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 || SA.isUndefined()) {
503 const MCSymbolData &DataA = getSymbolData(SA);
504 IsResolved = getWriter().IsSymbolRefDifferenceFullyResolvedImpl(
505 *this, DataA, nullptr, *DF, false, true);
509 IsResolved = Target.isAbsolute();
512 Value = Target.getConstant();
514 if (const MCSymbolRefExpr *A = Target.getSymA()) {
515 const MCSymbol &Sym = A->getSymbol();
517 Value += Layout.getSymbolOffset(&getSymbolData(Sym));
519 if (const MCSymbolRefExpr *B = Target.getSymB()) {
520 const MCSymbol &Sym = B->getSymbol();
522 Value -= Layout.getSymbolOffset(&getSymbolData(Sym));
526 bool ShouldAlignPC = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
527 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits;
528 assert((ShouldAlignPC ? IsPCRel : true) &&
529 "FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!");
532 uint32_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset();
534 // A number of ARM fixups in Thumb mode require that the effective PC
535 // address be determined as the 32-bit aligned version of the actual offset.
536 if (ShouldAlignPC) Offset &= ~0x3;
540 // Let the backend adjust the fixup value if necessary, including whether
541 // we need a relocation.
542 Backend.processFixupValue(*this, Layout, Fixup, DF, Target, Value,
548 uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
549 const MCFragment &F) const {
550 switch (F.getKind()) {
551 case MCFragment::FT_Data:
552 case MCFragment::FT_Relaxable:
553 case MCFragment::FT_CompactEncodedInst:
554 return cast<MCEncodedFragment>(F).getContents().size();
555 case MCFragment::FT_Fill:
556 return cast<MCFillFragment>(F).getSize();
558 case MCFragment::FT_LEB:
559 return cast<MCLEBFragment>(F).getContents().size();
561 case MCFragment::FT_Align: {
562 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
563 unsigned Offset = Layout.getFragmentOffset(&AF);
564 unsigned Size = OffsetToAlignment(Offset, AF.getAlignment());
565 // If we are padding with nops, force the padding to be larger than the
567 if (Size > 0 && AF.hasEmitNops()) {
568 while (Size % getBackend().getMinimumNopSize())
569 Size += AF.getAlignment();
571 if (Size > AF.getMaxBytesToEmit())
576 case MCFragment::FT_Org: {
577 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
578 int64_t TargetLocation;
579 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, Layout))
580 report_fatal_error("expected assembly-time absolute expression");
582 // FIXME: We need a way to communicate this error.
583 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
584 int64_t Size = TargetLocation - FragmentOffset;
585 if (Size < 0 || Size >= 0x40000000)
586 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
587 "' (at offset '" + Twine(FragmentOffset) + "')");
591 case MCFragment::FT_Dwarf:
592 return cast<MCDwarfLineAddrFragment>(F).getContents().size();
593 case MCFragment::FT_DwarfFrame:
594 return cast<MCDwarfCallFrameFragment>(F).getContents().size();
597 llvm_unreachable("invalid fragment kind");
600 void MCAsmLayout::layoutFragment(MCFragment *F) {
601 MCFragment *Prev = F->getPrevNode();
603 // We should never try to recompute something which is valid.
604 assert(!isFragmentValid(F) && "Attempt to recompute a valid fragment!");
605 // We should never try to compute the fragment layout if its predecessor
607 assert((!Prev || isFragmentValid(Prev)) &&
608 "Attempt to compute fragment before its predecessor!");
610 ++stats::FragmentLayouts;
612 // Compute fragment offset and size.
614 F->Offset = Prev->Offset + getAssembler().computeFragmentSize(*this, *Prev);
617 LastValidFragment[F->getParent()] = F;
619 // If bundling is enabled and this fragment has instructions in it, it has to
620 // obey the bundling restrictions. With padding, we'll have:
625 // -------------------------------------
626 // Prev |##########| F |
627 // -------------------------------------
632 // The fragment's offset will point to after the padding, and its computed
633 // size won't include the padding.
