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/ADT/Statistic.h"
13 #include "llvm/ADT/StringExtras.h"
14 #include "llvm/ADT/Twine.h"
15 #include "llvm/MC/MCAsmBackend.h"
16 #include "llvm/MC/MCAsmLayout.h"
17 #include "llvm/MC/MCCodeEmitter.h"
18 #include "llvm/MC/MCContext.h"
19 #include "llvm/MC/MCDwarf.h"
20 #include "llvm/MC/MCExpr.h"
21 #include "llvm/MC/MCFixupKindInfo.h"
22 #include "llvm/MC/MCObjectWriter.h"
23 #include "llvm/MC/MCSection.h"
24 #include "llvm/MC/MCSymbol.h"
25 #include "llvm/MC/MCValue.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/LEB128.h"
29 #include "llvm/Support/TargetRegistry.h"
30 #include "llvm/Support/raw_ostream.h"
36 STATISTIC(EmittedFragments, "Number of emitted assembler fragments - total");
37 STATISTIC(EmittedInstFragments,
38 "Number of emitted assembler fragments - instruction");
39 STATISTIC(EmittedDataFragments,
40 "Number of emitted assembler fragments - data");
41 STATISTIC(EmittedAlignFragments,
42 "Number of emitted assembler fragments - align");
43 STATISTIC(EmittedFillFragments,
44 "Number of emitted assembler fragments - fill");
45 STATISTIC(EmittedOrgFragments,
46 "Number of emitted assembler fragments - org");
47 STATISTIC(evaluateFixup, "Number of evaluated fixups");
48 STATISTIC(FragmentLayouts, "Number of fragment layouts");
49 STATISTIC(ObjectBytes, "Number of emitted object file bytes");
50 STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps");
51 STATISTIC(RelaxedInstructions, "Number of relaxed instructions");
55 // FIXME FIXME FIXME: There are number of places in this file where we convert
56 // what is a 64-bit assembler value used for computation into a value in the
57 // object file, which may truncate it. We should detect that truncation where
58 // invalid and report errors back.
62 MCAsmLayout::MCAsmLayout(MCAssembler &Asm)
63 : Assembler(Asm), LastValidFragment()
65 // Compute the section layout order. Virtual sections must go last.
66 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
67 if (!it->getSection().isVirtualSection())
68 SectionOrder.push_back(&*it);
69 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
70 if (it->getSection().isVirtualSection())
71 SectionOrder.push_back(&*it);
74 bool MCAsmLayout::isFragmentValid(const MCFragment *F) const {
75 const MCSectionData &SD = *F->getParent();
76 const MCFragment *LastValid = LastValidFragment.lookup(&SD);
79 assert(LastValid->getParent() == F->getParent());
80 return F->getLayoutOrder() <= LastValid->getLayoutOrder();
83 void MCAsmLayout::invalidateFragmentsAfter(MCFragment *F) {
84 // If this fragment wasn't already valid, we don't need to do anything.
85 if (!isFragmentValid(F))
88 // Otherwise, reset the last valid fragment to this fragment.
89 const MCSectionData &SD = *F->getParent();
90 LastValidFragment[&SD] = F;
93 void MCAsmLayout::ensureValid(const MCFragment *F) const {
94 MCSectionData &SD = *F->getParent();
96 MCFragment *Cur = LastValidFragment[&SD];
100 Cur = Cur->getNextNode();
102 // Advance the layout position until the fragment is valid.
103 while (!isFragmentValid(F)) {
104 assert(Cur && "Layout bookkeeping error");
105 const_cast<MCAsmLayout*>(this)->layoutFragment(Cur);
106 Cur = Cur->getNextNode();
110 uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
112 assert(F->Offset != ~UINT64_C(0) && "Address not set!");
116 uint64_t MCAsmLayout::getSymbolOffset(const MCSymbolData *SD) const {
117 const MCSymbol &S = SD->getSymbol();
119 // If this is a variable, then recursively evaluate now.
