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From: "acoplan at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/99216] ICE in aarch64_sve::function_expander::expand()
 with LTO
Date: Fri, 05 Mar 2021 10:00:29 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99216

--- Comment #4 from Alex Coplan <acoplan at gcc dot gnu.org> ---
Right, the problem appears to be to do with the way that overloaded functio=
ns
are implemented for the ACLE. Specifically the m_direct_overloads flag in
aarch64_sve::function_builder. If this flag is set, we register a separate
builtin (with a separate function code) for each overload as opposed to
registering the overloaded function once and resolving it later. The two
different schemes end up with each builtin having a different code.

We set m_direct_overloads to be true if the language is C++:

m_direct_overloads =3D lang_GNU_CXX ();

so in cc1plus, we use one numbering scheme, but in lto1, we use a different
numbering scheme, with predictably disastrous consequences (we try and expa=
nd
svaddv as an svbic).

So one options would be that for LTO we instantiate both sets of tree nodes.
Then, when expanding a tree node that came from LTO, we dispatch on a flag =
in
the tree node (essentially just whether it came from C++ or not) to determi=
ne
which set of functions to use. Seems a bit messy though.

@Richard: does that sound at all sane? Any ideas for a better approach?=