Handle HCheckInstanceType and HIsStringAndBranch in check elimination.

src/hydrogen-instructions.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.
 
 #include "v8.h"
 
 #include "double.h"
 #include "factory.h"
 #include "hydrogen-infer-representation.h"
 #include "property-details-inl.h"
@@ skipping 3233 matching lines @@
     *block = ConstantIsObject(HConstant::cast(value()), isolate())
         ? FirstSuccessor() : SecondSuccessor();
     return true;
   }
   *block = NULL;
   return false;
 }
 
 
 bool HIsStringAndBranch::KnownSuccessorBlock(HBasicBlock** block) {
+  if (known_successor_index() != kNoKnownSuccessorIndex) {
+    *block = SuccessorAt(known_successor_index());
+    return true;
+  }
   if (FLAG_fold_constants && value()->IsConstant()) {
     *block = HConstant::cast(value())->HasStringValue()
         ? FirstSuccessor() : SecondSuccessor();
     return true;
   }
+  if (value()->type().IsString()) {
+    *block = FirstSuccessor();
+    return true;
+  }
+  if (value()->type().IsSmi() ||
+      value()->type().IsNull() ||
+      value()->type().IsBoolean() ||
+      value()->type().IsUndefined() ||
+      value()->type().IsJSObject()) {
+    *block = SecondSuccessor();
+    return true;
+  }
   *block = NULL;
   return false;
 }
 
 
 bool HIsUndetectableAndBranch::KnownSuccessorBlock(HBasicBlock** block) {
   if (FLAG_fold_constants && value()->IsConstant()) {
     *block = HConstant::cast(value())->IsUndetectable()
         ? FirstSuccessor() : SecondSuccessor();
     return true;
@@ skipping 1478 matching lines @@
       break;
     case kExternalMemory:
       stream->Add("[external-memory]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal