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Groups > comp.lang.c > #111984
| From | Ben Bacarisse <ben.usenet@bsb.me.uk> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: C speed |
| Date | 2017-06-11 23:47 +0100 |
| Organization | A noiseless patient Spider |
| Message-ID | <8760g2dtw4.fsf@bsb.me.uk> (permalink) |
| References | (3 earlier) <ohh8tu$sbv$1@dont-email.me> <b1f00fa2-7ebd-484e-91bb-9c86457eefbf@googlegroups.com> <ohk6hu$j6g$1@dont-email.me> <87bmpue0jw.fsf@bsb.me.uk> <73f34d0e-c8dc-4f6f-9780-d09b2903f5a9@googlegroups.com> |
supercat@casperkitty.com writes: > On Sunday, June 11, 2017 at 3:23:22 PM UTC-5, Ben Bacarisse wrote: >> Is this always the case? In languages were the compiler knows that the >> pointer is to the start of an array (and this may be a pointer generated >> internally -- the language may not have pointers as such) the compiler >> may be able to assume things about alignment that could be helpful for >> optimisation (particularly vectorisation). > > If a compiler knows that arr1 is the start of one array and arr2 is the start > of a (not necessarily different) array, then it will be entitled to assume > that for any *unequal* integer values i and j, nothing that is accessed as > arr1[i] will also be accessed as arr2[j]. That's a *very* useful assumption > for vectorization. 'restrict' will do that in C, though that makes a rather more general guarantee. -- Ben.
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Re: C speed "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-09 18:58 -0400
Re: C speed supercat@casperkitty.com - 2017-06-09 16:21 -0700
Re: C speed David Brown <david.brown@hesbynett.no> - 2017-06-10 19:09 +0200
Re: C speed supercat@casperkitty.com - 2017-06-10 12:37 -0700
Re: C speed David Brown <david.brown@hesbynett.no> - 2017-06-11 21:47 +0200
Re: C speed Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-11 21:23 +0100
Re: C speed supercat@casperkitty.com - 2017-06-11 13:33 -0700
Re: C speed Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-11 23:47 +0100
Re: C speed David Brown <david.brown@hesbynett.no> - 2017-06-12 09:12 +0200
Re: C speed supercat@casperkitty.com - 2017-06-11 13:30 -0700
Re: C speed David Brown <david.brown@hesbynett.no> - 2017-06-12 09:15 +0200
Re: C speed supercat@casperkitty.com - 2017-06-12 07:14 -0700
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