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-rw-r--r--llvm/lib/MC/MCAssembler.cpp1155
1 files changed, 1155 insertions, 0 deletions
diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
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+++ b/llvm/lib/MC/MCAssembler.cpp
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+//===- lib/MC/MCAssembler.cpp - Assembler Backend Implementation ----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/MC/MCAssembler.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/StringRef.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/MCCodeView.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCDwarf.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCFixup.h"
+#include "llvm/MC/MCFixupKindInfo.h"
+#include "llvm/MC/MCFragment.h"
+#include "llvm/MC/MCInst.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/Alignment.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/LEB128.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <cstdint>
+#include <cstring>
+#include <tuple>
+#include <utility>
+
+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");
+STATISTIC(PaddingFragmentsRelaxations,
+ "Number of Padding Fragments relaxations");
+STATISTIC(PaddingFragmentsBytes,
+ "Total size of all padding from adding Fragments");
+
+} // end namespace stats
+} // end anonymous namespace
+
+// 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,
+ std::unique_ptr<MCAsmBackend> Backend,
+ std::unique_ptr<MCCodeEmitter> Emitter,
+ std::unique_ptr<MCObjectWriter> Writer)
+ : Context(Context), Backend(std::move(Backend)),
+ Emitter(std::move(Emitter)), Writer(std::move(Writer)),
+ BundleAlignSize(0), RelaxAll(false), SubsectionsViaSymbols(false),
+ IncrementalLinkerCompatible(false), ELFHeaderEFlags(0) {
+ VersionInfo.Major = 0; // Major version == 0 for "none specified"
+}
+
+MCAssembler::~MCAssembler() = default;
+
+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();
+ VersionInfo.Major = 0;
+ VersionInfo.SDKVersion = VersionTuple();
+
+ // reset objects owned by us
+ if (getBackendPtr())
+ getBackendPtr()->reset();
+ if (getEmitterPtr())
+ getEmitterPtr()->reset();
+ if (getWriterPtr())
+ getWriterPtr()->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;
+
+ const MCExpr *Expr = Symbol->getVariableValue();
+
+ MCValue V;
+ if (!Expr->evaluateAsRelocatable(V, nullptr, nullptr))
+ return false;
+
+ if (V.getSymB() || V.getRefKind() != MCSymbolRefExpr::VK_None)
+ return false;
+
+ const MCSymbolRefExpr *Ref = V.getSymA();
+ 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,
+ bool &WasForced) 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.
+
+ // On error claim to have completely evaluated the fixup, to prevent any
+ // further processing from being done.
+ const MCExpr *Expr = Fixup.getValue();
+ MCContext &Ctx = getContext();
+ Value = 0;
+ WasForced = false;
+ if (!Expr->evaluateAsRelocatable(Target, &Layout, &Fixup)) {
+ Ctx.reportError(Fixup.getLoc(), "expected relocatable expression");
+ return true;
+ }
+ if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
+ if (RefB->getKind() != MCSymbolRefExpr::VK_None) {
+ Ctx.reportError(Fixup.getLoc(),
+ "unsupported subtraction of qualified symbol");
+ return true;
+ }
+ }
+
+ assert(getBackendPtr() && "Expected assembler backend");
+ bool IsPCRel = getBackendPtr()->getFixupKindInfo(Fixup.getKind()).Flags &
+ MCFixupKindInfo::FKF_IsPCRel;
+
+ bool IsResolved = false;
+ 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 if (auto *Writer = getWriterPtr()) {
+ IsResolved = Writer->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 = getBackend().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 force a relocation if needed.
