Saltwell Outperforming A15...With Less Power!!!

By: Sylvain Collange (full.name.delete.delete@this.this.gmail.com), July 12, 2013 5:00 am
Room: Moderated Discussions
Wilco (Wilco.Dijkstra.delete@this.ntlworld.com) on July 12, 2013 3:51 am wrote:
> Denormals are rarely used in FP code, but like most RISCs, the default setting for ARM is flush-to-zero,
> so it won't make a difference in the results even if you do encounter them. Compilers typically default
> to a non-IEEE compatible mode as well, so IEEE compliance of denormals is not really relevant.

I believe gcc still defaults to IEEE-754 mode and avoids NEON unless invoked with -mfast-math:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43703

By the way, wasn't the case of gradual underflow settled 30 years ago? If subnormals are rarely used, most of the time the way they are handled does not matter. Now for the remaining times, would you rather compute a certainly-wrong answer quickly or a potentially-correct answer for some performance penalty?

Either way, there is little point in handling subnormals in software/microcode nowadays. An FMA can be implemented with full-speed hardware subnormal support for very little overhead (ARM has a paper on that...)
In 2013, there is no excuse for not even providing a slower mode that complies with 28 year-old standards...
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ARM at Computexanon2013/06/03 07:54 AM
  ARM at ComputexExophase2013/06/03 08:31 AM
    ARM at ComputexWilco2013/06/03 09:52 AM
      ARM at ComputexExophase2013/06/03 11:02 AM
        ARM at Computexnone2013/06/03 12:28 PM
          ARM at ComputexAlberto2013/06/04 09:41 AM
            ARM at Computexanon2013/06/04 12:36 PM
              ARM at ComputexWilco2013/06/04 02:56 PM
                ARM at ComputexDavid Kanter2013/06/04 03:51 PM
                  ARM at ComputexNobodyatAll2013/06/04 04:53 PM
                  ARM at Computexanon2013/06/04 05:53 PM
        ARM at ComputexWilco2013/06/03 12:47 PM
    ARM at Computexanon2013/06/04 03:03 AM
      ARM at ComputexDavid Kanter2013/06/04 07:16 AM
      ARM at ComputexExophase2013/06/04 09:36 AM
        ARM at ComputexWilco2013/06/04 03:09 PM
          ARM at ComputexNobodyatAll2013/06/04 03:23 PM
          ARM at ComputexDavid Kanter2013/06/04 04:00 PM
            ARM at Computexnone2013/06/05 04:26 AM
              ARM at Computexanon2013/06/05 06:19 AM
              ARM at Computexaaron spink2013/06/05 02:04 PM
                Saltwell Outperforming A15...With Less Power!!!Jason2013/06/07 12:56 PM
                  Saltwell Outperforming A15...With Less Power!!!John2013/06/08 05:28 AM
                    Saltwell Outperforming A15...With Less Power!!!Kevin G2013/06/08 01:18 PM
                      Saltwell Outperforming A15...With Less Power!!!David Kanter2013/06/08 07:43 PM
                      Saltwell Outperforming A15...With Less Power!!!tarlinian2013/06/09 01:00 PM
                        Saltwell Outperforming A15...With Less Power!!!none2013/06/09 02:11 PM
                          Saltwell Outperforming A15...With Less Power!!!none2013/07/10 10:46 AM
                            Saltwell Outperforming A15...With Less Power!!!Wilco2013/07/10 06:59 PM
                              Saltwell Outperforming A15...With Less Power!!!Klimax2013/07/10 09:03 PM
                                Saltwell Outperforming A15...With Less Power!!!anon2013/07/10 09:29 PM
                                  Saltwell Outperforming A15...With Less Power!!!Klimax2013/07/10 10:30 PM
                                    Saltwell Outperforming A15...With Less Power!!!Wilco2013/07/11 12:04 AM
                                      Saltwell Outperforming A15...With Less Power!!!Klimax2013/07/11 02:10 AM
                                        Saltwell Outperforming A15...With Less Power!!!anon2013/07/11 03:10 AM
                                        Saltwell Outperforming A15...With Less Power!!!Wilco2013/07/11 03:43 AM
                                        Saltwell Outperforming A15...With Less Power!!!Steve2013/07/14 07:10 PM
                                          Saltwell Outperforming A15...With Less Power!!!Klimax2013/07/14 09:55 PM
