1 //===- lib/MC/MCAssembler.cpp - Assembler Backend Implementation ----------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #define DEBUG_TYPE "assembler"
11 #include "llvm/MC/MCAssembler.h"
12 #include "llvm/MC/MCAsmLayout.h"
13 #include "llvm/MC/MCCodeEmitter.h"
14 #include "llvm/MC/MCExpr.h"
15 #include "llvm/MC/MCObjectWriter.h"
16 #include "llvm/MC/MCSymbol.h"
17 #include "llvm/MC/MCValue.h"
18 #include "llvm/ADT/OwningPtr.h"
19 #include "llvm/ADT/Statistic.h"
20 #include "llvm/ADT/StringExtras.h"
21 #include "llvm/ADT/Twine.h"
22 #include "llvm/Support/Debug.h"
23 #include "llvm/Support/ErrorHandling.h"
24 #include "llvm/Support/raw_ostream.h"
25 #include "llvm/Target/TargetRegistry.h"
26 #include "llvm/Target/TargetAsmBackend.h"
33 STATISTIC(EmittedFragments, "Number of emitted assembler fragments");
34 STATISTIC(EvaluateFixup, "Number of evaluated fixups");
35 STATISTIC(FragmentLayouts, "Number of fragment layouts");
36 STATISTIC(ObjectBytes, "Number of emitted object file bytes");
37 STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps");
38 STATISTIC(RelaxedInstructions, "Number of relaxed instructions");
39 STATISTIC(SectionLayouts, "Number of section layouts");
43 // FIXME FIXME FIXME: There are number of places in this file where we convert
44 // what is a 64-bit assembler value used for computation into a value in the
45 // object file, which may truncate it. We should detect that truncation where
46 // invalid and report errors back.
50 MCAsmLayout::MCAsmLayout(MCAssembler &Asm)
51 : Assembler(Asm), LastValidFragment(0)
53 // Compute the section layout order. Virtual sections must go last.
54 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
55 if (!Asm.getBackend().isVirtualSection(it->getSection()))
56 SectionOrder.push_back(&*it);
57 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
58 if (Asm.getBackend().isVirtualSection(it->getSection()))
59 SectionOrder.push_back(&*it);
62 bool MCAsmLayout::isSectionUpToDate(const MCSectionData *SD) const {
63 // The first section is always up-to-date.
64 unsigned Index = SD->getLayoutOrder();
68 // Otherwise, sections are always implicitly computed when the preceeding
69 // fragment is layed out.
70 const MCSectionData *Prev = getSectionOrder()[Index - 1];
71 return isFragmentUpToDate(&(Prev->getFragmentList().back()));
74 bool MCAsmLayout::isFragmentUpToDate(const MCFragment *F) const {
75 return (LastValidFragment &&
76 F->getLayoutOrder() <= LastValidFragment->getLayoutOrder());
79 void MCAsmLayout::UpdateForSlide(MCFragment *F, int SlideAmount) {
80 // If this fragment wasn't already up-to-date, we don't need to do anything.
81 if (!isFragmentUpToDate(F))
84 // Otherwise, reset the last valid fragment to the predecessor of the
85 // invalidated fragment.
86 LastValidFragment = F->getPrevNode();
87 if (!LastValidFragment) {
88 unsigned Index = F->getParent()->getLayoutOrder();
90 MCSectionData *Prev = getSectionOrder()[Index - 1];
91 LastValidFragment = &(Prev->getFragmentList().back());
96 void MCAsmLayout::EnsureValid(const MCFragment *F) const {
97 // Advance the layout position until the fragment is up-to-date.
98 while (!isFragmentUpToDate(F)) {
99 // Advance to the next fragment.
100 MCFragment *Cur = LastValidFragment;
102 Cur = Cur->getNextNode();
104 unsigned NextIndex = 0;
105 if (LastValidFragment)
106 NextIndex = LastValidFragment->getParent()->getLayoutOrder() + 1;
107 Cur = SectionOrder[NextIndex]->begin();
110 const_cast<MCAsmLayout*>(this)->LayoutFragment(Cur);
114 void MCAsmLayout::FragmentReplaced(MCFragment *Src, MCFragment *Dst) {
115 if (LastValidFragment == Src)
116 LastValidFragment = Dst;
118 Dst->Offset = Src->Offset;
119 Dst->EffectiveSize = Src->EffectiveSize;
122 uint64_t MCAsmLayout::getFragmentAddress(const MCFragment *F) const {
123 assert(F->getParent() && "Missing section()!");
124 return getSectionAddress(F->getParent()) + getFragmentOffset(F);
127 uint64_t MCAsmLayout::getFragmentEffectiveSize(const MCFragment *F) const {
129 assert(F->EffectiveSize != ~UINT64_C(0) && "Address not set!");
130 return F->EffectiveSize;
133 uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
135 assert(F->Offset != ~UINT64_C(0) && "Address not set!");
139 uint64_t MCAsmLayout::getSymbolAddress(const MCSymbolData *SD) const {
140 assert(SD->getFragment() && "Invalid getAddress() on undefined symbol!");
141 return getFragmentAddress(SD->getFragment()) + SD->getOffset();
144 uint64_t MCAsmLayout::getSectionAddress(const MCSectionData *SD) const {
145 EnsureValid(SD->begin());
146 assert(SD->Address != ~UINT64_C(0) && "Address not set!");
150 uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const {
151 // The size is the last fragment's end offset.
152 const MCFragment &F = SD->getFragmentList().back();
153 return getFragmentOffset(&F) + getFragmentEffectiveSize(&F);
156 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
157 // Virtual sections have no file size.
158 if (getAssembler().getBackend().isVirtualSection(SD->getSection()))
161 // Otherwise, the file size is the same as the address space size.
162 return getSectionAddressSize(SD);
165 uint64_t MCAsmLayout::getSectionSize(const MCSectionData *SD) const {
166 // The logical size is the address space size minus any tail padding.
167 uint64_t Size = getSectionAddressSize(SD);
168 const MCAlignFragment *AF =
169 dyn_cast<MCAlignFragment>(&(SD->getFragmentList().back()));
170 if (AF && AF->hasOnlyAlignAddress())
171 Size -= getFragmentEffectiveSize(AF);
178 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
181 MCFragment::~MCFragment() {
184 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
185 : Kind(_Kind), Parent(_Parent), Atom(0), Offset(~UINT64_C(0)),
186 EffectiveSize(~UINT64_C(0))
189 Parent->getFragmentList().push_back(this);
194 MCSectionData::MCSectionData() : Section(0) {}
196 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
197 : Section(&_Section),
199 Address(~UINT64_C(0)),
200 HasInstructions(false)
203 A->getSectionList().push_back(this);
208 MCSymbolData::MCSymbolData() : Symbol(0) {}
210 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
211 uint64_t _Offset, MCAssembler *A)
212 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
213 IsExternal(false), IsPrivateExtern(false),
214 CommonSize(0), SymbolSize(0), CommonAlign(0),
218 A->getSymbolList().push_back(this);
223 MCAssembler::MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
224 MCCodeEmitter &_Emitter, bool _PadSectionToAlignment,
226 : Context(_Context), Backend(_Backend), Emitter(_Emitter),
227 OS(_OS), RelaxAll(false), SubsectionsViaSymbols(false),
228 PadSectionToAlignment(_PadSectionToAlignment)
232 MCAssembler::~MCAssembler() {
235 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
236 // Non-temporary labels should always be visible to the linker.
237 if (!Symbol.isTemporary())
240 // Absolute temporary labels are never visible.
241 if (!Symbol.isInSection())
244 // Otherwise, check if the section requires symbols even for temporary labels.
245 return getBackend().doesSectionRequireSymbols(Symbol.getSection());
248 const MCSymbolData *MCAssembler::getAtom(const MCSymbolData *SD) const {
249 // Linker visible symbols define atoms.
250 if (isSymbolLinkerVisible(SD->getSymbol()))
253 // Absolute and undefined symbols have no defining atom.
254 if (!SD->getFragment())
257 // Non-linker visible symbols in sections which can't be atomized have no
259 if (!getBackend().isSectionAtomizable(
260 SD->getFragment()->getParent()->getSection()))
263 // Otherwise, return the atom for the containing fragment.
264 return SD->getFragment()->getAtom();
267 bool MCAssembler::EvaluateFixup(const MCObjectWriter &Writer,
268 const MCAsmLayout &Layout,
269 const MCFixup &Fixup, const MCFragment *DF,
270 MCValue &Target, uint64_t &Value) const {
271 ++stats::EvaluateFixup;
273 if (!Fixup.getValue()->EvaluateAsRelocatable(Target, &Layout))
274 report_fatal_error("expected relocatable expression");
276 // FIXME: How do non-scattered symbols work in ELF? I presume the linker
277 // doesn't support small relocations, but then under what criteria does the
278 // assembler allow symbol differences?
280 Value = Target.getConstant();
282 bool IsPCRel = Emitter.getFixupKindInfo(
283 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
284 bool IsResolved = true;
285 if (const MCSymbolRefExpr *A = Target.getSymA()) {
286 if (A->getSymbol().isDefined())
287 Value += Layout.getSymbolAddress(&getSymbolData(A->getSymbol()));
291 if (const MCSymbolRefExpr *B = Target.getSymB()) {
292 if (B->getSymbol().isDefined())
293 Value -= Layout.getSymbolAddress(&getSymbolData(B->getSymbol()));
299 IsResolved = Writer.IsFixupFullyResolved(*this, Target, IsPCRel, DF);
302 Value -= Layout.getFragmentAddress(DF) + Fixup.getOffset();
307 uint64_t MCAssembler::ComputeFragmentSize(MCAsmLayout &Layout,
309 uint64_t SectionAddress,
310 uint64_t FragmentOffset) const {
311 switch (F.getKind()) {
312 case MCFragment::FT_Data:
313 return cast<MCDataFragment>(F).getContents().size();
314 case MCFragment::FT_Fill:
315 return cast<MCFillFragment>(F).getSize();
316 case MCFragment::FT_Inst:
317 return cast<MCInstFragment>(F).getInstSize();
319 case MCFragment::FT_Align: {
320 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
322 assert((!AF.hasOnlyAlignAddress() || !AF.getNextNode()) &&
323 "Invalid OnlyAlignAddress bit, not the last fragment!");
325 uint64_t Size = OffsetToAlignment(SectionAddress + FragmentOffset,
328 // Honor MaxBytesToEmit.
329 if (Size > AF.getMaxBytesToEmit())
335 case MCFragment::FT_Org: {
336 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
338 // FIXME: We should compute this sooner, we don't want to recurse here, and
339 // we would like to be more functional.
340 int64_t TargetLocation;
341 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
342 report_fatal_error("expected assembly-time absolute expression");
344 // FIXME: We need a way to communicate this error.
345 int64_t Offset = TargetLocation - FragmentOffset;
346 if (Offset < 0 || Offset >= 0x40000000)
347 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
348 "' (at offset '" + Twine(FragmentOffset) + "')");
354 assert(0 && "invalid fragment kind");
358 void MCAsmLayout::LayoutFile() {
359 // Initialize the first section and set the valid fragment layout point. All
360 // actual layout computations are done lazily.
361 LastValidFragment = 0;
362 if (!getSectionOrder().empty())
363 getSectionOrder().front()->Address = 0;
366 void MCAsmLayout::LayoutFragment(MCFragment *F) {
367 MCFragment *Prev = F->getPrevNode();
369 // We should never try to recompute something which is up-to-date.
370 assert(!isFragmentUpToDate(F) && "Attempt to recompute up-to-date fragment!");
371 // We should never try to compute the fragment layout if the section isn't
373 assert(isSectionUpToDate(F->getParent()) &&
374 "Attempt to compute fragment before it's section!");
375 // We should never try to compute the fragment layout if it's predecessor
377 assert((!Prev || isFragmentUpToDate(Prev)) &&
378 "Attempt to compute fragment before it's predecessor!");
380 ++stats::FragmentLayouts;
382 // Compute the fragment start address.
383 uint64_t StartAddress = F->getParent()->Address;
384 uint64_t Address = StartAddress;
386 Address += Prev->Offset + Prev->EffectiveSize;
388 // Compute fragment offset and size.
389 F->Offset = Address - StartAddress;
390 F->EffectiveSize = getAssembler().ComputeFragmentSize(*this, *F, StartAddress,
392 LastValidFragment = F;
394 // If this is the last fragment in a section, update the next section address.
395 if (!F->getNextNode()) {
396 unsigned NextIndex = F->getParent()->getLayoutOrder() + 1;
397 if (NextIndex != getSectionOrder().size())
398 LayoutSection(getSectionOrder()[NextIndex]);
402 void MCAsmLayout::LayoutSection(MCSectionData *SD) {
403 unsigned SectionOrderIndex = SD->getLayoutOrder();
405 ++stats::SectionLayouts;
407 // Compute the section start address.
408 uint64_t StartAddress = 0;
409 if (SectionOrderIndex) {
410 MCSectionData *Prev = getSectionOrder()[SectionOrderIndex - 1];
411 StartAddress = getSectionAddress(Prev) + getSectionAddressSize(Prev);
414 // Honor the section alignment requirements.
415 StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
417 // Set the section address.
418 SD->Address = StartAddress;
421 /// WriteFragmentData - Write the \arg F data to the output file.
422 static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
423 const MCFragment &F, MCObjectWriter *OW) {
424 uint64_t Start = OW->getStream().tell();
427 ++stats::EmittedFragments;
429 // FIXME: Embed in fragments instead?
430 uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
431 switch (F.getKind()) {
432 case MCFragment::FT_Align: {
433 MCAlignFragment &AF = cast<MCAlignFragment>(F);
434 uint64_t Count = FragmentSize / AF.getValueSize();
436 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
438 // FIXME: This error shouldn't actually occur (the front end should emit
439 // multiple .align directives to enforce the semantics it wants), but is
440 // severe enough that we want to report it. How to handle this?
441 if (Count * AF.getValueSize() != FragmentSize)
442 report_fatal_error("undefined .align directive, value size '" +
443 Twine(AF.getValueSize()) +
444 "' is not a divisor of padding size '" +
445 Twine(FragmentSize) + "'");
447 // See if we are aligning with nops, and if so do that first to try to fill
448 // the Count bytes. Then if that did not fill any bytes or there are any
449 // bytes left to fill use the the Value and ValueSize to fill the rest.
450 // If we are aligning with nops, ask that target to emit the right data.
451 if (AF.hasEmitNops()) {
452 if (!Asm.getBackend().WriteNopData(Count, OW))
453 report_fatal_error("unable to write nop sequence of " +
454 Twine(Count) + " bytes");
458 // Otherwise, write out in multiples of the value size.
459 for (uint64_t i = 0; i != Count; ++i) {
460 switch (AF.getValueSize()) {
462 assert(0 && "Invalid size!");
463 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
464 case 2: OW->Write16(uint16_t(AF.getValue())); break;
465 case 4: OW->Write32(uint32_t(AF.getValue())); break;
466 case 8: OW->Write64(uint64_t(AF.getValue())); break;
472 case MCFragment::FT_Data: {
473 MCDataFragment &DF = cast<MCDataFragment>(F);
474 assert(FragmentSize == DF.getContents().size() && "Invalid size!");
475 OW->WriteBytes(DF.getContents().str());
479 case MCFragment::FT_Fill: {
480 MCFillFragment &FF = cast<MCFillFragment>(F);
482 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
484 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
485 switch (FF.getValueSize()) {
487 assert(0 && "Invalid size!");
488 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
489 case 2: OW->Write16(uint16_t(FF.getValue())); break;
490 case 4: OW->Write32(uint32_t(FF.getValue())); break;
491 case 8: OW->Write64(uint64_t(FF.getValue())); break;
497 case MCFragment::FT_Inst:
498 llvm_unreachable("unexpected inst fragment after lowering");
501 case MCFragment::FT_Org: {
502 MCOrgFragment &OF = cast<MCOrgFragment>(F);
504 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
505 OW->Write8(uint8_t(OF.getValue()));
511 assert(OW->getStream().tell() - Start == FragmentSize);
514 void MCAssembler::WriteSectionData(const MCSectionData *SD,
515 const MCAsmLayout &Layout,
516 MCObjectWriter *OW) const {
517 // Ignore virtual sections.
