Extend JSBuiltinReducer to cover Math.fround as well.

test/mjsunit/asm/math-fround.js

+// 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.
+
+// Flags: --turbo-asm
+
+function Module(stdlib) {
+  "use asm";
+
+  var fround = stdlib.Math.fround;
+
+  // f: double -> float
+  function f(a) {
+    a = +a;
+    return fround(a);
+  }
+
+  return { f: f };
+}
+
+var f = Module({ Math: Math }).f;
+
+assertTrue(isNaN(f(NaN)));
+assertTrue(isNaN(f(undefined)));
+assertTrue(isNaN(f(function() {})));
+
+assertEquals("Infinity", String(1/f(0)));
+assertEquals("-Infinity", String(1/f(-0)));
+assertEquals("Infinity", String(f(Infinity)));
+assertEquals("-Infinity", String(f(-Infinity)));
+assertEquals("Infinity", String(f(1E200)));
+assertEquals("-Infinity", String(f(-1E200)));
+assertEquals("Infinity", String(1/f(1E-300)));
+assertEquals("-Infinity", String(1/f(-1E-300)));
+
+assertEquals(0,                  f(0));
+assertEquals(1,                  f(1));
+assertEquals(1.5,                f(1.5));
+assertEquals(1.3370000123977661, f(1.337));
+assertEquals(-4.300000190734863, f(-4.3));