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::Invalidate(MCFragment *F) {
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::ReplaceFragment(MCFragment *Src, MCFragment *Dst) {
117 MCSectionData *SD = Src->getParent();
119 // Insert Dst immediately before Src
120 SD->getFragmentList().insert(Src, Dst);
122 // Set the data fragment's layout data.
123 Dst->setParent(Src->getParent());
124 Dst->setAtom(Src->getAtom());
125 Dst->setLayoutOrder(Src->getLayoutOrder());
127 if (LastValidFragment == Src)
128 LastValidFragment = Dst;
130 Dst->Offset = Src->Offset;
131 Dst->EffectiveSize = Src->EffectiveSize;
133 // Remove Src, but don't delete it yet.
134 SD->getFragmentList().remove(Src);
137 void MCAsmLayout::CoalesceFragments(MCFragment *Src, MCFragment *Dst) {
138 assert(Src->getPrevNode() == Dst);
140 if (isFragmentUpToDate(Src)) {
141 if (LastValidFragment == Src)
142 LastValidFragment = Dst;
143 Dst->EffectiveSize += Src->EffectiveSize;
145 // We don't know the effective size of Src, so we have to invalidate Dst.
148 // Remove Src, but don't delete it yet.
149 Src->getParent()->getFragmentList().remove(Src);
152 uint64_t MCAsmLayout::getFragmentAddress(const MCFragment *F) const {
153 assert(F->getParent() && "Missing section()!");
154 return getSectionAddress(F->getParent()) + getFragmentOffset(F);
157 uint64_t MCAsmLayout::getFragmentEffectiveSize(const MCFragment *F) const {
159 assert(F->EffectiveSize != ~UINT64_C(0) && "Address not set!");
160 return F->EffectiveSize;
163 uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
165 assert(F->Offset != ~UINT64_C(0) && "Address not set!");
169 uint64_t MCAsmLayout::getSymbolAddress(const MCSymbolData *SD) const {
170 assert(SD->getFragment() && "Invalid getAddress() on undefined symbol!");
171 return getFragmentAddress(SD->getFragment()) + SD->getOffset();
174 uint64_t MCAsmLayout::getSectionAddress(const MCSectionData *SD) const {
175 EnsureValid(SD->begin());
176 assert(SD->Address != ~UINT64_C(0) && "Address not set!");
180 uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const {
181 // The size is the last fragment's end offset.
182 const MCFragment &F = SD->getFragmentList().back();
183 return getFragmentOffset(&F) + getFragmentEffectiveSize(&F);
186 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
187 // Virtual sections have no file size.
188 if (SD->getSection().isVirtualSection())
191 // Otherwise, the file size is the same as the address space size.
192 return getSectionAddressSize(SD);
195 uint64_t MCAsmLayout::getSectionSize(const MCSectionData *SD) const {
196 // The logical size is the address space size minus any tail padding.
197 uint64_t Size = getSectionAddressSize(SD);
198 const MCAlignFragment *AF =
199 dyn_cast<MCAlignFragment>(&(SD->getFragmentList().back()));
200 if (AF && AF->hasOnlyAlignAddress())
201 Size -= getFragmentEffectiveSize(AF);
208 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
211 MCFragment::~MCFragment() {
214 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
215 : Kind(_Kind), Parent(_Parent), Atom(0), Offset(~UINT64_C(0)),
216 EffectiveSize(~UINT64_C(0))
219 Parent->getFragmentList().push_back(this);
224 MCSectionData::MCSectionData() : Section(0) {}
226 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
227 : Section(&_Section),
229 Address(~UINT64_C(0)),
230 HasInstructions(false)
233 A->getSectionList().push_back(this);
238 MCSymbolData::MCSymbolData() : Symbol(0) {}
240 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
241 uint64_t _Offset, MCAssembler *A)
242 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
243 IsExternal(false), IsPrivateExtern(false),
244 CommonSize(0), SymbolSize(0), CommonAlign(0),
248 A->getSymbolList().push_back(this);
253 MCAssembler::MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
254 MCCodeEmitter &_Emitter, bool _PadSectionToAlignment,
256 : Context(_Context), Backend(_Backend), Emitter(_Emitter),
257 OS(_OS), RelaxAll(false), SubsectionsViaSymbols(false),
258 PadSectionToAlignment(_PadSectionToAlignment)
262 MCAssembler::~MCAssembler() {
265 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
266 // Non-temporary labels should always be visible to the linker.
267 if (!Symbol.isTemporary())
270 // Absolute temporary labels are never visible.
271 if (!Symbol.isInSection())
274 // Otherwise, check if the section requires symbols even for temporary labels.
275 return getBackend().doesSectionRequireSymbols(Symbol.getSection());
278 const MCSymbolData *MCAssembler::getAtom(const MCSymbolData *SD) const {
279 // Linker visible symbols define atoms.
280 if (isSymbolLinkerVisible(SD->getSymbol()))
283 // Absolute and undefined symbols have no defining atom.
284 if (!SD->getFragment())
287 // Non-linker visible symbols in sections which can't be atomized have no
289 if (!getBackend().isSectionAtomizable(
290 SD->getFragment()->getParent()->getSection()))
293 // Otherwise, return the atom for the containing fragment.
294 return SD->getFragment()->getAtom();
297 bool MCAssembler::EvaluateFixup(const MCObjectWriter &Writer,
298 const MCAsmLayout &Layout,
299 const MCFixup &Fixup, const MCFragment *DF,
300 MCValue &Target, uint64_t &Value) const {
301 ++stats::EvaluateFixup;
303 if (!Fixup.getValue()->EvaluateAsRelocatable(Target, &Layout))
304 report_fatal_error("expected relocatable expression");
306 // FIXME: How do non-scattered symbols work in ELF? I presume the linker
307 // doesn't support small relocations, but then under what criteria does the
308 // assembler allow symbol differences?
310 Value = Target.getConstant();
312 bool IsPCRel = Emitter.getFixupKindInfo(
313 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
314 bool IsResolved = true;
315 if (const MCSymbolRefExpr *A = Target.getSymA()) {
316 const MCSymbol &Sym = A->getSymbol().AliasedSymbol();
318 Value += Layout.getSymbolAddress(&getSymbolData(Sym));
322 if (const MCSymbolRefExpr *B = Target.getSymB()) {
323 const MCSymbol &Sym = B->getSymbol().AliasedSymbol();
325 Value -= Layout.getSymbolAddress(&getSymbolData(Sym));
331 IsResolved = Writer.IsFixupFullyResolved(*this, Target, IsPCRel, DF);
334 Value -= Layout.getFragmentAddress(DF) + Fixup.getOffset();
339 uint64_t MCAssembler::ComputeFragmentSize(const MCFragment &F,
340 uint64_t SectionAddress,
341 uint64_t FragmentOffset) const {
342 switch (F.getKind()) {
343 case MCFragment::FT_Data:
344 return cast<MCDataFragment>(F).getContents().size();
345 case MCFragment::FT_Fill:
346 return cast<MCFillFragment>(F).getSize();
347 case MCFragment::FT_Inst:
348 return cast<MCInstFragment>(F).getInstSize();
350 case MCFragment::FT_LEB:
351 return cast<MCLEBFragment>(F).getSize();
353 case MCFragment::FT_Align: {
354 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
356 assert((!AF.hasOnlyAlignAddress() || !AF.getNextNode()) &&
357 "Invalid OnlyAlignAddress bit, not the last fragment!");
359 uint64_t Size = OffsetToAlignment(SectionAddress + FragmentOffset,
362 // Honor MaxBytesToEmit.
363 if (Size > AF.getMaxBytesToEmit())
369 case MCFragment::FT_Org:
370 return cast<MCOrgFragment>(F).getSize();
372 case MCFragment::FT_Dwarf:
373 return cast<MCDwarfLineAddrFragment>(F).getSize();
376 assert(0 && "invalid fragment kind");
380 void MCAsmLayout::LayoutFile() {
381 // Initialize the first section and set the valid fragment layout point. All
382 // actual layout computations are done lazily.
383 LastValidFragment = 0;
384 if (!getSectionOrder().empty())
385 getSectionOrder().front()->Address = 0;
388 void MCAsmLayout::LayoutFragment(MCFragment *F) {
389 MCFragment *Prev = F->getPrevNode();
391 // We should never try to recompute something which is up-to-date.
392 assert(!isFragmentUpToDate(F) && "Attempt to recompute up-to-date fragment!");
393 // We should never try to compute the fragment layout if the section isn't
395 assert(isSectionUpToDate(F->getParent()) &&
396 "Attempt to compute fragment before it's section!");
397 // We should never try to compute the fragment layout if it's predecessor
399 assert((!Prev || isFragmentUpToDate(Prev)) &&
400 "Attempt to compute fragment before it's predecessor!");
402 ++stats::FragmentLayouts;
404 // Compute the fragment start address.
