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Add optimization of tristate buffer with constant control input 

Signed-off-by: Clifford Wolf <clifford@clifford.at>
This commit is contained in:
Clifford Wolf 2018-05-12 15:18:27 +02:00
parent 11406a8082
commit 587056447e
1 changed files with 17 additions and 0 deletions
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17
passes/opt/opt_expr.cc
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@ -718,6 +718,23 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
}
}
if (cell->type == "$_TBUF_" || cell->type == "$tribuf") {
RTLIL::SigSpec input = cell->getPort(cell->type == "$_TBUF_" ? "\\E" : "\\EN");
RTLIL::SigSpec a = cell->getPort("\\A");
assign_map.apply(input);
assign_map.apply(a);
if (input == State::S1)
ACTION_DO("\\Y", cell->getPort("\\A"));
if (input == State::S0 && !a.is_fully_undef()) {
cover("opt.opt_expr.action_" S__LINE__);
log("Replacing data input of %s cell `%s' in module `%s' with constant undef.\n",
cell->type.c_str(), cell->name.c_str(), module->name.c_str());
cell->setPort("\\A", SigSpec(State::Sx, GetSize(a)));
did_something = true;
goto next_cell;
}
}
if (cell->type == "$eq" || cell->type == "$ne" || cell->type == "$eqx" || cell->type == "$nex")
{
RTLIL::SigSpec a = cell->getPort("\\A");