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//===-- llvm/MC/MCAsmInfo.h - Asm info --------------------------*- 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
// This file contains a class to be used as the basis for target specific
// asm writers. This class primarily takes care of global printing constants,
// which are used in very similar ways across all targets.
#include "llvm/ADT/StringRef.h"
#include "llvm/MC/MCDirectives.h"
#include "llvm/MC/MCTargetOptions.h"
#include <vector>
namespace llvm {
class MCContext;
class MCCFIInstruction;
class MCExpr;
class MCSection;
class MCStreamer;
class MCSubtargetInfo;
class MCSymbol;
namespace WinEH {
enum class EncodingType {
Invalid, /// Invalid
Alpha, /// Windows Alpha
Alpha64, /// Windows AXP64
ARM, /// Windows NT (Windows on ARM)
CE, /// Windows CE ARM, PowerPC, SH3, SH4
Itanium, /// Windows x64, Windows Itanium (IA-64)
X86, /// Windows x86, uses no CFI, just EH tables
MIPS = Alpha,
} // end namespace WinEH
namespace LCOMM {
enum LCOMMType { NoAlignment, ByteAlignment, Log2Alignment };
} // end namespace LCOMM
/// This class is intended to be used as a base class for asm
/// properties and features specific to the target.
class MCAsmInfo {
// Properties to be set by the target writer, used to configure asm printer.
/// Code pointer size in bytes. Default is 4.
unsigned CodePointerSize = 4;
/// Size of the stack slot reserved for callee-saved registers, in bytes.
/// Default is same as pointer size.
unsigned CalleeSaveStackSlotSize = 4;
/// True if target is little endian. Default is true.
bool IsLittleEndian = true;
/// True if target stack grow up. Default is false.
bool StackGrowsUp = false;
/// True if this target has the MachO .subsections_via_symbols directive.
/// Default is false.
bool HasSubsectionsViaSymbols = false;
/// True if this is a MachO target that supports the macho-specific .zerofill
/// directive for emitting BSS Symbols. Default is false.
bool HasMachoZeroFillDirective = false;
/// True if this is a MachO target that supports the macho-specific .tbss
/// directive for emitting thread local BSS Symbols. Default is false.
bool HasMachoTBSSDirective = false;
/// True if this is a non-GNU COFF target. The COFF port of the GNU linker
/// doesn't handle associative comdats in the way that we would like to use
/// them.
bool HasCOFFAssociativeComdats = false;
/// True if this is a non-GNU COFF target. For GNU targets, we don't generate
/// constants into comdat sections.
bool HasCOFFComdatConstants = false;
/// This is the maximum possible length of an instruction, which is needed to
/// compute the size of an inline asm. Defaults to 4.
unsigned MaxInstLength = 4;
/// Every possible instruction length is a multiple of this value. Factored
/// out in .debug_frame and .debug_line. Defaults to 1.
unsigned MinInstAlignment = 1;
/// The '$' token, when not referencing an identifier or constant, refers to
/// the current PC. Defaults to false.
bool DollarIsPC = false;
/// This string, if specified, is used to separate instructions from each
/// other when on the same line. Defaults to ';'
const char *SeparatorString;
/// This indicates the comment character used by the assembler. Defaults to
/// "#"
StringRef CommentString;
/// This is appended to emitted labels. Defaults to ":"
const char *LabelSuffix;
// Print the EH begin symbol with an assignment. Defaults to false.
bool UseAssignmentForEHBegin = false;
// Do we need to create a local symbol for .size?
bool NeedsLocalForSize = false;
/// This prefix is used for globals like constant pool entries that are
/// completely private to the .s file and should not have names in the .o
/// file. Defaults to "L"
StringRef PrivateGlobalPrefix;
/// This prefix is used for labels for basic blocks. Defaults to the same as
/// PrivateGlobalPrefix.
StringRef PrivateLabelPrefix;
/// This prefix is used for symbols that should be passed through the
/// assembler but be removed by the linker. This is 'l' on Darwin, currently
/// used for some ObjC metadata. The default of "" meast that for this system
/// a plain private symbol should be used. Defaults to "".
