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"
33 #define DEBUG_TYPE "assembler"
37 STATISTIC(EmittedFragments, "Number of emitted assembler fragments - total");
38 STATISTIC(EmittedRelaxableFragments,
39 "Number of emitted assembler fragments - relaxable");
40 STATISTIC(EmittedDataFragments,
41 "Number of emitted assembler fragments - data");
42 STATISTIC(EmittedCompactEncodedInstFragments,
43 "Number of emitted assembler fragments - compact encoded inst");
44 STATISTIC(EmittedAlignFragments,
45 "Number of emitted assembler fragments - align");
46 STATISTIC(EmittedFillFragments,
47 "Number of emitted assembler fragments - fill");
48 STATISTIC(EmittedOrgFragments,
49 "Number of emitted assembler fragments - org");
50 STATISTIC(evaluateFixup, "Number of evaluated fixups");
51 STATISTIC(FragmentLayouts, "Number of fragment layouts");
52 STATISTIC(ObjectBytes, "Number of emitted object file bytes");
53 STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps");
54 STATISTIC(RelaxedInstructions, "Number of relaxed instructions");
58 // FIXME FIXME FIXME: There are number of places in this file where we convert
59 // what is a 64-bit assembler value used for computation into a value in the
60 // object file, which may truncate it. We should detect that truncation where
61 // invalid and report errors back.
65 MCAsmLayout::MCAsmLayout(MCAssembler &Asm)
66 : Assembler(Asm), LastValidFragment()
68 // Compute the section layout order. Virtual sections must go last.
69 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
70 if (!it->getSection().isVirtualSection())
71 SectionOrder.push_back(&*it);
72 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
73 if (it->getSection().isVirtualSection())
74 SectionOrder.push_back(&*it);
77 bool MCAsmLayout::isFragmentValid(const MCFragment *F) const {
78 const MCSectionData &SD = *F->getParent();
79 const MCFragment *LastValid = LastValidFragment.lookup(&SD);
82 assert(LastValid->getParent() == F->getParent());
83 return F->getLayoutOrder() <= LastValid->getLayoutOrder();
86 void MCAsmLayout::invalidateFragmentsFrom(MCFragment *F) {
87 // If this fragment wasn't already valid, we don't need to do anything.
88 if (!isFragmentValid(F))
91 // Otherwise, reset the last valid fragment to the previous fragment
92 // (if this is the first fragment, it will be NULL).
93 const MCSectionData &SD = *F->getParent();
94 LastValidFragment[&SD] = F->getPrevNode();
97 void MCAsmLayout::ensureValid(const MCFragment *F) const {
98 MCSectionData &SD = *F->getParent();
100 MCFragment *Cur = LastValidFragment[&SD];
104 Cur = Cur->getNextNode();
106 // Advance the layout position until the fragment is valid.
107 while (!isFragmentValid(F)) {
108 assert(Cur && "Layout bookkeeping error");
109 const_cast<MCAsmLayout*>(this)->layoutFragment(Cur);
110 Cur = Cur->getNextNode();
114 uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
116 assert(F->Offset != ~UINT64_C(0) && "Address not set!");
120 // Simple getSymbolOffset helper for the non-varibale case.
121 static bool getLabelOffset(const MCAsmLayout &Layout, const MCSymbolData &SD,
122 bool ReportError, uint64_t &Val) {
123 if (!SD.getFragment()) {
125 report_fatal_error("unable to evaluate offset to undefined symbol '" +
126 SD.getSymbol().getName() + "'");
129 Val = Layout.getFragmentOffset(SD.getFragment()) + SD.getOffset();
133 static bool getSymbolOffsetImpl(const MCAsmLayout &Layout,
134 const MCSymbolData *SD, bool ReportError,
136 const MCSymbol &S = SD->getSymbol();
139 return getLabelOffset(Layout, *SD, ReportError, Val);
141 // If SD is a variable, evaluate it.
143 if (!S.getVariableValue()->EvaluateAsValue(Target, &Layout))
144 report_fatal_error("unable to evaluate offset for variable '" +
147 uint64_t Offset = Target.getConstant();
149 const MCAssembler &Asm = Layout.getAssembler();
151 const MCSymbolRefExpr *A = Target.getSymA();
154 if (!getLabelOffset(Layout, Asm.getSymbolData(A->getSymbol()), ReportError,
160 const MCSymbolRefExpr *B = Target.getSymB();
163 if (!getLabelOffset(Layout, Asm.getSymbolData(B->getSymbol()), ReportError,
173 bool MCAsmLayout::getSymbolOffset(const MCSymbolData *SD, uint64_t &Val) const {
174 return getSymbolOffsetImpl(*this, SD, false, Val);
177 uint64_t MCAsmLayout::getSymbolOffset(const MCSymbolData *SD) const {
179 getSymbolOffsetImpl(*this, SD, true, Val);
183 const MCSymbol *MCAsmLayout::getBaseSymbol(const MCSymbol &Symbol) const {
184 if (!Symbol.isVariable())
187 const MCExpr *Expr = Symbol.getVariableValue();
189 if (!Expr->EvaluateAsValue(Value, this))
190 llvm_unreachable("Invalid Expression");
192 const MCSymbolRefExpr *RefB = Value.getSymB();
194 Assembler.getContext().FatalError(
195 SMLoc(), Twine("symbol '") + RefB->getSymbol().getName() +
196 "' could not be evaluated in a subtraction expression");
198 const MCSymbolRefExpr *A = Value.getSymA();
202 return &A->getSymbol();
205 uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const {
206 // The size is the last fragment's end offset.
