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///////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////
//
//
// Filename:    idecode.v
// Filename:    idecode.v
//
//
// Project:     Zip CPU -- a small, lightweight, RISC CPU soft core
// Project:     Zip CPU -- a small, lightweight, RISC CPU soft core
//
//
// Purpose:     This RTL file specifies how instructions are to be decoded
// Purpose:     This RTL file specifies how instructions are to be decoded
//              into their underlying meanings.  This is specifically a version
//              into their underlying meanings.  This is specifically a version
//      designed to support a "Next Generation", or "Version 2" instruction
//      designed to support a "Next Generation", or "Version 2" instruction
//      set as (currently) activated by the OPT_NEW_INSTRUCTION_SET option
//      set as (currently) activated by the OPT_NEW_INSTRUCTION_SET option
//      in cpudefs.v.
//      in cpudefs.v.
//
//
//      I expect to (eventually) retire the old instruction set, at which point
//      I expect to (eventually) retire the old instruction set, at which point
//      this will become the default instruction set decoder.
//      this will become the default instruction set decoder.
//
//
//
//
// Creator:     Dan Gisselquist, Ph.D.
// Creator:     Dan Gisselquist, Ph.D.
//              Gisselquist Technology, LLC
//              Gisselquist Technology, LLC
//
//
///////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////
//
//
// Copyright (C) 2015, Gisselquist Technology, LLC
// Copyright (C) 2015, Gisselquist Technology, LLC
//
//
// This program is free software (firmware): you can redistribute it and/or
// This program is free software (firmware): you can redistribute it and/or
// modify it under the terms of  the GNU General Public License as published
// modify it under the terms of  the GNU General Public License as published
// by the Free Software Foundation, either version 3 of the License, or (at
// by the Free Software Foundation, either version 3 of the License, or (at
// your option) any later version.
// your option) any later version.
//
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// for more details.
// for more details.
//
//
// License:     GPL, v3, as defined and found on www.gnu.org,
// License:     GPL, v3, as defined and found on www.gnu.org,
//              http://www.gnu.org/licenses/gpl.html
//              http://www.gnu.org/licenses/gpl.html
//
//
//
//
///////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////
//
//
//
//
//
//
`define CPU_CC_REG      4'he
`define CPU_CC_REG      4'he
`define CPU_PC_REG      4'hf
`define CPU_PC_REG      4'hf
//
//
`include "cpudefs.v"
`include "cpudefs.v"
//
//
//
//
//
//
module  idecode(i_clk, i_rst, i_ce, i_stalled,
module  idecode(i_clk, i_rst, i_ce, i_stalled,
                i_instruction, i_gie, i_pc, i_pf_valid,
                i_instruction, i_gie, i_pc, i_pf_valid,
                        i_illegal,
                        i_illegal,
                o_phase, o_illegal,
                o_phase, o_illegal,
                o_pc, o_gie,
                o_pc, o_gie,
                o_dcdR, o_dcdA, o_dcdB, o_I, o_zI,
                o_dcdR, o_dcdA, o_dcdB, o_I, o_zI,
                o_cond, o_wF,
                o_cond, o_wF,
                o_op, o_ALU, o_M, o_DV, o_FP, o_break, o_lock,
                o_op, o_ALU, o_M, o_DV, o_FP, o_break, o_lock,
                o_wR, o_rA, o_rB,
                o_wR, o_rA, o_rB,
                o_early_branch, o_branch_pc, o_ljmp,
                o_early_branch, o_branch_pc, o_ljmp,
                o_pipe
                o_pipe
                );
                );
        parameter       ADDRESS_WIDTH=24, IMPLEMENT_MPY=1, EARLY_BRANCHING=1,
        parameter       ADDRESS_WIDTH=24, IMPLEMENT_MPY=1, EARLY_BRANCHING=1,
                        IMPLEMENT_DIVIDE=1, IMPLEMENT_FPU=0, AW = ADDRESS_WIDTH;
                        IMPLEMENT_DIVIDE=1, IMPLEMENT_FPU=0, AW = ADDRESS_WIDTH;
        input                   i_clk, i_rst, i_ce, i_stalled;
        input                   i_clk, i_rst, i_ce, i_stalled;
        input   [31:0]           i_instruction;
        input   [31:0]           i_instruction;
        input                   i_gie;
        input                   i_gie;
        input   [(AW-1):0]       i_pc;
        input   [(AW-1):0]       i_pc;
        input                   i_pf_valid, i_illegal;
        input                   i_pf_valid, i_illegal;
        output  wire            o_phase;
        output  wire            o_phase;
        output  reg             o_illegal;
        output  reg             o_illegal;
        output  reg     [(AW-1):0]       o_pc;
        output  reg     [(AW-1):0]       o_pc;
        output  reg             o_gie;
        output  reg             o_gie;
        output  reg     [6:0]    o_dcdR, o_dcdA, o_dcdB;
        output  reg     [6:0]    o_dcdR, o_dcdA, o_dcdB;
        output  wire    [31:0]   o_I;
        output  wire    [31:0]   o_I;
        output  reg             o_zI;
        output  wire            o_zI;
        output  reg     [3:0]    o_cond;
        output  reg     [3:0]    o_cond;
        output  reg             o_wF;
        output  reg             o_wF;
        output  reg     [3:0]    o_op;
        output  reg     [3:0]    o_op;
        output  reg             o_ALU, o_M, o_DV, o_FP, o_break;
        output  reg             o_ALU, o_M, o_DV, o_FP, o_break;
        output  wire            o_lock;
        output  wire            o_lock;
        output  reg             o_wR, o_rA, o_rB;
        output  reg             o_wR, o_rA, o_rB;
        output  wire            o_early_branch;
        output  wire            o_early_branch;
        output  wire    [(AW-1):0]       o_branch_pc;
        output  wire    [(AW-1):0]       o_branch_pc;
        output  wire            o_ljmp;
        output  wire            o_ljmp;
        output  wire            o_pipe;
        output  wire            o_pipe;
 
