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/**

 * @file

 * @copyright  Copyright 2016 GNSS Sensor Ltd. All right reserved.

 * @author     Sergey Khabarov - sergeykhbr@gmail.com

 * @brief      Branch Predictor.

 * @details    This module gives about 5% of performance improvement (CPI)

 */

#include "br_predic.h"

namespace debugger {

BranchPredictor::BranchPredictor(sc_module_name name_) : sc_module(name_) {

    SC_METHOD(comb);

    sensitive << i_nrst;

    sensitive << i_req_mem_fire;

    sensitive << i_resp_mem_valid;

    sensitive << i_resp_mem_addr;

    sensitive << i_resp_mem_data;

    sensitive << i_f_predic_miss;

    sensitive << i_e_npc;

    sensitive << i_ra;

    sensitive << r.npc;

    SC_METHOD(registers);

    sensitive << i_clk.pos();

};

void BranchPredictor::generateVCD(sc_trace_file *i_vcd, sc_trace_file *o_vcd) {

    if (o_vcd) {

        sc_trace(o_vcd, i_req_mem_fire, "/top/proc0/bp0/i_req_mem_fire");

        sc_trace(o_vcd, i_resp_mem_valid, "/top/proc0/bp0/i_resp_mem_valid");

        sc_trace(o_vcd, i_resp_mem_addr, "/top/proc0/bp0/i_resp_mem_addr");

        sc_trace(o_vcd, i_resp_mem_data, "/top/proc0/bp0/i_resp_mem_data");

        sc_trace(o_vcd, i_f_predic_miss, "/top/proc0/bp0/i_f_predic_miss");

        sc_trace(o_vcd, i_e_npc, "/top/proc0/bp0/i_e_npc");

        sc_trace(o_vcd, i_ra, "/top/proc0/bp0/i_ra");

        sc_trace(o_vcd, o_npc_predict, "/top/proc0/bp0/o_npc_predict");

        sc_trace(o_vcd, r.npc, "/top/proc0/bp0/r_npc");

    }

}

void BranchPredictor::comb() {

    v = r;

    sc_uint<32> wb_tmp;

    sc_uint<BUS_ADDR_WIDTH> wb_npc;

    sc_uint<BUS_ADDR_WIDTH> wb_off;

    wb_tmp = i_resp_mem_data.read();

    if (i_f_predic_miss.read()) {

        wb_npc = i_e_npc.read() + 4;

    } else {

        wb_npc = r.npc.read() + 4;

    }

    if (wb_tmp[31]) {

        wb_off(BUS_ADDR_WIDTH-1, 20) = ~0;

    } else {

        wb_off(BUS_ADDR_WIDTH-1, 20) = 0;

    }

    wb_off(19, 12) = wb_tmp(19, 12);

    wb_off[11] = wb_tmp[20];

    wb_off(10, 1) = wb_tmp(30, 21);

    wb_off[0] = 0;

    if (i_resp_mem_valid.read()) {

        if (wb_tmp == 0x00008067) {

            // ret pseudo-instruction: Dhry score 34816 -> 35136

            v.npc = i_ra.read()(BUS_ADDR_WIDTH-1, 0);

        } else if (wb_tmp(6, 0) == 0x6f) {

            // jal instruction: Dhry score 35136 -> 36992

            v.npc = i_resp_mem_addr.read() + wb_off;

        } else if (i_req_mem_fire.read()) {

            v.npc = wb_npc;

        }

    } else if (i_req_mem_fire.read()) {

        v.npc = wb_npc;

    }

    if (!i_nrst.read()) {

        v.npc = RESET_VECTOR;

    }

    o_npc_predict = r.npc;

}

void BranchPredictor::registers() {

    r = v;

}

}  // namespace debugger