running ABC inside YOSYS returns ' Warning: Detected 1 multi-output gates' - abc

Question

When using YOSYS I call abc command:
abc -liberty mycells3.lib
mycells3.lib is a simple custom technology library based on the example library provided in YOSYS distribution where I added ADDER cell (named FAX1):
library(demo) {
cell(BUF) {
area: 6;
pin(A) { direction: input; }
pin(Y) { direction: output;
function: "A"; }
}
}
cell(XOR) {
area: 0;
pin(A) { direction: input; }
pin(B) { direction: input; }
pin(Y) { direction: output;
function: "(A^B)"; }
}
cell(AND) {
area: 10;
pin(A) { direction: input; }
pin(B) { direction: input; }
pin(Y) { direction: output;
function: "A*B"; }
}
cell(NOT) {
area: 0;
pin(A) { direction: input; }
pin(Y) { direction: output;
function: "A'"; }
}
cell(DFF) {
area: 18;
ff(IQ, IQN) { clocked_on: C;
next_state: D; }
pin(C) { direction: input;
clock: true; }
pin(D) { direction: input; }
pin(Q) { direction: output;
function: "IQ"; }
}
cell(FAX1) {
area : 10;
pin(A) {direction : input; }
pin(B) {direction : input;}
pin(C) {direction : input;}
pin(S) {direction : output;
function : "((A^B)^C)";}
pin(C) {direction : output;
function : "C^((A^C)*(B^C))";}
}
}
}
When running I receive the following warning:
ABC: Warning: Detected 1 multi-output gates (for example, "FAX1")
and indeed non of my modules use this cells (which can be caused from other reasons as well, but my question is independent of this fact).
I know that the liberty format and ABC supports multiple outputs in cells. My question is how to make the YOSYS interface to ABC to accept multiple output cells?
I know this is possible because Qflow is using ABC with liberty file containing cells with multiple output, for example, in the file "osu035_stdcells.lib" we have YC and YS as output from the same cell
/* ------------- *
* Design : FAX1 *
* ------------- */
cell (FAX1) {
area : 480;
cell_leakage_power : 0.162133;
pin(A) {
direction : input;
capacitance : 0.101702;
rise_capacitance : 0.100648;
fall_capacitance : 0.101702;
}
pin(B) {
direction : input;
capacitance : 0.0912748;
rise_capacitance : 0.0912748;
fall_capacitance : 0.0860056;
}
pin(C) {
direction : input;
capacitance : 0.064336;
rise_capacitance : 0.064336;
fall_capacitance : 0.064233;
}
pin(YC) {
direction : output;
capacitance : 0;
rise_capacitance : 0;
fall_capacitance : 0;
max_capacitance : 0.405612;
function : "(((A B)+(B C))+(C A))";
timing() {
related_pin : "A";
timing_sense : positive_unate;
cell_rise(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.192937, 0.202293, 0.222417, 0.23603, 0.262001", \
"0.252032, 0.261902, 0.282854, 0.297212, 0.327113", \
"0.336688, 0.345538, 0.368228, 0.382804, 0.417572", \
"0.575869, 0.585084, 0.608065, 0.623073, 0.660902", \
"0.965229, 0.974557, 0.997456, 1.01213, 1.05025");
}
rise_transition(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.0816, 0.0804, 0.0879, 0.0939, 0.1068", \
"0.1503, 0.1476, 0.1527, 0.1587, 0.1722", \
"0.2637, 0.2625, 0.2661, 0.2682, 0.2817", \
"0.606, 0.606, 0.6069, 0.6087, 0.6159", \
