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), 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),
198 Address(~UINT64_C(0)),
199 HasInstructions(false)
202 A->getSectionList().push_back(this);
207 MCSymbolData::MCSymbolData() : Symbol(0) {}
209 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
210 uint64_t _Offset, MCAssembler *A)
211 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
212 IsExternal(false), IsPrivateExtern(false),
213 CommonSize(0), CommonAlign(0), Flags(0), Index(0)
216 A->getSymbolList().push_back(this);
221 MCAssembler::MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
222 MCCodeEmitter &_Emitter, raw_ostream &_OS)
223 : Context(_Context), Backend(_Backend), Emitter(_Emitter),
224 OS(_OS), RelaxAll(false), SubsectionsViaSymbols(false)
228 MCAssembler::~MCAssembler() {
231 static bool isScatteredFixupFullyResolvedSimple(const MCAssembler &Asm,
232 const MCFixup &Fixup,
233 const MCValue Target,
234 const MCSection *BaseSection) {
235 // The effective fixup address is
236 // addr(atom(A)) + offset(A)
237 // - addr(atom(B)) - offset(B)
238 // - addr(<base symbol>) + <fixup offset from base symbol>
239 // and the offsets are not relocatable, so the fixup is fully resolved when
240 // addr(atom(A)) - addr(atom(B)) - addr(<base symbol>)) == 0.
242 // The simple (Darwin, except on x86_64) way of dealing with this was to
243 // assume that any reference to a temporary symbol *must* be a temporary
244 // symbol in the same atom, unless the sections differ. Therefore, any PCrel
245 // relocation to a temporary symbol (in the same section) is fully
246 // resolved. This also works in conjunction with absolutized .set, which
247 // requires the compiler to use .set to absolutize the differences between
248 // symbols which the compiler knows to be assembly time constants, so we don't
249 // need to worry about considering symbol differences fully resolved.
251 // Non-relative fixups are only resolved if constant.
253 return Target.isAbsolute();
255 // Otherwise, relative fixups are only resolved if not a difference and the
256 // target is a temporary in the same section.
257 if (Target.isAbsolute() || Target.getSymB())
260 const MCSymbol *A = &Target.getSymA()->getSymbol();
261 if (!A->isTemporary() || !A->isInSection() ||
262 &A->getSection() != BaseSection)
268 static bool isScatteredFixupFullyResolved(const MCAssembler &Asm,
269 const MCAsmLayout &Layout,
270 const MCFixup &Fixup,
271 const MCValue Target,
272 const MCSymbolData *BaseSymbol) {
273 // The effective fixup address is
274 // addr(atom(A)) + offset(A)
275 // - addr(atom(B)) - offset(B)
276 // - addr(BaseSymbol) + <fixup offset from base symbol>
277 // and the offsets are not relocatable, so the fixup is fully resolved when
278 // addr(atom(A)) - addr(atom(B)) - addr(BaseSymbol) == 0.
280 // Note that "false" is almost always conservatively correct (it means we emit
281 // a relocation which is unnecessary), except when it would force us to emit a
282 // relocation which the target cannot encode.
284 const MCSymbolData *A_Base = 0, *B_Base = 0;
285 if (const MCSymbolRefExpr *A = Target.getSymA()) {
286 // Modified symbol references cannot be resolved.
287 if (A->getKind() != MCSymbolRefExpr::VK_None)
290 A_Base = Asm.getAtom(Layout, &Asm.getSymbolData(A->getSymbol()));
295 if (const MCSymbolRefExpr *B = Target.getSymB()) {
296 // Modified symbol references cannot be resolved.
297 if (B->getKind() != MCSymbolRefExpr::VK_None)
300 B_Base = Asm.getAtom(Layout, &Asm.getSymbolData(B->getSymbol()));
305 // If there is no base, A and B have to be the same atom for this fixup to be
308 return A_Base == B_Base;
310 // Otherwise, B must be missing and A must be the base.
311 return !B_Base && BaseSymbol == A_Base;
314 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
315 // Non-temporary labels should always be visible to the linker.
316 if (!Symbol.isTemporary())
319 // Absolute temporary labels are never visible.
320 if (!Symbol.isInSection())
323 // Otherwise, check if the section requires symbols even for temporary labels.
