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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/108370] gcc doesn't merge bitwise-AND if an explicit comparison against 0 is given
Date: Wed, 11 Jan 2023 14:24:45 +0000	[thread overview]
Message-ID: <bug-108370-4-j87lWQWESa@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-108370-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108370

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
ifcombine seems to assume that

     D.1987_7 = op0 & 1;
     if (D.1987_7 != 0)

is canonical but we see

  _9 = (_Bool) _6;
  if (_9 != 0)

instead.  That's already the form introduced by inlining from

_Bool bio_flagged (struct bio * bio, unsigned int bit)
{
  short unsigned int _1;
  unsigned int _2;
  unsigned int _3;
  unsigned int _4;
  _Bool _8;

  <bb 2> :
  _1 = bio_6(D)->bi_flags;
  _2 = (unsigned int) _1;
  _3 = _2 >> bit_7(D);
  _4 = _3 & 1;
  _8 = _4 != 0;
  return _8;

and

  <bb 2> :
  _1 = bio_flagged (bio_7(D), 0);
  if (_1 != 0)
    goto <bb 4>; [INV]
  else
    goto <bb 3>; [INV]

  parent reply	other threads:[~2023-01-11 14:24 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-11 13:47 [Bug c/108370] New: " dhowells at redhat dot com
2023-01-11 14:04 ` [Bug c/108370] " rguenth at gcc dot gnu.org
2023-01-11 14:24 ` rguenth at gcc dot gnu.org [this message]
2023-01-11 14:42 ` dhowells at redhat dot com
2023-02-08 20:30 ` [Bug middle-end/108370] " pinskia at gcc dot gnu.org
2023-09-16 22:58 ` pinskia at gcc dot gnu.org
2023-09-16 23:16 ` pinskia at gcc dot gnu.org
2023-09-16 23:48 ` pinskia at gcc dot gnu.org
2023-09-17  0:35 ` pinskia at gcc dot gnu.org

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