X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=include%2Fllvm%2FMC%2FMCSymbol.h;h=b2910dfccd637abc15622fa3d736f5a252360100;hb=00552e3875ee5f382db6c98286a241a7d0efe1b8;hp=7f74f378d465102a949a409a8d23103225d53227;hpb=2ca8f0f5d6b258c53bcf781124e01d264cd8ff1a;p=oota-llvm.git diff --git a/include/llvm/MC/MCSymbol.h b/include/llvm/MC/MCSymbol.h index 7f74f378d46..b2910dfccd6 100644 --- a/include/llvm/MC/MCSymbol.h +++ b/include/llvm/MC/MCSymbol.h @@ -14,12 +14,14 @@ #ifndef LLVM_MC_MCSYMBOL_H #define LLVM_MC_MCSYMBOL_H +#include "llvm/ADT/PointerIntPair.h" +#include "llvm/ADT/PointerUnion.h" #include "llvm/ADT/StringMap.h" #include "llvm/MC/MCAssembler.h" -#include "llvm/MC/MCExpr.h" #include "llvm/Support/Compiler.h" namespace llvm { +class MCAsmInfo; class MCExpr; class MCSymbol; class MCFragment; @@ -35,32 +37,47 @@ class raw_ostream; /// 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, + }; + + /// 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, + }; + // Special sentinal value for the absolute pseudo section. // // FIXME: Use a PointerInt wrapper for this? static MCSection *AbsolutePseudoSection; - /// Name - The name of the symbol. The referred-to string data is actually - /// held by the StringMap that lives in MCContext. - const StringMapEntry *Name; - /// If a symbol has a Fragment, the section is implied, so we only need /// one pointer. /// FIXME: We might be able to simplify this by having the asm streamer create /// dummy fragments. - union { - /// The section the symbol is defined in. This is null for undefined - /// symbols, and the special AbsolutePseudoSection value for absolute - /// symbols. If this is a variable symbol, this caches the variable value's - /// section. - mutable MCSection *Section; - - /// The fragment this symbol's value is relative to, if any. - mutable MCFragment *Fragment; - }; - - /// Value - If non-null, the value for a variable symbol. - const MCExpr *Value; + /// If this is a section, then it gives the symbol is defined in. This is null + /// for undefined symbols, and the special AbsolutePseudoSection value for + /// absolute symbols. If this is a variable symbol, this caches the variable + /// value's section. + /// + /// 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, 1> + SectionOrFragmentAndHasName; /// IsTemporary - True if this is an assembler temporary label, which /// typically does not survive in the .o file's symbol table. Usually @@ -81,9 +98,29 @@ class MCSymbol { /// This symbol is private extern. mutable unsigned IsPrivateExtern : 1; - mutable unsigned HasFragment : 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 : 2; + + /// 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 : 2; + + /// 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; - unsigned IsELF : 1; + /// 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; @@ -94,47 +131,90 @@ class MCSymbol { /// The size of the symbol, if it is 'common'. uint64_t CommonSize; - }; - - /// The alignment of the symbol, if it is 'common', or -1. - // - // FIXME: Pack this in with other fields? - unsigned CommonAlign = -1U; - /// The Flags field is used by object file implementations to store - /// additional per symbol information which is not easily classified. - mutable uint32_t Flags = 0; + /// If non-null, the value for a variable symbol. + const MCExpr *Value; + }; protected: // MCContext creates and uniques these. friend class MCExpr; friend class MCContext; - MCSymbol(bool IsELF, const StringMapEntry *Name, bool isTemporary) - : Name(Name), Section(nullptr), Value(nullptr), IsTemporary(isTemporary), - IsRedefinable(false), IsUsed(false), IsRegistered(false), - IsExternal(false), IsPrivateExtern(false), HasFragment(false), - IsELF(IsELF) { + + /// \brief 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. + typedef union { + const StringMapEntry *NameEntry; + uint64_t AlignmentPadding; + } NameEntryStorageTy; + + 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; + SectionOrFragmentAndHasName.