1 //===- lib/MC/MCObjectStreamer.cpp - Object File MCStreamer Interface -----===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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"
26 MCObjectStreamer::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), OS)),
32 EmitEHFrame(true), EmitDebugFrame(false) {}
34 MCObjectStreamer::~MCObjectStreamer() {
35 delete &Assembler->getBackend();
36 delete &Assembler->getEmitter();
37 delete &Assembler->getWriter();
41 void MCObjectStreamer::flushPendingLabels(MCFragment *F, uint64_t FOffset) {
42 if (PendingLabels.size()) {
44 F = new MCDataFragment();
45 MCSection *CurSection = getCurrentSectionOnly();
46 CurSection->getFragmentList().insert(CurInsertionPoint, F);
47 F->setParent(CurSection);
49 for (MCSymbolData *SD : PendingLabels) {
51 SD->setOffset(FOffset);
53 PendingLabels.clear();
57 bool MCObjectStreamer::emitAbsoluteSymbolDiff(const MCSymbol *Hi,
60 // Must have symbol data.
61 if (!Assembler->hasSymbolData(*Hi) || !Assembler->hasSymbolData(*Lo))
63 auto &HiD = Hi->getData();
64 auto &LoD = Lo->getData();
66 // Must both be assigned to the same (valid) fragment.
67 if (!HiD.getFragment() || HiD.getFragment() != LoD.getFragment())
70 // Must be a data fragment.
71 if (!isa<MCDataFragment>(HiD.getFragment()))
74 assert(HiD.getOffset() >= LoD.getOffset() &&
75 "Expected Hi to be greater than Lo");
76 EmitIntValue(HiD.getOffset() - LoD.getOffset(), Size);
80 void MCObjectStreamer::reset() {
83 CurInsertionPoint = MCSection::iterator();
85 EmitDebugFrame = false;
86 PendingLabels.clear();
90 void MCObjectStreamer::EmitFrames(MCAsmBackend *MAB) {
91 if (!getNumFrameInfos())
95 MCDwarfFrameEmitter::Emit(*this, MAB, true);
98 MCDwarfFrameEmitter::Emit(*this, MAB, false);
101 MCFragment *MCObjectStreamer::getCurrentFragment() const {
102 assert(getCurrentSectionOnly() && "No current section!");
104 if (CurInsertionPoint != getCurrentSectionOnly()->getFragmentList().begin())
105 return std::prev(CurInsertionPoint);
110 MCDataFragment *MCObjectStreamer::getOrCreateDataFragment() {
111 MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
112 // When bundling is enabled, we don't want to add data to a fragment that
113 // already has instructions (see MCELFStreamer::EmitInstToData for details)
114 if (!F || (Assembler->isBundlingEnabled() && !Assembler->getRelaxAll() &&
115 F->hasInstructions())) {
116 F = new MCDataFragment();
122 void MCObjectStreamer::visitUsedSymbol(const MCSymbol &Sym) {
123 Assembler->getOrCreateSymbolData(Sym);
126 void MCObjectStreamer::EmitCFISections(bool EH, bool Debug) {
127 MCStreamer::EmitCFISections(EH, Debug);
129 EmitDebugFrame = Debug;
132 void MCObjectStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
134 MCStreamer::EmitValueImpl(Value, Size, Loc);
135 MCDataFragment *DF = getOrCreateDataFragment();
137 MCLineEntry::Make(this, getCurrentSection().first);
139 // Avoid fixups when possible.
141 if (Value->EvaluateAsAbsolute(AbsValue, getAssembler())) {
142 EmitIntValue(AbsValue, Size);
145 DF->getFixups().push_back(
146 MCFixup::create(DF->getContents().size(), Value,
147 MCFixup::getKindForSize(Size, false), Loc));
148 DF->getContents().resize(DF->getContents().size() + Size, 0);
151 void MCObjectStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) {
152 // We need to create a local symbol to avoid relocations.
153 Frame.Begin = getContext().createTempSymbol();
154 EmitLabel(Frame.Begin);
157 void MCObjectStreamer::EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) {
158 Frame.End = getContext().createTempSymbol();
159 EmitLabel(Frame.End);
162 void MCObjectStreamer::EmitLabel(MCSymbol *Symbol) {
163 MCStreamer::EmitLabel(Symbol);
165 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
166 assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
168 // If there is a current fragment, mark the symbol as pointing into it.
