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(FragmentType _Kind, MCSectionData *_Parent)
182 : Kind(_Kind), Parent(_Parent), Atom(0), EffectiveSize(~UINT64_C(0))
185 Parent->getFragmentList().push_back(this);
188 MCFragment::~MCFragment() {
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 MCAsmFixup &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 MCAsmFixup &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 MCSymbolData *SD) const {
315 // Non-temporary labels should always be visible to the linker.
316 if (!SD->getSymbol().isTemporary())
319 // Absolute temporary labels are never visible.
320 if (!SD->getFragment())
323 // Otherwise, check if the section requires symbols even for temporary labels.
324 return getBackend().doesSectionRequireSymbols(
325 SD->getFragment()->getParent()->getSection());
328 const MCSymbolData *MCAssembler::getAtom(const MCAsmLayout &Layout,
329 const MCSymbolData *SD) const {
330 // Linker visible symbols define atoms.
331 if (isSymbolLinkerVisible(SD))
334 // Absolute and undefined symbols have no defining atom.
335 if (!SD->getFragment())
338 // Non-linker visible symbols in sections which can't be atomized have no
340 if (!getBackend().isSectionAtomizable(
341 SD->getFragment()->getParent()->getSection()))
344 // Otherwise, return the atom for the containing fragment.
345 return SD->getFragment()->getAtom();
348 bool MCAssembler::EvaluateFixup(const MCAsmLayout &Layout,
349 const MCAsmFixup &Fixup, const MCFragment *DF,
350 MCValue &Target, uint64_t &Value) const {
351 ++stats::EvaluateFixup;
353 if (!Fixup.Value->EvaluateAsRelocatable(Target, &Layout))
354 report_fatal_error("expected relocatable expression");
356 // FIXME: How do non-scattered symbols work in ELF? I presume the linker
357 // doesn't support small relocations, but then under what criteria does the
358 // assembler allow symbol differences?
360 Value = Target.getConstant();
363 Emitter.getFixupKindInfo(Fixup.Kind).Flags & MCFixupKindInfo::FKF_IsPCRel;
364 bool IsResolved = true;
365 if (const MCSymbolRefExpr *A = Target.getSymA()) {
366 if (A->getSymbol().isDefined())
367 Value += Layout.getSymbolAddress(&getSymbolData(A->getSymbol()));
371 if (const MCSymbolRefExpr *B = Target.getSymB()) {
372 if (B->getSymbol().isDefined())
373 Value -= Layout.getSymbolAddress(&getSymbolData(B->getSymbol()));
378 // If we are using scattered symbols, determine whether this value is actually
379 // resolved; scattering may cause atoms to move.
380 if (IsResolved && getBackend().hasScatteredSymbols()) {
381 if (getBackend().hasReliableSymbolDifference()) {
382 // If this is a PCrel relocation, find the base atom (identified by its
383 // symbol) that the fixup value is relative to.
384 const MCSymbolData *BaseSymbol = 0;
386 BaseSymbol = DF->getAtom();
392 IsResolved = isScatteredFixupFullyResolved(*this, Layout, Fixup, Target,
395 const MCSection *BaseSection = 0;
397 BaseSection = &DF->getParent()->getSection();
399 IsResolved = isScatteredFixupFullyResolvedSimple(*this, Fixup, Target,
405 Value -= Layout.getFragmentAddress(DF) + Fixup.Offset;
410 uint64_t MCAssembler::ComputeFragmentSize(MCAsmLayout &Layout,
412 uint64_t SectionAddress,
413 uint64_t FragmentOffset) const {
414 switch (F.getKind()) {
415 case MCFragment::FT_Data:
416 return cast<MCDataFragment>(F).getContents().size();
417 case MCFragment::FT_Fill:
418 return cast<MCFillFragment>(F).getSize();
419 case MCFragment::FT_Inst:
420 return cast<MCInstFragment>(F).getInstSize();
422 case MCFragment::FT_Align: {
423 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
425 assert((!AF.hasOnlyAlignAddress() || !AF.getNextNode()) &&
426 "Invalid OnlyAlignAddress bit, not the last fragment!");
428 uint64_t Size = OffsetToAlignment(SectionAddress + FragmentOffset,
431 // Honor MaxBytesToEmit.