 
        wire    dcdA_stall, dcdB_stall, dcdF_stall;
        wire    dcdA_stall, dcdB_stall, dcdF_stall;
        wire                    o_dcd_early_branch;
        wire                    o_dcd_early_branch;
        wire    [(AW-1):0]       o_dcd_branch_pc;
        wire    [(AW-1):0]       o_dcd_branch_pc;
        reg     o_dcdI, o_dcdIz;
 
`ifdef  OPT_PIPELINED
`ifdef  OPT_PIPELINED
        reg     r_lock, r_pipe;
        reg     r_lock, r_pipe, r_zI;
`endif
`endif
 
 
 
 
        wire    [4:0]    w_op;
        wire    [4:0]    w_op;
        wire            w_ldi, w_mov, w_cmptst, w_ldilo, w_ALU, w_brev, w_noop;
        wire            w_ldi, w_mov, w_cmptst, w_ldilo, w_ALU, w_brev, w_noop;
        wire    [4:0]    w_dcdR, w_dcdB, w_dcdA;
        wire    [4:0]    w_dcdR, w_dcdB, w_dcdA;
        wire            w_dcdR_pc, w_dcdR_cc;
        wire            w_dcdR_pc, w_dcdR_cc;
        wire            w_dcdA_pc, w_dcdA_cc;
        wire            w_dcdA_pc, w_dcdA_cc;
        wire            w_dcdB_pc, w_dcdB_cc;
        wire            w_dcdB_pc, w_dcdB_cc;
        wire    [3:0]    w_cond;
        wire    [3:0]    w_cond;
        wire            w_wF, w_dcdM, w_dcdDV, w_dcdFP;
        wire            w_wF, w_dcdM, w_dcdDV, w_dcdFP;
        wire            w_wR, w_rA, w_rB, w_wR_n;
        wire            w_wR, w_rA, w_rB, w_wR_n;
        wire            w_ljmp;
        wire            w_ljmp;
        wire    [31:0]   iword;
        wire    [31:0]   iword;
 
 
 
 
`ifdef  OPT_VLIW
`ifdef  OPT_VLIW
        reg     [16:0]   r_nxt_half;
        reg     [16:0]   r_nxt_half;
        assign  iword = (o_phase)
        assign  iword = (o_phase)
                                // set second half as a NOOP ... but really 
                                // set second half as a NOOP ... but really 
                                // shouldn't matter
                                // shouldn't matter
                        ? { r_nxt_half[16:7], 1'b0, r_nxt_half[6:0], 5'b11000, 3'h7, 6'h00 }
                        ? { r_nxt_half[16:7], 1'b0, r_nxt_half[6:0], 5'b11000, 3'h7, 6'h00 }
                        : i_instruction;
                        : i_instruction;
`else
`else
        assign  iword = { 1'b0, i_instruction[30:0] };
        assign  iword = { 1'b0, i_instruction[30:0] };
`endif
`endif
 
 
        generate
        generate
        if (EARLY_BRANCHING != 0)
        if (EARLY_BRANCHING != 0)
                assign  w_ljmp = (iword == 32'h7c87c000);
                assign  w_ljmp = (iword == 32'h7c87c000);
        else
        else
                assign  w_ljmp = 1'b0;
                assign  w_ljmp = 1'b0;
        endgenerate
        endgenerate
 
 
 
 
        assign  w_op= iword[26:22];
        assign  w_op= iword[26:22];
        assign  w_mov    = (w_op      == 5'h0f);
        assign  w_mov    = (w_op      == 5'h0f);
        assign  w_ldi    = (w_op[4:1] == 4'hb);
        assign  w_ldi    = (w_op[4:1] == 4'hb);
        assign  w_brev   = (w_op      == 5'hc);
        assign  w_brev   = (w_op      == 5'hc);
        assign  w_cmptst = (w_op[4:1] == 4'h8);
        assign  w_cmptst = (w_op[4:1] == 4'h8);
        assign  w_ldilo  = (w_op[4:0] == 5'h9);
        assign  w_ldilo  = (w_op[4:0] == 5'h9);
        assign  w_ALU    = (~w_op[4]);
        assign  w_ALU    = (~w_op[4]);
 