518 if (getBackend().isVirtualSection(SD->getSection())) {
519 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
521 // Check that contents are only things legal inside a virtual section.
522 for (MCSectionData::const_iterator it = SD->begin(),
523 ie = SD->end(); it != ie; ++it) {
524 switch (it->getKind()) {
526 assert(0 && "Invalid fragment in virtual section!");
527 case MCFragment::FT_Data: {
528 // Check that we aren't trying to write a non-zero contents (or fixups)
529 // into a virtual section. This is to support clients which use standard
530 // directives to fill the contents of virtual sections.
531 MCDataFragment &DF = cast<MCDataFragment>(*it);
532 assert(DF.fixup_begin() == DF.fixup_end() &&
533 "Cannot have fixups in virtual section!");
534 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
535 assert(DF.getContents()[i] == 0 &&
536 "Invalid data value for virtual section!");
539 case MCFragment::FT_Align:
540 // Check that we aren't trying to write a non-zero value into a virtual
542 assert((!cast<MCAlignFragment>(it)->getValueSize() ||
543 !cast<MCAlignFragment>(it)->getValue()) &&
544 "Invalid align in virtual section!");
546 case MCFragment::FT_Fill:
547 assert(!cast<MCFillFragment>(it)->getValueSize() &&
548 "Invalid fill in virtual section!");
556 uint64_t Start = OW->getStream().tell();
559 for (MCSectionData::const_iterator it = SD->begin(),
560 ie = SD->end(); it != ie; ++it)
561 WriteFragmentData(*this, Layout, *it, OW);
563 assert(OW->getStream().tell() - Start == Layout.getSectionFileSize(SD));
566 void MCAssembler::AddSectionToTheEnd(const MCObjectWriter &Writer,
567 MCSectionData &SD, MCAsmLayout &Layout) {
568 // Create dummy fragments and assign section ordinals.
569 unsigned SectionIndex = 0;
570 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it)
573 SD.setOrdinal(SectionIndex);
575 // Assign layout order indices to sections and fragments.
576 unsigned FragmentIndex = 0;
578 for (unsigned e = Layout.getSectionOrder().size(); i != e; ++i) {
579 MCSectionData *SD = Layout.getSectionOrder()[i];
581 for (MCSectionData::iterator it2 = SD->begin(),
582 ie2 = SD->end(); it2 != ie2; ++it2)
586 SD.setLayoutOrder(i);
587 for (MCSectionData::iterator it2 = SD.begin(),
588 ie2 = SD.end(); it2 != ie2; ++it2) {
589 it2->setLayoutOrder(FragmentIndex++);
591 Layout.getSectionOrder().push_back(&SD);
593 Layout.LayoutSection(&SD);
595 // Layout until everything fits.
596 while (LayoutOnce(Writer, Layout))
601 void MCAssembler::Finish(MCObjectWriter *Writer) {
602 DEBUG_WITH_TYPE("mc-dump", {
603 llvm::errs() << "assembler backend - pre-layout\n--\n";
606 // Create the layout object.
607 MCAsmLayout Layout(*this);
609 // Insert additional align fragments for concrete sections to explicitly pad
610 // the previous section to match their alignment requirements. This is for
611 // 'gas' compatibility, it shouldn't strictly be necessary.
612 if (PadSectionToAlignment) {
613 for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
614 MCSectionData *SD = Layout.getSectionOrder()[i];
616 // Ignore sections without alignment requirements.
617 unsigned Align = SD->getAlignment();
621 // Ignore virtual sections, they don't cause file size modifications.
622 if (getBackend().isVirtualSection(SD->getSection()))
625 // Otherwise, create a new align fragment at the end of the previous
627 MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
628 Layout.getSectionOrder()[i - 1]);
629 AF->setOnlyAlignAddress(true);
633 // Create dummy fragments and assign section ordinals.
634 unsigned SectionIndex = 0;
635 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
636 // Create dummy fragments to eliminate any empty sections, this simplifies
638 if (it->getFragmentList().empty())
639 new MCDataFragment(it);
641 it->setOrdinal(SectionIndex++);
644 // Assign layout order indices to sections and fragments.
