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//===- MCAssembler.h - Object File Generation -------------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/iterator.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/BinaryFormat/MachO.h"
#include "llvm/MC/MCDirectives.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/MC/MCFragment.h"
#include "llvm/MC/MCLinkerOptimizationHint.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/VersionTuple.h"
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <string>
#include <utility>
#include <vector>
namespace llvm {
class MCAsmBackend;
class MCAsmLayout;
class MCContext;
class MCCodeEmitter;
class MCFragment;
class MCObjectWriter;
class MCSection;
class MCValue;
// FIXME: This really doesn't belong here. See comments below.
struct IndirectSymbolData {
MCSymbol *Symbol;
MCSection *Section;
// FIXME: Ditto this. Purely so the Streamer and the ObjectWriter can talk
// to one another.
struct DataRegionData {
// This enum should be kept in sync w/ the mach-o definition in
// llvm/Object/MachOFormat.h.
enum KindTy { Data = 1, JumpTable8, JumpTable16, JumpTable32 } Kind;
MCSymbol *Start;
MCSymbol *End;
class MCAssembler {
friend class MCAsmLayout;
using SectionListType = std::vector<MCSection *>;
using SymbolDataListType = std::vector<const MCSymbol *>;
using const_iterator = pointee_iterator<SectionListType::const_iterator>;
using iterator = pointee_iterator<SectionListType::iterator>;
using const_symbol_iterator =
using symbol_iterator = pointee_iterator<SymbolDataListType::iterator>;
using symbol_range = iterator_range<symbol_iterator>;
using const_symbol_range = iterator_range<const_symbol_iterator>;
using const_indirect_symbol_iterator =
using indirect_symbol_iterator = std::vector<IndirectSymbolData>::iterator;
using const_data_region_iterator =
using data_region_iterator = std::vector<DataRegionData>::iterator;
/// MachO specific deployment target version info.
// A Major version of 0 indicates that no version information was supplied
// and so the corresponding load command should not be emitted.
using VersionInfoType = struct {
bool EmitBuildVersion;
union {
MCVersionMinType Type; ///< Used when EmitBuildVersion==false.
MachO::PlatformType Platform; ///< Used when EmitBuildVersion==true.
} TypeOrPlatform;
unsigned Major;
unsigned Minor;
unsigned Update;
/// An optional version of the SDK that was used to build the source.
VersionTuple SDKVersion;
MCContext &Context;
std::unique_ptr<MCAsmBackend> Backend;
std::unique_ptr<MCCodeEmitter> Emitter;
std::unique_ptr<MCObjectWriter> Writer;
SectionListType Sections;
SymbolDataListType Symbols;
std::vector<IndirectSymbolData> IndirectSymbols;
std::vector<DataRegionData> DataRegions;
/// The list of linker options to propagate into the object file.
std::vector<std::vector<std::string>> LinkerOptions;
/// List of declared file names
std::vector<std::pair<std::string, size_t>> FileNames;
MCDwarfLineTableParams LTParams;
/// The set of function symbols for which a .thumb_func directive has
/// been seen.
// FIXME: We really would like this in target specific code rather than
// here. Maybe when the relocation stuff moves to target specific,
// this can go with it? The streamer would need some target specific
// refactoring too.
mutable SmallPtrSet<const MCSymbol *, 32> ThumbFuncs;
/// The bundle alignment size currently set in the assembler.
/// By default it's 0, which means bundling is disabled.
unsigned BundleAlignSize;
bool RelaxAll : 1;
bool SubsectionsViaSymbols : 1;
bool IncrementalLinkerCompatible : 1;
/// ELF specific e_header flags
// It would be good if there were an MCELFAssembler class to hold this.
// ELF header flags are used both by the integrated and standalone assemblers.
// Access to the flags is necessary in cases where assembler directives affect
// which flags to be set.
unsigned ELFHeaderEFlags;
/// Used to communicate Linker Optimization Hint information between
/// the Streamer and the .o writer
MCLOHContainer LOHContainer;
VersionInfoType VersionInfo;
/// Evaluate a fixup to a relocatable expression and the value which should be
/// placed into the fixup.
