Fix bug in SSA discovery when LogicStructures are used (#540)

Author: mkorbel1

lib/src/modules/conditionals/combinational.dart

@@ -1,4 +1,4 @@
-// Copyright (C) 2021-2024 Intel Corporation
+// Copyright (C) 2021-2025 Intel Corporation
 // SPDX-License-Identifier: BSD-3-Clause
 //
 // combinational.dart
@@ -137,6 +137,20 @@ class Combinational extends Always {
       } else {
         toParse.addAll(tpi.dstConnections);
       }
+
+      // This is critical to make sure we are notifying downstream SSA's even
+      // if they are driven as a result of being a part of a modified structure.
+      if (tpi.parentStructure != null) {
+        toParse.add(tpi.parentStructure!);
+      }
+
+      // This is probably unnecessary, as the SSA would not allow someone to
+      // reference an element of a structure without separately SSA'ing it.
+      // However, leaving this in here just in case (probably negligible perf
+      // impact).
+      if (tpi is LogicStructure) {
+        toParse.addAll(tpi.elements);
+      }
     }
   }
 

test/pipeline_test.dart

@@ -1,4 +1,4 @@
-// Copyright (C) 2021-2024 Intel Corporation
+// Copyright (C) 2021-2025 Intel Corporation
 // SPDX-License-Identifier: BSD-3-Clause
 //
 // pipeline_test.dart
@@ -247,7 +247,7 @@ void main() {
           throwsRangeError);
     });
 
-    test('getting unregisterd signal on pipeline is error', () {
+    test('getting unregistered signal on pipeline is error', () {
       expect(
           () => Pipeline(Logic(), signals: [
                 Logic()

test/ssa_test.dart

@@ -1,4 +1,4 @@
-// Copyright (C) 2023 Intel Corporation
+// Copyright (C) 2023-2025 Intel Corporation
 // SPDX-License-Identifier: BSD-3-Clause
 //
 // ssa_test.dart
@@ -21,6 +21,90 @@ abstract class SsaTestModule extends Module {
   int model(int a);
 }
 
+class SimpleStruct extends LogicStructure {
+  SimpleStruct()
+      : super([Logic(width: 4), Logic(width: 4)], name: 'simple_struct');
+}
+
+class StructOpRepack extends Module {
+  late final SimpleStruct x = SimpleStruct()..gets(output('x'));
+
+  StructOpRepack(SimpleStruct a) {
+    a = SimpleStruct()..gets(addInput('a', a, width: 8));
+    final x_ = SimpleStruct();
+
+    x_.elements[0] <= a.elements[0] + 1;
+    x_.elements[1] <= a.elements[1] + 2;
+
+    addOutput('x', width: 8) <= x_;
+  }
+}
+
+class SsaModWithStructElements extends SsaTestModule {
+  SsaModWithStructElements(Logic a) : super(name: 'struct_elements') {
+    a = addInput('a', a, width: 8);
+    final x = addOutput('x', width: 8);
+
+    final s1 = SimpleStruct();
+
+    final sx = SimpleStruct();
+
+    Combinational.ssa((s) => [
+          s(s1) < a,
+          s(sx) < StructOpRepack(SimpleStruct()..gets(s(s1))).x,
+        ]);
+
+    x <= sx;
+  }
+
+  @override
+  int model(int a) {
+    final orig = LogicValue.ofInt(a, 8);
+    return [
+      orig.getRange(0, 4) + 1,
+      orig.getRange(4, 8) + 2,
+    ].rswizzle().toInt();
+  }
+}
+
+class StructOpSplit extends Module {
+  Logic get x0 => output('x0');
+  Logic get x1 => output('x1');
+
+  StructOpSplit(SimpleStruct a) {
+    a = SimpleStruct()..gets(addInput('a', a, width: 8));
+    final x0 = addOutput('x0', width: 4);
+    final x1 = addOutput('x1', width: 4);
+
+    x0 <= a.elements[0] + 1;
+    x1 <= a.elements[1] + 2;
+  }
+}
+
+class SsaModWithStructSplit extends SsaTestModule {
+  SsaModWithStructSplit(Logic a) : super(name: 'struct_split') {
+    a = addInput('a', a, width: 8);
+    final x = addOutput('x', width: 8);
+
+    final s1 = SimpleStruct();
+
+    Combinational.ssa((s) => [
+          s(s1) < a,
+          s(x) <
+              () {
+                final splitMod = StructOpSplit(SimpleStruct()..gets(s(s1)));
+                return (splitMod.x0 + splitMod.x1).zeroExtend(8);
+              }(),
+        ]);
+  }
+
+  @override
+  int model(int a) {
+    final orig = LogicValue.ofInt(a, 8);
+    return (orig.getRange(0, 4) + 1 + orig.getRange(4, 8) + 2).toInt();
+  }
+}
+
 class SsaModAssignsOnly extends SsaTestModule {
   SsaModAssignsOnly(Logic a) : super(name: 'assigns_only') {
     a = addInput('a', a, width: 8);
@@ -338,6 +422,8 @@ void main() {
       SsaMix(aInput),
       SsaNested(aInput),
       SsaMultiDep(aInput),
+      SsaModWithStructElements(aInput),
+      SsaModWithStructSplit(aInput),
     ];
 
     for (final mod in mods) {