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 MCSymbolData &SD,
124 bool ReportError, uint64_t &Val) {
125 if (!SD.getFragment()) {
127 report_fatal_error("unable to evaluate offset to undefined symbol '" +
128 SD.getSymbol().getName() + "'");
131 Val = Layout.getFragmentOffset(SD.getFragment()) + SD.getOffset();
135 static bool getSymbolOffsetImpl(const MCAsmLayout &Layout,
136 const MCSymbolData *SD, bool ReportError,
138 const MCSymbol &S = SD->getSymbol();
141 return getLabelOffset(Layout, *SD, ReportError, Val);
143 // If SD is a variable, evaluate it.
145 if (!S.getVariableValue()->EvaluateAsRelocatable(Target, &Layout, nullptr))
146 report_fatal_error("unable to evaluate offset for variable '" +
149 uint64_t Offset = Target.getConstant();
151 const MCAssembler &Asm = Layout.getAssembler();
153 const MCSymbolRefExpr *A = Target.getSymA();
156 if (!getLabelOffset(Layout, Asm.getSymbolData(A->getSymbol()), ReportError,
162 const MCSymbolRefExpr *B = Target.getSymB();
165 if (!getLabelOffset(Layout, Asm.getSymbolData(B->getSymbol()), ReportError,
175 bool MCAsmLayout::getSymbolOffset(const MCSymbolData *SD, uint64_t &Val) const {
176 return getSymbolOffsetImpl(*this, SD, false, Val);
179 uint64_t MCAsmLayout::getSymbolOffset(const MCSymbolData *SD) const {
181 getSymbolOffsetImpl(*this, SD, true, Val);
185 const MCSymbol *MCAsmLayout::getBaseSymbol(const MCSymbol &Symbol) const {
186 if (!Symbol.isVariable())
189 const MCExpr *Expr = Symbol.getVariableValue();
191 if (!Expr->evaluateAsValue(Value, *this))
192 llvm_unreachable("Invalid Expression");
194 const MCSymbolRefExpr *RefB = Value.getSymB();
196 Assembler.getContext().FatalError(
197 SMLoc(), Twine("symbol '") + RefB->getSymbol().getName() +
198 "' could not be evaluated in a subtraction expression");
200 const MCSymbolRefExpr *A = Value.getSymA();
204 const MCSymbol &ASym = A->getSymbol();
205 const MCAssembler &Asm = getAssembler();
206 const MCSymbolData &ASD = Asm.getSymbolData(ASym);
207 if (ASD.isCommon()) {
208 // FIXME: we should probably add a SMLoc to MCExpr.
209 Asm.getContext().FatalError(SMLoc(),
210 "Common symbol " + ASym.getName() +
211 " cannot be used in assignment expr");
217 uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const {
218 // The size is the last fragment's end offset.
219 const MCFragment &F = SD->getFragmentList().back();
220 return getFragmentOffset(&F) + getAssembler().computeFragmentSize(*this, F);
223 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
224 // Virtual sections have no file size.
225 if (SD->getSection().isVirtualSection())
228 // Otherwise, the file size is the same as the address space size.
229 return getSectionAddressSize(SD);
232 uint64_t MCAsmLayout::computeBundlePadding(const MCFragment *F,
233 uint64_t FOffset, uint64_t FSize) {
234 uint64_t BundleSize = Assembler.getBundleAlignSize();
235 assert(BundleSize > 0 &&
236 "computeBundlePadding should only be called if bundling is enabled");
237 uint64_t BundleMask = BundleSize - 1;
238 uint64_t OffsetInBundle = FOffset & BundleMask;
239 uint64_t EndOfFragment = OffsetInBundle + FSize;
241 // There are two kinds of bundling restrictions:
243 // 1) For alignToBundleEnd(), add padding to ensure that the fragment will
244 // *end* on a bundle boundary.
245 // 2) Otherwise, check if the fragment would cross a bundle boundary. If it
246 // would, add padding until the end of the bundle so that the fragment
247 // will start in a new one.
248 if (F->alignToBundleEnd()) {
249 // Three possibilities here:
251 // A) The fragment just happens to end at a bundle boundary, so we're good.
252 // B) The fragment ends before the current bundle boundary: pad it just
253 // enough to reach the boundary.
254 // C) The fragment ends after the current bundle boundary: pad it until it
255 // reaches the end of the next bundle boundary.
257 // Note: this code could be made shorter with some modulo trickery, but it's
258 // intentionally kept in its more explicit form for simplicity.
