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      1 //===-- llvm/MC/MCAsmInfo.h - Asm info --------------------------*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file contains a class to be used as the basis for target specific
     11 // asm writers.  This class primarily takes care of global printing constants,
     12 // which are used in very similar ways across all targets.
     13 //
     14 //===----------------------------------------------------------------------===//
     15 
     16 #ifndef LLVM_MC_MCASMINFO_H
     17 #define LLVM_MC_MCASMINFO_H
     18 
     19 #include "llvm/MC/MCDirectives.h"
     20 #include "llvm/MC/MCDwarf.h"
     21 #include "llvm/MC/MachineLocation.h"
     22 #include <cassert>
     23 #include <vector>
     24 
     25 namespace llvm {
     26 class MCExpr;
     27 class MCSection;
     28 class MCStreamer;
     29 class MCSymbol;
     30 class MCContext;
     31 
     32 namespace WinEH {
     33 enum class EncodingType {
     34   ET_Invalid, /// Invalid
     35   ET_Alpha,   /// Windows Alpha
     36   ET_Alpha64, /// Windows AXP64
     37   ET_ARM,     /// Windows NT (Windows on ARM)
     38   ET_CE,      /// Windows CE ARM, PowerPC, SH3, SH4
     39   ET_Itanium, /// Windows x64, Windows Itanium (IA-64)
     40   ET_MIPS = ET_Alpha,
     41 };
     42 }
     43 
     44 enum class ExceptionHandling {
     45   None,     /// No exception support
     46   DwarfCFI, /// DWARF-like instruction based exceptions
     47   SjLj,     /// setjmp/longjmp based exceptions
     48   ARM,      /// ARM EHABI
     49   WinEH,    /// Windows Exception Handling
     50 };
     51 
     52 namespace LCOMM {
     53 enum LCOMMType { NoAlignment, ByteAlignment, Log2Alignment };
     54 }
     55 
     56 /// This class is intended to be used as a base class for asm
     57 /// properties and features specific to the target.
     58 class MCAsmInfo {
     59 protected:
     60   //===------------------------------------------------------------------===//
     61   // Properties to be set by the target writer, used to configure asm printer.
     62   //
     63 
     64   /// Pointer size in bytes.  Default is 4.
     65   unsigned PointerSize;
     66 
     67   /// Size of the stack slot reserved for callee-saved registers, in bytes.
     68   /// Default is same as pointer size.
     69   unsigned CalleeSaveStackSlotSize;
     70 
     71   /// True if target is little endian.  Default is true.
     72   bool IsLittleEndian;
     73 
     74   /// True if target stack grow up.  Default is false.
     75   bool StackGrowsUp;
     76 
     77   /// True if this target has the MachO .subsections_via_symbols directive.
     78   /// Default is false.
     79   bool HasSubsectionsViaSymbols;
     80 
     81   /// True if this is a MachO target that supports the macho-specific .zerofill
     82   /// directive for emitting BSS Symbols.  Default is false.
     83   bool HasMachoZeroFillDirective;
     84 
     85   /// True if this is a MachO target that supports the macho-specific .tbss
     86   /// directive for emitting thread local BSS Symbols.  Default is false.
     87   bool HasMachoTBSSDirective;
     88 
     89   /// True if the compiler should emit a ".reference .constructors_used" or
     90   /// ".reference .destructors_used" directive after the a static ctor/dtor
     91   /// list.  This directive is only emitted in Static relocation model.  Default
     92   /// is false.
     93   bool HasStaticCtorDtorReferenceInStaticMode;
     94 
     95   /// True if the linker has a bug and requires that the debug_line section be
     96   /// of a minimum size. In practice such a linker requires a non-empty line
     97   /// sequence if a file is present.  Default to false.
     98   bool LinkerRequiresNonEmptyDwarfLines;
     99 
    100   /// This is the maximum possible length of an instruction, which is needed to
    101   /// compute the size of an inline asm.  Defaults to 4.
