define_peephol2 insn

[Joern Rennecke]

> To solve the above issue, can I use the "define_peephole2" insn pattern?

No.  At most you could abuse it to hide the issue some of the time.
You probably have one or more of your target macros / hooks wrong,
e.g. HARD_REGNO_NREGS.

> Any comments or suggestions most welcome.

read and understand all the documentation on porting gcc in the doc
directory.  Or work with someone who has.