1 //===- lib/MC/MCAssembler.cpp - Assembler Backend Implementation ----------===//
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 #define DEBUG_TYPE "assembler"
11 #include "llvm/MC/MCAssembler.h"
12 #include "llvm/MC/MCAsmLayout.h"
13 #include "llvm/MC/MCCodeEmitter.h"
14 #include "llvm/MC/MCExpr.h"
15 #include "llvm/MC/MCObjectWriter.h"
16 #include "llvm/MC/MCSection.h"
17 #include "llvm/MC/MCSymbol.h"
18 #include "llvm/MC/MCValue.h"
19 #include "llvm/MC/MCDwarf.h"
20 #include "llvm/ADT/OwningPtr.h"
21 #include "llvm/ADT/Statistic.h"
22 #include "llvm/ADT/StringExtras.h"
23 #include "llvm/ADT/Twine.h"
24 #include "llvm/Support/Debug.h"
25 #include "llvm/Support/ErrorHandling.h"
26 #include "llvm/Support/raw_ostream.h"
27 #include "llvm/Target/TargetRegistry.h"
28 #include "llvm/Target/TargetAsmBackend.h"
35 STATISTIC(EmittedFragments, "Number of emitted assembler fragments");
36 STATISTIC(EvaluateFixup, "Number of evaluated fixups");
37 STATISTIC(FragmentLayouts, "Number of fragment layouts");
38 STATISTIC(ObjectBytes, "Number of emitted object file bytes");
39 STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps");
40 STATISTIC(RelaxedInstructions, "Number of relaxed instructions");
41 STATISTIC(SectionLayouts, "Number of section layouts");
45 // FIXME FIXME FIXME: There are number of places in this file where we convert
46 // what is a 64-bit assembler value used for computation into a value in the
47 // object file, which may truncate it. We should detect that truncation where
48 // invalid and report errors back.
52 MCAsmLayout::MCAsmLayout(MCAssembler &Asm)
53 : Assembler(Asm), LastValidFragment(0)
55 // Compute the section layout order. Virtual sections must go last.
56 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
57 if (!it->getSection().isVirtualSection())
58 SectionOrder.push_back(&*it);
59 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
60 if (it->getSection().isVirtualSection())
61 SectionOrder.push_back(&*it);
64 bool MCAsmLayout::isSectionUpToDate(const MCSectionData *SD) const {
65 // The first section is always up-to-date.
66 unsigned Index = SD->getLayoutOrder();
70 // Otherwise, sections are always implicitly computed when the preceeding
71 // fragment is layed out.
72 const MCSectionData *Prev = getSectionOrder()[Index - 1];
73 return isFragmentUpToDate(&(Prev->getFragmentList().back()));
76 bool MCAsmLayout::isFragmentUpToDate(const MCFragment *F) const {
77 return (LastValidFragment &&
78 F->getLayoutOrder() <= LastValidFragment->getLayoutOrder());
81 void MCAsmLayout::UpdateForSlide(MCFragment *F, int SlideAmount) {
82 // If this fragment wasn't already up-to-date, we don't need to do anything.
83 if (!isFragmentUpToDate(F))
86 // Otherwise, reset the last valid fragment to the predecessor of the
87 // invalidated fragment.
88 LastValidFragment = F->getPrevNode();
89 if (!LastValidFragment) {
90 unsigned Index = F->getParent()->getLayoutOrder();
92 MCSectionData *Prev = getSectionOrder()[Index - 1];
93 LastValidFragment = &(Prev->getFragmentList().back());
98 void MCAsmLayout::EnsureValid(const MCFragment *F) const {
99 // Advance the layout position until the fragment is up-to-date.
100 while (!isFragmentUpToDate(F)) {
101 // Advance to the next fragment.
