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_Align: {
322 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
324 assert((!AF.hasOnlyAlignAddress() || !AF.getNextNode()) &&
325 "Invalid OnlyAlignAddress bit, not the last fragment!");
327 uint64_t Size = OffsetToAlignment(SectionAddress + FragmentOffset,
330 // Honor MaxBytesToEmit.
331 if (Size > AF.getMaxBytesToEmit())
337 case MCFragment::FT_Org: {
338 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
340 // FIXME: We should compute this sooner, we don't want to recurse here, and
341 // we would like to be more functional.
342 int64_t TargetLocation;
343 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
344 report_fatal_error("expected assembly-time absolute expression");
346 // FIXME: We need a way to communicate this error.
347 int64_t Offset = TargetLocation - FragmentOffset;
348 if (Offset < 0 || Offset >= 0x40000000)
349 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
350 "' (at offset '" + Twine(FragmentOffset) + "')");
355 case MCFragment::FT_Dwarf: {
356 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
358 // The AddrDelta is really unsigned and it can only increase.
361 OF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, &Layout);
364 LineDelta = OF.getLineDelta();
366 return MCDwarfLineAddr::ComputeSize(LineDelta, AddrDelta);
370 assert(0 && "invalid fragment kind");
374 void MCAsmLayout::LayoutFile() {
375 // Initialize the first section and set the valid fragment layout point. All
376 // actual layout computations are done lazily.
377 LastValidFragment = 0;
378 if (!getSectionOrder().empty())
379 getSectionOrder().front()->Address = 0;
382 void MCAsmLayout::LayoutFragment(MCFragment *F) {
383 MCFragment *Prev = F->getPrevNode();
385 // We should never try to recompute something which is up-to-date.
386 assert(!isFragmentUpToDate(F) && "Attempt to recompute up-to-date fragment!");
387 // We should never try to compute the fragment layout if the section isn't
389 assert(isSectionUpToDate(F->getParent()) &&
390 "Attempt to compute fragment before it's section!");
391 // We should never try to compute the fragment layout if it's predecessor
393 assert((!Prev || isFragmentUpToDate(Prev)) &&
394 "Attempt to compute fragment before it's predecessor!");
396 ++stats::FragmentLayouts;
398 // Compute the fragment start address.
399 uint64_t StartAddress = F->getParent()->Address;
400 uint64_t Address = StartAddress;
402 Address += Prev->Offset + Prev->EffectiveSize;
404 // Compute fragment offset and size.
405 F->Offset = Address - StartAddress;
406 F->EffectiveSize = getAssembler().ComputeFragmentSize(*this, *F, StartAddress,
408 LastValidFragment = F;
410 // If this is the last fragment in a section, update the next section address.
411 if (!F->getNextNode()) {
412 unsigned NextIndex = F->getParent()->getLayoutOrder() + 1;
413 if (NextIndex != getSectionOrder().size())
414 LayoutSection(getSectionOrder()[NextIndex]);
418 void MCAsmLayout::LayoutSection(MCSectionData *SD) {
419 unsigned SectionOrderIndex = SD->getLayoutOrder();
421 ++stats::SectionLayouts;
423 // Compute the section start address.
424 uint64_t StartAddress = 0;
425 if (SectionOrderIndex) {
426 MCSectionData *Prev = getSectionOrder()[SectionOrderIndex - 1];
427 StartAddress = getSectionAddress(Prev) + getSectionAddressSize(Prev);
430 // Honor the section alignment requirements.
431 StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
433 // Set the section address.
434 SD->Address = StartAddress;
437 /// WriteFragmentData - Write the \arg F data to the output file.
438 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
439 const MCFragment &F, MCObjectWriter *OW) {
440 uint64_t Start = OW->getStream().tell();
443 ++stats::EmittedFragments;
445 // FIXME: Embed in fragments instead?
446 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
447 switch (F.getKind()) {
448 case MCFragment::FT_Align: {
449 MCAlignFragment &AF = cast<MCAlignFragment>(F);
450 uint64_t Count = FragmentSize / AF.getValueSize();
452 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
454 // FIXME: This error shouldn't actually occur (the front end should emit
455 // multiple .align directives to enforce the semantics it wants), but is
456 // severe enough that we want to report it. How to handle this?
