//===- MCSymbol.h - Machine Code Symbols ------------------------*- C++ -*-===// // // 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 // //===----------------------------------------------------------------------===// // // This file contains the declaration of the MCSymbol class. // //===----------------------------------------------------------------------===// #ifndef LLVM_MC_MCSYMBOL_H #define LLVM_MC_MCSYMBOL_H #include "llvm/ADT/PointerIntPair.h" #include "llvm/ADT/StringMap.h" #include "llvm/ADT/StringRef.h" #include "llvm/MC/MCFragment.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/Support/MathExtras.h" #include #include #include namespace llvm { class MCAsmInfo; class MCContext; class MCExpr; class MCSection; class raw_ostream; /// MCSymbol - Instances of this class represent a symbol name in the MC file, /// and MCSymbols are created and uniqued by the MCContext class. MCSymbols /// should only be constructed with valid names for the object file. /// /// If the symbol is defined/emitted into the current translation unit, the /// Section member is set to indicate what section it lives in. Otherwise, if /// it is a reference to an external entity, it has a null section. class MCSymbol { protected: /// The kind of the symbol. If it is any value other than unset then this /// class is actually one of the appropriate subclasses of MCSymbol. enum SymbolKind { SymbolKindUnset, SymbolKindCOFF, SymbolKindELF, SymbolKindMachO, SymbolKindWasm, SymbolKindXCOFF, }; /// A symbol can contain an Offset, or Value, or be Common, but never more /// than one of these. enum Contents : uint8_t { SymContentsUnset, SymContentsOffset, SymContentsVariable, SymContentsCommon, SymContentsTargetCommon, // Index stores the section index }; // Special sentinal value for the absolute pseudo fragment. static MCFragment *AbsolutePseudoFragment; /// If a symbol has a Fragment, the section is implied, so we only need /// one pointer. /// The special AbsolutePseudoFragment value is for absolute symbols. /// If this is a variable symbol, this caches the variable value's fragment. /// FIXME: We might be able to simplify this by having the asm streamer create /// dummy fragments. /// If this is a section, then it gives the symbol is defined in. This is null /// for undefined symbols. /// /// If this is a fragment, then it gives the fragment this symbol's value is /// relative to, if any. /// /// For the 'HasName' integer, this is true if this symbol is named. /// A named symbol will have a pointer to the name allocated in the bytes /// immediately prior to the MCSymbol. mutable PointerIntPair FragmentAndHasName; /// IsTemporary - True if this is an assembler temporary label, which /// typically does not survive in the .o file's symbol table. Usually /// "Lfoo" or ".foo". unsigned IsTemporary : 1; /// True if this symbol can be redefined. unsigned IsRedefinable : 1; /// IsUsed - True if this symbol has been used. mutable unsigned IsUsed : 1; mutable unsigned IsRegistered : 1; /// This symbol is visible outside this translation unit. mutable unsigned IsExternal : 1; /// This symbol is private extern. mutable unsigned IsPrivateExtern : 1; /// LLVM RTTI discriminator. This is actually a SymbolKind enumerator, but is /// unsigned to avoid sign extension and achieve better bitpacking with MSVC. unsigned Kind : 3; /// True if we have created a relocation that uses this symbol. mutable unsigned IsUsedInReloc : 1; /// This is actually a Contents enumerator, but is unsigned to avoid sign /// extension and achieve better bitpacking with MSVC. unsigned SymbolContents : 3; /// The alignment of the symbol, if it is 'common', or -1. /// /// The alignment is stored as log2(align) + 1. This allows all values from /// 0 to 2^31 to be stored which is every power of 2 representable by an /// unsigned. enum : unsigned { NumCommonAlignmentBits = 5 }; unsigned CommonAlignLog2 : NumCommonAlignmentBits; /// The Flags field is used by object file implementations to store /// additional per symbol information which is not easily classified. enum : unsigned { NumFlagsBits = 16 }; mutable uint32_t Flags : NumFlagsBits; /// Index field, for use by the object file implementation. mutable uint32_t Index = 0; union { /// The offset to apply to the fragment address to form this symbol's value. uint64_t