Separate the OoO-ness from speculative-ness

Article: PhysX87: Software Deficiency
By: anon (anon.delete@this.anon.com), July 22, 2010 1:57 am
Room: Moderated Discussions
slacker (s@lack.er) on 7/21/10 wrote:
---------------------------
>? (0xe2.0x9a.0x9b@gmail.com) on 7/21/10 wrote:
>---------------------------
>>anon (anon@anon.com) on 7/21/10 wrote:
>>---------------------------
>>>On the contrary, I think your assertion that pipelining requires speculative execution is wrong.
>>
>>I am not saying that. I am saying this:....
>
>"Even mere pipelining entails a small dose of speculative execution !!!
>
>I will repeat it one more time, because it seems to me that you are
>completely missing this: Even mere pipelining entails a small dose of
>speculation !!!"
>
>How foolish of us to confuse your words with your intentions!
>
>
>>Code: Hi there, CPU, my friend. I want you to execute me.
>>
>>CPU: No problem. Hand me the first couple of your instructions.
>>
>>Code: Only a couple of them? You mean you don't want to see all of them?
>>
>>CPU: That's right.
>>
>>Code: But but, then, you aren't going to know what I am going to do.
>>
>>CPU: Don't worry. I will manage.
>>
>>Code: How?
>
>I knew this was the problem; you are playing loose and fast with your terminology.
>
>
>>>Caches have nothing to do with speculative execution that you were talking about.
>>
>>What are you saying? That if a contemporary CPU (Core2 or whatever) decides to
>>allocate a cache-line for data at address 0x1230, it is not making any speculations
>>about future uses of that piece of data?
>
>You are expanding and abusing the term "speculative execution," which is both pointless
>and inane. It has a narrow definition in hardware circles; speculative execution
>is the execution of code which has not yet been determined by the program stream to be necessary.
>
>- Prefetching code and data is not speculative execution
>- Decoding instructions in to microops is not speculative execution
>- Caching data is not speculative execution

There would even be no requirement for the pipeline to do any sort of speculation if it were do designed. Instructions could be fetched one at a time, and fetch suppressed on the next cycle if it were decoded to a branch.
This would require that decode happen in the same cycle as fetch which is probably not very sane, but we're being theoretical here.

So pipelining does not entail any dose of speculation at all, let alone speculative execution.
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                                          Separate the OoO-ness from speculative-nessanon2010/07/22 04:27 AM
                                      Separate the OoO-ness from speculative-nessslacker2010/07/21 07:45 PM
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                                        Separate the OoO-ness from speculative-ness?2010/07/22 05:26 AM
                                          Separate the OoO-ness from speculative-nessDan Downs2010/07/22 08:14 AM
                                          Confusing and not very useful definitionDavid Kanter2010/07/22 12:41 PM
                                            Confusing and not very useful definition?2010/07/22 10:58 PM
                                              Confusing and not very useful definitionUngo2010/07/24 12:06 PM
                                                Confusing and not very useful definition?2010/07/25 10:23 PM
                            Separate the OoO-ness from speculative-nesssomeone2010/07/20 08:02 PM
                              Separate the OoO-ness from speculative-nessThiago Kurovski2010/07/21 04:13 PM
            You are just quoting SINGLE precision flops? OMG what planet do you live? Vincent Diepeveen2010/07/19 10:26 AM
              The prior poster was talking about SP (NT)David Kanter2010/07/19 11:34 AM
                All FFT's need double precisionVincent Diepeveen2010/07/19 02:02 PM
                  All FFT's need double precisionDavid Kanter2010/07/19 02:09 PM
                    All FFT's need double precisionVincent Diepeveen2010/07/19 04:06 PM
                  All FFT's need double precision - notMichael S2010/07/20 01:16 AM
                    All FFT's need double precision - notUngo2010/07/21 12:04 AM
                      All FFT's need double precision - notMichael S2010/07/21 02:35 PM
                      All FFT's need double precision - notEduardoS2010/07/21 02:52 PM
                        All FFT's need double precision - notAnon2010/07/21 05:23 PM
                          All FFT's need double precision - notRicardo B2010/07/26 07:46 AM
                        I'm on a boat!anon2010/07/22 11:42 AM
                        All FFT's need double precision - notVincent Diepeveen2010/07/24 11:39 PM
                          All FFT's need double precision - notslacker2010/07/25 03:27 AM
                            All FFT's need double precision - notRicardo B2010/07/26 07:40 AM
                          All FFT's need double precision - notEduardoS2010/07/25 08:37 AM
                            All FFT's need double precision - notMichael S2010/07/25 10:43 AM
                    All FFT's need double precision - notVincent Diepeveen2010/07/24 11:19 PM
      A bit off baseEduardoS2010/07/08 04:08 PM
        A bit off baseGroo2010/07/08 06:11 PM
          A bit off basejohn mann2010/07/08 06:58 PM
            All right...let's cool it...David Kanter2010/07/08 07:54 PM
    A bit off baseVincent Diepeveen2010/07/19 03:36 PM
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