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 uint64_t MCAsmLayout::getFragmentAddress(const MCFragment *F) const {
117 assert(F->getParent() && "Missing section()!");
118 return getSectionAddress(F->getParent()) + getFragmentOffset(F);
121 uint64_t MCAsmLayout::getFragmentEffectiveSize(const MCFragment *F) const {
123 assert(F->EffectiveSize != ~UINT64_C(0) && "Address not set!");
124 return F->EffectiveSize;
127 uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
129 assert(F->Offset != ~UINT64_C(0) && "Address not set!");
133 uint64_t MCAsmLayout::getSymbolOffset(const MCSymbolData *SD) const {
134 assert(SD->getFragment() && "Invalid getOffset() on undefined symbol!");
135 return getFragmentOffset(SD->getFragment()) + SD->getOffset();
138 uint64_t MCAsmLayout::getSymbolAddress(const MCSymbolData *SD) const {
139 assert(SD->getFragment() && "Invalid getAddress() on undefined symbol!");
140 return getFragmentAddress(SD->getFragment()) + SD->getOffset();
143 uint64_t MCAsmLayout::getSectionAddress(const MCSectionData *SD) const {
144 EnsureValid(SD->begin());
145 assert(SD->Address != ~UINT64_C(0) && "Address not set!");
149 uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const {
150 // The size is the last fragment's end offset.
151 const MCFragment &F = SD->getFragmentList().back();
152 return getFragmentOffset(&F) + getFragmentEffectiveSize(&F);
155 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
156 // Virtual sections have no file size.
157 if (SD->getSection().isVirtualSection())
160 // Otherwise, the file size is the same as the address space size.
161 return getSectionAddressSize(SD);
164 uint64_t MCAsmLayout::getSectionSize(const MCSectionData *SD) const {
165 // The logical size is the address space size minus any tail padding.
166 uint64_t Size = getSectionAddressSize(SD);
167 const MCAlignFragment *AF =
168 dyn_cast<MCAlignFragment>(&(SD->getFragmentList().back()));
169 if (AF && AF->hasOnlyAlignAddress())
170 Size -= getFragmentEffectiveSize(AF);
177 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
180 MCFragment::~MCFragment() {
183 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
184 : Kind(_Kind), Parent(_Parent), Atom(0), Offset(~UINT64_C(0)),
185 EffectiveSize(~UINT64_C(0))
188 Parent->getFragmentList().push_back(this);
193 MCSectionData::MCSectionData() : Section(0) {}
195 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
196 : Section(&_Section),
197 Ordinal(~UINT32_C(0)),
199 Address(~UINT64_C(0)),
200 HasInstructions(false)
203 A->getSectionList().push_back(this);
208 MCSymbolData::MCSymbolData() : Symbol(0) {}
210 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
211 uint64_t _Offset, MCAssembler *A)
212 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
213 IsExternal(false), IsPrivateExtern(false),
214 CommonSize(0), SymbolSize(0), CommonAlign(0),
218 A->getSymbolList().push_back(this);
223 MCAssembler::MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
224 MCCodeEmitter &_Emitter, bool _PadSectionToAlignment,
226 : Context(_Context), Backend(_Backend), Emitter(_Emitter),
227 OS(_OS), RelaxAll(false), SubsectionsViaSymbols(false),
228 PadSectionToAlignment(_PadSectionToAlignment)
232 MCAssembler::~MCAssembler() {
235 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
236 // Non-temporary labels should always be visible to the linker.
237 if (!Symbol.isTemporary())
240 // Absolute temporary labels are never visible.
241 if (!Symbol.isInSection())
244 // Otherwise, check if the section requires symbols even for temporary labels.
245 return getBackend().doesSectionRequireSymbols(Symbol.getSection());
248 const MCSymbolData *MCAssembler::getAtom(const MCSymbolData *SD) const {
249 // Linker visible symbols define atoms.
250 if (isSymbolLinkerVisible(SD->getSymbol()))
253 // Absolute and undefined symbols have no defining atom.
