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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: Thu, 20 Jun 2024 13:24:03 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D115337

--- Comment #16 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:b724525c9779bbf93c4905dc3d54296f5e39e607

commit r11-11514-gb724525c9779bbf93c4905dc3d54296f5e39e607
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Tue Jun 4 15:49:41 2024 +0200

    fold-const: Fix up CLZ handling in tree_call_nonnegative_warnv_p [PR115=
337]

    The function currently incorrectly assumes all the __builtin_clz* and .=
CLZ
    calls have non-negative result.  That is the case of the former which i=
s UB
    on zero and has [0, prec-1] return value otherwise, and is the case of =
the
    single argument .CLZ as well (again, UB on zero), but for two argument
    .CLZ is the case only if the second argument is also nonnegative (or if=
 we
    know the argument can't be zero, but let's do that just in the ranger
IMHO).

    The following patch does that.

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

            PR tree-optimization/115337
            * fold-const.c (tree_call_nonnegative_warnv_p) <CASE_CFN_CLZ>:
            If fn is CFN_CLZ, use CLZ_DEFINED_VALUE_AT.

    (cherry picked from commit b82a816000791e7a286c7836b3a473ec0e2a577b)=