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1 // The MIT License
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2
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3 // Copyright (c) 2009 Massachusetts Institute of Technology
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4
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5 // Permission is hereby granted, free of charge, to any person obtaining a copy
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6 // of this software and associated documentation files (the "Software"), to deal
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7 // in the Software without restriction, including without limitation the rights
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8 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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9 // copies of the Software, and to permit persons to whom the Software is
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10 // furnished to do so, subject to the following conditions:
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11
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12 // The above copyright notice and this permission notice shall be included in
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13 // all copies or substantial portions of the Software.
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14
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15 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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16 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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17 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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18 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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19 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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20 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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21 // THE SOFTWARE.
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22
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23 import Connectable::*;
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24 import GetPut::*;
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25 import ClientServer::*;
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26 import RegFile::*;
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27 import FIFO::*;
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28 import FIFOF::*;
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29 import RWire::*;
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30
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31 // Local includes
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32 `include "asim/provides/low_level_platform_interface.bsh"
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33 `include "asim/provides/soft_connections.bsh"
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34 `include "asim/provides/processor_library.bsh"
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35 `include "asim/provides/fpga_components.bsh"
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36 `include "asim/provides/common_services.bsh"
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37 `include "asim/dict/STATS_INST_CACHE.bsh"
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38
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39 interface ICache#( type req_t, type resp_t );
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40
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41 // Interface from processor to cache
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42 interface Server#(req_t,resp_t) proc_server;
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43
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44 // Interface from cache to main memory
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45 interface Client#(MainMemReq,MainMemResp) mmem_client;
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46
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47 // Interface for enabling/disabling statistics
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48 interface Put#(Bool) statsEn_put;
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49
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50 endinterface
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51
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52 //----------------------------------------------------------------------
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53 // Cache Types
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54 //----------------------------------------------------------------------
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55
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56 typedef 10 CacheLineIndexSz;
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57 typedef 20 CacheLineTagSz;
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58 typedef 32 CacheLineSz;
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59
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60 typedef Bit#(CacheLineIndexSz) CacheLineIndex;
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61 typedef Bit#(CacheLineTagSz) CacheLineTag;
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62 typedef Bit#(CacheLineSz) CacheLine;
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63
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64 typedef enum
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65 {
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66 Init,
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67 Access,
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68 Evict,
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69 RefillReq,
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70 RefillResp
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71 }
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72 CacheStage
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73 deriving (Eq,Bits);
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74
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75 //----------------------------------------------------------------------
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76 // Helper functions
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77 //----------------------------------------------------------------------
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78
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79 function Bit#(AddrSz) getAddr( InstReq req );
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80
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81 Bit#(AddrSz) addr = ?;
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82 case ( req ) matches
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83 tagged LoadReq .ld : addr = ld.addr;
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84 tagged StoreReq .st : addr = st.addr;
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85 endcase
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86
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87 return addr;
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88
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89 endfunction
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90
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91 function CacheLineIndex getCacheLineIndex( InstReq req );
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92 Bit#(AddrSz) addr = getAddr(req);
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93 Bit#(CacheLineIndexSz) index = truncate( addr >> 2 );
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94 return index;
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95 endfunction
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96
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97 function CacheLineTag getCacheLineTag( InstReq req );
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98 Bit#(AddrSz) addr = getAddr(req);
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99 Bit#(CacheLineTagSz) tag = truncate( addr >> fromInteger(valueOf(CacheLineIndexSz)) >> 2 );
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100 return tag;
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101 endfunction
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102
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103 function Bit#(AddrSz) getCacheLineAddr( InstReq req );
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104 Bit#(AddrSz) addr = getAddr(req);
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105 return ((addr >> 2) << 2);
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106 endfunction
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107
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108 //----------------------------------------------------------------------
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109 // Main module
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110 //----------------------------------------------------------------------
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111
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112 module [CONNECTED_MODULE] mkInstCache( ICache#(InstReq,InstResp) );
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113
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114 //-----------------------------------------------------------
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115 // State
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116
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117 Reg#(CacheStage) stage <- mkReg(Init);
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118
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119 LUTRAM#(CacheLineIndex,Maybe#(CacheLineTag)) cacheTagRam <- mkLUTRAMU_RegFile();
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120 LUTRAM#(CacheLineIndex,CacheLine) cacheDataRam <- mkLUTRAMU_RegFile();
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121
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122 FIFO#(InstReq) reqQ <- mkFIFO();
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123 FIFOF#(InstResp) respQ <- mkBFIFOF1();
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124
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125 FIFO#(MainMemReq) mainMemReqQ <- mkBFIFO1();
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126 FIFO#(MainMemResp) mainMemRespQ <- mkFIFO();
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127
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128 Reg#(CacheLineIndex) initCounter <- mkReg(1);
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129
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130 // Statistics state
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131
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132 Reg#(Bool) statsEn <- mkReg(False);
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133
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134 STAT num_accesses <- mkStatCounter(`STATS_INST_CACHE_NUM_ACCESSES);
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135 STAT num_misses <- mkStatCounter(`STATS_INST_CACHE_NUM_MISSES);
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136 STAT num_evictions <- mkStatCounter(`STATS_INST_CACHE_NUM_EVICTIONS);
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137
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138 //-----------------------------------------------------------
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139 // Name some wires
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140
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141 let req = reqQ.first();
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142 let reqIndex = getCacheLineIndex(req);
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143 let reqTag = getCacheLineTag(req);
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144 let reqCacheLineAddr = getCacheLineAddr(req);
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145 let refill = mainMemRespQ.first();
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146
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147 //-----------------------------------------------------------
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148 // Initialize
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149
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150 rule init ( stage == Init );
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151 traceTiny("mkInstCacheBlocking", "stage","i");
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152 initCounter <= initCounter + 1;
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153 cacheTagRam.upd(initCounter,Invalid);
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154 if ( initCounter == 0 )
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155 stage <= Access;
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156 endrule
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157
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158 //-----------------------------------------------------------
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159 // Cache access rule
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160
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161 rule access ( (stage == Access) && respQ.notFull() );
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162
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163 // Statistics
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164
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165 if ( statsEn )
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166 num_accesses.incr();
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167
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168 // Check tag and valid bit to see if this is a hit or a miss
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169
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170 Maybe#(CacheLineTag) cacheLineTag = cacheTagRam.sub(reqIndex);
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171
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172 // Handle cache hits ...
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173
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174 if ( isValid(cacheLineTag) && ( unJust(cacheLineTag) == reqTag ) )
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175 begin
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176 traceTiny("mkInstCacheBlocking", "hitMiss","h");
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177 reqQ.deq();
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178
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179 case ( req ) matches
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180
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181 tagged LoadReq .ld :
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182 respQ.enq( LoadResp { tag : ld.tag, data : cacheDataRam.sub(reqIndex) } );
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183
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184 tagged StoreReq .st :
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185 $display( " RTL-ERROR : %m : Stores are not allowed on the inst port!" );
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186
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187 endcase
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188
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189 end
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190
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191 // Handle cache misses - since lines in instruction cache are
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192 // never dirty we can always immediately issue a refill request
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193
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194 else
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195 begin
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196 traceTiny("mkInstCacheBlocking", "hitMiss","m");
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197 if ( statsEn )
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198 num_misses.incr();
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199 if ( statsEn )
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200 if ( isJust(cacheLineTag) )
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201 num_evictions.incr();
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202
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203 MainMemReq rfReq
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204 = LoadReq { tag : 0,
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205 addr : reqCacheLineAddr };
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206
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207 mainMemReqQ.enq(rfReq);
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208 stage <= RefillResp;
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209 end
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210
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211 endrule
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212
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213 //-----------------------------------------------------------
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214 // Refill response rule
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215
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216 rule refillResp ( stage == RefillResp );
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217 traceTiny("mkInstCacheBlocking", "stage","R");
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218 traceTiny("mkInstCacheBlocking", "refill",refill);
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219
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220 // Write the new data into the cache and update the tag
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221
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222 mainMemRespQ.deq();
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223 case ( mainMemRespQ.first() ) matches
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224
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225 tagged LoadResp .ld :
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226 begin
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227 cacheTagRam.upd(reqIndex,Valid(reqTag));
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228 cacheDataRam.upd(reqIndex,ld.data);
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229 end
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230
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231 tagged StoreResp .st :
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232 noAction;
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233
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234 endcase
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235
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236 stage <= Access;
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237 endrule
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238
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239 //-----------------------------------------------------------
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240 // Methods
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241
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242 interface Client mmem_client;
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243 interface Get request = fifoToGet(mainMemReqQ);
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244 interface Put response = fifoToPut(mainMemRespQ);
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245 endinterface
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246
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247 interface Server proc_server;
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248 interface Put request = tracePut("mkInstCacheBlocking", "reqTiny",fifoToPut(reqQ));
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249 interface Get response = traceGet("mkInstCacheBlocking", "respTiny",fifofToGet(respQ));
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250 endinterface
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251
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252 interface Put statsEn_put = regToPut(statsEn);
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253
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254 endmodule
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255
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