169 // Otherwise queue the label and set its fragment pointer when we emit the
171 auto *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
172 if (F && !(getAssembler().isBundlingEnabled() &&
173 getAssembler().getRelaxAll())) {
175 SD.setOffset(F->getContents().size());
177 PendingLabels.push_back(&SD);
181 void MCObjectStreamer::EmitULEB128Value(const MCExpr *Value) {
183 if (Value->EvaluateAsAbsolute(IntValue, getAssembler())) {
184 EmitULEB128IntValue(IntValue);
187 insert(new MCLEBFragment(*Value, false));
190 void MCObjectStreamer::EmitSLEB128Value(const MCExpr *Value) {
192 if (Value->EvaluateAsAbsolute(IntValue, getAssembler())) {
193 EmitSLEB128IntValue(IntValue);
196 insert(new MCLEBFragment(*Value, true));
199 void MCObjectStreamer::EmitWeakReference(MCSymbol *Alias,
200 const MCSymbol *Symbol) {
201 report_fatal_error("This file format doesn't support weak aliases.");
204 void MCObjectStreamer::ChangeSection(MCSection *Section,
205 const MCExpr *Subsection) {
206 changeSectionImpl(Section, Subsection);
209 bool MCObjectStreamer::changeSectionImpl(MCSection *Section,
210 const MCExpr *Subsection) {
211 assert(Section && "Cannot switch to a null section!");
212 flushPendingLabels(nullptr);
214 bool Created = getAssembler().registerSection(*Section);
216 int64_t IntSubsection = 0;
218 !Subsection->EvaluateAsAbsolute(IntSubsection, getAssembler()))
219 report_fatal_error("Cannot evaluate subsection number");
220 if (IntSubsection < 0 || IntSubsection > 8192)
221 report_fatal_error("Subsection number out of range");
223 Section->getSubsectionInsertionPoint(unsigned(IntSubsection));
227 void MCObjectStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
228 getAssembler().getOrCreateSymbolData(*Symbol);
229 MCStreamer::EmitAssignment(Symbol, Value);
232 bool MCObjectStreamer::mayHaveInstructions(MCSection &Sec) const {
233 return Sec.hasInstructions();
236 void MCObjectStreamer::EmitInstruction(const MCInst &Inst,
237 const MCSubtargetInfo &STI) {
238 MCStreamer::EmitInstruction(Inst, STI);
240 MCSection *Sec = getCurrentSectionOnly();
241 Sec->setHasInstructions(true);
243 // Now that a machine instruction has been assembled into this section, make
244 // a line entry for any .loc directive that has been seen.
245 MCLineEntry::Make(this, getCurrentSection().first);
247 // If this instruction doesn't need relaxation, just emit it as data.
248 MCAssembler &Assembler = getAssembler();
249 if (!Assembler.getBackend().mayNeedRelaxation(Inst)) {
250 EmitInstToData(Inst, STI);
254 // Otherwise, relax and emit it as data if either:
255 // - The RelaxAll flag was passed
256 // - Bundling is enabled and this instruction is inside a bundle-locked
257 // group. We want to emit all such instructions into the same data
259 if (Assembler.getRelaxAll() ||
260 (Assembler.isBundlingEnabled() && Sec->isBundleLocked())) {
262 getAssembler().getBackend().relaxInstruction(Inst, Relaxed);
263 while (getAssembler().getBackend().mayNeedRelaxation(Relaxed))
264 getAssembler().getBackend().relaxInstruction(Relaxed, Relaxed);
265 EmitInstToData(Relaxed, STI);
269 // Otherwise emit to a separate fragment.
270 EmitInstToFragment(Inst, STI);
273 void MCObjectStreamer::EmitInstToFragment(const MCInst &Inst,
274 const MCSubtargetInfo &STI) {
275 if (getAssembler().getRelaxAll() && getAssembler().isBundlingEnabled())
276 llvm_unreachable("All instructions should have already been relaxed");
278 // Always create a new, separate fragment here, because its size can change
279 // during relaxation.
280 MCRelaxableFragment *IF = new MCRelaxableFragment(Inst, STI);
283 SmallString<128> Code;
284 raw_svector_ostream VecOS(Code);
285 getAssembler().getEmitter().encodeInstruction(Inst, VecOS, IF->getFixups(),
288 IF->getContents().append(Code.begin(), Code.end());
292 static const char *const BundlingNotImplementedMsg =
293 "Aligned bundling is not implemented for this object format";
296 void MCObjectStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
297 llvm_unreachable(BundlingNotImplementedMsg);
300 void MCObjectStreamer::EmitBundleLock(bool AlignToEnd) {
301 llvm_unreachable(BundlingNotImplementedMsg);
304 void MCObjectStreamer::EmitBundleUnlock() {
305 llvm_unreachable(BundlingNotImplementedMsg);
308 void MCObjectStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
309 unsigned Column, unsigned Flags,
311 unsigned Discriminator,
312 StringRef FileName) {
313 // In case we see two .loc directives in a row, make sure the
314 // first one gets a line entry.
315 MCLineEntry::Make(this, getCurrentSection().first);
317 this->MCStreamer::EmitDwarfLocDirective(FileNo, Line, Column, Flags,
318 Isa, Discriminator, FileName);
321 static const MCExpr *buildSymbolDiff(MCObjectStreamer &OS, const MCSymbol *A,
323 MCContext &Context = OS.getContext();
324 MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
325 const MCExpr *ARef = MCSymbolRefExpr::Create(A, Variant, Context);
326 const MCExpr *BRef = MCSymbolRefExpr::Create(B, Variant, Context);
327 const MCExpr *AddrDelta =
328 MCBinaryExpr::Create(MCBinaryExpr::Sub, ARef, BRef, Context);
332 static void emitDwarfSetLineAddr(MCObjectStreamer &OS, int64_t LineDelta,
333 const MCSymbol *Label, int PointerSize) {
334 // emit the sequence to set the address
335 OS.EmitIntValue(dwarf::DW_LNS_extended_op, 1);
336 OS.EmitULEB128IntValue(PointerSize + 1);
337 OS.EmitIntValue(dwarf::DW_LNE_set_address, 1);
338 OS.EmitSymbolValue(Label, PointerSize);
340 // emit the sequence for the LineDelta (from 1) and a zero address delta.
