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/MCSymbol.h"
17 #include "llvm/MC/MCValue.h"
18 #include "llvm/ADT/OwningPtr.h"
19 #include "llvm/ADT/Statistic.h"
20 #include "llvm/ADT/StringExtras.h"
21 #include "llvm/ADT/Twine.h"
22 #include "llvm/Support/Debug.h"
23 #include "llvm/Support/ErrorHandling.h"
24 #include "llvm/Support/raw_ostream.h"
25 #include "llvm/Target/TargetRegistry.h"
26 #include "llvm/Target/TargetAsmBackend.h"
33 STATISTIC(EmittedFragments, "Number of emitted assembler fragments");
34 STATISTIC(EvaluateFixup, "Number of evaluated fixups");
35 STATISTIC(FragmentLayouts, "Number of fragment layouts");
36 STATISTIC(ObjectBytes, "Number of emitted object file bytes");
37 STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps");
38 STATISTIC(RelaxedInstructions, "Number of relaxed instructions");
39 STATISTIC(SectionLayouts, "Number of section layouts");
43 // FIXME FIXME FIXME: There are number of places in this file where we convert
44 // what is a 64-bit assembler value used for computation into a value in the
45 // object file, which may truncate it. We should detect that truncation where
46 // invalid and report errors back.
50 MCAsmLayout::MCAsmLayout(MCAssembler &Asm)
51 : Assembler(Asm), LastValidFragment(0)
53 // Compute the section layout order. Virtual sections must go last.
54 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
55 if (!Asm.getBackend().isVirtualSection(it->getSection()))
56 SectionOrder.push_back(&*it);
57 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
58 if (Asm.getBackend().isVirtualSection(it->getSection()))
59 SectionOrder.push_back(&*it);
62 bool MCAsmLayout::isSectionUpToDate(const MCSectionData *SD) const {
63 // The first section is always up-to-date.
64 unsigned Index = SD->getLayoutOrder();
68 // Otherwise, sections are always implicitly computed when the preceeding
69 // fragment is layed out.
70 const MCSectionData *Prev = getSectionOrder()[Index - 1];
71 return isFragmentUpToDate(&(Prev->getFragmentList().back()));
74 bool MCAsmLayout::isFragmentUpToDate(const MCFragment *F) const {
75 return (LastValidFragment &&
76 F->getLayoutOrder() <= LastValidFragment->getLayoutOrder());
79 void MCAsmLayout::UpdateForSlide(MCFragment *F, int SlideAmount) {
80 // If this fragment wasn't already up-to-date, we don't need to do anything.
81 if (!isFragmentUpToDate(F))
84 // Otherwise, reset the last valid fragment to the predecessor of the
85 // invalidated fragment.
86 LastValidFragment = F->getPrevNode();
87 if (!LastValidFragment) {
88 unsigned Index = F->getParent()->getLayoutOrder();
90 MCSectionData *Prev = getSectionOrder()[Index - 1];
91 LastValidFragment = &(Prev->getFragmentList().back());
96 void MCAsmLayout::EnsureValid(const MCFragment *F) const {
97 // Advance the layout position until the fragment is up-to-date.
98 while (!isFragmentUpToDate(F)) {
99 // Advance to the next fragment.
