1 //===- lib/MC/MCAssembler.cpp - Assembler Backend 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/MCAssembler.h" 10 #include "llvm/ADT/ArrayRef.h" 11 #include "llvm/ADT/SmallString.h" 12 #include "llvm/ADT/SmallVector.h" 13 #include "llvm/ADT/Statistic.h" 14 #include "llvm/ADT/StringRef.h" 15 #include "llvm/ADT/Twine.h" 16 #include "llvm/MC/MCAsmBackend.h" 17 #include "llvm/MC/MCAsmInfo.h" 18 #include "llvm/MC/MCAsmLayout.h" 19 #include "llvm/MC/MCCodeEmitter.h" 20 #include "llvm/MC/MCCodeView.h" 21 #include "llvm/MC/MCContext.h" 22 #include "llvm/MC/MCDwarf.h" 23 #include "llvm/MC/MCExpr.h" 24 #include "llvm/MC/MCFixup.h" 25 #include "llvm/MC/MCFixupKindInfo.h" 26 #include "llvm/MC/MCFragment.h" 27 #include "llvm/MC/MCInst.h" 28 #include "llvm/MC/MCObjectWriter.h" 29 #include "llvm/MC/MCSection.h" 30 #include "llvm/MC/MCSectionELF.h" 31 #include "llvm/MC/MCSymbol.h" 32 #include "llvm/MC/MCValue.h" 33 #include "llvm/Support/Alignment.h" 34 #include "llvm/Support/Casting.h" 35 #include "llvm/Support/Debug.h" 36 #include "llvm/Support/EndianStream.h" 37 #include "llvm/Support/ErrorHandling.h" 38 #include "llvm/Support/LEB128.h" 39 #include "llvm/Support/MathExtras.h" 40 #include "llvm/Support/raw_ostream.h" 41 #include <cassert> 42 #include <cstdint> 43 #include <cstring> 44 #include <tuple> 45 #include <utility> 46 47 using namespace llvm; 48 49 #define DEBUG_TYPE "assembler" 50 51 namespace { 52 namespace stats { 53 54 STATISTIC(EmittedFragments, "Number of emitted assembler fragments - total"); 55 STATISTIC(EmittedRelaxableFragments, 56 "Number of emitted assembler fragments - relaxable"); 57 STATISTIC(EmittedDataFragments, 58 "Number of emitted assembler fragments - data"); 59 STATISTIC(EmittedCompactEncodedInstFragments, 60 "Number of emitted assembler fragments - compact encoded inst"); 61 STATISTIC(EmittedAlignFragments, 62 "Number of emitted assembler fragments - align"); 63 STATISTIC(EmittedFillFragments, 64 "Number of emitted assembler fragments - fill"); 65 STATISTIC(EmittedNopsFragments, "Number of emitted assembler fragments - nops"); 66 STATISTIC(EmittedOrgFragments, "Number of emitted assembler fragments - org"); 67 STATISTIC(evaluateFixup, "Number of evaluated fixups"); 68 STATISTIC(FragmentLayouts, "Number of fragment layouts"); 69 STATISTIC(ObjectBytes, "Number of emitted object file bytes"); 70 STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps"); 71 STATISTIC(RelaxedInstructions, "Number of relaxed instructions"); 72 73 } // end namespace stats 74 } // end anonymous namespace 75 76 // FIXME FIXME FIXME: There are number of places in this file where we convert 77 // what is a 64-bit assembler value used for computation into a value in the 78 // object file, which may truncate it. We should detect that truncation where 79 // invalid and report errors back. 80 81 /* *** */ 82 83 MCAssembler::MCAssembler(MCContext &Context, 84 std::unique_ptr<MCAsmBackend> Backend, 85 std::unique_ptr<MCCodeEmitter> Emitter, 86 std::unique_ptr<MCObjectWriter> Writer) 87 : Context(Context), Backend(std::move(Backend)), 88 Emitter(std::move(Emitter)), Writer(std::move(Writer)), 89 BundleAlignSize(0), RelaxAll(false), SubsectionsViaSymbols(false), 90 IncrementalLinkerCompatible(false), ELFHeaderEFlags(0) { 91 VersionInfo.Major = 0; // Major version == 0 for "none specified" 92 } 93 94 MCAssembler::~MCAssembler() = default; 95 96 void MCAssembler::reset() { 97 Sections.clear(); 98 Symbols.clear(); 99 IndirectSymbols.clear(); 100 DataRegions.clear(); 101 LinkerOptions.clear(); 102 FileNames.clear(); 103 ThumbFuncs.clear(); 104 BundleAlignSize = 0; 105 RelaxAll = false; 106 SubsectionsViaSymbols = false; 107 IncrementalLinkerCompatible = false; 108 ELFHeaderEFlags = 0; 109 LOHContainer.reset(); 110 VersionInfo.Major = 0; 111 VersionInfo.SDKVersion = VersionTuple(); 112 113 // reset objects owned by us 114 if (getBackendPtr()) 115 getBackendPtr()->reset(); 116 if (getEmitterPtr()) 117 getEmitterPtr()->reset(); 118 if (getWriterPtr()) 119 getWriterPtr()->reset(); 120 getLOHContainer().reset(); 121 } 122 123 bool MCAssembler::registerSection(MCSection &Section) { 124 if (Section.isRegistered()) 125 return false; 126 Sections.push_back(&Section); 127 Section.setIsRegistered(true); 128 return true; 129 } 130 131 bool MCAssembler::isThumbFunc(const MCSymbol *Symbol) const { 132 if (ThumbFuncs.count(Symbol)) 133 return true; 134 135 if (!Symbol->isVariable()) 136 return false; 137 138 const MCExpr *Expr = Symbol->getVariableValue(); 139 140 MCValue V; 141 if (!Expr->evaluateAsRelocatable(V, nullptr, nullptr)) 142 return false; 143 144 if (V.getSymB() || V.getRefKind() != MCSymbolRefExpr::VK_None) 145 return false; 146 147 const MCSymbolRefExpr *Ref = V.getSymA(); 148 if (!Ref) 149 return false; 150 151 if (Ref->getKind() != MCSymbolRefExpr::VK_None) 152 return false; 153 154 const MCSymbol &Sym = Ref->getSymbol(); 155 if (!isThumbFunc(&Sym)) 156 return false; 157 158 ThumbFuncs.insert(Symbol); // Cache it. 159 return true; 160 } 161 162 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const { 163 // Non-temporary labels should always be visible to the linker. 164 if (!Symbol.isTemporary()) 165 return true; 166 167 if (Symbol.isUsedInReloc()) 168 return true; 169 170 return false; 171 } 172 173 const MCSymbol *MCAssembler::getAtom(const MCSymbol &S) const { 174 // Linker visible symbols define atoms. 