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 #include "llvm/MC/MCAssembler.h"
11 #include "llvm/ADT/Statistic.h"
12 #include "llvm/ADT/StringExtras.h"
13 #include "llvm/ADT/Twine.h"
14 #include "llvm/MC/MCAsmBackend.h"
15 #include "llvm/MC/MCAsmInfo.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/MCSectionELF.h"
25 #include "llvm/MC/MCSymbol.h"
26 #include "llvm/MC/MCValue.h"
27 #include "llvm/Support/Debug.h"
28 #include "llvm/Support/ErrorHandling.h"
29 #include "llvm/Support/LEB128.h"
30 #include "llvm/Support/TargetRegistry.h"
31 #include "llvm/Support/raw_ostream.h"
35 #define DEBUG_TYPE "assembler"
39 STATISTIC(EmittedFragments, "Number of emitted assembler fragments - total");
40 STATISTIC(EmittedRelaxableFragments,
41 "Number of emitted assembler fragments - relaxable");
42 STATISTIC(EmittedDataFragments,
43 "Number of emitted assembler fragments - data");
44 STATISTIC(EmittedCompactEncodedInstFragments,
45 "Number of emitted assembler fragments - compact encoded inst");
46 STATISTIC(EmittedAlignFragments,
47 "Number of emitted assembler fragments - align");
48 STATISTIC(EmittedFillFragments,
49 "Number of emitted assembler fragments - fill");
50 STATISTIC(EmittedOrgFragments,
51 "Number of emitted assembler fragments - org");
52 STATISTIC(evaluateFixup, "Number of evaluated fixups");
53 STATISTIC(FragmentLayouts, "Number of fragment layouts");
54 STATISTIC(ObjectBytes, "Number of emitted object file bytes");
55 STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps");
56 STATISTIC(RelaxedInstructions, "Number of relaxed instructions");
60 // FIXME FIXME FIXME: There are number of places in this file where we convert
61 // what is a 64-bit assembler value used for computation into a value in the
62 // object file, which may truncate it. We should detect that truncation where
63 // invalid and report errors back.
67 MCAsmLayout::MCAsmLayout(MCAssembler &Asm)
68 : Assembler(Asm), LastValidFragment()
70 // Compute the section layout order. Virtual sections must go last.
71 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
72 if (!it->getSection().isVirtualSection())
73 SectionOrder.push_back(&*it);
74 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
75 if (it->getSection().isVirtualSection())
76 SectionOrder.push_back(&*it);
79 bool MCAsmLayout::isFragmentValid(const MCFragment *F) const {
80 const MCSectionData &SD = *F->getParent();
81 const MCFragment *LastValid = LastValidFragment.lookup(&SD);
84 assert(LastValid->getParent() == F->getParent());
85 return F->getLayoutOrder() <= LastValid->getLayoutOrder();
88 void MCAsmLayout::invalidateFragmentsFrom(MCFragment *F) {
89 // If this fragment wasn't already valid, we don't need to do anything.
90 if (!isFragmentValid(F))
93 // Otherwise, reset the last valid fragment to the previous fragment
94 // (if this is the first fragment, it will be NULL).
95 const MCSectionData &SD = *F->getParent();
96 LastValidFragment[&SD] = F->getPrevNode();
99 void MCAsmLayout::ensureValid(const MCFragment *F) const {
100 MCSectionData &SD = *F->getParent();
102 MCFragment *Cur = LastValidFragment[&SD];
106 Cur = Cur->getNextNode();
108 // Advance the layout position until the fragment is valid.
109 while (!isFragmentValid(F)) {
110 assert(Cur && "Layout bookkeeping error");
111 const_cast<MCAsmLayout*>(this)->layoutFragment(Cur);
112 Cur = Cur->getNextNode();
116 uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
118 assert(F->Offset != ~UINT64_C(0) && "Address not set!");
122 // Simple getSymbolOffset helper for the non-varibale case.
123 static bool getLabelOffset(const MCAsmLayout &Layout, const MCSymbol &S,
124 bool ReportError, uint64_t &Val) {
125 const MCSymbolData &SD = S.getData();
126 if (!SD.getFragment()) {
128 report_fatal_error("unable to evaluate offset to undefined symbol '" +
132 Val = Layout.getFragmentOffset(SD.getFragment()) + SD.getOffset();
136 static bool getSymbolOffsetImpl(const MCAsmLayout &Layout, const MCSymbol &S,
137 bool ReportError, uint64_t &Val) {
139 return getLabelOffset(Layout, S, ReportError, Val);
141 // If SD is a variable, evaluate it.
