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 uint64_t MCAsmLayout::getFragmentAddress(const MCFragment *F) const {
77 assert(F->getParent() && "Missing section()!");
78 return getSectionAddress(F->getParent()) + getFragmentOffset(F);
81 uint64_t MCAsmLayout::getFragmentEffectiveSize(const MCFragment *F) const {
82 assert(F->EffectiveSize != ~UINT64_C(0) && "Address not set!");
83 return F->EffectiveSize;
86 void MCAsmLayout::setFragmentEffectiveSize(MCFragment *F, uint64_t Value) {
87 F->EffectiveSize = Value;
90 uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
91 assert(F->Offset != ~UINT64_C(0) && "Address not set!");
95 void MCAsmLayout::setFragmentOffset(MCFragment *F, uint64_t Value) {
99 uint64_t MCAsmLayout::getSymbolAddress(const MCSymbolData *SD) const {
100 assert(SD->getFragment() && "Invalid getAddress() on undefined symbol!");
101 return getFragmentAddress(SD->getFragment()) + SD->getOffset();
104 uint64_t MCAsmLayout::getSectionAddress(const MCSectionData *SD) const {
105 assert(SD->Address != ~UINT64_C(0) && "Address not set!");
109 void MCAsmLayout::setSectionAddress(MCSectionData *SD, uint64_t Value) {
113 uint64_t MCAsmLayout::getSectionSize(const MCSectionData *SD) const {
114 assert(SD->Size != ~UINT64_C(0) && "File size not set!");
117 void MCAsmLayout::setSectionSize(MCSectionData *SD, uint64_t Value) {
121 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
122 assert(SD->FileSize != ~UINT64_C(0) && "File size not set!");
125 void MCAsmLayout::setSectionFileSize(MCSectionData *SD, uint64_t Value) {
126 SD->FileSize = Value;
129 uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const {
130 assert(SD->AddressSize != ~UINT64_C(0) && "Address size not set!");
131 return SD->AddressSize;
133 void MCAsmLayout::setSectionAddressSize(MCSectionData *SD, uint64_t Value) {
134 SD->AddressSize = Value;
139 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
142 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
143 : Kind(_Kind), Parent(_Parent), Atom(0), EffectiveSize(~UINT64_C(0))
146 Parent->getFragmentList().push_back(this);
149 MCFragment::~MCFragment() {
154 MCSectionData::MCSectionData() : Section(0) {}
156 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
157 : Section(&_Section),
159 Address(~UINT64_C(0)),
161 AddressSize(~UINT64_C(0)),
162 FileSize(~UINT64_C(0)),
163 HasInstructions(false)
166 A->getSectionList().push_back(this);
171 MCSymbolData::MCSymbolData() : Symbol(0) {}
173 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
174 uint64_t _Offset, MCAssembler *A)
175 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
176 IsExternal(false), IsPrivateExtern(false),
177 CommonSize(0), CommonAlign(0), Flags(0), Index(0)
180 A->getSymbolList().push_back(this);
185 MCAssembler::MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
186 MCCodeEmitter &_Emitter, raw_ostream &_OS)
187 : Context(_Context), Backend(_Backend), Emitter(_Emitter),
188 OS(_OS), RelaxAll(false), SubsectionsViaSymbols(false)
192 MCAssembler::~MCAssembler() {
195 static bool isScatteredFixupFullyResolvedSimple(const MCAssembler &Asm,
196 const MCAsmFixup &Fixup,
197 const MCValue Target,
198 const MCSection *BaseSection) {
199 // The effective fixup address is
200 // addr(atom(A)) + offset(A)
201 // - addr(atom(B)) - offset(B)
202 // - addr(<base symbol>) + <fixup offset from base symbol>
203 // and the offsets are not relocatable, so the fixup is fully resolved when
204 // addr(atom(A)) - addr(atom(B)) - addr(<base symbol>)) == 0.
206 // The simple (Darwin, except on x86_64) way of dealing with this was to
207 // assume that any reference to a temporary symbol *must* be a temporary
208 // symbol in the same atom, unless the sections differ. Therefore, any PCrel
209 // relocation to a temporary symbol (in the same section) is fully
210 // resolved. This also works in conjunction with absolutized .set, which
211 // requires the compiler to use .set to absolutize the differences between
212 // symbols which the compiler knows to be assembly time constants, so we don't
213 // need to worry about considering symbol differences fully resolved.
