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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug middle-end/100604] GCC generates invalid LO_SYM for unaligned
 global
Date: Mon, 17 May 2021 12:24:47 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100604

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to dragan.mladjenovic from comment #2)
> It seems so. Something like this helps in this case:
>=20
> diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
> index 07e908624a0..a102a9288c5 100644
> --- a/gcc/emit-rtl.c
> +++ b/gcc/emit-rtl.c
> @@ -2385,7 +2385,7 @@ adjust_address_1 (rtx memref, machine_mode mode,
> poly_int64 offset,
>        if (GET_MODE (memref) !=3D BLKmode
>           && GET_CODE (addr) =3D=3D LO_SUM
>           && known_in_range_p (offset,
> -                              0, (GET_MODE_ALIGNMENT (GET_MODE (memref))
> +                              0, (MIN (GET_MODE_ALIGNMENT (GET_MODE
> (memref)), attrs.align)
>                                    / BITS_PER_UNIT)))
>         addr =3D gen_rtx_LO_SUM (address_mode, XEXP (addr, 0),
>                                plus_constant (address_mode,
>=20
> Don't know which one to trust. The memref has SImode. Caller wants to cre=
ate
> HImode one. The attrs.align matches that of HImode.

on a strict-align target if the MEM has SImode it should be aligned to
the SImode alignment.  Of course generally you should never look at
GET_MODE_ALIGNMENT but use attrs.align unconditionally (aka MEM_ALIGN).

Now the question is where the HImode aligned MEM:SI comes from for
a strict-alignment target.  That said, unconditionally using attrs.align
looks like the correct fix.=