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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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punk@28
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30 import Trace::*;
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31
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32 // Local includes
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33 `include "asim/provides/low_level_platform_interface.bsh"
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34 `include "asim/provides/soft_connections.bsh"
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35 `include "asim/provides/processor_library.bsh"
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36 `include "asim/provides/fpga_components.bsh"
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37 `include "asim/provides/common_services.bsh"
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38 `include "asim/dict/STATS_INST_CACHE.bsh"
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39
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40 interface ICache#( type req_t, type resp_t );
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41
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42 // Interface from processor to cache
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43 interface Server#(req_t,resp_t) proc_server;
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44
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45 // Interface from cache to main memory
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46 interface Client#(MainMemReq,MainMemResp) mmem_client;
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47
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48 // Interface for enabling/disabling statistics
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49 interface Put#(Bool) statsEn_put;
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50
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51 endinterface
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52
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53 //----------------------------------------------------------------------
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54 // Cache Types
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55 //----------------------------------------------------------------------
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56
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57 typedef 10 CacheLineIndexSz;
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58 typedef 20 CacheLineTagSz;
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59 typedef 32 CacheLineSz;
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60
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61 typedef Bit#(CacheLineIndexSz) CacheLineIndex;
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62 typedef Bit#(CacheLineTagSz) CacheLineTag;
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63 typedef Bit#(CacheLineSz) CacheLine;
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64
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65 typedef enum
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66 {
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67 Init,
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68 Access,
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69 Evict,
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70 RefillReq,
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71 RefillResp
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72 }
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73 CacheStage
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74 deriving (Eq,Bits);
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75
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76 //----------------------------------------------------------------------
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77 // Helper functions
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78 //----------------------------------------------------------------------
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79
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80 function Bit#(AddrSz) getAddr( InstReq req );
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81
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82 Bit#(AddrSz) addr = ?;
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83 case ( req ) matches
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84 tagged LoadReq .ld : addr = ld.addr;
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85 tagged StoreReq .st : addr = st.addr;
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86 endcase
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87
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88 return addr;
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89
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90 endfunction
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91
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92 function CacheLineIndex getCacheLineIndex( InstReq req );
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93 Bit#(AddrSz) addr = getAddr(req);
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94 Bit#(CacheLineIndexSz) index = truncate( addr >> 2 );
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95 return index;
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96 endfunction
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97
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98 function CacheLineTag getCacheLineTag( InstReq req );
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99 Bit#(AddrSz) addr = getAddr(req);
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100 Bit#(CacheLineTagSz) tag = truncate( addr >> fromInteger(valueOf(CacheLineIndexSz)) >> 2 );
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101 return tag;
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102 endfunction
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103
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104 function Bit#(AddrSz) getCacheLineAddr( InstReq req );
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105 Bit#(AddrSz) addr = getAddr(req);
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106 return ((addr >> 2) << 2);
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107 endfunction
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108
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109 //----------------------------------------------------------------------
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110 // Main module
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111 //----------------------------------------------------------------------
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112
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113 module [CONNECTED_MODULE] mkInstCache( ICache#(InstReq,InstResp) );
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114
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115 //-----------------------------------------------------------
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116 // State
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117
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118 Reg#(CacheStage) stage <- mkReg(Init);
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119
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120 LUTRAM#(CacheLineIndex,Maybe#(CacheLineTag)) cacheTagRam <- mkLUTRAMU_RegFile();
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121 LUTRAM#(CacheLineIndex,CacheLine) cacheDataRam <- mkLUTRAMU_RegFile();
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122
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123 FIFO#(InstReq) reqQ <- mkFIFO();
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124 FIFOF#(InstResp) respQ <- mkBFIFOF1();
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125
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126 FIFO#(MainMemReq) mainMemReqQ <- mkBFIFO1();
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127 FIFO#(MainMemResp) mainMemRespQ <- mkFIFO();
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128
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129 Reg#(CacheLineIndex) initCounter <- mkReg(1);
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130
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131 // Statistics state
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132
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133 Reg#(Bool) statsEn <- mkReg(False);
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134
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135 STAT num_accesses <- mkStatCounter(`STATS_INST_CACHE_NUM_ACCESSES);
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136 STAT num_misses <- mkStatCounter(`STATS_INST_CACHE_NUM_MISSES);
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137 STAT num_evictions <- mkStatCounter(`STATS_INST_CACHE_NUM_EVICTIONS);
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138
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139 //-----------------------------------------------------------
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140 // Name some wires
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141
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142 let req = reqQ.first();
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143 let reqIndex = getCacheLineIndex(req);
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144 let reqTag = getCacheLineTag(req);
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145 let reqCacheLineAddr = getCacheLineAddr(req);
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146 let refill = mainMemRespQ.first();
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147
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148 //-----------------------------------------------------------
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149 // Initialize
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150
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151 rule init ( stage == Init );
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152 traceTiny("mkInstCacheBlocking", "stage","i");
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153 initCounter <= initCounter + 1;
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154 cacheTagRam.upd(initCounter,Invalid);
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155 if ( initCounter == 0 )
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156 stage <= Access;
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157 endrule
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158
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159 //-----------------------------------------------------------
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160 // Cache access rule
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161
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162 rule access ( (stage == Access) && respQ.notFull() );
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163
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164 // Statistics
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165
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166 if ( statsEn )
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167 num_accesses.incr();
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168
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169 // Check tag and valid bit to see if this is a hit or a miss
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170
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171 Maybe#(CacheLineTag) cacheLineTag = cacheTagRam.sub(reqIndex);
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172
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173 // Handle cache hits ...
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174
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175 if ( isValid(cacheLineTag) && ( unJust(cacheLineTag) == reqTag ) )
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176 begin
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177 traceTiny("mkInstCacheBlocking", "hitMiss","h");
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178 reqQ.deq();
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179
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180 case ( req ) matches
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181
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182 tagged LoadReq .ld :
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183 respQ.enq( LoadResp { tag : ld.tag, data : cacheDataRam.sub(reqIndex) } );
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184
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185 tagged StoreReq .st :
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186 $display( " RTL-ERROR : %m : Stores are not allowed on the inst port!" );
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187
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188 endcase
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189
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190 end
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191
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192 // Handle cache misses - since lines in instruction cache are
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193 // never dirty we can always immediately issue a refill request
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194
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195 else
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196 begin
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197 traceTiny("mkInstCacheBlocking", "hitMiss","m");
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198 if ( statsEn )
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199 num_misses.incr();
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200 if ( statsEn )
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201 if ( isJust(cacheLineTag) )
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202 num_evictions.incr();
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203
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204 MainMemReq rfReq
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205 = LoadReq { tag : 0,
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206 addr : reqCacheLineAddr };
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207
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208 mainMemReqQ.enq(rfReq);
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209 stage <= RefillResp;
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210 end
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211
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212 endrule
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213
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214 //-----------------------------------------------------------
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215 // Refill response rule
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216
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217 rule refillResp ( stage == RefillResp );
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218 traceTiny("mkInstCacheBlocking", "stage","R");
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219 traceTiny("mkInstCacheBlocking", "refill",refill);
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220
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221 // Write the new data into the cache and update the tag
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222
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223 mainMemRespQ.deq();
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224 case ( mainMemRespQ.first() ) matches
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225
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226 tagged LoadResp .ld :
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227 begin
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228 cacheTagRam.upd(reqIndex,Valid(reqTag));
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229 cacheDataRam.upd(reqIndex,ld.data);
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230 end
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231
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232 tagged StoreResp .st :
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233 noAction;
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234
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235 endcase
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236
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237 stage <= Access;
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238 endrule
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239
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240 //-----------------------------------------------------------
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241 // Methods
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242
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243 interface Client mmem_client;
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244 interface Get request = fifoToGet(mainMemReqQ);
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245 interface Put response = fifoToPut(mainMemRespQ);
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246 endinterface
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247
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248 interface Server proc_server;
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249 interface Put request = tracePut("mkInstCacheBlocking", "reqTiny",fifoToPut(reqQ));
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250 interface Get response = traceGet("mkInstCacheBlocking", "respTiny",fifofToGet(respQ));
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251 endinterface
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252
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253 interface Put statsEn_put = regToPut(statsEn);
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254
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255 endmodule
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256
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