120 if (S.isVariable()) {
122 if (!S.getVariableValue()->EvaluateAsRelocatable(Target, *this))
123 report_fatal_error("unable to evaluate offset for variable '" +
126 // Verify that any used symbols are defined.
127 if (Target.getSymA() && Target.getSymA()->getSymbol().isUndefined())
128 report_fatal_error("unable to evaluate offset to undefined symbol '" +
129 Target.getSymA()->getSymbol().getName() + "'");
130 if (Target.getSymB() && Target.getSymB()->getSymbol().isUndefined())
131 report_fatal_error("unable to evaluate offset to undefined symbol '" +
132 Target.getSymB()->getSymbol().getName() + "'");
134 uint64_t Offset = Target.getConstant();
135 if (Target.getSymA())
136 Offset += getSymbolOffset(&Assembler.getSymbolData(
137 Target.getSymA()->getSymbol()));
138 if (Target.getSymB())
139 Offset -= getSymbolOffset(&Assembler.getSymbolData(
140 Target.getSymB()->getSymbol()));
144 assert(SD->getFragment() && "Invalid getOffset() on undefined symbol!");
145 return getFragmentOffset(SD->getFragment()) + SD->getOffset();
148 uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const {
149 // The size is the last fragment's end offset.
150 const MCFragment &F = SD->getFragmentList().back();
151 return getFragmentOffset(&F) + getAssembler().computeFragmentSize(*this, F);
154 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
155 // Virtual sections have no file size.
156 if (SD->getSection().isVirtualSection())
159 // Otherwise, the file size is the same as the address space size.
160 return getSectionAddressSize(SD);
163 uint64_t MCAsmLayout::computeBundlePadding(const MCFragment *F,
164 uint64_t FOffset, uint64_t FSize) {
165 uint64_t BundleSize = Assembler.getBundleAlignSize();
166 assert(BundleSize > 0 &&
167 "computeBundlePadding should only be called if bundling is enabled");
168 uint64_t BundleMask = BundleSize - 1;
169 uint64_t OffsetInBundle = FOffset & BundleMask;
171 // If the fragment would cross a bundle boundary, add enough padding until
172 // the end of the current bundle.
173 if (OffsetInBundle + FSize > BundleSize)
174 return BundleSize - OffsetInBundle;
181 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
184 MCFragment::~MCFragment() {
187 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
188 : Kind(_Kind), Parent(_Parent), Atom(0), Offset(~UINT64_C(0))
191 Parent->getFragmentList().push_back(this);
196 MCEncodedFragment::~MCEncodedFragment() {
201 MCSectionData::MCSectionData() : Section(0) {}
203 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
204 : Section(&_Section),
205 Ordinal(~UINT32_C(0)),
207 BundleLocked(false), BundleGroupBeforeFirstInst(false),
208 HasInstructions(false)
211 A->getSectionList().push_back(this);
216 MCSymbolData::MCSymbolData() : Symbol(0) {}
218 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
219 uint64_t _Offset, MCAssembler *A)
220 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
221 IsExternal(false), IsPrivateExtern(false),
222 CommonSize(0), SymbolSize(0), CommonAlign(0),
226 A->getSymbolList().push_back(this);
231 MCAssembler::MCAssembler(MCContext &Context_, MCAsmBackend &Backend_,
232 MCCodeEmitter &Emitter_, MCObjectWriter &Writer_,
234 : Context(Context_), Backend(Backend_), Emitter(Emitter_), Writer(Writer_),
235 OS(OS_), RelaxAll(false), NoExecStack(false), SubsectionsViaSymbols(false) {
238 MCAssembler::~MCAssembler() {
241 void MCAssembler::reset() {
246 IndirectSymbols.clear();
251 SubsectionsViaSymbols = false;
253 // reset objects owned by us
254 getBackend().reset();
255 getEmitter().reset();
259 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
260 // Non-temporary labels should always be visible to the linker.
261 if (!Symbol.isTemporary())
264 // Absolute temporary labels are never visible.
265 if (!Symbol.isInSection())
268 // Otherwise, check if the section requires symbols even for temporary labels.
269 return getBackend().doesSectionRequireSymbols(Symbol.getSection());
272 const MCSymbolData *MCAssembler::getAtom(const MCSymbolData *SD) const {
273 // Linker visible symbols define atoms.
274 if (isSymbolLinkerVisible(SD->getSymbol()))
277 // Absolute and undefined symbols have no defining atom.
278 if (!SD->getFragment())
281 // Non-linker visible symbols in sections which can't be atomized have no
283 if (!getBackend().isSectionAtomizable(
284 SD->getFragment()->getParent()->getSection()))
287 // Otherwise, return the atom for the containing fragment.
288 return SD->getFragment()->getAtom();
291 bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout,
292 const MCFixup &Fixup, const MCFragment *DF,
293 MCValue &Target, uint64_t &Value) const {
294 ++stats::evaluateFixup;
296 if (!Fixup.getValue()->EvaluateAsRelocatable(Target, Layout))
297 getContext().FatalError(Fixup.getLoc(), "expected relocatable expression");
299 bool IsPCRel = Backend.getFixupKindInfo(
300 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
304 if (Target.getSymB()) {
306 } else if (!Target.getSymA()) {
309 const MCSymbolRefExpr *A = Target.getSymA();
310 const MCSymbol &SA = A->getSymbol();
311 if (A->getKind() != MCSymbolRefExpr::VK_None ||
312 SA.AliasedSymbol().isUndefined()) {
315 const MCSymbolData &DataA = getSymbolData(SA);
317 getWriter().IsSymbolRefDifferenceFullyResolvedImpl(*this, DataA,
322 IsResolved = Target.isAbsolute();
325 Value = Target.getConstant();
327 if (const MCSymbolRefExpr *A = Target.getSymA()) {
328 const MCSymbol &Sym = A->getSymbol().AliasedSymbol();
330 Value += Layout.getSymbolOffset(&getSymbolData(Sym));
332 if (const MCSymbolRefExpr *B = Target.getSymB()) {
333 const MCSymbol &Sym = B->getSymbol().AliasedSymbol();
335 Value -= Layout.getSymbolOffset(&getSymbolData(Sym));
339 bool ShouldAlignPC = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
340 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits;
341 assert((ShouldAlignPC ? IsPCRel : true) &&
342 "FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!");
345 uint32_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset();
347 // A number of ARM fixups in Thumb mode require that the effective PC
348 // address be determined as the 32-bit aligned version of the actual offset.
349 if (ShouldAlignPC) Offset &= ~0x3;
353 // Let the backend adjust the fixup value if necessary, including whether
354 // we need a relocation.
355 Backend.processFixupValue(*this, Layout, Fixup, DF, Target, Value,
361 uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
362 const MCFragment &F) const {
363 switch (F.getKind()) {
364 case MCFragment::FT_Data:
365 return cast<MCDataFragment>(F).getContents().size();
366 case MCFragment::FT_Fill:
367 return cast<MCFillFragment>(F).getSize();
368 case MCFragment::FT_Inst:
369 return cast<MCInstFragment>(F).getInstSize();
371 case MCFragment::FT_LEB:
372 return cast<MCLEBFragment>(F).getContents().size();
374 case MCFragment::FT_Align: {
375 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
376 unsigned Offset = Layout.getFragmentOffset(&AF);
377 unsigned Size = OffsetToAlignment(Offset, AF.getAlignment());
378 // If we are padding with nops, force the padding to be larger than the
380 if (Size > 0 && AF.hasEmitNops()) {
381 while (Size % getBackend().getMinimumNopSize())
382 Size += AF.getAlignment();
384 if (Size > AF.getMaxBytesToEmit())
389 case MCFragment::FT_Org: {
390 MCOrgFragment &OF = cast<MCOrgFragment>(F);
391 int64_t TargetLocation;
392 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, Layout))
393 report_fatal_error("expected assembly-time absolute expression");
395 // FIXME: We need a way to communicate this error.
396 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
397 int64_t Size = TargetLocation - FragmentOffset;
398 if (Size < 0 || Size >= 0x40000000)
399 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
400 "' (at offset '" + Twine(FragmentOffset) + "')");
404 case MCFragment::FT_Dwarf:
405 return cast<MCDwarfLineAddrFragment>(F).getContents().size();
406 case MCFragment::FT_DwarfFrame:
407 return cast<MCDwarfCallFrameFragment>(F).getContents().size();
410 llvm_unreachable("invalid fragment kind");
413 void MCAsmLayout::layoutFragment(MCFragment *F) {
414 MCFragment *Prev = F->getPrevNode();
416 // We should never try to recompute something which is valid.
417 assert(!isFragmentValid(F) && "Attempt to recompute a valid fragment!");
418 // We should never try to compute the fragment layout if its predecessor
420 assert((!Prev || isFragmentValid(Prev)) &&
421 "Attempt to compute fragment before its predecessor!");
423 ++stats::FragmentLayouts;
425 // Compute fragment offset and size.
427 F->Offset = Prev->Offset + getAssembler().computeFragmentSize(*this, *Prev);
430 LastValidFragment[F->getParent()] = F;
432 // If bundling is enabled and this fragment has instructions in it, it has to
433 // obey the bundling restrictions. With padding, we'll have:
438 // -------------------------------------
439 // Prev |##########| F |
440 // -------------------------------------
445 // The fragment's offset will point to after the padding, and its computed
446 // size won't include the padding.
448 if (Assembler.isBundlingEnabled() && F->hasInstructions()) {
449 assert(isa<MCEncodedFragment>(F) &&
450 "Only MCEncodedFragment implementations have instructions");
451 uint64_t FSize = Assembler.computeFragmentSize(*this, *F);
453 if (FSize > Assembler.getBundleAlignSize())
454 report_fatal_error("Fragment can't be larger than a bundle size");
456 uint64_t RequiredBundlePadding = computeBundlePadding(F, F->Offset, FSize);
457 if (RequiredBundlePadding > UINT8_MAX)
458 report_fatal_error("Padding cannot exceed 255 bytes");
459 F->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
460 F->Offset += RequiredBundlePadding;
464 /// \brief Write the contents of a fragment to the given object writer. Expects
465 /// a MCEncodedFragment.
466 static void writeFragmentContents(const MCFragment &F, MCObjectWriter *OW) {
467 MCEncodedFragment &EF = cast<MCEncodedFragment>(F);
468 OW->WriteBytes(EF.getContents());
471 /// \brief Write the fragment \p F to the output file.
472 static void writeFragment(const MCAssembler &Asm, const MCAsmLayout &Layout,
473 const MCFragment &F) {
474 MCObjectWriter *OW = &Asm.getWriter();
476 // Should NOP padding be written out before this fragment?
477 unsigned BundlePadding = F.getBundlePadding();
478 if (BundlePadding > 0) {
479 assert(Asm.isBundlingEnabled() &&
480 "Writing bundle padding with disabled bundling");
481 assert(F.hasInstructions() &&
482 "Writing bundle padding for a fragment without instructions");
484 if (!Asm.getBackend().writeNopData(BundlePadding, OW))
485 report_fatal_error("unable to write NOP sequence of " +
486 Twine(BundlePadding) + " bytes");
489 // This variable (and its dummy usage) is to participate in the assert at
490 // the end of the function.
491 uint64_t Start = OW->getStream().tell();
494 ++stats::EmittedFragments;
496 // FIXME: Embed in fragments instead?
497 uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F);
498 switch (F.getKind()) {
499 case MCFragment::FT_Align: {
500 ++stats::EmittedAlignFragments;
501 MCAlignFragment &AF = cast<MCAlignFragment>(F);
502 uint64_t Count = FragmentSize / AF.getValueSize();
504 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
506 // FIXME: This error shouldn't actually occur (the front end should emit
507 // multiple .align directives to enforce the semantics it wants), but is
508 // severe enough that we want to report it. How to handle this?
