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),
222 Address(~UINT64_C(0)),
223 HasInstructions(false)
226 A->getSectionList().push_back(this);
231 MCSymbolData::MCSymbolData() : Symbol(0) {}
233 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
234 uint64_t _Offset, MCAssembler *A)
235 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
236 IsExternal(false), IsPrivateExtern(false),
237 CommonSize(0), SymbolSize(0), CommonAlign(0),
241 A->getSymbolList().push_back(this);
246 MCAssembler::MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
247 MCCodeEmitter &_Emitter, bool _PadSectionToAlignment,
249 : Context(_Context), Backend(_Backend), Emitter(_Emitter),
250 OS(_OS), RelaxAll(false), SubsectionsViaSymbols(false),
251 PadSectionToAlignment(_PadSectionToAlignment)
255 MCAssembler::~MCAssembler() {
258 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
259 // Non-temporary labels should always be visible to the linker.
260 if (!Symbol.isTemporary())
263 // Absolute temporary labels are never visible.
264 if (!Symbol.isInSection())
267 // Otherwise, check if the section requires symbols even for temporary labels.
268 return getBackend().doesSectionRequireSymbols(Symbol.getSection());
271 const MCSymbolData *MCAssembler::getAtom(const MCSymbolData *SD) const {
272 // Linker visible symbols define atoms.
273 if (isSymbolLinkerVisible(SD->getSymbol()))
276 // Absolute and undefined symbols have no defining atom.
277 if (!SD->getFragment())
280 // Non-linker visible symbols in sections which can't be atomized have no
282 if (!getBackend().isSectionAtomizable(
283 SD->getFragment()->getParent()->getSection()))
286 // Otherwise, return the atom for the containing fragment.
287 return SD->getFragment()->getAtom();
290 bool MCAssembler::EvaluateFixup(const MCObjectWriter &Writer,
291 const MCAsmLayout &Layout,
292 const MCFixup &Fixup, const MCFragment *DF,
293 MCValue &Target, uint64_t &Value) const {
294 ++stats::EvaluateFixup;
296 if (!Fixup.getValue()->EvaluateAsRelocatable(Target, &Layout))
297 report_fatal_error("expected relocatable expression");
299 // FIXME: How do non-scattered symbols work in ELF? I presume the linker
300 // doesn't support small relocations, but then under what criteria does the
301 // assembler allow symbol differences?
303 Value = Target.getConstant();
305 bool IsPCRel = Emitter.getFixupKindInfo(
306 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
307 bool IsResolved = true;
308 if (const MCSymbolRefExpr *A = Target.getSymA()) {
309 const MCSymbol &Sym = A->getSymbol().AliasedSymbol();
311 Value += Layout.getSymbolAddress(&getSymbolData(Sym));
315 if (const MCSymbolRefExpr *B = Target.getSymB()) {
316 const MCSymbol &Sym = B->getSymbol().AliasedSymbol();
318 Value -= Layout.getSymbolAddress(&getSymbolData(Sym));
324 IsResolved = Writer.IsFixupFullyResolved(*this, Target, IsPCRel, DF);
327 Value -= Layout.getFragmentAddress(DF) + Fixup.getOffset();
332 uint64_t MCAssembler::ComputeFragmentSize(const MCFragment &F,
333 uint64_t SectionAddress,
334 uint64_t FragmentOffset) const {
335 switch (F.getKind()) {
336 case MCFragment::FT_Data:
337 return cast<MCDataFragment>(F).getContents().size();
338 case MCFragment::FT_Fill:
339 return cast<MCFillFragment>(F).getSize();
340 case MCFragment::FT_Inst:
341 return cast<MCInstFragment>(F).getInstSize();
343 case MCFragment::FT_LEB:
344 return cast<MCLEBFragment>(F).getContents().size();
346 case MCFragment::FT_Align: {
347 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
349 assert((!AF.hasOnlyAlignAddress() || !AF.getNextNode()) &&
350 "Invalid OnlyAlignAddress bit, not the last fragment!");
352 uint64_t Size = OffsetToAlignment(SectionAddress + FragmentOffset,
355 // Honor MaxBytesToEmit.
