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/MCAsmLayout.h"
16 #include "llvm/MC/MCCodeEmitter.h"
17 #include "llvm/MC/MCContext.h"
18 #include "llvm/MC/MCDwarf.h"
19 #include "llvm/MC/MCExpr.h"
20 #include "llvm/MC/MCFixupKindInfo.h"
21 #include "llvm/MC/MCObjectWriter.h"
22 #include "llvm/MC/MCSection.h"
23 #include "llvm/MC/MCSymbol.h"
24 #include "llvm/MC/MCValue.h"
25 #include "llvm/Support/Debug.h"
26 #include "llvm/Support/ErrorHandling.h"
27 #include "llvm/Support/LEB128.h"
28 #include "llvm/Support/TargetRegistry.h"
29 #include "llvm/Support/raw_ostream.h"
30 #include "llvm/MC/MCSectionELF.h"
34 #define DEBUG_TYPE "assembler"
38 STATISTIC(EmittedFragments, "Number of emitted assembler fragments - total");
39 STATISTIC(EmittedRelaxableFragments,
40 "Number of emitted assembler fragments - relaxable");
41 STATISTIC(EmittedDataFragments,
42 "Number of emitted assembler fragments - data");
43 STATISTIC(EmittedCompactEncodedInstFragments,
44 "Number of emitted assembler fragments - compact encoded inst");
45 STATISTIC(EmittedAlignFragments,
46 "Number of emitted assembler fragments - align");
47 STATISTIC(EmittedFillFragments,
48 "Number of emitted assembler fragments - fill");
49 STATISTIC(EmittedOrgFragments,
50 "Number of emitted assembler fragments - org");
51 STATISTIC(evaluateFixup, "Number of evaluated fixups");
52 STATISTIC(FragmentLayouts, "Number of fragment layouts");
53 STATISTIC(ObjectBytes, "Number of emitted object file bytes");
54 STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps");
55 STATISTIC(RelaxedInstructions, "Number of relaxed instructions");
59 // FIXME FIXME FIXME: There are number of places in this file where we convert
60 // what is a 64-bit assembler value used for computation into a value in the
61 // object file, which may truncate it. We should detect that truncation where
62 // invalid and report errors back.
66 MCAsmLayout::MCAsmLayout(MCAssembler &Asm)
67 : Assembler(Asm), LastValidFragment()
69 // Compute the section layout order. Virtual sections must go last.
70 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
71 if (!it->getSection().isVirtualSection())
72 SectionOrder.push_back(&*it);
73 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
74 if (it->getSection().isVirtualSection())
75 SectionOrder.push_back(&*it);
78 bool MCAsmLayout::isFragmentValid(const MCFragment *F) const {
79 const MCSectionData &SD = *F->getParent();
80 const MCFragment *LastValid = LastValidFragment.lookup(&SD);
83 assert(LastValid->getParent() == F->getParent());
84 return F->getLayoutOrder() <= LastValid->getLayoutOrder();
87 void MCAsmLayout::invalidateFragmentsFrom(MCFragment *F) {
88 // If this fragment wasn't already valid, we don't need to do anything.
89 if (!isFragmentValid(F))
92 // Otherwise, reset the last valid fragment to the previous fragment
93 // (if this is the first fragment, it will be NULL).
94 const MCSectionData &SD = *F->getParent();
95 LastValidFragment[&SD] = F->getPrevNode();
98 void MCAsmLayout::ensureValid(const MCFragment *F) const {
99 MCSectionData &SD = *F->getParent();
101 MCFragment *Cur = LastValidFragment[&SD];
105 Cur = Cur->getNextNode();
107 // Advance the layout position until the fragment is valid.
108 while (!isFragmentValid(F)) {
109 assert(Cur && "Layout bookkeeping error");
110 const_cast<MCAsmLayout*>(this)->layoutFragment(Cur);
111 Cur = Cur->getNextNode();
115 uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
117 assert(F->Offset != ~UINT64_C(0) && "Address not set!");
121 // Simple getSymbolOffset helper for the non-varibale case.
122 static bool getLabelOffset(const MCAsmLayout &Layout, const MCSymbolData &SD,
123 bool ReportError, uint64_t &Val) {
124 if (!SD.getFragment()) {
126 report_fatal_error("unable to evaluate offset to undefined symbol '" +
127 SD.getSymbol().getName() + "'");
130 Val = Layout.getFragmentOffset(SD.getFragment()) + SD.getOffset();
134 static bool getSymbolOffsetImpl(const MCAsmLayout &Layout,
135 const MCSymbolData *SD, bool ReportError,
137 const MCSymbol &S = SD->getSymbol();
140 return getLabelOffset(Layout, *SD, ReportError, Val);
142 // If SD is a variable, evaluate it.