 
        // 4 LUTs
        // 4 LUTs
        //
        //
        // Two parts to the result register: the register set, given for
        // Two parts to the result register: the register set, given for
        // moves in i_word[18] but only for the supervisor, and the other
        // moves in i_word[18] but only for the supervisor, and the other
        // four bits encoded in the instruction.
        // four bits encoded in the instruction.
        //
        //
        assign  w_dcdR = { ((~iword[31])&&(w_mov)&&(~i_gie))?iword[18]:i_gie,
        assign  w_dcdR = { ((~iword[31])&&(w_mov)&&(~i_gie))?iword[18]:i_gie,
                                iword[30:27] };
                                iword[30:27] };
        // 2 LUTs
        // 2 LUTs
        //
        //
        // If the result register is either CC or PC, and this would otherwise
        // If the result register is either CC or PC, and this would otherwise
        // be a floating point instruction with floating point opcode of 0,
        // be a floating point instruction with floating point opcode of 0,
        // then this is a NOOP.
        // then this is a NOOP.
        assign  w_noop   = (w_op[4:0] == 5'h18)&&(w_dcdR[3:1] == 3'h7);
        assign  w_noop   = (w_op[4:0] == 5'h18)&&(w_dcdR[3:1] == 3'h7);
 
 
        // 4 LUTs
        // 4 LUTs
        assign  w_dcdB = { ((~iword[31])&&(w_mov)&&(~i_gie))?iword[13]:i_gie,
        assign  w_dcdB = { ((~iword[31])&&(w_mov)&&(~i_gie))?iword[13]:i_gie,
                                iword[17:14] };
                                iword[17:14] };
 
 
        // 0 LUTs
        // 0 LUTs
        assign  w_dcdA = w_dcdR;
        assign  w_dcdA = w_dcdR;
        // 2 LUTs, 1 delay each
        // 2 LUTs, 1 delay each
        assign  w_dcdR_pc = (w_dcdR == {i_gie, `CPU_PC_REG});
        assign  w_dcdR_pc = (w_dcdR == {i_gie, `CPU_PC_REG});
        assign  w_dcdR_cc = (w_dcdR == {i_gie, `CPU_CC_REG});
        assign  w_dcdR_cc = (w_dcdR == {i_gie, `CPU_CC_REG});
        // 0 LUTs
        // 0 LUTs
        assign  w_dcdA_pc = w_dcdR_pc;
        assign  w_dcdA_pc = w_dcdR_pc;
        assign  w_dcdA_cc = w_dcdR_cc;
        assign  w_dcdA_cc = w_dcdR_cc;
        // 2 LUTs, 1 delays each
        // 2 LUTs, 1 delays each
        assign  w_dcdB_pc = (w_dcdB[3:0] == `CPU_PC_REG);
        assign  w_dcdB_pc = (w_dcdB[3:0] == `CPU_PC_REG);
        assign  w_dcdB_cc = (w_dcdB[3:0] == `CPU_CC_REG);
        assign  w_dcdB_cc = (w_dcdB[3:0] == `CPU_CC_REG);
 
 
        // Under what condition will we execute this
        // Under what condition will we execute this
        // instruction?  Only the load immediate instruction
        // instruction?  Only the load immediate instruction
        // is completely unconditional.
        // is completely unconditional.
        //
        //
        // 3+4 LUTs
        // 3+4 LUTs
        assign  w_cond = (w_ldi) ? 4'h8 :
        assign  w_cond = (w_ldi) ? 4'h8 :
                        (iword[31])?{(iword[20:19]==2'b00),
                        (iword[31])?{(iword[20:19]==2'b00),
                                        1'b0,iword[20:19]}
                                        1'b0,iword[20:19]}
                        : { (iword[21:19]==3'h0), iword[21:19] };
                        : { (iword[21:19]==3'h0), iword[21:19] };
 