356 if (Size > AF.getMaxBytesToEmit())
362 case MCFragment::FT_Org:
363 return cast<MCOrgFragment>(F).getSize();
365 case MCFragment::FT_Dwarf:
366 return cast<MCDwarfLineAddrFragment>(F).getContents().size();
369 assert(0 && "invalid fragment kind");
373 void MCAsmLayout::LayoutFile() {
374 // Initialize the first section and set the valid fragment layout point. All
375 // actual layout computations are done lazily.
376 LastValidFragment = 0;
377 if (!getSectionOrder().empty())
378 getSectionOrder().front()->Address = 0;
381 void MCAsmLayout::LayoutFragment(MCFragment *F) {
382 MCFragment *Prev = F->getPrevNode();
384 // We should never try to recompute something which is up-to-date.
385 assert(!isFragmentUpToDate(F) && "Attempt to recompute up-to-date fragment!");
386 // We should never try to compute the fragment layout if the section isn't
388 assert(isSectionUpToDate(F->getParent()) &&
389 "Attempt to compute fragment before it's section!");
390 // We should never try to compute the fragment layout if it's predecessor
392 assert((!Prev || isFragmentUpToDate(Prev)) &&
393 "Attempt to compute fragment before it's predecessor!");
395 ++stats::FragmentLayouts;
397 // Compute the fragment start address.
398 uint64_t StartAddress = F->getParent()->Address;
399 uint64_t Address = StartAddress;
401 Address += Prev->Offset + Prev->EffectiveSize;
403 // Compute fragment offset and size.
404 F->Offset = Address - StartAddress;
405 F->EffectiveSize = getAssembler().ComputeFragmentSize(*F, StartAddress,
407 LastValidFragment = F;
409 // If this is the last fragment in a section, update the next section address.
410 if (!F->getNextNode()) {
411 unsigned NextIndex = F->getParent()->getLayoutOrder() + 1;
412 if (NextIndex != getSectionOrder().size())
413 LayoutSection(getSectionOrder()[NextIndex]);
417 void MCAsmLayout::LayoutSection(MCSectionData *SD) {
418 unsigned SectionOrderIndex = SD->getLayoutOrder();
420 ++stats::SectionLayouts;
422 // Compute the section start address.
423 uint64_t StartAddress = 0;
424 if (SectionOrderIndex) {
425 MCSectionData *Prev = getSectionOrder()[SectionOrderIndex - 1];
426 StartAddress = getSectionAddress(Prev) + getSectionAddressSize(Prev);
429 // Honor the section alignment requirements.
430 StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
432 // Set the section address.
433 SD->Address = StartAddress;
436 /// WriteFragmentData - Write the \arg F data to the output file.
437 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
438 const MCFragment &F, MCObjectWriter *OW) {
439 uint64_t Start = OW->getStream().tell();
442 ++stats::EmittedFragments;
444 // FIXME: Embed in fragments instead?
445 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
446 switch (F.getKind()) {
447 case MCFragment::FT_Align: {
448 MCAlignFragment &AF = cast<MCAlignFragment>(F);
449 uint64_t Count = FragmentSize / AF.getValueSize();
451 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
453 // FIXME: This error shouldn't actually occur (the front end should emit
454 // multiple .align directives to enforce the semantics it wants), but is
455 // severe enough that we want to report it. How to handle this?
456 if (Count * AF.getValueSize() != FragmentSize)
457 report_fatal_error("undefined .align directive, value size '" +
458 Twine(AF.getValueSize()) +
459 "' is not a divisor of padding size '" +
460 Twine(FragmentSize) + "'");
462 // See if we are aligning with nops, and if so do that first to try to fill
463 // the Count bytes. Then if that did not fill any bytes or there are any
464 // bytes left to fill use the the Value and ValueSize to fill the rest.
465 // If we are aligning with nops, ask that target to emit the right data.
466 if (AF.hasEmitNops()) {
467 if (!Asm.getBackend().WriteNopData(Count, OW))
468 report_fatal_error("unable to write nop sequence of " +
469 Twine(Count) + " bytes");
473 // Otherwise, write out in multiples of the value size.
