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    SubjectRe: BUG: GCC-4.4.x changes the function frame on some functions
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    On Thu, Nov 19, 2009 at 4:45 PM, H. Peter Anvin <hpa@zytor.com> wrote:
    > On 11/19/2009 07:37 AM, Thomas Gleixner wrote:
    >>
    >> modified function start on a handful of functions only seen with gcc
    >> 4.4.x on x86 32 bit:
    >>
    >>       push   %edi
    >>       lea    0x8(%esp),%edi
    >>       and    $0xfffffff0,%esp
    >>       pushl  -0x4(%edi)
    >>       push   %ebp
    >>       mov    %esp,%ebp
    >>       ...
    >>       call   mcount
    >>
    >
    > The real questions is why we're aligning the stack in the kernel.  It is
    > probably not what we want -- we don't use SSE for anything but a handful
    > of special cases in the kernel, and we don't want the overhead.

    It's likely because you have long long vars on the stack which is
    faster when they are aligned. -mno-stackrealign may do what you
    want (or may not, I have not checked). I assume you already
    use -mpreferred-stack-boundary=2.

    Richard.
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