Allow multi-source packet flows; fix pathfinder silent drop

lib/Dialect/AIE/IR/AIEDialect.cpp

@@ -1715,9 +1715,8 @@ LogicalResult PacketFlowOp::verify() {
       ++numDests;
   }
 
-  if (numSources != 1)
-    return emitOpError("must have exactly one aie.packet_source (got ")
-           << numSources << ")";
+  if (numSources < 1)
+    return emitOpError("must have at least one aie.packet_source");
   if (numDests < 1)
     return emitOpError("must have at least one aie.packet_dest");
 

lib/Dialect/AIE/Transforms/AIECreatePathFindFlows.cpp

@@ -297,60 +297,60 @@ AIEPathfinderPass::runOnPacketFlow(DeviceOp device, OpBuilder &builder,
     Region &r = pktFlowOp.getPorts();
     Block &b = r.front();
     int flowID = pktFlowOp.IDInt();
-    Port srcPort, destPort;
-    TileOp srcTile, destTile;
-    TileID srcCoords, destCoords;
+    SmallVector<std::pair<TileID, Port>, 4> sources;
 
-    // Pass 1: extract source (order-independent: dest may appear before source)
+    // Pass 1: collect all sources (order-independent; supports fan-in).
     for (Operation &Op : b.getOperations()) {
       if (auto pktSource = dyn_cast<PacketSourceOp>(Op)) {
-        srcTile = dyn_cast<TileOp>(pktSource.getTile().getDefiningOp());
-        srcPort = pktSource.port();
-        srcCoords = {srcTile.colIndex(), srcTile.rowIndex()};
+        auto srcTile = dyn_cast<TileOp>(pktSource.getTile().getDefiningOp());
+        sources.push_back(
+            {{srcTile.colIndex(), srcTile.rowIndex()}, pktSource.port()});
       }
     }
-    if (!srcTile)
+    if (sources.empty())
       return pktFlowOp.emitOpError("packet_flow has no packet_source");
-    // Pass 2: process each destination using the source extracted above
+    // Pass 2: lower each (source, destination) pair so fan-in flows lay
+    // down switchbox connections for every source, not just the last one.
     for (Operation &Op : b.getOperations()) {
-      if (auto pktDest = dyn_cast<PacketDestOp>(Op)) {
-        destTile = dyn_cast<TileOp>(pktDest.getTile().getDefiningOp());
-        destPort = pktDest.port();
-        destCoords = {destTile.colIndex(), destTile.rowIndex()};
-        // Assign "keep_pkt_header flag"
-        auto keep = pktFlowOp.getKeepPktHeader();
-        keepPktHeaderAttr[{destTile.getTileID(), destPort}] =
-            keep ? BoolAttr::get(Op.getContext(), *keep) : nullptr;
-
+      auto pktDest = dyn_cast<PacketDestOp>(Op);
+      if (!pktDest)
+        continue;
+      auto destTile = dyn_cast<TileOp>(pktDest.getTile().getDefiningOp());
+      Port destPort = pktDest.port();
+      TileID destCoords = {destTile.colIndex(), destTile.rowIndex()};
+      // Assign "keep_pkt_header flag"
+      auto keep = pktFlowOp.getKeepPktHeader();
+      keepPktHeaderAttr[{destTile.getTileID(), destPort}] =
+          keep ? BoolAttr::get(Op.getContext(), *keep) : nullptr;
+
+      for (auto &[srcCoords, srcPort] : sources) {
         TileID srcSB = {srcCoords.col, srcCoords.row};
-        if (PathEndPoint srcPoint = {srcSB, srcPort};
-            !analyzer.processedFlows[srcPoint]) {
-          SwitchSettings settings = analyzer.flowSolutions[srcPoint];
-          // add connections for all the Switchboxes in SwitchSettings
-          for (const auto &[curr, setting] : settings) {
-            assert(setting.srcs.size() == setting.dsts.size());
-            TileID currTile = {curr.col, curr.row};
-            for (size_t i = 0; i < setting.srcs.size(); i++) {
-              Port src = setting.srcs[i];
-              Port dest = setting.dsts[i];
-              // reject false broadcast
-              if (!findPathToDest(settings, currTile, dest.bundle, dest.channel,
-                                  destCoords, destPort.bundle,
-                                  destPort.channel))
-                continue;
-              Connect connect = {{src.bundle, src.channel},
-                                 {dest.bundle, dest.channel}};
-              if (std::find(switchboxes[currTile].begin(),
-                            switchboxes[currTile].end(),
-                            std::pair{connect, flowID}) ==
-                  switchboxes[currTile].end())
-                switchboxes[currTile].push_back({connect, flowID});
-              // Assign "control packet flows" flag per switchbox, based on
-              // packet flow op attribute
-              auto ctrlPkt = pktFlowOp.getPriorityRoute();
-              ctrlPktFlows[{{currTile, dest}, flowID}] =
-                  ctrlPkt ? *ctrlPkt : false;
-            }
+        PathEndPoint srcPoint = {srcSB, srcPort};
+        if (analyzer.processedFlows[srcPoint])
+          continue;
+        SwitchSettings settings = analyzer.flowSolutions[srcPoint];
+        // add connections for all the Switchboxes in SwitchSettings
+        for (const auto &[curr, setting] : settings) {
+          assert(setting.srcs.size() == setting.dsts.size());
+          TileID currTile = {curr.col, curr.row};
+          for (size_t i = 0; i < setting.srcs.size(); i++) {
+            Port src = setting.srcs[i];
+            Port dest = setting.dsts[i];
+            // reject false broadcast
+            if (!findPathToDest(settings, currTile, dest.bundle, dest.channel,
+                                destCoords, destPort.bundle, destPort.channel))
+              continue;
+            Connect connect = {{src.bundle, src.channel},
+                               {dest.bundle, dest.channel}};
+            if (std::find(
+                    switchboxes[currTile].begin(), switchboxes[currTile].end(),
+                    std::pair{connect, flowID}) == switchboxes[currTile].end())
+              switchboxes[currTile].push_back({connect, flowID});
+            // Assign "control packet flows" flag per switchbox, based on
+            // packet flow op attribute
+            auto ctrlPkt = pktFlowOp.getPriorityRoute();
+            ctrlPktFlows[{{currTile, dest}, flowID}] =
+                ctrlPkt ? *ctrlPkt : false;
           }
         }
       }

