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opt_expr: Optimize bitwise logic ops with one fully const input

This commit is contained in:
Jannis Harder 2022-11-02 17:57:14 +01:00
parent 661fa5ff92
commit c08242ba41
1 changed files with 81 additions and 0 deletions
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81
passes/opt/opt_expr.cc
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@ -643,6 +643,87 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
goto next_cell;
}
if (cell->type.in(ID($and), ID($or), ID($xor), ID($xnor)))
{
RTLIL::SigSpec sig_a = assign_map(cell->getPort(ID::A));
RTLIL::SigSpec sig_b = assign_map(cell->getPort(ID::B));
bool a_fully_const = (sig_a.is_fully_const() && (!keepdc || !sig_a.is_fully_undef()));
bool b_fully_const = (sig_b.is_fully_const() && (!keepdc || !sig_b.is_fully_undef()));
if (a_fully_const != b_fully_const)
{
cover("opt.opt_expr.bitwise_logic_one_const");
log_debug("Replacing %s cell `%s' in module `%s' having one fully constant input\n",
log_id(cell->type), log_id(cell->name), log_id(module));
RTLIL::SigSpec sig_y = assign_map(cell->getPort(ID::Y));
int width = GetSize(cell->getPort(ID::Y));
sig_a.extend_u0(width, cell->getParam(ID::A_SIGNED).as_bool());
sig_b.extend_u0(width, cell->getParam(ID::B_SIGNED).as_bool());
if (!a_fully_const)
std::swap(sig_a, sig_b);
RTLIL::SigSpec b_group_0, b_group_1, b_group_x;
RTLIL::SigSpec y_group_0, y_group_1, y_group_x;
for (int i = 0; i < width; i++) {
auto bit_a = sig_a[i].data;
if (bit_a == State::S0) b_group_0.append(sig_b[i]), y_group_0.append(sig_y[i]);
if (bit_a == State::S1) b_group_1.append(sig_b[i]), y_group_1.append(sig_y[i]);
if (bit_a == State::Sx) b_group_x.append(sig_b[i]), y_group_x.append(sig_y[i]);
}
if (cell->type == ID($xnor)) {
std::swap(b_group_0, b_group_1);
std::swap(y_group_0, y_group_1);
}
RTLIL::SigSpec y_new_0, y_new_1, y_new_x;
if (cell->type == ID($and)) {
if (!y_group_0.empty()) y_new_0 = Const(State::S0, GetSize(y_group_0));
if (!y_group_1.empty()) y_new_1 = b_group_1;
if (!y_group_x.empty()) {
if (keepdc)
y_new_x = module->And(NEW_ID, Const(State::Sx, GetSize(y_group_x)), b_group_x);
else
y_new_x = Const(State::S0, GetSize(y_group_x));
}
} else if (cell->type == ID($or)) {
if (!y_group_0.empty()) y_new_0 = b_group_0;
if (!y_group_1.empty()) y_new_1 = Const(State::S1, GetSize(y_group_1));
if (!y_group_x.empty()) {
if (keepdc)
y_new_x = module->Or(NEW_ID, Const(State::Sx, GetSize(y_group_x)), b_group_x);
else
y_new_x = Const(State::S1, GetSize(y_group_x));
}
} else if (cell->type.in(ID($xor), ID($xnor))) {
if (!y_group_0.empty()) y_new_0 = b_group_0;
if (!y_group_1.empty()) y_new_1 = module->Not(NEW_ID, b_group_1);
if (!y_group_x.empty()) {
if (keepdc)
y_new_x = module->Xor(NEW_ID, Const(State::Sx, GetSize(y_group_x)), b_group_x);
else // This should be fine even with keepdc, but opt_expr_xor.ys wants to keep the xor
y_new_x = Const(State::Sx, GetSize(y_group_x));
}
} else {
log_abort();
}
assign_map.add(y_group_0, y_new_0); module->connect(y_group_0, y_new_0);
assign_map.add(y_group_1, y_new_1); module->connect(y_group_1, y_new_1);
assign_map.add(y_group_x, y_new_x); module->connect(y_group_x, y_new_x);
module->remove(cell);
did_something = true;
goto next_cell;
}
}
if (do_fine)
{
if (cell->type.in(ID($not), ID($pos), ID($and), ID($or), ID($xor), ID($xnor)))