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::getSymbolAddress(const MCSymbolData *SD) const {
158 assert(SD->getFragment() && "Invalid getAddress() on undefined symbol!");
159 return getFragmentAddress(SD->getFragment()) + SD->getOffset();
162 uint64_t MCAsmLayout::getSectionAddress(const MCSectionData *SD) const {
163 EnsureValid(SD->begin());
164 assert(SD->Address != ~UINT64_C(0) && "Address not set!");
168 uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const {
169 // The size is the last fragment's end offset.
170 const MCFragment &F = SD->getFragmentList().back();
171 return getFragmentOffset(&F) + getFragmentEffectiveSize(&F);
174 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
175 // Virtual sections have no file size.
176 if (SD->getSection().isVirtualSection())
179 // Otherwise, the file size is the same as the address space size.
180 return getSectionAddressSize(SD);
183 uint64_t MCAsmLayout::getSectionSize(const MCSectionData *SD) const {
184 // The logical size is the address space size minus any tail padding.
185 uint64_t Size = getSectionAddressSize(SD);
186 const MCAlignFragment *AF =
187 dyn_cast<MCAlignFragment>(&(SD->getFragmentList().back()));
188 if (AF && AF->hasOnlyAlignAddress())
189 Size -= getFragmentEffectiveSize(AF);
196 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
199 MCFragment::~MCFragment() {
202 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
203 : Kind(_Kind), Parent(_Parent), Atom(0), Offset(~UINT64_C(0)),
204 EffectiveSize(~UINT64_C(0))
207 Parent->getFragmentList().push_back(this);
212 MCSectionData::MCSectionData() : Section(0) {}
214 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
215 : Section(&_Section),
217 Address(~UINT64_C(0)),
218 HasInstructions(false)
221 A->getSectionList().push_back(this);
226 MCSymbolData::MCSymbolData() : Symbol(0) {}
228 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
229 uint64_t _Offset, MCAssembler *A)
230 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
231 IsExternal(false), IsPrivateExtern(false),
232 CommonSize(0), SymbolSize(0), CommonAlign(0),
236 A->getSymbolList().push_back(this);
241 MCAssembler::MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
242 MCCodeEmitter &_Emitter, bool _PadSectionToAlignment,
244 : Context(_Context), Backend(_Backend), Emitter(_Emitter),
245 OS(_OS), RelaxAll(false), SubsectionsViaSymbols(false),
246 PadSectionToAlignment(_PadSectionToAlignment)
250 MCAssembler::~MCAssembler() {
253 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
254 // Non-temporary labels should always be visible to the linker.
255 if (!Symbol.isTemporary())
258 // Absolute temporary labels are never visible.
259 if (!Symbol.isInSection())
262 // Otherwise, check if the section requires symbols even for temporary labels.
263 return getBackend().doesSectionRequireSymbols(Symbol.getSection());
266 const MCSymbolData *MCAssembler::getAtom(const MCSymbolData *SD) const {
267 // Linker visible symbols define atoms.
268 if (isSymbolLinkerVisible(SD->getSymbol()))
271 // Absolute and undefined symbols have no defining atom.
272 if (!SD->getFragment())
275 // Non-linker visible symbols in sections which can't be atomized have no
277 if (!getBackend().isSectionAtomizable(
278 SD->getFragment()->getParent()->getSection()))
281 // Otherwise, return the atom for the containing fragment.
282 return SD->getFragment()->getAtom();
285 bool MCAssembler::EvaluateFixup(const MCObjectWriter &Writer,
286 const MCAsmLayout &Layout,
287 const MCFixup &Fixup, const MCFragment *DF,
288 MCValue &Target, uint64_t &Value) const {
289 ++stats::EvaluateFixup;
291 if (!Fixup.getValue()->EvaluateAsRelocatable(Target, &Layout))
292 report_fatal_error("expected relocatable expression");
294 // FIXME: How do non-scattered symbols work in ELF? I presume the linker
295 // doesn't support small relocations, but then under what criteria does the
296 // assembler allow symbol differences?
