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From: "hjl.tools at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/95162] -mpreferred-stack-boundary=2 doesn't work with
 libgcc functions
Date: Sat, 16 May 2020 12:22:51 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95162

--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> ---
GCC manual says

'-mpreferred-stack-boundary=3DNUM'
     Attempt to keep the stack boundary aligned to a 2 raised to NUM
     byte boundary.  If '-mpreferred-stack-boundary' is not specified,
     the default is 4 (16 bytes or 128-bits).

     *Warning:* If you use this switch, then you must build all modules
     with the same value, including any libraries.  This includes the
     system libraries and startup modules.

c-c++-common/dfp/func-vararg-mixed-2.c has

/* { dg-do run { target { { i?86-*-* x86_64-*-* } && ia32 } } } */
/* { dg-options "-mpreferred-stack-boundary=3D2" } */

which works by pure luck.=