MCObjectStreamer.cpp revision dce4a407a24b04eebc6a376f8e62b41aaa7b071f 
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
86const MCExpr *MCObjectStreamer::AddValueSymbols(const MCExpr *Value) {
87  switch (Value->getKind()) {
88  case MCExpr::Target:
89    cast<MCTargetExpr>(Value)->AddValueSymbols(Assembler);
90    break;
91
92  case MCExpr::Constant:
93    break;
94
95  case MCExpr::Binary: {
96    const MCBinaryExpr *BE = cast<MCBinaryExpr>(Value);
97    AddValueSymbols(BE->getLHS());
98    AddValueSymbols(BE->getRHS());
99    break;
100  }
101
102  case MCExpr::SymbolRef:
103    Assembler->getOrCreateSymbolData(cast<MCSymbolRefExpr>(Value)->getSymbol());
104    break;
105
106  case MCExpr::Unary:
107    AddValueSymbols(cast<MCUnaryExpr>(Value)->getSubExpr());
108    break;
109  }
110
111  return Value;
112}
113
114void MCObjectStreamer::EmitCFISections(bool EH, bool Debug) {
115  MCStreamer::EmitCFISections(EH, Debug);
116  EmitEHFrame = EH;
117  EmitDebugFrame = Debug;
118}
119
120void MCObjectStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
121                                     const SMLoc &Loc) {
122  MCDataFragment *DF = getOrCreateDataFragment();
123
124  MCLineEntry::Make(this, getCurrentSection().first);
125
126  // Avoid fixups when possible.
127  int64_t AbsValue;
128  if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue, getAssembler())) {
129    EmitIntValue(AbsValue, Size);
130    return;
131  }
132  DF->getFixups().push_back(
133      MCFixup::Create(DF->getContents().size(), Value,
134                      MCFixup::getKindForSize(Size, false), Loc));
135  DF->getContents().resize(DF->getContents().size() + Size, 0);
136}
137
138void MCObjectStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) {
139  RecordProcStart(Frame);
140}
141
142void MCObjectStreamer::EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) {
143  RecordProcEnd(Frame);
144}
145
146void MCObjectStreamer::EmitLabel(MCSymbol *Symbol) {
147  MCStreamer::EmitLabel(Symbol);
148
149  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
150
151  // FIXME: This is wasteful, we don't necessarily need to create a data
152  // fragment. Instead, we should mark the symbol as pointing into the data
153  // fragment if it exists, otherwise we should just queue the label and set its
154  // fragment pointer when we emit the next fragment.
155  MCDataFragment *F = getOrCreateDataFragment();
156  assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
157  SD.setFragment(F);
158  SD.setOffset(F->getContents().size());
159}
160
161void MCObjectStreamer::EmitDebugLabel(MCSymbol *Symbol) {
162  EmitLabel(Symbol);
163}
164
165void MCObjectStreamer::EmitULEB128Value(const MCExpr *Value) {
166  int64_t IntValue;
167  if (Value->EvaluateAsAbsolute(IntValue, getAssembler())) {
168    EmitULEB128IntValue(IntValue);
169    return;
170  }
171  Value = ForceExpAbs(Value);
172  insert(new MCLEBFragment(*Value, false));
173}
174
175void MCObjectStreamer::EmitSLEB128Value(const MCExpr *Value) {
176  int64_t IntValue;
177  if (Value->EvaluateAsAbsolute(IntValue, getAssembler())) {
178    EmitSLEB128IntValue(IntValue);
179    return;
180  }
181  Value = ForceExpAbs(Value);
182  insert(new MCLEBFragment(*Value, true));
183}
184
185void MCObjectStreamer::EmitWeakReference(MCSymbol *Alias,
186                                         const MCSymbol *Symbol) {
187  report_fatal_error("This file format doesn't support weak aliases.");
188}
189
190void MCObjectStreamer::ChangeSection(const MCSection *Section,
191                                     const MCExpr *Subsection) {
192  assert(Section && "Cannot switch to a null section!");
193
194  CurSectionData = &getAssembler().getOrCreateSectionData(*Section);
195
196  int64_t IntSubsection = 0;
197  if (Subsection &&
198      !Subsection->EvaluateAsAbsolute(IntSubsection, getAssembler()))
199    report_fatal_error("Cannot evaluate subsection number");
200  if (IntSubsection < 0 || IntSubsection > 8192)
201    report_fatal_error("Subsection number out of range");
202  CurInsertionPoint =
203    CurSectionData->getSubsectionInsertionPoint(unsigned(IntSubsection));
204}
205
206void MCObjectStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
207  getAssembler().getOrCreateSymbolData(*Symbol);
208  AddValueSymbols(Value);
209  MCStreamer::EmitAssignment(Symbol, Value);
210}
211
212void MCObjectStreamer::EmitInstruction(const MCInst &Inst, const MCSubtargetInfo &STI) {
213  // Scan for values.
214  for (unsigned i = Inst.getNumOperands(); i--; )
215    if (Inst.getOperand(i).isExpr())
216      AddValueSymbols(Inst.getOperand(i).getExpr());
217
218  MCSectionData *SD = getCurrentSectionData();
219  SD->setHasInstructions(true);
220
221  // Now that a machine instruction has been assembled into this section, make
222  // a line entry for any .loc directive that has been seen.
223  MCLineEntry::Make(this, getCurrentSection().first);
224
225  // If this instruction doesn't need relaxation, just emit it as data.
226  MCAssembler &Assembler = getAssembler();
227  if (!Assembler.getBackend().mayNeedRelaxation(Inst)) {
228    EmitInstToData(Inst, STI);
229    return;
230  }
231
232  // Otherwise, relax and emit it as data if either:
233  // - The RelaxAll flag was passed
234  // - Bundling is enabled and this instruction is inside a bundle-locked
235  //   group. We want to emit all such instructions into the same data
236  //   fragment.
237  if (Assembler.getRelaxAll() ||
238      (Assembler.isBundlingEnabled() && SD->isBundleLocked())) {
239    MCInst Relaxed;
240    getAssembler().getBackend().relaxInstruction(Inst, Relaxed);
241    while (getAssembler().getBackend().mayNeedRelaxation(Relaxed))
242      getAssembler().getBackend().relaxInstruction(Relaxed, Relaxed);
243    EmitInstToData(Relaxed, STI);
244    return;
245  }
246
247  // Otherwise emit to a separate fragment.
248  EmitInstToFragment(Inst, STI);
249}
250
251void MCObjectStreamer::EmitInstToFragment(const MCInst &Inst,
252                                          const MCSubtargetInfo &STI) {
253  // Always create a new, separate fragment here, because its size can change
254  // during relaxation.
255  MCRelaxableFragment *IF = new MCRelaxableFragment(Inst, STI);
256  insert(IF);
257
258  SmallString<128> Code;
259  raw_svector_ostream VecOS(Code);
260  getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, IF->getFixups(),
261                                                STI);
262  VecOS.flush();
263  IF->getContents().append(Code.begin(), Code.end());
264}
265
266#ifndef NDEBUG
267static const char *const BundlingNotImplementedMsg =
268  "Aligned bundling is not implemented for this object format";
269#endif
270
271void MCObjectStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
272  llvm_unreachable(BundlingNotImplementedMsg);
273}
274
275void MCObjectStreamer::EmitBundleLock(bool AlignToEnd) {
276  llvm_unreachable(BundlingNotImplementedMsg);
277}
278
279void MCObjectStreamer::EmitBundleUnlock() {
280  llvm_unreachable(BundlingNotImplementedMsg);
281}
282
283void MCObjectStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
284                                             unsigned Column, unsigned Flags,
285                                             unsigned Isa,
286                                             unsigned Discriminator,
287                                             StringRef FileName) {
288  // In case we see two .loc directives in a row, make sure the
289  // first one gets a line entry.
