xref: /freebsd/contrib/llvm-project/llvm/lib/MC/MCAssembler.cpp (revision c66ec88fed842fbaad62c30d510644ceb7bd2d71)
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(EmittedOrgFragments,
66           "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_LEB:
316     return cast<MCLEBFragment>(F).getContents().size();
317 
318   case MCFragment::FT_BoundaryAlign:
319     return cast<MCBoundaryAlignFragment>(F).getSize();
320 
321   case MCFragment::FT_SymbolId:
322     return 4;
323 
324   case MCFragment::FT_Align: {
325     const MCAlignFragment &AF = cast<MCAlignFragment>(F);
326     unsigned Offset = Layout.getFragmentOffset(&AF);
327     unsigned Size = offsetToAlignment(Offset, Align(AF.getAlignment()));
328 
329     // Insert extra Nops for code alignment if the target define
330     // shouldInsertExtraNopBytesForCodeAlign target hook.
331     if (AF.getParent()->UseCodeAlign() && AF.hasEmitNops() &&
332         getBackend().shouldInsertExtraNopBytesForCodeAlign(AF, Size))
333       return Size;
334 
335     // If we are padding with nops, force the padding to be larger than the
336     // minimum nop size.
337     if (Size > 0 && AF.hasEmitNops()) {
338       while (Size % getBackend().getMinimumNopSize())
339         Size += AF.getAlignment();
340     }
341     if (Size > AF.getMaxBytesToEmit())
342       return 0;
343     return Size;
344   }
345 
346   case MCFragment::FT_Org: {
347     const MCOrgFragment &OF = cast<MCOrgFragment>(F);
348     MCValue Value;
349     if (!OF.getOffset().evaluateAsValue(Value, Layout)) {
350       getContext().reportError(OF.getLoc(),
351                                "expected assembly-time absolute expression");
352         return 0;
353     }
354 
355     uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
356     int64_t TargetLocation = Value.getConstant();
357     if (const MCSymbolRefExpr *A = Value.getSymA()) {
358       uint64_t Val;
359       if (!Layout.getSymbolOffset(A->getSymbol(), Val)) {
360         getContext().reportError(OF.getLoc(), "expected absolute expression");
361         return 0;
362       }
363       TargetLocation += Val;
364     }
365     int64_t Size = TargetLocation - FragmentOffset;
366     if (Size < 0 || Size >= 0x40000000) {
367       getContext().reportError(
368           OF.getLoc(), "invalid .org offset '" + Twine(TargetLocation) +
369                            "' (at offset '" + Twine(FragmentOffset) + "')");
370       return 0;
371     }
372     return Size;
373   }
374 
375   case MCFragment::FT_Dwarf:
376     return cast<MCDwarfLineAddrFragment>(F).getContents().size();
377   case MCFragment::FT_DwarfFrame:
378     return cast<MCDwarfCallFrameFragment>(F).getContents().size();
379   case MCFragment::FT_CVInlineLines:
380     return cast<MCCVInlineLineTableFragment>(F).getContents().size();
381   case MCFragment::FT_CVDefRange:
382     return cast<MCCVDefRangeFragment>(F).getContents().size();
383   case MCFragment::FT_Dummy:
384     llvm_unreachable("Should not have been added");
385   }
386 
387   llvm_unreachable("invalid fragment kind");
388 }
389 
390 void MCAsmLayout::layoutFragment(MCFragment *F) {
391   MCFragment *Prev = F->getPrevNode();
392 
393   // We should never try to recompute something which is valid.
394   assert(!isFragmentValid(F) && "Attempt to recompute a valid fragment!");
395   // We should never try to compute the fragment layout if its predecessor
396   // isn't valid.
397   assert((!Prev || isFragmentValid(Prev)) &&
398          "Attempt to compute fragment before its predecessor!");
399 
400   assert(!F->IsBeingLaidOut && "Already being laid out!");
401   F->IsBeingLaidOut = true;
402 
403   ++stats::FragmentLayouts;
404 
405   // Compute fragment offset and size.
406   if (Prev)
407     F->Offset = Prev->Offset + getAssembler().computeFragmentSize(*this, *Prev);
408   else
409     F->Offset = 0;
410   F->IsBeingLaidOut = false;
411   LastValidFragment[F->getParent()] = F;
412 
413   // If bundling is enabled and this fragment has instructions in it, it has to
414   // obey the bundling restrictions. With padding, we'll have:
415   //
416   //
417   //        BundlePadding
418   //             |||
419   // -------------------------------------
420   //   Prev  |##########|       F        |
421   // -------------------------------------
422   //                    ^
423   //                    |
424   //                    F->Offset
425   //
426   // The fragment's offset will point to after the padding, and its computed
427   // size won't include the padding.
