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 #define DEBUG_TYPE "assembler"
11 #include "llvm/MC/MCAssembler.h"
12 #include "llvm/ADT/Statistic.h"
13 #include "llvm/ADT/StringExtras.h"
14 #include "llvm/ADT/Twine.h"
15 #include "llvm/MC/MCAsmBackend.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/MCSymbol.h"
25 #include "llvm/MC/MCValue.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/LEB128.h"
29 #include "llvm/Support/TargetRegistry.h"
30 #include "llvm/Support/raw_ostream.h"
36 STATISTIC(EmittedFragments, "Number of emitted assembler fragments - total");
37 STATISTIC(EmittedRelaxableFragments,
38 "Number of emitted assembler fragments - relaxable");
39 STATISTIC(EmittedDataFragments,
40 "Number of emitted assembler fragments - data");
41 STATISTIC(EmittedCompactEncodedInstFragments,
42 "Number of emitted assembler fragments - compact encoded inst");
43 STATISTIC(EmittedAlignFragments,
44 "Number of emitted assembler fragments - align");
45 STATISTIC(EmittedFillFragments,
46 "Number of emitted assembler fragments - fill");
47 STATISTIC(EmittedOrgFragments,
48 "Number of emitted assembler fragments - org");
49 STATISTIC(evaluateFixup, "Number of evaluated fixups");
50 STATISTIC(FragmentLayouts, "Number of fragment layouts");
51 STATISTIC(ObjectBytes, "Number of emitted object file bytes");
52 STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps");
53 STATISTIC(RelaxedInstructions, "Number of relaxed instructions");
57 // FIXME FIXME FIXME: There are number of places in this file where we convert
58 // what is a 64-bit assembler value used for computation into a value in the
59 // object file, which may truncate it. We should detect that truncation where
60 // invalid and report errors back.
64 MCAsmLayout::MCAsmLayout(MCAssembler &Asm)
65 : Assembler(Asm), LastValidFragment()
67 // Compute the section layout order. Virtual sections must go last.
68 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
69 if (!it->getSection().isVirtualSection())
70 SectionOrder.push_back(&*it);
71 for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
72 if (it->getSection().isVirtualSection())
73 SectionOrder.push_back(&*it);
76 bool MCAsmLayout::isFragmentValid(const MCFragment *F) const {
77 const MCSectionData &SD = *F->getParent();
78 const MCFragment *LastValid = LastValidFragment.lookup(&SD);
81 assert(LastValid->getParent() == F->getParent());
82 return F->getLayoutOrder() <= LastValid->getLayoutOrder();
85 void MCAsmLayout::invalidateFragmentsFrom(MCFragment *F) {
86 // If this fragment wasn't already valid, we don't need to do anything.
87 if (!isFragmentValid(F))
90 // Otherwise, reset the last valid fragment to the previous fragment
91 // (if this is the first fragment, it will be NULL).
92 const MCSectionData &SD = *F->getParent();
93 LastValidFragment[&SD] = F->getPrevNode();
96 void MCAsmLayout::ensureValid(const MCFragment *F) const {
97 MCSectionData &SD = *F->getParent();
99 MCFragment *Cur = LastValidFragment[&SD];
103 Cur = Cur->getNextNode();
105 // Advance the layout position until the fragment is valid.
106 while (!isFragmentValid(F)) {
107 assert(Cur && "Layout bookkeeping error");
108 const_cast<MCAsmLayout*>(this)->layoutFragment(Cur);
109 Cur = Cur->getNextNode();
113 uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
115 assert(F->Offset != ~UINT64_C(0) && "Address not set!");
119 uint64_t MCAsmLayout::getSymbolOffset(const MCSymbolData *SD) const {
120 const MCSymbol &S = SD->getSymbol();
122 // If this is a variable, then recursively evaluate now.
123 if (S.isVariable()) {
125 if (!S.getVariableValue()->EvaluateAsRelocatable(Target, *this))
126 report_fatal_error("unable to evaluate offset for variable '" +
129 // Verify that any used symbols are defined.
130 if (Target.getSymA() && Target.getSymA()->getSymbol().isUndefined())
131 report_fatal_error("unable to evaluate offset to undefined symbol '" +
132 Target.getSymA()->getSymbol().getName() + "'");
133 if (Target.getSymB() && Target.getSymB()->getSymbol().isUndefined())
134 report_fatal_error("unable to evaluate offset to undefined symbol '" +
135 Target.getSymB()->getSymbol().getName() + "'");
137 uint64_t Offset = Target.getConstant();
138 if (Target.getSymA())
139 Offset += getSymbolOffset(&Assembler.getSymbolData(
140 Target.getSymA()->getSymbol()));
141 if (Target.getSymB())
142 Offset -= getSymbolOffset(&Assembler.getSymbolData(
143 Target.getSymB()->getSymbol()));
147 assert(SD->getFragment() && "Invalid getOffset() on undefined symbol!");
148 return getFragmentOffset(SD->getFragment()) + SD->getOffset();
151 uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const {
152 // The size is the last fragment's end offset.
