RE: [MIPS] RFA: Use new rtl iterators in mips_kernel_reg_p

[Matthew Fortune]

> gcc/
>       * config/mips/mips.c (mips_kernel_reg_p): Replace with...
>       (mips_refers_to_kernel_reg_p): ...this new function.
>       (mips_expand_prologue): Update accordingly.

OK