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rtl: div: optimization 

Signed-off-by: liangkangnan <liangkangnan@163.com>
pull/1/head
liangkangnan 2020-09-06 23:17:56 +08:00
parent 0ed81ff1a8
commit b6754f002c
3 changed files with 73 additions and 93 deletions
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112
rtl/core/div.v
View File

@ -18,7 +18,7 @@
// 除法模块
// 试商法实现32位整数除法
// 每次除法运算至少需要32个时钟周期才能完成
// 每次除法运算需要33个时钟周期才能完成
module div(
input wire clk,
@ -32,91 +32,104 @@ module div(
input wire[`RegAddrBus] reg_waddr_i, // 运算结束后需要写的寄存器
// to ex
output reg[`DoubleRegBus] result_o, // 除法结果，高32位是余数，低32位是商
output reg[`RegBus] result_o, // 除法结果
output reg ready_o, // 运算结束信号
output wire busy_o, // 正在运算信号
output reg[2:0] op_o, // 具体是哪一条指令
output reg busy_o, // 正在运算信号
output reg[`RegAddrBus] reg_waddr_o // 运算结束后需要写的寄存器
);
// 状态定义
localparam STATE_IDLE = 0;
localparam STATE_START = 1;
localparam STATE_INVERT = 2;
localparam STATE_END = 3;
localparam STATE_IDLE = 4'b0001;
localparam STATE_START = 4'b0010;
localparam STATE_INVERT = 4'b0100;
localparam STATE_END = 4'b1000;
reg[`RegBus] dividend_temp;
reg[`RegBus] divisor_temp;
reg[1:0] state;
reg[6:0] count;
reg[3:0] state;
reg[31:0] count;
reg[`RegBus] div_result;
reg[`RegBus] div_remain;
reg[`RegBus] minuend;
reg[`RegBus] divisor_zero_result;
reg invert_result;
reg inst_div;
reg inst_divu;
wire[31:0] dividend_invert = -dividend_i;
wire[31:0] divisor_invert = -divisor_i;
wire[31:0] minuend_sub_res = minuend - divisor_temp;
wire minuend_ge_divisor = minuend >= divisor_temp;
assign busy_o = (state != STATE_IDLE)? `True : `False;
wire op_div = (op_i == `INST_DIV);
wire op_divu = (op_i == `INST_DIVU);
wire op_rem = (op_i == `INST_REM);
wire op_remu = (op_i == `INST_REMU);
// 状态机实现
always @ (posedge clk) begin
if (rst == `RstEnable) begin
state <= STATE_IDLE;
ready_o <= `DivResultNotReady;
result_o <= {`ZeroWord, `ZeroWord};
result_o <= `ZeroWord;
div_result <= `ZeroWord;
div_remain <= `ZeroWord;
divisor_zero_result <= ~32'b00000001 + 1'b1;
op_o <= 3'h0;
reg_waddr_o <= `ZeroWord;
dividend_temp <= `ZeroWord;
divisor_temp <= `ZeroWord;
minuend <= `ZeroWord;
count <= `ZeroWord;
invert_result <= 1'b0;
busy_o <= `False;
inst_div <= 1'b0;
inst_divu <= 1'b0;
end else begin
case (state)
STATE_IDLE: begin
busy_o <= `False;
if (start_i == `DivStart) begin
op_o <= op_i;
reg_waddr_o <= reg_waddr_i;
inst_div <= op_div;
inst_divu <= op_divu;
// 除数为0
if (divisor_i == `ZeroWord) begin
ready_o <= `DivResultReady;
result_o <= {dividend_i, divisor_zero_result};
if (op_div | op_divu) begin
result_o <= 32'hffffffff;
end else begin
result_o <= dividend_i;
end
// 除数不为0
end else begin
count <= 7'd31;
count <= 32'h80000000;
state <= STATE_START;
div_result <= `ZeroWord;
div_remain <= `ZeroWord;
// DIV和REM这两条指令是有符号数运算
if ((op_i == `INST_DIV) || (op_i == `INST_REM)) begin
if ((op_div) || (op_rem)) begin
// 被除数求补码
if (dividend_i[31] == 1'b1) begin