428   //
429   // When the -mc-relax-all flag is used, we optimize bundling by writting the
430   // padding directly into fragments when the instructions are emitted inside
431   // the streamer. When the fragment is larger than the bundle size, we need to
432   // ensure that it's bundle aligned. This means that if we end up with
433   // multiple fragments, we must emit bundle padding between fragments.
434   //
435   // ".align N" is an example of a directive that introduces multiple
436   // fragments. We could add a special case to handle ".align N" by emitting
437   // within-fragment padding (which would produce less padding when N is less
438   // than the bundle size), but for now we don't.
439   //
440   if (Assembler.isBundlingEnabled() && F->hasInstructions()) {
441     assert(isa<MCEncodedFragment>(F) &&
442            "Only MCEncodedFragment implementations have instructions");
443     MCEncodedFragment *EF = cast<MCEncodedFragment>(F);
444     uint64_t FSize = Assembler.computeFragmentSize(*this, *EF);
445 
446     if (!Assembler.getRelaxAll() && FSize > Assembler.getBundleAlignSize())
447       report_fatal_error("Fragment can't be larger than a bundle size");
448 
449     uint64_t RequiredBundlePadding =
450         computeBundlePadding(Assembler, EF, EF->Offset, FSize);
451     if (RequiredBundlePadding > UINT8_MAX)
452       report_fatal_error("Padding cannot exceed 255 bytes");
453     EF->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
454     EF->Offset += RequiredBundlePadding;
455   }
456 }
457 
458 void MCAssembler::registerSymbol(const MCSymbol &Symbol, bool *Created) {
459   bool New = !Symbol.isRegistered();
460   if (Created)
461     *Created = New;
462   if (New) {
463     Symbol.setIsRegistered(true);
464     Symbols.push_back(&Symbol);
465   }
466 }
467 
468 void MCAssembler::writeFragmentPadding(raw_ostream &OS,
469                                        const MCEncodedFragment &EF,
470                                        uint64_t FSize) const {
471   assert(getBackendPtr() && "Expected assembler backend");
472   // Should NOP padding be written out before this fragment?
473   unsigned BundlePadding = EF.getBundlePadding();
474   if (BundlePadding > 0) {
475     assert(isBundlingEnabled() &&
476            "Writing bundle padding with disabled bundling");
477     assert(EF.hasInstructions() &&
478            "Writing bundle padding for a fragment without instructions");
479 
480     unsigned TotalLength = BundlePadding + static_cast<unsigned>(FSize);
481     if (EF.alignToBundleEnd() && TotalLength > getBundleAlignSize()) {
482       // If the padding itself crosses a bundle boundary, it must be emitted
483       // in 2 pieces, since even nop instructions must not cross boundaries.
484       //             v--------------v   <- BundleAlignSize
485       //        v---------v             <- BundlePadding
486       // ----------------------------
487       // | Prev |####|####|    F    |
488       // ----------------------------
489       //        ^-------------------^   <- TotalLength
490       unsigned DistanceToBoundary = TotalLength - getBundleAlignSize();
491       if (!getBackend().writeNopData(OS, DistanceToBoundary))
492         report_fatal_error("unable to write NOP sequence of " +
493                            Twine(DistanceToBoundary) + " bytes");
494       BundlePadding -= DistanceToBoundary;
495     }
496     if (!getBackend().writeNopData(OS, BundlePadding))
497       report_fatal_error("unable to write NOP sequence of " +
498                          Twine(BundlePadding) + " bytes");
499   }
500 }
501 
502 /// Write the fragment \p F to the output file.
503 static void writeFragment(raw_ostream &OS, const MCAssembler &Asm,
504                           const MCAsmLayout &Layout, const MCFragment &F) {
505   // FIXME: Embed in fragments instead?
506   uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F);
507 
508   support::endianness Endian = Asm.getBackend().Endian;
509 
510   if (const MCEncodedFragment *EF = dyn_cast<MCEncodedFragment>(&F))
511     Asm.writeFragmentPadding(OS, *EF, FragmentSize);
512 
513   // This variable (and its dummy usage) is to participate in the assert at
514   // the end of the function.
515   uint64_t Start = OS.tell();
516   (void) Start;
517 
518   ++stats::EmittedFragments;
519 
520   switch (F.getKind()) {
521   case MCFragment::FT_Align: {
522     ++stats::EmittedAlignFragments;
523     const MCAlignFragment &AF = cast<MCAlignFragment>(F);
524     assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
525 
526     uint64_t Count = FragmentSize / AF.getValueSize();
527 
528     // FIXME: This error shouldn't actually occur (the front end should emit
529     // multiple .align directives to enforce the semantics it wants), but is
530     // severe enough that we want to report it. How to handle this?