432 if (Size > AF.getMaxBytesToEmit())
438 case MCFragment::FT_Org: {
439 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
441 // FIXME: We should compute this sooner, we don't want to recurse here, and
442 // we would like to be more functional.
443 int64_t TargetLocation;
444 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
445 report_fatal_error("expected assembly-time absolute expression");
447 // FIXME: We need a way to communicate this error.
448 int64_t Offset = TargetLocation - FragmentOffset;
450 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
451 "' (at offset '" + Twine(FragmentOffset) + "'");
457 assert(0 && "invalid fragment kind");
461 void MCAsmLayout::LayoutFile() {
462 // Initialize the first section and set the valid fragment layout point. All
463 // actual layout computations are done lazily.
464 LastValidFragment = 0;
465 if (!getSectionOrder().empty())
466 getSectionOrder().front()->Address = 0;
469 void MCAsmLayout::LayoutFragment(MCFragment *F) {
470 MCFragment *Prev = F->getPrevNode();
472 // We should never try to recompute something which is up-to-date.
473 assert(!isFragmentUpToDate(F) && "Attempt to recompute up-to-date fragment!");
474 // We should never try to compute the fragment layout if the section isn't
476 assert(isSectionUpToDate(F->getParent()) &&
477 "Attempt to compute fragment before it's section!");
478 // We should never try to compute the fragment layout if it's predecessor
480 assert((!Prev || isFragmentUpToDate(Prev)) &&
481 "Attempt to compute fragment before it's predecessor!");
483 ++stats::FragmentLayouts;
485 // Compute the fragment start address.
486 uint64_t StartAddress = F->getParent()->Address;
487 uint64_t Address = StartAddress;
489 Address += Prev->Offset + Prev->EffectiveSize;
491 // Compute fragment offset and size.
492 F->Offset = Address - StartAddress;
493 F->EffectiveSize = getAssembler().ComputeFragmentSize(*this, *F, StartAddress,
495 LastValidFragment = F;
497 // If this is the last fragment in a section, update the next section address.
498 if (!F->getNextNode()) {
499 unsigned NextIndex = F->getParent()->getLayoutOrder() + 1;
500 if (NextIndex != getSectionOrder().size())
501 LayoutSection(getSectionOrder()[NextIndex]);
505 void MCAsmLayout::LayoutSection(MCSectionData *SD) {
506 unsigned SectionOrderIndex = SD->getLayoutOrder();
508 ++stats::SectionLayouts;
510 // Compute the section start address.
511 uint64_t StartAddress = 0;
512 if (SectionOrderIndex) {
513 MCSectionData *Prev = getSectionOrder()[SectionOrderIndex - 1];
514 StartAddress = getSectionAddress(Prev) + getSectionAddressSize(Prev);
517 // Honor the section alignment requirements.
518 StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
520 // Set the section address.
521 SD->Address = StartAddress;
524 /// WriteFragmentData - Write the \arg F data to the output file.
525 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
526 const MCFragment &F, MCObjectWriter *OW) {
527 uint64_t Start = OW->getStream().tell();
530 ++stats::EmittedFragments;
532 // FIXME: Embed in fragments instead?
533 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
534 switch (F.getKind()) {
535 case MCFragment::FT_Align: {
536 MCAlignFragment &AF = cast<MCAlignFragment>(F);
537 uint64_t Count = FragmentSize / AF.getValueSize();
539 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
541 // FIXME: This error shouldn't actually occur (the front end should emit
542 // multiple .align directives to enforce the semantics it wants), but is
543 // severe enough that we want to report it. How to handle this?
