cvw/wally-pipelined/src/cache/icache.sv

///////////////////////////////////////////
// icache.sv
//
// Written: jaallen@g.hmc.edu 2021-03-02
// Modified: 
//
// Purpose: Cache instructions for the ifu so it can access memory less often, saving cycles
// 
// A component of the Wally configurable RISC-V project.
// 
// Copyright (C) 2021 Harvey Mudd College & Oklahoma State University
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, 
// modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software 
// is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES 
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS 
// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT 
// OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
///////////////////////////////////////////

`include "wally-config.vh"

module icache
  (
   // Basic pipeline stuff
   input logic 		    clk, reset,
   input logic 		    StallF, StallD,
   input logic 		    FlushD,
   input logic [`PA_BITS-1:0]  PCNextF,
   input logic [`PA_BITS-1:0]  PCPF, 
   // Data read in from the ebu unit
   input logic [`XLEN-1:0]  InstrInF,
   input logic 		    InstrAckF,
   // Read requested from the ebu unit
   output logic [`XLEN-1:0] InstrPAdrF,
   output logic 	    InstrReadF,
   // High if the instruction currently in the fetch stage is compressed
   output logic 	    CompressedF,
   // High if the icache is requesting a stall
   output logic 	    ICacheStallF,
   // The raw (not decompressed) instruction that was requested
   // If this instruction is compressed, upper 16 bits may be the next 16 bits or may be zeros
   output logic [31:0] 	    InstrRawD
   );

  // Configuration parameters
  // TODO Move these to a config file
  localparam integer 	    BLOCKLEN = 256;
  localparam integer 	    NUMLINES = 512;

  // Input signals to cache memory
  logic 		    FlushMem;
  logic 		    ICacheMemWriteEnable;
  logic [BLOCKLEN-1:0] 	    ICacheMemWriteData;
  logic 		    EndFetchState;
  logic [`PA_BITS-1:0] 	    PCTagF, PCNextIndexF;  
  // Output signals from cache memory
  logic [31:0] 		    ICacheMemReadData;
  logic 		    ICacheMemReadValid;
  logic 		    ICacheReadEn;
  logic [BLOCKLEN-1:0] 	    ReadLineF;
  
  
  ICacheMem #(.BLOCKLEN(BLOCKLEN), .NUMLINES(NUMLINES)) 
  cachemem(
           .*,
           // Stall it if the pipeline is stalled, unless we're stalling it and we're ending our stall
           .flush(FlushMem),
           .WriteEnable(ICacheMemWriteEnable),
           .WriteLine(ICacheMemWriteData),
           .ReadLineF(ReadLineF),
           .HitF(ICacheMemReadValid)
	   );

  always_comb begin
    case (PCTagF[4:1])
      0: ICacheMemReadData = ReadLineF[31:0];
      1: ICacheMemReadData = ReadLineF[47:16];
      2: ICacheMemReadData = ReadLineF[63:32];
      3: ICacheMemReadData = ReadLineF[79:48];

      4: ICacheMemReadData = ReadLineF[95:64];
      5: ICacheMemReadData = ReadLineF[111:80];
      6: ICacheMemReadData = ReadLineF[127:96];
      7: ICacheMemReadData = ReadLineF[143:112];      

      8: ICacheMemReadData = ReadLineF[159:128];      
      9: ICacheMemReadData = ReadLineF[175:144];      
      10: ICacheMemReadData = ReadLineF[191:160];      
      11: ICacheMemReadData = ReadLineF[207:176];

      12: ICacheMemReadData = ReadLineF[223:192];
      13: ICacheMemReadData = ReadLineF[239:208];
      14: ICacheMemReadData = ReadLineF[255:224];
      15: ICacheMemReadData = {16'b0, ReadLineF[255:240]};
    endcase
  end


  ICacheCntrl #(.BLOCKLEN(BLOCKLEN)) controller(.*);

  // For now, assume no writes to executable memory
  assign FlushMem = 1'b0;
endmodule