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/MCSymbol.h" 31 #include "llvm/MC/MCValue.h" 32 #include "llvm/Support/Alignment.h" 33 #include "llvm/Support/Casting.h" 34 #include "llvm/Support/Debug.h" 35 #include "llvm/Support/EndianStream.h" 36 #include "llvm/Support/ErrorHandling.h" 37 #include "llvm/Support/LEB128.h" 38 #include "llvm/Support/raw_ostream.h" 39 #include <cassert> 40 #include <cstdint> 41 #include <tuple> 42 #include <utility> 43 44 using namespace llvm; 45 46 namespace llvm { 47 class MCSubtargetInfo; 48 } 49 50 #define DEBUG_TYPE "assembler" 51 52 namespace { 53 namespace stats { 54 55 STATISTIC(EmittedFragments, "Number of emitted assembler fragments - total"); 56 STATISTIC(EmittedRelaxableFragments, 57 "Number of emitted assembler fragments - relaxable"); 58 STATISTIC(EmittedDataFragments, 59 "Number of emitted assembler fragments - data"); 60 STATISTIC(EmittedCompactEncodedInstFragments, 61 "Number of emitted assembler fragments - compact encoded inst"); 62 STATISTIC(EmittedAlignFragments, 63 "Number of emitted assembler fragments - align"); 64 STATISTIC(EmittedFillFragments, 65 "Number of emitted assembler fragments - fill"); 66 STATISTIC(EmittedNopsFragments, "Number of emitted assembler fragments - nops"); 67 STATISTIC(EmittedOrgFragments, "Number of emitted assembler fragments - org"); 68 STATISTIC(evaluateFixup, "Number of evaluated fixups"); 69 STATISTIC(FragmentLayouts, "Number of fragment layouts"); 70 STATISTIC(ObjectBytes, "Number of emitted object file bytes"); 71 STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps"); 72 STATISTIC(RelaxedInstructions, "Number of relaxed instructions"); 73 74 } // end namespace stats 75 } // end anonymous namespace 76 77 // FIXME FIXME FIXME: There are number of places in this file where we convert 78 // what is a 64-bit assembler value used for computation into a value in the 79 // object file, which may truncate it. We should detect that truncation where 80 // invalid and report errors back. 81 82 /* *** */ 83 84 MCAssembler::MCAssembler(MCContext &Context, 85 std::unique_ptr<MCAsmBackend> Backend, 86 std::unique_ptr<MCCodeEmitter> Emitter, 87 std::unique_ptr<MCObjectWriter> Writer) 88 : Context(Context), Backend(std::move(Backend)), 89 Emitter(std::move(Emitter)), Writer(std::move(Writer)), 90 BundleAlignSize(0), RelaxAll(false), SubsectionsViaSymbols(false), 91 IncrementalLinkerCompatible(false), ELFHeaderEFlags(0) { 92 VersionInfo.Major = 0; // Major version == 0 for "none specified" 93 DarwinTargetVariantVersionInfo.Major = 0; 94 } 95 96 MCAssembler::~MCAssembler() = default; 97 98 void MCAssembler::reset() { 99 Sections.clear(); 100 Symbols.clear(); 101 IndirectSymbols.clear(); 102 DataRegions.clear(); 103 LinkerOptions.clear(); 104 FileNames.clear(); 105 ThumbFuncs.clear(); 106 BundleAlignSize = 0; 107 RelaxAll = false; 108 SubsectionsViaSymbols = false; 109 IncrementalLinkerCompatible = false; 110 ELFHeaderEFlags = 0; 111 LOHContainer.reset(); 112 VersionInfo.Major = 0; 113 VersionInfo.SDKVersion = VersionTuple(); 114 DarwinTargetVariantVersionInfo.Major = 0; 115 DarwinTargetVariantVersionInfo.SDKVersion = VersionTuple(); 116 117 // reset objects owned by us 118 if (getBackendPtr()) 119 getBackendPtr()->reset(); 120 if (getEmitterPtr()) 121 getEmitterPtr()->reset(); 122 if (getWriterPtr()) 123 getWriterPtr()->reset(); 124 getLOHContainer().reset(); 125 } 126 127 bool MCAssembler::registerSection(MCSection &Section) { 128 if (Section.isRegistered()) 129 return false; 130 Sections.push_back(&Section); 131 Section.setIsRegistered(true); 132 return true; 133 } 134 135 bool MCAssembler::isThumbFunc(const MCSymbol *Symbol) const { 136 if (ThumbFuncs.count(Symbol)) 137 return true; 138 139 if (!Symbol->isVariable()) 140 return false; 141 142 const MCExpr *Expr = Symbol->getVariableValue(); 143 144 MCValue V; 145 if (!Expr->evaluateAsRelocatable(V, nullptr, nullptr)) 146 return false; 147 148 if (V.getSymB() || V.getRefKind() != MCSymbolRefExpr::VK_None) 149 return false; 150 151 const MCSymbolRefExpr *Ref = V.getSymA(); 152 if (!Ref) 153 return false; 154 155 if (Ref->getKind() != MCSymbolRefExpr::VK_None) 156 return false; 157 158 const MCSymbol &Sym = Ref->getSymbol(); 159 if (!isThumbFunc(&Sym)) 160 return false; 161 162 ThumbFuncs.insert(Symbol); // Cache it. 163 return true; 164 } 165 166 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const { 167 // Non-temporary labels should always be visible to the linker. 168 if (!Symbol.isTemporary()) 169 return true; 170 171 if (Symbol.isUsedInReloc()) 172 return true; 173 174 return false; 175 } 176 177 const MCSymbol *MCAssembler::getAtom(const MCSymbol &S) const { 178 // Linker visible symbols define atoms. 179 if (isSymbolLinkerVisible(S)) 180 return &S; 181 182 // Absolute and undefined symbols have no defining atom. 183 if (!S.isInSection()) 184 return nullptr; 185 186 // Non-linker visible symbols in sections which can't be atomized have no 187 // defining atom. 188 if (!getContext().getAsmInfo()->isSectionAtomizableBySymbols( 189 *S.getFragment()->getParent())) 190 return nullptr; 191 192 // Otherwise, return the atom for the containing fragment. 193 return S.getFragment()->getAtom(); 194 } 195 196 bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout, const MCFixup &Fixup, 197 const MCFragment *DF, MCValue &Target, 198 const MCSubtargetInfo *STI, uint64_t &Value, 199 bool &WasForced) const { 200 ++stats::evaluateFixup; 201 202 // FIXME: This code has some duplication with recordRelocation. We should 203 // probably merge the two into a single callback that tries to evaluate a 204 // fixup and records a relocation if one is needed. 