    102   unsigned MaxInstLength;
    103 
    104   /// Every possible instruction length is a multiple of this value.  Factored
    105   /// out in .debug_frame and .debug_line.  Defaults to 1.
    106   unsigned MinInstAlignment;
    107 
    108   /// The '$' token, when not referencing an identifier or constant, refers to
    109   /// the current PC.  Defaults to false.
    110   bool DollarIsPC;
    111 
    112   /// This string, if specified, is used to separate instructions from each
    113   /// other when on the same line.  Defaults to ';'
    114   const char *SeparatorString;
    115 
    116   /// This indicates the comment character used by the assembler.  Defaults to
    117   /// "#"
    118   const char *CommentString;
    119 
    120   /// This is appended to emitted labels.  Defaults to ":"
    121   const char *LabelSuffix;
    122 
    123   // Print the EH begin symbol with an assignment. Defaults to false.
    124   bool UseAssignmentForEHBegin;
    125 
    126   /// This prefix is used for globals like constant pool entries that are
    127   /// completely private to the .s file and should not have names in the .o
    128   /// file.  Defaults to "L"
    129   const char *PrivateGlobalPrefix;
    130 
    131   /// This prefix is used for symbols that should be passed through the
    132   /// assembler but be removed by the linker.  This is 'l' on Darwin, currently
    133   /// used for some ObjC metadata.  The default of "" meast that for this system
    134   /// a plain private symbol should be used.  Defaults to "".
    135   const char *LinkerPrivateGlobalPrefix;
    136 
    137   /// If these are nonempty, they contain a directive to emit before and after
    138   /// an inline assembly statement.  Defaults to "#APP\n", "#NO_APP\n"
    139   const char *InlineAsmStart;
    140   const char *InlineAsmEnd;
    141 
    142   /// These are assembly directives that tells the assembler to interpret the
    143   /// following instructions differently.  Defaults to ".code16", ".code32",
    144   /// ".code64".
    145   const char *Code16Directive;
    146   const char *Code32Directive;
    147   const char *Code64Directive;
    148 
    149   /// Which dialect of an assembler variant to use.  Defaults to 0
    150   unsigned AssemblerDialect;
    151 
    152   /// This is true if the assembler allows @ characters in symbol names.
    153   /// Defaults to false.
    154   bool AllowAtInName;
    155 
    156   /// This is true if data region markers should be printed as
    157   /// ".data_region/.end_data_region" directives. If false, use "$d/$a" labels
    158   /// instead.
    159   bool UseDataRegionDirectives;
    160 
    161   //===--- Data Emission Directives -------------------------------------===//
    162 
    163   /// This should be set to the directive used to get some number of zero bytes
    164   /// emitted to the current section.  Common cases are "\t.zero\t" and
    165   /// "\t.space\t".  If this is set to null, the Data*bitsDirective's will be
    166   /// used to emit zero bytes.  Defaults to "\t.zero\t"
    167   const char *ZeroDirective;
    168 
    169   /// This directive allows emission of an ascii string with the standard C
    170   /// escape characters embedded into it.  Defaults to "\t.ascii\t"
    171   const char *AsciiDirective;
    172 
    173   /// If not null, this allows for special handling of zero terminated strings
    174   /// on this target.  This is commonly supported as ".asciz".  If a target
    175   /// doesn't support this, it can be set to null.  Defaults to "\t.asciz\t"
    176   const char *AscizDirective;
    177 
    178   /// These directives are used to output some unit of integer data to the
    179   /// current section.  If a data directive is set to null, smaller data
    180   /// directives will be used to emit the large sizes.  Defaults to "\t.byte\t",
    181   /// "\t.short\t", "\t.long\t", "\t.quad\t"
    182   const char *Data8bitsDirective;
    183   const char *Data16bitsDirective;
    184   const char *Data32bitsDirective;
    185   const char *Data64bitsDirective;
    186 
    187   /// If non-null, a directive that is used to emit a word which should be
    188   /// relocated as a 64-bit GP-relative offset, e.g. .gpdword on Mips.  Defaults
    189   /// to NULL.
