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synth_lattice: Merge NOT gates on DFF control signals 

`dfflegalize` will emit NOT gates to drive control signals on flip-flops
when mapping to supported flip-flop polarities. Typically in a design
this will produce a number of NOT gates driven by the same signal. For
one reason or another ABC doesn't fully cancel this redundancy during
LUT mapping. Insert an explicit `opt_merge` pass to improve synthesis
QoR.
This commit is contained in:
Martin Povišer 2023-11-07 16:21:39 +01:00
parent 63cec22a0c
commit ee3a4ce14d
1 changed files with 1 additions and 0 deletions
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techlibs/lattice/synth_lattice.cc
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@ -409,6 +409,7 @@ struct SynthLatticePass : public ScriptPass
dfflegalize_args += " -cell $_DLATCH_?_ x";
}
run("dfflegalize" + dfflegalize_args, "($_ALDFF_*_ only if -asyncprld, $_DLATCH_* only if not -asyncprld, $_*DFFE_* only if not -nodffe)");
run("opt_merge");
if ((abc9 && dff) || help_mode)
run("zinit -all w:* t:$_DFF_?_ t:$_DFFE_??_ t:$_SDFF*", "(only if -abc9 and -dff)");
run("techmap -D NO_LUT -map +/lattice/cells_map.v");