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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/115337] wrong code with _BitInt()
 __builtin_stdc_first_leading_one/__builtin_clzg (with -1 as second arg) at
 -O2
Date: Tue, 04 Jun 2024 14:17:41 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D115337

--- Comment #10 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:591d30c5c97e757f63ce0d99ae9a3dbe8c75a50a

commit r15-1014-g591d30c5c97e757f63ce0d99ae9a3dbe8c75a50a
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Tue Jun 4 16:16:49 2024 +0200

    ranger: Improve CLZ fold_range [PR115337]

    cfn_ctz::fold_range includes special cases for the case where .CTZ has
    two arguments and so is well defined at zero, and the second argument is
    equal to prec or -1, but cfn_clz::fold_range does that only for the prec
    case.  -1 is fairly common as well though, because the <stdbit.h> built=
ins
    do use it now, so I think it is worth special casing that.
    If we don't know anything about the argument, the difference for
    .CLZ (arg, -1) is that previously the result was varying, now it will be
    [-1, prec-1].  If we knew arg can't be zero, it used to be optimized be=
fore
    as well into e.g. [0, prec-1] or similar.

    2024-06-04  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/115337
            * gimple-range-op.cc (cfn_clz::fold_range): For
            m_gimple_call_internal_p handle as a special case also second
argument
            of -1 next to prec.=