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 void MCAsmLayout::UpdateForSlide(MCFragment *F, int SlideAmount) {
51 // We shouldn't have to do anything special to support negative slides, and it
52 // is a perfectly valid thing to do as long as other parts of the system are
53 // can guarantee convergence.
54 assert(SlideAmount >= 0 && "Negative slides not yet supported");
56 // Update the layout by simply recomputing the layout for the entire
57 // file. This is trivially correct, but very slow.
59 // FIXME-PERF: This is O(N^2), but will be eliminated once we get smarter.
61 // Layout the concrete sections and fragments.
62 MCAssembler &Asm = getAssembler();
64 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it) {
65 // Skip virtual sections.
66 if (Asm.getBackend().isVirtualSection(it->getSection()))
69 // Layout the section fragments and its size.
70 Address = Asm.LayoutSection(*it, *this, Address);
73 // Layout the virtual sections.
74 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it) {
75 if (!Asm.getBackend().isVirtualSection(it->getSection()))
78 // Layout the section fragments and its size.
79 Address = Asm.LayoutSection(*it, *this, Address);
83 uint64_t MCAsmLayout::getFragmentAddress(const MCFragment *F) const {
84 assert(F->getParent() && "Missing section()!");
85 return getSectionAddress(F->getParent()) + getFragmentOffset(F);
88 uint64_t MCAsmLayout::getFragmentEffectiveSize(const MCFragment *F) const {
89 assert(F->EffectiveSize != ~UINT64_C(0) && "Address not set!");
90 return F->EffectiveSize;
93 void MCAsmLayout::setFragmentEffectiveSize(MCFragment *F, uint64_t Value) {
94 F->EffectiveSize = Value;
97 uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
98 assert(F->Offset != ~UINT64_C(0) && "Address not set!");
102 void MCAsmLayout::setFragmentOffset(MCFragment *F, uint64_t Value) {
106 uint64_t MCAsmLayout::getSymbolAddress(const MCSymbolData *SD) const {
107 assert(SD->getFragment() && "Invalid getAddress() on undefined symbol!");
108 return getFragmentAddress(SD->getFragment()) + SD->getOffset();
111 uint64_t MCAsmLayout::getSectionAddress(const MCSectionData *SD) const {
112 assert(SD->Address != ~UINT64_C(0) && "Address not set!");
116 void MCAsmLayout::setSectionAddress(MCSectionData *SD, uint64_t Value) {
120 uint64_t MCAsmLayout::getSectionSize(const MCSectionData *SD) const {
121 assert(SD->Size != ~UINT64_C(0) && "File size not set!");
124 void MCAsmLayout::setSectionSize(MCSectionData *SD, uint64_t Value) {
128 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
129 assert(SD->FileSize != ~UINT64_C(0) && "File size not set!");
132 void MCAsmLayout::setSectionFileSize(MCSectionData *SD, uint64_t Value) {
133 SD->FileSize = Value;
140 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
143 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
146 EffectiveSize(~UINT64_C(0))
149 Parent->getFragmentList().push_back(this);
152 MCFragment::~MCFragment() {
157 MCSectionData::MCSectionData() : Section(0) {}
159 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
160 : Section(&_Section),
162 Address(~UINT64_C(0)),
164 FileSize(~UINT64_C(0)),
165 HasInstructions(false)
168 A->getSectionList().push_back(this);
173 MCSymbolData::MCSymbolData() : Symbol(0) {}
175 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
176 uint64_t _Offset, MCAssembler *A)
177 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
178 IsExternal(false), IsPrivateExtern(false),
179 CommonSize(0), CommonAlign(0), Flags(0), Index(0)
182 A->getSymbolList().push_back(this);
187 MCAssembler::MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
188 MCCodeEmitter &_Emitter, raw_ostream &_OS)
189 : Context(_Context), Backend(_Backend), Emitter(_Emitter),
190 OS(_OS), RelaxAll(false), SubsectionsViaSymbols(false)
194 MCAssembler::~MCAssembler() {
197 static bool isScatteredFixupFullyResolvedSimple(const MCAssembler &Asm,
198 const MCAsmFixup &Fixup,
199 const MCValue Target,
200 const MCSection *BaseSection) {
201 // The effective fixup address is
202 // addr(atom(A)) + offset(A)
203 // - addr(atom(B)) - offset(B)
204 // - addr(<base symbol>) + <fixup offset from base symbol>
205 // and the offsets are not relocatable, so the fixup is fully resolved when
206 // addr(atom(A)) - addr(atom(B)) - addr(<base symbol>)) == 0.
208 // The simple (Darwin, except on x86_64) way of dealing with this was to
209 // assume that any reference to a temporary symbol *must* be a temporary
210 // symbol in the same atom, unless the sections differ. Therefore, any PCrel
211 // relocation to a temporary symbol (in the same section) is fully
212 // resolved. This also works in conjunction with absolutized .set, which
213 // requires the compiler to use .set to absolutize the differences between
214 // symbols which the compiler knows to be assembly time constants, so we don't
215 // need to worry about consider symbol differences fully resolved.
217 // Non-relative fixups are only resolved if constant.
219 return Target.isAbsolute();
221 // Otherwise, relative fixups are only resolved if not a difference and the
222 // target is a temporary in the same section.
223 if (Target.isAbsolute() || Target.getSymB())
226 const MCSymbol *A = &Target.getSymA()->getSymbol();
227 if (!A->isTemporary() || !A->isInSection() ||
228 &A->getSection() != BaseSection)
234 static bool isScatteredFixupFullyResolved(const MCAssembler &Asm,
235 const MCAsmLayout &Layout,
236 const MCAsmFixup &Fixup,
237 const MCValue Target,
238 const MCSymbolData *BaseSymbol) {
239 // The effective fixup address is
240 // addr(atom(A)) + offset(A)
241 // - addr(atom(B)) - offset(B)
242 // - addr(BaseSymbol) + <fixup offset from base symbol>
243 // and the offsets are not relocatable, so the fixup is fully resolved when
244 // addr(atom(A)) - addr(atom(B)) - addr(BaseSymbol) == 0.
246 // Note that "false" is almost always conservatively correct (it means we emit
247 // a relocation which is unnecessary), except when it would force us to emit a
248 // relocation which the target cannot encode.
250 const MCSymbolData *A_Base = 0, *B_Base = 0;
251 if (const MCSymbolRefExpr *A = Target.getSymA()) {
252 // Modified symbol references cannot be resolved.
253 if (A->getKind() != MCSymbolRefExpr::VK_None)
256 A_Base = Asm.getAtom(Layout, &Asm.getSymbolData(A->getSymbol()));
261 if (const MCSymbolRefExpr *B = Target.getSymB()) {
262 // Modified symbol references cannot be resolved.
263 if (B->getKind() != MCSymbolRefExpr::VK_None)
266 B_Base = Asm.getAtom(Layout, &Asm.getSymbolData(B->getSymbol()));
271 // If there is no base, A and B have to be the same atom for this fixup to be
274 return A_Base == B_Base;
276 // Otherwise, B must be missing and A must be the base.
277 return !B_Base && BaseSymbol == A_Base;
280 bool MCAssembler::isSymbolLinkerVisible(const MCSymbolData *SD) const {
281 // Non-temporary labels should always be visible to the linker.
282 if (!SD->getSymbol().isTemporary())
285 // Absolute temporary labels are never visible.
286 if (!SD->getFragment())
289 // Otherwise, check if the section requires symbols even for temporary labels.
290 return getBackend().doesSectionRequireSymbols(
291 SD->getFragment()->getParent()->getSection());
294 // FIXME-PERF: This routine is really slow.
295 const MCSymbolData *MCAssembler::getAtomForAddress(const MCAsmLayout &Layout,
296 const MCSectionData *Section,
297 uint64_t Address) const {
298 const MCSymbolData *Best = 0;
299 uint64_t BestAddress = 0;
301 for (MCAssembler::const_symbol_iterator it = symbol_begin(),
302 ie = symbol_end(); it != ie; ++it) {
303 // Ignore non-linker visible symbols.
304 if (!isSymbolLinkerVisible(it))
307 // Ignore symbols not in the same section.
308 if (!it->getFragment() || it->getFragment()->getParent() != Section)
311 // Otherwise, find the closest symbol preceding this address (ties are
312 // resolved in favor of the last defined symbol).
313 uint64_t SymbolAddress = Layout.getSymbolAddress(it);
314 if (SymbolAddress <= Address && (!Best || SymbolAddress >= BestAddress)) {
316 BestAddress = SymbolAddress;
323 // FIXME-PERF: This routine is really slow.
