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// ============================================================================
// __
// \\__/ o\ (C) 2006-2020 Robert Finch, Waterloo
// \ __ / All rights reserved.
// \/_// robfinch<remove>@finitron.ca
// ||
//
// DFPMultiply.v
// - decimal floating point multiplier
// - can issue every clock cycle
// - parameterized width
//
//
// BSD 3-Clause License
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
// list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
//
// Floating Point Multiplier
//
// This multiplier handles denormalized numbers.
// The output format is of an internal expanded representation
// in preparation to be fed into a normalization unit, then
// rounding. Basically, it's the same as the regular format
// except the mantissa is doubled in size, the leading two
// bits of which are assumed to be whole bits.
//
//
// Floating Point Multiplier
//
// Properties:
// +-inf * +-inf = -+inf (this is handled by exOver)
// +-inf * 0 = QNaN
//
// ============================================================================
import fp::*;
//`define DFPMUL_PARALLEL 1'b1
module DFPMultiply(clk, ce, ld, a, b, o, sign_exe, inf, overflow, underflow, done);
parameter N=33;
input clk;
input ce;
input ld;
input [N*4+16+4-1:0] a, b;
output [(N+1)*4*2+16+4-1:0] o;
output sign_exe;
output inf;
output overflow;
output underflow;
output done;
parameter DELAY =
(FPWID == 128 ? 17 :
FPWID == 80 ? 17 :
FPWID == 64 ? 13 :
FPWID == 40 ? 8 :
FPWID == 32 ? 2 :
FPWID == 16 ? 2 : 2);
reg [15:0] xo1; // extra bit for sign
reg [N*4*2-1:0] mo1;
// constants
wire [15:0] infXp = 16'h9999; // infinite / NaN - all ones
// The following is the value for an exponent of zero, with the offset
// eg. 8'h7f for eight bit exponent, 11'h7ff for eleven bit exponent, etc.
// The following is a template for a quiet nan. (MSB=1)
wire [N*4-1:0] qNaN = {4'h1,{104{1'b0}}};
// variables
reg [N*4*2-1:0] sig1;
wire [15:0] ex2;
// Decompose the operands
wire sa, sb; // sign bit
wire [15:0] xa, xb; // exponent bits
wire sxa, sxb;
wire [N*4-1:0] siga, sigb;
wire a_dn, b_dn; // a/b is denormalized
wire aNan, bNan, aNan1, bNan1;
wire az, bz;
wire aInf, bInf, aInf1, bInf1;
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Clock #1
// - decode the input operands
// - derive basic information
// - calculate exponent
// - calculate fraction
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// -----------------------------------------------------------
// First clock
// -----------------------------------------------------------
reg under, over;
reg [15:0] sum_ex, sum_ex1;
reg sx0;
wire done1;
DFPDecompose u1a (.i(a), .sgn(sa), .sx(sxa), .exp(xa), .sig(siga), .xz(a_dn), .vz(az), .inf(aInf), .nan(aNan) );
DFPDecompose u1b (.i(b), .sgn(sb), .sx(sxb), .exp(xb), .sig(sigb), .xz(b_dn), .vz(bz), .inf(bInf), .nan(bNan) );
// Compute the sum of the exponents.
// Exponents are sign-magnitude.
wire [15:0] xapxb, xamxb, xbmxa;
wire xapxbc, xamxbc, xbmxac;
BCDAddN #(.N(4)) u1c (.ci(1'b0), .a(xa), .b(xb), .o(xapxb), .co(xapxbc));
BCDSubN #(.N(4)) u1d (.ci(1'b0), .a(xa), .b(xb), .o(xamxb), .co(xamxbc));
BCDSubN #(.N(4)) u1e (.ci(1'b0), .a(xb), .b(xa), .o(xbmxa), .co(xbmxac));
BCDSubN #(.N(5)) u1h (.ci(1'b0), .a(20'h10000), .b(sum_ex1), .o(sum_ex2), .co());
always @*
case({sxa,sxb})
2'b11: begin sum_ex1 <= xapxb; over <= xapxbc; under <= 1'b0; sx0 <= sxa; end
2'b01: begin sum_ex1 <= xbmxa; over <= 1'b0; under <= 1'b0; sx0 <= ~xbmxac; end
2'b10: begin sum_ex1 <= xamxb; over <= 1'b0; under <= 1'b0; sx0 <= ~xamxbc; end
2'b00: begin sum_ex1 <= xapxb; over <= 1'b0; under <= xapxbc; sx0 <= sxa; end
endcase
// Take nine's complement if exponent sign changed.
