Revert of [regexp] Remove IsRegExp intrinsic

src/full-codegen/x87/full-codegen-x87.cc

Index: src/full-codegen/x87/full-codegen-x87.cc
diff --git a/src/full-codegen/x87/full-codegen-x87.cc b/src/full-codegen/x87/full-codegen-x87.cc
index b6cc898a620a9d0d66d8b5fe1d4d531373d558b1..725c1b5d82d09b18ae17f68208f03a4621cbf63f 100644
--- a/src/full-codegen/x87/full-codegen-x87.cc
+++ b/src/full-codegen/x87/full-codegen-x87.cc
@@ -1932,6 +1932,28 @@
 }
 
 
+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(eax, if_false);
+  __ CmpObjectType(eax, JS_REGEXP_TYPE, ebx);
+  PrepareForBailoutBeforeSplit(expr, true, if_true, if_false);
+  Split(equal, 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);