                                          Saltwell Outperforming A15...With Less Power!!!bakaneko2013/07/15 01:03 AM
                                            Saltwell Outperforming A15...With Less Power!!!anon2013/07/16 12:07 AM
                                              Saltwell Outperforming A15...With Less Power!!!bakaneko2013/07/16 05:25 AM
                                                Saltwell Outperforming A15...With Less Power!!!none2013/07/16 05:34 AM
                                                Saltwell Outperforming A15...With Less Power!!!Exophase2013/07/16 09:34 AM
                                                  Saltwell Outperforming A15...With Less Power!!!bakaneko2013/07/18 01:24 PM
                                                    Saltwell Outperforming A15...With Less Power!!!none2013/07/18 02:26 PM
                                    Saltwell Outperforming A15...With Less Power!!!anon2013/07/11 01:50 AM
                                      Saltwell Outperforming A15...With Less Power!!!Klimax2013/07/11 10:25 PM
                                        Saltwell Outperforming A15...With Less Power!!!anon2013/07/11 10:45 PM
                                          Saltwell Outperforming A15...With Less Power!!!Klimax2013/07/11 11:10 PM
                                            Saltwell Outperforming A15...With Less Power!!!anon2013/07/12 12:52 AM
                                    Saltwell Outperforming A15...With Less Power!!!Gabriele Svelto2013/07/11 03:20 AM
                                      Saltwell Outperforming A15...With Less Power!!!Klimax2013/07/11 10:51 PM
                                Saltwell Outperforming A15...With Less Power!!!bakaneko2013/07/10 11:02 PM
                                  Saltwell Outperforming A15...With Less Power!!!Klimax2013/07/10 11:28 PM
                                    Saltwell Outperforming A15...With Less Power!!!none2013/07/11 12:49 AM
                                      Saltwell Outperforming A15...With Less Power!!!Klimax2013/07/11 02:00 AM
                                        Saltwell Outperforming A15...With Less Power!!!Klimax2013/07/11 02:02 AM
                                        Saltwell Outperforming A15...With Less Power!!!none2013/07/11 03:44 AM
                                          Saltwell Outperforming A15...With Less Power!!!Michael S2013/07/11 04:33 AM
                                            Saltwell Outperforming A15...With Less Power!!!none2013/07/11 04:58 AM
                                              Saltwell Outperforming A15...With Less Power!!!none2013/07/11 04:59 AM
                                              Saltwell Outperforming A15...With Less Power!!!Wilco2013/07/11 06:40 AM
                                                Saltwell Outperforming A15...With Less Power!!!Michael S2013/07/11 07:34 AM
                                                  Saltwell Outperforming A15...With Less Power!!!none2013/07/11 07:50 AM
                                              Saltwell Outperforming A15...With Less Power!!!Michael S2013/07/11 08:02 AM
                                          Saltwell Outperforming A15...With Less Power!!!Klimax2013/07/11 09:11 PM
                                      Saltwell Outperforming A15...With Less Power!!!Michael S2013/07/11 03:12 AM
                                        Saltwell Outperforming A15...With Less Power!!!none2013/07/11 03:51 AM
                                          Saltwell Outperforming A15...With Less Power!!!Wilco2013/07/11 04:03 AM
                                            Saltwell Outperforming A15...With Less Power!!!none2013/07/11 04:12 AM
                                              Saltwell Outperforming A15...With Less Power!!!Wilco2013/07/11 06:26 AM
                                                Saltwell Outperforming A15...With Less Power!!!none2013/07/11 07:29 AM
                                                Saltwell Outperforming A15...With Less Power!!!Wilco2013/07/12 03:08 AM
                                                  Saltwell Outperforming A15...With Less Power!!!Michael S2013/07/12 03:25 AM