175 if (isSymbolLinkerVisible(S)) 176 return &S; 177 178 // Absolute and undefined symbols have no defining atom. 179 if (!S.isInSection()) 180 return nullptr; 181 182 // Non-linker visible symbols in sections which can't be atomized have no 183 // defining atom. 184 if (!getContext().getAsmInfo()->isSectionAtomizableBySymbols( 185 *S.getFragment()->getParent())) 186 return nullptr; 187 188 // Otherwise, return the atom for the containing fragment. 189 return S.getFragment()->getAtom(); 190 } 191 192 bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout, 193 const MCFixup &Fixup, const MCFragment *DF, 194 MCValue &Target, uint64_t &Value, 195 bool &WasForced) const { 196 ++stats::evaluateFixup; 197 198 // FIXME: This code has some duplication with recordRelocation. We should 199 // probably merge the two into a single callback that tries to evaluate a 200 // fixup and records a relocation if one is needed. 201 202 // On error claim to have completely evaluated the fixup, to prevent any 203 // further processing from being done. 204 const MCExpr *Expr = Fixup.getValue(); 205 MCContext &Ctx = getContext(); 206 Value = 0; 207 WasForced = false; 208 if (!Expr->evaluateAsRelocatable(Target, &Layout, &Fixup)) { 209 Ctx.reportError(Fixup.getLoc(), "expected relocatable expression"); 210 return true; 211 } 212 if (const MCSymbolRefExpr *RefB = Target.getSymB()) { 213 if (RefB->getKind() != MCSymbolRefExpr::VK_None) { 214 Ctx.reportError(Fixup.getLoc(), 215 "unsupported subtraction of qualified symbol"); 216 return true; 217 } 218 } 219 220 assert(getBackendPtr() && "Expected assembler backend"); 221 bool IsTarget = getBackendPtr()->getFixupKindInfo(Fixup.getKind()).Flags & 222 MCFixupKindInfo::FKF_IsTarget; 223 224 if (IsTarget) 225 return getBackend().evaluateTargetFixup(*this, Layout, Fixup, DF, Target, 226 Value, WasForced); 227 228 unsigned FixupFlags = getBackendPtr()->getFixupKindInfo(Fixup.getKind()).Flags; 229 bool IsPCRel = getBackendPtr()->getFixupKindInfo(Fixup.getKind()).Flags & 230 MCFixupKindInfo::FKF_IsPCRel; 231 232 bool IsResolved = false; 233 if (IsPCRel) { 234 if (Target.getSymB()) { 235 IsResolved = false; 236 } else if (!Target.getSymA()) { 237 IsResolved = false; 238 } else { 239 const MCSymbolRefExpr *A = Target.getSymA(); 240 const MCSymbol &SA = A->getSymbol(); 241 if (A->getKind() != MCSymbolRefExpr::VK_None || SA.isUndefined()) { 242 IsResolved = false; 243 } else if (auto *Writer = getWriterPtr()) { 244 IsResolved = (FixupFlags & MCFixupKindInfo::FKF_Constant) || 245 Writer->isSymbolRefDifferenceFullyResolvedImpl( 246 *this, SA, *DF, false, true); 247 } 248 } 249 } else { 250 IsResolved = Target.isAbsolute(); 251 } 252 253 Value = Target.getConstant(); 254 255 if (const MCSymbolRefExpr *A = Target.getSymA()) { 256 const MCSymbol &Sym = A->getSymbol(); 257 if (Sym.isDefined()) 258 Value += Layout.getSymbolOffset(Sym); 259 } 260 if (const MCSymbolRefExpr *B = Target.getSymB()) { 261 const MCSymbol &Sym = B->getSymbol(); 262 if (Sym.isDefined()) 263 Value -= Layout.getSymbolOffset(Sym); 264 } 265 266 bool ShouldAlignPC = getBackend().getFixupKindInfo(Fixup.getKind()).Flags & 267 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits; 268 assert((ShouldAlignPC ? IsPCRel : true) && 269 "FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!"); 270 271 if (IsPCRel) { 272 uint32_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset(); 273 274 // A number of ARM fixups in Thumb mode require that the effective PC 275 // address be determined as the 32-bit aligned version of the actual offset. 276 if (ShouldAlignPC) Offset &= ~0x3; 277 Value -= Offset; 278 } 279 280 // Let the backend force a relocation if needed. 281 if (IsResolved && getBackend().shouldForceRelocation(*this, Fixup, Target)) { 282 IsResolved = false; 283 WasForced = true; 284 } 285 286 return IsResolved; 287 } 288 289 uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout, 290 const MCFragment &F) const { 291 assert(getBackendPtr() && "Requires assembler backend"); 292 switch (F.getKind()) { 293 case MCFragment::FT_Data: 294 return cast<MCDataFragment>(F).getContents().size(); 295 case MCFragment::FT_Relaxable: 296 return cast<MCRelaxableFragment>(F).getContents().size(); 297 case MCFragment::FT_CompactEncodedInst: 298 return cast<MCCompactEncodedInstFragment>(F).getContents().size(); 299 case MCFragment::FT_Fill: { 300 auto &FF = cast<MCFillFragment>(F); 301 int64_t NumValues = 0; 302 if (!FF.getNumValues().evaluateAsAbsolute(NumValues, Layout)) { 303 getContext().reportError(FF.getLoc(), 304 "expected assembly-time absolute expression"); 305 return 0; 306 } 307 int64_t Size = NumValues * FF.getValueSize(); 308 if (Size < 0) { 309 getContext().reportError(FF.getLoc(), "invalid number of bytes"); 310 return 0; 311 } 312 return Size; 313 } 314 315 case MCFragment::FT_Nops: 316 return cast<MCNopsFragment>(F).getNumBytes(); 317 318 case MCFragment::FT_LEB: 319 return cast<MCLEBFragment>(F).getContents().size(); 320 321 case MCFragment::FT_BoundaryAlign: 322 return cast<MCBoundaryAlignFragment>(F).getSize(); 323 324 case MCFragment::FT_SymbolId: 325 return 4; 326 327 case MCFragment::FT_Align: { 328 const MCAlignFragment &AF = cast<MCAlignFragment>(F); 329 unsigned Offset = Layout.getFragmentOffset(&AF); 330 unsigned Size = offsetToAlignment(Offset, Align(AF.getAlignment())); 331 332 // Insert extra Nops for code alignment if the target define 333 // shouldInsertExtraNopBytesForCodeAlign target hook. 334 if (AF.getParent()->UseCodeAlign() && AF.hasEmitNops() && 335 getBackend().shouldInsertExtraNopBytesForCodeAlign(AF, Size)) 336 return Size; 337 338 // If we are padding with nops, force the padding to be larger than the 339 // minimum nop size. 340 if (Size > 0 && AF.hasEmitNops()) { 341 while (Size % getBackend().getMinimumNopSize()) 342 Size += AF.getAlignment(); 343 } 344 if (Size > AF.getMaxBytesToEmit()) 345 return 0; 346 return Size; 347 } 348 349 case MCFragment::FT_Org: { 350 const MCOrgFragment &OF = cast<MCOrgFragment>(F); 351 MCValue Value; 352 if (!OF.getOffset().evaluateAsValue(Value, Layout)) { 353 getContext().reportError(OF.getLoc(), 354 "expected assembly-time absolute expression"); 355 return 0; 356 } 357 358 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF); 359 int64_t TargetLocation = Value.getConstant(); 360 if (const MCSymbolRefExpr *A = Value.getSymA()) { 361 uint64_t Val; 362 if (!Layout.getSymbolOffset(A->getSymbol(), Val)) { 363 getContext().reportError(OF.getLoc(), "expected absolute expression"); 364 return 0; 365 } 366 TargetLocation += Val; 367 } 368 int64_t Size = TargetLocation - FragmentOffset; 369 if (Size < 0 || Size >= 0x40000000) { 370 getContext().reportError( 371 OF.getLoc(), "invalid .org offset '" + Twine(TargetLocation) + 372 "' (at offset '" + Twine(FragmentOffset) + "')"); 373 return 0; 374 } 375 return Size; 376 } 377 378 case MCFragment::FT_Dwarf: 379 return cast<MCDwarfLineAddrFragment>(F).getContents().size(); 380 case MCFragment::FT_DwarfFrame: 381 return cast<MCDwarfCallFrameFragment>(F).getContents().size(); 382 case MCFragment::FT_CVInlineLines: 383 return cast<MCCVInlineLineTableFragment>(F).getContents().size(); 384 case MCFragment::FT_CVDefRange: 385 return cast<MCCVDefRangeFragment>(F).getContents().size(); 386 case MCFragment::FT_PseudoProbe: 387 return cast<MCPseudoProbeAddrFragment>(F).getContents().size(); 388 case MCFragment::FT_Dummy: 389 llvm_unreachable("Should not have been added"); 390 } 391 392 llvm_unreachable("invalid fragment kind"); 393 } 394 395 void MCAsmLayout::layoutFragment(MCFragment *F) { 396 MCFragment *Prev = F->getPrevNode(); 397 398 // We should never try to recompute something which is valid. 399 assert(!isFragmentValid(F) && "Attempt to recompute a valid fragment!"); 400 // We should never try to compute the fragment layout if its predecessor 401 // isn't valid. 402 assert((!Prev || isFragmentValid(Prev)) && 403 "Attempt to compute fragment before its predecessor!"); 404 405 assert(!F->IsBeingLaidOut && "Already being laid out!"); 406 F->IsBeingLaidOut = true; 407 408 ++stats::FragmentLayouts; 409 410 // Compute fragment offset and size. 411 if (Prev) 412 F->Offset = Prev->Offset + getAssembler().computeFragmentSize(*this, *Prev); 413 else 414 F->Offset = 0; 415 F->IsBeingLaidOut = false; 416 LastValidFragment[F->getParent()] = F; 417 418 // If bundling is enabled and this fragment has instructions in it, it has to 419 // obey the bundling restrictions. With padding, we'll have: 420 // 421 // 422 // BundlePadding 423 // ||| 424 // ------------------------------------- 425 // Prev |##########| F | 426 // ------------------------------------- 427 // ^ 428 // | 429 // F->Offset 430 // 431 // The fragment's offset will point to after the padding, and its computed 432 // size won't include the padding. 433 // 434 // When the -mc-relax-all flag is used, we optimize bundling by writting the 435 // padding directly into fragments when the instructions are emitted inside 436 // the streamer. When the fragment is larger than the bundle size, we need to 437 // ensure that it's bundle aligned. This means that if we end up with 438 // multiple fragments, we must emit bundle padding between fragments. 439 // 440 // ".align N" is an example of a directive that introduces multiple 441 // fragments. We could add a special case to handle ".align N" by emitting 442 // within-fragment padding (which would produce less padding when N is less 443 // than the bundle size), but for now we don't. 444 // 445 if (Assembler.isBundlingEnabled() && F->hasInstructions()) { 446 assert(isa<MCEncodedFragment>(F) && 447 "Only MCEncodedFragment implementations have instructions"); 448 MCEncodedFragment *EF = cast<MCEncodedFragment>(F); 449 uint64_t FSize = Assembler.computeFragmentSize(*this, *EF); 450 451 if (!Assembler.getRelaxAll() && FSize > Assembler.getBundleAlignSize()) 452 report_fatal_error("Fragment can't be larger than a bundle size"); 453 454 uint64_t RequiredBundlePadding = 455 computeBundlePadding(Assembler, EF, EF->Offset, FSize); 456 if (RequiredBundlePadding > UINT8_MAX) 457 report_fatal_error("Padding cannot exceed 255 bytes"); 458 EF->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding)); 459 EF->Offset += RequiredBundlePadding; 460 } 461 } 462 463 void MCAssembler::registerSymbol(const MCSymbol &Symbol, bool *Created) { 464 bool New = !Symbol.isRegistered(); 465 if (Created) 466 *Created = New; 467 if (New) { 468 Symbol.setIsRegistered(true); 469 Symbols.push_back(&Symbol); 470 } 471 } 472 473 void MCAssembler::writeFragmentPadding(raw_ostream &OS, 474 const MCEncodedFragment &EF, 475 uint64_t FSize) const { 476 assert(getBackendPtr() && "Expected assembler backend"); 477 // Should NOP padding be written out before this fragment? 478 unsigned BundlePadding = EF.getBundlePadding(); 479 if (BundlePadding > 0) { 480 assert(isBundlingEnabled() && 481 "Writing bundle padding with disabled bundling"); 482 assert(EF.hasInstructions() && 483 "Writing bundle padding for a fragment without instructions"); 484 485 unsigned TotalLength = BundlePadding + static_cast<unsigned>(FSize); 486 if (EF.alignToBundleEnd() && TotalLength > getBundleAlignSize()) { 487 // If the padding itself crosses a bundle boundary, it must be emitted 488 // in 2 pieces, since even nop instructions must not cross boundaries. 489 // v--------------v <- BundleAlignSize 490 // v---------v <- BundlePadding 491 // ---------------------------- 492 // | Prev |####|####| F | 493 // ---------------------------- 494 // ^-------------------^ <- TotalLength 495 unsigned DistanceToBoundary = TotalLength - getBundleAlignSize(); 496 if (!getBackend().writeNopData(OS, DistanceToBoundary)) 497 report_fatal_error("unable to write NOP sequence of " + 498 Twine(DistanceToBoundary) + " bytes"); 499 BundlePadding -= DistanceToBoundary; 500 } 501 if (!getBackend().writeNopData(OS, BundlePadding)) 502 report_fatal_error("unable to write NOP sequence of " + 503 Twine(BundlePadding) + " bytes"); 504 } 505 } 506 507 /// Write the fragment \p F to the output file. 508 static void writeFragment(raw_ostream &OS, const MCAssembler &Asm, 509 const MCAsmLayout &Layout, const MCFragment &F) { 510 // FIXME: Embed in fragments instead? 511 uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F); 512 513 support::endianness Endian = Asm.getBackend().Endian; 514 515 if (const MCEncodedFragment *EF = dyn_cast<MCEncodedFragment>(&F)) 516 Asm.writeFragmentPadding(OS, *EF, FragmentSize); 517 518 // This variable (and its dummy usage) is to participate in the assert at 519 // the end of the function. 520 uint64_t Start = OS.tell(); 521 (void) Start; 522 523 ++stats::EmittedFragments; 524 525 switch (F.getKind()) { 526 case MCFragment::FT_Align: { 527 ++stats::EmittedAlignFragments; 528 const MCAlignFragment &AF = cast<MCAlignFragment>(F); 529 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!"); 530 531 uint64_t Count = FragmentSize / AF.getValueSize(); 532 533 // FIXME: This error shouldn't actually occur (the front end should emit 534 // multiple .align directives to enforce the semantics it wants), but is 535 // severe enough that we want to report it. How to handle this? 536 if (Count * AF.getValueSize() != FragmentSize) 537 report_fatal_error("undefined .align directive, value size '" + 538 Twine(AF.getValueSize()) + 539 "' is not a divisor of padding size '" + 540 Twine(FragmentSize) + "'"); 541 542 // See if we are aligning with nops, and if so do that first to try to fill 543 // the Count bytes. Then if that did not fill any bytes or there are any 544 // bytes left to fill use the Value and ValueSize to fill the rest. 545 // If we are aligning with nops, ask that target to emit the right data. 546 if (AF.hasEmitNops()) { 547 if (!Asm.getBackend().writeNopData(OS, Count)) 548 report_fatal_error("unable to write nop sequence of " + 549 Twine(Count) + " bytes"); 550 break; 551 } 552 553 // Otherwise, write out in multiples of the value size. 554 for (uint64_t i = 0; i != Count; ++i) { 555 switch (AF.getValueSize()) { 556 default: llvm_unreachable("Invalid size!"); 557 case 1: OS << char(AF.getValue()); break; 558 case 2: 559 support::endian::write<uint16_t>(OS, AF.getValue(), Endian); 560 break; 561 case 4: 562 support::endian::write<uint32_t>(OS, AF.getValue(), Endian); 563 break; 564 case 8: 565 support::endian::write<uint64_t>(OS, AF.getValue(), Endian); 566 break; 567 } 568 } 569 break; 570 } 571 572 case MCFragment::FT_Data: 573 ++stats::EmittedDataFragments; 574 OS << cast<MCDataFragment>(F).getContents(); 575 break; 576 577 case MCFragment::FT_Relaxable: 578 ++stats::EmittedRelaxableFragments; 579 OS << cast<MCRelaxableFragment>(F).getContents(); 580 break; 581 582 case MCFragment::FT_CompactEncodedInst: 583 ++stats::EmittedCompactEncodedInstFragments; 584 OS << cast<MCCompactEncodedInstFragment>(F).getContents(); 585 break; 586 587 case MCFragment::FT_Fill: { 588 ++stats::EmittedFillFragments; 589 const MCFillFragment &FF = cast<MCFillFragment>(F); 590 uint64_t V = FF.getValue(); 591 unsigned VSize = FF.getValueSize(); 592 const unsigned MaxChunkSize = 16; 593 char Data[MaxChunkSize]; 594 assert(0 < VSize && VSize <= MaxChunkSize && "Illegal fragment fill size"); 595 // Duplicate V into Data as byte vector to reduce number of 596 // writes done. As such, do endian conversion here. 597 for (unsigned I = 0; I != VSize; ++I) { 598 unsigned index = Endian == support::little ? I : (VSize - I - 1); 599 Data[I] = uint8_t(V >> (index * 8)); 600 } 601 for (unsigned I = VSize; I < MaxChunkSize; ++I) 602 Data[I] = Data[I - VSize]; 603 604 // Set to largest multiple of VSize in Data. 605 const unsigned NumPerChunk = MaxChunkSize / VSize; 606 // Set ChunkSize to largest multiple of VSize in Data 607 const unsigned ChunkSize = VSize * NumPerChunk; 608 609 // Do copies by chunk. 610 StringRef Ref(Data, ChunkSize); 611 for (uint64_t I = 0, E = FragmentSize / ChunkSize; I != E; ++I) 612 OS << Ref; 613 614 // do remainder if needed. 