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/*
* Copyright (c) 2013-2014 ARM Limited
* All rights reserved
*
* The license below extends only to copyright in the software and shall
* not be construed as granting a license to any other intellectual
* property including but not limited to intellectual property relating
* to a hardware implementation of the functionality of the software
* licensed hereunder. You may use the software subject to the license
* terms below provided that you ensure that this notice is replicated
* unmodified and in its entirety in all distributions of the software,
* modified or unmodified, in source code or in binary form.
*
* Copyright (c) 2012 Google
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Gabe Black
*/
#ifndef __ARCH_ARM_DECODER_HH__
#define __ARCH_ARM_DECODER_HH__
#include <cassert>
#include "arch/arm/miscregs.hh"
#include "arch/arm/types.hh"
#include "arch/generic/decode_cache.hh"
#include "base/types.hh"
#include "cpu/static_inst.hh"
#include "enums/DecoderFlavour.hh"
namespace ArmISA
{
class ISA;
class Decoder
{
protected:
//The extended machine instruction being generated
ExtMachInst emi;
MachInst data;
bool bigThumb;
bool instDone;
bool outOfBytes;
int offset;
bool foundIt;
ITSTATE itBits;
int fpscrLen;
int fpscrStride;
Enums::DecoderFlavour decoderFlavour;
/// A cache of decoded instruction objects.
static GenericISA::BasicDecodeCache defaultCache;
/**
* Pre-decode an instruction from the current state of the
* decoder.
*/
void process();
/**
* Consume bytes by moving the offset into the data word and
* sanity check the results.
*/
void consumeBytes(int numBytes);
public: // Decoder API
Decoder(ISA* isa = nullptr);
/** Reset the decoders internal state. */
void reset();
/**
* 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.
*/
bool needMoreBytes() const { return outOfBytes; }
/**
* 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.
*/
bool instReady() const { return instDone; }
/**
* 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)).
*
* @param pc Instruction pointer that we are decoding.
* @param fetchPC The address this chunk was fetched from.
* @param inst Raw instruction data.
*/
void moreBytes(const PCState &pc, Addr fetchPC, MachInst inst);
/**
* 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.
*
* @param pc Instruction pointer that we are decoding.
* @return A pointer to a static instruction or NULL if the
* decoder isn't ready (see instReady()).
*/
StaticInstPtr decode(ArmISA::PCState &pc);
/**
* Decode a pre-decoded machine instruction.
*
* @warn This method takes a pre-decoded instruction as its
* argument. It should typically not be called directly.
*
* @param mach_inst A pre-decoded instruction
* @retval A pointer to the corresponding StaticInst object.
*/
StaticInstPtr decode(ExtMachInst mach_inst, Addr addr)
{
return defaultCache.decode(this, mach_inst, addr);
}
/**
* Decode a machine instruction without calling the cache.
*
* @note The implementation of this method is generated by the ISA
* parser script.
*
* @warn This method takes a pre-decoded instruction as its
* argument. It should typically not be called directly.
*
* @param mach_inst The binary instruction to decode.
* @retval A pointer to the corresponding StaticInst object.
*/
StaticInstPtr decodeInst(ExtMachInst mach_inst);
/**
* Take over the state from an old decoder when switching CPUs.
*
* @param old Decoder used in old CPU
*/
void takeOverFrom(Decoder *old) {}
public: // ARM-specific decoder state manipulation
void setContext(FPSCR fpscr)
{
fpscrLen = fpscr.len;
fpscrStride = fpscr.stride;
}
};
} // namespace ArmISA
#endif // __ARCH_ARM_DECODER_HH__
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