                                              Saltwell Outperforming A15...With Less Power!!!Klimax2013/07/11 10:55 PM
                                                Saltwell Outperforming A15...With Less Power!!!Megol2013/07/13 06:20 AM
                                    Java/Dalvik benchmarksbakaneko2013/07/11 01:26 AM
                                  Saltwell Outperforming A15...With Less Power!!!Linus Torvalds2013/07/11 09:57 AM
                                    Saltwell Outperforming A15...With Less Power!!!Linus Torvalds2013/07/11 10:20 AM
                                      Saltwell Outperforming A15...With Less Power!!!Ian Ameline2013/07/11 02:20 PM
                                      Saltwell Outperforming A15...With Less Power!!!Sylvain Collange2013/07/12 01:29 AM
                                        Saltwell Outperforming A15...With Less Power!!!Wilco2013/07/12 02:51 AM
                                          Saltwell Outperforming A15...With Less Power!!!Sylvain Collange2013/07/12 05:00 AM
                                      Saltwell Outperforming A15...With Less Power!!!bakaneko2013/07/12 02:28 AM
                                        Saltwell Outperforming A15...With Less Power!!!Linus Torvalds2013/07/12 08:11 AM
                                          Saltwell Outperforming A15...With Less Power!!!bakaneko2013/07/12 09:12 AM
                                          Saltwell Outperforming A15...With Less Power!!!2013/07/12 09:48 AM
                                            Saltwell Outperforming A15...With Less Power!!!Linus Torvalds2013/07/12 10:14 AM
                                              JIT2013/07/13 04:50 AM
                                                How'd you get this flower symbol as your user name ?anon2013/07/13 08:20 AM
                                                  How'd you get this flower symbol as your user name ?Doug S Ꭳ❂〄☢⚓♜☎♬⚄☠2013/07/13 09:12 AM
                                                JITx2013/07/15 05:43 AM
                                    Not reallyAnon2013/07/11 10:21 AM
                                    consistency, pleaseMichael S2013/07/11 10:22 AM
                                      consistency, pleaseLinus Torvalds2013/07/11 10:52 AM
                                        consistency, pleaseMichael S2013/07/11 01:43 PM
                                          consistency, pleaseLinus Torvalds2013/07/11 02:12 PM
                                            consistency, pleaseMark Roulo2013/07/11 02:54 PM
                                              the discussion was about absence of AVX in Silvermont (NT)Michael S2013/07/11 02:59 PM
                                                the discussion was about absence of AVX in SilvermontMark Roulo2013/07/11 03:19 PM
                                                  the discussion was about absence of AVX in SilvermontLinus Torvalds2013/07/12 08:16 AM
                                                    Thank youMark Roulo2013/07/12 08:58 AM
                                                    the discussion was about absence of AVX in Silvermontanon2013/07/12 09:10 AM
                                                      Not really (again)Anon2013/07/12 09:26 AM
                                                        Not really (again)anon2013/07/12 04:40 PM
                                                    the discussion was about absence of AVX in SilvermontLinus Torvalds2013/07/12 09:31 AM
                                                      you are wrong at about 100% of you saidMichael S2013/07/13 10:22 AM
                                                        you are wrong at about 100% of you saidLinus Torvalds2013/07/13 11:08 AM
                                                          you are wrong at about 100% of you saidMichael S2013/07/13 12:13 PM
                                                            you are wrong at about 100% of you saidLinus Torvalds2013/07/13 01:11 PM
                                                            you are wrong at about 100% of you saidvvid2013/07/13 02:20 PM
                                                              you are wrong at about 100% of you saidMichael S2013/07/14 12:38 AM
