clang __builtin_addcll

By: Michael S (, October 21, 2017 11:05 am
Room: Moderated Discussions
Wilco ( on October 21, 2017 7:16 am wrote:
> Adrian ( on October 21, 2017 1:49 am wrote:
> > Maynard Handley ( on October 20, 2017 8:16 pm wrote:
> > The low performance for multi-precision operations is not surprising.
> >
> > While this version of Mathematica can probably be improved a lot, it cannot not reach parity
> > with x86, because this (support for multi-precision operations) is exactly the area were the
> > ARMv8 ISA is the most deficient compared with the x86 ISA (especially since Broadwell, but
> > also Intel since Nehalem & the AMD before Bulldozer were far above any competition).
> What essential instructions do you think are missing? It's trivial to do fast bignums on AArch64, so
> adding new instructions cannot give much gain, let alone 20x. Most likely the difference is due to using
> a badly written generic C implementation in one case and hand optimized assembly in the other.
> Wilco

clang has primitives for exactly that sort of tasks, but right now they appear to do more harm that good, at least on x86. Generated code is horrible.

So far I didn't figure out how to force clang of goldbolt to generate aarch64 code.

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TopicPosted ByDate
Mathematica on iPadMaynard Handley2017/10/20 01:34 AM
  Mathematica on iPaddmcq2017/10/20 07:26 AM
    Mathematica on iPadMaynard Handley2017/10/20 01:41 PM
      Mathematica on iPadMaynard Handley2017/10/20 08:16 PM
        Does this give better formatting?Maynard Handley2017/10/20 08:20 PM
          Does this give better formatting?anon2017/10/20 09:37 PM
            Does this give better formatting?Maynard Handley2017/10/20 10:29 PM
              Does this give better formatting?anon2017/10/21 12:52 AM
                Does this give better formatting?Maynard Handley2017/10/21 09:48 AM
                  Does this give better formatting?anon2017/10/21 10:01 AM
        Mathematica on iPadAdrian2017/10/21 01:49 AM
          Sorry for the typoAdrian2017/10/21 01:51 AM
          Mathematica on iPaddmcq2017/10/21 07:03 AM
            Mathematica on iPadMaynard Handley2017/10/21 09:58 AM
          Mathematica on iPadWilco2017/10/21 07:16 AM
            Mathematica on iPadDoug S2017/10/21 09:02 AM
              Mathematica on iPadMegol2017/10/22 05:24 AM
            clang __builtin_addcllMichael S2017/10/21 11:05 AM
          Mathematica on iPadMaynard Handley2017/10/21 09:55 AM
  Mathematica on iPadAnon2017/10/21 04:20 PM
    Mathematica on iPadMaynard Handley2017/10/21 05:51 PM
      Mathematica on iPadAnon2017/10/21 09:56 PM
        Mathematica on iPadMaynard Handley2017/10/22 12:23 AM
      A quick search shows that Mathematica is using Intel MKLGabriele Svelto2017/10/21 11:38 PM
        A quick search shows that Mathematica is using Intel MKLAnon2017/10/22 05:12 PM
          A quick search shows that Mathematica is using Intel MKLMaynard Handley2017/10/22 06:08 PM
            A quick search shows that Mathematica is using Intel MKLDoug S2017/10/22 10:40 PM
            A quick search shows that Mathematica is using Intel MKLMichael S2017/10/23 05:32 AM
  Mathematica on iPadnone2017/10/22 06:06 AM
    Mathematica on iPaddmcq2017/10/23 03:43 AM
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