405 uint64_t StartAddress = F->getParent()->Address;
406 uint64_t Address = StartAddress;
408 Address += Prev->Offset + Prev->EffectiveSize;
410 // Compute fragment offset and size.
411 F->Offset = Address - StartAddress;
412 F->EffectiveSize = getAssembler().ComputeFragmentSize(*F, StartAddress,
414 LastValidFragment = F;
416 // If this is the last fragment in a section, update the next section address.
417 if (!F->getNextNode()) {
418 unsigned NextIndex = F->getParent()->getLayoutOrder() + 1;
419 if (NextIndex != getSectionOrder().size())
420 LayoutSection(getSectionOrder()[NextIndex]);
424 void MCAsmLayout::LayoutSection(MCSectionData *SD) {
425 unsigned SectionOrderIndex = SD->getLayoutOrder();
427 ++stats::SectionLayouts;
429 // Compute the section start address.
430 uint64_t StartAddress = 0;
431 if (SectionOrderIndex) {
432 MCSectionData *Prev = getSectionOrder()[SectionOrderIndex - 1];
433 StartAddress = getSectionAddress(Prev) + getSectionAddressSize(Prev);
436 // Honor the section alignment requirements.
437 StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
439 // Set the section address.
440 SD->Address = StartAddress;
443 /// WriteFragmentData - Write the \arg F data to the output file.
444 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
445 const MCFragment &F, MCObjectWriter *OW) {
446 uint64_t Start = OW->getStream().tell();
449 ++stats::EmittedFragments;
451 // FIXME: Embed in fragments instead?
452 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
453 switch (F.getKind()) {
454 case MCFragment::FT_Align: {
455 MCAlignFragment &AF = cast<MCAlignFragment>(F);
456 uint64_t Count = FragmentSize / AF.getValueSize();
458 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
460 // FIXME: This error shouldn't actually occur (the front end should emit
461 // multiple .align directives to enforce the semantics it wants), but is
462 // severe enough that we want to report it. How to handle this?
463 if (Count * AF.getValueSize() != FragmentSize)
464 report_fatal_error("undefined .align directive, value size '" +
465 Twine(AF.getValueSize()) +
466 "' is not a divisor of padding size '" +
467 Twine(FragmentSize) + "'");
469 // See if we are aligning with nops, and if so do that first to try to fill
470 // the Count bytes. Then if that did not fill any bytes or there are any
471 // bytes left to fill use the the Value and ValueSize to fill the rest.
472 // If we are aligning with nops, ask that target to emit the right data.
473 if (AF.hasEmitNops()) {
474 if (!Asm.getBackend().WriteNopData(Count, OW))
475 report_fatal_error("unable to write nop sequence of " +
476 Twine(Count) + " bytes");
480 // Otherwise, write out in multiples of the value size.
481 for (uint64_t i = 0; i != Count; ++i) {
482 switch (AF.getValueSize()) {
484 assert(0 && "Invalid size!");
485 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
486 case 2: OW->Write16(uint16_t(AF.getValue())); break;
487 case 4: OW->Write32(uint32_t(AF.getValue())); break;
488 case 8: OW->Write64(uint64_t(AF.getValue())); break;
494 case MCFragment::FT_Data: {
495 MCDataFragment &DF = cast<MCDataFragment>(F);
496 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
497 OW->WriteBytes(DF.getContents().str());
501 case MCFragment::FT_Fill: {
502 MCFillFragment &FF = cast<MCFillFragment>(F);
504 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
506 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
507 switch (FF.getValueSize()) {
509 assert(0 && "Invalid size!");
510 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
511 case 2: OW->Write16(uint16_t(FF.getValue())); break;
512 case 4: OW->Write32(uint32_t(FF.getValue())); break;
513 case 8: OW->Write64(uint64_t(FF.getValue())); break;
519 case MCFragment::FT_Inst:
520 llvm_unreachable("unexpected inst fragment after lowering");
523 case MCFragment::FT_LEB: {
524 MCLEBFragment &LF = cast<MCLEBFragment>(F);
526 // FIXME: It is probably better if we don't call EvaluateAsAbsolute in
529 bool IsAbs = LF.getValue().EvaluateAsAbsolute(Value, &Layout);
533 raw_svector_ostream OSE(Tmp);
535 MCObjectWriter::EncodeSLEB128(Value, OSE);
537 MCObjectWriter::EncodeULEB128(Value, OSE);
538 OW->WriteBytes(OSE.str());
542 case MCFragment::FT_Org: {
543 MCOrgFragment &OF = cast<MCOrgFragment>(F);
545 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
546 OW->Write8(uint8_t(OF.getValue()));
551 case MCFragment::FT_Dwarf: {
552 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
554 // The AddrDelta is really unsigned and it can only increase.
