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 "arch/types.hh"
  37 #include "base/types.hh"
  38 #include "config/the_isa.hh"
  39
  40 /** Return address stack class, implements a simple RAS. */
  41 class ReturnAddrStack
  42 {
  43   public:
  44     /** Creates a return address stack, but init() must be called prior to
  45      *  use.
  46      */
  47     ReturnAddrStack() {}
  48
  49     /** Initializes RAS with a specified number of entries.
  50      *  @param numEntries Number of entries in the RAS.
  51      */
  52     void init(unsigned numEntries);
  53
  54     void reset();
  55
  56     /** Returns the top address on the RAS. */
  57     TheISA::PCState top()
  58     { return addrStack[tos]; }
  59
  60     /** Returns the index of the top of the RAS. */
  61     unsigned topIdx()
  62     { return tos; }
  63
  64     /** Pushes an address onto the RAS. */
  65     void push(const TheISA::PCState &return_addr);
  66
  67     /** Pops the top address from the RAS. */
  68     void pop();
  69
  70     /** Changes index to the top of the RAS, and replaces the top address with
  71      *  a new target.
  72      *  @param top_entry_idx The index of the RAS that will now be the top.
  73      *  @param restored The new target address of the new top of the RAS.
  74      */
  75     void restore(unsigned top_entry_idx, const TheISA::PCState &restored);
  76
  77      bool empty() { return usedEntries == 0; }
  78
  79      bool full() { return usedEntries == numEntries; }
  80   private:
  81     /** Increments the top of stack index. */
  82     inline void incrTos()
  83     { if (++tos == numEntries) tos = 0; }
  84
  85     /** Decrements the top of stack index. */
  86     inline void decrTos()
  87     { tos = (tos == 0 ? numEntries - 1 : tos - 1); }
  88
  89     /** The RAS itself. */
  90     std::vector<TheISA::PCState> addrStack;
  91
  92     /** The number of entries in the RAS. */
  93     unsigned numEntries;
  94
  95     /** The number of used entries in the RAS. */
  96     unsigned usedEntries;
  97
  98     /** The top of stack index. */
  99     unsigned tos;
 100 };
 101
 102 #endif // __CPU_O3_RAS_HH__