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;
138 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
141 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
142 : Kind(_Kind), Parent(_Parent), Atom(0), EffectiveSize(~UINT64_C(0))
145 Parent->getFragmentList().push_back(this);
148 MCFragment::~MCFragment() {
153 MCSectionData::MCSectionData() : Section(0) {}
155 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
156 : Section(&_Section),
158 Address(~UINT64_C(0)),
160 FileSize(~UINT64_C(0)),
161 HasInstructions(false)
164 A->getSectionList().push_back(this);
169 MCSymbolData::MCSymbolData() : Symbol(0) {}
171 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
172 uint64_t _Offset, MCAssembler *A)
173 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
174 IsExternal(false), IsPrivateExtern(false),
175 CommonSize(0), CommonAlign(0), Flags(0), Index(0)
178 A->getSymbolList().push_back(this);
183 MCAssembler::MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
184 MCCodeEmitter &_Emitter, raw_ostream &_OS)
185 : Context(_Context), Backend(_Backend), Emitter(_Emitter),
186 OS(_OS), RelaxAll(false), SubsectionsViaSymbols(false)
190 MCAssembler::~MCAssembler() {
193 static bool isScatteredFixupFullyResolvedSimple(const MCAssembler &Asm,
194 const MCAsmFixup &Fixup,
195 const MCValue Target,
196 const MCSection *BaseSection) {
197 // The effective fixup address is
198 // addr(atom(A)) + offset(A)
199 // - addr(atom(B)) - offset(B)
200 // - addr(<base symbol>) + <fixup offset from base symbol>
201 // and the offsets are not relocatable, so the fixup is fully resolved when
202 // addr(atom(A)) - addr(atom(B)) - addr(<base symbol>)) == 0.
204 // The simple (Darwin, except on x86_64) way of dealing with this was to
205 // assume that any reference to a temporary symbol *must* be a temporary
206 // symbol in the same atom, unless the sections differ. Therefore, any PCrel
207 // relocation to a temporary symbol (in the same section) is fully
208 // resolved. This also works in conjunction with absolutized .set, which
209 // requires the compiler to use .set to absolutize the differences between
210 // symbols which the compiler knows to be assembly time constants, so we don't
211 // need to worry about considering symbol differences fully resolved.
213 // Non-relative fixups are only resolved if constant.
215 return Target.isAbsolute();
217 // Otherwise, relative fixups are only resolved if not a difference and the
218 // target is a temporary in the same section.
219 if (Target.isAbsolute() || Target.getSymB())
222 const MCSymbol *A = &Target.getSymA()->getSymbol();
223 if (!A->isTemporary() || !A->isInSection() ||
224 &A->getSection() != BaseSection)
230 static bool isScatteredFixupFullyResolved(const MCAssembler &Asm,
231 const MCAsmLayout &Layout,
232 const MCAsmFixup &Fixup,
233 const MCValue Target,
234 const MCSymbolData *BaseSymbol) {
235 // The effective fixup address is
236 // addr(atom(A)) + offset(A)
237 // - addr(atom(B)) - offset(B)
238 // - addr(BaseSymbol) + <fixup offset from base symbol>
239 // and the offsets are not relocatable, so the fixup is fully resolved when
240 // addr(atom(A)) - addr(atom(B)) - addr(BaseSymbol) == 0.
242 // Note that "false" is almost always conservatively correct (it means we emit
243 // a relocation which is unnecessary), except when it would force us to emit a
244 // relocation which the target cannot encode.
246 const MCSymbolData *A_Base = 0, *B_Base = 0;
247 if (const MCSymbolRefExpr *A = Target.getSymA()) {
248 // Modified symbol references cannot be resolved.
249 if (A->getKind() != MCSymbolRefExpr::VK_None)
252 A_Base = Asm.getAtom(Layout, &Asm.getSymbolData(A->getSymbol()));
257 if (const MCSymbolRefExpr *B = Target.getSymB()) {
258 // Modified symbol references cannot be resolved.
259 if (B->getKind() != MCSymbolRefExpr::VK_None)
262 B_Base = Asm.getAtom(Layout, &Asm.getSymbolData(B->getSymbol()));
267 // If there is no base, A and B have to be the same atom for this fixup to be
270 return A_Base == B_Base;
272 // Otherwise, B must be missing and A must be the base.