457 if (Count * AF.getValueSize() != FragmentSize)
458 report_fatal_error("undefined .align directive, value size '" +
459 Twine(AF.getValueSize()) +
460 "' is not a divisor of padding size '" +
461 Twine(FragmentSize) + "'");
463 // See if we are aligning with nops, and if so do that first to try to fill
464 // the Count bytes. Then if that did not fill any bytes or there are any
465 // bytes left to fill use the the Value and ValueSize to fill the rest.
466 // If we are aligning with nops, ask that target to emit the right data.
467 if (AF.hasEmitNops()) {
468 if (!Asm.getBackend().WriteNopData(Count, OW))
469 report_fatal_error("unable to write nop sequence of " +
470 Twine(Count) + " bytes");
474 // Otherwise, write out in multiples of the value size.
475 for (uint64_t i = 0; i != Count; ++i) {
476 switch (AF.getValueSize()) {
478 assert(0 && "Invalid size!");
479 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
480 case 2: OW->Write16(uint16_t(AF.getValue())); break;
481 case 4: OW->Write32(uint32_t(AF.getValue())); break;
482 case 8: OW->Write64(uint64_t(AF.getValue())); break;
488 case MCFragment::FT_Data: {
489 MCDataFragment &DF = cast<MCDataFragment>(F);
490 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
491 OW->WriteBytes(DF.getContents().str());
495 case MCFragment::FT_Fill: {
496 MCFillFragment &FF = cast<MCFillFragment>(F);
498 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
500 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
501 switch (FF.getValueSize()) {
503 assert(0 && "Invalid size!");
504 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
505 case 2: OW->Write16(uint16_t(FF.getValue())); break;
506 case 4: OW->Write32(uint32_t(FF.getValue())); break;
507 case 8: OW->Write64(uint64_t(FF.getValue())); break;
513 case MCFragment::FT_Inst:
514 llvm_unreachable("unexpected inst fragment after lowering");
517 case MCFragment::FT_Org: {
518 MCOrgFragment &OF = cast<MCOrgFragment>(F);
520 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
521 OW->Write8(uint8_t(OF.getValue()));
526 case MCFragment::FT_Dwarf: {
527 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
529 // The AddrDelta is really unsigned and it can only increase.
531 OF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, &Layout);
534 LineDelta = OF.getLineDelta();
536 MCDwarfLineAddr::Write(OW, LineDelta, (uint64_t)AddrDelta);
541 assert(OW->getStream().tell() - Start == FragmentSize);
544 void MCAssembler::WriteSectionData(const MCSectionData *SD,
545 const MCAsmLayout &Layout,
546 MCObjectWriter *OW) const {
547 // Ignore virtual sections.
548 if (getBackend().isVirtualSection(SD->getSection())) {
549 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
551 // Check that contents are only things legal inside a virtual section.
552 for (MCSectionData::const_iterator it = SD->begin(),
553 ie = SD->end(); it != ie; ++it) {
554 switch (it->getKind()) {
556 assert(0 && "Invalid fragment in virtual section!");
557 case MCFragment::FT_Data: {
558 // Check that we aren't trying to write a non-zero contents (or fixups)
559 // into a virtual section. This is to support clients which use standard
560 // directives to fill the contents of virtual sections.
561 MCDataFragment &DF = cast<MCDataFragment>(*it);
562 assert(DF.fixup_begin() == DF.fixup_end() &&
563 "Cannot have fixups in virtual section!");
564 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
565 assert(DF.getContents()[i] == 0 &&
566 "Invalid data value for virtual section!");
569 case MCFragment::FT_Align:
570 // Check that we aren't trying to write a non-zero value into a virtual
572 assert((!cast<MCAlignFragment>(it)->getValueSize() ||
573 !cast<MCAlignFragment>(it)->getValue()) &&
574 "Invalid align in virtual section!");
576 case MCFragment::FT_Fill:
577 assert(!cast<MCFillFragment>(it)->getValueSize() &&
578 "Invalid fill in virtual section!");
586 uint64_t Start = OW->getStream().tell();
589 for (MCSectionData::const_iterator it = SD->begin(),
590 ie = SD->end(); it != ie; ++it)
591 WriteFragmentData(*this, Layout, *it, OW);
593 assert(OW->getStream().tell() - Start == Layout.getSectionFileSize(SD));
596 void MCAssembler::AddSectionToTheEnd(const MCObjectWriter &Writer,
597 MCSectionData &SD, MCAsmLayout &Layout) {
598 // Create dummy fragments and assign section ordinals.
