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Add copyright header, comment on cascade

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Eddie Hung 2019-07-24 10:49:09 -07:00
parent 79fd6edc5a
commit c39ccc65e9
1 changed files with 34 additions and 4 deletions
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38
techlibs/common/mul2dsp.v
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@ -1,7 +1,31 @@
// From Eddie Hung
// extracted from: https://github.com/eddiehung/vtr-with-yosys/blob/vtr7-with-yosys/vtr_flow/misc/yosys_models.v#L220
// revised by Andre DeHon
// further revised by David Shah
/*
* yosys -- Yosys Open SYnthesis Suite
*
* Copyright (C) 2012 Clifford Wolf <clifford@clifford.at>
* 2019 Eddie Hung <eddie@fpgeh.com>
* 2019 David Shah <dave@ds0.me>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* ---
*
* Tech-mapping rules for decomposing arbitrarily-sized $mul cells
* into an equivalent collection of smaller `DSP_NAME cells (with the
* same interface as $mul) no larger than `DSP_[AB]_MAXWIDTH, attached
* to $shl and $add cells.
*
*/
`ifndef DSP_A_MAXWIDTH
$error("Macro DSP_A_MAXWIDTH must be defined");
`endif
@ -125,6 +149,9 @@ module \$__mul (A, B, Y);
.B(B),
.Y(partial[i])
);
// TODO: Currently a 'cascade' approach to summing the partial
// products is taken here, but a more efficient 'binary
// reduction' approach also exists...
assign partial_sum[i] = (partial[i] << i*(`DSP_A_MAXWIDTH-sign_headroom)) + partial_sum[i-1];
end
@ -182,6 +209,9 @@ module \$__mul (A, B, Y);
.B({{sign_headroom{1'b0}}, B[i*(`DSP_B_MAXWIDTH-sign_headroom) +: `DSP_B_MAXWIDTH-sign_headroom]}),
.Y(partial[i])
);
// TODO: Currently a 'cascade' approach to summing the partial
// products is taken here, but a more efficient 'binary
// reduction' approach also exists...
assign partial_sum[i] = (partial[i] << i*(`DSP_B_MAXWIDTH-sign_headroom)) + partial_sum[i-1];
end