[Bug tree-optimization/102134] [12 Regression] wrong code at -O1

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102134

--- Comment #10 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:74cb45e67d14624c3e2fafa99a8920d1866a5f0c

commit r12-3372-g74cb45e67d14624c3e2fafa99a8920d1866a5f0c
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Mon Sep 6 22:48:53 2021 +0100

    Correct implementation of wi::clz

    As diagnosed with Jakub and Richard in the analysis of PR 102134, the
    current implementation of wi::clz has incorrect/inconsistent behaviour.
    As mentioned by Richard in comment #7, clz should (always) return zero
    for negative values, but the current implementation can only return 0
    when precision is a multiple of HOST_BITS_PER_WIDE_INT.  The fix is
    simply to reorder/shuffle the existing tests.

    2021-09-06  Roger Sayle  <roger@nextmovesoftware.com>

    gcc/ChangeLog
            * wide-int.cc (wi::clz): Reorder tests to ensure the result
            is zero for all negative values.