254 if (!SD->getFragment())
257 // Non-linker visible symbols in sections which can't be atomized have no
259 if (!getBackend().isSectionAtomizable(
260 SD->getFragment()->getParent()->getSection()))
263 // Otherwise, return the atom for the containing fragment.
264 return SD->getFragment()->getAtom();
267 bool MCAssembler::EvaluateFixup(const MCObjectWriter &Writer,
268 const MCAsmLayout &Layout,
269 const MCFixup &Fixup, const MCFragment *DF,
270 MCValue &Target, uint64_t &Value) const {
271 ++stats::EvaluateFixup;
273 if (!Fixup.getValue()->EvaluateAsRelocatable(Target, &Layout))
274 report_fatal_error("expected relocatable expression");
276 // FIXME: How do non-scattered symbols work in ELF? I presume the linker
277 // doesn't support small relocations, but then under what criteria does the
278 // assembler allow symbol differences?
280 Value = Target.getConstant();
282 bool IsPCRel = Emitter.getFixupKindInfo(
283 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
284 bool IsResolved = true;
285 if (const MCSymbolRefExpr *A = Target.getSymA()) {
286 const MCSymbol &Sym = A->getSymbol().AliasedSymbol();
288 Value += Layout.getSymbolAddress(&getSymbolData(Sym));
292 if (const MCSymbolRefExpr *B = Target.getSymB()) {
293 const MCSymbol &Sym = B->getSymbol().AliasedSymbol();
295 Value -= Layout.getSymbolAddress(&getSymbolData(Sym));
301 IsResolved = Writer.IsFixupFullyResolved(*this, Target, IsPCRel, DF);
304 Value -= Layout.getFragmentAddress(DF) + Fixup.getOffset();
309 uint64_t MCAssembler::ComputeFragmentSize(const MCFragment &F,
310 uint64_t SectionAddress,
311 uint64_t FragmentOffset) const {
312 switch (F.getKind()) {
313 case MCFragment::FT_Data:
314 return cast<MCDataFragment>(F).getContents().size();
315 case MCFragment::FT_Fill:
316 return cast<MCFillFragment>(F).getSize();
317 case MCFragment::FT_Inst:
318 return cast<MCInstFragment>(F).getInstSize();
320 case MCFragment::FT_LEB:
321 return cast<MCLEBFragment>(F).getContents().size();
323 case MCFragment::FT_Align: {
324 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
326 assert((!AF.hasOnlyAlignAddress() || !AF.getNextNode()) &&
327 "Invalid OnlyAlignAddress bit, not the last fragment!");
329 uint64_t Size = OffsetToAlignment(SectionAddress + FragmentOffset,
332 // Honor MaxBytesToEmit.
333 if (Size > AF.getMaxBytesToEmit())
339 case MCFragment::FT_Org:
340 return cast<MCOrgFragment>(F).getSize();
342 case MCFragment::FT_Dwarf:
343 return cast<MCDwarfLineAddrFragment>(F).getContents().size();
346 assert(0 && "invalid fragment kind");
350 void MCAsmLayout::LayoutFile() {
351 // Initialize the first section and set the valid fragment layout point. All
352 // actual layout computations are done lazily.
353 LastValidFragment = 0;
354 if (!getSectionOrder().empty())
355 getSectionOrder().front()->Address = 0;
358 void MCAsmLayout::LayoutFragment(MCFragment *F) {
359 MCFragment *Prev = F->getPrevNode();
361 // We should never try to recompute something which is up-to-date.
362 assert(!isFragmentUpToDate(F) && "Attempt to recompute up-to-date fragment!");
363 // We should never try to compute the fragment layout if the section isn't
365 assert(isSectionUpToDate(F->getParent()) &&
366 "Attempt to compute fragment before it's section!");
367 // We should never try to compute the fragment layout if it's predecessor
369 assert((!Prev || isFragmentUpToDate(Prev)) &&
370 "Attempt to compute fragment before it's predecessor!");
372 ++stats::FragmentLayouts;
374 // Compute the fragment start address.