100 MCFragment *Cur = LastValidFragment;
102 Cur = Cur->getNextNode();
104 unsigned NextIndex = 0;
105 if (LastValidFragment)
106 NextIndex = LastValidFragment->getParent()->getLayoutOrder() + 1;
107 Cur = SectionOrder[NextIndex]->begin();
110 const_cast<MCAsmLayout*>(this)->LayoutFragment(Cur);
114 void MCAsmLayout::FragmentReplaced(MCFragment *Src, MCFragment *Dst) {
115 if (LastValidFragment == Src)
116 LastValidFragment = Dst;
118 Dst->Offset = Src->Offset;
119 Dst->EffectiveSize = Src->EffectiveSize;
122 uint64_t MCAsmLayout::getFragmentAddress(const MCFragment *F) const {
123 assert(F->getParent() && "Missing section()!");
124 return getSectionAddress(F->getParent()) + getFragmentOffset(F);
127 uint64_t MCAsmLayout::getFragmentEffectiveSize(const MCFragment *F) const {
129 assert(F->EffectiveSize != ~UINT64_C(0) && "Address not set!");
130 return F->EffectiveSize;
133 uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
135 assert(F->Offset != ~UINT64_C(0) && "Address not set!");
139 uint64_t MCAsmLayout::getSymbolAddress(const MCSymbolData *SD) const {
140 assert(SD->getFragment() && "Invalid getAddress() on undefined symbol!");
141 return getFragmentAddress(SD->getFragment()) + SD->getOffset();
144 uint64_t MCAsmLayout::getSectionAddress(const MCSectionData *SD) const {
145 EnsureValid(SD->begin());
146 assert(SD->Address != ~UINT64_C(0) && "Address not set!");
150 uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const {
151 // The size is the last fragment's end offset.
152 const MCFragment &F = SD->getFragmentList().back();
153 return getFragmentOffset(&F) + getFragmentEffectiveSize(&F);
156 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
157 // Virtual sections have no file size.
158 if (getAssembler().getBackend().isVirtualSection(SD->getSection()))
161 // Otherwise, the file size is the same as the address space size.
162 return getSectionAddressSize(SD);
165 uint64_t MCAsmLayout::getSectionSize(const MCSectionData *SD) const {
166 // The logical size is the address space size minus any tail padding.
167 uint64_t Size = getSectionAddressSize(SD);
168 const MCAlignFragment *AF =
169 dyn_cast<MCAlignFragment>(&(SD->getFragmentList().back()));
170 if (AF && AF->hasOnlyAlignAddress())
171 Size -= getFragmentEffectiveSize(AF);
178 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
181 MCFragment::~MCFragment() {
184 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
185 : Kind(_Kind), Parent(_Parent), Atom(0), Offset(~UINT64_C(0)),
186 EffectiveSize(~UINT64_C(0))
189 Parent->getFragmentList().push_back(this);
194 MCSectionData::MCSectionData() : Section(0) {}
196 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
197 : Section(&_Section),
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 static bool isScatteredFixupFullyResolvedSimple(const MCAssembler &Asm,
236 const MCFixup &Fixup,
237 const MCValue Target,
238 const MCSection *BaseSection) {
239 // The effective fixup address is
240 // addr(atom(A)) + offset(A)
241 // - addr(atom(B)) - offset(B)
242 // - addr(<base symbol>) + <fixup offset from base symbol>
243 // and the offsets are not relocatable, so the fixup is fully resolved when
244 // addr(atom(A)) - addr(atom(B)) - addr(<base symbol>)) == 0.
246 // The simple (Darwin, except on x86_64) way of dealing with this was to
247 // assume that any reference to a temporary symbol *must* be a temporary
248 // symbol in the same atom, unless the sections differ. Therefore, any PCrel
249 // relocation to a temporary symbol (in the same section) is fully
250 // resolved. This also works in conjunction with absolutized .set, which
251 // requires the compiler to use .set to absolutize the differences between
252 // symbols which the compiler knows to be assembly time constants, so we don't
253 // need to worry about considering symbol differences fully resolved.
255 // Non-relative fixups are only resolved if constant.
257 return Target.isAbsolute();
259 // Otherwise, relative fixups are only resolved if not a difference and the
260 // target is a temporary in the same section.
261 if (Target.isAbsolute() || Target.getSymB())
264 const MCSymbol *A = &Target.getSymA()->getSymbol();
265 if (!A->isTemporary() || !A->isInSection() ||
266 &A->getSection() != BaseSection)
272 static bool isScatteredFixupFullyResolved(const MCAssembler &Asm,
273 const MCAsmLayout &Layout,
274 const MCFixup &Fixup,
275 const MCValue Target,
276 const MCSymbolData *BaseSymbol) {
277 // The effective fixup address is
278 // addr(atom(A)) + offset(A)
279 // - addr(atom(B)) - offset(B)
280 // - addr(BaseSymbol) + <fixup offset from base symbol>
281 // and the offsets are not relocatable, so the fixup is fully resolved when
282 // addr(atom(A)) - addr(atom(B)) - addr(BaseSymbol) == 0.
284 // Note that "false" is almost always conservatively correct (it means we emit
285 // a relocation which is unnecessary), except when it would force us to emit a
286 // relocation which the target cannot encode.
288 const MCSymbolData *A_Base = 0, *B_Base = 0;
289 if (const MCSymbolRefExpr *A = Target.getSymA()) {
290 // Modified symbol references cannot be resolved.
291 if (A->getKind() != MCSymbolRefExpr::VK_None)
294 A_Base = Asm.getAtom(Layout, &Asm.getSymbolData(A->getSymbol()));
299 if (const MCSymbolRefExpr *B = Target.getSymB()) {
300 // Modified symbol references cannot be resolved.
301 if (B->getKind() != MCSymbolRefExpr::VK_None)
304 B_Base = Asm.getAtom(Layout, &Asm.getSymbolData(B->getSymbol()));
309 // If there is no base, A and B have to be the same atom for this fixup to be
312 return A_Base == B_Base;
314 // Otherwise, B must be missing and A must be the base.
315 return !B_Base && BaseSymbol == A_Base;
318 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
319 // Non-temporary labels should always be visible to the linker.
320 if (!Symbol.isTemporary())
323 // Absolute temporary labels are never visible.
324 if (!Symbol.isInSection())
327 // Otherwise, check if the section requires symbols even for temporary labels.
328 return getBackend().doesSectionRequireSymbols(Symbol.getSection());
331 const MCSymbolData *MCAssembler::getAtom(const MCAsmLayout &Layout,
332 const MCSymbolData *SD) const {
333 // Linker visible symbols define atoms.
334 if (isSymbolLinkerVisible(SD->getSymbol()))
337 // Absolute and undefined symbols have no defining atom.
338 if (!SD->getFragment())
341 // Non-linker visible symbols in sections which can't be atomized have no
343 if (!getBackend().isSectionAtomizable(
344 SD->getFragment()->getParent()->getSection()))
347 // Otherwise, return the atom for the containing fragment.
348 return SD->getFragment()->getAtom();
351 bool MCAssembler::EvaluateFixup(const MCAsmLayout &Layout,
352 const MCFixup &Fixup, const MCFragment *DF,
353 MCValue &Target, uint64_t &Value) const {
354 ++stats::EvaluateFixup;
356 if (!Fixup.getValue()->EvaluateAsRelocatable(Target, &Layout))
357 report_fatal_error("expected relocatable expression");
359 // FIXME: How do non-scattered symbols work in ELF? I presume the linker
360 // doesn't support small relocations, but then under what criteria does the
361 // assembler allow symbol differences?
363 Value = Target.getConstant();
365 bool IsPCRel = Emitter.getFixupKindInfo(
366 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
367 bool IsResolved = true;
368 if (const MCSymbolRefExpr *A = Target.getSymA()) {
369 if (A->getSymbol().isDefined())
370 Value += Layout.getSymbolAddress(&getSymbolData(A->getSymbol()));
374 if (const MCSymbolRefExpr *B = Target.getSymB()) {
375 if (B->getSymbol().isDefined())
376 Value -= Layout.getSymbolAddress(&getSymbolData(B->getSymbol()));
381 // If we are using scattered symbols, determine whether this value is actually
382 // resolved; scattering may cause atoms to move.
383 if (IsResolved && getBackend().hasScatteredSymbols()) {
384 if (getBackend().hasReliableSymbolDifference()) {
385 // If this is a PCrel relocation, find the base atom (identified by its
386 // symbol) that the fixup value is relative to.