273 return !B_Base && BaseSymbol == A_Base;
276 bool MCAssembler::isSymbolLinkerVisible(const MCSymbolData *SD) const {
277 // Non-temporary labels should always be visible to the linker.
278 if (!SD->getSymbol().isTemporary())
281 // Absolute temporary labels are never visible.
282 if (!SD->getFragment())
285 // Otherwise, check if the section requires symbols even for temporary labels.
286 return getBackend().doesSectionRequireSymbols(
287 SD->getFragment()->getParent()->getSection());
290 // FIXME-PERF: This routine is really slow.
291 const MCSymbolData *MCAssembler::getAtomForAddress(const MCAsmLayout &Layout,
292 const MCSectionData *Section,
293 uint64_t Address) const {
294 const MCSymbolData *Best = 0;
295 uint64_t BestAddress = 0;
297 for (MCAssembler::const_symbol_iterator it = symbol_begin(),
298 ie = symbol_end(); it != ie; ++it) {
299 // Ignore non-linker visible symbols.
300 if (!isSymbolLinkerVisible(it))
303 // Ignore symbols not in the same section.
304 if (!it->getFragment() || it->getFragment()->getParent() != Section)
307 // Otherwise, find the closest symbol preceding this address (ties are
308 // resolved in favor of the last defined symbol).
309 uint64_t SymbolAddress = Layout.getSymbolAddress(it);
310 if (SymbolAddress <= Address && (!Best || SymbolAddress >= BestAddress)) {
312 BestAddress = SymbolAddress;
319 // FIXME-PERF: This routine is really slow.
320 const MCSymbolData *MCAssembler::getAtom(const MCAsmLayout &Layout,
321 const MCSymbolData *SD) const {
322 // Linker visible symbols define atoms.
323 if (isSymbolLinkerVisible(SD))
326 // Absolute and undefined symbols have no defining atom.
327 if (!SD->getFragment())
330 // Otherwise, search by address.
331 return getAtomForAddress(Layout, SD->getFragment()->getParent(),
332 Layout.getSymbolAddress(SD));
335 bool MCAssembler::EvaluateFixup(const MCAsmLayout &Layout,
336 const MCAsmFixup &Fixup, const MCFragment *DF,
337 MCValue &Target, uint64_t &Value) const {
338 ++stats::EvaluateFixup;
340 if (!Fixup.Value->EvaluateAsRelocatable(Target, &Layout))
341 report_fatal_error("expected relocatable expression");
343 // FIXME: How do non-scattered symbols work in ELF? I presume the linker
344 // doesn't support small relocations, but then under what criteria does the
345 // assembler allow symbol differences?
347 Value = Target.getConstant();
350 Emitter.getFixupKindInfo(Fixup.Kind).Flags & MCFixupKindInfo::FKF_IsPCRel;
351 bool IsResolved = true;
352 if (const MCSymbolRefExpr *A = Target.getSymA()) {
353 if (A->getSymbol().isDefined())
354 Value += Layout.getSymbolAddress(&getSymbolData(A->getSymbol()));
358 if (const MCSymbolRefExpr *B = Target.getSymB()) {
359 if (B->getSymbol().isDefined())
360 Value -= Layout.getSymbolAddress(&getSymbolData(B->getSymbol()));
365 // If we are using scattered symbols, determine whether this value is actually
366 // resolved; scattering may cause atoms to move.
367 if (IsResolved && getBackend().hasScatteredSymbols()) {
368 if (getBackend().hasReliableSymbolDifference()) {
369 // If this is a PCrel relocation, find the base atom (identified by its
370 // symbol) that the fixup value is relative to.
371 const MCSymbolData *BaseSymbol = 0;
373 BaseSymbol = getAtomForAddress(
374 Layout, DF->getParent(), Layout.getFragmentAddress(DF)+Fixup.Offset);
380 IsResolved = isScatteredFixupFullyResolved(*this, Layout, Fixup, Target,
383 const MCSection *BaseSection = 0;
385 BaseSection = &DF->getParent()->getSection();
387 IsResolved = isScatteredFixupFullyResolvedSimple(*this, Fixup, Target,
393 Value -= Layout.getFragmentAddress(DF) + Fixup.Offset;
398 uint64_t MCAssembler::LayoutSection(MCSectionData &SD,
400 uint64_t StartAddress) {
401 bool IsVirtual = getBackend().isVirtualSection(SD.getSection());
403 ++stats::SectionLayouts;
405 // Align this section if necessary by adding padding bytes to the previous
406 // section. It is safe to adjust this out-of-band, because no symbol or
407 // fragment is allowed to point past the end of the section at any time.
