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 Decoder
  43 {
  44   protected:
  45     // The extended machine instruction being generated
  46     ExtMachInst ext_inst;
  47     bool instDone;
  48
  49   public:
  50     Decoder() : instDone(false)
  51     {}
  52
  53     void
  54     process()
  55     { }
  56
  57     void
  58     reset()
  59     {
  60         instDone = false;
  61     }
  62
  63     // Use this to give data to the predecoder. This should be used
  64     // when there is control flow.
  65     void
  66     moreBytes(const PCState &pc, Addr fetchPC, MachInst inst)
  67     {
  68         ext_inst = inst;
  69         instDone = true;
  70         if (FullSystem)
  71             ext_inst |= (static_cast<ExtMachInst>(pc.pc() & 0x1) << 32);
  72     }
  73
  74     bool
  75     needMoreBytes()
  76     {
  77         return true;
  78     }
  79
  80     bool
  81     instReady()
  82     {
  83         return instDone;
  84     }
  85
  86     void takeOverFrom(Decoder * old) {}
  87
  88   protected:
  89     /// A cache of decoded instruction objects.
  90     static GenericISA::BasicDecodeCache defaultCache;
  91
  92   public:
  93     StaticInstPtr decodeInst(ExtMachInst mach_inst);
  94
  95     /// Decode a machine instruction.
  96     /// @param mach_inst The binary instruction to decode.
  97     /// @retval A pointer to the corresponding StaticInst object.
  98     StaticInstPtr
  99     decode(ExtMachInst mach_inst, Addr addr)
 100     {
 101         return defaultCache.decode(this, mach_inst, addr);
 102     }
 103
 104     StaticInstPtr
 105     decode(AlphaISA::PCState &nextPC)
 106     {
 107         if (!instDone)
 108             return NULL;
 109         instDone = false;
 110         return decode(ext_inst, nextPC.instAddr());
 111     }
 112 };
 113
 114 } // namespace AlphaISA
 115
 116 #endif // __ARCH_ALPHA_DECODER_HH__