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

#include "llvm/MC/MCAsmBackend.h"

Inheritance diagram for llvm::MCAsmBackend:

[legend]

Collaboration diagram for llvm::MCAsmBackend:

Public Member Functions
	MCAsmBackend (const MCAsmBackend &)=delete

MCAsmBackend &	operator= (const MCAsmBackend &)=delete

virtual	~MCAsmBackend ()

virtual void	reset ()
	lifetime management More...

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. More...

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. More...

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

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

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

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

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

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

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

void	handleCodePaddingBasicBlockStart (MCObjectStreamer *OS, const MCCodePaddingContext &Context)
	Handles all target related code padding when starting to write a new basic block to an object file. More...

void	handleCodePaddingBasicBlockEnd (const MCCodePaddingContext &Context)
	Handles all target related code padding after writing a block to an object file. More...

void	handleCodePaddingInstructionBegin (const MCInst &Inst)
	Handles all target related code padding before writing a new instruction to an object file. More...

void	handleCodePaddingInstructionEnd (const MCInst &Inst)
	Handles all target related code padding after writing an instruction to an object file. More...

bool	relaxFragment (MCPaddingFragment *PF, MCAsmLayout &Layout)
	Relaxes a fragment (changes the size of the padding) according to target requirements. More...

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

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

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

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. More...

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. More...

virtual bool	requiresDiffExpressionRelocations () const
	Check whether the given target requires emitting differences of two symbols as a set of relocations. More...

Target Relaxation Interfaces
virtual bool	mayNeedRelaxation (const MCInst &Inst, const MCSubtargetInfo &STI) const =0
	Check whether the given instruction may need relaxation. More...

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. More...

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. More...

virtual void	relaxInstruction (const MCInst &Inst, const MCSubtargetInfo &STI, MCInst &Res) const =0
	Relax the instruction in the given fragment to the next wider instruction. More...

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 42 of file MCAsmBackend.h.

Constructor & Destructor Documentation

◆ MCAsmBackend() [1/2]

MCAsmBackend::MCAsmBackend ( support::endianness Endian )

protected

Definition at line 26 of file MCAsmBackend.cpp.

References ~MCAsmBackend().

◆ MCAsmBackend() [2/2]

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

delete

◆ ~MCAsmBackend()

MCAsmBackend::~MCAsmBackend ( )

virtualdefault

Referenced by MCAsmBackend().

Member Function Documentation

◆ 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::MipsAsmBackend, llvm::RISCVAsmBackend, and llvm::AVRAsmBackend.

Referenced by llvm::MCAssembler::layout(), and shouldForceRelocation().

◆ 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 53 of file MCAsmBackend.cpp.

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

Referenced by llvm::LLVMTargetMachine::addAsmPrinter(), and reset().

◆ createObjectTargetWriter()

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

pure virtual

Implemented in llvm::RISCVAsmBackend, llvm::MipsAsmBackend, llvm::AVRAsmBackend, and llvm::ARMAsmBackendDarwin.

Referenced by createDwoObjectWriter(), createObjectWriter(), and reset().

◆ 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 32 of file MCAsmBackend.cpp.

References llvm::Triple::COFF, llvm::createELFObjectWriter(), llvm::createMachObjectWriter(), createObjectTargetWriter(), llvm::createWasmObjectWriter(), llvm::createWinCOFFObjectWriter(), llvm::Triple::ELF, Endian, llvm::support::little, llvm_unreachable, llvm::Triple::MachO, and llvm::Triple::Wasm.

Referenced by llvm::LLVMTargetMachine::addAsmPrinter(), llvm::LLVMTargetMachine::addPassesToEmitMC(), and reset().

◆ 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 156 of file MCAsmBackend.h.

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

◆ 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::MipsAsmBackend, llvm::ARMAsmBackend, llvm::AVRAsmBackend, and llvm::RISCVAsmBackend.

Referenced by fixupNeedsRelaxationAdvanced(), and requiresDiffExpressionRelocations().

◆ 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::RISCVAsmBackend.

Definition at line 101 of file MCAsmBackend.cpp.

References fixupNeedsRelaxation().

Referenced by llvm::MCAssembler::Finish(), and requiresDiffExpressionRelocations().

◆ 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 164 of file MCAsmBackend.h.

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

◆ getFixupKind()

Optional< MCFixupKind > MCAsmBackend::getFixupKind ( StringRef Name ) const

virtual

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

Reimplemented in llvm::MipsAsmBackend.

Definition at line 62 of file MCAsmBackend.cpp.

References llvm::None.

Referenced by llvm::MipsAsmBackend::getFixupKind(), getRelaxedOpcode(), and reset().

◆ getFixupKindInfo()

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

virtual

Get information on a fixup kind.

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

Definition at line 66 of file MCAsmBackend.cpp.

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

Referenced by adjustFixupValue(), extractBitsForFixup(), llvm::MCAssembler::getAtom(), llvm::ARMAsmBackend::getFixupKindInfo(), llvm::AVRAsmBackend::getFixupKindInfo(), llvm::MipsAsmBackend::getFixupKindInfo(), llvm::RISCVAsmBackend::getFixupKindInfo(), getFixupKindLog2Size(), getFixupKindNumBytes(), llvm::MachObjectWriter::isFixupKindPCRel(), isWeak(), and reset().

◆ 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 147 of file MCAsmBackend.h.

References writeNopData().

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

◆ getNumFixupKinds()

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

pure virtual

Get the number of target specific fixup kinds.

Implemented in llvm::RISCVAsmBackend, llvm::MipsAsmBackend, llvm::AVRAsmBackend, and llvm::ARMAsmBackend.

Referenced by reset().

◆ 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 160 of file MCAsmBackend.h.

Referenced by llvm::MCELFStreamer::EmitAssemblerFlag(), and llvm::MCWasmStreamer::EmitAssemblerFlag().

◆ handleCodePaddingBasicBlockEnd()

void MCAsmBackend::handleCodePaddingBasicBlockEnd ( const MCCodePaddingContext & Context )

Handles all target related code padding after writing a block to an object file.

Parameters

Context the context of the padding, Embeds the basic block's parameters.

Definition at line 115 of file MCAsmBackend.cpp.

Referenced by llvm::MCObjectStreamer::EmitCodePaddingBasicBlockEnd(), and isMicroMips().

◆ handleCodePaddingBasicBlockStart()

void MCAsmBackend::handleCodePaddingBasicBlockStart	(	MCObjectStreamer *	OS,
		const MCCodePaddingContext &	Context
	)

Handles all target related code padding when starting to write a new basic block to an object file.

Parameters

OS	The streamer used for writing the padding data and function.
Context	the context of the padding, Embeds the basic block's parameters.

Definition at line 110 of file MCAsmBackend.cpp.

Referenced by llvm::MCObjectStreamer::EmitCodePaddingBasicBlockStart(), and isMicroMips().

◆ handleCodePaddingInstructionBegin()

void MCAsmBackend::handleCodePaddingInstructionBegin ( const MCInst & Inst )

Handles all target related code padding before writing a new instruction to an object file.

Parameters

Inst	the instruction.

Definition at line 120 of file MCAsmBackend.cpp.

Referenced by llvm::MCObjectStreamer::EmitInstruction(), and isMicroMips().

◆ handleCodePaddingInstructionEnd()

void MCAsmBackend::handleCodePaddingInstructionEnd ( const MCInst & Inst )

Handles all target related code padding after writing an instruction to an object file.

Parameters

Inst	the instruction.

Definition at line 124 of file MCAsmBackend.cpp.

Referenced by llvm::MCObjectStreamer::EmitInstruction(), and isMicroMips().

◆ 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 169 of file MCAsmBackend.h.

References Context, handleCodePaddingBasicBlockEnd(), handleCodePaddingBasicBlockStart(), handleCodePaddingInstructionBegin(), handleCodePaddingInstructionEnd(), and relaxFragment().

◆ mayNeedRelaxation()

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

pure virtual

Check whether the given instruction may need relaxation.

Parameters

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

Implemented in llvm::RISCVAsmBackend, llvm::MipsAsmBackend, llvm::ARMAsmBackend, and llvm::AVRAsmBackend.

Referenced by llvm::MCObjectStreamer::EmitInstruction(), and requiresDiffExpressionRelocations().

◆ operator=()

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

delete

◆ relaxFragment()

bool MCAsmBackend::relaxFragment	(	MCPaddingFragment *	PF,
		MCAsmLayout &	Layout
	)

Relaxes a fragment (changes the size of the padding) according to target requirements.

The new size computation is done w.r.t a layout.

Parameters

PF	The fragment to relax.
Layout	Code layout information.

Returns: true iff any relaxation occurred.

Definition at line 128 of file MCAsmBackend.cpp.

Referenced by isMicroMips().

◆ relaxInstruction()

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

pure virtual

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

Parameters

	Inst	The instruction to relax, which may be the same as the output.
	STI	the subtarget information for the associated instruction.
[out]	Res	On return, the relaxed instruction.

Implemented in llvm::RISCVAsmBackend, llvm::MipsAsmBackend, llvm::ARMAsmBackend, and llvm::AVRAsmBackend.

Referenced by llvm::MCObjectStreamer::EmitInstruction(), llvm::MCAssembler::Finish(), and requiresDiffExpressionRelocations().