324 const MCSymbolData *MCAssembler::getAtom(const MCAsmLayout &Layout,
325 const MCSymbolData *SD) const {
326 // Linker visible symbols define atoms.
327 if (isSymbolLinkerVisible(SD))
330 // Absolute and undefined symbols have no defining atom.
331 if (!SD->getFragment())
334 // Otherwise, search by address.
335 return getAtomForAddress(Layout, SD->getFragment()->getParent(),
336 Layout.getSymbolAddress(SD));
339 bool MCAssembler::EvaluateFixup(const MCAsmLayout &Layout,
340 const MCAsmFixup &Fixup, const MCFragment *DF,
341 MCValue &Target, uint64_t &Value) const {
342 ++stats::EvaluateFixup;
344 if (!Fixup.Value->EvaluateAsRelocatable(Target, &Layout))
345 report_fatal_error("expected relocatable expression");
347 // FIXME: How do non-scattered symbols work in ELF? I presume the linker
348 // doesn't support small relocations, but then under what criteria does the
349 // assembler allow symbol differences?
351 Value = Target.getConstant();
354 Emitter.getFixupKindInfo(Fixup.Kind).Flags & MCFixupKindInfo::FKF_IsPCRel;
355 bool IsResolved = true;
356 if (const MCSymbolRefExpr *A = Target.getSymA()) {
357 if (A->getSymbol().isDefined())
358 Value += Layout.getSymbolAddress(&getSymbolData(A->getSymbol()));
362 if (const MCSymbolRefExpr *B = Target.getSymB()) {
363 if (B->getSymbol().isDefined())
364 Value -= Layout.getSymbolAddress(&getSymbolData(B->getSymbol()));
369 // If we are using scattered symbols, determine whether this value is actually
370 // resolved; scattering may cause atoms to move.
371 if (IsResolved && getBackend().hasScatteredSymbols()) {
372 if (getBackend().hasReliableSymbolDifference()) {
373 // If this is a PCrel relocation, find the base atom (identified by its
374 // symbol) that the fixup value is relative to.
375 const MCSymbolData *BaseSymbol = 0;
377 BaseSymbol = getAtomForAddress(
378 Layout, DF->getParent(), Layout.getFragmentAddress(DF)+Fixup.Offset);
384 IsResolved = isScatteredFixupFullyResolved(*this, Layout, Fixup, Target,
387 const MCSection *BaseSection = 0;
389 BaseSection = &DF->getParent()->getSection();
391 IsResolved = isScatteredFixupFullyResolvedSimple(*this, Fixup, Target,
397 Value -= Layout.getFragmentAddress(DF) + Fixup.Offset;
402 uint64_t MCAssembler::LayoutSection(MCSectionData &SD,
404 uint64_t StartAddress) {
405 bool IsVirtual = getBackend().isVirtualSection(SD.getSection());
407 ++stats::SectionLayouts;
409 // Align this section if necessary by adding padding bytes to the previous
410 // section. It is safe to adjust this out-of-band, because no symbol or
411 // fragment is allowed to point past the end of the section at any time.
412 if (uint64_t Pad = OffsetToAlignment(StartAddress, SD.getAlignment())) {
413 // Unless this section is virtual (where we are allowed to adjust the offset
414 // freely), the padding goes in the previous section.
416 // Find the previous non-virtual section.
418 assert(it != begin() && "Invalid initial section address!");
419 for (--it; getBackend().isVirtualSection(it->getSection()); --it) ;
420 Layout.setSectionFileSize(&*it, Layout.getSectionFileSize(&*it) + Pad);
426 // Set the aligned section address.
427 Layout.setSectionAddress(&SD, StartAddress);
429 uint64_t Address = StartAddress;
430 for (MCSectionData::iterator it = SD.begin(), ie = SD.end(); it != ie; ++it) {
433 ++stats::FragmentLayouts;
435 uint64_t FragmentOffset = Address - StartAddress;
436 Layout.setFragmentOffset(&F, FragmentOffset);
438 // Evaluate fragment size.
