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    SubjectRe: BUG: GCC-4.4.x changes the function frame on some functions
    From
    On Thu, Nov 19, 2009 at 4:49 PM, Richard Guenther
    <richard.guenther@gmail.com> wrote:
    > 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.

    Just checking it seems you must be using -mincoming-stack-boundary=2
    instead but keep the preferred stack boundary at 4.

    Richard.
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