/// \param Layout The layout to use for evaluation.
/// \param Fixup The fixup to evaluate.
/// \param DF The fragment the fixup is inside.
/// \param Target [out] On return, the relocatable expression the fixup
/// evaluates to.
/// \param Value [out] On return, the value of the fixup as currently laid
/// out.
/// \param WasForced [out] On return, the value in the fixup is set to the
/// correct value if WasForced is true, even if evaluateFixup returns false.
/// \return Whether the fixup value was fully resolved. This is true if the
/// \p Value result is fixed, otherwise the value may change due to
/// relocation.
bool evaluateFixup(const MCAsmLayout &Layout, const MCFixup &Fixup,
const MCFragment *DF, MCValue &Target,
uint64_t &Value, bool &WasForced) const;
/// Check whether a fixup can be satisfied, or whether it needs to be relaxed
/// (increased in size, in order to hold its value correctly).
bool fixupNeedsRelaxation(const MCFixup &Fixup, const MCRelaxableFragment *DF,
const MCAsmLayout &Layout) const;
/// Check whether the given fragment needs relaxation.
bool fragmentNeedsRelaxation(const MCRelaxableFragment *IF,
const MCAsmLayout &Layout) const;
/// Perform one layout iteration and return true if any offsets
/// were adjusted.
bool layoutOnce(MCAsmLayout &Layout);
/// Perform one layout iteration of the given section and return true
/// if any offsets were adjusted.
bool layoutSectionOnce(MCAsmLayout &Layout, MCSection &Sec);
/// Perform relaxation on a single fragment - returns true if the fragment
/// changes as a result of relaxation.
bool relaxFragment(MCAsmLayout &Layout, MCFragment &F);
bool relaxInstruction(MCAsmLayout &Layout, MCRelaxableFragment &IF);
bool relaxLEB(MCAsmLayout &Layout, MCLEBFragment &IF);
bool relaxBoundaryAlign(MCAsmLayout &Layout, MCBoundaryAlignFragment &BF);
bool relaxDwarfLineAddr(MCAsmLayout &Layout, MCDwarfLineAddrFragment &DF);
bool relaxDwarfCallFrameFragment(MCAsmLayout &Layout,
MCDwarfCallFrameFragment &DF);
bool relaxCVInlineLineTable(MCAsmLayout &Layout,
MCCVInlineLineTableFragment &DF);
bool relaxCVDefRange(MCAsmLayout &Layout, MCCVDefRangeFragment &DF);
bool relaxPseudoProbeAddr(MCAsmLayout &Layout, MCPseudoProbeAddrFragment &DF);
/// finishLayout - Finalize a layout, including fragment lowering.
void finishLayout(MCAsmLayout &Layout);
std::tuple<MCValue, uint64_t, bool>
handleFixup(const MCAsmLayout &Layout, MCFragment &F, const MCFixup &Fixup);
struct Symver {
SMLoc Loc;
const MCSymbol *Sym;
StringRef Name;
// True if .symver *, *@@@* or .symver *, *, remove.
bool KeepOriginalSym;
std::vector<Symver> Symvers;
/// Construct a new assembler instance.
// FIXME: How are we going to parameterize this? Two obvious options are stay
// concrete and require clients to pass in a target like object. The other
// option is to make this abstract, and have targets provide concrete
// implementations as we do with AsmParser.
MCAssembler(MCContext &Context, std::unique_ptr<MCAsmBackend> Backend,
std::unique_ptr<MCCodeEmitter> Emitter,
std::unique_ptr<MCObjectWriter> Writer);
MCAssembler(const MCAssembler &) = delete;
MCAssembler &operator=(const MCAssembler &) = delete;
/// Compute the effective fragment size assuming it is laid out at the given
/// \p SectionAddress and \p FragmentOffset.
uint64_t computeFragmentSize(const MCAsmLayout &Layout,
const MCFragment &F) const;
/// Find the symbol which defines the atom containing the given symbol, or
/// null if there is no such symbol.
const MCSymbol *getAtom(const MCSymbol &S) const;
/// Check whether a particular symbol is visible to the linker and is required
/// in the symbol table, or whether it can be discarded by the assembler. This
/// also effects whether the assembler treats the label as potentially
/// defining a separate atom.
bool isSymbolLinkerVisible(const MCSymbol &SD) const;
/// Emit the section contents to \p OS.
void writeSectionData(raw_ostream &OS, const MCSection *Section,
const MCAsmLayout &Layout) const;
/// Check whether a given symbol has been flagged with .thumb_func.
bool isThumbFunc(const MCSymbol *Func) const;
/// Flag a function symbol as the target of a .thumb_func directive.
void setIsThumbFunc(const MCSymbol *Func) { ThumbFuncs.insert(Func); }
/// ELF e_header flags
unsigned getELFHeaderEFlags() const { return ELFHeaderEFlags; }
void setELFHeaderEFlags(unsigned Flags) { ELFHeaderEFlags = Flags; }
/// MachO deployment target version information.
const VersionInfoType &getVersionInfo() const { return VersionInfo; }
void setVersionMin(MCVersionMinType Type, unsigned Major, unsigned Minor,
unsigned Update,
VersionTuple SDKVersion = VersionTuple()) {
VersionInfo.EmitBuildVersion = false;
VersionInfo.TypeOrPlatform.Type = Type;
VersionInfo.Major = Major;
VersionInfo.Minor = Minor;
VersionInfo.Update = Update;
VersionInfo.SDKVersion = SDKVersion;
void setBuildVersion(MachO::PlatformType Platform, unsigned Major,
unsigned Minor, unsigned Update,
VersionTuple SDKVersion = VersionTuple()) {
VersionInfo.EmitBuildVersion = true;
VersionInfo.TypeOrPlatform.Platform = Platform;
VersionInfo.Major = Major;
VersionInfo.Minor = Minor;
VersionInfo.Update = Update;
VersionInfo.SDKVersion = SDKVersion;
/// Reuse an assembler instance
void reset();
MCContext &getContext() const { return Context; }
MCAsmBackend *getBackendPtr() const { return Backend.get(); }
MCCodeEmitter *getEmitterPtr() const { return Emitter.get(); }
MCObjectWriter *getWriterPtr() const { return Writer.get(); }
MCAsmBackend &getBackend() const { return *Backend; }
MCCodeEmitter &getEmitter() const { return *Emitter; }
MCObjectWriter &getWriter() const { return *Writer; }
MCDwarfLineTableParams getDWARFLinetableParams() const { return LTParams; }
void setDWARFLinetableParams(MCDwarfLineTableParams P) { LTParams = P; }
/// Finish - Do final processing and write the object to the output stream.
/// \p Writer is used for custom object writer (as the MCJIT does),
/// if not specified it is automatically created from backend.
void Finish();
// Layout all section and prepare them for emission.
void layout(MCAsmLayout &Layout);
// FIXME: This does not belong here.
