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    SubjectRe: [PATCH] Use -fno-unit-at-a-time if gcc supports it
    > > How much work would be to fix kernel in this regard?
    > The big problem is that -funit-at-a-time is not widely used yet,
    > so even if we fix the kernel at some point it would likely
    > get broken again all the time by people who use older kernels
    > (= most kernel developers currently)
    > > Are there some cases where this is esential? Kernel would be nice
    > > target to whole program optimization and GCC is not that far from it
    > > right now.
    > I'm not sure that is that good an idea. When I was still hacking
    > TCP I especially moved some stuff out-of-line in the fast path to avoid
    > register pressure. Otherwise gcc would inline rarely used sub functions
    > and completely mess up the register allocation in the fast path.
    > Of course just a call alone messes up the registers somewhat because
    > of its clobbers, but a full inlining is usually worse.

    You can use -O2 and rely on inline done by hand. I can add option
    -fno-inline-functions-called-once. That should avoid such a problems.
    Anyway it would be nice to mark functions that exist for this reason by
    noinline attribute so compiler knows about it, but that is different
    > Also I fear cross module inlining would expose a lot of latent bugs
    > (missing barriers etc.) when the optimizer becomes more aggressive.
    > I'm not saying this would be a bad thing, just that it may be a lot
    > of work to fix (both for compiler and kernel people)

    Some of this should be already tested by folks using Intel compiler I
    would hope.

    > -Andi
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