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Re: Ne(ish) IBM z196 synchronization instructions

Message-ID <4F58E783.2080205@SPAM.comp-arch.net> (permalink)
Date 2012-03-08 09:08 -0800
From "Andy (Super) Glew" <andy@SPAM.comp-arch.net>
Organization comp-arch.net
Newsgroups comp.arch
Subject Re: Ne(ish) IBM z196 synchronization instructions
References <4F56E21F.2010903@SPAM.comp-arch.net> <5rnk29-riq.ln1@ntp6.tmsw.no> <1432328.1752.1331156586117.JavaMail.geo-discussion-forums@ynkz21>

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On 3/7/2012 1:43 PM, MitchAlsup wrote:
> On Wednesday, March 7, 2012 1:00:20 PM UTC-6, Terje Mathisen wrote:
>> I have some problem figuring out the intended usage for the AND/OR/XOR
>> versions of this operation:
>
> XOR is useful for setting bits and resetting bits (from the same constant).
>
> So one can "check in their request" and "checkout their request" using the same value. Otherwise one has to ADD a bit to check in a request and then ADD in the 2's complement to check it back out (or OR on a bit and AND-NOT it back off).
>
> Most of the statemachine logic in my simulators uses XOR as in:
>
>       if( p->state&  STATE1 )
>           p->state ^= STATE1 | STATE2;
>       else
>
> // where it is known STATE1 and STATE2 have no common bits
> // but may have more than one bit set.
>
> Mitch


Right.  But do you need that to be atomic?

Can you have multiple threads using the same p->state at the same time? 
  Setting the same bits?

Or possibly setting disjoint bits in the same word?

To get XOR the safely set and clear different bits, you have to know the 
prior state.  Perhaps and AND-OR instruction?

     AND-OR
           tmp := mem
           tmp &= and_mask (or ~and_mask)
           tmp |= or_mask
           mem := tmp

A nice instruction, but it really wants two immediates.

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Ne(ish) IBM z196 synchronization instructions "Andy (Super) Glew" <andy@SPAM.comp-arch.net> - 2012-03-06 20:20 -0800
  Re: Ne(ish) IBM z196 synchronization instructions "Paul A. Clayton" <paaronclayton@gmail.com> - 2012-03-07 05:43 -0800
    Re: Ne(ish) IBM z196 synchronization instructions "Andy (Super) Glew" <andy@SPAM.comp-arch.net> - 2012-03-07 07:00 -0800
      Re: Ne(ish) IBM z196 synchronization instructions nmm1@cam.ac.uk - 2012-03-07 15:25 +0000
      Re: Ne(ish) IBM z196 synchronization instructions "Paul A. Clayton" <paaronclayton@gmail.com> - 2012-03-09 11:05 -0800
  Re: Ne(ish) IBM z196 synchronization instructions Terje Mathisen <"terje.mathisen at tmsw.no"> - 2012-03-07 20:00 +0100
    Re: Ne(ish) IBM z196 synchronization instructions MitchAlsup <MitchAlsup@aol.com> - 2012-03-07 13:43 -0800
      Re: Ne(ish) IBM z196 synchronization instructions "Andy (Super) Glew" <andy@SPAM.comp-arch.net> - 2012-03-08 09:08 -0800
        Re: Ne(ish) IBM z196 synchronization instructions Terje Mathisen <"terje.mathisen at tmsw.no"> - 2012-03-08 18:39 +0100
          Re: Ne(ish) IBM z196 synchronization instructions Nomen Nescio <nobody@dizum.com> - 2012-03-08 22:33 +0100
          Re: Ne(ish) IBM z196 synchronization instructions "Andy (Super) Glew" <andy@SPAM.comp-arch.net> - 2012-03-08 17:17 -0800
          Re: Ne(ish) IBM z196 synchronization instructions MitchAlsup <MitchAlsup@aol.com> - 2012-03-09 08:19 -0800
            Re: Ne(ish) IBM z196 synchronization instructions Terje Mathisen <"terje.mathisen at tmsw.no"> - 2012-03-09 17:45 +0100
    Re: Ne(ish) IBM z196 synchronization instructions jgk@panix.com (Joe keane) - 2012-03-09 20:30 +0000
      Re: Ne(ish) IBM z196 synchronization instructions MitchAlsup <MitchAlsup@aol.com> - 2012-03-09 13:10 -0800

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