635 if (Assembler.isBundlingEnabled() && F->hasInstructions()) {
636 assert(isa<MCEncodedFragment>(F) &&
637 "Only MCEncodedFragment implementations have instructions");
638 uint64_t FSize = Assembler.computeFragmentSize(*this, *F);
640 if (FSize > Assembler.getBundleAlignSize())
641 report_fatal_error("Fragment can't be larger than a bundle size");
643 uint64_t RequiredBundlePadding = computeBundlePadding(F, F->Offset, FSize);
644 if (RequiredBundlePadding > UINT8_MAX)
645 report_fatal_error("Padding cannot exceed 255 bytes");
646 F->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
647 F->Offset += RequiredBundlePadding;
651 /// \brief Write the contents of a fragment to the given object writer. Expects
652 /// a MCEncodedFragment.
653 static void writeFragmentContents(const MCFragment &F, MCObjectWriter *OW) {
654 const MCEncodedFragment &EF = cast<MCEncodedFragment>(F);
655 OW->WriteBytes(EF.getContents());
658 /// \brief Write the fragment \p F to the output file.
659 static void writeFragment(const MCAssembler &Asm, const MCAsmLayout &Layout,
660 const MCFragment &F) {
661 MCObjectWriter *OW = &Asm.getWriter();
663 // FIXME: Embed in fragments instead?
664 uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F);
666 // Should NOP padding be written out before this fragment?
667 unsigned BundlePadding = F.getBundlePadding();
668 if (BundlePadding > 0) {
669 assert(Asm.isBundlingEnabled() &&
670 "Writing bundle padding with disabled bundling");
671 assert(F.hasInstructions() &&
672 "Writing bundle padding for a fragment without instructions");
674 unsigned TotalLength = BundlePadding + static_cast<unsigned>(FragmentSize);
675 if (F.alignToBundleEnd() && TotalLength > Asm.getBundleAlignSize()) {
676 // If the padding itself crosses a bundle boundary, it must be emitted
677 // in 2 pieces, since even nop instructions must not cross boundaries.
678 // v--------------v <- BundleAlignSize
679 // v---------v <- BundlePadding
680 // ----------------------------
681 // | Prev |####|####| F |
682 // ----------------------------
683 // ^-------------------^ <- TotalLength
684 unsigned DistanceToBoundary = TotalLength - Asm.getBundleAlignSize();
685 if (!Asm.getBackend().writeNopData(DistanceToBoundary, OW))
686 report_fatal_error("unable to write NOP sequence of " +
687 Twine(DistanceToBoundary) + " bytes");
688 BundlePadding -= DistanceToBoundary;
690 if (!Asm.getBackend().writeNopData(BundlePadding, OW))
691 report_fatal_error("unable to write NOP sequence of " +
692 Twine(BundlePadding) + " bytes");
695 // This variable (and its dummy usage) is to participate in the assert at
696 // the end of the function.
697 uint64_t Start = OW->getStream().tell();
700 ++stats::EmittedFragments;
702 switch (F.getKind()) {
703 case MCFragment::FT_Align: {
704 ++stats::EmittedAlignFragments;
705 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
706 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
708 uint64_t Count = FragmentSize / AF.getValueSize();
710 // FIXME: This error shouldn't actually occur (the front end should emit
711 // multiple .align directives to enforce the semantics it wants), but is
712 // severe enough that we want to report it. How to handle this?
713 if (Count * AF.getValueSize() != FragmentSize)
714 report_fatal_error("undefined .align directive, value size '" +
715 Twine(AF.getValueSize()) +
716 "' is not a divisor of padding size '" +
717 Twine(FragmentSize) + "'");
719 // See if we are aligning with nops, and if so do that first to try to fill
720 // the Count bytes. Then if that did not fill any bytes or there are any
721 // bytes left to fill use the Value and ValueSize to fill the rest.
722 // If we are aligning with nops, ask that target to emit the right data.
723 if (AF.hasEmitNops()) {
724 if (!Asm.getBackend().writeNopData(Count, OW))
725 report_fatal_error("unable to write nop sequence of " +
726 Twine(Count) + " bytes");
730 // Otherwise, write out in multiples of the value size.
