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// $Id: aeMB_xecu.v,v 1.4 2007-11-08 14:17:47 sybreon Exp $

//

// AEMB MAIN EXECUTION ALU

//

// Copyright (C) 2004-2007 Shawn Tan Ser Ngiap <shawn.tan@aeste.net>

//  

// This library is free software; you can redistribute it and/or

// modify it under the terms of the GNU Lesser General Public License

// as published by the Free Software Foundation; either version 2.1 of

// the License, or (at your option) any later version.

//

// This library is distributed in the hope that it will be useful, but

// WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

// Lesser General Public License for more details.

//  

// You should have received a copy of the GNU Lesser General Public

// License along with this library; if not, write to the Free Software

// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307

// USA

//

// $Log: not supported by cvs2svn $

// Revision 1.3  2007/11/03 08:34:55  sybreon

// Minor code cleanup.

//

// Revision 1.2  2007/11/02 19:20:58  sybreon

// Added better (beta) interrupt support.

// Changed MSR_IE to disabled at reset as per MB docs.

//

// Revision 1.1  2007/11/02 03:25:41  sybreon

// New EDK 3.2 compatible design with optional barrel-shifter and multiplier.

// Fixed various minor data hazard bugs.

// Code compatible with -O0/1/2/3/s generated code.

//

module aeMB_xecu (/*AUTOARG*/

   // Outputs

   dwb_adr_o, dwb_sel_o, rRESULT, rDWBSEL, rMSR_IE, rMSR_BIP,

   // Inputs

   rXCE, rREGA, rREGB, rMXSRC, rMXTGT, rRA, rMXALU, rBRA, rDLY, rALT,

   rSIMM, rIMM, rOPC, rRD, rDWBDI, rPC, gclk, grst, gena

   );

   parameter DW=32;

   parameter MUL=0;

   parameter BSF=0;

   // DATA WISHBONE

   output [DW-1:2] dwb_adr_o;

   output [3:0]    dwb_sel_o;

   // INTERNAL

   output [31:0]   rRESULT;

   output [3:0]    rDWBSEL;

   output          rMSR_IE;

   output          rMSR_BIP;

   input [1:0]      rXCE;

   input [31:0]    rREGA, rREGB;

   input [1:0]      rMXSRC, rMXTGT;

   input [4:0]      rRA;

   input [2:0]      rMXALU;

   input           rBRA, rDLY;

   input [10:0]    rALT;

   input [31:0]    rSIMM;

   input [15:0]    rIMM;

   input [5:0]      rOPC;

   input [4:0]      rRD;

   input [31:0]    rDWBDI;

   input [31:2]    rPC;

   //input [31:0]    rRES_MUL; // External Multiplier

   //input [31:0]    rRES_BSF; // External Barrel Shifter

   // SYSTEM

   input           gclk, grst, gena;

   reg             rMSR_C, xMSR_C;

   reg             rMSR_IE, xMSR_IE;

   reg             rMSR_BE, xMSR_BE;

   reg             rMSR_BIP, xMSR_BIP;

   wire            fSKIP = rBRA & !rDLY;

   // --- OPERAND SELECT

   reg [31:0]       rOPA, rOPB;

   always @(/*AUTOSENSE*/rDWBDI or rMXSRC or rPC or rREGA or rRESULT)

     case (rMXSRC)

       2'o0: rOPA <= rREGA;

       2'o1: rOPA <= rRESULT;

       2'o2: rOPA <= rDWBDI;

       2'o3: rOPA <= {rPC, 2'o0};

     endcase // case (rMXSRC)

   always @(/*AUTOSENSE*/rDWBDI or rMXTGT or rREGB or rRESULT or rSIMM)

     case (rMXTGT)

       2'o0: rOPB <= rREGB;

       2'o1: rOPB <= rRESULT;

       2'o2: rOPB <= rDWBDI;

       2'o3: rOPB <= rSIMM;

     endcase // case (rMXTGT)

   // --- ADD/SUB SELECTOR ----

   // FIXME: Redesign

   // TODO: Refactor

   // TODO: Verify signed compare

   wire             wADDC, wSUBC, wRES_AC, wCMPC, wOPC;

   wire [31:0]       wADD, wSUB, wRES_A, wCMP, wOPX;

   wire             wCMPU = (rOPA > rOPB);

   wire             wCMPF = (rIMM[1]) ? wCMPU :

