diff options
Diffstat (limited to 'passes/opt')
| -rw-r--r-- | passes/opt/opt_expr.cc | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/passes/opt/opt_expr.cc b/passes/opt/opt_expr.cc index 3229dd1b2..2b35ace5e 100644 --- a/passes/opt/opt_expr.cc +++ b/passes/opt/opt_expr.cc @@ -1135,9 +1135,24 @@ skip_fine_alu: cell->type.c_str(), cell->name.c_str(), module->name.c_str(), identity_wrt_a ? 'A' : 'B'); if (cell->type == ID($alu)) { + bool a_signed = cell->parameters[ID::A_SIGNED].as_bool(); + bool b_signed = cell->parameters[ID::B_SIGNED].as_bool(); + bool is_signed = a_signed && b_signed; + RTLIL::SigBit sig_ci = assign_map(cell->getPort(ID::CI)); int y_width = GetSize(cell->getPort(ID::Y)); - module->connect(cell->getPort(ID::X), RTLIL::Const(State::S0, y_width)); - module->connect(cell->getPort(ID::CO), RTLIL::Const(State::S0, y_width)); + if (sig_ci == State::S1) { + /* sub, b is 0 */ + RTLIL::SigSpec a = cell->getPort(ID::A); + a.extend_u0(y_width, is_signed); + module->connect(cell->getPort(ID::X), module->Not(NEW_ID, a)); + module->connect(cell->getPort(ID::CO), RTLIL::Const(State::S1, y_width)); + } else { + /* add */ + RTLIL::SigSpec ab = cell->getPort(identity_wrt_a ? ID::A : ID::B); + ab.extend_u0(y_width, is_signed); + module->connect(cell->getPort(ID::X), ab); + module->connect(cell->getPort(ID::CO), RTLIL::Const(State::S0, y_width)); + } cell->unsetPort(ID::BI); cell->unsetPort(ID::CI); cell->unsetPort(ID::X); |