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 (MCSymbol *Sym : PendingLabels) {
51 Sym->setOffset(FOffset);
53 PendingLabels.clear();
57 void MCObjectStreamer::emitAbsoluteSymbolDiff(const MCSymbol *Hi,
60 // If not assigned to the same (valid) fragment, fallback.
61 if (!Hi->getFragment() || Hi->getFragment() != Lo->getFragment()) {
62 MCStreamer::emitAbsoluteSymbolDiff(Hi, Lo, Size);
66 assert(Hi->getOffset() >= Lo->getOffset() &&
67 "Expected Hi to be greater than Lo");
68 EmitIntValue(Hi->getOffset() - Lo->getOffset(), Size);
71 void MCObjectStreamer::reset() {
74 CurInsertionPoint = MCSection::iterator();
76 EmitDebugFrame = false;
77 PendingLabels.clear();
81 void MCObjectStreamer::EmitFrames(MCAsmBackend *MAB) {
82 if (!getNumFrameInfos())
86 MCDwarfFrameEmitter::Emit(*this, MAB, true);
89 MCDwarfFrameEmitter::Emit(*this, MAB, false);
92 MCFragment *MCObjectStreamer::getCurrentFragment() const {
93 assert(getCurrentSectionOnly() && "No current section!");
95 if (CurInsertionPoint != getCurrentSectionOnly()->getFragmentList().begin())
96 return std::prev(CurInsertionPoint);
101 MCDataFragment *MCObjectStreamer::getOrCreateDataFragment() {
102 MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
103 // When bundling is enabled, we don't want to add data to a fragment that
104 // already has instructions (see MCELFStreamer::EmitInstToData for details)
105 if (!F || (Assembler->isBundlingEnabled() && !Assembler->getRelaxAll() &&
106 F->hasInstructions())) {
107 F = new MCDataFragment();
113 void MCObjectStreamer::visitUsedSymbol(const MCSymbol &Sym) {
114 Assembler->registerSymbol(Sym);
117 void MCObjectStreamer::EmitCFISections(bool EH, bool Debug) {
118 MCStreamer::EmitCFISections(EH, Debug);
120 EmitDebugFrame = Debug;
123 void MCObjectStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
125 MCStreamer::EmitValueImpl(Value, Size, Loc);
126 MCDataFragment *DF = getOrCreateDataFragment();
127 flushPendingLabels(DF, DF->getContents().size());
129 MCLineEntry::Make(this, getCurrentSection().first);
131 // Avoid fixups when possible.
133 if (Value->evaluateAsAbsolute(AbsValue, getAssembler())) {
134 EmitIntValue(AbsValue, Size);
137 DF->getFixups().push_back(
138 MCFixup::create(DF->getContents().size(), Value,
139 MCFixup::getKindForSize(Size, false), Loc));
140 DF->getContents().resize(DF->getContents().size() + Size, 0);
143 void MCObjectStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) {
144 // We need to create a local symbol to avoid relocations.
145 Frame.Begin = getContext().createTempSymbol();
146 EmitLabel(Frame.Begin);
149 void MCObjectStreamer::EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) {
150 Frame.End = getContext().createTempSymbol();
151 EmitLabel(Frame.End);
154 void MCObjectStreamer::EmitLabel(MCSymbol *Symbol) {
155 MCStreamer::EmitLabel(Symbol);
157 getAssembler().registerSymbol(*Symbol);
158 assert(!Symbol->getFragment() && "Unexpected fragment on symbol data!");
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
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());
169 PendingLabels.push_back(Symbol);
173 void MCObjectStreamer::EmitULEB128Value(const MCExpr *Value) {
175 if (Value->evaluateAsAbsolute(IntValue, getAssembler())) {
176 EmitULEB128IntValue(IntValue);
179 insert(new MCLEBFragment(*Value, false));
182 void MCObjectStreamer::EmitSLEB128Value(const MCExpr *Value) {
184 if (Value->evaluateAsAbsolute(IntValue, getAssembler())) {
185 EmitSLEB128IntValue(IntValue);
188 insert(new MCLEBFragment(*Value, true));
191 void MCObjectStreamer::EmitWeakReference(MCSymbol *Alias,
192 const MCSymbol *Symbol) {
193 report_fatal_error("This file format doesn't support weak aliases.");
196 void MCObjectStreamer::ChangeSection(MCSection *Section,
197 const MCExpr *Subsection) {
198 changeSectionImpl(Section, Subsection);
201 bool MCObjectStreamer::changeSectionImpl(MCSection *Section,
202 const MCExpr *Subsection) {
203 assert(Section && "Cannot switch to a null section!");
204 flushPendingLabels(nullptr);
206 bool Created = getAssembler().registerSection(*Section);
208 int64_t IntSubsection = 0;
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");
215 Section->getSubsectionInsertionPoint(unsigned(IntSubsection));
219 void MCObjectStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
220 getAssembler().registerSymbol(*Symbol);
221 MCStreamer::EmitAssignment(Symbol, Value);
224 bool MCObjectStreamer::mayHaveInstructions(MCSection &Sec) const {
225 return Sec.hasInstructions();
228 void MCObjectStreamer::EmitInstruction(const MCInst &Inst,
229 const MCSubtargetInfo &STI) {
230 MCStreamer::EmitInstruction(Inst, STI);
232 MCSection *Sec = getCurrentSectionOnly();
233 Sec->setHasInstructions(true);
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);
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);
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
251 if (Assembler.getRelaxAll() ||
252 (Assembler.isBundlingEnabled() && Sec->isBundleLocked())) {
254 getAssembler().getBackend().relaxInstruction(Inst, Relaxed);
255 while (getAssembler().getBackend().mayNeedRelaxation(Relaxed))
256 getAssembler().getBackend().relaxInstruction(Relaxed, Relaxed);
257 EmitInstToData(Relaxed, STI);
261 // Otherwise emit to a separate fragment.
262 EmitInstToFragment(Inst, STI);
265 void 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");
270 // Always create a new, separate fragment here, because its size can change
271 // during relaxation.
272 MCRelaxableFragment *IF = new MCRelaxableFragment(Inst, STI);
275 SmallString<128> Code;
276 raw_svector_ostream VecOS(Code);
277 getAssembler().getEmitter().encodeInstruction(Inst, VecOS, IF->getFixups(),
280 IF->getContents().append(Code.begin(), Code.end());
284 static const char *const BundlingNotImplementedMsg =
285 "Aligned bundling is not implemented for this object format";
288 void MCObjectStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
289 llvm_unreachable(BundlingNotImplementedMsg);
292 void MCObjectStreamer::EmitBundleLock(bool AlignToEnd) {
293 llvm_unreachable(BundlingNotImplementedMsg);
296 void MCObjectStreamer::EmitBundleUnlock() {
297 llvm_unreachable(BundlingNotImplementedMsg);
300 void MCObjectStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
301 unsigned Column, unsigned Flags,
303 unsigned Discriminator,
304 StringRef FileName) {
305 // In case we see two .loc directives in a row, make sure the
306 // first one gets a line entry.
307 MCLineEntry::Make(this, getCurrentSection().first);
309 this->MCStreamer::EmitDwarfLocDirective(FileNo, Line, Column, Flags,
310 Isa, Discriminator, FileName);
313 static const MCExpr *buildSymbolDiff(MCObjectStreamer &OS, const MCSymbol *A,
315 MCContext &Context = OS.getContext();
316 MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
317 const MCExpr *ARef = MCSymbolRefExpr::create(A, Variant, Context);
318 const MCExpr *BRef = MCSymbolRefExpr::create(B, Variant, Context);
319 const MCExpr *AddrDelta =
320 MCBinaryExpr::create(MCBinaryExpr::Sub, ARef, BRef, Context);
324 static void emitDwarfSetLineAddr(MCObjectStreamer &OS, int64_t LineDelta,
325 const MCSymbol *Label, int PointerSize) {
326 // emit the sequence to set the address
327 OS.EmitIntValue(dwarf::DW_LNS_extended_op, 1);
328 OS.EmitULEB128IntValue(PointerSize + 1);
329 OS.EmitIntValue(dwarf::DW_LNE_set_address, 1);
330 OS.EmitSymbolValue(Label, PointerSize);
332 // emit the sequence for the LineDelta (from 1) and a zero address delta.