153 const MCFragment &F = SD->getFragmentList().back();
154 return getFragmentOffset(&F) + getAssembler().computeFragmentSize(*this, F);
157 uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
158 // Virtual sections have no file size.
159 if (SD->getSection().isVirtualSection())
162 // Otherwise, the file size is the same as the address space size.
163 return getSectionAddressSize(SD);
166 uint64_t MCAsmLayout::computeBundlePadding(const MCFragment *F,
167 uint64_t FOffset, uint64_t FSize) {
168 uint64_t BundleSize = Assembler.getBundleAlignSize();
169 assert(BundleSize > 0 &&
170 "computeBundlePadding should only be called if bundling is enabled");
171 uint64_t BundleMask = BundleSize - 1;
172 uint64_t OffsetInBundle = FOffset & BundleMask;
173 uint64_t EndOfFragment = OffsetInBundle + FSize;
175 // There are two kinds of bundling restrictions:
177 // 1) For alignToBundleEnd(), add padding to ensure that the fragment will
178 // *end* on a bundle boundary.
179 // 2) Otherwise, check if the fragment would cross a bundle boundary. If it
180 // would, add padding until the end of the bundle so that the fragment
181 // will start in a new one.
182 if (F->alignToBundleEnd()) {
183 // Three possibilities here:
185 // A) The fragment just happens to end at a bundle boundary, so we're good.
186 // B) The fragment ends before the current bundle boundary: pad it just
187 // enough to reach the boundary.
188 // C) The fragment ends after the current bundle boundary: pad it until it
189 // reaches the end of the next bundle boundary.
191 // Note: this code could be made shorter with some modulo trickery, but it's
192 // intentionally kept in its more explicit form for simplicity.
193 if (EndOfFragment == BundleSize)
195 else if (EndOfFragment < BundleSize)
196 return BundleSize - EndOfFragment;
197 else { // EndOfFragment > BundleSize
198 return 2 * BundleSize - EndOfFragment;
200 } else if (EndOfFragment > BundleSize)
201 return BundleSize - OffsetInBundle;
208 MCFragment::MCFragment() : Kind(FragmentType(~0)) {
211 MCFragment::~MCFragment() {
214 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
215 : Kind(_Kind), Parent(_Parent), Atom(0), Offset(~UINT64_C(0))
218 Parent->getFragmentList().push_back(this);
223 MCEncodedFragment::~MCEncodedFragment() {
228 MCEncodedFragmentWithFixups::~MCEncodedFragmentWithFixups() {
233 MCSectionData::MCSectionData() : Section(0) {}
235 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
236 : Section(&_Section),
237 Ordinal(~UINT32_C(0)),
239 BundleLockState(NotBundleLocked), BundleGroupBeforeFirstInst(false),
240 HasInstructions(false)
243 A->getSectionList().push_back(this);
248 MCSymbolData::MCSymbolData() : Symbol(0) {}
250 MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
251 uint64_t _Offset, MCAssembler *A)
252 : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
253 IsExternal(false), IsPrivateExtern(false),
254 CommonSize(0), SymbolSize(0), CommonAlign(0),
258 A->getSymbolList().push_back(this);
263 MCAssembler::MCAssembler(MCContext &Context_, MCAsmBackend &Backend_,
264 MCCodeEmitter &Emitter_, MCObjectWriter &Writer_,
266 : Context(Context_), Backend(Backend_), Emitter(Emitter_), Writer(Writer_),
267 OS(OS_), BundleAlignSize(0), RelaxAll(false), NoExecStack(false),
268 SubsectionsViaSymbols(false), ELFHeaderEFlags(0) {
271 MCAssembler::~MCAssembler() {
274 void MCAssembler::reset() {
279 IndirectSymbols.clear();
284 SubsectionsViaSymbols = false;
287 // reset objects owned by us
288 getBackend().reset();
289 getEmitter().reset();
293 bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
294 // Non-temporary labels should always be visible to the linker.
295 if (!Symbol.isTemporary())
298 // Absolute temporary labels are never visible.
299 if (!Symbol.isInSection())
302 // Otherwise, check if the section requires symbols even for temporary labels.