"1.185, 1.185, 1.185, 1.1856, 1.1886");
}
cell_fall(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.212316, 0.230368, 0.271993, 0.301851, 0.392584", \
"0.274262, 0.291144, 0.334346, 0.364751, 0.461587", \
"0.355791, 0.3728, 0.417563, 0.448945, 0.550937", \
"0.569312, 0.586364, 0.631171, 0.663795, 0.770166", \
"0.910578, 0.927654, 0.972381, 1.00471, 1.11225");
}
fall_transition(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.0756, 0.0777, 0.0837, 0.0891, 0.105", \
"0.1362, 0.1368, 0.1386, 0.1446, 0.162", \
"0.2247, 0.2247, 0.2292, 0.2319, 0.2487", \
"0.4911, 0.4911, 0.4917, 0.4947, 0.5031", \
"0.9528, 0.9528, 0.9528, 0.9534, 0.957");
}
}
timing() {
related_pin : "B";
timing_sense : positive_unate;
cell_rise(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.201655, 0.213928, 0.238544, 0.251321, 0.282216", \
"0.259034, 0.272741, 0.300326, 0.314485, 0.347352", \
"0.344335, 0.358175, 0.387437, 0.402523, 0.438405", \
"0.584089, 0.597845, 0.62806, 0.645074, 0.683716", \
"0.97336, 0.98699, 1.01703, 1.03436, 1.07543");
}
rise_transition(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.0831, 0.0819, 0.0876, 0.0897, 0.0969", \
"0.15, 0.1515, 0.1563, 0.1596, 0.1704", \
"0.2637, 0.264, 0.2691, 0.2715, 0.2832", \
"0.6066, 0.6066, 0.6081, 0.6102, 0.6186", \
"1.185, 1.185, 1.185, 1.1859, 1.1907");
}
cell_fall(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.221213, 0.240731, 0.285449, 0.315389, 0.41356", \
"0.283246, 0.303871, 0.352007, 0.382508, 0.482071", \
"0.366584, 0.387835, 0.439518, 0.471404, 0.573799", \
"0.583619, 0.604617, 0.657663, 0.693503, 0.801186", \
"0.925474, 0.94676, 0.999626, 1.03604, 1.14957");
}
fall_transition(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.0786, 0.0768, 0.0831, 0.0906, 0.1008", \
"0.1389, 0.1404, 0.1467, 0.1485, 0.1608", \
"0.2298, 0.2289, 0.2367, 0.2424, 0.2532", \
"0.495, 0.4953, 0.4974, 0.5025, 0.5145", \
"0.9543, 0.9549, 0.9546, 0.9561, 0.966");
}
}
timing() {
related_pin : "C";
timing_sense : positive_unate;
cell_rise(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.185775, 0.210399, 0.245686, 0.266778, 0.312469", \
"0.243892, 0.27024, 0.307336, 0.328971, 0.375209", \
"0.329181, 0.355023, 0.394669, 0.415937, 0.465802", \
"0.568872, 0.594357, 0.633929, 0.655734, 0.706132", \
"0.957725, 0.98325, 1.0226, 1.04421, 1.09553");
}
rise_transition(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.0852, 0.0807, 0.0921, 0.0945, 0.1008", \
"0.1524, 0.1509, 0.1548, 0.1602, 0.1707", \
"0.2637, 0.2634, 0.2685, 0.2706, 0.2817", \
"0.606, 0.606, 0.606, 0.6081, 0.6135", \
"1.1841, 1.1844, 1.1841, 1.1847, 1.188");
}
cell_fall(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.203317, 0.232392, 0.29518, 0.334702, 0.453856", \
"0.264792, 0.295214, 0.360803, 0.400337, 0.521061", \
"0.348261, 0.378841, 0.445571, 0.486885, 0.609869", \
"0.565673, 0.595953, 0.662919, 0.706274, 0.83131", \
"0.90777, 0.938204, 1.00512, 1.04815, 1.17621");
}
fall_transition(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.0792, 0.0765, 0.0843, 0.0912, 0.1044", \
"0.1365, 0.1401, 0.1476, 0.1494, 0.162", \