324 return getBackend().doesSectionRequireSymbols(Symbol.getSection());
327 const MCSymbolData *MCAssembler::getAtom(const MCAsmLayout &Layout,
328 const MCSymbolData *SD) const {
329 // Linker visible symbols define atoms.
330 if (isSymbolLinkerVisible(SD->getSymbol()))
333 // Absolute and undefined symbols have no defining atom.
334 if (!SD->getFragment())
337 // Non-linker visible symbols in sections which can't be atomized have no
339 if (!getBackend().isSectionAtomizable(
340 SD->getFragment()->getParent()->getSection()))
343 // Otherwise, return the atom for the containing fragment.
344 return SD->getFragment()->getAtom();
347 bool MCAssembler::EvaluateFixup(const MCAsmLayout &Layout,
348 const MCFixup &Fixup, const MCFragment *DF,
349 MCValue &Target, uint64_t &Value) const {
350 ++stats::EvaluateFixup;
352 if (!Fixup.getValue()->EvaluateAsRelocatable(Target, &Layout))
353 report_fatal_error("expected relocatable expression");
355 // FIXME: How do non-scattered symbols work in ELF? I presume the linker
356 // doesn't support small relocations, but then under what criteria does the
357 // assembler allow symbol differences?
359 Value = Target.getConstant();
361 bool IsPCRel = Emitter.getFixupKindInfo(
362 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
363 bool IsResolved = true;
364 if (const MCSymbolRefExpr *A = Target.getSymA()) {
365 if (A->getSymbol().isDefined())
366 Value += Layout.getSymbolAddress(&getSymbolData(A->getSymbol()));
370 if (const MCSymbolRefExpr *B = Target.getSymB()) {
371 if (B->getSymbol().isDefined())
372 Value -= Layout.getSymbolAddress(&getSymbolData(B->getSymbol()));
377 // If we are using scattered symbols, determine whether this value is actually
378 // resolved; scattering may cause atoms to move.
379 if (IsResolved && getBackend().hasScatteredSymbols()) {
380 if (getBackend().hasReliableSymbolDifference()) {
381 // If this is a PCrel relocation, find the base atom (identified by its
382 // symbol) that the fixup value is relative to.
383 const MCSymbolData *BaseSymbol = 0;
385 BaseSymbol = DF->getAtom();
391 IsResolved = isScatteredFixupFullyResolved(*this, Layout, Fixup, Target,
394 const MCSection *BaseSection = 0;
396 BaseSection = &DF->getParent()->getSection();
398 IsResolved = isScatteredFixupFullyResolvedSimple(*this, Fixup, Target,
404 Value -= Layout.getFragmentAddress(DF) + Fixup.getOffset();
409 uint64_t MCAssembler::ComputeFragmentSize(MCAsmLayout &Layout,
411 uint64_t SectionAddress,
412 uint64_t FragmentOffset) const {
413 switch (F.getKind()) {
414 case MCFragment::FT_Data:
415 return cast<MCDataFragment>(F).getContents().size();
416 case MCFragment::FT_Fill:
417 return cast<MCFillFragment>(F).getSize();
418 case MCFragment::FT_Inst:
419 return cast<MCInstFragment>(F).getInstSize();
421 case MCFragment::FT_Align: {
422 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
424 assert((!AF.hasOnlyAlignAddress() || !AF.getNextNode()) &&
425 "Invalid OnlyAlignAddress bit, not the last fragment!");
427 uint64_t Size = OffsetToAlignment(SectionAddress + FragmentOffset,
430 // Honor MaxBytesToEmit.
431 if (Size > AF.getMaxBytesToEmit())
437 case MCFragment::FT_Org: {
438 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
440 // FIXME: We should compute this sooner, we don't want to recurse here, and
441 // we would like to be more functional.
442 int64_t TargetLocation;
443 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
444 report_fatal_error("expected assembly-time absolute expression");
446 // FIXME: We need a way to communicate this error.
447 int64_t Offset = TargetLocation - FragmentOffset;
449 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
450 "' (at offset '" + Twine(FragmentOffset) + "'");
456 assert(0 && "invalid fragment kind");
460 void MCAsmLayout::LayoutFile() {
461 // Initialize the first section and set the valid fragment layout point. All
462 // actual layout computations are done lazily.