531     if (Count * AF.getValueSize() != FragmentSize)
532       report_fatal_error("undefined .align directive, value size '" +
533                         Twine(AF.getValueSize()) +
534                         "' is not a divisor of padding size '" +
535                         Twine(FragmentSize) + "'");
536 
537     // See if we are aligning with nops, and if so do that first to try to fill
538     // the Count bytes.  Then if that did not fill any bytes or there are any
539     // bytes left to fill use the Value and ValueSize to fill the rest.
540     // If we are aligning with nops, ask that target to emit the right data.
541     if (AF.hasEmitNops()) {
542       if (!Asm.getBackend().writeNopData(OS, Count))
543         report_fatal_error("unable to write nop sequence of " +
544                           Twine(Count) + " bytes");
545       break;
546     }
547 
548     // Otherwise, write out in multiples of the value size.
549     for (uint64_t i = 0; i != Count; ++i) {
550       switch (AF.getValueSize()) {
551       default: llvm_unreachable("Invalid size!");
552       case 1: OS << char(AF.getValue()); break;
553       case 2:
554         support::endian::write<uint16_t>(OS, AF.getValue(), Endian);
555         break;
556       case 4:
557         support::endian::write<uint32_t>(OS, AF.getValue(), Endian);
558         break;
559       case 8:
560         support::endian::write<uint64_t>(OS, AF.getValue(), Endian);
561         break;
562       }
563     }
564     break;
565   }
566 
567   case MCFragment::FT_Data:
568     ++stats::EmittedDataFragments;
569     OS << cast<MCDataFragment>(F).getContents();
570     break;
571 
572   case MCFragment::FT_Relaxable:
573     ++stats::EmittedRelaxableFragments;
574     OS << cast<MCRelaxableFragment>(F).getContents();
575     break;
576 
577   case MCFragment::FT_CompactEncodedInst:
578     ++stats::EmittedCompactEncodedInstFragments;
579     OS << cast<MCCompactEncodedInstFragment>(F).getContents();
580     break;
581 
582   case MCFragment::FT_Fill: {
583     ++stats::EmittedFillFragments;
584     const MCFillFragment &FF = cast<MCFillFragment>(F);
585     uint64_t V = FF.getValue();
586     unsigned VSize = FF.getValueSize();
587     const unsigned MaxChunkSize = 16;
588     char Data[MaxChunkSize];
589     assert(0 < VSize && VSize <= MaxChunkSize && "Illegal fragment fill size");
590     // Duplicate V into Data as byte vector to reduce number of
591     // writes done. As such, do endian conversion here.
592     for (unsigned I = 0; I != VSize; ++I) {
593       unsigned index = Endian == support::little ? I : (VSize - I - 1);
594       Data[I] = uint8_t(V >> (index * 8));
595     }
596     for (unsigned I = VSize; I < MaxChunkSize; ++I)
597       Data[I] = Data[I - VSize];
598 
599     // Set to largest multiple of VSize in Data.
600     const unsigned NumPerChunk = MaxChunkSize / VSize;
601     // Set ChunkSize to largest multiple of VSize in Data
602     const unsigned ChunkSize = VSize * NumPerChunk;
603 
604     // Do copies by chunk.
605     StringRef Ref(Data, ChunkSize);
606     for (uint64_t I = 0, E = FragmentSize / ChunkSize; I != E; ++I)
607       OS << Ref;
608 
609     // do remainder if needed.
610     unsigned TrailingCount = FragmentSize % ChunkSize;
611     if (TrailingCount)
612       OS.write(Data, TrailingCount);
613     break;
614   }
615 
616   case MCFragment::FT_LEB: {
617     const MCLEBFragment &LF = cast<MCLEBFragment>(F);
618     OS << LF.getContents();
619     break;
620   }
621 
622   case MCFragment::FT_BoundaryAlign: {
623     if (!Asm.getBackend().writeNopData(OS, FragmentSize))
624       report_fatal_error("unable to write nop sequence of " +
625                          Twine(FragmentSize) + " bytes");
626     break;
627   }
628 
629   case MCFragment::FT_SymbolId: {
630     const MCSymbolIdFragment &SF = cast<MCSymbolIdFragment>(F);
631     support::endian::write<uint32_t>(OS, SF.getSymbol()->getIndex(), Endian);
632     break;
633   }
634 
635   case MCFragment::FT_Org: {
636     ++stats::EmittedOrgFragments;
637     const MCOrgFragment &OF = cast<MCOrgFragment>(F);
638 
639     for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
640       OS << char(OF.getValue());
641 
642     break;
643   }
644 
645   case MCFragment::FT_Dwarf: {
646     const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
647     OS << OF.getContents();
648     break;
649   }
650   case MCFragment::FT_DwarfFrame: {
651     const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F);
652     OS << CF.getContents();
653     break;
654   }
655   case MCFragment::FT_CVInlineLines: {
656     const auto &OF = cast<MCCVInlineLineTableFragment>(F);
657     OS << OF.getContents();
658     break;
659   }
660   case MCFragment::FT_CVDefRange: {
661     const auto &DRF = cast<MCCVDefRangeFragment>(F);
662     OS << DRF.getContents();
663     break;
664   }
665   case MCFragment::FT_Dummy:
666     llvm_unreachable("Should not have been added");
667   }
668 
669   assert(OS.tell() - Start == FragmentSize &&
670          "The stream should advance by fragment size");
671 }
672 
673 void MCAssembler::writeSectionData(raw_ostream &OS, const MCSection *Sec,
674                                    const MCAsmLayout &Layout) const {
675   assert(getBackendPtr() && "Expected assembler backend");
676 
677   // Ignore virtual sections.
678   if (Sec->isVirtualSection()) {
679     assert(Layout.getSectionFileSize(Sec) == 0 && "Invalid size for section!");
680 
681     // Check that contents are only things legal inside a virtual section.
682     for (const MCFragment &F : *Sec) {
683       switch (F.getKind()) {
684       default: llvm_unreachable("Invalid fragment in virtual section!");
685       case MCFragment::FT_Data: {
686         // Check that we aren't trying to write a non-zero contents (or fixups)
687         // into a virtual section. This is to support clients which use standard
688         // directives to fill the contents of virtual sections.
689         const MCDataFragment &DF = cast<MCDataFragment>(F);
690         if (DF.fixup_begin() != DF.fixup_end())
691           getContext().reportError(SMLoc(), Sec->getVirtualSectionKind() +
692                                                 " section '" + Sec->getName() +
693                                                 "' cannot have fixups");
694         for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
695           if (DF.getContents()[i]) {
696             getContext().reportError(SMLoc(),
697                                      Sec->getVirtualSectionKind() +
698                                          " section '" + Sec->getName() +
699                                          "' cannot have non-zero initializers");
700             break;
701           }
702         break;
703       }
704       case MCFragment::FT_Align:
705         // Check that we aren't trying to write a non-zero value into a virtual
706         // section.
707         assert((cast<MCAlignFragment>(F).getValueSize() == 0 ||
708                 cast<MCAlignFragment>(F).getValue() == 0) &&
709                "Invalid align in virtual section!");
710         break;
711       case MCFragment::FT_Fill:
712         assert((cast<MCFillFragment>(F).getValue() == 0) &&
713                "Invalid fill in virtual section!");
714         break;
715       }
716     }
717 
718     return;
719   }
720 
721   uint64_t Start = OS.tell();
722   (void)Start;
723 
724   for (const MCFragment &F : *Sec)
725     writeFragment(OS, *this, Layout, F);
726 
727   assert(OS.tell() - Start == Layout.getSectionAddressSize(Sec));
728 }
729 
730 std::tuple<MCValue, uint64_t, bool>
731 MCAssembler::handleFixup(const MCAsmLayout &Layout, MCFragment &F,
732                          const MCFixup &Fixup) {
733   // Evaluate the fixup.
734   MCValue Target;
735   uint64_t FixedValue;
736   bool WasForced;
737   bool IsResolved = evaluateFixup(Layout, Fixup, &F, Target, FixedValue,
738                                   WasForced);
739   if (!IsResolved) {
740     // The fixup was unresolved, we need a relocation. Inform the object
741     // writer of the relocation, and give it an opportunity to adjust the
742     // fixup value if need be.
743     if (Target.getSymA() && Target.getSymB() &&
744         getBackend().requiresDiffExpressionRelocations()) {
745       // The fixup represents the difference between two symbols, which the
746       // backend has indicated must be resolved at link time. Split up the fixup
747       // into two relocations, one for the add, and one for the sub, and emit
748       // both of these. The constant will be associated with the add half of the
749       // expression.
750       MCFixup FixupAdd = MCFixup::createAddFor(Fixup);
751       MCValue TargetAdd =
752           MCValue::get(Target.getSymA(), nullptr, Target.getConstant());
753       getWriter().recordRelocation(*this, Layout, &F, FixupAdd, TargetAdd,
754                                    FixedValue);
755       MCFixup FixupSub = MCFixup::createSubFor(Fixup);
756       MCValue TargetSub = MCValue::get(Target.getSymB());
757       getWriter().recordRelocation(*this, Layout, &F, FixupSub, TargetSub,
758                                    FixedValue);
759     } else {
760       getWriter().recordRelocation(*this, Layout, &F, Fixup, Target,
761                                    FixedValue);
762     }
763   }
764   return std::make_tuple(Target, FixedValue, IsResolved);
765 }
766 
767 void MCAssembler::layout(MCAsmLayout &Layout) {
768   assert(getBackendPtr() && "Expected assembler backend");
769   DEBUG_WITH_TYPE("mc-dump", {
770       errs() << "assembler backend - pre-layout\n--\n";
771       dump(); });
772 
773   // Create dummy fragments and assign section ordinals.