StringRef LinkerPrivateGlobalPrefix;
/// If these are nonempty, they contain a directive to emit before and after
/// an inline assembly statement. Defaults to "#APP\n", "#NO_APP\n"
const char *InlineAsmStart;
const char *InlineAsmEnd;
/// These are assembly directives that tells the assembler to interpret the
/// following instructions differently. Defaults to ".code16", ".code32",
/// ".code64".
const char *Code16Directive;
const char *Code32Directive;
const char *Code64Directive;
/// Which dialect of an assembler variant to use. Defaults to 0
unsigned AssemblerDialect = 0;
/// This is true if the assembler allows @ characters in symbol names.
/// Defaults to false.
bool AllowAtInName = false;
/// If this is true, symbol names with invalid characters will be printed in
/// quotes.
bool SupportsQuotedNames = true;
/// This is true if data region markers should be printed as
/// ".data_region/.end_data_region" directives. If false, use "$d/$a" labels
/// instead.
bool UseDataRegionDirectives = false;
/// True if .align is to be used for alignment. Only power-of-two
/// alignment is supported.
bool UseDotAlignForAlignment = false;
//===--- Data Emission Directives -------------------------------------===//
/// This should be set to the directive used to get some number of zero bytes
/// emitted to the current section. Common cases are "\\t" and
/// "\\t". If this is set to null, the Data*bitsDirective's will be
/// used to emit zero bytes. Defaults to "\\t"
const char *ZeroDirective;
/// This directive allows emission of an ascii string with the standard C
/// escape characters embedded into it. If a target doesn't support this, it
/// can be set to null. Defaults to "\t.ascii\t"
const char *AsciiDirective;
/// If not null, this allows for special handling of zero terminated strings
/// on this target. This is commonly supported as ".asciz". If a target
/// doesn't support this, it can be set to null. Defaults to "\t.asciz\t"
const char *AscizDirective;
/// These directives are used to output some unit of integer data to the
/// current section. If a data directive is set to null, smaller data
/// directives will be used to emit the large sizes. Defaults to "\t.byte\t",
/// "\t.short\t", "\t.long\t", "\t.quad\t"
const char *Data8bitsDirective;
const char *Data16bitsDirective;
const char *Data32bitsDirective;
const char *Data64bitsDirective;
/// If non-null, a directive that is used to emit a word which should be
/// relocated as a 64-bit GP-relative offset, e.g. .gpdword on Mips. Defaults
/// to nullptr.
const char *GPRel64Directive = nullptr;
/// If non-null, a directive that is used to emit a word which should be
/// relocated as a 32-bit GP-relative offset, e.g. .gpword on Mips or .gprel32
/// on Alpha. Defaults to nullptr.
const char *GPRel32Directive = nullptr;
/// If non-null, directives that are used to emit a word/dword which should
/// be relocated as a 32/64-bit DTP/TP-relative offset, e.g. .dtprelword/
/// .dtpreldword/.tprelword/.tpreldword on Mips.
const char *DTPRel32Directive = nullptr;
const char *DTPRel64Directive = nullptr;
const char *TPRel32Directive = nullptr;
const char *TPRel64Directive = nullptr;
/// This is true if this target uses "Sun Style" syntax for section switching
/// ("#alloc,#write" etc) instead of the normal ELF syntax (,"a,w") in
/// .section directives. Defaults to false.
bool SunStyleELFSectionSwitchSyntax = false;
/// This is true if this target uses ELF '.section' directive before the
/// '.bss' one. It's used for PPC/Linux which doesn't support the '.bss'
/// directive only. Defaults to false.
bool UsesELFSectionDirectiveForBSS = false;
bool NeedsDwarfSectionOffsetDirective = false;
//===--- Alignment Information ----------------------------------------===//
/// If this is true (the default) then the asmprinter emits ".align N"
/// directives, where N is the number of bytes to align to. Otherwise, it
/// emits ".align log2(N)", e.g. 3 to align to an 8 byte boundary. Defaults
/// to true.