290  MCLineEntry::Make(this, getCurrentSection().first);
291
292  this->MCStreamer::EmitDwarfLocDirective(FileNo, Line, Column, Flags,
293                                          Isa, Discriminator, FileName);
294}
295
296void MCObjectStreamer::EmitDwarfAdvanceLineAddr(int64_t LineDelta,
297                                                const MCSymbol *LastLabel,
298                                                const MCSymbol *Label,
299                                                unsigned PointerSize) {
300  if (!LastLabel) {
301    EmitDwarfSetLineAddr(LineDelta, Label, PointerSize);
302    return;
303  }
304  const MCExpr *AddrDelta = BuildSymbolDiff(getContext(), Label, LastLabel);
305  int64_t Res;
306  if (AddrDelta->EvaluateAsAbsolute(Res, getAssembler())) {
307    MCDwarfLineAddr::Emit(this, LineDelta, Res);
308    return;
309  }
310  AddrDelta = ForceExpAbs(AddrDelta);
311  insert(new MCDwarfLineAddrFragment(LineDelta, *AddrDelta));
312}
313
314void MCObjectStreamer::EmitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel,
315                                                 const MCSymbol *Label) {
316  const MCExpr *AddrDelta = BuildSymbolDiff(getContext(), Label, LastLabel);
317  int64_t Res;
318  if (AddrDelta->EvaluateAsAbsolute(Res, getAssembler())) {
319    MCDwarfFrameEmitter::EmitAdvanceLoc(*this, Res);
320    return;
321  }
322  AddrDelta = ForceExpAbs(AddrDelta);
323  insert(new MCDwarfCallFrameFragment(*AddrDelta));
324}
325
326void MCObjectStreamer::EmitBytes(StringRef Data) {
327  MCLineEntry::Make(this, getCurrentSection().first);
328  getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
329}
330
331void MCObjectStreamer::EmitValueToAlignment(unsigned ByteAlignment,
332                                            int64_t Value,
333                                            unsigned ValueSize,
334                                            unsigned MaxBytesToEmit) {
335  if (MaxBytesToEmit == 0)
336    MaxBytesToEmit = ByteAlignment;
337  insert(new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit));
338
339  // Update the maximum alignment on the current section if necessary.
340  if (ByteAlignment > getCurrentSectionData()->getAlignment())
341    getCurrentSectionData()->setAlignment(ByteAlignment);
342}
343
344void MCObjectStreamer::EmitCodeAlignment(unsigned ByteAlignment,
345                                         unsigned MaxBytesToEmit) {
346  EmitValueToAlignment(ByteAlignment, 0, 1, MaxBytesToEmit);
347  cast<MCAlignFragment>(getCurrentFragment())->setEmitNops(true);
348}
349
350bool MCObjectStreamer::EmitValueToOffset(const MCExpr *Offset,
351                                         unsigned char Value) {
352  int64_t Res;
353  if (Offset->EvaluateAsAbsolute(Res, getAssembler())) {
354    insert(new MCOrgFragment(*Offset, Value));
355    return false;
356  }
357
358  MCSymbol *CurrentPos = getContext().CreateTempSymbol();
359  EmitLabel(CurrentPos);
360  MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
361  const MCExpr *Ref =
362    MCSymbolRefExpr::Create(CurrentPos, Variant, getContext());
363  const MCExpr *Delta =
364    MCBinaryExpr::Create(MCBinaryExpr::Sub, Offset, Ref, getContext());
365
366  if (!Delta->EvaluateAsAbsolute(Res, getAssembler()))
367    return true;
368  EmitFill(Res, Value);
369  return false;
370}
371
372// Associate GPRel32 fixup with data and resize data area
373void MCObjectStreamer::EmitGPRel32Value(const MCExpr *Value) {
374  MCDataFragment *DF = getOrCreateDataFragment();
375
376  DF->getFixups().push_back(MCFixup::Create(DF->getContents().size(),
377                                            Value, FK_GPRel_4));
378  DF->getContents().resize(DF->getContents().size() + 4, 0);
379}
380
381// Associate GPRel32 fixup with data and resize data area
382void MCObjectStreamer::EmitGPRel64Value(const MCExpr *Value) {
383  MCDataFragment *DF = getOrCreateDataFragment();
384
385  DF->getFixups().push_back(MCFixup::Create(DF->getContents().size(),
386                                            Value, FK_GPRel_4));
387  DF->getContents().resize(DF->getContents().size() + 8, 0);
388}
389
390void MCObjectStreamer::EmitFill(uint64_t NumBytes, uint8_t FillValue) {
391  // FIXME: A MCFillFragment would be more memory efficient but MCExpr has
392  //        problems evaluating expressions across multiple fragments.
393  getOrCreateDataFragment()->getContents().append(NumBytes, FillValue);
394}
395
396void MCObjectStreamer::EmitZeros(uint64_t NumBytes) {
397  unsigned ItemSize = getCurrentSection().first->isVirtualSection() ? 0 : 1;
398  insert(new MCFillFragment(0, ItemSize, NumBytes));
399}
400
401void MCObjectStreamer::FinishImpl() {
402  // If we are generating dwarf for assembly source files dump out the sections.
403  if (getContext().getGenDwarfForAssembly())
404    MCGenDwarfInfo::Emit(this);
405
406  // Dump out the dwarf file & directory tables and line tables.
407  MCDwarfLineTable::Emit(this);
408
409  getAssembler().Finish();
410}
411