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);
190 MCSectionData::MCSectionData() : Section(0) {}
192 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
193 : Section(&_Section),
195 Address(~UINT64_C(0)),
196 HasInstructions(false)
199 A->getSectionList().push_back(this);
204 MCSymbolData::MCSymbolData() : Symbol(0) {}
206 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
207 uint64_t _Offset, MCAssembler *A)
208 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
209 IsExternal(false), IsPrivateExtern(false),
210 CommonSize(0), CommonAlign(0), Flags(0), Index(0)
213 A->getSymbolList().push_back(this);
218 MCAssembler::MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
219 MCCodeEmitter &_Emitter, raw_ostream &_OS)
220 : Context(_Context), Backend(_Backend), Emitter(_Emitter),
221 OS(_OS), RelaxAll(false), SubsectionsViaSymbols(false)
225 MCAssembler::~MCAssembler() {
228 static bool isScatteredFixupFullyResolvedSimple(const MCAssembler &Asm,
229 const MCFixup &Fixup,
230 const MCValue Target,
231 const MCSection *BaseSection) {
232 // The effective fixup address is
233 // addr(atom(A)) + offset(A)
234 // - addr(atom(B)) - offset(B)
235 // - addr(<base symbol>) + <fixup offset from base symbol>
236 // and the offsets are not relocatable, so the fixup is fully resolved when
237 // addr(atom(A)) - addr(atom(B)) - addr(<base symbol>)) == 0.
239 // The simple (Darwin, except on x86_64) way of dealing with this was to
240 // assume that any reference to a temporary symbol *must* be a temporary
241 // symbol in the same atom, unless the sections differ. Therefore, any PCrel
242 // relocation to a temporary symbol (in the same section) is fully
243 // resolved. This also works in conjunction with absolutized .set, which
244 // requires the compiler to use .set to absolutize the differences between
245 // symbols which the compiler knows to be assembly time constants, so we don't
246 // need to worry about considering symbol differences fully resolved.
248 // Non-relative fixups are only resolved if constant.
250 return Target.isAbsolute();
252 // Otherwise, relative fixups are only resolved if not a difference and the
253 // target is a temporary in the same section.
254 if (Target.isAbsolute() || Target.getSymB())
257 const MCSymbol *A = &Target.getSymA()->getSymbol();
258 if (!A->isTemporary() || !A->isInSection() ||
259 &A->getSection() != BaseSection)
265 static bool isScatteredFixupFullyResolved(const MCAssembler &Asm,
266 const MCAsmLayout &Layout,
267 const MCFixup &Fixup,
268 const MCValue Target,
269 const MCSymbolData *BaseSymbol) {
270 // The effective fixup address is
271 // addr(atom(A)) + offset(A)
272 // - addr(atom(B)) - offset(B)
273 // - addr(BaseSymbol) + <fixup offset from base symbol>
274 // and the offsets are not relocatable, so the fixup is fully resolved when
275 // addr(atom(A)) - addr(atom(B)) - addr(BaseSymbol) == 0.
277 // Note that "false" is almost always conservatively correct (it means we emit
278 // a relocation which is unnecessary), except when it would force us to emit a
279 // relocation which the target cannot encode.
281 const MCSymbolData *A_Base = 0, *B_Base = 0;
282 if (const MCSymbolRefExpr *A = Target.getSymA()) {
283 // Modified symbol references cannot be resolved.
284 if (A->getKind() != MCSymbolRefExpr::VK_None)
287 A_Base = Asm.getAtom(Layout, &Asm.getSymbolData(A->getSymbol()));
292 if (const MCSymbolRefExpr *B = Target.getSymB()) {
293 // Modified symbol references cannot be resolved.
294 if (B->getKind() != MCSymbolRefExpr::VK_None)
297 B_Base = Asm.getAtom(Layout, &Asm.getSymbolData(B->getSymbol()));
302 // If there is no base, A and B have to be the same atom for this fixup to be
305 return A_Base == B_Base;
307 // Otherwise, B must be missing and A must be the base.
308 return !B_Base && BaseSymbol == A_Base;
311 bool MCAssembler::isSymbolLinkerVisible(const MCSymbolData *SD) const {
312 // Non-temporary labels should always be visible to the linker.
313 if (!SD->getSymbol().isTemporary())
316 // Absolute temporary labels are never visible.
317 if (!SD->getFragment())
320 // Otherwise, check if the section requires symbols even for temporary labels.
321 return getBackend().doesSectionRequireSymbols(
322 SD->getFragment()->getParent()->getSection());
325 const MCSymbolData *MCAssembler::getAtom(const MCAsmLayout &Layout,
326 const MCSymbolData *SD) const {
327 // Linker visible symbols define atoms.
328 if (isSymbolLinkerVisible(SD))
331 // Absolute and undefined symbols have no defining atom.
332 if (!SD->getFragment())
335 // Non-linker visible symbols in sections which can't be atomized have no
337 if (!getBackend().isSectionAtomizable(
338 SD->getFragment()->getParent()->getSection()))
341 // Otherwise, return the atom for the containing fragment.
342 return SD->getFragment()->getAtom();
345 bool MCAssembler::EvaluateFixup(const MCAsmLayout &Layout,
346 const MCFixup &Fixup, const MCFragment *DF,
347 MCValue &Target, uint64_t &Value) const {
348 ++stats::EvaluateFixup;
350 if (!Fixup.getValue()->EvaluateAsRelocatable(Target, &Layout))
351 report_fatal_error("expected relocatable expression");
353 // FIXME: How do non-scattered symbols work in ELF? I presume the linker
354 // doesn't support small relocations, but then under what criteria does the
355 // assembler allow symbol differences?
357 Value = Target.getConstant();
359 bool IsPCRel = Emitter.getFixupKindInfo(
360 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
361 bool IsResolved = true;
362 if (const MCSymbolRefExpr *A = Target.getSymA()) {
363 if (A->getSymbol().isDefined())
364 Value += Layout.getSymbolAddress(&getSymbolData(A->getSymbol()));
368 if (const MCSymbolRefExpr *B = Target.getSymB()) {
369 if (B->getSymbol().isDefined())
370 Value -= Layout.getSymbolAddress(&getSymbolData(B->getSymbol()));
375 // If we are using scattered symbols, determine whether this value is actually
376 // resolved; scattering may cause atoms to move.
377 if (IsResolved && getBackend().hasScatteredSymbols()) {
378 if (getBackend().hasReliableSymbolDifference()) {
379 // If this is a PCrel relocation, find the base atom (identified by its
380 // symbol) that the fixup value is relative to.
381 const MCSymbolData *BaseSymbol = 0;
383 BaseSymbol = DF->getAtom();
389 IsResolved = isScatteredFixupFullyResolved(*this, Layout, Fixup, Target,
392 const MCSection *BaseSection = 0;
394 BaseSection = &DF->getParent()->getSection();
396 IsResolved = isScatteredFixupFullyResolvedSimple(*this, Fixup, Target,
402 Value -= Layout.getFragmentAddress(DF) + Fixup.getOffset();
407 uint64_t MCAssembler::ComputeFragmentSize(MCAsmLayout &Layout,
409 uint64_t SectionAddress,
410 uint64_t FragmentOffset) const {
411 switch (F.getKind()) {
412 case MCFragment::FT_Data:
413 return cast<MCDataFragment>(F).getContents().size();
414 case MCFragment::FT_Fill:
415 return cast<MCFillFragment>(F).getSize();
416 case MCFragment::FT_Inst:
417 return cast<MCInstFragment>(F).getInstSize();
419 case MCFragment::FT_Align: {
420 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
422 assert((!AF.hasOnlyAlignAddress() || !AF.getNextNode()) &&
423 "Invalid OnlyAlignAddress bit, not the last fragment!");
425 uint64_t Size = OffsetToAlignment(SectionAddress + FragmentOffset,
428 // Honor MaxBytesToEmit.
429 if (Size > AF.getMaxBytesToEmit())
435 case MCFragment::FT_Org: {
436 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
438 // FIXME: We should compute this sooner, we don't want to recurse here, and
439 // we would like to be more functional.
440 int64_t TargetLocation;
441 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
442 report_fatal_error("expected assembly-time absolute expression");
444 // FIXME: We need a way to communicate this error.