375 uint64_t StartAddress = F->getParent()->Address;
376 uint64_t Address = StartAddress;
378 Address += Prev->Offset + Prev->EffectiveSize;
380 // Compute fragment offset and size.
381 F->Offset = Address - StartAddress;
382 F->EffectiveSize = getAssembler().ComputeFragmentSize(*F, StartAddress,
384 LastValidFragment = F;
386 // If this is the last fragment in a section, update the next section address.
387 if (!F->getNextNode()) {
388 unsigned NextIndex = F->getParent()->getLayoutOrder() + 1;
389 if (NextIndex != getSectionOrder().size())
390 LayoutSection(getSectionOrder()[NextIndex]);
394 void MCAsmLayout::LayoutSection(MCSectionData *SD) {
395 unsigned SectionOrderIndex = SD->getLayoutOrder();
397 ++stats::SectionLayouts;
399 // Compute the section start address.
400 uint64_t StartAddress = 0;
401 if (SectionOrderIndex) {
402 MCSectionData *Prev = getSectionOrder()[SectionOrderIndex - 1];
403 StartAddress = getSectionAddress(Prev) + getSectionAddressSize(Prev);
406 // Honor the section alignment requirements.
407 StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
409 // Set the section address.
410 SD->Address = StartAddress;
413 /// WriteFragmentData - Write the \arg F data to the output file.
414 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
415 const MCFragment &F, MCObjectWriter *OW) {
416 uint64_t Start = OW->getStream().tell();
419 ++stats::EmittedFragments;
421 // FIXME: Embed in fragments instead?
422 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
423 switch (F.getKind()) {
424 case MCFragment::FT_Align: {
425 MCAlignFragment &AF = cast<MCAlignFragment>(F);
426 uint64_t Count = FragmentSize / AF.getValueSize();
428 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
430 // FIXME: This error shouldn't actually occur (the front end should emit
431 // multiple .align directives to enforce the semantics it wants), but is
432 // severe enough that we want to report it. How to handle this?
433 if (Count * AF.getValueSize() != FragmentSize)
434 report_fatal_error("undefined .align directive, value size '" +
435 Twine(AF.getValueSize()) +
436 "' is not a divisor of padding size '" +
437 Twine(FragmentSize) + "'");
439 // See if we are aligning with nops, and if so do that first to try to fill
440 // the Count bytes. Then if that did not fill any bytes or there are any
441 // bytes left to fill use the the Value and ValueSize to fill the rest.
442 // If we are aligning with nops, ask that target to emit the right data.
443 if (AF.hasEmitNops()) {
444 if (!Asm.getBackend().WriteNopData(Count, OW))
445 report_fatal_error("unable to write nop sequence of " +
446 Twine(Count) + " bytes");
450 // Otherwise, write out in multiples of the value size.
451 for (uint64_t i = 0; i != Count; ++i) {
452 switch (AF.getValueSize()) {
454 assert(0 && "Invalid size!");
455 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
456 case 2: OW->Write16(uint16_t(AF.getValue())); break;
457 case 4: OW->Write32(uint32_t(AF.getValue())); break;
458 case 8: OW->Write64(uint64_t(AF.getValue())); break;
464 case MCFragment::FT_Data: {
465 MCDataFragment &DF = cast<MCDataFragment>(F);
466 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
467 OW->WriteBytes(DF.getContents().str());
471 case MCFragment::FT_Fill: {
472 MCFillFragment &FF = cast<MCFillFragment>(F);
474 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
476 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
477 switch (FF.getValueSize()) {
479 assert(0 && "Invalid size!");
480 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
481 case 2: OW->Write16(uint16_t(FF.getValue())); break;
482 case 4: OW->Write32(uint32_t(FF.getValue())); break;
483 case 8: OW->Write64(uint64_t(FF.getValue())); break;
489 case MCFragment::FT_Inst: {
490 MCInstFragment &IF = cast<MCInstFragment>(F);
491 OW->WriteBytes(StringRef(IF.getCode().begin(), IF.getCode().size()));
495 case MCFragment::FT_LEB: {
496 MCLEBFragment &LF = cast<MCLEBFragment>(F);
497 OW->WriteBytes(LF.getContents().str());
501 case MCFragment::FT_Org: {
502 MCOrgFragment &OF = cast<MCOrgFragment>(F);
504 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
505 OW->Write8(uint8_t(OF.getValue()));
510 case MCFragment::FT_Dwarf: {
511 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
512 OW->WriteBytes(OF.getContents().str());
517 assert(OW->getStream().tell() - Start == FragmentSize);
520 void MCAssembler::WriteSectionData(const MCSectionData *SD,
521 const MCAsmLayout &Layout,
522 MCObjectWriter *OW) const {
523 // Ignore virtual sections.
