From: dewar@gnat.com (Robert Dewar)
To: aoliva@redhat.com, kenner@vlsi1.ultra.nyu.edu
Cc: gcc@gcc.gnu.org
Subject: Re: Bug in loop optimize (invalid postinc to preinc transformation)
Date: Thu, 28 Dec 2000 05:40:00 -0000 [thread overview]
Message-ID: <20001228134026.EC58D34D93@nile.gnat.com> (raw)
<<The implementation of pointers is indeed unsigned on most machines,but
they are not "unsigned types", which would mean integral unsigned types.
So overflow is indeed undefined.
>>
Once again, this is confused.
If you increment a pointer
p++;
then this is defined only if the resulting pointer remains within the
same object, or in the csae of arrays it can go just past the end. Overflow
per se does not arise with pointers because of this stricter rule.
No optimization of pointer arithmetic can possibly be correct if it does
not preserve this fundamental semantic appearence.
next reply other threads:[~2000-12-28 5:40 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-12-28 5:40 Robert Dewar [this message]
2000-12-28 12:21 ` Alexandre Oliva
2000-12-28 14:32 ` Geoff Keating
2000-12-28 15:22 ` Tim Hollebeek
2000-12-28 22:20 ` Dave Korn
2000-12-29 0:52 ` Richard Henderson
2000-12-29 1:51 ` Tim Hollebeek
-- strict thread matches above, loose matches on Subject: below --
2000-12-31 8:30 dewar
2001-01-03 0:52 ` Jamie Lokier
2000-12-29 18:43 dewar
2000-12-30 15:18 ` Toon Moene
2000-12-28 20:33 dewar
2000-12-28 1:14 Richard Kenner
2000-12-27 22:40 Robert Dewar
2000-12-29 18:36 ` Jamie Lokier
2000-12-27 3:04 Bug in loop optimize (TREE stage) David Korn
2000-12-27 15:42 ` Bug in loop optimize (invalid postinc to preinc transformation) Peter Osterlund
2000-12-27 19:55 ` Alexandre Oliva
2000-12-27 21:09 ` Torbjorn Granlund
2000-12-27 21:20 ` Alexandre Oliva
2000-12-27 22:24 ` Jamie Lokier
2000-12-31 8:25 ` Andreas Schwab
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