205 206 // On error claim to have completely evaluated the fixup, to prevent any 207 // further processing from being done. 208 const MCExpr *Expr = Fixup.getValue(); 209 MCContext &Ctx = getContext(); 210 Value = 0; 211 WasForced = false; 212 if (!Expr->evaluateAsRelocatable(Target, &Layout, &Fixup)) { 213 Ctx.reportError(Fixup.getLoc(), "expected relocatable expression"); 214 return true; 215 } 216 if (const MCSymbolRefExpr *RefB = Target.getSymB()) { 217 if (RefB->getKind() != MCSymbolRefExpr::VK_None) { 218 Ctx.reportError(Fixup.getLoc(), 219 "unsupported subtraction of qualified symbol"); 220 return true; 221 } 222 } 223 224 assert(getBackendPtr() && "Expected assembler backend"); 225 bool IsTarget = getBackendPtr()->getFixupKindInfo(Fixup.getKind()).Flags & 226 MCFixupKindInfo::FKF_IsTarget; 227 228 if (IsTarget) 229 return getBackend().evaluateTargetFixup(*this, Layout, Fixup, DF, Target, 230 STI, Value, WasForced); 231 232 unsigned FixupFlags = getBackendPtr()->getFixupKindInfo(Fixup.getKind()).Flags; 233 bool IsPCRel = getBackendPtr()->getFixupKindInfo(Fixup.getKind()).Flags & 234 MCFixupKindInfo::FKF_IsPCRel; 235 236 bool IsResolved = false; 237 if (IsPCRel) { 238 if (Target.getSymB()) { 239 IsResolved = false; 240 } else if (!Target.getSymA()) { 241 IsResolved = false; 242 } else { 243 const MCSymbolRefExpr *A = Target.getSymA(); 244 const MCSymbol &SA = A->getSymbol(); 245 if (A->getKind() != MCSymbolRefExpr::VK_None || SA.isUndefined()) { 246 IsResolved = false; 247 } else if (auto *Writer = getWriterPtr()) { 248 IsResolved = (FixupFlags & MCFixupKindInfo::FKF_Constant) || 249 Writer->isSymbolRefDifferenceFullyResolvedImpl( 250 *this, SA, *DF, false, true); 251 } 252 } 253 } else { 254 IsResolved = Target.isAbsolute(); 255 } 256 257 Value = Target.getConstant(); 258 259 if (const MCSymbolRefExpr *A = Target.getSymA()) { 260 const MCSymbol &Sym = A->getSymbol(); 261 if (Sym.isDefined()) 262 Value += Layout.getSymbolOffset(Sym); 263 } 264 if (const MCSymbolRefExpr *B = Target.getSymB()) { 265 const MCSymbol &Sym = B->getSymbol(); 266 if (Sym.isDefined()) 267 Value -= Layout.getSymbolOffset(Sym); 268 } 269 270 bool ShouldAlignPC = getBackend().getFixupKindInfo(Fixup.getKind()).Flags & 271 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits; 272 assert((ShouldAlignPC ? IsPCRel : true) && 273 "FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!"); 274 275 if (IsPCRel) { 276 uint64_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset(); 277 278 // A number of ARM fixups in Thumb mode require that the effective PC 279 // address be determined as the 32-bit aligned version of the actual offset. 280 if (ShouldAlignPC) Offset &= ~0x3; 281 Value -= Offset; 282 } 283 284 // Let the backend force a relocation if needed. 285 if (IsResolved && 286 getBackend().shouldForceRelocation(*this, Fixup, Target, STI)) { 287 IsResolved = false; 288 WasForced = true; 289 } 290 291 // A linker relaxation target may emit ADD/SUB relocations for A-B+C. Let 292 // recordRelocation handle non-VK_None cases like A@plt-B+C. 293 if (!IsResolved && Target.getSymA() && Target.getSymB() && 294 Target.getSymA()->getKind() == MCSymbolRefExpr::VK_None && 295 getBackend().handleAddSubRelocations(Layout, *DF, Fixup, Target, Value)) 296 return true; 297 298 return IsResolved; 299 } 300 301 uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout, 302 const MCFragment &F) const { 303 assert(getBackendPtr() && "Requires assembler backend"); 304 switch (F.getKind()) { 305 case MCFragment::FT_Data: 306 return cast<MCDataFragment>(F).getContents().size(); 307 case MCFragment::FT_Relaxable: 308 return cast<MCRelaxableFragment>(F).getContents().size(); 309 case MCFragment::FT_CompactEncodedInst: 310 return cast<MCCompactEncodedInstFragment>(F).getContents().size(); 311 case MCFragment::FT_Fill: { 312 auto &FF = cast<MCFillFragment>(F); 313 int64_t NumValues = 0; 314 if (!FF.getNumValues().evaluateKnownAbsolute(NumValues, Layout)) { 315 getContext().reportError(FF.getLoc(), 316 "expected assembly-time absolute expression"); 317 return 0; 318 } 319 int64_t Size = NumValues * FF.getValueSize(); 320 if (Size < 0) { 321 getContext().reportError(FF.getLoc(), "invalid number of bytes"); 322 return 0; 323 } 324 return Size; 325 } 326 327 case MCFragment::FT_Nops: 328 return cast<MCNopsFragment>(F).getNumBytes(); 329 330 case MCFragment::FT_LEB: 331 return cast<MCLEBFragment>(F).getContents().size(); 332 333 case MCFragment::FT_BoundaryAlign: 334 return cast<MCBoundaryAlignFragment>(F).getSize(); 335 336 case MCFragment::FT_SymbolId: 337 return 4; 338 339 case MCFragment::FT_Align: { 340 const MCAlignFragment &AF = cast<MCAlignFragment>(F); 341 unsigned Offset = Layout.getFragmentOffset(&AF); 342 unsigned Size = offsetToAlignment(Offset, AF.getAlignment()); 343 344 // Insert extra Nops for code alignment if the target define 345 // shouldInsertExtraNopBytesForCodeAlign target hook. 346 if (AF.getParent()->useCodeAlign() && AF.hasEmitNops() && 347 getBackend().shouldInsertExtraNopBytesForCodeAlign(AF, Size)) 348 return Size; 349 350 // If we are padding with nops, force the padding to be larger than the 351 // minimum nop size. 352 if (Size > 0 && AF.hasEmitNops()) { 353 while (Size % getBackend().getMinimumNopSize()) 354 Size += AF.getAlignment().value(); 355 } 356 if (Size > AF.getMaxBytesToEmit()) 357 return 0; 358 return Size; 