From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
 id D7727393C033; Wed, 28 Apr 2021 11:52:06 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org D7727393C033
From: "stefansf at linux dot ibm.com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/100263] [11/12 Regression] RTL optimizers
 miscompile loop
Date: Wed, 28 Apr 2021 11:52:06 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: rtl-optimization
X-Bugzilla-Version: 11.0
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: stefansf at linux dot ibm.com
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P2
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 11.2
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-100263-4-roMZdZFzQD@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-100263-4@http.gcc.gnu.org/bugzilla/>
References: <bug-100263-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Wed, 28 Apr 2021 11:52:07 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100263

--- Comment #9 from Stefan Schulze Frielinghaus <stefansf at linux dot ibm.=
com> ---
Shouldn't we rather check for REG_CAN_CHANGE_MODE_P? A check for
TARGET_HARD_REGNO_MODE_OK for a FP register and QImode is successful.

Using the following also fixes the test for me:

diff --git a/gcc/postreload.c b/gcc/postreload.c
index dc67643384d..3dccbe63cf4 100644
--- a/gcc/postreload.c
+++ b/gcc/postreload.c
@@ -1733,7 +1733,7 @@ move2add_valid_value_p (int regno, scalar_int_mode mo=
de)
         regno of the lowpart might be different.  */
       poly_int64 s_off =3D subreg_lowpart_offset (mode, old_mode);
       s_off =3D subreg_regno_offset (regno, old_mode, s_off, mode);
-      if (maybe_ne (s_off, 0))
+      if (maybe_ne (s_off, 0) || !REG_CAN_CHANGE_MODE_P (regno, old_mode,
mode))
        /* We could in principle adjust regno, check reg_mode[regno] to be
           BLKmode, and return s_off to the caller (vs. -1 for failure),
           but we currently have no callers that could make use of this=