463 LastValidFragment = 0;
464 if (!getSectionOrder().empty())
465 getSectionOrder().front()->Address = 0;
468 void MCAsmLayout::LayoutFragment(MCFragment *F) {
469 MCFragment *Prev = F->getPrevNode();
471 // We should never try to recompute something which is up-to-date.
472 assert(!isFragmentUpToDate(F) && "Attempt to recompute up-to-date fragment!");
473 // We should never try to compute the fragment layout if the section isn't
475 assert(isSectionUpToDate(F->getParent()) &&
476 "Attempt to compute fragment before it's section!");
477 // We should never try to compute the fragment layout if it's predecessor
479 assert((!Prev || isFragmentUpToDate(Prev)) &&
480 "Attempt to compute fragment before it's predecessor!");
482 ++stats::FragmentLayouts;
484 // Compute the fragment start address.
485 uint64_t StartAddress = F->getParent()->Address;
486 uint64_t Address = StartAddress;
488 Address += Prev->Offset + Prev->EffectiveSize;
490 // Compute fragment offset and size.
491 F->Offset = Address - StartAddress;
492 F->EffectiveSize = getAssembler().ComputeFragmentSize(*this, *F, StartAddress,
494 LastValidFragment = F;
496 // If this is the last fragment in a section, update the next section address.
497 if (!F->getNextNode()) {
498 unsigned NextIndex = F->getParent()->getLayoutOrder() + 1;
499 if (NextIndex != getSectionOrder().size())
500 LayoutSection(getSectionOrder()[NextIndex]);
504 void MCAsmLayout::LayoutSection(MCSectionData *SD) {
505 unsigned SectionOrderIndex = SD->getLayoutOrder();
507 ++stats::SectionLayouts;
509 // Compute the section start address.
510 uint64_t StartAddress = 0;
511 if (SectionOrderIndex) {
512 MCSectionData *Prev = getSectionOrder()[SectionOrderIndex - 1];
513 StartAddress = getSectionAddress(Prev) + getSectionAddressSize(Prev);
516 // Honor the section alignment requirements.
517 StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
519 // Set the section address.
520 SD->Address = StartAddress;
523 /// WriteFragmentData - Write the \arg F data to the output file.
524 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
525 const MCFragment &F, MCObjectWriter *OW) {
526 uint64_t Start = OW->getStream().tell();
529 ++stats::EmittedFragments;
531 // FIXME: Embed in fragments instead?
532 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
533 switch (F.getKind()) {
534 case MCFragment::FT_Align: {
535 MCAlignFragment &AF = cast<MCAlignFragment>(F);
536 uint64_t Count = FragmentSize / AF.getValueSize();
538 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
540 // FIXME: This error shouldn't actually occur (the front end should emit
541 // multiple .align directives to enforce the semantics it wants), but is
542 // severe enough that we want to report it. How to handle this?
543 if (Count * AF.getValueSize() != FragmentSize)
544 report_fatal_error("undefined .align directive, value size '" +
545 Twine(AF.getValueSize()) +
546 "' is not a divisor of padding size '" +
547 Twine(FragmentSize) + "'");
549 // See if we are aligning with nops, and if so do that first to try to fill
550 // the Count bytes. Then if that did not fill any bytes or there are any
551 // bytes left to fill use the the Value and ValueSize to fill the rest.
552 // If we are aligning with nops, ask that target to emit the right data.
553 if (AF.hasEmitNops()) {
554 if (!Asm.getBackend().WriteNopData(Count, OW))
555 report_fatal_error("unable to write nop sequence of " +
556 Twine(Count) + " bytes");
560 // Otherwise, write out in multiples of the value size.
