MCAssembler.cpp revision 234353
1//===- lib/MC/MCAssembler.cpp - Assembler Backend Implementation ----------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9 10#define DEBUG_TYPE "assembler" 11#include "llvm/MC/MCAssembler.h" 12#include "llvm/MC/MCAsmLayout.h" 13#include "llvm/MC/MCCodeEmitter.h" 14#include "llvm/MC/MCContext.h" 15#include "llvm/MC/MCExpr.h" 16#include "llvm/MC/MCFixupKindInfo.h" 17#include "llvm/MC/MCObjectWriter.h" 18#include "llvm/MC/MCSection.h" 19#include "llvm/MC/MCSymbol.h" 20#include "llvm/MC/MCValue.h" 21#include "llvm/MC/MCDwarf.h" 22#include "llvm/MC/MCAsmBackend.h" 23#include "llvm/ADT/Statistic.h" 24#include "llvm/ADT/StringExtras.h" 25#include "llvm/ADT/Twine.h" 26#include "llvm/Support/Debug.h" 27#include "llvm/Support/ErrorHandling.h" 28#include "llvm/Support/raw_ostream.h" 29#include "llvm/Support/TargetRegistry.h" 30 31using namespace llvm; 32 33namespace { 34namespace stats { 35STATISTIC(EmittedFragments, "Number of emitted assembler fragments"); 36STATISTIC(evaluateFixup, "Number of evaluated fixups"); 37STATISTIC(FragmentLayouts, "Number of fragment layouts"); 38STATISTIC(ObjectBytes, "Number of emitted object file bytes"); 39STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps"); 40STATISTIC(RelaxedInstructions, "Number of relaxed instructions"); 41} 42} 43 44// FIXME FIXME FIXME: There are number of places in this file where we convert 45// what is a 64-bit assembler value used for computation into a value in the 46// object file, which may truncate it. We should detect that truncation where 47// invalid and report errors back. 48 49/* *** */ 50 51MCAsmLayout::MCAsmLayout(MCAssembler &Asm) 52 : Assembler(Asm), LastValidFragment() 53 { 54 // Compute the section layout order. Virtual sections must go last. 55 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it) 56 if (!it->getSection().isVirtualSection()) 57 SectionOrder.push_back(&*it); 58 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it) 59 if (it->getSection().isVirtualSection()) 60 SectionOrder.push_back(&*it); 61} 62 63bool MCAsmLayout::isFragmentUpToDate(const MCFragment *F) const { 64 const MCSectionData &SD = *F->getParent(); 65 const MCFragment *LastValid = LastValidFragment.lookup(&SD); 66 if (!LastValid) 67 return false; 68 assert(LastValid->getParent() == F->getParent()); 69 return F->getLayoutOrder() <= LastValid->getLayoutOrder(); 70} 71 72void MCAsmLayout::Invalidate(MCFragment *F) { 73 // If this fragment wasn't already up-to-date, we don't need to do anything. 74 if (!isFragmentUpToDate(F)) 75 return; 76 77 // Otherwise, reset the last valid fragment to this fragment. 78 const MCSectionData &SD = *F->getParent(); 79 LastValidFragment[&SD] = F; 80} 81 82void MCAsmLayout::EnsureValid(const MCFragment *F) const { 83 MCSectionData &SD = *F->getParent(); 84 85 MCFragment *Cur = LastValidFragment[&SD]; 86 if (!Cur) 87 Cur = &*SD.begin(); 88 else 89 Cur = Cur->getNextNode(); 90 91 // Advance the layout position until the fragment is up-to-date. 92 while (!isFragmentUpToDate(F)) { 93 const_cast<MCAsmLayout*>(this)->LayoutFragment(Cur); 94 Cur = Cur->getNextNode(); 95 } 96} 97 98uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const { 99 EnsureValid(F); 100 assert(F->Offset != ~UINT64_C(0) && "Address not set!"); 101 return F->Offset; 102} 103 104uint64_t MCAsmLayout::getSymbolOffset(const MCSymbolData *SD) const { 105 const MCSymbol &S = SD->getSymbol(); 106 107 // If this is a variable, then recursively evaluate now. 108 if (S.isVariable()) { 109 MCValue Target; 110 if (!S.getVariableValue()->EvaluateAsRelocatable(Target, *this)) 111 report_fatal_error("unable to evaluate offset for variable '" + 112 S.getName() + "'"); 113 114 // Verify that any used symbols are defined. 115 if (Target.getSymA() && Target.getSymA()->getSymbol().isUndefined()) 116 report_fatal_error("unable to evaluate offset to undefined symbol '" + 117 Target.getSymA()->getSymbol().getName() + "'"); 118 if (Target.getSymB() && Target.getSymB()->getSymbol().isUndefined()) 119 report_fatal_error("unable to evaluate offset to undefined symbol '" + 120 Target.getSymB()->getSymbol().getName() + "'"); 121 122 uint64_t Offset = Target.getConstant(); 123 if (Target.getSymA()) 124 Offset += getSymbolOffset(&Assembler.getSymbolData( 125 Target.getSymA()->getSymbol())); 126 if (Target.getSymB()) 127 Offset -= getSymbolOffset(&Assembler.getSymbolData( 128 Target.getSymB()->getSymbol())); 129 return Offset; 130 } 131 132 assert(SD->getFragment() && "Invalid getOffset() on undefined symbol!"); 133 return getFragmentOffset(SD->getFragment()) + SD->getOffset(); 134} 135 136uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const { 137 // The size is the last fragment's end offset. 138 const MCFragment &F = SD->getFragmentList().back(); 139 return getFragmentOffset(&F) + getAssembler().computeFragmentSize(*this, F); 140} 141 142uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const { 143 // Virtual sections have no file size. 144 if (SD->getSection().isVirtualSection()) 145 return 0; 146 147 // Otherwise, the file size is the same as the address space size. 148 return getSectionAddressSize(SD); 149} 150 151/* *** */ 152 153MCFragment::MCFragment() : Kind(FragmentType(~0)) { 154} 155 156MCFragment::~MCFragment() { 157} 158 159MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent) 160 : Kind(_Kind), Parent(_Parent), Atom(0), Offset(~UINT64_C(0)) 161{ 162 if (Parent) 163 Parent->getFragmentList().push_back(this); 164} 165 166/* *** */ 167 168MCSectionData::MCSectionData() : Section(0) {} 169 170MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A) 171 : Section(&_Section), 172 Ordinal(~UINT32_C(0)), 173 Alignment(1), 174 HasInstructions(false) 175{ 176 if (A) 177 A->getSectionList().push_back(this); 178} 179 180/* *** */ 181 182MCSymbolData::MCSymbolData() : Symbol(0) {} 183 184MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment, 185 uint64_t _Offset, MCAssembler *A) 186 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset), 187 IsExternal(false), IsPrivateExtern(false), 188 CommonSize(0), SymbolSize(0), CommonAlign(0), 189 Flags(0), Index(0) 190{ 191 if (A) 192 A->getSymbolList().push_back(this); 193} 194 195/* *** */ 196 197MCAssembler::MCAssembler(MCContext &Context_, MCAsmBackend &Backend_, 198 MCCodeEmitter &Emitter_, MCObjectWriter &Writer_, 199 raw_ostream &OS_) 200 : Context(Context_), Backend(Backend_), Emitter(Emitter_), Writer(Writer_), 201 OS(OS_), RelaxAll(false), NoExecStack(false), SubsectionsViaSymbols(false) 202{ 203} 204 205MCAssembler::~MCAssembler() { 206} 207 208bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const { 209 // Non-temporary labels should always be visible to the linker. 210 if (!Symbol.isTemporary()) 211 return true; 212 213 // Absolute temporary labels are never visible. 214 if (!Symbol.isInSection()) 215 return false; 216 217 // Otherwise, check if the section requires symbols even for temporary labels. 218 return getBackend().doesSectionRequireSymbols(Symbol.getSection()); 219} 220 221const MCSymbolData *MCAssembler::getAtom(const MCSymbolData *SD) const { 222 // Linker visible symbols define atoms. 223 if (isSymbolLinkerVisible(SD->getSymbol())) 224 return SD; 225 226 // Absolute and undefined symbols have no defining atom. 227 if (!SD->getFragment()) 228 return 0; 229 230 // Non-linker visible symbols in sections which can't be atomized have no 231 // defining atom. 232 if (!getBackend().isSectionAtomizable( 233 SD->getFragment()->getParent()->getSection())) 234 return 0; 235 236 // Otherwise, return the atom for the containing fragment. 