#include <decoder.hh>

Public Member Functions
	Decoder (ISA *isa=nullptr)

void	reset ()
	Reset the decoders internal state. More...

bool	needMoreBytes () const
	Can the decoder accept more data? More...

bool	instReady () const
	Is an instruction ready to be decoded? More...

void	moreBytes (const PCState &pc, Addr fetchPC, MachInst inst)
	Feed data to the decoder. More...

StaticInstPtr	decode (ArmISA::PCState &pc)
	Decode an instruction or fetch it from the code cache. More...

StaticInstPtr	decode (ExtMachInst mach_inst, Addr addr)
	Decode a pre-decoded machine instruction. More...

StaticInstPtr	decodeInst (ExtMachInst mach_inst)
	Decode a machine instruction without calling the cache. More...

void	takeOverFrom (Decoder *old)
	Take over the state from an old decoder when switching CPUs. More...

void	setContext (FPSCR fpscr)

Protected Member Functions
void	process ()
	Pre-decode an instruction from the current state of the decoder. More...

void	consumeBytes (int numBytes)
	Consume bytes by moving the offset into the data word and sanity check the results. More...

Protected Attributes
ExtMachInst	emi

MachInst	data

bool	bigThumb

bool	instDone

bool	outOfBytes

int	offset

bool	foundIt

ITSTATE	itBits

int	fpscrLen

int	fpscrStride

Enums::DecoderFlavour	decoderFlavour

Static Protected Attributes
static GenericISA::BasicDecodeCache	defaultCache
	A cache of decoded instruction objects. More...

Detailed Description

Definition at line 59 of file decoder.hh.

Constructor & Destructor Documentation

ArmISA::Decoder::Decoder ( ISA * isa = nullptr )

Definition at line 56 of file decoder.cc.

References reset().

Member Function Documentation

void ArmISA::Decoder::consumeBytes ( int numBytes )

protected

Consume bytes by moving the offset into the data word and sanity check the results.

Definition at line 143 of file decoder.cc.

References emi, offset, and outOfBytes.

Referenced by process().

StaticInstPtr ArmISA::Decoder::decode ( ArmISA::PCState & pc )

Decode an instruction or fetch it from the code cache.

This method decodes the currently pending pre-decoded instruction. Data must be fed to the decoder using moreBytes() until instReady() is true before calling this method.

Parameters

pc	Instruction pointer that we are decoding.

Returns: A pointer to a static instruction or NULL if the decoder isn't ready (see instReady()).

Definition at line 170 of file decoder.cc.

References emi, foundIt, instDone, and itBits.

StaticInstPtr ArmISA::Decoder::decode	(	ExtMachInst	mach_inst,
		Addr	addr
	)

inline

Decode a pre-decoded machine instruction.

This method takes a pre-decoded instruction as its argument. It should typically not be called directly.

Parameters

mach_inst A pre-decoded instruction

Return values

A	pointer to the corresponding StaticInst object.

Definition at line 167 of file decoder.hh.

References GenericISA::BasicDecodeCache::decode(), and defaultCache.

StaticInstPtr ArmISA::Decoder::decodeInst ( ExtMachInst mach_inst )

Decode a machine instruction without calling the cache.

Note: The implementation of this method is generated by the ISA parser script.

This method takes a pre-decoded instruction as its argument. It should typically not be called directly.

Parameters

mach_inst The binary instruction to decode.

Return values

A	pointer to the corresponding StaticInst object.

bool ArmISA::Decoder::instReady ( ) const

inline

Is an instruction ready to be decoded?

CPU models call this method to determine if decode() will return a new instruction on the next call. It typically only returns false if the decoder hasn't received enough data to decode a full instruction.

Definition at line 115 of file decoder.hh.

References instDone.

void ArmISA::Decoder::moreBytes	(	const PCState &	pc,
		Addr	fetchPC,
		MachInst	inst
	)

Feed data to the decoder.

A CPU model uses this interface to load instruction data into the decoder. Once enough data has been loaded (check with instReady()), a decoded instruction can be retrieved using decode(ArmISA::PCState).

This method is intended to support both fixed-length and variable-length instructions. Instruction data is fetch in MachInst blocks (which correspond to the size of a typical insturction). The method might need to be called multiple times if the instruction spans multiple blocks, in that case needMoreBytes() will return true and instReady() will return false.

The fetchPC parameter is used to indicate where in memory the instruction was fetched from. This is should be the same address as the pc. If fetching multiple blocks, it indicates where subsequent blocks are fetched from (pc + n * sizeof(MachInst)).

Parameters

pc	Instruction pointer that we are decoding.
fetchPC	The address this chunk was fetched from.
inst	Raw instruction data.

Definition at line 152 of file decoder.cc.

References data, emi, fpscrLen, fpscrStride, offset, ArmISA::OK, outOfBytes, process(), and ArmISA::UNALIGNED.

bool ArmISA::Decoder::needMoreBytes ( ) const

inline

Can the decoder accept more data?

A CPU model uses this method to determine if the decoder can accept more data. Note that an instruction can be ready (see instReady() even if this method returns true.

Definition at line 105 of file decoder.hh.

References outOfBytes.

void ArmISA::Decoder::process ( )

protected

Pre-decode an instruction from the current state of the decoder.

Definition at line 76 of file decoder.cc.

References bigThumb, bits(), ArmISA::COND_UC, consumeBytes(), data, DPRINTF, emi, foundIt, instDone, itBits, and offset.

Referenced by moreBytes().

void ArmISA::Decoder::reset ( )

Reset the decoders internal state.

Definition at line 65 of file decoder.cc.

References bigThumb, emi, foundIt, instDone, offset, and outOfBytes.

Referenced by Decoder().

void ArmISA::Decoder::setContext ( FPSCR fpscr )

inline

Definition at line 195 of file decoder.hh.

References fpscrLen, and fpscrStride.

void ArmISA::Decoder::takeOverFrom ( Decoder * old )

inline

Take over the state from an old decoder when switching CPUs.

Parameters

old	Decoder used in old CPU

Definition at line 191 of file decoder.hh.

Member Data Documentation

bool ArmISA::Decoder::bigThumb

protected

Definition at line 65 of file decoder.hh.

Referenced by process(), and reset().

MachInst ArmISA::Decoder::data

protected

Definition at line 64 of file decoder.hh.

Referenced by moreBytes(), and process().

Enums::DecoderFlavour ArmISA::Decoder::decoderFlavour

protected

Definition at line 75 of file decoder.hh.

GenericISA::BasicDecodeCache ArmISA::Decoder::defaultCache

staticprotected

A cache of decoded instruction objects.

Definition at line 78 of file decoder.hh.

Referenced by decode().

ExtMachInst ArmISA::Decoder::emi

protected

Definition at line 63 of file decoder.hh.

Referenced by consumeBytes(), decode(), moreBytes(), process(), and reset().

bool ArmISA::Decoder::foundIt

protected

Definition at line 69 of file decoder.hh.

Referenced by decode(), process(), and reset().

int ArmISA::Decoder::fpscrLen

protected

Definition at line 72 of file decoder.hh.

Referenced by moreBytes(), and setContext().

int ArmISA::Decoder::fpscrStride

protected

Definition at line 73 of file decoder.hh.

Referenced by moreBytes(), and setContext().

bool ArmISA::Decoder::instDone

protected

Definition at line 66 of file decoder.hh.

Referenced by decode(), instReady(), process(), and reset().

ITSTATE ArmISA::Decoder::itBits

protected

Definition at line 70 of file decoder.hh.

Referenced by decode(), and process().

int ArmISA::Decoder::offset

protected

Definition at line 68 of file decoder.hh.

Referenced by consumeBytes(), moreBytes(), process(), and reset().

bool ArmISA::Decoder::outOfBytes

protected

Definition at line 67 of file decoder.hh.

Referenced by consumeBytes(), moreBytes(), needMoreBytes(), and reset().

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

arch/arm/decoder.hh
arch/arm/decoder.cc

Public Member Functions

Protected Member Functions

Protected Attributes

Static Protected Attributes

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation