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Removed carry-save multiplier option from muldiv

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David Harris 2021-12-30 21:14:57 +00:00
parent 2327f4b6bf
commit 7847ff33fc
2 changed files with 0 additions and 103 deletions
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101
wally-pipelined/src/muldiv/mult_cs.sv
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@ -1,101 +0,0 @@
///////////////////////////////////////////
// mul_cs.sv
//
// Written: james.stine@okstate.edu 17 October 2021
// Modified:
//
// Purpose: Carry/Save Multiplier output with Wallace Reduction
//
// A component of the Wally configurable RISC-V project.
//
// Copyright (C) 2021 Harvey Mudd College & Oklahoma State University
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy,
// modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software
// is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
// OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
///////////////////////////////////////////
module mult_cs #(parameter WIDTH = 8)
(a, b, tc, sum, carry);
input logic [WIDTH-1:0] a;
input logic [WIDTH-1:0] b;
input logic tc;
output logic [2*WIDTH-1:0] sum;
output logic [2*WIDTH-1:0] carry;
// PP array
logic [2*WIDTH-1:0] pp_array [0:WIDTH-1];
logic [2*WIDTH-1:0] next_pp_array [0:WIDTH-1];
logic [2*WIDTH-1:0] tmp_sum, tmp_carry;
logic [2*WIDTH-1:0] temp_pp;
logic [2*WIDTH-1:0] tmp_pp_carry;
logic [WIDTH-1:0] temp_b;
logic temp_bitgroup;
integer bit_pair, height, i;
always_comb
begin
// For each multiplicand PP generation
for (bit_pair=0; bit_pair < WIDTH; bit_pair=bit_pair+1)
begin
// Shift to the right via P&H
temp_b = (b >> (bit_pair));
temp_bitgroup = temp_b[0];
// PP generation
case (temp_bitgroup)
1'b0 : temp_pp = {2*WIDTH-1{1'b0}};
1'b1 : temp_pp = a;
default : temp_pp = {2*WIDTH-1{1'b0}};
endcase
// Shift to the left via P&H
temp_pp = temp_pp << (bit_pair);
pp_array[bit_pair] = temp_pp;
end
// Height is multiplier
height = WIDTH;
// Wallace Tree PP reduction
while (height > 2)
begin
for (i=0; i < (height/3); i=i+1)
begin
next_pp_array[i*2] = pp_array[i*3]^pp_array[i*3+1]^pp_array[i*3+2];
tmp_pp_carry = (pp_array[i*3] & pp_array[i*3+1]) |
(pp_array[i*3+1] & pp_array[i*3+2]) |
(pp_array[i*3] & pp_array[i*3+2]);
next_pp_array[i*2+1] = tmp_pp_carry << 1;
end
// Reasssign not divisible by 3 rows to next_pp_array
if ((height % 3) > 0)
begin
for (i=0; i < (height % 3); i=i+1)
next_pp_array[2 * (height/3) + i] = pp_array[3 * (height/3) + i];
end
// Put back values in pp_array to start again
for (i=0; i < WIDTH; i=i+1)
pp_array[i] = next_pp_array[i];
// Reduce height
height = height - (height/3);
end
// Sum is first row in reduced array
tmp_sum = pp_array[0];
// Carry is second row in reduced array
tmp_carry = pp_array[1];
end
assign sum = tmp_sum;
assign carry = tmp_carry;
endmodule // mult_cs

2
wally-pipelined/src/muldiv/redundantmul.sv
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@ -47,8 +47,6 @@ module redundantmul #(parameter WIDTH =8)(
DW02_multp #(WIDTH, WIDTH, 2*WIDTH+2) mul(.a, .b, .tc(1'b0), .out0(tmp_out0), .out1(tmp_out1));
assign out0 = tmp_out0[2*WIDTH-1:0];
assign out1 = tmp_out1[2*WIDTH-1:0];
end else if (`DESIGN_COMPILER == 2) begin:mul // *** need to remove this
mult_cs #(WIDTH) mul(.a, .b, .tc(1'b0), .sum(out0), .carry(out1));
end else begin:mul // force a nonredunant multipler. This will simulate properly and also is appropriate for FPGAs.
assign out0 = a * b;
assign out1 = 0;