From 213a8955898282163d237944e2eef12e9e0e3e24 Mon Sep 17 00:00:00 2001 From: Eddie Hung Date: Thu, 19 Mar 2020 14:34:10 -0700 Subject: [PATCH] opt_expr: optimise $sub when both A[i] and B[i] == 1'b1 --- passes/opt/opt_expr.cc | 29 ++++++++++++++++++++--------- 1 file changed, 20 insertions(+), 9 deletions(-) diff --git a/passes/opt/opt_expr.cc b/passes/opt/opt_expr.cc index 94084bf62..c818fefc5 100644 --- a/passes/opt/opt_expr.cc +++ b/passes/opt/opt_expr.cc @@ -651,10 +651,14 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons int i; for (i = 0; i < GetSize(sig_y); i++) { - if (sig_b.at(i, State::Sx) == State::S0 && sig_a.at(i, State::Sx) != State::Sx) - module->connect(sig_y[i], sig_a[i]); - else if (!sub && sig_a.at(i, State::Sx) == State::S0 && sig_b.at(i, State::Sx) != State::Sx) - module->connect(sig_y[i], sig_b[i]); + RTLIL::SigBit b = sig_b.at(i, State::Sx); + RTLIL::SigBit a = sig_a.at(i, State::Sx); + if (b == State::S0 && a != State::Sx) + module->connect(sig_y[i], a); + else if (sub && b == State::S1 && a == State::S1) + module->connect(sig_y[i], State::S0); + else if (!sub && a == State::S0 && b != State::Sx) + module->connect(sig_y[i], b); else break; } @@ -690,14 +694,21 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons int i; for (i = 0; i < GetSize(sig_y); i++) { - if (sig_b.at(i, State::Sx) == State::S0 && sig_a.at(i, State::Sx) != State::Sx) { - module->connect(sig_x[i], sub ? module->Not(NEW_ID, sig_a[i]).as_bit() : sig_a[i]); + RTLIL::SigBit b = sig_b.at(i, State::Sx); + RTLIL::SigBit a = sig_a.at(i, State::Sx); + if (b == State::S0 && a != State::Sx) { module->connect(sig_y[i], sig_a[i]); + module->connect(sig_x[i], sub ? module->Not(NEW_ID, a).as_bit() : a); module->connect(sig_co[i], sub ? State::S1 : State::S0); } - else if (!sub && sig_a.at(i, State::Sx) == State::S0 && sig_b.at(i, State::Sx) != State::Sx) { - module->connect(sig_x[i], sig_b[i]); - module->connect(sig_y[i], sig_b[i]); + else if (sub && b == State::S1 && a == State::S1) { + module->connect(sig_y[i], State::S0); + module->connect(sig_x[i], module->Not(NEW_ID, a)); + module->connect(sig_co[i], State::S0); + } + else if (!sub && a == State::S0 && b != State::Sx) { + module->connect(sig_y[i], b); + module->connect(sig_x[i], b); module->connect(sig_co[i], State::S0); } else