556 OF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, &Layout);
559 LineDelta = OF.getLineDelta();
561 MCDwarfLineAddr::Write(OW, LineDelta, (uint64_t)AddrDelta);
566 assert(OW->getStream().tell() - Start == FragmentSize);
569 void MCAssembler::WriteSectionData(const MCSectionData *SD,
570 const MCAsmLayout &Layout,
571 MCObjectWriter *OW) const {
572 // Ignore virtual sections.
573 if (SD->getSection().isVirtualSection()) {
574 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
576 // Check that contents are only things legal inside a virtual section.
577 for (MCSectionData::const_iterator it = SD->begin(),
578 ie = SD->end(); it != ie; ++it) {
579 switch (it->getKind()) {
581 assert(0 && "Invalid fragment in virtual section!");
582 case MCFragment::FT_Data: {
583 // Check that we aren't trying to write a non-zero contents (or fixups)
584 // into a virtual section. This is to support clients which use standard
585 // directives to fill the contents of virtual sections.
586 MCDataFragment &DF = cast<MCDataFragment>(*it);
587 assert(DF.fixup_begin() == DF.fixup_end() &&
588 "Cannot have fixups in virtual section!");
589 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
590 assert(DF.getContents()[i] == 0 &&
591 "Invalid data value for virtual section!");
594 case MCFragment::FT_Align:
595 // Check that we aren't trying to write a non-zero value into a virtual
597 assert((!cast<MCAlignFragment>(it)->getValueSize() ||
598 !cast<MCAlignFragment>(it)->getValue()) &&
599 "Invalid align in virtual section!");
601 case MCFragment::FT_Fill:
602 assert(!cast<MCFillFragment>(it)->getValueSize() &&
603 "Invalid fill in virtual section!");
611 uint64_t Start = OW->getStream().tell();
614 for (MCSectionData::const_iterator it = SD->begin(),
615 ie = SD->end(); it != ie; ++it)
616 WriteFragmentData(*this, Layout, *it, OW);
618 assert(OW->getStream().tell() - Start == Layout.getSectionFileSize(SD));
621 void MCAssembler::AddSectionToTheEnd(const MCObjectWriter &Writer,
622 MCSectionData &SD, MCAsmLayout &Layout) {
623 // Create dummy fragments and assign section ordinals.
624 unsigned SectionIndex = size();
625 SD.setOrdinal(SectionIndex);
627 // Assign layout order indices to sections and fragments.
628 const MCFragment &Last = *Layout.getSectionOrder().back()->rbegin();
629 unsigned FragmentIndex = Last.getLayoutOrder() + 1;
631 SD.setLayoutOrder(Layout.getSectionOrder().size());
632 for (MCSectionData::iterator it2 = SD.begin(),
633 ie2 = SD.end(); it2 != ie2; ++it2) {
634 it2->setLayoutOrder(FragmentIndex++);
636 Layout.getSectionOrder().push_back(&SD);
638 Layout.LayoutSection(&SD);
641 void MCAssembler::Finish(MCObjectWriter *Writer) {
642 DEBUG_WITH_TYPE("mc-dump", {
643 llvm::errs() << "assembler backend - pre-layout\n--\n";
646 // Create the layout object.
647 MCAsmLayout Layout(*this);
649 // Insert additional align fragments for concrete sections to explicitly pad
650 // the previous section to match their alignment requirements. This is for
651 // 'gas' compatibility, it shouldn't strictly be necessary.
652 if (PadSectionToAlignment) {
653 for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
654 MCSectionData *SD = Layout.getSectionOrder()[i];
656 // Ignore sections without alignment requirements.
657 unsigned Align = SD->getAlignment();
661 // Ignore virtual sections, they don't cause file size modifications.
662 if (SD->getSection().isVirtualSection())
665 // Otherwise, create a new align fragment at the end of the previous
667 MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
668 Layout.getSectionOrder()[i - 1]);
669 AF->setOnlyAlignAddress(true);
673 // Create dummy fragments and assign section ordinals.
674 unsigned SectionIndex = 0;
675 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
676 // Create dummy fragments to eliminate any empty sections, this simplifies
678 if (it->getFragmentList().empty())
679 new MCDataFragment(it);
681 it->setOrdinal(SectionIndex++);
684 // Assign layout order indices to sections and fragments.
685 unsigned FragmentIndex = 0;
686 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
687 MCSectionData *SD = Layout.getSectionOrder()[i];
688 SD->setLayoutOrder(i);
690 for (MCSectionData::iterator it2 = SD->begin(),
691 ie2 = SD->end(); it2 != ie2; ++it2)
692 it2->setLayoutOrder(FragmentIndex++);
695 llvm::OwningPtr<MCObjectWriter> OwnWriter(0);
697 //no custom Writer_ : create the default one life-managed by OwningPtr
698 OwnWriter.reset(getBackend().createObjectWriter(OS));
699 Writer = OwnWriter.get();
701 report_fatal_error("unable to create object writer!");
704 // Layout until everything fits.
705 while (LayoutOnce(*Writer, Layout))
708 DEBUG_WITH_TYPE("mc-dump", {
709 llvm::errs() << "assembler backend - post-relaxation\n--\n";
712 // Finalize the layout, including fragment lowering.
713 FinishLayout(Layout);
715 DEBUG_WITH_TYPE("mc-dump", {
716 llvm::errs() << "assembler backend - final-layout\n--\n";
719 uint64_t StartOffset = OS.tell();
721 // Allow the object writer a chance to perform post-layout binding (for
722 // example, to set the index fields in the symbol data).
723 Writer->ExecutePostLayoutBinding(*this);
725 // Evaluate and apply the fixups, generating relocation entries as necessary.
726 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
727 for (MCSectionData::iterator it2 = it->begin(),
728 ie2 = it->end(); it2 != ie2; ++it2) {
729 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
733 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
734 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
735 MCFixup &Fixup = *it3;
737 // Evaluate the fixup.
740 if (!EvaluateFixup(*Writer, Layout, Fixup, DF, Target, FixedValue)) {
741 // The fixup was unresolved, we need a relocation. Inform the object
742 // writer of the relocation, and give it an opportunity to adjust the
743 // fixup value if need be.
744 Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
747 getBackend().ApplyFixup(Fixup, *DF, FixedValue);
752 // Write the object file.
753 Writer->WriteObject(*this, Layout);
755 stats::ObjectBytes += OS.tell() - StartOffset;
758 bool MCAssembler::FixupNeedsRelaxation(const MCObjectWriter &Writer,
759 const MCFixup &Fixup,
760 const MCFragment *DF,
761 const MCAsmLayout &Layout) const {
765 // If we cannot resolve the fixup value, it requires relaxation.
768 if (!EvaluateFixup(Writer, Layout, Fixup, DF, Target, Value))
771 // Otherwise, relax if the value is too big for a (signed) i8.
773 // FIXME: This is target dependent!
774 return int64_t(Value) != int64_t(int8_t(Value));
777 bool MCAssembler::FragmentNeedsRelaxation(const MCObjectWriter &Writer,
778 const MCInstFragment *IF,
779 const MCAsmLayout &Layout) const {
780 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
781 // are intentionally pushing out inst fragments, or because we relaxed a
782 // previous instruction to one that doesn't need relaxation.
783 if (!getBackend().MayNeedRelaxation(IF->getInst()))
786 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
787 ie = IF->fixup_end(); it != ie; ++it)
788 if (FixupNeedsRelaxation(Writer, *it, IF, Layout))
794 bool MCAssembler::RelaxInstruction(const MCObjectWriter &Writer,
796 MCInstFragment &IF) {
797 if (!FragmentNeedsRelaxation(Writer, &IF, Layout))
800 ++stats::RelaxedInstructions;
802 // FIXME-PERF: We could immediately lower out instructions if we can tell
803 // they are fully resolved, to avoid retesting on later passes.
805 // Relax the fragment.
808 getBackend().RelaxInstruction(IF.getInst(), Relaxed);
810 // Encode the new instruction.
812 // FIXME-PERF: If it matters, we could let the target do this. It can
813 // probably do so more efficiently in many cases.
814 SmallVector<MCFixup, 4> Fixups;
815 SmallString<256> Code;
816 raw_svector_ostream VecOS(Code);
817 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
820 // Update the instruction fragment.
823 IF.getFixups().clear();
824 // FIXME: Eliminate copy.
825 for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
826 IF.getFixups().push_back(Fixups[i]);
831 bool MCAssembler::RelaxOrg(const MCObjectWriter &Writer,
834 int64_t TargetLocation;
835 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
836 report_fatal_error("expected assembly-time absolute expression");
838 // FIXME: We need a way to communicate this error.
839 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
840 int64_t Offset = TargetLocation - FragmentOffset;
841 if (Offset < 0 || Offset >= 0x40000000)
842 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
843 "' (at offset '" + Twine(FragmentOffset) + "')");
845 unsigned OldSize = OF.getSize();
847 return OldSize != OF.getSize();
850 bool MCAssembler::RelaxLEB(const MCObjectWriter &Writer,
854 LF.getValue().EvaluateAsAbsolute(Value, &Layout);
856 raw_svector_ostream OSE(Tmp);
858 MCObjectWriter::EncodeSLEB128(Value, OSE);
860 MCObjectWriter::EncodeULEB128(Value, OSE);
861 uint64_t OldSize = LF.getSize();
862 LF.setSize(OSE.GetNumBytesInBuffer());
863 return OldSize != LF.getSize();
866 bool MCAssembler::RelaxDwarfLineAddr(const MCObjectWriter &Writer,
868 MCDwarfLineAddrFragment &DF) {
870 DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, &Layout);
872 LineDelta = DF.getLineDelta();
873 uint64_t OldSize = DF.getSize();
874 DF.setSize(MCDwarfLineAddr::ComputeSize(LineDelta, AddrDelta));
875 return OldSize != DF.getSize();
878 bool MCAssembler::LayoutOnce(const MCObjectWriter &Writer,
879 MCAsmLayout &Layout) {
880 ++stats::RelaxationSteps;
882 // Layout the sections in order.
885 // Scan for fragments that need relaxation.
886 bool WasRelaxed = false;
887 for (iterator it = begin(), ie = end(); it != ie; ++it) {
888 MCSectionData &SD = *it;
890 for (MCSectionData::iterator it2 = SD.begin(),
891 ie2 = SD.end(); it2 != ie2; ++it2) {
892 // Check if this is an fragment that needs relaxation.
893 bool relaxedFrag = false;
894 switch(it2->getKind()) {
897 case MCFragment::FT_Inst:
898 relaxedFrag = RelaxInstruction(Writer, Layout,
899 *cast<MCInstFragment>(it2));
901 case MCFragment::FT_Org:
902 relaxedFrag = RelaxOrg(Writer, Layout, *cast<MCOrgFragment>(it2));
904 case MCFragment::FT_Dwarf:
905 relaxedFrag = RelaxDwarfLineAddr(Writer, Layout,
906 *cast<MCDwarfLineAddrFragment>(it2));
908 case MCFragment::FT_LEB:
909 relaxedFrag = RelaxLEB(Writer, Layout, *cast<MCLEBFragment>(it2));
912 // Update the layout, and remember that we relaxed.
914 Layout.Invalidate(it2);
915 WasRelaxed |= relaxedFrag;
922 static void LowerInstFragment(MCInstFragment *IF,
923 MCDataFragment *DF) {
925 uint64_t DataOffset = DF->getContents().size();
928 DF->getContents().append(IF->getCode().begin(), IF->getCode().end());
930 // Adjust the fixup offsets and add them to the data fragment.
931 for (unsigned i = 0, e = IF->getFixups().size(); i != e; ++i) {
932 MCFixup &F = IF->getFixups()[i];
933 F.setOffset(DataOffset + F.getOffset());
934 DF->getFixups().push_back(F);
938 void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
939 // Lower out any instruction fragments, to simplify the fixup application and
942 // FIXME-PERF: We don't have to do this, but the assumption is that it is
943 // cheap (we will mostly end up eliminating fragments and appending on to data
944 // fragments), so the extra complexity downstream isn't worth it. Evaluate
946 unsigned FragmentIndex = 0;
947 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
948 MCSectionData &SD = *Layout.getSectionOrder()[i];
949 MCDataFragment *CurDF = NULL;
951 for (MCSectionData::iterator it2 = SD.begin(),
952 ie2 = SD.end(); it2 != ie2; ++it2) {
953 switch (it2->getKind()) {
957 case MCFragment::FT_Data:
958 CurDF = cast<MCDataFragment>(it2);
960 case MCFragment::FT_Inst: {
961 MCInstFragment *IF = cast<MCInstFragment>(it2);
962 // Use the existing data fragment if possible.