bool AlignmentIsInBytes = true;
/// If non-zero, this is used to fill the executable space created as the
/// result of a alignment directive. Defaults to 0
unsigned TextAlignFillValue = 0;
//===--- Global Variable Emission Directives --------------------------===//
/// This is the directive used to declare a global entity. Defaults to
/// ".globl".
const char *GlobalDirective;
/// True if the expression
/// .long f - g
/// uses a relocation but it can be suppressed by writing
/// a = f - g
/// .long a
bool SetDirectiveSuppressesReloc = false;
/// False if the assembler requires that we use
/// \code
/// Lc = a - b
/// .long Lc
/// \endcode
/// instead of
/// \code
/// .long a - b
/// \endcode
/// Defaults to true.
bool HasAggressiveSymbolFolding = true;
/// True is .comm's and .lcomms optional alignment is to be specified in bytes
/// instead of log2(n). Defaults to true.
bool COMMDirectiveAlignmentIsInBytes = true;
/// Describes if the .lcomm directive for the target supports an alignment
/// argument and how it is interpreted. Defaults to NoAlignment.
LCOMM::LCOMMType LCOMMDirectiveAlignmentType = LCOMM::NoAlignment;
// True if the target allows .align directives on functions. This is true for
// most targets, so defaults to true.
bool HasFunctionAlignment = true;
/// True if the target has .type and .size directives, this is true for most
/// ELF targets. Defaults to true.
bool HasDotTypeDotSizeDirective = true;
/// True if the target has a single parameter .file directive, this is true
/// for ELF targets. Defaults to true.
bool HasSingleParameterDotFile = true;
/// True if the target has a .ident directive, this is true for ELF targets.
/// Defaults to false.
bool HasIdentDirective = false;
/// True if this target supports the MachO .no_dead_strip directive. Defaults
/// to false.
bool HasNoDeadStrip = false;
/// True if this target supports the MachO .alt_entry directive. Defaults to
/// false.
bool HasAltEntry = false;
/// Used to declare a global as being a weak symbol. Defaults to ".weak".
const char *WeakDirective;
/// This directive, if non-null, is used to declare a global as being a weak
/// undefined symbol. Defaults to nullptr.
const char *WeakRefDirective = nullptr;
/// True if we have a directive to declare a global as being a weak defined
/// symbol. Defaults to false.
bool HasWeakDefDirective = false;
/// True if we have a directive to declare a global as being a weak defined
/// symbol that can be hidden (unexported). Defaults to false.
bool HasWeakDefCanBeHiddenDirective = false;
/// True if we have a .linkonce directive. This is used on cygwin/mingw.
/// Defaults to false.
bool HasLinkOnceDirective = false;
/// True if we have a .lglobl directive, which is used to emit the information
/// of a static symbol into the symbol table. Defaults to false.
bool HasDotLGloblDirective = false;
/// This attribute, if not MCSA_Invalid, is used to declare a symbol as having
/// hidden visibility. Defaults to MCSA_Hidden.
MCSymbolAttr HiddenVisibilityAttr = MCSA_Hidden;
/// This attribute, if not MCSA_Invalid, is used to declare an undefined
/// symbol as having hidden visibility. Defaults to MCSA_Hidden.
MCSymbolAttr HiddenDeclarationVisibilityAttr = MCSA_Hidden;
/// This attribute, if not MCSA_Invalid, is used to declare a symbol as having
/// protected visibility. Defaults to MCSA_Protected
MCSymbolAttr ProtectedVisibilityAttr = MCSA_Protected;
//===--- Dwarf Emission Directives -----------------------------------===//
/// True if target supports emission of debugging information. Defaults to
/// false.
bool SupportsDebugInformation = false;
/// Exception handling format for the target. Defaults to None.
ExceptionHandling ExceptionsType = ExceptionHandling::None;
/// Windows exception handling data (.pdata) encoding. Defaults to Invalid.