599 unsigned SectionIndex = 0;
600 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it)
603 SD.setOrdinal(SectionIndex);
605 // Assign layout order indices to sections and fragments.
606 unsigned FragmentIndex = 0;
608 for (unsigned e = Layout.getSectionOrder().size(); i != e; ++i) {
609 MCSectionData *SD = Layout.getSectionOrder()[i];
611 for (MCSectionData::iterator it2 = SD->begin(),
612 ie2 = SD->end(); it2 != ie2; ++it2)
616 SD.setLayoutOrder(i);
617 for (MCSectionData::iterator it2 = SD.begin(),
618 ie2 = SD.end(); it2 != ie2; ++it2) {
619 it2->setLayoutOrder(FragmentIndex++);
621 Layout.getSectionOrder().push_back(&SD);
623 Layout.LayoutSection(&SD);
625 // Layout until everything fits.
626 while (LayoutOnce(Writer, Layout))
631 void MCAssembler::Finish(MCObjectWriter *Writer) {
632 DEBUG_WITH_TYPE("mc-dump", {
633 llvm::errs() << "assembler backend - pre-layout\n--\n";
636 // Create the layout object.
637 MCAsmLayout Layout(*this);
639 // Insert additional align fragments for concrete sections to explicitly pad
640 // the previous section to match their alignment requirements. This is for
641 // 'gas' compatibility, it shouldn't strictly be necessary.
642 if (PadSectionToAlignment) {
643 for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
644 MCSectionData *SD = Layout.getSectionOrder()[i];
646 // Ignore sections without alignment requirements.
647 unsigned Align = SD->getAlignment();
651 // Ignore virtual sections, they don't cause file size modifications.
652 if (getBackend().isVirtualSection(SD->getSection()))
655 // Otherwise, create a new align fragment at the end of the previous
657 MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
658 Layout.getSectionOrder()[i - 1]);
659 AF->setOnlyAlignAddress(true);
663 // Create dummy fragments and assign section ordinals.
664 unsigned SectionIndex = 0;
665 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
666 // Create dummy fragments to eliminate any empty sections, this simplifies
668 if (it->getFragmentList().empty())
669 new MCDataFragment(it);
671 it->setOrdinal(SectionIndex++);
674 // Assign layout order indices to sections and fragments.
675 unsigned FragmentIndex = 0;
676 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
677 MCSectionData *SD = Layout.getSectionOrder()[i];
678 SD->setLayoutOrder(i);
680 for (MCSectionData::iterator it2 = SD->begin(),
681 ie2 = SD->end(); it2 != ie2; ++it2)
682 it2->setLayoutOrder(FragmentIndex++);
685 llvm::OwningPtr<MCObjectWriter> OwnWriter(0);
687 //no custom Writer_ : create the default one life-managed by OwningPtr
688 OwnWriter.reset(getBackend().createObjectWriter(OS));
689 Writer = OwnWriter.get();
691 report_fatal_error("unable to create object writer!");
694 // Layout until everything fits.
695 while (LayoutOnce(*Writer, Layout))
698 DEBUG_WITH_TYPE("mc-dump", {
699 llvm::errs() << "assembler backend - post-relaxation\n--\n";
702 // Finalize the layout, including fragment lowering.
703 FinishLayout(Layout);
705 DEBUG_WITH_TYPE("mc-dump", {
706 llvm::errs() << "assembler backend - final-layout\n--\n";
709 uint64_t StartOffset = OS.tell();
711 // Allow the object writer a chance to perform post-layout binding (for
712 // example, to set the index fields in the symbol data).