963 if (CurDF && CurDF->getAtom() == IF->getAtom()) {
964 Layout.CoalesceFragments(IF, CurDF);
966 // Otherwise, create a new data fragment.
967 CurDF = new MCDataFragment();
968 Layout.ReplaceFragment(IF, CurDF);
971 // Lower the Instruction Fragment
972 LowerInstFragment(IF, CurDF);
974 // Delete the instruction fragment and update the iterator.
980 // Since we may have merged fragments, fix the layout order.
981 it2->setLayoutOrder(FragmentIndex++);
990 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
991 OS << "<MCFixup" << " Offset:" << AF.getOffset()
992 << " Value:" << *AF.getValue()
993 << " Kind:" << AF.getKind() << ">";
999 void MCFragment::dump() {
1000 raw_ostream &OS = llvm::errs();
1003 switch (getKind()) {
1004 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
1005 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
1006 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
1007 case MCFragment::FT_Inst: OS << "MCInstFragment"; break;
1008 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
1009 case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
1010 case MCFragment::FT_LEB: OS << "MCLEBFragment"; break;
1013 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
1014 << " Offset:" << Offset << " EffectiveSize:" << EffectiveSize << ">";
1016 switch (getKind()) {
1017 case MCFragment::FT_Align: {
1018 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
1019 if (AF->hasEmitNops())
1020 OS << " (emit nops)";
1021 if (AF->hasOnlyAlignAddress())
1022 OS << " (only align section)";
1024 OS << " Alignment:" << AF->getAlignment()
1025 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
1026 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
1029 case MCFragment::FT_Data: {
1030 const MCDataFragment *DF = cast<MCDataFragment>(this);
1032 OS << " Contents:[";
1033 const SmallVectorImpl<char> &Contents = DF->getContents();
1034 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
1036 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1038 OS << "] (" << Contents.size() << " bytes)";
1040 if (!DF->getFixups().empty()) {
1043 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
1044 ie = DF->fixup_end(); it != ie; ++it) {
1045 if (it != DF->fixup_begin()) OS << ",\n ";
1052 case MCFragment::FT_Fill: {
1053 const MCFillFragment *FF = cast<MCFillFragment>(this);
1054 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
1055 << " Size:" << FF->getSize();
1058 case MCFragment::FT_Inst: {
1059 const MCInstFragment *IF = cast<MCInstFragment>(this);
1062 IF->getInst().dump_pretty(OS);
1065 case MCFragment::FT_Org: {
1066 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
1068 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
1071 case MCFragment::FT_Dwarf: {
1072 const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
1074 OS << " AddrDelta:" << OF->getAddrDelta()
1075 << " LineDelta:" << OF->getLineDelta();
1078 case MCFragment::FT_LEB: {
1079 const MCLEBFragment *LF = cast<MCLEBFragment>(this);
1081 OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
1088 void MCSectionData::dump() {
1089 raw_ostream &OS = llvm::errs();
1091 OS << "<MCSectionData";
1092 OS << " Alignment:" << getAlignment() << " Address:" << Address
1093 << " Fragments:[\n ";
1094 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1095 if (it != begin()) OS << ",\n ";
1101 void MCSymbolData::dump() {
1102 raw_ostream &OS = llvm::errs();
1104 OS << "<MCSymbolData Symbol:" << getSymbol()
1105 << " Fragment:" << getFragment() << " Offset:" << getOffset()
1106 << " Flags:" << getFlags() << " Index:" << getIndex();
1108 OS << " (common, size:" << getCommonSize()
1109 << " align: " << getCommonAlignment() << ")";
1111 OS << " (external)";
1112 if (isPrivateExtern())
1113 OS << " (private extern)";
1117 void MCAssembler::dump() {
1118 raw_ostream &OS = llvm::errs();
1120 OS << "<MCAssembler\n";
1121 OS << " Sections:[\n ";
1122 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1123 if (it != begin()) OS << ",\n ";
1129 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1130 if (it != symbol_begin()) OS << ",\n ";