439 uint64_t EffectiveSize = 0;
440 switch (F.getKind()) {
441 case MCFragment::FT_Align: {
442 MCAlignFragment &AF = cast<MCAlignFragment>(F);
444 EffectiveSize = OffsetToAlignment(Address, AF.getAlignment());
445 if (EffectiveSize > AF.getMaxBytesToEmit())
450 case MCFragment::FT_Data:
451 EffectiveSize = cast<MCDataFragment>(F).getContents().size();
454 case MCFragment::FT_Fill: {
455 MCFillFragment &FF = cast<MCFillFragment>(F);
456 EffectiveSize = FF.getValueSize() * FF.getCount();
460 case MCFragment::FT_Inst:
461 EffectiveSize = cast<MCInstFragment>(F).getInstSize();
464 case MCFragment::FT_Org: {
465 MCOrgFragment &OF = cast<MCOrgFragment>(F);
467 int64_t TargetLocation;
468 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
469 report_fatal_error("expected assembly-time absolute expression");
471 // FIXME: We need a way to communicate this error.
472 int64_t Offset = TargetLocation - FragmentOffset;
474 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
475 "' (at offset '" + Twine(FragmentOffset) + "'");
477 EffectiveSize = Offset;
481 case MCFragment::FT_ZeroFill: {
482 MCZeroFillFragment &ZFF = cast<MCZeroFillFragment>(F);
484 // Align the fragment offset; it is safe to adjust the offset freely since
485 // this is only in virtual sections.
487 // FIXME: We shouldn't be doing this here.
488 Address = RoundUpToAlignment(Address, ZFF.getAlignment());
489 Layout.setFragmentOffset(&F, Address - StartAddress);
491 EffectiveSize = ZFF.getSize();
496 Layout.setFragmentEffectiveSize(&F, EffectiveSize);
497 Address += EffectiveSize;
500 // Set the section sizes.
501 Layout.setSectionSize(&SD, Address - StartAddress);
503 Layout.setSectionFileSize(&SD, 0);
505 Layout.setSectionFileSize(&SD, Address - StartAddress);
510 /// WriteFragmentData - Write the \arg F data to the output file.
511 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
512 const MCFragment &F, MCObjectWriter *OW) {
513 uint64_t Start = OW->getStream().tell();
516 ++stats::EmittedFragments;
518 // FIXME: Embed in fragments instead?
519 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
520 switch (F.getKind()) {
521 case MCFragment::FT_Align: {
522 MCAlignFragment &AF = cast<MCAlignFragment>(F);
523 uint64_t Count = FragmentSize / AF.getValueSize();
525 // FIXME: This error shouldn't actually occur (the front end should emit
526 // multiple .align directives to enforce the semantics it wants), but is
527 // severe enough that we want to report it. How to handle this?
528 if (Count * AF.getValueSize() != FragmentSize)
529 report_fatal_error("undefined .align directive, value size '" +
530 Twine(AF.getValueSize()) +
531 "' is not a divisor of padding size '" +
532 Twine(FragmentSize) + "'");
534 // See if we are aligning with nops, and if so do that first to try to fill
535 // the Count bytes. Then if that did not fill any bytes or there are any
536 // bytes left to fill use the the Value and ValueSize to fill the rest.
537 // If we are aligning with nops, ask that target to emit the right data.
538 if (AF.getEmitNops()) {
539 if (!Asm.getBackend().WriteNopData(Count, OW))
540 report_fatal_error("unable to write nop sequence of " +
541 Twine(Count) + " bytes");
545 // Otherwise, write out in multiples of the value size.