774   unsigned SectionIndex = 0;
775   for (MCSection &Sec : *this) {
776     // Create dummy fragments to eliminate any empty sections, this simplifies
777     // layout.
778     if (Sec.getFragmentList().empty())
779       new MCDataFragment(&Sec);
780 
781     Sec.setOrdinal(SectionIndex++);
782   }
783 
784   // Assign layout order indices to sections and fragments.
785   for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
786     MCSection *Sec = Layout.getSectionOrder()[i];
787     Sec->setLayoutOrder(i);
788 
789     unsigned FragmentIndex = 0;
790     for (MCFragment &Frag : *Sec)
791       Frag.setLayoutOrder(FragmentIndex++);
792   }
793 
794   // Layout until everything fits.
795   while (layoutOnce(Layout)) {
796     if (getContext().hadError())
797       return;
798     // Size of fragments in one section can depend on the size of fragments in
799     // another. If any fragment has changed size, we have to re-layout (and
800     // as a result possibly further relax) all.
801     for (MCSection &Sec : *this)
802       Layout.invalidateFragmentsFrom(&*Sec.begin());
803   }
804 
805   DEBUG_WITH_TYPE("mc-dump", {
806       errs() << "assembler backend - post-relaxation\n--\n";
807       dump(); });
808 
809   // Finalize the layout, including fragment lowering.
810   finishLayout(Layout);
811 
812   DEBUG_WITH_TYPE("mc-dump", {
813       errs() << "assembler backend - final-layout\n--\n";
814       dump(); });
815 
816   // Allow the object writer a chance to perform post-layout binding (for
817   // example, to set the index fields in the symbol data).
818   getWriter().executePostLayoutBinding(*this, Layout);
819 
820   // Evaluate and apply the fixups, generating relocation entries as necessary.
821   for (MCSection &Sec : *this) {
822     for (MCFragment &Frag : Sec) {
823       ArrayRef<MCFixup> Fixups;
824       MutableArrayRef<char> Contents;
825       const MCSubtargetInfo *STI = nullptr;
826 
827       // Process MCAlignFragment and MCEncodedFragmentWithFixups here.
828       switch (Frag.getKind()) {
829       default:
830         continue;
831       case MCFragment::FT_Align: {
832         MCAlignFragment &AF = cast<MCAlignFragment>(Frag);
833         // Insert fixup type for code alignment if the target define
834         // shouldInsertFixupForCodeAlign target hook.
835         if (Sec.UseCodeAlign() && AF.hasEmitNops())
836           getBackend().shouldInsertFixupForCodeAlign(*this, Layout, AF);
837         continue;
838       }
839       case MCFragment::FT_Data: {
840         MCDataFragment &DF = cast<MCDataFragment>(Frag);
841         Fixups = DF.getFixups();
842         Contents = DF.getContents();
843         STI = DF.getSubtargetInfo();
844         assert(!DF.hasInstructions() || STI != nullptr);
845         break;
846       }
847       case MCFragment::FT_Relaxable: {
848         MCRelaxableFragment &RF = cast<MCRelaxableFragment>(Frag);
849         Fixups = RF.getFixups();
850         Contents = RF.getContents();
851         STI = RF.getSubtargetInfo();
852         assert(!RF.hasInstructions() || STI != nullptr);
853         break;
854       }
855       case MCFragment::FT_CVDefRange: {
856         MCCVDefRangeFragment &CF = cast<MCCVDefRangeFragment>(Frag);
857         Fixups = CF.getFixups();
858         Contents = CF.getContents();
859         break;
860       }
861       case MCFragment::FT_Dwarf: {
862         MCDwarfLineAddrFragment &DF = cast<MCDwarfLineAddrFragment>(Frag);
863         Fixups = DF.getFixups();
864         Contents = DF.getContents();
865         break;
866       }
867       case MCFragment::FT_DwarfFrame: {
868         MCDwarfCallFrameFragment &DF = cast<MCDwarfCallFrameFragment>(Frag);
869         Fixups = DF.getFixups();
870         Contents = DF.getContents();
871         break;
872       }
873       }
874       for (const MCFixup &Fixup : Fixups) {
875         uint64_t FixedValue;
876         bool IsResolved;
877         MCValue Target;
878         std::tie(Target, FixedValue, IsResolved) =
879             handleFixup(Layout, Frag, Fixup);
880         getBackend().applyFixup(*this, Fixup, Target, Contents, FixedValue,
881                                 IsResolved, STI);
882       }
883     }
884   }
885 }
886 
887 void MCAssembler::Finish() {
888   // Create the layout object.
889   MCAsmLayout Layout(*this);
890   layout(Layout);
891 
892   // Write the object file.