524 if (SD->getSection().isVirtualSection()) {
525 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
527 // Check that contents are only things legal inside a virtual section.
528 for (MCSectionData::const_iterator it = SD->begin(),
529 ie = SD->end(); it != ie; ++it) {
530 switch (it->getKind()) {
532 assert(0 && "Invalid fragment in virtual section!");
533 case MCFragment::FT_Data: {
534 // Check that we aren't trying to write a non-zero contents (or fixups)
535 // into a virtual section. This is to support clients which use standard
536 // directives to fill the contents of virtual sections.
537 MCDataFragment &DF = cast<MCDataFragment>(*it);
538 assert(DF.fixup_begin() == DF.fixup_end() &&
539 "Cannot have fixups in virtual section!");
540 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
541 assert(DF.getContents()[i] == 0 &&
542 "Invalid data value for virtual section!");
545 case MCFragment::FT_Align:
546 // Check that we aren't trying to write a non-zero value into a virtual
548 assert((!cast<MCAlignFragment>(it)->getValueSize() ||
549 !cast<MCAlignFragment>(it)->getValue()) &&
550 "Invalid align in virtual section!");
552 case MCFragment::FT_Fill:
553 assert(!cast<MCFillFragment>(it)->getValueSize() &&
554 "Invalid fill in virtual section!");
562 uint64_t Start = OW->getStream().tell();
565 for (MCSectionData::const_iterator it = SD->begin(),
566 ie = SD->end(); it != ie; ++it)
567 WriteFragmentData(*this, Layout, *it, OW);
569 assert(OW->getStream().tell() - Start == Layout.getSectionFileSize(SD));
573 uint64_t MCAssembler::HandleFixup(MCObjectWriter &Writer,
574 const MCAsmLayout &Layout,
576 const MCFixup &Fixup) {
577 // Evaluate the fixup.
580 if (!EvaluateFixup(Writer, Layout, Fixup, &F, Target, FixedValue)) {
581 // The fixup was unresolved, we need a relocation. Inform the object
582 // writer of the relocation, and give it an opportunity to adjust the
583 // fixup value if need be.
584 Writer.RecordRelocation(*this, Layout, &F, Fixup, Target, FixedValue);
589 void MCAssembler::Finish(MCObjectWriter *Writer) {
590 DEBUG_WITH_TYPE("mc-dump", {
591 llvm::errs() << "assembler backend - pre-layout\n--\n";
594 // Create the layout object.
595 MCAsmLayout Layout(*this);
597 // Insert additional align fragments for concrete sections to explicitly pad
598 // the previous section to match their alignment requirements. This is for
599 // 'gas' compatibility, it shouldn't strictly be necessary.
600 if (PadSectionToAlignment) {
601 for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
602 MCSectionData *SD = Layout.getSectionOrder()[i];
604 // Ignore sections without alignment requirements.
605 unsigned Align = SD->getAlignment();
609 // Ignore virtual sections, they don't cause file size modifications.
