1/*
2 * Copyright (c) 2005-2006 The Regents of The University of Michigan
3 * Copyright (c) 2013 Advanced Micro Devices, Inc.
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions are
8 * met: redistributions of source code must retain the above copyright

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41#include "base/trace.hh"
42#include "config/the_isa.hh"
43#include "cpu/o3/comm.hh"
44#include "debug/Scoreboard.hh"
45
46/**
47 * Implements a simple scoreboard to track which registers are
48 * ready. This class operates on the unified physical register space,
49 * so integer and floating-point registers are not distinguished. For
50 * convenience, it also accepts operations on the physical-space
51 * mapping of misc registers, which are numbered starting after the
52 * end of the actual physical register file. However, there is no
53 * actual scoreboard for misc registers, and they are always
54 * considered ready.
55 */
56class Scoreboard
57{
58 private:
59 /** The object name, for DPRINTF. We have to declare this
60 * explicitly because Scoreboard is not a SimObject. */
61 const std::string _name;
62
63 /** Scoreboard of physical integer registers, saying whether or not they
64 * are ready. */
65 std::vector<bool> regScoreBoard;
66
67 /** The number of actual physical registers */
68 unsigned numPhysRegs;
69
70 /**
71 * The total number of registers which can be indexed, including
72 * the misc registers that come after the physical registers and
73 * which are hardwired to be always considered ready.
74 */
75 unsigned M5_CLASS_VAR_USED numTotalRegs;
76
77 /** The index of the zero register. */
78 PhysRegIndex zeroRegIdx;
79
80 /** The index of the FP zero register. */
81 PhysRegIndex fpZeroRegIdx;
82
83 bool isZeroReg(PhysRegIndex idx) const
84 {
85 return (idx == zeroRegIdx ||
86 (THE_ISA == ALPHA_ISA && idx == fpZeroRegIdx));
87 }
88
89 public:
90 /** Constructs a scoreboard.
91 * @param _numPhysicalRegs Number of physical registers.
92 * @param _numMiscRegs Number of miscellaneous registers.
93 * @param _zeroRegIdx Index of the zero register.
94 * @param _fpZeroRegIdx Index of the FP zero register (if any, currently
95 * used only for Alpha).
96 */
97 Scoreboard(const std::string &_my_name,
98 unsigned _numPhysicalRegs,
99 unsigned _numMiscRegs,
100 PhysRegIndex _zeroRegIdx,
101 PhysRegIndex _fpZeroRegIdx);
102
103 /** Destructor. */
104 ~Scoreboard() {}
105
106 /** Returns the name of the scoreboard. */
107 std::string name() const { return _name; };
108
109 /** Checks if the register is ready. */
110 bool getReg(PhysRegIndex reg_idx) const
111 {
112 assert(reg_idx < numTotalRegs);
113
114 if (reg_idx >= numPhysRegs) {
115 // misc regs are always ready
116 return true;
117 }
118
119 bool ready = regScoreBoard[reg_idx];
120
121 if (isZeroReg(reg_idx))
122 assert(ready);
123
124 return ready;
125 }
126
127 /** Sets the register as ready. */
128 void setReg(PhysRegIndex reg_idx)
129 {
130 assert(reg_idx < numTotalRegs);
131
132 if (reg_idx >= numPhysRegs) {
133 // misc regs are always ready, ignore attempts to change that
134 return;
135 }
136
137 DPRINTF(Scoreboard, "Setting reg %i as ready\n", reg_idx);
138
139 assert(reg_idx < numTotalRegs);
140 regScoreBoard[reg_idx] = true;
141 }
142
143 /** Sets the register as not ready. */
144 void unsetReg(PhysRegIndex reg_idx)
145 {
146 assert(reg_idx < numTotalRegs);
147
148 if (reg_idx >= numPhysRegs) {
149 // misc regs are always ready, ignore attempts to change that
150 return;
151 }
152
153 // zero reg should never be marked unready
154 if (isZeroReg(reg_idx))
155 return;
156
157 regScoreBoard[reg_idx] = false;
158 }
159
160};
161
162#endif