893   stats::ObjectBytes += getWriter().writeObject(*this, Layout);
894 }
895 
896 bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup,
897                                        const MCRelaxableFragment *DF,
898                                        const MCAsmLayout &Layout) const {
899   assert(getBackendPtr() && "Expected assembler backend");
900   MCValue Target;
901   uint64_t Value;
902   bool WasForced;
903   bool Resolved = evaluateFixup(Layout, Fixup, DF, Target, Value, WasForced);
904   if (Target.getSymA() &&
905       Target.getSymA()->getKind() == MCSymbolRefExpr::VK_X86_ABS8 &&
906       Fixup.getKind() == FK_Data_1)
907     return false;
908   return getBackend().fixupNeedsRelaxationAdvanced(Fixup, Resolved, Value, DF,
909                                                    Layout, WasForced);
910 }
911 
912 bool MCAssembler::fragmentNeedsRelaxation(const MCRelaxableFragment *F,
913                                           const MCAsmLayout &Layout) const {
914   assert(getBackendPtr() && "Expected assembler backend");
915   // If this inst doesn't ever need relaxation, ignore it. This occurs when we
916   // are intentionally pushing out inst fragments, or because we relaxed a
917   // previous instruction to one that doesn't need relaxation.
918   if (!getBackend().mayNeedRelaxation(F->getInst(), *F->getSubtargetInfo()))
919     return false;
920 
921   for (const MCFixup &Fixup : F->getFixups())
922     if (fixupNeedsRelaxation(Fixup, F, Layout))
923       return true;
924 
925   return false;
926 }
927 
928 bool MCAssembler::relaxInstruction(MCAsmLayout &Layout,
929                                    MCRelaxableFragment &F) {
930   assert(getEmitterPtr() &&
931          "Expected CodeEmitter defined for relaxInstruction");
932   if (!fragmentNeedsRelaxation(&F, Layout))
933     return false;
934 
935   ++stats::RelaxedInstructions;
936 
937   // FIXME-PERF: We could immediately lower out instructions if we can tell
938   // they are fully resolved, to avoid retesting on later passes.
939 
940   // Relax the fragment.
941 
942   MCInst Relaxed = F.getInst();
943   getBackend().relaxInstruction(Relaxed, *F.getSubtargetInfo());
944 
945   // Encode the new instruction.
946   //
947   // FIXME-PERF: If it matters, we could let the target do this. It can
948   // probably do so more efficiently in many cases.
949   SmallVector<MCFixup, 4> Fixups;
950   SmallString<256> Code;
951   raw_svector_ostream VecOS(Code);
952   getEmitter().encodeInstruction(Relaxed, VecOS, Fixups, *F.getSubtargetInfo());
953 
954   // Update the fragment.
955   F.setInst(Relaxed);
956   F.getContents() = Code;
957   F.getFixups() = Fixups;
958 
959   return true;
960 }
961 
962 bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) {
963   uint64_t OldSize = LF.getContents().size();
964   int64_t Value;
965   bool Abs = LF.getValue().evaluateKnownAbsolute(Value, Layout);
966   if (!Abs)
967     report_fatal_error("sleb128 and uleb128 expressions must be absolute");
968   SmallString<8> &Data = LF.getContents();
969   Data.clear();
970   raw_svector_ostream OSE(Data);
971   // The compiler can generate EH table assembly that is impossible to assemble
972   // without either adding padding to an LEB fragment or adding extra padding
973   // to a later alignment fragment. To accommodate such tables, relaxation can
974   // only increase an LEB fragment size here, not decrease it. See PR35809.
975   if (LF.isSigned())
976     encodeSLEB128(Value, OSE, OldSize);
977   else
978     encodeULEB128(Value, OSE, OldSize);
979   return OldSize != LF.getContents().size();
980 }
981 
982 /// Check if the branch crosses the boundary.
983 ///
984 /// \param StartAddr start address of the fused/unfused branch.
985 /// \param Size size of the fused/unfused branch.
986 /// \param BoundaryAlignment alignment requirement of the branch.
987 /// \returns true if the branch cross the boundary.
988 static bool mayCrossBoundary(uint64_t StartAddr, uint64_t Size,
989                              Align BoundaryAlignment) {
990   uint64_t EndAddr = StartAddr + Size;
991   return (StartAddr >> Log2(BoundaryAlignment)) !=
992          ((EndAddr - 1) >> Log2(BoundaryAlignment));
993 }
994 
995 /// Check if the branch is against the boundary.
996 ///
997 /// \param StartAddr start address of the fused/unfused branch.
998 /// \param Size size of the fused/unfused branch.
999 /// \param BoundaryAlignment alignment requirement of the branch.
1000 /// \returns true if the branch is against the boundary.
1001 static bool isAgainstBoundary(uint64_t StartAddr, uint64_t Size,
1002                               Align BoundaryAlignment) {
1003   uint64_t EndAddr = StartAddr + Size;
1004   return (EndAddr & (BoundaryAlignment.value() - 1)) == 0;
1005 }
1006 
1007 /// Check if the branch needs padding.
1008 ///
1009 /// \param StartAddr start address of the fused/unfused branch.
1010 /// \param Size size of the fused/unfused branch.
1011 /// \param BoundaryAlignment alignment requirement of the branch.
1012 /// \returns true if the branch needs padding.
1013 static bool needPadding(uint64_t StartAddr, uint64_t Size,
1014                         Align BoundaryAlignment) {
1015   return mayCrossBoundary(StartAddr, Size, BoundaryAlignment) ||
1016          isAgainstBoundary(StartAddr, Size, BoundaryAlignment);
1017 }
1018 
1019 bool MCAssembler::relaxBoundaryAlign(MCAsmLayout &Layout,
1020                                      MCBoundaryAlignFragment &BF) {
1021   // BoundaryAlignFragment that doesn't need to align any fragment should not be
1022   // relaxed.
1023   if (!BF.getLastFragment())
1024     return false;
1025 
1026   uint64_t AlignedOffset = Layout.getFragmentOffset(&BF);
1027   uint64_t AlignedSize = 0;
1028   for (const MCFragment *F = BF.getLastFragment(); F != &BF;
1029        F = F->getPrevNode())
1030     AlignedSize += computeFragmentSize(Layout, *F);
1031 
1032   Align BoundaryAlignment = BF.getAlignment();
1033   uint64_t NewSize = needPadding(AlignedOffset, AlignedSize, BoundaryAlignment)
1034                          ? offsetToAlignment(AlignedOffset, BoundaryAlignment)
1035                          : 0U;
1036   if (NewSize == BF.getSize())
1037     return false;
1038   BF.setSize(NewSize);
1039   Layout.invalidateFragmentsFrom(&BF);
1040   return true;
1041 }
1042 
1043 bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout,
1044                                      MCDwarfLineAddrFragment &DF) {
1045   MCContext &Context = Layout.getAssembler().getContext();
1046   uint64_t OldSize = DF.getContents().size();
1047   int64_t AddrDelta;
1048   bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
1049   assert(Abs && "We created a line delta with an invalid expression");
1050   (void)Abs;
1051   int64_t LineDelta;
1052   LineDelta = DF.getLineDelta();
1053   SmallVectorImpl<char> &Data = DF.getContents();
1054   Data.clear();
1055   raw_svector_ostream OSE(Data);
1056   DF.getFixups().clear();
1057 
1058   if (!getBackend().requiresDiffExpressionRelocations()) {
1059     MCDwarfLineAddr::Encode(Context, getDWARFLinetableParams(), LineDelta,
1060                             AddrDelta, OSE);
1061   } else {
1062     uint32_t Offset;
1063     uint32_t Size;
1064     bool SetDelta = MCDwarfLineAddr::FixedEncode(Context,
1065                                                  getDWARFLinetableParams(),
1066                                                  LineDelta, AddrDelta,
1067                                                  OSE, &Offset, &Size);
1068     // Add Fixups for address delta or new address.
1069     const MCExpr *FixupExpr;
1070     if (SetDelta) {
1071       FixupExpr = &DF.getAddrDelta();
1072     } else {
1073       const MCBinaryExpr *ABE = cast<MCBinaryExpr>(&DF.getAddrDelta());
1074       FixupExpr = ABE->getLHS();
1075     }
1076     DF.getFixups().push_back(
1077         MCFixup::create(Offset, FixupExpr,
1078                         MCFixup::getKindForSize(Size, false /*isPCRel*/)));
1079   }
1080 
1081   return OldSize != Data.size();
1082 }
1083 
1084 bool MCAssembler::relaxDwarfCallFrameFragment(MCAsmLayout &Layout,
1085                                               MCDwarfCallFrameFragment &DF) {
1086   MCContext &Context = Layout.getAssembler().getContext();
1087   uint64_t OldSize = DF.getContents().size();
1088   int64_t AddrDelta;
1089   bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
1090   assert(Abs && "We created call frame with an invalid expression");
1091   (void) Abs;
1092   SmallVectorImpl<char> &Data = DF.getContents();
1093   Data.clear();
1094   raw_svector_ostream OSE(Data);
1095   DF.getFixups().clear();
1096 
1097   if (getBackend().requiresDiffExpressionRelocations()) {
1098     uint32_t Offset;
1099     uint32_t Size;
1100     MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE, &Offset,
1101                                           &Size);
1102     if (Size) {
1103       DF.getFixups().push_back(MCFixup::create(
1104           Offset, &DF.getAddrDelta(),
1105           MCFixup::getKindForSizeInBits(Size /*In bits.*/, false /*isPCRel*/)));
1106     }
