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 CurSectionData(nullptr), 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 CurSectionData->getFragmentList().insert(CurInsertionPoint, F);
46 F->setParent(CurSectionData);
48 for (MCSymbolData *SD : PendingLabels) {
50 SD->setOffset(FOffset);
52 PendingLabels.clear();
56 bool MCObjectStreamer::emitAbsoluteSymbolDiff(const MCSymbol *Hi,
59 // Must have symbol data.
60 if (!Assembler->hasSymbolData(*Hi) || !Assembler->hasSymbolData(*Lo))
62 auto &HiD = Assembler->getSymbolData(*Hi);
63 auto &LoD = Assembler->getSymbolData(*Lo);
65 // Must both be assigned to the same (valid) fragment.
66 if (!HiD.getFragment() || HiD.getFragment() != LoD.getFragment())
69 // Must be a data fragment.
70 if (!isa<MCDataFragment>(HiD.getFragment()))
73 assert(HiD.getOffset() >= LoD.getOffset() &&
74 "Expected Hi to be greater than Lo");
75 EmitIntValue(HiD.getOffset() - LoD.getOffset(), Size);
79 void MCObjectStreamer::reset() {
82 CurSectionData = nullptr;
83 CurInsertionPoint = MCSectionData::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(getCurrentSectionData() && "No current section!");
104 if (CurInsertionPoint != getCurrentSectionData()->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);
215 CurSectionData = &getAssembler().getOrCreateSectionData(*Section, &Created);
217 int64_t IntSubsection = 0;
219 !Subsection->EvaluateAsAbsolute(IntSubsection, getAssembler()))
220 report_fatal_error("Cannot evaluate subsection number");
221 if (IntSubsection < 0 || IntSubsection > 8192)
222 report_fatal_error("Subsection number out of range");
224 CurSectionData->getSubsectionInsertionPoint(unsigned(IntSubsection));
228 void MCObjectStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
229 getAssembler().getOrCreateSymbolData(*Symbol);
230 MCStreamer::EmitAssignment(Symbol, Value);
233 void MCObjectStreamer::EmitInstruction(const MCInst &Inst,
234 const MCSubtargetInfo &STI) {
235 MCStreamer::EmitInstruction(Inst, STI);
237 MCSectionData *SD = getCurrentSectionData();
238 SD->setHasInstructions(true);
240 // Now that a machine instruction has been assembled into this section, make
241 // a line entry for any .loc directive that has been seen.
242 MCLineEntry::Make(this, getCurrentSection().first);
244 // If this instruction doesn't need relaxation, just emit it as data.
245 MCAssembler &Assembler = getAssembler();
246 if (!Assembler.getBackend().mayNeedRelaxation(Inst)) {
247 EmitInstToData(Inst, STI);
251 // Otherwise, relax and emit it as data if either:
252 // - The RelaxAll flag was passed
253 // - Bundling is enabled and this instruction is inside a bundle-locked
254 // group. We want to emit all such instructions into the same data
256 if (Assembler.getRelaxAll() ||
257 (Assembler.isBundlingEnabled() && SD->getSection().isBundleLocked())) {
259 getAssembler().getBackend().relaxInstruction(Inst, Relaxed);
260 while (getAssembler().getBackend().mayNeedRelaxation(Relaxed))
261 getAssembler().getBackend().relaxInstruction(Relaxed, Relaxed);
262 EmitInstToData(Relaxed, STI);
266 // Otherwise emit to a separate fragment.
267 EmitInstToFragment(Inst, STI);
270 void MCObjectStreamer::EmitInstToFragment(const MCInst &Inst,
271 const MCSubtargetInfo &STI) {
272 if (getAssembler().getRelaxAll() && getAssembler().isBundlingEnabled())
273 llvm_unreachable("All instructions should have already been relaxed");
275 // Always create a new, separate fragment here, because its size can change
276 // during relaxation.
277 MCRelaxableFragment *IF = new MCRelaxableFragment(Inst, STI);
280 SmallString<128> Code;
281 raw_svector_ostream VecOS(Code);
282 getAssembler().getEmitter().encodeInstruction(Inst, VecOS, IF->getFixups(),
285 IF->getContents().append(Code.begin(), Code.end());
289 static const char *const BundlingNotImplementedMsg =
290 "Aligned bundling is not implemented for this object format";
293 void MCObjectStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
294 llvm_unreachable(BundlingNotImplementedMsg);
297 void MCObjectStreamer::EmitBundleLock(bool AlignToEnd) {
298 llvm_unreachable(BundlingNotImplementedMsg);
301 void MCObjectStreamer::EmitBundleUnlock() {
302 llvm_unreachable(BundlingNotImplementedMsg);
305 void MCObjectStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
306 unsigned Column, unsigned Flags,
308 unsigned Discriminator,
309 StringRef FileName) {
310 // In case we see two .loc directives in a row, make sure the
311 // first one gets a line entry.
