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) : Assembler(Asm) {
51 // Compute the section layout order. Virtual sections must go last.
52 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
53 if (!Asm.getBackend().isVirtualSection(it->getSection()))
54 SectionOrder.push_back(&*it);
55 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
56 if (Asm.getBackend().isVirtualSection(it->getSection()))
57 SectionOrder.push_back(&*it);
60 void MCAsmLayout::UpdateForSlide(MCFragment *F, int SlideAmount) {
61 // We shouldn't have to do anything special to support negative slides, and it
62 // is a perfectly valid thing to do as long as other parts of the system can
63 // guarantee convergence.
64 assert(SlideAmount >= 0 && "Negative slides not yet supported");
66 // Update the layout by simply recomputing the layout for the entire
67 // file. This is trivially correct, but very slow.
69 // FIXME-PERF: This is O(N^2), but will be eliminated once we get smarter.
71 // Layout the sections in order.
72 for (unsigned i = 0, e = getSectionOrder().size(); i != e; ++i)
73 getAssembler().LayoutSection(*this, i);
76 void MCAsmLayout::FragmentReplaced(MCFragment *Src, MCFragment *Dst) {
77 Dst->Offset = Src->Offset;
78 Dst->EffectiveSize = Src->EffectiveSize;
81 uint64_t MCAsmLayout::getFragmentAddress(const MCFragment *F) const {
82 assert(F->getParent() && "Missing section()!");
83 return getSectionAddress(F->getParent()) + getFragmentOffset(F);
86 uint64_t MCAsmLayout::getFragmentEffectiveSize(const MCFragment *F) const {
87 assert(F->EffectiveSize != ~UINT64_C(0) && "Address not set!");
88 return F->EffectiveSize;
91 void MCAsmLayout::setFragmentEffectiveSize(MCFragment *F, uint64_t Value) {
92 F->EffectiveSize = Value;
95 uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
96 assert(F->Offset != ~UINT64_C(0) && "Address not set!");
100 void MCAsmLayout::setFragmentOffset(MCFragment *F, uint64_t Value) {
104 uint64_t MCAsmLayout::getSymbolAddress(const MCSymbolData *SD) const {
105 assert(SD->getFragment() && "Invalid getAddress() on undefined symbol!");
106 return getFragmentAddress(SD->getFragment()) + SD->getOffset();
109 uint64_t MCAsmLayout::getSectionAddress(const MCSectionData *SD) const {
110 assert(SD->Address != ~UINT64_C(0) && "Address not set!");
114 void MCAsmLayout::setSectionAddress(MCSectionData *SD, uint64_t Value) {
118 uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const {
119 // Otherwise, the size is the last fragment's end offset.
120 const MCFragment &F = SD->getFragmentList().back();
121 return getFragmentOffset(&F) + getFragmentEffectiveSize(&F);
124 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
125 // Virtual sections have no file size.
126 if (getAssembler().getBackend().isVirtualSection(SD->getSection()))
129 // Otherwise, the file size is the same as the address space size.
130 return getSectionAddressSize(SD);
133 uint64_t MCAsmLayout::getSectionSize(const MCSectionData *SD) const {
134 // The logical size is the address space size minus any tail padding.
135 uint64_t Size = getSectionAddressSize(SD);
136 const MCAlignFragment *AF =
137 dyn_cast<MCAlignFragment>(&(SD->getFragmentList().back()));
138 if (AF && AF->hasOnlyAlignAddress())
139 Size -= getFragmentEffectiveSize(AF);
146 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
149 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
150 : Kind(_Kind), Parent(_Parent), Atom(0), EffectiveSize(~UINT64_C(0))
153 Parent->getFragmentList().push_back(this);
156 MCFragment::~MCFragment() {
161 MCSectionData::MCSectionData() : Section(0) {}
163 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
164 : Section(&_Section),
166 Address(~UINT64_C(0)),
167 HasInstructions(false)
170 A->getSectionList().push_back(this);
175 MCSymbolData::MCSymbolData() : Symbol(0) {}
177 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
178 uint64_t _Offset, MCAssembler *A)
179 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
180 IsExternal(false), IsPrivateExtern(false),
181 CommonSize(0), CommonAlign(0), Flags(0), Index(0)
184 A->getSymbolList().push_back(this);
189 MCAssembler::MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
190 MCCodeEmitter &_Emitter, raw_ostream &_OS)
191 : Context(_Context), Backend(_Backend), Emitter(_Emitter),
192 OS(_OS), RelaxAll(false), SubsectionsViaSymbols(false)
196 MCAssembler::~MCAssembler() {
199 static bool isScatteredFixupFullyResolvedSimple(const MCAssembler &Asm,
200 const MCAsmFixup &Fixup,
201 const MCValue Target,
202 const MCSection *BaseSection) {
203 // The effective fixup address is
204 // addr(atom(A)) + offset(A)
205 // - addr(atom(B)) - offset(B)
206 // - addr(<base symbol>) + <fixup offset from base symbol>
207 // and the offsets are not relocatable, so the fixup is fully resolved when
208 // addr(atom(A)) - addr(atom(B)) - addr(<base symbol>)) == 0.
210 // The simple (Darwin, except on x86_64) way of dealing with this was to
211 // assume that any reference to a temporary symbol *must* be a temporary
212 // symbol in the same atom, unless the sections differ. Therefore, any PCrel
213 // relocation to a temporary symbol (in the same section) is fully
214 // resolved. This also works in conjunction with absolutized .set, which
215 // requires the compiler to use .set to absolutize the differences between
216 // symbols which the compiler knows to be assembly time constants, so we don't
217 // need to worry about considering symbol differences fully resolved.
219 // Non-relative fixups are only resolved if constant.
221 return Target.isAbsolute();
223 // Otherwise, relative fixups are only resolved if not a difference and the
224 // target is a temporary in the same section.
225 if (Target.isAbsolute() || Target.getSymB())
228 const MCSymbol *A = &Target.getSymA()->getSymbol();
229 if (!A->isTemporary() || !A->isInSection() ||
230 &A->getSection() != BaseSection)
236 static bool isScatteredFixupFullyResolved(const MCAssembler &Asm,
237 const MCAsmLayout &Layout,
238 const MCAsmFixup &Fixup,
239 const MCValue Target,
240 const MCSymbolData *BaseSymbol) {
241 // The effective fixup address is
242 // addr(atom(A)) + offset(A)
243 // - addr(atom(B)) - offset(B)
244 // - addr(BaseSymbol) + <fixup offset from base symbol>
245 // and the offsets are not relocatable, so the fixup is fully resolved when
246 // addr(atom(A)) - addr(atom(B)) - addr(BaseSymbol) == 0.
248 // Note that "false" is almost always conservatively correct (it means we emit
249 // a relocation which is unnecessary), except when it would force us to emit a
250 // relocation which the target cannot encode.
252 const MCSymbolData *A_Base = 0, *B_Base = 0;
253 if (const MCSymbolRefExpr *A = Target.getSymA()) {
254 // Modified symbol references cannot be resolved.
255 if (A->getKind() != MCSymbolRefExpr::VK_None)
258 A_Base = Asm.getAtom(Layout, &Asm.getSymbolData(A->getSymbol()));
263 if (const MCSymbolRefExpr *B = Target.getSymB()) {
264 // Modified symbol references cannot be resolved.
265 if (B->getKind() != MCSymbolRefExpr::VK_None)
268 B_Base = Asm.getAtom(Layout, &Asm.getSymbolData(B->getSymbol()));
273 // If there is no base, A and B have to be the same atom for this fixup to be
276 return A_Base == B_Base;
278 // Otherwise, B must be missing and A must be the base.
279 return !B_Base && BaseSymbol == A_Base;
282 bool MCAssembler::isSymbolLinkerVisible(const MCSymbolData *SD) const {
283 // Non-temporary labels should always be visible to the linker.
284 if (!SD->getSymbol().isTemporary())
287 // Absolute temporary labels are never visible.
288 if (!SD->getFragment())
291 // Otherwise, check if the section requires symbols even for temporary labels.
292 return getBackend().doesSectionRequireSymbols(
293 SD->getFragment()->getParent()->getSection());
296 const MCSymbolData *MCAssembler::getAtom(const MCAsmLayout &Layout,
297 const MCSymbolData *SD) const {
298 // Linker visible symbols define atoms.