                                    Saltwell Outperforming A15...With Less Power!!!anon2013/07/11 05:41 PM
                                    Saltwell Outperforming A15...With Less Power!!!bakaneko2013/07/12 02:22 AM
                  Round 2: Baytrail benchmark (yes Antutu!) crushes Snapdragon 800.sammy2013/07/12 10:28 AM
                    Round 2: AnTuTu scores drop dramatically for AtomWilco2013/07/12 10:59 AM
                      Round 2: AnTuTu scores drop dramatically for AtomSteve2013/07/14 07:16 PM
                        Round 2: AnTuTu scores drop dramatically for AtomKlimax2013/07/14 09:59 PM
                        Round 2: AnTuTu scores drop dramatically for AtomDavid Kanter2013/07/15 12:57 PM
                          Intel is cheating AnTuTuWilco2013/07/15 02:43 PM
                            Intel is cheating AnTuTubakaneko2013/07/15 06:47 PM
                              Intel is cheating AnTuTuLinus Torvalds2013/07/15 07:45 PM
                                Intel is cheating AnTuTubakaneko2013/07/16 01:42 AM
                                  Intel is cheating AnTuTuWilco2013/07/16 02:47 AM
                                    Intel is cheating AnTuTubakaneko2013/07/16 04:50 AM
                                      Intel is cheating AnTuTuWilco2013/07/17 02:33 PM
                                        Intel is cheating AnTuTuKlimax2013/07/17 10:29 PM
                                          Intel is cheating AnTuTunone2013/07/17 10:35 PM
                                            Intel is cheating AnTuTuKlimax2013/07/18 12:41 AM
                                              Intel is cheating AnTuTuanon2013/07/18 01:10 AM
                                                Intel is cheating AnTuTuMichael S2013/07/18 02:39 AM
                                                Intel is cheating AnTuTuWilco2013/07/18 03:07 AM
                                                  Intel is cheating AnTuTunone2013/07/18 03:15 AM
                                                    Intel is cheating AnTuTuWilco2013/07/18 04:18 AM
                                                    Intel is cheating AnTuTuMichael S2013/07/18 05:44 AM
                                                      Intel is cheating AnTuTunone2013/07/18 06:47 AM
                                                        strict aliasingMichael S2013/07/18 07:10 AM
                                                          strict aliasing rules have existed since C89 (NT)Ricardo B2013/07/18 04:28 PM
                                                  Intel is cheating AnTuTuKlimax2013/07/18 10:30 AM
                                                Intel is cheating AnTuTuKlimax2013/07/18 10:39 AM
                                                  Intel is cheating AnTuTuanon2013/07/18 11:05 AM
                                                    Intel is cheating AnTuTuKlimax2013/07/19 11:05 PM
                                                      Intel is cheating AnTuTunone2013/07/20 01:50 AM
                                                  Intel is cheating AnTuTunone2013/07/18 11:38 AM
                                                    Intel is cheating AnTuTuKlimax2013/07/19 10:57 PM
                                  Intel is cheating AnTuTuLinus Torvalds2013/07/16 11:32 AM
                                Intel is cheating AnTuTu2013/07/16 02:16 AM
                                  Intel is cheating AnTuTubakaneko2013/07/16 03:55 AM
                                    Intel is cheating AnTuTuWilco2013/07/17 02:46 PM
                                      Intel is cheating AnTuTubakaneko2013/07/18 01:05 PM
                                      Intel is cheating AnTuTuDavid Kanter2013/07/19 01:31 AM
                          Round 2: AnTuTu scores drop dramatically for Atomanon2013/07/15 03:43 PM
                            Round 2: AnTuTu scores drop dramatically for Atomnone2013/07/15 11:15 PM
                          Round 2: AnTuTu scores drop dramatically for AtomGroo2013/07/16 06:35 AM
        ARM at Computexanon2013/06/04 09:43 PM
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