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());
126 Dst->Offset = Src->Offset;
127 Dst->EffectiveSize = Src->EffectiveSize;
129 // Remove Src, but don't delete it yet.
130 SD->getFragmentList().remove(Src);
133 void MCAsmLayout::CoalesceFragments(MCFragment *Src, MCFragment *Dst) {
134 assert(Src->getPrevNode() == Dst);
135 Dst->EffectiveSize += Src->EffectiveSize;
136 // Remove Src, but don't delete it yet.
137 Src->getParent()->getFragmentList().remove(Src);
140 uint64_t MCAsmLayout::getFragmentAddress(const MCFragment *F) const {
141 assert(F->getParent() && "Missing section()!");
142 return getSectionAddress(F->getParent()) + getFragmentOffset(F);
145 uint64_t MCAsmLayout::getFragmentEffectiveSize(const MCFragment *F) const {
147 assert(F->EffectiveSize != ~UINT64_C(0) && "Address not set!");
148 return F->EffectiveSize;
151 uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
153 assert(F->Offset != ~UINT64_C(0) && "Address not set!");
157 uint64_t MCAsmLayout::getSymbolOffset(const MCSymbolData *SD) const {
158 assert(SD->getFragment() && "Invalid getOffset() on undefined symbol!");
159 return getFragmentOffset(SD->getFragment()) + SD->getOffset();
162 uint64_t MCAsmLayout::getSymbolAddress(const MCSymbolData *SD) const {
163 assert(SD->getFragment() && "Invalid getAddress() on undefined symbol!");
164 return getFragmentAddress(SD->getFragment()) + SD->getOffset();
167 uint64_t MCAsmLayout::getSectionAddress(const MCSectionData *SD) const {
168 EnsureValid(SD->begin());
169 assert(SD->Address != ~UINT64_C(0) && "Address not set!");
173 uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const {
174 // The size is the last fragment's end offset.
175 const MCFragment &F = SD->getFragmentList().back();
176 return getFragmentOffset(&F) + getFragmentEffectiveSize(&F);
179 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
180 // Virtual sections have no file size.
181 if (SD->getSection().isVirtualSection())
184 // Otherwise, the file size is the same as the address space size.
185 return getSectionAddressSize(SD);
188 uint64_t MCAsmLayout::getSectionSize(const MCSectionData *SD) const {
189 // The logical size is the address space size minus any tail padding.
190 uint64_t Size = getSectionAddressSize(SD);
191 const MCAlignFragment *AF =
192 dyn_cast<MCAlignFragment>(&(SD->getFragmentList().back()));
193 if (AF && AF->hasOnlyAlignAddress())
194 Size -= getFragmentEffectiveSize(AF);
201 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
204 MCFragment::~MCFragment() {
207 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
208 : Kind(_Kind), Parent(_Parent), Atom(0), Offset(~UINT64_C(0)),
209 EffectiveSize(~UINT64_C(0))
212 Parent->getFragmentList().push_back(this);
217 MCSectionData::MCSectionData() : Section(0) {}
219 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
220 : Section(&_Section),
221 Ordinal(~UINT32_C(0)),
223 Address(~UINT64_C(0)),
224 HasInstructions(false)
227 A->getSectionList().push_back(this);
232 MCSymbolData::MCSymbolData() : Symbol(0) {}
234 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
235 uint64_t _Offset, MCAssembler *A)
236 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
237 IsExternal(false), IsPrivateExtern(false),
238 CommonSize(0), SymbolSize(0), CommonAlign(0),
242 A->getSymbolList().push_back(this);
247 MCAssembler::MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
248 MCCodeEmitter &_Emitter, bool _PadSectionToAlignment,
250 : Context(_Context), Backend(_Backend), Emitter(_Emitter),
251 OS(_OS), RelaxAll(false), SubsectionsViaSymbols(false),
252 PadSectionToAlignment(_PadSectionToAlignment)
256 MCAssembler::~MCAssembler() {
259 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
260 // Non-temporary labels should always be visible to the linker.