+ if (IsResolved && getBackend().shouldForceRelocation(*this, Fixup, Target)) {
+ IsResolved = false;
+ WasForced = true;
+ }
+
+ return IsResolved;
+}
+
+uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
+ const MCFragment &F) const {
+ assert(getBackendPtr() && "Requires assembler backend");
+ 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: {
+ auto &FF = cast<MCFillFragment>(F);
+ int64_t NumValues = 0;
+ if (!FF.getNumValues().evaluateAsAbsolute(NumValues, Layout)) {
+ getContext().reportError(FF.getLoc(),
+ "expected assembly-time absolute expression");
+ return 0;
+ }
+ int64_t Size = NumValues * FF.getValueSize();
+ if (Size < 0) {
+ getContext().reportError(FF.getLoc(), "invalid number of bytes");
+ return 0;
+ }
+ return Size;
+ }
+
+ case MCFragment::FT_LEB:
+ return cast<MCLEBFragment>(F).getContents().size();
+
+ case MCFragment::FT_Padding:
+ return cast<MCPaddingFragment>(F).getSize();
+
+ case MCFragment::FT_SymbolId:
+ return 4;
+
+ case MCFragment::FT_Align: {
+ const MCAlignFragment &AF = cast<MCAlignFragment>(F);
+ unsigned Offset = Layout.getFragmentOffset(&AF);
+ unsigned Size = offsetToAlignment(Offset, Align(AF.getAlignment()));
+
+ // Insert extra Nops for code alignment if the target define
+ // shouldInsertExtraNopBytesForCodeAlign target hook.
+ if (AF.getParent()->UseCodeAlign() && AF.hasEmitNops() &&
+ getBackend().shouldInsertExtraNopBytesForCodeAlign(AF, Size))
+ return Size;
+
+ // 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)) {
+ getContext().reportError(OF.getLoc(),
+ "expected assembly-time absolute expression");
+ return 0;
+ }
+
+ 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)) {
+ getContext().reportError(OF.getLoc(), "expected absolute expression");
+ return 0;
+ }
+ TargetLocation += Val;
+ }
+ int64_t Size = TargetLocation - FragmentOffset;
+ if (Size < 0 || Size >= 0x40000000) {
+ getContext().reportError(
+ OF.getLoc(), "invalid .org offset '" + Twine(TargetLocation) +
+ "' (at offset '" + Twine(FragmentOffset) + "')");
+ return 0;
+ }
+ 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_CVInlineLines:
+ return cast<MCCVInlineLineTableFragment>(F).getContents().size();
+ case MCFragment::FT_CVDefRange:
+ return cast<MCCVDefRangeFragment>(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");
+ MCEncodedFragment *EF = cast<MCEncodedFragment>(F);
+ uint64_t FSize = Assembler.computeFragmentSize(*this, *EF);
+
+ if (!Assembler.getRelaxAll() && FSize > Assembler.getBundleAlignSize())
+ report_fatal_error("Fragment can't be larger than a bundle size");
+
+ uint64_t RequiredBundlePadding =
+ computeBundlePadding(Assembler, EF, EF->Offset, FSize);
+ if (RequiredBundlePadding > UINT8_MAX)
+ report_fatal_error("Padding cannot exceed 255 bytes");
+ EF->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
+ EF->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(raw_ostream &OS,
+ const MCEncodedFragment &EF,
+ uint64_t FSize) const {
+ assert(getBackendPtr() && "Expected assembler backend");
+ // Should NOP padding be written out before this fragment?
+ unsigned BundlePadding = EF.getBundlePadding();
+ if (BundlePadding > 0) {
+ assert(isBundlingEnabled() &&
+ "Writing bundle padding with disabled bundling");
+ assert(EF.hasInstructions() &&
+ "Writing bundle padding for a fragment without instructions");
+
+ unsigned TotalLength = BundlePadding + static_cast<unsigned>(FSize);
+ if (EF.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(OS, DistanceToBoundary))
+ report_fatal_error("unable to write NOP sequence of " +
+ Twine(DistanceToBoundary) + " bytes");
+ BundlePadding -= DistanceToBoundary;
+ }
+ if (!getBackend().writeNopData(OS, BundlePadding))
+ report_fatal_error("unable to write NOP sequence of " +
+ Twine(BundlePadding) + " bytes");
+ }
+}
+
+/// Write the fragment \p F to the output file.
+static void writeFragment(raw_ostream &OS, const MCAssembler &Asm,
+ const MCAsmLayout &Layout, const MCFragment &F) {
+ // FIXME: Embed in fragments instead?
+ uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F);
+
+ support::endianness Endian = Asm.getBackend().Endian;
+
+ if (const MCEncodedFragment *EF = dyn_cast<MCEncodedFragment>(&F))
+ Asm.writeFragmentPadding(OS, *EF, FragmentSize);
+
+ // This variable (and its dummy usage) is to participate in the assert at
+ // the end of the function.
+ uint64_t Start = OS.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(OS, Count))
+ 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: OS << char(AF.getValue()); break;
+ case 2:
+ support::endian::write<uint16_t>(OS, AF.getValue(), Endian);
+ break;
+ case 4:
+ support::endian::write<uint32_t>(OS, AF.getValue(), Endian);
+ break;
+ case 8:
+ support::endian::write<uint64_t>(OS, AF.getValue(), Endian);
+ break;
+ }
+ }
+ break;
+ }
+
+ case MCFragment::FT_Data:
+ ++stats::EmittedDataFragments;
+ OS << cast<MCDataFragment>(F).getContents();
+ break;
+
+ case MCFragment::FT_Relaxable:
+ ++stats::EmittedRelaxableFragments;
+ OS << cast<MCRelaxableFragment>(F).getContents();
+ break;
+
+ case MCFragment::FT_CompactEncodedInst:
+ ++stats::EmittedCompactEncodedInstFragments;
+ OS << cast<MCCompactEncodedInstFragment>(F).getContents();
+ break;
+
+ case MCFragment::FT_Fill: {
+ ++stats::EmittedFillFragments;
+ const MCFillFragment &FF = cast<MCFillFragment>(F);
+ uint64_t V = FF.getValue();
+ unsigned VSize = FF.getValueSize();
+ const unsigned MaxChunkSize = 16;
+ char Data[MaxChunkSize];
+ // Duplicate V into Data as byte vector to reduce number of
+ // writes done. As such, do endian conversion here.
+ for (unsigned I = 0; I != VSize; ++I) {
+ unsigned index = Endian == support::little ? I : (VSize - I - 1);
+ Data[I] = uint8_t(V >> (index * 8));
+ }
+ for (unsigned I = VSize; I < MaxChunkSize; ++I)
+ Data[I] = Data[I - VSize];
+
+ // Set to largest multiple of VSize in Data.
+ const unsigned NumPerChunk = MaxChunkSize / VSize;
+ // Set ChunkSize to largest multiple of VSize in Data
+ const unsigned ChunkSize = VSize * NumPerChunk;
+
+ // Do copies by chunk.
+ StringRef Ref(Data, ChunkSize);
+ for (uint64_t I = 0, E = FragmentSize / ChunkSize; I != E; ++I)
+ OS << Ref;
+
+ // do remainder if needed.
+ unsigned TrailingCount = FragmentSize % ChunkSize;
+ if (TrailingCount)
+ OS.write(Data, TrailingCount);
+ break;
+ }
+
+ case MCFragment::FT_LEB: {
+ const MCLEBFragment &LF = cast<MCLEBFragment>(F);
+ OS << LF.getContents();
+ break;
+ }
+
+ case MCFragment::FT_Padding: {
+ if (!Asm.getBackend().writeNopData(OS, FragmentSize))
+ report_fatal_error("unable to write nop sequence of " +
+ Twine(FragmentSize) + " bytes");
+ break;
+ }
+
+ case MCFragment::FT_SymbolId: {
+ const MCSymbolIdFragment &SF = cast<MCSymbolIdFragment>(F);
+ support::endian::write<uint32_t>(OS, SF.getSymbol()->getIndex(), Endian);
+ break;
+ }
+
+ case MCFragment::FT_Org: {
+ ++stats::EmittedOrgFragments;
+ const MCOrgFragment &OF = cast<MCOrgFragment>(F);
+
+ for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
+ OS << char(OF.getValue());
+
+ break;
+ }
+
+ case MCFragment::FT_Dwarf: {
+ const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
+ OS << OF.getContents();
+ break;
+ }
+ case MCFragment::FT_DwarfFrame: {
+ const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F);
+ OS << CF.getContents();
+ break;
+ }
+ case MCFragment::FT_CVInlineLines: {
+ const auto &OF = cast<MCCVInlineLineTableFragment>(F);
+ OS << OF.getContents();
+ break;
+ }
+ case MCFragment::FT_CVDefRange: {
+ const auto &DRF = cast<MCCVDefRangeFragment>(F);
+ OS << DRF.getContents();
+ break;
+ }
+ case MCFragment::FT_Dummy:
+ llvm_unreachable("Should not have been added");
+ }
+
+ assert(OS.tell() - Start == FragmentSize &&
+ "The stream should advance by fragment size");
+}
+
+void MCAssembler::writeSectionData(raw_ostream &OS, const MCSection *Sec,
+ const MCAsmLayout &Layout) const {
+ assert(getBackendPtr() && "Expected assembler backend");
+
+ // 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);
+ if (DF.fixup_begin() != DF.fixup_end())
+ report_fatal_error("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).getValue() == 0) &&
+ "Invalid fill in virtual section!");
+ break;
+ }
+ }
+
+ return;
+ }
+
+ uint64_t Start = OS.tell();
+ (void)Start;
+
+ for (const MCFragment &F : *Sec)
+ writeFragment(OS, *this, Layout, F);
+
+ assert(OS.tell() - Start == Layout.getSectionAddressSize(Sec));
+}
+
+std::tuple<MCValue, uint64_t, bool>
+MCAssembler::handleFixup(const MCAsmLayout &Layout, MCFragment &F,
+ const MCFixup &Fixup) {
+ // Evaluate the fixup.