731 for (uint64_t i = 0; i != Count; ++i) {
732 switch (AF.getValueSize()) {
733 default: llvm_unreachable("Invalid size!");
734 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
735 case 2: OW->Write16(uint16_t(AF.getValue())); break;
736 case 4: OW->Write32(uint32_t(AF.getValue())); break;
737 case 8: OW->Write64(uint64_t(AF.getValue())); break;
743 case MCFragment::FT_Data:
744 ++stats::EmittedDataFragments;
745 writeFragmentContents(F, OW);
748 case MCFragment::FT_Relaxable:
749 ++stats::EmittedRelaxableFragments;
750 writeFragmentContents(F, OW);
753 case MCFragment::FT_CompactEncodedInst:
754 ++stats::EmittedCompactEncodedInstFragments;
755 writeFragmentContents(F, OW);
758 case MCFragment::FT_Fill: {
759 ++stats::EmittedFillFragments;
760 const MCFillFragment &FF = cast<MCFillFragment>(F);
762 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
764 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
765 switch (FF.getValueSize()) {
766 default: llvm_unreachable("Invalid size!");
767 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
768 case 2: OW->Write16(uint16_t(FF.getValue())); break;
769 case 4: OW->Write32(uint32_t(FF.getValue())); break;
770 case 8: OW->Write64(uint64_t(FF.getValue())); break;
776 case MCFragment::FT_LEB: {
777 const MCLEBFragment &LF = cast<MCLEBFragment>(F);
778 OW->WriteBytes(LF.getContents());
782 case MCFragment::FT_Org: {
783 ++stats::EmittedOrgFragments;
784 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
786 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
787 OW->Write8(uint8_t(OF.getValue()));
792 case MCFragment::FT_Dwarf: {
793 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
794 OW->WriteBytes(OF.getContents());
797 case MCFragment::FT_DwarfFrame: {
798 const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F);
799 OW->WriteBytes(CF.getContents());
804 assert(OW->getStream().tell() - Start == FragmentSize &&
805 "The stream should advance by fragment size");
808 void MCAssembler::writeSectionData(const MCSectionData *SD,
809 const MCAsmLayout &Layout) const {
810 // Ignore virtual sections.
811 if (SD->getSection().isVirtualSection()) {
812 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
814 // Check that contents are only things legal inside a virtual section.
815 for (MCSectionData::const_iterator it = SD->begin(),
816 ie = SD->end(); it != ie; ++it) {
817 switch (it->getKind()) {
818 default: llvm_unreachable("Invalid fragment in virtual section!");
819 case MCFragment::FT_Data: {
820 // Check that we aren't trying to write a non-zero contents (or fixups)
821 // into a virtual section. This is to support clients which use standard
822 // directives to fill the contents of virtual sections.
823 const MCDataFragment &DF = cast<MCDataFragment>(*it);
824 assert(DF.fixup_begin() == DF.fixup_end() &&
825 "Cannot have fixups in virtual section!");
826 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
827 if (DF.getContents()[i]) {
828 if (auto *ELFSec = dyn_cast<const MCSectionELF>(&SD->getSection()))
829 report_fatal_error("non-zero initializer found in section '" +
830 ELFSec->getSectionName() + "'");
832 report_fatal_error("non-zero initializer found in virtual section");
836 case MCFragment::FT_Align:
837 // Check that we aren't trying to write a non-zero value into a virtual
839 assert((cast<MCAlignFragment>(it)->getValueSize() == 0 ||
840 cast<MCAlignFragment>(it)->getValue() == 0) &&
841 "Invalid align in virtual section!");
843 case MCFragment::FT_Fill:
844 assert((cast<MCFillFragment>(it)->getValueSize() == 0 ||
845 cast<MCFillFragment>(it)->getValue() == 0) &&
846 "Invalid fill in virtual section!");
854 uint64_t Start = getWriter().getStream().tell();
857 for (MCSectionData::const_iterator it = SD->begin(), ie = SD->end();
859 writeFragment(*this, Layout, *it);
861 assert(getWriter().getStream().tell() - Start ==
862 Layout.getSectionAddressSize(SD));
865 std::pair<uint64_t, bool> MCAssembler::handleFixup(const MCAsmLayout &Layout,
867 const MCFixup &Fixup) {
868 // Evaluate the fixup.
871 bool IsPCRel = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
872 MCFixupKindInfo::FKF_IsPCRel;
873 if (!evaluateFixup(Layout, Fixup, &F, Target, FixedValue)) {
874 // The fixup was unresolved, we need a relocation. Inform the object
875 // writer of the relocation, and give it an opportunity to adjust the
876 // fixup value if need be.
877 getWriter().RecordRelocation(*this, Layout, &F, Fixup, Target, IsPCRel,
880 return std::make_pair(FixedValue, IsPCRel);
883 void MCAssembler::Finish() {
884 DEBUG_WITH_TYPE("mc-dump", {
885 llvm::errs() << "assembler backend - pre-layout\n--\n";
888 // Create the layout object.
889 MCAsmLayout Layout(*this);
891 // Create dummy fragments and assign section ordinals.
892 unsigned SectionIndex = 0;
893 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
894 // Create dummy fragments to eliminate any empty sections, this simplifies
896 if (it->getFragmentList().empty())
897 new MCDataFragment(it);
899 it->setOrdinal(SectionIndex++);
902 // Assign layout order indices to sections and fragments.
903 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
904 MCSectionData *SD = Layout.getSectionOrder()[i];
905 SD->setLayoutOrder(i);
907 unsigned FragmentIndex = 0;
908 for (MCSectionData::iterator iFrag = SD->begin(), iFragEnd = SD->end();
909 iFrag != iFragEnd; ++iFrag)
910 iFrag->setLayoutOrder(FragmentIndex++);
913 // Layout until everything fits.
914 while (layoutOnce(Layout))
917 DEBUG_WITH_TYPE("mc-dump", {
918 llvm::errs() << "assembler backend - post-relaxation\n--\n";
921 // Finalize the layout, including fragment lowering.
922 finishLayout(Layout);
924 DEBUG_WITH_TYPE("mc-dump", {
925 llvm::errs() << "assembler backend - final-layout\n--\n";
928 uint64_t StartOffset = OS.tell();
930 // Allow the object writer a chance to perform post-layout binding (for
931 // example, to set the index fields in the symbol data).
932 getWriter().ExecutePostLayoutBinding(*this, Layout);
934 // Evaluate and apply the fixups, generating relocation entries as necessary.
935 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
936 for (MCSectionData::iterator it2 = it->begin(),
937 ie2 = it->end(); it2 != ie2; ++it2) {
938 MCEncodedFragmentWithFixups *F =
939 dyn_cast<MCEncodedFragmentWithFixups>(it2);
941 for (MCEncodedFragmentWithFixups::fixup_iterator it3 = F->fixup_begin(),
942 ie3 = F->fixup_end(); it3 != ie3; ++it3) {
943 MCFixup &Fixup = *it3;
946 std::tie(FixedValue, IsPCRel) = handleFixup(Layout, *F, Fixup);
947 getBackend().applyFixup(Fixup, F->getContents().data(),
948 F->getContents().size(), FixedValue, IsPCRel);
954 // Write the object file.
955 getWriter().WriteObject(*this, Layout);
957 stats::ObjectBytes += OS.tell() - StartOffset;
960 bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup,
961 const MCRelaxableFragment *DF,
962 const MCAsmLayout &Layout) const {
963 // If we cannot resolve the fixup value, it requires relaxation.
966 if (!evaluateFixup(Layout, Fixup, DF, Target, Value))
969 return getBackend().fixupNeedsRelaxation(Fixup, Value, DF, Layout);
972 bool MCAssembler::fragmentNeedsRelaxation(const MCRelaxableFragment *F,
973 const MCAsmLayout &Layout) const {
974 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
975 // are intentionally pushing out inst fragments, or because we relaxed a
976 // previous instruction to one that doesn't need relaxation.
977 if (!getBackend().mayNeedRelaxation(F->getInst()))
980 for (MCRelaxableFragment::const_fixup_iterator it = F->fixup_begin(),
981 ie = F->fixup_end(); it != ie; ++it)
982 if (fixupNeedsRelaxation(*it, F, Layout))
988 bool MCAssembler::relaxInstruction(MCAsmLayout &Layout,
989 MCRelaxableFragment &F) {
990 if (!fragmentNeedsRelaxation(&F, Layout))
993 ++stats::RelaxedInstructions;
995 // FIXME-PERF: We could immediately lower out instructions if we can tell
996 // they are fully resolved, to avoid retesting on later passes.
998 // Relax the fragment.
1001 getBackend().relaxInstruction(F.getInst(), Relaxed);
1003 // Encode the new instruction.
1005 // FIXME-PERF: If it matters, we could let the target do this. It can
1006 // probably do so more efficiently in many cases.
1007 SmallVector<MCFixup, 4> Fixups;
1008 SmallString<256> Code;
1009 raw_svector_ostream VecOS(Code);
1010 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups, F.getSubtargetInfo());
1013 // Update the fragment.