237 return SD->getFragment()->getAtom(); 238} 239 240bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout, 241 const MCFixup &Fixup, const MCFragment *DF, 242 MCValue &Target, uint64_t &Value) const { 243 ++stats::evaluateFixup; 244 245 if (!Fixup.getValue()->EvaluateAsRelocatable(Target, Layout)) 246 getContext().FatalError(Fixup.getLoc(), "expected relocatable expression"); 247 248 bool IsPCRel = Backend.getFixupKindInfo( 249 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel; 250 251 bool IsResolved; 252 if (IsPCRel) { 253 if (Target.getSymB()) { 254 IsResolved = false; 255 } else if (!Target.getSymA()) { 256 IsResolved = false; 257 } else { 258 const MCSymbolRefExpr *A = Target.getSymA(); 259 const MCSymbol &SA = A->getSymbol(); 260 if (A->getKind() != MCSymbolRefExpr::VK_None || 261 SA.AliasedSymbol().isUndefined()) { 262 IsResolved = false; 263 } else { 264 const MCSymbolData &DataA = getSymbolData(SA); 265 IsResolved = 266 getWriter().IsSymbolRefDifferenceFullyResolvedImpl(*this, DataA, 267 *DF, false, true); 268 } 269 } 270 } else { 271 IsResolved = Target.isAbsolute(); 272 } 273 274 Value = Target.getConstant(); 275 276 if (const MCSymbolRefExpr *A = Target.getSymA()) { 277 const MCSymbol &Sym = A->getSymbol().AliasedSymbol(); 278 if (Sym.isDefined()) 279 Value += Layout.getSymbolOffset(&getSymbolData(Sym)); 280 } 281 if (const MCSymbolRefExpr *B = Target.getSymB()) { 282 const MCSymbol &Sym = B->getSymbol().AliasedSymbol(); 283 if (Sym.isDefined()) 284 Value -= Layout.getSymbolOffset(&getSymbolData(Sym)); 285 } 286 287 288 bool ShouldAlignPC = Backend.getFixupKindInfo(Fixup.getKind()).Flags & 289 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits; 290 assert((ShouldAlignPC ? IsPCRel : true) && 291 "FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!"); 292 293 if (IsPCRel) { 294 uint32_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset(); 295 296 // A number of ARM fixups in Thumb mode require that the effective PC 297 // address be determined as the 32-bit aligned version of the actual offset. 298 if (ShouldAlignPC) Offset &= ~0x3; 299 Value -= Offset; 300 } 301 302 // Let the backend adjust the fixup value if necessary, including whether 303 // we need a relocation. 304 Backend.processFixupValue(*this, Layout, Fixup, DF, Target, Value, 305 IsResolved); 306 307 return IsResolved; 308} 309 310uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout, 311 const MCFragment &F) const { 312 switch (F.getKind()) { 313 case MCFragment::FT_Data: 314 return cast<MCDataFragment>(F).getContents().size(); 315 case MCFragment::FT_Fill: 316 return cast<MCFillFragment>(F).getSize(); 317 case MCFragment::FT_Inst: 318 return cast<MCInstFragment>(F).getInstSize(); 319 320 case MCFragment::FT_LEB: 321 return cast<MCLEBFragment>(F).getContents().size(); 322 323 case MCFragment::FT_Align: { 324 const MCAlignFragment &AF = cast<MCAlignFragment>(F); 325 unsigned Offset = Layout.getFragmentOffset(&AF); 326 unsigned Size = OffsetToAlignment(Offset, AF.getAlignment()); 327 if (Size > AF.getMaxBytesToEmit()) 328 return 0; 329 return Size; 330 } 331 332 case MCFragment::FT_Org: { 333 MCOrgFragment &OF = cast<MCOrgFragment>(F); 334 int64_t TargetLocation; 335 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, Layout)) 336 report_fatal_error("expected assembly-time absolute expression"); 337 338 // FIXME: We need a way to communicate this error. 339 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF); 340 int64_t Size = TargetLocation - FragmentOffset; 341 if (Size < 0 || Size >= 0x40000000) 342 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) + 343 "' (at offset '" + Twine(FragmentOffset) + "')"); 344 return Size; 345 } 346 347 case MCFragment::FT_Dwarf: 348 return cast<MCDwarfLineAddrFragment>(F).getContents().size(); 349 case MCFragment::FT_DwarfFrame: 350 return cast<MCDwarfCallFrameFragment>(F).getContents().size(); 351 } 352 353 llvm_unreachable("invalid fragment kind"); 354} 355 356void MCAsmLayout::LayoutFragment(MCFragment *F) { 357 MCFragment *Prev = F->getPrevNode(); 358 359 // We should never try to recompute something which is up-to-date. 360 assert(!isFragmentUpToDate(F) && "Attempt to recompute up-to-date fragment!"); 361 // We should never try to compute the fragment layout if it's predecessor 362 // isn't up-to-date. 363 assert((!Prev || isFragmentUpToDate(Prev)) && 364 "Attempt to compute fragment before it's predecessor!"); 365 366 ++stats::FragmentLayouts; 367 368 // Compute fragment offset and size. 369 uint64_t Offset = 0; 370 if (Prev) 371 Offset += Prev->Offset + getAssembler().computeFragmentSize(*this, *Prev); 372 373 F->Offset = Offset; 374 LastValidFragment[F->getParent()] = F; 375} 376 377/// WriteFragmentData - Write the \arg F data to the output file. 378static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout, 379 const MCFragment &F) { 380 MCObjectWriter *OW = &Asm.getWriter(); 381 uint64_t Start = OW->getStream().tell(); 382 (void) Start; 383 384 ++stats::EmittedFragments; 385 386 // FIXME: Embed in fragments instead? 387 uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F); 388 switch (F.getKind()) { 389 case MCFragment::FT_Align: { 390 MCAlignFragment &AF = cast<MCAlignFragment>(F); 391 uint64_t Count = FragmentSize / AF.getValueSize(); 392 393 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!"); 394 395 // FIXME: This error shouldn't actually occur (the front end should emit 396 // multiple .align directives to enforce the semantics it wants), but is 397 // severe enough that we want to report it. How to handle this? 398 if (Count * AF.getValueSize() != FragmentSize) 399 report_fatal_error("undefined .align directive, value size '" + 400 Twine(AF.getValueSize()) + 401 "' is not a divisor of padding size '" + 402 Twine(FragmentSize) + "'"); 403 404 // See if we are aligning with nops, and if so do that first to try to fill 405 // the Count bytes. Then if that did not fill any bytes or there are any 406 // bytes left to fill use the the Value and ValueSize to fill the rest. 407 // If we are aligning with nops, ask that target to emit the right data. 408 if (AF.hasEmitNops()) { 409 if (!Asm.getBackend().writeNopData(Count, OW)) 410 report_fatal_error("unable to write nop sequence of " + 411 Twine(Count) + " bytes"); 412 break; 413 } 414 415 // Otherwise, write out in multiples of the value size. 416 for (uint64_t i = 0; i != Count; ++i) { 417 switch (AF.getValueSize()) { 418 default: llvm_unreachable("Invalid size!"); 419 case 1: OW->Write8 (uint8_t (AF.getValue())); break; 420 case 2: OW->Write16(uint16_t(AF.getValue())); break; 421 case 4: OW->Write32(uint32_t(AF.getValue())); break; 422 case 8: OW->Write64(uint64_t(AF.getValue())); break; 423 } 424 } 425 break; 426 } 427 428 case MCFragment::FT_Data: { 429 MCDataFragment &DF = cast<MCDataFragment>(F); 430 assert(FragmentSize == DF.getContents().size() && "Invalid size!"); 431 OW->WriteBytes(DF.getContents().str()); 432 break; 433 } 434 435 case MCFragment::FT_Fill: { 436 MCFillFragment &FF = cast<MCFillFragment>(F); 437 438 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!"); 439 440 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) { 441 switch (FF.getValueSize()) { 442 default: llvm_unreachable("Invalid size!"); 443 case 1: OW->Write8 (uint8_t (FF.getValue())); break; 444 case 2: OW->Write16(uint16_t(FF.getValue())); break; 445 case 4: OW->Write32(uint32_t(FF.getValue())); break; 446 case 8: OW->Write64(uint64_t(FF.getValue())); break; 447 } 448 } 449 break; 450 } 451 452 case MCFragment::FT_Inst: { 453 MCInstFragment &IF = cast<MCInstFragment>(F); 454 OW->WriteBytes(StringRef(IF.getCode().begin(), IF.getCode().size())); 455 break; 456 } 457 458 case MCFragment::FT_LEB: { 459 MCLEBFragment &LF = cast<MCLEBFragment>(F); 460 OW->WriteBytes(LF.getContents().str()); 461 break; 462 } 463 464 case MCFragment::FT_Org: { 465 MCOrgFragment &OF = cast<MCOrgFragment>(F); 466 467 for (uint64_t i = 0, e = FragmentSize; i != e; ++i) 468 OW->Write8(uint8_t(OF.getValue())); 469 470 break; 471 } 472 473 case MCFragment::FT_Dwarf: { 474 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F); 475 OW->WriteBytes(OF.getContents().str()); 476 break; 477 } 478 case MCFragment::FT_DwarfFrame: { 479 const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F); 480 OW->WriteBytes(CF.getContents().str()); 481 break; 482 } 483 } 484 485 assert(OW->getStream().tell() - Start == FragmentSize); 486} 487 488void MCAssembler::writeSectionData(const MCSectionData *SD, 489 const MCAsmLayout &Layout) const { 490 // Ignore virtual sections. 491 if (SD->getSection().isVirtualSection()) { 492 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!"); 493 494 // Check that contents are only things legal inside a virtual section. 495 for (MCSectionData::const_iterator it = SD->begin(), 496 ie = SD->end(); it != ie; ++it) { 497 switch (it->getKind()) { 498 default: llvm_unreachable("Invalid fragment in virtual section!"); 499 case MCFragment::FT_Data: { 500 // Check that we aren't trying to write a non-zero contents (or fixups) 501 // into a virtual section. This is to support clients which use standard 502 // directives to fill the contents of virtual sections. 503 MCDataFragment &DF = cast<MCDataFragment>(*it); 504 assert(DF.fixup_begin() == DF.fixup_end() && 505 "Cannot have fixups in virtual section!"); 506 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i) 507 assert(DF.getContents()[i] == 0 && 508 "Invalid data value for virtual section!"); 509 break; 510 } 511 case MCFragment::FT_Align: 512 // Check that we aren't trying to write a non-zero value into a virtual 513 // section. 514 assert((!cast<MCAlignFragment>(it)->getValueSize() || 515 !cast<MCAlignFragment>(it)->getValue()) && 516 "Invalid align in virtual section!"); 517 break; 518 case MCFragment::FT_Fill: 519 assert(!cast<MCFillFragment>(it)->getValueSize() && 520 "Invalid fill in virtual section!"); 521 break; 522 } 523 } 524 525 return; 526 } 527 528 uint64_t Start = getWriter().getStream().tell(); 529 (void) Start; 530 531 for (MCSectionData::const_iterator it = SD->begin(), 532 ie = SD->end(); it != ie; ++it) 533 WriteFragmentData(*this, Layout, *it); 534 535 assert(getWriter().getStream().tell() - Start == 536 Layout.getSectionAddressSize(SD)); 537} 538 539 540uint64_t MCAssembler::handleFixup(const MCAsmLayout &Layout, 541 MCFragment &F, 542 const MCFixup &Fixup) { 543 // Evaluate the fixup. 544 MCValue Target; 545 uint64_t FixedValue; 546 if (!evaluateFixup(Layout, Fixup, &F, Target, FixedValue)) { 547 // The fixup was unresolved, we need a relocation. Inform the object 548 // writer of the relocation, and give it an opportunity to adjust the 549 // fixup value if need be. 550 getWriter().RecordRelocation(*this, Layout, &F, Fixup, Target, FixedValue); 551 } 552 return FixedValue; 553 } 554 555void MCAssembler::Finish() { 556 DEBUG_WITH_TYPE("mc-dump", { 557 llvm::errs() << "assembler backend - pre-layout\n--\n"; 558 dump(); }); 559 560 // Create the layout object. 561 MCAsmLayout Layout(*this); 562 563 // Create dummy fragments and assign section ordinals. 564 unsigned SectionIndex = 0; 565 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) { 566 // Create dummy fragments to eliminate any empty sections, this simplifies 567 // layout. 568 if (it->getFragmentList().empty()) 569 new MCDataFragment(it); 570 571 it->setOrdinal(SectionIndex++); 572 } 573 574 // Assign layout order indices to sections and fragments. 575 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) { 576 MCSectionData *SD = Layout.getSectionOrder()[i]; 577 SD->setLayoutOrder(i); 578 579 unsigned FragmentIndex = 0; 580 for (MCSectionData::iterator it2 = SD->begin(), 581 ie2 = SD->end(); it2 != ie2; ++it2) 582 it2->setLayoutOrder(FragmentIndex++); 583 } 584 585 // Layout until everything fits. 586 while (layoutOnce(Layout)) 587 continue; 588 589 DEBUG_WITH_TYPE("mc-dump", { 590 llvm::errs() << "assembler backend - post-relaxation\n--\n"; 591 dump(); }); 592 593 // Finalize the layout, including fragment lowering. 