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-rw-r--r--contrib/llvm/lib/MC/MCAssembler.cpp875
1 files changed, 875 insertions, 0 deletions
diff --git a/contrib/llvm/lib/MC/MCAssembler.cpp b/contrib/llvm/lib/MC/MCAssembler.cpp
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+++ b/contrib/llvm/lib/MC/MCAssembler.cpp
@@ -0,0 +1,875 @@
+//===- lib/MC/MCAssembler.cpp - Assembler Backend Implementation ----------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/MC/MCAssembler.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/Twine.h"
+#include "llvm/MC/MCAsmBackend.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCAsmLayout.h"
+#include "llvm/MC/MCCodeEmitter.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCDwarf.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCFixupKindInfo.h"
+#include "llvm/MC/MCObjectWriter.h"
+#include "llvm/MC/MCSection.h"
+#include "llvm/MC/MCSectionELF.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCValue.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/LEB128.h"
+#include "llvm/Support/TargetRegistry.h"
+#include "llvm/Support/raw_ostream.h"
+#include <tuple>
+using namespace llvm;
+
+#define DEBUG_TYPE "assembler"
+
+namespace {
+namespace stats {
+STATISTIC(EmittedFragments, "Number of emitted assembler fragments - total");
+STATISTIC(EmittedRelaxableFragments,
+ "Number of emitted assembler fragments - relaxable");
+STATISTIC(EmittedDataFragments,
+ "Number of emitted assembler fragments - data");
+STATISTIC(EmittedCompactEncodedInstFragments,
+ "Number of emitted assembler fragments - compact encoded inst");
+STATISTIC(EmittedAlignFragments,
+ "Number of emitted assembler fragments - align");
+STATISTIC(EmittedFillFragments,
+ "Number of emitted assembler fragments - fill");
+STATISTIC(EmittedOrgFragments,
+ "Number of emitted assembler fragments - org");
+STATISTIC(evaluateFixup, "Number of evaluated fixups");
+STATISTIC(FragmentLayouts, "Number of fragment layouts");
+STATISTIC(ObjectBytes, "Number of emitted object file bytes");
+STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps");
+STATISTIC(RelaxedInstructions, "Number of relaxed instructions");
+}
+}
+
+// FIXME FIXME FIXME: There are number of places in this file where we convert
+// what is a 64-bit assembler value used for computation into a value in the
+// object file, which may truncate it. We should detect that truncation where
+// invalid and report errors back.
+
+/* *** */
+
+MCAssembler::MCAssembler(MCContext &Context_, MCAsmBackend &Backend_,
+ MCCodeEmitter &Emitter_, MCObjectWriter &Writer_)
+ : Context(Context_), Backend(Backend_), Emitter(Emitter_), Writer(Writer_),
+ BundleAlignSize(0), RelaxAll(false), SubsectionsViaSymbols(false),
+ IncrementalLinkerCompatible(false), ELFHeaderEFlags(0) {
+ VersionMinInfo.Major = 0; // Major version == 0 for "none specified"
+}
+
+MCAssembler::~MCAssembler() {
+}
+
+void MCAssembler::reset() {
+ Sections.clear();
+ Symbols.clear();
+ IndirectSymbols.clear();
+ DataRegions.clear();
+ LinkerOptions.clear();
+ FileNames.clear();
+ ThumbFuncs.clear();
+ BundleAlignSize = 0;
+ RelaxAll = false;
+ SubsectionsViaSymbols = false;
+ IncrementalLinkerCompatible = false;
+ ELFHeaderEFlags = 0;
+ LOHContainer.reset();
+ VersionMinInfo.Major = 0;
+
+ // reset objects owned by us
+ getBackend().reset();
+ getEmitter().reset();
+ getWriter().reset();
+ getLOHContainer().reset();
+}
+
+bool MCAssembler::registerSection(MCSection &Section) {
+ if (Section.isRegistered())
+ return false;
+ Sections.push_back(&Section);
+ Section.setIsRegistered(true);
+ return true;
+}
+
+bool MCAssembler::isThumbFunc(const MCSymbol *Symbol) const {
+ if (ThumbFuncs.count(Symbol))
+ return true;
+
+ if (!Symbol->isVariable())
+ return false;
+
+ // FIXME: It looks like gas supports some cases of the form "foo + 2". It
+ // is not clear if that is a bug or a feature.