    190   const char *GPRel64Directive;
    191 
    192   /// If non-null, a directive that is used to emit a word which should be
    193   /// relocated as a 32-bit GP-relative offset, e.g. .gpword on Mips or .gprel32
    194   /// on Alpha.  Defaults to NULL.
    195   const char *GPRel32Directive;
    196 
    197   /// This is true if this target uses "Sun Style" syntax for section switching
    198   /// ("#alloc,#write" etc) instead of the normal ELF syntax (,"a,w") in
    199   /// .section directives.  Defaults to false.
    200   bool SunStyleELFSectionSwitchSyntax;
    201 
    202   /// This is true if this target uses ELF '.section' directive before the
    203   /// '.bss' one. It's used for PPC/Linux which doesn't support the '.bss'
    204   /// directive only.  Defaults to false.
    205   bool UsesELFSectionDirectiveForBSS;
    206 
    207   bool NeedsDwarfSectionOffsetDirective;
    208 
    209   //===--- Alignment Information ----------------------------------------===//
    210 
    211   /// If this is true (the default) then the asmprinter emits ".align N"
    212   /// directives, where N is the number of bytes to align to.  Otherwise, it
    213   /// emits ".align log2(N)", e.g. 3 to align to an 8 byte boundary.  Defaults
    214   /// to true.
    215   bool AlignmentIsInBytes;
    216 
    217   /// If non-zero, this is used to fill the executable space created as the
    218   /// result of a alignment directive.  Defaults to 0
    219   unsigned TextAlignFillValue;
    220 
    221   //===--- Global Variable Emission Directives --------------------------===//
    222 
    223   /// This is the directive used to declare a global entity.  Defaults to NULL.
    224   const char *GlobalDirective;
    225 
    226   /// True if the assembler supports the .set directive.  Defaults to true.
    227   bool HasSetDirective;
    228 
    229   /// False if the assembler requires that we use
    230   /// \code
    231   ///   Lc = a - b
    232   ///   .long Lc
    233   /// \endcode
    234   //
    235   /// instead of
    236   //
    237   /// \code
    238   ///   .long a - b
    239   /// \endcode
    240   ///
    241   ///  Defaults to true.
    242   bool HasAggressiveSymbolFolding;
    243 
    244   /// True is .comm's and .lcomms optional alignment is to be specified in bytes
    245   /// instead of log2(n).  Defaults to true.
    246   bool COMMDirectiveAlignmentIsInBytes;
    247 
    248   /// Describes if the .lcomm directive for the target supports an alignment
    249   /// argument and how it is interpreted.  Defaults to NoAlignment.
    250   LCOMM::LCOMMType LCOMMDirectiveAlignmentType;
    251 
    252   /// True if the target has .type and .size directives, this is true for most
    253   /// ELF targets.  Defaults to true.
    254   bool HasDotTypeDotSizeDirective;
    255 
    256   /// True if the target has a single parameter .file directive, this is true
    257   /// for ELF targets.  Defaults to true.
    258   bool HasSingleParameterDotFile;
    259 
    260   /// True if the target has a .ident directive, this is true for ELF targets.
    261   /// Defaults to false.
    262   bool HasIdentDirective;
    263 
    264   /// True if this target supports the MachO .no_dead_strip directive.  Defaults
    265   /// to false.
    266   bool HasNoDeadStrip;
    267 
    268   /// This directive, if non-null, is used to declare a global as being a weak
    269   /// undefined symbol.  Defaults to NULL.
    270   const char *WeakRefDirective;
    271 
    272   /// True if we have a directive to declare a global as being a weak defined
    273   /// symbol.  Defaults to false.
    274   bool HasWeakDefDirective;
    275 
    276   /// True if we have a directive to declare a global as being a weak defined
    277   /// symbol that can be hidden (unexported).  Defaults to false.
    278   bool HasWeakDefCanBeHiddenDirective;
    279 
    280   /// True if we have a .linkonce directive.  This is used on cygwin/mingw.