always @*
if ((sxa^sxb)) begin
if ((sxa & xamxbc) || (sxb & xbmxac))
sum_ex <= sum_ex2;
else
sum_ex <= sum_ex1;
end
else
sum_ex <= sum_ex1;
wire [N*4*2-1:0] sigoo;
`ifdef DFPMUL_PARALLEL
BCDMul32 u1f (.a({20'h0,siga}),.b({20'h0,sigb}),.o(sigoo));
`else
dfmul #(.N(N)) u1g
(
.clk(clk),
.ld(ld),
.a(siga),
.b(sigb),
.p(sigoo),
.done(done1)
);
`endif
always @(posedge clk)
if (ce) sig1 <= sigoo[N*4*2-1:0];
// Status
wire under1, over1;
delay #(.WID(16),.DEP(DELAY)) u3 (.clk(clk), .ce(ce), .i(sum_ex), .o(ex2) );
delay #(.WID(1),.DEP(DELAY)) u2a (.clk(clk), .ce(ce), .i(aInf), .o(aInf1) );
delay #(.WID(1),.DEP(DELAY)) u2b (.clk(clk), .ce(ce), .i(bInf), .o(bInf1) );
delay #(.WID(1),.DEP(DELAY)) u6 (.clk(clk), .ce(ce), .i(under), .o(under1) );
delay #(.WID(1),.DEP(DELAY)) u7 (.clk(clk), .ce(ce), .i(over), .o(over1) );
// determine when a NaN is output
wire qNaNOut;
wire [N*4+16+4-1:0] a1,b1;
delay #(.WID(1),.DEP(DELAY)) u5 (.clk(clk), .ce(ce), .i((aInf&bz)|(bInf&az)), .o(qNaNOut) );
delay #(.WID(1),.DEP(DELAY)) u14 (.clk(clk), .ce(ce), .i(aNan), .o(aNan1) );
delay #(.WID(1),.DEP(DELAY)) u15 (.clk(clk), .ce(ce), .i(bNan), .o(bNan1) );
delay #(.WID(N*4+16+4),.DEP(DELAY)) u16 (.clk(clk), .ce(ce), .i(a), .o(a1) );
delay #(.WID(N*4+16+4),.DEP(DELAY)) u17 (.clk(clk), .ce(ce), .i(b), .o(b1) );
// -----------------------------------------------------------
// Second clock
// - correct xponent and mantissa for exceptional conditions
// -----------------------------------------------------------
wire so1, sx1;
reg [3:0] st;
wire done1a;
delay #(.WID(1),.DEP(1)) u8 (.clk(clk), .ce(ce), .i(~(sa ^ sb)), .o(so1) );// two clock delay!
delay #(.WID(1),.DEP(1)) u9 (.clk(clk), .ce(ce), .i(sx0), .o(sx1) );// two clock delay!
always @(posedge clk)
if (ce)
casez({qNaNOut|aNan1|bNan1,aInf1,bInf1,over1,under1})
5'b1????: xo1 = infXp; // qNaN - infinity * zero
5'b01???: xo1 = infXp; // 'a' infinite
5'b001??: xo1 = infXp; // 'b' infinite
5'b0001?: xo1 = infXp; // result overflow
5'b00001: xo1 = ex2[15:0];//0; // underflow
default: xo1 = ex2[15:0]; // situation normal
endcase
// Force mantissa to zero when underflow or zero exponent when not supporting denormals.
always @(posedge clk)
if (ce)
casez({aNan1,bNan1,qNaNOut,aInf1,bInf1,over1|under1})
6'b1?????: mo1 = {4'h1,a1[N*4-4-1:0],{N*4{1'b0}}};
6'b01????: mo1 = {4'h1,b1[N*4-4-1:0],{N*4{1'b0}}};
6'b001???: mo1 = {4'h1,qNaN|3'd4,{N*4{1'b0}}}; // multiply inf * zero
6'b0001??: mo1 = 0; // mul inf's
6'b00001?: mo1 = 0; // mul inf's
6'b000001: mo1 = 0; // mul overflow
default: mo1 = sig1;
endcase
always @(posedge clk)
if (ce) begin
st[3] <= aNan1|bNan1;
st[2] <= so1;
st[1] <= aInf|bInf|over;
st[0] <= sx1;
end
delay #(.WID(1),.DEP(DELAY+1)) u10 (.clk(clk), .ce(ce), .i(sa & sb), .o(sign_exe) );
delay1 u11 (.clk(clk), .ce(ce), .i(over1), .o(overflow) );
delay1 u12 (.clk(clk), .ce(ce), .i(over1), .o(inf) );
delay1 u13 (.clk(clk), .ce(ce), .i(under1), .o(underflow) );
delay #(.WID(1),.DEP(3)) u18 (.clk(clk), .ce(ce), .i(done1), .o(done1a) );
assign o = {st,xo1,mo1,8'h00};
assign done = done1&done1a;
endmodule
// Multiplier with normalization and rounding.
module DFPMultiplynr(clk, ce, ld, a, b, o, rm, sign_exe, inf, overflow, underflow, done);
parameter N=33;
input clk;
input ce;
input ld;
input [N*4+16+4-1:0] a, b;
output [N*4+16+4-1:0] o;
input [2:0] rm;
output sign_exe;
output inf;
output overflow;
output underflow;
output done;
wire done1, done1a;
wire [(N+1)*4*2+16+4-1:0] o1;
wire sign_exe1, inf1, overflow1, underflow1;
wire [N*4+16+4-1+4:0] fpn0;
DFPMultiply u1 (clk, ce, ld, a, b, o1, sign_exe1, inf1, overflow1, underflow1, done1);
DFPNormalize u2(.clk(clk), .ce(ce), .under_i(underflow1), .i(o1), .o(fpn0) );
DFPRound u3(.clk(clk), .ce(ce), .rm(rm), .i(fpn0), .o(o) );
delay2 #(1) u4(.clk(clk), .ce(ce), .i(sign_exe1), .o(sign_exe));
delay2 #(1) u5(.clk(clk), .ce(ce), .i(inf1), .o(inf));
delay2 #(1) u6(.clk(clk), .ce(ce), .i(overflow1), .o(overflow));
delay2 #(1) u7(.clk(clk), .ce(ce), .i(underflow1), .o(underflow));
delay #(.WID(1),.DEP(11)) u10 (.clk(clk), .ce(ce), .i(done1), .o(done1a) );
assign done = done1 & done1a;
endmodule
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