Revert of [regexp] Remove IsRegExp intrinsic

src/full-codegen/mips64/full-codegen-mips64.cc

 // Copyright 2012 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.
 
 #if V8_TARGET_ARCH_MIPS64
 
 // Note on Mips implementation:
 //
 // The result_register() for mips is the 'v0' register, which is defined
 // by the ABI to contain function return values. However, the first
@@ skipping 2021 matching lines @@
   context()->PrepareTest(&materialize_true, &materialize_false, &if_true,
                          &if_false, &fall_through);
 
   __ JumpIfSmi(v0, if_false);
   __ GetObjectType(v0, a1, a1);
   PrepareForBailoutBeforeSplit(expr, true, if_true, if_false);
   Split(eq, a1, Operand(JS_TYPED_ARRAY_TYPE), if_true, if_false, fall_through);
 
   context()->Plug(if_true, if_false);
 }
+
+
+void FullCodeGenerator::EmitIsRegExp(CallRuntime* expr) {
+  ZoneList<Expression*>* args = expr->arguments();
+  DCHECK(args->length() == 1);
+
+  VisitForAccumulatorValue(args->at(0));
+
+  Label materialize_true, materialize_false;
+  Label* if_true = NULL;
+  Label* if_false = NULL;
+  Label* fall_through = NULL;
+  context()->PrepareTest(&materialize_true, &materialize_false,
+                         &if_true, &if_false, &fall_through);
+
+  __ JumpIfSmi(v0, if_false);
+  __ GetObjectType(v0, a1, a1);
+  PrepareForBailoutBeforeSplit(expr, true, if_true, if_false);
+  Split(eq, a1, Operand(JS_REGEXP_TYPE), if_true, if_false, fall_through);
+
+  context()->Plug(if_true, if_false);
+}
 
 
 void FullCodeGenerator::EmitIsJSProxy(CallRuntime* expr) {
   ZoneList<Expression*>* args = expr->arguments();
   DCHECK(args->length() == 1);
 
   VisitForAccumulatorValue(args->at(0));
 
   Label materialize_true, materialize_false;
   Label* if_true = NULL;
@@ skipping 812 matching lines @@
          reinterpret_cast<uint64_t>(
              isolate->builtins()->OnStackReplacement()->entry()));
   return ON_STACK_REPLACEMENT;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS64