[Bug target/110588] New: btl (on x86_64) not always generated

[Bug target/110588] New: btl (on x86_64) not always generated

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110588

            Bug ID: 110588
           Summary: btl (on x86_64) not always generated
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---
            Target: x86_64-linux-gnu

Take C+ code (since I am too lazy to figure out the types):
```
unsigned char clr1_bb (unsigned char x, int y)
{
  return (x & (1<<y)) == 0;
}


unsigned char clr1_bb1 (unsigned char x, int y)
{
  auto  _1 = (int) x;
 auto _2 = _1 >> y;
 auto _3 = _2 & 1;
 auto _8 = (unsigned char) _3;
auto  _6 = _8 ^ 1;

  return _6;
}

unsigned char clr1_bb2 (unsigned char x, int y)
{
  auto  _1 = (int) x;
 auto _2 = _1 >> y;
 auto _3 = _2 & 1;
auto  _6 = _3 ^ 1;
 auto _8 = (unsigned char) _6;

  return _6;
}
```

Right now clr1_bb and clr1_bb2 produce the btl/setnc but clr1_bb1 does not.

Note I noticed this while working on PR 110539 (I changed my patch to put the
cast after the ^1 rather than before so this is not blocking that patch).

[Bug target/110588] btl (on x86_64) not always generated

[roger at nextmovesoftware dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110588

Roger Sayle <roger at nextmovesoftware dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |roger at nextmovesoftware dot com
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
           Assignee|unassigned at gcc dot gnu.org      |roger at nextmovesoftware dot com
   Last reconfirmed|                            |2023-07-08

--- Comment #1 from Roger Sayle <roger at nextmovesoftware dot com> ---
Thanks Andrew.  I have a patch (a define_split in i386.md) that's currently
bootstrapping and regression testing.  But perhaps this should also be fixed at
the tree-level by match.pd canonicalizing ((T)(x & C)) ^ C to (T)((~x) & C)
when T is not wider than X and X is not wider than WORD_MODE.  It's tricky to
compare the costs of integer operations in different precisions, but WORD_MODE
(and int) operations are (typically) always cheap (and I believe unary
operations are preferred over binary operations (with immediate constants)).

[Bug target/110588] btl (on x86_64) not always generated

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110588

Uroš Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=107671

--- Comment #2 from Uroš Bizjak <ubizjak at gmail dot com> ---
Similar missed optimization is reported in PR107671.

[Bug target/110588] btl (on x86_64) not always generated

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110588

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Roger Sayle <sayle@gcc.gnu.org>:

https://gcc.gnu.org/g:43a0a5cd57eefd5a5bbead606ec4f6959af31802

commit r14-2528-g43a0a5cd57eefd5a5bbead606ec4f6959af31802
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Fri Jul 14 18:21:56 2023 +0100

    PR target/110588: Add *bt<mode>_setncqi_2 to generate btl on x86.

    This patch resolves PR target/110588 to catch another case in combine
    where the i386 backend should be generating a btl instruction.  This adds
    another define_insn_and_split to recognize the RTL representation for this
    case.

    I also noticed that two related define_insn_and_split weren't using the
    preferred string style for single statement preparation-statements, so
    I've reformatted these to be consistent in style with the new one.

    2023-07-14  Roger Sayle  <roger@nextmovesoftware.com>

    gcc/ChangeLog
            PR target/110588
            * config/i386/i386.md (*bt<mode>_setcqi): Prefer string form
            preparation statement over braces for a single statement.
            (*bt<mode>_setncqi): Likewise.
            (*bt<mode>_setncqi_2): New define_insn_and_split.

    gcc/testsuite/ChangeLog
            PR target/110588
            * gcc.target/i386/pr110588.c: New test case.

[Bug target/110588] btl (on x86_64) not always generated

[roger at nextmovesoftware dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110588

Roger Sayle <roger at nextmovesoftware dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from Roger Sayle <roger at nextmovesoftware dot com> ---
This is now fixed on mainline for GCC 14.