298 Value = Target.getConstant();
300 bool IsPCRel = Emitter.getFixupKindInfo(
301 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
302 bool IsResolved = true;
303 if (const MCSymbolRefExpr *A = Target.getSymA()) {
304 const MCSymbol &Sym = A->getSymbol().AliasedSymbol();
306 Value += Layout.getSymbolAddress(&getSymbolData(Sym));
310 if (const MCSymbolRefExpr *B = Target.getSymB()) {
311 const MCSymbol &Sym = B->getSymbol().AliasedSymbol();
313 Value -= Layout.getSymbolAddress(&getSymbolData(Sym));
319 IsResolved = Writer.IsFixupFullyResolved(*this, Target, IsPCRel, DF);
322 Value -= Layout.getFragmentAddress(DF) + Fixup.getOffset();
327 uint64_t MCAssembler::ComputeFragmentSize(const MCFragment &F,
328 uint64_t SectionAddress,
329 uint64_t FragmentOffset) const {
330 switch (F.getKind()) {
331 case MCFragment::FT_Data:
332 return cast<MCDataFragment>(F).getContents().size();
333 case MCFragment::FT_Fill:
334 return cast<MCFillFragment>(F).getSize();
335 case MCFragment::FT_Inst:
336 return cast<MCInstFragment>(F).getInstSize();
338 case MCFragment::FT_LEB:
339 return cast<MCLEBFragment>(F).getContents().size();
341 case MCFragment::FT_Align: {
342 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
344 assert((!AF.hasOnlyAlignAddress() || !AF.getNextNode()) &&
345 "Invalid OnlyAlignAddress bit, not the last fragment!");
347 uint64_t Size = OffsetToAlignment(SectionAddress + FragmentOffset,
350 // Honor MaxBytesToEmit.
351 if (Size > AF.getMaxBytesToEmit())
357 case MCFragment::FT_Org:
358 return cast<MCOrgFragment>(F).getSize();
360 case MCFragment::FT_Dwarf:
361 return cast<MCDwarfLineAddrFragment>(F).getContents().size();
364 assert(0 && "invalid fragment kind");
368 void MCAsmLayout::LayoutFile() {
369 // Initialize the first section and set the valid fragment layout point. All
370 // actual layout computations are done lazily.
371 LastValidFragment = 0;
372 if (!getSectionOrder().empty())
373 getSectionOrder().front()->Address = 0;
376 void MCAsmLayout::LayoutFragment(MCFragment *F) {
377 MCFragment *Prev = F->getPrevNode();
379 // We should never try to recompute something which is up-to-date.
380 assert(!isFragmentUpToDate(F) && "Attempt to recompute up-to-date fragment!");
381 // We should never try to compute the fragment layout if the section isn't
383 assert(isSectionUpToDate(F->getParent()) &&
384 "Attempt to compute fragment before it's section!");
385 // We should never try to compute the fragment layout if it's predecessor
387 assert((!Prev || isFragmentUpToDate(Prev)) &&
388 "Attempt to compute fragment before it's predecessor!");
390 ++stats::FragmentLayouts;
392 // Compute the fragment start address.
393 uint64_t StartAddress = F->getParent()->Address;
394 uint64_t Address = StartAddress;
396 Address += Prev->Offset + Prev->EffectiveSize;
398 // Compute fragment offset and size.
399 F->Offset = Address - StartAddress;
400 F->EffectiveSize = getAssembler().ComputeFragmentSize(*F, StartAddress,
402 LastValidFragment = F;
404 // If this is the last fragment in a section, update the next section address.
405 if (!F->getNextNode()) {
406 unsigned NextIndex = F->getParent()->getLayoutOrder() + 1;
407 if (NextIndex != getSectionOrder().size())
408 LayoutSection(getSectionOrder()[NextIndex]);
412 void MCAsmLayout::LayoutSection(MCSectionData *SD) {
413 unsigned SectionOrderIndex = SD->getLayoutOrder();
415 ++stats::SectionLayouts;
417 // Compute the section start address.