645 unsigned FragmentIndex = 0;
646 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
647 MCSectionData *SD = Layout.getSectionOrder()[i];
648 SD->setLayoutOrder(i);
650 for (MCSectionData::iterator it2 = SD->begin(),
651 ie2 = SD->end(); it2 != ie2; ++it2)
652 it2->setLayoutOrder(FragmentIndex++);
655 llvm::OwningPtr<MCObjectWriter> OwnWriter(0);
657 //no custom Writer_ : create the default one life-managed by OwningPtr
658 OwnWriter.reset(getBackend().createObjectWriter(OS));
659 Writer = OwnWriter.get();
661 report_fatal_error("unable to create object writer!");
664 // Layout until everything fits.
665 while (LayoutOnce(*Writer, Layout))
668 DEBUG_WITH_TYPE("mc-dump", {
669 llvm::errs() << "assembler backend - post-relaxation\n--\n";
672 // Finalize the layout, including fragment lowering.
673 FinishLayout(Layout);
675 DEBUG_WITH_TYPE("mc-dump", {
676 llvm::errs() << "assembler backend - final-layout\n--\n";
679 uint64_t StartOffset = OS.tell();
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 MCFixup &Fixup = *it3;
697 // Evaluate the fixup.
700 if (!EvaluateFixup(*Writer, 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);
715 stats::ObjectBytes += OS.tell() - StartOffset;
718 bool MCAssembler::FixupNeedsRelaxation(const MCObjectWriter &Writer,
719 const MCFixup &Fixup,
720 const MCFragment *DF,
721 const MCAsmLayout &Layout) const {
725 // If we cannot resolve the fixup value, it requires relaxation.
728 if (!EvaluateFixup(Writer, 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 MCObjectWriter &Writer,
738 const MCInstFragment *IF,
739 const MCAsmLayout &Layout) const {
740 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
741 // are intentionally pushing out inst fragments, or because we relaxed a
742 // previous instruction to one that doesn't need relaxation.
743 if (!getBackend().MayNeedRelaxation(IF->getInst()))
746 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
747 ie = IF->fixup_end(); it != ie; ++it)
748 if (FixupNeedsRelaxation(Writer, *it, IF, Layout))
754 bool MCAssembler::LayoutOnce(const MCObjectWriter &Writer,
755 MCAsmLayout &Layout) {
756 ++stats::RelaxationSteps;
758 // Layout the sections in order.
761 // Scan for fragments that need relaxation.
762 bool WasRelaxed = false;
763 for (iterator it = begin(), ie = end(); it != ie; ++it) {
764 MCSectionData &SD = *it;
766 for (MCSectionData::iterator it2 = SD.begin(),
767 ie2 = SD.end(); it2 != ie2; ++it2) {
768 // Check if this is an instruction fragment that needs relaxation.
769 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
770 if (!IF || !FragmentNeedsRelaxation(Writer, IF, Layout))
773 ++stats::RelaxedInstructions;
775 // FIXME-PERF: We could immediately lower out instructions if we can tell
776 // they are fully resolved, to avoid retesting on later passes.
778 // Relax the fragment.
781 getBackend().RelaxInstruction(IF->getInst(), Relaxed);
783 // Encode the new instruction.
785 // FIXME-PERF: If it matters, we could let the target do this. It can
786 // probably do so more efficiently in many cases.
787 SmallVector<MCFixup, 4> Fixups;
788 SmallString<256> Code;
789 raw_svector_ostream VecOS(Code);
790 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
793 // Update the instruction fragment.
794 int SlideAmount = Code.size() - IF->getInstSize();
795 IF->setInst(Relaxed);
796 IF->getCode() = Code;
797 IF->getFixups().clear();
798 // FIXME: Eliminate copy.
799 for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
800 IF->getFixups().push_back(Fixups[i]);
802 // Update the layout, and remember that we relaxed.
