Revert of [regexp] Remove IsRegExp intrinsic

src/full-codegen/mips/full-codegen-mips.cc

Index: src/full-codegen/mips/full-codegen-mips.cc
diff --git a/src/full-codegen/mips/full-codegen-mips.cc b/src/full-codegen/mips/full-codegen-mips.cc
index 52aed1d0b12b3e11461fa8694b653dab4eea1734..7f3be4e34dafa0860a15a97efa849c4dbb868040 100644
--- a/src/full-codegen/mips/full-codegen-mips.cc
+++ b/src/full-codegen/mips/full-codegen-mips.cc
@@ -2035,6 +2035,28 @@
   __ 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);
 }