LHS.getSymA(); 469 const MCSymbolRefExpr *LHS_B = LHS.getSymB(); 470 int64_t LHS_Cst = LHS.getConstant(); 471 472 // Fold the result constant immediately. 473 int64_t Result_Cst = LHS_Cst + RHS_Cst; 474 475 assert((!Layout || Asm) && 476 "Must have an assembler object if layout is given!"); 477 478 // If we have a layout, we can fold resolved differences. 479 if (Asm) { 480 // First, fold out any differences which are fully resolved. By 481 // reassociating terms in 482 // Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst). 483 // we have the four possible differences: 484 // (LHS_A - LHS_B), 485 // (LHS_A - RHS_B), 486 // (RHS_A - LHS_B), 487 // (RHS_A - RHS_B). 488 // Since we are attempting to be as aggressive as possible about folding, we 489 // attempt to evaluate each possible alternative. 490 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, LHS_B, 491 Result_Cst); 492 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, RHS_B, 493 Result_Cst); 494 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, LHS_B, 495 Result_Cst); 496 AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, RHS_B, 497 Result_Cst); 498 } 499 500 // We can't represent the addition or subtraction of two symbols. 501 if ((LHS_A && RHS_A) || (LHS_B && RHS_B)) 502 return false; 503 504 // At this point, we have at most one additive symbol and one subtractive 505 // symbol -- find them. 506 const MCSymbolRefExpr *A = LHS_A ? LHS_A : RHS_A; 507 const MCSymbolRefExpr *B = LHS_B ? LHS_B : RHS_B; 508 509 // If we have a negated symbol, then we must have also have a non-negated 510 // symbol in order to encode the expression. 511 if (B && !A) 512 return false; 513 514 Res = MCValue::get(A, B, Result_Cst); 515 return true; 516 } 517 518 bool MCExpr::EvaluateAsRelocatable(MCValue &Res, 519 const MCAsmLayout &Layout) const { 520 return EvaluateAsRelocatableImpl(Res, &Layout.getAssembler(), &Layout, 521 0, false); 522 } 523 524 bool MCExpr::EvaluateAsRelocatableImpl(MCValue &Res, 525 const MCAssembler *Asm, 526 const MCAsmLayout *Layout, 527 const SectionAddrMap *Addrs, 528 bool InSet) const { 529 ++stats::MCExprEvaluate; 530 531 switch (getKind()) { 532 case Target: 533 return cast<MCTargetExpr>(this)->EvaluateAsRelocatableImpl(Res, Layout); 534 535 case Constant: 536 Res = MCValue::get(cast<MCConstantExpr>(this)->getValue()); 537 return true; 538 539 case SymbolRef: { 540 const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this); 541 const MCSymbol &Sym = SRE->getSymbol(); 542 543 // Evaluate recursively if this is a variable. 544 if (Sym.isVariable() && SRE->getKind() == MCSymbolRefExpr::VK_None) { 545 bool Ret = Sym.getVariableValue()->EvaluateAsRelocatableImpl(Res, Asm, 546 Layout, 547 Addrs, 548 true); 549 // If we failed to simplify this to a constant, let the target 550 // handle it. 551 if (Ret && !Res.getSymA() && !Res.getSymB()) 552 return true; 553 } 554 555 Res = MCValue::get(SRE, 0, 0); 556 return true; 557 } 558 559 case Unary: { 560 const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this); 561 MCValue Value; 562 563 if (!AUE->getSubExpr()->EvaluateAsRelocatableImpl(Value, Asm, Layout, 564 Addrs, InSet)) 565 return false; 566 567 switch (AUE->getOpcode()) { 568 case MCUnaryExpr::LNot: 569 if (!Value.isAbsolute()) 570 return false; 571 Res = MCValue::get(!Value.getConstant()); 572 break; 573 case MCUnaryExpr::Minus: 574 /// -(a - b + const) ==> (b - a - const) 575 if (Value.getSymA() && !Value.getSymB()) 576 return false; 577 Res = MCValue::get(Value.getSymB(), Value.getSymA(), 578 -Value.getConstant()); 579 break; 580 case MCUnaryExpr::Not: 581 if (!Value.isAbsolute()) 582 return false; 583 Res = MCValue::get(~Value.getConstant()); 584 break; 585 case MCUnaryExpr::Plus: 586 Res = Value; 587 break; 588 } 589 590 return true; 591 } 592 593 case Binary: { 594 const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this); 595 MCValue LHSValue, RHSValue; 596 597 if (!ABE->getLHS()->EvaluateAsRelocatableImpl(LHSValue, Asm, Layout, 598 Addrs, InSet) || 599 !ABE->getRHS()->EvaluateAsRelocatableImpl(RHSValue, Asm, Layout, 600 Addrs, InSet)) 601 return false; 602 603 // We only support a few operations on non-constant expressions, handle 604 // those first. 