215 // Non-relative fixups are only resolved if constant.
217 return Target.isAbsolute();
219 // Otherwise, relative fixups are only resolved if not a difference and the
220 // target is a temporary in the same section.
221 if (Target.isAbsolute() || Target.getSymB())
224 const MCSymbol *A = &Target.getSymA()->getSymbol();
225 if (!A->isTemporary() || !A->isInSection() ||
226 &A->getSection() != BaseSection)
232 static bool isScatteredFixupFullyResolved(const MCAssembler &Asm,
233 const MCAsmLayout &Layout,
234 const MCAsmFixup &Fixup,
235 const MCValue Target,
236 const MCSymbolData *BaseSymbol) {
237 // The effective fixup address is
238 // addr(atom(A)) + offset(A)
239 // - addr(atom(B)) - offset(B)
240 // - addr(BaseSymbol) + <fixup offset from base symbol>
241 // and the offsets are not relocatable, so the fixup is fully resolved when
242 // addr(atom(A)) - addr(atom(B)) - addr(BaseSymbol) == 0.
244 // Note that "false" is almost always conservatively correct (it means we emit
245 // a relocation which is unnecessary), except when it would force us to emit a
246 // relocation which the target cannot encode.
248 const MCSymbolData *A_Base = 0, *B_Base = 0;
249 if (const MCSymbolRefExpr *A = Target.getSymA()) {
250 // Modified symbol references cannot be resolved.
251 if (A->getKind() != MCSymbolRefExpr::VK_None)
254 A_Base = Asm.getAtom(Layout, &Asm.getSymbolData(A->getSymbol()));
259 if (const MCSymbolRefExpr *B = Target.getSymB()) {
260 // Modified symbol references cannot be resolved.
261 if (B->getKind() != MCSymbolRefExpr::VK_None)
264 B_Base = Asm.getAtom(Layout, &Asm.getSymbolData(B->getSymbol()));
269 // If there is no base, A and B have to be the same atom for this fixup to be
272 return A_Base == B_Base;
274 // Otherwise, B must be missing and A must be the base.
275 return !B_Base && BaseSymbol == A_Base;
278 bool MCAssembler::isSymbolLinkerVisible(const MCSymbolData *SD) const {
279 // Non-temporary labels should always be visible to the linker.
280 if (!SD->getSymbol().isTemporary())
283 // Absolute temporary labels are never visible.
284 if (!SD->getFragment())
287 // Otherwise, check if the section requires symbols even for temporary labels.
288 return getBackend().doesSectionRequireSymbols(
289 SD->getFragment()->getParent()->getSection());
292 const MCSymbolData *MCAssembler::getAtom(const MCAsmLayout &Layout,
293 const MCSymbolData *SD) const {
294 // Linker visible symbols define atoms.
295 if (isSymbolLinkerVisible(SD))
298 // Absolute and undefined symbols have no defining atom.
299 if (!SD->getFragment())
302 // Non-linker visible symbols in sections which can't be atomized have no
304 if (!getBackend().isSectionAtomizable(
305 SD->getFragment()->getParent()->getSection()))
308 // Otherwise, return the atom for the containing fragment.
309 return SD->getFragment()->getAtom();
312 bool MCAssembler::EvaluateFixup(const MCAsmLayout &Layout,
313 const MCAsmFixup &Fixup, const MCFragment *DF,
314 MCValue &Target, uint64_t &Value) const {
315 ++stats::EvaluateFixup;
317 if (!Fixup.Value->EvaluateAsRelocatable(Target, &Layout))
318 report_fatal_error("expected relocatable expression");
320 // FIXME: How do non-scattered symbols work in ELF? I presume the linker
321 // doesn't support small relocations, but then under what criteria does the
322 // assembler allow symbol differences?
324 Value = Target.getConstant();
327 Emitter.getFixupKindInfo(Fixup.Kind).Flags & MCFixupKindInfo::FKF_IsPCRel;
328 bool IsResolved = true;
329 if (const MCSymbolRefExpr *A = Target.getSymA()) {
330 if (A->getSymbol().isDefined())
331 Value += Layout.getSymbolAddress(&getSymbolData(A->getSymbol()));
335 if (const MCSymbolRefExpr *B = Target.getSymB()) {
336 if (B->getSymbol().isDefined())
337 Value -= Layout.getSymbolAddress(&getSymbolData(B->getSymbol()));
342 // If we are using scattered symbols, determine whether this value is actually
343 // resolved; scattering may cause atoms to move.
344 if (IsResolved && getBackend().hasScatteredSymbols()) {
345 if (getBackend().hasReliableSymbolDifference()) {
346 // If this is a PCrel relocation, find the base atom (identified by its
347 // symbol) that the fixup value is relative to.
348 const MCSymbolData *BaseSymbol = 0;
350 BaseSymbol = DF->getAtom();
356 IsResolved = isScatteredFixupFullyResolved(*this, Layout, Fixup, Target,
359 const MCSection *BaseSection = 0;
361 BaseSection = &DF->getParent()->getSection();
363 IsResolved = isScatteredFixupFullyResolvedSimple(*this, Fixup, Target,
369 Value -= Layout.getFragmentAddress(DF) + Fixup.Offset;
374 void MCAssembler::LayoutFragment(MCAsmLayout &Layout, MCFragment &F) {
375 uint64_t StartAddress = Layout.getSectionAddress(F.getParent());
377 // Get the fragment start address.
378 uint64_t Address = StartAddress;
379 MCSectionData::iterator it = &F;
380 if (MCFragment *Prev = F.getPrevNode())
381 Address = (StartAddress + Layout.getFragmentOffset(Prev) +
382 Layout.getFragmentEffectiveSize(Prev));
384 ++stats::FragmentLayouts;
386 uint64_t FragmentOffset = Address - StartAddress;
387 Layout.setFragmentOffset(&F, FragmentOffset);
389 // Evaluate fragment size.
390 uint64_t EffectiveSize = 0;
391 switch (F.getKind()) {
392 case MCFragment::FT_Align: {
393 MCAlignFragment &AF = cast<MCAlignFragment>(F);
395 assert((!AF.hasOnlyAlignAddress() || !AF.getNextNode()) &&
396 "Invalid OnlyAlignAddress bit, not the last fragment!");
398 EffectiveSize = OffsetToAlignment(Address, AF.getAlignment());
399 if (EffectiveSize > AF.getMaxBytesToEmit())
404 case MCFragment::FT_Data:
405 EffectiveSize = cast<MCDataFragment>(F).getContents().size();
408 case MCFragment::FT_Fill: {
409 EffectiveSize = cast<MCFillFragment>(F).getSize();
413 case MCFragment::FT_Inst:
414 EffectiveSize = cast<MCInstFragment>(F).getInstSize();
417 case MCFragment::FT_Org: {
418 MCOrgFragment &OF = cast<MCOrgFragment>(F);
420 int64_t TargetLocation;
421 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
422 report_fatal_error("expected assembly-time absolute expression");
424 // FIXME: We need a way to communicate this error.
425 int64_t Offset = TargetLocation - FragmentOffset;
427 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
428 "' (at offset '" + Twine(FragmentOffset) + "'");
430 EffectiveSize = Offset;
435 Layout.setFragmentEffectiveSize(&F, EffectiveSize);
438 void MCAssembler::LayoutSection(MCAsmLayout &Layout,
439 unsigned SectionOrderIndex) {
440 MCSectionData &SD = *Layout.getSectionOrder()[SectionOrderIndex];
441 bool IsVirtual = getBackend().isVirtualSection(SD.getSection());
443 ++stats::SectionLayouts;
445 // Compute the section start address.
446 uint64_t StartAddress = 0;
447 if (SectionOrderIndex) {
448 MCSectionData *Prev = Layout.getSectionOrder()[SectionOrderIndex - 1];
449 StartAddress = (Layout.getSectionAddress(Prev) +
450 Layout.getSectionAddressSize(Prev));
453 // Honor the section alignment requirements.
454 StartAddress = RoundUpToAlignment(StartAddress, SD.getAlignment());
456 // Set the section address.
457 Layout.setSectionAddress(&SD, StartAddress);
459 for (MCSectionData::iterator it = SD.begin(), ie = SD.end(); it != ie; ++it)
460 LayoutFragment(Layout, *it);
462 // Set the section sizes.