Offset; /// The size of the symbol, if it is 'common'. uint64_t CommonSize; /// If non-null, the value for a variable symbol. const MCExpr *Value; }; // MCContext creates and uniques these. friend class MCExpr; friend class MCContext; /// The name for a symbol. /// MCSymbol contains a uint64_t so is probably aligned to 8. On a 32-bit /// system, the name is a pointer so isn't going to satisfy the 8 byte /// alignment of uint64_t. Account for that here. using NameEntryStorageTy = union { const StringMapEntry *NameEntry; uint64_t AlignmentPadding; }; MCSymbol(SymbolKind Kind, const StringMapEntry *Name, bool isTemporary) : IsTemporary(isTemporary), IsRedefinable(false), IsUsed(false), IsRegistered(false), IsExternal(false), IsPrivateExtern(false), Kind(Kind), IsUsedInReloc(false), SymbolContents(SymContentsUnset), CommonAlignLog2(0), Flags(0) { Offset = 0; FragmentAndHasName.setInt(!!Name); if (Name) getNameEntryPtr() = Name; } // Provide custom new/delete as we will only allocate space for a name // if we need one. void *operator new(size_t s, const StringMapEntry *Name, MCContext &Ctx); private: void operator delete(void *); /// Placement delete - required by std, but never called. void operator delete(void*, unsigned) { llvm_unreachable("Constructor throws?"); } /// Placement delete - required by std, but never called. void operator delete(void*, unsigned, bool) { llvm_unreachable("Constructor throws?"); } MCSection *getSectionPtr() const { if (MCFragment *F = getFragment()) { assert(F != AbsolutePseudoFragment); return F->getParent(); } return nullptr; } /// Get a reference to the name field. Requires that we have a name const StringMapEntry *&getNameEntryPtr() { assert(FragmentAndHasName.getInt() && "Name is required"); NameEntryStorageTy *Name = reinterpret_cast(this); return (*(Name - 1)).NameEntry; } const StringMapEntry *&getNameEntryPtr() const { return const_cast(this)->getNameEntryPtr(); } public: MCSymbol(const MCSymbol &) = delete; MCSymbol &operator=(const MCSymbol &) = delete; /// getName - Get the symbol name. StringRef getName() const { if (!FragmentAndHasName.getInt()) return StringRef(); return getNameEntryPtr()->first(); } bool isRegistered() const { return IsRegistered; } void setIsRegistered(bool Value) const { IsRegistered = Value; } void setUsedInReloc() const { IsUsedInReloc = true; } bool isUsedInReloc() const { return IsUsedInReloc; } /// \name Accessors /// @{ /// isTemporary - Check if this is an assembler temporary symbol. bool isTemporary() const { return IsTemporary; } /// isUsed - Check if this is used. bool isUsed() const { return IsUsed; } /// Check if this symbol is redefinable. bool isRedefinable() const { return IsRedefinable; } /// Mark this symbol as redefinable. void setRedefinable(bool Value) { IsRedefinable = Value; } /// Prepare this symbol to be redefined. void redefineIfPossible() { if (IsRedefinable) { if (SymbolContents == SymContentsVariable) { Value = nullptr; SymbolContents = SymContentsUnset; } setUndefined(); IsRedefinable = false; } } /// @} /// \name Associated Sections /// @{ /// isDefined - Check if this symbol is defined (i.e., it has an address). /// /// Defined symbols are either absolute or in some section. bool isDefined() const { return !isUndefined(); } /// isInSection - Check if this symbol is defined in some section (i.e., it /// is defined but not absolute). bool isInSection() const { return isDefined() && !isAbsolute(); } /// isUndefined - Check if this symbol undefined (i.e., implicitly defined). bool isUndefined(bool SetUsed = true) const { return getFragment(SetUsed) == nullptr; } /// isAbsolute - Check if this is an absolute symbol. bool isAbsolute() const { return getFragment() == AbsolutePseudoFragment; } /// Get the section associated with a defined, non-absolute symbol. MCSection &getSection() const { assert(isInSection() && "Invalid accessor!"); return *getSectionPtr(); } /// Mark the symbol as defined in the fragment \p F. void setFragment(MCFragment *F) const { assert(!isVariable() && "Cannot set fragment of variable"); FragmentAndHasName.setPointer(F); } /// Mark the symbol as undefined. void setUndefined() { FragmentAndHasName.setPointer(nullptr); } bool isELF() const { return Kind == SymbolKindELF; } bool isCOFF() const { return Kind == SymbolKindCOFF; } bool