Generic interface to target specific assembler backends. More...

#include "llvm/MC/MCAsmBackend.h"

Inheritance diagram for llvm::MCAsmBackend:

[legend]

Public Member Functions
	MCAsmBackend (const MCAsmBackend &)=delete

MCAsmBackend &	operator= (const MCAsmBackend &)=delete

virtual	~MCAsmBackend ()

virtual bool	allowAutoPadding () const
	Return true if this target might automatically pad instructions and thus need to emit padding enable/disable directives around sensative code.

virtual bool	allowEnhancedRelaxation () const
	Return true if this target allows an unrelaxable instruction to be emitted into RelaxableFragment and then we can increase its size in a tricky way for optimization.

virtual void	emitInstructionBegin (MCObjectStreamer &OS, const MCInst &Inst, const MCSubtargetInfo &STI)
	Give the target a chance to manipulate state related to instruction alignment (e.g.

virtual void	emitInstructionEnd (MCObjectStreamer &OS, const MCInst &Inst)

virtual void	reset ()
	lifetime management

std::unique_ptr< MCObjectWriter >	createObjectWriter (raw_pwrite_stream &OS) const
	Create a new MCObjectWriter instance for use by the assembler backend to emit the final object file.

std::unique_ptr< MCObjectWriter >	createDwoObjectWriter (raw_pwrite_stream &OS, raw_pwrite_stream &DwoOS) const
	Create an MCObjectWriter that writes two object files: a .o file which is linked into the final program and a .dwo file which is used by debuggers.

virtual std::unique_ptr< MCObjectTargetWriter >	createObjectTargetWriter () const =0

virtual unsigned	getMinimumNopSize () const
	Returns the minimum size of a nop in bytes on this target.

virtual unsigned	getMaximumNopSize (const MCSubtargetInfo &STI) const
	Returns the maximum size of a nop in bytes on this target.

virtual bool	writeNopData (raw_ostream &OS, uint64_t Count, const MCSubtargetInfo *STI) const =0
	Write an (optimal) nop sequence of Count bytes to the given output.

virtual void	finishLayout (MCAssembler const &Asm, MCAsmLayout &Layout) const
	Give backend an opportunity to finish layout after relaxation.

virtual void	handleAssemblerFlag (MCAssemblerFlag Flag)
	Handle any target-specific assembler flags. By default, do nothing.

virtual uint32_t	generateCompactUnwindEncoding (ArrayRef< MCCFIInstruction >) const
	Generate the compact unwind encoding for the CFI instructions.

virtual bool	isMicroMips (const MCSymbol *Sym) const
	Check whether a given symbol has been flagged with MICROMIPS flag.

Target Fixup Interfaces
virtual unsigned	getNumFixupKinds () const =0
	Get the number of target specific fixup kinds.

virtual std::optional< MCFixupKind >	getFixupKind (StringRef Name) const
	Map a relocation name used in .reloc to a fixup kind.

virtual const MCFixupKindInfo &	getFixupKindInfo (MCFixupKind Kind) const
	Get information on a fixup kind.

virtual bool	shouldForceRelocation (const MCAssembler &Asm, const MCFixup &Fixup, const MCValue &Target)
	Hook to check if a relocation is needed for some target specific reason.

virtual bool	shouldInsertExtraNopBytesForCodeAlign (const MCAlignFragment &AF, unsigned &Size)
	Hook to check if extra nop bytes must be inserted for alignment directive.

virtual bool	shouldInsertFixupForCodeAlign (MCAssembler &Asm, const MCAsmLayout &Layout, MCAlignFragment &AF)
	Hook which indicates if the target requires a fixup to be generated when handling an align directive in an executable section.

virtual bool	evaluateTargetFixup (const MCAssembler &Asm, const MCAsmLayout &Layout, const MCFixup &Fixup, const MCFragment *DF, const MCValue &Target, uint64_t &Value, bool &WasForced)

virtual void	applyFixup (const MCAssembler &Asm, const MCFixup &Fixup, const MCValue &Target, MutableArrayRef< char > Data, uint64_t Value, bool IsResolved, const MCSubtargetInfo *STI) const =0
	Apply the `Value` for given `Fixup` into the provided data fragment, at the offset specified by the fixup and following the fixup kind as appropriate.

