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    SubjectRe: Does Itanium permit speculative stores?
    On Tue, Nov 26, 2013 at 11:55:58PM -0500, Jon Masters wrote:
    > On 11/11/2013 12:13 PM, Paul E. McKenney wrote:
    > > Hello, Tony,
    > >
    > > Does Itanium permit speculative stores? For example, on Itanium what are
    > > the permitted outcomes of the following litmus test, where both x and y
    > > are initially zero?
    > >
    > > CPU 0 CPU 1
    > >
    > > r1 = ACCESS_ONCE(x); r2 = ACCESS_ONCE(y);
    > > if (r1) if (r2)
    > > ACCESS_ONCE(y) = 1; ACCESS_ONCE(x) = 1;
    > >
    > > In particular, is the outcome (r1 == 1 && r2 == 1) possible on Itanium
    > > given this litmus test?
    > >
    > > Thanx, Paul
    > >
    > > --
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    > > Please read the FAQ at http://www.tux.org/lkml/
    >
    > Btw, I was reading through some UEFI docs and noticed a reference to "A
    > Formal Specification of Intel Itanium Processor Family Memory Ordering",
    > then remembered this thread. In case it's of use:
    >
    > http://www.intel.com/design/itanium/downloads/251429.htm

    I have seen this, but there have been too many times when I have fooled
    myself about what the words mean (with DEC Alpha back in the late 90s
    being the most impressive example). So while I do learn what I can from
    them, they are unfortunately not a substitute for asking. ;-)

    Besides, some of the Itanium locking code uses instructions that the
    above manual is silent about.

    Thanx, Paul



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