610 if (SD->getSection().isVirtualSection())
613 // Otherwise, create a new align fragment at the end of the previous
615 MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
616 Layout.getSectionOrder()[i - 1]);
617 AF->setOnlyAlignAddress(true);
621 // Create dummy fragments and assign section ordinals.
622 unsigned SectionIndex = 0;
623 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
624 // Create dummy fragments to eliminate any empty sections, this simplifies
626 if (it->getFragmentList().empty())
627 new MCDataFragment(it);
629 it->setOrdinal(SectionIndex++);
632 // Assign layout order indices to sections and fragments.
633 unsigned FragmentIndex = 0;
634 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
635 MCSectionData *SD = Layout.getSectionOrder()[i];
636 SD->setLayoutOrder(i);
638 for (MCSectionData::iterator it2 = SD->begin(),
639 ie2 = SD->end(); it2 != ie2; ++it2)
640 it2->setLayoutOrder(FragmentIndex++);
643 llvm::OwningPtr<MCObjectWriter> OwnWriter(0);
645 //no custom Writer_ : create the default one life-managed by OwningPtr
646 OwnWriter.reset(getBackend().createObjectWriter(OS));
647 Writer = OwnWriter.get();
649 report_fatal_error("unable to create object writer!");
652 // Layout until everything fits.
653 while (LayoutOnce(*Writer, Layout))
656 DEBUG_WITH_TYPE("mc-dump", {
657 llvm::errs() << "assembler backend - post-relaxation\n--\n";
660 // Finalize the layout, including fragment lowering.
661 FinishLayout(Layout);
663 DEBUG_WITH_TYPE("mc-dump", {
664 llvm::errs() << "assembler backend - final-layout\n--\n";
667 uint64_t StartOffset = OS.tell();
669 // Allow the object writer a chance to perform post-layout binding (for
670 // example, to set the index fields in the symbol data).
671 Writer->ExecutePostLayoutBinding(*this);
673 // Evaluate and apply the fixups, generating relocation entries as necessary.
674 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
675 for (MCSectionData::iterator it2 = it->begin(),
676 ie2 = it->end(); it2 != ie2; ++it2) {
677 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
679 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
680 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
681 MCFixup &Fixup = *it3;
682 uint64_t FixedValue = HandleFixup(*Writer, Layout, *DF, Fixup);
683 getBackend().ApplyFixup(Fixup, DF->getContents().data(),
684 DF->getContents().size(), FixedValue);
687 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
689 for (MCInstFragment::fixup_iterator it3 = IF->fixup_begin(),
690 ie3 = IF->fixup_end(); it3 != ie3; ++it3) {
691 MCFixup &Fixup = *it3;
692 uint64_t FixedValue = HandleFixup(*Writer, Layout, *IF, Fixup);
693 getBackend().ApplyFixup(Fixup, IF->getCode().data(),
694 IF->getCode().size(), FixedValue);
700 // Write the object file.
701 Writer->WriteObject(*this, Layout);
703 stats::ObjectBytes += OS.tell() - StartOffset;
706 bool MCAssembler::FixupNeedsRelaxation(const MCObjectWriter &Writer,
707 const MCFixup &Fixup,
708 const MCFragment *DF,
709 const MCAsmLayout &Layout) const {
713 // If we cannot resolve the fixup value, it requires relaxation.
716 if (!EvaluateFixup(Writer, Layout, Fixup, DF, Target, Value))
719 // Otherwise, relax if the value is too big for a (signed) i8.
721 // FIXME: This is target dependent!
722 return int64_t(Value) != int64_t(int8_t(Value));
725 bool MCAssembler::FragmentNeedsRelaxation(const MCObjectWriter &Writer,
726 const MCInstFragment *IF,
727 const MCAsmLayout &Layout) const {
728 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
729 // are intentionally pushing out inst fragments, or because we relaxed a
730 // previous instruction to one that doesn't need relaxation.