387 const MCSymbolData *BaseSymbol = 0;
389 BaseSymbol = DF->getAtom();
395 IsResolved = isScatteredFixupFullyResolved(*this, Layout, Fixup, Target,
398 const MCSection *BaseSection = 0;
400 BaseSection = &DF->getParent()->getSection();
402 IsResolved = isScatteredFixupFullyResolvedSimple(*this, Fixup, Target,
408 Value -= Layout.getFragmentAddress(DF) + Fixup.getOffset();
413 uint64_t MCAssembler::ComputeFragmentSize(MCAsmLayout &Layout,
415 uint64_t SectionAddress,
416 uint64_t FragmentOffset) const {
417 switch (F.getKind()) {
418 case MCFragment::FT_Data:
419 return cast<MCDataFragment>(F).getContents().size();
420 case MCFragment::FT_Fill:
421 return cast<MCFillFragment>(F).getSize();
422 case MCFragment::FT_Inst:
423 return cast<MCInstFragment>(F).getInstSize();
425 case MCFragment::FT_Align: {
426 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
428 assert((!AF.hasOnlyAlignAddress() || !AF.getNextNode()) &&
429 "Invalid OnlyAlignAddress bit, not the last fragment!");
431 uint64_t Size = OffsetToAlignment(SectionAddress + FragmentOffset,
434 // Honor MaxBytesToEmit.
435 if (Size > AF.getMaxBytesToEmit())
441 case MCFragment::FT_Org: {
442 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
444 // FIXME: We should compute this sooner, we don't want to recurse here, and
445 // we would like to be more functional.
446 int64_t TargetLocation;
447 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
448 report_fatal_error("expected assembly-time absolute expression");
450 // FIXME: We need a way to communicate this error.
451 int64_t Offset = TargetLocation - FragmentOffset;
452 if (Offset < 0 || Offset >= 0x40000000)
453 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
454 "' (at offset '" + Twine(FragmentOffset) + "'");
460 assert(0 && "invalid fragment kind");
464 void MCAsmLayout::LayoutFile() {
465 // Initialize the first section and set the valid fragment layout point. All
466 // actual layout computations are done lazily.
467 LastValidFragment = 0;
468 if (!getSectionOrder().empty())
469 getSectionOrder().front()->Address = 0;
472 void MCAsmLayout::LayoutFragment(MCFragment *F) {
473 MCFragment *Prev = F->getPrevNode();
475 // We should never try to recompute something which is up-to-date.
476 assert(!isFragmentUpToDate(F) && "Attempt to recompute up-to-date fragment!");
477 // We should never try to compute the fragment layout if the section isn't
479 assert(isSectionUpToDate(F->getParent()) &&
480 "Attempt to compute fragment before it's section!");
481 // We should never try to compute the fragment layout if it's predecessor
483 assert((!Prev || isFragmentUpToDate(Prev)) &&
484 "Attempt to compute fragment before it's predecessor!");
486 ++stats::FragmentLayouts;
488 // Compute the fragment start address.
489 uint64_t StartAddress = F->getParent()->Address;
490 uint64_t Address = StartAddress;
492 Address += Prev->Offset + Prev->EffectiveSize;
494 // Compute fragment offset and size.
495 F->Offset = Address - StartAddress;
496 F->EffectiveSize = getAssembler().ComputeFragmentSize(*this, *F, StartAddress,
498 LastValidFragment = F;
500 // If this is the last fragment in a section, update the next section address.
501 if (!F->getNextNode()) {
502 unsigned NextIndex = F->getParent()->getLayoutOrder() + 1;
503 if (NextIndex != getSectionOrder().size())
504 LayoutSection(getSectionOrder()[NextIndex]);
508 void MCAsmLayout::LayoutSection(MCSectionData *SD) {
509 unsigned SectionOrderIndex = SD->getLayoutOrder();
511 ++stats::SectionLayouts;
513 // Compute the section start address.
514 uint64_t StartAddress = 0;
515 if (SectionOrderIndex) {
516 MCSectionData *Prev = getSectionOrder()[SectionOrderIndex - 1];
517 StartAddress = getSectionAddress(Prev) + getSectionAddressSize(Prev);
520 // Honor the section alignment requirements.
521 StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
523 // Set the section address.
524 SD->Address = StartAddress;
527 /// WriteFragmentData - Write the \arg F data to the output file.