Target Relaxation Interfaces
virtual bool	mayNeedRelaxation (const MCInst &Inst, const MCSubtargetInfo &STI) const
	Check whether the given instruction may need relaxation.

virtual bool	fixupNeedsRelaxationAdvanced (const MCFixup &Fixup, bool Resolved, uint64_t Value, const MCRelaxableFragment *DF, const MCAsmLayout &Layout, const bool WasForced) const
	Target specific predicate for whether a given fixup requires the associated instruction to be relaxed.

virtual bool	fixupNeedsRelaxation (const MCFixup &Fixup, uint64_t Value, const MCRelaxableFragment *DF, const MCAsmLayout &Layout) const =0
	Simple predicate for targets where !Resolved implies requiring relaxation.

virtual void	relaxInstruction (MCInst &Inst, const MCSubtargetInfo &STI) const
	Relax the instruction in the given fragment to the next wider instruction.

virtual bool	relaxDwarfLineAddr (MCDwarfLineAddrFragment &DF, MCAsmLayout &Layout, bool &WasRelaxed) const

virtual bool	relaxDwarfCFA (MCDwarfCallFrameFragment &DF, MCAsmLayout &Layout, bool &WasRelaxed) const

Public Attributes
const support::endianness	Endian

Protected Member Functions
	MCAsmBackend (support::endianness Endian)

Detailed Description

Generic interface to target specific assembler backends.

Definition at line 41 of file MCAsmBackend.h.

Constructor & Destructor Documentation

◆ MCAsmBackend() [1/2]

MCAsmBackend::MCAsmBackend ( support::endianness Endian )

protected

Definition at line 25 of file MCAsmBackend.cpp.

References Endian.

◆ MCAsmBackend() [2/2]

llvm::MCAsmBackend::MCAsmBackend ( const MCAsmBackend & )

delete

◆ ~MCAsmBackend()

MCAsmBackend::~MCAsmBackend ( )

virtualdefault

Member Function Documentation

◆ allowAutoPadding()

virtual bool llvm::MCAsmBackend::allowAutoPadding ( ) const

inlinevirtual

Return true if this target might automatically pad instructions and thus need to emit padding enable/disable directives around sensative code.

Definition at line 54 of file MCAsmBackend.h.

◆ allowEnhancedRelaxation()

virtual bool llvm::MCAsmBackend::allowEnhancedRelaxation ( ) const

inlinevirtual

Return true if this target allows an unrelaxable instruction to be emitted into RelaxableFragment and then we can increase its size in a tricky way for optimization.

Definition at line 58 of file MCAsmBackend.h.

◆ applyFixup()

virtual void llvm::MCAsmBackend::applyFixup	(	const MCAssembler &	Asm,
		const MCFixup &	Fixup,
		const MCValue &	Target,
		MutableArrayRef< char >	Data,
		uint64_t	Value,
		bool	IsResolved,
		const MCSubtargetInfo *	STI
	)		const

pure virtual

Apply the Value for given Fixup into the provided data fragment, at the offset specified by the fixup and following the fixup kind as appropriate.

Errors (such as an out of range fixup value) should be reported via Ctx. The STI is present only for fragments of type MCRelaxableFragment and MCDataFragment with hasInstructions() == true.

Implemented in llvm::ARMAsmBackend, llvm::AVRAsmBackend, llvm::CSKYAsmBackend, llvm::LoongArchAsmBackend, llvm::MipsAsmBackend, llvm::RISCVAsmBackend, and llvm::XtensaMCAsmBackend.

Referenced by llvm::MCAssembler::layout().

◆ createDwoObjectWriter()

std::unique_ptr< MCObjectWriter > MCAsmBackend::createDwoObjectWriter	(	raw_pwrite_stream &	OS,
		raw_pwrite_stream &	DwoOS
	)		const

Create an MCObjectWriter that writes two object files: a .o file which is linked into the final program and a .dwo file which is used by debuggers.

