Subversion Repositories ft816float

// ============================================================================

//        __

//   \\__/ o\    (C) 2006-2019  Robert Finch, Waterloo

//    \  __ /    All rights reserved.

//     \/_//     robfinch<remove>@finitron.ca

//       ||

//

//      fpNormalize.v

//    - floating point normalization unit

//    - eight cycle latency

//    - parameterized FPWIDth

//    - IEEE 754 representation

//

//

// This source file 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 3 of the License, or     

// (at your option) any later version.                                      

//                                                                          

// This source file 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 General Public License for more details.                             

//                                                                          

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

// along with this program.  If not, see <http://www.gnu.org/licenses/>.    

//                                                                          

//      This unit takes a floating point number in an intermediate

// format and normalizes it. No normalization occurs

// for NaN's or infinities. The unit has a two cycle latency.

//

// The mantissa is assumed to start with two whole bits on

// the left. The remaining bits are fractional.

//

// The FPWIDth of the incoming format is reduced via a generation

// of sticky bit in place of the low order fractional bits.

//

// On an underflowed input, the incoming exponent is assumed

// to be negative. A right shift is needed.

// ============================================================================

`include "fpConfig.sv"

module fpNormalize(clk, ce, i, o, under_i, under_o, inexact_o);

parameter FPWID = 80;

`include "fpSize.sv"

input clk;

input ce;

input [EX:0] i;          // expanded format input

output [MSB+3:0] o;              // normalized output + guard, sticky and round bits, + 1 whole digit

input under_i;

output under_o;

output inexact_o;

// ----------------------------------------------------------------------------

// No Clock required

// ----------------------------------------------------------------------------

reg [EMSB:0] xo0;

reg so0;

always @*

        xo0 <= i[EX-1:FX+1];

always @*

        so0 <= i[EX];           // sign doesn't change

// ----------------------------------------------------------------------------

// Clock #1

// - Capture exponent information

// ----------------------------------------------------------------------------

reg xInf1a, xInf1b, xInf1c;

wire [FX:0] i1;

delay1 #(FX+1) u11 (.clk(clk), .ce(ce), .i(i), .o(i1));

always @(posedge clk)

        if (ce) xInf1a <= &xo0 & !under_i;

always @(posedge clk)

        if (ce) xInf1b <= &xo0[EMSB:1] & !under_i;

always @(posedge clk)

        if (ce) xInf1c = &xo0;

// ----------------------------------------------------------------------------

// Clock #2

// - determine exponent increment

// Since the there are *three* whole digits in the incoming format

// the number of whole digits needs to be reduced. If the MSB is

// set, then increment the exponent and no shift is needed.

// ----------------------------------------------------------------------------

wire xInf2c, xInf2b;

wire [EMSB:0] xo2;

reg incExpByOne2, incExpByTwo2;

delay1 u21 (.clk(clk), .ce(ce), .i(xInf1c), .o(xInf2c));

delay1 u22 (.clk(clk), .ce(ce), .i(xInf1b), .o(xInf2b));

delay2 #(EMSB+1) u23 (.clk(clk), .ce(ce), .i(xo0), .o(xo2));

delay2 u24 (.clk(clk), .ce(ce), .i(under_i), .o(under2));

always @(posedge clk)

        if (ce) incExpByTwo2 <= !xInf1b & i1[FX];

always @(posedge clk)

        if (ce) incExpByOne2 <= !xInf1a & i1[FX-1];

// ----------------------------------------------------------------------------

// Clock #3

// - increment exponent

// - detect a zero mantissa

// ----------------------------------------------------------------------------

wire incExpByTwo3;

wire incExpByOne3;

wire [FX:0] i3;

reg [EMSB:0] xo3;

reg zeroMan3;

delay1 u31 (.clk(clk), .ce(ce), .i(incExpByTwo2), .o(incExpByTwo3));

delay1 u32 (.clk(clk), .ce(ce), .i(incExpByOne2), .o(incExpByOne3));

delay3 #(FX+1) u33 (.clk(clk), .ce(ce), .i(i[FX:0]), .o(i3));

wire [EMSB+1:0] xv3a = xo2 + {incExpByTwo2,1'b0};

wire [EMSB+1:0] xv3b = xo2 + incExpByOne2;

always @(posedge clk)

        if (ce) xo3 <= xo2 + (incExpByTwo2 ? 2'd2 : incExpByOne2 ? 2'd1 : 2'd0);

always @(posedge clk)

        if(ce) zeroMan3 <= ((xv3b[EMSB+1]|| &xv3b[EMSB:0])||(xv3a[EMSB+1]| &xv3a[EMSB:0]))

                                                                                         && !under2 && !xInf2c;

// ----------------------------------------------------------------------------

// Clock #4

// - Shift mantissa left

// - If infinity is reached then set the mantissa to zero

//   shift mantissa left to reduce to a single whole digit

// - create sticky bit

// ----------------------------------------------------------------------------

reg [FMSB+4:0] mo4;

reg inexact4;

always @(posedge clk)

if(ce)

casez({zeroMan3,incExpByTwo3,incExpByOne3})

3'b1??: mo4 <= 1'd0;

3'b01?: mo4 <= {i3[FX:FMSB+1],|i3[FMSB:0]};

3'b001: mo4 <= {i3[FX-1:FMSB],|i3[FMSB-1:0]};

default:        mo4 <= {i3[FX-2:FMSB-1],|i3[FMSB-2:0]};

endcase

always @(posedge clk)

if(ce)

casez({zeroMan3,incExpByTwo3,incExpByOne3})