"0.2298, 0.2289, 0.2343, 0.2388, 0.2496", \
"0.4947, 0.495, 0.4965, 0.4998, 0.5079", \
"0.9543, 0.9546, 0.9546, 0.9552, 0.9612");
}
}
internal_power() {
related_pin : "A";
rise_power(energy_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"-0.007976, -0.001582, 0.046036, 0.096632, 0.303378", \
"0.003901, 0.006036, 0.053579, 0.102898, 0.293237", \
"0.004187, 0.006911, 0.054089, 0.101705, 0.286621", \
"0.002743, 0.005395, 0.051254, 0.098395, 0.279569", \
"0.001821, 0.004696, 0.050175, 0.096875, 0.276158");
}
fall_power(energy_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.751435, 0.756822, 0.815911, 0.870229, 1.07082", \
"0.753113, 0.756525, 0.814098, 0.868209, 1.05967", \
"0.752309, 0.755483, 0.812912, 0.865268, 1.05629", \
"0.751447, 0.754547, 0.811504, 0.863135, 1.04992", \
"0.751138, 0.754253, 0.811014, 0.862398, 1.04726");
}
}
internal_power() {
related_pin : "B";
rise_power(energy_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.079095, 0.071988, 0.108511, 0.145461, 0.323354", \
"0.087668, 0.081948, 0.11915, 0.154305, 0.313515", \
"0.088238, 0.082519, 0.119066, 0.154328, 0.306697", \
"0.086954, 0.081108, 0.116745, 0.152259, 0.302454", \
"0.086343, 0.080371, 0.115854, 0.151083, 0.299904");
}
fall_power(energy_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.697594, 0.691911, 0.738172, 0.776694, 0.94822", \
"0.698733, 0.693453, 0.736748, 0.780343, 0.935934", \
"0.69733, 0.692467, 0.734847, 0.777073, 0.936829", \
"0.694698, 0.690931, 0.732109, 0.774157, 0.931782", \
"0.694056, 0.690307, 0.731288, 0.773142, 0.929401");
}
}
internal_power() {
related_pin : "C";
rise_power(energy_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.163673, 0.165668, 0.189463, 0.22829, 0.390871", \
"0.165439, 0.17055, 0.197339, 0.235655, 0.382059", \
"0.166138, 0.169989, 0.199144, 0.23583, 0.377468", \
"0.166578, 0.169587, 0.197806, 0.233484, 0.371962", \
"0.166896, 0.169673, 0.197451, 0.232882, 0.369249");
}
fall_power(energy_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.583181, 0.587626, 0.631498, 0.669882, 0.82487", \
"0.585184, 0.588504, 0.631341, 0.669054, 0.811996", \
"0.585161, 0.586867, 0.628181, 0.667229, 0.810344", \
"0.582139, 0.584993, 0.625643, 0.66373, 0.805293", \
"0.581744, 0.584612, 0.625012, 0.662479, 0.802606");
}
}
}
pin(YS) {
direction : output;
capacitance : 0;
rise_capacitance : 0;
fall_capacitance : 0;
max_capacitance : 0.409456;
function : "((A^B)^C)";
timing() {
related_pin : "A";
timing_sense : non_unate;
cell_rise(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.311797, 0.328706, 0.370858, 0.401209, 0.489974", \
"0.367147, 0.383417, 0.426146, 0.453648, 0.544812", \
"0.446564, 0.463136, 0.505936, 0.532612, 0.62307", \
"0.679909, 0.69597, 0.739454, 0.766625, 0.856786", \
"1.06837, 1.08444, 1.12769, 1.15482, 1.24479");
}
rise_transition(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.0762, 0.0753, 0.0768, 0.0777, 0.078", \
"0.1437, 0.1443, 0.1437, 0.1428, 0.1455", \
"0.2535, 0.2544, 0.2544, 0.2538, 0.2538", \
"0.5994, 0.5994, 0.5997, 0.5997, 0.6", \
