[Bug tree-optimization/64992] More optimize opportunity

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64992

--- Comment #12 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:418b71c0d535bf91df78bad2e198c57934682eaa

commit r13-2048-g418b71c0d535bf91df78bad2e198c57934682eaa
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Mon Aug 15 17:39:47 2022 +0100

    PR tree-optimization/64992: (B << 2) != 0 is B when B is Boolean.

    This patch resolves both PR tree-optimization/64992 and PR
    tree-optimization/98956 which are missed optimization enhancement
    request, for which Andrew Pinski already has a proposed solution
    (related to a fix for PR tree-optimization/98954).  Yesterday,
    I proposed an alternate improved patch for PR98954, which although
    superior in most respects, alas didn't address this case [which
    doesn't include a BIT_AND_EXPR], hence this follow-up fix.

    For many functions, F(B), of a (zero-one) Boolean value B, the
    expression F(B) != 0 can often be simplified to just B.  Hence
    "(B * 5) != 0" is B, "-B != 0" is B, "bswap(B) != 0" is B,
    "(B >>r 3) != 0" is B.  These are all currently optimized by GCC,
    with the strange exception of left shifts by a constant (possibly
    due to the undefined/implementation defined behaviour when the
    shift constant is larger than the first operand's precision).
    This patch adds support for this particular case, when the shift
    constant is valid.

    2022-08-15  Roger Sayle  <roger@nextmovesoftware.com>

    gcc/ChangeLog
            PR tree-optimization/64992
            PR tree-optimization/98956
            * match.pd (ne (lshift @0 @1) 0): Simplify (X << C) != 0 to X
            when X is zero_one_valued_p and the shift constant C is valid.
            (eq (lshift @0 @1) 0): Likewise, simplify (X << C) == 0 to !X
            when X is zero_one_valued_p and the shift constant C is valid.

    gcc/testsuite/ChangeLog
            PR tree-optimization/64992
            * gcc.dg/pr64992.c: New test case.