The Tor Browser / file revision

 var buf = new ArrayBuffer(4096);

 var f64 = new Float64Array(buf);

 var i32 = new Int32Array(buf);

 var u32 = new Uint32Array(buf);

 function ffi(d) {

   str = String(d);

 }

 function FFI1(glob, imp, b) {

     "use asm";

     var i8=new glob.Int8Array(b);var u8=new glob.Uint8Array(b);

     var i16=new glob.Int16Array(b);var u16=new glob.Uint16Array(b);

     var i32=new glob.Int32Array(b);var u32=new glob.Uint32Array(b);

     var f32=new glob.Float32Array(b);var f64=new glob.Float64Array(b);

     var ffi=imp.ffi;

     function g() {

       ffi(+f64[0])

     }

     return g

 }

 g = FFI1(this, {ffi:ffi}, buf);

 // that sounds dangerous!

 var a = [0,1,0xffff0000,0x7fff0000,0xfff80000,0x7ff80000,0xfffc0000,0x7ffc0000,0xffffffff,0x0000ffff,0x00008fff7];

 for (i of a) {

     for (j of a) {

         u32[0] = i;

         u32[1] = j;

         print(f64[0]+" (input)");

         //assertEq(f(), f64[0]);

         g();

         assertEq(str, String(f64[0]));

     }

 }