359 } 360 361 case MCFragment::FT_Org: { 362 const MCOrgFragment &OF = cast<MCOrgFragment>(F); 363 MCValue Value; 364 if (!OF.getOffset().evaluateAsValue(Value, Layout)) { 365 getContext().reportError(OF.getLoc(), 366 "expected assembly-time absolute expression"); 367 return 0; 368 } 369 370 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF); 371 int64_t TargetLocation = Value.getConstant(); 372 if (const MCSymbolRefExpr *A = Value.getSymA()) { 373 uint64_t Val; 374 if (!Layout.getSymbolOffset(A->getSymbol(), Val)) { 375 getContext().reportError(OF.getLoc(), "expected absolute expression"); 376 return 0; 377 } 378 TargetLocation += Val; 379 } 380 int64_t Size = TargetLocation - FragmentOffset; 381 if (Size < 0 || Size >= 0x40000000) { 382 getContext().reportError( 383 OF.getLoc(), "invalid .org offset '" + Twine(TargetLocation) + 384 "' (at offset '" + Twine(FragmentOffset) + "')"); 385 return 0; 386 } 387 return Size; 388 } 389 390 case MCFragment::FT_Dwarf: 391 return cast<MCDwarfLineAddrFragment>(F).getContents().size(); 392 case MCFragment::FT_DwarfFrame: 393 return cast<MCDwarfCallFrameFragment>(F).getContents().size(); 394 case MCFragment::FT_CVInlineLines: 395 return cast<MCCVInlineLineTableFragment>(F).getContents().size(); 396 case MCFragment::FT_CVDefRange: 397 return cast<MCCVDefRangeFragment>(F).getContents().size(); 398 case MCFragment::FT_PseudoProbe: 399 return cast<MCPseudoProbeAddrFragment>(F).getContents().size(); 400 case MCFragment::FT_Dummy: 401 llvm_unreachable("Should not have been added"); 402 } 403 404 llvm_unreachable("invalid fragment kind"); 405 } 406 407 void MCAsmLayout::layoutFragment(MCFragment *F) { 408 MCFragment *Prev = F->getPrevNode(); 409 410 // We should never try to recompute something which is valid. 411 assert(!isFragmentValid(F) && "Attempt to recompute a valid fragment!"); 412 // We should never try to compute the fragment layout if its predecessor 413 // isn't valid. 414 assert((!Prev || isFragmentValid(Prev)) && 415 "Attempt to compute fragment before its predecessor!"); 416 417 assert(!F->IsBeingLaidOut && "Already being laid out!"); 418 F->IsBeingLaidOut = true; 419 420 ++stats::FragmentLayouts; 421 422 // Compute fragment offset and size. 423 if (Prev) 424 F->Offset = Prev->Offset + getAssembler().computeFragmentSize(*this, *Prev); 425 else 426 F->Offset = 0; 427 F->IsBeingLaidOut = false; 428 LastValidFragment[F->getParent()] = F; 429 430 // If bundling is enabled and this fragment has instructions in it, it has to 431 // obey the bundling restrictions. With padding, we'll have: 432 // 433 // 434 // BundlePadding 435 // ||| 436 // ------------------------------------- 437 // Prev |##########| F | 438 // ------------------------------------- 439 // ^ 440 // | 441 // F->Offset 442 // 443 // The fragment's offset will point to after the padding, and its computed 444 // size won't include the padding. 445 // 446 // When the -mc-relax-all flag is used, we optimize bundling by writting the 447 // padding directly into fragments when the instructions are emitted inside 448 // the streamer. When the fragment is larger than the bundle size, we need to 449 // ensure that it's bundle aligned. This means that if we end up with 450 // multiple fragments, we must emit bundle padding between fragments. 451 // 452 // ".align N" is an example of a directive that introduces multiple 453 // fragments. We could add a special case to handle ".align N" by emitting 454 // within-fragment padding (which would produce less padding when N is less 455 // than the bundle size), but for now we don't. 456 // 457 if (Assembler.isBundlingEnabled() && F->hasInstructions()) { 458 assert(isa<MCEncodedFragment>(F) && 459 "Only MCEncodedFragment implementations have instructions"); 460 MCEncodedFragment *EF = cast<MCEncodedFragment>(F); 461 uint64_t FSize = Assembler.computeFragmentSize(*this, *EF); 462 463 if (!Assembler.getRelaxAll() && FSize > Assembler.getBundleAlignSize()) 464 report_fatal_error("Fragment can't be larger than a bundle size"); 465 466 uint64_t RequiredBundlePadding = 467 computeBundlePadding(Assembler, EF, EF->Offset, FSize); 468 if (RequiredBundlePadding > UINT8_MAX) 469 report_fatal_error("Padding cannot exceed 255 bytes"); 470 EF->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding)); 471 EF->Offset += RequiredBundlePadding; 472 } 473 } 474 475 bool MCAssembler::registerSymbol(const MCSymbol &Symbol) { 476 bool Changed = !Symbol.isRegistered(); 477 if (Changed) { 478 Symbol.setIsRegistered(true); 479 Symbols.push_back(&Symbol); 480 } 481 return Changed; 482 } 483 484 void MCAssembler::writeFragmentPadding(raw_ostream &OS, 485 const MCEncodedFragment &EF, 486 uint64_t FSize) const { 487 assert(getBackendPtr() && "Expected assembler backend"); 488 // Should NOP padding be written out before this fragment? 489 unsigned BundlePadding = EF.getBundlePadding(); 490 if (BundlePadding > 0) { 491 assert(isBundlingEnabled() && 492 "Writing bundle padding with disabled bundling"); 493 assert(EF.hasInstructions() && 494 "Writing bundle padding for a fragment without instructions"); 495 496 unsigned TotalLength = BundlePadding + static_cast<unsigned>(FSize); 497 const MCSubtargetInfo *STI = EF.getSubtargetInfo(); 498 if (EF.alignToBundleEnd() && TotalLength > getBundleAlignSize()) { 499 // If the padding itself crosses a bundle boundary, it must be emitted 500 // in 2 pieces, since even nop instructions must not cross boundaries. 