This function is only supported with ELF targets.

Definition at line 60 of file MCAsmBackend.cpp.

References llvm::createELFDwoObjectWriter(), createObjectTargetWriter(), llvm::createWasmDwoObjectWriter(), llvm::Triple::ELF, Endian, llvm::support::little, OS, llvm::report_fatal_error(), and llvm::Triple::Wasm.

Referenced by llvm::LLVMTargetMachine::createMCStreamer().

◆ createObjectTargetWriter()

virtual std::unique_ptr< MCObjectTargetWriter > llvm::MCAsmBackend::createObjectTargetWriter ( ) const

pure virtual

Implemented in llvm::ARMAsmBackendDarwin, llvm::AVRAsmBackend, llvm::CSKYAsmBackend, llvm::LoongArchAsmBackend, llvm::MipsAsmBackend, llvm::RISCVAsmBackend, and llvm::XtensaMCAsmBackend.

Referenced by createDwoObjectWriter(), and createObjectWriter().

◆ createObjectWriter()

std::unique_ptr< MCObjectWriter > MCAsmBackend::createObjectWriter ( raw_pwrite_stream & OS ) const

Create a new MCObjectWriter instance for use by the assembler backend to emit the final object file.

Definition at line 30 of file MCAsmBackend.cpp.

References llvm::Triple::COFF, llvm::createDXContainerObjectWriter(), llvm::createELFObjectWriter(), llvm::createMachObjectWriter(), createObjectTargetWriter(), llvm::createSPIRVObjectWriter(), llvm::createWasmObjectWriter(), llvm::createWinCOFFObjectWriter(), llvm::createXCOFFObjectWriter(), llvm::Triple::DXContainer, llvm::Triple::ELF, Endian, llvm::support::little, llvm_unreachable, llvm::Triple::MachO, OS, llvm::Triple::SPIRV, llvm::Triple::Wasm, and llvm::Triple::XCOFF.

Referenced by llvm::LLVMTargetMachine::createMCStreamer(), and llvm::DwarfStreamer::init().

◆ emitInstructionBegin()

virtual void llvm::MCAsmBackend::emitInstructionBegin	(	MCObjectStreamer &	OS,
		const MCInst &	Inst,
		const MCSubtargetInfo &	STI
	)

inlinevirtual

Give the target a chance to manipulate state related to instruction alignment (e.g.

padding for optimization), instruction relaxablility, etc. before and after actually emitting the instruction.

Definition at line 63 of file MCAsmBackend.h.

Referenced by llvm::MCObjectStreamer::emitInstruction().

◆ emitInstructionEnd()

virtual void llvm::MCAsmBackend::emitInstructionEnd	(	MCObjectStreamer &	OS,
		const MCInst &	Inst
	)

inlinevirtual

Definition at line 65 of file MCAsmBackend.h.

Referenced by llvm::MCObjectStreamer::emitInstruction().

◆ evaluateTargetFixup()

virtual bool llvm::MCAsmBackend::evaluateTargetFixup	(	const MCAssembler &	Asm,
		const MCAsmLayout &	Layout,
		const MCFixup &	Fixup,
		const MCFragment *	DF,
		const MCValue &	Target,
		uint64_t &	Value,
		bool &	WasForced
	)

inlinevirtual

Reimplemented in llvm::RISCVAsmBackend.

Definition at line 119 of file MCAsmBackend.h.

References llvm_unreachable.

◆ finishLayout()

virtual void llvm::MCAsmBackend::finishLayout	(	MCAssembler const &	Asm,
		MCAsmLayout &	Layout
	)		const

inlinevirtual

Give backend an opportunity to finish layout after relaxation.

Definition at line 206 of file MCAsmBackend.h.

◆ fixupNeedsRelaxation()

virtual bool llvm::MCAsmBackend::fixupNeedsRelaxation	(	const MCFixup &	Fixup,
		uint64_t	Value,
		const MCRelaxableFragment *	DF,
		const MCAsmLayout &	Layout
	)		const

pure virtual

Simple predicate for targets where !Resolved implies requiring relaxation.

