llvm/lib/MC/MCFragment.cpp

   1 //===- lib/MC/MCFragment.cpp - Assembler Fragment Implementation ----------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "llvm/MC/MCFragment.h"
  10 #include "llvm/ADT/SmallVector.h"
  11 #include "llvm/ADT/StringExtras.h"
  12 #include "llvm/ADT/Twine.h"
  13 #include "llvm/Config/llvm-config.h"
  14 #include "llvm/MC/MCAsmLayout.h"
  15 #include "llvm/MC/MCAssembler.h"
  16 #include "llvm/MC/MCContext.h"
  17 #include "llvm/MC/MCExpr.h"
  18 #include "llvm/MC/MCFixup.h"
  19 #include "llvm/MC/MCSection.h"
  20 #include "llvm/MC/MCSymbol.h"
  21 #include "llvm/MC/MCValue.h"
  22 #include "llvm/Support/Casting.h"
  23 #include "llvm/Support/Compiler.h"
  24 #include "llvm/Support/ErrorHandling.h"
  25 #include "llvm/Support/raw_ostream.h"
  26 #include <cassert>
  27 #include <cstdint>
  28 #include <utility>
  29
  30 using namespace llvm;
  31
  32 MCAsmLayout::MCAsmLayout(MCAssembler &Asm) : Assembler(Asm) {
  33   // Compute the section layout order. Virtual sections must go last.
  34   for (MCSection &Sec : Asm)
  35     if (!Sec.isVirtualSection())
  36       SectionOrder.push_back(&Sec);
  37   for (MCSection &Sec : Asm)
  38     if (Sec.isVirtualSection())
  39       SectionOrder.push_back(&Sec);
  40 }
  41
  42 bool MCAsmLayout::isFragmentValid(const MCFragment *F) const {
  43   const MCSection *Sec = F->getParent();
  44   const MCFragment *LastValid = LastValidFragment.lookup(Sec);
  45   if (!LastValid)
  46     return false;
  47   assert(LastValid->getParent() == Sec);
  48   return F->getLayoutOrder() <= LastValid->getLayoutOrder();
  49 }
  50
  51 bool MCAsmLayout::canGetFragmentOffset(const MCFragment *F) const {
  52   MCSection *Sec = F->getParent();
  53   MCSection::iterator I;
  54   if (MCFragment *LastValid = LastValidFragment[Sec]) {
  55     // Fragment already valid, offset is available.
  56     if (F->getLayoutOrder() <= LastValid->getLayoutOrder())
  57       return true;
  58     I = ++MCSection::iterator(LastValid);
  59   } else
  60     I = Sec->begin();
  61
  62   // A fragment ordered before F is currently being laid out.
  63   const MCFragment *FirstInvalidFragment = &*I;
  64   if (FirstInvalidFragment->IsBeingLaidOut)
  65     return false;
  66
  67   return true;
  68 }
  69
  70 void MCAsmLayout::invalidateFragmentsFrom(MCFragment *F) {
  71   // If this fragment wasn't already valid, we don't need to do anything.
  72   if (!isFragmentValid(F))
  73     return;
  74
  75   // Otherwise, reset the last valid fragment to the previous fragment
  76   // (if this is the first fragment, it will be NULL).
  77   LastValidFragment[F->getParent()] = F->getPrevNode();
  78 }
  79
  80 void MCAsmLayout::ensureValid(const MCFragment *F) const {
  81   MCSection *Sec = F->getParent();
  82   MCSection::iterator I;
  83   if (MCFragment *Cur = LastValidFragment[Sec])
  84     I = ++MCSection::iterator(Cur);
  85   else
  86     I = Sec->begin();
  87
  88   // Advance the layout position until the fragment is valid.
  89   while (!isFragmentValid(F)) {
  90     assert(I != Sec->end() && "Layout bookkeeping error");
  91     const_cast<MCAsmLayout *>(this)->layoutFragment(&*I);
  92     ++I;
  93   }
  94 }
  95
  96 uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
  97   ensureValid(F);
  98   assert(F->Offset != ~UINT64_C(0) && "Address not set!");
  99   return F->Offset;
 100 }
 101
 102 // Simple getSymbolOffset helper for the non-variable case.
