1//===- lib/MC/MCObjectStreamer.cpp - Object File MCStreamer Interface -----===//
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#include "llvm/MC/MCObjectStreamer.h"
11#include "llvm/ADT/STLExtras.h"
12#include "llvm/MC/MCAsmBackend.h"
13#include "llvm/MC/MCAsmInfo.h"
14#include "llvm/MC/MCAssembler.h"
15#include "llvm/MC/MCCodeEmitter.h"
16#include "llvm/MC/MCContext.h"
17#include "llvm/MC/MCDwarf.h"
18#include "llvm/MC/MCExpr.h"
19#include "llvm/MC/MCObjectWriter.h"
20#include "llvm/MC/MCSection.h"
21#include "llvm/MC/MCSymbol.h"
22#include "llvm/Support/ErrorHandling.h"
23#include "llvm/Support/TargetRegistry.h"
24using namespace llvm;
25
26MCObjectStreamer::MCObjectStreamer(MCContext &Context, MCAsmBackend &TAB,
27                                   raw_pwrite_stream &OS,
28                                   MCCodeEmitter *Emitter_)
29    : MCStreamer(Context),
30      Assembler(new MCAssembler(Context, TAB, *Emitter_,
31                                *TAB.createObjectWriter(OS))),
32      EmitEHFrame(true), EmitDebugFrame(false) {}
33
34MCObjectStreamer::~MCObjectStreamer() {
35  delete &Assembler->getBackend();
36  delete &Assembler->getEmitter();
37  delete &Assembler->getWriter();
38  delete Assembler;
39}
40
41void MCObjectStreamer::flushPendingLabels(MCFragment *F, uint64_t FOffset) {
42  if (PendingLabels.empty())
43    return;
44  if (!F) {
45    F = new MCDataFragment();
46    MCSection *CurSection = getCurrentSectionOnly();
47    CurSection->getFragmentList().insert(CurInsertionPoint, F);
48    F->setParent(CurSection);
49  }
50  for (MCSymbol *Sym : PendingLabels) {
51    Sym->setFragment(F);
52    Sym->setOffset(FOffset);
53  }
54  PendingLabels.clear();
55}
56
57void MCObjectStreamer::emitAbsoluteSymbolDiff(const MCSymbol *Hi,
58                                              const MCSymbol *Lo,
59                                              unsigned Size) {
60  // If not assigned to the same (valid) fragment, fallback.
61  if (!Hi->getFragment() || Hi->getFragment() != Lo->getFragment() ||
62      Hi->isVariable() || Lo->isVariable()) {
63    MCStreamer::emitAbsoluteSymbolDiff(Hi, Lo, Size);
64    return;
65  }
66
67  assert(Hi->getOffset() >= Lo->getOffset() &&
68         "Expected Hi to be greater than Lo");
69  EmitIntValue(Hi->getOffset() - Lo->getOffset(), Size);
70}
71
72void MCObjectStreamer::reset() {
73  if (Assembler)
74    Assembler->reset();
75  CurInsertionPoint = MCSection::iterator();
76  EmitEHFrame = true;
77  EmitDebugFrame = false;
78  PendingLabels.clear();
79  MCStreamer::reset();
80}
81
82void MCObjectStreamer::EmitFrames(MCAsmBackend *MAB) {
83  if (!getNumFrameInfos())
84    return;
85
86  if (EmitEHFrame)
87    MCDwarfFrameEmitter::Emit(*this, MAB, true);
88
89  if (EmitDebugFrame)
90    MCDwarfFrameEmitter::Emit(*this, MAB, false);
91}
92
93MCFragment *MCObjectStreamer::getCurrentFragment() const {
94  assert(getCurrentSectionOnly() && "No current section!");
95
96  if (CurInsertionPoint != getCurrentSectionOnly()->getFragmentList().begin())
97    return &*std::prev(CurInsertionPoint);
98
99  return nullptr;
100}
101
102MCDataFragment *MCObjectStreamer::getOrCreateDataFragment() {
103  MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
104  // When bundling is enabled, we don't want to add data to a fragment that
105  // already has instructions (see MCELFStreamer::EmitInstToData for details)
106  if (!F || (Assembler->isBundlingEnabled() && !Assembler->getRelaxAll() &&
107             F->hasInstructions())) {
108    F = new MCDataFragment();
109    insert(F);
110  }
111  return F;
112}
113
114void MCObjectStreamer::visitUsedSymbol(const MCSymbol &Sym) {
115  Assembler->registerSymbol(Sym);
116}
117
118void MCObjectStreamer::EmitCFISections(bool EH, bool Debug) {
119  MCStreamer::EmitCFISections(EH, Debug);
120  EmitEHFrame = EH;
121  EmitDebugFrame = Debug;
122}
123
124void MCObjectStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
125                                     SMLoc Loc) {
126  MCStreamer::EmitValueImpl(Value, Size, Loc);
127  MCDataFragment *DF = getOrCreateDataFragment();
128  flushPendingLabels(DF, DF->getContents().size());
129
130  MCLineEntry::Make(this, getCurrentSection().first);
131
132  // Avoid fixups when possible.
