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Subject: [Bug target/99234] [10/11 regression] wrong result for 1.0/3.0 with
 -O2 -fno-omit-frame-pointer -frounding-math
Date: Wed, 05 May 2021 20:58:02 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99234

--- Comment #29 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Eric Botcazou
<ebotcazou@gcc.gnu.org>:

https://gcc.gnu.org/g:e3abcc56d2604b9d2652b615ff9e68981cb7f79e

commit r10-9804-ge3abcc56d2604b9d2652b615ff9e68981cb7f79e
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Wed May 5 22:48:51 2021 +0200

    Fix PR target/100402

    This is a regression for 64-bit Windows present from mainline down to t=
he 9
    branch and introduced by the fix for PR target/99234.  Again SEH, but w=
ith
    a twist related to the way MinGW implements setjmp/longjmp, which turns=
 out
    to be piggybacked on SEH with recent versions of MinGW, i.e. the longjmp
    performs a bona-fide unwinding of the stack, because it calls RtlUnwind=
Ex
    with the second argument initially passed to setjmp, which is the resul=
t of
    __builtin_frame_address (0) in the MinGW header file:

      define setjmp(BUF) _setjmp((BUF), __builtin_frame_address (0))

    This means that we directly expose the frame pointer to the SEH machine=
ry
    here (unlike with regular exception handling where we use an intermedia=
te
    CFA) and thus that we cannot do whatever we want with it.  The old code
    would leave it unaligned, i.e. not multiple of 16, whereas the new code
    aligns it, but this breaks for some reason; at least it appears that a
    .seh_setframe directive with 0 as second argument always works, so the
    fix aligns it this way.

    gcc/
            PR target/100402
            * config/i386/i386.c (ix86_compute_frame_layout): For a SEH tar=
get,
            always return the establisher frame for __builtin_frame_address
(0).
    gcc/testsuite/
            * gcc.c-torture/execute/20210505-1.c: New test.=