509 if (Count * AF.getValueSize() != FragmentSize)
510 report_fatal_error("undefined .align directive, value size '" +
511 Twine(AF.getValueSize()) +
512 "' is not a divisor of padding size '" +
513 Twine(FragmentSize) + "'");
515 // See if we are aligning with nops, and if so do that first to try to fill
516 // the Count bytes. Then if that did not fill any bytes or there are any
517 // bytes left to fill use the Value and ValueSize to fill the rest.
518 // If we are aligning with nops, ask that target to emit the right data.
519 if (AF.hasEmitNops()) {
520 if (!Asm.getBackend().writeNopData(Count, OW))
521 report_fatal_error("unable to write nop sequence of " +
522 Twine(Count) + " bytes");
526 // Otherwise, write out in multiples of the value size.
527 for (uint64_t i = 0; i != Count; ++i) {
528 switch (AF.getValueSize()) {
529 default: llvm_unreachable("Invalid size!");
530 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
531 case 2: OW->Write16(uint16_t(AF.getValue())); break;
532 case 4: OW->Write32(uint32_t(AF.getValue())); break;
533 case 8: OW->Write64(uint64_t(AF.getValue())); break;
539 case MCFragment::FT_Data:
540 ++stats::EmittedDataFragments;
541 writeFragmentContents(F, OW);
544 case MCFragment::FT_Inst:
545 ++stats::EmittedInstFragments;
546 writeFragmentContents(F, OW);
549 case MCFragment::FT_Fill: {
550 ++stats::EmittedFillFragments;
551 MCFillFragment &FF = cast<MCFillFragment>(F);
553 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
555 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
556 switch (FF.getValueSize()) {
557 default: llvm_unreachable("Invalid size!");
558 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
559 case 2: OW->Write16(uint16_t(FF.getValue())); break;
560 case 4: OW->Write32(uint32_t(FF.getValue())); break;
561 case 8: OW->Write64(uint64_t(FF.getValue())); break;
567 case MCFragment::FT_LEB: {
568 MCLEBFragment &LF = cast<MCLEBFragment>(F);
569 OW->WriteBytes(LF.getContents().str());
573 case MCFragment::FT_Org: {
574 ++stats::EmittedOrgFragments;
575 MCOrgFragment &OF = cast<MCOrgFragment>(F);
577 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
578 OW->Write8(uint8_t(OF.getValue()));
583 case MCFragment::FT_Dwarf: {
584 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
585 OW->WriteBytes(OF.getContents().str());
588 case MCFragment::FT_DwarfFrame: {
589 const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F);
590 OW->WriteBytes(CF.getContents().str());
595 assert(OW->getStream().tell() - Start == FragmentSize &&
596 "The stream should advance by fragment size");
599 void MCAssembler::writeSectionData(const MCSectionData *SD,
600 const MCAsmLayout &Layout) const {
601 // Ignore virtual sections.
602 if (SD->getSection().isVirtualSection()) {
603 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
605 // Check that contents are only things legal inside a virtual section.
606 for (MCSectionData::const_iterator it = SD->begin(),
607 ie = SD->end(); it != ie; ++it) {
608 switch (it->getKind()) {
609 default: llvm_unreachable("Invalid fragment in virtual section!");
610 case MCFragment::FT_Data: {
611 // Check that we aren't trying to write a non-zero contents (or fixups)
612 // into a virtual section. This is to support clients which use standard
613 // directives to fill the contents of virtual sections.
614 MCDataFragment &DF = cast<MCDataFragment>(*it);
615 assert(DF.fixup_begin() == DF.fixup_end() &&
616 "Cannot have fixups in virtual section!");
617 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
618 assert(DF.getContents()[i] == 0 &&
619 "Invalid data value for virtual section!");
622 case MCFragment::FT_Align:
623 // Check that we aren't trying to write a non-zero value into a virtual
625 assert((!cast<MCAlignFragment>(it)->getValueSize() ||
626 !cast<MCAlignFragment>(it)->getValue()) &&
627 "Invalid align in virtual section!");
629 case MCFragment::FT_Fill:
630 assert(!cast<MCFillFragment>(it)->getValueSize() &&
631 "Invalid fill in virtual section!");
639 uint64_t Start = getWriter().getStream().tell();
642 for (MCSectionData::const_iterator it = SD->begin(), ie = SD->end();
644 writeFragment(*this, Layout, *it);
646 assert(getWriter().getStream().tell() - Start ==
647 Layout.getSectionAddressSize(SD));
651 uint64_t MCAssembler::handleFixup(const MCAsmLayout &Layout,
653 const MCFixup &Fixup) {
654 // Evaluate the fixup.