133  int64_t AbsValue;
134  if (Value->evaluateAsAbsolute(AbsValue, getAssembler())) {
135    EmitIntValue(AbsValue, Size);
136    return;
137  }
138  DF->getFixups().push_back(
139      MCFixup::create(DF->getContents().size(), Value,
140                      MCFixup::getKindForSize(Size, false), Loc));
141  DF->getContents().resize(DF->getContents().size() + Size, 0);
142}
143
144void MCObjectStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) {
145  // We need to create a local symbol to avoid relocations.
146  Frame.Begin = getContext().createTempSymbol();
147  EmitLabel(Frame.Begin);
148}
149
150void MCObjectStreamer::EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) {
151  Frame.End = getContext().createTempSymbol();
152  EmitLabel(Frame.End);
153}
154
155void MCObjectStreamer::EmitLabel(MCSymbol *Symbol) {
156  MCStreamer::EmitLabel(Symbol);
157
158  getAssembler().registerSymbol(*Symbol);
159
160  // If there is a current fragment, mark the symbol as pointing into it.
161  // Otherwise queue the label and set its fragment pointer when we emit the
162  // next fragment.
163  auto *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
164  if (F && !(getAssembler().isBundlingEnabled() &&
165             getAssembler().getRelaxAll())) {
166    Symbol->setFragment(F);
167    Symbol->setOffset(F->getContents().size());
168  } else {
169    PendingLabels.push_back(Symbol);
170  }
171}
172
173void MCObjectStreamer::EmitULEB128Value(const MCExpr *Value) {
174  int64_t IntValue;
175  if (Value->evaluateAsAbsolute(IntValue, getAssembler())) {
176    EmitULEB128IntValue(IntValue);
177    return;
178  }
179  insert(new MCLEBFragment(*Value, false));
180}
181
182void MCObjectStreamer::EmitSLEB128Value(const MCExpr *Value) {
183  int64_t IntValue;
184  if (Value->evaluateAsAbsolute(IntValue, getAssembler())) {
185    EmitSLEB128IntValue(IntValue);
186    return;
187  }
188  insert(new MCLEBFragment(*Value, true));
189}
190
191void MCObjectStreamer::EmitWeakReference(MCSymbol *Alias,
192                                         const MCSymbol *Symbol) {
193  report_fatal_error("This file format doesn't support weak aliases.");
194}
195
196void MCObjectStreamer::ChangeSection(MCSection *Section,
197                                     const MCExpr *Subsection) {
198  changeSectionImpl(Section, Subsection);
199}
200
201bool MCObjectStreamer::changeSectionImpl(MCSection *Section,
202                                         const MCExpr *Subsection) {
203  assert(Section && "Cannot switch to a null section!");
204  flushPendingLabels(nullptr);
205
206  bool Created = getAssembler().registerSection(*Section);
207
208  int64_t IntSubsection = 0;
209  if (Subsection &&
210      !Subsection->evaluateAsAbsolute(IntSubsection, getAssembler()))
211    report_fatal_error("Cannot evaluate subsection number");
212  if (IntSubsection < 0 || IntSubsection > 8192)
213    report_fatal_error("Subsection number out of range");
214  CurInsertionPoint =
215      Section->getSubsectionInsertionPoint(unsigned(IntSubsection));
216  return Created;
217}
218
219void MCObjectStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
220  getAssembler().registerSymbol(*Symbol);
221  MCStreamer::EmitAssignment(Symbol, Value);
222}
223
224bool MCObjectStreamer::mayHaveInstructions(MCSection &Sec) const {
225  return Sec.hasInstructions();
226}
227
228void MCObjectStreamer::EmitInstruction(const MCInst &Inst,
229                                       const MCSubtargetInfo &STI) {
230  MCStreamer::EmitInstruction(Inst, STI);
231
232  MCSection *Sec = getCurrentSectionOnly();
233  Sec->setHasInstructions(true);
234
235  // Now that a machine instruction has been assembled into this section, make
236  // a line entry for any .loc directive that has been seen.
237  MCLineEntry::Make(this, getCurrentSection().first);
238
239  // If this instruction doesn't need relaxation, just emit it as data.