731 if (!getBackend().MayNeedRelaxation(IF->getInst()))
734 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
735 ie = IF->fixup_end(); it != ie; ++it)
736 if (FixupNeedsRelaxation(Writer, *it, IF, Layout))
742 bool MCAssembler::RelaxInstruction(const MCObjectWriter &Writer,
744 MCInstFragment &IF) {
745 if (!FragmentNeedsRelaxation(Writer, &IF, Layout))
748 ++stats::RelaxedInstructions;
750 // FIXME-PERF: We could immediately lower out instructions if we can tell
751 // they are fully resolved, to avoid retesting on later passes.
753 // Relax the fragment.
756 getBackend().RelaxInstruction(IF.getInst(), Relaxed);
758 // Encode the new instruction.
760 // FIXME-PERF: If it matters, we could let the target do this. It can
761 // probably do so more efficiently in many cases.
762 SmallVector<MCFixup, 4> Fixups;
763 SmallString<256> Code;
764 raw_svector_ostream VecOS(Code);
765 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
768 // Update the instruction fragment.
771 IF.getFixups().clear();
772 // FIXME: Eliminate copy.
773 for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
774 IF.getFixups().push_back(Fixups[i]);
779 bool MCAssembler::RelaxOrg(const MCObjectWriter &Writer,
782 int64_t TargetLocation;
783 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, Layout))
784 report_fatal_error("expected assembly-time absolute expression");
786 // FIXME: We need a way to communicate this error.
787 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
788 int64_t Offset = TargetLocation - FragmentOffset;
789 if (Offset < 0 || Offset >= 0x40000000)
790 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
791 "' (at offset '" + Twine(FragmentOffset) + "')");
793 unsigned OldSize = OF.getSize();
795 return OldSize != OF.getSize();
798 bool MCAssembler::RelaxLEB(const MCObjectWriter &Writer,
802 uint64_t OldSize = LF.getContents().size();
803 LF.getValue().EvaluateAsAbsolute(Value, Layout);
804 SmallString<8> &Data = LF.getContents();
806 raw_svector_ostream OSE(Data);
808 MCObjectWriter::EncodeSLEB128(Value, OSE);
810 MCObjectWriter::EncodeULEB128(Value, OSE);
812 return OldSize != LF.getContents().size();
815 bool MCAssembler::RelaxDwarfLineAddr(const MCObjectWriter &Writer,
817 MCDwarfLineAddrFragment &DF) {
818 int64_t AddrDelta = 0;
819 uint64_t OldSize = DF.getContents().size();
820 DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, Layout);
822 LineDelta = DF.getLineDelta();
823 SmallString<8> &Data = DF.getContents();
825 raw_svector_ostream OSE(Data);
826 MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OSE);
828 return OldSize != Data.size();
831 bool MCAssembler::LayoutOnce(const MCObjectWriter &Writer,
832 MCAsmLayout &Layout) {
833 ++stats::RelaxationSteps;
835 // Layout the sections in order.
838 // Scan for fragments that need relaxation.
839 bool WasRelaxed = false;
840 for (iterator it = begin(), ie = end(); it != ie; ++it) {
841 MCSectionData &SD = *it;
843 for (MCSectionData::iterator it2 = SD.begin(),
844 ie2 = SD.end(); it2 != ie2; ++it2) {
845 // Check if this is an fragment that needs relaxation.
846 bool relaxedFrag = false;
847 switch(it2->getKind()) {
850 case MCFragment::FT_Inst:
851 relaxedFrag = RelaxInstruction(Writer, Layout,
852 *cast<MCInstFragment>(it2));
854 case MCFragment::FT_Org:
855 relaxedFrag = RelaxOrg(Writer, Layout, *cast<MCOrgFragment>(it2));
857 case MCFragment::FT_Dwarf:
858 relaxedFrag = RelaxDwarfLineAddr(Writer, Layout,
859 *cast<MCDwarfLineAddrFragment>(it2));
861 case MCFragment::FT_LEB:
862 relaxedFrag = RelaxLEB(Writer, Layout, *cast<MCLEBFragment>(it2));
865 // Update the layout, and remember that we relaxed.
