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    SubjectRe: Compilers and RCU readers: Once more unto the breach!
    On Wed, May 20, 2015 at 02:44:30PM +0100, Ramana Radhakrishnan wrote:
    >
    >
    > On 20/05/15 14:37, David Howells wrote:
    > >Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:
    > >
    > >>I was thinking of "y" as a simple variable, but if it is something more
    > >>complex, then the compiler could do this, right?
    > >>
    > >> char *x;
    > >>
    > >> y;
    > >> x = z;
    > >
    > >Yeah. I presume it has to maintain the ordering, though.
    >
    > The scheduler for e.g. is free to reorder if it can prove there is
    > no dependence (or indeed side-effects for y) between insns produced
    > for y and `x = z'.

    So for example, if y is independent of z, the compiler can do the
    following:

    char *x;

    x = z;
    y;

    But the dependency ordering is still maintained from z to x, so this
    is not a problem.

    Or am I missing something subtle here?

    Thanx, Paul



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