657 if (!evaluateFixup(Layout, Fixup, &F, Target, FixedValue)) {
658 // The fixup was unresolved, we need a relocation. Inform the object
659 // writer of the relocation, and give it an opportunity to adjust the
660 // fixup value if need be.
661 getWriter().RecordRelocation(*this, Layout, &F, Fixup, Target, FixedValue);
666 void MCAssembler::Finish() {
667 DEBUG_WITH_TYPE("mc-dump", {
668 llvm::errs() << "assembler backend - pre-layout\n--\n";
671 // Create the layout object.
672 MCAsmLayout Layout(*this);
674 // Create dummy fragments and assign section ordinals.
675 unsigned SectionIndex = 0;
676 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
677 // Create dummy fragments to eliminate any empty sections, this simplifies
679 if (it->getFragmentList().empty())
680 new MCDataFragment(it);
682 it->setOrdinal(SectionIndex++);
685 // Assign layout order indices to sections and fragments.
686 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
687 MCSectionData *SD = Layout.getSectionOrder()[i];
688 SD->setLayoutOrder(i);
690 unsigned FragmentIndex = 0;
691 for (MCSectionData::iterator iFrag = SD->begin(), iFragEnd = SD->end();
692 iFrag != iFragEnd; ++iFrag)
693 iFrag->setLayoutOrder(FragmentIndex++);
696 // Layout until everything fits.
697 while (layoutOnce(Layout))
700 DEBUG_WITH_TYPE("mc-dump", {
701 llvm::errs() << "assembler backend - post-relaxation\n--\n";
704 // Finalize the layout, including fragment lowering.
705 finishLayout(Layout);
707 DEBUG_WITH_TYPE("mc-dump", {
708 llvm::errs() << "assembler backend - final-layout\n--\n";
711 uint64_t StartOffset = OS.tell();
713 // Allow the object writer a chance to perform post-layout binding (for
714 // example, to set the index fields in the symbol data).
715 getWriter().ExecutePostLayoutBinding(*this, Layout);
717 // Evaluate and apply the fixups, generating relocation entries as necessary.
718 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
719 for (MCSectionData::iterator it2 = it->begin(),
720 ie2 = it->end(); it2 != ie2; ++it2) {
721 MCEncodedFragment *F = dyn_cast<MCEncodedFragment>(it2);
723 for (MCEncodedFragment::fixup_iterator it3 = F->fixup_begin(),
724 ie3 = F->fixup_end(); it3 != ie3; ++it3) {
725 MCFixup &Fixup = *it3;
726 uint64_t FixedValue = handleFixup(Layout, *F, Fixup);
727 getBackend().applyFixup(Fixup, F->getContents().data(),
728 F->getContents().size(), FixedValue);
734 // Write the object file.
735 getWriter().WriteObject(*this, Layout);
737 stats::ObjectBytes += OS.tell() - StartOffset;
740 bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup,
741 const MCInstFragment *DF,
742 const MCAsmLayout &Layout) const {
743 // If we cannot resolve the fixup value, it requires relaxation.
746 if (!evaluateFixup(Layout, Fixup, DF, Target, Value))
749 return getBackend().fixupNeedsRelaxation(Fixup, Value, DF, Layout);
752 bool MCAssembler::fragmentNeedsRelaxation(const MCInstFragment *IF,
753 const MCAsmLayout &Layout) const {
754 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
755 // are intentionally pushing out inst fragments, or because we relaxed a
756 // previous instruction to one that doesn't need relaxation.