445 int64_t Offset = TargetLocation - FragmentOffset;
447 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
448 "' (at offset '" + Twine(FragmentOffset) + "'");
454 assert(0 && "invalid fragment kind");
458 void MCAsmLayout::LayoutFile() {
459 // Initialize the first section and set the valid fragment layout point. All
460 // actual layout computations are done lazily.
461 LastValidFragment = 0;
462 if (!getSectionOrder().empty())
463 getSectionOrder().front()->Address = 0;
466 void MCAsmLayout::LayoutFragment(MCFragment *F) {
467 MCFragment *Prev = F->getPrevNode();
469 // We should never try to recompute something which is up-to-date.
470 assert(!isFragmentUpToDate(F) && "Attempt to recompute up-to-date fragment!");
471 // We should never try to compute the fragment layout if the section isn't
473 assert(isSectionUpToDate(F->getParent()) &&
474 "Attempt to compute fragment before it's section!");
475 // We should never try to compute the fragment layout if it's predecessor
477 assert((!Prev || isFragmentUpToDate(Prev)) &&
478 "Attempt to compute fragment before it's predecessor!");
480 ++stats::FragmentLayouts;
482 // Compute the fragment start address.
483 uint64_t StartAddress = F->getParent()->Address;
484 uint64_t Address = StartAddress;
486 Address += Prev->Offset + Prev->EffectiveSize;
488 // Compute fragment offset and size.
489 F->Offset = Address - StartAddress;
490 F->EffectiveSize = getAssembler().ComputeFragmentSize(*this, *F, StartAddress,
492 LastValidFragment = F;
494 // If this is the last fragment in a section, update the next section address.
495 if (!F->getNextNode()) {
496 unsigned NextIndex = F->getParent()->getLayoutOrder() + 1;
497 if (NextIndex != getSectionOrder().size())
498 LayoutSection(getSectionOrder()[NextIndex]);
502 void MCAsmLayout::LayoutSection(MCSectionData *SD) {
503 unsigned SectionOrderIndex = SD->getLayoutOrder();
505 ++stats::SectionLayouts;
507 // Compute the section start address.
508 uint64_t StartAddress = 0;
509 if (SectionOrderIndex) {
510 MCSectionData *Prev = getSectionOrder()[SectionOrderIndex - 1];
511 StartAddress = getSectionAddress(Prev) + getSectionAddressSize(Prev);
514 // Honor the section alignment requirements.
515 StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
517 // Set the section address.
518 SD->Address = StartAddress;
521 /// WriteFragmentData - Write the \arg F data to the output file.
522 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
523 const MCFragment &F, MCObjectWriter *OW) {
524 uint64_t Start = OW->getStream().tell();
527 ++stats::EmittedFragments;
529 // FIXME: Embed in fragments instead?
530 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
531 switch (F.getKind()) {
532 case MCFragment::FT_Align: {
533 MCAlignFragment &AF = cast<MCAlignFragment>(F);
534 uint64_t Count = FragmentSize / AF.getValueSize();
536 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
538 // FIXME: This error shouldn't actually occur (the front end should emit
539 // multiple .align directives to enforce the semantics it wants), but is
540 // severe enough that we want to report it. How to handle this?
541 if (Count * AF.getValueSize() != FragmentSize)
542 report_fatal_error("undefined .align directive, value size '" +
543 Twine(AF.getValueSize()) +
544 "' is not a divisor of padding size '" +
545 Twine(FragmentSize) + "'");
547 // See if we are aligning with nops, and if so do that first to try to fill
548 // the Count bytes. Then if that did not fill any bytes or there are any
549 // bytes left to fill use the the Value and ValueSize to fill the rest.
550 // If we are aligning with nops, ask that target to emit the right data.
551 if (AF.hasEmitNops()) {
552 if (!Asm.getBackend().WriteNopData(Count, OW))
553 report_fatal_error("unable to write nop sequence of " +
554 Twine(Count) + " bytes");
558 // Otherwise, write out in multiples of the value size.
559 for (uint64_t i = 0; i != Count; ++i) {
560 switch (AF.getValueSize()) {
562 assert(0 && "Invalid size!");
563 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
564 case 2: OW->Write16(uint16_t(AF.getValue())); break;
565 case 4: OW->Write32(uint32_t(AF.getValue())); break;
566 case 8: OW->Write64(uint64_t(AF.getValue())); break;
572 case MCFragment::FT_Data: {
573 MCDataFragment &DF = cast<MCDataFragment>(F);
574 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
575 OW->WriteBytes(DF.getContents().str());
579 case MCFragment::FT_Fill: {
580 MCFillFragment &FF = cast<MCFillFragment>(F);
582 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
584 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
585 switch (FF.getValueSize()) {
587 assert(0 && "Invalid size!");
588 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
589 case 2: OW->Write16(uint16_t(FF.getValue())); break;
590 case 4: OW->Write32(uint32_t(FF.getValue())); break;
591 case 8: OW->Write64(uint64_t(FF.getValue())); break;
597 case MCFragment::FT_Inst:
598 llvm_unreachable("unexpected inst fragment after lowering");
601 case MCFragment::FT_Org: {
602 MCOrgFragment &OF = cast<MCOrgFragment>(F);
604 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
605 OW->Write8(uint8_t(OF.getValue()));
611 assert(OW->getStream().tell() - Start == FragmentSize);
614 void MCAssembler::WriteSectionData(const MCSectionData *SD,
615 const MCAsmLayout &Layout,
616 MCObjectWriter *OW) const {
617 // Ignore virtual sections.
618 if (getBackend().isVirtualSection(SD->getSection())) {
619 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
621 // Check that contents are only things legal inside a virtual section.
622 for (MCSectionData::const_iterator it = SD->begin(),
623 ie = SD->end(); it != ie; ++it) {
624 switch (it->getKind()) {
626 assert(0 && "Invalid fragment in virtual section!");
627 case MCFragment::FT_Align:
628 assert(!cast<MCAlignFragment>(it)->getValueSize() &&
629 "Invalid align in virtual section!");
631 case MCFragment::FT_Fill:
632 assert(!cast<MCFillFragment>(it)->getValueSize() &&
633 "Invalid fill in virtual section!");
641 uint64_t Start = OW->getStream().tell();
644 for (MCSectionData::const_iterator it = SD->begin(),
645 ie = SD->end(); it != ie; ++it)
646 WriteFragmentData(*this, Layout, *it, OW);
648 assert(OW->getStream().tell() - Start == Layout.getSectionFileSize(SD));
651 void MCAssembler::Finish() {
652 DEBUG_WITH_TYPE("mc-dump", {
653 llvm::errs() << "assembler backend - pre-layout\n--\n";
656 // Create the layout object.
657 MCAsmLayout Layout(*this);
659 // Insert additional align fragments for concrete sections to explicitly pad
660 // the previous section to match their alignment requirements. This is for
661 // 'gas' compatibility, it shouldn't strictly be necessary.
663 // FIXME: This may be Mach-O specific.
664 for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
665 MCSectionData *SD = Layout.getSectionOrder()[i];
667 // Ignore sections without alignment requirements.
668 unsigned Align = SD->getAlignment();
672 // Ignore virtual sections, they don't cause file size modifications.
673 if (getBackend().isVirtualSection(SD->getSection()))
676 // Otherwise, create a new align fragment at the end of the previous
678 MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
679 Layout.getSectionOrder()[i - 1]);
680 AF->setOnlyAlignAddress(true);
683 // Create dummy fragments and assign section ordinals.
684 unsigned SectionIndex = 0;
685 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
686 // Create dummy fragments to eliminate any empty sections, this simplifies
688 if (it->getFragmentList().empty()) {
689 unsigned ValueSize = 1;
690 if (getBackend().isVirtualSection(it->getSection()))
692 new MCFillFragment(0, 1, 0, it);
695 it->setOrdinal(SectionIndex++);
698 // Assign layout order indices to sections and fragments.
699 unsigned FragmentIndex = 0;
700 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
701 MCSectionData *SD = Layout.getSectionOrder()[i];
702 SD->setLayoutOrder(i);
704 for (MCSectionData::iterator it2 = SD->begin(),
705 ie2 = SD->end(); it2 != ie2; ++it2)
706 it2->setLayoutOrder(FragmentIndex++);
709 // Layout until everything fits.
710 while (LayoutOnce(Layout))
713 DEBUG_WITH_TYPE("mc-dump", {
714 llvm::errs() << "assembler backend - post-relaxation\n--\n";
717 // Finalize the layout, including fragment lowering.
718 FinishLayout(Layout);
720 DEBUG_WITH_TYPE("mc-dump", {
721 llvm::errs() << "assembler backend - final-layout\n--\n";
724 uint64_t StartOffset = OS.tell();
725 llvm::OwningPtr<MCObjectWriter> Writer(getBackend().createObjectWriter(OS));
727 report_fatal_error("unable to create object writer!");
729 // Allow the object writer a chance to perform post-layout binding (for
730 // example, to set the index fields in the symbol data).
731 Writer->ExecutePostLayoutBinding(*this);
733 // Evaluate and apply the fixups, generating relocation entries as necessary.
734 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
735 for (MCSectionData::iterator it2 = it->begin(),
736 ie2 = it->end(); it2 != ie2; ++it2) {
737 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
741 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
742 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
743 MCFixup &Fixup = *it3;
745 // Evaluate the fixup.
748 if (!EvaluateFixup(Layout, Fixup, DF, Target, FixedValue)) {
749 // The fixup was unresolved, we need a relocation. Inform the object
750 // writer of the relocation, and give it an opportunity to adjust the
751 // fixup value if need be.
752 Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
755 getBackend().ApplyFixup(Fixup, *DF, FixedValue);
760 // Write the object file.
761 Writer->WriteObject(*this, Layout);
764 stats::ObjectBytes += OS.tell() - StartOffset;
767 bool MCAssembler::FixupNeedsRelaxation(const MCFixup &Fixup,
768 const MCFragment *DF,
769 const MCAsmLayout &Layout) const {
773 // If we cannot resolve the fixup value, it requires relaxation.
776 if (!EvaluateFixup(Layout, Fixup, DF, Target, Value))
779 // Otherwise, relax if the value is too big for a (signed) i8.
781 // FIXME: This is target dependent!
782 return int64_t(Value) != int64_t(int8_t(Value));
785 bool MCAssembler::FragmentNeedsRelaxation(const MCInstFragment *IF,
786 const MCAsmLayout &Layout) const {
787 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
788 // are intentionally pushing out inst fragments, or because we relaxed a
789 // previous instruction to one that doesn't need relaxation.
790 if (!getBackend().MayNeedRelaxation(IF->getInst(), IF->getFixups()))
793 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
794 ie = IF->fixup_end(); it != ie; ++it)
795 if (FixupNeedsRelaxation(*it, IF, Layout))
801 bool MCAssembler::LayoutOnce(MCAsmLayout &Layout) {
802 ++stats::RelaxationSteps;
804 // Layout the sections in order.
807 // Scan for fragments that need relaxation.
808 bool WasRelaxed = false;
809 for (iterator it = begin(), ie = end(); it != ie; ++it) {
810 MCSectionData &SD = *it;
812 for (MCSectionData::iterator it2 = SD.begin(),
813 ie2 = SD.end(); it2 != ie2; ++it2) {
814 // Check if this is an instruction fragment that needs relaxation.
815 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
816 if (!IF || !FragmentNeedsRelaxation(IF, Layout))
819 ++stats::RelaxedInstructions;
821 // FIXME-PERF: We could immediately lower out instructions if we can tell
822 // they are fully resolved, to avoid retesting on later passes.
824 // Relax the fragment.
827 getBackend().RelaxInstruction(IF, Relaxed);
829 // Encode the new instruction.
831 // FIXME-PERF: If it matters, we could let the target do this. It can
832 // probably do so more efficiently in many cases.
833 SmallVector<MCFixup, 4> Fixups;
834 SmallString<256> Code;
835 raw_svector_ostream VecOS(Code);
836 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
839 // Update the instruction fragment.
840 int SlideAmount = Code.size() - IF->getInstSize();
841 IF->setInst(Relaxed);
842 IF->getCode() = Code;
843 IF->getFixups().clear();
844 // FIXME: Eliminate copy.
845 for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
846 IF->getFixups().push_back(Fixups[i]);
848 // Update the layout, and remember that we relaxed. If we are relaxing
849 // everything, we can skip this step since nothing will depend on updating
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 ";