src/arch/alpha/decoder.hh

   1 /*
   2  * Copyright (c) 2012 Google
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met: redistributions of source code must retain the above copyright
   8  * notice, this list of conditions and the following disclaimer;
   9  * redistributions in binary form must reproduce the above copyright
  10  * notice, this list of conditions and the following disclaimer in the
  11  * documentation and/or other materials provided with the distribution;
  12  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  *
  28  * Authors: Gabe Black
  29  */
  30
  31 #ifndef __ARCH_ALPHA_DECODER_HH__
  32 #define __ARCH_ALPHA_DECODER_HH__
  33
  34 #include "arch/generic/decode_cache.hh"
  35 #include "arch/types.hh"
  36 #include "cpu/static_inst.hh"
  37 #include "sim/full_system.hh"
  38
  39 namespace AlphaISA
  40 {
  41
  42 class ISA;
  43 class Decoder
  44 {
  45   protected:
  46     // The extended machine instruction being generated
  47     ExtMachInst ext_inst;
  48     bool instDone;
  49
  50   public:
  51     Decoder(ISA* isa = nullptr) : instDone(false)
  52     {}
  53
  54     void
  55     process()
  56     { }
  57
  58     void
  59     reset()
  60     {
  61         instDone = false;
  62     }
  63
  64     // Use this to give data to the predecoder. This should be used
  65     // when there is control flow.
  66     void
  67     moreBytes(const PCState &pc, Addr fetchPC, MachInst inst)
  68     {
  69         ext_inst = inst;
  70         instDone = true;
  71         if (FullSystem)
  72             ext_inst |= (static_cast<ExtMachInst>(pc.pc() & 0x1) << 32);
  73     }
  74
  75     bool
  76     needMoreBytes()
  77     {
  78         return true;
  79     }
  80
  81     bool
  82     instReady()
  83     {
  84         return instDone;
  85     }
  86
  87     void takeOverFrom(Decoder * old) {}
  88
  89   protected:
  90     /// A cache of decoded instruction objects.
  91     static GenericISA::BasicDecodeCache defaultCache;
  92
  93   public:
  94     StaticInstPtr decodeInst(ExtMachInst mach_inst);
  95
  96     /// Decode a machine instruction.
  97     /// @param mach_inst The binary instruction to decode.
  98     /// @retval A pointer to the corresponding StaticInst object.
  99     StaticInstPtr
 100     decode(ExtMachInst mach_inst, Addr addr)
 101     {
 102         return defaultCache.decode(this, mach_inst, addr);
 103     }
 104
 105     StaticInstPtr
 106     decode(AlphaISA::PCState &nextPC)
 107     {
 108         if (!instDone)
 109             return NULL;
 110         instDone = false;
 111         return decode(ext_inst, nextPC.instAddr());
 112     }
 113 };
 114
 115 } // namespace AlphaISA
 116
 117 #endif // __ARCH_ALPHA_DECODER_HH__