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 (!Asm.getBackend().isVirtualSection(it->getSection()))
58 SectionOrder.push_back(&*it);
59 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
60 if (Asm.getBackend().isVirtualSection(it->getSection()))
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 (getAssembler().getBackend().isVirtualSection(SD->getSection()))
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 if (A->getSymbol().isDefined())
289 Value += Layout.getSymbolAddress(&getSymbolData(A->getSymbol()));
293 if (const MCSymbolRefExpr *B = Target.getSymB()) {
294 if (B->getSymbol().isDefined())
295 Value -= Layout.getSymbolAddress(&getSymbolData(B->getSymbol()));
301 IsResolved = Writer.IsFixupFullyResolved(*this, Target, IsPCRel, DF);
304 Value -= Layout.getFragmentAddress(DF) + Fixup.getOffset();
309 uint64_t MCAssembler::ComputeFragmentSize(MCAsmLayout &Layout,
311 uint64_t SectionAddress,
312 uint64_t FragmentOffset) const {
313 switch (F.getKind()) {
314 case MCFragment::FT_Data:
315 return cast<MCDataFragment>(F).getContents().size();
316 case MCFragment::FT_Fill:
317 return cast<MCFillFragment>(F).getSize();
318 case MCFragment::FT_Inst:
319 return cast<MCInstFragment>(F).getInstSize();
321 case MCFragment::FT_LEB:
322 return cast<MCLEBFragment>(F).getSize();
324 case MCFragment::FT_Align: {
325 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
327 assert((!AF.hasOnlyAlignAddress() || !AF.getNextNode()) &&
328 "Invalid OnlyAlignAddress bit, not the last fragment!");
330 uint64_t Size = OffsetToAlignment(SectionAddress + FragmentOffset,
333 // Honor MaxBytesToEmit.
334 if (Size > AF.getMaxBytesToEmit())
340 case MCFragment::FT_Org:
341 return cast<MCOrgFragment>(F).getSize();
343 case MCFragment::FT_Dwarf:
344 return cast<MCDwarfLineAddrFragment>(F).getSize();
347 assert(0 && "invalid fragment kind");
351 void MCAsmLayout::LayoutFile() {
352 // Initialize the first section and set the valid fragment layout point. All
353 // actual layout computations are done lazily.
354 LastValidFragment = 0;
355 if (!getSectionOrder().empty())
356 getSectionOrder().front()->Address = 0;
359 void MCAsmLayout::LayoutFragment(MCFragment *F) {
360 MCFragment *Prev = F->getPrevNode();
362 // We should never try to recompute something which is up-to-date.
363 assert(!isFragmentUpToDate(F) && "Attempt to recompute up-to-date fragment!");
364 // We should never try to compute the fragment layout if the section isn't
366 assert(isSectionUpToDate(F->getParent()) &&
367 "Attempt to compute fragment before it's section!");
368 // We should never try to compute the fragment layout if it's predecessor
370 assert((!Prev || isFragmentUpToDate(Prev)) &&
371 "Attempt to compute fragment before it's predecessor!");
373 ++stats::FragmentLayouts;
375 // Compute the fragment start address.
376 uint64_t StartAddress = F->getParent()->Address;
377 uint64_t Address = StartAddress;
379 Address += Prev->Offset + Prev->EffectiveSize;
381 // Compute fragment offset and size.
382 F->Offset = Address - StartAddress;
383 F->EffectiveSize = getAssembler().ComputeFragmentSize(*this, *F, StartAddress,
385 LastValidFragment = F;
387 // If this is the last fragment in a section, update the next section address.
388 if (!F->getNextNode()) {
389 unsigned NextIndex = F->getParent()->getLayoutOrder() + 1;
390 if (NextIndex != getSectionOrder().size())
391 LayoutSection(getSectionOrder()[NextIndex]);
395 void MCAsmLayout::LayoutSection(MCSectionData *SD) {
396 unsigned SectionOrderIndex = SD->getLayoutOrder();
398 ++stats::SectionLayouts;
400 // Compute the section start address.
401 uint64_t StartAddress = 0;
402 if (SectionOrderIndex) {
403 MCSectionData *Prev = getSectionOrder()[SectionOrderIndex - 1];
404 StartAddress = getSectionAddress(Prev) + getSectionAddressSize(Prev);
407 // Honor the section alignment requirements.
408 StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
410 // Set the section address.
411 SD->Address = StartAddress;
414 /// WriteFragmentData - Write the \arg F data to the output file.
415 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
416 const MCFragment &F, MCObjectWriter *OW) {
417 uint64_t Start = OW->getStream().tell();
420 ++stats::EmittedFragments;
422 // FIXME: Embed in fragments instead?
423 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
424 switch (F.getKind()) {
425 case MCFragment::FT_Align: {
426 MCAlignFragment &AF = cast<MCAlignFragment>(F);
427 uint64_t Count = FragmentSize / AF.getValueSize();
429 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
431 // FIXME: This error shouldn't actually occur (the front end should emit
432 // multiple .align directives to enforce the semantics it wants), but is
433 // severe enough that we want to report it. How to handle this?
434 if (Count * AF.getValueSize() != FragmentSize)
435 report_fatal_error("undefined .align directive, value size '" +
436 Twine(AF.getValueSize()) +
437 "' is not a divisor of padding size '" +
438 Twine(FragmentSize) + "'");
440 // See if we are aligning with nops, and if so do that first to try to fill
441 // the Count bytes. Then if that did not fill any bytes or there are any
442 // bytes left to fill use the the Value and ValueSize to fill the rest.
443 // If we are aligning with nops, ask that target to emit the right data.
444 if (AF.hasEmitNops()) {
445 if (!Asm.getBackend().WriteNopData(Count, OW))
446 report_fatal_error("unable to write nop sequence of " +
447 Twine(Count) + " bytes");
451 // Otherwise, write out in multiples of the value size.
452 for (uint64_t i = 0; i != Count; ++i) {
453 switch (AF.getValueSize()) {
455 assert(0 && "Invalid size!");
456 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
457 case 2: OW->Write16(uint16_t(AF.getValue())); break;
458 case 4: OW->Write32(uint32_t(AF.getValue())); break;
459 case 8: OW->Write64(uint64_t(AF.getValue())); break;
465 case MCFragment::FT_Data: {
466 MCDataFragment &DF = cast<MCDataFragment>(F);
467 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
468 OW->WriteBytes(DF.getContents().str());
472 case MCFragment::FT_Fill: {
473 MCFillFragment &FF = cast<MCFillFragment>(F);
475 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
477 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
478 switch (FF.getValueSize()) {
480 assert(0 && "Invalid size!");
481 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
482 case 2: OW->Write16(uint16_t(FF.getValue())); break;
483 case 4: OW->Write32(uint32_t(FF.getValue())); break;
484 case 8: OW->Write64(uint64_t(FF.getValue())); break;
490 case MCFragment::FT_Inst:
491 llvm_unreachable("unexpected inst fragment after lowering");
494 case MCFragment::FT_LEB: {
495 MCLEBFragment &LF = cast<MCLEBFragment>(F);
497 // FIXME: It is probably better if we don't call EvaluateAsAbsolute in
500 LF.getValue().EvaluateAsAbsolute(Value, &Layout);
502 raw_svector_ostream OSE(Tmp);
504 MCObjectWriter::EncodeSLEB128(Value, OSE);
506 MCObjectWriter::EncodeULEB128(Value, OSE);
507 OW->WriteBytes(OSE.str());
511 case MCFragment::FT_Org: {
512 MCOrgFragment &OF = cast<MCOrgFragment>(F);
514 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
515 OW->Write8(uint8_t(OF.getValue()));
520 case MCFragment::FT_Dwarf: {
521 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
523 // The AddrDelta is really unsigned and it can only increase.
525 OF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, &Layout);
528 LineDelta = OF.getLineDelta();
530 MCDwarfLineAddr::Write(OW, LineDelta, (uint64_t)AddrDelta);
535 assert(OW->getStream().tell() - Start == FragmentSize);
538 void MCAssembler::WriteSectionData(const MCSectionData *SD,
539 const MCAsmLayout &Layout,
540 MCObjectWriter *OW) const {
541 // Ignore virtual sections.