546 for (uint64_t i = 0; i != Count; ++i) {
547 switch (AF.getValueSize()) {
549 assert(0 && "Invalid size!");
550 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
551 case 2: OW->Write16(uint16_t(AF.getValue())); break;
552 case 4: OW->Write32(uint32_t(AF.getValue())); break;
553 case 8: OW->Write64(uint64_t(AF.getValue())); break;
559 case MCFragment::FT_Data: {
560 MCDataFragment &DF = cast<MCDataFragment>(F);
561 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
562 OW->WriteBytes(DF.getContents().str());
566 case MCFragment::FT_Fill: {
567 MCFillFragment &FF = cast<MCFillFragment>(F);
568 for (uint64_t i = 0, e = FF.getCount(); i != e; ++i) {
569 switch (FF.getValueSize()) {
571 assert(0 && "Invalid size!");
572 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
573 case 2: OW->Write16(uint16_t(FF.getValue())); break;
574 case 4: OW->Write32(uint32_t(FF.getValue())); break;
575 case 8: OW->Write64(uint64_t(FF.getValue())); break;
581 case MCFragment::FT_Inst:
582 llvm_unreachable("unexpected inst fragment after lowering");
585 case MCFragment::FT_Org: {
586 MCOrgFragment &OF = cast<MCOrgFragment>(F);
588 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
589 OW->Write8(uint8_t(OF.getValue()));
594 case MCFragment::FT_ZeroFill: {
595 assert(0 && "Invalid zero fill fragment in concrete section!");
600 assert(OW->getStream().tell() - Start == FragmentSize);
603 void MCAssembler::WriteSectionData(const MCSectionData *SD,
604 const MCAsmLayout &Layout,
605 MCObjectWriter *OW) const {
606 uint64_t SectionSize = Layout.getSectionSize(SD);
607 uint64_t SectionFileSize = Layout.getSectionFileSize(SD);
609 // Ignore virtual sections.
610 if (getBackend().isVirtualSection(SD->getSection())) {
611 assert(SectionFileSize == 0 && "Invalid size for section!");
615 uint64_t Start = OW->getStream().tell();
618 for (MCSectionData::const_iterator it = SD->begin(),
619 ie = SD->end(); it != ie; ++it)
620 WriteFragmentData(*this, Layout, *it, OW);
622 // Add section padding.
623 assert(SectionFileSize >= SectionSize && "Invalid section sizes!");
624 OW->WriteZeros(SectionFileSize - SectionSize);
626 assert(OW->getStream().tell() - Start == SectionFileSize);
629 void MCAssembler::Finish() {
630 DEBUG_WITH_TYPE("mc-dump", {
631 llvm::errs() << "assembler backend - pre-layout\n--\n";
634 // Assign section and fragment ordinals, all subsequent backend code is
635 // responsible for updating these in place.
636 unsigned SectionIndex = 0;
637 unsigned FragmentIndex = 0;
638 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
639 it->setOrdinal(SectionIndex++);
641 for (MCSectionData::iterator it2 = it->begin(),
642 ie2 = it->end(); it2 != ie2; ++it2)
643 it2->setOrdinal(FragmentIndex++);
646 // Layout until everything fits.
647 MCAsmLayout Layout(*this);
648 while (LayoutOnce(Layout))
651 DEBUG_WITH_TYPE("mc-dump", {
652 llvm::errs() << "assembler backend - post-relaxation\n--\n";
655 // Finalize the layout, including fragment lowering.
656 FinishLayout(Layout);
658 DEBUG_WITH_TYPE("mc-dump", {
659 llvm::errs() << "assembler backend - final-layout\n--\n";
662 uint64_t StartOffset = OS.tell();
663 llvm::OwningPtr<MCObjectWriter> Writer(getBackend().createObjectWriter(OS));
665 report_fatal_error("unable to create object writer!");
667 // Allow the object writer a chance to perform post-layout binding (for
668 // example, to set the index fields in the symbol data).
669 Writer->ExecutePostLayoutBinding(*this);
671 // Evaluate and apply the fixups, generating relocation entries as necessary.
672 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
673 for (MCSectionData::iterator it2 = it->begin(),
674 ie2 = it->end(); it2 != ie2; ++it2) {
675 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
679 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
680 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
681 MCAsmFixup &Fixup = *it3;
683 // Evaluate the fixup.
686 if (!EvaluateFixup(Layout, Fixup, DF, Target, FixedValue)) {
687 // The fixup was unresolved, we need a relocation. Inform the object
688 // writer of the relocation, and give it an opportunity to adjust the
689 // fixup value if need be.
690 Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
693 getBackend().ApplyFixup(Fixup, *DF, FixedValue);
698 // Write the object file.
699 Writer->WriteObject(*this, Layout);
702 stats::ObjectBytes += OS.tell() - StartOffset;
705 bool MCAssembler::FixupNeedsRelaxation(const MCAsmFixup &Fixup,
706 const MCFragment *DF,
707 const MCAsmLayout &Layout) const {
711 // If we cannot resolve the fixup value, it requires relaxation.
714 if (!EvaluateFixup(Layout, Fixup, DF, Target, Value))
717 // Otherwise, relax if the value is too big for a (signed) i8.