259 if (EndOfFragment == BundleSize)
261 else if (EndOfFragment < BundleSize)
262 return BundleSize - EndOfFragment;
263 else { // EndOfFragment > BundleSize
264 return 2 * BundleSize - EndOfFragment;
266 } else if (EndOfFragment > BundleSize)
267 return BundleSize - OffsetInBundle;
274 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
277 MCFragment::~MCFragment() {
280 MCFragment::MCFragment(FragmentType Kind, MCSectionData *Parent)
281 : Kind(Kind), Parent(Parent), Atom(nullptr), Offset(~UINT64_C(0)) {
283 Parent->getFragmentList().push_back(this);
288 MCEncodedFragment::~MCEncodedFragment() {
293 MCEncodedFragmentWithFixups::~MCEncodedFragmentWithFixups() {
298 MCSectionData::MCSectionData() : Section(nullptr) {}
300 MCSectionData::MCSectionData(const MCSection &Section, MCAssembler *A)
301 : Section(&Section), Ordinal(~UINT32_C(0)), Alignment(1),
302 BundleLockState(NotBundleLocked), BundleLockNestingDepth(0),
303 BundleGroupBeforeFirstInst(false), HasInstructions(false) {
305 A->getSectionList().push_back(this);
308 MCSectionData::iterator
309 MCSectionData::getSubsectionInsertionPoint(unsigned Subsection) {
310 if (Subsection == 0 && SubsectionFragmentMap.empty())
313 SmallVectorImpl<std::pair<unsigned, MCFragment *> >::iterator MI =
314 std::lower_bound(SubsectionFragmentMap.begin(), SubsectionFragmentMap.end(),
315 std::make_pair(Subsection, (MCFragment *)nullptr));
316 bool ExactMatch = false;
317 if (MI != SubsectionFragmentMap.end()) {
318 ExactMatch = MI->first == Subsection;
323 if (MI == SubsectionFragmentMap.end())
327 if (!ExactMatch && Subsection != 0) {
328 // The GNU as documentation claims that subsections have an alignment of 4,
329 // although this appears not to be the case.
330 MCFragment *F = new MCDataFragment();
331 SubsectionFragmentMap.insert(MI, std::make_pair(Subsection, F));
332 getFragmentList().insert(IP, F);
338 void MCSectionData::setBundleLockState(BundleLockStateType NewState) {
339 if (NewState == NotBundleLocked) {
340 if (BundleLockNestingDepth == 0) {
341 report_fatal_error("Mismatched bundle_lock/unlock directives");
343 if (--BundleLockNestingDepth == 0) {
344 BundleLockState = NotBundleLocked;
349 // If any of the directives is an align_to_end directive, the whole nested
350 // group is align_to_end. So don't downgrade from align_to_end to just locked.
351 if (BundleLockState != BundleLockedAlignToEnd) {
352 BundleLockState = NewState;
354 ++BundleLockNestingDepth;
359 MCSymbolData::MCSymbolData() : Symbol(nullptr) {}
361 MCSymbolData::MCSymbolData(const MCSymbol &Symbol, MCFragment *Fragment,
362 uint64_t Offset, MCAssembler *A)
363 : Symbol(&Symbol), Fragment(Fragment), Offset(Offset), SymbolSize(nullptr),
364 CommonAlign(-1U), Flags(0), Index(0) {
366 A->getSymbolList().push_back(this);
371 MCAssembler::MCAssembler(MCContext &Context_, MCAsmBackend &Backend_,
372 MCCodeEmitter &Emitter_, MCObjectWriter &Writer_,
374 : Context(Context_), Backend(Backend_), Emitter(Emitter_), Writer(Writer_),
375 OS(OS_), BundleAlignSize(0), RelaxAll(false),
376 SubsectionsViaSymbols(false), ELFHeaderEFlags(0) {
377 VersionMinInfo.Major = 0; // Major version == 0 for "none specified"
380 MCAssembler::~MCAssembler() {
383 void MCAssembler::reset() {
388 IndirectSymbols.clear();
390 LinkerOptions.clear();
395 SubsectionsViaSymbols = false;
397 LOHContainer.reset();
398 VersionMinInfo.Major = 0;
400 // reset objects owned by us
401 getBackend().reset();
402 getEmitter().reset();
404 getLOHContainer().reset();
407 bool MCAssembler::isThumbFunc(const MCSymbol *Symbol) const {
408 if (ThumbFuncs.count(Symbol))
411 if (!Symbol->isVariable())
414 // FIXME: It looks like gas supports some cases of the form "foo + 2". It
415 // is not clear if that is a bug or a feature.
416 const MCExpr *Expr = Symbol->getVariableValue();
417 const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Expr);
421 if (Ref->getKind() != MCSymbolRefExpr::VK_None)
424 const MCSymbol &Sym = Ref->getSymbol();
425 if (!isThumbFunc(&Sym))
428 ThumbFuncs.insert(Symbol); // Cache it.
432 void MCAssembler::addLocalUsedInReloc(const MCSymbol &Sym) {
433 assert(Sym.isTemporary());
434 LocalsUsedInReloc.insert(&Sym);
437 bool MCAssembler::isLocalUsedInReloc(const MCSymbol &Sym) const {
438 assert(Sym.isTemporary());
439 return LocalsUsedInReloc.count(&Sym);
442 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
443 // Non-temporary labels should always be visible to the linker.