474 for (uint64_t i = 0; i != Count; ++i) {
475 switch (AF.getValueSize()) {
477 assert(0 && "Invalid size!");
478 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
479 case 2: OW->Write16(uint16_t(AF.getValue())); break;
480 case 4: OW->Write32(uint32_t(AF.getValue())); break;
481 case 8: OW->Write64(uint64_t(AF.getValue())); break;
487 case MCFragment::FT_Data: {
488 MCDataFragment &DF = cast<MCDataFragment>(F);
489 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
490 OW->WriteBytes(DF.getContents().str());
494 case MCFragment::FT_Fill: {
495 MCFillFragment &FF = cast<MCFillFragment>(F);
497 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
499 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
500 switch (FF.getValueSize()) {
502 assert(0 && "Invalid size!");
503 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
504 case 2: OW->Write16(uint16_t(FF.getValue())); break;
505 case 4: OW->Write32(uint32_t(FF.getValue())); break;
506 case 8: OW->Write64(uint64_t(FF.getValue())); break;
512 case MCFragment::FT_Inst:
513 llvm_unreachable("unexpected inst fragment after lowering");
516 case MCFragment::FT_LEB: {
517 MCLEBFragment &LF = cast<MCLEBFragment>(F);
518 OW->WriteBytes(LF.getContents().str());
522 case MCFragment::FT_Org: {
523 MCOrgFragment &OF = cast<MCOrgFragment>(F);
525 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
526 OW->Write8(uint8_t(OF.getValue()));
531 case MCFragment::FT_Dwarf: {
532 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
533 OW->WriteBytes(OF.getContents().str());
538 assert(OW->getStream().tell() - Start == FragmentSize);
541 void MCAssembler::WriteSectionData(const MCSectionData *SD,
542 const MCAsmLayout &Layout,
543 MCObjectWriter *OW) const {
544 // Ignore virtual sections.
545 if (SD->getSection().isVirtualSection()) {
546 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
548 // Check that contents are only things legal inside a virtual section.
549 for (MCSectionData::const_iterator it = SD->begin(),
550 ie = SD->end(); it != ie; ++it) {
551 switch (it->getKind()) {
553 assert(0 && "Invalid fragment in virtual section!");
554 case MCFragment::FT_Data: {
555 // Check that we aren't trying to write a non-zero contents (or fixups)
556 // into a virtual section. This is to support clients which use standard
557 // directives to fill the contents of virtual sections.
558 MCDataFragment &DF = cast<MCDataFragment>(*it);
559 assert(DF.fixup_begin() == DF.fixup_end() &&
560 "Cannot have fixups in virtual section!");
561 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
562 assert(DF.getContents()[i] == 0 &&
563 "Invalid data value for virtual section!");
566 case MCFragment::FT_Align:
567 // Check that we aren't trying to write a non-zero value into a virtual
569 assert((!cast<MCAlignFragment>(it)->getValueSize() ||
570 !cast<MCAlignFragment>(it)->getValue()) &&
571 "Invalid align in virtual section!");
573 case MCFragment::FT_Fill:
574 assert(!cast<MCFillFragment>(it)->getValueSize() &&
575 "Invalid fill in virtual section!");
583 uint64_t Start = OW->getStream().tell();
586 for (MCSectionData::const_iterator it = SD->begin(),
587 ie = SD->end(); it != ie; ++it)
588 WriteFragmentData(*this, Layout, *it, OW);
590 assert(OW->getStream().tell() - Start == Layout.getSectionFileSize(SD));
593 void MCAssembler::Finish(MCObjectWriter *Writer) {
594 DEBUG_WITH_TYPE("mc-dump", {
595 llvm::errs() << "assembler backend - pre-layout\n--\n";
598 // Create the layout object.
599 MCAsmLayout Layout(*this);
601 // Insert additional align fragments for concrete sections to explicitly pad
602 // the previous section to match their alignment requirements. This is for
603 // 'gas' compatibility, it shouldn't strictly be necessary.
604 if (PadSectionToAlignment) {
605 for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
606 MCSectionData *SD = Layout.getSectionOrder()[i];
608 // Ignore sections without alignment requirements.
609 unsigned Align = SD->getAlignment();
613 // Ignore virtual sections, they don't cause file size modifications.
614 if (SD->getSection().isVirtualSection())
617 // Otherwise, create a new align fragment at the end of the previous
619 MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
620 Layout.getSectionOrder()[i - 1]);
621 AF->setOnlyAlignAddress(true);
625 // Create dummy fragments and assign section ordinals.