 
        // 1 LUT
        // 1 LUT
        assign  w_dcdM    = (w_op[4:1] == 4'h9);
        assign  w_dcdM    = (w_op[4:1] == 4'h9);
        // 1 LUT
        // 1 LUT
        assign  w_dcdDV   = (w_op[4:1] == 4'ha);
        assign  w_dcdDV   = (w_op[4:1] == 4'ha);
        // 1 LUT
        // 1 LUT
        assign  w_dcdFP   = (w_op[4:3] == 2'b11)&&(w_dcdR[3:1] != 3'h7);
        assign  w_dcdFP   = (w_op[4:3] == 2'b11)&&(w_dcdR[3:1] != 3'h7);
        // 4 LUT's--since it depends upon FP/NOOP condition (vs 1 before)
        // 4 LUT's--since it depends upon FP/NOOP condition (vs 1 before)
        //      Everything reads A but ... NOOP/BREAK/LOCK, LDI, LOD, MOV
        //      Everything reads A but ... NOOP/BREAK/LOCK, LDI, LOD, MOV
        assign  w_rA     = (w_dcdFP)
        assign  w_rA     = (w_dcdFP)
                                // Divide's read A
                                // Divide's read A
                                ||(w_dcdDV)
                                ||(w_dcdDV)
                                // ALU read's A, unless it's a MOV to A
                                // ALU read's A, unless it's a MOV to A
                                // This includes LDIHI/LDILO
                                // This includes LDIHI/LDILO
                                ||((~w_op[4])&&(w_op[3:0]!=4'hf))
                                ||((~w_op[4])&&(w_op[3:0]!=4'hf))
                                // STO's read A
                                // STO's read A
                                ||((w_dcdM)&&(w_op[0]))
                                ||((w_dcdM)&&(w_op[0]))
                                // Test/compares
                                // Test/compares
                                ||(w_op[4:1]== 4'h8);
                                ||(w_op[4:1]== 4'h8);
        // 1 LUTs -- do we read a register for operand B?  Specifically, do
        // 1 LUTs -- do we read a register for operand B?  Specifically, do
        // we need to stall if the register is not (yet) ready?
        // we need to stall if the register is not (yet) ready?
        assign  w_rB     = (w_mov)||((iword[18])&&(~w_ldi));
        assign  w_rB     = (w_mov)||((iword[18])&&(~w_ldi));
        // 1 LUT: All but STO, NOOP/BREAK/LOCK, and CMP/TST write back to w_dcdR
        // 1 LUT: All but STO, NOOP/BREAK/LOCK, and CMP/TST write back to w_dcdR
        assign  w_wR_n   = ((w_dcdM)&&(w_op[0]))
        assign  w_wR_n   = ((w_dcdM)&&(w_op[0]))
                                ||((w_op[4:3]==2'b11)&&(w_dcdR[3:1]==3'h7))
                                ||((w_op[4:3]==2'b11)&&(w_dcdR[3:1]==3'h7))
                                ||(w_cmptst);
                                ||(w_cmptst);
        assign  w_wR     = ~w_wR_n;
        assign  w_wR     = ~w_wR_n;
        //
        //
        // 1-output bit (5 Opcode bits, 4 out-reg bits, 3 condition bits)
        // 1-output bit (5 Opcode bits, 4 out-reg bits, 3 condition bits)
        //      
        //      
        //      This'd be 4 LUTs, save that we have the carve out for NOOPs
        //      This'd be 4 LUTs, save that we have the carve out for NOOPs
        //      and writes to the PC/CC register(s).
        //      and writes to the PC/CC register(s).
        assign  w_wF     = (w_cmptst)
        assign  w_wF     = (w_cmptst)
                        ||((w_cond[3])&&((w_dcdFP)||(w_dcdDV)
                        ||((w_cond[3])&&((w_dcdFP)||(w_dcdDV)
                                ||((w_ALU)&&(~w_mov)&&(~w_ldilo)&&(~w_brev)
                                ||((w_ALU)&&(~w_mov)&&(~w_ldilo)&&(~w_brev)
                                        &&(iword[30:28] != 3'h7))));
                                        &&(iword[30:28] != 3'h7))));
 
 
        // Bottom 13 bits: no LUT's
        // Bottom 13 bits: no LUT's
        // w_dcd[12: 0] -- no LUTs
        // w_dcd[12: 0] -- no LUTs
        // w_dcd[   13] -- 2 LUTs
        // w_dcd[   13] -- 2 LUTs
        // w_dcd[17:14] -- (5+i0+i1) = 3 LUTs, 1 delay
        // w_dcd[17:14] -- (5+i0+i1) = 3 LUTs, 1 delay
        // w_dcd[22:18] : 5 LUTs, 1 delay (assuming high bit is o/w determined)
        // w_dcd[22:18] : 5 LUTs, 1 delay (assuming high bit is o/w determined)
        reg     [22:0]   r_I;
        reg     [22:0]   r_I;
        wire    [22:0]   w_I, w_fullI;
        wire    [22:0]   w_I, w_fullI;
        wire            w_Iz;
        wire            w_Iz;
 
 
        assign  w_fullI = (w_ldi) ? { iword[22:0] } // LDI
        assign  w_fullI = (w_ldi) ? { iword[22:0] } // LDI
                        :((w_mov) ?{ {(23-13){iword[12]}}, iword[12:0] } // Move
                        :((w_mov) ?{ {(23-13){iword[12]}}, iword[12:0] } // Move
                        :((~iword[18]) ? { {(23-18){iword[17]}}, iword[17:0] }
                        :((~iword[18]) ? { {(23-18){iword[17]}}, iword[17:0] }
                        : { {(23-14){iword[13]}}, iword[13:0] }
                        : { {(23-14){iword[13]}}, iword[13:0] }
                        ));
                        ));
 