544 if (Count * AF.getValueSize() != FragmentSize)
545 report_fatal_error("undefined .align directive, value size '" +
546 Twine(AF.getValueSize()) +
547 "' is not a divisor of padding size '" +
548 Twine(FragmentSize) + "'");
550 // See if we are aligning with nops, and if so do that first to try to fill
551 // the Count bytes. Then if that did not fill any bytes or there are any
552 // bytes left to fill use the the Value and ValueSize to fill the rest.
553 // If we are aligning with nops, ask that target to emit the right data.
554 if (AF.hasEmitNops()) {
555 if (!Asm.getBackend().WriteNopData(Count, OW))
556 report_fatal_error("unable to write nop sequence of " +
557 Twine(Count) + " bytes");
561 // Otherwise, write out in multiples of the value size.
562 for (uint64_t i = 0; i != Count; ++i) {
563 switch (AF.getValueSize()) {
565 assert(0 && "Invalid size!");
566 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
567 case 2: OW->Write16(uint16_t(AF.getValue())); break;
568 case 4: OW->Write32(uint32_t(AF.getValue())); break;
569 case 8: OW->Write64(uint64_t(AF.getValue())); break;
575 case MCFragment::FT_Data: {
576 MCDataFragment &DF = cast<MCDataFragment>(F);
577 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
578 OW->WriteBytes(DF.getContents().str());
582 case MCFragment::FT_Fill: {
583 MCFillFragment &FF = cast<MCFillFragment>(F);
585 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
587 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
588 switch (FF.getValueSize()) {
590 assert(0 && "Invalid size!");
591 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
592 case 2: OW->Write16(uint16_t(FF.getValue())); break;
593 case 4: OW->Write32(uint32_t(FF.getValue())); break;
594 case 8: OW->Write64(uint64_t(FF.getValue())); break;
600 case MCFragment::FT_Inst:
601 llvm_unreachable("unexpected inst fragment after lowering");
604 case MCFragment::FT_Org: {
605 MCOrgFragment &OF = cast<MCOrgFragment>(F);
607 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
608 OW->Write8(uint8_t(OF.getValue()));
614 assert(OW->getStream().tell() - Start == FragmentSize);
617 void MCAssembler::WriteSectionData(const MCSectionData *SD,
618 const MCAsmLayout &Layout,
619 MCObjectWriter *OW) const {
620 // Ignore virtual sections.
621 if (getBackend().isVirtualSection(SD->getSection())) {
622 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
624 // Check that contents are only things legal inside a virtual section.
625 for (MCSectionData::const_iterator it = SD->begin(),
626 ie = SD->end(); it != ie; ++it) {
627 switch (it->getKind()) {
629 assert(0 && "Invalid fragment in virtual section!");
630 case MCFragment::FT_Align:
631 assert(!cast<MCAlignFragment>(it)->getValueSize() &&
632 "Invalid align in virtual section!");
634 case MCFragment::FT_Fill:
635 assert(!cast<MCFillFragment>(it)->getValueSize() &&
636 "Invalid fill in virtual section!");
644 uint64_t Start = OW->getStream().tell();
647 for (MCSectionData::const_iterator it = SD->begin(),
648 ie = SD->end(); it != ie; ++it)
649 WriteFragmentData(*this, Layout, *it, OW);
651 assert(OW->getStream().tell() - Start == Layout.getSectionFileSize(SD));
654 void MCAssembler::Finish() {
655 DEBUG_WITH_TYPE("mc-dump", {
656 llvm::errs() << "assembler backend - pre-layout\n--\n";
659 // Create the layout object.
660 MCAsmLayout Layout(*this);
662 // Insert additional align fragments for concrete sections to explicitly pad
663 // the previous section to match their alignment requirements. This is for
664 // 'gas' compatibility, it shouldn't strictly be necessary.
666 // FIXME: This may be Mach-O specific.
667 for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
668 MCSectionData *SD = Layout.getSectionOrder()[i];
670 // Ignore sections without alignment requirements.
671 unsigned Align = SD->getAlignment();
675 // Ignore virtual sections, they don't cause file size modifications.
