[Bug tree-optimization/57359] store motion causes wrong code for union access at -O3

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57359

--- Comment #32 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:283cb9ea6293e813e48a1b769e1e0779918ea20a

commit r11-161-g283cb9ea6293e813e48a1b769e1e0779918ea20a
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Apr 27 14:45:54 2020 +0200

    tree-optimization/57359 - rewrite SM code

    This rewrites store-motion to process candidates where we can
    ensure order preserving separately and with no need to disambiguate
    against all stores.  Those candidates we cannot handle this way
    are validated to be independent on all stores (w/o TBAA) and then
    processed as "unordered" (all conditionally executed stores are so
    as well).

    This will necessary cause
      FAIL: gcc.dg/graphite/pr80906.c scan-tree-dump graphite "isl AST to
Gimple succeeded"
    because the SM previously performed is not valid for exactly the PR57359
    reason, we still perform SM of qc for the innermost loop but that's not
enough.

    There is still room for improvements because we still check some
constraints
    for the order preserving cases that are only necessary in the current
    strict way for the unordered ones.  Leaving that for the furture.

    2020-05-07  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/57359
            * tree-ssa-loop-im.c (im_mem_ref::indep_loop): Remove.
            (in_mem_ref::dep_loop): Repurpose.
            (LOOP_DEP_BIT): Remove.
            (enum dep_kind): New.
            (enum dep_state): Likewise.
            (record_loop_dependence): New function to populate the
            dependence cache.
            (query_loop_dependence): New function to query the dependence
            cache.
            (memory_accesses::refs_in_loop): Rename to ...
            (memory_accesses::refs_loaded_in_loop): ... this and change to
            only record loads.
            (outermost_indep_loop): Adjust.
            (mem_ref_alloc): Likewise.
            (gather_mem_refs_stmt): Likewise.
            (mem_refs_may_alias_p): Add tbaa_p parameter and pass it down.
            (struct sm_aux): New.
            (execute_sm): Split code generation on exits, record state
            into new hash-map.
            (enum sm_kind): New.
            (execute_sm_exit): Exit code generation part.
            (sm_seq_push_down): Helper for sm_seq_valid_bb performing
            dependence checking on stores reached from exits.
            (sm_seq_valid_bb): New function gathering SM stores on exits.
            (hoist_memory_references): Re-implement.
            (refs_independent_p): Add tbaa_p parameter and pass it down.
            (record_dep_loop): Remove.
            (ref_indep_loop_p_1): Fold into ...
            (ref_indep_loop_p): ... this and generalize for three kinds
            of dependence queries.
            (can_sm_ref_p): Adjust according to hoist_memory_references
            changes.
            (store_motion_loop): Don't do anything if the set of SM
            candidates is empty.
            (tree_ssa_lim_initialize): Adjust.
            (tree_ssa_lim_finalize): Likewise.

            * gcc.dg/torture/pr57359-1.c: New testcase.
            * gcc.dg/torture/pr57359-1.c: Likewise.
            * gcc.dg/tree-ssa/ssa-lim-14.c: Likewise.
            * gcc.dg/graphite/pr80906.c: XFAIL.