SVE alignment with non power-of-2 widths

By: -.- (blarg.delete@this.mailinator.com), September 25, 2021 5:35 pm
Room: Moderated Discussions
Andrey (andrey.semashev.delete@this.gmail.com) on September 25, 2021 4:46 am wrote:
> Again, you're talking about the spec, and I'm talking about the actual hardware. If all or the absolute
> majority of implementations don't care about alignment then that's great and developers don't need
> to optimize for it. But we don't have that many SVE implementations, and for other kind of instructions
> real hardware does care about alignment, so I'm going do assume SVE won't be an exception. Hardware
> designers will have to prove that alignment doesn't matter, they haven't done that yet.

Both matter. It doesn't matter what properties the hardware has if the software doesn't take advantage of it.
I very much believe alignment is a thing in hardware. But all that is for naught if no-one actually writes code with that in consideration (which is something the SVE spec seems to encourage).

> Rumor has it that AMD is also working on a hybrid CPU, possibly in Zen 5. I
> think, eventually hybrid designs will settle in x86 desktops and servers.

Not sure about servers (even ARM doesn't do heterogeneous cores there), but it does make sense for client systems.

> AMD SkyBridge (https://www.extremetech.com/computing/181867-amds-project-skybridge-new-arm-and-x86-chips-that-are-pin-compatible)
> though was in the works. I imagine, in multi-socket systems you could use both x86 and ARM cores
> together. The project is dead now, so we probably will never know.

Nothing says you can run the two together, and I see basically no advantage in introducing such ridiculous complexity to enable such.
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TopicPosted ByDate
Armv8.8-A and Armv9.3-Aanonymou52021/09/16 03:25 PM
  Armv8.8-A and Armv9.3-ADoug S2021/09/16 10:57 PM
    Armv8.8-A and Armv9.3-ABrett2021/09/16 11:32 PM
      Armv8.8-A and Armv9.3-Aanon2021/09/16 11:55 PM
        Armv8.8-A and Armv9.3-Anone2021/09/17 12:51 AM
      Armv8.8-A and Armv9.3-AJörn Engel2021/09/17 05:42 AM
        Armv8.8-A and Armv9.3-AMichael S2021/09/17 07:48 AM
          Armv8.8-A and Armv9.3-AJörn Engel2021/09/18 02:01 PM
            Armv8.8-A and Armv9.3-AMichael S2021/09/18 03:58 PM
              microbenchmark resultsMichael S2021/09/19 04:46 PM
                microbenchmark source codeMichael S2021/09/19 04:58 PM
                  microbenchmark source code-.-2021/09/20 04:49 PM
                    microbenchmark source codeMichael S2021/09/21 10:17 AM
                      microbenchmark source code-.-2021/09/21 04:33 PM
                        microbenchmark source codeMichael S2021/09/21 06:05 PM
                microbenchmark resultsAnon2021/09/19 05:32 PM
                  microbenchmark resultsJörn Engel2021/09/19 08:46 PM
                    microbenchmark resultsdmcq2021/09/20 02:19 AM
                      microbenchmark resultsMichael S2021/09/20 05:12 AM
                      microbenchmark results-.-2021/09/20 04:44 PM
                        microbenchmark resultsMichael S2021/09/21 10:23 AM
                          microbenchmark results-.-2021/09/21 04:35 PM
                            microbenchmark resultsAndrey2021/09/21 05:25 PM
                              I agree (NT)Michael S2021/09/21 06:07 PM
                              microbenchmark results-.-2021/09/22 05:56 PM
                                microbenchmark resultsMichael S2021/09/23 06:11 AM
                                  microbenchmark resultsdmcq2021/09/23 07:53 AM
                                  microbenchmark resultsAndrey2021/09/23 10:20 AM
                                microbenchmark resultsAndrey2021/09/23 10:11 AM
                                  microbenchmark results-.-2021/09/23 08:01 PM
                                    microbenchmark resultsSimon Farnsworth2021/09/24 02:47 AM
                                      microbenchmark results-.-2021/09/24 06:00 PM
