This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: optimisation question
- From: Andreas Schwab <schwab at suse dot de>
- To: Robert Dewar <dewar at adacore dot com>
- Cc: "Remy X.O. Martin" <vsxo at hotmail dot com>,Joe Buck <Joe dot Buck at synopsys dot COM>, gcc at gcc dot gnu dot org
- Date: Wed, 02 Feb 2005 14:25:55 +0100
- Subject: Re: optimisation question
- References: <20050131152659.0dc92d6c@portia.local><41FE6ADB.3070706@adacore.com> <20050131234317.GA4737@synopsys.com><20050201182110.192883b1@portia.local> <jevf9cdwe9.fsf@sykes.suse.de><4200CBF3.3090901@adacore.com>
Robert Dewar <dewar@adacore.com> writes:
> Andreas Schwab wrote:
>> "Remy X.O. Martin" <vsxo@hotmail.com> writes:
>>
>>>Here's another 'trick' I learned in those days: use a=b, c=d, e=f; rather
>>>than a=b; c=d; e=f; (like in the initialisation expression of a for
>>>loop). "The first version might be executed in parallel. Of course we
>>>don't have parellel machines here, but you never know..."
>
> Also nonsense of course
>> And of course it is wrong, because the comma operator creates a sequence
>> point (but K&R C didn't have sequence points yet).
>
> Irrelevant, the assignments can be done in parallel regardless of which
> form they are written in. Sequence points create as-if sequencing, but
> a compiler can always reorder etc if it has no effect on the result.
Irrelevant, because semicolon is no different from comma in this point.
Andreas.
--
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."