    281   /// Defaults to false.
    282   bool HasLinkOnceDirective;
    283 
    284   /// This attribute, if not MCSA_Invalid, is used to declare a symbol as having
    285   /// hidden visibility.  Defaults to MCSA_Hidden.
    286   MCSymbolAttr HiddenVisibilityAttr;
    287 
    288   /// This attribute, if not MCSA_Invalid, is used to declare an undefined
    289   /// symbol as having hidden visibility. Defaults to MCSA_Hidden.
    290   MCSymbolAttr HiddenDeclarationVisibilityAttr;
    291 
    292   /// This attribute, if not MCSA_Invalid, is used to declare a symbol as having
    293   /// protected visibility.  Defaults to MCSA_Protected
    294   MCSymbolAttr ProtectedVisibilityAttr;
    295 
    296   //===--- Dwarf Emission Directives -----------------------------------===//
    297 
    298   /// True if target asm supports leb128 directives.  Defaults to false.
    299   bool HasLEB128;
    300 
    301   /// True if target supports emission of debugging information.  Defaults to
    302   /// false.
    303   bool SupportsDebugInformation;
    304 
    305   /// Exception handling format for the target.  Defaults to None.
    306   ExceptionHandling ExceptionsType;
    307 
    308   /// Windows exception handling data (.pdata) encoding.  Defaults to Invalid.
    309   WinEH::EncodingType WinEHEncodingType;
    310 
    311   /// True if Dwarf2 output generally uses relocations for references to other
    312   /// .debug_* sections.
    313   bool DwarfUsesRelocationsAcrossSections;
    314 
    315   /// True if DWARF FDE symbol reference relocations should be replaced by an
    316   /// absolute difference.
    317   bool DwarfFDESymbolsUseAbsDiff;
    318 
    319   /// True if dwarf register numbers are printed instead of symbolic register
    320   /// names in .cfi_* directives.  Defaults to false.
    321   bool DwarfRegNumForCFI;
    322 
    323   /// True if target uses parens to indicate the symbol variant instead of @.
    324   /// For example, foo(plt) instead of foo@plt.  Defaults to false.
    325   bool UseParensForSymbolVariant;
    326 
    327   //===--- Prologue State ----------------------------------------------===//
    328 
    329   std::vector<MCCFIInstruction> InitialFrameState;
    330 
    331   //===--- Integrated Assembler State ----------------------------------===//
    332 
    333   /// Should we use the integrated assembler?
    334   /// The integrated assembler should be enabled by default (by the
    335   /// constructors) when failing to parse a valid piece of assembly (inline
    336   /// or otherwise) is considered a bug. It may then be overridden after
    337   /// construction (see LLVMTargetMachine::initAsmInfo()).
    338   bool UseIntegratedAssembler;
    339 
    340   /// Compress DWARF debug sections. Defaults to false.
    341   bool CompressDebugSections;
    342 
    343 public:
    344   explicit MCAsmInfo();
    345   virtual ~MCAsmInfo();
    346 
    347   /// Get the pointer size in bytes.
    348   unsigned getPointerSize() const { return PointerSize; }
    349 
    350   /// Get the callee-saved register stack slot
    351   /// size in bytes.
    352   unsigned getCalleeSaveStackSlotSize() const {
    353     return CalleeSaveStackSlotSize;
    354   }
    355 
    356   /// True if the target is little endian.
    357   bool isLittleEndian() const { return IsLittleEndian; }
    358 
    359   /// True if target stack grow up.
    360   bool isStackGrowthDirectionUp() const { return StackGrowsUp; }
    361 
    362   bool hasSubsectionsViaSymbols() const { return HasSubsectionsViaSymbols; }
    363 
    364   // Data directive accessors.