 103 static bool getLabelOffset(const MCAsmLayout &Layout, const MCSymbol &S,
 104                            bool ReportError, uint64_t &Val) {
 105   if (!S.getFragment()) {
 106     if (ReportError)
 107       report_fatal_error("unable to evaluate offset to undefined symbol '" +
 108                          S.getName() + "'");
 109     return false;
 110   }
 111   Val = Layout.getFragmentOffset(S.getFragment()) + S.getOffset();
 112   return true;
 113 }
 114
 115 static bool getSymbolOffsetImpl(const MCAsmLayout &Layout, const MCSymbol &S,
 116                                 bool ReportError, uint64_t &Val) {
 117   if (!S.isVariable())
 118     return getLabelOffset(Layout, S, ReportError, Val);
 119
 120   // If SD is a variable, evaluate it.
 121   MCValue Target;
 122   if (!S.getVariableValue()->evaluateAsValue(Target, Layout))
 123     report_fatal_error("unable to evaluate offset for variable '" +
 124                        S.getName() + "'");
 125
 126   uint64_t Offset = Target.getConstant();
 127
 128   const MCSymbolRefExpr *A = Target.getSymA();
 129   if (A) {
 130     uint64_t ValA;
 131     if (!getLabelOffset(Layout, A->getSymbol(), ReportError, ValA))
 132       return false;
 133     Offset += ValA;
 134   }
 135
 136   const MCSymbolRefExpr *B = Target.getSymB();
 137   if (B) {
 138     uint64_t ValB;
 139     if (!getLabelOffset(Layout, B->getSymbol(), ReportError, ValB))
 140       return false;
 141     Offset -= ValB;
 142   }
 143
 144   Val = Offset;
 145   return true;
 146 }
 147
 148 bool MCAsmLayout::getSymbolOffset(const MCSymbol &S, uint64_t &Val) const {
 149   return getSymbolOffsetImpl(*this, S, false, Val);
 150 }
 151
 152 uint64_t MCAsmLayout::getSymbolOffset(const MCSymbol &S) const {
 153   uint64_t Val;
 154   getSymbolOffsetImpl(*this, S, true, Val);
 155   return Val;
 156 }
 157
 158 const MCSymbol *MCAsmLayout::getBaseSymbol(const MCSymbol &Symbol) const {
 159   if (!Symbol.isVariable())
 160     return &Symbol;
 161
 162   const MCExpr *Expr = Symbol.getVariableValue();
 163   MCValue Value;
 164   if (!Expr->evaluateAsValue(Value, *this)) {
 165     Assembler.getContext().reportError(
 166         Expr->getLoc(), "expression could not be evaluated");
 167     return nullptr;
 168   }
 169
 170   const MCSymbolRefExpr *RefB = Value.getSymB();
 171   if (RefB) {
 172     Assembler.getContext().reportError(
 173         Expr->getLoc(), Twine("symbol '") + RefB->getSymbol().getName() +
 174                      "' could not be evaluated in a subtraction expression");
 175     return nullptr;
 176   }
 177
 178   const MCSymbolRefExpr *A = Value.getSymA();
 179   if (!A)
 180     return nullptr;
 181
 182   const MCSymbol &ASym = A->getSymbol();
 183   const MCAssembler &Asm = getAssembler();
 184   if (ASym.isCommon()) {
 185     Asm.getContext().reportError(Expr->getLoc(),
 186                                  "Common symbol '" + ASym.getName() +
 187                                      "' cannot be used in assignment expr");
 188     return nullptr;
 189   }
 190
 191   return &ASym;
 192 }
 193
 194 uint64_t MCAsmLayout::getSectionAddressSize(const MCSection *Sec) const {
 195   // The size is the last fragment's end offset.
 196   const MCFragment &F = Sec->getFragmentList().back();
 197   return getFragmentOffset(&F) + getAssembler().computeFragmentSize(*this, F);
 198 }
 199
 200 uint64_t MCAsmLayout::getSectionFileSize(const MCSection *Sec) const {
 201   // Virtual sections have no file size.
 202   if (Sec->isVirtualSection())
 203     return 0;
 204
 205   // Otherwise, the file size is the same as the address space size.
 206   return getSectionAddressSize(Sec);
 207 }
 208
 209 uint64_t llvm::computeBundlePadding(const MCAssembler &Assembler,
 210                                     const MCEncodedFragment *F,
 211                                     uint64_t FOffset, uint64_t FSize) {
 212   uint64_t BundleSize = Assembler.getBundleAlignSize();
 213   assert(BundleSize > 0 &&
 214          "computeBundlePadding should only be called if bundling is enabled");
 215   uint64_t BundleMask = BundleSize - 1;
 216   uint64_t OffsetInBundle = FOffset & BundleMask;
 217   uint64_t EndOfFragment = OffsetInBundle + FSize;
 218
 219   // There are two kinds of bundling restrictions:
 220   //
 221   // 1) For alignToBundleEnd(), add padding to ensure that the fragment will
 222   //    *end* on a bundle boundary.
 223   // 2) Otherwise, check if the fragment would cross a bundle boundary. If it
 224   //    would, add padding until the end of the bundle so that the fragment
 225   //    will start in a new one.
 226   if (F->alignToBundleEnd()) {
 227     // Three possibilities here:
 228     //
 229     // A) The fragment just happens to end at a bundle boundary, so we're good.
 230     // B) The fragment ends before the current bundle boundary: pad it just
 231     //    enough to reach the boundary.
 232     // C) The fragment ends after the current bundle boundary: pad it until it
 233     //    reaches the end of the next bundle boundary.
 234     //
 235     // Note: this code could be made shorter with some modulo trickery, but it's
 236     // intentionally kept in its more explicit form for simplicity.
 237     if (EndOfFragment == BundleSize)
 238       return 0;
 239     else if (EndOfFragment < BundleSize)
 240       return BundleSize - EndOfFragment;
 241     else { // EndOfFragment > BundleSize
 242       return 2 * BundleSize - EndOfFragment;
 243     }
 244   } else if (OffsetInBundle > 0 && EndOfFragment > BundleSize)
 245     return BundleSize - OffsetInBundle;
 246   else
 247     return 0;
 248 }
 249
 250 /* *** */
 251
 252 void ilist_alloc_traits<MCFragment>::deleteNode(MCFragment *V) { V->destroy(); }
 253
 254 MCFragment::MCFragment(FragmentType Kind, bool HasInstructions,
 255                        MCSection *Parent)
 256     : Parent(Parent), Atom(nullptr), Offset(~UINT64_C(0)), LayoutOrder(0),
 257       Kind(Kind), IsBeingLaidOut(false), HasInstructions(HasInstructions) {
 258   if (Parent && !isa<MCDummyFragment>(*this))
 259     Parent->getFragmentList().push_back(this);
 260 }
 261
 262 void MCFragment::destroy() {
 263   // First check if we are the sentinal.
 264   if (Kind == FragmentType(~0)) {
 265     delete this;
 266     return;
 267   }
 268
 269   switch (Kind) {
 270     case FT_Align:
 271       delete cast<MCAlignFragment>(this);
 272       return;
 273     case FT_Data:
 274       delete cast<MCDataFragment>(this);
 275       return;
 276     case FT_CompactEncodedInst:
 277       delete cast<MCCompactEncodedInstFragment>(this);
 278       return;
 279     case FT_Fill:
 280       delete cast<MCFillFragment>(this);
 281       return;
 282     case FT_Nops:
 283       delete cast<MCNopsFragment>(this);
 284       return;
 285     case FT_Relaxable:
 286       delete cast<MCRelaxableFragment>(this);
 287       return;
 288     case FT_Org:
 289       delete cast<MCOrgFragment>(this);
 290       return;
 291     case FT_Dwarf:
 292       delete cast<MCDwarfLineAddrFragment>(this);
 293       return;
 294     case FT_DwarfFrame:
 295       delete cast<MCDwarfCallFrameFragment>(this);
 296       return;
 297     case FT_LEB:
 298       delete cast<MCLEBFragment>(this);
 299       return;
 300     case FT_BoundaryAlign:
 301       delete cast<MCBoundaryAlignFragment>(this);
 302       return;
 303     case FT_SymbolId:
 304       delete cast<MCSymbolIdFragment>(this);
 305       return;
 306     case FT_CVInlineLines:
 307       delete cast<MCCVInlineLineTableFragment>(this);
 308       return;
 309     case FT_CVDefRange:
 310       delete cast<MCCVDefRangeFragment>(this);
 311       return;
 312     case FT_PseudoProbe:
 313       delete cast<MCPseudoProbeAddrFragment>(this);
 314       return;
 315     case FT_Dummy:
 316       delete cast<MCDummyFragment>(this);
 317       return;
 318   }
 319 }
 320
 321 // Debugging methods
 322
 323 namespace llvm {
 324
 325 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
 326   OS << "<MCFixup" << " Offset:" << AF.getOffset()
 327      << " Value:" << *AF.getValue()
 328      << " Kind:" << AF.getKind() << ">";
 329   return OS;
 330 }
 331
 332 } // end namespace llvm
 333
 334 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 335 LLVM_DUMP_METHOD void MCFragment::dump() const {
 336   raw_ostream &OS = errs();
 337
 338   OS << "<";
 339   switch (getKind()) {
 340   case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
 341   case MCFragment::FT_Data:  OS << "MCDataFragment"; break;
 342   case MCFragment::FT_CompactEncodedInst:
 343     OS << "MCCompactEncodedInstFragment"; break;
 344   case MCFragment::FT_Fill:  OS << "MCFillFragment"; break;
 345   case MCFragment::FT_Nops:
 346     OS << "MCFNopsFragment";
 347     break;
 348   case MCFragment::FT_Relaxable:  OS << "MCRelaxableFragment"; break;
 349   case MCFragment::FT_Org:   OS << "MCOrgFragment"; break;
 350   case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
 351   case MCFragment::FT_DwarfFrame: OS << "MCDwarfCallFrameFragment"; break;
 352   case MCFragment::FT_LEB:   OS << "MCLEBFragment"; break;
 353   case MCFragment::FT_BoundaryAlign: OS<<"MCBoundaryAlignFragment"; break;
 354   case MCFragment::FT_SymbolId:    OS << "MCSymbolIdFragment"; break;
 355   case MCFragment::FT_CVInlineLines: OS << "MCCVInlineLineTableFragment"; break;
 356   case MCFragment::FT_CVDefRange: OS << "MCCVDefRangeTableFragment"; break;
 357   case MCFragment::FT_PseudoProbe:
 358     OS << "MCPseudoProbe";
 359     break;
 360   case MCFragment::FT_Dummy: OS << "MCDummyFragment"; break;
 361   }
 362
 363   OS << "<MCFragment " << (const void *)this << " LayoutOrder:" << LayoutOrder
 364      << " Offset:" << Offset << " HasInstructions:" << hasInstructions();
 365   if (const auto *EF = dyn_cast<MCEncodedFragment>(this))
 366     OS << " BundlePadding:" << static_cast<unsigned>(EF->getBundlePadding());
 367   OS << ">";
 368
 369   switch (getKind()) {
 370   case MCFragment::FT_Align: {
 371     const auto *AF = cast<MCAlignFragment>(this);
 372     if (AF->hasEmitNops())
 373       OS << " (emit nops)";
 374     OS << "\n       ";
 375     OS << " Alignment:" << AF->getAlignment()
 376        << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
 377        << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
 378     break;
 379   }
 380   case MCFragment::FT_Data:  {
 381     const auto *DF = cast<MCDataFragment>(this);
 382     OS << "\n       ";
 383     OS << " Contents:[";
 384     const SmallVectorImpl<char> &Contents = DF->getContents();
 385     for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
 386       if (i) OS << ",";
 387       OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
 388     }
 389     OS << "] (" << Contents.size() << " bytes)";
 390
 391     if (DF->fixup_begin() != DF->fixup_end()) {
 392       OS << ",\n       ";
 393       OS << " Fixups:[";
 394       for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
 395              ie = DF->fixup_end(); it != ie; ++it) {
 396         if (it != DF->fixup_begin()) OS << ",\n                ";
 397         OS << *it;
 398       }
 399       OS << "]";
 400     }
 401     break;
 402   }
 403   case MCFragment::FT_CompactEncodedInst: {
 404     const auto *CEIF =
 405       cast<MCCompactEncodedInstFragment>(this);
 406     OS << "\n       ";
 407     OS << " Contents:[";
 408     const SmallVectorImpl<char> &Contents = CEIF->getContents();
 409     for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
 410       if (i) OS << ",";
 411       OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
 412     }
 413     OS << "] (" << Contents.size() << " bytes)";
 414     break;
 415   }
 416   case MCFragment::FT_Fill:  {
 417     const auto *FF = cast<MCFillFragment>(this);
 418     OS << " Value:" << static_cast<unsigned>(FF->getValue())
 419        << " ValueSize:" << static_cast<unsigned>(FF->getValueSize())
 420        << " NumValues:" << FF->getNumValues();
 421     break;
 422   }
 423   case MCFragment::FT_Nops: {
 424     const auto *NF = cast<MCNopsFragment>(this);
 425     OS << " NumBytes:" << NF->getNumBytes()
 426        << " ControlledNopLength:" << NF->getControlledNopLength();
 427     break;
 428   }
 429   case MCFragment::FT_Relaxable:  {
 430     const auto *F = cast<MCRelaxableFragment>(this);
 431     OS << "\n       ";
 432     OS << " Inst:";
 433     F->getInst().dump_pretty(OS);
 434     OS << " (" << F->getContents().size() << " bytes)";
 435     break;
 436   }
 437   case MCFragment::FT_Org:  {
 438     const auto *OF = cast<MCOrgFragment>(this);
 439     OS << "\n       ";
 440     OS << " Offset:" << OF->getOffset()
 441        << " Value:" << static_cast<unsigned>(OF->getValue());
 442     break;
 443   }
 444   case MCFragment::FT_Dwarf:  {
 445     const auto *OF = cast<MCDwarfLineAddrFragment>(this);
 446     OS << "\n       ";
 447     OS << " AddrDelta:" << OF->getAddrDelta()
 448        << " LineDelta:" << OF->getLineDelta();
 449     break;
 450   }
 451   case MCFragment::FT_DwarfFrame:  {
 452     const auto *CF = cast<MCDwarfCallFrameFragment>(this);
 453     OS << "\n       ";
 454     OS << " AddrDelta:" << CF->getAddrDelta();
 455     break;
 456   }
 457   case MCFragment::FT_LEB: {
 458     const auto *LF = cast<MCLEBFragment>(this);
 459     OS << "\n       ";
 460     OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
 461     break;
 462   }
 463   case MCFragment::FT_BoundaryAlign: {
 464     const auto *BF = cast<MCBoundaryAlignFragment>(this);
 465     OS << "\n       ";
 466     OS << " BoundarySize:" << BF->getAlignment().value()
 467        << " LastFragment:" << BF->getLastFragment()
 468        << " Size:" << BF->getSize();
 469     break;
 470   }
 471   case MCFragment::FT_SymbolId: {
 472     const auto *F = cast<MCSymbolIdFragment>(this);
 473     OS << "\n       ";
 474     OS << " Sym:" << F->getSymbol();
 475     break;
 476   }
 477   case MCFragment::FT_CVInlineLines: {
 478     const auto *F = cast<MCCVInlineLineTableFragment>(this);
 479     OS << "\n       ";
 480     OS << " Sym:" << *F->getFnStartSym();
 481     break;
 482   }
 483   case MCFragment::FT_CVDefRange: {
 484     const auto *F = cast<MCCVDefRangeFragment>(this);
 485     OS << "\n       ";
 486     for (std::pair<const MCSymbol *, const MCSymbol *> RangeStartEnd :
 487          F->getRanges()) {
 488       OS << " RangeStart:" << RangeStartEnd.first;
 489       OS << " RangeEnd:" << RangeStartEnd.second;
 490     }
 491     break;
 492   }
 493   case MCFragment::FT_PseudoProbe: {
 494     const auto *OF = cast<MCPseudoProbeAddrFragment>(this);
 495     OS << "\n       ";
 496     OS << " AddrDelta:" << OF->getAddrDelta();
 497     break;
 498   }
 499   case MCFragment::FT_Dummy:
 500     break;
 501   }
 502   OS << ">";
 503 }
 504 #endif