102 MCFragment *Cur = LastValidFragment;
104 Cur = Cur->getNextNode();
106 unsigned NextIndex = 0;
107 if (LastValidFragment)
108 NextIndex = LastValidFragment->getParent()->getLayoutOrder() + 1;
109 Cur = SectionOrder[NextIndex]->begin();
112 const_cast<MCAsmLayout*>(this)->LayoutFragment(Cur);
116 void MCAsmLayout::FragmentReplaced(MCFragment *Src, MCFragment *Dst) {
117 if (LastValidFragment == Src)
118 LastValidFragment = Dst;
120 Dst->Offset = Src->Offset;
121 Dst->EffectiveSize = Src->EffectiveSize;
124 uint64_t MCAsmLayout::getFragmentAddress(const MCFragment *F) const {
125 assert(F->getParent() && "Missing section()!");
126 return getSectionAddress(F->getParent()) + getFragmentOffset(F);
129 uint64_t MCAsmLayout::getFragmentEffectiveSize(const MCFragment *F) const {
131 assert(F->EffectiveSize != ~UINT64_C(0) && "Address not set!");
132 return F->EffectiveSize;
135 uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
137 assert(F->Offset != ~UINT64_C(0) && "Address not set!");
141 uint64_t MCAsmLayout::getSymbolAddress(const MCSymbolData *SD) const {
142 assert(SD->getFragment() && "Invalid getAddress() on undefined symbol!");
143 return getFragmentAddress(SD->getFragment()) + SD->getOffset();
146 uint64_t MCAsmLayout::getSectionAddress(const MCSectionData *SD) const {
147 EnsureValid(SD->begin());
148 assert(SD->Address != ~UINT64_C(0) && "Address not set!");
152 uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const {
153 // The size is the last fragment's end offset.
154 const MCFragment &F = SD->getFragmentList().back();
155 return getFragmentOffset(&F) + getFragmentEffectiveSize(&F);
158 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
159 // Virtual sections have no file size.
160 if (SD->getSection().isVirtualSection())
163 // Otherwise, the file size is the same as the address space size.
164 return getSectionAddressSize(SD);
167 uint64_t MCAsmLayout::getSectionSize(const MCSectionData *SD) const {
168 // The logical size is the address space size minus any tail padding.
169 uint64_t Size = getSectionAddressSize(SD);
170 const MCAlignFragment *AF =
171 dyn_cast<MCAlignFragment>(&(SD->getFragmentList().back()));
172 if (AF && AF->hasOnlyAlignAddress())
173 Size -= getFragmentEffectiveSize(AF);
180 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
183 MCFragment::~MCFragment() {
186 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
187 : Kind(_Kind), Parent(_Parent), Atom(0), Offset(~UINT64_C(0)),
188 EffectiveSize(~UINT64_C(0))
191 Parent->getFragmentList().push_back(this);
196 MCSectionData::MCSectionData() : Section(0) {}
198 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
199 : Section(&_Section),
201 Address(~UINT64_C(0)),
202 HasInstructions(false)
205 A->getSectionList().push_back(this);
210 MCSymbolData::MCSymbolData() : Symbol(0) {}
212 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
213 uint64_t _Offset, MCAssembler *A)
214 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
215 IsExternal(false), IsPrivateExtern(false),
216 CommonSize(0), SymbolSize(0), CommonAlign(0),
220 A->getSymbolList().push_back(this);
225 MCAssembler::MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
226 MCCodeEmitter &_Emitter, bool _PadSectionToAlignment,
228 : Context(_Context), Backend(_Backend), Emitter(_Emitter),
229 OS(_OS), RelaxAll(false), SubsectionsViaSymbols(false),
230 PadSectionToAlignment(_PadSectionToAlignment)
234 MCAssembler::~MCAssembler() {
237 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
238 // Non-temporary labels should always be visible to the linker.
239 if (!Symbol.isTemporary())
242 // Absolute temporary labels are never visible.
243 if (!Symbol.isInSection())
246 // Otherwise, check if the section requires symbols even for temporary labels.
247 return getBackend().doesSectionRequireSymbols(Symbol.getSection());
250 const MCSymbolData *MCAssembler::getAtom(const MCSymbolData *SD) const {
251 // Linker visible symbols define atoms.
252 if (isSymbolLinkerVisible(SD->getSymbol()))
255 // Absolute and undefined symbols have no defining atom.
256 if (!SD->getFragment())
259 // Non-linker visible symbols in sections which can't be atomized have no
261 if (!getBackend().isSectionAtomizable(
262 SD->getFragment()->getParent()->getSection()))
265 // Otherwise, return the atom for the containing fragment.