528 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
529 const MCFragment &F, MCObjectWriter *OW) {
530 uint64_t Start = OW->getStream().tell();
533 ++stats::EmittedFragments;
535 // FIXME: Embed in fragments instead?
536 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
537 switch (F.getKind()) {
538 case MCFragment::FT_Align: {
539 MCAlignFragment &AF = cast<MCAlignFragment>(F);
540 uint64_t Count = FragmentSize / AF.getValueSize();
542 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
544 // FIXME: This error shouldn't actually occur (the front end should emit
545 // multiple .align directives to enforce the semantics it wants), but is
546 // severe enough that we want to report it. How to handle this?
547 if (Count * AF.getValueSize() != FragmentSize)
548 report_fatal_error("undefined .align directive, value size '" +
549 Twine(AF.getValueSize()) +
550 "' is not a divisor of padding size '" +
551 Twine(FragmentSize) + "'");
553 // See if we are aligning with nops, and if so do that first to try to fill
554 // the Count bytes. Then if that did not fill any bytes or there are any
555 // bytes left to fill use the the Value and ValueSize to fill the rest.
556 // If we are aligning with nops, ask that target to emit the right data.
557 if (AF.hasEmitNops()) {
558 if (!Asm.getBackend().WriteNopData(Count, OW))
559 report_fatal_error("unable to write nop sequence of " +
560 Twine(Count) + " bytes");
564 // Otherwise, write out in multiples of the value size.
565 for (uint64_t i = 0; i != Count; ++i) {
566 switch (AF.getValueSize()) {
568 assert(0 && "Invalid size!");
569 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
570 case 2: OW->Write16(uint16_t(AF.getValue())); break;
571 case 4: OW->Write32(uint32_t(AF.getValue())); break;
572 case 8: OW->Write64(uint64_t(AF.getValue())); break;
578 case MCFragment::FT_Data: {
579 MCDataFragment &DF = cast<MCDataFragment>(F);
580 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
581 OW->WriteBytes(DF.getContents().str());
585 case MCFragment::FT_Fill: {
586 MCFillFragment &FF = cast<MCFillFragment>(F);
588 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
590 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
591 switch (FF.getValueSize()) {
593 assert(0 && "Invalid size!");
594 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
595 case 2: OW->Write16(uint16_t(FF.getValue())); break;
596 case 4: OW->Write32(uint32_t(FF.getValue())); break;
597 case 8: OW->Write64(uint64_t(FF.getValue())); break;
603 case MCFragment::FT_Inst:
604 llvm_unreachable("unexpected inst fragment after lowering");
607 case MCFragment::FT_Org: {
608 MCOrgFragment &OF = cast<MCOrgFragment>(F);
610 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
611 OW->Write8(uint8_t(OF.getValue()));
617 assert(OW->getStream().tell() - Start == FragmentSize);
620 void MCAssembler::WriteSectionData(const MCSectionData *SD,
621 const MCAsmLayout &Layout,
622 MCObjectWriter *OW) const {
623 // Ignore virtual sections.
624 if (getBackend().isVirtualSection(SD->getSection())) {
625 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
627 // Check that contents are only things legal inside a virtual section.
628 for (MCSectionData::const_iterator it = SD->begin(),
629 ie = SD->end(); it != ie; ++it) {
630 switch (it->getKind()) {
632 assert(0 && "Invalid fragment in virtual section!");
633 case MCFragment::FT_Data: {
634 // Check that we aren't trying to write a non-zero contents (or fixups)
635 // into a virtual section. This is to support clients which use standard
636 // directives to fill the contents of virtual sections.