144 if (!S.getVariableValue()->EvaluateAsValue(Target, &Layout, nullptr))
145 report_fatal_error("unable to evaluate offset for variable '" +
148 uint64_t Offset = Target.getConstant();
150 const MCAssembler &Asm = Layout.getAssembler();
152 const MCSymbolRefExpr *A = Target.getSymA();
155 if (!getLabelOffset(Layout, Asm.getSymbolData(A->getSymbol()), ReportError,
161 const MCSymbolRefExpr *B = Target.getSymB();
164 if (!getLabelOffset(Layout, Asm.getSymbolData(B->getSymbol()), ReportError,
174 bool MCAsmLayout::getSymbolOffset(const MCSymbolData *SD, uint64_t &Val) const {
175 return getSymbolOffsetImpl(*this, SD, false, Val);
178 uint64_t MCAsmLayout::getSymbolOffset(const MCSymbolData *SD) const {
180 getSymbolOffsetImpl(*this, SD, true, Val);
184 const MCSymbol *MCAsmLayout::getBaseSymbol(const MCSymbol &Symbol) const {
185 if (!Symbol.isVariable())
188 const MCExpr *Expr = Symbol.getVariableValue();
190 if (!Expr->EvaluateAsValue(Value, this, nullptr))
191 llvm_unreachable("Invalid Expression");
193 const MCSymbolRefExpr *RefB = Value.getSymB();
195 Assembler.getContext().FatalError(
196 SMLoc(), Twine("symbol '") + RefB->getSymbol().getName() +
197 "' could not be evaluated in a subtraction expression");
199 const MCSymbolRefExpr *A = Value.getSymA();
203 return &A->getSymbol();
206 uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const {
207 // The size is the last fragment's end offset.
208 const MCFragment &F = SD->getFragmentList().back();
209 return getFragmentOffset(&F) + getAssembler().computeFragmentSize(*this, F);
212 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
213 // Virtual sections have no file size.
214 if (SD->getSection().isVirtualSection())
217 // Otherwise, the file size is the same as the address space size.
218 return getSectionAddressSize(SD);
221 uint64_t MCAsmLayout::computeBundlePadding(const MCFragment *F,
222 uint64_t FOffset, uint64_t FSize) {
223 uint64_t BundleSize = Assembler.getBundleAlignSize();
224 assert(BundleSize > 0 &&
225 "computeBundlePadding should only be called if bundling is enabled");
226 uint64_t BundleMask = BundleSize - 1;
227 uint64_t OffsetInBundle = FOffset & BundleMask;
228 uint64_t EndOfFragment = OffsetInBundle + FSize;
230 // There are two kinds of bundling restrictions:
232 // 1) For alignToBundleEnd(), add padding to ensure that the fragment will
233 // *end* on a bundle boundary.
234 // 2) Otherwise, check if the fragment would cross a bundle boundary. If it
235 // would, add padding until the end of the bundle so that the fragment
236 // will start in a new one.
237 if (F->alignToBundleEnd()) {
238 // Three possibilities here:
240 // A) The fragment just happens to end at a bundle boundary, so we're good.
241 // B) The fragment ends before the current bundle boundary: pad it just
242 // enough to reach the boundary.
243 // C) The fragment ends after the current bundle boundary: pad it until it
244 // reaches the end of the next bundle boundary.
246 // Note: this code could be made shorter with some modulo trickery, but it's
247 // intentionally kept in its more explicit form for simplicity.
248 if (EndOfFragment == BundleSize)
250 else if (EndOfFragment < BundleSize)
251 return BundleSize - EndOfFragment;
252 else { // EndOfFragment > BundleSize
253 return 2 * BundleSize - EndOfFragment;
255 } else if (EndOfFragment > BundleSize)
256 return BundleSize - OffsetInBundle;
263 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
266 MCFragment::~MCFragment() {
269 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
270 : Kind(_Kind), Parent(_Parent), Atom(nullptr), Offset(~UINT64_C(0))
273 Parent->getFragmentList().push_back(this);
278 MCEncodedFragment::~MCEncodedFragment() {
283 MCEncodedFragmentWithFixups::~MCEncodedFragmentWithFixups() {
288 MCSectionData::MCSectionData() : Section(nullptr) {}
290 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
291 : Section(&_Section),
292 Ordinal(~UINT32_C(0)),
294 BundleLockState(NotBundleLocked), BundleGroupBeforeFirstInst(false),
295 HasInstructions(false)
298 A->getSectionList().push_back(this);
301 MCSectionData::iterator
302 MCSectionData::getSubsectionInsertionPoint(unsigned Subsection) {
303 if (Subsection == 0 && SubsectionFragmentMap.empty())
306 SmallVectorImpl<std::pair<unsigned, MCFragment *> >::iterator MI =
307 std::lower_bound(SubsectionFragmentMap.begin(), SubsectionFragmentMap.end(),
308 std::make_pair(Subsection, (MCFragment *)nullptr));
309 bool ExactMatch = false;
310 if (MI != SubsectionFragmentMap.end()) {
311 ExactMatch = MI->first == Subsection;
316 if (MI == SubsectionFragmentMap.end())
320 if (!ExactMatch && Subsection != 0) {
321 // The GNU as documentation claims that subsections have an alignment of 4,
322 // although this appears not to be the case.
