From: dewar@gnat.com (Robert Dewar)
To: gcc-bugs@gcc.gnu.org, js@convergence.de, sirl@gcc.gnu.org
Cc: gcc@gcc.gnu.org
Subject: Re: optimization/7557: gcc-3.1.1 (debian/i386): wrong code with -O2 / bitfields / pointer aliasing
Date: Mon, 12 Aug 2002 15:05:00 -0000 [thread overview]
Message-ID: <20020812220548.7462CF2D45@nile.gnat.com> (raw)
> I wonder: Thousands of software packages use -O2 by default.
> How many of them will fail mysteriously when compiled with gcc-3.1,
> just because of the implied -fstrict-aliasing?
Who knows? But it is just a special case of the general phenomenon that junk
code which people get away with often falls foul of perfectly legitimate
optimizations, and as compilers improve, such code fails.
It is nice of GCC to provide facilities for keeping old junk code running (there
is certainly no requirement for a C compiler to do so), but it seems clear that
the default for the highest optimization level should be to take advantage
of the aliasing rules, which are after all there *precisely* to enable effective
optimization.
next reply other threads:[~2002-08-12 15:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-08-12 15:05 Robert Dewar [this message]
2002-08-13 9:51 ` Johannes Stezenbach
2002-08-14 1:14 ` PATCH for Re: optimization/7557: gcc-3.1.1 (debian/i386): wrong codewith " Gerald Pfeifer
-- strict thread matches above, loose matches on Subject: below --
2002-08-13 10:00 optimization/7557: gcc-3.1.1 (debian/i386): wrong code with " Robert Dewar
2002-08-13 11:28 ` Johannes Stezenbach
[not found] <20020809190500.22817.qmail@sources.redhat.com>
2002-08-12 8:53 ` Johannes Stezenbach
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