637 MCDataFragment &DF = cast<MCDataFragment>(*it);
638 assert(DF.fixup_begin() == DF.fixup_end() &&
639 "Cannot have fixups in virtual section!");
640 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
641 assert(DF.getContents()[i] == 0 &&
642 "Invalid data value for virtual section!");
645 case MCFragment::FT_Align:
646 // Check that we aren't trying to write a non-zero value into a virtual
648 assert((!cast<MCAlignFragment>(it)->getValueSize() ||
649 !cast<MCAlignFragment>(it)->getValue()) &&
650 "Invalid align in virtual section!");
652 case MCFragment::FT_Fill:
653 assert(!cast<MCFillFragment>(it)->getValueSize() &&
654 "Invalid fill in virtual section!");
662 uint64_t Start = OW->getStream().tell();
665 for (MCSectionData::const_iterator it = SD->begin(),
666 ie = SD->end(); it != ie; ++it)
667 WriteFragmentData(*this, Layout, *it, OW);
669 assert(OW->getStream().tell() - Start == Layout.getSectionFileSize(SD));
672 void MCAssembler::AddSectionToTheEnd(MCSectionData &SD, MCAsmLayout &Layout) {
673 // Create dummy fragments and assign section ordinals.
674 unsigned SectionIndex = 0;
675 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it)
678 SD.setOrdinal(SectionIndex);
680 // Assign layout order indices to sections and fragments.
681 unsigned FragmentIndex = 0;
683 for (unsigned e = Layout.getSectionOrder().size(); i != e; ++i) {
684 MCSectionData *SD = Layout.getSectionOrder()[i];
686 for (MCSectionData::iterator it2 = SD->begin(),
687 ie2 = SD->end(); it2 != ie2; ++it2)
691 SD.setLayoutOrder(i);
692 for (MCSectionData::iterator it2 = SD.begin(),
693 ie2 = SD.end(); it2 != ie2; ++it2) {
694 it2->setLayoutOrder(FragmentIndex++);
696 Layout.getSectionOrder().push_back(&SD);
698 Layout.LayoutSection(&SD);
700 // Layout until everything fits.
701 while (LayoutOnce(Layout))
706 void MCAssembler::Finish(MCObjectWriter *Writer) {
707 DEBUG_WITH_TYPE("mc-dump", {
708 llvm::errs() << "assembler backend - pre-layout\n--\n";
711 // Create the layout object.
712 MCAsmLayout Layout(*this);
714 // Insert additional align fragments for concrete sections to explicitly pad
715 // the previous section to match their alignment requirements. This is for
716 // 'gas' compatibility, it shouldn't strictly be necessary.
717 if (PadSectionToAlignment) {
718 for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
719 MCSectionData *SD = Layout.getSectionOrder()[i];
721 // Ignore sections without alignment requirements.
722 unsigned Align = SD->getAlignment();
726 // Ignore virtual sections, they don't cause file size modifications.
727 if (getBackend().isVirtualSection(SD->getSection()))
730 // Otherwise, create a new align fragment at the end of the previous
732 MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
733 Layout.getSectionOrder()[i - 1]);
734 AF->setOnlyAlignAddress(true);
738 // Create dummy fragments and assign section ordinals.
739 unsigned SectionIndex = 0;
740 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
741 // Create dummy fragments to eliminate any empty sections, this simplifies
743 if (it->getFragmentList().empty())
744 new MCDataFragment(it);
746 it->setOrdinal(SectionIndex++);
749 // Assign layout order indices to sections and fragments.
750 unsigned FragmentIndex = 0;
751 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
752 MCSectionData *SD = Layout.getSectionOrder()[i];
753 SD->setLayoutOrder(i);
755 for (MCSectionData::iterator it2 = SD->begin(),
756 ie2 = SD->end(); it2 != ie2; ++it2)
757 it2->setLayoutOrder(FragmentIndex++);
760 // Layout until everything fits.
761 while (LayoutOnce(Layout))
764 DEBUG_WITH_TYPE("mc-dump", {
765 llvm::errs() << "assembler backend - post-relaxation\n--\n";
768 // Finalize the layout, including fragment lowering.
769 FinishLayout(Layout);
771 DEBUG_WITH_TYPE("mc-dump", {
772 llvm::errs() << "assembler backend - final-layout\n--\n";
775 uint64_t StartOffset = OS.tell();
777 llvm::OwningPtr<MCObjectWriter> OwnWriter(0);
779 //no custom Writer_ : create the default one life-managed by OwningPtr
780 OwnWriter.reset(getBackend().createObjectWriter(OS));
781 Writer = OwnWriter.get();
783 report_fatal_error("unable to create object writer!");
786 // Allow the object writer a chance to perform post-layout binding (for
787 // example, to set the index fields in the symbol data).