501 // v--------------v <- BundleAlignSize 502 // v---------v <- BundlePadding 503 // ---------------------------- 504 // | Prev |####|####| F | 505 // ---------------------------- 506 // ^-------------------^ <- TotalLength 507 unsigned DistanceToBoundary = TotalLength - getBundleAlignSize(); 508 if (!getBackend().writeNopData(OS, DistanceToBoundary, STI)) 509 report_fatal_error("unable to write NOP sequence of " + 510 Twine(DistanceToBoundary) + " bytes"); 511 BundlePadding -= DistanceToBoundary; 512 } 513 if (!getBackend().writeNopData(OS, BundlePadding, STI)) 514 report_fatal_error("unable to write NOP sequence of " + 515 Twine(BundlePadding) + " bytes"); 516 } 517 } 518 519 /// Write the fragment \p F to the output file. 520 static void writeFragment(raw_ostream &OS, const MCAssembler &Asm, 521 const MCAsmLayout &Layout, const MCFragment &F) { 522 // FIXME: Embed in fragments instead? 523 uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F); 524 525 llvm::endianness Endian = Asm.getBackend().Endian; 526 527 if (const MCEncodedFragment *EF = dyn_cast<MCEncodedFragment>(&F)) 528 Asm.writeFragmentPadding(OS, *EF, FragmentSize); 529 530 // This variable (and its dummy usage) is to participate in the assert at 531 // the end of the function. 532 uint64_t Start = OS.tell(); 533 (void) Start; 534 535 ++stats::EmittedFragments; 536 537 switch (F.getKind()) { 538 case MCFragment::FT_Align: { 539 ++stats::EmittedAlignFragments; 540 const MCAlignFragment &AF = cast<MCAlignFragment>(F); 541 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!"); 542 543 uint64_t Count = FragmentSize / AF.getValueSize(); 544 545 // FIXME: This error shouldn't actually occur (the front end should emit 546 // multiple .align directives to enforce the semantics it wants), but is 547 // severe enough that we want to report it. How to handle this? 548 if (Count * AF.getValueSize() != FragmentSize) 549 report_fatal_error("undefined .align directive, value size '" + 550 Twine(AF.getValueSize()) + 551 "' is not a divisor of padding size '" + 552 Twine(FragmentSize) + "'"); 553 554 // See if we are aligning with nops, and if so do that first to try to fill 555 // the Count bytes. Then if that did not fill any bytes or there are any 556 // bytes left to fill use the Value and ValueSize to fill the rest. 557 // If we are aligning with nops, ask that target to emit the right data. 558 if (AF.hasEmitNops()) { 559 if (!Asm.getBackend().writeNopData(OS, Count, AF.getSubtargetInfo())) 560 report_fatal_error("unable to write nop sequence of " + 561 Twine(Count) + " bytes"); 562 break; 563 } 564 565 // Otherwise, write out in multiples of the value size. 566 for (uint64_t i = 0; i != Count; ++i) { 567 switch (AF.getValueSize()) { 568 default: llvm_unreachable("Invalid size!"); 569 case 1: OS << char(AF.getValue()); break; 570 case 2: 571 support::endian::write<uint16_t>(OS, AF.getValue(), Endian); 572 break; 573 case 4: 574 support::endian::write<uint32_t>(OS, AF.getValue(), Endian); 575 break; 576 case 8: 577 support::endian::write<uint64_t>(OS, AF.getValue(), Endian); 578 break; 579 } 580 } 581 break; 582 } 583 584 case MCFragment::FT_Data: 585 ++stats::EmittedDataFragments; 586 OS << cast<MCDataFragment>(F).getContents(); 587 break; 588 589 case MCFragment::FT_Relaxable: 590 ++stats::EmittedRelaxableFragments; 591 OS << cast<MCRelaxableFragment>(F).getContents(); 592 break; 593 594 case MCFragment::FT_CompactEncodedInst: 595 ++stats::EmittedCompactEncodedInstFragments; 596 OS << cast<MCCompactEncodedInstFragment>(F).getContents(); 597 break; 598 599 case MCFragment::FT_Fill: { 600 ++stats::EmittedFillFragments; 601 const MCFillFragment &FF = cast<MCFillFragment>(F); 602 uint64_t V = FF.getValue(); 603 unsigned VSize = FF.getValueSize(); 604 const unsigned MaxChunkSize = 16; 605 char Data[MaxChunkSize]; 606 assert(0 < VSize && VSize <= MaxChunkSize && "Illegal fragment fill size"); 607 // Duplicate V into Data as byte vector to reduce number of 608 // writes done. As such, do endian conversion here. 609 for (unsigned I = 0; I != VSize; ++I) { 610 unsigned index = Endian == llvm::endianness::little ? I : (VSize - I - 1); 611 Data[I] = uint8_t(V >> (index * 8)); 612 } 613 for (unsigned I = VSize; I < MaxChunkSize; ++I) 614 Data[I] = Data[I - VSize]; 615 616 // Set to largest multiple of VSize in Data. 617 const unsigned NumPerChunk = MaxChunkSize / VSize; 618 // Set ChunkSize to largest multiple of VSize in Data 619 const unsigned ChunkSize = VSize * NumPerChunk; 620 621 // Do copies by chunk. 622 StringRef Ref(Data, ChunkSize); 623 for (uint64_t I = 0, E = FragmentSize / ChunkSize; I != E; ++I) 624 OS << Ref; 625 626 // do remainder if needed. 627 unsigned TrailingCount = FragmentSize % ChunkSize; 628 if (TrailingCount) 629 OS.write(Data, TrailingCount); 630 break; 631 } 632 633 case MCFragment::FT_Nops: { 634 ++stats::EmittedNopsFragments; 635 const MCNopsFragment &NF = cast<MCNopsFragment>(F); 636 637 int64_t NumBytes = NF.getNumBytes(); 638 int64_t ControlledNopLength = NF.getControlledNopLength(); 639 int64_t MaximumNopLength = 640 Asm.getBackend().getMaximumNopSize(*NF.getSubtargetInfo()); 641 642 assert(NumBytes > 0 && "Expected positive NOPs fragment size"); 643 assert(ControlledNopLength >= 0 && "Expected non-negative NOP size"); 644 645 if (ControlledNopLength > MaximumNopLength) { 646 Asm.getContext().reportError(NF.getLoc(), 647 "illegal NOP size " + 648 std::to_string(ControlledNopLength) + 649 ". (expected within [0, " + 650 std::to_string(MaximumNopLength) + "])"); 651 // Clamp the NOP length as reportError does not stop the execution 652 // immediately. 