 
`ifdef  OPT_VLIW
`ifdef  OPT_VLIW
        wire    [5:0]    w_halfI;
        wire    [5:0]    w_halfI;
        assign  w_halfI = (w_ldi) ? iword[5:0]
        assign  w_halfI = (w_ldi) ? iword[5:0]
                                :((iword[5]) ? 6'h00 : {iword[4],iword[4:0]});
                                :((iword[5]) ? 6'h00 : {iword[4],iword[4:0]});
        assign  w_I  = (iword[31])? {{(23-6){w_halfI[5]}}, w_halfI }:w_fullI;
        assign  w_I  = (iword[31])? {{(23-6){w_halfI[5]}}, w_halfI }:w_fullI;
`else
`else
        assign  w_I  = w_fullI;
        assign  w_I  = w_fullI;
`endif
`endif
        assign  w_Iz = (w_I == 0);
        assign  w_Iz = (w_I == 0);
 
 
 
 
`ifdef  OPT_VLIW
`ifdef  OPT_VLIW
        //
        //
        // The o_phase parameter is special.  It needs to let the software
        // The o_phase parameter is special.  It needs to let the software
        // following know that it cannot break/interrupt on an o_phase asserted
        // following know that it cannot break/interrupt on an o_phase asserted
        // instruction, lest the break take place between the first and second
        // instruction, lest the break take place between the first and second
        // half of a VLIW instruction.  To do this, o_phase must be asserted
        // half of a VLIW instruction.  To do this, o_phase must be asserted
        // when the first instruction half is valid, but not asserted on either
        // when the first instruction half is valid, but not asserted on either
        // a 32-bit instruction or the second half of a 2x16-bit instruction.
        // a 32-bit instruction or the second half of a 2x16-bit instruction.
        reg     r_phase;
        reg     r_phase;
        initial r_phase = 1'b0;
        initial r_phase = 1'b0;
        always @(posedge i_clk)
        always @(posedge i_clk)
                if (i_rst) // When no instruction is in the pipe, phase is zero
                if (i_rst) // When no instruction is in the pipe, phase is zero
                        r_phase <= 1'b0;
                        r_phase <= 1'b0;
                else if (i_ce)
                else if (i_ce)
                        r_phase <= (o_phase)? 1'b0:(i_instruction[31]);
                        r_phase <= (o_phase)? 1'b0:(i_instruction[31]);
        // Phase is '1' on the first instruction of a two-part set
        // Phase is '1' on the first instruction of a two-part set
        // But, due to the delay in processing, it's '1' when our output is
        // But, due to the delay in processing, it's '1' when our output is
        // valid for that first part, but that'll be the same time we
        // valid for that first part, but that'll be the same time we
        // are processing the second part ... so it may look to us like a '1'
        // are processing the second part ... so it may look to us like a '1'
        // on the second half of processing.
        // on the second half of processing.
 
 
        assign  o_phase = r_phase;
        assign  o_phase = r_phase;
`else
`else
        assign  o_phase = 1'b0;
        assign  o_phase = 1'b0;
`endif
`endif
 
 
 
 
        initial o_illegal = 1'b0;
        initial o_illegal = 1'b0;
        always @(posedge i_clk)
        always @(posedge i_clk)
                if (i_rst)
                if (i_rst)
                        o_illegal <= 1'b0;
                        o_illegal <= 1'b0;
                else if (i_ce)
                else if (i_ce)
                begin
                begin
`ifdef  OPT_VLIW
`ifdef  OPT_VLIW
                        o_illegal <= (i_illegal);
                        o_illegal <= (i_illegal);
`else
`else
                        o_illegal <= ((i_illegal) || (i_instruction[31]));
                        o_illegal <= ((i_illegal) || (i_instruction[31]));
`endif
`endif
                        if ((IMPLEMENT_MPY!=1)&&(w_op[4:1]==4'h5))
                        if ((IMPLEMENT_MPY!=1)&&(w_op[4:1]==4'h5))
                                o_illegal <= 1'b1;
                                o_illegal <= 1'b1;
 
 
                        if ((IMPLEMENT_DIVIDE==0)&&(w_dcdDV))
                        if ((IMPLEMENT_DIVIDE==0)&&(w_dcdDV))
                                o_illegal <= 1'b1;
                                o_illegal <= 1'b1;
                        else if ((IMPLEMENT_DIVIDE!=0)&&(w_dcdDV)&&(w_dcdR[3:1]==3'h7))
                        else if ((IMPLEMENT_DIVIDE!=0)&&(w_dcdDV)&&(w_dcdR[3:1]==3'h7))
                                o_illegal <= 1'b1;
                                o_illegal <= 1'b1;
 
 
 
 
                        if ((IMPLEMENT_FPU!=0)&&(w_dcdFP)&&(w_dcdR[3:1]==3'h7))
                        if ((IMPLEMENT_FPU!=0)&&(w_dcdFP)&&(w_dcdR[3:1]==3'h7))
                                o_illegal <= 1'b1;
                                o_illegal <= 1'b1;
                        else if ((IMPLEMENT_FPU==0)&&(w_dcdFP))
                        else if ((IMPLEMENT_FPU==0)&&(w_dcdFP))
                                o_illegal <= 1'b1;
                                o_illegal <= 1'b1;
 
