[Bug tree-optimization/97325] [11 Regression] wrong code with __builtin_ffs() at -O2

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97325

--- Comment #7 from CVS 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:600cf1128e49f086522bfddc54490b4e39e30383

commit r11-3743-g600cf1128e49f086522bfddc54490b4e39e30383
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri Oct 9 10:16:57 2020 +0200

    match.pd: Fix up FFS -> CTZ + 1 optimization [PR97325]

    And no testcase was included, I'm including one below.

    Anyway, this PR and the other CTZ related discussions led me to discover a
    bug I've made earlier, CLZ/CTZ builtins have unsigned arguments and e.g.
    both the vr-values.cc and now gimple-range.cc code heavily relies on that,
    but __builtin_ffs has a signed operand and this optimization was
incorrectly
    making the operand signed too, so I guess it would greatly confuse VRP in
    some cases.

    2020-10-09  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/97325
            * match.pd (FFS(nonzero) -> CTZ(nonzero) + 1): Cast argument to
            corresponding unsigned type.

            * gcc.c-torture/execute/pr97325.c: New test.