561 for (uint64_t i = 0; i != Count; ++i) {
562 switch (AF.getValueSize()) {
564 assert(0 && "Invalid size!");
565 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
566 case 2: OW->Write16(uint16_t(AF.getValue())); break;
567 case 4: OW->Write32(uint32_t(AF.getValue())); break;
568 case 8: OW->Write64(uint64_t(AF.getValue())); break;
574 case MCFragment::FT_Data: {
575 MCDataFragment &DF = cast<MCDataFragment>(F);
576 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
577 OW->WriteBytes(DF.getContents().str());
581 case MCFragment::FT_Fill: {
582 MCFillFragment &FF = cast<MCFillFragment>(F);
584 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
586 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
587 switch (FF.getValueSize()) {
589 assert(0 && "Invalid size!");
590 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
591 case 2: OW->Write16(uint16_t(FF.getValue())); break;
592 case 4: OW->Write32(uint32_t(FF.getValue())); break;
593 case 8: OW->Write64(uint64_t(FF.getValue())); break;
599 case MCFragment::FT_Inst:
600 llvm_unreachable("unexpected inst fragment after lowering");
603 case MCFragment::FT_Org: {
604 MCOrgFragment &OF = cast<MCOrgFragment>(F);
606 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
607 OW->Write8(uint8_t(OF.getValue()));
613 assert(OW->getStream().tell() - Start == FragmentSize);
616 void MCAssembler::WriteSectionData(const MCSectionData *SD,
617 const MCAsmLayout &Layout,
618 MCObjectWriter *OW) const {
619 // Ignore virtual sections.
620 if (getBackend().isVirtualSection(SD->getSection())) {
621 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
623 // Check that contents are only things legal inside a virtual section.
624 for (MCSectionData::const_iterator it = SD->begin(),
625 ie = SD->end(); it != ie; ++it) {
626 switch (it->getKind()) {
628 assert(0 && "Invalid fragment in virtual section!");
629 case MCFragment::FT_Align:
630 assert(!cast<MCAlignFragment>(it)->getValueSize() &&
631 "Invalid align in virtual section!");
633 case MCFragment::FT_Fill:
634 assert(!cast<MCFillFragment>(it)->getValueSize() &&
635 "Invalid fill in virtual section!");
643 uint64_t Start = OW->getStream().tell();
646 for (MCSectionData::const_iterator it = SD->begin(),
647 ie = SD->end(); it != ie; ++it)
648 WriteFragmentData(*this, Layout, *it, OW);
650 assert(OW->getStream().tell() - Start == Layout.getSectionFileSize(SD));
653 void MCAssembler::Finish(MCObjectWriter *Writer) {
654 DEBUG_WITH_TYPE("mc-dump", {
655 llvm::errs() << "assembler backend - pre-layout\n--\n";
658 // Create the layout object.
659 MCAsmLayout Layout(*this);
661 // Insert additional align fragments for concrete sections to explicitly pad
662 // the previous section to match their alignment requirements. This is for
663 // 'gas' compatibility, it shouldn't strictly be necessary.
665 // FIXME: This may be Mach-O specific.
666 for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
667 MCSectionData *SD = Layout.getSectionOrder()[i];
669 // Ignore sections without alignment requirements.
670 unsigned Align = SD->getAlignment();
674 // Ignore virtual sections, they don't cause file size modifications.
675 if (getBackend().isVirtualSection(SD->getSection()))
678 // Otherwise, create a new align fragment at the end of the previous
680 MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
681 Layout.getSectionOrder()[i - 1]);
682 AF->setOnlyAlignAddress(true);
685 // Create dummy fragments and assign section ordinals.
686 unsigned SectionIndex = 0;
687 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
688 // Create dummy fragments to eliminate any empty sections, this simplifies
690 if (it->getFragmentList().empty())
691 new MCFillFragment(0, 1, 0, it);
693 it->setOrdinal(SectionIndex++);
696 // Assign layout order indices to sections and fragments.
697 unsigned FragmentIndex = 0;
698 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
699 MCSectionData *SD = Layout.getSectionOrder()[i];
700 SD->setLayoutOrder(i);
702 for (MCSectionData::iterator it2 = SD->begin(),
703 ie2 = SD->end(); it2 != ie2; ++it2)
704 it2->setLayoutOrder(FragmentIndex++);
707 // Layout until everything fits.
708 while (LayoutOnce(Layout))
711 DEBUG_WITH_TYPE("mc-dump", {
712 llvm::errs() << "assembler backend - post-relaxation\n--\n";
715 // Finalize the layout, including fragment lowering.