+ const MCExpr *Expr = Symbol->getVariableValue();
+ const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Expr);
+ if (!Ref)
+ return false;
+
+ if (Ref->getKind() != MCSymbolRefExpr::VK_None)
+ return false;
+
+ const MCSymbol &Sym = Ref->getSymbol();
+ if (!isThumbFunc(&Sym))
+ return false;
+
+ ThumbFuncs.insert(Symbol); // Cache it.
+ return true;
+}
+
+bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
+ // Non-temporary labels should always be visible to the linker.
+ if (!Symbol.isTemporary())
+ return true;
+
+ // Absolute temporary labels are never visible.
+ if (!Symbol.isInSection())
+ return false;
+
+ if (Symbol.isUsedInReloc())
+ return true;
+
+ return false;
+}
+
+const MCSymbol *MCAssembler::getAtom(const MCSymbol &S) const {
+ // Linker visible symbols define atoms.
+ if (isSymbolLinkerVisible(S))
+ return &S;
+
+ // Absolute and undefined symbols have no defining atom.
+ if (!S.isInSection())
+ return nullptr;
+
+ // Non-linker visible symbols in sections which can't be atomized have no
+ // defining atom.
+ if (!getContext().getAsmInfo()->isSectionAtomizableBySymbols(
+ *S.getFragment()->getParent()))
+ return nullptr;
+
+ // Otherwise, return the atom for the containing fragment.
+ return S.getFragment()->getAtom();
+}
+
+bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout,
+ const MCFixup &Fixup, const MCFragment *DF,
+ MCValue &Target, uint64_t &Value) const {
+ ++stats::evaluateFixup;
+
+ // FIXME: This code has some duplication with recordRelocation. We should
+ // probably merge the two into a single callback that tries to evaluate a
+ // fixup and records a relocation if one is needed.
+ const MCExpr *Expr = Fixup.getValue();
+ if (!Expr->evaluateAsRelocatable(Target, &Layout, &Fixup)) {
+ getContext().reportError(Fixup.getLoc(), "expected relocatable expression");
+ // Claim to have completely evaluated the fixup, to prevent any further
+ // processing from being done.
+ Value = 0;
+ return true;
+ }
+
+ bool IsPCRel = Backend.getFixupKindInfo(
+ Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
+
+ bool IsResolved;
+ if (IsPCRel) {
+ if (Target.getSymB()) {
+ IsResolved = false;
+ } else if (!Target.getSymA()) {
+ IsResolved = false;
+ } else {
+ const MCSymbolRefExpr *A = Target.getSymA();
+ const MCSymbol &SA = A->getSymbol();
+ if (A->getKind() != MCSymbolRefExpr::VK_None || SA.isUndefined()) {
+ IsResolved = false;
+ } else {
+ IsResolved = getWriter().isSymbolRefDifferenceFullyResolvedImpl(
+ *this, SA, *DF, false, true);
+ }
+ }
+ } else {
+ IsResolved = Target.isAbsolute();
+ }
+
+ Value = Target.getConstant();
+
+ if (const MCSymbolRefExpr *A = Target.getSymA()) {
+ const MCSymbol &Sym = A->getSymbol();
+ if (Sym.isDefined())
+ Value += Layout.getSymbolOffset(Sym);
+ }
+ if (const MCSymbolRefExpr *B = Target.getSymB()) {
+ const MCSymbol &Sym = B->getSymbol();
+ if (Sym.isDefined())
+ Value -= Layout.getSymbolOffset(Sym);
+ }
+
+
+ bool ShouldAlignPC = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
+ MCFixupKindInfo::FKF_IsAlignedDownTo32Bits;
+ assert((ShouldAlignPC ? IsPCRel : true) &&
+ "FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!");
+
+ if (IsPCRel) {
+ uint32_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset();
+
+ // A number of ARM fixups in Thumb mode require that the effective PC
+ // address be determined as the 32-bit aligned version of the actual offset.
+ if (ShouldAlignPC) Offset &= ~0x3;
+ Value -= Offset;
+ }
+
+ // Let the backend adjust the fixup value if necessary, including whether
+ // we need a relocation.
