4 files changed, 12 insertions, 0 deletions
diff --git a/src/ir/ReFinalize.cpp b/src/ir/ReFinalize.cpp
index 8acffaa34..102d701b9 100644
--- a/src/ir/ReFinalize.cpp
+++ b/src/ir/ReFinalize.cpp
@@ -176,6 +176,7 @@ void ReFinalize::visitStringNew(StringNew* curr) { curr->finalize(); }
 void ReFinalize::visitStringConst(StringConst* curr) { curr->finalize(); }
 void ReFinalize::visitStringMeasure(StringMeasure* curr) { curr->finalize(); }
 void ReFinalize::visitStringEncode(StringEncode* curr) { curr->finalize(); }
+void ReFinalize::visitStringConcat(StringConcat* curr) { curr->finalize(); }
 
 void ReFinalize::visitFunction(Function* curr) {
   // we may have changed the body from unreachable to none, which might be bad
diff --git a/src/ir/cost.h b/src/ir/cost.h
index afc091ffb..2dcf7c456 100644
--- a/src/ir/cost.h
+++ b/src/ir/cost.h
@@ -681,6 +681,9 @@ struct CostAnalyzer : public OverriddenVisitor<CostAnalyzer, CostType> {
   CostType visitStringEncode(StringEncode* curr) {
     return 6 + visit(curr->ref) + visit(curr->ptr);
   }
+  CostType visitStringConcat(StringConcat* curr) {
+    return 10 + visit(curr->left) + visit(curr->right);
+  }
 
 private:
   CostType nullCheckCost(Expression* ref) {
diff --git a/src/ir/effects.h b/src/ir/effects.h
index 8e33f65bf..dbd1bb48f 100644
--- a/src/ir/effects.h
+++ b/src/ir/effects.h
@@ -742,6 +742,10 @@ private:
       // traps when ref is null or we write out of bounds.
       parent.implicitTrap = true;
     }
+    void visitStringConcat(StringConcat* curr) {
+      // traps when an input is null.
+      parent.implicitTrap = true;
+    }
   };
 
 public:
diff --git a/src/ir/possible-contents.cpp b/src/ir/possible-contents.cpp
index c865585f1..21eadc50b 100644
--- a/src/ir/possible-contents.cpp
+++ b/src/ir/possible-contents.cpp
@@ -689,6 +689,10 @@ struct InfoCollector
     // TODO: optimize when possible
     addRoot(curr);
   }
+  void visitStringConcat(StringConcat* curr) {
+    // TODO: optimize when possible
+    addRoot(curr);
+  }
 
   // TODO: Model which throws can go to which catches. For now, anything thrown
   //       is sent to the location of that tag, and any catch of that tag can