[Bug ld/30358] bfd very slow (> 4 minutes) to link busybox with -Wl,--sort-section,alignment (regression in binutils-2.40) since af31506c31a59a6edbb13498d6075fa704b801cd

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30358

--- Comment #13 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot 
gnu.org> ---
The master branch has been updated by Michael Matz <matz@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=670c91c0c5eb3fb16d42fe5b2d48a33c64e3ec52

commit 670c91c0c5eb3fb16d42fe5b2d48a33c64e3ec52
Author: Michael Matz <matz@suse.de>
Date:   Tue Apr 25 17:10:05 2023 +0200

    Fix PR30358, performance with --sort-section

    since af31506c we only use the binary tree when section sorting is
    required.  While its unbalanced and hence can degrade to a linear list
    it should otherwise have been equivalent to the old code relying on
    insertion sort.  Unfortunately it was not.  The old code directly used
    lang_add_section to populate the sorted list, the new code first
    populates the tree and only then does lang_add_section on the sorted
    result.

    In the testcase we have very many linkonce section groups, and hence
    lang_add_section won't actually insert anything for most of them.  That
    limited the to-be-sorted list length previously.  The tree-sorting code
    OTOH first created a tree of all candidates sections, including those
    that wouldn't be inserted by lang_add_section, hence increasing the size
    of the sorting problem.  In the testcase the chain length went from
    about 1500 to 106000, and in the degenerated case (as in the testcase)
    that goes in quadratically.

    This splits out most of the early-out code from lang_add_section to its
    own function and uses the latter to avoid inserting into the tree.  This
    refactoring slightly changes the order of early-out tests (the ones
    based on section flags is now done last, and only in lang_add_section).
    The new function is not a pure predicate: it can give warnings and it
    might change output_section, like the old early-out code did.  I have
    also added a skip-warning case in the first discard case, whose
    non-existence seemed to have been an oversight.

            PR 30358
            * ldlang.c (wont_add_section_p): Split out from ...
            (lang_add_section): ... here.
            (output_section_callback_sort): Use wont_add_section_p to not
            always add sections to the sort tree.

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