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 C1C2F3858D33; Sun, 24 Apr 2022 07:37:38 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org C1C2F3858D33
From: "lili.cui at intel dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/104723] [12 regression] Redundant usage of stack
Date: Sun, 24 Apr 2022 07:37:38 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Version: 12.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: lili.cui at intel dot com
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 12.0
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-104723-4-tSlYepSfVl@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-104723-4@http.gcc.gnu.org/bugzilla/>
References: <bug-104723-4@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: Sun, 24 Apr 2022 07:37:38 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104723

--- Comment #11 from cuilili <lili.cui at intel dot com> ---
(In reply to Jakub Jelinek from comment #10)

> And for the backend, the question is how big the penalty for the overlapp=
ing
> store is compared to doing multiple non-overlapping stores.  Say for those
> 49 bytes one could do one OI, one TI/V1TI and one QI load/store as oppose=
d to
> one aligned and one misaligned OI load/store.
>=20
> For say:
> void
> foo (void *p, void *q)
> {
>   __builtin_memcpy (p, q, 49);
> }
> we emit the 2 overlapping loads/stores for -mavx512f and 4 non-overlapping
> loads/stores with say -mavx2.

I execute both code sequence 100000 times on ICX and znver3 machines.

For ICX: 2 overlapping loads/stores are 3.5x faster than 4 non-overlapping
loads/stores.
For Znver3: 2 overlapping loads/stores are 1.39x faster than 4 non-overlapp=
ing
loads/stores.

------------------------------------
vmovdqu ymm0, YMMWORD PTR [rsi]
vmovdqu YMMWORD PTR [rdi], ymm0
vmovdqu ymm1, YMMWORD PTR [rsi+17]
vmovdqu YMMWORD PTR [rdi+17], ymm1

------------------------------------
vmovdqu xmm0, XMMWORD PTR [rsi]
vmovdqu XMMWORD PTR [rdi], xmm0
vmovdqu xmm1, XMMWORD PTR [rsi+16]
vmovdqu XMMWORD PTR [rdi+16], xmm1
vmovdqu xmm2, XMMWORD PTR [rsi+32]
vmovdqu XMMWORD PTR [rdi+32], xmm2
movzx   eax, BYTE PTR [rsi+48]
mov     BYTE PTR [rdi+48], al
-----------------------------------=