From: Paul Koning <pkoning@equallogic.com>
To: mattheww@chiark.greenend.org.uk
Cc: gcc@gcc.gnu.org
Subject: Re: Where does the C standard describe overflow of signed integers?
Date: Thu, 14 Jul 2005 18:36:00 -0000 [thread overview]
Message-ID: <17110.45219.484000.417340@gargle.gargle.HOWL> (raw)
In-Reply-To: <20050714175713.GA16889@chiark.greenend.org.uk>
>>>>> "Matthew" == Matthew Woodcraft <mattheww@chiark.greenend.org.uk> writes:
Matthew> Paul Schlie wrote:
>> As optimization seems to be a non-argument, as by analogy all
>> optimizations which are available for unsigned arithmetic are
>> correspondingly available for signed integer operations; as any
>> signed value may then be thought of as being unsigned for the
>> purposes of computation and/or comparison.
Matthew> What about optimising x*2/2 to x?
If that doesn't overflow then it's valid, and if overflow is undefined
it's valid in that case, too. :-)
Of course this would be an example where overflow isn't treated as 2s
complement wrap...
paul
next prev parent reply other threads:[~2005-07-14 18:36 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-07-14 1:10 Paul Schlie
2005-07-14 1:59 ` Robert Dewar
2005-07-14 5:28 ` Paul Schlie
2005-07-14 17:57 ` Matthew Woodcraft
2005-07-14 18:36 ` Paul Koning [this message]
-- strict thread matches above, loose matches on Subject: below --
2005-07-14 19:09 Paul Schlie
2005-07-14 19:13 ` Robert Dewar
2005-07-14 19:28 ` Paul Schlie
2005-07-14 19:33 ` Robert Dewar
2005-07-14 20:13 ` Paul Schlie
2005-07-15 13:20 ` Georg Bauhaus
2005-07-15 13:33 ` Georg Bauhaus
2005-07-15 14:31 ` Dave Korn
2005-07-16 12:04 ` Georg Bauhaus
2005-07-16 14:26 ` Paul Schlie
2005-07-15 15:03 ` Paul Schlie
2005-07-16 12:12 ` Georg Bauhaus
2005-07-14 20:35 ` Paul Koning
2005-07-14 21:58 ` Paul Schlie
2005-07-15 7:04 ` Avi Kivity
2005-07-11 14:58 Nicholas Nethercote
2005-07-11 15:07 ` Dave Korn
2005-07-11 16:07 ` Nicholas Nethercote
2005-07-11 17:04 ` Dave Korn
2005-07-11 15:15 ` Nathan Sidwell
2005-07-11 15:23 ` Dave Korn
2005-07-12 23:13 ` Michael Meissner
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