    365 
    366   const char *getData8bitsDirective() const { return Data8bitsDirective; }
    367   const char *getData16bitsDirective() const { return Data16bitsDirective; }
    368   const char *getData32bitsDirective() const { return Data32bitsDirective; }
    369   const char *getData64bitsDirective() const { return Data64bitsDirective; }
    370   const char *getGPRel64Directive() const { return GPRel64Directive; }
    371   const char *getGPRel32Directive() const { return GPRel32Directive; }
    372 
    373   /// Targets can implement this method to specify a section to switch to if the
    374   /// translation unit doesn't have any trampolines that require an executable
    375   /// stack.
    376   virtual const MCSection *getNonexecutableStackSection(MCContext &Ctx) const {
    377     return nullptr;
    378   }
    379 
    380   virtual const MCExpr *getExprForPersonalitySymbol(const MCSymbol *Sym,
    381                                                     unsigned Encoding,
    382                                                     MCStreamer &Streamer) const;
    383 
    384   virtual const MCExpr *getExprForFDESymbol(const MCSymbol *Sym,
    385                                             unsigned Encoding,
    386                                             MCStreamer &Streamer) const;
    387 
    388   bool usesSunStyleELFSectionSwitchSyntax() const {
    389     return SunStyleELFSectionSwitchSyntax;
    390   }
    391 
    392   bool usesELFSectionDirectiveForBSS() const {
    393     return UsesELFSectionDirectiveForBSS;
    394   }
    395 
    396   bool needsDwarfSectionOffsetDirective() const {
    397     return NeedsDwarfSectionOffsetDirective;
    398   }
    399 
    400   // Accessors.
    401 
    402   bool hasMachoZeroFillDirective() const { return HasMachoZeroFillDirective; }
    403   bool hasMachoTBSSDirective() const { return HasMachoTBSSDirective; }
    404   bool hasStaticCtorDtorReferenceInStaticMode() const {
    405     return HasStaticCtorDtorReferenceInStaticMode;
    406   }
    407   bool getLinkerRequiresNonEmptyDwarfLines() const {
    408     return LinkerRequiresNonEmptyDwarfLines;
    409   }
    410   unsigned getMaxInstLength() const { return MaxInstLength; }
    411   unsigned getMinInstAlignment() const { return MinInstAlignment; }
    412   bool getDollarIsPC() const { return DollarIsPC; }
    413   const char *getSeparatorString() const { return SeparatorString; }
    414 
    415   /// This indicates the column (zero-based) at which asm comments should be
    416   /// printed.
    417   unsigned getCommentColumn() const { return 40; }
    418 
    419   const char *getCommentString() const { return CommentString; }
    420   const char *getLabelSuffix() const { return LabelSuffix; }
    421 
    422   bool useAssignmentForEHBegin() const { return UseAssignmentForEHBegin; }
    423   const char *getPrivateGlobalPrefix() const { return PrivateGlobalPrefix; }
    424   bool hasLinkerPrivateGlobalPrefix() const {
    425     return LinkerPrivateGlobalPrefix[0] != '\0';
    426   }
    427   const char *getLinkerPrivateGlobalPrefix() const {
    428     if (hasLinkerPrivateGlobalPrefix())
    429       return LinkerPrivateGlobalPrefix;
    430     return getPrivateGlobalPrefix();
    431   }
    432   const char *getInlineAsmStart() const { return InlineAsmStart; }
    433   const char *getInlineAsmEnd() const { return InlineAsmEnd; }
    434   const char *getCode16Directive() const { return Code16Directive; }
    435   const char *getCode32Directive() const { return Code32Directive; }
    436   const char *getCode64Directive() const { return Code64Directive; }
    437   unsigned getAssemblerDialect() const { return AssemblerDialect; }
    438   bool doesAllowAtInName() const { return AllowAtInName; }
    439   bool doesSupportDataRegionDirectives() const {
    440     return UseDataRegionDirectives;
    441   }