lib/Dialect/AIE/Transforms/AIEPathFinder.cpp

@@ -37,41 +37,38 @@ LogicalResult DynamicTileAnalysis::runAnalysis(DeviceOp &device) {
   for (PacketFlowOp pktFlowOp : device.getOps<PacketFlowOp>()) {
     Region &r = pktFlowOp.getPorts();
     Block &b = r.front();
-    Port srcPort, dstPort;
-    TileOp srcTile, dstTile;
-    TileID srcCoords, dstCoords;
-    // Pass 1: extract source (order-independent: dest may appear before source)
+    SmallVector<std::pair<TileID, Port>, 4> sources;
+    // Pass 1: collect all sources (order-independent; supports fan-in).
     for (Operation &Op : b.getOperations()) {
       if (auto pktSource = dyn_cast<PacketSourceOp>(Op)) {
-        srcTile = dyn_cast<TileOp>(pktSource.getTile().getDefiningOp());
-        srcPort = pktSource.port();
-        srcCoords = {srcTile.colIndex(), srcTile.rowIndex()};
+        auto srcTile = dyn_cast<TileOp>(pktSource.getTile().getDefiningOp());
+        sources.push_back(
+            {{srcTile.colIndex(), srcTile.rowIndex()}, pktSource.port()});
       }
     }
-    if (!srcTile)
+    if (sources.empty())
       return pktFlowOp.emitOpError("packet_flow has no packet_source");
 
-    // Pass 2: process each destination using the source extracted above
+    bool priorityFlow =
+        pktFlowOp.getPriorityRoute() ? *pktFlowOp.getPriorityRoute() : false;
+    // Pass 2: add a flow from every source to every destination so
+    // fan-in topologies are routed (not just the last source).
     for (Operation &Op : b.getOperations()) {
       if (auto pktDest = dyn_cast<PacketDestOp>(Op)) {
-        dstTile = dyn_cast<TileOp>(pktDest.getTile().getDefiningOp());
-        dstPort = pktDest.port();
-        dstCoords = {dstTile.colIndex(), dstTile.rowIndex()};
-        LLVM_DEBUG(llvm::dbgs()
-                   << "\tAdding Packet Flow: (" << srcCoords.col << ", "
-                   << srcCoords.row << ")"
-                   << stringifyWireBundle(srcPort.bundle) << srcPort.channel
-                   << " -> (" << dstCoords.col << ", " << dstCoords.row << ")"
-                   << stringifyWireBundle(dstPort.bundle) << dstPort.channel
-                   << "\n");
-        // todo: support many-to-one & many-to-many?
-        bool priorityFlow =
-            pktFlowOp.getPriorityRoute()
-                ? *pktFlowOp.getPriorityRoute()
-                : false; // Flows such as control packet flows are routed in
-                         // priority, to ensure routing consistency.
-        pathfinder->addFlow(srcCoords, srcPort, dstCoords, dstPort,
-                            /*isPktFlow*/ true, priorityFlow);
+        auto dstTile = dyn_cast<TileOp>(pktDest.getTile().getDefiningOp());
+        Port dstPort = pktDest.port();
+        TileID dstCoords = {dstTile.colIndex(), dstTile.rowIndex()};
+        for (auto &[srcCoords, srcPort] : sources) {
+          LLVM_DEBUG(llvm::dbgs()
+                     << "\tAdding Packet Flow: (" << srcCoords.col << ", "
+                     << srcCoords.row << ")"
+                     << stringifyWireBundle(srcPort.bundle) << srcPort.channel
+                     << " -> (" << dstCoords.col << ", " << dstCoords.row << ")"
+                     << stringifyWireBundle(dstPort.bundle) << dstPort.channel
+                     << "\n");
+          pathfinder->addFlow(srcCoords, srcPort, dstCoords, dstPort,
+                              /*isPktFlow*/ true, priorityFlow);
+        }
       }
     }
   }

test/create-packet-flows/badpacket_flow_source_count.mlir

@@ -11,15 +11,15 @@
 // RUN: aie-opt --verify-diagnostics --split-input-file %s
 
 // Regression tests for issue #2583 verifier gap:
-// PacketFlowOp must have exactly one packet_source and at least one
-// packet_dest. Verify that the verifier rejects zero-source and
-// multiple-source flows.
+// PacketFlowOp must have at least one packet_source and at least one
+// packet_dest. Verify that the verifier rejects zero-source and zero-dest
+// flows. (Multi-source flows are valid; see multi_source_packet_flow.mlir.)
 
 // Test 1: zero sources — must be rejected by verifier.
 module {
   aie.device(xcvc1902) {
     %t11 = aie.tile(1, 1)
-    // expected-error@+1 {{must have exactly one aie.packet_source (got 0)}}
+    // expected-error@+1 {{must have at least one aie.packet_source}}
     aie.packet_flow(0x0) {
       aie.packet_dest<%t11, Core : 0>
     }
@@ -28,23 +28,7 @@ module {
 