464 if (!SD.getFragmentList().empty()) {
465 MCFragment *F = &SD.getFragmentList().back();
466 Size = Layout.getFragmentOffset(F) + Layout.getFragmentEffectiveSize(F);
468 Layout.setSectionAddressSize(&SD, Size);
469 Layout.setSectionFileSize(&SD, IsVirtual ? 0 : Size);
471 // Handle OnlyAlignAddress bit.
472 if (!SD.getFragmentList().empty()) {
473 MCAlignFragment *AF =
474 dyn_cast<MCAlignFragment>(&SD.getFragmentList().back());
475 if (AF && AF->hasOnlyAlignAddress())
476 Size -= Layout.getFragmentEffectiveSize(AF);
479 Layout.setSectionSize(&SD, Size);
482 /// WriteFragmentData - Write the \arg F data to the output file.
483 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
484 const MCFragment &F, MCObjectWriter *OW) {
485 uint64_t Start = OW->getStream().tell();
488 ++stats::EmittedFragments;
490 // FIXME: Embed in fragments instead?
491 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
492 switch (F.getKind()) {
493 case MCFragment::FT_Align: {
494 MCAlignFragment &AF = cast<MCAlignFragment>(F);
495 uint64_t Count = FragmentSize / AF.getValueSize();
497 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
499 // FIXME: This error shouldn't actually occur (the front end should emit
500 // multiple .align directives to enforce the semantics it wants), but is
501 // severe enough that we want to report it. How to handle this?
502 if (Count * AF.getValueSize() != FragmentSize)
503 report_fatal_error("undefined .align directive, value size '" +
504 Twine(AF.getValueSize()) +
505 "' is not a divisor of padding size '" +
506 Twine(FragmentSize) + "'");
508 // See if we are aligning with nops, and if so do that first to try to fill
509 // the Count bytes. Then if that did not fill any bytes or there are any
510 // bytes left to fill use the the Value and ValueSize to fill the rest.
511 // If we are aligning with nops, ask that target to emit the right data.
512 if (AF.hasEmitNops()) {
513 if (!Asm.getBackend().WriteNopData(Count, OW))
514 report_fatal_error("unable to write nop sequence of " +
515 Twine(Count) + " bytes");
519 // Otherwise, write out in multiples of the value size.
520 for (uint64_t i = 0; i != Count; ++i) {
521 switch (AF.getValueSize()) {
523 assert(0 && "Invalid size!");
524 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
525 case 2: OW->Write16(uint16_t(AF.getValue())); break;
526 case 4: OW->Write32(uint32_t(AF.getValue())); break;
527 case 8: OW->Write64(uint64_t(AF.getValue())); break;
533 case MCFragment::FT_Data: {
534 MCDataFragment &DF = cast<MCDataFragment>(F);
535 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
536 OW->WriteBytes(DF.getContents().str());
540 case MCFragment::FT_Fill: {
541 MCFillFragment &FF = cast<MCFillFragment>(F);
543 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
545 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
546 switch (FF.getValueSize()) {
548 assert(0 && "Invalid size!");
549 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
550 case 2: OW->Write16(uint16_t(FF.getValue())); break;
551 case 4: OW->Write32(uint32_t(FF.getValue())); break;
552 case 8: OW->Write64(uint64_t(FF.getValue())); break;
558 case MCFragment::FT_Inst:
559 llvm_unreachable("unexpected inst fragment after lowering");
562 case MCFragment::FT_Org: {
563 MCOrgFragment &OF = cast<MCOrgFragment>(F);
565 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
566 OW->Write8(uint8_t(OF.getValue()));
572 assert(OW->getStream().tell() - Start == FragmentSize);
575 void MCAssembler::WriteSectionData(const MCSectionData *SD,
576 const MCAsmLayout &Layout,
577 MCObjectWriter *OW) const {
578 uint64_t SectionFileSize = Layout.getSectionFileSize(SD);
580 // Ignore virtual sections.
581 if (getBackend().isVirtualSection(SD->getSection())) {
582 assert(SectionFileSize == 0 && "Invalid size for section!");
584 // Check that contents are only things legal inside a virtual section.
