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Add FF support to wreduce

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Signed-off-by: Clifford Wolf <clifford@clifford.at>
This commit is contained in:
Clifford Wolf 2019-02-20 16:36:42 +01:00
parent 7bf4e4a185
commit 246391200e
2 changed files with 73 additions and 1 deletions
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71
passes/opt/wreduce.cc
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@ -38,7 +38,8 @@ struct WreduceConfig
"$shl", "$shr", "$sshl", "$sshr", "$shift", "$shiftx",
"$lt", "$le", "$eq", "$ne", "$eqx", "$nex", "$ge", "$gt",
"$add", "$sub", "$mul", // "$div", "$mod", "$pow",
"$mux", "$pmux"
"$mux", "$pmux",
"$dff", "$adff"
});
}
};
@ -134,6 +135,71 @@ struct WreduceWorker
module->connect(sig_y.extract(n_kept, n_removed), sig_removed);
}
void run_cell_dff(Cell *cell)
{
// Reduce size of FF if inputs are just sign/zero extended or output bit is not used
SigSpec sig_d = mi.sigmap(cell->getPort("\\D"));
SigSpec sig_q = mi.sigmap(cell->getPort("\\Q"));
int width_before = GetSize(sig_q);
if (width_before == 0)
return;
bool zero_ext = sig_d[GetSize(sig_d)-1] == State::S0;
bool sign_ext = !zero_ext;
for (int i = GetSize(sig_q)-1; i >= 0; i--)
{
if (zero_ext && sig_d[i] == State::S0) {
module->connect(sig_q[i], State::S0);
sig_d.remove(i);
sig_q.remove(i);
continue;
}
if (sign_ext && i > 0 && sig_d[i] == sig_d[i-1]) {
module->connect(sig_q[i], sig_q[i-1]);
sig_d.remove(i);
sig_q.remove(i);
continue;
}
auto info = mi.query(sig_q[i]);
if (!info->is_output && GetSize(info->ports) <= 1 && !keep_bits.count(mi.sigmap(sig_q[i]))) {
sig_d.remove(i);
sig_q.remove(i);
zero_ext = false;
sign_ext = false;
continue;
}
break;
}
if (width_before == GetSize(sig_q))
return;
if (GetSize(sig_q) == 0) {
log("Removed cell %s.%s (%s).\n", log_id(module), log_id(cell), log_id(cell->type));
return;
}
log("Removed top %d bits (of %d) from mux cell %s.%s (%s).\n", width_before - GetSize(sig_q), width_before,
log_id(module), log_id(cell), log_id(cell->type));
for (auto bit : sig_d)
work_queue_bits.insert(bit);
for (auto bit : sig_q)
work_queue_bits.insert(bit);
cell->setPort("\\D", sig_d);
cell->setPort("\\Q", sig_q);
cell->fixup_parameters();
}
void run_reduce_inport(Cell *cell, char port, int max_port_size, bool &port_signed, bool &did_something)
{
port_signed = cell->getParam(stringf("\\%c_SIGNED", port)).as_bool();
@ -176,6 +242,9 @@ struct WreduceWorker
if (cell->type.in("$mux", "$pmux"))
return run_cell_mux(cell);
if (cell->type.in("$dff", "$adff"))
return run_cell_dff(cell);
SigSpec sig = mi.sigmap(cell->getPort("\\Y"));
if (sig.has_const())