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 9B8B4385840A; Mon, 24 Oct 2022 07:48:14 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 9B8B4385840A
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1666597694;
	bh=/ZS+njNamh7AvPjaNgW7F5QQiRU8GTJkpQzch+7NH/g=;
	h=From:To:Subject:Date:From;
	b=WzvYTvO/eWKtmN1flI/h5DAP8qGW9BhIANBK8jIh8VUJs86CQ4LXt++oRp10XQfDB
	 uBiZ8eKzAYzg2R2wH2Y6s/FRo/M2M0P5ZzwANAspGMKgrzmlsE89l3vg/IAHgOTr1Z
	 rcDaxe4CnFVrnyD1W7HmmpWeFzKpRniy2/bMITM4=
From: "krebbel at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/107372] New: Loop distribution create memcpy
 between structs with different storage order
Date: Mon, 24 Oct 2022 07:48:12 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: krebbel 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 target_milestone
Message-ID: <bug-107372-4@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=3D107372

            Bug ID: 107372
           Summary: Loop distribution create memcpy between structs with
                    different storage order
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: krebbel at gcc dot gnu.org
  Target Milestone: ---

For t.c with "gcc -O3 t.c":

struct L
{
  unsigned int val[256];
} __attribute__((scalar_storage_order ("little-endian")));

struct B
{
  unsigned int val[256];
} __attribute__((scalar_storage_order ("big-endian")));

void
foo (struct L *restrict l, struct B *restrict b)
{
  int i;
  for (i =3D 0; i < 256; i++)
    l->val[i] =3D b->val[i];
}


The loop distribution pass currently generates a memcpy although it recogni=
zes
correctly that both sides of the assignment have different storage order:

Analyzing # of iterations of loop 1
  exit condition [255, + , 4294967295] !=3D 0
  bounds on difference of bases: -255 ... -255
  result:
    # of iterations 255, bounded by 255
Creating dr for *b_5(D).val[i_11]
analyze_innermost: t.c:16:23: missed: failed: reverse storage order.

...

void foo (struct L * restrict l, struct B * restrict b)
{
  int i;

  <bb 2> [local count: 10737416]:
  __builtin_memcpy (l_6(D), b_5(D), 1024);
  return;

}=