 
                        if ((w_op[4:3]==2'b11)&&(w_dcdR[3:1]==3'h7)
                        if ((w_op[4:3]==2'b11)&&(w_dcdR[3:1]==3'h7)
                                &&(
                                &&(
                                        (w_op[2:0] != 3'h1)      // BREAK
                                        (w_op[2:0] != 3'h1)      // BREAK
`ifdef  OPT_PIPELINED
`ifdef  OPT_PIPELINED
                                        &&(w_op[2:0] != 3'h2)    // LOCK
                                        &&(w_op[2:0] != 3'h2)    // LOCK
`endif
`endif
                                        &&(w_op[2:0] != 3'h0)))  // NOOP
                                        &&(w_op[2:0] != 3'h0)))  // NOOP
                                o_illegal <= 1'b1;
                                o_illegal <= 1'b1;
                end
                end
 
 
 
 
        always @(posedge i_clk)
        always @(posedge i_clk)
                if (i_ce)
                if (i_ce)
                begin
                begin
`ifdef  OPT_VLIW
`ifdef  OPT_VLIW
                        if (~o_phase)
                        if (~o_phase)
                        begin
                        begin
                                o_gie<= i_gie;
                                o_gie<= i_gie;
                                // i.e. dcd_pc+1
                                // i.e. dcd_pc+1
                                o_pc <= i_pc+{{(AW-1){1'b0}},1'b1};
                                o_pc <= i_pc+{{(AW-1){1'b0}},1'b1};
                        end
                        end
`else
`else
                        o_gie<= i_gie;
                        o_gie<= i_gie;
                        o_pc <= i_pc+{{(AW-1){1'b0}},1'b1};
                        o_pc <= i_pc+{{(AW-1){1'b0}},1'b1};
`endif
`endif
 
 
                        // Under what condition will we execute this
                        // Under what condition will we execute this
                        // instruction?  Only the load immediate instruction
                        // instruction?  Only the load immediate instruction
                        // is completely unconditional.
                        // is completely unconditional.
                        o_cond <= w_cond;
                        o_cond <= w_cond;
                        // Don't change the flags on conditional instructions,
                        // Don't change the flags on conditional instructions,
                        // UNLESS: the conditional instruction was a CMP
                        // UNLESS: the conditional instruction was a CMP
                        // or TST instruction.
                        // or TST instruction.
                        o_wF <= w_wF;
                        o_wF <= w_wF;
 
 
                        // Record what operation/op-code (4-bits) we are doing
                        // Record what operation/op-code (4-bits) we are doing
                        //      Note that LDI magically becomes a MOV
                        //      Note that LDI magically becomes a MOV
                        //      instruction here.  That way it's a pass through
                        //      instruction here.  That way it's a pass through
                        //      the ALU.  Likewise, the two compare instructions
                        //      the ALU.  Likewise, the two compare instructions
                        //      CMP and TST becomes SUB and AND here as well.
                        //      CMP and TST becomes SUB and AND here as well.
                        // We keep only the bottom four bits, since we've
                        // We keep only the bottom four bits, since we've
                        // already done the rest of the decode necessary to 
                        // already done the rest of the decode necessary to 
                        // settle between the other instructions.  For example,
                        // settle between the other instructions.  For example,
                        // o_FP plus these four bits uniquely defines the FP
                        // o_FP plus these four bits uniquely defines the FP
                        // instruction, o_DV plus the bottom of these defines
                        // instruction, o_DV plus the bottom of these defines
                        // the divide, etc.
                        // the divide, etc.
                        o_op <= (w_ldi)||(w_noop)? 4'hf:w_op[3:0];
                        o_op <= (w_ldi)||(w_noop)? 4'hf:w_op[3:0];
 
 
                        // Default values
                        // Default values
                        o_dcdR <= { w_dcdR_cc, w_dcdR_pc, w_dcdR};
                        o_dcdR <= { w_dcdR_cc, w_dcdR_pc, w_dcdR};
                        o_dcdA <= { w_dcdA_cc, w_dcdA_pc, w_dcdA};
                        o_dcdA <= { w_dcdA_cc, w_dcdA_pc, w_dcdA};
                        o_dcdB <= { w_dcdB_cc, w_dcdB_pc, w_dcdB};
                        o_dcdB <= { w_dcdB_cc, w_dcdB_pc, w_dcdB};
                        o_wR  <= w_wR;
                        o_wR  <= w_wR;
                        o_rA  <= w_rA;
                        o_rA  <= w_rA;
                        o_rB  <= w_rB;
                        o_rB  <= w_rB;
                        r_I    <= w_I;
                        r_I    <= w_I;
                        o_zI   <= w_Iz;
`ifdef  OPT_PIPELINED
 
                        r_zI   <= w_Iz;
 