1015 F.getContents() = Code;
1016 F.getFixups() = Fixups;
1021 bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) {
1022 uint64_t OldSize = LF.getContents().size();
1024 bool Abs = LF.getValue().evaluateKnownAbsolute(Value, Layout);
1026 report_fatal_error("sleb128 and uleb128 expressions must be absolute");
1027 SmallString<8> &Data = LF.getContents();
1029 raw_svector_ostream OSE(Data);
1031 encodeSLEB128(Value, OSE);
1033 encodeULEB128(Value, OSE);
1035 return OldSize != LF.getContents().size();
1038 bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout,
1039 MCDwarfLineAddrFragment &DF) {
1040 MCContext &Context = Layout.getAssembler().getContext();
1041 uint64_t OldSize = DF.getContents().size();
1043 bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
1044 assert(Abs && "We created a line delta with an invalid expression");
1047 LineDelta = DF.getLineDelta();
1048 SmallString<8> &Data = DF.getContents();
1050 raw_svector_ostream OSE(Data);
1051 MCDwarfLineAddr::Encode(Context, LineDelta, AddrDelta, OSE);
1053 return OldSize != Data.size();
1056 bool MCAssembler::relaxDwarfCallFrameFragment(MCAsmLayout &Layout,
1057 MCDwarfCallFrameFragment &DF) {
1058 MCContext &Context = Layout.getAssembler().getContext();
1059 uint64_t OldSize = DF.getContents().size();
1061 bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
1062 assert(Abs && "We created call frame with an invalid expression");
1064 SmallString<8> &Data = DF.getContents();
1066 raw_svector_ostream OSE(Data);
1067 MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE);
1069 return OldSize != Data.size();
1072 bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSectionData &SD) {
1073 // Holds the first fragment which needed relaxing during this layout. It will
1074 // remain NULL if none were relaxed.
1075 // When a fragment is relaxed, all the fragments following it should get
1076 // invalidated because their offset is going to change.
1077 MCFragment *FirstRelaxedFragment = nullptr;
1079 // Attempt to relax all the fragments in the section.
1080 for (MCSectionData::iterator I = SD.begin(), IE = SD.end(); I != IE; ++I) {
1081 // Check if this is a fragment that needs relaxation.
1082 bool RelaxedFrag = false;
1083 switch(I->getKind()) {
1086 case MCFragment::FT_Relaxable:
1087 assert(!getRelaxAll() &&
1088 "Did not expect a MCRelaxableFragment in RelaxAll mode");
1089 RelaxedFrag = relaxInstruction(Layout, *cast<MCRelaxableFragment>(I));
1091 case MCFragment::FT_Dwarf:
1092 RelaxedFrag = relaxDwarfLineAddr(Layout,
1093 *cast<MCDwarfLineAddrFragment>(I));
1095 case MCFragment::FT_DwarfFrame:
1097 relaxDwarfCallFrameFragment(Layout,
1098 *cast<MCDwarfCallFrameFragment>(I));
1100 case MCFragment::FT_LEB:
1101 RelaxedFrag = relaxLEB(Layout, *cast<MCLEBFragment>(I));
1104 if (RelaxedFrag && !FirstRelaxedFragment)
1105 FirstRelaxedFragment = I;
1107 if (FirstRelaxedFragment) {
1108 Layout.invalidateFragmentsFrom(FirstRelaxedFragment);
1114 bool MCAssembler::layoutOnce(MCAsmLayout &Layout) {
1115 ++stats::RelaxationSteps;
1117 bool WasRelaxed = false;
1118 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1119 MCSectionData &SD = *it;
1120 while (layoutSectionOnce(Layout, SD))
1127 void MCAssembler::finishLayout(MCAsmLayout &Layout) {
1128 // The layout is done. Mark every fragment as valid.