718 return int64_t(Value) != int64_t(int8_t(Value));
721 bool MCAssembler::FragmentNeedsRelaxation(const MCInstFragment *IF,
722 const MCAsmLayout &Layout) const {
723 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
724 // are intentionally pushing out inst fragments, or because we relaxed a
725 // previous instruction to one that doesn't need relaxation.
726 if (!getBackend().MayNeedRelaxation(IF->getInst(), IF->getFixups()))
729 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
730 ie = IF->fixup_end(); it != ie; ++it)
731 if (FixupNeedsRelaxation(*it, IF, Layout))
737 bool MCAssembler::LayoutOnce(MCAsmLayout &Layout) {
738 ++stats::RelaxationSteps;
740 // Layout the concrete sections and fragments.
741 uint64_t Address = 0;
742 for (iterator it = begin(), ie = end(); it != ie; ++it) {
743 // Skip virtual sections.
744 if (getBackend().isVirtualSection(it->getSection()))
747 // Layout the section fragments and its size.
748 Address = LayoutSection(*it, Layout, Address);
751 // Layout the virtual sections.
752 for (iterator it = begin(), ie = end(); it != ie; ++it) {
753 if (!getBackend().isVirtualSection(it->getSection()))
756 // Layout the section fragments and its size.
757 Address = LayoutSection(*it, Layout, Address);
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.
840 // FIXME: Add MCAsmLayout utility for this.
841 DF->setParent(IF->getParent());
842 DF->setOrdinal(IF->getOrdinal());
843 Layout.setFragmentOffset(DF, Layout.getFragmentOffset(IF));
844 Layout.setFragmentEffectiveSize(DF, Layout.getFragmentEffectiveSize(IF));
846 // Copy in the data and the fixups.
847 DF->getContents().append(IF->getCode().begin(), IF->getCode().end());
848 for (unsigned i = 0, e = IF->getFixups().size(); i != e; ++i)
849 DF->getFixups().push_back(IF->getFixups()[i]);
851 // Delete the instruction fragment and update the iterator.
852 SD.getFragmentList().erase(IF);
862 raw_ostream &operator<<(raw_ostream &OS, const MCAsmFixup &AF) {
863 OS << "<MCAsmFixup" << " Offset:" << AF.Offset << " Value:" << *AF.Value
864 << " Kind:" << AF.Kind << ">";
870 void MCFragment::dump() {
871 raw_ostream &OS = llvm::errs();
873 OS << "<MCFragment " << (void*) this << " Offset:" << Offset
874 << " EffectiveSize:" << EffectiveSize;
879 void MCAlignFragment::dump() {
880 raw_ostream &OS = llvm::errs();
882 OS << "<MCAlignFragment ";
883 this->MCFragment::dump();
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 << " Count:" << getCount() << ">";
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 MCZeroFillFragment::dump() {
947 raw_ostream &OS = llvm::errs();
949 OS << "<MCZeroFillFragment ";
950 this->MCFragment::dump();
952 OS << " Size:" << getSize() << " Alignment:" << getAlignment() << ">";
955 void MCSectionData::dump() {
956 raw_ostream &OS = llvm::errs();
958 OS << "<MCSectionData";
959 OS << " Alignment:" << getAlignment() << " Address:" << Address
960 << " Size:" << Size << " FileSize:" << FileSize
961 << " Fragments:[\n ";
962 for (iterator it = begin(), ie = end(); it != ie; ++it) {
963 if (it != begin()) OS << ",\n ";
969 void MCSymbolData::dump() {
970 raw_ostream &OS = llvm::errs();
972 OS << "<MCSymbolData Symbol:" << getSymbol()
973 << " Fragment:" << getFragment() << " Offset:" << getOffset()
974 << " Flags:" << getFlags() << " Index:" << getIndex();
976 OS << " (common, size:" << getCommonSize()
977 << " align: " << getCommonAlignment() << ")";
980 if (isPrivateExtern())
981 OS << " (private extern)";
985 void MCAssembler::dump() {
986 raw_ostream &OS = llvm::errs();
988 OS << "<MCAssembler\n";
989 OS << " Sections:[\n ";
990 for (iterator it = begin(), ie = end(); it != ie; ++it) {
991 if (it != begin()) OS << ",\n ";
997 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
998 if (it != symbol_begin()) OS << ",\n ";