[Bug ld/28827] [2.38 Regression] ld hits assertion building LLVM 9 on powerpc64le-linux-gnu

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28827

--- Comment #4 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot 
gnu.org> ---
The master branch has been updated by Alan Modra <amodra@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=0441f94fba61998b4bd18487aacf70a672df099c

commit 0441f94fba61998b4bd18487aacf70a672df099c
Author: Alan Modra <amodra@gmail.com>
Date:   Fri Jan 28 09:46:13 2022 +1030

    PR28827, assertion building LLVM 9 on powerpc64le-linux-gnu

    The assertion is this one in ppc_build_one_stub
      BFD_ASSERT (stub_entry->stub_offset >=
stub_entry->group->stub_sec->size);
    It is checking that a stub doesn't overwrite the tail of a previous
    stub, so not something trivial.

    Normally, stub sizing iterates until no stubs are added, detected by
    no change in stub section size.  Iteration also continues if no stubs
    are added but one or more stubs increases in size, which also can be
    detected by a change in stub section size.  But there is a
    pathological case where stub section sizing decreases one iteration
    then increases the next.  To handle that situation, stub sizing also
    stops at more than STUB_SHRINK_ITER (20) iterations when calculated
    stub section size is smaller.  The previous larger size is kept for
    the actual layout (so that building the stubs, which behaves like
    another iteration of stub sizing, will see the stub section sizes
    shrink).  The problem with that stopping condition is that it assumes
    that stub sizing is only affected by addresses external to the stub
    sections, which isn't always true.

    This patch fixes that by also keeping larger individual stub_offset
    addresses past STUB_SHRINK_ITER.  It also catches a further
    pathological case where one stub shrinks and another expands in such a
    way that no stub section size change is seen.

            PR 28827
            * elf64-ppc.c (struct ppc_link_hash_table): Add stub_changed.
            (STUB_SHRINK_ITER): Move earlier in file.
            (ppc_size_one_stub): Detect any change in stub_offset.  Keep
            larger one if past STUB_SHRINK_ITER.
            (ppc64_elf_size_stubs): Iterate on stub_changed too.

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