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    SubjectRe: GCC 3.4 and broken inlining.
    On Sat, Jul 10, 2004 at 12:17:55AM +0200, Adrian Bunk wrote:
    > On Fri, Jul 09, 2004 at 11:54:15PM +0200, Andi Kleen wrote:
    > > > Runtime errors caused with gcc 3.4 are IMHO much worse than such a small
    > > > improvement or three dozen compile errors with gcc 3.4 .
    > >
    > > What runtime errors?
    > >
    > > Actually requiring inlining is extremly rare and such functions should
    > > get that an explicit always inline just for documentation purposes.
    > > (another issue is not optimized away checks, but that shows at link time)
    > First of all, your proposed patch seems to be broken WRT gcc < 3.1 .

    The latest version does fallback #define __always_inline inline
    That was indeed broken in the original patch.

    > > In the x86-64 case it was vsyscalls, in Nigel's case it was swsusp.
    > > Both are quite exceptional in what they do.
    > >
    > > > Wouldn't it be a better solution if you would audit the existing inlines
    > > > in the kernel for abuse of inline and fix those instead?
    > >
    > > I don't see any point in going through ~1.2MLOC of code by hand
    > > when a compiler can do it for me.
    > How can a compiler decide whether an "inline" was for a possible small
    > speed benefit or whether it's required for correct working?

    It can't, but the 0.001% of needed for inlines that are required
    for correctness should be always marked __always_inline
    just for documentation alone.
    You probably don't realize how special a case this is.

    > And I'm not that happy with the fact that gcc 3.3 and gcc 3.4 will
    > produce significantly different code for the same file. Besides from the
    > 3 dozen compile errors I'm currently sorting out, gcc 3.3 and 3.4 should
    > behave similar with __attribute__((always_inline)).

    They are different compiler versiopns, they generate different code.

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