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    SubjectRe: [PATCH] [RFC] [2.5 i386] GCC 3.1 -march support, PPRO_FENCE reduction, prefetch fixes and other CPU-related changes
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    On Sun, 2002-08-04 at 23:54, Alan Cox wrote:
    > On Sun, 2002-08-04 at 21:23, Luca Barbieri wrote:
    > > Added, with the exception that sfence is only used if CONFIG_X86_OOSTORE
    > > is not defined (currently never).
    >
    > Ok sorry I follow what you are doing. What I don't understand is why you
    > are generating unneeded sfence/mfence instructions in the other cases ?
    It was my fault: I explained it incorrectly. sfence is only used if both
    CONFIG_X86_OOSTORE and CONFIG_MMXEXT are set, which currently never
    happens with the existing processors.

    > When we use MMX/SSE we need the view to be consistent anyway so the
    > various copying routines already handle this internally.
    That's why sfence is not used unless CONFIG_X86_OOSTORE (and
    CONFIG_X86_MMXEXT) is defined.
    mfence and lfence instead replace the "lock; addl $0,0(%%esp)". Is this
    wrong?

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