Extend JSBuiltinReducer to cover Math.fround as well.

src/compiler/js-builtin-reducer.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/graph-inl.h"
 #include "src/compiler/js-builtin-reducer.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties-inl.h"
 #include "src/types.h"
 
@@ skipping 133 matching lines @@
   JSCallReduction r(node);
   if (r.InputsMatchTwo(Type::Integral32(), Type::Integral32())) {
     // Math.imul(a:int32, b:int32) -> Int32Mul(a, b)
     Node* value = graph()->NewNode(machine()->Int32Mul(), r.left(), r.right());
     return Replace(value);
   }
   return NoChange();
 }
 
 
+// ES6 draft 08-24-14, section 20.2.2.17.
+Reduction JSBuiltinReducer::ReduceMathFround(Node* node) {
+  JSCallReduction r(node);
+  if (r.InputsMatchOne(Type::Number())) {
+    // Math.fround(a:number) -> TruncateFloat64ToFloat32(a)
+    Node* value =
+        graph()->NewNode(machine()->TruncateFloat64ToFloat32(), r.left());
+    return Replace(value);
+  }
+  return NoChange();
+}
+
+
 Reduction JSBuiltinReducer::Reduce(Node* node) {
   JSCallReduction r(node);
 
   // Dispatch according to the BuiltinFunctionId if present.
   if (!r.HasBuiltinFunctionId()) return NoChange();
   switch (r.GetBuiltinFunctionId()) {
     case kMathSqrt:
       return ReplaceWithPureReduction(node, ReduceMathSqrt(node));
     case kMathMax:
       return ReplaceWithPureReduction(node, ReduceMathMax(node));
     case kMathImul:
       return ReplaceWithPureReduction(node, ReduceMathImul(node));
+    case kMathFround:
+      return ReplaceWithPureReduction(node, ReduceMathFround(node));
     default:
       break;
   }
   return NoChange();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8