                                    microbenchmark resultsAndrey2021/09/24 08:29 AM
                                      microbenchmark resultsdmcq2021/09/24 01:05 PM
                                        microbenchmark resultsDoug S2021/09/24 02:12 PM
                                          microbenchmark results---2021/09/24 07:06 PM
                                            microbenchmark resultsDoug S2021/09/24 11:46 PM
                                              microbenchmark results---2021/09/25 09:56 AM
                                                microbenchmark resultsJukka Larja2021/09/26 02:01 AM
                                                microbenchmark resultsDoug S2021/09/26 09:41 AM
                                                  microbenchmark resultsdmcq2021/09/26 01:37 PM
                                                    microbenchmark resultsDoug S2021/09/27 10:32 AM
                                                      microbenchmark resultsdmcq2021/09/28 07:56 AM
                                              microbenchmark resultsDummond D. Slow2021/09/25 12:49 PM
                                                microbenchmark resultsBrett2021/09/25 03:31 PM
                                              microbenchmark resultsdmcq2021/09/25 12:51 PM
                                                microbenchmark resultsDoug S2021/09/26 09:45 AM
                                            microbenchmark resultsRichard S2021/09/25 01:51 AM
                                              microbenchmark resultsDummond D. Slow2021/09/25 12:52 PM
                                                microbenchmark results---2021/09/25 03:04 PM
                                      SVE alignment with non power-of-2 widths-.-2021/09/24 06:10 PM
                                        SVE alignment with non power-of-2 widthsAndrey2021/09/25 04:46 AM
                                          SVE alignment with non power-of-2 widths-.-2021/09/25 05:35 PM
                                          SVE alignment with non power-of-2 widthsKevin G2021/09/27 09:46 AM
                                            SVE alignment with non power-of-2 widths-.-2021/09/27 09:06 PM
                                              SVE alignment with non power-of-2 widthsJukka Larja2021/09/28 06:37 AM
                                                SVE alignment with non power-of-2 widthsAndrey2021/09/28 12:12 PM
                                                  SVE alignment with non power-of-2 widthsdmcq2021/09/28 02:29 PM
                                                SVE alignment with non power-of-2 widths-.-2021/09/28 06:37 PM
                                                  SVE alignment with non power-of-2 widthsJukka Larja2021/09/29 06:50 AM
                    microbenchmark results---2021/09/20 07:11 AM
                    microbenchmark resultsJörn Engel2021/09/23 05:10 AM
                      microbenchmark resultsMichael S2021/09/23 05:55 AM
                        microbenchmark resultsJörn Engel2021/09/23 09:24 AM
                          microbenchmark resultsRoyi2021/09/26 04:25 PM
                      microbenchmark resultsdmcq2021/09/23 10:42 AM
                        microbenchmark results---2021/09/23 11:53 AM
                      microbenchmark resultsanon22021/09/23 02:40 PM
                microbenchmark results: Zen 3Adrian2021/09/22 01:57 AM
                  microbenchmark results: Zen 3Adrian2021/09/22 02:08 AM
                    microbenchmark results: Zen 3Michael S2021/09/22 05:48 AM
                      microbenchmark results: Zen 3Adrian2021/09/22 06:05 AM
        Armv8.8-A and Armv9.3-AKonrad Schwarz2021/09/28 05:45 AM
    Armv8.8-A and Armv9.3-ALinus Torvalds2021/09/17 08:59 AM
      Armv8.8-A and Armv9.3-ADoug S2021/09/17 11:35 AM
        Armv8.8-A and Armv9.3-Anksingh2021/09/17 12:23 PM
          Armv8.8-A and Armv9.3-ADoug S2021/09/17 02:35 PM
