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