408 if (uint64_t Pad = OffsetToAlignment(StartAddress, SD.getAlignment())) {
409 // Unless this section is virtual (where we are allowed to adjust the offset
410 // freely), the padding goes in the previous section.
412 // Find the previous non-virtual section.
414 assert(it != begin() && "Invalid initial section address!");
415 for (--it; getBackend().isVirtualSection(it->getSection()); --it) ;
416 Layout.setSectionFileSize(&*it, Layout.getSectionFileSize(&*it) + Pad);
422 // Set the aligned section address.
423 Layout.setSectionAddress(&SD, StartAddress);
425 uint64_t Address = StartAddress;
426 for (MCSectionData::iterator it = SD.begin(), ie = SD.end(); it != ie; ++it) {
429 ++stats::FragmentLayouts;
431 uint64_t FragmentOffset = Address - StartAddress;
432 Layout.setFragmentOffset(&F, FragmentOffset);
434 // Evaluate fragment size.
435 uint64_t EffectiveSize = 0;
436 switch (F.getKind()) {
437 case MCFragment::FT_Align: {
438 MCAlignFragment &AF = cast<MCAlignFragment>(F);
440 EffectiveSize = OffsetToAlignment(Address, AF.getAlignment());
441 if (EffectiveSize > AF.getMaxBytesToEmit())
446 case MCFragment::FT_Data:
447 EffectiveSize = cast<MCDataFragment>(F).getContents().size();
450 case MCFragment::FT_Fill: {
451 MCFillFragment &FF = cast<MCFillFragment>(F);
452 EffectiveSize = FF.getValueSize() * FF.getCount();
456 case MCFragment::FT_Inst:
457 EffectiveSize = cast<MCInstFragment>(F).getInstSize();
460 case MCFragment::FT_Org: {
461 MCOrgFragment &OF = cast<MCOrgFragment>(F);
463 int64_t TargetLocation;
464 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
465 report_fatal_error("expected assembly-time absolute expression");
467 // FIXME: We need a way to communicate this error.
468 int64_t Offset = TargetLocation - FragmentOffset;
470 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
471 "' (at offset '" + Twine(FragmentOffset) + "'");
473 EffectiveSize = Offset;
477 case MCFragment::FT_ZeroFill: {
478 MCZeroFillFragment &ZFF = cast<MCZeroFillFragment>(F);
480 // Align the fragment offset; it is safe to adjust the offset freely since
481 // this is only in virtual sections.
483 // FIXME: We shouldn't be doing this here.
484 Address = RoundUpToAlignment(Address, ZFF.getAlignment());
485 Layout.setFragmentOffset(&F, Address - StartAddress);
487 EffectiveSize = ZFF.getSize();
492 Layout.setFragmentEffectiveSize(&F, EffectiveSize);
493 Address += EffectiveSize;
496 // Set the section sizes.
497 Layout.setSectionSize(&SD, Address - StartAddress);
499 Layout.setSectionFileSize(&SD, 0);
501 Layout.setSectionFileSize(&SD, Address - StartAddress);
506 /// WriteFragmentData - Write the \arg F data to the output file.
507 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
508 const MCFragment &F, MCObjectWriter *OW) {
509 uint64_t Start = OW->getStream().tell();
512 ++stats::EmittedFragments;
514 // FIXME: Embed in fragments instead?
515 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
516 switch (F.getKind()) {
517 case MCFragment::FT_Align: {
518 MCAlignFragment &AF = cast<MCAlignFragment>(F);
519 uint64_t Count = FragmentSize / AF.getValueSize();
521 // FIXME: This error shouldn't actually occur (the front end should emit
522 // multiple .align directives to enforce the semantics it wants), but is
523 // severe enough that we want to report it. How to handle this?
524 if (Count * AF.getValueSize() != FragmentSize)
525 report_fatal_error("undefined .align directive, value size '" +
526 Twine(AF.getValueSize()) +
527 "' is not a divisor of padding size '" +
528 Twine(FragmentSize) + "'");
530 // See if we are aligning with nops, and if so do that first to try to fill
531 // the Count bytes. Then if that did not fill any bytes or there are any
532 // bytes left to fill use the the Value and ValueSize to fill the rest.
533 // If we are aligning with nops, ask that target to emit the right data.
534 if (AF.getEmitNops()) {
535 if (!Asm.getBackend().WriteNopData(Count, OW))
536 report_fatal_error("unable to write nop sequence of " +
537 Twine(Count) + " bytes");
541 // Otherwise, write out in multiples of the value size.
542 for (uint64_t i = 0; i != Count; ++i) {
543 switch (AF.getValueSize()) {
545 assert(0 && "Invalid size!");
546 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
547 case 2: OW->Write16(uint16_t(AF.getValue())); break;
548 case 4: OW->Write32(uint32_t(AF.getValue())); break;
549 case 8: OW->Write64(uint64_t(AF.getValue())); break;
555 case MCFragment::FT_Data: {
556 MCDataFragment &DF = cast<MCDataFragment>(F);
557 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
558 OW->WriteBytes(DF.getContents().str());
562 case MCFragment::FT_Fill: {
563 MCFillFragment &FF = cast<MCFillFragment>(F);
564 for (uint64_t i = 0, e = FF.getCount(); i != e; ++i) {
565 switch (FF.getValueSize()) {
567 assert(0 && "Invalid size!");
568 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
569 case 2: OW->Write16(uint16_t(FF.getValue())); break;
570 case 4: OW->Write32(uint32_t(FF.getValue())); break;
571 case 8: OW->Write64(uint64_t(FF.getValue())); break;
577 case MCFragment::FT_Inst:
578 llvm_unreachable("unexpected inst fragment after lowering");
581 case MCFragment::FT_Org: {
582 MCOrgFragment &OF = cast<MCOrgFragment>(F);
584 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
585 OW->Write8(uint8_t(OF.getValue()));
590 case MCFragment::FT_ZeroFill: {
591 assert(0 && "Invalid zero fill fragment in concrete section!");
596 assert(OW->getStream().tell() - Start == FragmentSize);
599 void MCAssembler::WriteSectionData(const MCSectionData *SD,
600 const MCAsmLayout &Layout,
601 MCObjectWriter *OW) const {
602 uint64_t SectionSize = Layout.getSectionSize(SD);
603 uint64_t SectionFileSize = Layout.getSectionFileSize(SD);
605 // Ignore virtual sections.
606 if (getBackend().isVirtualSection(SD->getSection())) {
607 assert(SectionFileSize == 0 && "Invalid size for section!");
611 uint64_t Start = OW->getStream().tell();
614 for (MCSectionData::const_iterator it = SD->begin(),
615 ie = SD->end(); it != ie; ++it)
616 WriteFragmentData(*this, Layout, *it, OW);
618 // Add section padding.
619 assert(SectionFileSize >= SectionSize && "Invalid section sizes!");
620 OW->WriteZeros(SectionFileSize - SectionSize);
622 assert(OW->getStream().tell() - Start == SectionFileSize);
625 void MCAssembler::Finish() {
626 DEBUG_WITH_TYPE("mc-dump", {
627 llvm::errs() << "assembler backend - pre-layout\n--\n";
630 // Assign section and fragment ordinals, all subsequent backend code is
631 // responsible for updating these in place.
632 unsigned SectionIndex = 0;
633 unsigned FragmentIndex = 0;
634 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
635 it->setOrdinal(SectionIndex++);
637 for (MCSectionData::iterator it2 = it->begin(),
638 ie2 = it->end(); it2 != ie2; ++it2)
639 it2->setOrdinal(FragmentIndex++);
642 // Layout until everything fits.
643 MCAsmLayout Layout(*this);
644 while (LayoutOnce(Layout))
647 DEBUG_WITH_TYPE("mc-dump", {
648 llvm::errs() << "assembler backend - post-relaxation\n--\n";
651 // Finalize the layout, including fragment lowering.
652 FinishLayout(Layout);
654 DEBUG_WITH_TYPE("mc-dump", {
655 llvm::errs() << "assembler backend - final-layout\n--\n";
658 uint64_t StartOffset = OS.tell();
659 llvm::OwningPtr<MCObjectWriter> Writer(getBackend().createObjectWriter(OS));
661 report_fatal_error("unable to create object writer!");
663 // Allow the object writer a chance to perform post-layout binding (for
664 // example, to set the index fields in the symbol data).
665 Writer->ExecutePostLayoutBinding(*this);
667 // Evaluate and apply the fixups, generating relocation entries as necessary.
668 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
669 for (MCSectionData::iterator it2 = it->begin(),
670 ie2 = it->end(); it2 != ie2; ++it2) {
671 MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
675 for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
676 ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
677 MCAsmFixup &Fixup = *it3;
679 // Evaluate the fixup.
682 if (!EvaluateFixup(Layout, Fixup, DF, Target, FixedValue)) {
683 // The fixup was unresolved, we need a relocation. Inform the object
684 // writer of the relocation, and give it an opportunity to adjust the
685 // fixup value if need be.
686 Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
689 getBackend().ApplyFixup(Fixup, *DF, FixedValue);
694 // Write the object file.
695 Writer->WriteObject(*this, Layout);
698 stats::ObjectBytes += OS.tell() - StartOffset;
701 bool MCAssembler::FixupNeedsRelaxation(const MCAsmFixup &Fixup,
702 const MCFragment *DF,
703 const MCAsmLayout &Layout) const {
707 // If we cannot resolve the fixup value, it requires relaxation.
710 if (!EvaluateFixup(Layout, Fixup, DF, Target, Value))
713 // Otherwise, relax if the value is too big for a (signed) i8.
715 // FIXME: This is target dependent!
716 return int64_t(Value) != int64_t(int8_t(Value));
719 bool MCAssembler::FragmentNeedsRelaxation(const MCInstFragment *IF,
720 const MCAsmLayout &Layout) const {
721 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
722 // are intentionally pushing out inst fragments, or because we relaxed a
723 // previous instruction to one that doesn't need relaxation.
724 if (!getBackend().MayNeedRelaxation(IF->getInst(), IF->getFixups()))
727 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
728 ie = IF->fixup_end(); it != ie; ++it)
729 if (FixupNeedsRelaxation(*it, IF, Layout))
735 bool MCAssembler::LayoutOnce(MCAsmLayout &Layout) {
736 ++stats::RelaxationSteps;
738 // Layout the concrete sections and fragments.
739 uint64_t Address = 0;
740 for (iterator it = begin(), ie = end(); it != ie; ++it) {
741 // Skip virtual sections.
742 if (getBackend().isVirtualSection(it->getSection()))
745 // Layout the section fragments and its size.
746 Address = LayoutSection(*it, Layout, Address);
749 // Layout the virtual sections.
750 for (iterator it = begin(), ie = end(); it != ie; ++it) {
751 if (!getBackend().isVirtualSection(it->getSection()))
754 // Layout the section fragments and its size.
755 Address = LayoutSection(*it, Layout, Address);
758 // Scan for fragments that need relaxation.
759 bool WasRelaxed = false;
760 for (iterator it = begin(), ie = end(); it != ie; ++it) {
761 MCSectionData &SD = *it;
763 for (MCSectionData::iterator it2 = SD.begin(),
764 ie2 = SD.end(); it2 != ie2; ++it2) {
765 // Check if this is an instruction fragment that needs relaxation.
766 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
767 if (!IF || !FragmentNeedsRelaxation(IF, Layout))
770 ++stats::RelaxedInstructions;
772 // FIXME-PERF: We could immediately lower out instructions if we can tell
773 // they are fully resolved, to avoid retesting on later passes.
775 // Relax the fragment.
778 getBackend().RelaxInstruction(IF, Relaxed);
780 // Encode the new instruction.
782 // FIXME-PERF: If it matters, we could let the target do this. It can
783 // probably do so more efficiently in many cases.
784 SmallVector<MCFixup, 4> Fixups;
785 SmallString<256> Code;
786 raw_svector_ostream VecOS(Code);
787 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
790 // Update the instruction fragment.