444 if (!Symbol.isTemporary())
447 // Absolute temporary labels are never visible.
448 if (!Symbol.isInSection())
451 if (isLocalUsedInReloc(Symbol))
457 const MCSymbolData *MCAssembler::getAtom(const MCSymbolData *SD) const {
458 // Linker visible symbols define atoms.
459 if (isSymbolLinkerVisible(SD->getSymbol()))
462 // Absolute and undefined symbols have no defining atom.
463 if (!SD->getFragment())
466 // Non-linker visible symbols in sections which can't be atomized have no
468 if (!getContext().getAsmInfo()->isSectionAtomizableBySymbols(
469 SD->getFragment()->getParent()->getSection()))
472 // Otherwise, return the atom for the containing fragment.
473 return SD->getFragment()->getAtom();
476 bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout,
477 const MCFixup &Fixup, const MCFragment *DF,
478 MCValue &Target, uint64_t &Value) const {
479 ++stats::evaluateFixup;
481 // FIXME: This code has some duplication with RecordRelocation. We should
482 // probably merge the two into a single callback that tries to evaluate a
483 // fixup and records a relocation if one is needed.
484 const MCExpr *Expr = Fixup.getValue();
485 if (!Expr->EvaluateAsRelocatable(Target, &Layout, &Fixup))
486 getContext().FatalError(Fixup.getLoc(), "expected relocatable expression");
488 bool IsPCRel = Backend.getFixupKindInfo(
489 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
493 if (Target.getSymB()) {
495 } else if (!Target.getSymA()) {
498 const MCSymbolRefExpr *A = Target.getSymA();
499 const MCSymbol &SA = A->getSymbol();
500 if (A->getKind() != MCSymbolRefExpr::VK_None ||
501 SA.AliasedSymbol().isUndefined()) {
504 const MCSymbolData &DataA = getSymbolData(SA);
505 IsResolved = getWriter().IsSymbolRefDifferenceFullyResolvedImpl(
506 *this, DataA, nullptr, *DF, false, true);
510 IsResolved = Target.isAbsolute();
513 Value = Target.getConstant();
515 if (const MCSymbolRefExpr *A = Target.getSymA()) {
516 const MCSymbol &Sym = A->getSymbol().AliasedSymbol();
518 Value += Layout.getSymbolOffset(&getSymbolData(Sym));
520 if (const MCSymbolRefExpr *B = Target.getSymB()) {
521 const MCSymbol &Sym = B->getSymbol().AliasedSymbol();
523 Value -= Layout.getSymbolOffset(&getSymbolData(Sym));
527 bool ShouldAlignPC = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
528 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits;
529 assert((ShouldAlignPC ? IsPCRel : true) &&
530 "FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!");
533 uint32_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset();
535 // A number of ARM fixups in Thumb mode require that the effective PC
536 // address be determined as the 32-bit aligned version of the actual offset.
537 if (ShouldAlignPC) Offset &= ~0x3;
541 // Let the backend adjust the fixup value if necessary, including whether
542 // we need a relocation.
543 Backend.processFixupValue(*this, Layout, Fixup, DF, Target, Value,
549 uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
550 const MCFragment &F) const {
551 switch (F.getKind()) {
552 case MCFragment::FT_Data:
553 case MCFragment::FT_Relaxable:
554 case MCFragment::FT_CompactEncodedInst:
555 return cast<MCEncodedFragment>(F).getContents().size();
556 case MCFragment::FT_Fill:
557 return cast<MCFillFragment>(F).getSize();
559 case MCFragment::FT_LEB:
560 return cast<MCLEBFragment>(F).getContents().size();
562 case MCFragment::FT_Align: {
563 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
564 unsigned Offset = Layout.getFragmentOffset(&AF);
565 unsigned Size = OffsetToAlignment(Offset, AF.getAlignment());
566 // If we are padding with nops, force the padding to be larger than the
568 if (Size > 0 && AF.hasEmitNops()) {
569 while (Size % getBackend().getMinimumNopSize())
570 Size += AF.getAlignment();
572 if (Size > AF.getMaxBytesToEmit())
577 case MCFragment::FT_Org: {
578 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
579 int64_t TargetLocation;
580 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, Layout))
581 report_fatal_error("expected assembly-time absolute expression");
583 // FIXME: We need a way to communicate this error.