594 finishLayout(Layout); 595 596 DEBUG_WITH_TYPE("mc-dump", { 597 llvm::errs() << "assembler backend - final-layout\n--\n"; 598 dump(); }); 599 600 uint64_t StartOffset = OS.tell(); 601 602 // Allow the object writer a chance to perform post-layout binding (for 603 // example, to set the index fields in the symbol data). 604 getWriter().ExecutePostLayoutBinding(*this, Layout); 605 606 // Evaluate and apply the fixups, generating relocation entries as necessary. 607 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) { 608 for (MCSectionData::iterator it2 = it->begin(), 609 ie2 = it->end(); it2 != ie2; ++it2) { 610 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2); 611 if (DF) { 612 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(), 613 ie3 = DF->fixup_end(); it3 != ie3; ++it3) { 614 MCFixup &Fixup = *it3; 615 uint64_t FixedValue = handleFixup(Layout, *DF, Fixup); 616 getBackend().applyFixup(Fixup, DF->getContents().data(), 617 DF->getContents().size(), FixedValue); 618 } 619 } 620 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2); 621 if (IF) { 622 for (MCInstFragment::fixup_iterator it3 = IF->fixup_begin(), 623 ie3 = IF->fixup_end(); it3 != ie3; ++it3) { 624 MCFixup &Fixup = *it3; 625 uint64_t FixedValue = handleFixup(Layout, *IF, Fixup); 626 getBackend().applyFixup(Fixup, IF->getCode().data(), 627 IF->getCode().size(), FixedValue); 628 } 629 } 630 } 631 } 632 633 // Write the object file. 634 getWriter().WriteObject(*this, Layout); 635 636 stats::ObjectBytes += OS.tell() - StartOffset; 637} 638 639bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup, 640 const MCInstFragment *DF, 641 const MCAsmLayout &Layout) const { 642 if (getRelaxAll()) 643 return true; 644 645 // If we cannot resolve the fixup value, it requires relaxation. 646 MCValue Target; 647 uint64_t Value; 648 if (!evaluateFixup(Layout, Fixup, DF, Target, Value)) 649 return true; 650 651 return getBackend().fixupNeedsRelaxation(Fixup, Value, DF, Layout); 652} 653 654bool MCAssembler::fragmentNeedsRelaxation(const MCInstFragment *IF, 655 const MCAsmLayout &Layout) const { 656 // If this inst doesn't ever need relaxation, ignore it. This occurs when we 657 // are intentionally pushing out inst fragments, or because we relaxed a 658 // previous instruction to one that doesn't need relaxation. 659 if (!getBackend().mayNeedRelaxation(IF->getInst())) 660 return false; 661 662 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(), 663 ie = IF->fixup_end(); it != ie; ++it) 664 if (fixupNeedsRelaxation(*it, IF, Layout)) 665 return true; 666 667 return false; 668} 669 670bool MCAssembler::relaxInstruction(MCAsmLayout &Layout, 671 MCInstFragment &IF) { 672 if (!fragmentNeedsRelaxation(&IF, Layout)) 673 return false; 674 675 ++stats::RelaxedInstructions; 676 677 // FIXME-PERF: We could immediately lower out instructions if we can tell 678 // they are fully resolved, to avoid retesting on later passes. 679 680 // Relax the fragment. 681 682 MCInst Relaxed; 683 getBackend().relaxInstruction(IF.getInst(), Relaxed); 684 685 // Encode the new instruction. 686 // 687 // FIXME-PERF: If it matters, we could let the target do this. It can 688 // probably do so more efficiently in many cases. 689 SmallVector<MCFixup, 4> Fixups; 690 SmallString<256> Code; 691 raw_svector_ostream VecOS(Code); 692 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups); 693 VecOS.flush(); 694 695 // Update the instruction fragment. 