Revert of [regexp] Remove IsRegExp intrinsic

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

Index: src/full-codegen/mips64/full-codegen-mips64.cc
diff --git a/src/full-codegen/mips64/full-codegen-mips64.cc b/src/full-codegen/mips64/full-codegen-mips64.cc
index ac07297d210a7ffbd139d0fbc83eac3ab49b964d..a3118dc8138595c07269bb3810ac469821f8add7 100644
--- a/src/full-codegen/mips64/full-codegen-mips64.cc
+++ b/src/full-codegen/mips64/full-codegen-mips64.cc
@@ -2036,6 +2036,28 @@
   __ 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);
 }