+ Backend.processFixupValue(*this, Layout, Fixup, DF, Target, Value,
+ IsResolved);
+
+ return IsResolved;
+}
+
+uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
+ const MCFragment &F) const {
+ switch (F.getKind()) {
+ case MCFragment::FT_Data:
+ return cast<MCDataFragment>(F).getContents().size();
+ case MCFragment::FT_Relaxable:
+ return cast<MCRelaxableFragment>(F).getContents().size();
+ case MCFragment::FT_CompactEncodedInst:
+ return cast<MCCompactEncodedInstFragment>(F).getContents().size();
+ case MCFragment::FT_Fill:
+ return cast<MCFillFragment>(F).getSize();
+
+ case MCFragment::FT_LEB:
+ return cast<MCLEBFragment>(F).getContents().size();
+
+ case MCFragment::FT_SafeSEH:
+ return 4;
+
+ case MCFragment::FT_Align: {
+ const MCAlignFragment &AF = cast<MCAlignFragment>(F);
+ unsigned Offset = Layout.getFragmentOffset(&AF);
+ unsigned Size = OffsetToAlignment(Offset, AF.getAlignment());
+ // If we are padding with nops, force the padding to be larger than the
+ // minimum nop size.
+ if (Size > 0 && AF.hasEmitNops()) {
+ while (Size % getBackend().getMinimumNopSize())
+ Size += AF.getAlignment();
+ }
+ if (Size > AF.getMaxBytesToEmit())
+ return 0;
+ return Size;
+ }
+
+ case MCFragment::FT_Org: {
+ const MCOrgFragment &OF = cast<MCOrgFragment>(F);
+ MCValue Value;
+ if (!OF.getOffset().evaluateAsValue(Value, Layout))
+ report_fatal_error("expected assembly-time absolute expression");
+
+ // FIXME: We need a way to communicate this error.
+ uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
+ int64_t TargetLocation = Value.getConstant();
+ if (const MCSymbolRefExpr *A = Value.getSymA()) {
+ uint64_t Val;
+ if (!Layout.getSymbolOffset(A->getSymbol(), Val))
+ report_fatal_error("expected absolute expression");
+ TargetLocation += Val;
+ }
+ int64_t Size = TargetLocation - FragmentOffset;
+ if (Size < 0 || Size >= 0x40000000)
+ report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
+ "' (at offset '" + Twine(FragmentOffset) + "')");
+ return Size;
+ }
+
+ case MCFragment::FT_Dwarf:
+ return cast<MCDwarfLineAddrFragment>(F).getContents().size();
+ case MCFragment::FT_DwarfFrame:
+ return cast<MCDwarfCallFrameFragment>(F).getContents().size();
+ case MCFragment::FT_Dummy:
+ llvm_unreachable("Should not have been added");
+ }
+
+ llvm_unreachable("invalid fragment kind");
+}
+
+void MCAsmLayout::layoutFragment(MCFragment *F) {
+ MCFragment *Prev = F->getPrevNode();
+
+ // We should never try to recompute something which is valid.
+ assert(!isFragmentValid(F) && "Attempt to recompute a valid fragment!");
+ // We should never try to compute the fragment layout if its predecessor
+ // isn't valid.
+ assert((!Prev || isFragmentValid(Prev)) &&
+ "Attempt to compute fragment before its predecessor!");
+
+ ++stats::FragmentLayouts;
+
+ // Compute fragment offset and size.
+ if (Prev)
+ F->Offset = Prev->Offset + getAssembler().computeFragmentSize(*this, *Prev);
+ else
+ F->Offset = 0;
+ LastValidFragment[F->getParent()] = F;
+
+ // If bundling is enabled and this fragment has instructions in it, it has to
+ // obey the bundling restrictions. With padding, we'll have:
+ //
+ //
+ // BundlePadding
+ // |||
+ // -------------------------------------
+ // Prev |##########| F |
+ // -------------------------------------
+ // ^
+ // |
+ // F->Offset
+ //
+ // The fragment's offset will point to after the padding, and its computed
+ // size won't include the padding.
+ //
+ // When the -mc-relax-all flag is used, we optimize bundling by writting the
+ // padding directly into fragments when the instructions are emitted inside
+ // the streamer. When the fragment is larger than the bundle size, we need to
+ // ensure that it's bundle aligned. This means that if we end up with
+ // multiple fragments, we must emit bundle padding between fragments.
+ //
+ // ".align N" is an example of a directive that introduces multiple
+ // fragments. We could add a special case to handle ".align N" by emitting
+ // within-fragment padding (which would produce less padding when N is less
+ // than the bundle size), but for now we don't.
+ //
+ if (Assembler.isBundlingEnabled() && F->hasInstructions()) {
+ assert(isa<MCEncodedFragment>(F) &&
+ "Only MCEncodedFragment implementations have instructions");
+ uint64_t FSize = Assembler.computeFragmentSize(*this, *F);
+
+ if (!Assembler.getRelaxAll() && FSize > Assembler.getBundleAlignSize())
+ report_fatal_error("Fragment can't be larger than a bundle size");
+
+ uint64_t RequiredBundlePadding = computeBundlePadding(Assembler, F,
+ F->Offset, FSize);
+ if (RequiredBundlePadding > UINT8_MAX)
+ report_fatal_error("Padding cannot exceed 255 bytes");
+ F->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
+ F->Offset += RequiredBundlePadding;
+ }
+}
+
+void MCAssembler::registerSymbol(const MCSymbol &Symbol, bool *Created) {
+ bool New = !Symbol.isRegistered();
+ if (Created)
+ *Created = New;
+ if (New) {
+ Symbol.setIsRegistered(true);
+ Symbols.push_back(&Symbol);
+ }
+}
+
+void MCAssembler::writeFragmentPadding(const MCFragment &F, uint64_t FSize,
+ MCObjectWriter *OW) const {
+ // Should NOP padding be written out before this fragment?
+ unsigned BundlePadding = F.getBundlePadding();
+ if (BundlePadding > 0) {
+ assert(isBundlingEnabled() &&
+ "Writing bundle padding with disabled bundling");
+ assert(F.hasInstructions() &&
+ "Writing bundle padding for a fragment without instructions");
+
+ unsigned TotalLength = BundlePadding + static_cast<unsigned>(FSize);
+ if (F.alignToBundleEnd() && TotalLength > getBundleAlignSize()) {
+ // If the padding itself crosses a bundle boundary, it must be emitted
+ // in 2 pieces, since even nop instructions must not cross boundaries.
+ // v--------------v <- BundleAlignSize
+ // v---------v <- BundlePadding
+ // ----------------------------
+ // | Prev |####|####| F |
+ // ----------------------------
+ // ^-------------------^ <- TotalLength
+ unsigned DistanceToBoundary = TotalLength - getBundleAlignSize();
+ if (!getBackend().writeNopData(DistanceToBoundary, OW))
+ report_fatal_error("unable to write NOP sequence of " +
+ Twine(DistanceToBoundary) + " bytes");
+ BundlePadding -= DistanceToBoundary;
+ }
+ if (!getBackend().writeNopData(BundlePadding, OW))
+ report_fatal_error("unable to write NOP sequence of " +
+ Twine(BundlePadding) + " bytes");
+ }
+}
+
+/// \brief Write the fragment \p F to the output file.
+static void writeFragment(const MCAssembler &Asm, const MCAsmLayout &Layout,
+ const MCFragment &F) {
+ MCObjectWriter *OW = &Asm.getWriter();
+
+ // FIXME: Embed in fragments instead?
+ uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F);
+
+ Asm.writeFragmentPadding(F, FragmentSize, OW);
+
+ // This variable (and its dummy usage) is to participate in the assert at
+ // the end of the function.
+ uint64_t Start = OW->getStream().tell();
+ (void) Start;
+
+ ++stats::EmittedFragments;
+
+ switch (F.getKind()) {
+ case MCFragment::FT_Align: {
+ ++stats::EmittedAlignFragments;
+ const MCAlignFragment &AF = cast<MCAlignFragment>(F);
+ assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
+
+ uint64_t Count = FragmentSize / AF.getValueSize();
+
+ // FIXME: This error shouldn't actually occur (the front end should emit
+ // multiple .align directives to enforce the semantics it wants), but is
+ // severe enough that we want to report it. How to handle this?
+ if (Count * AF.getValueSize() != FragmentSize)
+ report_fatal_error("undefined .align directive, value size '" +
+ Twine(AF.getValueSize()) +
+ "' is not a divisor of padding size '" +
+ Twine(FragmentSize) + "'");
+
+ // See if we are aligning with nops, and if so do that first to try to fill
+ // the Count bytes. Then if that did not fill any bytes or there are any
+ // bytes left to fill use the Value and ValueSize to fill the rest.
+ // If we are aligning with nops, ask that target to emit the right data.
+ if (AF.hasEmitNops()) {
+ if (!Asm.getBackend().writeNopData(Count, OW))
+ report_fatal_error("unable to write nop sequence of " +
+ Twine(Count) + " bytes");
+ break;
+ }
+
+ // Otherwise, write out in multiples of the value size.
+ for (uint64_t i = 0; i != Count; ++i) {
+ switch (AF.getValueSize()) {
+ default: llvm_unreachable("Invalid size!");
+ case 1: OW->write8 (uint8_t (AF.getValue())); break;
+ case 2: OW->write16(uint16_t(AF.getValue())); break;
+ case 4: OW->write32(uint32_t(AF.getValue())); break;
+ case 8: OW->write64(uint64_t(AF.getValue())); break;
+ }
+ }
+ break;
+ }
+
+ case MCFragment::FT_Data:
+ ++stats::EmittedDataFragments;
+ OW->writeBytes(cast<MCDataFragment>(F).getContents());
+ break;
+
+ case MCFragment::FT_Relaxable:
+ ++stats::EmittedRelaxableFragments;
+ OW->writeBytes(cast<MCRelaxableFragment>(F).getContents());
+ break;
+
+ case MCFragment::FT_CompactEncodedInst:
+ ++stats::EmittedCompactEncodedInstFragments;
+ OW->writeBytes(cast<MCCompactEncodedInstFragment>(F).getContents());
+ break;
+
+ case MCFragment::FT_Fill: {
+ ++stats::EmittedFillFragments;
+ const MCFillFragment &FF = cast<MCFillFragment>(F);
+
+ assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
+
+ for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
+ switch (FF.getValueSize()) {
+ default: llvm_unreachable("Invalid size!");
+ case 1: OW->write8 (uint8_t (FF.getValue())); break;
+ case 2: OW->write16(uint16_t(FF.getValue())); break;
+ case 4: OW->write32(uint32_t(FF.getValue())); break;
+ case 8: OW->write64(uint64_t(FF.getValue())); break;
+ }
+ }
+ break;
+ }
+
+ case MCFragment::FT_LEB: {
+ const MCLEBFragment &LF = cast<MCLEBFragment>(F);
+ OW->writeBytes(LF.getContents());
+ break;
+ }
+
+ case MCFragment::FT_SafeSEH: {
+ const MCSafeSEHFragment &SF = cast<MCSafeSEHFragment>(F);
+ OW->write32(SF.getSymbol()->getIndex());
+ break;
+ }
+
+ case MCFragment::FT_Org: {
+ ++stats::EmittedOrgFragments;
+ const MCOrgFragment &OF = cast<MCOrgFragment>(F);
+
+ for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
+ OW->write8(uint8_t(OF.getValue()));
+
+ break;
+ }
+
+ case MCFragment::FT_Dwarf: {
+ const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
+ OW->writeBytes(OF.getContents());
+ break;
+ }
+ case MCFragment::FT_DwarfFrame: {
+ const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F);
+ OW->writeBytes(CF.getContents());
+ break;
+ }
+ case MCFragment::FT_Dummy:
+ llvm_unreachable("Should not have been added");
+ }
+
+ assert(OW->getStream().tell() - Start == FragmentSize &&
+ "The stream should advance by fragment size");
+}
+
+void MCAssembler::writeSectionData(const MCSection *Sec,
+ const MCAsmLayout &Layout) const {
+ // Ignore virtual sections.
+ if (Sec->isVirtualSection()) {
+ assert(Layout.getSectionFileSize(Sec) == 0 && "Invalid size for section!");
+
+ // Check that contents are only things legal inside a virtual section.
+ for (const MCFragment &F : *Sec) {
+ switch (F.getKind()) {
+ default: llvm_unreachable("Invalid fragment in virtual section!");
+ case MCFragment::FT_Data: {
+ // Check that we aren't trying to write a non-zero contents (or fixups)
+ // into a virtual section. This is to support clients which use standard
+ // directives to fill the contents of virtual sections.
+ const MCDataFragment &DF = cast<MCDataFragment>(F);
+ assert(DF.fixup_begin() == DF.fixup_end() &&
+ "Cannot have fixups in virtual section!");
+ for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
+ if (DF.getContents()[i]) {
+ if (auto *ELFSec = dyn_cast<const MCSectionELF>(Sec))
+ report_fatal_error("non-zero initializer found in section '" +
+ ELFSec->getSectionName() + "'");
+ else
+ report_fatal_error("non-zero initializer found in virtual section");
+ }
+ break;
+ }
+ case MCFragment::FT_Align:
+ // Check that we aren't trying to write a non-zero value into a virtual
+ // section.
+ assert((cast<MCAlignFragment>(F).getValueSize() == 0 ||
+ cast<MCAlignFragment>(F).getValue() == 0) &&
+ "Invalid align in virtual section!");
+ break;
+ case MCFragment::FT_Fill:
+ assert((cast<MCFillFragment>(F).getValueSize() == 0 ||
+ cast<MCFillFragment>(F).getValue() == 0) &&
+ "Invalid fill in virtual section!");
+ break;
+ }
+ }
+
+ return;
+ }
+
+ uint64_t Start = getWriter().getStream().tell();
+ (void)Start;
+
+ for (const MCFragment &F : *Sec)
+ writeFragment(*this, Layout, F);
+
+ assert(getWriter().getStream().tell() - Start ==
+ Layout.getSectionAddressSize(Sec));
+}
+
+std::pair<uint64_t, bool> MCAssembler::handleFixup(const MCAsmLayout &Layout,
+ MCFragment &F,
+ const MCFixup &Fixup) {
+ // Evaluate the fixup.
+ MCValue Target;
+ uint64_t FixedValue;
+ bool IsPCRel = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
+ MCFixupKindInfo::FKF_IsPCRel;
+ if (!evaluateFixup(Layout, Fixup, &F, Target, FixedValue)) {
+ // The fixup was unresolved, we need a relocation. Inform the object
+ // writer of the relocation, and give it an opportunity to adjust the
+ // fixup value if need be.
+ getWriter().recordRelocation(*this, Layout, &F, Fixup, Target, IsPCRel,
+ FixedValue);
+ }
+ return std::make_pair(FixedValue, IsPCRel);
+}
+
+void MCAssembler::layout(MCAsmLayout &Layout) {
+ DEBUG_WITH_TYPE("mc-dump", {
+ llvm::errs() << "assembler backend - pre-layout\n--\n";
+ dump(); });
+
+ // Create dummy fragments and assign section ordinals.
+ unsigned SectionIndex = 0;
+ for (MCSection &Sec : *this) {
+ // Create dummy fragments to eliminate any empty sections, this simplifies
+ // layout.
+ if (Sec.getFragmentList().empty())
+ new MCDataFragment(&Sec);
+
+ Sec.setOrdinal(SectionIndex++);
+ }
+
+ // Assign layout order indices to sections and fragments.
+ for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
+ MCSection *Sec = Layout.getSectionOrder()[i];
+ Sec->setLayoutOrder(i);
+
+ unsigned FragmentIndex = 0;
+ for (MCFragment &Frag : *Sec)
+ Frag.setLayoutOrder(FragmentIndex++);
+ }
+
+ // Layout until everything fits.
+ while (layoutOnce(Layout))
+ continue;
+
+ DEBUG_WITH_TYPE("mc-dump", {
+ llvm::errs() << "assembler backend - post-relaxation\n--\n";
+ dump(); });
+
+ // Finalize the layout, including fragment lowering.
+ finishLayout(Layout);
+
+ DEBUG_WITH_TYPE("mc-dump", {
+ llvm::errs() << "assembler backend - final-layout\n--\n";
+ dump(); });
+
+ // Allow the object writer a chance to perform post-layout binding (for
+ // example, to set the index fields in the symbol data).
+ getWriter().executePostLayoutBinding(*this, Layout);
+
+ // Evaluate and apply the fixups, generating relocation entries as necessary.
+ for (MCSection &Sec : *this) {
+ for (MCFragment &Frag : Sec) {
+ MCEncodedFragment *F = dyn_cast<MCEncodedFragment>(&Frag);
+ // Data and relaxable fragments both have fixups. So only process
+ // those here.
+ // FIXME: Is there a better way to do this? MCEncodedFragmentWithFixups
+ // being templated makes this tricky.
+ if (!F || isa<MCCompactEncodedInstFragment>(F))
+ continue;
+ ArrayRef<MCFixup> Fixups;
+ MutableArrayRef<char> Contents;
+ if (auto *FragWithFixups = dyn_cast<MCDataFragment>(F)) {
+ Fixups = FragWithFixups->getFixups();
+ Contents = FragWithFixups->getContents();
+ } else if (auto *FragWithFixups = dyn_cast<MCRelaxableFragment>(F)) {
+ Fixups = FragWithFixups->getFixups();
+ Contents = FragWithFixups->getContents();
+ } else
+ llvm_unreachable("Unknown fragment with fixups!");
+ for (const MCFixup &Fixup : Fixups) {
+ uint64_t FixedValue;
+ bool IsPCRel;
+ std::tie(FixedValue, IsPCRel) = handleFixup(Layout, *F, Fixup);
+ getBackend().applyFixup(Fixup, Contents.data(),
+ Contents.size(), FixedValue, IsPCRel);
+ }
+ }
+ }
+}
+
+void MCAssembler::Finish() {
+ // Create the layout object.
+ MCAsmLayout Layout(*this);
+ layout(Layout);
+
+ raw_ostream &OS = getWriter().getStream();
+ uint64_t StartOffset = OS.tell();
+
+ // Write the object file.
+ getWriter().writeObject(*this, Layout);
+
+ stats::ObjectBytes += OS.tell() - StartOffset;
+}
+
+bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup,
+ const MCRelaxableFragment *DF,
+ const MCAsmLayout &Layout) const {
+ MCValue Target;
+ uint64_t Value;
+ bool Resolved = evaluateFixup(Layout, Fixup, DF, Target, Value);
+ return getBackend().fixupNeedsRelaxationAdvanced(Fixup, Resolved, Value, DF,
+ Layout);
+}
+
+bool MCAssembler::fragmentNeedsRelaxation(const MCRelaxableFragment *F,
+ const MCAsmLayout &Layout) const {
+ // If this inst doesn't ever need relaxation, ignore it. This occurs when we
+ // are intentionally pushing out inst fragments, or because we relaxed a
+ // previous instruction to one that doesn't need relaxation.
+ if (!getBackend().mayNeedRelaxation(F->getInst()))
+ return false;
+
+ for (const MCFixup &Fixup : F->getFixups())
+ if (fixupNeedsRelaxation(Fixup, F, Layout))
+ return true;
+
+ return false;
+}
+
+bool MCAssembler::relaxInstruction(MCAsmLayout &Layout,
+ MCRelaxableFragment &F) {
+ if (!fragmentNeedsRelaxation(&F, Layout))
+ return false;
+
+ ++stats::RelaxedInstructions;
+
+ // FIXME-PERF: We could immediately lower out instructions if we can tell
+ // they are fully resolved, to avoid retesting on later passes.
+
+ // Relax the fragment.
+
+ MCInst Relaxed;
+ getBackend().relaxInstruction(F.getInst(), Relaxed);
+
+ // Encode the new instruction.
+ //
+ // FIXME-PERF: If it matters, we could let the target do this. It can
+ // probably do so more efficiently in many cases.
+ SmallVector<MCFixup, 4> Fixups;
+ SmallString<256> Code;
+ raw_svector_ostream VecOS(Code);
+ getEmitter().encodeInstruction(Relaxed, VecOS, Fixups, F.getSubtargetInfo());
+
+ // Update the fragment.