    442   const char *getZeroDirective() const { return ZeroDirective; }
    443   const char *getAsciiDirective() const { return AsciiDirective; }
    444   const char *getAscizDirective() const { return AscizDirective; }
    445   bool getAlignmentIsInBytes() const { return AlignmentIsInBytes; }
    446   unsigned getTextAlignFillValue() const { return TextAlignFillValue; }
    447   const char *getGlobalDirective() const { return GlobalDirective; }
    448   bool hasSetDirective() const { return HasSetDirective; }
    449   bool hasAggressiveSymbolFolding() const { return HasAggressiveSymbolFolding; }
    450   bool getCOMMDirectiveAlignmentIsInBytes() const {
    451     return COMMDirectiveAlignmentIsInBytes;
    452   }
    453   LCOMM::LCOMMType getLCOMMDirectiveAlignmentType() const {
    454     return LCOMMDirectiveAlignmentType;
    455   }
    456   bool hasDotTypeDotSizeDirective() const { return HasDotTypeDotSizeDirective; }
    457   bool hasSingleParameterDotFile() const { return HasSingleParameterDotFile; }
    458   bool hasIdentDirective() const { return HasIdentDirective; }
    459   bool hasNoDeadStrip() const { return HasNoDeadStrip; }
    460   const char *getWeakRefDirective() const { return WeakRefDirective; }
    461   bool hasWeakDefDirective() const { return HasWeakDefDirective; }
    462   bool hasWeakDefCanBeHiddenDirective() const {
    463     return HasWeakDefCanBeHiddenDirective;
    464   }
    465   bool hasLinkOnceDirective() const { return HasLinkOnceDirective; }
    466 
    467   MCSymbolAttr getHiddenVisibilityAttr() const { return HiddenVisibilityAttr; }
    468   MCSymbolAttr getHiddenDeclarationVisibilityAttr() const {
    469     return HiddenDeclarationVisibilityAttr;
    470   }
    471   MCSymbolAttr getProtectedVisibilityAttr() const {
    472     return ProtectedVisibilityAttr;
    473   }
    474   bool hasLEB128() const { return HasLEB128; }
    475   bool doesSupportDebugInformation() const { return SupportsDebugInformation; }
    476   bool doesSupportExceptionHandling() const {
    477     return ExceptionsType != ExceptionHandling::None;
    478   }
    479   ExceptionHandling getExceptionHandlingType() const { return ExceptionsType; }
    480   WinEH::EncodingType getWinEHEncodingType() const { return WinEHEncodingType; }
    481   bool isExceptionHandlingDwarf() const {
    482     return (ExceptionsType == ExceptionHandling::DwarfCFI ||
    483             ExceptionsType == ExceptionHandling::ARM ||
    484             // Windows handler data still uses DWARF LSDA encoding.
    485             ExceptionsType == ExceptionHandling::WinEH);
    486   }
    487   bool doesDwarfUseRelocationsAcrossSections() const {
    488     return DwarfUsesRelocationsAcrossSections;
    489   }
    490   bool doDwarfFDESymbolsUseAbsDiff() const { return DwarfFDESymbolsUseAbsDiff; }
    491   bool useDwarfRegNumForCFI() const { return DwarfRegNumForCFI; }
    492   bool useParensForSymbolVariant() const { return UseParensForSymbolVariant; }
    493 
    494   void addInitialFrameState(const MCCFIInstruction &Inst) {
    495     InitialFrameState.push_back(Inst);
    496   }
    497 
    498   const std::vector<MCCFIInstruction> &getInitialFrameState() const {
    499     return InitialFrameState;
    500   }
    501 
    502   /// Return true if assembly (inline or otherwise) should be parsed.
    503   bool useIntegratedAssembler() const { return UseIntegratedAssembler; }
    504 
    505   /// Set whether assembly (inline or otherwise) should be parsed.
    506   virtual void setUseIntegratedAssembler(bool Value) {
    507     UseIntegratedAssembler = Value;
    508   }
    509 
    510   bool compressDebugSections() const { return CompressDebugSections; }
    511 
    512   void setCompressDebugSections(bool CompressDebugSections) {
    513     this->CompressDebugSections = CompressDebugSections;
    514   }
    515 };
    516 }
    517 
    518 #endif
    519