605 if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) { 606 switch (ABE->getOpcode()) { 607 default: 608 return false; 609 case MCBinaryExpr::Sub: 610 // Negate RHS and add. 611 return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue, 612 RHSValue.getSymB(), RHSValue.getSymA(), 613 -RHSValue.getConstant(), 614 Res); 615 616 case MCBinaryExpr::Add: 617 return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue, 618 RHSValue.getSymA(), RHSValue.getSymB(), 619 RHSValue.getConstant(), 620 Res); 621 } 622 } 623 624 // FIXME: We need target hooks for the evaluation. It may be limited in 625 // width, and gas defines the result of comparisons and right shifts 626 // differently from Apple as. 627 int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant(); 628 int64_t Result = 0; 629 switch (ABE->getOpcode()) { 630 case MCBinaryExpr::Add: Result = LHS + RHS; break; 631 case MCBinaryExpr::And: Result = LHS & RHS; break; 632 case MCBinaryExpr::Div: Result = LHS / RHS; break; 633 case MCBinaryExpr::EQ: Result = LHS == RHS; break; 634 case MCBinaryExpr::GT: Result = LHS > RHS; break; 635 case MCBinaryExpr::GTE: Result = LHS >= RHS; break; 636 case MCBinaryExpr::LAnd: Result = LHS && RHS; break; 637 case MCBinaryExpr::LOr: Result = LHS || RHS; break; 638 case MCBinaryExpr::LT: Result = LHS < RHS; break; 639 case MCBinaryExpr::LTE: Result = LHS <= RHS; break; 640 case MCBinaryExpr::Mod: Result = LHS % RHS; break; 641 case MCBinaryExpr::Mul: Result = LHS * RHS; break; 642 case MCBinaryExpr::NE: Result = LHS != RHS; break; 643 case MCBinaryExpr::Or: Result = LHS | RHS; break; 644 case MCBinaryExpr::Shl: Result = LHS << RHS; break; 645 case MCBinaryExpr::Shr: Result = LHS >> RHS; break; 646 case MCBinaryExpr::Sub: Result = LHS - RHS; break; 647 case MCBinaryExpr::Xor: Result = LHS ^ RHS; break; 648 } 649 650 Res = MCValue::get(Result); 651 return true; 652 } 653 } 654 655 llvm_unreachable("Invalid assembly expression kind!"); 656 } 657 658 const MCSection *MCExpr::FindAssociatedSection() const { 659 switch (getKind()) { 660 case Target: 661 // We never look through target specific expressions. 662 return cast<MCTargetExpr>(this)->FindAssociatedSection(); 663 664 case Constant: 665 return MCSymbol::AbsolutePseudoSection; 666 667 case SymbolRef: { 668 const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this); 669 const MCSymbol &Sym = SRE->getSymbol(); 670 671 if (Sym.isDefined()) 672 return &Sym.getSection(); 673 674 return 0; 675 } 676 677 case Unary: 678 return cast<MCUnaryExpr>(this)->getSubExpr()->FindAssociatedSection(); 679 680 case Binary: { 681 const MCBinaryExpr *BE = cast<MCBinaryExpr>(this); 682 const MCSection *LHS_S = BE->getLHS()->FindAssociatedSection(); 683 const MCSection *RHS_S = BE->getRHS()->FindAssociatedSection(); 684 685 // If either section is absolute, return the other. 686 if (LHS_S == MCSymbol::AbsolutePseudoSection) 687 return RHS_S; 688 if (RHS_S == MCSymbol::AbsolutePseudoSection) 689 return LHS_S; 690 691 // Otherwise, return the first non-null section. 692 return LHS_S ? LHS_S : RHS_S; 693 } 694 } 695 696 llvm_unreachable("Invalid assembly expression kind!"); 697 } 698