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opt_merge: Add -keepdc option required for formal verification

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The `-keepdc` option prevents merging flipflops with dont-care bits in
their initial value, as, in general, this is not a valid transform for
formal verification.

The keepdc option of `opt` is passed along to `opt_merge` now.
This commit is contained in:
Jannis Harder 2022-04-01 21:03:20 +02:00
parent 2ec4af56e6
commit ca5b910296
3 changed files with 71 additions and 2 deletions
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50
tests/opt/opt_merge_init.ys
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@ -75,3 +75,53 @@ EOT
opt_merge
select -assert-count 2 t:$dff
design -reset
read_verilog -icells <<EOT
module top(input clk, i, (* init = 1'b0 *) output o, p);
\$dff #(
.CLK_POLARITY(1'h1),
.WIDTH(32'd1)
) ffo (
.CLK(clk),
.D(i),
.Q(o)
);
\$dff #(
.CLK_POLARITY(1'h1),
.WIDTH(32'd1)
) ffp (
.CLK(clk),
.D(i),
.Q(p)
);
endmodule
EOT
opt_merge -keepdc
select -assert-count 1 t:$dff
design -reset
read_verilog -icells <<EOT
module top(input clk, i, output o, p);
\$dff #(
.CLK_POLARITY(1'h1),
.WIDTH(32'd1)
) ffo (
.CLK(clk),
.D(i),
.Q(o)
);
\$dff #(
.CLK_POLARITY(1'h1),
.WIDTH(32'd1)
) ffp (
.CLK(clk),
.D(i),
.Q(p)
);
endmodule
EOT
opt_merge -keepdc
select -assert-count 2 t:$dff