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 B44DC385041B; Wed,  8 Mar 2023 03:16:54 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org B44DC385041B
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1678245414;
	bh=L2h5mgB8TbjAkpC/uCE75yCLD/JNdB8dR3lE5tPn9z4=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=NKpPCBJ5kgwhEpu/n6ORuUGCSV/OfjffQwVKOAkEM92ZEBGQJrq+D4lePu7flHi19
	 SsJJgDnJsyOKh1pgejvb2RysRuxSM4BlK4vffZpqWiEwxBfG4pwDVQwxWblngtKP76
	 cog8stqY+BwkBQv5Dm7g/IdASkRAiq//pg7f3QjY=
From: "chenglulu at loongson dot cn" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/109035] meaningless memory store on RISC-V and
 LoongArch
Date: Wed, 08 Mar 2023 03:16:53 +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: 13.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: chenglulu at loongson dot cn
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: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: cc
Message-ID: <bug-109035-4-DARF5c7TRB@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-109035-4@http.gcc.gnu.org/bugzilla/>
References: <bug-109035-4@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
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109035

chenglulu <chenglulu at loongson dot cn> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |chenglulu at loongson dot =
cn

--- Comment #2 from chenglulu <chenglulu at loongson dot cn> ---
I think this is most likely caused by the implementation of the public code=
. If
the immediate value is set to be large enough, such as 0xfffffff, aarch64 a=
lso
has the same problem.

$ cat t.c
int test(int x)
{
        char buf[0xfffffff];
        return buf[x];
}

$ ./cc1 t.c -o - -O2  2>/dev/null | grep test -A20
test:
.LFB0:
        .cfi_startproc
        mov     x12, 16
        mov     x2, 16
        movk    x12, 0x1000, lsl 16
        sub     sp, sp, x12
        .cfi_def_cfa_offset 268435472
        movk    x2, 0x1000, lsl 16
        mov     x1, -268435456
        add     x1, x2, x1
        add     x1, sp, x1
        str     x1, [sp, 8]
        ldrb    w0, [x1, w0, sxtw]
        add     sp, sp, x12
        .cfi_def_cfa_offset 0
        ret

The "str x1, [sp, 8]" instruction also has the same problem.=