418 uint64_t StartAddress = 0;
419 if (SectionOrderIndex) {
420 MCSectionData *Prev = getSectionOrder()[SectionOrderIndex - 1];
421 StartAddress = getSectionAddress(Prev) + getSectionAddressSize(Prev);
424 // Honor the section alignment requirements.
425 StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
427 // Set the section address.
428 SD->Address = StartAddress;
431 /// WriteFragmentData - Write the \arg F data to the output file.
432 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
433 const MCFragment &F, MCObjectWriter *OW) {
434 uint64_t Start = OW->getStream().tell();
437 ++stats::EmittedFragments;
439 // FIXME: Embed in fragments instead?
440 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
441 switch (F.getKind()) {
442 case MCFragment::FT_Align: {
443 MCAlignFragment &AF = cast<MCAlignFragment>(F);
444 uint64_t Count = FragmentSize / AF.getValueSize();
446 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
448 // FIXME: This error shouldn't actually occur (the front end should emit
449 // multiple .align directives to enforce the semantics it wants), but is
450 // severe enough that we want to report it. How to handle this?
451 if (Count * AF.getValueSize() != FragmentSize)
452 report_fatal_error("undefined .align directive, value size '" +
453 Twine(AF.getValueSize()) +
454 "' is not a divisor of padding size '" +
455 Twine(FragmentSize) + "'");
457 // See if we are aligning with nops, and if so do that first to try to fill
458 // the Count bytes. Then if that did not fill any bytes or there are any
459 // bytes left to fill use the the Value and ValueSize to fill the rest.
460 // If we are aligning with nops, ask that target to emit the right data.
461 if (AF.hasEmitNops()) {
462 if (!Asm.getBackend().WriteNopData(Count, OW))
463 report_fatal_error("unable to write nop sequence of " +
464 Twine(Count) + " bytes");
468 // Otherwise, write out in multiples of the value size.
469 for (uint64_t i = 0; i != Count; ++i) {
470 switch (AF.getValueSize()) {
472 assert(0 && "Invalid size!");
473 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
474 case 2: OW->Write16(uint16_t(AF.getValue())); break;
475 case 4: OW->Write32(uint32_t(AF.getValue())); break;
476 case 8: OW->Write64(uint64_t(AF.getValue())); break;
482 case MCFragment::FT_Data: {
483 MCDataFragment &DF = cast<MCDataFragment>(F);
484 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
485 OW->WriteBytes(DF.getContents().str());
489 case MCFragment::FT_Fill: {
490 MCFillFragment &FF = cast<MCFillFragment>(F);
492 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
494 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
495 switch (FF.getValueSize()) {
497 assert(0 && "Invalid size!");
498 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
499 case 2: OW->Write16(uint16_t(FF.getValue())); break;
500 case 4: OW->Write32(uint32_t(FF.getValue())); break;
501 case 8: OW->Write64(uint64_t(FF.getValue())); break;
507 case MCFragment::FT_Inst:
508 llvm_unreachable("unexpected inst fragment after lowering");
511 case MCFragment::FT_LEB: {
512 MCLEBFragment &LF = cast<MCLEBFragment>(F);
513 OW->WriteBytes(LF.getContents().str());
517 case MCFragment::FT_Org: {
518 MCOrgFragment &OF = cast<MCOrgFragment>(F);
520 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
521 OW->Write8(uint8_t(OF.getValue()));
526 case MCFragment::FT_Dwarf: {
527 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
528 OW->WriteBytes(OF.getContents().str());
533 assert(OW->getStream().tell() - Start == FragmentSize);
536 void MCAssembler::WriteSectionData(const MCSectionData *SD,
537 const MCAsmLayout &Layout,
538 MCObjectWriter *OW) const {
539 // Ignore virtual sections.