143 if (!S.getVariableValue()->EvaluateAsRelocatable(Target, &Layout, nullptr))
144 report_fatal_error("unable to evaluate offset for variable '" +
147 uint64_t Offset = Target.getConstant();
149 const MCSymbolRefExpr *A = Target.getSymA();
152 if (!getLabelOffset(Layout, A->getSymbol(), ReportError, ValA))
157 const MCSymbolRefExpr *B = Target.getSymB();
160 if (!getLabelOffset(Layout, B->getSymbol(), ReportError, ValB))
169 bool MCAsmLayout::getSymbolOffset(const MCSymbol &S, uint64_t &Val) const {
170 return getSymbolOffsetImpl(*this, S, false, Val);
173 uint64_t MCAsmLayout::getSymbolOffset(const MCSymbol &S) const {
175 getSymbolOffsetImpl(*this, S, true, Val);
179 const MCSymbol *MCAsmLayout::getBaseSymbol(const MCSymbol &Symbol) const {
180 if (!Symbol.isVariable())
183 const MCExpr *Expr = Symbol.getVariableValue();
185 if (!Expr->evaluateAsValue(Value, *this))
186 llvm_unreachable("Invalid Expression");
188 const MCSymbolRefExpr *RefB = Value.getSymB();
190 Assembler.getContext().reportFatalError(
191 SMLoc(), Twine("symbol '") + RefB->getSymbol().getName() +
192 "' could not be evaluated in a subtraction expression");
194 const MCSymbolRefExpr *A = Value.getSymA();
198 const MCSymbol &ASym = A->getSymbol();
199 const MCAssembler &Asm = getAssembler();
200 const MCSymbolData &ASD = Asm.getSymbolData(ASym);
201 if (ASD.isCommon()) {
202 // FIXME: we should probably add a SMLoc to MCExpr.
203 Asm.getContext().reportFatalError(SMLoc(),
204 "Common symbol " + ASym.getName() +
205 " cannot be used in assignment expr");
211 uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const {
212 // The size is the last fragment's end offset.
213 const MCFragment &F = SD->getFragmentList().back();
214 return getFragmentOffset(&F) + getAssembler().computeFragmentSize(*this, F);
217 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
218 // Virtual sections have no file size.
219 if (SD->getSection().isVirtualSection())
222 // Otherwise, the file size is the same as the address space size.
223 return getSectionAddressSize(SD);
226 uint64_t llvm::computeBundlePadding(const MCAssembler &Assembler,
228 uint64_t FOffset, uint64_t FSize) {
229 uint64_t BundleSize = Assembler.getBundleAlignSize();
230 assert(BundleSize > 0 &&
231 "computeBundlePadding should only be called if bundling is enabled");
232 uint64_t BundleMask = BundleSize - 1;
233 uint64_t OffsetInBundle = FOffset & BundleMask;
234 uint64_t EndOfFragment = OffsetInBundle + FSize;
236 // There are two kinds of bundling restrictions:
238 // 1) For alignToBundleEnd(), add padding to ensure that the fragment will
239 // *end* on a bundle boundary.
240 // 2) Otherwise, check if the fragment would cross a bundle boundary. If it
241 // would, add padding until the end of the bundle so that the fragment
242 // will start in a new one.
243 if (F->alignToBundleEnd()) {
244 // Three possibilities here:
246 // A) The fragment just happens to end at a bundle boundary, so we're good.
247 // B) The fragment ends before the current bundle boundary: pad it just
248 // enough to reach the boundary.
249 // C) The fragment ends after the current bundle boundary: pad it until it
250 // reaches the end of the next bundle boundary.
252 // Note: this code could be made shorter with some modulo trickery, but it's
253 // intentionally kept in its more explicit form for simplicity.
254 if (EndOfFragment == BundleSize)
256 else if (EndOfFragment < BundleSize)
257 return BundleSize - EndOfFragment;
258 else { // EndOfFragment > BundleSize
259 return 2 * BundleSize - EndOfFragment;
261 } else if (EndOfFragment > BundleSize)
262 return BundleSize - OffsetInBundle;
269 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
272 MCFragment::~MCFragment() {
275 MCFragment::MCFragment(FragmentType Kind, MCSectionData *Parent)
276 : Kind(Kind), Parent(Parent), Atom(nullptr), Offset(~UINT64_C(0)) {
278 Parent->getFragmentList().push_back(this);
283 MCEncodedFragment::~MCEncodedFragment() {
288 MCEncodedFragmentWithFixups::~MCEncodedFragmentWithFixups() {
293 MCSectionData::MCSectionData() : Section(nullptr) {}
295 MCSectionData::MCSectionData(MCSection &Section, MCAssembler *A)
296 : Section(&Section), BundleLockState(NotBundleLocked),
297 BundleLockNestingDepth(0), BundleGroupBeforeFirstInst(false),
298 HasInstructions(false) {
300 A->getSectionList().push_back(this);
303 unsigned MCSectionData::getOrdinal() const { return Section->getOrdinal(); }
304 void MCSectionData::setOrdinal(unsigned Value) { Section->setOrdinal(Value); }
306 MCSectionData::iterator
307 MCSectionData::getSubsectionInsertionPoint(unsigned Subsection) {
308 if (Subsection == 0 && SubsectionFragmentMap.empty())
311 SmallVectorImpl<std::pair<unsigned, MCFragment *> >::iterator MI =
312 std::lower_bound(SubsectionFragmentMap.begin(), SubsectionFragmentMap.end(),
313 std::make_pair(Subsection, (MCFragment *)nullptr));
314 bool ExactMatch = false;
315 if (MI != SubsectionFragmentMap.end()) {
316 ExactMatch = MI->first == Subsection;
321 if (MI == SubsectionFragmentMap.end())
325 if (!ExactMatch && Subsection != 0) {
326 // The GNU as documentation claims that subsections have an alignment of 4,
327 // although this appears not to be the case.
328 MCFragment *F = new MCDataFragment();
329 SubsectionFragmentMap.insert(MI, std::make_pair(Subsection, F));
330 getFragmentList().insert(IP, F);
337 void MCSectionData::setBundleLockState(BundleLockStateType NewState) {
338 if (NewState == NotBundleLocked) {
339 if (BundleLockNestingDepth == 0) {
340 report_fatal_error("Mismatched bundle_lock/unlock directives");
342 if (--BundleLockNestingDepth == 0) {
343 BundleLockState = NotBundleLocked;
348 // If any of the directives is an align_to_end directive, the whole nested
349 // group is align_to_end. So don't downgrade from align_to_end to just locked.
350 if (BundleLockState != BundleLockedAlignToEnd) {
351 BundleLockState = NewState;
353 ++BundleLockNestingDepth;
358 MCAssembler::MCAssembler(MCContext &Context_, MCAsmBackend &Backend_,
359 MCCodeEmitter &Emitter_, MCObjectWriter &Writer_,
361 : Context(Context_), Backend(Backend_), Emitter(Emitter_), Writer(Writer_),
362 OS(OS_), BundleAlignSize(0), RelaxAll(false),
363 SubsectionsViaSymbols(false), ELFHeaderEFlags(0) {
364 VersionMinInfo.Major = 0; // Major version == 0 for "none specified"
367 MCAssembler::~MCAssembler() {
370 void MCAssembler::reset() {
374 IndirectSymbols.clear();
376 LinkerOptions.clear();
381 SubsectionsViaSymbols = false;
383 LOHContainer.reset();
384 VersionMinInfo.Major = 0;
386 // reset objects owned by us
387 getBackend().reset();
388 getEmitter().reset();
390 getLOHContainer().reset();
393 bool MCAssembler::isThumbFunc(const MCSymbol *Symbol) const {
394 if (ThumbFuncs.count(Symbol))
397 if (!Symbol->isVariable())
400 // FIXME: It looks like gas supports some cases of the form "foo + 2". It
401 // is not clear if that is a bug or a feature.
402 const MCExpr *Expr = Symbol->getVariableValue();
403 const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Expr);
407 if (Ref->getKind() != MCSymbolRefExpr::VK_None)
410 const MCSymbol &Sym = Ref->getSymbol();
411 if (!isThumbFunc(&Sym))
414 ThumbFuncs.insert(Symbol); // Cache it.
418 void MCAssembler::addLocalUsedInReloc(const MCSymbol &Sym) {
419 assert(Sym.isTemporary());
420 LocalsUsedInReloc.insert(&Sym);
423 bool MCAssembler::isLocalUsedInReloc(const MCSymbol &Sym) const {
424 assert(Sym.isTemporary());
425 return LocalsUsedInReloc.count(&Sym);
428 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
429 // Non-temporary labels should always be visible to the linker.
430 if (!Symbol.isTemporary())
433 // Absolute temporary labels are never visible.
434 if (!Symbol.isInSection())
437 if (isLocalUsedInReloc(Symbol))
443 const MCSymbol *MCAssembler::getAtom(const MCSymbol &S) const {
444 // Linker visible symbols define atoms.
445 if (isSymbolLinkerVisible(S))
448 // Absolute and undefined symbols have no defining atom.
449 if (!S.getData().getFragment())
452 // Non-linker visible symbols in sections which can't be atomized have no
454 if (!getContext().getAsmInfo()->isSectionAtomizableBySymbols(
455 S.getData().getFragment()->getParent()->getSection()))
458 // Otherwise, return the atom for the containing fragment.
459 return S.getData().getFragment()->getAtom();
462 bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout,
463 const MCFixup &Fixup, const MCFragment *DF,
464 MCValue &Target, uint64_t &Value) const {
465 ++stats::evaluateFixup;
467 // FIXME: This code has some duplication with RecordRelocation. We should
468 // probably merge the two into a single callback that tries to evaluate a
469 // fixup and records a relocation if one is needed.
470 const MCExpr *Expr = Fixup.getValue();
471 if (!Expr->EvaluateAsRelocatable(Target, &Layout, &Fixup))
472 getContext().reportFatalError(Fixup.getLoc(), "expected relocatable expression");
474 bool IsPCRel = Backend.getFixupKindInfo(
475 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
479 if (Target.getSymB()) {
481 } else if (!Target.getSymA()) {
484 const MCSymbolRefExpr *A = Target.getSymA();
485 const MCSymbol &SA = A->getSymbol();
486 if (A->getKind() != MCSymbolRefExpr::VK_None || SA.isUndefined()) {
489 IsResolved = getWriter().IsSymbolRefDifferenceFullyResolvedImpl(
490 *this, SA, *DF, false, true);
494 IsResolved = Target.isAbsolute();
497 Value = Target.getConstant();
499 if (const MCSymbolRefExpr *A = Target.getSymA()) {
500 const MCSymbol &Sym = A->getSymbol();
502 Value += Layout.getSymbolOffset(Sym);
504 if (const MCSymbolRefExpr *B = Target.getSymB()) {
505 const MCSymbol &Sym = B->getSymbol();
507 Value -= Layout.getSymbolOffset(Sym);
511 bool ShouldAlignPC = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
512 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits;
513 assert((ShouldAlignPC ? IsPCRel : true) &&
514 "FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!");
517 uint32_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset();
519 // A number of ARM fixups in Thumb mode require that the effective PC
520 // address be determined as the 32-bit aligned version of the actual offset.