1129 for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) {
1130 Layout.getFragmentOffset(&*Layout.getSectionOrder()[i]->rbegin());
1134 // Debugging methods
1138 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
1139 OS << "<MCFixup" << " Offset:" << AF.getOffset()
1140 << " Value:" << *AF.getValue()
1141 << " Kind:" << AF.getKind() << ">";
1147 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1148 void MCFragment::dump() {
1149 raw_ostream &OS = llvm::errs();
1152 switch (getKind()) {
1153 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
1154 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
1155 case MCFragment::FT_CompactEncodedInst:
1156 OS << "MCCompactEncodedInstFragment"; break;
1157 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
1158 case MCFragment::FT_Relaxable: OS << "MCRelaxableFragment"; break;
1159 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
1160 case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
1161 case MCFragment::FT_DwarfFrame: OS << "MCDwarfCallFrameFragment"; break;
1162 case MCFragment::FT_LEB: OS << "MCLEBFragment"; break;
1165 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
1166 << " Offset:" << Offset
1167 << " HasInstructions:" << hasInstructions()
1168 << " BundlePadding:" << static_cast<unsigned>(getBundlePadding()) << ">";
1170 switch (getKind()) {
1171 case MCFragment::FT_Align: {
1172 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
1173 if (AF->hasEmitNops())
1174 OS << " (emit nops)";
1176 OS << " Alignment:" << AF->getAlignment()
1177 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
1178 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
1181 case MCFragment::FT_Data: {
1182 const MCDataFragment *DF = cast<MCDataFragment>(this);
1184 OS << " Contents:[";
1185 const SmallVectorImpl<char> &Contents = DF->getContents();
1186 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
1188 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1190 OS << "] (" << Contents.size() << " bytes)";
1192 if (DF->fixup_begin() != DF->fixup_end()) {
1195 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
1196 ie = DF->fixup_end(); it != ie; ++it) {
1197 if (it != DF->fixup_begin()) OS << ",\n ";
1204 case MCFragment::FT_CompactEncodedInst: {
1205 const MCCompactEncodedInstFragment *CEIF =
1206 cast<MCCompactEncodedInstFragment>(this);
1208 OS << " Contents:[";
1209 const SmallVectorImpl<char> &Contents = CEIF->getContents();
1210 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
1212 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1214 OS << "] (" << Contents.size() << " bytes)";
1217 case MCFragment::FT_Fill: {
1218 const MCFillFragment *FF = cast<MCFillFragment>(this);
1219 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
1220 << " Size:" << FF->getSize();
1223 case MCFragment::FT_Relaxable: {
1224 const MCRelaxableFragment *F = cast<MCRelaxableFragment>(this);
1227 F->getInst().dump_pretty(OS);
1230 case MCFragment::FT_Org: {
1231 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
1233 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
1236 case MCFragment::FT_Dwarf: {
1237 const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
1239 OS << " AddrDelta:" << OF->getAddrDelta()
1240 << " LineDelta:" << OF->getLineDelta();
1243 case MCFragment::FT_DwarfFrame: {
1244 const MCDwarfCallFrameFragment *CF = cast<MCDwarfCallFrameFragment>(this);
1246 OS << " AddrDelta:" << CF->getAddrDelta();
1249 case MCFragment::FT_LEB: {
1250 const MCLEBFragment *LF = cast<MCLEBFragment>(this);
1252 OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
1259 void MCSectionData::dump() {
1260 raw_ostream &OS = llvm::errs();
1262 OS << "<MCSectionData";
1263 OS << " Alignment:" << getAlignment()
1264 << " Fragments:[\n ";
1265 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1266 if (it != begin()) OS << ",\n ";
1272 void MCSymbolData::dump() const {
1273 raw_ostream &OS = llvm::errs();
1275 OS << "<MCSymbolData Symbol:" << getSymbol()
1276 << " Fragment:" << getFragment();
1278 OS << " Offset:" << getOffset();
1279 OS << " Flags:" << getFlags() << " Index:" << getIndex();
1281 OS << " (common, size:" << getCommonSize()
1282 << " align: " << getCommonAlignment() << ")";
1284 OS << " (external)";
1285 if (isPrivateExtern())
1286 OS << " (private extern)";
1290 void MCAssembler::dump() {
1291 raw_ostream &OS = llvm::errs();
1293 OS << "<MCAssembler\n";
1294 OS << " Sections:[\n ";
1295 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1296 if (it != begin()) OS << ",\n ";
1302 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1303 if (it != symbol_begin()) OS << ",\n ";
1310 // anchors for MC*Fragment vtables
1311 void MCEncodedFragment::anchor() { }
1312 void MCEncodedFragmentWithFixups::anchor() { }
1313 void MCDataFragment::anchor() { }
1314 void MCCompactEncodedInstFragment::anchor() { }
1315 void MCRelaxableFragment::anchor() { }
1316 void MCAlignFragment::anchor() { }
1317 void MCFillFragment::anchor() { }
1318 void MCOrgFragment::anchor() { }
1319 void MCLEBFragment::anchor() { }
1320 void MCDwarfLineAddrFragment::anchor() { }
1321 void MCDwarfCallFrameFragment::anchor() { }