540 if (SD->getSection().isVirtualSection()) {
541 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
543 // Check that contents are only things legal inside a virtual section.
544 for (MCSectionData::const_iterator it = SD->begin(),
545 ie = SD->end(); it != ie; ++it) {
546 switch (it->getKind()) {
548 assert(0 && "Invalid fragment in virtual section!");
549 case MCFragment::FT_Data: {
550 // Check that we aren't trying to write a non-zero contents (or fixups)
551 // into a virtual section. This is to support clients which use standard
552 // directives to fill the contents of virtual sections.
553 MCDataFragment &DF = cast<MCDataFragment>(*it);
554 assert(DF.fixup_begin() == DF.fixup_end() &&
555 "Cannot have fixups in virtual section!");
556 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
557 assert(DF.getContents()[i] == 0 &&
558 "Invalid data value for virtual section!");
561 case MCFragment::FT_Align:
562 // Check that we aren't trying to write a non-zero value into a virtual
564 assert((!cast<MCAlignFragment>(it)->getValueSize() ||
565 !cast<MCAlignFragment>(it)->getValue()) &&
566 "Invalid align in virtual section!");
568 case MCFragment::FT_Fill:
569 assert(!cast<MCFillFragment>(it)->getValueSize() &&
570 "Invalid fill in virtual section!");
578 uint64_t Start = OW->getStream().tell();
581 for (MCSectionData::const_iterator it = SD->begin(),
582 ie = SD->end(); it != ie; ++it)
583 WriteFragmentData(*this, Layout, *it, OW);
585 assert(OW->getStream().tell() - Start == Layout.getSectionFileSize(SD));
588 void MCAssembler::Finish(MCObjectWriter *Writer) {
589 DEBUG_WITH_TYPE("mc-dump", {
590 llvm::errs() << "assembler backend - pre-layout\n--\n";
593 // Create the layout object.
594 MCAsmLayout Layout(*this);
596 // Insert additional align fragments for concrete sections to explicitly pad
597 // the previous section to match their alignment requirements. This is for
598 // 'gas' compatibility, it shouldn't strictly be necessary.
599 if (PadSectionToAlignment) {
600 for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
601 MCSectionData *SD = Layout.getSectionOrder()[i];
603 // Ignore sections without alignment requirements.
604 unsigned Align = SD->getAlignment();
608 // Ignore virtual sections, they don't cause file size modifications.
609 if (SD->getSection().isVirtualSection())
612 // Otherwise, create a new align fragment at the end of the previous
614 MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
615 Layout.getSectionOrder()[i - 1]);
616 AF->setOnlyAlignAddress(true);
620 // Create dummy fragments and assign section ordinals.
621 unsigned SectionIndex = 0;
622 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
623 // Create dummy fragments to eliminate any empty sections, this simplifies
625 if (it->getFragmentList().empty())
626 new MCDataFragment(it);
628 it->setOrdinal(SectionIndex++);
631 // Assign layout order indices to sections and fragments.
632 unsigned FragmentIndex = 0;
633 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
634 MCSectionData *SD = Layout.getSectionOrder()[i];
635 SD->setLayoutOrder(i);
637 for (MCSectionData::iterator it2 = SD->begin(),
638 ie2 = SD->end(); it2 != ie2; ++it2)
639 it2->setLayoutOrder(FragmentIndex++);
642 llvm::OwningPtr<MCObjectWriter> OwnWriter(0);
644 //no custom Writer_ : create the default one life-managed by OwningPtr
645 OwnWriter.reset(getBackend().createObjectWriter(OS));
646 Writer = OwnWriter.get();
648 report_fatal_error("unable to create object writer!");
651 // Layout until everything fits.
652 while (LayoutOnce(*Writer, Layout))
655 DEBUG_WITH_TYPE("mc-dump", {
656 llvm::errs() << "assembler backend - post-relaxation\n--\n";
659 // Finalize the layout, including fragment lowering.
