Cross compiling NSPR for an xtensa processor (currently not supported)

Hello,
I have trying to cross compile firefox for an tensilica xtensa
processor. I am using a linux support package from Montavista which
does not have the libnspr. when the build tries to cross compile NSPR
it fails with an error:

Unknown architecture.

>From some previous posts, I noticed that i needed to create a
prcpucfg.h which I did. But looking into _linux.h, I noticed that
there was some additional information for each processor. Can I just
replicate the below linux code for my processor as I have libc in my
package ?

#if defined(__GLIBC__) && __GLIBC__ >= 2
#define _MD_GET_SP(_t) (_t)->md.context[0].__jmpbuf[0].__sp
#define _MD_SET_FP(_t, val) ((_t)->md.context[0].__jmpbuf[0].__fp =
(val))
#define _MD_GET_SP_PTR(_t) &(_MD_GET_SP(_t))
#define _MD_GET_FP_PTR(_t) (&(_t)->md.context[0].__jmpbuf[0].__fp)
#define _MD_SP_TYPE __ptr_t
#else
#error "Linux/MIPS pre-glibc2 not supported yet"
#endif /* defined(__GLIBC__) && __GLIBC__ >= 2 */

Also I noticed there was assembly code for some architectures in
_linux.h. Could you please help with information as to how I can
modify this source for a new architecture.

Thank you for any help.

Sincerely
Pradeep