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check_rr_graph: fix bug when checking multi-connections between nodes #1579

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Nov 2, 2020
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check_rr_graph: fix bug when checking multi-connections between nodes #1579

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28 changes: 19 additions & 9 deletions vpr/src/route/check_rr_graph.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -123,17 +123,27 @@ void check_rr_graph(const t_graph_type graph_type,

t_rr_type to_rr_type = device_ctx.rr_nodes[to_node].type();

/* Only expect the following cases to have multiple edges
* - chan <-> chan connections
* - IPIN <-> chan connections (unique rr_node for IPIN nodes on multiple sides)
* - OPIN <-> chan connections (unique rr_node for OPIN nodes on multiple sides)
/* It is unusual to have more than one programmable switch (in the same direction) between a from_node and a to_node,
* as the duplicate switch doesn't add more routing flexibility.
*
* However, such duplicate switches can occur for some types of nodes, which we allow below.
* Reasons one could have duplicate switches between two nodes include:
* - The two switches have different electrical characteristics.
* - Wires near the edges of an FPGA are often cut off, and the stubs connected together.
* A regular switch pattern could then result in one physical wire connecting multiple
* times to other wires, IPINs or OPINs.
*
* Only expect the following cases to have multiple edges
* - CHAN <-> CHAN connections
* - CHAN -> IPIN connections (unique rr_node for IPIN nodes on multiple sides)
* - OPIN -> CHAN connections (unique rr_node for OPIN nodes on multiple sides)
*/
if (((to_rr_type != CHANX && to_rr_type != CHANY && rr_type != IPIN)
|| (rr_type != CHANX && rr_type != CHANY))
&& ((to_rr_type != CHANX && to_rr_type != CHANY)
|| (rr_type != CHANX && rr_type != CHANY && rr_type != OPIN))) {
bool is_chan_to_chan = (rr_type == CHANX || rr_type == CHANY) && (to_rr_type == CHANY || to_rr_type == CHANX);
bool is_chan_to_ipin = (rr_type == CHANX || rr_type == CHANY) && to_rr_type == IPIN;
bool is_opin_to_chan = rr_type == OPIN && (to_rr_type == CHANX || to_rr_type == CHANY);
if (!(is_chan_to_chan || is_chan_to_ipin || is_opin_to_chan)) {
VPR_ERROR(VPR_ERROR_ROUTE,
"in check_rr_graph: node %d (%s) connects to node %d (%s) %zu times - multi-connections only expected for CHAN->CHAN.\n",
"in check_rr_graph: node %d (%s) connects to node %d (%s) %zu times - multi-connections only expected for CHAN<->CHAN, CHAN->IPIN, OPIN->CHAN.\n",
inode, rr_node_typename[rr_type], to_node, rr_node_typename[to_rr_type], num_edges_to_node);
}

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