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    SubjectRe: using gcc built-ins for bitops?
    On Thu, Jun 24, 2004 at 02:00:22AM -0700, Andrew Morton wrote:
    > Arjan van de Ven <arjanv@redhat.com> wrote:
    > >
    > > gcc 3.4 gained support for several typical bitops as builtin directives.
    > > Using these over inline asm has a few advantages:
    > > * gcc can optimize constants into these better
    > > * gcc can reorder and schedule the code better
    > > * gcc can allocate registers etc better for the code
    > >
    > > The question is if we consider it desirable to go down this road or not. In
    > > order to help that discussion I've attached a patch below that switches the
    > > i386 ffz() function to the gcc builtin version, conditional on gcc having
    > > support for this. Before I go down the road of converting more functions
    > > and/or architectures.... is this worth doing?
    >
    > I guess it depends on the resulting code size and quality. Some extra
    > conversions would be needed for that.

    for ffz() the exact same assembly instructions are generated in the cases I looked at
    (kernel/signal.c); eg no extra code at all.


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