Re: [PATCH/RFC] hash: Let gcc decide how to multiply
From: David Miller
Date: Mon Aug 25 2014 - 14:48:03 EST
From: Daniel Borkmann <dborkman@xxxxxxxxxx>
Date: Mon, 25 Aug 2014 14:58:37 +0200
> On 08/25/2014 02:13 PM, Rasmus Villemoes wrote:
>> A 9+ years old comment in hash_64 says that gcc can't optimize
>> multiplication by GOLDEN_RATIO_PRIME_64. Well, compilers get smarter
>> and CPUs get faster all the time, so it is perhaps about time to
>> revisit that assumption.
> Seems fine by me, but Cc'ing a couple of others (as those you have
> haven't written that code :)). You might want to let your changes go
> Andrew's tree, too, perhaps ...
You need to test the code generation for a cpu where the multiply
instruction is more expensive than the shifts and adds.
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