542 if (getBackend().isVirtualSection(SD->getSection())) {
543 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
545 // Check that contents are only things legal inside a virtual section.
546 for (MCSectionData::const_iterator it = SD->begin(),
547 ie = SD->end(); it != ie; ++it) {
548 switch (it->getKind()) {
550 assert(0 && "Invalid fragment in virtual section!");
551 case MCFragment::FT_Data: {
552 // Check that we aren't trying to write a non-zero contents (or fixups)
553 // into a virtual section. This is to support clients which use standard
554 // directives to fill the contents of virtual sections.
555 MCDataFragment &DF = cast<MCDataFragment>(*it);
556 assert(DF.fixup_begin() == DF.fixup_end() &&
557 "Cannot have fixups in virtual section!");
558 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
559 assert(DF.getContents()[i] == 0 &&
560 "Invalid data value for virtual section!");
563 case MCFragment::FT_Align:
564 // Check that we aren't trying to write a non-zero value into a virtual
566 assert((!cast<MCAlignFragment>(it)->getValueSize() ||
567 !cast<MCAlignFragment>(it)->getValue()) &&
568 "Invalid align in virtual section!");
570 case MCFragment::FT_Fill:
571 assert(!cast<MCFillFragment>(it)->getValueSize() &&
572 "Invalid fill in virtual section!");
580 uint64_t Start = OW->getStream().tell();
583 for (MCSectionData::const_iterator it = SD->begin(),
584 ie = SD->end(); it != ie; ++it)
585 WriteFragmentData(*this, Layout, *it, OW);
587 assert(OW->getStream().tell() - Start == Layout.getSectionFileSize(SD));
590 void MCAssembler::AddSectionToTheEnd(const MCObjectWriter &Writer,
591 MCSectionData &SD, MCAsmLayout &Layout) {
592 // Create dummy fragments and assign section ordinals.
593 unsigned SectionIndex = 0;
594 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it)
597 SD.setOrdinal(SectionIndex);
599 // Assign layout order indices to sections and fragments.
600 unsigned FragmentIndex = 0;
602 for (unsigned e = Layout.getSectionOrder().size(); i != e; ++i) {
603 MCSectionData *SD = Layout.getSectionOrder()[i];
605 for (MCSectionData::iterator it2 = SD->begin(),
606 ie2 = SD->end(); it2 != ie2; ++it2)
610 SD.setLayoutOrder(i);
611 for (MCSectionData::iterator it2 = SD.begin(),
612 ie2 = SD.end(); it2 != ie2; ++it2) {
613 it2->setLayoutOrder(FragmentIndex++);
615 Layout.getSectionOrder().push_back(&SD);
617 Layout.LayoutSection(&SD);
619 // Layout until everything fits.
620 while (LayoutOnce(Writer, Layout))
625 void MCAssembler::Finish(MCObjectWriter *Writer) {
626 DEBUG_WITH_TYPE("mc-dump", {
627 llvm::errs() << "assembler backend - pre-layout\n--\n";
630 // Create the layout object.
631 MCAsmLayout Layout(*this);
633 // Insert additional align fragments for concrete sections to explicitly pad
634 // the previous section to match their alignment requirements. This is for
635 // 'gas' compatibility, it shouldn't strictly be necessary.
636 if (PadSectionToAlignment) {
637 for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
638 MCSectionData *SD = Layout.getSectionOrder()[i];
640 // Ignore sections without alignment requirements.
641 unsigned Align = SD->getAlignment();
645 // Ignore virtual sections, they don't cause file size modifications.
646 if (getBackend().isVirtualSection(SD->getSection()))
649 // Otherwise, create a new align fragment at the end of the previous
651 MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
652 Layout.getSectionOrder()[i - 1]);
653 AF->setOnlyAlignAddress(true);
657 // Create dummy fragments and assign section ordinals.
658 unsigned SectionIndex = 0;
659 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
660 // Create dummy fragments to eliminate any empty sections, this simplifies
662 if (it->getFragmentList().empty())
663 new MCDataFragment(it);
665 it->setOrdinal(SectionIndex++);
668 // Assign layout order indices to sections and fragments.
669 unsigned FragmentIndex = 0;
670 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
671 MCSectionData *SD = Layout.getSectionOrder()[i];
672 SD->setLayoutOrder(i);
674 for (MCSectionData::iterator it2 = SD->begin(),
675 ie2 = SD->end(); it2 != ie2; ++it2)
676 it2->setLayoutOrder(FragmentIndex++);
679 llvm::OwningPtr<MCObjectWriter> OwnWriter(0);
681 //no custom Writer_ : create the default one life-managed by OwningPtr
682 OwnWriter.reset(getBackend().createObjectWriter(OS));
683 Writer = OwnWriter.get();
685 report_fatal_error("unable to create object writer!");
688 // Layout until everything fits.
689 while (LayoutOnce(*Writer, Layout))
692 DEBUG_WITH_TYPE("mc-dump", {
693 llvm::errs() << "assembler backend - post-relaxation\n--\n";
696 // Finalize the layout, including fragment lowering.
697 FinishLayout(Layout);
699 DEBUG_WITH_TYPE("mc-dump", {
700 llvm::errs() << "assembler backend - final-layout\n--\n";
703 uint64_t StartOffset = OS.tell();
705 // Allow the object writer a chance to perform post-layout binding (for
706 // example, to set the index fields in the symbol data).
707 Writer->ExecutePostLayoutBinding(*this);
709 // Evaluate and apply the fixups, generating relocation entries as necessary.
710 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
711 for (MCSectionData::iterator it2 = it->begin(),
712 ie2 = it->end(); it2 != ie2; ++it2) {
713 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
717 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
718 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
719 MCFixup &Fixup = *it3;
721 // Evaluate the fixup.
724 if (!EvaluateFixup(*Writer, Layout, Fixup, DF, Target, FixedValue)) {
725 // The fixup was unresolved, we need a relocation. Inform the object
726 // writer of the relocation, and give it an opportunity to adjust the
727 // fixup value if need be.
728 Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
731 getBackend().ApplyFixup(Fixup, *DF, FixedValue);
736 // Write the object file.
737 Writer->WriteObject(*this, Layout);
739 stats::ObjectBytes += OS.tell() - StartOffset;
742 bool MCAssembler::FixupNeedsRelaxation(const MCObjectWriter &Writer,
743 const MCFixup &Fixup,
744 const MCFragment *DF,
745 const MCAsmLayout &Layout) const {
749 // If we cannot resolve the fixup value, it requires relaxation.
752 if (!EvaluateFixup(Writer, Layout, Fixup, DF, Target, Value))
755 // Otherwise, relax if the value is too big for a (signed) i8.
757 // FIXME: This is target dependent!
758 return int64_t(Value) != int64_t(int8_t(Value));
761 bool MCAssembler::FragmentNeedsRelaxation(const MCObjectWriter &Writer,
762 const MCInstFragment *IF,
763 const MCAsmLayout &Layout) const {
764 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
765 // are intentionally pushing out inst fragments, or because we relaxed a
766 // previous instruction to one that doesn't need relaxation.
767 if (!getBackend().MayNeedRelaxation(IF->getInst()))
770 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
771 ie = IF->fixup_end(); it != ie; ++it)
772 if (FixupNeedsRelaxation(Writer, *it, IF, Layout))
778 bool MCAssembler::RelaxInstruction(const MCObjectWriter &Writer,
780 MCInstFragment &IF) {
781 if (!FragmentNeedsRelaxation(Writer, &IF, Layout))
784 ++stats::RelaxedInstructions;
786 // FIXME-PERF: We could immediately lower out instructions if we can tell
787 // they are fully resolved, to avoid retesting on later passes.
789 // Relax the fragment.
792 getBackend().RelaxInstruction(IF.getInst(), Relaxed);
794 // Encode the new instruction.
796 // FIXME-PERF: If it matters, we could let the target do this. It can
797 // probably do so more efficiently in many cases.
798 SmallVector<MCFixup, 4> Fixups;
799 SmallString<256> Code;
800 raw_svector_ostream VecOS(Code);
801 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
804 // Update the instruction fragment.
805 int SlideAmount = Code.size() - IF.getInstSize();
808 IF.getFixups().clear();
809 // FIXME: Eliminate copy.
810 for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
811 IF.getFixups().push_back(Fixups[i]);
813 // Update the layout, and remember that we relaxed.
814 Layout.UpdateForSlide(&IF, SlideAmount);
818 bool MCAssembler::RelaxOrg(const MCObjectWriter &Writer,
821 int64_t TargetLocation;
822 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
823 report_fatal_error("expected assembly-time absolute expression");
825 // FIXME: We need a way to communicate this error.
826 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
827 int64_t Offset = TargetLocation - FragmentOffset;
828 if (Offset < 0 || Offset >= 0x40000000)
829 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
830 "' (at offset '" + Twine(FragmentOffset) + "')");
832 unsigned OldSize = OF.getSize();
834 return OldSize != OF.getSize();
837 bool MCAssembler::RelaxLEB(const MCObjectWriter &Writer,
841 LF.getValue().EvaluateAsAbsolute(Value, &Layout);
843 raw_svector_ostream OSE(Tmp);
845 MCObjectWriter::EncodeSLEB128(Value, OSE);
847 MCObjectWriter::EncodeULEB128(Value, OSE);
848 uint64_t OldSize = LF.getSize();
849 LF.setSize(OSE.GetNumBytesInBuffer());
850 return OldSize != LF.getSize();
853 bool MCAssembler::RelaxDwarfLineAddr(const MCObjectWriter &Writer,
855 MCDwarfLineAddrFragment &DF) {
857 DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, &Layout);
859 LineDelta = DF.getLineDelta();
860 uint64_t OldSize = DF.getSize();
861 DF.setSize(MCDwarfLineAddr::ComputeSize(LineDelta, AddrDelta));
862 return OldSize != DF.getSize();
865 bool MCAssembler::LayoutOnce(const MCObjectWriter &Writer,
866 MCAsmLayout &Layout) {
867 ++stats::RelaxationSteps;
869 // Layout the sections in order.
872 // Scan for fragments that need relaxation.
873 bool WasRelaxed = false;
874 for (iterator it = begin(), ie = end(); it != ie; ++it) {
875 MCSectionData &SD = *it;
877 for (MCSectionData::iterator it2 = SD.begin(),
878 ie2 = SD.end(); it2 != ie2; ++it2) {
879 // Check if this is an fragment that needs relaxation.
880 switch(it2->getKind()) {
883 case MCFragment::FT_Inst:
884 WasRelaxed |= RelaxInstruction(Writer, Layout,
885 *cast<MCInstFragment>(it2));
887 case MCFragment::FT_Org:
888 WasRelaxed |= RelaxOrg(Writer, Layout, *cast<MCOrgFragment>(it2));
890 case MCFragment::FT_Dwarf:
891 WasRelaxed |= RelaxDwarfLineAddr(Writer, Layout,
892 *cast<MCDwarfLineAddrFragment>(it2));
894 case MCFragment::FT_LEB:
895 WasRelaxed |= RelaxLEB(Writer, Layout, *cast<MCLEBFragment>(it2));
904 void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
905 // Lower out any instruction fragments, to simplify the fixup application and
908 // FIXME-PERF: We don't have to do this, but the assumption is that it is
909 // cheap (we will mostly end up eliminating fragments and appending on to data
910 // fragments), so the extra complexity downstream isn't worth it. Evaluate
912 for (iterator it = begin(), ie = end(); it != ie; ++it) {
913 MCSectionData &SD = *it;
915 for (MCSectionData::iterator it2 = SD.begin(),
916 ie2 = SD.end(); it2 != ie2; ++it2) {
917 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
921 // Create a new data fragment for the instruction.