266 return SD->getFragment()->getAtom();
269 bool MCAssembler::EvaluateFixup(const MCObjectWriter &Writer,
270 const MCAsmLayout &Layout,
271 const MCFixup &Fixup, const MCFragment *DF,
272 MCValue &Target, uint64_t &Value) const {
273 ++stats::EvaluateFixup;
275 if (!Fixup.getValue()->EvaluateAsRelocatable(Target, &Layout))
276 report_fatal_error("expected relocatable expression");
278 // FIXME: How do non-scattered symbols work in ELF? I presume the linker
279 // doesn't support small relocations, but then under what criteria does the
280 // assembler allow symbol differences?
282 Value = Target.getConstant();
284 bool IsPCRel = Emitter.getFixupKindInfo(
285 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
286 bool IsResolved = true;
287 if (const MCSymbolRefExpr *A = Target.getSymA()) {
288 const MCSymbol &Sym = A->getSymbol().AliasedSymbol();
290 Value += Layout.getSymbolAddress(&getSymbolData(Sym));
294 if (const MCSymbolRefExpr *B = Target.getSymB()) {
295 const MCSymbol &Sym = B->getSymbol().AliasedSymbol();
297 Value -= Layout.getSymbolAddress(&getSymbolData(Sym));
303 IsResolved = Writer.IsFixupFullyResolved(*this, Target, IsPCRel, DF);
306 Value -= Layout.getFragmentAddress(DF) + Fixup.getOffset();
311 uint64_t MCAssembler::ComputeFragmentSize(MCAsmLayout &Layout,
313 uint64_t SectionAddress,
314 uint64_t FragmentOffset) const {
315 switch (F.getKind()) {
316 case MCFragment::FT_Data:
317 return cast<MCDataFragment>(F).getContents().size();
318 case MCFragment::FT_Fill:
319 return cast<MCFillFragment>(F).getSize();
320 case MCFragment::FT_Inst:
321 return cast<MCInstFragment>(F).getInstSize();
323 case MCFragment::FT_LEB:
324 return cast<MCLEBFragment>(F).getSize();
326 case MCFragment::FT_Align: {
327 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
329 assert((!AF.hasOnlyAlignAddress() || !AF.getNextNode()) &&
330 "Invalid OnlyAlignAddress bit, not the last fragment!");
332 uint64_t Size = OffsetToAlignment(SectionAddress + FragmentOffset,
335 // Honor MaxBytesToEmit.
336 if (Size > AF.getMaxBytesToEmit())
342 case MCFragment::FT_Org:
343 return cast<MCOrgFragment>(F).getSize();
345 case MCFragment::FT_Dwarf:
346 return cast<MCDwarfLineAddrFragment>(F).getSize();
349 assert(0 && "invalid fragment kind");
353 void MCAsmLayout::LayoutFile() {
354 // Initialize the first section and set the valid fragment layout point. All
355 // actual layout computations are done lazily.
356 LastValidFragment = 0;
357 if (!getSectionOrder().empty())
358 getSectionOrder().front()->Address = 0;
361 void MCAsmLayout::LayoutFragment(MCFragment *F) {
362 MCFragment *Prev = F->getPrevNode();
364 // We should never try to recompute something which is up-to-date.
365 assert(!isFragmentUpToDate(F) && "Attempt to recompute up-to-date fragment!");
366 // We should never try to compute the fragment layout if the section isn't
368 assert(isSectionUpToDate(F->getParent()) &&
369 "Attempt to compute fragment before it's section!");
370 // We should never try to compute the fragment layout if it's predecessor
372 assert((!Prev || isFragmentUpToDate(Prev)) &&
373 "Attempt to compute fragment before it's predecessor!");
375 ++stats::FragmentLayouts;
377 // Compute the fragment start address.
378 uint64_t StartAddress = F->getParent()->Address;
379 uint64_t Address = StartAddress;
381 Address += Prev->Offset + Prev->EffectiveSize;
383 // Compute fragment offset and size.
