From: Richard Biener <rguenther@suse.de>
To: "Andre Vieira (lists)" <andre.simoesdiasvieira@arm.com>
Cc: "gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>,
Richard Sandiford <richard.sandiford@arm.com>
Subject: Re: ifcvt: Fix bitpos calculation in bitfield lowering [PR107229]
Date: Thu, 13 Oct 2022 10:18:20 +0000 (UTC) [thread overview]
Message-ID: <nycvar.YFH.7.77.849.2210131017530.18337@jbgna.fhfr.qr> (raw)
In-Reply-To: <0e62cd70-b461-7ad8-8d37-a39ed4f4a9cd@arm.com>
On Thu, 13 Oct 2022, Andre Vieira (lists) wrote:
> Added some extra comments to describe what is going on there.
Just to note I was confused and DECL_FIELD_OFFSET can indeed be
different (but then are guaranteed to be constant), so the patch
looks correct.
> On 13/10/2022 09:14, Richard Biener wrote:
> > On Wed, 12 Oct 2022, Andre Vieira (lists) wrote:
> >
> >> Hi,
> >>
> >> The bitposition calculation for the bitfield lowering in loop if conversion
> >> was not
> >> taking DECL_FIELD_OFFSET into account, which meant that it would result in
> >> wrong bitpositions for bitfields that did not end up having representations
> >> starting at the beginning of the struct.
> >>
> >> Bootstrappend and regression tested on aarch64-none-linux-gnu and
> >> x86_64-pc-linux-gnu.
> > + {
> > + tree bf_pos = fold_build2 (MULT_EXPR, bitsizetype,
> > + DECL_FIELD_OFFSET (field_decl),
> > + build_int_cst (bitsizetype, 8));
> > + bf_pos = fold_build2 (PLUS_EXPR, bitsizetype, bf_pos,
> > + DECL_FIELD_BIT_OFFSET (field_decl));
> > + tree rep_pos = fold_build2 (MULT_EXPR, bitsizetype,
> > + DECL_FIELD_OFFSET (rep_decl),
> > + build_int_cst (bitsizetype, 8));
> > + rep_pos = fold_build2 (PLUS_EXPR, bitsizetype, rep_pos,
> > + DECL_FIELD_BIT_OFFSET (rep_decl));
> >
> > you can use the invariant that DECL_FIELD_OFFSET of rep_decl
> > and field_decl are always the same. Also please use BITS_PER_UNIT
> > instead of '8'.
> >
> > Richard.
>
--
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg,
Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman;
HRB 36809 (AG Nuernberg)
next prev parent reply other threads:[~2022-10-13 10:18 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-12 17:29 Andre Vieira (lists)
2022-10-13 8:14 ` Richard Biener
2022-10-13 10:15 ` Andre Vieira (lists)
2022-10-13 10:18 ` Richard Biener [this message]
2022-10-13 11:39 ` Rainer Orth
2022-10-13 13:55 ` Andre Vieira (lists)
2022-10-13 14:15 ` Richard Biener
2022-10-13 14:42 ` Andre Vieira (lists)
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