788 Writer->ExecutePostLayoutBinding(*this);
790 // Evaluate and apply the fixups, generating relocation entries as necessary.
791 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
792 for (MCSectionData::iterator it2 = it->begin(),
793 ie2 = it->end(); it2 != ie2; ++it2) {
794 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
798 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
799 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
800 MCFixup &Fixup = *it3;
802 // Evaluate the fixup.
805 if (!EvaluateFixup(Layout, Fixup, DF, Target, FixedValue)) {
806 // The fixup was unresolved, we need a relocation. Inform the object
807 // writer of the relocation, and give it an opportunity to adjust the
808 // fixup value if need be.
809 Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
812 getBackend().ApplyFixup(Fixup, *DF, FixedValue);
817 // Write the object file.
818 Writer->WriteObject(*this, Layout);
820 stats::ObjectBytes += OS.tell() - StartOffset;
823 bool MCAssembler::FixupNeedsRelaxation(const MCFixup &Fixup,
824 const MCFragment *DF,
825 const MCAsmLayout &Layout) const {
829 // If we cannot resolve the fixup value, it requires relaxation.
832 if (!EvaluateFixup(Layout, Fixup, DF, Target, Value))
835 // Otherwise, relax if the value is too big for a (signed) i8.
837 // FIXME: This is target dependent!
838 return int64_t(Value) != int64_t(int8_t(Value));
841 bool MCAssembler::FragmentNeedsRelaxation(const MCInstFragment *IF,
842 const MCAsmLayout &Layout) const {
843 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
844 // are intentionally pushing out inst fragments, or because we relaxed a
845 // previous instruction to one that doesn't need relaxation.
846 if (!getBackend().MayNeedRelaxation(IF->getInst()))
849 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
850 ie = IF->fixup_end(); it != ie; ++it)
851 if (FixupNeedsRelaxation(*it, IF, Layout))
857 bool MCAssembler::LayoutOnce(MCAsmLayout &Layout) {
858 ++stats::RelaxationSteps;
860 // Layout the sections in order.
863 // Scan for fragments that need relaxation.
864 bool WasRelaxed = false;
865 for (iterator it = begin(), ie = end(); it != ie; ++it) {
866 MCSectionData &SD = *it;
868 for (MCSectionData::iterator it2 = SD.begin(),
869 ie2 = SD.end(); it2 != ie2; ++it2) {
870 // Check if this is an instruction fragment that needs relaxation.
871 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
872 if (!IF || !FragmentNeedsRelaxation(IF, Layout))
875 ++stats::RelaxedInstructions;
877 // FIXME-PERF: We could immediately lower out instructions if we can tell
878 // they are fully resolved, to avoid retesting on later passes.
880 // Relax the fragment.
883 getBackend().RelaxInstruction(IF->getInst(), Relaxed);
885 // Encode the new instruction.
887 // FIXME-PERF: If it matters, we could let the target do this. It can
888 // probably do so more efficiently in many cases.
889 SmallVector<MCFixup, 4> Fixups;
890 SmallString<256> Code;
891 raw_svector_ostream VecOS(Code);
892 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
895 // Update the instruction fragment.
896 int SlideAmount = Code.size() - IF->getInstSize();
897 IF->setInst(Relaxed);
898 IF->getCode() = Code;
899 IF->getFixups().clear();
900 // FIXME: Eliminate copy.
901 for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
902 IF->getFixups().push_back(Fixups[i]);
904 // Update the layout, and remember that we relaxed.