299 if (isSymbolLinkerVisible(SD))
302 // Absolute and undefined symbols have no defining atom.
303 if (!SD->getFragment())
306 // Non-linker visible symbols in sections which can't be atomized have no
308 if (!getBackend().isSectionAtomizable(
309 SD->getFragment()->getParent()->getSection()))
312 // Otherwise, return the atom for the containing fragment.
313 return SD->getFragment()->getAtom();
316 bool MCAssembler::EvaluateFixup(const MCAsmLayout &Layout,
317 const MCAsmFixup &Fixup, const MCFragment *DF,
318 MCValue &Target, uint64_t &Value) const {
319 ++stats::EvaluateFixup;
321 if (!Fixup.Value->EvaluateAsRelocatable(Target, &Layout))
322 report_fatal_error("expected relocatable expression");
324 // FIXME: How do non-scattered symbols work in ELF? I presume the linker
325 // doesn't support small relocations, but then under what criteria does the
326 // assembler allow symbol differences?
328 Value = Target.getConstant();
331 Emitter.getFixupKindInfo(Fixup.Kind).Flags & MCFixupKindInfo::FKF_IsPCRel;
332 bool IsResolved = true;
333 if (const MCSymbolRefExpr *A = Target.getSymA()) {
334 if (A->getSymbol().isDefined())
335 Value += Layout.getSymbolAddress(&getSymbolData(A->getSymbol()));
339 if (const MCSymbolRefExpr *B = Target.getSymB()) {
340 if (B->getSymbol().isDefined())
341 Value -= Layout.getSymbolAddress(&getSymbolData(B->getSymbol()));
346 // If we are using scattered symbols, determine whether this value is actually
347 // resolved; scattering may cause atoms to move.
348 if (IsResolved && getBackend().hasScatteredSymbols()) {
349 if (getBackend().hasReliableSymbolDifference()) {
350 // If this is a PCrel relocation, find the base atom (identified by its
351 // symbol) that the fixup value is relative to.
352 const MCSymbolData *BaseSymbol = 0;
354 BaseSymbol = DF->getAtom();
360 IsResolved = isScatteredFixupFullyResolved(*this, Layout, Fixup, Target,
363 const MCSection *BaseSection = 0;
365 BaseSection = &DF->getParent()->getSection();
367 IsResolved = isScatteredFixupFullyResolvedSimple(*this, Fixup, Target,
373 Value -= Layout.getFragmentAddress(DF) + Fixup.Offset;
378 uint64_t MCAssembler::ComputeFragmentSize(MCAsmLayout &Layout,
380 uint64_t SectionAddress,
381 uint64_t FragmentOffset) const {
382 switch (F.getKind()) {
383 case MCFragment::FT_Data:
384 return cast<MCDataFragment>(F).getContents().size();
385 case MCFragment::FT_Fill:
386 return cast<MCFillFragment>(F).getSize();
387 case MCFragment::FT_Inst:
388 return cast<MCInstFragment>(F).getInstSize();
390 case MCFragment::FT_Align: {
391 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
393 assert((!AF.hasOnlyAlignAddress() || !AF.getNextNode()) &&
394 "Invalid OnlyAlignAddress bit, not the last fragment!");
396 uint64_t Size = OffsetToAlignment(SectionAddress + FragmentOffset,
399 // Honor MaxBytesToEmit.
400 if (Size > AF.getMaxBytesToEmit())
406 case MCFragment::FT_Org: {
407 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
409 // FIXME: We should compute this sooner, we don't want to recurse here, and
410 // we would like to be more functional.
411 int64_t TargetLocation;
412 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
413 report_fatal_error("expected assembly-time absolute expression");
415 // FIXME: We need a way to communicate this error.
416 int64_t Offset = TargetLocation - FragmentOffset;
418 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
419 "' (at offset '" + Twine(FragmentOffset) + "'");
425 assert(0 && "invalid fragment kind");
429 void MCAssembler::LayoutFragment(MCAsmLayout &Layout, MCFragment &F) {
430 uint64_t StartAddress = Layout.getSectionAddress(F.getParent());
432 // Get the fragment start address.