626 unsigned SectionIndex = 0;
627 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
628 // Create dummy fragments to eliminate any empty sections, this simplifies
630 if (it->getFragmentList().empty())
631 new MCDataFragment(it);
633 it->setOrdinal(SectionIndex++);
636 // Assign layout order indices to sections and fragments.
637 unsigned FragmentIndex = 0;
638 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
639 MCSectionData *SD = Layout.getSectionOrder()[i];
640 SD->setLayoutOrder(i);
642 for (MCSectionData::iterator it2 = SD->begin(),
643 ie2 = SD->end(); it2 != ie2; ++it2)
644 it2->setLayoutOrder(FragmentIndex++);
647 llvm::OwningPtr<MCObjectWriter> OwnWriter(0);
649 //no custom Writer_ : create the default one life-managed by OwningPtr
650 OwnWriter.reset(getBackend().createObjectWriter(OS));
651 Writer = OwnWriter.get();
653 report_fatal_error("unable to create object writer!");
656 // Layout until everything fits.
657 while (LayoutOnce(*Writer, Layout))
660 DEBUG_WITH_TYPE("mc-dump", {
661 llvm::errs() << "assembler backend - post-relaxation\n--\n";
664 // Finalize the layout, including fragment lowering.
665 FinishLayout(Layout);
667 DEBUG_WITH_TYPE("mc-dump", {
668 llvm::errs() << "assembler backend - final-layout\n--\n";
671 uint64_t StartOffset = OS.tell();
673 // Allow the object writer a chance to perform post-layout binding (for
674 // example, to set the index fields in the symbol data).
675 Writer->ExecutePostLayoutBinding(*this);
677 // Evaluate and apply the fixups, generating relocation entries as necessary.
678 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
679 for (MCSectionData::iterator it2 = it->begin(),
680 ie2 = it->end(); it2 != ie2; ++it2) {
681 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
685 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
686 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
687 MCFixup &Fixup = *it3;
689 // Evaluate the fixup.
692 if (!EvaluateFixup(*Writer, Layout, Fixup, DF, Target, FixedValue)) {
693 // The fixup was unresolved, we need a relocation. Inform the object
694 // writer of the relocation, and give it an opportunity to adjust the
695 // fixup value if need be.
696 Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
699 getBackend().ApplyFixup(Fixup, *DF, FixedValue);
704 // Write the object file.
705 Writer->WriteObject(*this, Layout);
707 stats::ObjectBytes += OS.tell() - StartOffset;
710 bool MCAssembler::FixupNeedsRelaxation(const MCObjectWriter &Writer,
711 const MCFixup &Fixup,
712 const MCFragment *DF,
713 const MCAsmLayout &Layout) const {
717 // If we cannot resolve the fixup value, it requires relaxation.
720 if (!EvaluateFixup(Writer, Layout, Fixup, DF, Target, Value))
723 // Otherwise, relax if the value is too big for a (signed) i8.
725 // FIXME: This is target dependent!
726 return int64_t(Value) != int64_t(int8_t(Value));
729 bool MCAssembler::FragmentNeedsRelaxation(const MCObjectWriter &Writer,
730 const MCInstFragment *IF,
731 const MCAsmLayout &Layout) const {
732 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
733 // are intentionally pushing out inst fragments, or because we relaxed a
734 // previous instruction to one that doesn't need relaxation.
735 if (!getBackend().MayNeedRelaxation(IF->getInst()))
738 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
739 ie = IF->fixup_end(); it != ie; ++it)
740 if (FixupNeedsRelaxation(Writer, *it, IF, Layout))
746 bool MCAssembler::RelaxInstruction(const MCObjectWriter &Writer,
748 MCInstFragment &IF) {
749 if (!FragmentNeedsRelaxation(Writer, &IF, Layout))
752 ++stats::RelaxedInstructions;
754 // FIXME-PERF: We could immediately lower out instructions if we can tell
755 // they are fully resolved, to avoid retesting on later passes.
757 // Relax the fragment.
760 getBackend().RelaxInstruction(IF.getInst(), Relaxed);
762 // Encode the new instruction.
764 // FIXME-PERF: If it matters, we could let the target do this. It can
765 // probably do so more efficiently in many cases.
766 SmallVector<MCFixup, 4> Fixups;
767 SmallString<256> Code;
768 raw_svector_ostream VecOS(Code);
769 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
772 // Update the instruction fragment.