261 if (!Symbol.isTemporary())
264 // Absolute temporary labels are never visible.
265 if (!Symbol.isInSection())
268 // Otherwise, check if the section requires symbols even for temporary labels.
269 return getBackend().doesSectionRequireSymbols(Symbol.getSection());
272 const MCSymbolData *MCAssembler::getAtom(const MCSymbolData *SD) const {
273 // Linker visible symbols define atoms.
274 if (isSymbolLinkerVisible(SD->getSymbol()))
277 // Absolute and undefined symbols have no defining atom.
278 if (!SD->getFragment())
281 // Non-linker visible symbols in sections which can't be atomized have no
283 if (!getBackend().isSectionAtomizable(
284 SD->getFragment()->getParent()->getSection()))
287 // Otherwise, return the atom for the containing fragment.
288 return SD->getFragment()->getAtom();
291 bool MCAssembler::EvaluateFixup(const MCObjectWriter &Writer,
292 const MCAsmLayout &Layout,
293 const MCFixup &Fixup, const MCFragment *DF,
294 MCValue &Target, uint64_t &Value) const {
295 ++stats::EvaluateFixup;
297 if (!Fixup.getValue()->EvaluateAsRelocatable(Target, &Layout))
298 report_fatal_error("expected relocatable expression");
300 // FIXME: How do non-scattered symbols work in ELF? I presume the linker
301 // doesn't support small relocations, but then under what criteria does the
302 // assembler allow symbol differences?
304 Value = Target.getConstant();
306 bool IsPCRel = Emitter.getFixupKindInfo(
307 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
308 bool IsResolved = true;
309 if (const MCSymbolRefExpr *A = Target.getSymA()) {
310 const MCSymbol &Sym = A->getSymbol().AliasedSymbol();
312 Value += Layout.getSymbolAddress(&getSymbolData(Sym));
316 if (const MCSymbolRefExpr *B = Target.getSymB()) {
317 const MCSymbol &Sym = B->getSymbol().AliasedSymbol();
319 Value -= Layout.getSymbolAddress(&getSymbolData(Sym));
325 IsResolved = Writer.IsFixupFullyResolved(*this, Target, IsPCRel, DF);
328 Value -= Layout.getFragmentAddress(DF) + Fixup.getOffset();
333 uint64_t MCAssembler::ComputeFragmentSize(const MCFragment &F,
334 uint64_t SectionAddress,
335 uint64_t FragmentOffset) const {
336 switch (F.getKind()) {
337 case MCFragment::FT_Data:
338 return cast<MCDataFragment>(F).getContents().size();
339 case MCFragment::FT_Fill:
340 return cast<MCFillFragment>(F).getSize();
341 case MCFragment::FT_Inst:
342 return cast<MCInstFragment>(F).getInstSize();
344 case MCFragment::FT_LEB:
345 return cast<MCLEBFragment>(F).getContents().size();
347 case MCFragment::FT_Align: {
348 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
350 assert((!AF.hasOnlyAlignAddress() || !AF.getNextNode()) &&
351 "Invalid OnlyAlignAddress bit, not the last fragment!");
353 uint64_t Size = OffsetToAlignment(SectionAddress + FragmentOffset,
356 // Honor MaxBytesToEmit.
357 if (Size > AF.getMaxBytesToEmit())
363 case MCFragment::FT_Org:
364 return cast<MCOrgFragment>(F).getSize();
366 case MCFragment::FT_Dwarf:
367 return cast<MCDwarfLineAddrFragment>(F).getContents().size();
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(*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_LEB: {
518 MCLEBFragment &LF = cast<MCLEBFragment>(F);
519 OW->WriteBytes(LF.getContents().str());
523 case MCFragment::FT_Org: {
524 MCOrgFragment &OF = cast<MCOrgFragment>(F);
526 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
527 OW->Write8(uint8_t(OF.getValue()));
532 case MCFragment::FT_Dwarf: {
533 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
534 OW->WriteBytes(OF.getContents().str());
539 assert(OW->getStream().tell() - Start == FragmentSize);
542 void MCAssembler::WriteSectionData(const MCSectionData *SD,
543 const MCAsmLayout &Layout,
544 MCObjectWriter *OW) const {
545 // Ignore virtual sections.
