[Bug lto/106129] [12 Regression] LTO option merging broken

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106129

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:d2892faac6d760ebc47f8f6ebee51e5cf6255cc8

commit r12-8628-gd2892faac6d760ebc47f8f6ebee51e5cf6255cc8
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Thu Jun 30 16:41:40 2022 +0000

    lto: Fix option merging [PR106129]

    The LTO merging of options from different input files was broken by:

    commit 227a2ecf663d69972b851f51f1934d18927b62cd
    Author: Martin Liska <mliska@suse.cz>
    Date:   Fri Mar 12 11:53:47 2021 +0100

        lto-wrapper: Use vec<cl_decoded_option> data type.

    Previously, find_and_merge_options would merge options it read into
    those in *opts. After this commit, options in *opts on entry to
    find_and_merge_options are ignored; the only merging that takes place
    is between multiple sets of options in the same input file that are
    read in the same call to this function (not sure how that case can
    occur at all). The effects include, for example, that if some objects
    are built with PIC enabled and others with it disabled, and the last
    LTO object processed has PIC enabled, the choice of PIC for the last
    object will result in the whole program being built as PIC, when the
    merging logic is intended to ensure that a mixture of PIC and non-PIC
    objects results in the whole program being built as non-PIC.

    Fix this with an extra argument to find_and_merge_options to determine
    whether merging should take place.  This shows up a second issue with
    that commit (which I think wasn't actually intended to change code
    semantics at all): once merging is enabled again, the check for
    -Xassembler options became an infinite loop in the case where both
    inputs had -Xassembler options, with the same first option, so fix
    that loop to restore the previous semantics.

    Note that I'm not sure how LTO option merging might be tested in the
    testsuite (clearly there wasn't sufficient, if any, coverage to detect
    these bugs).

    Bootstrapped with no regressions for x86_64-pc-linux-gnu.

            PR lto/106129
            * lto-wrapper.cc (find_option): Add argument start.
            (merge_and_complain): Loop over existing_opt_index and
            existing_opt2_index for Xassembler check.  Update calls to
            find_option.
            (find_and_merge_options): Add argument first to determine whether
            to merge options with those passed in *opts.
            (run_gcc): Update calls to find_and_merge_options.

    (cherry picked from commit 8a8ee37a3325f1009034245676ef4e482c0444a2)