3'b1??: inexact4 <= 1'd0;

3'b01?: inexact4 <= |i3[FMSB:0];

3'b001: inexact4 <= |i3[FMSB-1:0];

default:        inexact4 <= |i3[FMSB-2:0];

endcase

// ----------------------------------------------------------------------------

// Clock edge #5

// - count leading zeros

// ----------------------------------------------------------------------------

wire [7:0] leadingZeros5;

wire [EMSB:0] xo5;

wire xInf5;

delay2 #(EMSB+1) u51 (.clk(clk), .ce(ce), .i(xo3), .o(xo5));

delay3 #(1)      u52 (.clk(clk), .ce(ce), .i(xInf2c), .o(xInf5) );

generate

begin

if (FPWID <= 32) begin

cntlz32Reg clz0 (.clk(clk), .ce(ce), .i({mo4,5'b0}), .o(leadingZeros5) );

assign leadingZeros5[7:6] = 2'b00;

end

else if (FPWID<=64) begin

assign leadingZeros5[7] = 1'b0;

cntlz64Reg clz0 (.clk(clk), .ce(ce), .i({mo4,8'h0}), .o(leadingZeros5) );

end

else if (FPWID<=80) begin

assign leadingZeros5[7] = 1'b0;

cntlz80Reg clz0 (.clk(clk), .ce(ce), .i({mo4,12'b0}), .o(leadingZeros5) );

end

else if (FPWID<=84) begin

assign leadingZeros5[7] = 1'b0;

cntlz96Reg clz0 (.clk(clk), .ce(ce), .i({mo4,24'b0}), .o(leadingZeros5) );

end

else if (FPWID<=96) begin

assign leadingZeros5[7] = 1'b0;

cntlz96Reg clz0 (.clk(clk), .ce(ce), .i({mo4,12'b0}), .o(leadingZeros5) );

end

else if (FPWID<=128)

cntlz128Reg clz0 (.clk(clk), .ce(ce), .i({mo4,12'b0}), .o(leadingZeros5) );

end

endgenerate

// ----------------------------------------------------------------------------

// Clock edge #6

// - Compute how much we want to decrement exponent by

// - compute amount to shift left and right

// - at infinity the exponent can't be incremented, so we can't shift right

//   otherwise it was an underflow situation so the exponent was negative

//   shift amount needs to be negated for shift register

// If the exponent underflowed, then the shift direction must be to the

// right regardless of mantissa bits; the number is denormalized.

// Otherwise the shift direction must be to the left.

// ----------------------------------------------------------------------------

reg [7:0] lshiftAmt6;

reg [7:0] rshiftAmt6;

wire rightOrLeft6;      // 0=left,1=right

wire xInf6;

wire [EMSB:0] xo6;

wire [FMSB+4:0] mo6;

wire zeroMan6;

vtdl #(1) u61 (.clk(clk), .ce(ce), .a(4'd5), .d(under_i), .q(rightOrLeft6) );

delay1 #(EMSB+1) u62 (.clk(clk), .ce(ce), .i(xo5), .o(xo6));

delay2 #(FMSB+5) u63 (.clk(clk), .ce(ce), .i(mo4), .o(mo6) );

delay1 #(1)      u64 (.clk(clk), .ce(ce), .i(xInf5), .o(xInf6) );

delay3 u65 (.clk(clk), .ce(ce),  .i(zeroMan3), .o(zeroMan6));

always @(posedge clk)

        if (ce) lshiftAmt6 <= leadingZeros5 > xo5 ? xo5 : leadingZeros5;

always @(posedge clk)

        if (ce) rshiftAmt6 <= xInf5 ? 1'd0 : $signed(xo5) > 1'd0 ? 1'd0 : ~xo5+2'd1;    // xo2 is negative !

// ----------------------------------------------------------------------------

// Clock edge #7

// - fogure exponent

// - shift mantissa

// ----------------------------------------------------------------------------

reg [EMSB:0] xo7;

wire rightOrLeft7;

reg [FMSB+4:0] mo7l, mo7r;

delay1 u71 (.clk(clk), .ce(ce), .i(rightOrLeft6), .o(rightOrLeft7));

always @(posedge clk)

if (ce)

        xo7 <= zeroMan6 ? xo6 :

                xInf6 ? xo6 :                                   // an infinite exponent is either a NaN or infinity; no need to change

                rightOrLeft6 ? 1'd0 :   // on a right shift, the exponent was negative, it's being made to zero

                xo6 - lshiftAmt6;                       // on a left shift, the exponent can't be decremented below zero

always @(posedge clk)

        if (ce) mo7r <= mo6 >> rshiftAmt6;

always @(posedge clk)

        if (ce) mo7l <= mo6 << lshiftAmt6;

// ----------------------------------------------------------------------------

// Clock edge #8

// - select mantissa

// ----------------------------------------------------------------------------

wire so;

wire [EMSB:0] xo;

reg [FMSB+4:0] mo;

vtdl #(1) u81 (.clk(clk), .ce(ce), .a(4'd7), .d(so0), .q(so) );

delay1 #(EMSB+1) u82 (.clk(clk), .ce(ce), .i(xo7), .o(xo));

vtdl u83 (.clk(clk), .ce(ce), .a(4'd3), .d(inexact4), .q(inexact_o));

delay1 u84 (.clk(clk), .ce(ce), .i(rightOrLeft7), .o(under_o));

always @(posedge clk)

        if (ce) mo <= rightOrLeft7 ? mo7r : mo7l;

assign o = {so,xo,mo[FMSB+4:1]};

endmodule