521 if (ShouldAlignPC) Offset &= ~0x3;
525 // Let the backend adjust the fixup value if necessary, including whether
526 // we need a relocation.
527 Backend.processFixupValue(*this, Layout, Fixup, DF, Target, Value,
533 uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
534 const MCFragment &F) const {
535 switch (F.getKind()) {
536 case MCFragment::FT_Data:
537 case MCFragment::FT_Relaxable:
538 case MCFragment::FT_CompactEncodedInst:
539 return cast<MCEncodedFragment>(F).getContents().size();
540 case MCFragment::FT_Fill:
541 return cast<MCFillFragment>(F).getSize();
543 case MCFragment::FT_LEB:
544 return cast<MCLEBFragment>(F).getContents().size();
546 case MCFragment::FT_Align: {
547 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
548 unsigned Offset = Layout.getFragmentOffset(&AF);
549 unsigned Size = OffsetToAlignment(Offset, AF.getAlignment());
550 // If we are padding with nops, force the padding to be larger than the
552 if (Size > 0 && AF.hasEmitNops()) {
553 while (Size % getBackend().getMinimumNopSize())
554 Size += AF.getAlignment();
556 if (Size > AF.getMaxBytesToEmit())
561 case MCFragment::FT_Org: {
562 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
563 int64_t TargetLocation;
564 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, Layout))
565 report_fatal_error("expected assembly-time absolute expression");
567 // FIXME: We need a way to communicate this error.
568 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
569 int64_t Size = TargetLocation - FragmentOffset;
570 if (Size < 0 || Size >= 0x40000000)
571 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
572 "' (at offset '" + Twine(FragmentOffset) + "')");
576 case MCFragment::FT_Dwarf:
577 return cast<MCDwarfLineAddrFragment>(F).getContents().size();
578 case MCFragment::FT_DwarfFrame:
579 return cast<MCDwarfCallFrameFragment>(F).getContents().size();
582 llvm_unreachable("invalid fragment kind");
585 void MCAsmLayout::layoutFragment(MCFragment *F) {
586 MCFragment *Prev = F->getPrevNode();
588 // We should never try to recompute something which is valid.
589 assert(!isFragmentValid(F) && "Attempt to recompute a valid fragment!");
590 // We should never try to compute the fragment layout if its predecessor
592 assert((!Prev || isFragmentValid(Prev)) &&
593 "Attempt to compute fragment before its predecessor!");
595 ++stats::FragmentLayouts;
597 // Compute fragment offset and size.
599 F->Offset = Prev->Offset + getAssembler().computeFragmentSize(*this, *Prev);
602 LastValidFragment[F->getParent()] = F;
604 // If bundling is enabled and this fragment has instructions in it, it has to
605 // obey the bundling restrictions. With padding, we'll have:
610 // -------------------------------------
611 // Prev |##########| F |
612 // -------------------------------------
617 // The fragment's offset will point to after the padding, and its computed
618 // size won't include the padding.
620 // When the -mc-relax-all flag is used, we optimize bundling by writting the
621 // bundle padding directly into fragments when the instructions are emitted
622 // inside the streamer.
624 if (Assembler.isBundlingEnabled() && !Assembler.getRelaxAll() &&
625 F->hasInstructions()) {
626 assert(isa<MCEncodedFragment>(F) &&
627 "Only MCEncodedFragment implementations have instructions");
628 uint64_t FSize = Assembler.computeFragmentSize(*this, *F);
630 if (FSize > Assembler.getBundleAlignSize())
631 report_fatal_error("Fragment can't be larger than a bundle size");
633 uint64_t RequiredBundlePadding = computeBundlePadding(Assembler, F,
635 if (RequiredBundlePadding > UINT8_MAX)
636 report_fatal_error("Padding cannot exceed 255 bytes");
637 F->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
638 F->Offset += RequiredBundlePadding;
642 /// \brief Write the contents of a fragment to the given object writer. Expects
643 /// a MCEncodedFragment.
644 static void writeFragmentContents(const MCFragment &F, MCObjectWriter *OW) {
645 const MCEncodedFragment &EF = cast<MCEncodedFragment>(F);
646 OW->WriteBytes(EF.getContents());
649 void MCAssembler::writeFragmentPadding(const MCFragment &F, uint64_t FSize,
650 MCObjectWriter *OW) const {
651 // Should NOP padding be written out before this fragment?
652 unsigned BundlePadding = F.getBundlePadding();
653 if (BundlePadding > 0) {
654 assert(isBundlingEnabled() &&
655 "Writing bundle padding with disabled bundling");
656 assert(F.hasInstructions() &&
657 "Writing bundle padding for a fragment without instructions");
659 unsigned TotalLength = BundlePadding + static_cast<unsigned>(FSize);
660 if (F.alignToBundleEnd() && TotalLength > getBundleAlignSize()) {
661 // If the padding itself crosses a bundle boundary, it must be emitted
662 // in 2 pieces, since even nop instructions must not cross boundaries.
663 // v--------------v <- BundleAlignSize
664 // v---------v <- BundlePadding
665 // ----------------------------
666 // | Prev |####|####| F |
667 // ----------------------------
668 // ^-------------------^ <- TotalLength
669 unsigned DistanceToBoundary = TotalLength - getBundleAlignSize();
670 if (!getBackend().writeNopData(DistanceToBoundary, OW))
671 report_fatal_error("unable to write NOP sequence of " +
672 Twine(DistanceToBoundary) + " bytes");
673 BundlePadding -= DistanceToBoundary;
675 if (!getBackend().writeNopData(BundlePadding, OW))
676 report_fatal_error("unable to write NOP sequence of " +
677 Twine(BundlePadding) + " bytes");
681 /// \brief Write the fragment \p F to the output file.
682 static void writeFragment(const MCAssembler &Asm, const MCAsmLayout &Layout,
683 const MCFragment &F) {
684 MCObjectWriter *OW = &Asm.getWriter();
686 // FIXME: Embed in fragments instead?
687 uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F);
689 Asm.writeFragmentPadding(F, FragmentSize, OW);
691 // This variable (and its dummy usage) is to participate in the assert at
692 // the end of the function.
693 uint64_t Start = OW->getStream().tell();
696 ++stats::EmittedFragments;
698 switch (F.getKind()) {
699 case MCFragment::FT_Align: {
700 ++stats::EmittedAlignFragments;
701 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
702 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
704 uint64_t Count = FragmentSize / AF.getValueSize();
706 // FIXME: This error shouldn't actually occur (the front end should emit
707 // multiple .align directives to enforce the semantics it wants), but is
708 // severe enough that we want to report it. How to handle this?
709 if (Count * AF.getValueSize() != FragmentSize)
710 report_fatal_error("undefined .align directive, value size '" +
711 Twine(AF.getValueSize()) +
712 "' is not a divisor of padding size '" +
713 Twine(FragmentSize) + "'");
715 // See if we are aligning with nops, and if so do that first to try to fill
716 // the Count bytes. Then if that did not fill any bytes or there are any
717 // bytes left to fill use the Value and ValueSize to fill the rest.
718 // If we are aligning with nops, ask that target to emit the right data.
719 if (AF.hasEmitNops()) {
720 if (!Asm.getBackend().writeNopData(Count, OW))
721 report_fatal_error("unable to write nop sequence of " +
722 Twine(Count) + " bytes");
726 // Otherwise, write out in multiples of the value size.
727 for (uint64_t i = 0; i != Count; ++i) {
728 switch (AF.getValueSize()) {
729 default: llvm_unreachable("Invalid size!");
730 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
731 case 2: OW->Write16(uint16_t(AF.getValue())); break;
732 case 4: OW->Write32(uint32_t(AF.getValue())); break;
733 case 8: OW->Write64(uint64_t(AF.getValue())); break;
739 case MCFragment::FT_Data:
740 ++stats::EmittedDataFragments;
741 writeFragmentContents(F, OW);
744 case MCFragment::FT_Relaxable:
745 ++stats::EmittedRelaxableFragments;
746 writeFragmentContents(F, OW);
749 case MCFragment::FT_CompactEncodedInst:
750 ++stats::EmittedCompactEncodedInstFragments;
751 writeFragmentContents(F, OW);
754 case MCFragment::FT_Fill: {
755 ++stats::EmittedFillFragments;
756 const MCFillFragment &FF = cast<MCFillFragment>(F);
758 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
760 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
761 switch (FF.getValueSize()) {
762 default: llvm_unreachable("Invalid size!");
763 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
764 case 2: OW->Write16(uint16_t(FF.getValue())); break;
765 case 4: OW->Write32(uint32_t(FF.getValue())); break;
766 case 8: OW->Write64(uint64_t(FF.getValue())); break;
772 case MCFragment::FT_LEB: {
773 const MCLEBFragment &LF = cast<MCLEBFragment>(F);
774 OW->WriteBytes(LF.getContents());
778 case MCFragment::FT_Org: {
779 ++stats::EmittedOrgFragments;
780 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
782 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
783 OW->Write8(uint8_t(OF.getValue()));
788 case MCFragment::FT_Dwarf: {
789 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
790 OW->WriteBytes(OF.getContents());
793 case MCFragment::FT_DwarfFrame: {
794 const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F);
795 OW->WriteBytes(CF.getContents());
800 assert(OW->getStream().tell() - Start == FragmentSize &&
801 "The stream should advance by fragment size");
804 void MCAssembler::writeSectionData(const MCSectionData *SD,
805 const MCAsmLayout &Layout) const {
806 // Ignore virtual sections.
807 if (SD->getSection().isVirtualSection()) {
808 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
810 // Check that contents are only things legal inside a virtual section.
811 for (MCSectionData::const_iterator it = SD->begin(),
812 ie = SD->end(); it != ie; ++it) {
813 switch (it->getKind()) {
814 default: llvm_unreachable("Invalid fragment in virtual section!");
815 case MCFragment::FT_Data: {
816 // Check that we aren't trying to write a non-zero contents (or fixups)
817 // into a virtual section. This is to support clients which use standard
818 // directives to fill the contents of virtual sections.