312 MCLineEntry::Make(this, getCurrentSection().first);
314 this->MCStreamer::EmitDwarfLocDirective(FileNo, Line, Column, Flags,
315 Isa, Discriminator, FileName);
318 static const MCExpr *buildSymbolDiff(MCObjectStreamer &OS, const MCSymbol *A,
320 MCContext &Context = OS.getContext();
321 MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
322 const MCExpr *ARef = MCSymbolRefExpr::Create(A, Variant, Context);
323 const MCExpr *BRef = MCSymbolRefExpr::Create(B, Variant, Context);
324 const MCExpr *AddrDelta =
325 MCBinaryExpr::Create(MCBinaryExpr::Sub, ARef, BRef, Context);
329 static void emitDwarfSetLineAddr(MCObjectStreamer &OS, int64_t LineDelta,
330 const MCSymbol *Label, int PointerSize) {
331 // emit the sequence to set the address
332 OS.EmitIntValue(dwarf::DW_LNS_extended_op, 1);
333 OS.EmitULEB128IntValue(PointerSize + 1);
334 OS.EmitIntValue(dwarf::DW_LNE_set_address, 1);
335 OS.EmitSymbolValue(Label, PointerSize);
337 // emit the sequence for the LineDelta (from 1) and a zero address delta.
338 MCDwarfLineAddr::Emit(&OS, LineDelta, 0);
341 void MCObjectStreamer::EmitDwarfAdvanceLineAddr(int64_t LineDelta,
342 const MCSymbol *LastLabel,
343 const MCSymbol *Label,
344 unsigned PointerSize) {
346 emitDwarfSetLineAddr(*this, LineDelta, Label, PointerSize);
349 const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel);
351 if (AddrDelta->EvaluateAsAbsolute(Res, getAssembler())) {
352 MCDwarfLineAddr::Emit(this, LineDelta, Res);
355 insert(new MCDwarfLineAddrFragment(LineDelta, *AddrDelta));
358 void MCObjectStreamer::EmitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel,
359 const MCSymbol *Label) {
360 const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel);
362 if (AddrDelta->EvaluateAsAbsolute(Res, getAssembler())) {
363 MCDwarfFrameEmitter::EmitAdvanceLoc(*this, Res);
366 insert(new MCDwarfCallFrameFragment(*AddrDelta));
369 void MCObjectStreamer::EmitBytes(StringRef Data) {
370 MCLineEntry::Make(this, getCurrentSection().first);
371 getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
374 void MCObjectStreamer::EmitValueToAlignment(unsigned ByteAlignment,
377 unsigned MaxBytesToEmit) {
378 if (MaxBytesToEmit == 0)
379 MaxBytesToEmit = ByteAlignment;
380 insert(new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit));
382 // Update the maximum alignment on the current section if necessary.
383 MCSection *CurSec = getCurrentSection().first;
384 if (ByteAlignment > CurSec->getAlignment())
385 CurSec->setAlignment(ByteAlignment);
388 void MCObjectStreamer::EmitCodeAlignment(unsigned ByteAlignment,
389 unsigned MaxBytesToEmit) {
390 EmitValueToAlignment(ByteAlignment, 0, 1, MaxBytesToEmit);
391 cast<MCAlignFragment>(getCurrentFragment())->setEmitNops(true);
394 bool MCObjectStreamer::EmitValueToOffset(const MCExpr *Offset,
395 unsigned char Value) {
397 if (Offset->EvaluateAsAbsolute(Res, getAssembler())) {
398 insert(new MCOrgFragment(*Offset, Value));
402 MCSymbol *CurrentPos = getContext().createTempSymbol();
403 EmitLabel(CurrentPos);
404 MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
406 MCSymbolRefExpr::Create(CurrentPos, Variant, getContext());
407 const MCExpr *Delta =
408 MCBinaryExpr::Create(MCBinaryExpr::Sub, Offset, Ref, getContext());
410 if (!Delta->EvaluateAsAbsolute(Res, getAssembler()))
412 EmitFill(Res, Value);
416 // Associate GPRel32 fixup with data and resize data area
417 void MCObjectStreamer::EmitGPRel32Value(const MCExpr *Value) {
418 MCDataFragment *DF = getOrCreateDataFragment();
420 DF->getFixups().push_back(MCFixup::create(DF->getContents().size(),
422 DF->getContents().resize(DF->getContents().size() + 4, 0);
425 // Associate GPRel32 fixup with data and resize data area
426 void MCObjectStreamer::EmitGPRel64Value(const MCExpr *Value) {
427 MCDataFragment *DF = getOrCreateDataFragment();
429 DF->getFixups().push_back(MCFixup::create(DF->getContents().size(),
431 DF->getContents().resize(DF->getContents().size() + 8, 0);
434 void MCObjectStreamer::EmitFill(uint64_t NumBytes, uint8_t FillValue) {
435 // FIXME: A MCFillFragment would be more memory efficient but MCExpr has
436 // problems evaluating expressions across multiple fragments.
437 getOrCreateDataFragment()->getContents().append(NumBytes, FillValue);
440 void MCObjectStreamer::EmitZeros(uint64_t NumBytes) {
441 const MCSection *Sec = getCurrentSection().first;
442 assert(Sec && "need a section");
443 unsigned ItemSize = Sec->isVirtualSection() ? 0 : 1;
444 insert(new MCFillFragment(0, ItemSize, NumBytes));
447 void MCObjectStreamer::FinishImpl() {
448 // If we are generating dwarf for assembly source files dump out the sections.
449 if (getContext().getGenDwarfForAssembly())
450 MCGenDwarfInfo::Emit(this);
452 // Dump out the dwarf file & directory tables and line tables.
453 MCDwarfLineTable::Emit(this);
455 flushPendingLabels(nullptr);
456 getAssembler().Finish();