696 IF.setInst(Relaxed); 697 IF.getCode() = Code; 698 IF.getFixups().clear(); 699 // FIXME: Eliminate copy. 700 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) 701 IF.getFixups().push_back(Fixups[i]); 702 703 return true; 704} 705 706bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) { 707 int64_t Value = 0; 708 uint64_t OldSize = LF.getContents().size(); 709 bool IsAbs = LF.getValue().EvaluateAsAbsolute(Value, Layout); 710 (void)IsAbs; 711 assert(IsAbs); 712 SmallString<8> &Data = LF.getContents(); 713 Data.clear(); 714 raw_svector_ostream OSE(Data); 715 if (LF.isSigned()) 716 MCObjectWriter::EncodeSLEB128(Value, OSE); 717 else 718 MCObjectWriter::EncodeULEB128(Value, OSE); 719 OSE.flush(); 720 return OldSize != LF.getContents().size(); 721} 722 723bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout, 724 MCDwarfLineAddrFragment &DF) { 725 int64_t AddrDelta = 0; 726 uint64_t OldSize = DF.getContents().size(); 727 bool IsAbs = DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, Layout); 728 (void)IsAbs; 729 assert(IsAbs); 730 int64_t LineDelta; 731 LineDelta = DF.getLineDelta(); 732 SmallString<8> &Data = DF.getContents(); 733 Data.clear(); 734 raw_svector_ostream OSE(Data); 735 MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OSE); 736 OSE.flush(); 737 return OldSize != Data.size(); 738} 739 740bool MCAssembler::relaxDwarfCallFrameFragment(MCAsmLayout &Layout, 741 MCDwarfCallFrameFragment &DF) { 742 int64_t AddrDelta = 0; 743 uint64_t OldSize = DF.getContents().size(); 744 bool IsAbs = DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, Layout); 745 (void)IsAbs; 746 assert(IsAbs); 747 SmallString<8> &Data = DF.getContents(); 748 Data.clear(); 749 raw_svector_ostream OSE(Data); 750 MCDwarfFrameEmitter::EncodeAdvanceLoc(AddrDelta, OSE); 751 OSE.flush(); 752 return OldSize != Data.size(); 753} 754 755bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, 756 MCSectionData &SD) { 757 MCFragment *FirstInvalidFragment = NULL; 758 // Scan for fragments that need relaxation. 759 for (MCSectionData::iterator it2 = SD.begin(), 760 ie2 = SD.end(); it2 != ie2; ++it2) { 761 // Check if this is an fragment that needs relaxation. 762 bool relaxedFrag = false; 763 switch(it2->getKind()) { 764 default: 765 break; 766 case MCFragment::FT_Inst: 767 relaxedFrag = relaxInstruction(Layout, *cast<MCInstFragment>(it2)); 768 break; 769 case MCFragment::FT_Dwarf: 770 relaxedFrag = relaxDwarfLineAddr(Layout, 771 *cast<MCDwarfLineAddrFragment>(it2)); 772 break; 773 case MCFragment::FT_DwarfFrame: 774 relaxedFrag = 775 relaxDwarfCallFrameFragment(Layout, 776 *cast<MCDwarfCallFrameFragment>(it2)); 777 break; 778 case MCFragment::FT_LEB: 779 relaxedFrag = relaxLEB(Layout, *cast<MCLEBFragment>(it2)); 780 break; 781 } 782 // Update the layout, and remember that we relaxed. 783 if (relaxedFrag && !FirstInvalidFragment) 784 FirstInvalidFragment = it2; 785 } 786 if (FirstInvalidFragment) { 787 Layout.Invalidate(FirstInvalidFragment); 788 return true; 789 } 790 return false; 791} 792 793bool MCAssembler::layoutOnce(MCAsmLayout &Layout) { 794 ++stats::RelaxationSteps; 795 796 bool WasRelaxed = false; 797 for (iterator it = begin(), ie = end(); it != ie; ++it) { 798 MCSectionData &SD = *it; 799 while(layoutSectionOnce(Layout, SD)) 800 WasRelaxed = true; 801 } 802 803 return WasRelaxed; 804} 805 806void MCAssembler::finishLayout(MCAsmLayout &Layout) { 807 // The layout is done. Mark every fragment as valid. 808 for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) { 809 Layout.getFragmentOffset(&*Layout.getSectionOrder()[i]->rbegin()); 810 } 811} 812 813// Debugging methods 814 815namespace llvm { 816 817raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) { 818 OS << "<MCFixup" << " Offset:" << AF.getOffset() 819 << " Value:" << *AF.getValue() 820 << " Kind:" << AF.getKind() << ">"; 821 return OS; 822} 823 824} 825 826void MCFragment::dump() { 827 raw_ostream &OS = llvm::errs(); 828 829 OS << "<"; 830 switch (getKind()) { 831 case MCFragment::FT_Align: OS << "MCAlignFragment"; break; 832 case MCFragment::FT_Data: OS << "MCDataFragment"; break; 833 case MCFragment::FT_Fill: OS << "MCFillFragment"; break; 834 case MCFragment::FT_Inst: OS << "MCInstFragment"; break; 835 case MCFragment::FT_Org: OS << "MCOrgFragment"; break; 836 case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break; 837 case MCFragment::FT_DwarfFrame: OS << "MCDwarfCallFrameFragment"; break; 838 case MCFragment::FT_LEB: OS << "MCLEBFragment"; break; 839 } 840 841 