716 FinishLayout(Layout);
718 DEBUG_WITH_TYPE("mc-dump", {
719 llvm::errs() << "assembler backend - final-layout\n--\n";
722 uint64_t StartOffset = OS.tell();
724 llvm::OwningPtr<MCObjectWriter> OwnWriter(0);
726 //no custom Writer_ : create the default one life-managed by OwningPtr
727 OwnWriter.reset(getBackend().createObjectWriter(OS));
728 Writer = OwnWriter.get();
730 report_fatal_error("unable to create object writer!");
733 // Allow the object writer a chance to perform post-layout binding (for
734 // example, to set the index fields in the symbol data).
735 Writer->ExecutePostLayoutBinding(*this);
737 // Evaluate and apply the fixups, generating relocation entries as necessary.
738 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
739 for (MCSectionData::iterator it2 = it->begin(),
740 ie2 = it->end(); it2 != ie2; ++it2) {
741 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
745 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
746 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
747 MCFixup &Fixup = *it3;
749 // Evaluate the fixup.
752 if (!EvaluateFixup(Layout, Fixup, DF, Target, FixedValue)) {
753 // The fixup was unresolved, we need a relocation. Inform the object
754 // writer of the relocation, and give it an opportunity to adjust the
755 // fixup value if need be.
756 Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
759 getBackend().ApplyFixup(Fixup, *DF, FixedValue);
764 // Write the object file.
765 Writer->WriteObject(*this, Layout);
767 stats::ObjectBytes += OS.tell() - StartOffset;
770 bool MCAssembler::FixupNeedsRelaxation(const MCFixup &Fixup,
771 const MCFragment *DF,
772 const MCAsmLayout &Layout) const {
776 // If we cannot resolve the fixup value, it requires relaxation.
779 if (!EvaluateFixup(Layout, Fixup, DF, Target, Value))
782 // Otherwise, relax if the value is too big for a (signed) i8.
784 // FIXME: This is target dependent!
785 return int64_t(Value) != int64_t(int8_t(Value));
788 bool MCAssembler::FragmentNeedsRelaxation(const MCInstFragment *IF,
789 const MCAsmLayout &Layout) const {
790 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
791 // are intentionally pushing out inst fragments, or because we relaxed a
792 // previous instruction to one that doesn't need relaxation.
793 if (!getBackend().MayNeedRelaxation(IF->getInst()))
796 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
797 ie = IF->fixup_end(); it != ie; ++it)
798 if (FixupNeedsRelaxation(*it, IF, Layout))
804 bool MCAssembler::LayoutOnce(MCAsmLayout &Layout) {
805 ++stats::RelaxationSteps;
807 // Layout the sections in order.
810 // Scan for fragments that need relaxation.
811 bool WasRelaxed = false;
812 for (iterator it = begin(), ie = end(); it != ie; ++it) {
813 MCSectionData &SD = *it;
815 for (MCSectionData::iterator it2 = SD.begin(),
816 ie2 = SD.end(); it2 != ie2; ++it2) {
817 // Check if this is an instruction fragment that needs relaxation.
818 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
819 if (!IF || !FragmentNeedsRelaxation(IF, Layout))
822 ++stats::RelaxedInstructions;
824 // FIXME-PERF: We could immediately lower out instructions if we can tell
825 // they are fully resolved, to avoid retesting on later passes.
827 // Relax the fragment.
830 getBackend().RelaxInstruction(IF->getInst(), Relaxed);
832 // Encode the new instruction.
834 // FIXME-PERF: If it matters, we could let the target do this. It can
835 // probably do so more efficiently in many cases.
836 SmallVector<MCFixup, 4> Fixups;
837 SmallString<256> Code;
838 raw_svector_ostream VecOS(Code);
839 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
842 // Update the instruction fragment.
843 int SlideAmount = Code.size() - IF->getInstSize();
844 IF->setInst(Relaxed);
845 IF->getCode() = Code;
846 IF->getFixups().clear();
847 // FIXME: Eliminate copy.
848 for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
849 IF->getFixups().push_back(Fixups[i]);
851 // Update the layout, and remember that we relaxed.
852 Layout.UpdateForSlide(IF, SlideAmount);
860 void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
861 // Lower out any instruction fragments, to simplify the fixup application and
864 // FIXME-PERF: We don't have to do this, but the assumption is that it is
865 // cheap (we will mostly end up eliminating fragments and appending on to data
866 // fragments), so the extra complexity downstream isn't worth it. Evaluate
868 for (iterator it = begin(), ie = end(); it != ie; ++it) {
869 MCSectionData &SD = *it;
871 for (MCSectionData::iterator it2 = SD.begin(),
872 ie2 = SD.end(); it2 != ie2; ++it2) {
873 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
877 // Create a new data fragment for the instruction.
879 // FIXME-PERF: Reuse previous data fragment if possible.
880 MCDataFragment *DF = new MCDataFragment();
881 SD.getFragmentList().insert(it2, DF);
883 // Update the data fragments layout data.
884 DF->setParent(IF->getParent());
885 DF->setAtom(IF->getAtom());
886 DF->setLayoutOrder(IF->getLayoutOrder());
887 Layout.FragmentReplaced(IF, DF);
889 // Copy in the data and the fixups.
890 DF->getContents().append(IF->getCode().begin(), IF->getCode().end());
891 for (unsigned i = 0, e = IF->getFixups().size(); i != e; ++i)
892 DF->getFixups().push_back(IF->getFixups()[i]);
894 // Delete the instruction fragment and update the iterator.
895 SD.getFragmentList().erase(IF);
905 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
906 OS << "<MCFixup" << " Offset:" << AF.getOffset()
907 << " Value:" << *AF.getValue()
908 << " Kind:" << AF.getKind() << ">";
914 void MCFragment::dump() {
915 raw_ostream &OS = llvm::errs();
919 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
920 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
921 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
922 case MCFragment::FT_Inst: OS << "MCInstFragment"; break;
923 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
926 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
927 << " Offset:" << Offset << " EffectiveSize:" << EffectiveSize << ">";
930 case MCFragment::FT_Align: {
931 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
932 if (AF->hasEmitNops())
933 OS << " (emit nops)";
934 if (AF->hasOnlyAlignAddress())
935 OS << " (only align section)";
937 OS << " Alignment:" << AF->getAlignment()
938 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
939 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
942 case MCFragment::FT_Data: {
943 const MCDataFragment *DF = cast<MCDataFragment>(this);
946 const SmallVectorImpl<char> &Contents = DF->getContents();
947 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
949 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
951 OS << "] (" << Contents.size() << " bytes)";
953 if (!DF->getFixups().empty()) {
956 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
957 ie = DF->fixup_end(); it != ie; ++it) {
958 if (it != DF->fixup_begin()) OS << ",\n ";
965 case MCFragment::FT_Fill: {
966 const MCFillFragment *FF = cast<MCFillFragment>(this);
967 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
968 << " Size:" << FF->getSize();
971 case MCFragment::FT_Inst: {
972 const MCInstFragment *IF = cast<MCInstFragment>(this);
975 IF->getInst().dump_pretty(OS);
978 case MCFragment::FT_Org: {
979 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
981 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
988 void MCSectionData::dump() {
989 raw_ostream &OS = llvm::errs();
991 OS << "<MCSectionData";
992 OS << " Alignment:" << getAlignment() << " Address:" << Address
993 << " Fragments:[\n ";
994 for (iterator it = begin(), ie = end(); it != ie; ++it) {
995 if (it != begin()) OS << ",\n ";
1001 void MCSymbolData::dump() {
1002 raw_ostream &OS = llvm::errs();
1004 OS << "<MCSymbolData Symbol:" << getSymbol()
1005 << " Fragment:" << getFragment() << " Offset:" << getOffset()
1006 << " Flags:" << getFlags() << " Index:" << getIndex();
1008 OS << " (common, size:" << getCommonSize()
1009 << " align: " << getCommonAlignment() << ")";
1011 OS << " (external)";
1012 if (isPrivateExtern())
1013 OS << " (private extern)";
1017 void MCAssembler::dump() {
1018 raw_ostream &OS = llvm::errs();
1020 OS << "<MCAssembler\n";
1021 OS << " Sections:[\n ";
1022 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1023 if (it != begin()) OS << ",\n ";
1029 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1030 if (it != symbol_begin()) OS << ",\n ";