207 const MCFragment &F = SD->getFragmentList().back();
208 return getFragmentOffset(&F) + getAssembler().computeFragmentSize(*this, F);
211 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
212 // Virtual sections have no file size.
213 if (SD->getSection().isVirtualSection())
216 // Otherwise, the file size is the same as the address space size.
217 return getSectionAddressSize(SD);
220 uint64_t MCAsmLayout::computeBundlePadding(const MCFragment *F,
221 uint64_t FOffset, uint64_t FSize) {
222 uint64_t BundleSize = Assembler.getBundleAlignSize();
223 assert(BundleSize > 0 &&
224 "computeBundlePadding should only be called if bundling is enabled");
225 uint64_t BundleMask = BundleSize - 1;
226 uint64_t OffsetInBundle = FOffset & BundleMask;
227 uint64_t EndOfFragment = OffsetInBundle + FSize;
229 // There are two kinds of bundling restrictions:
231 // 1) For alignToBundleEnd(), add padding to ensure that the fragment will
232 // *end* on a bundle boundary.
233 // 2) Otherwise, check if the fragment would cross a bundle boundary. If it
234 // would, add padding until the end of the bundle so that the fragment
235 // will start in a new one.
236 if (F->alignToBundleEnd()) {
237 // Three possibilities here:
239 // A) The fragment just happens to end at a bundle boundary, so we're good.
240 // B) The fragment ends before the current bundle boundary: pad it just
241 // enough to reach the boundary.
242 // C) The fragment ends after the current bundle boundary: pad it until it
243 // reaches the end of the next bundle boundary.
245 // Note: this code could be made shorter with some modulo trickery, but it's
246 // intentionally kept in its more explicit form for simplicity.
247 if (EndOfFragment == BundleSize)
249 else if (EndOfFragment < BundleSize)
250 return BundleSize - EndOfFragment;
251 else { // EndOfFragment > BundleSize
252 return 2 * BundleSize - EndOfFragment;
254 } else if (EndOfFragment > BundleSize)
255 return BundleSize - OffsetInBundle;
262 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
265 MCFragment::~MCFragment() {
268 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
269 : Kind(_Kind), Parent(_Parent), Atom(nullptr), Offset(~UINT64_C(0))
272 Parent->getFragmentList().push_back(this);
277 MCEncodedFragment::~MCEncodedFragment() {
282 MCEncodedFragmentWithFixups::~MCEncodedFragmentWithFixups() {
287 MCSectionData::MCSectionData() : Section(nullptr) {}
289 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
290 : Section(&_Section),
291 Ordinal(~UINT32_C(0)),
293 BundleLockState(NotBundleLocked), BundleGroupBeforeFirstInst(false),
294 HasInstructions(false)
297 A->getSectionList().push_back(this);
300 MCSectionData::iterator
301 MCSectionData::getSubsectionInsertionPoint(unsigned Subsection) {
302 if (Subsection == 0 && SubsectionFragmentMap.empty())
305 SmallVectorImpl<std::pair<unsigned, MCFragment *> >::iterator MI =
306 std::lower_bound(SubsectionFragmentMap.begin(), SubsectionFragmentMap.end(),
307 std::make_pair(Subsection, (MCFragment *)nullptr));
308 bool ExactMatch = false;
309 if (MI != SubsectionFragmentMap.end()) {
310 ExactMatch = MI->first == Subsection;
315 if (MI == SubsectionFragmentMap.end())
319 if (!ExactMatch && Subsection != 0) {
320 // The GNU as documentation claims that subsections have an alignment of 4,
321 // although this appears not to be the case.
322 MCFragment *F = new MCDataFragment();
323 SubsectionFragmentMap.insert(MI, std::make_pair(Subsection, F));
324 getFragmentList().insert(IP, F);
332 MCSymbolData::MCSymbolData() : Symbol(nullptr) {}
334 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
335 uint64_t _Offset, MCAssembler *A)
336 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
337 IsExternal(false), IsPrivateExtern(false),
338 CommonSize(0), SymbolSize(nullptr), CommonAlign(0),
342 A->getSymbolList().push_back(this);
347 MCAssembler::MCAssembler(MCContext &Context_, MCAsmBackend &Backend_,
348 MCCodeEmitter &Emitter_, MCObjectWriter &Writer_,
350 : Context(Context_), Backend(Backend_), Emitter(Emitter_), Writer(Writer_),
351 OS(OS_), BundleAlignSize(0), RelaxAll(false), NoExecStack(false),
352 SubsectionsViaSymbols(false), ELFHeaderEFlags(0) {
353 VersionMinInfo.Major = 0; // Major version == 0 for "none specified"
356 MCAssembler::~MCAssembler() {
359 void MCAssembler::reset() {
364 IndirectSymbols.clear();
369 SubsectionsViaSymbols = false;
372 // reset objects owned by us
373 getBackend().reset();
374 getEmitter().reset();
376 getLOHContainer().reset();
379 bool MCAssembler::isThumbFunc(const MCSymbol *Symbol) const {
380 if (ThumbFuncs.count(Symbol))
383 if (!Symbol->isVariable())
386 // FIXME: It looks like gas supports some cases of the form "foo + 2". It
387 // is not clear if that is a bug or a feature.
388 const MCExpr *Expr = Symbol->getVariableValue();
389 const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Expr);
393 if (Ref->getKind() != MCSymbolRefExpr::VK_None)
396 const MCSymbol &Sym = Ref->getSymbol();
397 if (!isThumbFunc(&Sym))
400 ThumbFuncs.insert(Symbol); // Cache it.
404 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
405 // Non-temporary labels should always be visible to the linker.
406 if (!Symbol.isTemporary())
409 // Absolute temporary labels are never visible.
410 if (!Symbol.isInSection())
413 // Otherwise, check if the section requires symbols even for temporary labels.
414 return getBackend().doesSectionRequireSymbols(Symbol.getSection());
417 const MCSymbolData *MCAssembler::getAtom(const MCSymbolData *SD) const {
418 // Linker visible symbols define atoms.
419 if (isSymbolLinkerVisible(SD->getSymbol()))
422 // Absolute and undefined symbols have no defining atom.
423 if (!SD->getFragment())
426 // Non-linker visible symbols in sections which can't be atomized have no
428 if (!getBackend().isSectionAtomizable(
429 SD->getFragment()->getParent()->getSection()))
432 // Otherwise, return the atom for the containing fragment.
433 return SD->getFragment()->getAtom();
436 bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout,
437 const MCFixup &Fixup, const MCFragment *DF,
438 MCValue &Target, uint64_t &Value) const {
439 ++stats::evaluateFixup;
441 if (!Fixup.getValue()->EvaluateAsRelocatable(Target, &Layout))
442 getContext().FatalError(Fixup.getLoc(), "expected relocatable expression");
444 bool IsPCRel = Backend.getFixupKindInfo(
445 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
449 if (Target.getSymB()) {
451 } else if (!Target.getSymA()) {
454 const MCSymbolRefExpr *A = Target.getSymA();
455 const MCSymbol &SA = A->getSymbol();
456 if (A->getKind() != MCSymbolRefExpr::VK_None ||
457 SA.AliasedSymbol().isUndefined()) {
460 const MCSymbolData &DataA = getSymbolData(SA);
462 getWriter().IsSymbolRefDifferenceFullyResolvedImpl(*this, DataA,
467 IsResolved = Target.isAbsolute();
470 Value = Target.getConstant();
472 if (const MCSymbolRefExpr *A = Target.getSymA()) {
473 const MCSymbol &Sym = A->getSymbol().AliasedSymbol();
475 Value += Layout.getSymbolOffset(&getSymbolData(Sym));
477 if (const MCSymbolRefExpr *B = Target.getSymB()) {
478 const MCSymbol &Sym = B->getSymbol().AliasedSymbol();
480 Value -= Layout.getSymbolOffset(&getSymbolData(Sym));
484 bool ShouldAlignPC = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
485 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits;
486 assert((ShouldAlignPC ? IsPCRel : true) &&
487 "FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!");
490 uint32_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset();
492 // A number of ARM fixups in Thumb mode require that the effective PC
493 // address be determined as the 32-bit aligned version of the actual offset.
494 if (ShouldAlignPC) Offset &= ~0x3;
498 // Let the backend adjust the fixup value if necessary, including whether
499 // we need a relocation.