323 MCFragment *F = new MCDataFragment();
324 SubsectionFragmentMap.insert(MI, std::make_pair(Subsection, F));
325 getFragmentList().insert(IP, F);
333 MCSymbolData::MCSymbolData() : Symbol(nullptr) {}
335 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
336 uint64_t _Offset, MCAssembler *A)
337 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
338 IsExternal(false), IsPrivateExtern(false),
339 CommonSize(0), SymbolSize(nullptr), CommonAlign(0),
343 A->getSymbolList().push_back(this);
348 MCAssembler::MCAssembler(MCContext &Context_, MCAsmBackend &Backend_,
349 MCCodeEmitter &Emitter_, MCObjectWriter &Writer_,
351 : Context(Context_), Backend(Backend_), Emitter(Emitter_), Writer(Writer_),
352 OS(OS_), BundleAlignSize(0), RelaxAll(false), NoExecStack(false),
353 SubsectionsViaSymbols(false), ELFHeaderEFlags(0) {
354 VersionMinInfo.Major = 0; // Major version == 0 for "none specified"
357 MCAssembler::~MCAssembler() {
360 void MCAssembler::reset() {
365 IndirectSymbols.clear();
367 LinkerOptions.clear();
373 SubsectionsViaSymbols = false;
375 LOHContainer.reset();
376 VersionMinInfo.Major = 0;
378 // reset objects owned by us
379 getBackend().reset();
380 getEmitter().reset();
382 getLOHContainer().reset();
385 bool MCAssembler::isThumbFunc(const MCSymbol *Symbol) const {
386 if (ThumbFuncs.count(Symbol))
389 if (!Symbol->isVariable())
392 // FIXME: It looks like gas supports some cases of the form "foo + 2". It
393 // is not clear if that is a bug or a feature.
394 const MCExpr *Expr = Symbol->getVariableValue();
395 const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Expr);
399 if (Ref->getKind() != MCSymbolRefExpr::VK_None)
402 const MCSymbol &Sym = Ref->getSymbol();
403 if (!isThumbFunc(&Sym))
406 ThumbFuncs.insert(Symbol); // Cache it.
410 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
411 // Non-temporary labels should always be visible to the linker.
412 if (!Symbol.isTemporary())
415 // Absolute temporary labels are never visible.
416 if (!Symbol.isInSection())
419 // Otherwise, check if the section requires symbols even for temporary labels.
420 return getBackend().doesSectionRequireSymbols(Symbol.getSection());
423 const MCSymbolData *MCAssembler::getAtom(const MCSymbolData *SD) const {
424 // Linker visible symbols define atoms.
425 if (isSymbolLinkerVisible(SD->getSymbol()))
428 // Absolute and undefined symbols have no defining atom.
429 if (!SD->getFragment())
432 // Non-linker visible symbols in sections which can't be atomized have no
434 if (!getBackend().isSectionAtomizable(
435 SD->getFragment()->getParent()->getSection()))
438 // Otherwise, return the atom for the containing fragment.
439 return SD->getFragment()->getAtom();
442 // Try to fully compute Expr to an absolute value and if that fails produce
443 // a relocatable expr.
444 // FIXME: Should this be the behavior of EvaluateAsRelocatable itself?
445 static bool evaluate(const MCExpr &Expr, const MCAsmLayout &Layout,
446 const MCFixup &Fixup, MCValue &Target) {
447 if (Expr.EvaluateAsValue(Target, &Layout, &Fixup)) {
448 if (Target.isAbsolute())
451 return Expr.EvaluateAsRelocatable(Target, &Layout, &Fixup);
454 bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout,
455 const MCFixup &Fixup, const MCFragment *DF,
456 MCValue &Target, uint64_t &Value) const {
457 ++stats::evaluateFixup;
459 // FIXME: This code has some duplication with RecordRelocation. We should
460 // probably merge the two into a single callback that tries to evaluate a
461 // fixup and records a relocation if one is needed.
462 const MCExpr *Expr = Fixup.getValue();
463 if (!evaluate(*Expr, Layout, Fixup, Target))
464 getContext().FatalError(Fixup.getLoc(), "expected relocatable expression");
466 bool IsPCRel = Backend.getFixupKindInfo(
467 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
471 if (Target.getSymB()) {
473 } else if (!Target.getSymA()) {
476 const MCSymbolRefExpr *A = Target.getSymA();
477 const MCSymbol &SA = A->getSymbol();
478 if (A->getKind() != MCSymbolRefExpr::VK_None ||
479 SA.AliasedSymbol().isUndefined()) {
482 const MCSymbolData &DataA = getSymbolData(SA);
484 getWriter().IsSymbolRefDifferenceFullyResolvedImpl(*this, DataA,
489 IsResolved = Target.isAbsolute();
492 Value = Target.getConstant();
494 if (const MCSymbolRefExpr *A = Target.getSymA()) {
495 const MCSymbol &Sym = A->getSymbol().AliasedSymbol();
497 Value += Layout.getSymbolOffset(&getSymbolData(Sym));
499 if (const MCSymbolRefExpr *B = Target.getSymB()) {
500 const MCSymbol &Sym = B->getSymbol().AliasedSymbol();
502 Value -= Layout.getSymbolOffset(&getSymbolData(Sym));
506 bool ShouldAlignPC = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
507 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits;
508 assert((ShouldAlignPC ? IsPCRel : true) &&
509 "FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!");
512 uint32_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset();
514 // A number of ARM fixups in Thumb mode require that the effective PC
515 // address be determined as the 32-bit aligned version of the actual offset.
