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Update some on mult_cs and delete DW02_mult.v

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James E. Stine 2021-10-18 05:06:49 -05:00
parent 5a1835622c
commit aafa988ca2
1 changed files with 59 additions and 45 deletions
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104
wally-pipelined/src/muldiv/mult_cs.sv
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@ -1,3 +1,28 @@
///////////////////////////////////////////
// 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);
@ -9,76 +34,65 @@ module mult_cs #(parameter WIDTH = 8)
// 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] a_padded;
logic [2*WIDTH-1:0] b_padded;
logic [2*WIDTH-1:0] product;
assign a_padded = a;
assign b_padded = b;
logic [2*WIDTH-1:0] temp_pp;
logic [2*WIDTH-1:0] tmp_pp_carry;
logic [WIDTH-1:0] temp_b_padded;
logic temp_bitgroup;
integer bit_pair, height, i;
always_comb
begin
logic [2*WIDTH-1:0] temp_pp_array [0 : WIDTH-1];
logic [2*WIDTH-1:0] next_pp_array [0 : WIDTH-1];
logic [2*WIDTH-1:0] temp_pp;
logic [2*WIDTH-1:0] tmp_pp_carry;
logic [WIDTH+2:0] temp_b_padded;
logic temp_bitgroup;
integer bit_pair, pp_count, i;
temp_pp_array[0] = {2*WIDTH{1'b0}};
// For each multiplicand
for (bit_pair=0; bit_pair < WIDTH; bit_pair=bit_pair+1)
begin
// Shift to the right multiplier
temp_b_padded = (b_padded >> (bit_pair));
// Shift to the right via P&H
temp_b_padded = (b >> (bit_pair));
temp_bitgroup = temp_b_padded[0];
// PP generation
case (temp_bitgroup)
1'b0 :
temp_pp = {2*WIDTH{1'b0}};
1'b1 :
temp_pp = a_padded;
default : temp_pp = {2*WIDTH{1'b0}};
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);
temp_pp_array[bit_pair] = temp_pp;
pp_array[bit_pair] = temp_pp;
end
pp_count = WIDTH;
// Wallace Tree (I do not think this is really a Wallace tree (misses HA))
while (pp_count > 2)
// Height is multiplier
height = WIDTH;
// Wallace Tree Reduction
while (height > 2)
begin
for (i=0 ; i < (pp_count/3) ; i = i+1)
for (i=0; i < (height/3); i=i+1)
begin
next_pp_array[i*2] = temp_pp_array[i*3]^temp_pp_array[i*3+1]^temp_pp_array[i*3+2];
tmp_pp_carry = (temp_pp_array[i*3] & temp_pp_array[i*3+1]) |
(temp_pp_array[i*3+1] & temp_pp_array[i*3+2]) |
(temp_pp_array[i*3] & temp_pp_array[i*3+2]);
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
if ((pp_count % 3) > 0)
if ((height % 3) > 0)
begin
for (i=0 ; i < (pp_count % 3) ; i=i+1)
next_pp_array[2 * (pp_count/3) + i] = temp_pp_array[3 * (pp_count/3) + i];
for (i=0; i < (height % 3); i=i+1)
next_pp_array[2 * (height/3) + i] = pp_array[3 * (height/3) + i];
end
for (i=0 ; i < WIDTH ; i=i+1)
temp_pp_array[i] = next_pp_array[i];
pp_count = pp_count - (pp_count/3);
for (i=0; i < WIDTH; i=i+1)
pp_array[i] = next_pp_array[i];
height = height - (height/3);
end
tmp_sum = temp_pp_array[0];
// Sum is first row in reduced array
tmp_sum = pp_array[0];
if (pp_count > 1)
tmp_carry = temp_pp_array[1];
// Carry is second row in reduced array
if (height > 1)
tmp_carry = pp_array[1];
else
tmp_carry = {2*WIDTH{1'b0}};
tmp_carry = {2*WIDTH-1{1'b0}};
end
assign sum = tmp_sum;