584 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
585 int64_t Size = TargetLocation - FragmentOffset;
586 if (Size < 0 || Size >= 0x40000000)
587 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
588 "' (at offset '" + Twine(FragmentOffset) + "')");
592 case MCFragment::FT_Dwarf:
593 return cast<MCDwarfLineAddrFragment>(F).getContents().size();
594 case MCFragment::FT_DwarfFrame:
595 return cast<MCDwarfCallFrameFragment>(F).getContents().size();
598 llvm_unreachable("invalid fragment kind");
601 void MCAsmLayout::layoutFragment(MCFragment *F) {
602 MCFragment *Prev = F->getPrevNode();
604 // We should never try to recompute something which is valid.
605 assert(!isFragmentValid(F) && "Attempt to recompute a valid fragment!");
606 // We should never try to compute the fragment layout if its predecessor
608 assert((!Prev || isFragmentValid(Prev)) &&
609 "Attempt to compute fragment before its predecessor!");
611 ++stats::FragmentLayouts;
613 // Compute fragment offset and size.
615 F->Offset = Prev->Offset + getAssembler().computeFragmentSize(*this, *Prev);
618 LastValidFragment[F->getParent()] = F;
620 // If bundling is enabled and this fragment has instructions in it, it has to
621 // obey the bundling restrictions. With padding, we'll have:
626 // -------------------------------------
627 // Prev |##########| F |
628 // -------------------------------------
633 // The fragment's offset will point to after the padding, and its computed
634 // size won't include the padding.
636 if (Assembler.isBundlingEnabled() && F->hasInstructions()) {
637 assert(isa<MCEncodedFragment>(F) &&
638 "Only MCEncodedFragment implementations have instructions");
639 uint64_t FSize = Assembler.computeFragmentSize(*this, *F);
641 if (FSize > Assembler.getBundleAlignSize())
642 report_fatal_error("Fragment can't be larger than a bundle size");
644 uint64_t RequiredBundlePadding = computeBundlePadding(F, F->Offset, FSize);
645 if (RequiredBundlePadding > UINT8_MAX)
646 report_fatal_error("Padding cannot exceed 255 bytes");
647 F->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
648 F->Offset += RequiredBundlePadding;
652 /// \brief Write the contents of a fragment to the given object writer. Expects
653 /// a MCEncodedFragment.
654 static void writeFragmentContents(const MCFragment &F, MCObjectWriter *OW) {
655 const MCEncodedFragment &EF = cast<MCEncodedFragment>(F);
656 OW->WriteBytes(EF.getContents());
659 /// \brief Write the fragment \p F to the output file.
660 static void writeFragment(const MCAssembler &Asm, const MCAsmLayout &Layout,
661 const MCFragment &F) {
662 MCObjectWriter *OW = &Asm.getWriter();
664 // FIXME: Embed in fragments instead?
665 uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F);
667 // Should NOP padding be written out before this fragment?
668 unsigned BundlePadding = F.getBundlePadding();
669 if (BundlePadding > 0) {
670 assert(Asm.isBundlingEnabled() &&
671 "Writing bundle padding with disabled bundling");
672 assert(F.hasInstructions() &&
673 "Writing bundle padding for a fragment without instructions");
675 unsigned TotalLength = BundlePadding + static_cast<unsigned>(FragmentSize);
676 if (F.alignToBundleEnd() && TotalLength > Asm.getBundleAlignSize()) {
677 // If the padding itself crosses a bundle boundary, it must be emitted
678 // in 2 pieces, since even nop instructions must not cross boundaries.
679 // v--------------v <- BundleAlignSize
680 // v---------v <- BundlePadding
681 // ----------------------------
682 // | Prev |####|####| F |
683 // ----------------------------
684 // ^-------------------^ <- TotalLength
685 unsigned DistanceToBoundary = TotalLength - Asm.getBundleAlignSize();
686 if (!Asm.getBackend().writeNopData(DistanceToBoundary, OW))
687 report_fatal_error("unable to write NOP sequence of " +
688 Twine(DistanceToBoundary) + " bytes");
689 BundlePadding -= DistanceToBoundary;
691 if (!Asm.getBackend().writeNopData(BundlePadding, OW))
692 report_fatal_error("unable to write NOP sequence of " +
693 Twine(BundlePadding) + " bytes");
696 // This variable (and its dummy usage) is to participate in the assert at
697 // the end of the function.
698 uint64_t Start = OW->getStream().tell();
701 ++stats::EmittedFragments;
703 switch (F.getKind()) {
704 case MCFragment::FT_Align: {
705 ++stats::EmittedAlignFragments;
706 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
707 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
709 uint64_t Count = FragmentSize / AF.getValueSize();
711 // FIXME: This error shouldn't actually occur (the front end should emit
712 // multiple .align directives to enforce the semantics it wants), but is
713 // severe enough that we want to report it. How to handle this?