384 F->Offset = Address - StartAddress;
385 F->EffectiveSize = getAssembler().ComputeFragmentSize(*this, *F, StartAddress,
387 LastValidFragment = F;
389 // If this is the last fragment in a section, update the next section address.
390 if (!F->getNextNode()) {
391 unsigned NextIndex = F->getParent()->getLayoutOrder() + 1;
392 if (NextIndex != getSectionOrder().size())
393 LayoutSection(getSectionOrder()[NextIndex]);
397 void MCAsmLayout::LayoutSection(MCSectionData *SD) {
398 unsigned SectionOrderIndex = SD->getLayoutOrder();
400 ++stats::SectionLayouts;
402 // Compute the section start address.
403 uint64_t StartAddress = 0;
404 if (SectionOrderIndex) {
405 MCSectionData *Prev = getSectionOrder()[SectionOrderIndex - 1];
406 StartAddress = getSectionAddress(Prev) + getSectionAddressSize(Prev);
409 // Honor the section alignment requirements.
410 StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
412 // Set the section address.
413 SD->Address = StartAddress;
416 /// WriteFragmentData - Write the \arg F data to the output file.
417 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
418 const MCFragment &F, MCObjectWriter *OW) {
419 uint64_t Start = OW->getStream().tell();
422 ++stats::EmittedFragments;
424 // FIXME: Embed in fragments instead?
425 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
426 switch (F.getKind()) {
427 case MCFragment::FT_Align: {
428 MCAlignFragment &AF = cast<MCAlignFragment>(F);
429 uint64_t Count = FragmentSize / AF.getValueSize();
431 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
433 // FIXME: This error shouldn't actually occur (the front end should emit
434 // multiple .align directives to enforce the semantics it wants), but is
435 // severe enough that we want to report it. How to handle this?
436 if (Count * AF.getValueSize() != FragmentSize)
437 report_fatal_error("undefined .align directive, value size '" +
438 Twine(AF.getValueSize()) +
439 "' is not a divisor of padding size '" +
440 Twine(FragmentSize) + "'");
442 // See if we are aligning with nops, and if so do that first to try to fill
443 // the Count bytes. Then if that did not fill any bytes or there are any
444 // bytes left to fill use the the Value and ValueSize to fill the rest.
445 // If we are aligning with nops, ask that target to emit the right data.
446 if (AF.hasEmitNops()) {
447 if (!Asm.getBackend().WriteNopData(Count, OW))
448 report_fatal_error("unable to write nop sequence of " +
449 Twine(Count) + " bytes");
453 // Otherwise, write out in multiples of the value size.
454 for (uint64_t i = 0; i != Count; ++i) {
455 switch (AF.getValueSize()) {
457 assert(0 && "Invalid size!");
458 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
459 case 2: OW->Write16(uint16_t(AF.getValue())); break;
460 case 4: OW->Write32(uint32_t(AF.getValue())); break;
461 case 8: OW->Write64(uint64_t(AF.getValue())); break;
467 case MCFragment::FT_Data: {
468 MCDataFragment &DF = cast<MCDataFragment>(F);
469 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
470 OW->WriteBytes(DF.getContents().str());
474 case MCFragment::FT_Fill: {
475 MCFillFragment &FF = cast<MCFillFragment>(F);
477 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
479 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
480 switch (FF.getValueSize()) {
482 assert(0 && "Invalid size!");
483 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
484 case 2: OW->Write16(uint16_t(FF.getValue())); break;
485 case 4: OW->Write32(uint32_t(FF.getValue())); break;
486 case 8: OW->Write64(uint64_t(FF.getValue())); break;
492 case MCFragment::FT_Inst:
493 llvm_unreachable("unexpected inst fragment after lowering");
496 case MCFragment::FT_LEB: {
497 MCLEBFragment &LF = cast<MCLEBFragment>(F);
499 // FIXME: It is probably better if we don't call EvaluateAsAbsolute in
502 bool IsAbs = LF.getValue().EvaluateAsAbsolute(Value, &Layout);
506 raw_svector_ostream OSE(Tmp);
508 MCObjectWriter::EncodeSLEB128(Value, OSE);
510 MCObjectWriter::EncodeULEB128(Value, OSE);
511 OW->WriteBytes(OSE.str());
515 case MCFragment::FT_Org: {
516 MCOrgFragment &OF = cast<MCOrgFragment>(F);
518 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
519 OW->Write8(uint8_t(OF.getValue()));
524 case MCFragment::FT_Dwarf: {
525 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
527 // The AddrDelta is really unsigned and it can only increase.