546 if (SD->getSection().isVirtualSection()) {
547 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
549 // Check that contents are only things legal inside a virtual section.
550 for (MCSectionData::const_iterator it = SD->begin(),
551 ie = SD->end(); it != ie; ++it) {
552 switch (it->getKind()) {
554 assert(0 && "Invalid fragment in virtual section!");
555 case MCFragment::FT_Data: {
556 // Check that we aren't trying to write a non-zero contents (or fixups)
557 // into a virtual section. This is to support clients which use standard
558 // directives to fill the contents of virtual sections.
559 MCDataFragment &DF = cast<MCDataFragment>(*it);
560 assert(DF.fixup_begin() == DF.fixup_end() &&
561 "Cannot have fixups in virtual section!");
562 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
563 assert(DF.getContents()[i] == 0 &&
564 "Invalid data value for virtual section!");
567 case MCFragment::FT_Align:
568 // Check that we aren't trying to write a non-zero value into a virtual
570 assert((!cast<MCAlignFragment>(it)->getValueSize() ||
571 !cast<MCAlignFragment>(it)->getValue()) &&
572 "Invalid align in virtual section!");
574 case MCFragment::FT_Fill:
575 assert(!cast<MCFillFragment>(it)->getValueSize() &&
576 "Invalid fill in virtual section!");
584 uint64_t Start = OW->getStream().tell();
587 for (MCSectionData::const_iterator it = SD->begin(),
588 ie = SD->end(); it != ie; ++it)
589 WriteFragmentData(*this, Layout, *it, OW);
591 assert(OW->getStream().tell() - Start == Layout.getSectionFileSize(SD));
594 void MCAssembler::Finish(MCObjectWriter *Writer) {
595 DEBUG_WITH_TYPE("mc-dump", {
596 llvm::errs() << "assembler backend - pre-layout\n--\n";
599 // Create the layout object.
600 MCAsmLayout Layout(*this);
602 // Insert additional align fragments for concrete sections to explicitly pad
603 // the previous section to match their alignment requirements. This is for
604 // 'gas' compatibility, it shouldn't strictly be necessary.
605 if (PadSectionToAlignment) {
606 for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
607 MCSectionData *SD = Layout.getSectionOrder()[i];
609 // Ignore sections without alignment requirements.
610 unsigned Align = SD->getAlignment();
614 // Ignore virtual sections, they don't cause file size modifications.
615 if (SD->getSection().isVirtualSection())
618 // Otherwise, create a new align fragment at the end of the previous
620 MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
621 Layout.getSectionOrder()[i - 1]);
622 AF->setOnlyAlignAddress(true);
626 // Create dummy fragments and assign section ordinals.
627 unsigned SectionIndex = 0;
628 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
629 // Create dummy fragments to eliminate any empty sections, this simplifies
631 if (it->getFragmentList().empty())
632 new MCDataFragment(it);
634 it->setOrdinal(SectionIndex++);
637 // Assign layout order indices to sections and fragments.
638 unsigned FragmentIndex = 0;
639 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
640 MCSectionData *SD = Layout.getSectionOrder()[i];
641 SD->setLayoutOrder(i);
643 for (MCSectionData::iterator it2 = SD->begin(),
644 ie2 = SD->end(); it2 != ie2; ++it2)
645 it2->setLayoutOrder(FragmentIndex++);
648 llvm::OwningPtr<MCObjectWriter> OwnWriter(0);
650 //no custom Writer_ : create the default one life-managed by OwningPtr
651 OwnWriter.reset(getBackend().createObjectWriter(OS));
652 Writer = OwnWriter.get();
654 report_fatal_error("unable to create object writer!");
657 // Layout until everything fits.