433 uint64_t Address = StartAddress;
434 MCSectionData::iterator it = &F;
435 if (MCFragment *Prev = F.getPrevNode())
436 Address = (StartAddress + Layout.getFragmentOffset(Prev) +
437 Layout.getFragmentEffectiveSize(Prev));
439 ++stats::FragmentLayouts;
441 uint64_t FragmentOffset = Address - StartAddress;
442 Layout.setFragmentOffset(&F, FragmentOffset);
444 // Evaluate fragment size.
445 uint64_t EffectiveSize = ComputeFragmentSize(Layout, F, StartAddress,
447 Layout.setFragmentEffectiveSize(&F, EffectiveSize);
450 void MCAssembler::LayoutSection(MCAsmLayout &Layout,
451 unsigned SectionOrderIndex) {
452 MCSectionData &SD = *Layout.getSectionOrder()[SectionOrderIndex];
454 ++stats::SectionLayouts;
456 // Compute the section start address.
457 uint64_t StartAddress = 0;
458 if (SectionOrderIndex) {
459 MCSectionData *Prev = Layout.getSectionOrder()[SectionOrderIndex - 1];
460 StartAddress = (Layout.getSectionAddress(Prev) +
461 Layout.getSectionAddressSize(Prev));
464 // Honor the section alignment requirements.
465 StartAddress = RoundUpToAlignment(StartAddress, SD.getAlignment());
467 // Set the section address.
468 Layout.setSectionAddress(&SD, StartAddress);
470 for (MCSectionData::iterator it = SD.begin(), ie = SD.end(); it != ie; ++it)
471 LayoutFragment(Layout, *it);
474 /// WriteFragmentData - Write the \arg F data to the output file.
475 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
476 const MCFragment &F, MCObjectWriter *OW) {
477 uint64_t Start = OW->getStream().tell();
480 ++stats::EmittedFragments;
482 // FIXME: Embed in fragments instead?
483 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
484 switch (F.getKind()) {
485 case MCFragment::FT_Align: {
486 MCAlignFragment &AF = cast<MCAlignFragment>(F);
487 uint64_t Count = FragmentSize / AF.getValueSize();
489 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
491 // FIXME: This error shouldn't actually occur (the front end should emit
492 // multiple .align directives to enforce the semantics it wants), but is
493 // severe enough that we want to report it. How to handle this?
494 if (Count * AF.getValueSize() != FragmentSize)
495 report_fatal_error("undefined .align directive, value size '" +
496 Twine(AF.getValueSize()) +
497 "' is not a divisor of padding size '" +
498 Twine(FragmentSize) + "'");
500 // See if we are aligning with nops, and if so do that first to try to fill
501 // the Count bytes. Then if that did not fill any bytes or there are any
502 // bytes left to fill use the the Value and ValueSize to fill the rest.
503 // If we are aligning with nops, ask that target to emit the right data.
504 if (AF.hasEmitNops()) {
505 if (!Asm.getBackend().WriteNopData(Count, OW))
506 report_fatal_error("unable to write nop sequence of " +
507 Twine(Count) + " bytes");
511 // Otherwise, write out in multiples of the value size.
512 for (uint64_t i = 0; i != Count; ++i) {
513 switch (AF.getValueSize()) {
515 assert(0 && "Invalid size!");
516 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
517 case 2: OW->Write16(uint16_t(AF.getValue())); break;
518 case 4: OW->Write32(uint32_t(AF.getValue())); break;
519 case 8: OW->Write64(uint64_t(AF.getValue())); break;
525 case MCFragment::FT_Data: {
526 MCDataFragment &DF = cast<MCDataFragment>(F);
527 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
528 OW->WriteBytes(DF.getContents().str());
532 case MCFragment::FT_Fill: {
533 MCFillFragment &FF = cast<MCFillFragment>(F);
535 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
537 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
538 switch (FF.getValueSize()) {
540 assert(0 && "Invalid size!");
541 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
542 case 2: OW->Write16(uint16_t(FF.getValue())); break;
543 case 4: OW->Write32(uint32_t(FF.getValue())); break;
544 case 8: OW->Write64(uint64_t(FF.getValue())); break;
550 case MCFragment::FT_Inst:
551 llvm_unreachable("unexpected inst fragment after lowering");
554 case MCFragment::FT_Org: {
555 MCOrgFragment &OF = cast<MCOrgFragment>(F);
557 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
558 OW->Write8(uint8_t(OF.getValue()));
564 assert(OW->getStream().tell() - Start == FragmentSize);
567 void MCAssembler::WriteSectionData(const MCSectionData *SD,
568 const MCAsmLayout &Layout,
569 MCObjectWriter *OW) const {
570 // Ignore virtual sections.
571 if (getBackend().isVirtualSection(SD->getSection())) {
572 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
574 // Check that contents are only things legal inside a virtual section.
575 for (MCSectionData::const_iterator it = SD->begin(),
576 ie = SD->end(); it != ie; ++it) {
577 switch (it->getKind()) {
579 assert(0 && "Invalid fragment in virtual section!");
580 case MCFragment::FT_Align:
581 assert(!cast<MCAlignFragment>(it)->getValueSize() &&
582 "Invalid align in virtual section!");
584 case MCFragment::FT_Fill:
585 assert(!cast<MCFillFragment>(it)->getValueSize() &&
586 "Invalid fill in virtual section!");
594 uint64_t Start = OW->getStream().tell();
597 for (MCSectionData::const_iterator it = SD->begin(),
598 ie = SD->end(); it != ie; ++it)
599 WriteFragmentData(*this, Layout, *it, OW);
601 assert(OW->getStream().tell() - Start == Layout.getSectionFileSize(SD));
604 void MCAssembler::Finish() {
605 DEBUG_WITH_TYPE("mc-dump", {
606 llvm::errs() << "assembler backend - pre-layout\n--\n";
609 // Create the layout object.
610 MCAsmLayout Layout(*this);
612 // Assign layout order indices.
613 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i)
614 Layout.getSectionOrder()[i]->setLayoutOrder(i);
616 // Insert additional align fragments for concrete sections to explicitly pad
617 // the previous section to match their alignment requirements. This is for
618 // 'gas' compatibility, it shouldn't strictly be necessary.
620 // FIXME: This may be Mach-O specific.
621 for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
622 MCSectionData *SD = Layout.getSectionOrder()[i];
624 // Ignore sections without alignment requirements.
625 unsigned Align = SD->getAlignment();
629 // Ignore virtual sections, they don't cause file size modifications.
630 if (getBackend().isVirtualSection(SD->getSection()))
633 // Otherwise, create a new align fragment at the end of the previous
635 MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
636 Layout.getSectionOrder()[i - 1]);
637 AF->setOnlyAlignAddress(true);
640 // Assign section and fragment ordinals, all subsequent backend code is
641 // responsible for updating these in place.
642 unsigned SectionIndex = 0;
643 unsigned FragmentIndex = 0;
644 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
645 // Create dummy fragments to eliminate any empty sections, this simplifies
647 if (it->getFragmentList().empty()) {
648 unsigned ValueSize = 1;
649 if (getBackend().isVirtualSection(it->getSection()))
651 new MCFillFragment(0, 1, 0, it);
654 it->setOrdinal(SectionIndex++);
656 for (MCSectionData::iterator it2 = it->begin(),
657 ie2 = it->end(); it2 != ie2; ++it2)
658 it2->setOrdinal(FragmentIndex++);
661 // Layout until everything fits.
662 while (LayoutOnce(Layout))
665 DEBUG_WITH_TYPE("mc-dump", {
666 llvm::errs() << "assembler backend - post-relaxation\n--\n";
669 // Finalize the layout, including fragment lowering.
670 FinishLayout(Layout);
672 DEBUG_WITH_TYPE("mc-dump", {
673 llvm::errs() << "assembler backend - final-layout\n--\n";
676 uint64_t StartOffset = OS.tell();
677 llvm::OwningPtr<MCObjectWriter> Writer(getBackend().createObjectWriter(OS));
679 report_fatal_error("unable to create object writer!");
681 // Allow the object writer a chance to perform post-layout binding (for
682 // example, to set the index fields in the symbol data).
683 Writer->ExecutePostLayoutBinding(*this);
685 // Evaluate and apply the fixups, generating relocation entries as necessary.