341 MCDwarfLineAddr::Emit(&OS, LineDelta, 0);
344 void MCObjectStreamer::EmitDwarfAdvanceLineAddr(int64_t LineDelta,
345 const MCSymbol *LastLabel,
346 const MCSymbol *Label,
347 unsigned PointerSize) {
349 emitDwarfSetLineAddr(*this, LineDelta, Label, PointerSize);
352 const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel);
354 if (AddrDelta->EvaluateAsAbsolute(Res, getAssembler())) {
355 MCDwarfLineAddr::Emit(this, LineDelta, Res);
358 insert(new MCDwarfLineAddrFragment(LineDelta, *AddrDelta));
361 void MCObjectStreamer::EmitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel,
362 const MCSymbol *Label) {
363 const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel);
365 if (AddrDelta->EvaluateAsAbsolute(Res, getAssembler())) {
366 MCDwarfFrameEmitter::EmitAdvanceLoc(*this, Res);
369 insert(new MCDwarfCallFrameFragment(*AddrDelta));
372 void MCObjectStreamer::EmitBytes(StringRef Data) {
373 MCLineEntry::Make(this, getCurrentSection().first);
374 getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
377 void MCObjectStreamer::EmitValueToAlignment(unsigned ByteAlignment,
380 unsigned MaxBytesToEmit) {
381 if (MaxBytesToEmit == 0)
382 MaxBytesToEmit = ByteAlignment;
383 insert(new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit));
385 // Update the maximum alignment on the current section if necessary.
386 MCSection *CurSec = getCurrentSection().first;
387 if (ByteAlignment > CurSec->getAlignment())
388 CurSec->setAlignment(ByteAlignment);
391 void MCObjectStreamer::EmitCodeAlignment(unsigned ByteAlignment,
392 unsigned MaxBytesToEmit) {
393 EmitValueToAlignment(ByteAlignment, 0, 1, MaxBytesToEmit);
394 cast<MCAlignFragment>(getCurrentFragment())->setEmitNops(true);
397 bool MCObjectStreamer::EmitValueToOffset(const MCExpr *Offset,
398 unsigned char Value) {
400 if (Offset->EvaluateAsAbsolute(Res, getAssembler())) {
401 insert(new MCOrgFragment(*Offset, Value));
405 MCSymbol *CurrentPos = getContext().createTempSymbol();
406 EmitLabel(CurrentPos);
407 MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
409 MCSymbolRefExpr::Create(CurrentPos, Variant, getContext());
410 const MCExpr *Delta =
411 MCBinaryExpr::Create(MCBinaryExpr::Sub, Offset, Ref, getContext());
413 if (!Delta->EvaluateAsAbsolute(Res, getAssembler()))
415 EmitFill(Res, Value);
419 // Associate GPRel32 fixup with data and resize data area
420 void MCObjectStreamer::EmitGPRel32Value(const MCExpr *Value) {
421 MCDataFragment *DF = getOrCreateDataFragment();
423 DF->getFixups().push_back(MCFixup::create(DF->getContents().size(),
425 DF->getContents().resize(DF->getContents().size() + 4, 0);
428 // Associate GPRel32 fixup with data and resize data area
429 void MCObjectStreamer::EmitGPRel64Value(const MCExpr *Value) {
430 MCDataFragment *DF = getOrCreateDataFragment();
432 DF->getFixups().push_back(MCFixup::create(DF->getContents().size(),
434 DF->getContents().resize(DF->getContents().size() + 8, 0);
437 void MCObjectStreamer::EmitFill(uint64_t NumBytes, uint8_t FillValue) {
438 // FIXME: A MCFillFragment would be more memory efficient but MCExpr has
439 // problems evaluating expressions across multiple fragments.
440 getOrCreateDataFragment()->getContents().append(NumBytes, FillValue);
443 void MCObjectStreamer::EmitZeros(uint64_t NumBytes) {
444 const MCSection *Sec = getCurrentSection().first;
445 assert(Sec && "need a section");
446 unsigned ItemSize = Sec->isVirtualSection() ? 0 : 1;
447 insert(new MCFillFragment(0, ItemSize, NumBytes));
450 void MCObjectStreamer::FinishImpl() {
451 // If we are generating dwarf for assembly source files dump out the sections.
452 if (getContext().getGenDwarfForAssembly())
453 MCGenDwarfInfo::Emit(this);
455 // Dump out the dwarf file & directory tables and line tables.
456 MCDwarfLineTable::Emit(this);
458 flushPendingLabels(nullptr);
459 getAssembler().Finish();