585 for (MCSectionData::const_iterator it = SD->begin(),
586 ie = SD->end(); it != ie; ++it) {
587 switch (it->getKind()) {
589 assert(0 && "Invalid fragment in virtual section!");
590 case MCFragment::FT_Align:
591 assert(!cast<MCAlignFragment>(it)->getValueSize() &&
592 "Invalid align in virtual section!");
594 case MCFragment::FT_Fill:
595 assert(!cast<MCFillFragment>(it)->getValueSize() &&
596 "Invalid fill in virtual section!");
604 uint64_t Start = OW->getStream().tell();
607 for (MCSectionData::const_iterator it = SD->begin(),
608 ie = SD->end(); it != ie; ++it)
609 WriteFragmentData(*this, Layout, *it, OW);
611 assert(OW->getStream().tell() - Start == SectionFileSize);
614 void MCAssembler::Finish() {
615 DEBUG_WITH_TYPE("mc-dump", {
616 llvm::errs() << "assembler backend - pre-layout\n--\n";
619 // Assign section and fragment ordinals, all subsequent backend code is
620 // responsible for updating these in place.
621 unsigned SectionIndex = 0;
622 unsigned FragmentIndex = 0;
623 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
624 it->setOrdinal(SectionIndex++);
626 for (MCSectionData::iterator it2 = it->begin(),
627 ie2 = it->end(); it2 != ie2; ++it2)
628 it2->setOrdinal(FragmentIndex++);
631 // Create the layout object.
632 MCAsmLayout Layout(*this);
634 // Insert additional align fragments for concrete sections to explicitly pad
635 // the previous section to match their alignment requirements. This is for
636 // 'gas' compatibility, it shouldn't strictly be necessary.
638 // FIXME: This may be Mach-O specific.
639 for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
640 MCSectionData *SD = Layout.getSectionOrder()[i];
642 // Ignore sections without alignment requirements.
643 unsigned Align = SD->getAlignment();
647 // Ignore virtual sections, they don't cause file size modifications.
648 if (getBackend().isVirtualSection(SD->getSection()))
651 // Otherwise, create a new align fragment at the end of the previous
653 MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
654 Layout.getSectionOrder()[i - 1]);
655 AF->setOnlyAlignAddress(true);
658 // Layout until everything fits.
659 while (LayoutOnce(Layout))
662 DEBUG_WITH_TYPE("mc-dump", {
663 llvm::errs() << "assembler backend - post-relaxation\n--\n";
666 // Finalize the layout, including fragment lowering.
667 FinishLayout(Layout);
669 DEBUG_WITH_TYPE("mc-dump", {
670 llvm::errs() << "assembler backend - final-layout\n--\n";
673 uint64_t StartOffset = OS.tell();
674 llvm::OwningPtr<MCObjectWriter> Writer(getBackend().createObjectWriter(OS));
676 report_fatal_error("unable to create object writer!");
678 // Allow the object writer a chance to perform post-layout binding (for
679 // example, to set the index fields in the symbol data).
680 Writer->ExecutePostLayoutBinding(*this);
682 // Evaluate and apply the fixups, generating relocation entries as necessary.
683 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
684 for (MCSectionData::iterator it2 = it->begin(),
685 ie2 = it->end(); it2 != ie2; ++it2) {
686 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
690 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
691 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
692 MCAsmFixup &Fixup = *it3;
694 // Evaluate the fixup.
697 if (!EvaluateFixup(Layout, Fixup, DF, Target, FixedValue)) {
698 // The fixup was unresolved, we need a relocation. Inform the object
699 // writer of the relocation, and give it an opportunity to adjust the
700 // fixup value if need be.
701 Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
704 getBackend().ApplyFixup(Fixup, *DF, FixedValue);
709 // Write the object file.
710 Writer->WriteObject(*this, Layout);
713 stats::ObjectBytes += OS.tell() - StartOffset;
716 bool MCAssembler::FixupNeedsRelaxation(const MCAsmFixup &Fixup,
717 const MCFragment *DF,
718 const MCAsmLayout &Layout) const {
722 // If we cannot resolve the fixup value, it requires relaxation.
725 if (!EvaluateFixup(Layout, Fixup, DF, Target, Value))
728 // Otherwise, relax if the value is too big for a (signed) i8.
730 // FIXME: This is target dependent!
731 return int64_t(Value) != int64_t(int8_t(Value));
734 bool MCAssembler::FragmentNeedsRelaxation(const MCInstFragment *IF,
735 const MCAsmLayout &Layout) const {
736 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
737 // are intentionally pushing out inst fragments, or because we relaxed a
738 // previous instruction to one that doesn't need relaxation.