+ MCValue Target;
+ uint64_t FixedValue;
+ bool WasForced;
+ bool IsResolved = evaluateFixup(Layout, Fixup, &F, Target, FixedValue,
+ WasForced);
+ if (!IsResolved) {
+ // 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.
+ if (Target.getSymA() && Target.getSymB() &&
+ getBackend().requiresDiffExpressionRelocations()) {
+ // The fixup represents the difference between two symbols, which the
+ // backend has indicated must be resolved at link time. Split up the fixup
+ // into two relocations, one for the add, and one for the sub, and emit
+ // both of these. The constant will be associated with the add half of the
+ // expression.
+ MCFixup FixupAdd = MCFixup::createAddFor(Fixup);
+ MCValue TargetAdd =
+ MCValue::get(Target.getSymA(), nullptr, Target.getConstant());
+ getWriter().recordRelocation(*this, Layout, &F, FixupAdd, TargetAdd,
+ FixedValue);
+ MCFixup FixupSub = MCFixup::createSubFor(Fixup);
+ MCValue TargetSub = MCValue::get(Target.getSymB());
+ getWriter().recordRelocation(*this, Layout, &F, FixupSub, TargetSub,
+ FixedValue);
+ } else {
+ getWriter().recordRelocation(*this, Layout, &F, Fixup, Target,
+ FixedValue);
+ }
+ }
+ return std::make_tuple(Target, FixedValue, IsResolved);
+}
+
+void MCAssembler::layout(MCAsmLayout &Layout) {
+ assert(getBackendPtr() && "Expected assembler backend");
+ DEBUG_WITH_TYPE("mc-dump", {
+ 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))
+ if (getContext().hadError())
+ return;
+
+ DEBUG_WITH_TYPE("mc-dump", {
+ errs() << "assembler backend - post-relaxation\n--\n";
+ dump(); });
+
+ // Finalize the layout, including fragment lowering.
+ finishLayout(Layout);
+
+ DEBUG_WITH_TYPE("mc-dump", {
+ 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) {
+ // 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 (isa<MCEncodedFragment>(&Frag) &&
+ isa<MCCompactEncodedInstFragment>(&Frag))
+ continue;
+ if (!isa<MCEncodedFragment>(&Frag) && !isa<MCCVDefRangeFragment>(&Frag) &&
+ !isa<MCAlignFragment>(&Frag))
+ continue;
+ ArrayRef<MCFixup> Fixups;
+ MutableArrayRef<char> Contents;
+ const MCSubtargetInfo *STI = nullptr;
+ if (auto *FragWithFixups = dyn_cast<MCDataFragment>(&Frag)) {
+ Fixups = FragWithFixups->getFixups();
+ Contents = FragWithFixups->getContents();
+ STI = FragWithFixups->getSubtargetInfo();
+ assert(!FragWithFixups->hasInstructions() || STI != nullptr);
+ } else if (auto *FragWithFixups = dyn_cast<MCRelaxableFragment>(&Frag)) {
+ Fixups = FragWithFixups->getFixups();
+ Contents = FragWithFixups->getContents();
+ STI = FragWithFixups->getSubtargetInfo();
+ assert(!FragWithFixups->hasInstructions() || STI != nullptr);
+ } else if (auto *FragWithFixups = dyn_cast<MCCVDefRangeFragment>(&Frag)) {
+ Fixups = FragWithFixups->getFixups();
+ Contents = FragWithFixups->getContents();
+ } else if (auto *FragWithFixups = dyn_cast<MCDwarfLineAddrFragment>(&Frag)) {
+ Fixups = FragWithFixups->getFixups();
+ Contents = FragWithFixups->getContents();
+ } else if (auto *AF = dyn_cast<MCAlignFragment>(&Frag)) {
+ // Insert fixup type for code alignment if the target define
+ // shouldInsertFixupForCodeAlign target hook.