WinEH::EncodingType WinEHEncodingType = WinEH::EncodingType::Invalid;
/// True if Dwarf2 output generally uses relocations for references to other
/// .debug_* sections.
bool DwarfUsesRelocationsAcrossSections = true;
/// True if DWARF FDE symbol reference relocations should be replaced by an
/// absolute difference.
bool DwarfFDESymbolsUseAbsDiff = false;
/// True if dwarf register numbers are printed instead of symbolic register
/// names in .cfi_* directives. Defaults to false.
bool DwarfRegNumForCFI = false;
/// True if target uses parens to indicate the symbol variant instead of @.
/// For example, foo(plt) instead of foo@plt. Defaults to false.
bool UseParensForSymbolVariant = false;
/// True if the target supports flags in ".loc" directive, false if only
/// location is allowed.
bool SupportsExtendedDwarfLocDirective = true;
//===--- Prologue State ----------------------------------------------===//
std::vector<MCCFIInstruction> InitialFrameState;
//===--- Integrated Assembler Information ----------------------------===//
/// Should we use the integrated assembler?
/// The integrated assembler should be enabled by default (by the
/// constructors) when failing to parse a valid piece of assembly (inline
/// or otherwise) is considered a bug. It may then be overridden after
/// construction (see LLVMTargetMachine::initAsmInfo()).
bool UseIntegratedAssembler;
/// Preserve Comments in assembly
bool PreserveAsmComments;
/// Compress DWARF debug sections. Defaults to no compression.
DebugCompressionType CompressDebugSections = DebugCompressionType::None;
/// True if the integrated assembler should interpret 'a >> b' constant
/// expressions as logical rather than arithmetic.
bool UseLogicalShr = true;
// If true, emit GOTPCRELX/REX_GOTPCRELX instead of GOTPCREL, on
// X86_64 ELF.
bool RelaxELFRelocations = true;
// If true, then the lexer and expression parser will support %neg(),
// %hi(), and similar unary operators.
bool HasMipsExpressions = false;
// If true, emit function descriptor symbol on AIX.
bool NeedsFunctionDescriptors = false;
explicit MCAsmInfo();
virtual ~MCAsmInfo();
/// Get the code pointer size in bytes.
unsigned getCodePointerSize() const { return CodePointerSize; }
/// Get the callee-saved register stack slot
/// size in bytes.
unsigned getCalleeSaveStackSlotSize() const {
return CalleeSaveStackSlotSize;
/// True if the target is little endian.
bool isLittleEndian() const { return IsLittleEndian; }
/// True if target stack grow up.
bool isStackGrowthDirectionUp() const { return StackGrowsUp; }
bool hasSubsectionsViaSymbols() const { return HasSubsectionsViaSymbols; }
// Data directive accessors.
const char *getData8bitsDirective() const { return Data8bitsDirective; }
const char *getData16bitsDirective() const { return Data16bitsDirective; }
const char *getData32bitsDirective() const { return Data32bitsDirective; }
const char *getData64bitsDirective() const { return Data64bitsDirective; }
const char *getGPRel64Directive() const { return GPRel64Directive; }
const char *getGPRel32Directive() const { return GPRel32Directive; }
const char *getDTPRel64Directive() const { return DTPRel64Directive; }
const char *getDTPRel32Directive() const { return DTPRel32Directive; }
const char *getTPRel64Directive() const { return TPRel64Directive; }
const char *getTPRel32Directive() const { return TPRel32Directive; }
/// Targets can implement this method to specify a section to switch to if the
/// translation unit doesn't have any trampolines that require an executable
/// stack.
virtual MCSection *getNonexecutableStackSection(MCContext &Ctx) const {
return nullptr;
/// True if the section is atomized using the symbols in it.
