[Bug ipa/108007] [11/12/13/14 Regression] wrong code at -Os and above with "-fno-dce -fno-tree-dce" on x86_64-linux-gnu

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108007

--- Comment #16 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Martin Jambor <jamborm@gcc.gnu.org>:

https://gcc.gnu.org/g:1be18ea110a2d69570dbc494588a7c73173883be

commit r14-4382-g1be18ea110a2d69570dbc494588a7c73173883be
Author: Martin Jambor <mjambor@suse.cz>
Date:   Tue Oct 3 18:44:51 2023 +0200

    ipa: Self-DCE of uses of removed call LHSs (PR 108007)

    PR 108007 is another manifestation where we rely on DCE to clean-up
    after IPA-SRA and if the user explicitely switches DCE off, IPA-SRA
    can leave behind statements which are fed uninitialized values and
    trap, even though their results are themselves never used.

    I have already fixed this for unused parameters in callees, this bug
    shows that almost the same thing can happen for removed returns, on
    the side of callers.  This means that the issue has to be fixed
    elsewhere, in call redirection.  This patch adds a function which
    looks for (and through, using a work-list) uses of operations fed
    specific SSA names and removes them all.

    That would have been easy if it wasn't for debug statements during
    tree-inline (from which call redirection is also invoked).  Debug
    statements are decoupled from the rest at this point and iterating
    over uses of SSAs does not bring them up.  During tree-inline they are
    handled especially at the end, I assume in order to make sure that
    relative ordering of UIDs are the same with and without debug info.

    This means that during tree-inline we need to make a hash of killed
    SSAs, that we already have in copy_body_data, available to the
    function making the purging.  So the patch duly does also that, making
    the interface slightly ugly.

    gcc/ChangeLog:

    2023-09-27  Martin Jambor  <mjambor@suse.cz>

            PR ipa/108007
            * cgraph.h (cgraph_edge): Add a parameter to
            redirect_call_stmt_to_callee.
            * ipa-param-manipulation.h (ipa_param_adjustments): Add a
            parameter to modify_call.
            * cgraph.cc (cgraph_edge::redirect_call_stmt_to_callee): New
            parameter killed_ssas, pass it to padjs->modify_call.
            * ipa-param-manipulation.cc (purge_transitive_uses): New function.
            (ipa_param_adjustments::modify_call): New parameter killed_ssas.
            Instead of substituting uses, invoke purge_transitive_uses.  If
            hash of killed SSAs has not been provided, create a temporary one
            and release SSAs that have been added to it.
            * tree-inline.cc (redirect_all_calls): Create
            id->killed_new_ssa_names earlier, pass it to edge redirection,
            adjust a comment.
            (copy_body): Release SSAs in id->killed_new_ssa_names.

    gcc/testsuite/ChangeLog:

    2023-05-11  Martin Jambor  <mjambor@suse.cz>

            PR ipa/108007
            * gcc.dg/ipa/pr108007.c: New test.