303 return getBackend().doesSectionRequireSymbols(Symbol.getSection());
306 const MCSymbolData *MCAssembler::getAtom(const MCSymbolData *SD) const {
307 // Linker visible symbols define atoms.
308 if (isSymbolLinkerVisible(SD->getSymbol()))
311 // Absolute and undefined symbols have no defining atom.
312 if (!SD->getFragment())
315 // Non-linker visible symbols in sections which can't be atomized have no
317 if (!getBackend().isSectionAtomizable(
318 SD->getFragment()->getParent()->getSection()))
321 // Otherwise, return the atom for the containing fragment.
322 return SD->getFragment()->getAtom();
325 bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout,
326 const MCFixup &Fixup, const MCFragment *DF,
327 MCValue &Target, uint64_t &Value) const {
328 ++stats::evaluateFixup;
330 if (!Fixup.getValue()->EvaluateAsRelocatable(Target, Layout))
331 getContext().FatalError(Fixup.getLoc(), "expected relocatable expression");
333 bool IsPCRel = Backend.getFixupKindInfo(
334 Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
338 if (Target.getSymB()) {
340 } else if (!Target.getSymA()) {
343 const MCSymbolRefExpr *A = Target.getSymA();
344 const MCSymbol &SA = A->getSymbol();
345 if (A->getKind() != MCSymbolRefExpr::VK_None ||
346 SA.AliasedSymbol().isUndefined()) {
349 const MCSymbolData &DataA = getSymbolData(SA);
351 getWriter().IsSymbolRefDifferenceFullyResolvedImpl(*this, DataA,
356 IsResolved = Target.isAbsolute();
359 Value = Target.getConstant();
361 if (const MCSymbolRefExpr *A = Target.getSymA()) {
362 const MCSymbol &Sym = A->getSymbol().AliasedSymbol();
364 Value += Layout.getSymbolOffset(&getSymbolData(Sym));
366 if (const MCSymbolRefExpr *B = Target.getSymB()) {
367 const MCSymbol &Sym = B->getSymbol().AliasedSymbol();
369 Value -= Layout.getSymbolOffset(&getSymbolData(Sym));
373 bool ShouldAlignPC = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
374 MCFixupKindInfo::FKF_IsAlignedDownTo32Bits;
375 assert((ShouldAlignPC ? IsPCRel : true) &&
376 "FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!");
379 uint32_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset();
381 // A number of ARM fixups in Thumb mode require that the effective PC
382 // address be determined as the 32-bit aligned version of the actual offset.
383 if (ShouldAlignPC) Offset &= ~0x3;
387 // Let the backend adjust the fixup value if necessary, including whether
388 // we need a relocation.
389 Backend.processFixupValue(*this, Layout, Fixup, DF, Target, Value,
395 uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
396 const MCFragment &F) const {
397 switch (F.getKind()) {
398 case MCFragment::FT_Data:
399 case MCFragment::FT_Relaxable:
400 case MCFragment::FT_CompactEncodedInst:
401 return cast<MCEncodedFragment>(F).getContents().size();
402 case MCFragment::FT_Fill:
403 return cast<MCFillFragment>(F).getSize();
405 case MCFragment::FT_LEB:
406 return cast<MCLEBFragment>(F).getContents().size();
408 case MCFragment::FT_Align: {
409 const MCAlignFragment &AF = cast<MCAlignFragment>(F);
410 unsigned Offset = Layout.getFragmentOffset(&AF);
411 unsigned Size = OffsetToAlignment(Offset, AF.getAlignment());
412 // If we are padding with nops, force the padding to be larger than the
414 if (Size > 0 && AF.hasEmitNops()) {
415 while (Size % getBackend().getMinimumNopSize())
416 Size += AF.getAlignment();
418 if (Size > AF.getMaxBytesToEmit())
423 case MCFragment::FT_Org: {
424 MCOrgFragment &OF = cast<MCOrgFragment>(F);
425 int64_t TargetLocation;
426 if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, Layout))
427 report_fatal_error("expected assembly-time absolute expression");
429 // FIXME: We need a way to communicate this error.
430 uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
431 int64_t Size = TargetLocation - FragmentOffset;
432 if (Size < 0 || Size >= 0x40000000)
433 report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
434 "' (at offset '" + Twine(FragmentOffset) + "')");
438 case MCFragment::FT_Dwarf:
439 return cast<MCDwarfLineAddrFragment>(F).getContents().size();
440 case MCFragment::FT_DwarfFrame:
441 return cast<MCDwarfCallFrameFragment>(F).getContents().size();
444 llvm_unreachable("invalid fragment kind");
447 void MCAsmLayout::layoutFragment(MCFragment *F) {
448 MCFragment *Prev = F->getPrevNode();
450 // We should never try to recompute something which is valid.
451 assert(!isFragmentValid(F) && "Attempt to recompute a valid fragment!");
452 // We should never try to compute the fragment layout if its predecessor
454 assert((!Prev || isFragmentValid(Prev)) &&
455 "Attempt to compute fragment before its predecessor!");
457 ++stats::FragmentLayouts;
459 // Compute fragment offset and size.
461 F->Offset = Prev->Offset + getAssembler().computeFragmentSize(*this, *Prev);
464 LastValidFragment[F->getParent()] = F;
466 // If bundling is enabled and this fragment has instructions in it, it has to
467 // obey the bundling restrictions. With padding, we'll have:
472 // -------------------------------------
473 // Prev |##########| F |
474 // -------------------------------------
479 // The fragment's offset will point to after the padding, and its computed
480 // size won't include the padding.
482 if (Assembler.isBundlingEnabled() && F->hasInstructions()) {
483 assert(isa<MCEncodedFragment>(F) &&
484 "Only MCEncodedFragment implementations have instructions");
485 uint64_t FSize = Assembler.computeFragmentSize(*this, *F);
487 if (FSize > Assembler.getBundleAlignSize())
488 report_fatal_error("Fragment can't be larger than a bundle size");
490 uint64_t RequiredBundlePadding = computeBundlePadding(F, F->Offset, FSize);
491 if (RequiredBundlePadding > UINT8_MAX)
492 report_fatal_error("Padding cannot exceed 255 bytes");
493 F->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
494 F->Offset += RequiredBundlePadding;
498 /// \brief Write the contents of a fragment to the given object writer. Expects
499 /// a MCEncodedFragment.
500 static void writeFragmentContents(const MCFragment &F, MCObjectWriter *OW) {
501 MCEncodedFragment &EF = cast<MCEncodedFragment>(F);
502 OW->WriteBytes(EF.getContents());
505 /// \brief Write the fragment \p F to the output file.
506 static void writeFragment(const MCAssembler &Asm, const MCAsmLayout &Layout,
507 const MCFragment &F) {
508 MCObjectWriter *OW = &Asm.getWriter();
510 // FIXME: Embed in fragments instead?
511 uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F);
513 // Should NOP padding be written out before this fragment?
514 unsigned BundlePadding = F.getBundlePadding();
515 if (BundlePadding > 0) {
516 assert(Asm.isBundlingEnabled() &&
517 "Writing bundle padding with disabled bundling");
518 assert(F.hasInstructions() &&
519 "Writing bundle padding for a fragment without instructions");
521 unsigned TotalLength = BundlePadding + static_cast<unsigned>(FragmentSize);
522 if (F.alignToBundleEnd() && TotalLength > Asm.getBundleAlignSize()) {
523 // If the padding itself crosses a bundle boundary, it must be emitted
524 // in 2 pieces, since even nop instructions must not cross boundaries.
525 // v--------------v <- BundleAlignSize
526 // v---------v <- BundlePadding
527 // ----------------------------
528 // | Prev |####|####| F |
529 // ----------------------------
530 // ^-------------------^ <- TotalLength
531 unsigned DistanceToBoundary = TotalLength - Asm.getBundleAlignSize();
532 if (!Asm.getBackend().writeNopData(DistanceToBoundary, OW))
533 report_fatal_error("unable to write NOP sequence of " +
534 Twine(DistanceToBoundary) + " bytes");
535 BundlePadding -= DistanceToBoundary;
537 if (!Asm.getBackend().writeNopData(BundlePadding, OW))
538 report_fatal_error("unable to write NOP sequence of " +
539 Twine(BundlePadding) + " bytes");
542 // This variable (and its dummy usage) is to participate in the assert at
543 // the end of the function.
544 uint64_t Start = OW->getStream().tell();
547 ++stats::EmittedFragments;
549 switch (F.getKind()) {
550 case MCFragment::FT_Align: {
551 ++stats::EmittedAlignFragments;
552 MCAlignFragment &AF = cast<MCAlignFragment>(F);
553 uint64_t Count = FragmentSize / AF.getValueSize();
555 assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
557 // FIXME: This error shouldn't actually occur (the front end should emit
558 // multiple .align directives to enforce the semantics it wants), but is
559 // severe enough that we want to report it. How to handle this?
560 if (Count * AF.getValueSize() != FragmentSize)
561 report_fatal_error("undefined .align directive, value size '" +
562 Twine(AF.getValueSize()) +
563 "' is not a divisor of padding size '" +
564 Twine(FragmentSize) + "'");
566 // See if we are aligning with nops, and if so do that first to try to fill
567 // the Count bytes. Then if that did not fill any bytes or there are any
568 // bytes left to fill use the Value and ValueSize to fill the rest.
569 // If we are aligning with nops, ask that target to emit the right data.
570 if (AF.hasEmitNops()) {
571 if (!Asm.getBackend().writeNopData(Count, OW))
572 report_fatal_error("unable to write nop sequence of " +
573 Twine(Count) + " bytes");
577 // Otherwise, write out in multiples of the value size.
578 for (uint64_t i = 0; i != Count; ++i) {
579 switch (AF.getValueSize()) {
580 default: llvm_unreachable("Invalid size!");
581 case 1: OW->Write8 (uint8_t (AF.getValue())); break;
582 case 2: OW->Write16(uint16_t(AF.getValue())); break;
583 case 4: OW->Write32(uint32_t(AF.getValue())); break;
584 case 8: OW->Write64(uint64_t(AF.getValue())); break;
590 case MCFragment::FT_Data:
591 ++stats::EmittedDataFragments;
592 writeFragmentContents(F, OW);
595 case MCFragment::FT_Relaxable:
596 ++stats::EmittedRelaxableFragments;
597 writeFragmentContents(F, OW);
600 case MCFragment::FT_CompactEncodedInst:
601 ++stats::EmittedCompactEncodedInstFragments;
602 writeFragmentContents(F, OW);
605 case MCFragment::FT_Fill: {
606 ++stats::EmittedFillFragments;
607 MCFillFragment &FF = cast<MCFillFragment>(F);
609 assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
611 for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
612 switch (FF.getValueSize()) {
613 default: llvm_unreachable("Invalid size!");
614 case 1: OW->Write8 (uint8_t (FF.getValue())); break;
615 case 2: OW->Write16(uint16_t(FF.getValue())); break;
616 case 4: OW->Write32(uint32_t(FF.getValue())); break;
617 case 8: OW->Write64(uint64_t(FF.getValue())); break;
623 case MCFragment::FT_LEB: {
624 MCLEBFragment &LF = cast<MCLEBFragment>(F);
625 OW->WriteBytes(LF.getContents().str());
629 case MCFragment::FT_Org: {
630 ++stats::EmittedOrgFragments;
631 MCOrgFragment &OF = cast<MCOrgFragment>(F);
633 for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
634 OW->Write8(uint8_t(OF.getValue()));
639 case MCFragment::FT_Dwarf: {
640 const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
641 OW->WriteBytes(OF.getContents().str());
644 case MCFragment::FT_DwarfFrame: {
645 const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F);
646 OW->WriteBytes(CF.getContents().str());
651 assert(OW->getStream().tell() - Start == FragmentSize &&
652 "The stream should advance by fragment size");
655 void MCAssembler::writeSectionData(const MCSectionData *SD,
656 const MCAsmLayout &Layout) const {
657 // Ignore virtual sections.
658 if (SD->getSection().isVirtualSection()) {
659 assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
661 // Check that contents are only things legal inside a virtual section.
662 for (MCSectionData::const_iterator it = SD->begin(),
663 ie = SD->end(); it != ie; ++it) {
664 switch (it->getKind()) {
665 default: llvm_unreachable("Invalid fragment in virtual section!");
666 case MCFragment::FT_Data: {
667 // Check that we aren't trying to write a non-zero contents (or fixups)
668 // into a virtual section. This is to support clients which use standard
669 // directives to fill the contents of virtual sections.
670 MCDataFragment &DF = cast<MCDataFragment>(*it);
671 assert(DF.fixup_begin() == DF.fixup_end() &&
672 "Cannot have fixups in virtual section!");
673 for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
674 assert(DF.getContents()[i] == 0 &&
675 "Invalid data value for virtual section!");
678 case MCFragment::FT_Align:
679 // Check that we aren't trying to write a non-zero value into a virtual
681 assert((!cast<MCAlignFragment>(it)->getValueSize() ||
682 !cast<MCAlignFragment>(it)->getValue()) &&
683 "Invalid align in virtual section!");
685 case MCFragment::FT_Fill:
686 assert(!cast<MCFillFragment>(it)->getValueSize() &&
687 "Invalid fill in virtual section!");
695 uint64_t Start = getWriter().getStream().tell();
698 for (MCSectionData::const_iterator it = SD->begin(), ie = SD->end();
700 writeFragment(*this, Layout, *it);
702 assert(getWriter().getStream().tell() - Start ==
703 Layout.getSectionAddressSize(SD));
707 uint64_t MCAssembler::handleFixup(const MCAsmLayout &Layout,
709 const MCFixup &Fixup) {
710 // Evaluate the fixup.
713 if (!evaluateFixup(Layout, Fixup, &F, Target, FixedValue)) {
714 // The fixup was unresolved, we need a relocation. Inform the object
715 // writer of the relocation, and give it an opportunity to adjust the
716 // fixup value if need be.
717 getWriter().RecordRelocation(*this, Layout, &F, Fixup, Target, FixedValue);
722 void MCAssembler::Finish() {
723 DEBUG_WITH_TYPE("mc-dump", {
724 llvm::errs() << "assembler backend - pre-layout\n--\n";
727 // Create the layout object.
728 MCAsmLayout Layout(*this);
730 // Create dummy fragments and assign section ordinals.
731 unsigned SectionIndex = 0;
732 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
733 // Create dummy fragments to eliminate any empty sections, this simplifies
735 if (it->getFragmentList().empty())
736 new MCDataFragment(it);
738 it->setOrdinal(SectionIndex++);
741 // Assign layout order indices to sections and fragments.
742 for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
743 MCSectionData *SD = Layout.getSectionOrder()[i];
744 SD->setLayoutOrder(i);
746 unsigned FragmentIndex = 0;
747 for (MCSectionData::iterator iFrag = SD->begin(), iFragEnd = SD->end();
748 iFrag != iFragEnd; ++iFrag)
749 iFrag->setLayoutOrder(FragmentIndex++);
752 // Layout until everything fits.
753 while (layoutOnce(Layout))
756 DEBUG_WITH_TYPE("mc-dump", {
757 llvm::errs() << "assembler backend - post-relaxation\n--\n";
760 // Finalize the layout, including fragment lowering.
761 finishLayout(Layout);
763 DEBUG_WITH_TYPE("mc-dump", {
764 llvm::errs() << "assembler backend - final-layout\n--\n";
767 uint64_t StartOffset = OS.tell();
769 // Allow the object writer a chance to perform post-layout binding (for
770 // example, to set the index fields in the symbol data).
771 getWriter().ExecutePostLayoutBinding(*this, Layout);
773 // Evaluate and apply the fixups, generating relocation entries as necessary.
774 for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
775 for (MCSectionData::iterator it2 = it->begin(),
776 ie2 = it->end(); it2 != ie2; ++it2) {
777 MCEncodedFragmentWithFixups *F =
778 dyn_cast<MCEncodedFragmentWithFixups>(it2);
780 for (MCEncodedFragmentWithFixups::fixup_iterator it3 = F->fixup_begin(),
781 ie3 = F->fixup_end(); it3 != ie3; ++it3) {
782 MCFixup &Fixup = *it3;
783 uint64_t FixedValue = handleFixup(Layout, *F, Fixup);
784 getBackend().applyFixup(Fixup, F->getContents().data(),
785 F->getContents().size(), FixedValue);
791 // Write the object file.
792 getWriter().WriteObject(*this, Layout);
794 stats::ObjectBytes += OS.tell() - StartOffset;
797 bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup,
798 const MCRelaxableFragment *DF,
799 const MCAsmLayout &Layout) const {
800 // If we cannot resolve the fixup value, it requires relaxation.
803 if (!evaluateFixup(Layout, Fixup, DF, Target, Value))
806 return getBackend().fixupNeedsRelaxation(Fixup, Value, DF, Layout);
809 bool MCAssembler::fragmentNeedsRelaxation(const MCRelaxableFragment *F,
810 const MCAsmLayout &Layout) const {
811 // If this inst doesn't ever need relaxation, ignore it. This occurs when we
812 // are intentionally pushing out inst fragments, or because we relaxed a
813 // previous instruction to one that doesn't need relaxation.
814 if (!getBackend().mayNeedRelaxation(F->getInst()))
817 for (MCRelaxableFragment::const_fixup_iterator it = F->fixup_begin(),
818 ie = F->fixup_end(); it != ie; ++it)
819 if (fixupNeedsRelaxation(*it, F, Layout))
825 bool MCAssembler::relaxInstruction(MCAsmLayout &Layout,
826 MCRelaxableFragment &F) {
827 if (!fragmentNeedsRelaxation(&F, Layout))
830 ++stats::RelaxedInstructions;
832 // FIXME-PERF: We could immediately lower out instructions if we can tell
833 // they are fully resolved, to avoid retesting on later passes.
835 // Relax the fragment.
838 getBackend().relaxInstruction(F.getInst(), Relaxed);
840 // Encode the new instruction.
