Live range splitting in new allocator

[dewar@gnat.com]

<<I don't know how hard it would be to do, but I feel that it would make
a lot of sense to make *sure* the uninitialized variables are set to
something completely different from 0 in -O0 mode. After all, we already
know that -O0 code is bad, performance-wise, why not take the plunge and
initialize variables to bad defaults so that stuff *will* crash at -O0 as
well ?
>>

Yes, this is a useful idea, it is part of the language for Ada (pragma
Normalize_Scalars, which requires deterministic initialization of all
scalars, preferably to values outside their range). 

It will definitely help find bugs, but it will not eliminate problems
that come from optimziation of incorrect code :-)