[U-Boot] printf in u-boot cannot support %f

[ITechnology]

Hi,
The codes below:
   ...
  	double result1 =  3.14;
	printf("result1:%f\n", result1);// error 
 .... 
  turn out:
	result1:%f
    How can I  get the correct result? Thanks a lot!
The U-boot version is:
=> ver
U-Boot 2008.10 (Jul 15 2009 - 21:56:05) MPC512X
    I wan to a little more complex program in standalone mode in u-boot. Is it possilbe to port g-libc to u-boot standalone mode?
Tanks.
 Best regards,
Michael Franklin