500 Backend.processFixupValue(*this, Layout, Fixup, DF, Target, Value,
506 uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
507 const MCFragment &F) const {
508 switch (F.getKind()) {
509 case MCFragment::FT_Data:
510 case MCFragment::FT_Relaxable:
511 case MCFragment::FT_CompactEncodedInst:
512 return cast<MCEncodedFragment>(F).getContents().size();
513 case MCFragment::FT_Fill:
514 return cast<MCFillFragment>(F).getSize();
516 case MCFragment::FT_LEB:
517 return cast<MCLEBFragment>(F).getContents().size();
519 case MCFragment::FT_Align: {
520 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
521 unsigned Offset = Layout.getFragmentOffset(&AF);
522 unsigned Size = OffsetToAlignment(Offset, AF.getAlignment());
523 // If we are padding with nops, force the padding to be larger than the
525 if (Size > 0 && AF.hasEmitNops()) {
526 while (Size % getBackend().getMinimumNopSize())
527 Size += AF.getAlignment();
529 if (Size > AF.getMaxBytesToEmit())
534 case MCFragment::FT_Org: {
535 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
536 int64_t TargetLocation;
537 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, Layout))
538 report_fatal_error("expected assembly-time absolute expression");
540 // FIXME: We need a way to communicate this error.
541 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
542 int64_t Size = TargetLocation - FragmentOffset;
543 if (Size < 0 || Size >= 0x40000000)
544 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
545 "' (at offset '" + Twine(FragmentOffset) + "')");
549 case MCFragment::FT_Dwarf:
550 return cast<MCDwarfLineAddrFragment>(F).getContents().size();
551 case MCFragment::FT_DwarfFrame:
552 return cast<MCDwarfCallFrameFragment>(F).getContents().size();
555 llvm_unreachable("invalid fragment kind");
558 void MCAsmLayout::layoutFragment(MCFragment *F) {
559 MCFragment *Prev = F->getPrevNode();
561 // We should never try to recompute something which is valid.
562 assert(!isFragmentValid(F) && "Attempt to recompute a valid fragment!");
563 // We should never try to compute the fragment layout if its predecessor
565 assert((!Prev || isFragmentValid(Prev)) &&
566 "Attempt to compute fragment before its predecessor!");
568 ++stats::FragmentLayouts;
570 // Compute fragment offset and size.
572 F->Offset = Prev->Offset + getAssembler().computeFragmentSize(*this, *Prev);
575 LastValidFragment[F->getParent()] = F;
577 // If bundling is enabled and this fragment has instructions in it, it has to
578 // obey the bundling restrictions. With padding, we'll have:
583 // -------------------------------------
584 // Prev |##########| F |
585 // -------------------------------------
590 // The fragment's offset will point to after the padding, and its computed
591 // size won't include the padding.
593 if (Assembler.isBundlingEnabled() && F->hasInstructions()) {
594 assert(isa<MCEncodedFragment>(F) &&
595 "Only MCEncodedFragment implementations have instructions");
596 uint64_t FSize = Assembler.computeFragmentSize(*this, *F);
598 if (FSize > Assembler.getBundleAlignSize())
599 report_fatal_error("Fragment can't be larger than a bundle size");
601 uint64_t RequiredBundlePadding = computeBundlePadding(F, F->Offset, FSize);
602 if (RequiredBundlePadding > UINT8_MAX)
603 report_fatal_error("Padding cannot exceed 255 bytes");
604 F->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
605 F->Offset += RequiredBundlePadding;
609 /// \brief Write the contents of a fragment to the given object writer. Expects
610 /// a MCEncodedFragment.
611 static void writeFragmentContents(const MCFragment &F, MCObjectWriter *OW) {
612 const MCEncodedFragment &EF = cast<MCEncodedFragment>(F);
613 OW->WriteBytes(EF.getContents());
616 /// \brief Write the fragment \p F to the output file.
617 static void writeFragment(const MCAssembler &Asm, const MCAsmLayout &Layout,
618 const MCFragment &F) {
619 MCObjectWriter *OW = &Asm.getWriter();
621 // FIXME: Embed in fragments instead?
622 uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F);
624 // Should NOP padding be written out before this fragment?
625 unsigned BundlePadding = F.getBundlePadding();
626 if (BundlePadding > 0) {
627 assert(Asm.isBundlingEnabled() &&
628 "Writing bundle padding with disabled bundling");
629 assert(F.hasInstructions() &&
630 "Writing bundle padding for a fragment without instructions");
632 unsigned TotalLength = BundlePadding + static_cast<unsigned>(FragmentSize);
633 if (F.alignToBundleEnd() && TotalLength > Asm.getBundleAlignSize()) {
634 // If the padding itself crosses a bundle boundary, it must be emitted
635 // in 2 pieces, since even nop instructions must not cross boundaries.
636 // v--------------v <- BundleAlignSize
637 // v---------v <- BundlePadding
638 // ----------------------------
639 // | Prev |####|####| F |
640 // ----------------------------
641 // ^-------------------^ <- TotalLength
642 unsigned DistanceToBoundary = TotalLength - Asm.getBundleAlignSize();
643 if (!Asm.getBackend().writeNopData(DistanceToBoundary, OW))
644 report_fatal_error("unable to write NOP sequence of " +
645 Twine(DistanceToBoundary) + " bytes");
646 BundlePadding -= DistanceToBoundary;
648 if (!Asm.getBackend().writeNopData(BundlePadding, OW))
649 report_fatal_error("unable to write NOP sequence of " +
650 Twine(BundlePadding) + " bytes");
653 // This variable (and its dummy usage) is to participate in the assert at
654 // the end of the function.