516 if (ShouldAlignPC) Offset &= ~0x3;
520 // Let the backend adjust the fixup value if necessary, including whether
521 // we need a relocation.
522 Backend.processFixupValue(*this, Layout, Fixup, DF, Target, Value,
528 uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
529 const MCFragment &F) const {
530 switch (F.getKind()) {
531 case MCFragment::FT_Data:
532 case MCFragment::FT_Relaxable:
533 case MCFragment::FT_CompactEncodedInst:
534 return cast<MCEncodedFragment>(F).getContents().size();
535 case MCFragment::FT_Fill:
536 return cast<MCFillFragment>(F).getSize();
538 case MCFragment::FT_LEB:
539 return cast<MCLEBFragment>(F).getContents().size();
541 case MCFragment::FT_Align: {
542 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
543 unsigned Offset = Layout.getFragmentOffset(&AF);
544 unsigned Size = OffsetToAlignment(Offset, AF.getAlignment());
545 // If we are padding with nops, force the padding to be larger than the
547 if (Size > 0 && AF.hasEmitNops()) {
548 while (Size % getBackend().getMinimumNopSize())
549 Size += AF.getAlignment();
551 if (Size > AF.getMaxBytesToEmit())
556 case MCFragment::FT_Org: {
557 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
558 int64_t TargetLocation;
559 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, Layout))
560 report_fatal_error("expected assembly-time absolute expression");
562 // FIXME: We need a way to communicate this error.
563 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
564 int64_t Size = TargetLocation - FragmentOffset;
565 if (Size < 0 || Size >= 0x40000000)
566 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
567 "' (at offset '" + Twine(FragmentOffset) + "')");
571 case MCFragment::FT_Dwarf:
572 return cast<MCDwarfLineAddrFragment>(F).getContents().size();
573 case MCFragment::FT_DwarfFrame:
574 return cast<MCDwarfCallFrameFragment>(F).getContents().size();
577 llvm_unreachable("invalid fragment kind");
580 void MCAsmLayout::layoutFragment(MCFragment *F) {
581 MCFragment *Prev = F->getPrevNode();
583 // We should never try to recompute something which is valid.
584 assert(!isFragmentValid(F) && "Attempt to recompute a valid fragment!");
585 // We should never try to compute the fragment layout if its predecessor
587 assert((!Prev || isFragmentValid(Prev)) &&
588 "Attempt to compute fragment before its predecessor!");
590 ++stats::FragmentLayouts;
592 // Compute fragment offset and size.
594 F->Offset = Prev->Offset + getAssembler().computeFragmentSize(*this, *Prev);
597 LastValidFragment[F->getParent()] = F;
599 // If bundling is enabled and this fragment has instructions in it, it has to
600 // obey the bundling restrictions. With padding, we'll have:
605 // -------------------------------------
606 // Prev |##########| F |
607 // -------------------------------------
612 // The fragment's offset will point to after the padding, and its computed
613 // size won't include the padding.
615 if (Assembler.isBundlingEnabled() && F->hasInstructions()) {
616 assert(isa<MCEncodedFragment>(F) &&
617 "Only MCEncodedFragment implementations have instructions");
618 uint64_t FSize = Assembler.computeFragmentSize(*this, *F);
620 if (FSize > Assembler.getBundleAlignSize())
621 report_fatal_error("Fragment can't be larger than a bundle size");
623 uint64_t RequiredBundlePadding = computeBundlePadding(F, F->Offset, FSize);
624 if (RequiredBundlePadding > UINT8_MAX)
625 report_fatal_error("Padding cannot exceed 255 bytes");
626 F->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
627 F->Offset += RequiredBundlePadding;
631 /// \brief Write the contents of a fragment to the given object writer. Expects
632 /// a MCEncodedFragment.
633 static void writeFragmentContents(const MCFragment &F, MCObjectWriter *OW) {
634 const MCEncodedFragment &EF = cast<MCEncodedFragment>(F);
635 OW->WriteBytes(EF.getContents());
638 /// \brief Write the fragment \p F to the output file.
639 static void writeFragment(const MCAssembler &Asm, const MCAsmLayout &Layout,
640 const MCFragment &F) {
641 MCObjectWriter *OW = &Asm.getWriter();
643 // FIXME: Embed in fragments instead?
644 uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F);
646 // Should NOP padding be written out before this fragment?
647 unsigned BundlePadding = F.getBundlePadding();
648 if (BundlePadding > 0) {
649 assert(Asm.isBundlingEnabled() &&
650 "Writing bundle padding with disabled bundling");
651 assert(F.hasInstructions() &&
652 "Writing bundle padding for a fragment without instructions");
654 unsigned TotalLength = BundlePadding + static_cast<unsigned>(FragmentSize);
655 if (F.alignToBundleEnd() && TotalLength > Asm.getBundleAlignSize()) {
656 // If the padding itself crosses a bundle boundary, it must be emitted
657 // in 2 pieces, since even nop instructions must not cross boundaries.