`endif
 
 
                        // Turn a NOOP into an ALU operation--subtract in 
                        // Turn a NOOP into an ALU operation--subtract in 
                        // particular, although it doesn't really matter as long
                        // particular, although it doesn't really matter as long
                        // as it doesn't take longer than one clock.  Note
                        // as it doesn't take longer than one clock.  Note
                        // also that this depends upon not setting any registers
                        // also that this depends upon not setting any registers
                        // or flags, which should already be true.
                        // or flags, which should already be true.
                        o_ALU  <=  (w_ALU)||(w_ldi)||(w_cmptst)||(w_noop); // 2 LUT
                        o_ALU  <=  (w_ALU)||(w_ldi)||(w_cmptst)||(w_noop); // 2 LUT
                        o_M    <=  w_dcdM;
                        o_M    <=  w_dcdM;
                        o_DV   <=  w_dcdDV;
                        o_DV   <=  w_dcdDV;
                        o_FP   <=  w_dcdFP;
                        o_FP   <=  w_dcdFP;
 
 
                        o_break <= (w_op[4:3]==2'b11)&&(w_dcdR[3:1]==3'h7)&&(w_op[2:0]==3'b001);
                        o_break <= (w_op[4:3]==2'b11)&&(w_dcdR[3:1]==3'h7)&&(w_op[2:0]==3'b001);
`ifdef  OPT_PIPELINED
`ifdef  OPT_PIPELINED
                        r_lock  <= (w_op[4:3]==2'b11)&&(w_dcdR[3:1]==3'h7)&&(w_op[2:0]==3'b010);
                        r_lock  <= (w_op[4:3]==2'b11)&&(w_dcdR[3:1]==3'h7)&&(w_op[2:0]==3'b010);
`endif
`endif
`ifdef  OPT_VLIW
`ifdef  OPT_VLIW
                        r_nxt_half <= { iword[31], iword[13:5],
                        r_nxt_half <= { iword[31], iword[13:5],
                                ((iword[21])? iword[20:19] : 2'h0),
                                ((iword[21])? iword[20:19] : 2'h0),
                                iword[4:0] };
                                iword[4:0] };
`endif
`endif
                end
                end
 
 
`ifdef  OPT_PIPELINED
`ifdef  OPT_PIPELINED
        assign  o_lock = r_lock;
        assign  o_lock = r_lock;
 
        assign  o_zI = r_zI;
`else
`else
        assign  o_lock = 1'b0;
        assign  o_lock = 1'b0;
 
        assign  o_zI = 1'b0;
`endif
`endif
 
 
        generate
        generate
        if (EARLY_BRANCHING!=0)
        if (EARLY_BRANCHING!=0)
        begin
        begin
                reg                     r_early_branch, r_ljmp;
                reg                     r_early_branch, r_ljmp;
                reg     [(AW-1):0]       r_branch_pc;
                reg     [(AW-1):0]       r_branch_pc;
 
 
                initial r_ljmp = 1'b0;
                initial r_ljmp = 1'b0;
                always @(posedge i_clk)
                always @(posedge i_clk)
                        if (i_rst)
                        if (i_rst)
                                r_ljmp <= 1'b0;
                                r_ljmp <= 1'b0;
                        else if ((i_ce)&&(i_pf_valid))
                        else if ((i_ce)&&(i_pf_valid))
                                r_ljmp <= (w_ljmp);
                                r_ljmp <= (w_ljmp);
                assign  o_ljmp = r_ljmp;
                assign  o_ljmp = r_ljmp;
 
 
                always @(posedge i_clk)
                always @(posedge i_clk)
                if (i_rst)
                if (i_rst)
                        r_early_branch <= 1'b0;
                        r_early_branch <= 1'b0;
                else if ((i_ce)&&(i_pf_valid))
                else if ((i_ce)&&(i_pf_valid))
                begin
                begin
                        if (r_ljmp)
                        if (r_ljmp)
                                // LOD (PC),PC
                                // LOD (PC),PC
                                r_early_branch <= 1'b1;
                                r_early_branch <= 1'b1;
                        else if ((~iword[31])&&(iword[30:27]==`CPU_PC_REG)&&(w_cond[3]))
                        else if ((~iword[31])&&(iword[30:27]==`CPU_PC_REG)&&(w_cond[3]))
                        begin
                        begin
                                if (w_op[4:1] == 4'hb) // LDI to PC
                                if (w_op[4:1] == 4'hb) // LDI to PC
                                        // LDI x,PC
                                        // LDI x,PC
                                        r_early_branch     <= 1'b1;
                                        r_early_branch     <= 1'b1;
                                else if ((w_op[4:0]==5'h02)&&(~iword[18]))
                                else if ((w_op[4:0]==5'h02)&&(~iword[18]))
                                        // Add x,PC
                                        // Add x,PC
                                        r_early_branch     <= 1'b1;
                                        r_early_branch     <= 1'b1;
                                else begin
                                else begin
                                        r_early_branch     <= 1'b0;
                                        r_early_branch     <= 1'b0;
                                end
                                end
                        end else
                        end else
                                r_early_branch <= 1'b0;
                                r_early_branch <= 1'b0;
                end else if (i_ce)
                end else if (i_ce)
                        r_early_branch <= 1'b0;
                        r_early_branch <= 1'b0;
 