529 OF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, &Layout);
532 LineDelta = OF.getLineDelta();
534 MCDwarfLineAddr::Write(OW, LineDelta, (uint64_t)AddrDelta);
539 assert(OW->getStream().tell() - Start == FragmentSize);
542 void MCAssembler::WriteSectionData(const MCSectionData *SD,
543 const MCAsmLayout &Layout,
544 MCObjectWriter *OW) const {
545 // Ignore virtual sections.
546 if (SD->getSection().isVirtualSection()) {
547 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
549 // Check that contents are only things legal inside a virtual section.
550 for (MCSectionData::const_iterator it = SD->begin(),
551 ie = SD->end(); it != ie; ++it) {
552 switch (it->getKind()) {
554 assert(0 && "Invalid fragment in virtual section!");
555 case MCFragment::FT_Data: {
556 // Check that we aren't trying to write a non-zero contents (or fixups)
557 // into a virtual section. This is to support clients which use standard
558 // directives to fill the contents of virtual sections.
559 MCDataFragment &DF = cast<MCDataFragment>(*it);
560 assert(DF.fixup_begin() == DF.fixup_end() &&
561 "Cannot have fixups in virtual section!");
562 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
563 assert(DF.getContents()[i] == 0 &&
564 "Invalid data value for virtual section!");
567 case MCFragment::FT_Align:
568 // Check that we aren't trying to write a non-zero value into a virtual
570 assert((!cast<MCAlignFragment>(it)->getValueSize() ||
571 !cast<MCAlignFragment>(it)->getValue()) &&
572 "Invalid align in virtual section!");
574 case MCFragment::FT_Fill:
575 assert(!cast<MCFillFragment>(it)->getValueSize() &&
576 "Invalid fill in virtual section!");
584 uint64_t Start = OW->getStream().tell();
587 for (MCSectionData::const_iterator it = SD->begin(),
588 ie = SD->end(); it != ie; ++it)
589 WriteFragmentData(*this, Layout, *it, OW);
591 assert(OW->getStream().tell() - Start == Layout.getSectionFileSize(SD));
594 void MCAssembler::AddSectionToTheEnd(const MCObjectWriter &Writer,
595 MCSectionData &SD, MCAsmLayout &Layout) {
596 // Create dummy fragments and assign section ordinals.
597 unsigned SectionIndex = size();
598 SD.setOrdinal(SectionIndex);
600 // Assign layout order indices to sections and fragments.
601 const MCFragment &Last = *Layout.getSectionOrder().back()->rbegin();
602 unsigned FragmentIndex = Last.getLayoutOrder() + 1;
604 SD.setLayoutOrder(Layout.getSectionOrder().size());
605 for (MCSectionData::iterator it2 = SD.begin(),
606 ie2 = SD.end(); it2 != ie2; ++it2) {
607 it2->setLayoutOrder(FragmentIndex++);
609 Layout.getSectionOrder().push_back(&SD);
611 Layout.LayoutSection(&SD);
614 void MCAssembler::Finish(MCObjectWriter *Writer) {
615 DEBUG_WITH_TYPE("mc-dump", {
616 llvm::errs() << "assembler backend - pre-layout\n--\n";
619 // Create the layout object.
620 MCAsmLayout Layout(*this);
622 // Insert additional align fragments for concrete sections to explicitly pad
623 // the previous section to match their alignment requirements. This is for
624 // 'gas' compatibility, it shouldn't strictly be necessary.
625 if (PadSectionToAlignment) {
626 for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
627 MCSectionData *SD = Layout.getSectionOrder()[i];
629 // Ignore sections without alignment requirements.
630 unsigned Align = SD->getAlignment();
634 // Ignore virtual sections, they don't cause file size modifications.