615 unsigned TrailingCount = FragmentSize % ChunkSize; 616 if (TrailingCount) 617 OS.write(Data, TrailingCount); 618 break; 619 } 620 621 case MCFragment::FT_Nops: { 622 ++stats::EmittedNopsFragments; 623 const MCNopsFragment &NF = cast<MCNopsFragment>(F); 624 int64_t NumBytes = NF.getNumBytes(); 625 int64_t ControlledNopLength = NF.getControlledNopLength(); 626 int64_t MaximumNopLength = Asm.getBackend().getMaximumNopSize(); 627 628 assert(NumBytes > 0 && "Expected positive NOPs fragment size"); 629 assert(ControlledNopLength >= 0 && "Expected non-negative NOP size"); 630 631 if (ControlledNopLength > MaximumNopLength) { 632 Asm.getContext().reportError(NF.getLoc(), 633 "illegal NOP size " + 634 std::to_string(ControlledNopLength) + 635 ". (expected within [0, " + 636 std::to_string(MaximumNopLength) + "])"); 637 // Clamp the NOP length as reportError does not stop the execution 638 // immediately. 639 ControlledNopLength = MaximumNopLength; 640 } 641 642 // Use maximum value if the size of each NOP is not specified 643 if (!ControlledNopLength) 644 ControlledNopLength = MaximumNopLength; 645 646 while (NumBytes) { 647 uint64_t NumBytesToEmit = 648 (uint64_t)std::min(NumBytes, ControlledNopLength); 649 assert(NumBytesToEmit && "try to emit empty NOP instruction"); 650 if (!Asm.getBackend().writeNopData(OS, NumBytesToEmit)) { 651 report_fatal_error("unable to write nop sequence of the remaining " + 652 Twine(NumBytesToEmit) + " bytes"); 653 break; 654 } 655 NumBytes -= NumBytesToEmit; 656 } 657 break; 658 } 659 660 case MCFragment::FT_LEB: { 661 const MCLEBFragment &LF = cast<MCLEBFragment>(F); 662 OS << LF.getContents(); 663 break; 664 } 665 666 case MCFragment::FT_BoundaryAlign: { 667 if (!Asm.getBackend().writeNopData(OS, FragmentSize)) 668 report_fatal_error("unable to write nop sequence of " + 669 Twine(FragmentSize) + " bytes"); 670 break; 671 } 672 673 case MCFragment::FT_SymbolId: { 674 const MCSymbolIdFragment &SF = cast<MCSymbolIdFragment>(F); 675 support::endian::write<uint32_t>(OS, SF.getSymbol()->getIndex(), Endian); 676 break; 677 } 678 679 case MCFragment::FT_Org: { 680 ++stats::EmittedOrgFragments; 681 const MCOrgFragment &OF = cast<MCOrgFragment>(F); 682 683 for (uint64_t i = 0, e = FragmentSize; i != e; ++i) 684 OS << char(OF.getValue()); 685 686 break; 687 } 688 689 case MCFragment::FT_Dwarf: { 690 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F); 691 OS << OF.getContents(); 692 break; 693 } 694 case MCFragment::FT_DwarfFrame: { 695 const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F); 696 OS << CF.getContents(); 697 break; 698 } 699 case MCFragment::FT_CVInlineLines: { 700 const auto &OF = cast<MCCVInlineLineTableFragment>(F); 701 OS << OF.getContents(); 702 break; 703 } 704 case MCFragment::FT_CVDefRange: { 705 const auto &DRF = cast<MCCVDefRangeFragment>(F); 706 OS << DRF.getContents(); 707 break; 708 } 709 case MCFragment::FT_PseudoProbe: { 710 const MCPseudoProbeAddrFragment &PF = cast<MCPseudoProbeAddrFragment>(F); 711 OS << PF.getContents(); 712 break; 713 } 714 case MCFragment::FT_Dummy: 715 llvm_unreachable("Should not have been added"); 716 } 717 718 assert(OS.tell() - Start == FragmentSize && 719 "The stream should advance by fragment size"); 720 } 721 722 void MCAssembler::writeSectionData(raw_ostream &OS, const MCSection *Sec, 723 const MCAsmLayout &Layout) const { 724 assert(getBackendPtr() && "Expected assembler backend"); 725 726 // Ignore virtual sections. 727 if (Sec->isVirtualSection()) { 728 assert(Layout.getSectionFileSize(Sec) == 0 && "Invalid size for section!"); 729 730 // Check that contents are only things legal inside a virtual section. 731 for (const MCFragment &F : *Sec) { 732 switch (F.getKind()) { 733 default: llvm_unreachable("Invalid fragment in virtual section!"); 734 case MCFragment::FT_Data: { 735 // Check that we aren't trying to write a non-zero contents (or fixups) 736 // into a virtual section. This is to support clients which use standard 737 // directives to fill the contents of virtual sections. 738 const MCDataFragment &DF = cast<MCDataFragment>(F); 739 if (DF.fixup_begin() != DF.fixup_end()) 740 getContext().reportError(SMLoc(), Sec->getVirtualSectionKind() + 741 " section '" + Sec->getName() + 742 "' cannot have fixups"); 743 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i) 744 if (DF.getContents()[i]) { 745 getContext().reportError(SMLoc(), 746 Sec->getVirtualSectionKind() + 747 " section '" + Sec->getName() + 748 "' cannot have non-zero initializers"); 749 break; 750 } 751 break; 752 } 753 case MCFragment::FT_Align: 754 // Check that we aren't trying to write a non-zero value into a virtual 755 // section. 756 assert((cast<MCAlignFragment>(F).getValueSize() == 0 || 757 cast<MCAlignFragment>(F).getValue() == 0) && 758 "Invalid align in virtual section!"); 759 break; 760 case MCFragment::FT_Fill: 761 assert((cast<MCFillFragment>(F).getValue() == 0) && 762 "Invalid fill in virtual section!"); 763 break; 764 case MCFragment::FT_Org: 765 break; 766 } 767 } 768 769 return; 770 } 771 772 uint64_t Start = OS.tell(); 773 (void)Start; 774 775 for (const MCFragment &F : *Sec) 776 writeFragment(OS, *this, Layout, F); 777 778 assert(getContext().hadError() || 779 OS.tell() - Start == Layout.getSectionAddressSize(Sec)); 780 } 781 782 std::tuple<MCValue, uint64_t, bool> 783 MCAssembler::handleFixup(const MCAsmLayout &Layout, MCFragment &F, 784 const MCFixup &Fixup) { 785 // Evaluate the fixup. 786 MCValue Target; 787 uint64_t FixedValue; 788 bool WasForced; 789 bool IsResolved = evaluateFixup(Layout, Fixup, &F, Target, FixedValue, 790 WasForced); 791 if (!IsResolved) { 792 // The fixup was unresolved, we need a relocation. Inform the object 793 // writer of the relocation, and give it an opportunity to adjust the 794 // fixup value if need be. 795 getWriter().recordRelocation(*this, Layout, &F, Fixup, Target, FixedValue); 796 } 797 return std::make_tuple(Target, FixedValue, IsResolved); 798 } 799 800 void MCAssembler::layout(MCAsmLayout &Layout) { 801 assert(getBackendPtr() && "Expected assembler backend"); 802 DEBUG_WITH_TYPE("mc-dump", { 803 errs() << "assembler backend - pre-layout\n--\n"; 804 dump(); }); 805 806 // Create dummy fragments and assign section ordinals. 807 unsigned SectionIndex = 0; 808 for (MCSection &Sec : *this) { 809 // Create dummy fragments to eliminate any empty sections, this simplifies 810 // layout. 811 if (Sec.getFragmentList().empty()) 812 new MCDataFragment(&Sec); 813 814 Sec.setOrdinal(SectionIndex++); 815 } 816 817 // Assign layout order indices to sections and fragments. 818 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) { 819 MCSection *Sec = Layout.getSectionOrder()[i]; 820 Sec->setLayoutOrder(i); 821 822 unsigned FragmentIndex = 0; 823 for (MCFragment &Frag : *Sec) 824 Frag.setLayoutOrder(FragmentIndex++); 825 } 826 827 // Layout until everything fits. 828 while (layoutOnce(Layout)) { 829 if (getContext().hadError()) 830 return; 831 // Size of fragments in one section can depend on the size of fragments in 832 // another. If any fragment has changed size, we have to re-layout (and 833 // as a result possibly further relax) all. 834 for (MCSection &Sec : *this) 835 Layout.invalidateFragmentsFrom(&*Sec.begin()); 836 } 837 838 DEBUG_WITH_TYPE("mc-dump", { 839 errs() << "assembler backend - post-relaxation\n--\n"; 840 dump(); }); 841 842 // Finalize the layout, including fragment lowering. 843 finishLayout(Layout); 844 845 DEBUG_WITH_TYPE("mc-dump", { 846 errs() << "assembler backend - final-layout\n--\n"; 847 dump(); }); 848 849 // Allow the object writer a chance to perform post-layout binding (for 850 // example, to set the index fields in the symbol data). 851 getWriter().executePostLayoutBinding(*this, Layout); 852 853 // Evaluate and apply the fixups, generating relocation entries as necessary. 854 for (MCSection &Sec : *this) { 855 for (MCFragment &Frag : Sec) { 856 ArrayRef<MCFixup> Fixups; 857 MutableArrayRef<char> Contents; 858 const MCSubtargetInfo *STI = nullptr; 859 860 // Process MCAlignFragment and MCEncodedFragmentWithFixups here. 861 switch (Frag.getKind()) { 862 default: 863 continue; 864 case MCFragment::FT_Align: { 865 MCAlignFragment &AF = cast<MCAlignFragment>(Frag); 866 // Insert fixup type for code alignment if the target define 867 // shouldInsertFixupForCodeAlign target hook. 868 if (Sec.UseCodeAlign() && AF.hasEmitNops()) 869 getBackend().shouldInsertFixupForCodeAlign(*this, Layout, AF); 870 continue; 871 } 872 case MCFragment::FT_Data: { 873 MCDataFragment &DF = cast<MCDataFragment>(Frag); 874 Fixups = DF.getFixups(); 875 Contents = DF.getContents(); 876 STI = DF.getSubtargetInfo(); 877 assert(!DF.hasInstructions() || STI != nullptr); 878 break; 879 } 880 case MCFragment::FT_Relaxable: { 881 MCRelaxableFragment &RF = cast<MCRelaxableFragment>(Frag); 882 Fixups = RF.getFixups(); 883 Contents = RF.getContents(); 884 STI = RF.getSubtargetInfo(); 885 assert(!RF.hasInstructions() || STI != nullptr); 886 break; 887 } 888 case MCFragment::FT_CVDefRange: { 889 MCCVDefRangeFragment &CF = cast<MCCVDefRangeFragment>(Frag); 890 Fixups = CF.getFixups(); 891 Contents = CF.getContents(); 892 break; 893 } 894 case MCFragment::FT_Dwarf: { 895 MCDwarfLineAddrFragment &DF = cast<MCDwarfLineAddrFragment>(Frag); 896 Fixups = DF.getFixups(); 897 Contents = DF.getContents(); 898 break; 899 } 900 case MCFragment::FT_DwarfFrame: { 901 MCDwarfCallFrameFragment &DF = cast<MCDwarfCallFrameFragment>(Frag); 902 Fixups = DF.getFixups(); 903 Contents = DF.getContents(); 904 break; 905 } 906 case MCFragment::FT_PseudoProbe: { 907 MCPseudoProbeAddrFragment &PF = cast<MCPseudoProbeAddrFragment>(Frag); 908 Fixups = PF.getFixups(); 909 Contents = PF.getContents(); 910 break; 911 } 912 } 913 for (const MCFixup &Fixup : Fixups) { 914 uint64_t FixedValue; 915 bool IsResolved; 916 MCValue Target; 917 std::tie(Target, FixedValue, IsResolved) = 918 handleFixup(Layout, Frag, Fixup); 919 getBackend().applyFixup(*this, Fixup, Target, Contents, FixedValue, 920 IsResolved, STI); 921 } 922 } 923 } 924 } 925 926 void MCAssembler::Finish() { 927 // Create the layout object. 928 MCAsmLayout Layout(*this); 929 layout(Layout); 930 931 // Write the object file. 932 stats::ObjectBytes += getWriter().writeObject(*this, Layout); 933 } 934 935 bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup, 936 const MCRelaxableFragment *DF, 937 const MCAsmLayout &Layout) const { 938 assert(getBackendPtr() && "Expected assembler backend"); 939 MCValue Target; 940 uint64_t Value; 941 bool WasForced; 942 bool Resolved = evaluateFixup(Layout, Fixup, DF, Target, Value, WasForced); 943 if (Target.getSymA() && 944 Target.getSymA()->getKind() == MCSymbolRefExpr::VK_X86_ABS8 && 945 Fixup.getKind() == FK_Data_1) 946 return false; 947 return getBackend().fixupNeedsRelaxationAdvanced(Fixup, Resolved, Value, DF, 948 Layout, WasForced); 949 } 950 951 bool MCAssembler::fragmentNeedsRelaxation(const MCRelaxableFragment *F, 952 const MCAsmLayout &Layout) const { 953 assert(getBackendPtr() && "Expected assembler backend"); 954 // If this inst doesn't ever need relaxation, ignore it. This occurs when we 955 // are intentionally pushing out inst fragments, or because we relaxed a 956 // previous instruction to one that doesn't need relaxation. 