dividend_temp <= ~dividend_i + 1;
minuend <= ((~dividend_i + 1) >> 7'd31) & 1'b1;
dividend_temp <= dividend_invert;
minuend <= dividend_invert[31];
end else begin
dividend_temp <= dividend_i;
minuend <= (dividend_i >> 7'd31) & 1'b1;
minuend <= dividend_i[31];
end
// 除数求补码
if (divisor_i[31] == 1'b1) begin
divisor_temp <= ~divisor_i + 1;
divisor_temp <= divisor_invert;
end else begin
divisor_temp <= divisor_i;
end
end else begin
dividend_temp <= dividend_i;
minuend <= (dividend_i >> 7'd31) & 1'b1;
minuend <= dividend_i[31];
divisor_temp <= divisor_i;
end
// 运算结束后是否要对结果取补码
if (((op_i == `INST_DIV) && (dividend_i[31] ^ divisor_i[31] == 1'b1))
|| ((op_i == `INST_REM) && (dividend_i[31] == 1'b1))) begin
if (((op_div) && (dividend_i[31] ^ divisor_i[31] == 1'b1))
|| ((op_rem) && (dividend_i[31] == 1'b1))) begin
invert_result <= 1'b1;
end else begin
invert_result <= 1'b0;
@ -124,60 +137,65 @@ module div(
end
end else begin
ready_o <= `DivResultNotReady;
result_o <= {`ZeroWord, `ZeroWord};
result_o <= `ZeroWord;
end
end
STATE_START: begin
busy_o <= `True;
if (start_i == `DivStart) begin
if (count >= 7'd1) begin
if (minuend >= divisor_temp) begin
div_result <= (div_result << 1'b1) | 1'b1;
minuend <= ((minuend - divisor_temp) << 1'b1) | ((dividend_temp >> (count - 1'b1)) & 1'b1);
div_result <= {div_result[30:0], minuend_ge_divisor};
if (|count) begin
if (minuend_ge_divisor) begin
minuend <= {minuend_sub_res[30:0], dividend_temp[31]};
end else begin
div_result <= (div_result << 1'b1) | 1'b0;
minuend <= (minuend << 1'b1) | ((dividend_temp >> (count - 1'b1)) & 1'b1);
minuend <= {minuend[30:0], dividend_temp[31]};
end
count <= count - 1'b1;
count <= {1'b0, count[31:1]};
dividend_temp <= {dividend_temp[30:0], 1'b0};
end else begin
state <= STATE_INVERT;
if (minuend >= divisor_temp) begin
div_result <= (div_result << 1'b1) | 1'b1;
div_remain <= minuend - divisor_temp;
if (minuend_ge_divisor) begin
div_remain <= minuend_sub_res;
end else begin
div_result <= (div_result << 1'b1) | 1'b0;
div_remain <= minuend;
end
end
end else begin
ready_o <= `DivResultNotReady;
result_o <= {`ZeroWord, `ZeroWord};
result_o <= `ZeroWord;
state <= STATE_IDLE;
end
end
STATE_INVERT: begin
busy_o <= `True;
if (start_i == `DivStart) begin
if (invert_result == 1'b1) begin
div_result <= ~div_result + 1'b1;
div_remain <= ~div_remain + 1'b1;
div_result <= -div_result;
div_remain <= -div_remain;
end
state <= STATE_END;
end else begin
ready_o <= `DivResultNotReady;
result_o <= {`ZeroWord, `ZeroWord};
result_o <= `ZeroWord;
state <= STATE_IDLE;
end
end
STATE_END: begin
busy_o <= `False;
if (start_i == `DivStart) begin
ready_o <= `DivResultReady;
result_o <= {div_remain, div_result};
if (inst_div | inst_divu) begin
result_o <= div_result;
end else begin
result_o <= div_remain;
end
state <= STATE_IDLE;
end else begin
state <= STATE_IDLE;
result_o <= {`ZeroWord, `ZeroWord};
result_o <= `ZeroWord;
ready_o <= `DivResultNotReady;
end
end

