Revert of [regexp] Remove IsRegExp intrinsic

src/interpreter/interpreter-intrinsics.cc

Index: src/interpreter/interpreter-intrinsics.cc
diff --git a/src/interpreter/interpreter-intrinsics.cc b/src/interpreter/interpreter-intrinsics.cc
index 2de7017f20f055adeba7f153144dffc3b3e527f8..d6bf616aa059b7856916ebb22e33245bc9419115 100644
--- a/src/interpreter/interpreter-intrinsics.cc
+++ b/src/interpreter/interpreter-intrinsics.cc
@@ -184,6 +184,10 @@
   return IsInstanceType(input, JS_PROXY_TYPE);
 }
 
+Node* IntrinsicsHelper::IsRegExp(Node* input, Node* arg_count, Node* context) {
+  return IsInstanceType(input, JS_REGEXP_TYPE);
+}
+
 Node* IntrinsicsHelper::IsTypedArray(Node* input, Node* arg_count,
                                      Node* context) {
   return IsInstanceType(input, JS_TYPED_ARRAY_TYPE);