803 Layout.UpdateForSlide(IF, SlideAmount);
811 void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
812 // Lower out any instruction fragments, to simplify the fixup application and
815 // FIXME-PERF: We don't have to do this, but the assumption is that it is
816 // cheap (we will mostly end up eliminating fragments and appending on to data
817 // fragments), so the extra complexity downstream isn't worth it. Evaluate
819 for (iterator it = begin(), ie = end(); it != ie; ++it) {
820 MCSectionData &SD = *it;
822 for (MCSectionData::iterator it2 = SD.begin(),
823 ie2 = SD.end(); it2 != ie2; ++it2) {
824 MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
828 // Create a new data fragment for the instruction.
830 // FIXME-PERF: Reuse previous data fragment if possible.
831 MCDataFragment *DF = new MCDataFragment();
832 SD.getFragmentList().insert(it2, DF);
834 // Update the data fragments layout data.
835 DF->setParent(IF->getParent());
836 DF->setAtom(IF->getAtom());
837 DF->setLayoutOrder(IF->getLayoutOrder());
838 Layout.FragmentReplaced(IF, DF);
840 // Copy in the data and the fixups.
841 DF->getContents().append(IF->getCode().begin(), IF->getCode().end());
842 for (unsigned i = 0, e = IF->getFixups().size(); i != e; ++i)
843 DF->getFixups().push_back(IF->getFixups()[i]);
845 // Delete the instruction fragment and update the iterator.
846 SD.getFragmentList().erase(IF);
856 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
857 OS << "<MCFixup" << " Offset:" << AF.getOffset()
858 << " Value:" << *AF.getValue()
859 << " Kind:" << AF.getKind() << ">";
865 void MCFragment::dump() {
866 raw_ostream &OS = llvm::errs();
870 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
871 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
872 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
873 case MCFragment::FT_Inst: OS << "MCInstFragment"; break;
874 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
877 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
878 << " Offset:" << Offset << " EffectiveSize:" << EffectiveSize << ">";
881 case MCFragment::FT_Align: {
882 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
883 if (AF->hasEmitNops())
884 OS << " (emit nops)";
885 if (AF->hasOnlyAlignAddress())
886 OS << " (only align section)";
888 OS << " Alignment:" << AF->getAlignment()
889 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
890 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
893 case MCFragment::FT_Data: {
894 const MCDataFragment *DF = cast<MCDataFragment>(this);
897 const SmallVectorImpl<char> &Contents = DF->getContents();
898 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
900 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
902 OS << "] (" << Contents.size() << " bytes)";
904 if (!DF->getFixups().empty()) {
907 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
908 ie = DF->fixup_end(); it != ie; ++it) {
909 if (it != DF->fixup_begin()) OS << ",\n ";
916 case MCFragment::FT_Fill: {
917 const MCFillFragment *FF = cast<MCFillFragment>(this);
918 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
919 << " Size:" << FF->getSize();
922 case MCFragment::FT_Inst: {
923 const MCInstFragment *IF = cast<MCInstFragment>(this);
926 IF->getInst().dump_pretty(OS);
929 case MCFragment::FT_Org: {
930 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
932 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
939 void MCSectionData::dump() {
940 raw_ostream &OS = llvm::errs();
942 OS << "<MCSectionData";
943 OS << " Alignment:" << getAlignment() << " Address:" << Address
944 << " Fragments:[\n ";
945 for (iterator it = begin(), ie = end(); it != ie; ++it) {
946 if (it != begin()) OS << ",\n ";
952 void MCSymbolData::dump() {
953 raw_ostream &OS = llvm::errs();
955 OS << "<MCSymbolData Symbol:" << getSymbol()
956 << " Fragment:" << getFragment() << " Offset:" << getOffset()
957 << " Flags:" << getFlags() << " Index:" << getIndex();
959 OS << " (common, size:" << getCommonSize()
960 << " align: " << getCommonAlignment() << ")";
963 if (isPrivateExtern())
964 OS << " (private extern)";
968 void MCAssembler::dump() {
969 raw_ostream &OS = llvm::errs();
971 OS << "<MCAssembler\n";
972 OS << " Sections:[\n ";
973 for (iterator it = begin(), ie = end(); it != ie; ++it) {
974 if (it != begin()) OS << ",\n ";
980 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
981 if (it != symbol_begin()) OS << ",\n ";