| /* |
| * Copyright 2020 Google, Inc. |
| * |
| * 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. |
| */ |
| |
| #ifndef __ARCH_GENERIC_DECODER_HH__ |
| #define __ARCH_GENERIC_DECODER_HH__ |
| |
| #include "arch/generic/pcstate.hh" |
| #include "base/bitfield.hh" |
| #include "base/intmath.hh" |
| #include "base/types.hh" |
| #include "cpu/static_inst_fwd.hh" |
| #include "params/InstDecoder.hh" |
| #include "sim/sim_object.hh" |
| |
| namespace gem5 |
| { |
| |
| class InstDecoder : public SimObject |
| { |
| protected: |
| void *_moreBytesPtr; |
| size_t _moreBytesSize; |
| Addr _pcMask; |
| |
| bool instDone = false; |
| bool outOfBytes = true; |
| |
| public: |
| template <typename MoreBytesType> |
| InstDecoder(const InstDecoderParams ¶ms, MoreBytesType *mb_buf) : |
| SimObject(params), _moreBytesPtr(mb_buf), |
| _moreBytesSize(sizeof(MoreBytesType)), |
| _pcMask(~mask(floorLog2(_moreBytesSize))) |
| {} |
| |
| virtual StaticInstPtr fetchRomMicroop( |
| MicroPC micropc, StaticInstPtr curMacroop); |
| virtual void |
| reset() |
| { |
| instDone = false; |
| outOfBytes = true; |
| } |
| |
| template <class Type> |
| Type & |
| as() |
| { |
| return *static_cast<Type *>(this); |
| } |
| |
| template <class Type> |
| const Type & |
| as() const |
| { |
| return *static_cast<const Type *>(this); |
| } |
| |
| /** |
| * Take over the state from an old decoder when switching CPUs. |
| * |
| * @param old Decoder used in old CPU |
| */ |
| virtual void |
| takeOverFrom(InstDecoder *old) |
| { |
| instDone = old->instDone; |
| outOfBytes = old->outOfBytes; |
| } |
| |
| void *moreBytesPtr() const { return _moreBytesPtr; } |
| size_t moreBytesSize() const { return _moreBytesSize; } |
| Addr pcMask() const { return _pcMask; } |
| |
| /** |
| * 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; } |
| |
| /** |
| * 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; } |
| |
| /** |
| * 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(PCStateBase &). |
| * |
| * 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. |
| */ |
| virtual void moreBytes(const PCStateBase &pc, Addr fetchPC) = 0; |
| |
| /** |
| * 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()). |
| */ |
| virtual StaticInstPtr decode(PCStateBase &pc) = 0; |
| }; |
| |
| } // namespace gem5 |
| |
| #endif // __ARCH_DECODER_GENERIC_HH__ |