655 uint64_t Start = OW->getStream().tell();
658 ++stats::EmittedFragments;
660 switch (F.getKind()) {
661 case MCFragment::FT_Align: {
662 ++stats::EmittedAlignFragments;
663 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
664 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
666 uint64_t Count = FragmentSize / AF.getValueSize();
668 // FIXME: This error shouldn't actually occur (the front end should emit
669 // multiple .align directives to enforce the semantics it wants), but is
670 // severe enough that we want to report it. How to handle this?
671 if (Count * AF.getValueSize() != FragmentSize)
672 report_fatal_error("undefined .align directive, value size '" +
673 Twine(AF.getValueSize()) +
674 "' is not a divisor of padding size '" +
675 Twine(FragmentSize) + "'");
677 // See if we are aligning with nops, and if so do that first to try to fill
678 // the Count bytes. Then if that did not fill any bytes or there are any
679 // bytes left to fill use the Value and ValueSize to fill the rest.
680 // If we are aligning with nops, ask that target to emit the right data.
681 if (AF.hasEmitNops()) {
682 if (!Asm.getBackend().writeNopData(Count, OW))
683 report_fatal_error("unable to write nop sequence of " +
684 Twine(Count) + " bytes");
688 // Otherwise, write out in multiples of the value size.
689 for (uint64_t i = 0; i != Count; ++i) {
690 switch (AF.getValueSize()) {
691 default: llvm_unreachable("Invalid size!");
692 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
693 case 2: OW->Write16(uint16_t(AF.getValue())); break;
694 case 4: OW->Write32(uint32_t(AF.getValue())); break;
695 case 8: OW->Write64(uint64_t(AF.getValue())); break;
701 case MCFragment::FT_Data:
702 ++stats::EmittedDataFragments;
703 writeFragmentContents(F, OW);
706 case MCFragment::FT_Relaxable:
707 ++stats::EmittedRelaxableFragments;
708 writeFragmentContents(F, OW);
711 case MCFragment::FT_CompactEncodedInst:
712 ++stats::EmittedCompactEncodedInstFragments;
713 writeFragmentContents(F, OW);
716 case MCFragment::FT_Fill: {
717 ++stats::EmittedFillFragments;
718 const MCFillFragment &FF = cast<MCFillFragment>(F);
720 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
722 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
723 switch (FF.getValueSize()) {
724 default: llvm_unreachable("Invalid size!");
725 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
726 case 2: OW->Write16(uint16_t(FF.getValue())); break;
727 case 4: OW->Write32(uint32_t(FF.getValue())); break;
728 case 8: OW->Write64(uint64_t(FF.getValue())); break;
734 case MCFragment::FT_LEB: {
735 const MCLEBFragment &LF = cast<MCLEBFragment>(F);
736 OW->WriteBytes(LF.getContents().str());
740 case MCFragment::FT_Org: {
741 ++stats::EmittedOrgFragments;
742 const MCOrgFragment &OF = cast<MCOrgFragment>(F);
744 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
745 OW->Write8(uint8_t(OF.getValue()));
750 case MCFragment::FT_Dwarf: {
751 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
752 OW->WriteBytes(OF.getContents().str());
755 case MCFragment::FT_DwarfFrame: {
756 const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F);
757 OW->WriteBytes(CF.getContents().str());
762 assert(OW->getStream().tell() - Start == FragmentSize &&
763 "The stream should advance by fragment size");
766 void MCAssembler::writeSectionData(const MCSectionData *SD,
767 const MCAsmLayout &Layout) const {
768 // Ignore virtual sections.
769 if (SD->getSection().isVirtualSection()) {
770 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
772 // Check that contents are only things legal inside a virtual section.
773 for (MCSectionData::const_iterator it = SD->begin(),
774 ie = SD->end(); it != ie; ++it) {
775 switch (it->getKind()) {
776 default: llvm_unreachable("Invalid fragment in virtual section!");
777 case MCFragment::FT_Data: {
778 // Check that we aren't trying to write a non-zero contents (or fixups)
779 // into a virtual section. This is to support clients which use standard
780 // directives to fill the contents of virtual sections.
781 const MCDataFragment &DF = cast<MCDataFragment>(*it);
782 assert(DF.fixup_begin() == DF.fixup_end() &&
783 "Cannot have fixups in virtual section!");
784 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
785 assert(DF.getContents()[i] == 0 &&
786 "Invalid data value for virtual section!");
789 case MCFragment::FT_Align:
790 // Check that we aren't trying to write a non-zero value into a virtual
792 assert((cast<MCAlignFragment>(it)->getValueSize() == 0 ||
793 cast<MCAlignFragment>(it)->getValue() == 0) &&
794 "Invalid align in virtual section!");
796 case MCFragment::FT_Fill:
797 assert((cast<MCFillFragment>(it)->getValueSize() == 0 ||
798 cast<MCFillFragment>(it)->getValue() == 0) &&
799 "Invalid fill in virtual section!");
807 uint64_t Start = getWriter().getStream().tell();
810 for (MCSectionData::const_iterator it = SD->begin(), ie = SD->end();
812 writeFragment(*this, Layout, *it);
814 assert(getWriter().getStream().tell() - Start ==
815 Layout.getSectionAddressSize(SD));
818 std::pair<uint64_t, bool> MCAssembler::handleFixup(const MCAsmLayout &Layout,
820 const MCFixup &Fixup) {
821 // Evaluate the fixup.
824 bool IsPCRel = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
825 MCFixupKindInfo::FKF_IsPCRel;
826 if (!evaluateFixup(Layout, Fixup, &F, Target, FixedValue)) {
827 // The fixup was unresolved, we need a relocation. Inform the object
828 // writer of the relocation, and give it an opportunity to adjust the
829 // fixup value if need be.
830 getWriter().RecordRelocation(*this, Layout, &F, Fixup, Target, IsPCRel,
833 return std::make_pair(FixedValue, IsPCRel);
836 void MCAssembler::Finish() {
837 DEBUG_WITH_TYPE("mc-dump", {
838 llvm::errs() << "assembler backend - pre-layout\n--\n";
841 // Create the layout object.
842 MCAsmLayout Layout(*this);
844 // Create dummy fragments and assign section ordinals.
845 unsigned SectionIndex = 0;
846 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
847 // Create dummy fragments to eliminate any empty sections, this simplifies
849 if (it->getFragmentList().empty())
850 new MCDataFragment(it);
852 it->setOrdinal(SectionIndex++);
855 // Assign layout order indices to sections and fragments.
856 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
857 MCSectionData *SD = Layout.getSectionOrder()[i];
858 SD->setLayoutOrder(i);
860 unsigned FragmentIndex = 0;
861 for (MCSectionData::iterator iFrag = SD->begin(), iFragEnd = SD->end();
862 iFrag != iFragEnd; ++iFrag)
863 iFrag->setLayoutOrder(FragmentIndex++);
866 // Layout until everything fits.
867 while (layoutOnce(Layout))
870 DEBUG_WITH_TYPE("mc-dump", {
871 llvm::errs() << "assembler backend - post-relaxation\n--\n";
874 // Finalize the layout, including fragment lowering.
875 finishLayout(Layout);
877 DEBUG_WITH_TYPE("mc-dump", {
878 llvm::errs() << "assembler backend - final-layout\n--\n";
881 uint64_t StartOffset = OS.tell();
883 // Allow the object writer a chance to perform post-layout binding (for
884 // example, to set the index fields in the symbol data).
885 getWriter().ExecutePostLayoutBinding(*this, Layout);
887 // Evaluate and apply the fixups, generating relocation entries as necessary.
888 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
889 for (MCSectionData::iterator it2 = it->begin(),
890 ie2 = it->end(); it2 != ie2; ++it2) {
891 MCEncodedFragmentWithFixups *F =
892 dyn_cast<MCEncodedFragmentWithFixups>(it2);
894 for (MCEncodedFragmentWithFixups::fixup_iterator it3 = F->fixup_begin(),
895 ie3 = F->fixup_end(); it3 != ie3; ++it3) {
896 MCFixup &Fixup = *it3;
899 std::tie(FixedValue, IsPCRel) = handleFixup(Layout, *F, Fixup);
900 getBackend().applyFixup(Fixup, F->getContents().data(),
901 F->getContents().size(), FixedValue, IsPCRel);
907 // Write the object file.
908 getWriter().WriteObject(*this, Layout);
910 stats::ObjectBytes += OS.tell() - StartOffset;
913 bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup,
914 const MCRelaxableFragment *DF,
915 const MCAsmLayout &Layout) const {
916 // If we cannot resolve the fixup value, it requires relaxation.
919 if (!evaluateFixup(Layout, Fixup, DF, Target, Value))
922 return getBackend().fixupNeedsRelaxation(Fixup, Value, DF, Layout);
925 bool MCAssembler::fragmentNeedsRelaxation(const MCRelaxableFragment *F,
926 const MCAsmLayout &Layout) const {
927 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
928 // are intentionally pushing out inst fragments, or because we relaxed a
929 // previous instruction to one that doesn't need relaxation.
930 if (!getBackend().mayNeedRelaxation(F->getInst()))
933 for (MCRelaxableFragment::const_fixup_iterator it = F->fixup_begin(),
934 ie = F->fixup_end(); it != ie; ++it)
935 if (fixupNeedsRelaxation(*it, F, Layout))
941 bool MCAssembler::relaxInstruction(MCAsmLayout &Layout,
942 MCRelaxableFragment &F) {
943 if (!fragmentNeedsRelaxation(&F, Layout))
946 ++stats::RelaxedInstructions;
948 // FIXME-PERF: We could immediately lower out instructions if we can tell
949 // they are fully resolved, to avoid retesting on later passes.
951 // Relax the fragment.
954 getBackend().relaxInstruction(F.getInst(), Relaxed);
956 // Encode the new instruction.
958 // FIXME-PERF: If it matters, we could let the target do this. It can
959 // probably do so more efficiently in many cases.
960 SmallVector<MCFixup, 4> Fixups;
961 SmallString<256> Code;
962 raw_svector_ostream VecOS(Code);
963 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups, F.getSubtargetInfo());
966 // Update the fragment.
968 F.getContents() = Code;
969 F.getFixups() = Fixups;
974 bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) {
976 uint64_t OldSize = LF.getContents().size();
977 bool IsAbs = LF.getValue().EvaluateAsAbsolute(Value, Layout);
980 SmallString<8> &Data = LF.getContents();
982 raw_svector_ostream OSE(Data);
984 encodeSLEB128(Value, OSE);
986 encodeULEB128(Value, OSE);
988 return OldSize != LF.getContents().size();
991 bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout,
992 MCDwarfLineAddrFragment &DF) {
993 MCContext &Context = Layout.getAssembler().getContext();
994 int64_t AddrDelta = 0;
995 uint64_t OldSize = DF.getContents().size();
996 bool IsAbs = DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, Layout);
1000 LineDelta = DF.getLineDelta();
1001 SmallString<8> &Data = DF.getContents();
1003 raw_svector_ostream OSE(Data);
1004 MCDwarfLineAddr::Encode(Context, LineDelta, AddrDelta, OSE);
1006 return OldSize != Data.size();
1009 bool MCAssembler::relaxDwarfCallFrameFragment(MCAsmLayout &Layout,
1010 MCDwarfCallFrameFragment &DF) {
1011 MCContext &Context = Layout.getAssembler().getContext();
1012 int64_t AddrDelta = 0;
1013 uint64_t OldSize = DF.getContents().size();
1014 bool IsAbs = DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, Layout);
1017 SmallString<8> &Data = DF.getContents();
1019 raw_svector_ostream OSE(Data);
1020 MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE);
1022 return OldSize != Data.size();
1025 bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSectionData &SD) {
1026 // Holds the first fragment which needed relaxing during this layout. It will
1027 // remain NULL if none were relaxed.
1028 // When a fragment is relaxed, all the fragments following it should get
1029 // invalidated because their offset is going to change.
1030 MCFragment *FirstRelaxedFragment = nullptr;
1032 // Attempt to relax all the fragments in the section.
1033 for (MCSectionData::iterator I = SD.begin(), IE = SD.end(); I != IE; ++I) {
1034 // Check if this is a fragment that needs relaxation.
1035 bool RelaxedFrag = false;
1036 switch(I->getKind()) {
1039 case MCFragment::FT_Relaxable:
1040 assert(!getRelaxAll() &&
1041 "Did not expect a MCRelaxableFragment in RelaxAll mode");
1042 RelaxedFrag = relaxInstruction(Layout, *cast<MCRelaxableFragment>(I));
1044 case MCFragment::FT_Dwarf:
1045 RelaxedFrag = relaxDwarfLineAddr(Layout,
1046 *cast<MCDwarfLineAddrFragment>(I));
1048 case MCFragment::FT_DwarfFrame:
1050 relaxDwarfCallFrameFragment(Layout,
1051 *cast<MCDwarfCallFrameFragment>(I));
1053 case MCFragment::FT_LEB:
1054 RelaxedFrag = relaxLEB(Layout, *cast<MCLEBFragment>(I));
1057 if (RelaxedFrag && !FirstRelaxedFragment)
1058 FirstRelaxedFragment = I;
1060 if (FirstRelaxedFragment) {
1061 Layout.invalidateFragmentsFrom(FirstRelaxedFragment);
1067 bool MCAssembler::layoutOnce(MCAsmLayout &Layout) {
1068 ++stats::RelaxationSteps;
1070 bool WasRelaxed = false;
1071 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1072 MCSectionData &SD = *it;
1073 while (layoutSectionOnce(Layout, SD))
1080 void MCAssembler::finishLayout(MCAsmLayout &Layout) {
1081 // The layout is done. Mark every fragment as valid.
