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