[Bug tree-optimization/90879] fold zero-equality of strcmp between a longer string and a smaller array

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90879

--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
Author: msebor
Date: Wed Oct  9 21:35:11 2019
New Revision: 276773

URL: https://gcc.gnu.org/viewcvs?rev=276773&root=gcc&view=rev
Log:
PR tree-optimization/90879 - fold zero-equality of strcmp between a longer
string and a smaller array

gcc/c-family/ChangeLog:

        PR tree-optimization/90879
        * c.opt (-Wstring-compare): New option.

gcc/testsuite/ChangeLog:

        PR tree-optimization/90879
        * gcc.dg/Wstring-compare-2.c: New test.
        * gcc.dg/Wstring-compare.c: New test.
        * gcc.dg/strcmpopt_3.c: Scan the optmized dump instead of strlen.
        * gcc.dg/strcmpopt_6.c: New test.
        * gcc.dg/strlenopt-65.c: Remove uinnecessary declarations, add
        test cases.
        * gcc.dg/strlenopt-66.c: Run it.
        * gcc.dg/strlenopt-68.c: New test.

gcc/ChangeLog:

        PR tree-optimization/90879
        * builtins.c (check_access): Avoid using maxbound when null.
        * calls.c (maybe_warn_nonstring_arg): Adjust to get_range_strlen
change.
        * doc/invoke.texi (-Wstring-compare): Document new warning option.
        * gimple-fold.c (get_range_strlen_tree): Make setting maxbound
        conditional.
        (get_range_strlen): Overwrite initial maxbound when non-null.
        * gimple-ssa-sprintf.c (get_string_length): Adjust to get_range_strlen
        changes.
        * tree-ssa-strlen.c (maybe_diag_stxncpy_trunc): Same.
        (used_only_for_zero_equality): New function.
        (handle_builtin_memcmp): Call it.
        (determine_min_objsize): Return an integer instead of tree.
        (get_len_or_size, strxcmp_eqz_result): New functions.
        (maybe_warn_pointless_strcmp): New function.
        (handle_builtin_string_cmp): Call it.  Fold zero-equality of strcmp
        between a longer string and a smaller array.
        (get_range_strlen_dynamic): Overwrite initial maxbound when non-null.


Added:
    trunk/gcc/testsuite/gcc.dg/Wstring-compare-2.c
    trunk/gcc/testsuite/gcc.dg/Wstring-compare.c
    trunk/gcc/testsuite/gcc.dg/strcmpopt_6.c
    trunk/gcc/testsuite/gcc.dg/strlenopt-69.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/builtins.c
    trunk/gcc/c-family/ChangeLog
    trunk/gcc/c-family/c.opt
    trunk/gcc/calls.c
    trunk/gcc/doc/invoke.texi
    trunk/gcc/gimple-fold.c
    trunk/gcc/gimple-ssa-sprintf.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.dg/strcmpopt_3.c
    trunk/gcc/testsuite/gcc.dg/strlenopt-65.c
    trunk/gcc/testsuite/gcc.dg/strlenopt-66.c
    trunk/gcc/tree-ssa-strlen.c