/// This is false if the section is not atomized at all (most ELF sections) or
/// if it is atomized based on its contents (MachO' __TEXT,__cstring for
/// example).
virtual bool isSectionAtomizableBySymbols(const MCSection &Section) const;
virtual const MCExpr *getExprForPersonalitySymbol(const MCSymbol *Sym,
unsigned Encoding,
MCStreamer &Streamer) const;
virtual const MCExpr *getExprForFDESymbol(const MCSymbol *Sym,
unsigned Encoding,
MCStreamer &Streamer) const;
/// Return true if the identifier \p Name does not need quotes to be
/// syntactically correct.
virtual bool isValidUnquotedName(StringRef Name) const;
/// Return true if the .section directive should be omitted when
/// emitting \p SectionName. For example:
/// shouldOmitSectionDirective(".text")
/// returns false => .section .text,#alloc,#execinstr
/// returns true => .text
virtual bool shouldOmitSectionDirective(StringRef SectionName) const;
bool usesSunStyleELFSectionSwitchSyntax() const {
return SunStyleELFSectionSwitchSyntax;
bool usesELFSectionDirectiveForBSS() const {
return UsesELFSectionDirectiveForBSS;
bool needsDwarfSectionOffsetDirective() const {
return NeedsDwarfSectionOffsetDirective;
// Accessors.
bool hasMachoZeroFillDirective() const { return HasMachoZeroFillDirective; }
bool hasMachoTBSSDirective() const { return HasMachoTBSSDirective; }
bool hasCOFFAssociativeComdats() const { return HasCOFFAssociativeComdats; }
bool hasCOFFComdatConstants() const { return HasCOFFComdatConstants; }
/// Returns the maximum possible encoded instruction size in bytes. If \p STI
/// is null, this should be the maximum size for any subtarget.
virtual unsigned getMaxInstLength(const MCSubtargetInfo *STI = nullptr) const {
return MaxInstLength;
unsigned getMinInstAlignment() const { return MinInstAlignment; }
bool getDollarIsPC() const { return DollarIsPC; }
const char *getSeparatorString() const { return SeparatorString; }
/// This indicates the column (zero-based) at which asm comments should be
/// printed.
unsigned getCommentColumn() const { return 40; }
StringRef getCommentString() const { return CommentString; }
const char *getLabelSuffix() const { return LabelSuffix; }
bool useAssignmentForEHBegin() const { return UseAssignmentForEHBegin; }
bool needsLocalForSize() const { return NeedsLocalForSize; }
StringRef getPrivateGlobalPrefix() const { return PrivateGlobalPrefix; }
StringRef getPrivateLabelPrefix() const { return PrivateLabelPrefix; }
bool hasLinkerPrivateGlobalPrefix() const {
return !LinkerPrivateGlobalPrefix.empty();
StringRef getLinkerPrivateGlobalPrefix() const {
if (hasLinkerPrivateGlobalPrefix())
return LinkerPrivateGlobalPrefix;
return getPrivateGlobalPrefix();
const char *getInlineAsmStart() const { return InlineAsmStart; }
const char *getInlineAsmEnd() const { return InlineAsmEnd; }
const char *getCode16Directive() const { return Code16Directive; }
const char *getCode32Directive() const { return Code32Directive; }
const char *getCode64Directive() const { return Code64Directive; }
unsigned getAssemblerDialect() const { return AssemblerDialect; }
bool doesAllowAtInName() const { return AllowAtInName; }
bool supportsNameQuoting() const { return SupportsQuotedNames; }
bool doesSupportDataRegionDirectives() const {
return UseDataRegionDirectives;
bool useDotAlignForAlignment() const {
return UseDotAlignForAlignment;
const char *getZeroDirective() const { return ZeroDirective; }
const char *getAsciiDirective() const { return AsciiDirective; }
const char *getAscizDirective() const { return AscizDirective; }
bool getAlignmentIsInBytes() const { return AlignmentIsInBytes; }
unsigned getTextAlignFillValue() const { return TextAlignFillValue; }
const char *getGlobalDirective() const { return GlobalDirective; }
bool doesSetDirectiveSuppressReloc() const {
return SetDirectiveSuppressesReloc;