867 Layout.Invalidate(it2);
868 WasRelaxed |= relaxedFrag;
875 void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
876 // Lower out any instruction fragments, to simplify the fixup application and
879 // FIXME-PERF: We don't have to do this, but the assumption is that it is
880 // cheap (we will mostly end up eliminating fragments and appending on to data
881 // fragments), so the extra complexity downstream isn't worth it. Evaluate
884 // The layout is done. Mark every fragment as valid.
885 Layout.getFragmentOffset(&*Layout.getSectionOrder().back()->rbegin());
892 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
893 OS << "<MCFixup" << " Offset:" << AF.getOffset()
894 << " Value:" << *AF.getValue()
895 << " Kind:" << AF.getKind() << ">";
901 void MCFragment::dump() {
902 raw_ostream &OS = llvm::errs();
906 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
907 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
908 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
909 case MCFragment::FT_Inst: OS << "MCInstFragment"; break;
910 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
911 case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
912 case MCFragment::FT_LEB: OS << "MCLEBFragment"; break;
915 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
916 << " Offset:" << Offset << " EffectiveSize:" << EffectiveSize << ">";
919 case MCFragment::FT_Align: {
920 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
921 if (AF->hasEmitNops())
922 OS << " (emit nops)";
923 if (AF->hasOnlyAlignAddress())
924 OS << " (only align section)";
926 OS << " Alignment:" << AF->getAlignment()
927 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
928 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
931 case MCFragment::FT_Data: {
932 const MCDataFragment *DF = cast<MCDataFragment>(this);
935 const SmallVectorImpl<char> &Contents = DF->getContents();
936 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
938 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
940 OS << "] (" << Contents.size() << " bytes)";
942 if (!DF->getFixups().empty()) {
945 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
946 ie = DF->fixup_end(); it != ie; ++it) {
947 if (it != DF->fixup_begin()) OS << ",\n ";
954 case MCFragment::FT_Fill: {
955 const MCFillFragment *FF = cast<MCFillFragment>(this);
956 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
957 << " Size:" << FF->getSize();
960 case MCFragment::FT_Inst: {
961 const MCInstFragment *IF = cast<MCInstFragment>(this);
964 IF->getInst().dump_pretty(OS);
967 case MCFragment::FT_Org: {
968 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
970 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
973 case MCFragment::FT_Dwarf: {
974 const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
976 OS << " AddrDelta:" << OF->getAddrDelta()
977 << " LineDelta:" << OF->getLineDelta();
980 case MCFragment::FT_LEB: {
981 const MCLEBFragment *LF = cast<MCLEBFragment>(this);
983 OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
990 void MCSectionData::dump() {
991 raw_ostream &OS = llvm::errs();
993 OS << "<MCSectionData";
994 OS << " Alignment:" << getAlignment() << " Address:" << Address
995 << " Fragments:[\n ";
996 for (iterator it = begin(), ie = end(); it != ie; ++it) {
997 if (it != begin()) OS << ",\n ";
1003 void MCSymbolData::dump() {
1004 raw_ostream &OS = llvm::errs();
1006 OS << "<MCSymbolData Symbol:" << getSymbol()
1007 << " Fragment:" << getFragment() << " Offset:" << getOffset()
1008 << " Flags:" << getFlags() << " Index:" << getIndex();
1010 OS << " (common, size:" << getCommonSize()
1011 << " align: " << getCommonAlignment() << ")";
1013 OS << " (external)";
1014 if (isPrivateExtern())
1015 OS << " (private extern)";
1019 void MCAssembler::dump() {
1020 raw_ostream &OS = llvm::errs();
1022 OS << "<MCAssembler\n";
1023 OS << " Sections:[\n ";
1024 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1025 if (it != begin()) OS << ",\n ";
1031 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1032 if (it != symbol_begin()) OS << ",\n ";