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder 842 << " Offset:" << Offset << ">"; 843 844 switch (getKind()) { 845 case MCFragment::FT_Align: { 846 const MCAlignFragment *AF = cast<MCAlignFragment>(this); 847 if (AF->hasEmitNops()) 848 OS << " (emit nops)"; 849 OS << "\n "; 850 OS << " Alignment:" << AF->getAlignment() 851 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize() 852 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">"; 853 break; 854 } 855 case MCFragment::FT_Data: { 856 const MCDataFragment *DF = cast<MCDataFragment>(this); 857 OS << "\n "; 858 OS << " Contents:["; 859 const SmallVectorImpl<char> &Contents = DF->getContents(); 860 for (unsigned i = 0, e = Contents.size(); i != e; ++i) { 861 if (i) OS << ","; 862 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF); 863 } 864 OS << "] (" << Contents.size() << " bytes)"; 865 866 if (!DF->getFixups().empty()) { 867 OS << ",\n "; 868 OS << " Fixups:["; 869 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(), 870 ie = DF->fixup_end(); it != ie; ++it) { 871 if (it != DF->fixup_begin()) OS << ",\n "; 872 OS << *it; 873 } 874 OS << "]"; 875 } 876 break; 877 } 878 case MCFragment::FT_Fill: { 879 const MCFillFragment *FF = cast<MCFillFragment>(this); 880 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize() 881 << " Size:" << FF->getSize(); 882 break; 883 } 884 case MCFragment::FT_Inst: { 885 const MCInstFragment *IF = cast<MCInstFragment>(this); 886 OS << "\n "; 887 OS << " Inst:"; 888 IF->getInst().dump_pretty(OS); 889 break; 890 } 891 case MCFragment::FT_Org: { 892 const MCOrgFragment *OF = cast<MCOrgFragment>(this); 893 OS << "\n "; 894 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue(); 895 break; 896 } 897 case MCFragment::FT_Dwarf: { 898 const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this); 899 OS << "\n "; 900 OS << " AddrDelta:" << OF->getAddrDelta() 901 << " LineDelta:" << OF->getLineDelta(); 902 break; 903 } 904 case MCFragment::FT_DwarfFrame: { 905 const MCDwarfCallFrameFragment *CF = cast<MCDwarfCallFrameFragment>(this); 906 OS << "\n "; 907 OS << " AddrDelta:" << CF->getAddrDelta(); 908 break; 909 } 910 case MCFragment::FT_LEB: { 911 const MCLEBFragment *LF = cast<MCLEBFragment>(this); 912 OS << "\n "; 913 OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned(); 914 break; 915 } 916 } 917 OS << ">"; 918} 919 920void MCSectionData::dump() { 921 raw_ostream &OS = llvm::errs(); 922 923 OS << "<MCSectionData"; 924 OS << " Alignment:" << getAlignment() << " Fragments:[\n "; 925 for (iterator it = begin(), ie = end(); it != ie; ++it) { 926 if (it != begin()) OS << ",\n "; 927 it->dump(); 928 } 929 OS << "]>"; 930} 931 932void MCSymbolData::dump() { 933 raw_ostream &OS = llvm::errs(); 934 935 OS << "<MCSymbolData Symbol:" << getSymbol() 936 << " Fragment:" << getFragment() << " Offset:" << getOffset() 937 << " Flags:" << getFlags() << " Index:" << getIndex(); 938 if (isCommon()) 939 OS << " (common, size:" << getCommonSize() 940 << " align: " << getCommonAlignment() << ")"; 941 if (isExternal()) 942 OS << " (external)"; 943 if (isPrivateExtern()) 944 OS << " (private extern)"; 945 OS << ">"; 946} 947 948void MCAssembler::dump() { 949 raw_ostream &OS = llvm::errs(); 950 951 OS << "<MCAssembler\n"; 952 OS << " Sections:[\n "; 953 for (iterator it = begin(), ie = end(); it != ie; ++it) { 954 if (it != begin()) OS << ",\n "; 955 it->dump(); 956 } 957 OS << "],\n"; 958 OS << " Symbols:["; 959 960 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) { 961 if (it != symbol_begin()) OS << ",\n "; 962 it->dump(); 963 } 964 OS << "]>\n"; 965} 966 967// anchors for MC*Fragment vtables 968void MCDataFragment::anchor() { } 969void MCInstFragment::anchor() { } 970void MCAlignFragment::anchor() { } 971void MCFillFragment::anchor() { } 972void MCOrgFragment::anchor() { } 973void MCLEBFragment::anchor() { } 974void MCDwarfLineAddrFragment::anchor() { } 975void MCDwarfCallFrameFragment::anchor() { } 976