658 while (LayoutOnce(*Writer, Layout))
661 DEBUG_WITH_TYPE("mc-dump", {
662 llvm::errs() << "assembler backend - post-relaxation\n--\n";
665 // Finalize the layout, including fragment lowering.
666 FinishLayout(Layout);
668 DEBUG_WITH_TYPE("mc-dump", {
669 llvm::errs() << "assembler backend - final-layout\n--\n";
672 uint64_t StartOffset = OS.tell();
674 // Allow the object writer a chance to perform post-layout binding (for
675 // example, to set the index fields in the symbol data).
676 Writer->ExecutePostLayoutBinding(*this);
678 // Evaluate and apply the fixups, generating relocation entries as necessary.
679 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
680 for (MCSectionData::iterator it2 = it->begin(),
681 ie2 = it->end(); it2 != ie2; ++it2) {
682 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
686 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
687 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
688 MCFixup &Fixup = *it3;
690 // Evaluate the fixup.
693 if (!EvaluateFixup(*Writer, Layout, Fixup, DF, Target, FixedValue)) {
694 // The fixup was unresolved, we need a relocation. Inform the object
695 // writer of the relocation, and give it an opportunity to adjust the
696 // fixup value if need be.
697 Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
700 getBackend().ApplyFixup(Fixup, *DF, FixedValue);
705 // Write the object file.
706 Writer->WriteObject(*this, Layout);
708 stats::ObjectBytes += OS.tell() - StartOffset;
711 bool MCAssembler::FixupNeedsRelaxation(const MCObjectWriter &Writer,
712 const MCFixup &Fixup,
713 const MCFragment *DF,
714 const MCAsmLayout &Layout) const {
718 // If we cannot resolve the fixup value, it requires relaxation.
721 if (!EvaluateFixup(Writer, Layout, Fixup, DF, Target, Value))
724 // Otherwise, relax if the value is too big for a (signed) i8.
726 // FIXME: This is target dependent!
727 return int64_t(Value) != int64_t(int8_t(Value));
730 bool MCAssembler::FragmentNeedsRelaxation(const MCObjectWriter &Writer,
731 const MCInstFragment *IF,
732 const MCAsmLayout &Layout) const {
733 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
734 // are intentionally pushing out inst fragments, or because we relaxed a
735 // previous instruction to one that doesn't need relaxation.
736 if (!getBackend().MayNeedRelaxation(IF->getInst()))
739 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
740 ie = IF->fixup_end(); it != ie; ++it)
741 if (FixupNeedsRelaxation(Writer, *it, IF, Layout))
747 bool MCAssembler::RelaxInstruction(const MCObjectWriter &Writer,
749 MCInstFragment &IF) {
750 if (!FragmentNeedsRelaxation(Writer, &IF, Layout))
753 ++stats::RelaxedInstructions;
755 // FIXME-PERF: We could immediately lower out instructions if we can tell
756 // they are fully resolved, to avoid retesting on later passes.
758 // Relax the fragment.
761 getBackend().RelaxInstruction(IF.getInst(), Relaxed);
763 // Encode the new instruction.
765 // FIXME-PERF: If it matters, we could let the target do this. It can
766 // probably do so more efficiently in many cases.
767 SmallVector<MCFixup, 4> Fixups;
768 SmallString<256> Code;
769 raw_svector_ostream VecOS(Code);
770 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
773 // Update the instruction fragment.
776 IF.getFixups().clear();
777 // FIXME: Eliminate copy.
778 for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
779 IF.getFixups().push_back(Fixups[i]);
784 bool MCAssembler::RelaxOrg(const MCObjectWriter &Writer,
787 int64_t TargetLocation;
788 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
789 report_fatal_error("expected assembly-time absolute expression");
791 // FIXME: We need a way to communicate this error.