Implemented in llvm::ARMAsmBackend, llvm::AVRAsmBackend, llvm::CSKYAsmBackend, llvm::LoongArchAsmBackend, llvm::MipsAsmBackend, llvm::RISCVAsmBackend, and llvm::XtensaMCAsmBackend.

Referenced by fixupNeedsRelaxationAdvanced().

◆ fixupNeedsRelaxationAdvanced()

bool MCAsmBackend::fixupNeedsRelaxationAdvanced	(	const MCFixup &	Fixup,
		bool	Resolved,
		uint64_t	Value,
		const MCRelaxableFragment *	DF,
		const MCAsmLayout &	Layout,
		const bool	WasForced
	)		const

virtual

Target specific predicate for whether a given fixup requires the associated instruction to be relaxed.

Reimplemented in llvm::CSKYAsmBackend, and llvm::RISCVAsmBackend.

Definition at line 110 of file MCAsmBackend.cpp.

References DF, Fixup, and fixupNeedsRelaxation().

◆ generateCompactUnwindEncoding()

virtual uint32_t llvm::MCAsmBackend::generateCompactUnwindEncoding ( ArrayRef< MCCFIInstruction > ) const

inlinevirtual

Generate the compact unwind encoding for the CFI instructions.

Reimplemented in llvm::ARMAsmBackendDarwin.

Definition at line 214 of file MCAsmBackend.h.

Referenced by llvm::MCStreamer::generateCompactUnwindEncodings().

◆ getFixupKind()

std::optional< MCFixupKind > MCAsmBackend::getFixupKind ( StringRef Name ) const

virtual

Map a relocation name used in .reloc to a fixup kind.

Reimplemented in llvm::ARMAsmBackend, llvm::AVRAsmBackend, llvm::LoongArchAsmBackend, llvm::MipsAsmBackend, and llvm::RISCVAsmBackend.

Definition at line 76 of file MCAsmBackend.cpp.

Referenced by llvm::MCObjectStreamer::emitRelocDirective(), llvm::MCXCOFFStreamer::emitXCOFFRefDirective(), and llvm::MipsAsmBackend::getFixupKind().

◆ getFixupKindInfo()

const MCFixupKindInfo & MCAsmBackend::getFixupKindInfo ( MCFixupKind Kind ) const

virtual

Get information on a fixup kind.

Reimplemented in llvm::ARMAsmBackend, llvm::AVRAsmBackend, llvm::CSKYAsmBackend, llvm::LoongArchAsmBackend, llvm::MipsAsmBackend, llvm::RISCVAsmBackend, and llvm::XtensaMCAsmBackend.

Definition at line 80 of file MCAsmBackend.cpp.

References assert(), and llvm::MCFixupKindInfo::FKF_IsPCRel.

Referenced by llvm::ARMAsmBackend::getFixupKindInfo(), llvm::AVRAsmBackend::getFixupKindInfo(), llvm::CSKYAsmBackend::getFixupKindInfo(), llvm::LoongArchAsmBackend::getFixupKindInfo(), llvm::MipsAsmBackend::getFixupKindInfo(), llvm::RISCVAsmBackend::getFixupKindInfo(), and llvm::XtensaMCAsmBackend::getFixupKindInfo().

◆ getMaximumNopSize()

virtual unsigned llvm::MCAsmBackend::getMaximumNopSize ( const MCSubtargetInfo & STI ) const

inlinevirtual

Returns the maximum size of a nop in bytes on this target.

Definition at line 194 of file MCAsmBackend.h.

◆ getMinimumNopSize()

virtual unsigned llvm::MCAsmBackend::getMinimumNopSize ( ) const

inlinevirtual

Returns the minimum size of a nop in bytes on this target.

The assembler will use this to emit excess padding in situations where the padding required for simple alignment would be less than the minimum nop size.

Definition at line 190 of file MCAsmBackend.h.

