[Bug middle-end/100604] GCC generates invalid LO_SYM for unaligned global
rguenth at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Mon May 17 12:24:47 GMT 2021
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100604
--- 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:
>
> 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) != BLKmode
> && GET_CODE (addr) == 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 = gen_rtx_LO_SUM (address_mode, XEXP (addr, 0),
> plus_constant (address_mode,
>
> Don't know which one to trust. The memref has SImode. Caller wants to create
> 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.
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