957 if (!getBackend().mayNeedRelaxation(F->getInst(), *F->getSubtargetInfo())) 958 return false; 959 960 for (const MCFixup &Fixup : F->getFixups()) 961 if (fixupNeedsRelaxation(Fixup, F, Layout)) 962 return true; 963 964 return false; 965 } 966 967 bool MCAssembler::relaxInstruction(MCAsmLayout &Layout, 968 MCRelaxableFragment &F) { 969 assert(getEmitterPtr() && 970 "Expected CodeEmitter defined for relaxInstruction"); 971 if (!fragmentNeedsRelaxation(&F, Layout)) 972 return false; 973 974 ++stats::RelaxedInstructions; 975 976 // FIXME-PERF: We could immediately lower out instructions if we can tell 977 // they are fully resolved, to avoid retesting on later passes. 978 979 // Relax the fragment. 980 981 MCInst Relaxed = F.getInst(); 982 getBackend().relaxInstruction(Relaxed, *F.getSubtargetInfo()); 983 984 // Encode the new instruction. 985 // 986 // FIXME-PERF: If it matters, we could let the target do this. It can 987 // probably do so more efficiently in many cases. 988 SmallVector<MCFixup, 4> Fixups; 989 SmallString<256> Code; 990 raw_svector_ostream VecOS(Code); 991 getEmitter().encodeInstruction(Relaxed, VecOS, Fixups, *F.getSubtargetInfo()); 992 993 // Update the fragment. 994 F.setInst(Relaxed); 995 F.getContents() = Code; 996 F.getFixups() = Fixups; 997 998 return true; 999 } 1000 1001 bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) { 1002 uint64_t OldSize = LF.getContents().size(); 1003 int64_t Value; 1004 bool Abs = LF.getValue().evaluateKnownAbsolute(Value, Layout); 1005 if (!Abs) 1006 report_fatal_error("sleb128 and uleb128 expressions must be absolute"); 1007 SmallString<8> &Data = LF.getContents(); 1008 Data.clear(); 1009 raw_svector_ostream OSE(Data); 1010 // The compiler can generate EH table assembly that is impossible to assemble 1011 // without either adding padding to an LEB fragment or adding extra padding 1012 // to a later alignment fragment. To accommodate such tables, relaxation can 1013 // only increase an LEB fragment size here, not decrease it. See PR35809. 1014 if (LF.isSigned()) 1015 encodeSLEB128(Value, OSE, OldSize); 1016 else 1017 encodeULEB128(Value, OSE, OldSize); 1018 return OldSize != LF.getContents().size(); 1019 } 1020 1021 /// Check if the branch crosses the boundary. 1022 /// 1023 /// \param StartAddr start address of the fused/unfused branch. 1024 /// \param Size size of the fused/unfused branch. 1025 /// \param BoundaryAlignment alignment requirement of the branch. 1026 /// \returns true if the branch cross the boundary. 1027 static bool mayCrossBoundary(uint64_t StartAddr, uint64_t Size, 1028 Align BoundaryAlignment) { 1029 uint64_t EndAddr = StartAddr + Size; 1030 return (StartAddr >> Log2(BoundaryAlignment)) != 1031 ((EndAddr - 1) >> Log2(BoundaryAlignment)); 1032 } 1033 1034 /// Check if the branch is against the boundary. 1035 /// 1036 /// \param StartAddr start address of the fused/unfused branch. 1037 /// \param Size size of the fused/unfused branch. 1038 /// \param BoundaryAlignment alignment requirement of the branch. 1039 /// \returns true if the branch is against the boundary. 1040 static bool isAgainstBoundary(uint64_t StartAddr, uint64_t Size, 1041 Align BoundaryAlignment) { 1042 uint64_t EndAddr = StartAddr + Size; 1043 return (EndAddr & (BoundaryAlignment.value() - 1)) == 0; 1044 } 1045 1046 /// Check if the branch needs padding. 1047 /// 1048 /// \param StartAddr start address of the fused/unfused branch. 1049 /// \param Size size of the fused/unfused branch. 1050 /// \param BoundaryAlignment alignment requirement of the branch. 1051 /// \returns true if the branch needs padding. 1052 static bool needPadding(uint64_t StartAddr, uint64_t Size, 1053 Align BoundaryAlignment) { 1054 return mayCrossBoundary(StartAddr, Size, BoundaryAlignment) || 1055 isAgainstBoundary(StartAddr, Size, BoundaryAlignment); 1056 } 1057 1058 bool MCAssembler::relaxBoundaryAlign(MCAsmLayout &Layout, 1059 MCBoundaryAlignFragment &BF) { 1060 // BoundaryAlignFragment that doesn't need to align any fragment should not be 1061 // relaxed. 1062 if (!BF.getLastFragment()) 1063 return false; 1064 1065 uint64_t AlignedOffset = Layout.getFragmentOffset(&BF); 1066 uint64_t AlignedSize = 0; 1067 for (const MCFragment *F = BF.getLastFragment(); F != &BF; 1068 F = F->getPrevNode()) 1069 AlignedSize += computeFragmentSize(Layout, *F); 1070 1071 Align BoundaryAlignment = BF.getAlignment(); 1072 uint64_t NewSize = needPadding(AlignedOffset, AlignedSize, BoundaryAlignment) 1073 ? offsetToAlignment(AlignedOffset, BoundaryAlignment) 1074 : 0U; 1075 if (NewSize == BF.getSize()) 1076 return false; 1077 BF.setSize(NewSize); 1078 Layout.invalidateFragmentsFrom(&BF); 1079 return true; 1080 } 1081 1082 bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout, 1083 MCDwarfLineAddrFragment &DF) { 1084 1085 bool WasRelaxed; 1086 if (getBackend().relaxDwarfLineAddr(DF, Layout, WasRelaxed)) 1087 return WasRelaxed; 1088 1089 MCContext &Context = Layout.getAssembler().getContext(); 1090 uint64_t OldSize = DF.getContents().size(); 1091 int64_t AddrDelta; 1092 bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout); 1093 assert(Abs && "We created a line delta with an invalid expression"); 1094 (void)Abs; 1095 int64_t LineDelta; 1096 LineDelta = DF.getLineDelta(); 1097 SmallVectorImpl<char> &Data = DF.getContents(); 1098 Data.clear(); 1099 raw_svector_ostream OSE(Data); 1100 DF.getFixups().clear(); 1101 1102 