[turbofan] Push JSToNumber conversions into Phis.

test/mjsunit/asm/if-tonumber.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.
+
+var stdlib = this;
+var buffer = new ArrayBuffer(64 * 1024);
+var foreign = {}
+
+function Module(stdlib, foreign, heap) {
+  "use asm";
+  function foo(i) {
+    i = i|0;
+    if (i > 0) {
+      i = i == 1;
+    } else {
+      i = 1;
+    }
+    return i & 1|0;
+  }
+  return { foo: foo };
+}
+
+var m = Module(stdlib, foreign, buffer);
+
+assertEquals(1, m.foo(-1));
+assertEquals(1, m.foo(-0));
+assertEquals(1, m.foo(0));
+assertEquals(1, m.foo(1));
+assertEquals(0, m.foo(2));
+assertEquals(1, m.foo(true));
+assertEquals(1, m.foo(false));