+ if (Sec.UseCodeAlign() && AF->hasEmitNops()) {
+ getBackend().shouldInsertFixupForCodeAlign(*this, Layout, *AF);
+ }
+ continue;
+ } else if (auto *FragWithFixups =
+ dyn_cast<MCDwarfCallFrameFragment>(&Frag)) {
+ Fixups = FragWithFixups->getFixups();
+ Contents = FragWithFixups->getContents();
+ } else
+ llvm_unreachable("Unknown fragment with fixups!");
+ for (const MCFixup &Fixup : Fixups) {
+ uint64_t FixedValue;
+ bool IsResolved;
+ MCValue Target;
+ std::tie(Target, FixedValue, IsResolved) =
+ handleFixup(Layout, Frag, Fixup);
+ getBackend().applyFixup(*this, Fixup, Target, Contents, FixedValue,
+ IsResolved, STI);
+ }
+ }
+ }
+}
+
+void MCAssembler::Finish() {
+ // Create the layout object.
+ MCAsmLayout Layout(*this);
+ layout(Layout);
+
+ // Write the object file.
+ stats::ObjectBytes += getWriter().writeObject(*this, Layout);
+}
+
+bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup,
+ const MCRelaxableFragment *DF,
+ const MCAsmLayout &Layout) const {
+ assert(getBackendPtr() && "Expected assembler backend");
+ MCValue Target;
+ uint64_t Value;
+ bool WasForced;
+ bool Resolved = evaluateFixup(Layout, Fixup, DF, Target, Value, WasForced);
+ if (Target.getSymA() &&
+ Target.getSymA()->getKind() == MCSymbolRefExpr::VK_X86_ABS8 &&
+ Fixup.getKind() == FK_Data_1)
+ return false;
+ return getBackend().fixupNeedsRelaxationAdvanced(Fixup, Resolved, Value, DF,
+ Layout, WasForced);
+}
+
+bool MCAssembler::fragmentNeedsRelaxation(const MCRelaxableFragment *F,
+ const MCAsmLayout &Layout) const {
+ assert(getBackendPtr() && "Expected assembler backend");
+ // 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(), *F->getSubtargetInfo()))
+ return false;
+
+ for (const MCFixup &Fixup : F->getFixups())
+ if (fixupNeedsRelaxation(Fixup, F, Layout))
+ return true;
+
+ return false;
+}
+
+bool MCAssembler::relaxInstruction(MCAsmLayout &Layout,
+ MCRelaxableFragment &F) {
+ assert(getEmitterPtr() &&
+ "Expected CodeEmitter defined for relaxInstruction");
+ 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(), *F.getSubtargetInfo(), 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::relaxPaddingFragment(MCAsmLayout &Layout,
+ MCPaddingFragment &PF) {
+ assert(getBackendPtr() && "Expected assembler backend");
+ uint64_t OldSize = PF.getSize();
+ if (!getBackend().relaxFragment(&PF, Layout))
+ return false;
+ uint64_t NewSize = PF.getSize();
+
+ ++stats::PaddingFragmentsRelaxations;
+ stats::PaddingFragmentsBytes += NewSize;
+ stats::PaddingFragmentsBytes -= OldSize;
+ 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);
+ // The compiler can generate EH table assembly that is impossible to assemble
+ // without either adding padding to an LEB fragment or adding extra padding
+ // to a later alignment fragment. To accommodate such tables, relaxation can
+ // only increase an LEB fragment size here, not decrease it. See PR35809.