658 // v--------------v <- BundleAlignSize
659 // v---------v <- BundlePadding
660 // ----------------------------
661 // | Prev |####|####| F |
662 // ----------------------------
663 // ^-------------------^ <- TotalLength
664 unsigned DistanceToBoundary = TotalLength - Asm.getBundleAlignSize();
665 if (!Asm.getBackend().writeNopData(DistanceToBoundary, OW))
666 report_fatal_error("unable to write NOP sequence of " +
667 Twine(DistanceToBoundary) + " bytes");
668 BundlePadding -= DistanceToBoundary;
670 if (!Asm.getBackend().writeNopData(BundlePadding, OW))
671 report_fatal_error("unable to write NOP sequence of " +
672 Twine(BundlePadding) + " bytes");
675 // This variable (and its dummy usage) is to participate in the assert at
676 // the end of the function.
677 uint64_t Start = OW->getStream().tell();
680 ++stats::EmittedFragments;
682 switch (F.getKind()) {
683 case MCFragment::FT_Align: {
684 ++stats::EmittedAlignFragments;
685 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
686 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
688 uint64_t Count = FragmentSize / AF.getValueSize();
690 // FIXME: This error shouldn't actually occur (the front end should emit
691 // multiple .align directives to enforce the semantics it wants), but is
692 // severe enough that we want to report it. How to handle this?
693 if (Count * AF.getValueSize() != FragmentSize)
694 report_fatal_error("undefined .align directive, value size '" +
695 Twine(AF.getValueSize()) +
696 "' is not a divisor of padding size '" +
697 Twine(FragmentSize) + "'");
699 // See if we are aligning with nops, and if so do that first to try to fill
700 // the Count bytes. Then if that did not fill any bytes or there are any
701 // bytes left to fill use the Value and ValueSize to fill the rest.
702 // If we are aligning with nops, ask that target to emit the right data.
703 if (AF.hasEmitNops()) {
704 if (!Asm.getBackend().writeNopData(Count, OW))
705 report_fatal_error("unable to write nop sequence of " +
706 Twine(Count) + " bytes");
710 // Otherwise, write out in multiples of the value size.
711 for (uint64_t i = 0; i != Count; ++i) {
712 switch (AF.getValueSize()) {
713 default: llvm_unreachable("Invalid size!");
714 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
715 case 2: OW->Write16(uint16_t(AF.getValue())); break;
716 case 4: OW->Write32(uint32_t(AF.getValue())); break;
717 case 8: OW->Write64(uint64_t(AF.getValue())); break;
723 case MCFragment::FT_Data:
724 ++stats::EmittedDataFragments;
725 writeFragmentContents(F, OW);
728 case MCFragment::FT_Relaxable:
729 ++stats::EmittedRelaxableFragments;
730 writeFragmentContents(F, OW);
733 case MCFragment::FT_CompactEncodedInst:
734 ++stats::EmittedCompactEncodedInstFragments;
735 writeFragmentContents(F, OW);
738 case MCFragment::FT_Fill: {
739 ++stats::EmittedFillFragments;
740 const MCFillFragment &FF = cast<MCFillFragment>(F);
742 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
744 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
745 switch (FF.getValueSize()) {
746 default: llvm_unreachable("Invalid size!");
747 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
748 case 2: OW->Write16(uint16_t(FF.getValue())); break;
749 case 4: OW->Write32(uint32_t(FF.getValue())); break;
750 case 8: OW->Write64(uint64_t(FF.getValue())); break;
756 case MCFragment::FT_LEB: {
757 const MCLEBFragment &LF = cast<MCLEBFragment>(F);
758 OW->WriteBytes(LF.getContents().str());
762 case MCFragment::FT_Org: {
763 ++stats::EmittedOrgFragments;
764 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
766 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
767 OW->Write8(uint8_t(OF.getValue()));
772 case MCFragment::FT_Dwarf: {
773 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
774 OW->WriteBytes(OF.getContents().str());
777 case MCFragment::FT_DwarfFrame: {
778 const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F);
779 OW->WriteBytes(CF.getContents().str());
784 assert(OW->getStream().tell() - Start == FragmentSize &&
785 "The stream should advance by fragment size");
788 void MCAssembler::writeSectionData(const MCSectionData *SD,
789 const MCAsmLayout &Layout) const {
790 // Ignore virtual sections.
791 if (SD->getSection().isVirtualSection()) {
792 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
794 // Check that contents are only things legal inside a virtual section.
795 for (MCSectionData::const_iterator it = SD->begin(),
796 ie = SD->end(); it != ie; ++it) {
797 switch (it->getKind()) {
798 default: llvm_unreachable("Invalid fragment in virtual section!");
799 case MCFragment::FT_Data: {
800 // Check that we aren't trying to write a non-zero contents (or fixups)
801 // into a virtual section. This is to support clients which use standard
802 // directives to fill the contents of virtual sections.