            Armv8.8-A and Armv9.3-AKonrad Schwarz2021/10/15 06:23 AM
              Armv8.8-A and Armv9.3-Arwessel2021/10/15 06:49 AM
        Armv8.8-A and Armv9.3-AAdrian2021/09/17 11:07 PM
          Armv8.8-A and Armv9.3-ADoug S2021/09/18 07:34 AM
            Armv8.8-A and Armv9.3-AAdrian2021/09/18 07:38 AM
      Armv8.8-A and Armv9.3-Ablaine2021/09/18 10:37 AM
      Armv8.8-A and Armv9.3-ABrett2021/09/19 01:06 PM
        Armv8.8-A and Armv9.3-Admcq2021/09/19 01:36 PM
        Armv8.8-A and Armv9.3-ADoug S2021/09/19 06:07 PM
          Armv8.8-A and Armv9.3-A - movesdmcq2021/09/28 09:54 AM
            Armv8.8-A and Armv9.3-A - movesDoug S2021/09/28 01:57 PM
              Armv8.8-A and Armv9.3-A - movesdmcq2021/09/28 02:21 PM
                Armv8.8-A and Armv9.3-A - movesNoSpammer2021/09/29 03:53 AM
                  Armv8.8-A and Armv9.3-A - movesrwessel2021/09/29 06:55 AM
                    Armv8.8-A and Armv9.3-A - movesdmcq2021/09/29 07:53 AM
                      Armv8.8-A and Armv9.3-A - movesrwessel2021/09/29 11:35 AM
                        Armv8.8-A and Armv9.3-A - movesdmcq2021/09/29 01:44 PM
                          Armv8.8-A and Armv9.3-A - movesrwessel2021/09/29 01:58 PM
                            Armv8.8-A and Armv9.3-A - movesdmcq2021/09/29 03:52 PM
                              Armv8.8-A and Armv9.3-A - movesrwessel2021/09/29 06:36 PM
                              Armv8.8-A and Armv9.3-A - movesAndrey2021/09/29 07:58 PM
                    Armv8.8-A and Armv9.3-A - movesDoug S2021/09/29 10:10 AM
                      Armv8.8-A and Armv9.3-A - movesrwessel2021/09/29 11:30 AM
                        Armv8.8-A and Armv9.3-A - movesDoug S2021/09/29 10:02 PM
                          Armv8.8-A and Armv9.3-A - movesrwessel2021/09/29 11:22 PM
                            Armv8.8-A and Armv9.3-A - movesMark Roulo2021/09/30 07:37 AM
                              Armv8.8-A and Armv9.3-A - movesrwessel2021/09/30 08:02 AM
                                Did they publish a full description? (NT)Michael S2021/09/30 08:12 AM
                                  Did they publish a full description?rwessel2021/09/30 09:18 AM
                                    Did they publish a full description?Michael S2021/09/30 10:24 AM
                                      Did they publish a full description?rwessel2021/09/30 10:42 AM
                                    Did they publish a full description?Adrian2021/10/01 12:22 AM
                                  Do we even okiw it's three instructions per move?Carson2021/09/30 10:28 PM
                                    Do we even okiw it's three instructions per move?Adrian2021/10/01 12:27 AM
                                    Do we even okiw it's three instructions per move?rwessel2021/10/01 04:19 AM
                            Armv8.8-A and Armv9.3-A - movesDoug S2021/09/30 09:48 AM
                              Armv8.8-A and Armv9.3-A - movesrwessel2021/09/30 10:39 AM
                                Armv8.8-A and Armv9.3-A - movesDoug S2021/09/30 02:56 PM
                                  Armv8.8-A and Armv9.3-A - movesrwessel2021/09/30 05:20 PM
                                    Armv8.8-A and Armv9.3-A - movesdmcq2021/10/01 04:38 AM
                                      Armv8.8-A and Armv9.3-A - movesMichael S2021/10/01 05:04 AM
                                        Armv8.8-A and Armv9.3-A - movesLinus Torvalds2021/10/01 11:01 AM
                                          memcpy - instruction cracking vs DMArpg2021/10/02 02:51 AM
                                            memcpy - instruction cracking vs DMAAdrian2021/10/02 03:45 AM
                                              memcpy - instruction cracking vs DMADoug S2021/10/02 09:47 AM
                                                memcpy - instruction cracking vs DMAAdrian2021/10/02 10:15 AM
                                                memcpy - instruction cracking vs DMArwessel2021/10/02 11:37 AM
                                                  memcpy - instruction cracking vs DMADoug S2021/10/02 06:49 PM
                                            memcpy - instruction cracking vs DMALinus Torvalds2021/10/02 10:43 AM
                                              memcpy - instruction cracking vs DMAdmcq2021/10/02 11:32 AM
                                              memcpy - instruction cracking vs DMABrett2021/10/02 11:45 AM
                                              memcpy - instruction cracking vs DMA---2021/10/02 03:03 PM
                                                memcpy - instruction cracking vs DMA---2021/10/02 03:12 PM
                                                  Moving copy to DRAM doesn't help for small copiesMark Roulo2021/10/02 03:59 PM
                                                    Moving copy to DRAM doesn't help for small copies---2021/10/02 07:32 PM
                                                      Moving copy to DRAM doesn't help for small copiesMichael S2021/10/03 01:40 AM
                                                        Moving copy to DRAM doesn't help for small copiesDoug S2021/10/03 10:09 AM
                                                          Moving copy to DRAM doesn't help for small copiesrwessel2021/10/03 10:51 AM
                                                          Moving copy to DRAM doesn't help for small copiesLinus Torvalds2021/10/03 11:09 AM
                                                            How about environments such as Java?Mark Roulo2021/10/03 12:41 PM
                                                              How about environments such as Java?rwessel2021/10/03 12:49 PM
                                                                How about environments such as Java?Mark Roulo2021/10/03 01:22 PM
                                                              How about environments such as Java?anon22021/10/03 07:58 PM
                                                                How about environments such as Java?Etienne Lorrain2021/10/04 05:08 AM
                                                                  Apart from "It depends" there is no short answer. (NT)Michael S2021/10/04 05:30 AM
                                                                  How about environments such as Java?Andrey2021/10/04 06:04 AM
                                                                  How about environments such as Java?anon22021/10/04 06:32 AM
                                                                How about environments such as Java?Mark Roulo2021/10/04 07:31 AM
                                                                How about environments such as Java?---2021/10/04 09:41 AM
                                                                  How about environments such as Java?Doug S2021/10/04 10:23 AM
                                                                    How about environments such as Java?Andrey2021/10/04 12:14 PM
                                                                      How about environments such as Java?Doug S2021/10/04 01:20 PM
                                                                  How about environments such as Java?anon22021/10/04 02:23 PM
                                                                  How about environments such as Java?rwessel2021/10/04 04:54 PM
                                                            Moving copy to DRAM doesn't help for small copiesJörn Engel2021/10/04 05:52 AM
                                                            Early software zeroing !=== early hardware zeroingPaul A. Clayton2021/10/05 11:19 AM
                                                              Early software zeroing !=== early hardware zeroingDoug S2021/10/05 12:21 PM
                                                memcpy - instruction cracking vs DMABrendan2021/10/02 04:53 PM
                                                  memcpy - instruction cracking vs DMALinus Torvalds2021/10/03 10:48 AM
