Revert of [regexp] Remove IsRegExp intrinsic

src/compiler/js-intrinsic-lowering.cc

Index: src/compiler/js-intrinsic-lowering.cc
diff --git a/src/compiler/js-intrinsic-lowering.cc b/src/compiler/js-intrinsic-lowering.cc
index 4cdd43a3133cbbf3a23eb1ecd50ef1ec54981596..857c0f50dba0fcef4b915ddf4d00a037024fc8b8 100644
--- a/src/compiler/js-intrinsic-lowering.cc
+++ b/src/compiler/js-intrinsic-lowering.cc
@@ -46,6 +46,8 @@
       return ReduceIsInstanceType(node, JS_ARRAY_TYPE);
     case Runtime::kInlineIsTypedArray:
       return ReduceIsInstanceType(node, JS_TYPED_ARRAY_TYPE);
+    case Runtime::kInlineIsRegExp:
+      return ReduceIsInstanceType(node, JS_REGEXP_TYPE);
     case Runtime::kInlineIsJSReceiver:
       return ReduceIsJSReceiver(node);
     case Runtime::kInlineIsSmi: