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"
23using namespace llvm;
24
25MCObjectStreamer::MCObjectStreamer(MCContext &Context, MCAsmBackend &TAB,
26                                   raw_ostream &OS, MCCodeEmitter *Emitter_)
27    : MCStreamer(Context),
28      Assembler(new MCAssembler(Context, TAB, *Emitter_,
29                                *TAB.createObjectWriter(OS), OS)),
30      CurSectionData(nullptr), EmitEHFrame(true), EmitDebugFrame(false) {}
31
32MCObjectStreamer::MCObjectStreamer(MCContext &Context, MCAsmBackend &TAB,
33                                   raw_ostream &OS, MCCodeEmitter *Emitter_,
34                                   MCAssembler *_Assembler)
35    : MCStreamer(Context), Assembler(_Assembler), CurSectionData(nullptr),
36      EmitEHFrame(true), EmitDebugFrame(false) {}
37
38MCObjectStreamer::~MCObjectStreamer() {
39  delete &Assembler->getBackend();
40  delete &Assembler->getEmitter();
41  delete &Assembler->getWriter();
42  delete Assembler;
43}
44
45void MCObjectStreamer::reset() {
46  if (Assembler)
47    Assembler->reset();
48  CurSectionData = nullptr;
49  CurInsertionPoint = MCSectionData::iterator();
50  EmitEHFrame = true;
51  EmitDebugFrame = false;
52  MCStreamer::reset();
53}
54
55void MCObjectStreamer::EmitFrames(MCAsmBackend *MAB) {
56  if (!getNumFrameInfos())
57    return;
58
59  if (EmitEHFrame)
60    MCDwarfFrameEmitter::Emit(*this, MAB, true);
61
62  if (EmitDebugFrame)
63    MCDwarfFrameEmitter::Emit(*this, MAB, false);
64}
65
66MCFragment *MCObjectStreamer::getCurrentFragment() const {
67  assert(getCurrentSectionData() && "No current section!");
68
69  if (CurInsertionPoint != getCurrentSectionData()->getFragmentList().begin())
70    return std::prev(CurInsertionPoint);
71
72  return nullptr;
73}
74
75MCDataFragment *MCObjectStreamer::getOrCreateDataFragment() const {
76  MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
77  // When bundling is enabled, we don't want to add data to a fragment that
78  // already has instructions (see MCELFStreamer::EmitInstToData for details)
79  if (!F || (Assembler->isBundlingEnabled() && F->hasInstructions())) {
80    F = new MCDataFragment();
81    insert(F);
82  }
83  return F;
84}
85
86void MCObjectStreamer::visitUsedSymbol(const MCSymbol &Sym) {
87  Assembler->getOrCreateSymbolData(Sym);
88}
89
90void MCObjectStreamer::EmitCFISections(bool EH, bool Debug) {
91  MCStreamer::EmitCFISections(EH, Debug);
92  EmitEHFrame = EH;
93  EmitDebugFrame = Debug;
94}
95
96void MCObjectStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
97                                     const SMLoc &Loc) {
98  MCStreamer::EmitValueImpl(Value, Size, Loc);
99  MCDataFragment *DF = getOrCreateDataFragment();
100
101  MCLineEntry::Make(this, getCurrentSection().first);
102
103  // Avoid fixups when possible.
104  int64_t AbsValue;
105  if (Value->EvaluateAsAbsolute(AbsValue, getAssembler())) {
106    EmitIntValue(AbsValue, Size);
107    return;
108  }
109  DF->getFixups().push_back(
110      MCFixup::Create(DF->getContents().size(), Value,
111                      MCFixup::getKindForSize(Size, false), Loc));
112  DF->getContents().resize(DF->getContents().size() + Size, 0);
113}
114
115void MCObjectStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) {
116  // We need to create a local symbol to avoid relocations.
117  Frame.Begin = getContext().CreateTempSymbol();
118  EmitLabel(Frame.Begin);
119}
120
121void MCObjectStreamer::EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) {
122  Frame.End = getContext().CreateTempSymbol();
123  EmitLabel(Frame.End);
124}
125
126void MCObjectStreamer::EmitLabel(MCSymbol *Symbol) {
127  MCStreamer::EmitLabel(Symbol);
128
129  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
130
131  // FIXME: This is wasteful, we don't necessarily need to create a data
132  // fragment. Instead, we should mark the symbol as pointing into the data
133  // fragment if it exists, otherwise we should just queue the label and set its
134  // fragment pointer when we emit the next fragment.
135  MCDataFragment *F = getOrCreateDataFragment();
136  assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
137  SD.setFragment(F);
138  SD.setOffset(F->getContents().size());
139}
140
141void MCObjectStreamer::EmitULEB128Value(const MCExpr *Value) {
142  int64_t IntValue;
143  if (Value->EvaluateAsAbsolute(IntValue, getAssembler())) {
144    EmitULEB128IntValue(IntValue);
145    return;
146  }
147  Value = ForceExpAbs(Value);
148  insert(new MCLEBFragment(*Value, false));
149}
150
151void MCObjectStreamer::EmitSLEB128Value(const MCExpr *Value) {
152  int64_t IntValue;
153  if (Value->EvaluateAsAbsolute(IntValue, getAssembler())) {
154    EmitSLEB128IntValue(IntValue);
155    return;
156  }
157  Value = ForceExpAbs(Value);
158  insert(new MCLEBFragment(*Value, true));
159}
160
161void MCObjectStreamer::EmitWeakReference(MCSymbol *Alias,
162                                         const MCSymbol *Symbol) {
163  report_fatal_error("This file format doesn't support weak aliases.");
164}
165
166void MCObjectStreamer::ChangeSection(const MCSection *Section,
167                                     const MCExpr *Subsection) {
168  assert(Section && "Cannot switch to a null section!");
169
170  CurSectionData = &getAssembler().getOrCreateSectionData(*Section);
171
172  int64_t IntSubsection = 0;
173  if (Subsection &&
174      !Subsection->EvaluateAsAbsolute(IntSubsection, getAssembler()))
175    report_fatal_error("Cannot evaluate subsection number");
176  if (IntSubsection < 0 || IntSubsection > 8192)
177    report_fatal_error("Subsection number out of range");
178  CurInsertionPoint =
179    CurSectionData->getSubsectionInsertionPoint(unsigned(IntSubsection));
180}
181
182void MCObjectStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
183  getAssembler().getOrCreateSymbolData(*Symbol);
184  MCStreamer::EmitAssignment(Symbol, Value);
185}
186
187void MCObjectStreamer::EmitInstruction(const MCInst &Inst,
188                                       const MCSubtargetInfo &STI) {
189  MCStreamer::EmitInstruction(Inst, STI);
190
191  MCSectionData *SD = getCurrentSectionData();
192  SD->setHasInstructions(true);
193
194  // Now that a machine instruction has been assembled into this section, make
195  // a line entry for any .loc directive that has been seen.
196  MCLineEntry::Make(this, getCurrentSection().first);
197
198  // If this instruction doesn't need relaxation, just emit it as data.
199  MCAssembler &Assembler = getAssembler();
200  if (!Assembler.getBackend().mayNeedRelaxation(Inst)) {
201    EmitInstToData(Inst, STI);
202    return;
203  }
204
205  // Otherwise, relax and emit it as data if either:
206  // - The RelaxAll flag was passed
207  // - Bundling is enabled and this instruction is inside a bundle-locked
208  //   group. We want to emit all such instructions into the same data
209  //   fragment.
210  if (Assembler.getRelaxAll() ||
211      (Assembler.isBundlingEnabled() && SD->isBundleLocked())) {
212    MCInst Relaxed;
213    getAssembler().getBackend().relaxInstruction(Inst, Relaxed);
214    while (getAssembler().getBackend().mayNeedRelaxation(Relaxed))
215      getAssembler().getBackend().relaxInstruction(Relaxed, Relaxed);
216    EmitInstToData(Relaxed, STI);
217    return;
218  }
219
220  // Otherwise emit to a separate fragment.
221  EmitInstToFragment(Inst, STI);
222}
223
224void MCObjectStreamer::EmitInstToFragment(const MCInst &Inst,
225                                          const MCSubtargetInfo &STI) {
226  // Always create a new, separate fragment here, because its size can change
227  // during relaxation.
228  MCRelaxableFragment *IF = new MCRelaxableFragment(Inst, STI);
229  insert(IF);
230
231  SmallString<128> Code;
232  raw_svector_ostream VecOS(Code);
233  getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, IF->getFixups(),
234                                                STI);
235  VecOS.flush();
236  IF->getContents().append(Code.begin(), Code.end());
237}
238
239#ifndef NDEBUG
240static const char *const BundlingNotImplementedMsg =
241  "Aligned bundling is not implemented for this object format";
242#endif
243
244void MCObjectStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
245  llvm_unreachable(BundlingNotImplementedMsg);
246}
247
248void MCObjectStreamer::EmitBundleLock(bool AlignToEnd) {
249  llvm_unreachable(BundlingNotImplementedMsg);
250}
251
252void MCObjectStreamer::EmitBundleUnlock() {
253  llvm_unreachable(BundlingNotImplementedMsg);
254}
255
256void MCObjectStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
257                                             unsigned Column, unsigned Flags,
258                                             unsigned Isa,
259                                             unsigned Discriminator,
260                                             StringRef FileName) {
261  // In case we see two .loc directives in a row, make sure the
262  // first one gets a line entry.
263  MCLineEntry::Make(this, getCurrentSection().first);
264
265  this->MCStreamer::EmitDwarfLocDirective(FileNo, Line, Column, Flags,
266                                          Isa, Discriminator, FileName);
267}
268
269void MCObjectStreamer::EmitDwarfAdvanceLineAddr(int64_t LineDelta,
270                                                const MCSymbol *LastLabel,
271                                                const MCSymbol *Label,
272                                                unsigned PointerSize) {
273  if (!LastLabel) {
274    EmitDwarfSetLineAddr(LineDelta, Label, PointerSize);
275    return;
276  }
277  const MCExpr *AddrDelta = BuildSymbolDiff(getContext(), Label, LastLabel);
278  int64_t Res;
279  if (AddrDelta->EvaluateAsAbsolute(Res, getAssembler())) {
280    MCDwarfLineAddr::Emit(this, LineDelta, Res);
281    return;
282  }
283  AddrDelta = ForceExpAbs(AddrDelta);
284  insert(new MCDwarfLineAddrFragment(LineDelta, *AddrDelta));
285}
286
287void MCObjectStreamer::EmitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel,
288                                                 const MCSymbol *Label) {
289  const MCExpr *AddrDelta = BuildSymbolDiff(getContext(), Label, LastLabel);
290  int64_t Res;
291  if (AddrDelta->EvaluateAsAbsolute(Res, getAssembler())) {
292    MCDwarfFrameEmitter::EmitAdvanceLoc(*this, Res);
293    return;
294  }
295  AddrDelta = ForceExpAbs(AddrDelta);
296  insert(new MCDwarfCallFrameFragment(*AddrDelta));
297}
298
299void MCObjectStreamer::EmitBytes(StringRef Data) {
300  MCLineEntry::Make(this, getCurrentSection().first);
301  getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
302}
303
304void MCObjectStreamer::EmitValueToAlignment(unsigned ByteAlignment,
305                                            int64_t Value,
306                                            unsigned ValueSize,
307                                            unsigned MaxBytesToEmit) {
308  if (MaxBytesToEmit == 0)
309    MaxBytesToEmit = ByteAlignment;
310  insert(new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit));
311
312  // Update the maximum alignment on the current section if necessary.
313  if (ByteAlignment > getCurrentSectionData()->getAlignment())
314    getCurrentSectionData()->setAlignment(ByteAlignment);
315}
316
317void MCObjectStreamer::EmitCodeAlignment(unsigned ByteAlignment,
318                                         unsigned MaxBytesToEmit) {
319  EmitValueToAlignment(ByteAlignment, 0, 1, MaxBytesToEmit);
320  cast<MCAlignFragment>(getCurrentFragment())->setEmitNops(true);
321}
322
323bool MCObjectStreamer::EmitValueToOffset(const MCExpr *Offset,
324                                         unsigned char Value) {
325  int64_t Res;
326  if (Offset->EvaluateAsAbsolute(Res, getAssembler())) {
327    insert(new MCOrgFragment(*Offset, Value));
328    return false;
329  }
330
331  MCSymbol *CurrentPos = getContext().CreateTempSymbol();
332  EmitLabel(CurrentPos);
333  MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
334  const MCExpr *Ref =
335    MCSymbolRefExpr::Create(CurrentPos, Variant, getContext());
336  const MCExpr *Delta =
337    MCBinaryExpr::Create(MCBinaryExpr::Sub, Offset, Ref, getContext());
338
339  if (!Delta->EvaluateAsAbsolute(Res, getAssembler()))
340    return true;
341  EmitFill(Res, Value);
342  return false;
343}
344
345// Associate GPRel32 fixup with data and resize data area
346void MCObjectStreamer::EmitGPRel32Value(const MCExpr *Value) {
347  MCDataFragment *DF = getOrCreateDataFragment();
348
349  DF->getFixups().push_back(MCFixup::Create(DF->getContents().size(),
350                                            Value, FK_GPRel_4));
351  DF->getContents().resize(DF->getContents().size() + 4, 0);
352}
353
354// Associate GPRel32 fixup with data and resize data area
355void MCObjectStreamer::EmitGPRel64Value(const MCExpr *Value) {
356  MCDataFragment *DF = getOrCreateDataFragment();
357
358  DF->getFixups().push_back(MCFixup::Create(DF->getContents().size(),
359                                            Value, FK_GPRel_4));
360  DF->getContents().resize(DF->getContents().size() + 8, 0);
361}
362
363void MCObjectStreamer::EmitFill(uint64_t NumBytes, uint8_t FillValue) {
364  // FIXME: A MCFillFragment would be more memory efficient but MCExpr has
365  //        problems evaluating expressions across multiple fragments.
366  getOrCreateDataFragment()->getContents().append(NumBytes, FillValue);
367}
368
369void MCObjectStreamer::EmitZeros(uint64_t NumBytes) {
370  unsigned ItemSize = getCurrentSection().first->isVirtualSection() ? 0 : 1;
371  insert(new MCFillFragment(0, ItemSize, NumBytes));
372}
373
374void MCObjectStreamer::FinishImpl() {
375  // If we are generating dwarf for assembly source files dump out the sections.
376  if (getContext().getGenDwarfForAssembly())
377    MCGenDwarfInfo::Emit(this);
378
379  // Dump out the dwarf file & directory tables and line tables.
380  MCDwarfLineTable::Emit(this);
381
382  getAssembler().Finish();
383}
384