                            ((wCMPU & ~(rOPB[31] ^ rOPA[31])) | (rOPB[31] & ~rOPA[31]));

   assign           {wCMPC,wCMP} = {wSUBC,wCMPF,wSUB[30:0]};

   assign           wOPX = (rOPC[0] & !rOPC[5]) ? ~rOPA : rOPA ;

   assign           wOPC = ((rMSR_C & rOPC[1]) | (rOPC[0] & !rOPC[1])) & (!rOPC[5] & ~&rOPC[5:4]);

   assign           {wSUBC,wSUB} = {wADDC,wADD};

   assign           {wADDC,wADD} = (rOPB + wOPX) + wOPC;

   reg              rRES_ADDC;

   reg [31:0]        rRES_ADD;

   always @(rIMM or rOPC or wADD or wADDC or wCMP

            or wCMPC or wSUB or wSUBC)

     case ({rOPC[3],rOPC[0],rIMM[0]})

       4'h2, 4'h6, 4'h7: {rRES_ADDC,rRES_ADD} <= #1 {~wSUBC,wSUB}; // SUB

       4'h3: {rRES_ADDC,rRES_ADD} <= #1 {~wCMPC,wCMP}; // CMP

       default: {rRES_ADDC,rRES_ADD} <= #1 {wADDC,wADD};

     endcase // case ({rOPC[3],rOPC[0],rIMM[0]})

   // --- LOGIC SELECTOR --------------------------------------

   reg [31:0]        rRES_LOG;

   always @(/*AUTOSENSE*/rOPA or rOPB or rOPC)

     case (rOPC[1:0])

       2'o0: rRES_LOG <= #1 rOPA | rOPB;

       2'o1: rRES_LOG <= #1 rOPA & rOPB;

       2'o2: rRES_LOG <= #1 rOPA ^ rOPB;

       2'o3: rRES_LOG <= #1 rOPA & ~rOPB;

     endcase // case (rOPC[1:0])

   // --- SHIFTER SELECTOR ------------------------------------

   reg [31:0]        rRES_SFT;

   reg              rRES_SFTC;

   always @(/*AUTOSENSE*/rIMM or rMSR_C or rOPA)

     case (rIMM[6:5])

       2'o0: {rRES_SFT, rRES_SFTC} <= #1 {rOPA[31],rOPA[31:0]};

       2'o1: {rRES_SFT, rRES_SFTC} <= #1 {rMSR_C,rOPA[31:0]};

       2'o2: {rRES_SFT, rRES_SFTC} <= #1 {1'b0,rOPA[31:0]};

       2'o3: {rRES_SFT, rRES_SFTC} <= #1 (rIMM[0]) ? { {(16){rOPA[15]}}, rOPA[15:0], rMSR_C} :

                                      { {(24){rOPA[7]}}, rOPA[7:0], rMSR_C};

     endcase // case (rIMM[6:5])

   // --- MOVE SELECTOR ---------------------------------------

   wire [31:0]       wMSR = {rMSR_C, 3'o0,

                            20'h0ED32,

                            4'h0, rMSR_BIP, rMSR_C, rMSR_IE, rMSR_BE};

   wire             fMFSR = (rOPC == 6'o45) & !rIMM[14] & rIMM[0];

   wire             fMFPC = (rOPC == 6'o45) & !rIMM[14] & !rIMM[0];

   reg [31:0]        rRES_MOV;

   always @(/*AUTOSENSE*/fMFPC or fMFSR or rOPA or rOPB or rPC or rRA

            or wMSR)

     rRES_MOV <= (fMFSR) ? wMSR :

                 (fMFPC) ? rPC :

                 (rRA[3]) ? rOPB :

                 rOPA;

   // --- MULTIPLIER ------------------------------------------

   reg [31:0]        rRES_MUL;

   always @(/*AUTOSENSE*/rOPA or rOPB) begin

      rRES_MUL <= (rOPA * rOPB);

   end

   // --- BARREL SHIFTER --------------------------------------

   reg [31:0]     rRES_BSF;

   reg [31:0]     xBSRL, xBSRA, xBSLL;

   // Infer a logical left barrel shifter.   

   always @(/*AUTOSENSE*/rOPA or rOPB)

     xBSLL <= rOPA << rOPB[4:0];

   // Infer a logical right barrel shifter.

