[Bug tree-optimization/91645] Missed optimization with sqrt(x*x)

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91645

--- Comment #14 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:e02c9d9116f243643c0daba8dbcc5d1795c827c3

commit r13-6956-ge02c9d9116f243643c0daba8dbcc5d1795c827c3
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri Mar 31 13:41:34 2023 +0200

    range-op-float, value-range: Fix up handling of UN{LT,LE,GT,GE,EQ}_EXPR and
handle comparisons in get_tree_range [PR91645]

    When looking into PR91645, I've noticed we handle UN{LT,LE,GT,GE,EQ}_EXPR
    comparisons incorrectly.
    All those are unordered or ..., we correctly return [1, 1] if one or
    both operands are known NANs, and correctly ask the non-UN prefixed
    op to fold_range if neither operand may be NAN.
    But for the case where one or both operands may be NAN, we always
    return [0, 1].  The UN* fold_range tries to handle it by asking
    the non-UN prefixed fold_range and if it returns [1, 1] return that,
    if it returns [0, 0] or [0, 1] return [0, 1], which makes sense,
    because the maybe NAN means that it is the non-UN prefixed fold_range
    unioned with [1, 1] in case the maybe NAN is actually NAN at runtime.
    The problem is that the non-UN prefixed fold_range always returns [0, 1]
    because those fold_range implementations are like:
      if (op1.known_isnan () || op2.known_isnan ())
        r = range_false (type);
      else if (!maybe_isnan (op1, op2))
        {
    ...
        }
      else
        r = range_true_and_false (type);
    and so if maybe_isnan, they always return [0, 1].  Now, thinking about it,
    this is unnecessary pessimization, for the case where the ... block
    returns range_false (type) we actually could do it also if maybe_isnan
(op1,
    op2), because if one or both operands are NAN, the comparison will be
false,
    and if neither is NAN, the comparison will be also false.  Will fix
    incrementally today.
    Anyway, the following patch fixes it by asking the non-UN prefixed
    fold_range on ranges with NAN cleared, which I think does the right
    thing in all cases.

    Another change in the patch is that range_query::get_tree_range
    always returned VARYING for comparisons, this patch allows to ask about
    those as well (they are very much like binary ops, except they take
    the important type from the types of the operands rather than result).

    Initially I've developed this patch together with changes to
tree-call-cdce.cc,
    but those result in one regression and apparently aren't actually needed to
    fix this bug, the range-op-float.cc changes are enough.

    2023-03-31  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/91645
            * range-op-float.cc (foperator_unordered_lt::fold_range,
            foperator_unordered_le::fold_range,
            foperator_unordered_gt::fold_range,
            foperator_unordered_ge::fold_range,
            foperator_unordered_equal::fold_range): Call the ordered
            fold_range on ranges with cleared NaNs.
            * value-query.cc (range_query::get_tree_range): Handle also
            COMPARISON_CLASS_P trees.

            * gcc.target/i386/pr103559-1.c: New test.
            * gcc.target/i386/pr103559-2.c: New test.
            * gcc.target/i386/pr103559-3.c: New test.
            * gcc.target/i386/pr103559-4.c: New test.