+ if (LF.isSigned())
+ encodeSLEB128(Value, OSE, OldSize);
+ else
+ encodeULEB128(Value, OSE, OldSize);
+ 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();
+ SmallVectorImpl<char> &Data = DF.getContents();
+ Data.clear();
+ raw_svector_ostream OSE(Data);
+ DF.getFixups().clear();
+
+ if (!getBackend().requiresDiffExpressionRelocations()) {
+ MCDwarfLineAddr::Encode(Context, getDWARFLinetableParams(), LineDelta,
+ AddrDelta, OSE);
+ } else {
+ uint32_t Offset;
+ uint32_t Size;
+ bool SetDelta = MCDwarfLineAddr::FixedEncode(Context,
+ getDWARFLinetableParams(),
+ LineDelta, AddrDelta,
+ OSE, &Offset, &Size);
+ // Add Fixups for address delta or new address.
+ const MCExpr *FixupExpr;
+ if (SetDelta) {
+ FixupExpr = &DF.getAddrDelta();
+ } else {
+ const MCBinaryExpr *ABE = cast<MCBinaryExpr>(&DF.getAddrDelta());
+ FixupExpr = ABE->getLHS();
+ }
+ DF.getFixups().push_back(
+ MCFixup::create(Offset, FixupExpr,
+ MCFixup::getKindForSize(Size, false /*isPCRel*/)));
+ }
+
+ 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;
+ SmallVectorImpl<char> &Data = DF.getContents();
+ Data.clear();
+ raw_svector_ostream OSE(Data);
+ DF.getFixups().clear();
+
+ if (getBackend().requiresDiffExpressionRelocations()) {
+ uint32_t Offset;
+ uint32_t Size;
+ MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE, &Offset,
+ &Size);
+ if (Size) {
+ DF.getFixups().push_back(MCFixup::create(
+ Offset, &DF.getAddrDelta(),
+ MCFixup::getKindForSizeInBits(Size /*In bits.*/, false /*isPCRel*/)));
+ }
+ } else {
+ MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE);
+ }
+
+ return OldSize != Data.size();
+}
+
+bool MCAssembler::relaxCVInlineLineTable(MCAsmLayout &Layout,
+ MCCVInlineLineTableFragment &F) {
+ unsigned OldSize = F.getContents().size();
+ getContext().getCVContext().encodeInlineLineTable(Layout, F);
+ return OldSize != F.getContents().size();
+}
+
+bool MCAssembler::relaxCVDefRange(MCAsmLayout &Layout,
+ MCCVDefRangeFragment &F) {
+ unsigned OldSize = F.getContents().size();
+ getContext().getCVContext().encodeDefRange(Layout, F);
+ return OldSize != F.getContents().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;
+ case MCFragment::FT_Padding:
+ RelaxedFrag = relaxPaddingFragment(Layout, *cast<MCPaddingFragment>(I));
+ break;
+ case MCFragment::FT_CVInlineLines:
+ RelaxedFrag =
+ relaxCVInlineLineTable(Layout, *cast<MCCVInlineLineTableFragment>(I));
+ break;
+ case MCFragment::FT_CVDefRange:
+ RelaxedFrag = relaxCVDefRange(Layout, *cast<MCCVDefRangeFragment>(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) {
+ assert(getBackendPtr() && "Expected assembler backend");
+ // The layout is done. Mark every fragment as valid.
+ for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) {
+ MCSection &Section = *Layout.getSectionOrder()[i];
+ Layout.getFragmentOffset(&*Section.rbegin());
+ computeFragmentSize(Layout, *Section.rbegin());
+ }
+ getBackend().finishLayout(*this, Layout);
+}
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+LLVM_DUMP_METHOD void MCAssembler::dump() const{
+ raw_ostream &OS = errs();
+
+ OS << "<MCAssembler\n";
+ OS << " Sections:[\n ";
+ for (const_iterator it = begin(), ie = end(); it != ie; ++it) {
+ if (it != begin()) OS << ",\n ";
+ it->dump();
+ }
+ OS << "],\n";
+ OS << " Symbols:[";
+
+ for (const_symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
+ if (it != symbol_begin()) OS << ",\n ";
+ OS << "(";
+ it->dump();
+ OS << ", Index:" << it->getIndex() << ", ";
+ OS << ")";
+ }
+ OS << "]>\n";
+}
+#endif
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