MCDwarfLineAddr::Encode(Context, getDWARFLinetableParams(), LineDelta, 1103 AddrDelta, OSE); 1104 return OldSize != Data.size(); 1105 } 1106 1107 bool MCAssembler::relaxDwarfCallFrameFragment(MCAsmLayout &Layout, 1108 MCDwarfCallFrameFragment &DF) { 1109 bool WasRelaxed; 1110 if (getBackend().relaxDwarfCFA(DF, Layout, WasRelaxed)) 1111 return WasRelaxed; 1112 1113 MCContext &Context = Layout.getAssembler().getContext(); 1114 uint64_t OldSize = DF.getContents().size(); 1115 int64_t AddrDelta; 1116 bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout); 1117 assert(Abs && "We created call frame with an invalid expression"); 1118 (void) Abs; 1119 SmallVectorImpl<char> &Data = DF.getContents(); 1120 Data.clear(); 1121 raw_svector_ostream OSE(Data); 1122 DF.getFixups().clear(); 1123 1124 MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE); 1125 return OldSize != Data.size(); 1126 } 1127 1128 bool MCAssembler::relaxCVInlineLineTable(MCAsmLayout &Layout, 1129 MCCVInlineLineTableFragment &F) { 1130 unsigned OldSize = F.getContents().size(); 1131 getContext().getCVContext().encodeInlineLineTable(Layout, F); 1132 return OldSize != F.getContents().size(); 1133 } 1134 1135 bool MCAssembler::relaxCVDefRange(MCAsmLayout &Layout, 1136 MCCVDefRangeFragment &F) { 1137 unsigned OldSize = F.getContents().size(); 1138 getContext().getCVContext().encodeDefRange(Layout, F); 1139 return OldSize != F.getContents().size(); 1140 } 1141 1142 bool MCAssembler::relaxPseudoProbeAddr(MCAsmLayout &Layout, 1143 MCPseudoProbeAddrFragment &PF) { 1144 uint64_t OldSize = PF.getContents().size(); 1145 int64_t AddrDelta; 1146 bool Abs = PF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout); 1147 assert(Abs && "We created a pseudo probe with an invalid expression"); 1148 (void)Abs; 1149 SmallVectorImpl<char> &Data = PF.getContents(); 1150 Data.clear(); 1151 raw_svector_ostream OSE(Data); 1152 PF.getFixups().clear(); 1153 1154 // AddrDelta is a signed integer 1155 encodeSLEB128(AddrDelta, OSE, OldSize); 1156 return OldSize != Data.size(); 1157 } 1158 1159 bool MCAssembler::relaxFragment(MCAsmLayout &Layout, MCFragment &F) { 1160 switch(F.getKind()) { 1161 default: 1162 return false; 1163 case MCFragment::FT_Relaxable: 1164 assert(!getRelaxAll() && 1165 "Did not expect a MCRelaxableFragment in RelaxAll mode"); 1166 return relaxInstruction(Layout, cast<MCRelaxableFragment>(F)); 1167 case MCFragment::FT_Dwarf: 1168 return relaxDwarfLineAddr(Layout, cast<MCDwarfLineAddrFragment>(F)); 1169 case MCFragment::FT_DwarfFrame: 1170 return relaxDwarfCallFrameFragment(Layout, 1171 cast<MCDwarfCallFrameFragment>(F)); 1172 case MCFragment::FT_LEB: 1173 return relaxLEB(Layout, cast<MCLEBFragment>(F)); 1174 case MCFragment::FT_BoundaryAlign: 1175 return relaxBoundaryAlign(Layout, cast<MCBoundaryAlignFragment>(F)); 1176 case MCFragment::FT_CVInlineLines: 1177 return relaxCVInlineLineTable(Layout, cast<MCCVInlineLineTableFragment>(F)); 1178 case MCFragment::FT_CVDefRange: 1179 return relaxCVDefRange(Layout, cast<MCCVDefRangeFragment>(F)); 1180 case MCFragment::FT_PseudoProbe: 1181 return relaxPseudoProbeAddr(Layout, cast<MCPseudoProbeAddrFragment>(F)); 1182 } 1183 } 1184 1185 bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSection &Sec) { 1186 // Holds the first fragment which needed relaxing during this layout. It will 1187 // remain NULL if none were relaxed. 1188 // When a fragment is relaxed, all the fragments following it should get 1189 // invalidated because their offset is going to change. 1190 MCFragment *FirstRelaxedFragment = nullptr; 1191 1192 // Attempt to relax all the fragments in the section. 1193 for (MCFragment &Frag : Sec) { 1194 // Check if this is a fragment that needs relaxation. 1195 bool RelaxedFrag = relaxFragment(Layout, Frag); 1196 if (RelaxedFrag && !FirstRelaxedFragment) 1197 FirstRelaxedFragment = &Frag; 1198 } 1199 if (FirstRelaxedFragment) { 1200 Layout.invalidateFragmentsFrom(FirstRelaxedFragment); 1201 return true; 1202 } 1203 return false; 1204 } 1205 1206 bool MCAssembler::layoutOnce(MCAsmLayout &Layout) { 1207 ++stats::RelaxationSteps; 1208 1209 bool WasRelaxed = false; 1210 for (MCSection &Sec : *this) { 1211 while (layoutSectionOnce(Layout, Sec)) 1212 WasRelaxed = true; 1213 } 1214 1215 return WasRelaxed; 1216 } 1217 1218 void MCAssembler::finishLayout(MCAsmLayout &Layout) { 1219 assert(getBackendPtr() && "Expected assembler backend"); 1220 // The layout is done. Mark every fragment as valid. 1221 for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) { 1222 MCSection &Section = *Layout.getSectionOrder()[i]; 1223 Layout.getFragmentOffset(&*Section.getFragmentList().rbegin()); 1224 computeFragmentSize(Layout, *Section.getFragmentList().rbegin()); 1225 } 1226 getBackend().finishLayout(*this, Layout); 1227 } 1228 1229 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 1230 LLVM_DUMP_METHOD void MCAssembler::dump() const{ 1231 raw_ostream &OS = errs(); 1232 1233 OS << "<MCAssembler\n"; 1234 OS << " Sections:[\n "; 1235 for (const_iterator it = begin(), ie = end(); it != ie; ++it) { 1236 if (it != begin()) OS << ",\n "; 1237 it->dump(); 1238 } 1239 OS << "],\n"; 1240 OS << " Symbols:["; 1241 1242 for (const_symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) { 1243 if (it != symbol_begin()) OS << ",\n "; 1244 OS << "("; 1245 it->dump(); 1246 OS << ", Index:" << it->getIndex() << ", "; 1247 OS << ")"; 1248 } 1249 OS << "]>\n"; 1250 } 1251 #endif 1252