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Simplify MUXZ if the select is constant. 

If the select of a MUXZ is constant 0 or 1, then we can elide the MUX
in place of a simple BUFZ. This should allow the dead code on the
unused side to be removed as well.
This commit is contained in:
Stephen Williams 2008-05-21 10:25:44 -07:00
parent be810c5ba6
commit 4c5f24c7a7
1 changed files with 21 additions and 0 deletions
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21
cprop.cc
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@ -828,6 +828,27 @@ void cprop_functor::lpm_mux(Design*des, NetMux*obj)
count += 1;
return;
}
/* If the select input is constant, then replace with a BUFZ */
flag = obj->pin_Sel().nexus()->drivers_constant();
verinum::V sel_val = flag? obj->pin_Data(1).nexus()->driven_value() : verinum::Vx;
if ((sel_val != verinum::Vz) && (sel_val != verinum::Vx)) {
NetBUFZ*tmp = new NetBUFZ(obj->scope(), obj->name(), obj->width());
tmp->set_line(*obj);
tmp->rise_time(obj->rise_time());
tmp->fall_time(obj->fall_time());
tmp->decay_time(obj->decay_time());
connect(tmp->pin(0), obj->pin_Result());
if (sel_val == verinum::V1)
connect(tmp->pin(1), obj->pin_Data(1));
else
connect(tmp->pin(1), obj->pin_Data(0));
delete obj;
des->add_node(tmp);
count += 1;
}
}
/*