   always @(/*AUTOSENSE*/rOPA or rOPB)

     xBSRL <= rOPA >> rOPB[4:0];

   // Infer a arithmetic right barrel shifter.

   always @(/*AUTOSENSE*/rOPA or rOPB)

     case (rOPB[4:0])

       5'd00: xBSRA <= rOPA;

       5'd01: xBSRA <= {{(1){rOPA[31]}}, rOPA[31:1]};

       5'd02: xBSRA <= {{(2){rOPA[31]}}, rOPA[31:2]};

       5'd03: xBSRA <= {{(3){rOPA[31]}}, rOPA[31:3]};

       5'd04: xBSRA <= {{(4){rOPA[31]}}, rOPA[31:4]};

       5'd05: xBSRA <= {{(5){rOPA[31]}}, rOPA[31:5]};

       5'd06: xBSRA <= {{(6){rOPA[31]}}, rOPA[31:6]};

       5'd07: xBSRA <= {{(7){rOPA[31]}}, rOPA[31:7]};

       5'd08: xBSRA <= {{(8){rOPA[31]}}, rOPA[31:8]};

       5'd09: xBSRA <= {{(9){rOPA[31]}}, rOPA[31:9]};

       5'd10: xBSRA <= {{(10){rOPA[31]}}, rOPA[31:10]};

       5'd11: xBSRA <= {{(11){rOPA[31]}}, rOPA[31:11]};

       5'd12: xBSRA <= {{(12){rOPA[31]}}, rOPA[31:12]};

       5'd13: xBSRA <= {{(13){rOPA[31]}}, rOPA[31:13]};

       5'd14: xBSRA <= {{(14){rOPA[31]}}, rOPA[31:14]};

       5'd15: xBSRA <= {{(15){rOPA[31]}}, rOPA[31:15]};

       5'd16: xBSRA <= {{(16){rOPA[31]}}, rOPA[31:16]};

       5'd17: xBSRA <= {{(17){rOPA[31]}}, rOPA[31:17]};

       5'd18: xBSRA <= {{(18){rOPA[31]}}, rOPA[31:18]};

       5'd19: xBSRA <= {{(19){rOPA[31]}}, rOPA[31:19]};

       5'd20: xBSRA <= {{(20){rOPA[31]}}, rOPA[31:20]};

       5'd21: xBSRA <= {{(21){rOPA[31]}}, rOPA[31:21]};

       5'd22: xBSRA <= {{(22){rOPA[31]}}, rOPA[31:22]};

       5'd23: xBSRA <= {{(23){rOPA[31]}}, rOPA[31:23]};

       5'd24: xBSRA <= {{(24){rOPA[31]}}, rOPA[31:24]};

       5'd25: xBSRA <= {{(25){rOPA[31]}}, rOPA[31:25]};

       5'd26: xBSRA <= {{(26){rOPA[31]}}, rOPA[31:26]};

       5'd27: xBSRA <= {{(27){rOPA[31]}}, rOPA[31:27]};

       5'd28: xBSRA <= {{(28){rOPA[31]}}, rOPA[31:28]};

       5'd29: xBSRA <= {{(29){rOPA[31]}}, rOPA[31:29]};

       5'd30: xBSRA <= {{(30){rOPA[31]}}, rOPA[31:30]};

       5'd31: xBSRA <= {{(31){rOPA[31]}}, rOPA[31]};

     endcase // case (rOPB[4:0])

   always @(/*AUTOSENSE*/rALT or xBSLL or xBSRA or xBSRL)

     case (rALT[10:9])

       2'd0: rRES_BSF <= xBSRL;

       2'd1: rRES_BSF <= xBSRA;

       2'd2: rRES_BSF <= xBSLL;

       default: rRES_BSF <= 32'hX;

     endcase // case (rALT[10:9])

   // --- MSR REGISTER -----------------

   // C

   wire            fMTS = (rOPC == 6'o45) & rIMM[14];

   wire            fADDC = ({rOPC[5:4], rOPC[2]} == 3'o0);

   always @(/*AUTOSENSE*/fADDC or fMTS or fSKIP or rMSR_C or rMXALU

            or rOPA or rRES_ADDC or rRES_SFTC or rXCE)

     if (fSKIP | |rXCE) begin

        xMSR_C <= rMSR_C;

     end else

       case (rMXALU)