842 // FIXME-PERF: If it matters, we could let the target do this. It can
843 // probably do so more efficiently in many cases.
844 SmallVector<MCFixup, 4> Fixups;
845 SmallString<256> Code;
846 raw_svector_ostream VecOS(Code);
847 getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
850 // Update the fragment.
852 F.getContents() = Code;
853 F.getFixups() = Fixups;
858 bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) {
860 uint64_t OldSize = LF.getContents().size();
861 bool IsAbs = LF.getValue().EvaluateAsAbsolute(Value, Layout);
864 SmallString<8> &Data = LF.getContents();
866 raw_svector_ostream OSE(Data);
868 encodeSLEB128(Value, OSE);
870 encodeULEB128(Value, OSE);
872 return OldSize != LF.getContents().size();
875 bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout,
876 MCDwarfLineAddrFragment &DF) {
877 int64_t AddrDelta = 0;
878 uint64_t OldSize = DF.getContents().size();
879 bool IsAbs = DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, Layout);
883 LineDelta = DF.getLineDelta();
884 SmallString<8> &Data = DF.getContents();
886 raw_svector_ostream OSE(Data);
887 MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OSE);
889 return OldSize != Data.size();
892 bool MCAssembler::relaxDwarfCallFrameFragment(MCAsmLayout &Layout,
893 MCDwarfCallFrameFragment &DF) {
894 int64_t AddrDelta = 0;
895 uint64_t OldSize = DF.getContents().size();
896 bool IsAbs = DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, Layout);
899 SmallString<8> &Data = DF.getContents();
901 raw_svector_ostream OSE(Data);
902 MCDwarfFrameEmitter::EncodeAdvanceLoc(AddrDelta, OSE);
904 return OldSize != Data.size();
907 bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSectionData &SD) {
908 // Holds the first fragment which needed relaxing during this layout. It will
909 // remain NULL if none were relaxed.
910 // When a fragment is relaxed, all the fragments following it should get
911 // invalidated because their offset is going to change.
912 MCFragment *FirstRelaxedFragment = NULL;
914 // Attempt to relax all the fragments in the section.
915 for (MCSectionData::iterator I = SD.begin(), IE = SD.end(); I != IE; ++I) {
916 // Check if this is a fragment that needs relaxation.
917 bool RelaxedFrag = false;
918 switch(I->getKind()) {
921 case MCFragment::FT_Relaxable:
922 assert(!getRelaxAll() &&
923 "Did not expect a MCRelaxableFragment in RelaxAll mode");
924 RelaxedFrag = relaxInstruction(Layout, *cast<MCRelaxableFragment>(I));
926 case MCFragment::FT_Dwarf:
927 RelaxedFrag = relaxDwarfLineAddr(Layout,
928 *cast<MCDwarfLineAddrFragment>(I));
930 case MCFragment::FT_DwarfFrame:
932 relaxDwarfCallFrameFragment(Layout,
933 *cast<MCDwarfCallFrameFragment>(I));
935 case MCFragment::FT_LEB:
936 RelaxedFrag = relaxLEB(Layout, *cast<MCLEBFragment>(I));
939 if (RelaxedFrag && !FirstRelaxedFragment)
940 FirstRelaxedFragment = I;
942 if (FirstRelaxedFragment) {
943 Layout.invalidateFragmentsFrom(FirstRelaxedFragment);
949 bool MCAssembler::layoutOnce(MCAsmLayout &Layout) {
950 ++stats::RelaxationSteps;
952 bool WasRelaxed = false;
953 for (iterator it = begin(), ie = end(); it != ie; ++it) {
954 MCSectionData &SD = *it;
955 while (layoutSectionOnce(Layout, SD))
962 void MCAssembler::finishLayout(MCAsmLayout &Layout) {
963 // The layout is done. Mark every fragment as valid.
964 for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) {
965 Layout.getFragmentOffset(&*Layout.getSectionOrder()[i]->rbegin());
973 raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
974 OS << "<MCFixup" << " Offset:" << AF.getOffset()
975 << " Value:" << *AF.getValue()
976 << " Kind:" << AF.getKind() << ">";
982 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
983 void MCFragment::dump() {
984 raw_ostream &OS = llvm::errs();
988 case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
989 case MCFragment::FT_Data: OS << "MCDataFragment"; break;
990 case MCFragment::FT_CompactEncodedInst:
991 OS << "MCCompactEncodedInstFragment"; break;
992 case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
993 case MCFragment::FT_Relaxable: OS << "MCRelaxableFragment"; break;
994 case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
995 case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
996 case MCFragment::FT_DwarfFrame: OS << "MCDwarfCallFrameFragment"; break;
997 case MCFragment::FT_LEB: OS << "MCLEBFragment"; break;
1000 OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
1001 << " Offset:" << Offset
1002 << " HasInstructions:" << hasInstructions()
1003 << " BundlePadding:" << static_cast<unsigned>(getBundlePadding()) << ">";
1005 switch (getKind()) {
1006 case MCFragment::FT_Align: {
1007 const MCAlignFragment *AF = cast<MCAlignFragment>(this);
1008 if (AF->hasEmitNops())
1009 OS << " (emit nops)";
1011 OS << " Alignment:" << AF->getAlignment()
1012 << " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
1013 << " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
1016 case MCFragment::FT_Data: {
1017 const MCDataFragment *DF = cast<MCDataFragment>(this);
1019 OS << " Contents:[";
1020 const SmallVectorImpl<char> &Contents = DF->getContents();
1021 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
1023 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1025 OS << "] (" << Contents.size() << " bytes)";
1027 if (DF->fixup_begin() != DF->fixup_end()) {
1030 for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
1031 ie = DF->fixup_end(); it != ie; ++it) {
1032 if (it != DF->fixup_begin()) OS << ",\n ";
1039 case MCFragment::FT_CompactEncodedInst: {
1040 const MCCompactEncodedInstFragment *CEIF =
1041 cast<MCCompactEncodedInstFragment>(this);
1043 OS << " Contents:[";
1044 const SmallVectorImpl<char> &Contents = CEIF->getContents();
1045 for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
1047 OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1049 OS << "] (" << Contents.size() << " bytes)";
1052 case MCFragment::FT_Fill: {
1053 const MCFillFragment *FF = cast<MCFillFragment>(this);
1054 OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
1055 << " Size:" << FF->getSize();
1058 case MCFragment::FT_Relaxable: {
1059 const MCRelaxableFragment *F = cast<MCRelaxableFragment>(this);
1062 F->getInst().dump_pretty(OS);
1065 case MCFragment::FT_Org: {
1066 const MCOrgFragment *OF = cast<MCOrgFragment>(this);
1068 OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
1071 case MCFragment::FT_Dwarf: {
1072 const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
1074 OS << " AddrDelta:" << OF->getAddrDelta()
1075 << " LineDelta:" << OF->getLineDelta();
1078 case MCFragment::FT_DwarfFrame: {
1079 const MCDwarfCallFrameFragment *CF = cast<MCDwarfCallFrameFragment>(this);
1081 OS << " AddrDelta:" << CF->getAddrDelta();
1084 case MCFragment::FT_LEB: {
1085 const MCLEBFragment *LF = cast<MCLEBFragment>(this);
1087 OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
1094 void MCSectionData::dump() {
1095 raw_ostream &OS = llvm::errs();
1097 OS << "<MCSectionData";
1098 OS << " Alignment:" << getAlignment()
1099 << " Fragments:[\n ";
1100 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1101 if (it != begin()) OS << ",\n ";
1107 void MCSymbolData::dump() {
1108 raw_ostream &OS = llvm::errs();
1110 OS << "<MCSymbolData Symbol:" << getSymbol()
1111 << " Fragment:" << getFragment() << " Offset:" << getOffset()
1112 << " Flags:" << getFlags() << " Index:" << getIndex();
1114 OS << " (common, size:" << getCommonSize()
1115 << " align: " << getCommonAlignment() << ")";
1117 OS << " (external)";
1118 if (isPrivateExtern())
1119 OS << " (private extern)";
1123 void MCAssembler::dump() {
1124 raw_ostream &OS = llvm::errs();
1126 OS << "<MCAssembler\n";
1127 OS << " Sections:[\n ";
1128 for (iterator it = begin(), ie = end(); it != ie; ++it) {
1129 if (it != begin()) OS << ",\n ";
1135 for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1136 if (it != symbol_begin()) OS << ",\n ";
1143 // anchors for MC*Fragment vtables
1144 void MCEncodedFragment::anchor() { }
1145 void MCEncodedFragmentWithFixups::anchor() { }
1146 void MCDataFragment::anchor() { }
1147 void MCCompactEncodedInstFragment::anchor() { }
1148 void MCRelaxableFragment::anchor() { }
1149 void MCAlignFragment::anchor() { }
1150 void MCFillFragment::anchor() { }
1151 void MCOrgFragment::anchor() { }
1152 void MCLEBFragment::anchor() { }
1153 void MCDwarfLineAddrFragment::anchor() { }
1154 void MCDwarfCallFrameFragment::anchor() { }