803 const MCDataFragment &DF = cast<MCDataFragment>(*it);
804 assert(DF.fixup_begin() == DF.fixup_end() &&
805 "Cannot have fixups in virtual section!");
806 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
807 if (DF.getContents()[i]) {
808 if (auto *ELFSec = dyn_cast<const MCSectionELF>(&SD->getSection()))
809 report_fatal_error("non-zero initializer found in section '" +
810 ELFSec->getSectionName() + "'");
812 report_fatal_error("non-zero initializer found in virtual section");
816 case MCFragment::FT_Align:
817 // Check that we aren't trying to write a non-zero value into a virtual
819 assert((cast<MCAlignFragment>(it)->getValueSize() == 0 ||
820 cast<MCAlignFragment>(it)->getValue() == 0) &&
821 "Invalid align in virtual section!");
823 case MCFragment::FT_Fill:
824 assert((cast<MCFillFragment>(it)->getValueSize() == 0 ||
825 cast<MCFillFragment>(it)->getValue() == 0) &&
826 "Invalid fill in virtual section!");
834 uint64_t Start = getWriter().getStream().tell();
837 for (MCSectionData::const_iterator it = SD->begin(), ie = SD->end();
839 writeFragment(*this, Layout, *it);
841 assert(getWriter().getStream().tell() - Start ==
842 Layout.getSectionAddressSize(SD));
845 std::pair<uint64_t, bool> MCAssembler::handleFixup(const MCAsmLayout &Layout,
847 const MCFixup &Fixup) {
848 // Evaluate the fixup.
851 bool IsPCRel = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
852 MCFixupKindInfo::FKF_IsPCRel;
853 if (!evaluateFixup(Layout, Fixup, &F, Target, FixedValue)) {
854 // The fixup was unresolved, we need a relocation. Inform the object
855 // writer of the relocation, and give it an opportunity to adjust the
856 // fixup value if need be.
857 getWriter().RecordRelocation(*this, Layout, &F, Fixup, Target, IsPCRel,
860 return std::make_pair(FixedValue, IsPCRel);
863 void MCAssembler::Finish() {
864 DEBUG_WITH_TYPE("mc-dump", {
865 llvm::errs() << "assembler backend - pre-layout\n--\n";
868 // Create the layout object.
869 MCAsmLayout Layout(*this);
871 // Create dummy fragments and assign section ordinals.
872 unsigned SectionIndex = 0;
873 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
874 // Create dummy fragments to eliminate any empty sections, this simplifies
876 if (it->getFragmentList().empty())
877 new MCDataFragment(it);
879 it->setOrdinal(SectionIndex++);
882 // Assign layout order indices to sections and fragments.
883 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
884 MCSectionData *SD = Layout.getSectionOrder()[i];
885 SD->setLayoutOrder(i);
887 unsigned FragmentIndex = 0;
888 for (MCSectionData::iterator iFrag = SD->begin(), iFragEnd = SD->end();
889 iFrag != iFragEnd; ++iFrag)
890 iFrag->setLayoutOrder(FragmentIndex++);
893 // Layout until everything fits.
894 while (layoutOnce(Layout))
897 DEBUG_WITH_TYPE("mc-dump", {
898 llvm::errs() << "assembler backend - post-relaxation\n--\n";
901 // Finalize the layout, including fragment lowering.
902 finishLayout(Layout);
904 DEBUG_WITH_TYPE("mc-dump", {
905 llvm::errs() << "assembler backend - final-layout\n--\n";
908 uint64_t StartOffset = OS.tell();
910 // Allow the object writer a chance to perform post-layout binding (for
911 // example, to set the index fields in the symbol data).
912 getWriter().ExecutePostLayoutBinding(*this, Layout);
914 // Evaluate and apply the fixups, generating relocation entries as necessary.
915 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
916 for (MCSectionData::iterator it2 = it->begin(),
917 ie2 = it->end(); it2 != ie2; ++it2) {
918 MCEncodedFragmentWithFixups *F =
919 dyn_cast<MCEncodedFragmentWithFixups>(it2);
921 for (MCEncodedFragmentWithFixups::fixup_iterator it3 = F->fixup_begin(),
922 ie3 = F->fixup_end(); it3 != ie3; ++it3) {
923 MCFixup &Fixup = *it3;
926 std::tie(FixedValue, IsPCRel) = handleFixup(Layout, *F, Fixup);
927 getBackend().applyFixup(Fixup, F->getContents().data(),
928 F->getContents().size(), FixedValue, IsPCRel);
934 // Write the object file.
935 getWriter().WriteObject(*this, Layout);
937 stats::ObjectBytes += OS.tell() - StartOffset;
940 bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup,
941 const MCRelaxableFragment *DF,
942 const MCAsmLayout &Layout) const {
943 // If we cannot resolve the fixup value, it requires relaxation.
946 if (!evaluateFixup(Layout, Fixup, DF, Target, Value))
949 return getBackend().fixupNeedsRelaxation(Fixup, Value, DF, Layout);
952 bool MCAssembler::fragmentNeedsRelaxation(const MCRelaxableFragment *F,
953 const MCAsmLayout &Layout) const {
954 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
955 // are intentionally pushing out inst fragments, or because we relaxed a
956 // previous instruction to one that doesn't need relaxation.
957 if (!getBackend().mayNeedRelaxation(F->getInst()))
960 for (MCRelaxableFragment::const_fixup_iterator it = F->fixup_begin(),
961 ie = F->fixup_end(); it != ie; ++it)
962 if (fixupNeedsRelaxation(*it, F, Layout))
968 bool MCAssembler::relaxInstruction(MCAsmLayout &Layout,
969 MCRelaxableFragment &F) {
970 if (!fragmentNeedsRelaxation(&F, Layout))
973 ++stats::RelaxedInstructions;
975 // FIXME-PERF: We could immediately lower out instructions if we can tell
976 // they are fully resolved, to avoid retesting on later passes.
978 // Relax the fragment.
981 getBackend().relaxInstruction(F.getInst(), Relaxed);
983 // Encode the new instruction.
985 // FIXME-PERF: If it matters, we could let the target do this. It can
986 // probably do so more efficiently in many cases.
987 SmallVector<MCFixup, 4> Fixups;
988 SmallString<256> Code;
989 raw_svector_ostream VecOS(Code);
990 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups, F.getSubtargetInfo());
993 // Update the fragment.
995 F.getContents() = Code;
996 F.getFixups() = Fixups;
1001 bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) {
1002 uint64_t OldSize = LF.getContents().size();
1003 int64_t Value = LF.getValue().evaluateKnownAbsolute(Layout);
1004 SmallString<8> &Data = LF.getContents();
1006 raw_svector_ostream OSE(Data);
1008 encodeSLEB128(Value, OSE);
1010 encodeULEB128(Value, OSE);
1012 return OldSize != LF.getContents().size();
1015 bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout,
1016 MCDwarfLineAddrFragment &DF) {
1017 MCContext &Context = Layout.getAssembler().getContext();
1018 uint64_t OldSize = DF.getContents().size();
1019 int64_t AddrDelta = DF.getAddrDelta().evaluateKnownAbsolute(Layout);
1021 LineDelta = DF.getLineDelta();
1022 SmallString<8> &Data = DF.getContents();
1024 raw_svector_ostream OSE(Data);
1025 MCDwarfLineAddr::Encode(Context, LineDelta, AddrDelta, OSE);
1027 return OldSize != Data.size();
1030 bool MCAssembler::relaxDwarfCallFrameFragment(MCAsmLayout &Layout,
1031 MCDwarfCallFrameFragment &DF) {
1032 MCContext &Context = Layout.getAssembler().getContext();
1033 uint64_t OldSize = DF.getContents().size();
1034 int64_t AddrDelta = DF.getAddrDelta().evaluateKnownAbsolute(Layout);
1035 SmallString<8> &Data = DF.getContents();
1037 raw_svector_ostream OSE(Data);
1038 MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE);
1040 return OldSize != Data.size();
1043 bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSectionData &SD) {
1044 // Holds the first fragment which needed relaxing during this layout. It will
1045 // remain NULL if none were relaxed.
1046 // When a fragment is relaxed, all the fragments following it should get
1047 // invalidated because their offset is going to change.
1048 MCFragment *FirstRelaxedFragment = nullptr;
1050 // Attempt to relax all the fragments in the section.
1051 for (MCSectionData::iterator I = SD.begin(), IE = SD.end(); I != IE; ++I) {
1052 // Check if this is a fragment that needs relaxation.
1053 bool RelaxedFrag = false;
1054 switch(I->getKind()) {
1057 case MCFragment::FT_Relaxable:
1058 assert(!getRelaxAll() &&
1059 "Did not expect a MCRelaxableFragment in RelaxAll mode");
1060 RelaxedFrag = relaxInstruction(Layout, *cast<MCRelaxableFragment>(I));
1062 case MCFragment::FT_Dwarf:
1063 RelaxedFrag = relaxDwarfLineAddr(Layout,
1064 *cast<MCDwarfLineAddrFragment>(I));
1066 case MCFragment::FT_DwarfFrame:
1068 relaxDwarfCallFrameFragment(Layout,
1069 *cast<MCDwarfCallFrameFragment>(I));
1071 case MCFragment::FT_LEB:
1072 RelaxedFrag = relaxLEB(Layout, *cast<MCLEBFragment>(I));
1075 if (RelaxedFrag && !FirstRelaxedFragment)
1076 FirstRelaxedFragment = I;
1078 if (FirstRelaxedFragment) {
1079 Layout.invalidateFragmentsFrom(FirstRelaxedFragment);
1085 bool MCAssembler::layoutOnce(MCAsmLayout &Layout) {
1086 ++stats::RelaxationSteps;
1088 bool WasRelaxed = false;
1089 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1090 MCSectionData &SD = *it;
1091 while (layoutSectionOnce(Layout, SD))
1098 void MCAssembler::finishLayout(MCAsmLayout &Layout) {
1099 // The layout is done. Mark every fragment as valid.
1100 for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) {
1101 Layout.getFragmentOffset(&*Layout.getSectionOrder()[i]->rbegin());
1105 // Debugging methods
1109 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
1110 OS << "<MCFixup" << " Offset:" << AF.getOffset()
1111 << " Value:" << *AF.getValue()
1112 << " Kind:" << AF.getKind() << ">";
1118 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1119 void MCFragment::dump() {
1120 raw_ostream &OS = llvm::errs();
1123 switch (getKind()) {
1124 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
1125 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
1126 case MCFragment::FT_CompactEncodedInst:
1127 OS << "MCCompactEncodedInstFragment"; break;
1128 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
1129 case MCFragment::FT_Relaxable: OS << "MCRelaxableFragment"; break;
1130 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
1131 case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
1132 case MCFragment::FT_DwarfFrame: OS << "MCDwarfCallFrameFragment"; break;
1133 case MCFragment::FT_LEB: OS << "MCLEBFragment"; break;
1136 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
1137 << " Offset:" << Offset
1138 << " HasInstructions:" << hasInstructions()
1139 << " BundlePadding:" << static_cast<unsigned>(getBundlePadding()) << ">";
1141 switch (getKind()) {
1142 case MCFragment::FT_Align: {
1143 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
1144 if (AF->hasEmitNops())
1145 OS << " (emit nops)";
1147 OS << " Alignment:" << AF->getAlignment()
1148 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
1149 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
1152 case MCFragment::FT_Data: {
1153 const MCDataFragment *DF = cast<MCDataFragment>(this);
1155 OS << " Contents:[";
1156 const SmallVectorImpl<char> &Contents = DF->getContents();
1157 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
1159 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1161 OS << "] (" << Contents.size() << " bytes)";
1163 if (DF->fixup_begin() != DF->fixup_end()) {
1166 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
1167 ie = DF->fixup_end(); it != ie; ++it) {
1168 if (it != DF->fixup_begin()) OS << ",\n ";
1175 case MCFragment::FT_CompactEncodedInst: {
1176 const MCCompactEncodedInstFragment *CEIF =
1177 cast<MCCompactEncodedInstFragment>(this);
1179 OS << " Contents:[";
1180 const SmallVectorImpl<char> &Contents = CEIF->getContents();
1181 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
1183 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1185 OS << "] (" << Contents.size() << " bytes)";
1188 case MCFragment::FT_Fill: {
1189 const MCFillFragment *FF = cast<MCFillFragment>(this);
1190 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
1191 << " Size:" << FF->getSize();
1194 case MCFragment::FT_Relaxable: {
1195 const MCRelaxableFragment *F = cast<MCRelaxableFragment>(this);
1198 F->getInst().dump_pretty(OS);
1201 case MCFragment::FT_Org: {
1202 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
1204 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
1207 case MCFragment::FT_Dwarf: {
1208 const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
1210 OS << " AddrDelta:" << OF->getAddrDelta()
1211 << " LineDelta:" << OF->getLineDelta();
1214 case MCFragment::FT_DwarfFrame: {
1215 const MCDwarfCallFrameFragment *CF = cast<MCDwarfCallFrameFragment>(this);
1217 OS << " AddrDelta:" << CF->getAddrDelta();
1220 case MCFragment::FT_LEB: {
1221 const MCLEBFragment *LF = cast<MCLEBFragment>(this);
1223 OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
1230 void MCSectionData::dump() {
1231 raw_ostream &OS = llvm::errs();
1233 OS << "<MCSectionData";
1234 OS << " Alignment:" << getAlignment()
1235 << " Fragments:[\n ";
1236 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1237 if (it != begin()) OS << ",\n ";
1243 void MCSymbolData::dump() const {
1244 raw_ostream &OS = llvm::errs();
1246 OS << "<MCSymbolData Symbol:" << getSymbol()
1247 << " Fragment:" << getFragment() << " Offset:" << getOffset()
1248 << " Flags:" << getFlags() << " Index:" << getIndex();
1250 OS << " (common, size:" << getCommonSize()
1251 << " align: " << getCommonAlignment() << ")";
1253 OS << " (external)";
1254 if (isPrivateExtern())
1255 OS << " (private extern)";
1259 void MCAssembler::dump() {
1260 raw_ostream &OS = llvm::errs();
1262 OS << "<MCAssembler\n";
1263 OS << " Sections:[\n ";
1264 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1265 if (it != begin()) OS << ",\n ";
1271 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1272 if (it != symbol_begin()) OS << ",\n ";
1279 // anchors for MC*Fragment vtables
1280 void MCEncodedFragment::anchor() { }
1281 void MCEncodedFragmentWithFixups::anchor() { }
1282 void MCDataFragment::anchor() { }
1283 void MCCompactEncodedInstFragment::anchor() { }
1284 void MCRelaxableFragment::anchor() { }
1285 void MCAlignFragment::anchor() { }
1286 void MCFillFragment::anchor() { }
1287 void MCOrgFragment::anchor() { }
1288 void MCLEBFragment::anchor() { }
1289 void MCDwarfLineAddrFragment::anchor() { }
1290 void MCDwarfCallFrameFragment::anchor() { }