mixing optimized and unoptimized code?

[Marat Boshernitsan]

Hello,

In my application I have several source files for which latest gcc is
unable to produce optimized code (runs out of memory on a 256M Ultra10
with -O1).  So, I was wondering what would be the implications of
compiling those few sources unoptimized and linking with the rest of the
application which is optimized?  Are there any optimizations I should
avoid? (I am thinking of those that change function call conventions)?
The code is C++, if that matters.

A related question: which optimizations are not especially memory hungry?
I was thinking I could selectively turn on *some* of them on those
problematic sources.

Thanks in advance,

Marat.