Revert of [regexp] Remove IsRegExp intrinsic

src/crankshaft/hydrogen.cc

Index: src/crankshaft/hydrogen.cc
diff --git a/src/crankshaft/hydrogen.cc b/src/crankshaft/hydrogen.cc
index 400e3559d6fc68684865586f2628b49dfb18174a..5fc7a6959c0c23b10d0a58936634d70b69b575c7 100644
--- a/src/crankshaft/hydrogen.cc
+++ b/src/crankshaft/hydrogen.cc
@@ -11943,6 +11943,16 @@
 }
 
 
+void HOptimizedGraphBuilder::GenerateIsRegExp(CallRuntime* call) {
+  DCHECK(call->arguments()->length() == 1);
+  CHECK_ALIVE(VisitForValue(call->arguments()->at(0)));
+  HValue* value = Pop();
+  HHasInstanceTypeAndBranch* result =
+      New<HHasInstanceTypeAndBranch>(value, JS_REGEXP_TYPE);
+  return ast_context()->ReturnControl(result, call->id());
+}
+
+
 void HOptimizedGraphBuilder::GenerateToInteger(CallRuntime* call) {
   DCHECK_EQ(1, call->arguments()->length());
   CHECK_ALIVE(VisitForValue(call->arguments()->at(0)));