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Added checking if all FFs added to an existing cluster have matching configuration

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Signed-off-by: Maciej Kurc <mkurc@antmicro.com>
This commit is contained in:
Maciej Kurc 2021-11-23 15:16:26 +01:00
parent 238da79e52
commit 41accf84ce
1 changed files with 44 additions and 0 deletions
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44
nexus/pack.cc
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@ -2304,6 +2304,23 @@ struct NexusPacker
}
}
FFControlSet gather_ff_settings(CellInfo* cell) {
NPNR_ASSERT(cell->type == id_OXIDE_FF);
FFControlSet ctrlset;
ctrlset.async = str_or_default(cell->params, id_SRMODE, "LSR_OVER_CE") == "ASYNC";
ctrlset.regddr_en = is_enabled(cell, id_REGDDR);
ctrlset.gsr_en = is_enabled(cell, id_GSR);
ctrlset.clkmux = ctx->id(str_or_default(cell->params, id_CLKMUX, "CLK")).index;
ctrlset.cemux = ctx->id(str_or_default(cell->params, id_CEMUX, "CE")).index;
ctrlset.lsrmux = ctx->id(str_or_default(cell->params, id_LSRMUX, "LSR")).index;
ctrlset.clk = get_net_or_empty(cell, id_CLK);
ctrlset.ce = get_net_or_empty(cell, id_CE);
ctrlset.lsr = get_net_or_empty(cell, id_LSR);
return ctrlset;
}
void pack_lutffs () {
log_info("Inferring LUT+FF pairs...\n");
@ -2312,6 +2329,12 @@ struct NexusPacker
carry_ratio = ctx->setting<float>("carry_lutff_ratio");
}
// FF control settings/signals are slice-wide. The dict below is used
// to track settings of FFs glued to clusters which may span more than
// one slice (eg. carry-chains). For now it is assumed that all FFs
// in one cluster share the same settings and control signals.
dict<IdString, FFControlSet> cluster_ffinfo;
size_t num_comb = 0;
size_t num_ff = 0;
size_t num_pair = 0;
@ -2364,6 +2387,9 @@ struct NexusPacker
continue;
}
// Get FF settings
auto ffinfo = gather_ff_settings(ff);
// A free LUT, create a new cluster
if (lut->cluster == ClusterId()) {
@ -2381,6 +2407,19 @@ struct NexusPacker
// Attach the FF to the existing cluster of the LUT
else {
// Check if the FF settings match those of others in this
// cluster. If not then reject this FF.
//
// This is a greedy approach - the first attached FF will
// enforce its settings on all following candidates. A better
// approach would be to first form groups of matching FFs for
// a cluster and then attach only the largest group to it.
if (cluster_ffinfo.count(lut->cluster)) {
if (ffinfo != cluster_ffinfo.at(lut->cluster)) {
continue;
}
}
// No order not to make too large carry clusters pack only the
// given fraction of FFs there.
if(str_or_default(lut->params, id_MODE, "LOGIC") == "CCU2") {
@ -2407,6 +2446,11 @@ struct NexusPacker
// Reconnect M to DI
rename_port(ctx, ff, id_M, id_DI);
ff->params[id_SEL] = std::string("DL");
// Store FF settings of the cluster
if (!cluster_ffinfo.count(lut->cluster)) {
cluster_ffinfo.emplace(lut->cluster, ffinfo);
}
}
// Count OXIDE_COMB, OXIDE_FF are already counted