Add getBelPinsForCellPin to Arch API

This is a basic implementation, without considering "M of N"
arrangements (e.g. for LUT permuation where you only want to route to 1
out of 4/6 sinks) or using a type other than IdString to identify bel
pins.

But this is also enough to start working out where in nextpnr will break
due to removing the 1:1 cell:bel pin cardinality, as a next step.

Signed-off-by: gatecat <gatecat@ds0.me>

1 files changed, 3 insertions, 0 deletions

diff --git a/fpga_interchange/arch.h b/fpga_interchange/arch.h
index fd2d16a2..e5c7551b 100644
--- a/fpga_interchange/arch.h
+++ b/fpga_interchange/arch.h
@@ -660,6 +660,7 @@ struct ArchRanges
     using TileBelsRangeT = BelRange;
     using BelAttrsRangeT = std::vector<std::pair<IdString, std::string>>;
     using BelPinsRangeT = IdStringRange;
+    using CellBelPinRangeT = std::array<IdString, 1>;
     // Wires
     using AllWiresRangeT = WireRange;
     using DownhillPipRangeT = DownhillPipRange;
@@ -866,6 +867,8 @@ struct Arch : ArchAPI<ArchRanges>
         return str_range;
     }
 
+    std::array<IdString, 1> getBelPinsForCellPin(CellInfo *cell_info, IdString pin) const override { return {pin}; }
+
     // -------------------------------------------------
 
     WireId getWireByName(IdStringList name) const override;