1107   } else {
1108     MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE);
1109   }
1110 
1111   return OldSize != Data.size();
1112 }
1113 
1114 bool MCAssembler::relaxCVInlineLineTable(MCAsmLayout &Layout,
1115                                          MCCVInlineLineTableFragment &F) {
1116   unsigned OldSize = F.getContents().size();
1117   getContext().getCVContext().encodeInlineLineTable(Layout, F);
1118   return OldSize != F.getContents().size();
1119 }
1120 
1121 bool MCAssembler::relaxCVDefRange(MCAsmLayout &Layout,
1122                                   MCCVDefRangeFragment &F) {
1123   unsigned OldSize = F.getContents().size();
1124   getContext().getCVContext().encodeDefRange(Layout, F);
1125   return OldSize != F.getContents().size();
1126 }
1127 
1128 bool MCAssembler::relaxFragment(MCAsmLayout &Layout, MCFragment &F) {
1129   switch(F.getKind()) {
1130   default:
1131     return false;
1132   case MCFragment::FT_Relaxable:
1133     assert(!getRelaxAll() &&
1134            "Did not expect a MCRelaxableFragment in RelaxAll mode");
1135     return relaxInstruction(Layout, cast<MCRelaxableFragment>(F));
1136   case MCFragment::FT_Dwarf:
1137     return relaxDwarfLineAddr(Layout, cast<MCDwarfLineAddrFragment>(F));
1138   case MCFragment::FT_DwarfFrame:
1139     return relaxDwarfCallFrameFragment(Layout,
1140                                        cast<MCDwarfCallFrameFragment>(F));
1141   case MCFragment::FT_LEB:
1142     return relaxLEB(Layout, cast<MCLEBFragment>(F));
1143   case MCFragment::FT_BoundaryAlign:
1144     return relaxBoundaryAlign(Layout, cast<MCBoundaryAlignFragment>(F));
1145   case MCFragment::FT_CVInlineLines:
1146     return relaxCVInlineLineTable(Layout, cast<MCCVInlineLineTableFragment>(F));
1147   case MCFragment::FT_CVDefRange:
1148     return relaxCVDefRange(Layout, cast<MCCVDefRangeFragment>(F));
1149   }
1150 }
1151 
1152 bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSection &Sec) {
1153   // Holds the first fragment which needed relaxing during this layout. It will
1154   // remain NULL if none were relaxed.
1155   // When a fragment is relaxed, all the fragments following it should get
1156   // invalidated because their offset is going to change.
1157   MCFragment *FirstRelaxedFragment = nullptr;
1158 
1159   // Attempt to relax all the fragments in the section.
1160   for (MCFragment &Frag : Sec) {
1161     // Check if this is a fragment that needs relaxation.
1162     bool RelaxedFrag = relaxFragment(Layout, Frag);
1163     if (RelaxedFrag && !FirstRelaxedFragment)
1164       FirstRelaxedFragment = &Frag;
1165   }
1166   if (FirstRelaxedFragment) {
1167     Layout.invalidateFragmentsFrom(FirstRelaxedFragment);
1168     return true;
1169   }
1170   return false;
1171 }
1172 
1173 bool MCAssembler::layoutOnce(MCAsmLayout &Layout) {
1174   ++stats::RelaxationSteps;
1175 
1176   bool WasRelaxed = false;
1177   for (MCSection &Sec : *this) {
1178     while (layoutSectionOnce(Layout, Sec))
1179       WasRelaxed = true;
1180   }
1181 
1182   return WasRelaxed;
1183 }
1184 
1185 void MCAssembler::finishLayout(MCAsmLayout &Layout) {
1186   assert(getBackendPtr() && "Expected assembler backend");
1187   // The layout is done. Mark every fragment as valid.
1188   for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) {
1189     MCSection &Section = *Layout.getSectionOrder()[i];
1190     Layout.getFragmentOffset(&*Section.getFragmentList().rbegin());
1191     computeFragmentSize(Layout, *Section.getFragmentList().rbegin());
1192   }
1193   getBackend().finishLayout(*this, Layout);
1194 }
1195 
1196 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1197 LLVM_DUMP_METHOD void MCAssembler::dump() const{
1198   raw_ostream &OS = errs();
1199 
1200   OS << "<MCAssembler\n";
1201   OS << "  Sections:[\n    ";
1202   for (const_iterator it = begin(), ie = end(); it != ie; ++it) {
1203     if (it != begin()) OS << ",\n    ";
1204     it->dump();
1205   }
1206   OS << "],\n";
1207   OS << "  Symbols:[";
1208 
1209   for (const_symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1210     if (it != symbol_begin()) OS << ",\n           ";
1211     OS << "(";
1212     it->dump();
1213     OS << ", Index:" << it->getIndex() << ", ";
1214     OS << ")";
1215   }
1216   OS << "]>\n";
1217 }
1218 #endif
1219