How to define PSImode

[Lev Yudalevich]

Hi,

While working on a port for my custom target I'm looking for some
advice on how to define a smaller-than-integer scalar mode.
I'm planning to use it together with __attribute__
((__libgcc_cmp_return__)) mode attribute.
In my xx-modes.def file I have PARTIAL_MODE_INT(SI) defined. And my
TARGET_LIBGCC_CMP_RETURN_MODE hook is set to a function returning
PSImode.
However, compilation of the libgcc fails in libgcc2.h at line 172 with
an error message: no data type for mode libgcc_cmp_return. The gcc
version I'm working on is 4.4.1.
PARTIAL_MODE_INT seems to be kind of undocumented feature. Can anybody
suggest the steps required to use it properly?

Sincerely,
-- Lev.