isMachO() const { return Kind == SymbolKindMachO; } bool isWasm() const { return Kind == SymbolKindWasm; } bool isXCOFF() const { return Kind == SymbolKindXCOFF; } /// @} /// \name Variable Symbols /// @{ /// isVariable - Check if this is a variable symbol. bool isVariable() const { return SymbolContents == SymContentsVariable; } /// getVariableValue - Get the value for variable symbols. const MCExpr *getVariableValue(bool SetUsed = true) const { assert(isVariable() && "Invalid accessor!"); IsUsed |= SetUsed; return Value; } void setVariableValue(const MCExpr *Value); /// @} /// Get the (implementation defined) index. uint32_t getIndex() const { return Index; } /// Set the (implementation defined) index. void setIndex(uint32_t Value) const { Index = Value; } bool isUnset() const { return SymbolContents == SymContentsUnset; } uint64_t getOffset() const { assert((SymbolContents == SymContentsUnset || SymbolContents == SymContentsOffset) && "Cannot get offset for a common/variable symbol"); return Offset; } void setOffset(uint64_t Value) { assert((SymbolContents == SymContentsUnset || SymbolContents == SymContentsOffset) && "Cannot set offset for a common/variable symbol"); Offset = Value; SymbolContents = SymContentsOffset; } /// Return the size of a 'common' symbol. uint64_t getCommonSize() const { assert(isCommon() && "Not a 'common' symbol!"); return CommonSize; } /// Mark this symbol as being 'common'. /// /// \param Size - The size of the symbol. /// \param Align - The alignment of the symbol. /// \param Target - Is the symbol a target-specific common-like symbol. void setCommon(uint64_t Size, unsigned Align, bool Target = false) { assert(getOffset() == 0); CommonSize = Size; SymbolContents = Target ? SymContentsTargetCommon : SymContentsCommon; assert((!Align || isPowerOf2_32(Align)) && "Alignment must be a power of 2"); unsigned Log2Align = Log2_32(Align) + 1; assert(Log2Align < (1U << NumCommonAlignmentBits) && "Out of range alignment"); CommonAlignLog2 = Log2Align; } /// Return the alignment of a 'common' symbol. unsigned getCommonAlignment() const { assert(isCommon() && "Not a 'common' symbol!"); return CommonAlignLog2 ? (1U << (CommonAlignLog2 - 1)) : 0; } /// Declare this symbol as being 'common'. /// /// \param Size - The size of the symbol. /// \param Align - The alignment of the symbol. /// \param Target - Is the symbol a target-specific common-like symbol. /// \return True if symbol was already declared as a different type bool declareCommon(uint64_t Size, unsigned Align, bool Target = false) { assert(isCommon() || getOffset() == 0); if(isCommon()) { if (CommonSize != Size || getCommonAlignment() != Align || isTargetCommon() != Target) return true; } else setCommon(Size, Align, Target); return false; } /// Is this a 'common' symbol. bool isCommon() const { return SymbolContents == SymContentsCommon || SymbolContents == SymContentsTargetCommon; } /// Is this a target-specific common-like symbol. bool isTargetCommon() const { return SymbolContents == SymContentsTargetCommon; } MCFragment *getFragment(bool SetUsed = true) const { MCFragment *Fragment = FragmentAndHasName.getPointer(); if (Fragment || !isVariable()) return Fragment; Fragment = getVariableValue(SetUsed)->findAssociatedFragment(); FragmentAndHasName.setPointer(Fragment); return Fragment; } bool isExternal() const { return IsExternal; } void setExternal(bool Value) const { IsExternal = Value; } bool isPrivateExtern() const { return IsPrivateExtern; } void setPrivateExtern(bool Value) { IsPrivateExtern = Value; } /// print - Print the value to the stream \p OS. void print(raw_ostream &OS, const MCAsmInfo *MAI) const; /// dump - Print the value to stderr. void dump() const; protected: /// Get the (implementation defined) symbol flags. uint32_t getFlags() const { return Flags; } /// Set the (implementation defined) symbol flags. void setFlags(uint32_t Value) const { assert(Value < (1U << NumFlagsBits) && "Out of range flags"); Flags = Value; } /// Modify the flags via a mask void modifyFlags(uint32_t Value, uint32_t Mask) const { assert(Value < (1U << NumFlagsBits) && "Out of range flags"); Flags = (Flags & ~Mask) | Value; } }; inline raw_ostream &operator<<(raw_ostream &OS, const MCSymbol &Sym) { Sym.print(OS, nullptr); return OS; } } // end namespace llvm #endif // LLVM_MC_MCSYMBOL_H