[turbofan] Handle Smi -> Float32 conversion in representation changer.

test/mjsunit/compiler/regress-693425.js

Index: test/mjsunit/compiler/regress-693425.js
diff --git a/test/mjsunit/compiler/regress-693425.js b/test/mjsunit/compiler/regress-693425.js
new file mode 100644
index 0000000000000000000000000000000000000000..c818d645aff36b68b43cd7eee90ff1a686a82e4a
--- /dev/null
+++ b/test/mjsunit/compiler/regress-693425.js
@@ -0,0 +1,11 @@
+// Copyright 2017 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 g = 0;
+g++;
+var f32 = new Float32Array();
+function foo() {
+  f32[0 >> 2] = g;
+}
+foo();