714 if (Count * AF.getValueSize() != FragmentSize)
715 report_fatal_error("undefined .align directive, value size '" +
716 Twine(AF.getValueSize()) +
717 "' is not a divisor of padding size '" +
718 Twine(FragmentSize) + "'");
720 // See if we are aligning with nops, and if so do that first to try to fill
721 // the Count bytes. Then if that did not fill any bytes or there are any
722 // bytes left to fill use the Value and ValueSize to fill the rest.
723 // If we are aligning with nops, ask that target to emit the right data.
724 if (AF.hasEmitNops()) {
725 if (!Asm.getBackend().writeNopData(Count, OW))
726 report_fatal_error("unable to write nop sequence of " +
727 Twine(Count) + " bytes");
731 // Otherwise, write out in multiples of the value size.
732 for (uint64_t i = 0; i != Count; ++i) {
733 switch (AF.getValueSize()) {
734 default: llvm_unreachable("Invalid size!");
735 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
736 case 2: OW->Write16(uint16_t(AF.getValue())); break;
737 case 4: OW->Write32(uint32_t(AF.getValue())); break;
738 case 8: OW->Write64(uint64_t(AF.getValue())); break;
744 case MCFragment::FT_Data:
745 ++stats::EmittedDataFragments;
746 writeFragmentContents(F, OW);
749 case MCFragment::FT_Relaxable:
750 ++stats::EmittedRelaxableFragments;
751 writeFragmentContents(F, OW);
754 case MCFragment::FT_CompactEncodedInst:
755 ++stats::EmittedCompactEncodedInstFragments;
756 writeFragmentContents(F, OW);
759 case MCFragment::FT_Fill: {
760 ++stats::EmittedFillFragments;
761 const MCFillFragment &FF = cast<MCFillFragment>(F);
763 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
765 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
766 switch (FF.getValueSize()) {
767 default: llvm_unreachable("Invalid size!");
768 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
769 case 2: OW->Write16(uint16_t(FF.getValue())); break;
770 case 4: OW->Write32(uint32_t(FF.getValue())); break;
771 case 8: OW->Write64(uint64_t(FF.getValue())); break;
777 case MCFragment::FT_LEB: {
778 const MCLEBFragment &LF = cast<MCLEBFragment>(F);
779 OW->WriteBytes(LF.getContents());
783 case MCFragment::FT_Org: {
784 ++stats::EmittedOrgFragments;
785 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
787 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
788 OW->Write8(uint8_t(OF.getValue()));
793 case MCFragment::FT_Dwarf: {
794 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
795 OW->WriteBytes(OF.getContents());
798 case MCFragment::FT_DwarfFrame: {
799 const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F);
800 OW->WriteBytes(CF.getContents());
805 assert(OW->getStream().tell() - Start == FragmentSize &&
806 "The stream should advance by fragment size");
809 void MCAssembler::writeSectionData(const MCSectionData *SD,
810 const MCAsmLayout &Layout) const {
811 // Ignore virtual sections.
812 if (SD->getSection().isVirtualSection()) {
813 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
815 // Check that contents are only things legal inside a virtual section.
816 for (MCSectionData::const_iterator it = SD->begin(),
817 ie = SD->end(); it != ie; ++it) {
818 switch (it->getKind()) {
819 default: llvm_unreachable("Invalid fragment in virtual section!");
820 case MCFragment::FT_Data: {
821 // Check that we aren't trying to write a non-zero contents (or fixups)
822 // into a virtual section. This is to support clients which use standard
823 // directives to fill the contents of virtual sections.
824 const MCDataFragment &DF = cast<MCDataFragment>(*it);
825 assert(DF.fixup_begin() == DF.fixup_end() &&
826 "Cannot have fixups in virtual section!");
827 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
828 if (DF.getContents()[i]) {
829 if (auto *ELFSec = dyn_cast<const MCSectionELF>(&SD->getSection()))
830 report_fatal_error("non-zero initializer found in section '" +
831 ELFSec->getSectionName() + "'");
833 report_fatal_error("non-zero initializer found in virtual section");
837 case MCFragment::FT_Align:
838 // Check that we aren't trying to write a non-zero value into a virtual
840 assert((cast<MCAlignFragment>(it)->getValueSize() == 0 ||
841 cast<MCAlignFragment>(it)->getValue() == 0) &&
842 "Invalid align in virtual section!");
844 case MCFragment::FT_Fill:
845 assert((cast<MCFillFragment>(it)->getValueSize() == 0 ||
846 cast<MCFillFragment>(it)->getValue() == 0) &&
847 "Invalid fill in virtual section!");
855 uint64_t Start = getWriter().getStream().tell();
858 for (MCSectionData::const_iterator it = SD->begin(), ie = SD->end();
860 writeFragment(*this, Layout, *it);
862 assert(getWriter().getStream().tell() - Start ==
863 Layout.getSectionAddressSize(SD));
866 std::pair<uint64_t, bool> MCAssembler::handleFixup(const MCAsmLayout &Layout,
868 const MCFixup &Fixup) {
869 // Evaluate the fixup.