653 ControlledNopLength = MaximumNopLength; 654 } 655 656 // Use maximum value if the size of each NOP is not specified 657 if (!ControlledNopLength) 658 ControlledNopLength = MaximumNopLength; 659 660 while (NumBytes) { 661 uint64_t NumBytesToEmit = 662 (uint64_t)std::min(NumBytes, ControlledNopLength); 663 assert(NumBytesToEmit && "try to emit empty NOP instruction"); 664 if (!Asm.getBackend().writeNopData(OS, NumBytesToEmit, 665 NF.getSubtargetInfo())) { 666 report_fatal_error("unable to write nop sequence of the remaining " + 667 Twine(NumBytesToEmit) + " bytes"); 668 break; 669 } 670 NumBytes -= NumBytesToEmit; 671 } 672 break; 673 } 674 675 case MCFragment::FT_LEB: { 676 const MCLEBFragment &LF = cast<MCLEBFragment>(F); 677 OS << LF.getContents(); 678 break; 679 } 680 681 case MCFragment::FT_BoundaryAlign: { 682 const MCBoundaryAlignFragment &BF = cast<MCBoundaryAlignFragment>(F); 683 if (!Asm.getBackend().writeNopData(OS, FragmentSize, BF.getSubtargetInfo())) 684 report_fatal_error("unable to write nop sequence of " + 685 Twine(FragmentSize) + " bytes"); 686 break; 687 } 688 689 case MCFragment::FT_SymbolId: { 690 const MCSymbolIdFragment &SF = cast<MCSymbolIdFragment>(F); 691 support::endian::write<uint32_t>(OS, SF.getSymbol()->getIndex(), Endian); 692 break; 693 } 694 695 case MCFragment::FT_Org: { 696 ++stats::EmittedOrgFragments; 697 const MCOrgFragment &OF = cast<MCOrgFragment>(F); 698 699 for (uint64_t i = 0, e = FragmentSize; i != e; ++i) 700 OS << char(OF.getValue()); 701 702 break; 703 } 704 705 case MCFragment::FT_Dwarf: { 706 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F); 707 OS << OF.getContents(); 708 break; 709 } 710 case MCFragment::FT_DwarfFrame: { 711 const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F); 712 OS << CF.getContents(); 713 break; 714 } 715 case MCFragment::FT_CVInlineLines: { 716 const auto &OF = cast<MCCVInlineLineTableFragment>(F); 717 OS << OF.getContents(); 718 break; 719 } 720 case MCFragment::FT_CVDefRange: { 721 const auto &DRF = cast<MCCVDefRangeFragment>(F); 722 OS << DRF.getContents(); 723 break; 724 } 725 case MCFragment::FT_PseudoProbe: { 726 const MCPseudoProbeAddrFragment &PF = cast<MCPseudoProbeAddrFragment>(F); 727 OS << PF.getContents(); 728 break; 729 } 730 case MCFragment::FT_Dummy: 731 llvm_unreachable("Should not have been added"); 732 } 733 734 assert(OS.tell() - Start == FragmentSize && 735 "The stream should advance by fragment size"); 736 } 737 738 void MCAssembler::writeSectionData(raw_ostream &OS, const MCSection *Sec, 739 const MCAsmLayout &Layout) const { 740 assert(getBackendPtr() && "Expected assembler backend"); 741 742 // Ignore virtual sections. 743 if (Sec->isVirtualSection()) { 744 assert(Layout.getSectionFileSize(Sec) == 0 && "Invalid size for section!"); 745 746 // Check that contents are only things legal inside a virtual section. 747 for (const MCFragment &F : *Sec) { 748 switch (F.getKind()) { 749 default: llvm_unreachable("Invalid fragment in virtual section!"); 750 case MCFragment::FT_Data: { 751 // Check that we aren't trying to write a non-zero contents (or fixups) 752 // into a virtual section. This is to support clients which use standard 753 // directives to fill the contents of virtual sections. 754 const MCDataFragment &DF = cast<MCDataFragment>(F); 755 if (DF.fixup_begin() != DF.fixup_end()) 756 getContext().reportError(SMLoc(), Sec->getVirtualSectionKind() + 757 " section '" + Sec->getName() + 758 "' cannot have fixups"); 759 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i) 760 if (DF.getContents()[i]) { 761 getContext().reportError(SMLoc(), 762 Sec->getVirtualSectionKind() + 763 " section '" + Sec->getName() + 764 "' cannot have non-zero initializers"); 765 break; 766 } 767 break; 768 } 769 case MCFragment::FT_Align: 770 // Check that we aren't trying to write a non-zero value into a virtual 771 // section. 772 assert((cast<MCAlignFragment>(F).getValueSize() == 0 || 773 cast<MCAlignFragment>(F).getValue() == 0) && 774 "Invalid align in virtual section!"); 775 break; 776 case MCFragment::FT_Fill: 777 assert((cast<MCFillFragment>(F).getValue() == 0) && 778 "Invalid fill in virtual section!"); 779 break; 780 case MCFragment::FT_Org: 781 break; 782 } 783 } 784 785 return; 786 } 787 788 uint64_t Start = OS.tell(); 789 (void)Start; 790 791 for (const MCFragment &F : *Sec) 792 writeFragment(OS, *this, Layout, F); 793 794 assert(getContext().hadError() || 795 OS.tell() - Start == Layout.getSectionAddressSize(Sec)); 796 } 797 798 std::tuple<MCValue, uint64_t, bool> 799 MCAssembler::handleFixup(const MCAsmLayout &Layout, MCFragment &F, 800 const MCFixup &Fixup, const MCSubtargetInfo *STI) { 801 // Evaluate the fixup. 802 MCValue Target; 803 uint64_t FixedValue; 804 bool WasForced; 805 bool IsResolved = 806 evaluateFixup(Layout, Fixup, &F, Target, STI, FixedValue, WasForced); 807 if (!IsResolved) { 808 // The fixup was unresolved, we need a relocation. Inform the object 809 // writer of the relocation, and give it an opportunity to adjust the 810 // fixup value if need be. 811 getWriter().recordRelocation(*this, Layout, &F, Fixup, Target, FixedValue); 812 } 813 return std::make_tuple(Target, FixedValue, IsResolved); 814 } 815 816 void MCAssembler::layout(MCAsmLayout &Layout) { 817 assert(getBackendPtr() && "Expected assembler backend"); 818 DEBUG_WITH_TYPE("mc-dump", { 819 errs() << "assembler backend - pre-layout\n--\n"; 820 dump(); }); 821 822 // Create dummy fragments and assign section ordinals. 