Take output type into account in JSTypedLowering reduction.

src/compiler/js-typed-lowering.cc

 // Copyright 2014 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 "src/compiler/access-builder.h"
 #include "src/compiler/graph-inl.h"
 #include "src/compiler/js-builtin-reducer.h"
 #include "src/compiler/js-typed-lowering.h"
 #include "src/compiler/node-aux-data-inl.h"
 #include "src/compiler/node-properties-inl.h"
@@ skipping 612 matching lines @@
 static Reduction ReplaceWithReduction(Node* node, Reduction reduction) {
   if (reduction.Changed()) {
     NodeProperties::ReplaceWithValue(node, reduction.replacement());
     return reduction;
   }
   return Reducer::NoChange();
 }
 
 
 Reduction JSTypedLowering::Reduce(Node* node) {
+  // Check if the output type is a singleton.  In that case we already know the
+  // result value and can simply replace the node unless there are effects.
+  if (node->bounds().upper->IsConstant() &&
+      !IrOpcode::IsLeafOpcode(node->opcode()) &&
+      !OperatorProperties::HasEffectOutput(node->op())) {
+    return ReplaceEagerly(node, jsgraph()->Constant(
+        node->bounds().upper->AsConstant()->Value()));
+    // TODO(neis): Extend this to Range(x,x), NaN, MinusZero, ...?
+  }
   switch (node->opcode()) {
     case IrOpcode::kJSEqual:
       return ReduceJSEqual(node, false);
     case IrOpcode::kJSNotEqual:
       return ReduceJSEqual(node, true);
     case IrOpcode::kJSStrictEqual:
       return ReduceJSStrictEqual(node, false);
     case IrOpcode::kJSStrictNotEqual:
       return ReduceJSStrictEqual(node, true);
     case IrOpcode::kJSLessThan:         // fall through
@@ skipping 59 matching lines @@
       return JSBuiltinReducer(jsgraph()).Reduce(node);
     default:
       break;
   }
   return NoChange();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8