1082 for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) {
1083 Layout.getFragmentOffset(&*Layout.getSectionOrder()[i]->rbegin());
1087 // Debugging methods
1091 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
1092 OS << "<MCFixup" << " Offset:" << AF.getOffset()
1093 << " Value:" << *AF.getValue()
1094 << " Kind:" << AF.getKind() << ">";
1100 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1101 void MCFragment::dump() {
1102 raw_ostream &OS = llvm::errs();
1105 switch (getKind()) {
1106 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
1107 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
1108 case MCFragment::FT_CompactEncodedInst:
1109 OS << "MCCompactEncodedInstFragment"; break;
1110 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
1111 case MCFragment::FT_Relaxable: OS << "MCRelaxableFragment"; break;
1112 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
1113 case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
1114 case MCFragment::FT_DwarfFrame: OS << "MCDwarfCallFrameFragment"; break;
1115 case MCFragment::FT_LEB: OS << "MCLEBFragment"; break;
1118 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
1119 << " Offset:" << Offset
1120 << " HasInstructions:" << hasInstructions()
1121 << " BundlePadding:" << static_cast<unsigned>(getBundlePadding()) << ">";
1123 switch (getKind()) {
1124 case MCFragment::FT_Align: {
1125 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
1126 if (AF->hasEmitNops())
1127 OS << " (emit nops)";
1129 OS << " Alignment:" << AF->getAlignment()
1130 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
1131 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
1134 case MCFragment::FT_Data: {
1135 const MCDataFragment *DF = cast<MCDataFragment>(this);
1137 OS << " Contents:[";
1138 const SmallVectorImpl<char> &Contents = DF->getContents();
1139 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
1141 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1143 OS << "] (" << Contents.size() << " bytes)";
1145 if (DF->fixup_begin() != DF->fixup_end()) {
1148 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
1149 ie = DF->fixup_end(); it != ie; ++it) {
1150 if (it != DF->fixup_begin()) OS << ",\n ";
1157 case MCFragment::FT_CompactEncodedInst: {
1158 const MCCompactEncodedInstFragment *CEIF =
1159 cast<MCCompactEncodedInstFragment>(this);
1161 OS << " Contents:[";
1162 const SmallVectorImpl<char> &Contents = CEIF->getContents();
1163 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
1165 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1167 OS << "] (" << Contents.size() << " bytes)";
1170 case MCFragment::FT_Fill: {
1171 const MCFillFragment *FF = cast<MCFillFragment>(this);
1172 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
1173 << " Size:" << FF->getSize();
1176 case MCFragment::FT_Relaxable: {
1177 const MCRelaxableFragment *F = cast<MCRelaxableFragment>(this);
1180 F->getInst().dump_pretty(OS);
1183 case MCFragment::FT_Org: {
1184 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
1186 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
1189 case MCFragment::FT_Dwarf: {
1190 const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
1192 OS << " AddrDelta:" << OF->getAddrDelta()
1193 << " LineDelta:" << OF->getLineDelta();
1196 case MCFragment::FT_DwarfFrame: {
1197 const MCDwarfCallFrameFragment *CF = cast<MCDwarfCallFrameFragment>(this);
1199 OS << " AddrDelta:" << CF->getAddrDelta();
1202 case MCFragment::FT_LEB: {
1203 const MCLEBFragment *LF = cast<MCLEBFragment>(this);
1205 OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
1212 void MCSectionData::dump() {
1213 raw_ostream &OS = llvm::errs();
1215 OS << "<MCSectionData";
1216 OS << " Alignment:" << getAlignment()
1217 << " Fragments:[\n ";
1218 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1219 if (it != begin()) OS << ",\n ";
1225 void MCSymbolData::dump() {
1226 raw_ostream &OS = llvm::errs();
1228 OS << "<MCSymbolData Symbol:" << getSymbol()
1229 << " Fragment:" << getFragment() << " Offset:" << getOffset()
1230 << " Flags:" << getFlags() << " Index:" << getIndex();
1232 OS << " (common, size:" << getCommonSize()
1233 << " align: " << getCommonAlignment() << ")";
1235 OS << " (external)";
1236 if (isPrivateExtern())
1237 OS << " (private extern)";
1241 void MCAssembler::dump() {
1242 raw_ostream &OS = llvm::errs();
1244 OS << "<MCAssembler\n";
1245 OS << " Sections:[\n ";
1246 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1247 if (it != begin()) OS << ",\n ";
1253 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1254 if (it != symbol_begin()) OS << ",\n ";
1261 // anchors for MC*Fragment vtables
1262 void MCEncodedFragment::anchor() { }
1263 void MCEncodedFragmentWithFixups::anchor() { }
1264 void MCDataFragment::anchor() { }
1265 void MCCompactEncodedInstFragment::anchor() { }
1266 void MCRelaxableFragment::anchor() { }
1267 void MCAlignFragment::anchor() { }
1268 void MCFillFragment::anchor() { }
1269 void MCOrgFragment::anchor() { }
1270 void MCLEBFragment::anchor() { }
1271 void MCDwarfLineAddrFragment::anchor() { }
1272 void MCDwarfCallFrameFragment::anchor() { }