src/cpu/pred/ras.hh

   1 /*
   2  * Copyright (c) 2004-2005 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: Kevin Lim
  29  */
  30
  31 #ifndef __CPU_O3_RAS_HH__
  32 #define __CPU_O3_RAS_HH__
  33
  34 #include <vector>
  35
  36 #include "base/types.hh"
  37
  38 /** Return address stack class, implements a simple RAS. */
  39 class ReturnAddrStack
  40 {
  41   public:
  42     /** Creates a return address stack, but init() must be called prior to
  43      *  use.
  44      */
  45     ReturnAddrStack() {}
  46
  47     /** Initializes RAS with a specified number of entries.
  48      *  @param numEntries Number of entries in the RAS.
  49      */
  50     void init(unsigned numEntries);
  51
  52     void reset();
  53
  54     /** Returns the top address on the RAS. */
  55     Addr top()
  56     { return addrStack[tos]; }
  57
  58     /** Returns the index of the top of the RAS. */
  59     unsigned topIdx()
  60     { return tos; }
  61
  62     /** Pushes an address onto the RAS. */
  63     void push(const Addr &return_addr);
  64
  65     /** Pops the top address from the RAS. */
  66     void pop();
  67
  68     /** Changes index to the top of the RAS, and replaces the top address with
  69      *  a new target.
  70      *  @param top_entry_idx The index of the RAS that will now be the top.
  71      *  @param restored_target The new target address of the new top of the RAS.
  72      */
  73     void restore(unsigned top_entry_idx, const Addr &restored_target);
  74
  75      bool empty() { return usedEntries == 0; }
  76
  77      bool full() { return usedEntries == numEntries; }
  78   private:
  79     /** Increments the top of stack index. */
  80     inline void incrTos()
  81     { if (++tos == numEntries) tos = 0; }
  82
  83     /** Decrements the top of stack index. */
  84     inline void decrTos()
  85     { tos = (tos == 0 ? numEntries - 1 : tos - 1); }
  86
  87     /** The RAS itself. */
  88     std::vector<Addr> addrStack;
  89
  90     /** The number of entries in the RAS. */
  91     unsigned numEntries;
  92
  93     /** The number of used entries in the RAS. */
  94     unsigned usedEntries;
  95
  96     /** The top of stack index. */
  97     unsigned tos;
  98 };
  99
 100 #endif // __CPU_O3_RAS_HH__