 // -----
 
-// Test 2: multiple sources — must be rejected by verifier.
-module {
-  aie.device(xcvc1902) {
-    %t11 = aie.tile(1, 1)
-    %t12 = aie.tile(1, 2)
-    // expected-error@+1 {{must have exactly one aie.packet_source (got 2)}}
-    aie.packet_flow(0x0) {
-      aie.packet_source<%t11, West : 0>
-      aie.packet_source<%t12, West : 0>
-      aie.packet_dest<%t11, Core : 0>
-    }
-  }
-}
-
-// -----
-
-// Test 3: zero dests — must be rejected by verifier.
+// Test 2: zero dests — must be rejected by verifier.
 module {
   aie.device(xcvc1902) {
     %t11 = aie.tile(1, 1)

test/create-packet-flows/multi_source_packet_flow.mlir

@@ -0,0 +1,30 @@
+//===- multi_source_packet_flow.mlir ----------------------------*- MLIR -*-===//
+//
+// This file is licensed under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// (c) Copyright 2026 Advanced Micro Devices, Inc.
+//
+//===----------------------------------------------------------------------===//
+
+// RUN: aie-opt %s | FileCheck %s
+
+// Regression test: a packet_flow with multiple aie.packet_source ops is valid
+// (fan-in: multiple source ports emit packets with the same flow ID).
+// Verifier must not reject this. Regression for issue #2583 / PR #2919.
+
+// CHECK-LABEL: module @multi_source_packet_flow
+module @multi_source_packet_flow {
+  aie.device(xcvc1902) {
+    %t11 = aie.tile(1, 1)
+    %t21 = aie.tile(2, 1)
+    %t31 = aie.tile(3, 1)
+    // CHECK: aie.packet_flow(0)
+    aie.packet_flow(0x0) {
+      aie.packet_source<%t11, West : 0>
+      aie.packet_source<%t21, West : 0>
+      aie.packet_dest<%t31, Core : 0>
+    }
+  }
+}

test/create-packet-flows/multi_source_pathfinder.mlir

@@ -0,0 +1,52 @@
+//===- multi_source_pathfinder.mlir ----------------------------*- MLIR -*-===//
+//
+// This file is licensed under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// (c) Copyright 2026 Advanced Micro Devices, Inc.
+//
+//===----------------------------------------------------------------------===//
+
+// RUN: aie-opt --aie-create-pathfinder-flows %s | FileCheck %s
+
+// Regression test: when a packet_flow has multiple aie.packet_source ops,
+// the pathfinder must route ALL sources to the destination, not just the last
+// one encountered (the "last source wins" bug).
+//
+// Topology: two sources (tiles 1,1 and 2,1) fan-in to one dest (tile 3,1).
+//
+//   (1,1) --East--> (2,1) --East--> (3,1)
+//    src0             src1            dest
+
+// Both source switchboxes must emit packet rules for flow id 0.
+// CHECK-LABEL: aie.device(xcvc1902)
+
+// Switchbox at (1,1): must have packet_rules routing Core:0 eastward.
+// CHECK:         %[[SW11:.*]] = aie.switchbox(%[[T11:.*]]) {
+// CHECK:           aie.packet_rules(Core : 0) {
+// CHECK:             aie.rule(31, 0,
+
+// Switchbox at (2,1): must have packet_rules routing Core:0 eastward
+// AND forwarding incoming West traffic toward (3,1).
+// CHECK:         %[[SW21:.*]] = aie.switchbox(%[[T21:.*]]) {
+// CHECK:           aie.packet_rules(Core : 0) {
+// CHECK:             aie.rule(31, 0,
+
+// Switchbox at (3,1): must receive and deliver to Core:0.
+// CHECK:         %[[SW31:.*]] = aie.switchbox(%[[T31:.*]]) {
+// CHECK:           aie.masterset(Core : 0,
+// CHECK:           aie.packet_rules(West :
+
+module @multi_source_pathfinder {
+  aie.device(xcvc1902) {
+    %t11 = aie.tile(1, 1)
+    %t21 = aie.tile(2, 1)
+    %t31 = aie.tile(3, 1)
+    aie.packet_flow(0x0) {
+      aie.packet_source<%t11, Core : 0>
+      aie.packet_source<%t21, Core : 0>
+      aie.packet_dest<%t31, Core : 0>
+    }
+  }
+}