bool getSubsectionsViaSymbols() const { return SubsectionsViaSymbols; }
void setSubsectionsViaSymbols(bool Value) { SubsectionsViaSymbols = Value; }
bool isIncrementalLinkerCompatible() const {
return IncrementalLinkerCompatible;
void setIncrementalLinkerCompatible(bool Value) {
IncrementalLinkerCompatible = Value;
bool getRelaxAll() const { return RelaxAll; }
void setRelaxAll(bool Value) { RelaxAll = Value; }
bool isBundlingEnabled() const { return BundleAlignSize != 0; }
unsigned getBundleAlignSize() const { return BundleAlignSize; }
void setBundleAlignSize(unsigned Size) {
assert((Size == 0 || !(Size & (Size - 1))) &&
"Expect a power-of-two bundle align size");
BundleAlignSize = Size;
/// \name Section List Access
/// @{
iterator begin() { return Sections.begin(); }
const_iterator begin() const { return Sections.begin(); }
iterator end() { return Sections.end(); }
const_iterator end() const { return Sections.end(); }
size_t size() const { return Sections.size(); }
/// @}
/// \name Symbol List Access
/// @{
symbol_iterator symbol_begin() { return Symbols.begin(); }
const_symbol_iterator symbol_begin() const { return Symbols.begin(); }
symbol_iterator symbol_end() { return Symbols.end(); }
const_symbol_iterator symbol_end() const { return Symbols.end(); }
symbol_range symbols() { return make_range(symbol_begin(), symbol_end()); }
const_symbol_range symbols() const {
return make_range(symbol_begin(), symbol_end());
size_t symbol_size() const { return Symbols.size(); }
/// @}
/// \name Indirect Symbol List Access
/// @{
// FIXME: This is a total hack, this should not be here. Once things are
// factored so that the streamer has direct access to the .o writer, it can
// disappear.
std::vector<IndirectSymbolData> &getIndirectSymbols() {
return IndirectSymbols;
indirect_symbol_iterator indirect_symbol_begin() {
return IndirectSymbols.begin();
const_indirect_symbol_iterator indirect_symbol_begin() const {
return IndirectSymbols.begin();
indirect_symbol_iterator indirect_symbol_end() {
return IndirectSymbols.end();
const_indirect_symbol_iterator indirect_symbol_end() const {
return IndirectSymbols.end();
size_t indirect_symbol_size() const { return IndirectSymbols.size(); }
/// @}
/// \name Linker Option List Access
/// @{
std::vector<std::vector<std::string>> &getLinkerOptions() {
return LinkerOptions;
/// @}
/// \name Data Region List Access
/// @{
// FIXME: This is a total hack, this should not be here. Once things are
// factored so that the streamer has direct access to the .o writer, it can
// disappear.
std::vector<DataRegionData> &getDataRegions() { return DataRegions; }
data_region_iterator data_region_begin() { return DataRegions.begin(); }
const_data_region_iterator data_region_begin() const {
return DataRegions.begin();
data_region_iterator data_region_end() { return DataRegions.end(); }
const_data_region_iterator data_region_end() const {
return DataRegions.end();
size_t data_region_size() const { return DataRegions.size(); }
/// @}
/// \name Data Region List Access
/// @{
// FIXME: This is a total hack, this should not be here. Once things are
// factored so that the streamer has direct access to the .o writer, it can
// disappear.
MCLOHContainer &getLOHContainer() { return LOHContainer; }
const MCLOHContainer &getLOHContainer() const {
return const_cast<MCAssembler *>(this)->getLOHContainer();
struct CGProfileEntry {
const MCSymbolRefExpr *From;
const MCSymbolRefExpr *To;
uint64_t Count;
std::vector<CGProfileEntry> CGProfile;
/// @}
/// \name Backend Data Access
/// @{
bool registerSection(MCSection &Section);
void registerSymbol(const MCSymbol &Symbol, bool *Created = nullptr);
MutableArrayRef<std::pair<std::string, size_t>> getFileNames() {
return FileNames;
void addFileName(StringRef FileName) {
FileNames.emplace_back(std::string(FileName), Symbols.size());
/// Write the necessary bundle padding to \p OS.
/// Expects a fragment \p F containing instructions and its size \p FSize.
void writeFragmentPadding(raw_ostream &OS, const MCEncodedFragment &F,
uint64_t FSize) const;
/// @}
void dump() const;
/// Compute the amount of padding required before the fragment \p F to
/// obey bundling restrictions, where \p FOffset is the fragment's offset in
/// its section and \p FSize is the fragment's size.
uint64_t computeBundlePadding(const MCAssembler &Assembler,
const MCEncodedFragment *F, uint64_t FOffset,
uint64_t FSize);
} // end namespace llvm