240  MCAssembler &Assembler = getAssembler();
241  if (!Assembler.getBackend().mayNeedRelaxation(Inst)) {
242    EmitInstToData(Inst, STI);
243    return;
244  }
245
246  // Otherwise, relax and emit it as data if either:
247  // - The RelaxAll flag was passed
248  // - Bundling is enabled and this instruction is inside a bundle-locked
249  //   group. We want to emit all such instructions into the same data
250  //   fragment.
251  if (Assembler.getRelaxAll() ||
252      (Assembler.isBundlingEnabled() && Sec->isBundleLocked())) {
253    MCInst Relaxed;
254    getAssembler().getBackend().relaxInstruction(Inst, Relaxed);
255    while (getAssembler().getBackend().mayNeedRelaxation(Relaxed))
256      getAssembler().getBackend().relaxInstruction(Relaxed, Relaxed);
257    EmitInstToData(Relaxed, STI);
258    return;
259  }
260
261  // Otherwise emit to a separate fragment.
262  EmitInstToFragment(Inst, STI);
263}
264
265void MCObjectStreamer::EmitInstToFragment(const MCInst &Inst,
266                                          const MCSubtargetInfo &STI) {
267  if (getAssembler().getRelaxAll() && getAssembler().isBundlingEnabled())
268    llvm_unreachable("All instructions should have already been relaxed");
269
270  // Always create a new, separate fragment here, because its size can change
271  // during relaxation.
272  MCRelaxableFragment *IF = new MCRelaxableFragment(Inst, STI);
273  insert(IF);
274
275  SmallString<128> Code;
276  raw_svector_ostream VecOS(Code);
277  getAssembler().getEmitter().encodeInstruction(Inst, VecOS, IF->getFixups(),
278                                                STI);
279  IF->getContents().append(Code.begin(), Code.end());
280}
281
282#ifndef NDEBUG
283static const char *const BundlingNotImplementedMsg =
284  "Aligned bundling is not implemented for this object format";
285#endif
286
287void MCObjectStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
288  llvm_unreachable(BundlingNotImplementedMsg);
289}
290
291void MCObjectStreamer::EmitBundleLock(bool AlignToEnd) {
292  llvm_unreachable(BundlingNotImplementedMsg);
293}
294
295void MCObjectStreamer::EmitBundleUnlock() {
296  llvm_unreachable(BundlingNotImplementedMsg);
297}
298
299void MCObjectStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
300                                             unsigned Column, unsigned Flags,
301                                             unsigned Isa,
302                                             unsigned Discriminator,
303                                             StringRef FileName) {
304  // In case we see two .loc directives in a row, make sure the
305  // first one gets a line entry.
306  MCLineEntry::Make(this, getCurrentSection().first);
307
308  this->MCStreamer::EmitDwarfLocDirective(FileNo, Line, Column, Flags,
309                                          Isa, Discriminator, FileName);
310}
311
312static const MCExpr *buildSymbolDiff(MCObjectStreamer &OS, const MCSymbol *A,
313                                     const MCSymbol *B) {
314  MCContext &Context = OS.getContext();
315  MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
316  const MCExpr *ARef = MCSymbolRefExpr::create(A, Variant, Context);
317  const MCExpr *BRef = MCSymbolRefExpr::create(B, Variant, Context);
318  const MCExpr *AddrDelta =
319      MCBinaryExpr::create(MCBinaryExpr::Sub, ARef, BRef, Context);
320  return AddrDelta;
321}
322
323static void emitDwarfSetLineAddr(MCObjectStreamer &OS,
324                                 MCDwarfLineTableParams Params,
325                                 int64_t LineDelta, const MCSymbol *Label,
326                                 int PointerSize) {
327  // emit the sequence to set the address
328  OS.EmitIntValue(dwarf::DW_LNS_extended_op, 1);
329  OS.EmitULEB128IntValue(PointerSize + 1);
330  OS.EmitIntValue(dwarf::DW_LNE_set_address, 1);
331  OS.EmitSymbolValue(Label, PointerSize);
332
333  // emit the sequence for the LineDelta (from 1) and a zero address delta.
334  MCDwarfLineAddr::Emit(&OS, Params, LineDelta, 0);
335}
336
337void MCObjectStreamer::EmitDwarfAdvanceLineAddr(int64_t LineDelta,
338                                                const MCSymbol *LastLabel,
339                                                const MCSymbol *Label,
340                                                unsigned PointerSize) {
341  if (!LastLabel) {
342    emitDwarfSetLineAddr(*this, Assembler->getDWARFLinetableParams(), LineDelta,
343                         Label, PointerSize);
344    return;
345  }
346  const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel);
347  int64_t Res;
348  if (AddrDelta->evaluateAsAbsolute(Res, getAssembler())) {
349    MCDwarfLineAddr::Emit(this, Assembler->getDWARFLinetableParams(), LineDelta,
350                          Res);
351    return;
352  }
353  insert(new MCDwarfLineAddrFragment(LineDelta, *AddrDelta));
354}
355
356void MCObjectStreamer::EmitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel,
357                                                 const MCSymbol *Label) {
358  const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel);
359  int64_t Res;
360  if (AddrDelta->evaluateAsAbsolute(Res, getAssembler())) {
361    MCDwarfFrameEmitter::EmitAdvanceLoc(*this, Res);
362    return;
363  }
364  insert(new MCDwarfCallFrameFragment(*AddrDelta));
365}
366
367void MCObjectStreamer::EmitBytes(StringRef Data) {
368  MCLineEntry::Make(this, getCurrentSection().first);
369  MCDataFragment *DF = getOrCreateDataFragment();
370  flushPendingLabels(DF, DF->getContents().size());
371  DF->getContents().append(Data.begin(), Data.end());
372}
373
374void MCObjectStreamer::EmitValueToAlignment(unsigned ByteAlignment,
375                                            int64_t Value,
376                                            unsigned ValueSize,
377                                            unsigned MaxBytesToEmit) {
378  if (MaxBytesToEmit == 0)
379    MaxBytesToEmit = ByteAlignment;
380  insert(new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit));
381
382  // Update the maximum alignment on the current section if necessary.
383  MCSection *CurSec = getCurrentSection().first;
384  if (ByteAlignment > CurSec->getAlignment())
385    CurSec->setAlignment(ByteAlignment);
386}
387
388void MCObjectStreamer::EmitCodeAlignment(unsigned ByteAlignment,
389                                         unsigned MaxBytesToEmit) {
390  EmitValueToAlignment(ByteAlignment, 0, 1, MaxBytesToEmit);
391  cast<MCAlignFragment>(getCurrentFragment())->setEmitNops(true);
392}
393
394void MCObjectStreamer::emitValueToOffset(const MCExpr *Offset,
395                                         unsigned char Value) {
396  insert(new MCOrgFragment(*Offset, Value));
397}
398
399// Associate GPRel32 fixup with data and resize data area
400void MCObjectStreamer::EmitGPRel32Value(const MCExpr *Value) {
401  MCDataFragment *DF = getOrCreateDataFragment();
402  flushPendingLabels(DF, DF->getContents().size());
403
404  DF->getFixups().push_back(MCFixup::create(DF->getContents().size(),
405                                            Value, FK_GPRel_4));
406  DF->getContents().resize(DF->getContents().size() + 4, 0);
407}
408
409// Associate GPRel32 fixup with data and resize data area
410void MCObjectStreamer::EmitGPRel64Value(const MCExpr *Value) {
411  MCDataFragment *DF = getOrCreateDataFragment();
412  flushPendingLabels(DF, DF->getContents().size());
413
414  DF->getFixups().push_back(MCFixup::create(DF->getContents().size(),
415                                            Value, FK_GPRel_4));
416  DF->getContents().resize(DF->getContents().size() + 8, 0);
417}
418
419bool MCObjectStreamer::EmitRelocDirective(const MCExpr &Offset, StringRef Name,
420                                          const MCExpr *Expr, SMLoc Loc) {
421  int64_t OffsetValue;
422  if (!Offset.evaluateAsAbsolute(OffsetValue))
423    llvm_unreachable("Offset is not absolute");
424
425  MCDataFragment *DF = getOrCreateDataFragment();
426  flushPendingLabels(DF, DF->getContents().size());
427
428  MCFixupKind Kind;
429  if (!Assembler->getBackend().getFixupKind(Name, Kind))
430    return true;
431
432  if (Expr == nullptr)
433    Expr =
434        MCSymbolRefExpr::create(getContext().createTempSymbol(), getContext());
435  DF->getFixups().push_back(MCFixup::create(OffsetValue, Expr, Kind, Loc));
436  return false;
437}
438
439void MCObjectStreamer::EmitFill(uint64_t NumBytes, uint8_t FillValue) {
440  const MCSection *Sec = getCurrentSection().first;
441  assert(Sec && "need a section");
442  unsigned ItemSize = Sec->isVirtualSection() ? 0 : 1;
443  insert(new MCFillFragment(FillValue, ItemSize, NumBytes));
444}
445
446void MCObjectStreamer::FinishImpl() {
447  // If we are generating dwarf for assembly source files dump out the sections.
448  if (getContext().getGenDwarfForAssembly())
449    MCGenDwarfInfo::Emit(this);
450
451  // Dump out the dwarf file & directory tables and line tables.
452  MCDwarfLineTable::Emit(this, getAssembler().getDWARFLinetableParams());
453
454  flushPendingLabels(nullptr);
455  getAssembler().Finish();
456}
457