rob.hh revision 1689 
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
29// Todo: Probably add in support for scheduling events (more than one as
30// well) on the case of the ROB being empty or full.  Considering tracking
31// free entries instead of insts in ROB.  Differentiate between squashing
32// all instructions after the instruction, and all instructions after *and*
33// including that instruction.
34
35#ifndef __CPU_BETA_CPU_ROB_HH__
36#define __CPU_BETA_CPU_ROB_HH__
37
38#include <utility>
39#include <vector>
40
41/**
42 * ROB class.  Uses the instruction list that exists within the CPU to
43 * represent the ROB.  This class doesn't contain that list, but instead
44 * a pointer to the CPU to get access to the list.  The ROB, in this first
45 * implementation, is largely what drives squashing.
46 */
47template <class Impl>
48class ROB
49{
50  public:
51    //Typedefs from the Impl.
52    typedef typename Impl::FullCPU FullCPU;
53    typedef typename Impl::DynInstPtr DynInstPtr;
54
55    typedef std::pair<RegIndex, PhysRegIndex> UnmapInfo_t;
56    typedef typename list<DynInstPtr>::iterator InstIt_t;
57
58  public:
59    /** ROB constructor.
60     *  @params _numEntries Number of entries in ROB.
61     *  @params _squashWidth Number of instructions that can be squashed in a
62     *                       single cycle.
63     */
64    ROB(unsigned _numEntries, unsigned _squashWidth);
65
66    /** Function to set the CPU pointer, necessary due to which object the ROB
67     *  is created within.
68     *  @params cpu_ptr Pointer to the implementation specific full CPU object.
69     */
70    void setCPU(FullCPU *cpu_ptr);
71
72    /** Function to insert an instruction into the ROB.  The parameter inst is
73     *  not truly required, but is useful for checking correctness.  Note
74     *  that whatever calls this function must ensure that there is enough
75     *  space within the ROB for the new instruction.
76     *  @params inst The instruction being inserted into the ROB.
77     *  @todo Remove the parameter once correctness is ensured.
78     */
79    void insertInst(DynInstPtr &inst);
80
81    /** Returns pointer to the head instruction within the ROB.  There is
82     *  no guarantee as to the return value if the ROB is empty.
83     *  @retval Pointer to the DynInst that is at the head of the ROB.
84     */
85    DynInstPtr readHeadInst() { return cpu->instList.front(); }
86
87    DynInstPtr readTailInst() { return (*tail); }
88
89    void retireHead();
90
91    bool isHeadReady();
92
93    unsigned numFreeEntries();
94
95    bool isFull()
96    { return numInstsInROB == numEntries; }
97
98    bool isEmpty()
99    { return numInstsInROB == 0; }
100
101    void doSquash();
102
103    void squash(InstSeqNum squash_num);
104
105    uint64_t readHeadPC();
106
107    uint64_t readHeadNextPC();
108
109    InstSeqNum readHeadSeqNum();
110
111    uint64_t readTailPC();
112
113    InstSeqNum readTailSeqNum();
114
115    /** Checks if the ROB is still in the process of squashing instructions.
116     *  @retval Whether or not the ROB is done squashing.
117     */
118    bool isDoneSquashing() const { return doneSquashing; }
119
120    /** This is more of a debugging function than anything.  Use
121     *  numInstsInROB to get the instructions in the ROB unless you are
122     *  double checking that variable.
123     */
124    int countInsts();
125
126  private:
127
128    /** Pointer to the CPU. */
129    FullCPU *cpu;
130
131    /** Number of instructions in the ROB. */
132    unsigned numEntries;
133
134    /** Number of instructions that can be squashed in a single cycle. */
135    unsigned squashWidth;
136
137    /** Iterator pointing to the instruction which is the last instruction
138     *  in the ROB.  This may at times be invalid (ie when the ROB is empty),
139     *  however it should never be incorrect.
140     */
141    InstIt_t tail;
142
143    /** Iterator used for walking through the list of instructions when
144     *  squashing.  Used so that there is persistent state between cycles;
145     *  when squashing, the instructions are marked as squashed but not
146     *  immediately removed, meaning the tail iterator remains the same before
147     *  and after a squash.
148     *  This will always be set to cpu->instList.end() if it is invalid.
149     */
150    InstIt_t squashIt;
151
152    /** Number of instructions in the ROB. */
153    int numInstsInROB;
154
155    /** The sequence number of the squashed instruction. */
156    InstSeqNum squashedSeqNum;
157
158    /** Is the ROB done squashing. */
159    bool doneSquashing;
160};
161
162#endif //__CPU_BETA_CPU_ROB_HH__
163