823 unsigned SectionIndex = 0; 824 for (MCSection &Sec : *this) { 825 // Create dummy fragments to eliminate any empty sections, this simplifies 826 // layout. 827 if (Sec.getFragmentList().empty()) 828 new MCDataFragment(&Sec); 829 830 Sec.setOrdinal(SectionIndex++); 831 } 832 833 // Assign layout order indices to sections and fragments. 834 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) { 835 MCSection *Sec = Layout.getSectionOrder()[i]; 836 Sec->setLayoutOrder(i); 837 838 unsigned FragmentIndex = 0; 839 for (MCFragment &Frag : *Sec) 840 Frag.setLayoutOrder(FragmentIndex++); 841 } 842 843 // Layout until everything fits. 844 while (layoutOnce(Layout)) { 845 if (getContext().hadError()) 846 return; 847 // Size of fragments in one section can depend on the size of fragments in 848 // another. If any fragment has changed size, we have to re-layout (and 849 // as a result possibly further relax) all. 850 for (MCSection &Sec : *this) 851 Layout.invalidateFragmentsFrom(&*Sec.begin()); 852 } 853 854 DEBUG_WITH_TYPE("mc-dump", { 855 errs() << "assembler backend - post-relaxation\n--\n"; 856 dump(); }); 857 858 // Finalize the layout, including fragment lowering. 859 finishLayout(Layout); 860 861 DEBUG_WITH_TYPE("mc-dump", { 862 errs() << "assembler backend - final-layout\n--\n"; 863 dump(); }); 864 865 // Allow the object writer a chance to perform post-layout binding (for 866 // example, to set the index fields in the symbol data). 867 getWriter().executePostLayoutBinding(*this, Layout); 868 869 // Evaluate and apply the fixups, generating relocation entries as necessary. 870 for (MCSection &Sec : *this) { 871 for (MCFragment &Frag : Sec) { 872 ArrayRef<MCFixup> Fixups; 873 MutableArrayRef<char> Contents; 874 const MCSubtargetInfo *STI = nullptr; 875 876 // Process MCAlignFragment and MCEncodedFragmentWithFixups here. 877 switch (Frag.getKind()) { 878 default: 879 continue; 880 case MCFragment::FT_Align: { 881 MCAlignFragment &AF = cast<MCAlignFragment>(Frag); 882 // Insert fixup type for code alignment if the target define 883 // shouldInsertFixupForCodeAlign target hook. 884 if (Sec.useCodeAlign() && AF.hasEmitNops()) 885 getBackend().shouldInsertFixupForCodeAlign(*this, Layout, AF); 886 continue; 887 } 888 case MCFragment::FT_Data: { 889 MCDataFragment &DF = cast<MCDataFragment>(Frag); 890 Fixups = DF.getFixups(); 891 Contents = DF.getContents(); 892 STI = DF.getSubtargetInfo(); 893 assert(!DF.hasInstructions() || STI != nullptr); 894 break; 895 } 896 case MCFragment::FT_Relaxable: { 897 MCRelaxableFragment &RF = cast<MCRelaxableFragment>(Frag); 898 Fixups = RF.getFixups(); 899 Contents = RF.getContents(); 900 STI = RF.getSubtargetInfo(); 901 assert(!RF.hasInstructions() || STI != nullptr); 902 break; 903 } 904 case MCFragment::FT_CVDefRange: { 905 MCCVDefRangeFragment &CF = cast<MCCVDefRangeFragment>(Frag); 906 Fixups = CF.getFixups(); 907 Contents = CF.getContents(); 908 break; 909 } 910 case MCFragment::FT_Dwarf: { 911 MCDwarfLineAddrFragment &DF = cast<MCDwarfLineAddrFragment>(Frag); 912 Fixups = DF.getFixups(); 913 Contents = DF.getContents(); 914 break; 915 } 916 case MCFragment::FT_DwarfFrame: { 917 MCDwarfCallFrameFragment &DF = cast<MCDwarfCallFrameFragment>(Frag); 918 Fixups = DF.getFixups(); 919 Contents = DF.getContents(); 920 break; 921 } 922 case MCFragment::FT_LEB: { 923 auto &LF = cast<MCLEBFragment>(Frag); 924 Fixups = LF.getFixups(); 925 Contents = LF.getContents(); 926 break; 927 } 928 case MCFragment::FT_PseudoProbe: { 929 MCPseudoProbeAddrFragment &PF = cast<MCPseudoProbeAddrFragment>(Frag); 930 Fixups = PF.getFixups(); 931 Contents = PF.getContents(); 932 break; 933 } 934 } 935 for (const MCFixup &Fixup : Fixups) { 936 uint64_t FixedValue; 937 bool IsResolved; 938 MCValue Target; 939 std::tie(Target, FixedValue, IsResolved) = 940 handleFixup(Layout, Frag, Fixup, STI); 941 getBackend().applyFixup(*this, Fixup, Target, Contents, FixedValue, 942 IsResolved, STI); 943 } 944 } 945 } 946 } 947 948 void MCAssembler::Finish() { 949 // Create the layout object. 950 MCAsmLayout Layout(*this); 951 layout(Layout); 952 953 // Write the object file. 954 stats::ObjectBytes += getWriter().writeObject(*this, Layout); 955 } 956 957 bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup, 958 const MCRelaxableFragment *DF, 959 const MCAsmLayout &Layout) const { 960 assert(getBackendPtr() && "Expected assembler backend"); 961 MCValue Target; 962 uint64_t Value; 963 bool WasForced; 964 bool Resolved = evaluateFixup(Layout, Fixup, DF, Target, 965 DF->getSubtargetInfo(), Value, WasForced); 966 if (Target.getSymA() && 967 Target.getSymA()->getKind() == MCSymbolRefExpr::VK_X86_ABS8 && 968 Fixup.getKind() == FK_Data_1) 969 return false; 970 return getBackend().fixupNeedsRelaxationAdvanced(Fixup, Resolved, Value, DF, 971 Layout, WasForced); 972 } 973 974 bool MCAssembler::fragmentNeedsRelaxation(const MCRelaxableFragment *F, 975 const MCAsmLayout &Layout) const { 976 assert(getBackendPtr() && "Expected assembler backend"); 977 // If this inst doesn't ever need relaxation, ignore it. This occurs when we 978 // are intentionally pushing out inst fragments, or because we relaxed a 979 // previous instruction to one that doesn't need relaxation. 980 if (!getBackend().mayNeedRelaxation(F->getInst(), *F->getSubtargetInfo())) 981 return false; 982 983 for (const MCFixup &Fixup : F->getFixups()) 984 if (fixupNeedsRelaxation(Fixup, F, Layout)) 985 return true; 986 987 return false; 988 } 989 990 bool MCAssembler::relaxInstruction(MCAsmLayout &Layout, 991 MCRelaxableFragment &F) { 992 assert(getEmitterPtr() && 993 "Expected CodeEmitter defined for relaxInstruction"); 994 if (!fragmentNeedsRelaxation(&F, Layout)) 995 return false; 996 997 ++stats::RelaxedInstructions; 998 999 // FIXME-PERF: We could immediately lower out instructions if we can tell 1000 // they are fully resolved, to avoid retesting on later passes. 1001 1002 // Relax the fragment. 1003 1004 MCInst Relaxed = F.getInst(); 1005 getBackend().relaxInstruction(Relaxed, *F.getSubtargetInfo()); 1006 1007 // Encode the new instruction. 1008 F.setInst(Relaxed); 1009 F.getFixups().clear(); 1010 F.getContents().clear(); 1011 getEmitter().encodeInstruction(Relaxed, F.getContents(), F.getFixups(), 1012 *F.getSubtargetInfo()); 1013 return true; 1014 } 1015 1016 bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) { 1017 const unsigned OldSize = static_cast<unsigned>(LF.getContents().size()); 1018 unsigned PadTo = OldSize; 1019 int64_t Value; 1020 SmallVectorImpl<char> &Data = LF.getContents(); 1021 LF.getFixups().clear(); 1022 // Use evaluateKnownAbsolute for Mach-O as a hack: .subsections_via_symbols 1023 // requires that .uleb128 A-B is foldable where A and B reside in different 1024 // fragments. This is used by __gcc_except_table. 1025 bool Abs = getSubsectionsViaSymbols() 1026 ? LF.getValue().evaluateKnownAbsolute(Value, Layout) 1027 : LF.getValue().evaluateAsAbsolute(Value, Layout); 1028 if (!Abs) { 1029 if (!getBackend().relaxLEB128(LF, Layout, Value)) { 1030 getContext().reportError(LF.getValue().getLoc(), 1031 Twine(LF.isSigned() ? ".s" : ".u") + 1032 "leb128 expression is not absolute"); 1033 LF.setValue(MCConstantExpr::create(0, Context)); 1034 } 1035 uint8_t Tmp[10]; // maximum size: ceil(64/7) 1036 PadTo = std::max(PadTo, encodeULEB128(uint64_t(Value), Tmp)); 1037 } 1038 Data.clear(); 1039 raw_svector_ostream OSE(Data); 1040 // The compiler can generate EH table assembly that is impossible to assemble 1041 // without either adding padding to an LEB fragment or adding extra padding 1042 // to a later alignment fragment. To accommodate such tables, relaxation can 1043 // only increase an LEB fragment size here, not decrease it. See PR35809. 1044 if (LF.isSigned()) 1045 encodeSLEB128(Value, OSE, PadTo); 1046 else 1047 encodeULEB128(Value, OSE, PadTo); 1048 return OldSize != LF.getContents().size(); 1049 } 1050 1051 /// Check if the branch crosses the boundary. 1052 /// 1053 /// \param StartAddr start address of the fused/unfused branch. 1054 /// \param Size size of the fused/unfused branch. 1055 /// \param BoundaryAlignment alignment requirement of the branch. 1056 /// \returns true if the branch cross the boundary. 1057 static bool mayCrossBoundary(uint64_t StartAddr, uint64_t Size, 1058 Align BoundaryAlignment) { 1059 uint64_t EndAddr = StartAddr + Size; 1060 return (StartAddr >> Log2(BoundaryAlignment)) != 1061 ((EndAddr - 1) >> Log2(BoundaryAlignment)); 1062 } 1063 1064 /// Check if the branch is against the boundary. 1065 /// 1066 /// \param StartAddr start address of the fused/unfused branch. 1067 /// \param Size size of the fused/unfused branch. 1068 /// \param BoundaryAlignment alignment requirement of the branch. 1069 /// \returns true if the branch is against the boundary. 1070 static bool isAgainstBoundary(uint64_t StartAddr, uint64_t Size, 1071 Align BoundaryAlignment) { 1072 uint64_t EndAddr = StartAddr + Size; 1073 return (EndAddr & (BoundaryAlignment.value() - 1)) == 0; 1074 } 1075 1076 /// Check if the branch needs padding. 1077 /// 1078 /// \param StartAddr start address of the fused/unfused branch. 1079 /// \param Size size of the fused/unfused branch. 1080 /// \param BoundaryAlignment alignment requirement of the branch. 1081 /// \returns true if the branch needs padding. 1082 static bool needPadding(uint64_t StartAddr, uint64_t Size, 1083 Align BoundaryAlignment) { 1084 return mayCrossBoundary(StartAddr, Size, BoundaryAlignment) || 1085 isAgainstBoundary(StartAddr, Size, BoundaryAlignment); 1086 } 1087 1088 bool MCAssembler::relaxBoundaryAlign(MCAsmLayout &Layout, 1089 MCBoundaryAlignFragment &BF) { 1090 // BoundaryAlignFragment that doesn't need to align any fragment should not be 1091 // relaxed. 1092 if (!BF.getLastFragment()) 1093 return false; 1094 1095 uint64_t AlignedOffset = Layout.getFragmentOffset(&BF); 1096 uint64_t AlignedSize = 0; 1097 for (const MCFragment *F = BF.getLastFragment(); F != &BF; 1098 F = F->getPrevNode()) 1099 AlignedSize += computeFragmentSize(Layout, *F); 1100 1101 Align BoundaryAlignment = BF.getAlignment(); 1102 uint64_t NewSize = needPadding(AlignedOffset, AlignedSize, BoundaryAlignment) 1103 ? offsetToAlignment(AlignedOffset, BoundaryAlignment) 1104 : 0U; 1105 if (NewSize == BF.getSize()) 1106 return false; 1107 BF.setSize(NewSize); 1108 Layout.invalidateFragmentsFrom(&BF); 1109 return true; 1110 } 1111 1112 bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout, 1113 MCDwarfLineAddrFragment &DF) { 1114 1115 bool WasRelaxed; 1116 if (getBackend().relaxDwarfLineAddr(DF, Layout, WasRelaxed)) 1117 return WasRelaxed; 1118 1119 MCContext &Context = Layout.getAssembler().getContext(); 1120 uint64_t OldSize = DF.getContents().size(); 1121 int64_t AddrDelta; 1122 bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout); 1123 assert(Abs && "We created a line delta with an invalid expression"); 1124 (void)Abs; 1125 int64_t LineDelta; 1126 LineDelta = DF.getLineDelta(); 1127 SmallVectorImpl<char> &Data = DF.getContents(); 1128 Data.clear(); 1129 DF.getFixups().clear(); 1130 