From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <aldyh@redhat.com>
Received: from us-smtp-delivery-124.mimecast.com
 (us-smtp-delivery-124.mimecast.com [170.10.129.124])
 by sourceware.org (Postfix) with ESMTPS id EAAA13858424
 for <gcc@gcc.gnu.org>; Fri, 29 Jul 2022 11:40:24 +0000 (GMT)
DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org EAAA13858424
Received: from mail-oo1-f70.google.com (mail-oo1-f70.google.com
 [209.85.161.70]) by relay.mimecast.com with ESMTP with STARTTLS
 (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id
 us-mta-307-plM2h1bDMoSwCdVeIG5W0g-1; Fri, 29 Jul 2022 07:40:23 -0400
X-MC-Unique: plM2h1bDMoSwCdVeIG5W0g-1
Received: by mail-oo1-f70.google.com with SMTP id
 x29-20020a4a395d000000b0043573840ab9so1871045oog.17
 for <gcc@gcc.gnu.org>; Fri, 29 Jul 2022 04:40:23 -0700 (PDT)
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
 d=1e100.net; s=20210112;
 h=x-gm-message-state:mime-version:from:date:message-id:subject:to:cc;
 bh=iUmYizOehdi/gDAvTZVUNrfImgxIRmOHzD/XfrDd9tE=;
 b=a+8HINfaW6PDmXjiQ4dT12Gg/4+DQbBXl2D7GmFGTh9a/kcGgfSKs9rjKDewEXXboc
 EyzB+AdqQgY6B8FUBE35K0r6526HSX8J0S9CRQxY6jIn0O9c+OOm+LeBlFxXAMLz+OFh
 85AWcNxZr96RBqBDntUChBU2gjXJh2Zjt9A2qyictg/E9hsvQInhddQLjyr7G/nWR5QP
 ld1bKMdt2fHx6a6mcXsrHLjRWn0iKNpOnezCx8XYKo7m30GW9vEQK+T7F9DEo3wYE/0I
 p66e4f3aNw8q0jNT4gpSevxTNACJSA9Rj2MLbhVluLjcjFRLX7JwG6vphyizxwyEwB7I
 FhiA==
X-Gm-Message-State: AJIora8PJ7QuA1N9OdH2D6Q0stYq38WtwAZPLNnZhXjDyX4bn1JW6t5x
 ibZlTdoUSL7VN+LbJTzLr8eKE3QNHv+TbYOScNSn0AuqucnbHnuRmDHJxZIyZsP7Qgxqu3coJx5
 wniLsQe4xqQ3UzNYbZ5PKRFo=
X-Received: by 2002:a05:6870:210b:b0:10b:ed11:4e2d with SMTP id
 f11-20020a056870210b00b0010bed114e2dmr1504858oae.265.1659094822856; 
 Fri, 29 Jul 2022 04:40:22 -0700 (PDT)
X-Google-Smtp-Source: AGRyM1uZP2paxGB9SxXFvkPCdKOI2E00dWTkxgaTUyoILadd1TMHBg75c37lQwUbsiBVs2cPwGGXRJQo7GRvRaxXGhw=
X-Received: by 2002:a05:6870:210b:b0:10b:ed11:4e2d with SMTP id
 f11-20020a056870210b00b0010bed114e2dmr1504849oae.265.1659094822643; Fri, 29
 Jul 2022 04:40:22 -0700 (PDT)
MIME-Version: 1.0
From: Aldy Hernandez <aldyh@redhat.com>
Date: Fri, 29 Jul 2022 13:40:12 +0200
Message-ID: <CAGm3qMVmdCFpDSvTSpmHbiK61ekpH4vA3zxNYZ7aOt+UYzg56Q@mail.gmail.com>
Subject: spaceship_replacement cannot see through simplified set of FP
 conditionals
To: Jakub Jelinek <jakub@redhat.com>, GCC Mailing List <gcc@gcc.gnu.org>
X-Mimecast-Spam-Score: 0
X-Mimecast-Originator: redhat.com
Content-Type: text/plain; charset="UTF-8"
X-Spam-Status: No, score=-6.0 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH,
 DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, KAM_SHORT,
 RCVD_IN_DNSWL_LOW, SPF_HELO_NONE, SPF_NONE,
 TXREP autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
 server2.sourceware.org
X-BeenThere: gcc@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc mailing list <gcc.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc>,
 <mailto:gcc-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc/>
List-Post: <mailto:gcc@gcc.gnu.org>
List-Help: <mailto:gcc-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc>,
 <mailto:gcc-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Fri, 29 Jul 2022 11:40:26 -0000

Hi.

With my upcoming patch enabling floating point VRP,
g++.dg/opt/pr94589-2.C is failing:

https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598788.html

The problem is that phiopt no longer sees the following snippet,
because we have folded away the final conditional as true:

bool f5 (double i, double j)
{
  signed char __v$_M_value;
  signed char c$_M_value;
  bool D.8519;
  struct partial_ordering __v;
  struct partial_ordering c;
  unsigned int _11;
  bool _16;

  <bb 2> :
  if (i_2(D) != j_4(D))
    goto <bb 3>; [INV]
  else
    goto <bb 6>; [INV]

  <bb 3> :
  if (i_2(D) >= j_4(D))
    goto <bb 4>; [INV]
  else
    goto <bb 6>; [INV]

  <bb 4> :
  if (i_2(D) > j_4(D))
    goto <bb 6>; [INV]
  else
    goto <bb 5>; [INV]

  <bb 5> :

  <bb 6> :
  # c$_M_value_3 = PHI <-1(3), 0(2), 2(5), 1(4)>
  _11 = (unsigned int) c$_M_value_3;
  _16 = _11 <= 1;
  return _16;
}

This means that spaceship_replacement()  now sees one less argument to the PHI:

  <bb 2> :
  if (i_2(D) != j_4(D))
    goto <bb 3>; [INV]
  else
    goto <bb 5>; [INV]

  <bb 3> :
  if (i_2(D) >= j_4(D))
    goto <bb 4>; [INV]
  else
    goto <bb 5>; [INV]

  <bb 4> :

  <bb 5> :
  # c$_M_value_3 = PHI <-1(3), 0(2), 1(4)>

...and we bail because we are expecting 4 arguments:

      if (EDGE_COUNT (phi_bb->preds) != 4)
    return false;

Could someone give me a hand here? Can spaceship_replacement easily be
adapted to handle this case, or should we be simplifying this
elsewhere?

Thanks.
Aldy