660 FinishLayout(Layout);
662 DEBUG_WITH_TYPE("mc-dump", {
663 llvm::errs() << "assembler backend - final-layout\n--\n";
666 uint64_t StartOffset = OS.tell();
668 // Allow the object writer a chance to perform post-layout binding (for
669 // example, to set the index fields in the symbol data).
670 Writer->ExecutePostLayoutBinding(*this);
672 // Evaluate and apply the fixups, generating relocation entries as necessary.
673 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
674 for (MCSectionData::iterator it2 = it->begin(),
675 ie2 = it->end(); it2 != ie2; ++it2) {
676 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
680 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
681 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
682 MCFixup &Fixup = *it3;
684 // Evaluate the fixup.
687 if (!EvaluateFixup(*Writer, Layout, Fixup, DF, Target, FixedValue)) {
688 // The fixup was unresolved, we need a relocation. Inform the object
689 // writer of the relocation, and give it an opportunity to adjust the
690 // fixup value if need be.
691 Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
694 getBackend().ApplyFixup(Fixup, *DF, FixedValue);
699 // Write the object file.
700 Writer->WriteObject(*this, Layout);
702 stats::ObjectBytes += OS.tell() - StartOffset;
705 bool MCAssembler::FixupNeedsRelaxation(const MCObjectWriter &Writer,
706 const MCFixup &Fixup,
707 const MCFragment *DF,
708 const MCAsmLayout &Layout) const {
712 // If we cannot resolve the fixup value, it requires relaxation.
715 if (!EvaluateFixup(Writer, Layout, Fixup, DF, Target, Value))
718 // Otherwise, relax if the value is too big for a (signed) i8.
720 // FIXME: This is target dependent!
721 return int64_t(Value) != int64_t(int8_t(Value));
724 bool MCAssembler::FragmentNeedsRelaxation(const MCObjectWriter &Writer,
725 const MCInstFragment *IF,
726 const MCAsmLayout &Layout) const {
727 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
728 // are intentionally pushing out inst fragments, or because we relaxed a
729 // previous instruction to one that doesn't need relaxation.
730 if (!getBackend().MayNeedRelaxation(IF->getInst()))
733 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
734 ie = IF->fixup_end(); it != ie; ++it)
735 if (FixupNeedsRelaxation(Writer, *it, IF, Layout))
741 bool MCAssembler::RelaxInstruction(const MCObjectWriter &Writer,
743 MCInstFragment &IF) {
744 if (!FragmentNeedsRelaxation(Writer, &IF, Layout))
747 ++stats::RelaxedInstructions;
749 // FIXME-PERF: We could immediately lower out instructions if we can tell
750 // they are fully resolved, to avoid retesting on later passes.
752 // Relax the fragment.
755 getBackend().RelaxInstruction(IF.getInst(), Relaxed);
757 // Encode the new instruction.
759 // FIXME-PERF: If it matters, we could let the target do this. It can
760 // probably do so more efficiently in many cases.
761 SmallVector<MCFixup, 4> Fixups;
762 SmallString<256> Code;
763 raw_svector_ostream VecOS(Code);
764 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
767 // Update the instruction fragment.
770 IF.getFixups().clear();
771 // FIXME: Eliminate copy.
772 for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
773 IF.getFixups().push_back(Fixups[i]);
778 bool MCAssembler::RelaxOrg(const MCObjectWriter &Writer,
781 int64_t TargetLocation;
782 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
783 report_fatal_error("expected assembly-time absolute expression");
785 // FIXME: We need a way to communicate this error.
