diff --git a/llvm-gofrontend/go-llvm-bnode.cpp b/llvm-gofrontend/go-llvm-bnode.cpp
index 71a3a0e..25822a5 100644
--- a/llvm-gofrontend/go-llvm-bnode.cpp
+++ b/llvm-gofrontend/go-llvm-bnode.cpp
@@ -267,14 +267,15 @@
     kid->osdump(os, ilevel + 2, linemap, terse);
 }
 
-void BnodeBuilder::destroy(Bnode *node, WhichDel which)
+void BnodeBuilder::destroy(Bnode *node, WhichDel which, bool recursive)
 {
   std::set<Bnode *> visited;
-  destroyRec(node, which, visited);
+  destroyRec(node, which, recursive, visited);
 }
 
 void BnodeBuilder::destroyRec(Bnode *node,
                               WhichDel which,
+                              bool recursive,
                               std::set<Bnode *> &visited)
 {
   if (visited.find(node) != visited.end())
@@ -283,14 +284,19 @@
   if (which != DelWrappers) {
     Bexpression *expr = node->castToBexpression();
     if (expr) {
-      for (auto inst : expr->instructions())
+      unsigned idx = 0;
+      for (auto inst : expr->instructions()) {
+        integrityVisitor_->unsetParent(inst, expr, idx);
         inst->dropAllReferences();
+      }
       for (auto inst : expr->instructions())
         inst->deleteValue();
+      expr->clear();
     }
   }
-  for (auto &kid : node->kids_)
-    destroyRec(kid, which, visited);
+  if (recursive)
+    for (auto &kid : node->kids_)
+      destroyRec(kid, which, true, visited);
   if (which != DelInstructions)
     freeNode(node);
 }
diff --git a/llvm-gofrontend/go-llvm-bnode.h b/llvm-gofrontend/go-llvm-bnode.h
index 16d5ec5..3751f63 100644
--- a/llvm-gofrontend/go-llvm-bnode.h
+++ b/llvm-gofrontend/go-llvm-bnode.h
@@ -345,7 +345,8 @@
   // LLVM instructions found in the subtree), DelWrappers (deletes
   // Bnodes but not instructions), or DelBoth (gets rid of nodes and
   // instructions).
-  void destroy(Bnode *node, WhichDel which = DelWrappers);
+  // If recursive is true, also delete its children recursively.
+  void destroy(Bnode *node, WhichDel which = DelWrappers, bool recursive = true);
 
   // Clone an expression subtree.
   Bexpression *cloneSubtree(Bexpression *expr);
@@ -378,7 +379,8 @@
   Bexpression *cloneSub(Bexpression *expr,
                         std::map<llvm::Value *, llvm::Value *> &vm);
   void checkTreeInteg(Bnode *node);
-  void destroyRec(Bnode *node, WhichDel which, std::set<Bnode *> &visited);
+  void destroyRec(Bnode *node, WhichDel which, bool recursive,
+                  std::set<Bnode *> &visited);
 
  private:
   std::unique_ptr<Bstatement> errorStatement_;
diff --git a/llvm-gofrontend/go-llvm-tree-integrity.cpp b/llvm-gofrontend/go-llvm-tree-integrity.cpp
index 0d57d1f..405ab49 100644
--- a/llvm-gofrontend/go-llvm-tree-integrity.cpp
+++ b/llvm-gofrontend/go-llvm-tree-integrity.cpp
@@ -92,6 +92,20 @@
     nparent_.erase(it);
 }
 
+void IntegrityVisitor::unsetParent(llvm::Instruction *inst,
+                                   Bexpression *exprParent,
+                                   unsigned slot)
+{
+  auto it = iparent_.find(inst);
+  if (it == iparent_.end())
+    return;
+  parslot pps = it->second;
+  Bnode *prevParent = pps.first;
+  unsigned prevSlot = pps.second;
+  if (prevParent == exprParent || prevSlot == slot)
+    iparent_.erase(it);
+}
+
 void IntegrityVisitor::setParent(Bnode *child, Bnode *parent, unsigned slot)
 {
   if (! shouldBeTracked(child))
diff --git a/llvm-gofrontend/go-llvm-tree-integrity.h b/llvm-gofrontend/go-llvm-tree-integrity.h
index 6cf8b6f..aa7347c 100644
--- a/llvm-gofrontend/go-llvm-tree-integrity.h
+++ b/llvm-gofrontend/go-llvm-tree-integrity.h
@@ -94,6 +94,11 @@
   // relationship (used when node child is deleted or repurposed).
   void unsetParent(Bnode *child, Bnode *parent, unsigned slot);
 
+  // Same as above, for instruction.
+  void unsetParent(llvm::Instruction *inst,
+                   Bexpression *exprParent,
+                   unsigned slot);
+
   // Tell the IntegrityVisitor we're about to delete the specified
   // node, so please remove any outstanding references to it.
   void deletePending(Bnode *node);
diff --git a/llvm-gofrontend/go-llvm.cpp b/llvm-gofrontend/go-llvm.cpp
index 56f9dbb..99febaa 100644
--- a/llvm-gofrontend/go-llvm.cpp
+++ b/llvm-gofrontend/go-llvm.cpp
@@ -2456,13 +2456,8 @@
   // Delete dead instructions before visiting the children,
   // as they may use values defined in the children. Uses
   // need to be deleted before deleting definition.
-  if (!curblock) {
-    for (auto originst : expr->instructions())
-      originst->dropAllReferences();
-    for (auto originst : expr->instructions())
-      originst->deleteValue();
-    expr->clear();
-  }
+  if (!curblock)
+    be_->nodeBuilder().destroy(expr, DelInstructions, false);
 
   // Visit children first
   const std::vector<Bnode *> &kids = expr->children();
@@ -2470,13 +2465,8 @@
     curblock = walk(child, curblock);
 
   // In case it becomes dead after visiting some child...
-  if (!curblock) {
-    for (auto originst : expr->instructions())
-      originst->dropAllReferences();
-    for (auto originst : expr->instructions())
-      originst->deleteValue();
-    expr->clear();
-  }
+  if (!curblock)
+    be_->nodeBuilder().destroy(expr, DelInstructions, false);
 
   // Now visit instructions for this expr
   // TODO: currently the control flow won't change from