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[/] [ft816float/] [trunk/] [rtl/] [verilog2/] [mult32x32combo.sv] - Blame information for rev 88

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1 74 robfinch
// ============================================================================
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//        __
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//   \\__/ o\    (C) 2020-2022  Robert Finch, Waterloo
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//    \  __ /    All rights reserved.
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//     \/_//     robfinch@finitron.ca
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//       ||
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//
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//      mult32x32combo.sv
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//  - Karatsuba multiply
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//  - combinational logic only
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//
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// BSD 3-Clause License
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice, this
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//    list of conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright notice,
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//    this list of conditions and the following disclaimer in the documentation
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//    and/or other materials provided with the distribution.
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//
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// 3. Neither the name of the copyright holder nor the names of its
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//    contributors may be used to endorse or promote products derived from
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//    this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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//
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// ============================================================================
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`define KARATSUBA       1
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`ifdef KARATSUBA
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module mult32x32combo(a, b, o);
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input [31:0] a;
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input [31:0] b;
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output reg [63:0] o='d0;
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reg [15:0] a2='d0, b2='d0;
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reg [16:0] a1='d0, b1='d0;
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reg [31:0] z0, z2, z0a, z2a, z0b, z2b, z0c, z2c, z0d, z2d, p3;
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reg [32:0] p4;
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reg [32:0] z1;  // extra bit for carry
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reg sgn2, sgn3, sgn4;
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always_comb
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        a1 <= a[15: 0] - a[31:16];  // x0-x1
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always_comb
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        b1 <= b[31:16] - b[15: 0];  // y1-y0
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always_comb
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        a2 <= a1[16] ? -a1 : a1;
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always_comb
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        b2 <= b1[16] ? -b1 : b1;
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always_comb
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  sgn2 <= a1[16]^b1[16];
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always_comb
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  sgn3 <= sgn2;
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always_comb
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  sgn4 <= sgn3;
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mult16x16combo u1 (
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  .a(a[31:16]),
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  .b(b[31:16]),
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  .o(z2)          // z2 = x1 * y1
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);
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mult16x16combo u2 (
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  .a(a[15:0]),
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  .b(b[15:0]),
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  .o(z0)          // z0 = x0 * y0
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);
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mult16x16combo u3 (
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  .a(a2[15:0]),
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  .b(b2[15:0]),
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  .o(p3)        // p3 = abs(x0-x1) * abs(y1-y0)
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);
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always_comb
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        p4 <= sgn3 ? -p3 : p3;
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always_comb
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  z2a <= z2;
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always_comb
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  z0a <= z0;
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always_comb
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  z2b <= z2a;
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always_comb
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  z0b <= z0a;
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always_comb
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  z2c <= z2b;
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always_comb
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  z0c <= z0b;
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always_comb
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        z1 <= {{32{p4[32]}},p4} + z2c + z0c;
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always_comb
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  z2d <= z2c;
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always_comb
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  z0d <= z0c;
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always_comb
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        o <= {z2d,z0d} + {z1,16'd0};
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endmodule
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`else
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// This version of the multiply has a parameterized pipeline depth and allows
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// the tools to perform the multiply. Relies on the ability of tools to retime.
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module mult32x32combo(a, b, o);
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parameter DEP = 6;
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input [31:0] a;
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input [31:0] b;
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output reg [63:0] o;
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reg [63:0] prod [0:DEP-1];
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reg [63:0] prd;
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integer n;
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always_comb
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        prd <= a * b;
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always_comb
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        prod[0] <= prd;
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always_comb
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        for (n = 0; n < DEP - 1; n = n + 1)
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                prod[n+1] <= prod[n];
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always_comb
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        o <= prod[DEP-1];
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endmodule
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`endif

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