786 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
787 int64_t Offset = TargetLocation - FragmentOffset;
788 if (Offset < 0 || Offset >= 0x40000000)
789 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
790 "' (at offset '" + Twine(FragmentOffset) + "')");
792 unsigned OldSize = OF.getSize();
794 return OldSize != OF.getSize();
797 bool MCAssembler::RelaxLEB(const MCObjectWriter &Writer,
801 uint64_t OldSize = LF.getContents().size();
802 LF.getValue().EvaluateAsAbsolute(Value, &Layout);
803 SmallString<8> &Data = LF.getContents();
805 raw_svector_ostream OSE(Data);
807 MCObjectWriter::EncodeSLEB128(Value, OSE);
809 MCObjectWriter::EncodeULEB128(Value, OSE);
811 return OldSize != LF.getContents().size();
814 bool MCAssembler::RelaxDwarfLineAddr(const MCObjectWriter &Writer,
816 MCDwarfLineAddrFragment &DF) {
817 int64_t AddrDelta = 0;
818 uint64_t OldSize = DF.getContents().size();
819 DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, &Layout);
821 LineDelta = DF.getLineDelta();
822 SmallString<8> &Data = DF.getContents();
824 raw_svector_ostream OSE(Data);
825 MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OSE);
827 return OldSize != Data.size();
830 bool MCAssembler::LayoutOnce(const MCObjectWriter &Writer,
831 MCAsmLayout &Layout) {
832 ++stats::RelaxationSteps;
834 // Layout the sections in order.
837 // Scan for fragments that need relaxation.
838 bool WasRelaxed = false;
839 for (iterator it = begin(), ie = end(); it != ie; ++it) {
840 MCSectionData &SD = *it;
842 for (MCSectionData::iterator it2 = SD.begin(),
843 ie2 = SD.end(); it2 != ie2; ++it2) {
844 // Check if this is an fragment that needs relaxation.
845 bool relaxedFrag = false;
846 switch(it2->getKind()) {
849 case MCFragment::FT_Inst:
850 relaxedFrag = RelaxInstruction(Writer, Layout,
851 *cast<MCInstFragment>(it2));
853 case MCFragment::FT_Org:
854 relaxedFrag = RelaxOrg(Writer, Layout, *cast<MCOrgFragment>(it2));
856 case MCFragment::FT_Dwarf:
857 relaxedFrag = RelaxDwarfLineAddr(Writer, Layout,
858 *cast<MCDwarfLineAddrFragment>(it2));
860 case MCFragment::FT_LEB:
861 relaxedFrag = RelaxLEB(Writer, Layout, *cast<MCLEBFragment>(it2));
864 // Update the layout, and remember that we relaxed.
866 Layout.Invalidate(it2);
867 WasRelaxed |= relaxedFrag;
874 static void LowerInstFragment(MCInstFragment *IF,
875 MCDataFragment *DF) {
877 uint64_t DataOffset = DF->getContents().size();
880 DF->getContents().append(IF->getCode().begin(), IF->getCode().end());
882 // Adjust the fixup offsets and add them to the data fragment.
883 for (unsigned i = 0, e = IF->getFixups().size(); i != e; ++i) {
884 MCFixup &F = IF->getFixups()[i];
885 F.setOffset(DataOffset + F.getOffset());
886 DF->getFixups().push_back(F);
890 void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
891 // Lower out any instruction fragments, to simplify the fixup application and
894 // FIXME-PERF: We don't have to do this, but the assumption is that it is
895 // cheap (we will mostly end up eliminating fragments and appending on to data
896 // fragments), so the extra complexity downstream isn't worth it. Evaluate
899 // The layout is done. Mark every fragment as valid.
900 Layout.getFragmentOffset(&*Layout.getSectionOrder().back()->rbegin());
902 unsigned FragmentIndex = 0;
903 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
904 MCSectionData &SD = *Layout.getSectionOrder()[i];
905 MCDataFragment *CurDF = NULL;
907 for (MCSectionData::iterator it2 = SD.begin(),
908 ie2 = SD.end(); it2 != ie2; ++it2) {
909 switch (it2->getKind()) {
913 case MCFragment::FT_Data:
914 CurDF = cast<MCDataFragment>(it2);
916 case MCFragment::FT_Inst: {
917 MCInstFragment *IF = cast<MCInstFragment>(it2);
918 // Use the existing data fragment if possible.