                                                    memcpy - instruction cracking vs DMAdmcq2021/10/03 01:54 PM
                                              memcpy - instruction cracking vs DMAYuhong Bao2021/10/03 01:30 AM
                                                memcpy - instruction cracking vs DMADavid Hess2021/10/05 05:19 PM
                                                  memcpy - instruction cracking vs DMAAdrian2021/10/05 11:28 PM
                                                    memcpy - instruction cracking vs DMAEtienne Lorrain2021/10/06 02:24 AM
                                                    memcpy - instruction cracking vs DMArwessel2021/10/06 03:38 AM
                                                      memcpy - instruction cracking vs DMAAdrian2021/10/06 04:04 AM
                                                        memcpy - instruction cracking vs DMArwessel2021/10/06 05:59 AM
                                                    memcpy - instruction cracking vs DMA---2021/10/06 09:07 AM
                                                      memcpy - instruction cracking vs DMAAndrey2021/10/06 02:59 PM
                                                    memcpy - instruction cracking vs DMAgallier22021/10/06 11:06 PM
                                                      memcpy - instruction cracking vs DMAAdrian2021/10/06 11:59 PM
                                              memcpy - instruction cracking vs DMAMichael S2021/10/03 01:51 AM
                                                memcpy - instruction cracking vs DMArwessel2021/10/03 05:06 AM
                                                  memcpy - instruction cracking vs DMAMichael S2021/10/03 05:24 AM
                                                    memcpy - instruction cracking vs DMAMatt Sayler2021/10/03 08:02 AM
                                                    memcpy - instruction cracking vs DMADoug S2021/10/03 10:14 AM
                                      Armv8.8-A and Armv9.3-A - movesrwessel2021/10/01 05:10 AM
                                        Armv8.8-A and Armv9.3-A - movesEtienne Lorrain2021/10/01 07:55 AM
                                          Armv8.8-A and Armv9.3-A - movesrwessel2021/10/01 08:14 AM
                                            Armv8.8-A and Armv9.3-A - movesDoug S2021/10/01 11:17 AM
                                              Armv8.8-A and Armv9.3-A - movesrwessel2021/10/02 04:57 AM
  Armv8.8-A and Armv9.3-Anone2021/10/13 06:06 AM
    Armv8.8-A and Armv9.3-AAdrian2021/10/13 06:22 AM
      Armv8.8-A and Armv9.3-ADoug S2021/10/13 09:01 AM
        Armv8.8-A and Armv9.3-Admcq2021/10/13 10:17 AM
          Armv8.8-A and Armv9.3-Anone2021/10/13 10:26 PM
            Armv8.8-A and Armv9.3-Admcq2021/10/14 08:22 AM
    Armv8.8-A and Armv9.3-Arwessel2021/10/14 09:01 AM
      Armv8.8-A and Armv9.3-AAnon2021/10/14 11:08 AM
        Armv8.8-A and Armv9.3-AMichael S2021/10/14 01:25 PM
      Armv8.8-A and Armv9.3-ADoug S2021/10/14 11:18 AM
        Armv8.8-A and Armv9.3-Arwessel2021/10/14 07:07 PM
          Armv8.8-A and Armv9.3-ADoug S2021/10/14 10:23 PM
            Armv8.8-A and Armv9.3-Admcq2021/10/15 01:41 AM
              Armv8.8-A and Armv9.3-AGabriele Svelto2021/10/15 05:07 AM
            Armv8.8-A and Armv9.3-Arwessel2021/10/15 04:49 AM
              Armv8.8-A and Armv9.3-ADoug S2021/10/15 10:44 AM
                Armv8.8-A and Armv9.3-Ame2021/10/15 06:34 PM
                  Armv8.8-A and Armv9.3-ADoug S2021/10/16 09:47 AM
                    Armv8.8-A and Armv9.3-Ame2021/10/17 05:19 AM
                      Armv8.8-A and Armv9.3-ADoug S2021/10/17 10:17 AM
                        Armv8.8-A and Armv9.3-Ame2021/10/17 12:31 PM
                          Armv8.8-A and Armv9.3-ADoug S2021/10/17 01:33 PM
                            Armv8.8-A and Armv9.3-AzArchJon2021/10/18 10:35 AM
                              Armv8.8-A and Armv9.3-ADoug S2021/10/18 02:35 PM
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