Messages in this thread | | | From | Rasmus Villemoes <> | Subject | Re: [PATCH/RFC] hash: Let gcc decide how to multiply | Date | Tue, 26 Aug 2014 10:17:57 +0200 |
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David Miller <davem@davemloft.net> writes:
> From: Daniel Borkmann <dborkman@redhat.com> > 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 >> Cc'ed haven't written that code :)). You might want to let your >> changes go via 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.
Yes, I should, but I'm afraid I can't. I only have x86 hardware, and even if I managed to set up some cross-compiler toolchain, I wouldn't know what CPUs to target. So I was hoping someone else could test this on appropriate platforms.
Thanks, Rasmus
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