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Re: Live range splitting in new allocator
- To: Joe Buck <jbuck at racerx dot synopsys dot com>
- Subject: Re: Live range splitting in new allocator
- From: Alexandre Oliva <aoliva at redhat dot com>
- Date: 30 Jan 2001 19:47:21 -0200
- Cc: espie at quatramaran dot ens dot fr (Marc Espie), dewar at gnat dot com, gcc at gcc dot gnu dot org
- Organization: GCC Team, Red Hat
- References: <200101301707.JAA05196@racerx.synopsys.com>
On Jan 30, 2001, Joe Buck <jbuck@racerx.synopsys.com> wrote:
> Marc Espie writes:
>> 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 ?
> For floating point on IEEE platforms, it's easy enough: use a NaN.
> However, for variables that are used as boolean values (whether a C++ bool
> or a C int used as a flag), you'll make things more deterministic than
> before: an uninitialized Boolean auto variable used to be random, under your
> proposal it will always be true.
How about using some bit in the return value of random() instead? :-)
--
Alexandre Oliva Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer aoliva@{cygnus.com, redhat.com}
CS PhD student at IC-Unicamp oliva@{lsd.ic.unicamp.br, gnu.org}
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