686 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
687 for (MCSectionData::iterator it2 = it->begin(),
688 ie2 = it->end(); it2 != ie2; ++it2) {
689 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
693 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
694 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
695 MCAsmFixup &Fixup = *it3;
697 // Evaluate the fixup.
700 if (!EvaluateFixup(Layout, Fixup, DF, Target, FixedValue)) {
701 // The fixup was unresolved, we need a relocation. Inform the object
702 // writer of the relocation, and give it an opportunity to adjust the
703 // fixup value if need be.
704 Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
707 getBackend().ApplyFixup(Fixup, *DF, FixedValue);
712 // Write the object file.
713 Writer->WriteObject(*this, Layout);
716 stats::ObjectBytes += OS.tell() - StartOffset;
719 bool MCAssembler::FixupNeedsRelaxation(const MCAsmFixup &Fixup,
720 const MCFragment *DF,
721 const MCAsmLayout &Layout) const {
725 // If we cannot resolve the fixup value, it requires relaxation.
728 if (!EvaluateFixup(Layout, Fixup, DF, Target, Value))
731 // Otherwise, relax if the value is too big for a (signed) i8.
733 // FIXME: This is target dependent!
734 return int64_t(Value) != int64_t(int8_t(Value));
737 bool MCAssembler::FragmentNeedsRelaxation(const MCInstFragment *IF,
738 const MCAsmLayout &Layout) const {
739 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
740 // are intentionally pushing out inst fragments, or because we relaxed a
741 // previous instruction to one that doesn't need relaxation.
742 if (!getBackend().MayNeedRelaxation(IF->getInst(), IF->getFixups()))
745 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
746 ie = IF->fixup_end(); it != ie; ++it)
747 if (FixupNeedsRelaxation(*it, IF, Layout))
753 bool MCAssembler::LayoutOnce(MCAsmLayout &Layout) {
754 ++stats::RelaxationSteps;
756 // Layout the sections in order.
757 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i)
758 LayoutSection(Layout, i);
760 // Scan for fragments that need relaxation.
761 bool WasRelaxed = false;
762 for (iterator it = begin(), ie = end(); it != ie; ++it) {
763 MCSectionData &SD = *it;
765 for (MCSectionData::iterator it2 = SD.begin(),
766 ie2 = SD.end(); it2 != ie2; ++it2) {
767 // Check if this is an instruction fragment that needs relaxation.
768 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
769 if (!IF || !FragmentNeedsRelaxation(IF, Layout))
772 ++stats::RelaxedInstructions;
774 // FIXME-PERF: We could immediately lower out instructions if we can tell
775 // they are fully resolved, to avoid retesting on later passes.
777 // Relax the fragment.
780 getBackend().RelaxInstruction(IF, Relaxed);
782 // Encode the new instruction.
784 // FIXME-PERF: If it matters, we could let the target do this. It can
785 // probably do so more efficiently in many cases.
786 SmallVector<MCFixup, 4> Fixups;
787 SmallString<256> Code;
788 raw_svector_ostream VecOS(Code);
789 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
792 // Update the instruction fragment.
793 int SlideAmount = Code.size() - IF->getInstSize();
794 IF->setInst(Relaxed);
795 IF->getCode() = Code;
796 IF->getFixups().clear();
797 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
798 MCFixup &F = Fixups[i];
799 IF->getFixups().push_back(MCAsmFixup(F.getOffset(), *F.getValue(),
803 // Update the layout, and remember that we relaxed. If we are relaxing
804 // everything, we can skip this step since nothing will depend on updating
807 Layout.UpdateForSlide(IF, SlideAmount);
815 void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
816 // Lower out any instruction fragments, to simplify the fixup application and
819 // FIXME-PERF: We don't have to do this, but the assumption is that it is
820 // cheap (we will mostly end up eliminating fragments and appending on to data
821 // fragments), so the extra complexity downstream isn't worth it. Evaluate
823 for (iterator it = begin(), ie = end(); it != ie; ++it) {
824 MCSectionData &SD = *it;
826 for (MCSectionData::iterator it2 = SD.begin(),
827 ie2 = SD.end(); it2 != ie2; ++it2) {
828 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
832 // Create a new data fragment for the instruction.
834 // FIXME-PERF: Reuse previous data fragment if possible.
