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From: "ebotcazou at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/102024] [12 Regression] zero width bitfields and ABIs
Date: Thu, 24 Mar 2022 09:39:17 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102024

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ebotcazou at gcc dot gnu.o=
rg

--- Comment #18 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> TYPE_MODE should be ok too, it is just passing of arguments by value and
> returning by value that could be problematic on
> aarch64, arm, i386, ia64, iq2000, mips, riscv, rs6000, s390, sh and sparc
> I think sh is ok, it ignores integer_zerop (DECL_SIZE (field)).

On SPARC, the 32-bit ABI passes structures by reference so is not concerned
while the 64-bit ABI does the same as SH:

  /* Walk the real fields, but skip those with no size or a zero size.
     ??? Fields with variable offset are handled as having zero offset.  */
  for (tree field =3D TYPE_FIELDS (type); field; field =3D DECL_CHAIN (fiel=
d))
    if (TREE_CODE (field) =3D=3D FIELD_DECL)
      {
        if (!DECL_SIZE (field) || integer_zerop (DECL_SIZE (field)))
          continue;

so is not affected either.=