[AIEPathfinder] Fix packet_dest-before-packet_source ordering crash (#2583)

lib/Dialect/AIE/IR/AIEDialect.cpp

@@ -1433,11 +1433,22 @@ LogicalResult PacketFlowOp::verify() {
   if (body.empty())
     return emitOpError("should have non-empty body");
 
+  int numSources = 0, numDests = 0;
   for (auto &ops : body.front()) {
     if (!isa<PacketSourceOp, PacketDestOp, EndOp>(ops))
       return ops.emitOpError("cannot be contained in a PacketFlow op");
+    if (isa<PacketSourceOp>(ops))
+      ++numSources;
+    if (isa<PacketDestOp>(ops))
+      ++numDests;
   }
 
+  if (numSources != 1)
+    return emitOpError("must have exactly one aie.packet_source (got ")
+           << numSources << ")";
+  if (numDests < 1)
+    return emitOpError("must have at least one aie.packet_dest");
+
   return success();
 }
 

lib/Dialect/AIE/Transforms/AIECreatePathFindFlows.cpp

@@ -301,12 +301,19 @@ AIEPathfinderPass::runOnPacketFlow(DeviceOp device, OpBuilder &builder,
     TileOp srcTile, destTile;
     TileID srcCoords, destCoords;
 
+    // Pass 1: extract source (order-independent: dest may appear before source)
     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()};
-      } else if (auto pktDest = dyn_cast<PacketDestOp>(Op)) {
+      }
+    }
+    if (!srcTile)
+      return pktFlowOp.emitOpError("packet_flow has no packet_source");
+    // Pass 2: process each destination using the source extracted above
+    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()};

lib/Dialect/AIE/Transforms/AIEPathFinder.cpp

@@ -40,12 +40,20 @@ LogicalResult DynamicTileAnalysis::runAnalysis(DeviceOp &device) {
     Port srcPort, dstPort;
     TileOp srcTile, dstTile;
     TileID srcCoords, dstCoords;
+    // Pass 1: extract source (order-independent: dest may appear before source)
     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()};
-      } else if (auto pktDest = dyn_cast<PacketDestOp>(Op)) {
+      }
+    }
+    if (!srcTile)
+      return pktFlowOp.emitOpError("packet_flow has no packet_source");
+
+    // Pass 2: process each destination using the source extracted above
+    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()};

test/create-packet-flows/badpacket_flow_source_count.mlir

@@ -0,0 +1,56 @@
+//===- badpacket_flow_source_count.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 --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.
+
+// 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)}}
+    aie.packet_flow(0x0) {
+      aie.packet_dest<%t11, Core : 0>
+    }
+  }
+}
+
+// -----
+
+// 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.
+module {
+  aie.device(xcvc1902) {
+    %t11 = aie.tile(1, 1)
+    // expected-error@+1 {{must have at least one aie.packet_dest}}
+    aie.packet_flow(0x0) {
+      aie.packet_source<%t11, West : 0>
+    }
+  }
+}

test/create-packet-flows/packet_flow_dest_before_source.mlir

@@ -0,0 +1,68 @@
+//===- packet_flow_dest_before_source.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 for issue #2583:
+// AIEPathfinderPass assumed packet_source always precedes packet_dest in a
+// block. MLIR provides no such ordering guarantee. This test verifies that
+// placing aie.packet_dest before aie.packet_source produces correct output.
+
+// Test 1: Single dest before source (basic reproducer from issue #2583)
+// CHECK-LABEL: aie.device(xcvc1902)
+// CHECK:         %[[T11:.*]] = aie.tile(1, 1)
+// CHECK:         %[[SW11:.*]] = aie.switchbox(%[[T11]]) {
+// CHECK:           %[[AMSEL0:.*]] = aie.amsel<0> (0)
+// CHECK:           aie.masterset(Core : 0, %[[AMSEL0]])
+// CHECK:           aie.packet_rules(West : 0) {
+// CHECK:             aie.rule(31, 0, %[[AMSEL0]])
+// CHECK:           }
+// CHECK:         }
+
+// Test 2: Multiple dests before source (fanout with dest-first ordering)
+// CHECK:         %[[T12:.*]] = aie.tile(1, 2)
+// CHECK:         %[[SW12:.*]] = aie.switchbox(%[[T12]]) {
+// CHECK:           aie.masterset(Core : 0,
+// CHECK:           aie.masterset(Core : 1,
+// CHECK:           aie.packet_rules(West : 0) {
+
+// Test 3: keep_pkt_header with dest-first ordering
+// CHECK:         %[[T13:.*]] = aie.tile(1, 3)
+// CHECK:         %[[SW13:.*]] = aie.switchbox(%[[T13]]) {
+// CHECK:           aie.masterset(Core : 0,
+// CHECK:           aie.packet_rules(West : 0) {
+
+module @packet_flow_dest_before_source {
+ aie.device(xcvc1902) {
+
+  // Test 1: single dest before source
+  %t11 = aie.tile(1, 1)
+  aie.packet_flow(0x0) {
+    aie.packet_dest<%t11, Core : 0>
+    aie.packet_source<%t11, West : 0>
+  }
+
+  // Test 2: multiple dests before source
+  %t12 = aie.tile(1, 2)
+  aie.packet_flow(0x0) {
+    aie.packet_dest<%t12, Core : 0>
+    aie.packet_dest<%t12, Core : 1>
+    aie.packet_source<%t12, West : 0>
+  }
+
+  // Test 3: keep_pkt_header with dest-first ordering
+  %t13 = aie.tile(1, 3)
+  aie.packet_flow(0x0) {
+    aie.packet_dest<%t13, Core : 0>
+    aie.packet_source<%t13, West : 0>
+  } {keep_pkt_header = true}
+
+ }
+}