◆ getNumFixupKinds()

virtual unsigned llvm::MCAsmBackend::getNumFixupKinds ( ) const

pure virtual

Get the number of target specific fixup kinds.

Implemented in llvm::ARMAsmBackend, llvm::AVRAsmBackend, llvm::CSKYAsmBackend, llvm::LoongArchAsmBackend, llvm::MipsAsmBackend, llvm::RISCVAsmBackend, and llvm::XtensaMCAsmBackend.

◆ handleAssemblerFlag()

virtual void llvm::MCAsmBackend::handleAssemblerFlag ( MCAssemblerFlag Flag )

inlinevirtual

Handle any target-specific assembler flags. By default, do nothing.

Reimplemented in llvm::ARMAsmBackend.

Definition at line 210 of file MCAsmBackend.h.

Referenced by llvm::MCELFStreamer::emitAssemblerFlag(), llvm::MCWasmStreamer::emitAssemblerFlag(), and llvm::MCWinCOFFStreamer::emitAssemblerFlag().

◆ isMicroMips()

virtual bool llvm::MCAsmBackend::isMicroMips ( const MCSymbol * Sym ) const

inlinevirtual

Check whether a given symbol has been flagged with MICROMIPS flag.

Reimplemented in llvm::MipsAsmBackend.

Definition at line 219 of file MCAsmBackend.h.

◆ mayNeedRelaxation()

virtual bool llvm::MCAsmBackend::mayNeedRelaxation	(	const MCInst &	Inst,
		const MCSubtargetInfo &	STI
	)		const

inlinevirtual

Check whether the given instruction may need relaxation.

Parameters

Inst	- The instruction to test.
STI	- The MCSubtargetInfo in effect when the instruction was encoded.

Reimplemented in llvm::ARMAsmBackend, llvm::CSKYAsmBackend, llvm::RISCVAsmBackend, and llvm::XtensaMCAsmBackend.

Definition at line 148 of file MCAsmBackend.h.

◆ operator=()

MCAsmBackend & llvm::MCAsmBackend::operator= ( const MCAsmBackend & )

delete

◆ relaxDwarfCFA()

virtual bool llvm::MCAsmBackend::relaxDwarfCFA	(	MCDwarfCallFrameFragment &	DF,
		MCAsmLayout &	Layout,
		bool &	WasRelaxed
	)		const

inlinevirtual

Reimplemented in llvm::RISCVAsmBackend.

Definition at line 179 of file MCAsmBackend.h.

◆ relaxDwarfLineAddr()

virtual bool llvm::MCAsmBackend::relaxDwarfLineAddr	(	MCDwarfLineAddrFragment &	DF,
		MCAsmLayout &	Layout,
		bool &	WasRelaxed
	)		const

inlinevirtual

Reimplemented in llvm::RISCVAsmBackend.

Definition at line 174 of file MCAsmBackend.h.

◆ relaxInstruction()

virtual void llvm::MCAsmBackend::relaxInstruction	(	MCInst &	Inst,
		const MCSubtargetInfo &	STI
	)		const

inlinevirtual

Relax the instruction in the given fragment to the next wider instruction.

Parameters

[out]	Inst	The instruction to relax, which is also the relaxed instruction.
	STI	the subtarget information for the associated instruction.

Reimplemented in llvm::ARMAsmBackend, llvm::CSKYAsmBackend, llvm::LoongArchAsmBackend, llvm::RISCVAsmBackend, and llvm::XtensaMCAsmBackend.

Definition at line 171 of file MCAsmBackend.h.

◆ reset()

virtual void llvm::MCAsmBackend::reset ( )

inlinevirtual

lifetime management

Definition at line 68 of file MCAsmBackend.h.

Referenced by llvm::MCAssembler::reset().

◆ shouldForceRelocation()

virtual bool llvm::MCAsmBackend::shouldForceRelocation	(	const MCAssembler &	Asm,
		const MCFixup &	Fixup,
		const MCValue &	Target
	)

inlinevirtual

Hook to check if a relocation is needed for some target specific reason.

