[Bug tree-optimization/107919] Possibly false-positive "maybe-uninitialized" with GCC 12 on complex variant-variant-tuple-unique_ptr types

[cvs-commit at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107919

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rgue...@gcc.gnu.org>:

https://gcc.gnu.org/g:b628cad9e093f7a33042fb9dd647f183394eefae

commit r13-4408-gb628cad9e093f7a33042fb9dd647f183394eefae
Author: Richard Biener <rguent...@suse.de>
Date:   Wed Nov 30 12:05:29 2022 +0100

    tree-optimization/107919 - predicate simplification in uninit

    The testcase from the PR at -O2 shows

        ((_277 == 2) AND (_79 == 0))
        OR ((NOT (_277 == 0)) AND (NOT (_277 > 2)) AND (NOT (_277 == 2)) AND
(_79 == 0))
        OR ((NOT (pretmp_300 == 255)) AND (_277 == 0) AND (NOT (_277 > 2)) AND
(NOT (_277 == 2)) AND (_79 == 0))

    which we fail to simplify.  The following patch makes us simplify
    the relations on _277, producing

        ((_79 == 0) AND (_277 == 2))
        OR ((_79 == 0) AND (_277 <= 1) AND (NOT (_277 == 0)))
        OR ((_79 == 0) AND (_277 == 0) AND (NOT (pretmp_300 == 255)))

    which might be an incremental step to resolve a bogus uninit
    diagnostic at -O2.  The patch uses maybe_fold_and_comparison for this.

            PR tree-optimization/107919
            * gimple-predicate-analysis.cc (simplify_1): Rename to ...
            (simplify_1a): .. this.
            (simplify_1b): New.
            (predicate::simplify): Call both simplify_1a and simplify_1b.