Gcc compile hello.c for c6x

I compiled hello.c program for c6x architecture: gcc-4.8 -o hello -march='c64x' hello.c.

But It got an error: error: bad value (c64x) for -march= switch

It seems that gcc can't recognize c64x architecture!

I am using Ubuntu 12.04 LTS & gcc-4.8 version.

Thank you!