757 if (!getBackend().mayNeedRelaxation(IF->getInst()))
760 for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
761 ie = IF->fixup_end(); it != ie; ++it)
762 if (fixupNeedsRelaxation(*it, IF, Layout))
768 bool MCAssembler::relaxInstruction(MCAsmLayout &Layout,
769 MCInstFragment &IF) {
770 if (!fragmentNeedsRelaxation(&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.
795 IF.getContents() = Code;
796 IF.getFixups() = Fixups;
801 bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) {
803 uint64_t OldSize = LF.getContents().size();
804 bool IsAbs = LF.getValue().EvaluateAsAbsolute(Value, Layout);
807 SmallString<8> &Data = LF.getContents();
809 raw_svector_ostream OSE(Data);
811 encodeSLEB128(Value, OSE);
813 encodeULEB128(Value, OSE);
815 return OldSize != LF.getContents().size();
818 bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout,
819 MCDwarfLineAddrFragment &DF) {
820 int64_t AddrDelta = 0;
821 uint64_t OldSize = DF.getContents().size();
822 bool IsAbs = DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, Layout);
826 LineDelta = DF.getLineDelta();
827 SmallString<8> &Data = DF.getContents();
829 raw_svector_ostream OSE(Data);
830 MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OSE);
832 return OldSize != Data.size();
835 bool MCAssembler::relaxDwarfCallFrameFragment(MCAsmLayout &Layout,
836 MCDwarfCallFrameFragment &DF) {
837 int64_t AddrDelta = 0;
838 uint64_t OldSize = DF.getContents().size();
839 bool IsAbs = DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, Layout);
842 SmallString<8> &Data = DF.getContents();
844 raw_svector_ostream OSE(Data);
845 MCDwarfFrameEmitter::EncodeAdvanceLoc(AddrDelta, OSE);
847 return OldSize != Data.size();
850 bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSectionData &SD) {
851 // Holds the first fragment which needed relaxing during this layout. It will
852 // remain NULL if none were relaxed.
853 // When a fragment is relaxed, all the fragments following it should get
854 // invalidated because their offset is going to change.
855 MCFragment *FirstRelaxedFragment = NULL;
857 // Attempt to relax all the fragments in the section.
858 for (MCSectionData::iterator I = SD.begin(), IE = SD.end(); I != IE; ++I) {
859 // Check if this is a fragment that needs relaxation.
860 bool RelaxedFrag = false;
861 switch(I->getKind()) {
864 case MCFragment::FT_Inst:
865 assert(!getRelaxAll() &&
866 "Did not expect a MCInstFragment in RelaxAll mode");
867 RelaxedFrag = relaxInstruction(Layout, *cast<MCInstFragment>(I));
869 case MCFragment::FT_Dwarf:
870 RelaxedFrag = relaxDwarfLineAddr(Layout,
871 *cast<MCDwarfLineAddrFragment>(I));
873 case MCFragment::FT_DwarfFrame:
875 relaxDwarfCallFrameFragment(Layout,
876 *cast<MCDwarfCallFrameFragment>(I));
878 case MCFragment::FT_LEB:
879 RelaxedFrag = relaxLEB(Layout, *cast<MCLEBFragment>(I));
882 if (RelaxedFrag && !FirstRelaxedFragment)
883 FirstRelaxedFragment = I;
885 if (FirstRelaxedFragment) {
886 Layout.invalidateFragmentsAfter(FirstRelaxedFragment);
892 bool MCAssembler::layoutOnce(MCAsmLayout &Layout) {
893 ++stats::RelaxationSteps;
895 bool WasRelaxed = false;
896 for (iterator it = begin(), ie = end(); it != ie; ++it) {
897 MCSectionData &SD = *it;
898 while (layoutSectionOnce(Layout, SD))
905 void MCAssembler::finishLayout(MCAsmLayout &Layout) {
906 // The layout is done. Mark every fragment as valid.