872 bool IsPCRel = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
873 MCFixupKindInfo::FKF_IsPCRel;
874 if (!evaluateFixup(Layout, Fixup, &F, Target, FixedValue)) {
875 // The fixup was unresolved, we need a relocation. Inform the object
876 // writer of the relocation, and give it an opportunity to adjust the
877 // fixup value if need be.
878 getWriter().RecordRelocation(*this, Layout, &F, Fixup, Target, IsPCRel,
881 return std::make_pair(FixedValue, IsPCRel);
884 void MCAssembler::Finish() {
885 DEBUG_WITH_TYPE("mc-dump", {
886 llvm::errs() << "assembler backend - pre-layout\n--\n";
889 // Create the layout object.
890 MCAsmLayout Layout(*this);
892 // Create dummy fragments and assign section ordinals.
893 unsigned SectionIndex = 0;
894 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
895 // Create dummy fragments to eliminate any empty sections, this simplifies
897 if (it->getFragmentList().empty())
898 new MCDataFragment(it);
900 it->setOrdinal(SectionIndex++);
903 // Assign layout order indices to sections and fragments.
904 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
905 MCSectionData *SD = Layout.getSectionOrder()[i];
906 SD->setLayoutOrder(i);
908 unsigned FragmentIndex = 0;
909 for (MCSectionData::iterator iFrag = SD->begin(), iFragEnd = SD->end();
910 iFrag != iFragEnd; ++iFrag)
911 iFrag->setLayoutOrder(FragmentIndex++);
914 // Layout until everything fits.
915 while (layoutOnce(Layout))
918 DEBUG_WITH_TYPE("mc-dump", {
919 llvm::errs() << "assembler backend - post-relaxation\n--\n";
922 // Finalize the layout, including fragment lowering.
923 finishLayout(Layout);
925 DEBUG_WITH_TYPE("mc-dump", {
926 llvm::errs() << "assembler backend - final-layout\n--\n";
929 uint64_t StartOffset = OS.tell();
931 // Allow the object writer a chance to perform post-layout binding (for
932 // example, to set the index fields in the symbol data).
933 getWriter().ExecutePostLayoutBinding(*this, Layout);
935 // Evaluate and apply the fixups, generating relocation entries as necessary.
936 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
937 for (MCSectionData::iterator it2 = it->begin(),
938 ie2 = it->end(); it2 != ie2; ++it2) {
939 MCEncodedFragmentWithFixups *F =
940 dyn_cast<MCEncodedFragmentWithFixups>(it2);
942 for (MCEncodedFragmentWithFixups::fixup_iterator it3 = F->fixup_begin(),
943 ie3 = F->fixup_end(); it3 != ie3; ++it3) {
944 MCFixup &Fixup = *it3;
947 std::tie(FixedValue, IsPCRel) = handleFixup(Layout, *F, Fixup);
948 getBackend().applyFixup(Fixup, F->getContents().data(),
949 F->getContents().size(), FixedValue, IsPCRel);
955 // Write the object file.
956 getWriter().WriteObject(*this, Layout);
958 stats::ObjectBytes += OS.tell() - StartOffset;
961 bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup,
962 const MCRelaxableFragment *DF,
963 const MCAsmLayout &Layout) const {
964 // If we cannot resolve the fixup value, it requires relaxation.
967 if (!evaluateFixup(Layout, Fixup, DF, Target, Value))
970 return getBackend().fixupNeedsRelaxation(Fixup, Value, DF, Layout);
973 bool MCAssembler::fragmentNeedsRelaxation(const MCRelaxableFragment *F,
974 const MCAsmLayout &Layout) const {
975 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
976 // are intentionally pushing out inst fragments, or because we relaxed a
977 // previous instruction to one that doesn't need relaxation.
978 if (!getBackend().mayNeedRelaxation(F->getInst()))
981 for (MCRelaxableFragment::const_fixup_iterator it = F->fixup_begin(),
982 ie = F->fixup_end(); it != ie; ++it)
983 if (fixupNeedsRelaxation(*it, F, Layout))
989 bool MCAssembler::relaxInstruction(MCAsmLayout &Layout,
990 MCRelaxableFragment &F) {
991 if (!fragmentNeedsRelaxation(&F, Layout))
994 ++stats::RelaxedInstructions;
996 // FIXME-PERF: We could immediately lower out instructions if we can tell
997 // they are fully resolved, to avoid retesting on later passes.
