Start making use of getBelPinsForCellPin API

This replaces getNetinfoSinkWire with 3 new functions for different use
cases.

At the moment all existing code has been moved to getNetinfoSinkWire
with phys_idx=0 so the build doesn't break; but this won't yet function
properly with more than one sink. But it provides a base on which to
work on refactoring the routers to support this case.

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

5 files changed, 83 insertions, 37 deletions

diff --git a/common/nextpnr.cc b/common/nextpnr.cc
index 880e0344..11acf991 100644
--- a/common/nextpnr.cc
+++ b/common/nextpnr.cc
@@ -354,19 +354,59 @@ WireId Context::getNetinfoSourceWire(const NetInfo *net_info) const
     if (src_bel == BelId())
         return WireId();
 
-    IdString driver_port = net_info->driver.port;
-    return getBelPinWire(src_bel, driver_port);
+    auto bel_pins = getBelPinsForCellPin(net_info->driver.cell, net_info->driver.port);
+    auto iter = bel_pins.begin();
+    if (iter == bel_pins.end())
+        return WireId();
+    WireId driver = getBelPinWire(src_bel, *iter);
+    ++iter;
+    NPNR_ASSERT(iter == bel_pins.end()); // assert there is only one driver bel pin;
+    return driver;
 }
 
-WireId Context::getNetinfoSinkWire(const NetInfo *net_info, const PortRef &user_info) const
+SSOArray<WireId, 2> Context::getNetinfoSinkWires(const NetInfo *net_info, const PortRef &user_info) const
 {
     auto dst_bel = user_info.cell->bel;
-
     if (dst_bel == BelId())
-        return WireId();
+        return SSOArray<WireId, 2>(0, WireId());
+    size_t bel_pin_count = 0;
+    // We use an SSOArray here because it avoids any heap allocation for the 99.9% case of 1 or 2 sink wires
+    // but as SSOArray doesn't (currently) support resizing to keep things simple it does mean we have to do
+    // two loops
+    for (auto s : getBelPinsForCellPin(user_info.cell, user_info.port)) {
+        (void)s; // unused
+        ++bel_pin_count;
+    }
+    SSOArray<WireId, 2> result(bel_pin_count, WireId());
+    bel_pin_count = 0;
+    for (auto pin : getBelPinsForCellPin(user_info.cell, user_info.port)) {
+        result[bel_pin_count++] = getBelPinWire(dst_bel, pin);
+    }
+    return result;
+}
 
-    IdString user_port = user_info.port;
-    return getBelPinWire(dst_bel, user_port);
+size_t Context::getNetinfoSinkWireCount(const NetInfo *net_info, const PortRef &sink) const
+{
+    size_t count = 0;
+    for (auto s : getNetinfoSinkWires(net_info, sink)) {
+        (void)s; // unused
+        ++count;
+    }
+    return count;
+}
+
+WireId Context::getNetinfoSinkWire(const NetInfo *net_info, const PortRef &sink, size_t phys_idx) const
+{
+    size_t count = 0;
+    for (auto s : getNetinfoSinkWires(net_info, sink)) {
+        if (count == phys_idx)
+            return s;
+        ++count;
+    }
+    /* TODO: This should be an assertion failure, but for the zero-wire case of unplaced sinks; legacy code currently
+    assumes WireId Remove once the refactoring process is complete.
+    */
+    return WireId();
 }
 
 delay_t Context::getNetinfoRouteDelay(const NetInfo *net_info, const PortRef &user_info) const
@@ -383,29 +423,33 @@ delay_t Context::getNetinfoRouteDelay(const NetInfo *net_info, const PortRef &us
     if (src_wire == WireId())
         return 0;
 
-    WireId dst_wire = getNetinfoSinkWire(net_info, user_info);
-    WireId cursor = dst_wire;
-    delay_t delay = 0;
+    delay_t max_delay = 0;
 
-    while (cursor != WireId() && cursor != src_wire) {
-        auto it = net_info->wires.find(cursor);
+    for (auto dst_wire : getNetinfoSinkWires(net_info, user_info)) {
+        WireId cursor = dst_wire;
+        delay_t delay = 0;
 
-        if (it == net_info->wires.end())
-            break;
+        while (cursor != WireId() && cursor != src_wire) {
+            auto it = net_info->wires.find(cursor);
 
-        PipId pip = it->second.pip;
-        if (pip == PipId())
-            break;
+            if (it == net_info->wires.end())
+                break;
 
-        delay += getPipDelay(pip).maxDelay();
-        delay += getWireDelay(cursor).maxDelay();
-        cursor = getPipSrcWire(pip);
-    }
+            PipId pip = it->second.pip;
+            if (pip == PipId())
+                break;
 
-    if (cursor == src_wire)
-        return delay + getWireDelay(src_wire).maxDelay();
+            delay += getPipDelay(pip).maxDelay();
+            delay += getWireDelay(cursor).maxDelay();
+            cursor = getPipSrcWire(pip);
+        }
 
-    return predictDelay(net_info, user_info);
+        if (cursor == src_wire)
+            max_delay = std::max(max_delay, delay + getWireDelay(src_wire).maxDelay()); // routed
+        else
+            max_delay = std::max(max_delay, predictDelay(net_info, user_info)); // unrouted
+    }
+    return max_delay;
 }
 
 static uint32_t xorshift32(uint32_t x)
diff --git a/common/nextpnr.h b/common/nextpnr.h
index cf04f831..cb4dbc28 100644
--- a/common/nextpnr.h
+++ b/common/nextpnr.h
@@ -1494,7 +1494,9 @@ struct Context : Arch, DeterministicRNG
     // --------------------------------------------------------------
 
     WireId getNetinfoSourceWire(const NetInfo *net_info) const;
-    WireId getNetinfoSinkWire(const NetInfo *net_info, const PortRef &sink) const;
+    SSOArray<WireId, 2> getNetinfoSinkWires(const NetInfo *net_info, const PortRef &sink) const;
+    size_t getNetinfoSinkWireCount(const NetInfo *net_info, const PortRef &sink) const;
+    WireId getNetinfoSinkWire(const NetInfo *net_info, const PortRef &sink, size_t phys_idx) const;
     delay_t getNetinfoRouteDelay(const NetInfo *net_info, const PortRef &sink) const;
 
     // provided by router1.cc
diff --git a/common/router1.cc b/common/router1.cc
index d2816c1e..51a356bc 100644
--- a/common/router1.cc
+++ b/common/router1.cc
@@ -144,7 +144,7 @@ struct Router1
         int user_idx = arc.user_idx;
 
         auto src_wire = ctx->getNetinfoSourceWire(net_info);
-        auto dst_wire = ctx->getNetinfoSinkWire(net_info, net_info->users[user_idx]);
+        auto dst_wire = ctx->getNetinfoSinkWire(net_info, net_info->users[user_idx], 0);
 
         arc_queue_insert(arc, src_wire, dst_wire);
     }
@@ -302,7 +302,7 @@ struct Router1
             log_assert(src_wire != WireId());
 
             for (int user_idx = 0; user_idx < int(net_info->users.size()); user_idx++) {
-                auto dst_wire = ctx->getNetinfoSinkWire(net_info, net_info->users[user_idx]);
+                auto dst_wire = ctx->getNetinfoSinkWire(net_info, net_info->users[user_idx], 0);
                 log_assert(dst_wire != WireId());
 
                 arc_key arc;
@@ -375,7 +375,7 @@ struct Router1
                           ctx->nameOf(dst_to_arc.at(src_wire).net_info), dst_to_arc.at(src_wire).user_idx);
 
             for (int user_idx = 0; user_idx < int(net_info->users.size()); user_idx++) {
-                auto dst_wire = ctx->getNetinfoSinkWire(net_info, net_info->users[user_idx]);
+                auto dst_wire = ctx->getNetinfoSinkWire(net_info, net_info->users[user_idx], 0);
 
                 if (dst_wire == WireId())
                     log_error("No wire found for port %s on destination cell %s.\n",
@@ -443,7 +443,7 @@ struct Router1
         int user_idx = arc.user_idx;
 
         auto src_wire = ctx->getNetinfoSourceWire(net_info);
-        auto dst_wire = ctx->getNetinfoSinkWire(net_info, net_info->users[user_idx]);
+        auto dst_wire = ctx->getNetinfoSinkWire(net_info, net_info->users[user_idx], 0);
         ripup_flag = false;
 
         if (ctx->debug) {
@@ -934,7 +934,7 @@ bool Context::checkRoutedDesign() const
 
         std::unordered_map<WireId, int> dest_wires;
         for (int user_idx = 0; user_idx < int(net_info->users.size()); user_idx++) {
-            auto dst_wire = ctx->getNetinfoSinkWire(net_info, net_info->users[user_idx]);
+            auto dst_wire = ctx->getNetinfoSinkWire(net_info, net_info->users[user_idx], 0);
             log_assert(dst_wire != WireId());
             dest_wires[dst_wire] = user_idx;
 
diff --git a/common/router2.cc b/common/router2.cc
index 49d5fdec..d1e4e347 100644
--- a/common/router2.cc
+++ b/common/router2.cc
@@ -150,7 +150,7 @@ struct Router2
 
             for (size_t j = 0; j < ni->users.size(); j++) {
                 auto &usr = ni->users.at(j);
-                WireId src_wire = ctx->getNetinfoSourceWire(ni), dst_wire = ctx->getNetinfoSinkWire(ni, usr);
+                WireId src_wire = ctx->getNetinfoSourceWire(ni), dst_wire = ctx->getNetinfoSinkWire(ni, usr, 0);
                 nets.at(i).src_wire = src_wire;
                 if (ni->driver.cell == nullptr)
                     src_wire = dst_wire;
@@ -405,7 +405,7 @@ struct Router2
     void reserve_wires_for_arc(NetInfo *net, size_t i)
     {
         WireId src = ctx->getNetinfoSourceWire(net);
-        WireId sink = ctx->getNetinfoSinkWire(net, net->users.at(i));
+        WireId sink = ctx->getNetinfoSinkWire(net, net->users.at(i), 0);
         if (sink == WireId())
             return;
         std::unordered_set<WireId> rsv;
@@ -479,7 +479,7 @@ struct Router2
         auto &usr = net->users.at(i);
         ROUTE_LOG_DBG("Routing arc %d of net '%s' (%d, %d) -> (%d, %d)\n", int(i), ctx->nameOf(net), ad.bb.x0, ad.bb.y0,
                       ad.bb.x1, ad.bb.y1);
-        WireId src_wire = ctx->getNetinfoSourceWire(net), dst_wire = ctx->getNetinfoSinkWire(net, usr);
+        WireId src_wire = ctx->getNetinfoSourceWire(net), dst_wire = ctx->getNetinfoSinkWire(net, usr, 0);
         if (src_wire == WireId())
             ARC_LOG_ERR("No wire found for port %s on source cell %s.\n", ctx->nameOf(net->driver.port),
                         ctx->nameOf(net->driver.cell));
@@ -726,7 +726,7 @@ struct Router2
             if (check_arc_routing(net, i))
                 continue;
             auto &usr = net->users.at(i);
-            WireId dst_wire = ctx->getNetinfoSinkWire(net, usr);
+            WireId dst_wire = ctx->getNetinfoSinkWire(net, usr, 0);
             // Case of arcs that were pre-routed strongly (e.g. clocks)
             if (net->wires.count(dst_wire) && net->wires.at(dst_wire).strength > STRENGTH_STRONG)
                 return ARC_SUCCESS;
@@ -751,7 +751,7 @@ struct Router2
                     if (res2 != ARC_SUCCESS)
                         log_error("Failed to route arc %d of net '%s', from %s to %s.\n", int(i), ctx->nameOf(net),
                                   ctx->nameOfWire(ctx->getNetinfoSourceWire(net)),
-                                  ctx->nameOfWire(ctx->getNetinfoSinkWire(net, net->users.at(i))));
+                                  ctx->nameOfWire(ctx->getNetinfoSinkWire(net, net->users.at(i), 0)));
                 }
             }
         }
@@ -803,7 +803,7 @@ struct Router2
         // Skip routes with no source
         if (src == WireId())
             return true;
-        WireId dst = ctx->getNetinfoSinkWire(net, usr);
+        WireId dst = ctx->getNetinfoSinkWire(net, usr, 0);
         // Skip routes where the destination is already bound
         if (dst == WireId() || ctx->getBoundWireNet(dst) == net)
             return true;
diff --git a/common/timing.cc b/common/timing.cc
index 9fb14a33..a741c6ee 100644
--- a/common/timing.cc
+++ b/common/timing.cc
@@ -869,7 +869,7 @@ void timing_analysis(Context *ctx, bool print_histogram, bool print_fmax, bool p
                 log_info("               Sink %s.%s\n", sink_cell->name.c_str(ctx), sink->port.c_str(ctx));
                 if (ctx->verbose) {
                     auto driver_wire = ctx->getNetinfoSourceWire(net);
-                    auto sink_wire = ctx->getNetinfoSinkWire(net, *sink);
+                    auto sink_wire = ctx->getNetinfoSinkWire(net, *sink, 0);
                     log_info("                 prediction: %f ns estimate: %f ns\n",
                              ctx->getDelayNS(ctx->predictDelay(net, *sink)),
                              ctx->getDelayNS(ctx->estimateDelay(driver_wire, sink_wire)));