792 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
793 int64_t Offset = TargetLocation - FragmentOffset;
794 if (Offset < 0 || Offset >= 0x40000000)
795 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
796 "' (at offset '" + Twine(FragmentOffset) + "')");
798 unsigned OldSize = OF.getSize();
800 return OldSize != OF.getSize();
803 bool MCAssembler::RelaxLEB(const MCObjectWriter &Writer,
807 uint64_t OldSize = LF.getContents().size();
808 LF.getValue().EvaluateAsAbsolute(Value, &Layout);
809 SmallString<8> &Data = LF.getContents();
811 raw_svector_ostream OSE(Data);
813 MCObjectWriter::EncodeSLEB128(Value, OSE);
815 MCObjectWriter::EncodeULEB128(Value, OSE);
817 return OldSize != LF.getContents().size();
820 bool MCAssembler::RelaxDwarfLineAddr(const MCObjectWriter &Writer,
822 MCDwarfLineAddrFragment &DF) {
823 int64_t AddrDelta = 0;
824 uint64_t OldSize = DF.getContents().size();
825 DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, &Layout);
827 LineDelta = DF.getLineDelta();
828 SmallString<8> &Data = DF.getContents();
830 raw_svector_ostream OSE(Data);
831 MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OSE);
833 return OldSize != Data.size();
836 bool MCAssembler::LayoutOnce(const MCObjectWriter &Writer,
837 MCAsmLayout &Layout) {
838 ++stats::RelaxationSteps;
840 // Layout the sections in order.
843 // Scan for fragments that need relaxation.
844 bool WasRelaxed = false;
845 for (iterator it = begin(), ie = end(); it != ie; ++it) {
846 MCSectionData &SD = *it;
848 for (MCSectionData::iterator it2 = SD.begin(),
849 ie2 = SD.end(); it2 != ie2; ++it2) {
850 // Check if this is an fragment that needs relaxation.
851 bool relaxedFrag = false;
852 switch(it2->getKind()) {
855 case MCFragment::FT_Inst:
856 relaxedFrag = RelaxInstruction(Writer, Layout,
857 *cast<MCInstFragment>(it2));
859 case MCFragment::FT_Org:
860 relaxedFrag = RelaxOrg(Writer, Layout, *cast<MCOrgFragment>(it2));
862 case MCFragment::FT_Dwarf:
863 relaxedFrag = RelaxDwarfLineAddr(Writer, Layout,
864 *cast<MCDwarfLineAddrFragment>(it2));
866 case MCFragment::FT_LEB:
867 relaxedFrag = RelaxLEB(Writer, Layout, *cast<MCLEBFragment>(it2));
870 // Update the layout, and remember that we relaxed.
872 Layout.Invalidate(it2);
873 WasRelaxed |= relaxedFrag;
880 static void LowerInstFragment(MCInstFragment *IF,
881 MCDataFragment *DF) {
883 uint64_t DataOffset = DF->getContents().size();
886 DF->getContents().append(IF->getCode().begin(), IF->getCode().end());
888 // Adjust the fixup offsets and add them to the data fragment.
889 for (unsigned i = 0, e = IF->getFixups().size(); i != e; ++i) {
890 MCFixup &F = IF->getFixups()[i];
891 F.setOffset(DataOffset + F.getOffset());
892 DF->getFixups().push_back(F);
896 void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
897 // Lower out any instruction fragments, to simplify the fixup application and
900 // FIXME-PERF: We don't have to do this, but the assumption is that it is
901 // cheap (we will mostly end up eliminating fragments and appending on to data
902 // fragments), so the extra complexity downstream isn't worth it. Evaluate
905 // The layout is done. Mark every fragment as valid.
906 Layout.getFragmentOffset(&*Layout.getSectionOrder().back()->rbegin());
908 unsigned FragmentIndex = 0;
909 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
910 MCSectionData &SD = *Layout.getSectionOrder()[i];
911 MCDataFragment *CurDF = NULL;
913 for (MCSectionData::iterator it2 = SD.begin(),
914 ie2 = SD.end(); it2 != ie2; ++it2) {
915 switch (it2->getKind()) {
919 case MCFragment::FT_Data:
920 CurDF = cast<MCDataFragment>(it2);
922 case MCFragment::FT_Inst: {
923 MCInstFragment *IF = cast<MCInstFragment>(it2);
924 // Use the existing data fragment if possible.