1131 MCDwarfLineAddr::encode(Context, getDWARFLinetableParams(), LineDelta, 1132 AddrDelta, Data); 1133 return OldSize != Data.size(); 1134 } 1135 1136 bool MCAssembler::relaxDwarfCallFrameFragment(MCAsmLayout &Layout, 1137 MCDwarfCallFrameFragment &DF) { 1138 bool WasRelaxed; 1139 if (getBackend().relaxDwarfCFA(DF, Layout, WasRelaxed)) 1140 return WasRelaxed; 1141 1142 MCContext &Context = Layout.getAssembler().getContext(); 1143 int64_t Value; 1144 bool Abs = DF.getAddrDelta().evaluateAsAbsolute(Value, Layout); 1145 if (!Abs) { 1146 getContext().reportError(DF.getAddrDelta().getLoc(), 1147 "invalid CFI advance_loc expression"); 1148 DF.setAddrDelta(MCConstantExpr::create(0, Context)); 1149 return false; 1150 } 1151 1152 SmallVectorImpl<char> &Data = DF.getContents(); 1153 uint64_t OldSize = Data.size(); 1154 Data.clear(); 1155 DF.getFixups().clear(); 1156 1157 MCDwarfFrameEmitter::encodeAdvanceLoc(Context, Value, Data); 1158 return OldSize != Data.size(); 1159 } 1160 1161 bool MCAssembler::relaxCVInlineLineTable(MCAsmLayout &Layout, 1162 MCCVInlineLineTableFragment &F) { 1163 unsigned OldSize = F.getContents().size(); 1164 getContext().getCVContext().encodeInlineLineTable(Layout, F); 1165 return OldSize != F.getContents().size(); 1166 } 1167 1168 bool MCAssembler::relaxCVDefRange(MCAsmLayout &Layout, 1169 MCCVDefRangeFragment &F) { 1170 unsigned OldSize = F.getContents().size(); 1171 getContext().getCVContext().encodeDefRange(Layout, F); 1172 return OldSize != F.getContents().size(); 1173 } 1174 1175 bool MCAssembler::relaxPseudoProbeAddr(MCAsmLayout &Layout, 1176 MCPseudoProbeAddrFragment &PF) { 1177 uint64_t OldSize = PF.getContents().size(); 1178 int64_t AddrDelta; 1179 bool Abs = PF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout); 1180 assert(Abs && "We created a pseudo probe with an invalid expression"); 1181 (void)Abs; 1182 SmallVectorImpl<char> &Data = PF.getContents(); 1183 Data.clear(); 1184 raw_svector_ostream OSE(Data); 1185 PF.getFixups().clear(); 1186 1187 // AddrDelta is a signed integer 1188 encodeSLEB128(AddrDelta, OSE, OldSize); 1189 return OldSize != Data.size(); 1190 } 1191 1192 bool MCAssembler::relaxFragment(MCAsmLayout &Layout, MCFragment &F) { 1193 switch(F.getKind()) { 1194 default: 1195 return false; 1196 case MCFragment::FT_Relaxable: 1197 assert(!getRelaxAll() && 1198 "Did not expect a MCRelaxableFragment in RelaxAll mode"); 1199 return relaxInstruction(Layout, cast<MCRelaxableFragment>(F)); 1200 case MCFragment::FT_Dwarf: 1201 return relaxDwarfLineAddr(Layout, cast<MCDwarfLineAddrFragment>(F)); 1202 case MCFragment::FT_DwarfFrame: 1203 return relaxDwarfCallFrameFragment(Layout, 1204 cast<MCDwarfCallFrameFragment>(F)); 1205 case MCFragment::FT_LEB: 1206 return relaxLEB(Layout, cast<MCLEBFragment>(F)); 1207 case MCFragment::FT_BoundaryAlign: 1208 return relaxBoundaryAlign(Layout, cast<MCBoundaryAlignFragment>(F)); 1209 case MCFragment::FT_CVInlineLines: 1210 return relaxCVInlineLineTable(Layout, cast<MCCVInlineLineTableFragment>(F)); 1211 case MCFragment::FT_CVDefRange: 1212 return relaxCVDefRange(Layout, cast<MCCVDefRangeFragment>(F)); 1213 case MCFragment::FT_PseudoProbe: 1214 return relaxPseudoProbeAddr(Layout, cast<MCPseudoProbeAddrFragment>(F)); 1215 } 1216 } 1217 1218 bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSection &Sec) { 1219 // Holds the first fragment which needed relaxing during this layout. It will 1220 // remain NULL if none were relaxed. 1221 // When a fragment is relaxed, all the fragments following it should get 1222 // invalidated because their offset is going to change. 1223 MCFragment *FirstRelaxedFragment = nullptr; 1224 1225 // Attempt to relax all the fragments in the section. 1226 for (MCFragment &Frag : Sec) { 1227 // Check if this is a fragment that needs relaxation. 1228 bool RelaxedFrag = relaxFragment(Layout, Frag); 1229 if (RelaxedFrag && !FirstRelaxedFragment) 1230 FirstRelaxedFragment = &Frag; 1231 } 1232 if (FirstRelaxedFragment) { 1233 Layout.invalidateFragmentsFrom(FirstRelaxedFragment); 1234 return true; 1235 } 1236 return false; 1237 } 1238 1239 bool MCAssembler::layoutOnce(MCAsmLayout &Layout) { 1240 ++stats::RelaxationSteps; 1241 1242 bool WasRelaxed = false; 1243 for (MCSection &Sec : *this) { 1244 while (layoutSectionOnce(Layout, Sec)) 1245 WasRelaxed = true; 1246 } 1247 1248 return WasRelaxed; 1249 } 1250 1251 void MCAssembler::finishLayout(MCAsmLayout &Layout) { 1252 assert(getBackendPtr() && "Expected assembler backend"); 1253 // The layout is done. Mark every fragment as valid. 1254 for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) { 1255 MCSection &Section = *Layout.getSectionOrder()[i]; 1256 Layout.getFragmentOffset(&*Section.getFragmentList().rbegin()); 1257 computeFragmentSize(Layout, *Section.getFragmentList().rbegin()); 1258 } 1259 getBackend().finishLayout(*this, Layout); 1260 } 1261 1262 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 1263 LLVM_DUMP_METHOD void MCAssembler::dump() const{ 1264 raw_ostream &OS = errs(); 1265 1266 OS << "<MCAssembler\n"; 1267 OS << " Sections:[\n "; 1268 for (const_iterator it = begin(), ie = end(); it != ie; ++it) { 1269 if (it != begin()) OS << ",\n "; 1270 it->dump(); 1271 } 1272 OS << "],\n"; 1273 OS << " Symbols:["; 1274 1275 for (const_symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) { 1276 if (it != symbol_begin()) OS << ",\n "; 1277 OS << "("; 1278 it->dump(); 1279 OS << ", Index:" << it->getIndex() << ", "; 1280 OS << ")"; 1281 } 1282 OS << "]>\n"; 1283 } 1284 #endif 1285