lib/MC/MCExpr.cpp

   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/MCObjectFormat.h"
  18 #include "llvm/MC/MCSymbol.h"
  19 #include "llvm/MC/MCValue.h"
  20 #include "llvm/Support/Debug.h"
  21 #include "llvm/Support/raw_ostream.h"
  22 #include "llvm/Target/TargetAsmBackend.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
  43     if (SRE.getKind() == MCSymbolRefExpr::VK_ARM_HI16 ||
  44         SRE.getKind() == MCSymbolRefExpr::VK_ARM_LO16)
  45       OS << MCSymbolRefExpr::getVariantKindName(SRE.getKind());
  46
  47     // Parenthesize names that start with $ so that they don't look like
  48     // absolute names.
  49     if (Sym.getName()[0] == '$')
  50       OS << '(' << Sym << ')';
  51     else
  52       OS << Sym;
  53
  54     if (SRE.getKind() == MCSymbolRefExpr::VK_ARM_PLT)
  55       OS << MCSymbolRefExpr::getVariantKindName(SRE.getKind());
  56     else if (SRE.getKind() != MCSymbolRefExpr::VK_None &&
  57              SRE.getKind() != MCSymbolRefExpr::VK_ARM_HI16 &&
  58              SRE.getKind() != MCSymbolRefExpr::VK_ARM_LO16)
  59       OS << '@' << MCSymbolRefExpr::getVariantKindName(SRE.getKind());
  60
  61     return;
  62   }
  63
  64   case MCExpr::Unary: {
  65     const MCUnaryExpr &UE = cast<MCUnaryExpr>(*this);
  66     switch (UE.getOpcode()) {
  67     default: assert(0 && "Invalid opcode!");
  68     case MCUnaryExpr::LNot:  OS << '!'; break;
  69     case MCUnaryExpr::Minus: OS << '-'; break;
  70     case MCUnaryExpr::Not:   OS << '~'; break;
  71     case MCUnaryExpr::Plus:  OS << '+'; break;
  72     }
  73     OS << *UE.getSubExpr();
  74     return;
  75   }
  76
  77   case MCExpr::Binary: {
  78     const MCBinaryExpr &BE = cast<MCBinaryExpr>(*this);
  79
  80     // Only print parens around the LHS if it is non-trivial.
  81     if (isa<MCConstantExpr>(BE.getLHS()) || isa<MCSymbolRefExpr>(BE.getLHS())) {
  82       OS << *BE.getLHS();
  83     } else {
  84       OS << '(' << *BE.getLHS() << ')';
  85     }
  86
  87     switch (BE.getOpcode()) {
  88     default: assert(0 && "Invalid opcode!");
  89     case MCBinaryExpr::Add:
  90       // Print "X-42" instead of "X+-42".
  91       if (const MCConstantExpr *RHSC = dyn_cast<MCConstantExpr>(BE.getRHS())) {
  92         if (RHSC->getValue() < 0) {
  93           OS << RHSC->getValue();
  94           return;
  95         }
  96       }
  97
  98       OS <<  '+';
  99       break;
 100     case MCBinaryExpr::And:  OS <<  '&'; break;
 101     case MCBinaryExpr::Div:  OS <<  '/'; break;
 102     case MCBinaryExpr::EQ:   OS << "=="; break;
 103     case MCBinaryExpr::GT:   OS <<  '>'; break;
 104     case MCBinaryExpr::GTE:  OS << ">="; break;
 105     case MCBinaryExpr::LAnd: OS << "&&"; break;
 106     case MCBinaryExpr::LOr:  OS << "||"; break;
 107     case MCBinaryExpr::LT:   OS <<  '<'; break;
 108     case MCBinaryExpr::LTE:  OS << "<="; break;
 109     case MCBinaryExpr::Mod:  OS <<  '%'; break;
 110     case MCBinaryExpr::Mul:  OS <<  '*'; break;
 111     case MCBinaryExpr::NE:   OS << "!="; break;
 112     case MCBinaryExpr::Or:   OS <<  '|'; break;
 113     case MCBinaryExpr::Shl:  OS << "<<"; break;
 114     case MCBinaryExpr::Shr:  OS << ">>"; break;
 115     case MCBinaryExpr::Sub:  OS <<  '-'; break;
 116     case MCBinaryExpr::Xor:  OS <<  '^'; break;
 117     }
 118
 119     // Only print parens around the LHS if it is non-trivial.
 120     if (isa<MCConstantExpr>(BE.getRHS()) || isa<MCSymbolRefExpr>(BE.getRHS())) {
 121       OS << *BE.getRHS();
 122     } else {
 123       OS << '(' << *BE.getRHS() << ')';
 124     }
 125     return;
 126   }
 127   }
 128
 129   assert(0 && "Invalid expression kind!");
 130 }
 131
 132 void MCExpr::dump() const {
 133   print(dbgs());
 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 const MCSymbolRefExpr *MCSymbolRefExpr::Create(const MCSymbol *Sym,
 156                                                VariantKind Kind,
 157                                                MCContext &Ctx) {
 158   return new (Ctx) MCSymbolRefExpr(Sym, Kind);
 159 }
 160
 161 const MCSymbolRefExpr *MCSymbolRefExpr::Create(StringRef Name, VariantKind Kind,
 162                                                MCContext &Ctx) {
 163   return Create(Ctx.GetOrCreateSymbol(Name), Kind, Ctx);
 164 }
 165
 166 StringRef MCSymbolRefExpr::getVariantKindName(VariantKind Kind) {
 167   switch (Kind) {
 168   default:
 169   case VK_Invalid: return "<<invalid>>";
 170   case VK_None: return "<<none>>";
 171
 172   case VK_GOT: return "GOT";
 173   case VK_GOTOFF: return "GOTOFF";
 174   case VK_GOTPCREL: return "GOTPCREL";
 175   case VK_GOTTPOFF: return "GOTTPOFF";
 176   case VK_INDNTPOFF: return "INDNTPOFF";
 177   case VK_NTPOFF: return "NTPOFF";
 178   case VK_GOTNTPOFF: return "GOTNTPOFF";
 179   case VK_PLT: return "PLT";
 180   case VK_TLSGD: return "TLSGD";
 181   case VK_TLSLD: return "TLSLD";
 182   case VK_TLSLDM: return "TLSLDM";
 183   case VK_TPOFF: return "TPOFF";
 184   case VK_DTPOFF: return "DTPOFF";
 185   case VK_ARM_HI16: return ":upper16:";
 186   case VK_ARM_LO16: return ":lower16:";
 187   case VK_ARM_PLT: return "(PLT)";
 188   case VK_TLVP: return "TLVP";
 189   }
 190 }
 191
 192 MCSymbolRefExpr::VariantKind
 193 MCSymbolRefExpr::getVariantKindForName(StringRef Name) {
 194   return StringSwitch<VariantKind>(Name)
 195     .Case("GOT", VK_GOT)
 196     .Case("GOTOFF", VK_GOTOFF)
 197     .Case("GOTPCREL", VK_GOTPCREL)
 198     .Case("GOTTPOFF", VK_GOTTPOFF)
 199     .Case("INDNTPOFF", VK_INDNTPOFF)
 200     .Case("NTPOFF", VK_NTPOFF)
 201     .Case("GOTNTPOFF", VK_GOTNTPOFF)
 202     .Case("PLT", VK_PLT)
 203     .Case("TLSGD", VK_TLSGD)
 204     .Case("TLSLD", VK_TLSLD)
 205     .Case("TLSLDM", VK_TLSLDM)
 206     .Case("TPOFF", VK_TPOFF)
 207     .Case("DTPOFF", VK_DTPOFF)
 208     .Case("TLVP", VK_TLVP)
 209     .Default(VK_Invalid);
 210 }
 211
 212 /* *** */
 213
 214 void MCTargetExpr::Anchor() {}
 215
 216 /* *** */
 217
 218 bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAsmLayout *Layout) const {
 219   MCValue Value;
 220
 221   // Fast path constants.
 222   if (const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(this)) {
 223     Res = CE->getValue();
 224     return true;
 225   }
 226
 227   if (!EvaluateAsRelocatable(Value, Layout) || !Value.isAbsolute()) {
 228     // EvaluateAsAbsolute is defined to return the "current value" of
 229     // the expression if we are given a Layout object, even in cases
 230     // when the value is not fixed.
