[Bug ipa/113907] [11/12/13/14 regression] ICU miscompiled since on x86 since r14-5109-ga291237b628f41

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113907

--- Comment #62 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:9f255e4baac68fc3568820cdca9412f67ff07940

commit r13-8451-g9f255e4baac68fc3568820cdca9412f67ff07940
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Mar 14 17:48:30 2024 +0100

    icf: Reset SSA_NAME_{PTR,RANGE}_INFO in successfully merged functions
[PR113907]

    AFAIK we have no code in LTO streaming to stream out or in
    SSA_NAME_{RANGE,PTR}_INFO, so LTO effectively throws it all away
    and let vrp1 and alias analysis after IPA recompute that.  There is
    just one spot, for IPA VRP and IPA bit CCP we save/restore ranges
    and set SSA_NAME_{PTR,RANGE}_INFO e.g. on parameters depending on what
    we saved and propagated, but that is after streaming in bodies for the
    post IPA optimizations.

    Now, without LTO SSA_NAME_{RANGE,PTR}_INFO is already computed from
    earlier in many cases (er.g. evrp and early alias analysis but other spots
    too), but IPA ICF is ignoring the ranges and points-to details when
    comparing the bodies.  I think ignoring that is just fine, that is
    effectively what we do for LTO where we throw that information away
    before the analysis, and not ignoring it could lead to fewer ICF merging
    possibilities.

    So, the following patch instead verifies that for LTO
SSA_NAME_{PTR,RANGE}_INFO
    just isn't there on SSA_NAMEs in functions into which other functions have
    been ICFed, and for non-LTO throws that information away (which matches the
    LTO behavior).

    Another possibility would be to remember the SSA_NAME <-> SSA_NAME mapping
    vector (just one of the 2) on successful sem_function::equals on the
    sem_function which is not the chosen leader (e.g. how SSA_NAMEs in the
    leader map to SSA_NAMEs in the other function) and use that vector
    to union the ranges in sem_function::merge.  I can implement that for
    comparison, but wanted to post this first if there is an agreement on
    doing that or if Honza thinks we should take SSA_NAME_{RANGE,PTR}_INFO
    into account.  I think we can compare SSA_NAME_RANGE_INFO, but have
    no idea how to try to compare points to info.  And I think it will result
    in less effective ICF for non-LTO vs. LTO unnecessarily.

    2024-03-12  Jakub Jelinek  <jakub@redhat.com>

            PR middle-end/113907
            * ipa-icf.cc (sem_item_optimizer::merge_classes): Reset
            SSA_NAME_RANGE_INFO and SSA_NAME_PTR_INFO on successfully ICF
merged
            functions.

            * gcc.dg/pr113907-1.c: New test.

    (cherry picked from commit 7580e39452b65ab5fb5a06f3f1ad7d59720269b5)