49
rtl/core/ex.v
View File

@ -44,9 +44,8 @@ module ex(
// from div
input wire div_ready_i, // 除法运算完成标志
input wire[`DoubleRegBus] div_result_i, // 除法运算结果
input wire[`RegBus] div_result_i, // 除法运算结果
input wire div_busy_i, // 除法运算忙标志
input wire[2:0] div_op_i, // 具体是哪一条除法指令
input wire[`RegAddrBus] div_reg_waddr_i,// 除法运算结束后要写的寄存器地址
// to mem
@ -67,7 +66,7 @@ module ex(
output wire[`MemAddrBus] csr_waddr_o, // 写CSR寄存器地址
// to div
output wire div_start_o, // 开始除法运算标志
output wire div_start_o, // 开始除法运算标志
output reg[`RegBus] div_dividend_o, // 被除数
output reg[`RegBus] div_divisor_o, // 除数
output reg[2:0] div_op_o, // 具体是哪一条除法指令
@ -251,23 +250,9 @@ module ex(
div_start = `DivStop;
div_hold_flag = `HoldDisable;
if (div_ready_i == `DivResultReady) begin
case (div_op_i)
`INST_DIV, `INST_DIVU: begin
div_wdata = div_result_i[31:0];
div_waddr = div_reg_waddr_i;
div_we = `WriteEnable;
end
`INST_REM, `INST_REMU: begin
div_wdata = div_result_i[63:32];
div_waddr = div_reg_waddr_i;
div_we = `WriteEnable;
end
default: begin
div_wdata = `ZeroWord;
div_waddr = `ZeroWord;
div_we = `WriteDisable;
end
endcase
div_wdata = div_result_i;
div_waddr = div_reg_waddr_i;
div_we = `WriteEnable;
end else begin
div_we = `WriteDisable;
div_wdata = `ZeroWord;
@ -822,7 +807,7 @@ module ex(
end
endcase
end
`INST_JAL: begin
`INST_JAL, `INST_JALR: begin
hold_flag = `HoldDisable;
mem_wdata_o = `ZeroWord;
mem_raddr_o = `ZeroWord;
@ -832,27 +817,7 @@ module ex(
jump_addr = op1_jump_add_op2_jump_res;
reg_wdata = op1_add_op2_res;
end
`INST_JALR: begin
hold_flag = `HoldDisable;
mem_wdata_o = `ZeroWord;
mem_raddr_o = `ZeroWord;
mem_waddr_o = `ZeroWord;
mem_we = `WriteDisable;
jump_flag = `JumpEnable;
jump_addr = op1_jump_add_op2_jump_res;
reg_wdata = op1_add_op2_res;
end
`INST_LUI: begin
hold_flag = `HoldDisable;
mem_wdata_o = `ZeroWord;
mem_raddr_o = `ZeroWord;
mem_waddr_o = `ZeroWord;
mem_we = `WriteDisable;
jump_addr = `ZeroWord;
jump_flag = `JumpDisable;
reg_wdata = op1_add_op2_res;
end
`INST_AUIPC: begin
`INST_LUI, `INST_AUIPC: begin
hold_flag = `HoldDisable;
mem_wdata_o = `ZeroWord;
mem_raddr_o = `ZeroWord;

5
rtl/core/tinyriscv.v
View File

@ -124,10 +124,9 @@ module tinyriscv(
wire[`InstAddrBus] ctrl_jump_addr_o;
// div模块输出信号
wire[`DoubleRegBus] div_result_o;
wire[`RegBus] div_result_o;
wire div_ready_o;
wire div_busy_o;
wire[2:0] div_op_o;
wire[`RegAddrBus] div_reg_waddr_o;
// clint模块输出信号
@ -313,7 +312,6 @@ module tinyriscv(
.div_ready_i(div_ready_o),
.div_result_i(div_result_o),
.div_busy_i(div_busy_o),
.div_op_i(div_op_o),
.div_reg_waddr_i(div_reg_waddr_o),
.div_start_o(ex_div_start_o),
.div_dividend_o(ex_div_dividend_o),
@ -340,7 +338,6 @@ module tinyriscv(
.result_o(div_result_o),
.ready_o(div_ready_o),
.busy_o(div_busy_o),
.op_o(div_op_o),
.reg_waddr_o(div_reg_waddr_o)
);