907 for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) {
908 Layout.getFragmentOffset(&*Layout.getSectionOrder()[i]->rbegin());
916 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
917 OS << "<MCFixup" << " Offset:" << AF.getOffset()
918 << " Value:" << *AF.getValue()
919 << " Kind:" << AF.getKind() << ">";
925 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
926 void MCFragment::dump() {
927 raw_ostream &OS = llvm::errs();
931 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
932 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
933 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
934 case MCFragment::FT_Inst: OS << "MCInstFragment"; break;
935 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
936 case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
937 case MCFragment::FT_DwarfFrame: OS << "MCDwarfCallFrameFragment"; break;
938 case MCFragment::FT_LEB: OS << "MCLEBFragment"; break;
941 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
942 << " Offset:" << Offset
943 << " HasInstructions:" << hasInstructions()
944 << " BundlePadding:" << getBundlePadding() << ">";
947 case MCFragment::FT_Align: {
948 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
949 if (AF->hasEmitNops())
950 OS << " (emit nops)";
952 OS << " Alignment:" << AF->getAlignment()
953 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
954 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
957 case MCFragment::FT_Data: {
958 const MCDataFragment *DF = cast<MCDataFragment>(this);
961 const SmallVectorImpl<char> &Contents = DF->getContents();
962 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
964 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
966 OS << "] (" << Contents.size() << " bytes)";
968 if (DF->fixup_begin() != DF->fixup_end()) {
971 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
972 ie = DF->fixup_end(); it != ie; ++it) {
973 if (it != DF->fixup_begin()) OS << ",\n ";
980 case MCFragment::FT_Fill: {
981 const MCFillFragment *FF = cast<MCFillFragment>(this);
982 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
983 << " Size:" << FF->getSize();
986 case MCFragment::FT_Inst: {
987 const MCInstFragment *IF = cast<MCInstFragment>(this);
990 IF->getInst().dump_pretty(OS);
993 case MCFragment::FT_Org: {
994 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
996 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
999 case MCFragment::FT_Dwarf: {
1000 const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
1002 OS << " AddrDelta:" << OF->getAddrDelta()
1003 << " LineDelta:" << OF->getLineDelta();
1006 case MCFragment::FT_DwarfFrame: {
1007 const MCDwarfCallFrameFragment *CF = cast<MCDwarfCallFrameFragment>(this);
1009 OS << " AddrDelta:" << CF->getAddrDelta();
1012 case MCFragment::FT_LEB: {
1013 const MCLEBFragment *LF = cast<MCLEBFragment>(this);
1015 OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
1022 void MCSectionData::dump() {
1023 raw_ostream &OS = llvm::errs();
1025 OS << "<MCSectionData";
1026 OS << " Alignment:" << getAlignment()
1027 << " Fragments:[\n ";
1028 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1029 if (it != begin()) OS << ",\n ";
1035 void MCSymbolData::dump() {
1036 raw_ostream &OS = llvm::errs();
1038 OS << "<MCSymbolData Symbol:" << getSymbol()
1039 << " Fragment:" << getFragment() << " Offset:" << getOffset()
1040 << " Flags:" << getFlags() << " Index:" << getIndex();
1042 OS << " (common, size:" << getCommonSize()
1043 << " align: " << getCommonAlignment() << ")";
1045 OS << " (external)";
1046 if (isPrivateExtern())
1047 OS << " (private extern)";
1051 void MCAssembler::dump() {
1052 raw_ostream &OS = llvm::errs();
1054 OS << "<MCAssembler\n";
1055 OS << " Sections:[\n ";
1056 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1057 if (it != begin()) OS << ",\n ";
1063 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1064 if (it != symbol_begin()) OS << ",\n ";
1071 // anchors for MC*Fragment vtables
1072 void MCEncodedFragment::anchor() { }
1073 void MCDataFragment::anchor() { }
1074 void MCInstFragment::anchor() { }
1075 void MCAlignFragment::anchor() { }
1076 void MCFillFragment::anchor() { }
1077 void MCOrgFragment::anchor() { }
1078 void MCLEBFragment::anchor() { }
1079 void MCDwarfLineAddrFragment::anchor() { }
1080 void MCDwarfCallFrameFragment::anchor() { }