3_02ifu

大型risc处理器设计源代码,这是书中的代码 基于流水线的risc cpu设计

                LAST_USE_PCU_PC,    // use delayed external PC                   a0149
                CLR_BTC,            // clear BTC                                 a0150
                CLR_MPC,            // clear MPC                                 a0151
                HIT,                // hit from caches                           a0152
                SHIFT;              // shift registers internal to IFU           a0153
                                                                                 a0154
                                                                                 a0155
  //                                                                             a0156
  // Combinational logic (outputs)                                               a0157
  //                                                                             a0158
  assign I_BUS = INSTR;     // instruction                                       a0159
  assign IFU_ADDR_BUS = PC; // PC is next fetch address for IFU                  a0160
                                                                                 a0161
  // Break memory access, if cache hit                                           a0162
  assign BREAK_MEM_ACC = (BTC_HIT | BTC_CORRECT | MPC_HIT) & ~NO_ACC & ~CP;      a0163
                                                                                 a0164
  // CTR in ID or BTC                                                            a0165
  assign CALL_NOW = (ID_BRANCH & ID_TYPE) | (BTC_HIT & BTC_TYPE) & ~BTC_CORRECT; a0166
                                                                                 a0167
  // Exception, if CTR in delay slot of another CTR                              a0168
  assign EXCEPT = (ID_BRANCH | ID_CTR) & (ID_LAST_BRANCH | ID_LAST_CTR);         a0169
                                                                                 a0170
  // Delay slot in IFU                                                           a0171
  assign DS_NOW = ID_BRANCH | ID_CTR;                                            a0172
                                                                                 a0173
  // IFU will fetch in next step                                                 a0174
  assign IFU_FETCH_RQ = ~NO_FETCH & WORK_IF;                                     a0175
                                                                                 a0176
  // BTC corrects branch                                                         a0177
  assign IFU_CORRECT = BTC_CORRECT;                                              a0178
                                                                                 a0179
  //                                                                             a0180
  // Combinational logic (internal)                                              a0181
  //                                                                             a0182
  assign BTC_CONFIG = CACHE_MODE[1:0]; // set BTC configuration                  a0183
  assign MPC_CONFIG = CACHE_MODE[3:2]; // set MPC configuration                  a0184
  assign CLR_BTC = CCLR | ~nRESET;     // clear BTC                              a0185
  assign CLR_MPC = CCLR | ~nRESET;     // clear MPC                              a0186
  assign HIT = BTC_HIT | MPC_HIT;      // hit in BTC or MPC                      a0187
                                                                                 a0188
  // Shift internal IFU pipeline                                                 a0189
  assign SHIFT = (~NO_ACC | HIT | BTC_CORRECT | EMERG_FETCH) & WORK_IF;          a0190
                                                                                 a0191
                                                                                 a0192
  //                                                                             a0193
  // Instances                                                                   a0194
  //                                                                             a0195
                                                                                 a0196
  // Branch-target cache                                                         a0197
  btc BTC (                                                                      a0198
     BTC_DELAYSLOT, BTC_PC, BTC_HIT, BTC_CORRECT, BTC_USE_LAST,                  a0199
     BTC_DIS_IDU, BTC_DIS_ALU, BTC_TAKEN, BTC_TYPE,                              a0200
     INSTR, PC, JPC, LPC, FLAGS_IF, FLAGS_FD, ID_CCODE,                          a0201
     BTC_CONFIG, ID_ANNUL, ID_BRANCH & ~EXT_BRANCH, ID_TYPE, DS_NOW, TAKEN,      a0202
     KU_MODE, LAST_KU_MODE, EMERG_FETCH, CLR_BTC, NEW_FLAGS, NO_ACC,             a0203
     WORK_IF, DO_IF, nRESET, CP                                                  a0204
  );                                                                             a0205
                                                                                 a0206
  // Multi-purpose cache                                                         a0207
  mpc MPC (                                                                      a0208
     MPC_INSTR, MPC_HIT,                                                         a0209
     ID_INSTR, PC, LPC, MPC_CONFIG, CLR_MPC,                                     a0210
     ID_BRANCH | ID_LAST_BRANCH | EXT_BRANCH,                                    a0211
     LAST_LDST, LAST_HIT, KU_MODE, LAST_KU_MODE, LAST_NO_ACC,                    a0212
     LAST_CORRECTION, WORK_IF, DO_IF, nRESET, CP                                 a0213
  );                                                                             a0214
                                                                                 a0215
  // Branch decision logic                                                       a0216
  bdl BDL (TAKEN, FLAGS_FD, ID_CCODE);                                           a0217
                                                                                 a0218
  // Program counter calculator                                                  a0219
  pcc PCC (                                                                      a0220
     PC, LPC, JPC, PC_1, PC_2, LPC_2,                                            a0221
     NEW_PC, ID_CPC, ID_DIST, ID_TYPE, SHIFT, CP                                 a0222
  );                                                                             a0223
                                                                                 a0224
  // Pipeline disable logic                                                      a0225
  pdl PDL (                                                                      a0226
     DIS_IDU, DIS_ALU,                                                           a0227
     MPC_HIT, BTC_HIT, BTC_CORRECT, BTC_DIS_IDU, BTC_DIS_ALU, NO_ACC,            a0228
     ID_BRANCH & ~ID_TYPE, ID_ANNUL, TAKEN                                       a0229
  );                                                                             a0230
                                                                                 a0231
  // Instruction decode logic                                                    a0232
  idl IDL (                                                                      a0233
     ID_INSTR, ID_CPC, ID_DIST, ID_CCODE,                                        a0234
     ID_ANNUL, ID_BRANCH, ID_LAST_BRANCH, ID_TYPE,                               a0235
     ID_CTR, ID_LAST_CTR,                                                        a0236
     INSTR, EMERG_FETCH, SHIFT, WORK_IF, WORK_FD, nRESET, CP                     a0237
   );                                                                            a0238
                                                                                 a0239
  // Serial mode controller                                                      a0240
  smc SMC (NO_FETCH, HIT, CACHE_MODE[4], WORK_IF, nRESET, CP);                   a0241
                                                                                 a0242
  // External PC logic                                                           a0243
  epl EPL (                                                                      a0244
     LAST_PC_BUS, LAST_USE_PCU_PC,                                               a0245
     PC_BUS, USE_PCU_PC, SHIFT, WORK_IF, nRESET, CP                              a0246
  );                                                                             a0247
                                                                                 a0248
  //                                                                             a0249
  // Reset status registers                                                      a0250
  //                                                                             a0251
  always @(negedge nRESET) begin                                                 a0252
    while (~nRESET) begin                                                        a0253
      NO_ACC = 1'b0;                                                             a0254
      EXT_BRANCH = 1'b0;                                                         a0255
      LAST_NO_ACC = 1'b0;                                                        a0256
      LAST_HIT = 1'b0;                                                           a0257
      LAST_CORRECTION = 1'b0;                                                    a0258
      LAST_KU_MODE = 1'b0;                                                       a0259
      #1;                                                                        a0260
    end                                                                          a0261
  end                                                                            a0262
                                                                                 a0263
  //                                                                             a0264
  // Save IFU status                                                             a0265
  //                                                                             a0266
  //                                                                             a0267
  // WORK_IF is only valid at the rising clock edge;                             a0268
  // because of this fact, it has to be saved in a register                      a0269
  //                                                                             a0270
  always @(posedge CP) DO_IF = WORK_IF;                                          a0271
                                                                                 a0272
  //                                                                             a0273
  // Internal status register                                                    a0274
  //                                                                             a0275
  // Set internal status registers with every clock                              a0276
  //                                                                             a0277
  always @(posedge CP) begin                                                     a0278
    if (WORK_IF) begin                                                           a0279
      fork                                                                       a0280
        NO_ACC = #`DELTA LDST_ACC_NOW | NO_FETCH; // 1: IFU must not fetch       a0281
        EXT_BRANCH = #`DELTA EMERG_FETCH;         // 1: external branch          a0282
        LAST_NO_ACC = #`DELTA NO_ACC;             // 1: IFU did not fetch before a0283
        LAST_HIT = #`DELTA HIT;                   // 1: BTC or MPC hit           a0284
        LAST_CORRECTION = #`DELTA BTC_CORRECT;    // 1: branch was corrected     a0285
        LAST_KU_MODE = #`DELTA KU_MODE;           // last kernel/user mode       a0286
      join                                                                       a0287
    end                                                                          a0288
  end                                                                            a0289
                                                                                 a0290
  //                                                                             a0291
  // LD/ST access pipeline                                                       a0292
  //                                                                             a0293
  always @(posedge CP) begin                                                     a0294
    if (SHIFT) begin                                                             a0295
      fork                                                                       a0296
        LDST_ACC = #`DELTA LDST_ACC_NOW;  // 1: IFU cannot fetch                 a0297