635 if (SD->getSection().isVirtualSection())
638 // Otherwise, create a new align fragment at the end of the previous
640 MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
641 Layout.getSectionOrder()[i - 1]);
642 AF->setOnlyAlignAddress(true);
646 // Create dummy fragments and assign section ordinals.
647 unsigned SectionIndex = 0;
648 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
649 // Create dummy fragments to eliminate any empty sections, this simplifies
651 if (it->getFragmentList().empty())
652 new MCDataFragment(it);
654 it->setOrdinal(SectionIndex++);
657 // Assign layout order indices to sections and fragments.
658 unsigned FragmentIndex = 0;
659 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
660 MCSectionData *SD = Layout.getSectionOrder()[i];
661 SD->setLayoutOrder(i);
663 for (MCSectionData::iterator it2 = SD->begin(),
664 ie2 = SD->end(); it2 != ie2; ++it2)
665 it2->setLayoutOrder(FragmentIndex++);
668 llvm::OwningPtr<MCObjectWriter> OwnWriter(0);
670 //no custom Writer_ : create the default one life-managed by OwningPtr
671 OwnWriter.reset(getBackend().createObjectWriter(OS));
672 Writer = OwnWriter.get();
674 report_fatal_error("unable to create object writer!");
677 // Layout until everything fits.
678 while (LayoutOnce(*Writer, Layout))
681 DEBUG_WITH_TYPE("mc-dump", {
682 llvm::errs() << "assembler backend - post-relaxation\n--\n";
685 // Finalize the layout, including fragment lowering.
686 FinishLayout(Layout);
688 DEBUG_WITH_TYPE("mc-dump", {
689 llvm::errs() << "assembler backend - final-layout\n--\n";
692 uint64_t StartOffset = OS.tell();
694 // Allow the object writer a chance to perform post-layout binding (for
695 // example, to set the index fields in the symbol data).
696 Writer->ExecutePostLayoutBinding(*this);
698 // Evaluate and apply the fixups, generating relocation entries as necessary.
699 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
700 for (MCSectionData::iterator it2 = it->begin(),
701 ie2 = it->end(); it2 != ie2; ++it2) {
702 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
706 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
707 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
708 MCFixup &Fixup = *it3;
710 // Evaluate the fixup.
713 if (!EvaluateFixup(*Writer, Layout, Fixup, DF, Target, FixedValue)) {
714 // The fixup was unresolved, we need a relocation. Inform the object
715 // writer of the relocation, and give it an opportunity to adjust the
716 // fixup value if need be.
717 Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
720 getBackend().ApplyFixup(Fixup, *DF, FixedValue);
725 // Write the object file.
726 Writer->WriteObject(*this, Layout);
728 stats::ObjectBytes += OS.tell() - StartOffset;
731 bool MCAssembler::FixupNeedsRelaxation(const MCObjectWriter &Writer,
732 const MCFixup &Fixup,
733 const MCFragment *DF,
734 const MCAsmLayout &Layout) const {
738 // If we cannot resolve the fixup value, it requires relaxation.
741 if (!EvaluateFixup(Writer, Layout, Fixup, DF, Target, Value))
744 // Otherwise, relax if the value is too big for a (signed) i8.
746 // FIXME: This is target dependent!
747 return int64_t(Value) != int64_t(int8_t(Value));
750 bool MCAssembler::FragmentNeedsRelaxation(const MCObjectWriter &Writer,
751 const MCInstFragment *IF,
752 const MCAsmLayout &Layout) const {
753 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
754 // are intentionally pushing out inst fragments, or because we relaxed a
755 // previous instruction to one that doesn't need relaxation.
756 if (!getBackend().MayNeedRelaxation(IF->getInst()))
759 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
760 ie = IF->fixup_end(); it != ie; ++it)
761 if (FixupNeedsRelaxation(Writer, *it, IF, Layout))
767 bool MCAssembler::RelaxInstruction(const MCObjectWriter &Writer,
769 MCInstFragment &IF) {
770 if (!FragmentNeedsRelaxation(Writer, &IF, Layout))
773 ++stats::RelaxedInstructions;
775 // FIXME-PERF: We could immediately lower out instructions if we can tell
776 // they are fully resolved, to avoid retesting on later passes.
778 // Relax the fragment.
781 getBackend().RelaxInstruction(IF.getInst(), Relaxed);
783 // Encode the new instruction.
785 // FIXME-PERF: If it matters, we could let the target do this. It can
786 // probably do so more efficiently in many cases.
787 SmallVector<MCFixup, 4> Fixups;
788 SmallString<256> Code;
789 raw_svector_ostream VecOS(Code);
790 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
793 // Update the instruction fragment.
794 int SlideAmount = Code.size() - IF.getInstSize();
797 IF.getFixups().clear();
798 // FIXME: Eliminate copy.
799 for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
800 IF.getFixups().push_back(Fixups[i]);
802 // Update the layout, and remember that we relaxed.
803 Layout.UpdateForSlide(&IF, SlideAmount);
807 bool MCAssembler::RelaxOrg(const MCObjectWriter &Writer,
810 int64_t TargetLocation;
811 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
812 report_fatal_error("expected assembly-time absolute expression");
814 // FIXME: We need a way to communicate this error.
815 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
816 int64_t Offset = TargetLocation - FragmentOffset;
817 if (Offset < 0 || Offset >= 0x40000000)
818 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
819 "' (at offset '" + Twine(FragmentOffset) + "')");
821 unsigned OldSize = OF.getSize();
823 return OldSize != OF.getSize();
826 bool MCAssembler::RelaxLEB(const MCObjectWriter &Writer,
830 LF.getValue().EvaluateAsAbsolute(Value, &Layout);
832 raw_svector_ostream OSE(Tmp);
834 MCObjectWriter::EncodeSLEB128(Value, OSE);
836 MCObjectWriter::EncodeULEB128(Value, OSE);
837 uint64_t OldSize = LF.getSize();
838 LF.setSize(OSE.GetNumBytesInBuffer());
839 return OldSize != LF.getSize();
842 bool MCAssembler::RelaxDwarfLineAddr(const MCObjectWriter &Writer,
844 MCDwarfLineAddrFragment &DF) {
846 DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, &Layout);
848 LineDelta = DF.getLineDelta();
849 uint64_t OldSize = DF.getSize();
850 DF.setSize(MCDwarfLineAddr::ComputeSize(LineDelta, AddrDelta));
851 return OldSize != DF.getSize();
854 bool MCAssembler::LayoutOnce(const MCObjectWriter &Writer,
855 MCAsmLayout &Layout) {
856 ++stats::RelaxationSteps;
858 // Layout the sections in order.
861 // Scan for fragments that need relaxation.
862 bool WasRelaxed = false;
863 for (iterator it = begin(), ie = end(); it != ie; ++it) {
864 MCSectionData &SD = *it;
866 for (MCSectionData::iterator it2 = SD.begin(),
867 ie2 = SD.end(); it2 != ie2; ++it2) {
868 // Check if this is an fragment that needs relaxation.
869 switch(it2->getKind()) {
872 case MCFragment::FT_Inst:
873 WasRelaxed |= RelaxInstruction(Writer, Layout,
874 *cast<MCInstFragment>(it2));
876 case MCFragment::FT_Org:
877 WasRelaxed |= RelaxOrg(Writer, Layout, *cast<MCOrgFragment>(it2));
879 case MCFragment::FT_Dwarf:
880 WasRelaxed |= RelaxDwarfLineAddr(Writer, Layout,
881 *cast<MCDwarfLineAddrFragment>(it2));
883 case MCFragment::FT_LEB:
884 WasRelaxed |= RelaxLEB(Writer, Layout, *cast<MCLEBFragment>(it2));
893 void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
894 // Lower out any instruction fragments, to simplify the fixup application and
897 // FIXME-PERF: We don't have to do this, but the assumption is that it is
898 // cheap (we will mostly end up eliminating fragments and appending on to data
899 // fragments), so the extra complexity downstream isn't worth it. Evaluate
901 for (iterator it = begin(), ie = end(); it != ie; ++it) {
902 MCSectionData &SD = *it;
904 for (MCSectionData::iterator it2 = SD.begin(),
905 ie2 = SD.end(); it2 != ie2; ++it2) {
906 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
910 // Create a new data fragment for the instruction.
