interchange: site router: add valid pips list to check during routing

Signed-off-by: Alessandro Comodi <acomodi@antmicro.com>

fpga_interchange/arch.cc

@@ -1776,15 +1776,15 @@ bool Arch::checkPipAvailForNet(PipId pip, NetInfo *net) const
         }
     }
 
+    auto tile_status_iter = tileStatus.find(pip.tile);
+
     if (pip_data.pseudo_cell_wires.size() > 0) {
         // FIXME: This pseudo pip check is incomplete, because constraint
         // failures will not be detected.  However the current FPGA
         // interchange schema does not provide a cell type to place.
-        auto iter = tileStatus.find(pip.tile);
-        if (iter != tileStatus.end()) {
-            if (!iter->second.pseudo_pip_model.checkPipAvail(getCtx(), pip)) {
-                return false;
-            }
+        if (tile_status_iter != tileStatus.end() &&
+            !tile_status_iter->second.pseudo_pip_model.checkPipAvail(getCtx(), pip)) {
+            return false;
         }
     }
 
@@ -1797,12 +1797,16 @@ bool Arch::checkPipAvailForNet(PipId pip, NetInfo *net) const
 
         bool valid_pip = false;
         if (pip.tile == net->driver.cell->bel.tile) {
-            const BelInfoPOD &bel_data = tile_type.bel_data[net->driver.cell->bel.index];
-            if (bel_data.site == pip_data.site) {
-                // Only allow site pips or output site ports.
-                if (dst_wire_data.site == -1) {
-                    // Allow output site port from this site.
-                    NPNR_ASSERT(src_wire_data.site == pip_data.site);
+            if (tile_status_iter == tileStatus.end()) {
+                // there is no tile status and nothing blocks the validity of this PIP
+                valid_pip = true;
+            } else {
+                const BelInfoPOD &bel_data = tile_type.bel_data[net->driver.cell->bel.index];
+                const SiteRouter &site_router = get_site_status(tile_status_iter->second, bel_data);
+
+                const auto& pips = site_router.valid_pips;
+                auto result = std::find(pips.begin(), pips.end(), pip);
+                if (result != pips.end()) {
                     valid_pip = true;
                 }
             }

fpga_interchange/site_router.cc

@@ -1070,6 +1070,47 @@ static void block_lut_outputs(SiteArch *site_arch,
     }
 }
 
+// Recursively visit downhill PIPs until a SITE_PORT_SINK is reached.
+// Marks all PIPs for all valid paths.
+static bool visit_downhill_pips(const SiteArch *site_arch, const SiteWire &site_wire, std::vector<PipId> &valid_pips) {
+    bool valid_path_exists = false;
+    for (SitePip site_pip : site_arch->getPipsDownhill(site_wire)) {
+        const SiteWire &dst_wire = site_arch->getPipDstWire(site_pip);
+        if (dst_wire.type == SiteWire::SITE_PORT_SINK) {
+            valid_pips.push_back(site_pip.pip);
+            return true;
+        }
+
+        bool path_ok = visit_downhill_pips(site_arch, dst_wire, valid_pips);
+        valid_path_exists |= path_ok;
+
+        if (path_ok) {
+            valid_pips.push_back(site_pip.pip);
+        }
+    }
+
+    return valid_path_exists;
+}
+
+// Checks all downhill PIPs starting from driver wires.
+// All valid PIPs are stored and returned in a vector.
+static std::vector<PipId> check_downhill_pips(Context *ctx, const SiteArch *site_arch) {
+    auto &cells_in_site = site_arch->site_info->cells_in_site;
+
+    std::vector<PipId> valid_pips;
+    for (auto &net_pair : site_arch->nets) {
+        NetInfo *net = net_pair.first;
+        const SiteNetInfo *site_net = &net_pair.second;
+
+        if (net->driver.cell && cells_in_site.count(net->driver.cell)) {
+            const SiteWire &site_wire = site_net->driver;
+
+            visit_downhill_pips(site_arch, site_wire, valid_pips);
+        }
+    }
+    return valid_pips;
+}
+
 bool SiteRouter::checkSiteRouting(const Context *ctx, const TileStatus &tile_status) const
 {
     // Overview:
@@ -1211,6 +1252,8 @@ void SiteRouter::bindSiteRouting(Context *ctx)
 
     check_routing(site_arch);
     apply_routing(ctx, site_arch);
+
+    valid_pips = check_downhill_pips(ctx, &site_arch);
     if (verbose_site_router(ctx)) {
         print_current_state(&site_arch);
     }

fpga_interchange/site_router.h

@@ -38,6 +38,7 @@ struct SiteRouter
     SiteRouter(int16_t site) : site(site), dirty(false), site_ok(true) {}
 
     std::unordered_set<CellInfo *> cells_in_site;
+    std::vector<PipId> valid_pips;
     const int16_t site;
 
     mutable bool dirty;