925 if (CurDF && CurDF->getAtom() == IF->getAtom()) {
926 Layout.CoalesceFragments(IF, CurDF);
928 // Otherwise, create a new data fragment.
929 CurDF = new MCDataFragment();
930 Layout.ReplaceFragment(IF, CurDF);
933 // Lower the Instruction Fragment
934 LowerInstFragment(IF, CurDF);
936 // Delete the instruction fragment and update the iterator.
942 // Since we may have merged fragments, fix the layout order.
943 it2->setLayoutOrder(FragmentIndex++);
952 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
953 OS << "<MCFixup" << " Offset:" << AF.getOffset()
954 << " Value:" << *AF.getValue()
955 << " Kind:" << AF.getKind() << ">";
961 void MCFragment::dump() {
962 raw_ostream &OS = llvm::errs();
966 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
967 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
968 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
969 case MCFragment::FT_Inst: OS << "MCInstFragment"; break;
970 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
971 case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
972 case MCFragment::FT_LEB: OS << "MCLEBFragment"; break;
975 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
976 << " Offset:" << Offset << " EffectiveSize:" << EffectiveSize << ">";
979 case MCFragment::FT_Align: {
980 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
981 if (AF->hasEmitNops())
982 OS << " (emit nops)";
983 if (AF->hasOnlyAlignAddress())
984 OS << " (only align section)";
986 OS << " Alignment:" << AF->getAlignment()
987 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
988 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
991 case MCFragment::FT_Data: {
992 const MCDataFragment *DF = cast<MCDataFragment>(this);
995 const SmallVectorImpl<char> &Contents = DF->getContents();
996 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
998 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1000 OS << "] (" << Contents.size() << " bytes)";
1002 if (!DF->getFixups().empty()) {
1005 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
1006 ie = DF->fixup_end(); it != ie; ++it) {
1007 if (it != DF->fixup_begin()) OS << ",\n ";
1014 case MCFragment::FT_Fill: {
1015 const MCFillFragment *FF = cast<MCFillFragment>(this);
1016 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
1017 << " Size:" << FF->getSize();
1020 case MCFragment::FT_Inst: {
1021 const MCInstFragment *IF = cast<MCInstFragment>(this);
1024 IF->getInst().dump_pretty(OS);
1027 case MCFragment::FT_Org: {
1028 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
1030 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
1033 case MCFragment::FT_Dwarf: {
1034 const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
1036 OS << " AddrDelta:" << OF->getAddrDelta()
1037 << " LineDelta:" << OF->getLineDelta();
1040 case MCFragment::FT_LEB: {
1041 const MCLEBFragment *LF = cast<MCLEBFragment>(this);
1043 OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
1050 void MCSectionData::dump() {
1051 raw_ostream &OS = llvm::errs();
1053 OS << "<MCSectionData";
1054 OS << " Alignment:" << getAlignment() << " Address:" << Address
1055 << " Fragments:[\n ";
1056 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1057 if (it != begin()) OS << ",\n ";
1063 void MCSymbolData::dump() {
1064 raw_ostream &OS = llvm::errs();
1066 OS << "<MCSymbolData Symbol:" << getSymbol()
1067 << " Fragment:" << getFragment() << " Offset:" << getOffset()
1068 << " Flags:" << getFlags() << " Index:" << getIndex();
1070 OS << " (common, size:" << getCommonSize()
1071 << " align: " << getCommonAlignment() << ")";
1073 OS << " (external)";
1074 if (isPrivateExtern())
1075 OS << " (private extern)";
1079 void MCAssembler::dump() {
1080 raw_ostream &OS = llvm::errs();
1082 OS << "<MCAssembler\n";
1083 OS << " Sections:[\n ";
1084 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1085 if (it != begin()) OS << ",\n ";
1091 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1092 if (it != symbol_begin()) OS << ",\n ";