src/arch/sparc/predecoder.hh

   1 /*
   2  * Copyright (c) 2006 The Regents of The University of Michigan
   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_SPARC_PREDECODER_HH__
  32 #define __ARCH_SPARC_PREDECODER_HH__
  33
  34 #include "arch/sparc/registers.hh"
  35 #include "arch/sparc/types.hh"
  36 #include "base/bitfield.hh"
  37 #include "base/misc.hh"
  38 #include "base/types.hh"
  39 #include "cpu/thread_context.hh"
  40
  41 class ThreadContext;
  42
  43 namespace SparcISA
  44 {
  45
  46 class Predecoder
  47 {
  48   protected:
  49     ThreadContext * tc;
  50     // The extended machine instruction being generated
  51     ExtMachInst emi;
  52     bool emiIsReady;
  53
  54   public:
  55     Predecoder(ThreadContext * _tc) : tc(_tc), emiIsReady(false)
  56     {}
  57
  58     ThreadContext *
  59     getTC()
  60     {
  61         return tc;
  62     }
  63
  64     void
  65     setTC(ThreadContext * _tc)
  66     {
  67         tc = _tc;
  68     }
  69
  70     void process() {}
  71
  72     void
  73     reset()
  74     {
  75         emiIsReady = false;
  76     }
  77
  78     // Use this to give data to the predecoder. This should be used
  79     // when there is control flow.
  80     void
  81     moreBytes(const PCState &pc, Addr fetchPC, MachInst inst)
  82     {
  83         emi = inst;
  84         // The I bit, bit 13, is used to figure out where the ASI
  85         // should come from. Use that in the ExtMachInst. This is
  86         // slightly redundant, but it removes the need to put a condition
  87         // into all the execute functions
  88         if (inst & (1 << 13)) {
  89             emi |= (static_cast<ExtMachInst>(
  90                         tc->readMiscRegNoEffect(MISCREG_ASI))
  91                     << (sizeof(MachInst) * 8));
  92         } else {
  93             emi |= (static_cast<ExtMachInst>(bits(inst, 12, 5))
  94                     << (sizeof(MachInst) * 8));
  95         }
  96         emiIsReady = true;
  97     }
  98
  99     bool
 100     needMoreBytes()
 101     {
 102         return true;
 103     }
 104
 105     bool
 106     extMachInstReady()
 107     {
 108         return emiIsReady;
 109     }
 110
 111     // This returns a constant reference to the ExtMachInst to avoid a copy
 112     const ExtMachInst &
 113     getExtMachInst(PCState &pcState)
 114     {
 115         emiIsReady = false;
 116         return emi;
 117     }
 118 };
 119 };
 120
 121 #endif // __ARCH_SPARC_PREDECODER_HH__