         3'o0: xMSR_C <= (fADDC) ? rRES_ADDC : rMSR_C;

         3'o1: xMSR_C <= rMSR_C; // LOGIC       

         3'o2: xMSR_C <= rRES_SFTC; // SHIFT

         3'o3: xMSR_C <= (fMTS) ? rOPA[2] : rMSR_C;

         3'o4: xMSR_C <= rMSR_C;

         3'o5: xMSR_C <= rMSR_C;

         default: xMSR_C <= 1'hX;

       endcase

   // IE/BIP/BE

   wire             fRTID = (rOPC == 6'o55) & rRD[0];

   wire             fRTBD = (rOPC == 6'o55) & rRD[1];

   wire             fBRK = ((rOPC == 6'o56) | (rOPC == 6'o66)) & (rRA[4:2] == 3'o3);

   always @(/*AUTOSENSE*/fMTS or fRTID or rMSR_IE or rOPA or rXCE)

     xMSR_IE <= (rXCE == 2'o2) ? 1'b0 :

                (fRTID) ? 1'b1 :

                (fMTS) ? rOPA[1] :

                rMSR_IE;

   always @(/*AUTOSENSE*/fBRK or fMTS or fRTBD or rMSR_BIP or rOPA)

     xMSR_BIP <= (fBRK) ? 1'b1 :

                 (fRTBD) ? 1'b0 :

                 (fMTS) ? rOPA[3] :

                 rMSR_BIP;

   always @(/*AUTOSENSE*/fMTS or rMSR_BE or rOPA)

     xMSR_BE <= (fMTS) ? rOPA[0] : rMSR_BE;

   // --- RESULT SELECTOR -------------------------------------------

   // Selects results from functional units. 

   reg [31:0]       rRESULT, xRESULT;

   // RESULT

   always @(/*AUTOSENSE*/fSKIP or rMXALU or rRES_ADD or rRES_BSF

            or rRES_LOG or rRES_MOV or rRES_MUL or rRES_SFT)

     if (fSKIP)

       /*AUTORESET*/

       // Beginning of autoreset for uninitialized flops

       xRESULT <= 32'h0;

       // End of automatics

     else

       case (rMXALU)

         3'o0: xRESULT <= rRES_ADD;

         3'o1: xRESULT <= rRES_LOG;

         3'o2: xRESULT <= rRES_SFT;

         3'o3: xRESULT <= rRES_MOV;

         3'o4: xRESULT <= (MUL) ? rRES_MUL : 32'hX;

         3'o5: xRESULT <= (BSF) ? rRES_BSF : 32'hX;

         default: xRESULT <= 32'hX;

       endcase // case (rMXALU)

   // --- DATA WISHBONE -----

   reg [3:0]         rDWBSEL, xDWBSEL;

   assign           dwb_adr_o = rRESULT[DW-1:2];

   assign           dwb_sel_o = rDWBSEL;

   always @(/*AUTOSENSE*/rOPC or wADD)

     case (rOPC[1:0])

       2'o0: case (wADD[1:0])

               2'o0: xDWBSEL <= 4'h8;

               2'o1: xDWBSEL <= 4'h4;

               2'o2: xDWBSEL <= 4'h2;

               2'o3: xDWBSEL <= 4'h1;

             endcase // case (wADD[1:0])

       2'o1: xDWBSEL <= (wADD[1]) ? 4'h3 : 4'hC;

       2'o2: xDWBSEL <= 4'hF;

       default: xDWBSEL <= 4'hX;

     endcase // case (rOPC[1:0])

   // --- SYNC ---

   always @(posedge gclk)

     if (grst) begin

        /*AUTORESET*/

        // Beginning of autoreset for uninitialized flops

        rDWBSEL <= 4'h0;

        rMSR_BE <= 1'h0;

        rMSR_BIP <= 1'h0;

        rMSR_C <= 1'h0;

        rMSR_IE <= 1'h0;

        rRESULT <= 32'h0;

        // End of automatics

     end else if (gena) begin

        rRESULT <= #1 xRESULT;

        rDWBSEL <= #1 xDWBSEL;

        rMSR_C <= #1 xMSR_C;

        rMSR_IE <= #1 xMSR_IE;

        rMSR_BE <= #1 xMSR_BE;

        rMSR_BIP <= #1 xMSR_BIP;

     end

endmodule // aeMB_xecu