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    SubjectRe: [3/10 PATCH] inline wake_up_bit
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    From: Denys Vlasenko <vda.linux@googlemail.com>
    Date: Wed, 25 Jun 2008 22:37:58 +0200

    > On Wednesday 25 June 2008 18:01, Mikulas Patocka wrote:
    > > > Ingo's suggestion to talk to gcc people to remedy
    > > > insane call convention sounds as a more workable solution.
    > > >
    > > > BTW, i386 uses regparm call convention, is similar trick
    > > > possible for sparc64?
    > >
    > > Sparc64 has register windows: it passes arguments in registers, but it
    > > must allocate space for that registers. If the call stack is too deep (8
    > > levels), the CPU runs out of registers and starts spilling the registers
    > > of the function 8-levels-deep to the stack.
    > >
    > > The stack usage could be reduced to 176 bytes with little work from gcc
    > > developers and to 128 bytes with more work (ABI change). If you wanted to
    >
    > Wow, it's nearly x2 reduction.
    >
    > ABI change in not a problem for kernel, since it is a "freestanding
    > application". Exactly like i386 switched to regparm, which is a different ABI.

    Except that nobody has written this code and therefore being about to
    use this unimplemented compiler facility to get correctness is not
    tenable.


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