775 IF.getFixups().clear();
776 // FIXME: Eliminate copy.
777 for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
778 IF.getFixups().push_back(Fixups[i]);
783 bool MCAssembler::RelaxOrg(const MCObjectWriter &Writer,
786 int64_t TargetLocation;
787 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
788 report_fatal_error("expected assembly-time absolute expression");
790 // FIXME: We need a way to communicate this error.
791 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
792 int64_t Offset = TargetLocation - FragmentOffset;
793 if (Offset < 0 || Offset >= 0x40000000)
794 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
795 "' (at offset '" + Twine(FragmentOffset) + "')");
797 unsigned OldSize = OF.getSize();
799 return OldSize != OF.getSize();
802 bool MCAssembler::RelaxLEB(const MCObjectWriter &Writer,
806 uint64_t OldSize = LF.getContents().size();
807 LF.getValue().EvaluateAsAbsolute(Value, &Layout);
808 SmallString<8> &Data = LF.getContents();
810 raw_svector_ostream OSE(Data);
812 MCObjectWriter::EncodeSLEB128(Value, OSE);
814 MCObjectWriter::EncodeULEB128(Value, OSE);
816 return OldSize != LF.getContents().size();
819 bool MCAssembler::RelaxDwarfLineAddr(const MCObjectWriter &Writer,
821 MCDwarfLineAddrFragment &DF) {
822 int64_t AddrDelta = 0;
823 uint64_t OldSize = DF.getContents().size();
824 DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, &Layout);
826 LineDelta = DF.getLineDelta();
827 SmallString<8> &Data = DF.getContents();
829 raw_svector_ostream OSE(Data);
830 MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OSE);
832 return OldSize != Data.size();
835 bool MCAssembler::LayoutOnce(const MCObjectWriter &Writer,
836 MCAsmLayout &Layout) {
837 ++stats::RelaxationSteps;
839 // Layout the sections in order.
842 // Scan for fragments that need relaxation.
843 bool WasRelaxed = false;
844 for (iterator it = begin(), ie = end(); it != ie; ++it) {
845 MCSectionData &SD = *it;
847 for (MCSectionData::iterator it2 = SD.begin(),
848 ie2 = SD.end(); it2 != ie2; ++it2) {
849 // Check if this is an fragment that needs relaxation.
850 bool relaxedFrag = false;
851 switch(it2->getKind()) {
854 case MCFragment::FT_Inst:
855 relaxedFrag = RelaxInstruction(Writer, Layout,
856 *cast<MCInstFragment>(it2));
858 case MCFragment::FT_Org:
859 relaxedFrag = RelaxOrg(Writer, Layout, *cast<MCOrgFragment>(it2));
861 case MCFragment::FT_Dwarf:
862 relaxedFrag = RelaxDwarfLineAddr(Writer, Layout,
863 *cast<MCDwarfLineAddrFragment>(it2));
865 case MCFragment::FT_LEB:
866 relaxedFrag = RelaxLEB(Writer, Layout, *cast<MCLEBFragment>(it2));
869 // Update the layout, and remember that we relaxed.
871 Layout.Invalidate(it2);
872 WasRelaxed |= relaxedFrag;
879 static void LowerInstFragment(MCInstFragment *IF,
880 MCDataFragment *DF) {
882 uint64_t DataOffset = DF->getContents().size();
885 DF->getContents().append(IF->getCode().begin(), IF->getCode().end());
887 // Adjust the fixup offsets and add them to the data fragment.
888 for (unsigned i = 0, e = IF->getFixups().size(); i != e; ++i) {
889 MCFixup &F = IF->getFixups()[i];
890 F.setOffset(DataOffset + F.getOffset());
891 DF->getFixups().push_back(F);
895 void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
896 // Lower out any instruction fragments, to simplify the fixup application and
899 // FIXME-PERF: We don't have to do this, but the assumption is that it is
900 // cheap (we will mostly end up eliminating fragments and appending on to data
901 // fragments), so the extra complexity downstream isn't worth it. Evaluate
904 // The layout is done. Mark every fragment as valid.