"1.1832, 1.1832, 1.1829, 1.1835, 1.1832");
}
cell_fall(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.299535, 0.309958, 0.329301, 0.341262, 0.363669", \
"0.357539, 0.367622, 0.38617, 0.399449, 0.421082", \
"0.434309, 0.445615, 0.464819, 0.476385, 0.49848", \
"0.644759, 0.656249, 0.67551, 0.68687, 0.70887", \
"0.985959, 0.997573, 1.01673, 1.02809, 1.04987");
}
fall_transition(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.0753, 0.0756, 0.0726, 0.0774, 0.0798", \
"0.1323, 0.1299, 0.1314, 0.1329, 0.1341", \
"0.2184, 0.2187, 0.2187, 0.2184, 0.2187", \
"0.4881, 0.4881, 0.4884, 0.4887, 0.4884", \
"0.9525, 0.9525, 0.9528, 0.9531, 0.9525");
}
}
timing() {
related_pin : "B";
timing_sense : non_unate;
cell_rise(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.326354, 0.343646, 0.392103, 0.426361, 0.525078", \
"0.381898, 0.400236, 0.44672, 0.478563, 0.576663", \
"0.462937, 0.480605, 0.527821, 0.559818, 0.65523", \
"0.698543, 0.715548, 0.762286, 0.793601, 0.888746", \
"1.08749, 1.10456, 1.15106, 1.18221, 1.27704");
}
rise_transition(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.0774, 0.0786, 0.0801, 0.0822, 0.0807", \
"0.1482, 0.1467, 0.1479, 0.1461, 0.1464", \
"0.2568, 0.2568, 0.2571, 0.2553, 0.2547", \
"0.6012, 0.6012, 0.6012, 0.6006, 0.6003", \
"1.1838, 1.1841, 1.1841, 1.1838, 1.1838");
}
cell_fall(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.311475, 0.321628, 0.34643, 0.359418, 0.388969", \
"0.368563, 0.378796, 0.403685, 0.415647, 0.443952", \
"0.446227, 0.456405, 0.482051, 0.493458, 0.521028", \
"0.656751, 0.667049, 0.692618, 0.704328, 0.731082", \
"0.998102, 1.00844, 1.03396, 1.04592, 1.07192");
}
fall_transition(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.0771, 0.0768, 0.075, 0.0765, 0.0768", \
"0.1341, 0.1341, 0.1326, 0.1314, 0.1314", \
"0.219, 0.2187, 0.2178, 0.2187, 0.2172", \
"0.4881, 0.4884, 0.4881, 0.4881, 0.4875", \
"0.9531, 0.9531, 0.9528, 0.9528, 0.9522");
}
}
timing() {
related_pin : "C";
timing_sense : non_unate;
cell_rise(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.322002, 0.346854, 0.408441, 0.447656, 0.560705", \
"0.376032, 0.403646, 0.463433, 0.50045, 0.613575", \
"0.455609, 0.483999, 0.542842, 0.580766, 0.69238", \
"0.690799, 0.71776, 0.777098, 0.815784, 0.926969", \
"1.07981, 1.10678, 1.16586, 1.20454, 1.31715");
}
rise_transition(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.0783, 0.0798, 0.0804, 0.0753, 0.0765", \
"0.1482, 0.1461, 0.1461, 0.1443, 0.1443", \
"0.2562, 0.2568, 0.2565, 0.2565, 0.255", \
"0.6012, 0.6012, 0.6018, 0.6021, 0.603", \
"1.1844, 1.1844, 1.1841, 1.1844, 1.1862");
}
cell_fall(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.296791, 0.3165, 0.344383, 0.367168, 0.404984", \
"0.350874, 0.372846, 0.399754, 0.421069, 0.455738", \
"0.424904, 0.447341, 0.475681, 0.494426, 0.531328", \
"0.632276, 0.654496, 0.683205, 0.702501, 0.738492", \
"0.973424, 0.995389, 1.02414, 1.04363, 1.07937");
}
fall_transition(delay_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.072, 0.0708, 0.0678, 0.0759, 0.0699", \
"0.1242, 0.1236, 0.1236, 0.1236, 0.1218", \
"0.2118, 0.2118, 0.2118, 0.21, 0.2106", \
"0.4839, 0.4839, 0.4842, 0.4848, 0.4839", \
"0.9513, 0.9516, 0.9519, 0.9519, 0.9519");
}
}
internal_power() {
related_pin : "A";
rise_power(energy_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.751435, 0.756822, 0.815911, 0.870229, 1.07082", \
"0.753113, 0.756525, 0.814098, 0.868209, 1.05967", \
"0.752309, 0.755483, 0.812912, 0.865268, 1.05629", \
"0.751447, 0.754547, 0.811504, 0.863135, 1.04992", \
"0.751138, 0.754253, 0.811014, 0.862398, 1.04726");
}
fall_power(energy_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"-0.007976, -0.001582, 0.046036, 0.096632, 0.303378", \
"0.003901, 0.006036, 0.053579, 0.102898, 0.293237", \
"0.004187, 0.006911, 0.054089, 0.101705, 0.286621", \
"0.002743, 0.005395, 0.051254, 0.098395, 0.279569", \
"0.001821, 0.004696, 0.050175, 0.096875, 0.276158");
}
}
internal_power() {
related_pin : "B";
rise_power(energy_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.697594, 0.691911, 0.738172, 0.776694, 0.94822", \
"0.698733, 0.693453, 0.736748, 0.780343, 0.935934", \
"0.69733, 0.692467, 0.734847, 0.777073, 0.936829", \
"0.694698, 0.690931, 0.732109, 0.774157, 0.931782", \
"0.694056, 0.690307, 0.731288, 0.773142, 0.929401");
}
fall_power(energy_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.079095, 0.071988, 0.108511, 0.145461, 0.323354", \
"0.087668, 0.081948, 0.11915, 0.154305, 0.313515", \
"0.088238, 0.082519, 0.119066, 0.154328, 0.306697", \
"0.086954, 0.081108, 0.116745, 0.152259, 0.302454", \
"0.086343, 0.080371, 0.115854, 0.151083, 0.299904");
}
}
internal_power() {
related_pin : "C";
rise_power(energy_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.583181, 0.587626, 0.631498, 0.669882, 0.82487", \
"0.585184, 0.588504, 0.631341, 0.669054, 0.811996", \
"0.585161, 0.586867, 0.628181, 0.667229, 0.810344", \
"0.582139, 0.584993, 0.625643, 0.66373, 0.805293", \
"0.581744, 0.584612, 0.625012, 0.662479, 0.802606");
}
fall_power(energy_template_5x5) {
index_1 ("0.015, 0.04, 0.08, 0.2, 0.4");
index_2 ("0.06, 0.18, 0.42, 0.6, 1.2");
values ( \
"0.163673, 0.165668, 0.189463, 0.22829, 0.390871", \
"0.165439, 0.17055, 0.197339, 0.235655, 0.382059", \
"0.166138, 0.169989, 0.199144, 0.23583, 0.377468", \
"0.166578, 0.169587, 0.197806, 0.233484, 0.371962", \
"0.166896, 0.169673, 0.197451, 0.232882, 0.369249");
}
}
}
}

Answer 1

Qflow only uses ABC through yosys, and like Clifford, I am not aware of ABC being able to map gates with multiple outputs. This does not have any bearing on the fact that the standard cell library contains gates with multiple outputs. Yosys handles flip-flops with multiple outputs, but that is done outside of ABC (which is combinational only). The one way around this is to write parts of your verilog code structurally; that is, you can instantiate an adder inside a verilog source file by explicitly writing out calls to FAX and HAX. Yosys will process those as "black-box" instances, without optimization, and they will otherwise be handled normally by placement and routing.