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    SubjectRe: [patch] string.h speedup, cld-2.3.30-A1
    On Sat, 27 Nov 1999, Linus Torvalds wrote:

    > On Sat, 27 Nov 1999, Oliver Xymoron wrote:
    > > On Sat, 27 Nov 1999, Ingo Molnar wrote:
    > >
    > > > much of the remaining 284 cld's is still unjustified, because '*a = *b;'
    > > > type of structure copies are inlined by GCC. (GCC generates a cld because
    > > > user-space has to be prepared to be interrupted by uncooperative signal
    > > > handlers and the like).
    > >
    > > What!? A signal handler can change flags? Then there's a lot more for GCC
    > > to worry about than the direction flag..
    > A normal signal handler cannot change flags, because they will obviously
    > be restored on signal exit.
    > However, I'm not sure that "longjmp()" does the same. You'd have to check
    > libc souces to see if setjmp saves the flags..

    It doesn't appear to, at least according to bits/setjmp.h. Surely, any
    point in a user app can quietly change flags, but Ingo's example of a
    signal handler doing it seemed unlikely.

    There's clearly no general fix for the existence of the direction flag
    though, short of getting a non-x86 machine. We could lobby the GCC
    folks for an -fassume-cld and maybe an -fpair-std, but it doesn't really
    fix the problem.

    "Love the dolphins," she advised him. "Write by W.A.S.T.E.."

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