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 *); + /// \brief Placement delete - required by std, but never called. + void operator delete(void*, unsigned) { + llvm_unreachable("Constructor throws?"); + } + /// \brief Placement delete - required by std, but never called. + void operator delete(void*, unsigned, bool) { + llvm_unreachable("Constructor throws?"); + } + MCSymbol(const MCSymbol &) = delete; void operator=(const MCSymbol &) = delete; MCSection *getSectionPtr() const { if (MCFragment *F = getFragment()) return F->getParent(); - assert(!HasFragment); - if (Section || !Value) + const auto &SectionOrFragment = SectionOrFragmentAndHasName.getPointer(); + assert(!SectionOrFragment.is() && "Section or null expected"); + MCSection *Section = SectionOrFragment.dyn_cast(); + if (Section || !isVariable()) return Section; - return Section = Value->findAssociatedSection(); + return Section = getVariableValue()->findAssociatedSection(); + } + + /// \brief Get a reference to the name field. Requires that we have a name + const StringMapEntry *&getNameEntryPtr() { + assert(SectionOrFragmentAndHasName.getInt() && "Name is required"); + NameEntryStorageTy *Name = reinterpret_cast(this); + return (*(Name - 1)).NameEntry; + } + const StringMapEntry *&getNameEntryPtr() const { + return const_cast(this)->getNameEntryPtr(); } public: /// getName - Get the symbol name. - StringRef getName() const { return Name ? Name->first() : ""; } + StringRef getName() const { + if (!SectionOrFragmentAndHasName.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 /// @{ @@ -152,9 +232,11 @@ public: /// \brief Prepare this symbol to be redefined. void redefineIfPossible() { if (IsRedefinable) { - Value = nullptr; - Section = nullptr; - HasFragment = false; + if (SymbolContents == SymContentsVariable) { + Value = nullptr; + SymbolContents = SymContentsUnset; + } + setUndefined(); IsRedefinable = false; } } @@ -187,24 +269,31 @@ public: /// Mark the symbol as defined in the section \p S. void setSection(MCSection &S) { assert(!isVariable() && "Cannot set section of variable"); - assert(!HasFragment); - Section = &S; + assert(!SectionOrFragmentAndHasName.getPointer().is() && + "Section or null expected"); + SectionOrFragmentAndHasName.setPointer(&S); } /// Mark the symbol as undefined. void setUndefined() { - HasFragment = false; - Section = nullptr; + SectionOrFragmentAndHasName.setPointer( + PointerUnion()); } - bool isELF() const { return IsELF; } + bool isELF() const { return Kind == SymbolKindELF; } + + bool isCOFF() const { return Kind == SymbolKindCOFF; } + + bool isMachO() const { return Kind == SymbolKindMachO; } /// @} /// \name Variable Symbols /// @{ /// isVariable - Check if this is a variable symbol. - bool isVariable() const { return Value != nullptr; } + bool isVariable() const { + return SymbolContents == SymContentsVariable; + } /// getVariableValue() - Get the value for variable symbols. const MCExpr *getVariableValue() const { @@ -228,12 +317,17 @@ public: } uint64_t getOffset() const { - assert(!isCommon()); + assert((SymbolContents == SymContentsUnset || + SymbolContents == SymContentsOffset) && + "Cannot get offset for a common/variable symbol"); return Offset; } void setOffset(uint64_t Value) { - assert(!isCommon()); + assert((SymbolContents == SymContentsUnset || + SymbolContents == SymContentsOffset) && + "Cannot set offset for a common/variable symbol"); Offset = Value; + SymbolContents = SymContentsOffset; } /// Return the size of a 'common' symbol. @@ -249,13 +343,20 @@ public: void setCommon(uint64_t Size, unsigned Align) { assert(getOffset() == 0); CommonSize = Size; - CommonAlign = Align; + SymbolContents = 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 CommonAlign; + return CommonAlignLog2 ? (1U << (CommonAlignLog2 - 1)) : 0; } /// Declare this symbol as being 'common'. @@ -266,7 +367,7 @@ public: bool declareCommon(uint64_t Size, unsigned Align) { assert(isCommon() || getOffset() == 0); if(isCommon()) { - if(CommonSize != Size || CommonAlign != Align) + if(CommonSize != Size || getCommonAlignment() != Align) return true; } else setCommon(Size, Align); @@ -274,27 +375,15 @@ public: } /// Is this a 'common' symbol. - bool isCommon() const { return CommonAlign != -1U; } - - /// Get the (implementation defined) symbol flags. - uint32_t getFlags() const { return Flags; } - - /// Set the (implementation defined) symbol flags. - void setFlags(uint32_t Value) const { Flags = Value; } - - /// Modify the flags via a mask - void modifyFlags(uint32_t Value, uint32_t Mask) const { - Flags = (Flags & ~Mask) | Value; + bool isCommon() const { + return SymbolContents == SymContentsCommon; } MCFragment *getFragment() const { - if (!HasFragment) - return nullptr; - return Fragment; + return SectionOrFragmentAndHasName.getPointer().dyn_cast(); } void setFragment(MCFragment *Value) const { - HasFragment = true; - Fragment = Value; + SectionOrFragmentAndHasName.setPointer(Value); } bool isExternal() const { return IsExternal; } @@ -304,14 +393,30 @@ public: void setPrivateExtern(bool Value) { IsPrivateExtern = Value; } /// print - Print the value to the stream \p OS. - void print(raw_ostream &OS) const; + 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); + Sym.print(OS, nullptr); return OS; } } // end namespace llvm