 231     if (Layout) {
 232       Res = Value.getConstant();
 233       if (Value.getSymA()) {
 234         Res += Layout->getSymbolAddress(
 235           &Layout->getAssembler().getSymbolData(Value.getSymA()->getSymbol()));
 236       }
 237       if (Value.getSymB()) {
 238         Res -= Layout->getSymbolAddress(
 239           &Layout->getAssembler().getSymbolData(Value.getSymB()->getSymbol()));
 240       }
 241     }
 242     return false;
 243   }
 244
 245   Res = Value.getConstant();
 246   return true;
 247 }
 248
 249 static bool EvaluateSymbolicAdd(const MCAsmLayout *Layout, bool InSet,
 250                                 const MCValue &LHS,const MCSymbolRefExpr *RHS_A,
 251                                 const MCSymbolRefExpr *RHS_B, int64_t RHS_Cst,
 252                                 MCValue &Res) {
 253   // We can't add or subtract two symbols.
 254   if ((LHS.getSymA() && RHS_A) ||
 255       (LHS.getSymB() && RHS_B))
 256     return false;
 257
 258   const MCSymbolRefExpr *A = LHS.getSymA() ? LHS.getSymA() : RHS_A;
 259   const MCSymbolRefExpr *B = LHS.getSymB() ? LHS.getSymB() : RHS_B;
 260   if (B) {
 261     // If we have a negated symbol, then we must have also have a non-negated
 262     // symbol in order to encode the expression. We can do this check later to
 263     // permit expressions which eventually fold to a representable form -- such
 264     // as (a + (0 - b)) -- if necessary.
 265     if (!A)
 266       return false;
 267   }
 268
 269   // Absolutize symbol differences between defined symbols when we have a
 270   // layout object and the target requests it.
 271
 272   if (Layout && A && B) {
 273     const MCSymbol &SA = A->getSymbol();
 274     const MCSymbol &SB = B->getSymbol();
 275     const MCObjectFormat &F =
 276       Layout->getAssembler().getBackend().getObjectFormat();
 277     if (SA.isDefined() && SB.isDefined() && F.isAbsolute(InSet, SA, SB)) {
 278       const MCAssembler &Asm = Layout->getAssembler();
 279       MCSymbolData &AD = Asm.getSymbolData(A->getSymbol());
 280       MCSymbolData &BD = Asm.getSymbolData(B->getSymbol());
 281       Res = MCValue::get(+ Layout->getSymbolAddress(&AD)
 282                          - Layout->getSymbolAddress(&BD)
 283                          + LHS.getConstant()
 284                          + RHS_Cst);
 285       return true;
 286     }
 287   }
 288
 289
 290   Res = MCValue::get(A, B, LHS.getConstant() + RHS_Cst);
 291   return true;
 292 }
 293
 294 bool MCExpr::EvaluateAsRelocatable(MCValue &Res,
 295                                    const MCAsmLayout *Layout) const {
 296   return EvaluateAsRelocatableImpl(Res, Layout, false);
 297 }
 298
 299 bool MCExpr::EvaluateAsRelocatableImpl(MCValue &Res,
 300                                        const MCAsmLayout *Layout,
 301                                        bool InSet) const {
 302   ++stats::MCExprEvaluate;
 303
 304   switch (getKind()) {
 305   case Target:
 306     return cast<MCTargetExpr>(this)->EvaluateAsRelocatableImpl(Res, Layout);
 307
 308   case Constant:
 309     Res = MCValue::get(cast<MCConstantExpr>(this)->getValue());
 310     return true;
 311
 312   case SymbolRef: {
 313     const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
 314     const MCSymbol &Sym = SRE->getSymbol();
 315
 316     // Evaluate recursively if this is a variable.
