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    SubjectRe: PPC should not use -fno-builtin (was Re: 2.3.47 imac build?)
    Date
    On Mon, 28 Feb 2000, Jeff Garzik wrote:

    > So... you are choosing to lose extremely valuable optimizations because
    > of a few prototype warnings? This logic seems bogus to me... it also

    OK, the problem is that gcc expects size_t to be an unsigned int. We use
    unsigned long for size_t in the kernel because we want it to be 64 bits on
    64-bit PPCs (like it is on the other 64-bit platforms). Gcc doesn't like a
    prototype for memcpy which has an unsigned long for the 3rd argument
    (unless you use -fno-builtin).

    The only optimization we lose with -fno-builtin (that I can see) is that
    the compiler won't turn explicit calls to memcpy with a small constant 3rd
    argument (<= 32) into a sequence of inline loads and stores. (It still
    does small struct copies with inline loads and stores even with
    -fno-builtin.)

    --
    Paul Mackerras, Senior Open Source Researcher, Linuxcare, Inc.
    +61 2 6262 8990 tel, +61 2 6262 8991 fax
    paulus@linuxcare.com.au, http://www.linuxcare.com.au/
    Linuxcare. Support for the revolution.

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