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Add handling of constant reset signals to opt_rmdff

This commit is contained in:
Clifford Wolf 2017-08-06 13:27:18 +02:00
parent 48b2b376d0
commit c4a7958f70
1 changed files with 23 additions and 1 deletions
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24
passes/opt/opt_rmdff.cc
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@ -186,7 +186,7 @@ bool handle_dff(RTLIL::Module *mod, RTLIL::Cell *dff)
goto delete_dff; goto delete_dff;
} }
if (sig_d == sig_q && (!sig_r.size() || !has_init || val_init == val_rv)) { if (sig_d == sig_q && (sig_r.empty() || !has_init || val_init == val_rv)) {
if (sig_r.size()) if (sig_r.size())
mod->connect(sig_q, val_rv); mod->connect(sig_q, val_rv);
if (has_init) if (has_init)
@ -194,6 +194,28 @@ bool handle_dff(RTLIL::Module *mod, RTLIL::Cell *dff)
goto delete_dff; goto delete_dff;
} }
if (!sig_r.empty() && sig_r.is_fully_const())
{
if (sig_r == val_rp || sig_r.is_fully_undef()) {
mod->connect(sig_q, val_rv);
goto delete_dff;
}
log("Removing unused reset from %s (%s) from module %s.\n", log_id(dff), log_id(dff->type), log_id(mod));
if (dff->type == "$adff") {
dff->type = "$dff";
dff->unsetPort("\\ARST");
dff->unsetParam("\\ARST_POLARITY");
dff->unsetParam("\\ARST_VALUE");
return true;
}
log_assert(dff->type.substr(0,6) == "$_DFF_");
dff->type = stringf("$_DFF_%c_", + dff->type[6]);
dff->unsetPort("\\R");
}
return false; return false;
delete_dff: delete_dff: