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dfflegalize: Add special support for const-D latches.

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Those can be created by `opt_dff` when optimizing `$adff` with const
clock, or with D == Q.  Make dfflegalize do the opposite transform
when such dlatches would be otherwise unimplementable.
This commit is contained in:
Marcelina Kościelnicka 2020-07-06 22:52:05 +02:00
parent 000fd08198
commit e9c2c1b717
2 changed files with 71 additions and 0 deletions
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53
tests/techmap/dfflegalize_dlatch_const.ys Normal file
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read_verilog -icells <<EOT
module dlatch(input E, D, (* init = 8'hf0 *) output [7:0] Q);
$_DLATCH_P_ ff0 (.E(E), .D(1'b0), .Q(Q[0]));
$_DLATCH_N_ ff1 (.E(E), .D(1'b0), .Q(Q[1]));
$_DLATCH_P_ ff2 (.E(E), .D(1'b1), .Q(Q[2]));
$_DLATCH_N_ ff3 (.E(E), .D(1'b1), .Q(Q[3]));
$_DLATCH_P_ ff4 (.E(E), .D(1'b0), .Q(Q[4]));
$_DLATCH_N_ ff5 (.E(E), .D(1'b0), .Q(Q[5]));
$_DLATCH_P_ ff6 (.E(E), .D(1'b1), .Q(Q[6]));
$_DLATCH_N_ ff7 (.E(E), .D(1'b1), .Q(Q[7]));
endmodule
EOT
design -save orig
equiv_opt -assert -multiclock -map +/simcells.v dfflegalize -cell $_DFF_PP0_ 01
equiv_opt -assert -multiclock -map +/simcells.v dfflegalize -cell $_DFF_PP?_ 0
equiv_opt -assert -multiclock -map +/simcells.v dfflegalize -cell $_DFFSRE_PPPP_ 0
equiv_opt -assert -multiclock -map +/simcells.v dfflegalize -cell $_DFFSRE_PPPP_ 1
# Convert everything to ADFFs.
design -load orig
dfflegalize -cell $_DFF_PP0_ 01
select -assert-count 12 t:$_NOT_
select -assert-count 8 t:$_DFF_PP0_
select -assert-none t:$_DFF_PP0_ t:$_NOT_ %% %n t:* %i
design -load orig
dfflegalize -cell $_DFF_PP?_ 0
select -assert-count 12 t:$_NOT_
select -assert-count 4 t:$_DFF_PP0_
select -assert-count 4 t:$_DFF_PP1_
select -assert-none t:$_DFF_PP0_ t:$_DFF_PP1_ t:$_NOT_ %% %n t:* %i
# Convert everything to DFFSREs.
design -load orig
dfflegalize -cell $_DFFSRE_PPPP_ 0
select -assert-count 12 t:$_NOT_
select -assert-count 8 t:$_DFFSRE_PPPP_
select -assert-none t:$_DFFSRE_PPPP_ t:$_NOT_ %% %n t:* %i
design -load orig
dfflegalize -cell $_DFFSRE_PPPP_ 1
select -assert-count 12 t:$_NOT_
select -assert-count 8 t:$_DFFSRE_PPPP_
select -assert-none t:$_DFFSRE_PPPP_ t:$_NOT_ %% %n t:* %i