905 Layout.UpdateForSlide(IF, SlideAmount);
913 void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
914 // Lower out any instruction fragments, to simplify the fixup application and
917 // FIXME-PERF: We don't have to do this, but the assumption is that it is
918 // cheap (we will mostly end up eliminating fragments and appending on to data
919 // fragments), so the extra complexity downstream isn't worth it. Evaluate
921 for (iterator it = begin(), ie = end(); it != ie; ++it) {
922 MCSectionData &SD = *it;
924 for (MCSectionData::iterator it2 = SD.begin(),
925 ie2 = SD.end(); it2 != ie2; ++it2) {
926 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
930 // Create a new data fragment for the instruction.
932 // FIXME-PERF: Reuse previous data fragment if possible.
933 MCDataFragment *DF = new MCDataFragment();
934 SD.getFragmentList().insert(it2, DF);
936 // Update the data fragments layout data.
937 DF->setParent(IF->getParent());
938 DF->setAtom(IF->getAtom());
939 DF->setLayoutOrder(IF->getLayoutOrder());
940 Layout.FragmentReplaced(IF, DF);
942 // Copy in the data and the fixups.
943 DF->getContents().append(IF->getCode().begin(), IF->getCode().end());
944 for (unsigned i = 0, e = IF->getFixups().size(); i != e; ++i)
945 DF->getFixups().push_back(IF->getFixups()[i]);
947 // Delete the instruction fragment and update the iterator.
948 SD.getFragmentList().erase(IF);
958 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
959 OS << "<MCFixup" << " Offset:" << AF.getOffset()
960 << " Value:" << *AF.getValue()
961 << " Kind:" << AF.getKind() << ">";
967 void MCFragment::dump() {
968 raw_ostream &OS = llvm::errs();
972 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
973 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
974 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
975 case MCFragment::FT_Inst: OS << "MCInstFragment"; break;
976 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
979 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
980 << " Offset:" << Offset << " EffectiveSize:" << EffectiveSize << ">";
983 case MCFragment::FT_Align: {
984 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
985 if (AF->hasEmitNops())
986 OS << " (emit nops)";
987 if (AF->hasOnlyAlignAddress())
988 OS << " (only align section)";
990 OS << " Alignment:" << AF->getAlignment()
991 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
992 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
995 case MCFragment::FT_Data: {
996 const MCDataFragment *DF = cast<MCDataFragment>(this);
999 const SmallVectorImpl<char> &Contents = DF->getContents();
1000 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
1002 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1004 OS << "] (" << Contents.size() << " bytes)";
1006 if (!DF->getFixups().empty()) {
1009 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
1010 ie = DF->fixup_end(); it != ie; ++it) {
1011 if (it != DF->fixup_begin()) OS << ",\n ";
1018 case MCFragment::FT_Fill: {
1019 const MCFillFragment *FF = cast<MCFillFragment>(this);
1020 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
1021 << " Size:" << FF->getSize();
1024 case MCFragment::FT_Inst: {
1025 const MCInstFragment *IF = cast<MCInstFragment>(this);
1028 IF->getInst().dump_pretty(OS);
1031 case MCFragment::FT_Org: {
1032 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
1034 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
1041 void MCSectionData::dump() {
1042 raw_ostream &OS = llvm::errs();
1044 OS << "<MCSectionData";
1045 OS << " Alignment:" << getAlignment() << " Address:" << Address
1046 << " Fragments:[\n ";
1047 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1048 if (it != begin()) OS << ",\n ";
1054 void MCSymbolData::dump() {
1055 raw_ostream &OS = llvm::errs();
1057 OS << "<MCSymbolData Symbol:" << getSymbol()
1058 << " Fragment:" << getFragment() << " Offset:" << getOffset()
1059 << " Flags:" << getFlags() << " Index:" << getIndex();
1061 OS << " (common, size:" << getCommonSize()
1062 << " align: " << getCommonAlignment() << ")";
1064 OS << " (external)";
1065 if (isPrivateExtern())
1066 OS << " (private extern)";
1070 void MCAssembler::dump() {
1071 raw_ostream &OS = llvm::errs();
1073 OS << "<MCAssembler\n";
1074 OS << " Sections:[\n ";
1075 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1076 if (it != begin()) OS << ",\n ";
1082 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1083 if (it != symbol_begin()) OS << ",\n ";