333 MCDwarfLineAddr::Emit(&OS, LineDelta, 0);
336 void MCObjectStreamer::EmitDwarfAdvanceLineAddr(int64_t LineDelta,
337 const MCSymbol *LastLabel,
338 const MCSymbol *Label,
339 unsigned PointerSize) {
341 emitDwarfSetLineAddr(*this, LineDelta, Label, PointerSize);
344 const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel);
346 if (AddrDelta->evaluateAsAbsolute(Res, getAssembler())) {
347 MCDwarfLineAddr::Emit(this, LineDelta, Res);
350 insert(new MCDwarfLineAddrFragment(LineDelta, *AddrDelta));
353 void MCObjectStreamer::EmitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel,
354 const MCSymbol *Label) {
355 const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel);
357 if (AddrDelta->evaluateAsAbsolute(Res, getAssembler())) {
358 MCDwarfFrameEmitter::EmitAdvanceLoc(*this, Res);
361 insert(new MCDwarfCallFrameFragment(*AddrDelta));
364 void MCObjectStreamer::EmitBytes(StringRef Data) {
365 MCLineEntry::Make(this, getCurrentSection().first);
366 MCDataFragment *DF = getOrCreateDataFragment();
367 flushPendingLabels(DF, DF->getContents().size());
368 DF->getContents().append(Data.begin(), Data.end());
371 void MCObjectStreamer::EmitValueToAlignment(unsigned ByteAlignment,
374 unsigned MaxBytesToEmit) {
375 if (MaxBytesToEmit == 0)
376 MaxBytesToEmit = ByteAlignment;
377 insert(new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit));
379 // Update the maximum alignment on the current section if necessary.
380 MCSection *CurSec = getCurrentSection().first;
381 if (ByteAlignment > CurSec->getAlignment())
382 CurSec->setAlignment(ByteAlignment);
385 void MCObjectStreamer::EmitCodeAlignment(unsigned ByteAlignment,
386 unsigned MaxBytesToEmit) {
387 EmitValueToAlignment(ByteAlignment, 0, 1, MaxBytesToEmit);
388 cast<MCAlignFragment>(getCurrentFragment())->setEmitNops(true);
391 bool MCObjectStreamer::EmitValueToOffset(const MCExpr *Offset,
392 unsigned char Value) {
394 if (Offset->evaluateAsAbsolute(Res, getAssembler())) {
395 insert(new MCOrgFragment(*Offset, Value));
399 MCSymbol *CurrentPos = getContext().createTempSymbol();
400 EmitLabel(CurrentPos);
401 MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
403 MCSymbolRefExpr::create(CurrentPos, Variant, getContext());
404 const MCExpr *Delta =
405 MCBinaryExpr::create(MCBinaryExpr::Sub, Offset, Ref, getContext());
407 if (!Delta->evaluateAsAbsolute(Res, getAssembler()))
409 EmitFill(Res, Value);
413 // Associate GPRel32 fixup with data and resize data area
414 void MCObjectStreamer::EmitGPRel32Value(const MCExpr *Value) {
415 MCDataFragment *DF = getOrCreateDataFragment();
416 flushPendingLabels(DF, DF->getContents().size());
418 DF->getFixups().push_back(MCFixup::create(DF->getContents().size(),
420 DF->getContents().resize(DF->getContents().size() + 4, 0);
423 // Associate GPRel32 fixup with data and resize data area
424 void MCObjectStreamer::EmitGPRel64Value(const MCExpr *Value) {
425 MCDataFragment *DF = getOrCreateDataFragment();
426 flushPendingLabels(DF, DF->getContents().size());
428 DF->getFixups().push_back(MCFixup::create(DF->getContents().size(),
430 DF->getContents().resize(DF->getContents().size() + 8, 0);
433 void MCObjectStreamer::EmitFill(uint64_t NumBytes, uint8_t FillValue) {
434 // FIXME: A MCFillFragment would be more memory efficient but MCExpr has
435 // problems evaluating expressions across multiple fragments.
436 MCDataFragment *DF = getOrCreateDataFragment();
437 flushPendingLabels(DF, DF->getContents().size());
438 DF->getContents().append(NumBytes, FillValue);
441 void MCObjectStreamer::EmitZeros(uint64_t NumBytes) {
442 const MCSection *Sec = getCurrentSection().first;
443 assert(Sec && "need a section");
444 unsigned ItemSize = Sec->isVirtualSection() ? 0 : 1;
445 insert(new MCFillFragment(0, ItemSize, NumBytes));
448 void MCObjectStreamer::FinishImpl() {
449 // If we are generating dwarf for assembly source files dump out the sections.
450 if (getContext().getGenDwarfForAssembly())
451 MCGenDwarfInfo::Emit(this);
453 // Dump out the dwarf file & directory tables and line tables.
454 MCDwarfLineTable::Emit(this);
456 flushPendingLabels(nullptr);
457 getAssembler().Finish();