676 if (getBackend().isVirtualSection(SD->getSection()))
679 // Otherwise, create a new align fragment at the end of the previous
681 MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
682 Layout.getSectionOrder()[i - 1]);
683 AF->setOnlyAlignAddress(true);
686 // Create dummy fragments and assign section ordinals.
687 unsigned SectionIndex = 0;
688 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
689 // Create dummy fragments to eliminate any empty sections, this simplifies
691 if (it->getFragmentList().empty()) {
692 unsigned ValueSize = 1;
693 if (getBackend().isVirtualSection(it->getSection()))
695 new MCFillFragment(0, 1, 0, it);
698 it->setOrdinal(SectionIndex++);
701 // Assign layout order indices to sections and fragments.
702 unsigned FragmentIndex = 0;
703 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
704 MCSectionData *SD = Layout.getSectionOrder()[i];
705 SD->setLayoutOrder(i);
707 for (MCSectionData::iterator it2 = SD->begin(),
708 ie2 = SD->end(); it2 != ie2; ++it2)
709 it2->setLayoutOrder(FragmentIndex++);
712 // Layout until everything fits.
713 while (LayoutOnce(Layout))
716 DEBUG_WITH_TYPE("mc-dump", {
717 llvm::errs() << "assembler backend - post-relaxation\n--\n";
720 // Finalize the layout, including fragment lowering.
721 FinishLayout(Layout);
723 DEBUG_WITH_TYPE("mc-dump", {
724 llvm::errs() << "assembler backend - final-layout\n--\n";
727 uint64_t StartOffset = OS.tell();
728 llvm::OwningPtr<MCObjectWriter> Writer(getBackend().createObjectWriter(OS));
730 report_fatal_error("unable to create object writer!");
732 // Allow the object writer a chance to perform post-layout binding (for
733 // example, to set the index fields in the symbol data).
734 Writer->ExecutePostLayoutBinding(*this);
736 // Evaluate and apply the fixups, generating relocation entries as necessary.
737 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
738 for (MCSectionData::iterator it2 = it->begin(),
739 ie2 = it->end(); it2 != ie2; ++it2) {
740 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
744 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
745 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
746 MCAsmFixup &Fixup = *it3;
748 // Evaluate the fixup.
751 if (!EvaluateFixup(Layout, Fixup, DF, Target, FixedValue)) {
752 // The fixup was unresolved, we need a relocation. Inform the object
753 // writer of the relocation, and give it an opportunity to adjust the
754 // fixup value if need be.
755 Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
758 getBackend().ApplyFixup(Fixup, *DF, FixedValue);
763 // Write the object file.
764 Writer->WriteObject(*this, Layout);
767 stats::ObjectBytes += OS.tell() - StartOffset;
770 bool MCAssembler::FixupNeedsRelaxation(const MCAsmFixup &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(), IF->getFixups()))
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, 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 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
848 MCFixup &F = Fixups[i];
849 IF->getFixups().push_back(MCAsmFixup(F.getOffset(), *F.getValue(),
853 // Update the layout, and remember that we relaxed. If we are relaxing
854 // everything, we can skip this step since nothing will depend on updating
857 Layout.UpdateForSlide(IF, SlideAmount);
865 void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
866 // Lower out any instruction fragments, to simplify the fixup application and
869 // FIXME-PERF: We don't have to do this, but the assumption is that it is
870 // cheap (we will mostly end up eliminating fragments and appending on to data
871 // fragments), so the extra complexity downstream isn't worth it. Evaluate
873 for (iterator it = begin(), ie = end(); it != ie; ++it) {
874 MCSectionData &SD = *it;
876 for (MCSectionData::iterator it2 = SD.begin(),
877 ie2 = SD.end(); it2 != ie2; ++it2) {
878 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
882 // Create a new data fragment for the instruction.
884 // FIXME-PERF: Reuse previous data fragment if possible.
885 MCDataFragment *DF = new MCDataFragment();
886 SD.getFragmentList().insert(it2, DF);
888 // Update the data fragments layout data.