Reimplemented in llvm::ARMAsmBackend, llvm::AVRAsmBackend, llvm::CSKYAsmBackend, llvm::LoongArchAsmBackend, llvm::MipsAsmBackend, and llvm::RISCVAsmBackend.

Definition at line 97 of file MCAsmBackend.h.

◆ shouldInsertExtraNopBytesForCodeAlign()

virtual bool llvm::MCAsmBackend::shouldInsertExtraNopBytesForCodeAlign	(	const MCAlignFragment &	AF,
		unsigned &	Size
	)

inlinevirtual

Hook to check if extra nop bytes must be inserted for alignment directive.

For some targets this may be necessary in order to support linker relaxation. The number of bytes to insert are returned in Size.

Reimplemented in llvm::RISCVAsmBackend.

Definition at line 106 of file MCAsmBackend.h.

◆ shouldInsertFixupForCodeAlign()

virtual bool llvm::MCAsmBackend::shouldInsertFixupForCodeAlign	(	MCAssembler &	Asm,
		const MCAsmLayout &	Layout,
		MCAlignFragment &	AF
	)

inlinevirtual

Hook which indicates if the target requires a fixup to be generated when handling an align directive in an executable section.

Reimplemented in llvm::RISCVAsmBackend.

Definition at line 113 of file MCAsmBackend.h.

Referenced by llvm::MCAssembler::layout().

◆ writeNopData()

virtual bool llvm::MCAsmBackend::writeNopData	(	raw_ostream &	OS,
		uint64_t	Count,
		const MCSubtargetInfo *	STI
	)		const

pure virtual

Write an (optimal) nop sequence of Count bytes to the given output.

If the target cannot generate such a sequence, it should return an error.

Returns: - True on success.

Implemented in llvm::ARMAsmBackend, llvm::AVRAsmBackend, llvm::CSKYAsmBackend, llvm::LoongArchAsmBackend, llvm::MipsAsmBackend, llvm::RISCVAsmBackend, and llvm::XtensaMCAsmBackend.

Member Data Documentation

◆ Endian

const support::endianness llvm::MCAsmBackend::Endian

Definition at line 50 of file MCAsmBackend.h.

Referenced by llvm::ARMAsmBackend::adjustFixupValue(), llvm::ARMAsmBackend::applyFixup(), llvm::CSKYAsmBackend::applyFixup(), llvm::MipsAsmBackend::applyFixup(), createDwoObjectWriter(), createObjectWriter(), llvm::ARMAsmBackend::getFixupKindInfo(), llvm::MipsAsmBackend::getFixupKindInfo(), and llvm::ARMAsmBackend::writeNopData().

The documentation for this class was generated from the following files:

include/llvm/MC/MCAsmBackend.h
lib/MC/MCAsmBackend.cpp

Public Member Functions

Public Attributes

Protected Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ MCAsmBackend() [1/2]

◆ MCAsmBackend() [2/2]

◆ ~MCAsmBackend()

Member Function Documentation

◆ allowAutoPadding()

◆ allowEnhancedRelaxation()

◆ applyFixup()

◆ createDwoObjectWriter()

◆ createObjectTargetWriter()

◆ createObjectWriter()

◆ emitInstructionBegin()

◆ emitInstructionEnd()

◆ evaluateTargetFixup()

◆ finishLayout()

◆ fixupNeedsRelaxation()

◆ fixupNeedsRelaxationAdvanced()

◆ generateCompactUnwindEncoding()

◆ getFixupKind()

◆ getFixupKindInfo()

◆ getMaximumNopSize()

◆ getMinimumNopSize()

◆ getNumFixupKinds()

◆ handleAssemblerFlag()

◆ isMicroMips()

◆ mayNeedRelaxation()

◆ operator=()

◆ relaxDwarfCFA()

◆ relaxDwarfLineAddr()

◆ relaxInstruction()

◆ reset()

◆ shouldForceRelocation()

◆ shouldInsertExtraNopBytesForCodeAlign()

◆ shouldInsertFixupForCodeAlign()

◆ writeNopData()

Member Data Documentation

◆ Endian