919 if (CurDF && CurDF->getAtom() == IF->getAtom()) {
920 Layout.CoalesceFragments(IF, CurDF);
922 // Otherwise, create a new data fragment.
923 CurDF = new MCDataFragment();
924 Layout.ReplaceFragment(IF, CurDF);
927 // Lower the Instruction Fragment
928 LowerInstFragment(IF, CurDF);
930 // Delete the instruction fragment and update the iterator.
936 // Since we may have merged fragments, fix the layout order.
937 it2->setLayoutOrder(FragmentIndex++);
946 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
947 OS << "<MCFixup" << " Offset:" << AF.getOffset()
948 << " Value:" << *AF.getValue()
949 << " Kind:" << AF.getKind() << ">";
955 void MCFragment::dump() {
956 raw_ostream &OS = llvm::errs();
960 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
961 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
962 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
963 case MCFragment::FT_Inst: OS << "MCInstFragment"; break;
964 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
965 case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
966 case MCFragment::FT_LEB: OS << "MCLEBFragment"; break;
969 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
970 << " Offset:" << Offset << " EffectiveSize:" << EffectiveSize << ">";
973 case MCFragment::FT_Align: {
974 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
975 if (AF->hasEmitNops())
976 OS << " (emit nops)";
977 if (AF->hasOnlyAlignAddress())
978 OS << " (only align section)";
980 OS << " Alignment:" << AF->getAlignment()
981 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
982 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
985 case MCFragment::FT_Data: {
986 const MCDataFragment *DF = cast<MCDataFragment>(this);
989 const SmallVectorImpl<char> &Contents = DF->getContents();
990 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
992 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
994 OS << "] (" << Contents.size() << " bytes)";
996 if (!DF->getFixups().empty()) {
999 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
1000 ie = DF->fixup_end(); it != ie; ++it) {
1001 if (it != DF->fixup_begin()) OS << ",\n ";
1008 case MCFragment::FT_Fill: {
1009 const MCFillFragment *FF = cast<MCFillFragment>(this);
1010 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
1011 << " Size:" << FF->getSize();
1014 case MCFragment::FT_Inst: {
1015 const MCInstFragment *IF = cast<MCInstFragment>(this);
1018 IF->getInst().dump_pretty(OS);
1021 case MCFragment::FT_Org: {
1022 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
1024 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
1027 case MCFragment::FT_Dwarf: {
1028 const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
1030 OS << " AddrDelta:" << OF->getAddrDelta()
1031 << " LineDelta:" << OF->getLineDelta();
1034 case MCFragment::FT_LEB: {
1035 const MCLEBFragment *LF = cast<MCLEBFragment>(this);
1037 OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
1044 void MCSectionData::dump() {
1045 raw_ostream &OS = llvm::errs();
1047 OS << "<MCSectionData";
1048 OS << " Alignment:" << getAlignment() << " Address:" << Address
1049 << " Fragments:[\n ";
1050 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1051 if (it != begin()) OS << ",\n ";
1057 void MCSymbolData::dump() {
1058 raw_ostream &OS = llvm::errs();
1060 OS << "<MCSymbolData Symbol:" << getSymbol()
1061 << " Fragment:" << getFragment() << " Offset:" << getOffset()
1062 << " Flags:" << getFlags() << " Index:" << getIndex();
1064 OS << " (common, size:" << getCommonSize()
1065 << " align: " << getCommonAlignment() << ")";
1067 OS << " (external)";
1068 if (isPrivateExtern())
1069 OS << " (private extern)";
1073 void MCAssembler::dump() {
1074 raw_ostream &OS = llvm::errs();
1076 OS << "<MCAssembler\n";
1077 OS << " Sections:[\n ";
1078 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1079 if (it != begin()) OS << ",\n ";
1085 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1086 if (it != symbol_begin()) OS << ",\n ";