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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/85927] ud2 instruction generated starting with gcc 8
Date: Fri, 31 Dec 2021 10:25:34 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D85927

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org,
                   |                            |uros at gcc dot gnu.org

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The ud2 is there since naked has been implemented for x86 in PR25967.
It is true it is a kind of debugging aid, so perhaps more suitable for
sanitization or if we add some option to decide preferred behavior on e.g.
__builtin_unreachable or for detected UB in the code (whether to use
__builtin_unreachable with its current behavior, just assume it doesn't hap=
pen
and don't emit anything in there, or whether to act as __builtin_trap etc.).
But without it e.g. the reporter wouldn't know so easily the function is
invalid and won't work correctly.=