791 int SlideAmount = Code.size() - IF->getInstSize();
792 IF->setInst(Relaxed);
793 IF->getCode() = Code;
794 IF->getFixups().clear();
795 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
796 MCFixup &F = Fixups[i];
797 IF->getFixups().push_back(MCAsmFixup(F.getOffset(), *F.getValue(),
801 // Update the layout, and remember that we relaxed. If we are relaxing
802 // everything, we can skip this step since nothing will depend on updating
805 Layout.UpdateForSlide(IF, SlideAmount);
813 void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
814 // Lower out any instruction fragments, to simplify the fixup application and
817 // FIXME-PERF: We don't have to do this, but the assumption is that it is
818 // cheap (we will mostly end up eliminating fragments and appending on to data
819 // fragments), so the extra complexity downstream isn't worth it. Evaluate
821 for (iterator it = begin(), ie = end(); it != ie; ++it) {
822 MCSectionData &SD = *it;
824 for (MCSectionData::iterator it2 = SD.begin(),
825 ie2 = SD.end(); it2 != ie2; ++it2) {
826 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
830 // Create a new data fragment for the instruction.
832 // FIXME-PERF: Reuse previous data fragment if possible.
833 MCDataFragment *DF = new MCDataFragment();
834 SD.getFragmentList().insert(it2, DF);
836 // Update the data fragments layout data.
838 // FIXME: Add MCAsmLayout utility for this.
839 DF->setParent(IF->getParent());
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;
877 void MCAlignFragment::dump() {
878 raw_ostream &OS = llvm::errs();
880 OS << "<MCAlignFragment ";
881 this->MCFragment::dump();
883 OS << " Alignment:" << getAlignment()
884 << " Value:" << getValue() << " ValueSize:" << getValueSize()
885 << " MaxBytesToEmit:" << getMaxBytesToEmit() << ">";
888 void MCDataFragment::dump() {
889 raw_ostream &OS = llvm::errs();
891 OS << "<MCDataFragment ";
892 this->MCFragment::dump();
895 for (unsigned i = 0, e = getContents().size(); i != e; ++i) {
897 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
899 OS << "] (" << getContents().size() << " bytes)";
901 if (!getFixups().empty()) {
904 for (fixup_iterator it = fixup_begin(), ie = fixup_end(); it != ie; ++it) {
905 if (it != fixup_begin()) OS << ",\n ";
914 void MCFillFragment::dump() {
915 raw_ostream &OS = llvm::errs();
917 OS << "<MCFillFragment ";
918 this->MCFragment::dump();
920 OS << " Value:" << getValue() << " ValueSize:" << getValueSize()
921 << " Count:" << getCount() << ">";
924 void MCInstFragment::dump() {
925 raw_ostream &OS = llvm::errs();
927 OS << "<MCInstFragment ";
928 this->MCFragment::dump();
931 getInst().dump_pretty(OS);
935 void MCOrgFragment::dump() {
936 raw_ostream &OS = llvm::errs();
938 OS << "<MCOrgFragment ";
939 this->MCFragment::dump();
941 OS << " Offset:" << getOffset() << " Value:" << getValue() << ">";
944 void MCZeroFillFragment::dump() {
945 raw_ostream &OS = llvm::errs();
947 OS << "<MCZeroFillFragment ";
948 this->MCFragment::dump();
950 OS << " Size:" << getSize() << " Alignment:" << getAlignment() << ">";
953 void MCSectionData::dump() {
954 raw_ostream &OS = llvm::errs();
956 OS << "<MCSectionData";
957 OS << " Alignment:" << getAlignment() << " Address:" << Address
958 << " Size:" << Size << " FileSize:" << FileSize
959 << " Fragments:[\n ";
960 for (iterator it = begin(), ie = end(); it != ie; ++it) {
961 if (it != begin()) OS << ",\n ";
967 void MCSymbolData::dump() {
968 raw_ostream &OS = llvm::errs();
970 OS << "<MCSymbolData Symbol:" << getSymbol()
971 << " Fragment:" << getFragment() << " Offset:" << getOffset()
972 << " Flags:" << getFlags() << " Index:" << getIndex();
974 OS << " (common, size:" << getCommonSize()
975 << " align: " << getCommonAlignment() << ")";
978 if (isPrivateExtern())
979 OS << " (private extern)";
983 void MCAssembler::dump() {
984 raw_ostream &OS = llvm::errs();
986 OS << "<MCAssembler\n";
987 OS << " Sections:[\n ";
988 for (iterator it = begin(), ie = end(); it != ie; ++it) {
989 if (it != begin()) OS << ",\n ";
995 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
996 if (it != symbol_begin()) OS << ",\n ";