835 MCDataFragment *DF = new MCDataFragment();
836 SD.getFragmentList().insert(it2, DF);
838 // Update the data fragments layout data.
839 DF->setParent(IF->getParent());
840 DF->setAtom(IF->getAtom());
841 DF->setOrdinal(IF->getOrdinal());
842 Layout.FragmentReplaced(IF, DF);
844 // Copy in the data and the fixups.
845 DF->getContents().append(IF->getCode().begin(), IF->getCode().end());
846 for (unsigned i = 0, e = IF->getFixups().size(); i != e; ++i)
847 DF->getFixups().push_back(IF->getFixups()[i]);
849 // Delete the instruction fragment and update the iterator.
850 SD.getFragmentList().erase(IF);
860 raw_ostream &operator<<(raw_ostream &OS, const MCAsmFixup &AF) {
861 OS << "<MCAsmFixup" << " Offset:" << AF.Offset << " Value:" << *AF.Value
862 << " Kind:" << AF.Kind << ">";
868 void MCFragment::dump() {
869 raw_ostream &OS = llvm::errs();
871 OS << "<MCFragment " << (void*) this << " Offset:" << Offset
872 << " EffectiveSize:" << EffectiveSize << ">";
875 void MCAlignFragment::dump() {
876 raw_ostream &OS = llvm::errs();
878 OS << "<MCAlignFragment ";
879 this->MCFragment::dump();
881 OS << " (emit nops)";
882 if (hasOnlyAlignAddress())
883 OS << " (only align section)";
885 OS << " Alignment:" << getAlignment()
886 << " Value:" << getValue() << " ValueSize:" << getValueSize()
887 << " MaxBytesToEmit:" << getMaxBytesToEmit() << ">";
890 void MCDataFragment::dump() {
891 raw_ostream &OS = llvm::errs();
893 OS << "<MCDataFragment ";
894 this->MCFragment::dump();
897 for (unsigned i = 0, e = getContents().size(); i != e; ++i) {
899 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
901 OS << "] (" << getContents().size() << " bytes)";
903 if (!getFixups().empty()) {
906 for (fixup_iterator it = fixup_begin(), ie = fixup_end(); it != ie; ++it) {
907 if (it != fixup_begin()) OS << ",\n ";
916 void MCFillFragment::dump() {
917 raw_ostream &OS = llvm::errs();
919 OS << "<MCFillFragment ";
920 this->MCFragment::dump();
922 OS << " Value:" << getValue() << " ValueSize:" << getValueSize()
923 << " Size:" << getSize() << ">";
926 void MCInstFragment::dump() {
927 raw_ostream &OS = llvm::errs();
929 OS << "<MCInstFragment ";
930 this->MCFragment::dump();
933 getInst().dump_pretty(OS);
937 void MCOrgFragment::dump() {
938 raw_ostream &OS = llvm::errs();
940 OS << "<MCOrgFragment ";
941 this->MCFragment::dump();
943 OS << " Offset:" << getOffset() << " Value:" << getValue() << ">";
946 void MCSectionData::dump() {
947 raw_ostream &OS = llvm::errs();
949 OS << "<MCSectionData";
950 OS << " Alignment:" << getAlignment() << " Address:" << Address
951 << " Fragments:[\n ";
952 for (iterator it = begin(), ie = end(); it != ie; ++it) {
953 if (it != begin()) OS << ",\n ";
959 void MCSymbolData::dump() {
960 raw_ostream &OS = llvm::errs();
962 OS << "<MCSymbolData Symbol:" << getSymbol()
963 << " Fragment:" << getFragment() << " Offset:" << getOffset()
964 << " Flags:" << getFlags() << " Index:" << getIndex();
966 OS << " (common, size:" << getCommonSize()
967 << " align: " << getCommonAlignment() << ")";
970 if (isPrivateExtern())
971 OS << " (private extern)";
975 void MCAssembler::dump() {
976 raw_ostream &OS = llvm::errs();
978 OS << "<MCAssembler\n";
979 OS << " Sections:[\n ";
980 for (iterator it = begin(), ie = end(); it != ie; ++it) {
981 if (it != begin()) OS << ",\n ";
987 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
988 if (it != symbol_begin()) OS << ",\n ";