+ F.setInst(Relaxed);
+ F.getContents() = Code;
+ F.getFixups() = Fixups;
+
+ return true;
+}
+
+bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) {
+ uint64_t OldSize = LF.getContents().size();
+ int64_t Value;
+ bool Abs = LF.getValue().evaluateKnownAbsolute(Value, Layout);
+ if (!Abs)
+ report_fatal_error("sleb128 and uleb128 expressions must be absolute");
+ SmallString<8> &Data = LF.getContents();
+ Data.clear();
+ raw_svector_ostream OSE(Data);
+ if (LF.isSigned())
+ encodeSLEB128(Value, OSE);
+ else
+ encodeULEB128(Value, OSE);
+ return OldSize != LF.getContents().size();
+}
+
+bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout,
+ MCDwarfLineAddrFragment &DF) {
+ MCContext &Context = Layout.getAssembler().getContext();
+ uint64_t OldSize = DF.getContents().size();
+ int64_t AddrDelta;
+ bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
+ assert(Abs && "We created a line delta with an invalid expression");
+ (void) Abs;
+ int64_t LineDelta;
+ LineDelta = DF.getLineDelta();
+ SmallString<8> &Data = DF.getContents();
+ Data.clear();
+ raw_svector_ostream OSE(Data);
+ MCDwarfLineAddr::Encode(Context, getDWARFLinetableParams(), LineDelta,
+ AddrDelta, OSE);
+ return OldSize != Data.size();
+}
+
+bool MCAssembler::relaxDwarfCallFrameFragment(MCAsmLayout &Layout,
+ MCDwarfCallFrameFragment &DF) {
+ MCContext &Context = Layout.getAssembler().getContext();
+ uint64_t OldSize = DF.getContents().size();
+ int64_t AddrDelta;
+ bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
+ assert(Abs && "We created call frame with an invalid expression");
+ (void) Abs;
+ SmallString<8> &Data = DF.getContents();
+ Data.clear();
+ raw_svector_ostream OSE(Data);
+ MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE);
+ return OldSize != Data.size();
+}
+
+bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSection &Sec) {
+ // Holds the first fragment which needed relaxing during this layout. It will
+ // remain NULL if none were relaxed.
+ // When a fragment is relaxed, all the fragments following it should get
+ // invalidated because their offset is going to change.
+ MCFragment *FirstRelaxedFragment = nullptr;
+
+ // Attempt to relax all the fragments in the section.
+ for (MCSection::iterator I = Sec.begin(), IE = Sec.end(); I != IE; ++I) {
+ // Check if this is a fragment that needs relaxation.
+ bool RelaxedFrag = false;
+ switch(I->getKind()) {
+ default:
+ break;
+ case MCFragment::FT_Relaxable:
+ assert(!getRelaxAll() &&
+ "Did not expect a MCRelaxableFragment in RelaxAll mode");
+ RelaxedFrag = relaxInstruction(Layout, *cast<MCRelaxableFragment>(I));
+ break;
+ case MCFragment::FT_Dwarf:
+ RelaxedFrag = relaxDwarfLineAddr(Layout,
+ *cast<MCDwarfLineAddrFragment>(I));
+ break;
+ case MCFragment::FT_DwarfFrame:
+ RelaxedFrag =
+ relaxDwarfCallFrameFragment(Layout,
+ *cast<MCDwarfCallFrameFragment>(I));
+ break;
+ case MCFragment::FT_LEB:
+ RelaxedFrag = relaxLEB(Layout, *cast<MCLEBFragment>(I));
+ break;
+ }
+ if (RelaxedFrag && !FirstRelaxedFragment)
+ FirstRelaxedFragment = &*I;
+ }
+ if (FirstRelaxedFragment) {
+ Layout.invalidateFragmentsFrom(FirstRelaxedFragment);
+ return true;
+ }
+ return false;
+}
+
+bool MCAssembler::layoutOnce(MCAsmLayout &Layout) {
+ ++stats::RelaxationSteps;
+
+ bool WasRelaxed = false;
+ for (iterator it = begin(), ie = end(); it != ie; ++it) {
+ MCSection &Sec = *it;
+ while (layoutSectionOnce(Layout, Sec))
+ WasRelaxed = true;
+ }
+
+ return WasRelaxed;
+}
+
+void MCAssembler::finishLayout(MCAsmLayout &Layout) {
+ // The layout is done. Mark every fragment as valid.
+ for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) {
+ Layout.getFragmentOffset(&*Layout.getSectionOrder()[i]->rbegin());
+ }
+}
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