713 Writer->ExecutePostLayoutBinding(*this);
715 // Evaluate and apply the fixups, generating relocation entries as necessary.
716 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
717 for (MCSectionData::iterator it2 = it->begin(),
718 ie2 = it->end(); it2 != ie2; ++it2) {
719 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
723 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
724 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
725 MCFixup &Fixup = *it3;
727 // Evaluate the fixup.
730 if (!EvaluateFixup(*Writer, Layout, Fixup, DF, Target, FixedValue)) {
731 // The fixup was unresolved, we need a relocation. Inform the object
732 // writer of the relocation, and give it an opportunity to adjust the
733 // fixup value if need be.
734 Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
737 getBackend().ApplyFixup(Fixup, *DF, FixedValue);
742 // Write the object file.
743 Writer->WriteObject(*this, Layout);
745 stats::ObjectBytes += OS.tell() - StartOffset;
748 bool MCAssembler::FixupNeedsRelaxation(const MCObjectWriter &Writer,
749 const MCFixup &Fixup,
750 const MCFragment *DF,
751 const MCAsmLayout &Layout) const {
755 // If we cannot resolve the fixup value, it requires relaxation.
758 if (!EvaluateFixup(Writer, Layout, Fixup, DF, Target, Value))
761 // Otherwise, relax if the value is too big for a (signed) i8.
763 // FIXME: This is target dependent!
764 return int64_t(Value) != int64_t(int8_t(Value));
767 bool MCAssembler::FragmentNeedsRelaxation(const MCObjectWriter &Writer,
768 const MCInstFragment *IF,
769 const MCAsmLayout &Layout) const {
770 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
771 // are intentionally pushing out inst fragments, or because we relaxed a
772 // previous instruction to one that doesn't need relaxation.
773 if (!getBackend().MayNeedRelaxation(IF->getInst()))
776 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
777 ie = IF->fixup_end(); it != ie; ++it)
778 if (FixupNeedsRelaxation(Writer, *it, IF, Layout))
784 bool MCAssembler::LayoutOnce(const MCObjectWriter &Writer,
785 MCAsmLayout &Layout) {
786 ++stats::RelaxationSteps;
788 // Layout the sections in order.
791 // Scan for fragments that need relaxation.
792 bool WasRelaxed = false;
793 for (iterator it = begin(), ie = end(); it != ie; ++it) {
794 MCSectionData &SD = *it;
796 for (MCSectionData::iterator it2 = SD.begin(),
797 ie2 = SD.end(); it2 != ie2; ++it2) {
798 // Check if this is an instruction fragment that needs relaxation.
799 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
800 if (!IF || !FragmentNeedsRelaxation(Writer, IF, Layout))
803 ++stats::RelaxedInstructions;
805 // FIXME-PERF: We could immediately lower out instructions if we can tell
806 // they are fully resolved, to avoid retesting on later passes.
808 // Relax the fragment.
811 getBackend().RelaxInstruction(IF->getInst(), Relaxed);
813 // Encode the new instruction.
815 // FIXME-PERF: If it matters, we could let the target do this. It can
816 // probably do so more efficiently in many cases.
817 SmallVector<MCFixup, 4> Fixups;
818 SmallString<256> Code;
819 raw_svector_ostream VecOS(Code);
820 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
823 // Update the instruction fragment.
824 int SlideAmount = Code.size() - IF->getInstSize();
825 IF->setInst(Relaxed);
826 IF->getCode() = Code;
827 IF->getFixups().clear();
828 // FIXME: Eliminate copy.
829 for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
830 IF->getFixups().push_back(Fixups[i]);
832 // Update the layout, and remember that we relaxed.
833 Layout.UpdateForSlide(IF, SlideAmount);
841 void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
842 // Lower out any instruction fragments, to simplify the fixup application and
845 // FIXME-PERF: We don't have to do this, but the assumption is that it is
846 // cheap (we will mostly end up eliminating fragments and appending on to data
847 // fragments), so the extra complexity downstream isn't worth it. Evaluate
849 for (iterator it = begin(), ie = end(); it != ie; ++it) {
850 MCSectionData &SD = *it;
852 for (MCSectionData::iterator it2 = SD.begin(),
853 ie2 = SD.end(); it2 != ie2; ++it2) {
854 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
858 // Create a new data fragment for the instruction.
860 // FIXME-PERF: Reuse previous data fragment if possible.
861 MCDataFragment *DF = new MCDataFragment();
862 SD.getFragmentList().insert(it2, DF);
864 // Update the data fragments layout data.
865 DF->setParent(IF->getParent());
866 DF->setAtom(IF->getAtom());
867 DF->setLayoutOrder(IF->getLayoutOrder());
868 Layout.FragmentReplaced(IF, DF);
870 // Copy in the data and the fixups.
871 DF->getContents().append(IF->getCode().begin(), IF->getCode().end());
872 for (unsigned i = 0, e = IF->getFixups().size(); i != e; ++i)
873 DF->getFixups().push_back(IF->getFixups()[i]);
875 // Delete the instruction fragment and update the iterator.
876 SD.getFragmentList().erase(IF);
886 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
887 OS << "<MCFixup" << " Offset:" << AF.getOffset()
888 << " Value:" << *AF.getValue()
889 << " Kind:" << AF.getKind() << ">";
895 void MCFragment::dump() {
896 raw_ostream &OS = llvm::errs();
900 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
901 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
902 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
903 case MCFragment::FT_Inst: OS << "MCInstFragment"; break;
904 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
905 case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
908 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
909 << " Offset:" << Offset << " EffectiveSize:" << EffectiveSize << ">";
912 case MCFragment::FT_Align: {
913 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
914 if (AF->hasEmitNops())
915 OS << " (emit nops)";
916 if (AF->hasOnlyAlignAddress())
917 OS << " (only align section)";
919 OS << " Alignment:" << AF->getAlignment()
920 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
921 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
924 case MCFragment::FT_Data: {
925 const MCDataFragment *DF = cast<MCDataFragment>(this);
928 const SmallVectorImpl<char> &Contents = DF->getContents();
929 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
931 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
933 OS << "] (" << Contents.size() << " bytes)";
935 if (!DF->getFixups().empty()) {
938 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
939 ie = DF->fixup_end(); it != ie; ++it) {
940 if (it != DF->fixup_begin()) OS << ",\n ";
947 case MCFragment::FT_Fill: {
948 const MCFillFragment *FF = cast<MCFillFragment>(this);
949 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
950 << " Size:" << FF->getSize();
953 case MCFragment::FT_Inst: {
954 const MCInstFragment *IF = cast<MCInstFragment>(this);
957 IF->getInst().dump_pretty(OS);
960 case MCFragment::FT_Org: {
961 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
963 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
966 case MCFragment::FT_Dwarf: {
967 const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
969 OS << " AddrDelta:" << OF->getAddrDelta()
970 << " LineDelta:" << OF->getLineDelta();
977 void MCSectionData::dump() {
978 raw_ostream &OS = llvm::errs();
980 OS << "<MCSectionData";
981 OS << " Alignment:" << getAlignment() << " Address:" << Address
982 << " Fragments:[\n ";
983 for (iterator it = begin(), ie = end(); it != ie; ++it) {
984 if (it != begin()) OS << ",\n ";
990 void MCSymbolData::dump() {
991 raw_ostream &OS = llvm::errs();
993 OS << "<MCSymbolData Symbol:" << getSymbol()
994 << " Fragment:" << getFragment() << " Offset:" << getOffset()
995 << " Flags:" << getFlags() << " Index:" << getIndex();
997 OS << " (common, size:" << getCommonSize()
998 << " align: " << getCommonAlignment() << ")";
1000 OS << " (external)";
1001 if (isPrivateExtern())
1002 OS << " (private extern)";
1006 void MCAssembler::dump() {
1007 raw_ostream &OS = llvm::errs();
1009 OS << "<MCAssembler\n";
1010 OS << " Sections:[\n ";
1011 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1012 if (it != begin()) OS << ",\n ";
1018 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1019 if (it != symbol_begin()) OS << ",\n ";