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 46F9839A183E; Fri,  6 Aug 2021 13:59:46 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 46F9839A183E
From: "stefansf at linux dot ibm.com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/101260] [10/11/12 Regression] Backport
 27381e78925 to GCC 11
Date: Fri, 06 Aug 2021 13:59:45 +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: 10.4
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-101260-4-R48cHCqwpf@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-101260-4@http.gcc.gnu.org/bugzilla/>
References: <bug-101260-4@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: Fri, 06 Aug 2021 13:59:46 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101260

--- Comment #10 from Stefan Schulze Frielinghaus <stefansf at linux dot ibm=
.com> ---
In regcprop we call find_oldest_value_reg which itself calls

  maybe_mode_change (TImode, TImode, DImode, 10, 18)

where we have

  regno +=3D subreg_regno_offset (regno, orig_mode, offset, new_mode);

The call is made where offset equals 8 which is wrong since we are interest=
ed
in the high part which is contained in r10 and not r11.  The following patch
fixes this:

diff --git a/gcc/regcprop.c b/gcc/regcprop.c
index d2a01130fe1..0e1ac12458a 100644
--- a/gcc/regcprop.c
+++ b/gcc/regcprop.c
@@ -414,9 +414,14 @@ maybe_mode_change (machine_mode orig_mode, machine_mode
copy_mode,
                            copy_nregs, &bytes_per_reg))
        return NULL_RTX;
       poly_uint64 copy_offset =3D bytes_per_reg * (copy_nregs - use_nregs);
-      poly_uint64 offset
-       =3D subreg_size_lowpart_offset (GET_MODE_SIZE (new_mode) + copy_off=
set,
-                                     GET_MODE_SIZE (orig_mode));
+      poly_uint64 offset =3D
+#if WORDS_BIG_ENDIAN
+       subreg_size_highpart_offset
+#else
+       subreg_size_lowpart_offset
+#endif
+                                   (GET_MODE_SIZE (new_mode) + copy_offset,
+                                    GET_MODE_SIZE (orig_mode));
       regno +=3D subreg_regno_offset (regno, orig_mode, offset, new_mode);
       if (targetm.hard_regno_mode_ok (regno, new_mode))
        return gen_raw_REG (new_mode, regno);

With the patch

(insn 234 222 235 14 (set (reg:DI 10 %r10 [ a ])
        (reg:DI 18 %f4)) 1376 {*movdi_64}
     (nil))

is first modified into a noop

(insn 234 222 235 14 (set (reg:DI 10 %r10 [ a ])
        (reg:DI 10 %r10 [18])) 1376 {*movdi_64}
     (nil))

and then deleted within regcprop.=