905 Layout.getFragmentOffset(&*Layout.getSectionOrder().back()->rbegin());
907 unsigned FragmentIndex = 0;
908 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
909 MCSectionData &SD = *Layout.getSectionOrder()[i];
910 MCDataFragment *CurDF = NULL;
912 for (MCSectionData::iterator it2 = SD.begin(),
913 ie2 = SD.end(); it2 != ie2; ++it2) {
914 switch (it2->getKind()) {
918 case MCFragment::FT_Data:
919 CurDF = cast<MCDataFragment>(it2);
921 case MCFragment::FT_Inst: {
922 MCInstFragment *IF = cast<MCInstFragment>(it2);
923 // Use the existing data fragment if possible.
924 if (CurDF && CurDF->getAtom() == IF->getAtom()) {
925 Layout.CoalesceFragments(IF, CurDF);
927 // Otherwise, create a new data fragment.
928 CurDF = new MCDataFragment();
929 Layout.ReplaceFragment(IF, CurDF);
932 // Lower the Instruction Fragment
933 LowerInstFragment(IF, CurDF);
935 // Delete the instruction fragment and update the iterator.
941 // Since we may have merged fragments, fix the layout order.
942 it2->setLayoutOrder(FragmentIndex++);
951 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
952 OS << "<MCFixup" << " Offset:" << AF.getOffset()
953 << " Value:" << *AF.getValue()
954 << " Kind:" << AF.getKind() << ">";
960 void MCFragment::dump() {
961 raw_ostream &OS = llvm::errs();
965 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
966 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
967 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
968 case MCFragment::FT_Inst: OS << "MCInstFragment"; break;
969 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
970 case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
971 case MCFragment::FT_LEB: OS << "MCLEBFragment"; break;
974 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
975 << " Offset:" << Offset << " EffectiveSize:" << EffectiveSize << ">";
978 case MCFragment::FT_Align: {
979 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
980 if (AF->hasEmitNops())
981 OS << " (emit nops)";
982 if (AF->hasOnlyAlignAddress())
983 OS << " (only align section)";
985 OS << " Alignment:" << AF->getAlignment()
986 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
987 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
990 case MCFragment::FT_Data: {
991 const MCDataFragment *DF = cast<MCDataFragment>(this);
994 const SmallVectorImpl<char> &Contents = DF->getContents();
995 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
997 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
999 OS << "] (" << Contents.size() << " bytes)";
1001 if (!DF->getFixups().empty()) {
1004 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
1005 ie = DF->fixup_end(); it != ie; ++it) {
1006 if (it != DF->fixup_begin()) OS << ",\n ";
1013 case MCFragment::FT_Fill: {
1014 const MCFillFragment *FF = cast<MCFillFragment>(this);
1015 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
1016 << " Size:" << FF->getSize();
1019 case MCFragment::FT_Inst: {
1020 const MCInstFragment *IF = cast<MCInstFragment>(this);
1023 IF->getInst().dump_pretty(OS);
1026 case MCFragment::FT_Org: {
1027 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
1029 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
1032 case MCFragment::FT_Dwarf: {
1033 const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
1035 OS << " AddrDelta:" << OF->getAddrDelta()
1036 << " LineDelta:" << OF->getLineDelta();
1039 case MCFragment::FT_LEB: {
1040 const MCLEBFragment *LF = cast<MCLEBFragment>(this);
1042 OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
1049 void MCSectionData::dump() {
1050 raw_ostream &OS = llvm::errs();
1052 OS << "<MCSectionData";
1053 OS << " Alignment:" << getAlignment() << " Address:" << Address
1054 << " Fragments:[\n ";
1055 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1056 if (it != begin()) OS << ",\n ";
1062 void MCSymbolData::dump() {
1063 raw_ostream &OS = llvm::errs();
1065 OS << "<MCSymbolData Symbol:" << getSymbol()
1066 << " Fragment:" << getFragment() << " Offset:" << getOffset()
1067 << " Flags:" << getFlags() << " Index:" << getIndex();
1069 OS << " (common, size:" << getCommonSize()
1070 << " align: " << getCommonAlignment() << ")";
1072 OS << " (external)";
1073 if (isPrivateExtern())
1074 OS << " (private extern)";
1078 void MCAssembler::dump() {
1079 raw_ostream &OS = llvm::errs();
1081 OS << "<MCAssembler\n";
1082 OS << " Sections:[\n ";
1083 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1084 if (it != begin()) OS << ",\n ";
1090 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1091 if (it != symbol_begin()) OS << ",\n ";