889 DF->setParent(IF->getParent());
890 DF->setAtom(IF->getAtom());
891 DF->setLayoutOrder(IF->getLayoutOrder());
892 Layout.FragmentReplaced(IF, DF);
894 // Copy in the data and the fixups.
895 DF->getContents().append(IF->getCode().begin(), IF->getCode().end());
896 for (unsigned i = 0, e = IF->getFixups().size(); i != e; ++i)
897 DF->getFixups().push_back(IF->getFixups()[i]);
899 // Delete the instruction fragment and update the iterator.
900 SD.getFragmentList().erase(IF);
910 raw_ostream &operator<<(raw_ostream &OS, const MCAsmFixup &AF) {
911 OS << "<MCAsmFixup" << " Offset:" << AF.Offset << " Value:" << *AF.Value
912 << " Kind:" << AF.Kind << ">";
918 void MCFragment::dump() {
919 raw_ostream &OS = llvm::errs();
921 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
922 << " Offset:" << Offset << " EffectiveSize:" << EffectiveSize << ">";
925 void MCAlignFragment::dump() {
926 raw_ostream &OS = llvm::errs();
928 OS << "<MCAlignFragment ";
929 this->MCFragment::dump();
931 OS << " (emit nops)";
932 if (hasOnlyAlignAddress())
933 OS << " (only align section)";
935 OS << " Alignment:" << getAlignment()
936 << " Value:" << getValue() << " ValueSize:" << getValueSize()
937 << " MaxBytesToEmit:" << getMaxBytesToEmit() << ">";
940 void MCDataFragment::dump() {
941 raw_ostream &OS = llvm::errs();
943 OS << "<MCDataFragment ";
944 this->MCFragment::dump();
947 for (unsigned i = 0, e = getContents().size(); i != e; ++i) {
949 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
951 OS << "] (" << getContents().size() << " bytes)";
953 if (!getFixups().empty()) {
956 for (fixup_iterator it = fixup_begin(), ie = fixup_end(); it != ie; ++it) {
957 if (it != fixup_begin()) OS << ",\n ";
966 void MCFillFragment::dump() {
967 raw_ostream &OS = llvm::errs();
969 OS << "<MCFillFragment ";
970 this->MCFragment::dump();
972 OS << " Value:" << getValue() << " ValueSize:" << getValueSize()
973 << " Size:" << getSize() << ">";
976 void MCInstFragment::dump() {
977 raw_ostream &OS = llvm::errs();
979 OS << "<MCInstFragment ";
980 this->MCFragment::dump();
983 getInst().dump_pretty(OS);
987 void MCOrgFragment::dump() {
988 raw_ostream &OS = llvm::errs();
990 OS << "<MCOrgFragment ";
991 this->MCFragment::dump();
993 OS << " Offset:" << getOffset() << " Value:" << getValue() << ">";
996 void MCSectionData::dump() {
997 raw_ostream &OS = llvm::errs();
999 OS << "<MCSectionData";
1000 OS << " Alignment:" << getAlignment() << " Address:" << Address
1001 << " Fragments:[\n ";
1002 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1003 if (it != begin()) OS << ",\n ";
1009 void MCSymbolData::dump() {
1010 raw_ostream &OS = llvm::errs();
1012 OS << "<MCSymbolData Symbol:" << getSymbol()
1013 << " Fragment:" << getFragment() << " Offset:" << getOffset()
1014 << " Flags:" << getFlags() << " Index:" << getIndex();
1016 OS << " (common, size:" << getCommonSize()
1017 << " align: " << getCommonAlignment() << ")";
1019 OS << " (external)";
1020 if (isPrivateExtern())
1021 OS << " (private extern)";
1025 void MCAssembler::dump() {
1026 raw_ostream &OS = llvm::errs();
1028 OS << "<MCAssembler\n";
1029 OS << " Sections:[\n ";
1030 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1031 if (it != begin()) OS << ",\n ";
1037 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1038 if (it != symbol_begin()) OS << ",\n ";