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 A4EAD38582A9; Thu,  8 Feb 2024 11:38:18 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org A4EAD38582A9
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1707392298;
	bh=hxUW09qjlx7yW/BN6jRWVn6194ZPrSfqErlva5JYGIE=;
	h=From:To:Subject:Date:From;
	b=prSgh96h5iAko2pTyEw5beKImrYDm2rNKH0/pQ3XKCTGni4G8083R1M9gYnRtCQ3U
	 Ql86TLoR9iDA6JrQFQ4vwtyM+pvWaJAAKsdyOIw+1teJOAO/jdnTtDJIQSmnZB3Aw1
	 s+bgthvCf+ij25MPzvexHmgT/WBxHwvAbqRcSlvc=
From: "rdapp at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/113827] New: MrBayes benchmark redundant load
Date: Thu, 08 Feb 2024 11:38:17 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: rdapp at gcc dot gnu.org
X-Bugzilla-Status: UNCONFIRMED
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: bug_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter cc blocked
 target_milestone cf_gcctarget
Message-ID: <bug-113827-4@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=3D113827

            Bug ID: 113827
           Summary: MrBayes benchmark redundant load
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rdapp at gcc dot gnu.org
                CC: juzhe.zhong at rivai dot ai, law at gcc dot gnu.org,
                    pan2.li at intel dot com
            Blocks: 79704
  Target Milestone: ---
            Target: riscv

A hot block in the MrBayes benchmark (as used in the Phoronix testsuite) ha=
s a
redundant scalar load when vectorized.

Minimal example, compiled with -march=3Drv64gcv -O3

int foo (float **a, float f, int n)
{
  for (int i =3D 0; i < n; i++)
    {
      a[i][0] /=3D f;
      a[i][1] /=3D f;
      a[i][2] /=3D f;
      a[i][3] /=3D f;
      a[i] +=3D 4;
    }
}

GCC:
.L3:
        ld      a5,0(a0)
        vle32.v v1,0(a5)
        vfmul.vv        v1,v1,v2
        vse32.v v1,0(a5)
        addi    a5,a5,16
        sd      a5,0(a0)
        addi    a0,a0,8
        bne     a0,a4,.L3

The value of a5 doesn't change after the store to 0(a0).

LLVM:
.L3
        vle32.v   v8,(a1)
        addi      a3,a1,16
        sd        a3,0(a2)
        vfdiv.vf  v8,v8,fa5
        addi      a2,a2,8
        vse32.v   v8,(a1)
        bne       a2,a0,.L3


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D79704
[Bug 79704] [meta-bug] Phoronix Test Suite compiler performance issues=