[FIRRTL][SpecializeLayers] Fix incorrect CF leading to double free (#7200)

As a part of specializing layers we have to remove any HierPathOps which
included a reference to deleted instances.  If any member of the path
array is contained in the deleted references list, we need to delete the
op.  There was incorrect use of `continue` which caused us to continue
processing the path instead of skipping to the next path operation,
which could lead to a double free when multiple instances in the path
were removed.

lib/Dialect/FIRRTL/Transforms/SpecializeLayers.cpp

@@ -655,17 +655,18 @@ struct SpecializeLayers {
     for (auto hierPath : llvm::make_early_inc_range(
              circuit.getBody().getOps<hw::HierPathOp>())) {
       auto namepath = hierPath.getNamepath().getValue();
-      for (auto ref : namepath.drop_back()) {
+      auto shouldDelete = [&](Attribute ref) {
-        if (removedSyms.contains(ref)) {
+        return removedSyms.contains(ref);
+      };
+      if (llvm::any_of(namepath.drop_back(), shouldDelete)) {
         removedPaths.insert(SymbolTable::getSymbolName(hierPath));
         hierPath->erase();
         continue;
       }
-      }
       // If we deleted the target of the hierpath, we don't need to add it to
       // the list of removedPaths, since no annotation will be left around to
       // reference this path.
-      if (removedSyms.contains(namepath.back()))
+      if (shouldDelete(namepath.back()))
         hierPath->erase();
     }
 

test/Dialect/FIRRTL/specialize-layers.mlir

@@ -371,6 +371,41 @@ firrtl.circuit "HierPathDelete" attributes {
   firrtl.extmodule @Deleted() attributes {layers = [@Layer]}
 }
 
+// CHECK-LABEL: firrtl.circuit "HierPathDelete"
+firrtl.circuit "HierPathDelete" attributes {
+  disable_layers = [@Layer]
+} {
+  firrtl.layer @Layer bind { }
+
+  // CHECK-NOT: hw.hierpath private @hierpath1 [@HierPathDelete::@middle, @Middle::@leaf, @Leaf]
+  hw.hierpath private @hierpath1 [@HierPathDelete::@middle, @Middle::@leaf, @Leaf]
+  // CHECK-NOT: hw.hierpath private @hierpath2 [@HierPathDelete::@middle, @Middle::@leaf]
+  hw.hierpath private @hierpath2 [@HierPathDelete::@middle, @Middle::@leaf]
+  // CHECK-NOT: hw.hierpath private @hierpath3 [@Middle::@leaf, @Leaf]
+  hw.hierpath private @hierpath3 [@Middle::@leaf, @Leaf]
+  // CHECK-NOT: hw.hierpath private @hierpath4 [@Middle::@leaf]
+  hw.hierpath private @hierpath4 [@Middle::@leaf]
+
+  firrtl.module @HierPathDelete() {
+    firrtl.layerblock @Layer {
+      firrtl.instance middle sym @middle @Middle()
+    }
+  }
+  
+  firrtl.module @Middle() {
+    firrtl.layerblock @Layer {
+      firrtl.instance leaf sym @leaf @Leaf()
+    }
+  }
+  
+  firrtl.extmodule @Leaf()
+
+  // CHECK-NOT: hw.hierpath private @DeletedPath [@Deleted]
+  hw.hierpath private @DeletedPath [@Deleted]
+  firrtl.extmodule @Deleted() attributes {layers = [@Layer]}
+}
+
+
 //===----------------------------------------------------------------------===//
 // Annotations
 //===----------------------------------------------------------------------===//