912 // FIXME-PERF: Reuse previous data fragment if possible.
913 MCDataFragment *DF = new MCDataFragment();
914 SD.getFragmentList().insert(it2, DF);
916 // Update the data fragments layout data.
917 DF->setParent(IF->getParent());
918 DF->setAtom(IF->getAtom());
919 DF->setLayoutOrder(IF->getLayoutOrder());
920 Layout.FragmentReplaced(IF, DF);
922 // Copy in the data and the fixups.
923 DF->getContents().append(IF->getCode().begin(), IF->getCode().end());
924 for (unsigned i = 0, e = IF->getFixups().size(); i != e; ++i)
925 DF->getFixups().push_back(IF->getFixups()[i]);
927 // Delete the instruction fragment and update the iterator.
928 SD.getFragmentList().erase(IF);
938 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
939 OS << "<MCFixup" << " Offset:" << AF.getOffset()
940 << " Value:" << *AF.getValue()
941 << " Kind:" << AF.getKind() << ">";
947 void MCFragment::dump() {
948 raw_ostream &OS = llvm::errs();
952 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
953 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
954 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
955 case MCFragment::FT_Inst: OS << "MCInstFragment"; break;
956 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
957 case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
958 case MCFragment::FT_LEB: OS << "MCLEBFragment"; break;
961 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
962 << " Offset:" << Offset << " EffectiveSize:" << EffectiveSize << ">";
965 case MCFragment::FT_Align: {
966 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
967 if (AF->hasEmitNops())
968 OS << " (emit nops)";
969 if (AF->hasOnlyAlignAddress())
970 OS << " (only align section)";
972 OS << " Alignment:" << AF->getAlignment()
973 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
974 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
977 case MCFragment::FT_Data: {
978 const MCDataFragment *DF = cast<MCDataFragment>(this);
981 const SmallVectorImpl<char> &Contents = DF->getContents();
982 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
984 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
986 OS << "] (" << Contents.size() << " bytes)";
988 if (!DF->getFixups().empty()) {
991 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
992 ie = DF->fixup_end(); it != ie; ++it) {
993 if (it != DF->fixup_begin()) OS << ",\n ";
1000 case MCFragment::FT_Fill: {
1001 const MCFillFragment *FF = cast<MCFillFragment>(this);
1002 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
1003 << " Size:" << FF->getSize();
1006 case MCFragment::FT_Inst: {
1007 const MCInstFragment *IF = cast<MCInstFragment>(this);
1010 IF->getInst().dump_pretty(OS);
1013 case MCFragment::FT_Org: {
1014 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
1016 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
1019 case MCFragment::FT_Dwarf: {
1020 const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
1022 OS << " AddrDelta:" << OF->getAddrDelta()
1023 << " LineDelta:" << OF->getLineDelta();
1026 case MCFragment::FT_LEB: {
1027 const MCLEBFragment *LF = cast<MCLEBFragment>(this);
1029 OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
1036 void MCSectionData::dump() {
1037 raw_ostream &OS = llvm::errs();
1039 OS << "<MCSectionData";
1040 OS << " Alignment:" << getAlignment() << " Address:" << Address
1041 << " Fragments:[\n ";
1042 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1043 if (it != begin()) OS << ",\n ";
1049 void MCSymbolData::dump() {
1050 raw_ostream &OS = llvm::errs();
1052 OS << "<MCSymbolData Symbol:" << getSymbol()
1053 << " Fragment:" << getFragment() << " Offset:" << getOffset()
1054 << " Flags:" << getFlags() << " Index:" << getIndex();
1056 OS << " (common, size:" << getCommonSize()
1057 << " align: " << getCommonAlignment() << ")";
1059 OS << " (external)";
1060 if (isPrivateExtern())
1061 OS << " (private extern)";
1065 void MCAssembler::dump() {
1066 raw_ostream &OS = llvm::errs();
1068 OS << "<MCAssembler\n";
1069 OS << " Sections:[\n ";
1070 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1071 if (it != begin()) OS << ",\n ";
1077 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1078 if (it != symbol_begin()) OS << ",\n ";