819 const MCDataFragment &DF = cast<MCDataFragment>(*it);
820 assert(DF.fixup_begin() == DF.fixup_end() &&
821 "Cannot have fixups in virtual section!");
822 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
823 if (DF.getContents()[i]) {
824 if (auto *ELFSec = dyn_cast<const MCSectionELF>(&SD->getSection()))
825 report_fatal_error("non-zero initializer found in section '" +
826 ELFSec->getSectionName() + "'");
828 report_fatal_error("non-zero initializer found in virtual section");
832 case MCFragment::FT_Align:
833 // Check that we aren't trying to write a non-zero value into a virtual
835 assert((cast<MCAlignFragment>(it)->getValueSize() == 0 ||
836 cast<MCAlignFragment>(it)->getValue() == 0) &&
837 "Invalid align in virtual section!");
839 case MCFragment::FT_Fill:
840 assert((cast<MCFillFragment>(it)->getValueSize() == 0 ||
841 cast<MCFillFragment>(it)->getValue() == 0) &&
842 "Invalid fill in virtual section!");
850 uint64_t Start = getWriter().getStream().tell();
853 for (MCSectionData::const_iterator it = SD->begin(), ie = SD->end();
855 writeFragment(*this, Layout, *it);
857 assert(getWriter().getStream().tell() - Start ==
858 Layout.getSectionAddressSize(SD));
861 std::pair<uint64_t, bool> MCAssembler::handleFixup(const MCAsmLayout &Layout,
863 const MCFixup &Fixup) {
864 // Evaluate the fixup.
867 bool IsPCRel = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
868 MCFixupKindInfo::FKF_IsPCRel;
869 if (!evaluateFixup(Layout, Fixup, &F, Target, FixedValue)) {
870 // The fixup was unresolved, we need a relocation. Inform the object
871 // writer of the relocation, and give it an opportunity to adjust the
872 // fixup value if need be.
873 getWriter().RecordRelocation(*this, Layout, &F, Fixup, Target, IsPCRel,
876 return std::make_pair(FixedValue, IsPCRel);
879 void MCAssembler::Finish() {
880 DEBUG_WITH_TYPE("mc-dump", {
881 llvm::errs() << "assembler backend - pre-layout\n--\n";
884 // Create the layout object.
885 MCAsmLayout Layout(*this);
887 // Create dummy fragments and assign section ordinals.
888 unsigned SectionIndex = 0;
889 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
890 // Create dummy fragments to eliminate any empty sections, this simplifies
892 if (it->getFragmentList().empty())
893 new MCDataFragment(it);
895 it->setOrdinal(SectionIndex++);
898 // Assign layout order indices to sections and fragments.
899 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
900 MCSectionData *SD = Layout.getSectionOrder()[i];
901 SD->setLayoutOrder(i);
903 unsigned FragmentIndex = 0;
904 for (MCSectionData::iterator iFrag = SD->begin(), iFragEnd = SD->end();
905 iFrag != iFragEnd; ++iFrag)
906 iFrag->setLayoutOrder(FragmentIndex++);
909 // Layout until everything fits.
910 while (layoutOnce(Layout))
913 DEBUG_WITH_TYPE("mc-dump", {
914 llvm::errs() << "assembler backend - post-relaxation\n--\n";
917 // Finalize the layout, including fragment lowering.
918 finishLayout(Layout);
920 DEBUG_WITH_TYPE("mc-dump", {
921 llvm::errs() << "assembler backend - final-layout\n--\n";
924 uint64_t StartOffset = OS.tell();
926 // Allow the object writer a chance to perform post-layout binding (for
927 // example, to set the index fields in the symbol data).
928 getWriter().ExecutePostLayoutBinding(*this, Layout);
930 // Evaluate and apply the fixups, generating relocation entries as necessary.
931 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
932 for (MCSectionData::iterator it2 = it->begin(),
933 ie2 = it->end(); it2 != ie2; ++it2) {
934 MCEncodedFragmentWithFixups *F =
935 dyn_cast<MCEncodedFragmentWithFixups>(it2);
937 for (MCEncodedFragmentWithFixups::fixup_iterator it3 = F->fixup_begin(),
938 ie3 = F->fixup_end(); it3 != ie3; ++it3) {
939 MCFixup &Fixup = *it3;
942 std::tie(FixedValue, IsPCRel) = handleFixup(Layout, *F, Fixup);
943 getBackend().applyFixup(Fixup, F->getContents().data(),
944 F->getContents().size(), FixedValue, IsPCRel);
950 // Write the object file.
951 getWriter().WriteObject(*this, Layout);
953 stats::ObjectBytes += OS.tell() - StartOffset;
956 bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup,
957 const MCRelaxableFragment *DF,
958 const MCAsmLayout &Layout) const {
959 // If we cannot resolve the fixup value, it requires relaxation.
962 if (!evaluateFixup(Layout, Fixup, DF, Target, Value))
965 return getBackend().fixupNeedsRelaxation(Fixup, Value, DF, Layout);
968 bool MCAssembler::fragmentNeedsRelaxation(const MCRelaxableFragment *F,
969 const MCAsmLayout &Layout) const {
970 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
971 // are intentionally pushing out inst fragments, or because we relaxed a
972 // previous instruction to one that doesn't need relaxation.
973 if (!getBackend().mayNeedRelaxation(F->getInst()))
976 for (MCRelaxableFragment::const_fixup_iterator it = F->fixup_begin(),
977 ie = F->fixup_end(); it != ie; ++it)
978 if (fixupNeedsRelaxation(*it, F, Layout))
984 bool MCAssembler::relaxInstruction(MCAsmLayout &Layout,
985 MCRelaxableFragment &F) {
986 if (!fragmentNeedsRelaxation(&F, Layout))
989 ++stats::RelaxedInstructions;
991 // FIXME-PERF: We could immediately lower out instructions if we can tell
992 // they are fully resolved, to avoid retesting on later passes.
994 // Relax the fragment.
997 getBackend().relaxInstruction(F.getInst(), Relaxed);
999 // Encode the new instruction.
1001 // FIXME-PERF: If it matters, we could let the target do this. It can
1002 // probably do so more efficiently in many cases.
1003 SmallVector<MCFixup, 4> Fixups;
1004 SmallString<256> Code;
1005 raw_svector_ostream VecOS(Code);
1006 getEmitter().encodeInstruction(Relaxed, VecOS, Fixups, F.getSubtargetInfo());
1009 // Update the fragment.
1011 F.getContents() = Code;
1012 F.getFixups() = Fixups;
1017 bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) {
1018 uint64_t OldSize = LF.getContents().size();
1020 bool Abs = LF.getValue().evaluateKnownAbsolute(Value, Layout);
1022 report_fatal_error("sleb128 and uleb128 expressions must be absolute");
1023 SmallString<8> &Data = LF.getContents();
1025 raw_svector_ostream OSE(Data);
1027 encodeSLEB128(Value, OSE);
1029 encodeULEB128(Value, OSE);
1031 return OldSize != LF.getContents().size();
1034 bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout,
1035 MCDwarfLineAddrFragment &DF) {
1036 MCContext &Context = Layout.getAssembler().getContext();
1037 uint64_t OldSize = DF.getContents().size();
1039 bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
1040 assert(Abs && "We created a line delta with an invalid expression");
1043 LineDelta = DF.getLineDelta();
1044 SmallString<8> &Data = DF.getContents();
1046 raw_svector_ostream OSE(Data);
1047 MCDwarfLineAddr::Encode(Context, LineDelta, AddrDelta, OSE);
1049 return OldSize != Data.size();
1052 bool MCAssembler::relaxDwarfCallFrameFragment(MCAsmLayout &Layout,
1053 MCDwarfCallFrameFragment &DF) {
1054 MCContext &Context = Layout.getAssembler().getContext();
1055 uint64_t OldSize = DF.getContents().size();
1057 bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
1058 assert(Abs && "We created call frame with an invalid expression");
1060 SmallString<8> &Data = DF.getContents();
1062 raw_svector_ostream OSE(Data);
1063 MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE);
1065 return OldSize != Data.size();
1068 bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSectionData &SD) {
1069 // Holds the first fragment which needed relaxing during this layout. It will
1070 // remain NULL if none were relaxed.
1071 // When a fragment is relaxed, all the fragments following it should get
1072 // invalidated because their offset is going to change.
1073 MCFragment *FirstRelaxedFragment = nullptr;
1075 // Attempt to relax all the fragments in the section.
1076 for (MCSectionData::iterator I = SD.begin(), IE = SD.end(); I != IE; ++I) {
1077 // Check if this is a fragment that needs relaxation.
1078 bool RelaxedFrag = false;
1079 switch(I->getKind()) {
1082 case MCFragment::FT_Relaxable:
1083 assert(!getRelaxAll() &&
1084 "Did not expect a MCRelaxableFragment in RelaxAll mode");
1085 RelaxedFrag = relaxInstruction(Layout, *cast<MCRelaxableFragment>(I));
1087 case MCFragment::FT_Dwarf:
1088 RelaxedFrag = relaxDwarfLineAddr(Layout,
1089 *cast<MCDwarfLineAddrFragment>(I));
1091 case MCFragment::FT_DwarfFrame:
1093 relaxDwarfCallFrameFragment(Layout,
1094 *cast<MCDwarfCallFrameFragment>(I));
1096 case MCFragment::FT_LEB:
1097 RelaxedFrag = relaxLEB(Layout, *cast<MCLEBFragment>(I));
1100 if (RelaxedFrag && !FirstRelaxedFragment)
1101 FirstRelaxedFragment = I;
1103 if (FirstRelaxedFragment) {
1104 Layout.invalidateFragmentsFrom(FirstRelaxedFragment);
1110 bool MCAssembler::layoutOnce(MCAsmLayout &Layout) {
1111 ++stats::RelaxationSteps;
1113 bool WasRelaxed = false;
1114 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1115 MCSectionData &SD = *it;
1116 while (layoutSectionOnce(Layout, SD))
1123 void MCAssembler::finishLayout(MCAsmLayout &Layout) {
1124 // The layout is done. Mark every fragment as valid.
1125 for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) {
1126 Layout.getFragmentOffset(&*Layout.getSectionOrder()[i]->rbegin());
1130 // Debugging methods
1134 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
1135 OS << "<MCFixup" << " Offset:" << AF.getOffset()
1136 << " Value:" << *AF.getValue()
1137 << " Kind:" << AF.getKind() << ">";
1143 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1144 void MCFragment::dump() {
1145 raw_ostream &OS = llvm::errs();
1148 switch (getKind()) {
1149 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
1150 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
1151 case MCFragment::FT_CompactEncodedInst:
1152 OS << "MCCompactEncodedInstFragment"; break;
1153 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
1154 case MCFragment::FT_Relaxable: OS << "MCRelaxableFragment"; break;
1155 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
1156 case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
1157 case MCFragment::FT_DwarfFrame: OS << "MCDwarfCallFrameFragment"; break;
1158 case MCFragment::FT_LEB: OS << "MCLEBFragment"; break;
1161 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
1162 << " Offset:" << Offset
1163 << " HasInstructions:" << hasInstructions()
1164 << " BundlePadding:" << static_cast<unsigned>(getBundlePadding()) << ">";
1166 switch (getKind()) {
1167 case MCFragment::FT_Align: {
1168 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
1169 if (AF->hasEmitNops())
1170 OS << " (emit nops)";
1172 OS << " Alignment:" << AF->getAlignment()
1173 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
1174 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
1177 case MCFragment::FT_Data: {
1178 const MCDataFragment *DF = cast<MCDataFragment>(this);
1180 OS << " Contents:[";
1181 const SmallVectorImpl<char> &Contents = DF->getContents();
1182 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
1184 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1186 OS << "] (" << Contents.size() << " bytes)";
1188 if (DF->fixup_begin() != DF->fixup_end()) {
1191 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
1192 ie = DF->fixup_end(); it != ie; ++it) {
1193 if (it != DF->fixup_begin()) OS << ",\n ";
1200 case MCFragment::FT_CompactEncodedInst: {
1201 const MCCompactEncodedInstFragment *CEIF =
1202 cast<MCCompactEncodedInstFragment>(this);
1204 OS << " Contents:[";
1205 const SmallVectorImpl<char> &Contents = CEIF->getContents();
1206 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
1208 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1210 OS << "] (" << Contents.size() << " bytes)";
1213 case MCFragment::FT_Fill: {
1214 const MCFillFragment *FF = cast<MCFillFragment>(this);
1215 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
1216 << " Size:" << FF->getSize();
1219 case MCFragment::FT_Relaxable: {
1220 const MCRelaxableFragment *F = cast<MCRelaxableFragment>(this);
1223 F->getInst().dump_pretty(OS);
1226 case MCFragment::FT_Org: {
1227 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
1229 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
1232 case MCFragment::FT_Dwarf: {
1233 const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
1235 OS << " AddrDelta:" << OF->getAddrDelta()
1236 << " LineDelta:" << OF->getLineDelta();
1239 case MCFragment::FT_DwarfFrame: {
1240 const MCDwarfCallFrameFragment *CF = cast<MCDwarfCallFrameFragment>(this);
1242 OS << " AddrDelta:" << CF->getAddrDelta();
1245 case MCFragment::FT_LEB: {
1246 const MCLEBFragment *LF = cast<MCLEBFragment>(this);
1248 OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
1255 void MCSectionData::dump() {
1256 raw_ostream &OS = llvm::errs();
1258 OS << "<MCSectionData";
1259 OS << " Fragments:[\n ";
1260 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1261 if (it != begin()) OS << ",\n ";
1267 void MCSymbolData::dump() const {
1268 raw_ostream &OS = llvm::errs();
1270 OS << "<MCSymbolData"
1271 << " Fragment:" << getFragment();
1273 OS << " Offset:" << getOffset();
1274 OS << " Flags:" << getFlags();
1276 OS << " (common, size:" << getCommonSize()
1277 << " align: " << getCommonAlignment() << ")";
1279 OS << " (external)";
1280 if (isPrivateExtern())
1281 OS << " (private extern)";
1285 void MCAssembler::dump() {
1286 raw_ostream &OS = llvm::errs();
1288 OS << "<MCAssembler\n";
1289 OS << " Sections:[\n ";
1290 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1291 if (it != begin()) OS << ",\n ";
1297 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1298 if (it != symbol_begin()) OS << ",\n ";
1301 OS << ", Index:" << it->getIndex() << ", ";
1302 it->getData().dump();
1309 // anchors for MC*Fragment vtables
1310 void MCEncodedFragment::anchor() { }
1311 void MCEncodedFragmentWithFixups::anchor() { }
1312 void MCDataFragment::anchor() { }
1313 void MCCompactEncodedInstFragment::anchor() { }
1314 void MCRelaxableFragment::anchor() { }
1315 void MCAlignFragment::anchor() { }
1316 void MCFillFragment::anchor() { }
1317 void MCOrgFragment::anchor() { }
1318 void MCLEBFragment::anchor() { }
1319 void MCDwarfLineAddrFragment::anchor() { }
1320 void MCDwarfCallFrameFragment::anchor() { }