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[Bug target/47522] [4.4/4.5/4.6 Regression] wrong code at -O3 -ffast-math
- From: "rguenther at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Mon, 31 Jan 2011 10:48:09 +0000
- Subject: [Bug target/47522] [4.4/4.5/4.6 Regression] wrong code at -O3 -ffast-math
- Auto-submitted: auto-generated
- References: <bug-47522-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47522
--- Comment #4 from rguenther at suse dot de <rguenther at suse dot de> 2011-01-31 10:47:53 UTC ---
On Mon, 31 Jan 2011, Joost.VandeVondele at pci dot uzh.ch wrote:
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47522
>
> --- Comment #3 from Joost VandeVondele <Joost.VandeVondele at pci dot uzh.ch> 2011-01-31 10:16:24 UTC ---
> (In reply to comment #2)
> > Target piece, if there is one. PR44183 for the vectorizer piece, if there is
> > one.
>
> I'm almost certain that this is a dup of PR44183. As far as I can judge, the
> result of the calculation is indeed correct.
>
> The annoying thing is that this makes valgrind's 'out of bounds checking' kind
> of useless.
I think valgrind should simply special-case these kind of out of bounds
checks based on the instruction that was used. This is an optimization
that is useful (even glibc memcpy routines do that, but they have
exception rules in valgrind ...)
Richard.