739 if (!getBackend().MayNeedRelaxation(IF->getInst(), IF->getFixups()))
742 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
743 ie = IF->fixup_end(); it != ie; ++it)
744 if (FixupNeedsRelaxation(*it, IF, Layout))
750 bool MCAssembler::LayoutOnce(MCAsmLayout &Layout) {
751 ++stats::RelaxationSteps;
753 // Layout the sections in order.
754 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i)
755 LayoutSection(Layout, i);
757 // Scan for fragments that need relaxation.
758 bool WasRelaxed = false;
759 for (iterator it = begin(), ie = end(); it != ie; ++it) {
760 MCSectionData &SD = *it;
762 for (MCSectionData::iterator it2 = SD.begin(),
763 ie2 = SD.end(); it2 != ie2; ++it2) {
764 // Check if this is an instruction fragment that needs relaxation.
765 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
766 if (!IF || !FragmentNeedsRelaxation(IF, Layout))
769 ++stats::RelaxedInstructions;
771 // FIXME-PERF: We could immediately lower out instructions if we can tell
772 // they are fully resolved, to avoid retesting on later passes.
774 // Relax the fragment.
777 getBackend().RelaxInstruction(IF, Relaxed);
779 // Encode the new instruction.
781 // FIXME-PERF: If it matters, we could let the target do this. It can
782 // probably do so more efficiently in many cases.
783 SmallVector<MCFixup, 4> Fixups;
784 SmallString<256> Code;
785 raw_svector_ostream VecOS(Code);
786 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
789 // Update the instruction fragment.
790 int SlideAmount = Code.size() - IF->getInstSize();
791 IF->setInst(Relaxed);
792 IF->getCode() = Code;
793 IF->getFixups().clear();
794 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
795 MCFixup &F = Fixups[i];
796 IF->getFixups().push_back(MCAsmFixup(F.getOffset(), *F.getValue(),
800 // Update the layout, and remember that we relaxed. If we are relaxing
801 // everything, we can skip this step since nothing will depend on updating
804 Layout.UpdateForSlide(IF, SlideAmount);
812 void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
813 // Lower out any instruction fragments, to simplify the fixup application and
816 // FIXME-PERF: We don't have to do this, but the assumption is that it is
817 // cheap (we will mostly end up eliminating fragments and appending on to data
818 // fragments), so the extra complexity downstream isn't worth it. Evaluate
820 for (iterator it = begin(), ie = end(); it != ie; ++it) {
821 MCSectionData &SD = *it;
823 for (MCSectionData::iterator it2 = SD.begin(),
824 ie2 = SD.end(); it2 != ie2; ++it2) {
825 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
829 // Create a new data fragment for the instruction.
831 // FIXME-PERF: Reuse previous data fragment if possible.
832 MCDataFragment *DF = new MCDataFragment();
833 SD.getFragmentList().insert(it2, DF);
835 // Update the data fragments layout data.
837 // FIXME: Add MCAsmLayout utility for this.
838 DF->setParent(IF->getParent());
839 DF->setAtom(IF->getAtom());
840 DF->setOrdinal(IF->getOrdinal());
841 Layout.setFragmentOffset(DF, Layout.getFragmentOffset(IF));
842 Layout.setFragmentEffectiveSize(DF, Layout.getFragmentEffectiveSize(IF));
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 << " Size:" << Size << " AddressSize:" << AddressSize
952 << " FileSize:" << FileSize << " Fragments:[\n ";
953 for (iterator it = begin(), ie = end(); it != ie; ++it) {
954 if (it != begin()) OS << ",\n ";
960 void MCSymbolData::dump() {
961 raw_ostream &OS = llvm::errs();
963 OS << "<MCSymbolData Symbol:" << getSymbol()
964 << " Fragment:" << getFragment() << " Offset:" << getOffset()
965 << " Flags:" << getFlags() << " Index:" << getIndex();
967 OS << " (common, size:" << getCommonSize()
968 << " align: " << getCommonAlignment() << ")";
971 if (isPrivateExtern())
972 OS << " (private extern)";
976 void MCAssembler::dump() {
977 raw_ostream &OS = llvm::errs();
979 OS << "<MCAssembler\n";
980 OS << " Sections:[\n ";
981 for (iterator it = begin(), ie = end(); it != ie; ++it) {
982 if (it != begin()) OS << ",\n ";
988 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
989 if (it != symbol_begin()) OS << ",\n ";