999 // Relax the fragment.
1002 getBackend().relaxInstruction(F.getInst(), Relaxed);
1004 // Encode the new instruction.
1006 // FIXME-PERF: If it matters, we could let the target do this. It can
1007 // probably do so more efficiently in many cases.
1008 SmallVector<MCFixup, 4> Fixups;
1009 SmallString<256> Code;
1010 raw_svector_ostream VecOS(Code);
1011 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups, F.getSubtargetInfo());
1014 // Update the fragment.
1016 F.getContents() = Code;
1017 F.getFixups() = Fixups;
1022 bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) {
1023 uint64_t OldSize = LF.getContents().size();
1025 bool Abs = LF.getValue().evaluateKnownAbsolute(Value, Layout);
1027 report_fatal_error("sleb128 and uleb128 expressions must be absolute");
1028 SmallString<8> &Data = LF.getContents();
1030 raw_svector_ostream OSE(Data);
1032 encodeSLEB128(Value, OSE);
1034 encodeULEB128(Value, OSE);
1036 return OldSize != LF.getContents().size();
1039 bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout,
1040 MCDwarfLineAddrFragment &DF) {
1041 MCContext &Context = Layout.getAssembler().getContext();
1042 uint64_t OldSize = DF.getContents().size();
1044 bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
1045 assert(Abs && "We created a line delta with an invalid expression");
1048 LineDelta = DF.getLineDelta();
1049 SmallString<8> &Data = DF.getContents();
1051 raw_svector_ostream OSE(Data);
1052 MCDwarfLineAddr::Encode(Context, LineDelta, AddrDelta, OSE);
1054 return OldSize != Data.size();
1057 bool MCAssembler::relaxDwarfCallFrameFragment(MCAsmLayout &Layout,
1058 MCDwarfCallFrameFragment &DF) {
1059 MCContext &Context = Layout.getAssembler().getContext();
1060 uint64_t OldSize = DF.getContents().size();
1062 bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
1063 assert(Abs && "We created call frame with an invalid expression");
1065 SmallString<8> &Data = DF.getContents();
1067 raw_svector_ostream OSE(Data);
1068 MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE);
1070 return OldSize != Data.size();
1073 bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSectionData &SD) {
1074 // Holds the first fragment which needed relaxing during this layout. It will
1075 // remain NULL if none were relaxed.
1076 // When a fragment is relaxed, all the fragments following it should get
1077 // invalidated because their offset is going to change.
1078 MCFragment *FirstRelaxedFragment = nullptr;
1080 // Attempt to relax all the fragments in the section.
1081 for (MCSectionData::iterator I = SD.begin(), IE = SD.end(); I != IE; ++I) {
1082 // Check if this is a fragment that needs relaxation.
1083 bool RelaxedFrag = false;
1084 switch(I->getKind()) {
1087 case MCFragment::FT_Relaxable:
1088 assert(!getRelaxAll() &&
1089 "Did not expect a MCRelaxableFragment in RelaxAll mode");
1090 RelaxedFrag = relaxInstruction(Layout, *cast<MCRelaxableFragment>(I));
1092 case MCFragment::FT_Dwarf:
1093 RelaxedFrag = relaxDwarfLineAddr(Layout,
1094 *cast<MCDwarfLineAddrFragment>(I));
1096 case MCFragment::FT_DwarfFrame:
1098 relaxDwarfCallFrameFragment(Layout,
1099 *cast<MCDwarfCallFrameFragment>(I));
1101 case MCFragment::FT_LEB:
1102 RelaxedFrag = relaxLEB(Layout, *cast<MCLEBFragment>(I));
1105 if (RelaxedFrag && !FirstRelaxedFragment)
1106 FirstRelaxedFragment = I;
1108 if (FirstRelaxedFragment) {
1109 Layout.invalidateFragmentsFrom(FirstRelaxedFragment);
1115 bool MCAssembler::layoutOnce(MCAsmLayout &Layout) {
1116 ++stats::RelaxationSteps;
1118 bool WasRelaxed = false;
1119 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1120 MCSectionData &SD = *it;
1121 while (layoutSectionOnce(Layout, SD))
1128 void MCAssembler::finishLayout(MCAsmLayout &Layout) {
1129 // The layout is done. Mark every fragment as valid.
