Revert of [regexp] Remove IsRegExp intrinsic

src/compiler/js-intrinsic-lowering.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/js-intrinsic-lowering.h"
 
 #include <stack>
 
 #include "src/code-factory.h"
 #include "src/compiler/access-builder.h"
@@ skipping 28 matching lines @@
     case Runtime::kInlineGeneratorClose:
       return ReduceGeneratorClose(node);
     case Runtime::kInlineGeneratorGetInputOrDebugPos:
       return ReduceGeneratorGetInputOrDebugPos(node);
     case Runtime::kInlineGeneratorGetResumeMode:
       return ReduceGeneratorGetResumeMode(node);
     case Runtime::kInlineIsArray:
       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:
       return ReduceIsSmi(node);
     case Runtime::kInlineFixedArrayGet:
       return ReduceFixedArrayGet(node);
     case Runtime::kInlineFixedArraySet:
       return ReduceFixedArraySet(node);
     case Runtime::kInlineRegExpExec:
       return ReduceRegExpExec(node);
@@ skipping 304 matching lines @@
   return jsgraph_->javascript();
 }
 
 SimplifiedOperatorBuilder* JSIntrinsicLowering::simplified() const {
   return jsgraph()->simplified();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8