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Add "opt_expr -fine" feature to remove neutral bits from reduce and logic operators

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This commit is contained in:
Clifford Wolf 2017-07-26 18:28:55 +02:00
parent 530040ba6f
commit 649bb9374f
1 changed files with 47 additions and 0 deletions
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47
passes/opt/opt_expr.cc
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@ -449,6 +449,53 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
if (group_cell_inputs(module, cell, true, assign_map)) if (group_cell_inputs(module, cell, true, assign_map))
goto next_cell; goto next_cell;
if (cell->type == "$logic_not" || cell->type == "$logic_and" || cell->type == "$logic_or" ||
cell->type == "$reduce_or" || cell->type == "$reduce_and" || cell->type == "$reduce_bool")
{
SigBit neutral_bit = cell->type == "$reduce_and" ? State::S1 : State::S0;
RTLIL::SigSpec sig_a = assign_map(cell->getPort("\\A"));
RTLIL::SigSpec new_sig_a;
for (auto bit : sig_a)
if (bit != neutral_bit) new_sig_a.append(bit);
if (GetSize(new_sig_a) == 0)
new_sig_a.append(neutral_bit);
if (GetSize(new_sig_a) < GetSize(sig_a)) {
cover_list("opt.opt_expr.fine.neutral_A", "$logic_not", "$logic_and", "$logic_or", "$reduce_or", "$reduce_and", "$reduce_bool", cell->type.str());
log("Replacing port A of %s cell `%s' in module `%s' with shorter expression: %s -> %s\n",
cell->type.c_str(), cell->name.c_str(), module->name.c_str(), log_signal(sig_a), log_signal(new_sig_a));
cell->setPort("\\A", new_sig_a);
cell->parameters.at("\\A_WIDTH") = GetSize(new_sig_a);
did_something = true;
}
}
if (cell->type == "$logic_and" || cell->type == "$logic_or")
{
SigBit neutral_bit = State::S0;
RTLIL::SigSpec sig_b = assign_map(cell->getPort("\\B"));
RTLIL::SigSpec new_sig_b;
for (auto bit : sig_b)
if (bit != neutral_bit) new_sig_b.append(bit);
if (GetSize(new_sig_b) == 0)
new_sig_b.append(neutral_bit);
if (GetSize(new_sig_b) < GetSize(sig_b)) {
cover_list("opt.opt_expr.fine.neutral_B", "$logic_and", "$logic_or", cell->type.str());
log("Replacing port B of %s cell `%s' in module `%s' with shorter expression: %s -> %s\n",
cell->type.c_str(), cell->name.c_str(), module->name.c_str(), log_signal(sig_b), log_signal(new_sig_b));
cell->setPort("\\B", new_sig_b);
cell->parameters.at("\\B_WIDTH") = GetSize(new_sig_b);
did_something = true;
}
}
if (cell->type == "$reduce_and") if (cell->type == "$reduce_and")
{ {
RTLIL::SigSpec sig_a = assign_map(cell->getPort("\\A")); RTLIL::SigSpec sig_a = assign_map(cell->getPort("\\A"));