1130 for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) {
1131 Layout.getFragmentOffset(&*Layout.getSectionOrder()[i]->rbegin());
1135 // Debugging methods
1139 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
1140 OS << "<MCFixup" << " Offset:" << AF.getOffset()
1141 << " Value:" << *AF.getValue()
1142 << " Kind:" << AF.getKind() << ">";
1148 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1149 void MCFragment::dump() {
1150 raw_ostream &OS = llvm::errs();
1153 switch (getKind()) {
1154 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
1155 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
1156 case MCFragment::FT_CompactEncodedInst:
1157 OS << "MCCompactEncodedInstFragment"; break;
1158 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
1159 case MCFragment::FT_Relaxable: OS << "MCRelaxableFragment"; break;
1160 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
1161 case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
1162 case MCFragment::FT_DwarfFrame: OS << "MCDwarfCallFrameFragment"; break;
1163 case MCFragment::FT_LEB: OS << "MCLEBFragment"; break;
1166 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
1167 << " Offset:" << Offset
1168 << " HasInstructions:" << hasInstructions()
1169 << " BundlePadding:" << static_cast<unsigned>(getBundlePadding()) << ">";
1171 switch (getKind()) {
1172 case MCFragment::FT_Align: {
1173 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
1174 if (AF->hasEmitNops())
1175 OS << " (emit nops)";
1177 OS << " Alignment:" << AF->getAlignment()
1178 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
1179 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
1182 case MCFragment::FT_Data: {
1183 const MCDataFragment *DF = cast<MCDataFragment>(this);
1185 OS << " Contents:[";
1186 const SmallVectorImpl<char> &Contents = DF->getContents();
1187 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
1189 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1191 OS << "] (" << Contents.size() << " bytes)";
1193 if (DF->fixup_begin() != DF->fixup_end()) {
1196 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
1197 ie = DF->fixup_end(); it != ie; ++it) {
1198 if (it != DF->fixup_begin()) OS << ",\n ";
1205 case MCFragment::FT_CompactEncodedInst: {
1206 const MCCompactEncodedInstFragment *CEIF =
1207 cast<MCCompactEncodedInstFragment>(this);
1209 OS << " Contents:[";
1210 const SmallVectorImpl<char> &Contents = CEIF->getContents();
1211 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
1213 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1215 OS << "] (" << Contents.size() << " bytes)";
1218 case MCFragment::FT_Fill: {
1219 const MCFillFragment *FF = cast<MCFillFragment>(this);
1220 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
1221 << " Size:" << FF->getSize();
1224 case MCFragment::FT_Relaxable: {
1225 const MCRelaxableFragment *F = cast<MCRelaxableFragment>(this);
1228 F->getInst().dump_pretty(OS);
1231 case MCFragment::FT_Org: {
1232 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
1234 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
1237 case MCFragment::FT_Dwarf: {
1238 const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
1240 OS << " AddrDelta:" << OF->getAddrDelta()
1241 << " LineDelta:" << OF->getLineDelta();
1244 case MCFragment::FT_DwarfFrame: {
1245 const MCDwarfCallFrameFragment *CF = cast<MCDwarfCallFrameFragment>(this);
1247 OS << " AddrDelta:" << CF->getAddrDelta();
1250 case MCFragment::FT_LEB: {
1251 const MCLEBFragment *LF = cast<MCLEBFragment>(this);
1253 OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
1260 void MCSectionData::dump() {
1261 raw_ostream &OS = llvm::errs();
1263 OS << "<MCSectionData";
1264 OS << " Alignment:" << getAlignment()
1265 << " Fragments:[\n ";
1266 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1267 if (it != begin()) OS << ",\n ";
1273 void MCSymbolData::dump() const {
1274 raw_ostream &OS = llvm::errs();
1276 OS << "<MCSymbolData Symbol:" << getSymbol()
1277 << " Fragment:" << getFragment();
1279 OS << " Offset:" << getOffset();
1280 OS << " Flags:" << getFlags() << " Index:" << getIndex();
1282 OS << " (common, size:" << getCommonSize()
1283 << " align: " << getCommonAlignment() << ")";
1285 OS << " (external)";
1286 if (isPrivateExtern())
1287 OS << " (private extern)";
1291 void MCAssembler::dump() {
1292 raw_ostream &OS = llvm::errs();
1294 OS << "<MCAssembler\n";
1295 OS << " Sections:[\n ";
1296 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1297 if (it != begin()) OS << ",\n ";
1303 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1304 if (it != symbol_begin()) OS << ",\n ";
1311 // anchors for MC*Fragment vtables
1312 void MCEncodedFragment::anchor() { }
1313 void MCEncodedFragmentWithFixups::anchor() { }
1314 void MCDataFragment::anchor() { }
1315 void MCCompactEncodedInstFragment::anchor() { }
1316 void MCRelaxableFragment::anchor() { }
1317 void MCAlignFragment::anchor() { }
1318 void MCFillFragment::anchor() { }
1319 void MCOrgFragment::anchor() { }
1320 void MCLEBFragment::anchor() { }
1321 void MCDwarfLineAddrFragment::anchor() { }
1322 void MCDwarfCallFrameFragment::anchor() { }