 317     if (Sym.isVariable() && SRE->getKind() == MCSymbolRefExpr::VK_None)
 318       return Sym.getVariableValue()->EvaluateAsRelocatableImpl(Res, Layout,
 319                                                                true);
 320
 321     Res = MCValue::get(SRE, 0, 0);
 322     return true;
 323   }
 324
 325   case Unary: {
 326     const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this);
 327     MCValue Value;
 328
 329     if (!AUE->getSubExpr()->EvaluateAsRelocatableImpl(Value, Layout, InSet))
 330       return false;
 331
 332     switch (AUE->getOpcode()) {
 333     case MCUnaryExpr::LNot:
 334       if (!Value.isAbsolute())
 335         return false;
 336       Res = MCValue::get(!Value.getConstant());
 337       break;
 338     case MCUnaryExpr::Minus:
 339       /// -(a - b + const) ==> (b - a - const)
 340       if (Value.getSymA() && !Value.getSymB())
 341         return false;
 342       Res = MCValue::get(Value.getSymB(), Value.getSymA(),
 343                          -Value.getConstant());
 344       break;
 345     case MCUnaryExpr::Not:
 346       if (!Value.isAbsolute())
 347         return false;
 348       Res = MCValue::get(~Value.getConstant());
 349       break;
 350     case MCUnaryExpr::Plus:
 351       Res = Value;
 352       break;
 353     }
 354
 355     return true;
 356   }
 357
 358   case Binary: {
 359     const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this);
 360     MCValue LHSValue, RHSValue;
 361
 362     if (!ABE->getLHS()->EvaluateAsRelocatableImpl(LHSValue, Layout, InSet) ||
 363         !ABE->getRHS()->EvaluateAsRelocatableImpl(RHSValue, Layout, InSet))
 364       return false;
 365
 366     // We only support a few operations on non-constant expressions, handle
 367     // those first.
 368     if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) {
 369       switch (ABE->getOpcode()) {
 370       default:
 371         return false;
 372       case MCBinaryExpr::Sub:
 373         // Negate RHS and add.
 374         return EvaluateSymbolicAdd(Layout, InSet, LHSValue,
 375                                    RHSValue.getSymB(), RHSValue.getSymA(),
 376                                    -RHSValue.getConstant(),
 377                                    Res);
 378
 379       case MCBinaryExpr::Add:
 380         return EvaluateSymbolicAdd(Layout, InSet, LHSValue,
 381                                    RHSValue.getSymA(), RHSValue.getSymB(),
 382                                    RHSValue.getConstant(),
 383                                    Res);
 384       }
 385     }
 386
 387     // FIXME: We need target hooks for the evaluation. It may be limited in
 388     // width, and gas defines the result of comparisons and right shifts
 389     // differently from Apple as.
 390     int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant();
 391     int64_t Result = 0;
 392     switch (ABE->getOpcode()) {
 393     case MCBinaryExpr::Add:  Result = LHS + RHS; break;
 394     case MCBinaryExpr::And:  Result = LHS & RHS; break;
 395     case MCBinaryExpr::Div:  Result = LHS / RHS; break;
 396     case MCBinaryExpr::EQ:   Result = LHS == RHS; break;
 397     case MCBinaryExpr::GT:   Result = LHS > RHS; break;
 398     case MCBinaryExpr::GTE:  Result = LHS >= RHS; break;
 399     case MCBinaryExpr::LAnd: Result = LHS && RHS; break;
 400     case MCBinaryExpr::LOr:  Result = LHS || RHS; break;
 401     case MCBinaryExpr::LT:   Result = LHS < RHS; break;
 402     case MCBinaryExpr::LTE:  Result = LHS <= RHS; break;
 403     case MCBinaryExpr::Mod:  Result = LHS % RHS; break;
 404     case MCBinaryExpr::Mul:  Result = LHS * RHS; break;
 405     case MCBinaryExpr::NE:   Result = LHS != RHS; break;
 406     case MCBinaryExpr::Or:   Result = LHS | RHS; break;
 407     case MCBinaryExpr::Shl:  Result = LHS << RHS; break;
 408     case MCBinaryExpr::Shr:  Result = LHS >> RHS; break;
 409     case MCBinaryExpr::Sub:  Result = LHS - RHS; break;
 410     case MCBinaryExpr::Xor:  Result = LHS ^ RHS; break;
 411     }
 412
 413     Res = MCValue::get(Result);
 414     return true;
 415   }
 416   }
 417
 418   assert(0 && "Invalid assembly expression kind!");
 419   return false;
 420 }