923 // FIXME-PERF: Reuse previous data fragment if possible.
924 MCDataFragment *DF = new MCDataFragment();
925 SD.getFragmentList().insert(it2, DF);
927 // Update the data fragments layout data.
928 DF->setParent(IF->getParent());
929 DF->setAtom(IF->getAtom());
930 DF->setLayoutOrder(IF->getLayoutOrder());
931 Layout.FragmentReplaced(IF, DF);
933 // Copy in the data and the fixups.
934 DF->getContents().append(IF->getCode().begin(), IF->getCode().end());
935 for (unsigned i = 0, e = IF->getFixups().size(); i != e; ++i)
936 DF->getFixups().push_back(IF->getFixups()[i]);
938 // Delete the instruction fragment and update the iterator.
939 SD.getFragmentList().erase(IF);
949 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
950 OS << "<MCFixup" << " Offset:" << AF.getOffset()
951 << " Value:" << *AF.getValue()
952 << " Kind:" << AF.getKind() << ">";
958 void MCFragment::dump() {
959 raw_ostream &OS = llvm::errs();
963 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
964 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
965 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
966 case MCFragment::FT_Inst: OS << "MCInstFragment"; break;
967 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
968 case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
969 case MCFragment::FT_LEB: OS << "MCLEBFragment"; break;
972 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
973 << " Offset:" << Offset << " EffectiveSize:" << EffectiveSize << ">";
976 case MCFragment::FT_Align: {
977 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
978 if (AF->hasEmitNops())
979 OS << " (emit nops)";
980 if (AF->hasOnlyAlignAddress())
981 OS << " (only align section)";
983 OS << " Alignment:" << AF->getAlignment()
984 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
985 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
988 case MCFragment::FT_Data: {
989 const MCDataFragment *DF = cast<MCDataFragment>(this);
992 const SmallVectorImpl<char> &Contents = DF->getContents();
993 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
995 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
997 OS << "] (" << Contents.size() << " bytes)";
999 if (!DF->getFixups().empty()) {
1002 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
1003 ie = DF->fixup_end(); it != ie; ++it) {
1004 if (it != DF->fixup_begin()) OS << ",\n ";
1011 case MCFragment::FT_Fill: {
1012 const MCFillFragment *FF = cast<MCFillFragment>(this);
1013 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
1014 << " Size:" << FF->getSize();
1017 case MCFragment::FT_Inst: {
1018 const MCInstFragment *IF = cast<MCInstFragment>(this);
1021 IF->getInst().dump_pretty(OS);
1024 case MCFragment::FT_Org: {
1025 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
1027 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
1030 case MCFragment::FT_Dwarf: {
1031 const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
1033 OS << " AddrDelta:" << OF->getAddrDelta()
1034 << " LineDelta:" << OF->getLineDelta();
1037 case MCFragment::FT_LEB: {
1038 const MCLEBFragment *LF = cast<MCLEBFragment>(this);
1040 OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
1047 void MCSectionData::dump() {
1048 raw_ostream &OS = llvm::errs();
1050 OS << "<MCSectionData";
1051 OS << " Alignment:" << getAlignment() << " Address:" << Address
1052 << " Fragments:[\n ";
1053 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1054 if (it != begin()) OS << ",\n ";
1060 void MCSymbolData::dump() {
1061 raw_ostream &OS = llvm::errs();
1063 OS << "<MCSymbolData Symbol:" << getSymbol()
1064 << " Fragment:" << getFragment() << " Offset:" << getOffset()
1065 << " Flags:" << getFlags() << " Index:" << getIndex();
1067 OS << " (common, size:" << getCommonSize()
1068 << " align: " << getCommonAlignment() << ")";
1070 OS << " (external)";
1071 if (isPrivateExtern())
1072 OS << " (private extern)";
1076 void MCAssembler::dump() {
1077 raw_ostream &OS = llvm::errs();
1079 OS << "<MCAssembler\n";
1080 OS << " Sections:[\n ";
1081 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1082 if (it != begin()) OS << ",\n ";
1088 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1089 if (it != symbol_begin()) OS << ",\n ";