bool hasAggressiveSymbolFolding() const { return HasAggressiveSymbolFolding; }
bool getCOMMDirectiveAlignmentIsInBytes() const {
return COMMDirectiveAlignmentIsInBytes;
LCOMM::LCOMMType getLCOMMDirectiveAlignmentType() const {
return LCOMMDirectiveAlignmentType;
bool hasFunctionAlignment() const { return HasFunctionAlignment; }
bool hasDotTypeDotSizeDirective() const { return HasDotTypeDotSizeDirective; }
bool hasSingleParameterDotFile() const { return HasSingleParameterDotFile; }
bool hasIdentDirective() const { return HasIdentDirective; }
bool hasNoDeadStrip() const { return HasNoDeadStrip; }
bool hasAltEntry() const { return HasAltEntry; }
const char *getWeakDirective() const { return WeakDirective; }
const char *getWeakRefDirective() const { return WeakRefDirective; }
bool hasWeakDefDirective() const { return HasWeakDefDirective; }
bool hasWeakDefCanBeHiddenDirective() const {
return HasWeakDefCanBeHiddenDirective;
bool hasLinkOnceDirective() const { return HasLinkOnceDirective; }
bool hasDotLGloblDirective() const { return HasDotLGloblDirective; }
MCSymbolAttr getHiddenVisibilityAttr() const { return HiddenVisibilityAttr; }
MCSymbolAttr getHiddenDeclarationVisibilityAttr() const {
return HiddenDeclarationVisibilityAttr;
MCSymbolAttr getProtectedVisibilityAttr() const {
return ProtectedVisibilityAttr;
bool doesSupportDebugInformation() const { return SupportsDebugInformation; }
bool doesSupportExceptionHandling() const {
return ExceptionsType != ExceptionHandling::None;
ExceptionHandling getExceptionHandlingType() const { return ExceptionsType; }
WinEH::EncodingType getWinEHEncodingType() const { return WinEHEncodingType; }
void setExceptionsType(ExceptionHandling EH) {
ExceptionsType = EH;
/// Returns true if the exception handling method for the platform uses call
/// frame information to unwind.
bool usesCFIForEH() const {
return (ExceptionsType == ExceptionHandling::DwarfCFI ||
ExceptionsType == ExceptionHandling::ARM || usesWindowsCFI());
bool usesWindowsCFI() const {
return ExceptionsType == ExceptionHandling::WinEH &&
(WinEHEncodingType != WinEH::EncodingType::Invalid &&
WinEHEncodingType != WinEH::EncodingType::X86);
bool doesDwarfUseRelocationsAcrossSections() const {
return DwarfUsesRelocationsAcrossSections;
bool doDwarfFDESymbolsUseAbsDiff() const { return DwarfFDESymbolsUseAbsDiff; }
bool useDwarfRegNumForCFI() const { return DwarfRegNumForCFI; }
bool useParensForSymbolVariant() const { return UseParensForSymbolVariant; }
bool supportsExtendedDwarfLocDirective() const {
return SupportsExtendedDwarfLocDirective;
void addInitialFrameState(const MCCFIInstruction &Inst);
const std::vector<MCCFIInstruction> &getInitialFrameState() const {
return InitialFrameState;
/// Return true if assembly (inline or otherwise) should be parsed.
bool useIntegratedAssembler() const { return UseIntegratedAssembler; }
/// Set whether assembly (inline or otherwise) should be parsed.
virtual void setUseIntegratedAssembler(bool Value) {
UseIntegratedAssembler = Value;
/// Return true if assembly (inline or otherwise) should be parsed.
bool preserveAsmComments() const { return PreserveAsmComments; }
/// Set whether assembly (inline or otherwise) should be parsed.
virtual void setPreserveAsmComments(bool Value) {
PreserveAsmComments = Value;
DebugCompressionType compressDebugSections() const {
return CompressDebugSections;
void setCompressDebugSections(DebugCompressionType CompressDebugSections) {
this->CompressDebugSections = CompressDebugSections;
bool shouldUseLogicalShr() const { return UseLogicalShr; }
bool canRelaxRelocations() const { return RelaxELFRelocations; }
void setRelaxELFRelocations(bool V) { RelaxELFRelocations = V; }
bool hasMipsExpressions() const { return HasMipsExpressions; }
bool needsFunctionDescriptors() const { return NeedsFunctionDescriptors; }
} // end namespace llvm