[Bug tree-optimization/79095] [7 regression] spurious stringop-overflow warning

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79095

--- Comment #13 from Jeffrey A. Law <law at gcc dot gnu.org> ---
Author: law
Date: Tue Feb 14 15:54:09 2017
New Revision: 245434

URL: https://gcc.gnu.org/viewcvs?rev=245434&root=gcc&view=rev
Log:
        PR tree-optimization/79095
        * tree-vrp.c (extract_range_from_binary_expr_1): For EXACT_DIV_EXPR,
        if the numerator has the range ~[0,0] make the resultant range ~[0,0].
        (extract_range_from_binary_expr): For MINUS_EXPR with no derived range,
        if the operands are known to be not equal, then the resulting range
        is ~[0,0].
        (intersect_ranges): If the new range is ~[0,0] and the old range is
        wide, then prefer ~[0,0].
        * tree-vrp.c (overflow_comparison_p_1): New function.
        (overflow_comparison_p): New function.
        * tree-vrp.c (register_edge_assert_for_2): Register additional asserts
        if NAME is used in an overflow test.
        (vrp_evaluate_conditional_warnv_with_ops): If the ops represent an
        overflow check that can be expressed as an equality test, then adjust
        ops to be that equality test.

        PR tree-optimization/79095
        * g++.dg/pr79095-1.C: New test
        * g++.dg/pr79095-2.C: New test
        * g++.dg/pr79095-3.C: New test
        * g++.dg/pr79095-4.C: New test
        * g++.dg/pr79095-5.C: New test
        * gcc.c-torture/execute/arith-1.c: Update with more cases.
        * gcc.dg/tree-ssa/pr79095-1.c: New test.

Added:
    trunk/gcc/testsuite/g++.dg/pr79095-1.C
    trunk/gcc/testsuite/g++.dg/pr79095-2.C
    trunk/gcc/testsuite/g++.dg/pr79095-3.C
    trunk/gcc/testsuite/g++.dg/pr79095-4.C
    trunk/gcc/testsuite/g++.dg/pr79095-5.C
    trunk/gcc/testsuite/gcc.dg/tree-ssa/pr79095.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.c-torture/execute/arith-1.c
    trunk/gcc/tree-vrp.c