Pipelining affects the ISA

Article: PhysX87: Software Deficiency
By: Gabriele Svelto (gabriele.svelto.delete@this.gmail.com), July 26, 2010 2:50 am
Room: Moderated Discussions
? (0xe2.0x9a.0x9b@gmail.com) on 7/22/10 wrote:
---------------------------
>Notice that you cannot reorder the ADD and CMP because it works with the-same-and-only-one
>FLAGS register. (If you force the reordering and save the FLAGS into memory, it will do more harm than good.)

I am not sure if the current x86 implementation do it but there's an architectural way of solving this problem: renaming the FLAGS register so WAW hazards go away and you can actually execute the relevant instruction way ahead of the branch. Recent POWER processors do rename their condition registers in spite of having 8 of them so I guess x86 is also doing it even though I have no hard data to back my guess.
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                                        Pipelining affects the ISA?2010/07/22 10:58 PM
                                          Pipelining affects the ISA?2010/07/22 11:14 PM
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            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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