 
                always @(posedge i_clk)
                always @(posedge i_clk)
                        if (i_ce)
                        if (i_ce)
                        begin
                        begin
                                if (r_ljmp)
                                if (r_ljmp)
                                        r_branch_pc <= iword[(AW-1):0];
                                        r_branch_pc <= iword[(AW-1):0];
                                else if (w_op[4:1] == 4'hb) // LDI
                                else if (w_op[4:1] == 4'hb) // LDI
                                        r_branch_pc <= {{(AW-23){iword[22]}},iword[22:0]};
                                        r_branch_pc <= {{(AW-23){iword[22]}},iword[22:0]};
                                else // Add x,PC
                                else // Add x,PC
                                r_branch_pc <= i_pc
                                r_branch_pc <= i_pc
                                        + {{(AW-17){iword[17]}},iword[16:0]}
                                        + {{(AW-17){iword[17]}},iword[16:0]}
                                        + {{(AW-1){1'b0}},1'b1};
                                        + {{(AW-1){1'b0}},1'b1};
                        end
                        end
 
 
                assign  o_early_branch     = r_early_branch;
                assign  o_early_branch     = r_early_branch;
                assign  o_branch_pc        = r_branch_pc;
                assign  o_branch_pc        = r_branch_pc;
        end else begin
        end else begin
                assign  o_early_branch = 1'b0;
                assign  o_early_branch = 1'b0;
                assign  o_branch_pc = {(AW){1'b0}};
                assign  o_branch_pc = {(AW){1'b0}};
                assign  o_ljmp = 1'b0;
                assign  o_ljmp = 1'b0;
        end endgenerate
        end endgenerate
 
 
 
 
        // To be a pipeable operation there must be ...
        // To be a pipeable operation there must be ...
        //      1. Two valid adjacent instructions
        //      1. Two valid adjacent instructions
        //      2. Both must be memory operations, of the same time (both lods
        //      2. Both must be memory operations, of the same time (both lods
        //              or both stos)
        //              or both stos)
        //      3. Both must use the same register base address
        //      3. Both must use the same register base address
        //      4. Both must be to the same address, or the address incremented
        //      4. Both must be to the same address, or the address incremented
        //              by one
        //              by one
        // Note that we're not using iword here ... there's a lot of logic
        // Note that we're not using iword here ... there's a lot of logic
        // taking place, and it's only valid if the new word is not compressed.
        // taking place, and it's only valid if the new word is not compressed.
        //
        //
        reg     r_valid;
 
`ifdef  OPT_PIPELINED
`ifdef  OPT_PIPELINED
 
        reg     r_valid;
        reg     r_pipe;
        reg     r_pipe;
        initial r_pipe = 1'b0;
        initial r_pipe = 1'b0;
        always @(posedge i_clk)
        always @(posedge i_clk)
                if (i_ce)
                if (i_ce)
                        r_pipe <= (r_valid)&&(i_pf_valid)&&(~i_instruction[31])
                        r_pipe <= (r_valid)&&(i_pf_valid)&&(~i_instruction[31])
                                &&(w_dcdM)&&(o_M)&&(o_op[0] ==i_instruction[22])
                                &&(w_dcdM)&&(o_M)&&(o_op[0] ==i_instruction[22])
                                &&(i_instruction[17:14] == o_dcdB[3:0])
                                &&(i_instruction[17:14] == o_dcdB[3:0])
                                &&(i_instruction[17:14] != o_dcdA[3:0])
                                &&(i_instruction[17:14] != o_dcdA[3:0])
                                &&(i_gie == o_gie)
                                &&(i_gie == o_gie)
                                &&((i_instruction[21:19]==o_cond[2:0])
                                &&((i_instruction[21:19]==o_cond[2:0])
                                        ||(o_cond[2:0] == 3'h0))
                                        ||(o_cond[2:0] == 3'h0))
                                &&((i_instruction[13:0]==r_I[13:0])
                                &&((i_instruction[13:0]==r_I[13:0])
                                        ||({1'b0, i_instruction[13:0]}==(r_I[13:0]+14'h1)));
                                        ||({1'b0, i_instruction[13:0]}==(r_I[13:0]+14'h1)));
        assign o_pipe = r_pipe;
        assign o_pipe = r_pipe;
`else
 
        assign o_pipe = 1'b0;
 
`endif
 
 
 
        always @(posedge i_clk)
        always @(posedge i_clk)
                if (i_rst)
                if (i_rst)
                        r_valid <= 1'b0;
                        r_valid <= 1'b0;
                else if ((i_ce)&&(o_ljmp))
                else if ((i_ce)&&(o_ljmp))
                        r_valid <= 1'b0;
                        r_valid <= 1'b0;
                else if ((i_ce)&&(i_pf_valid))
                else if ((i_ce)&&(i_pf_valid))
                        r_valid <= 1'b1;
                        r_valid <= 1'b1;
                else if (~i_stalled)
                else if (~i_stalled)
                        r_valid <= 1'b0;
                        r_valid <= 1'b0;
 
`else
 
        assign o_pipe = 1'b0;
 
`endif
 
 
 
 
        assign  o_I = { {(32-22){r_I[22]}}, r_I[21:0] };
        assign  o_I = { {(32-22){r_I[22]}}, r_I[21:0] };
 
 
endmodule
endmodule
 
 

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