[Bug middle-end/22141] [5/6/7 Regression] Missing optimization when storing structures

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=22141

--- Comment #47 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Author: jakub
Date: Mon Oct 30 11:04:49 2017
New Revision: 254213

URL: https://gcc.gnu.org/viewcvs?rev=254213&root=gcc&view=rev
Log:
        PR middle-end/22141
        * gimple-ssa-store-merging.c: Include rtl.h and expr.h.
        (struct store_immediate_info): Add bitregion_start and bitregion_end
        fields.
        (store_immediate_info::store_immediate_info): Add brs and bre
        arguments and initialize bitregion_{start,end} from those.
        (struct merged_store_group): Add bitregion_start, bitregion_end,
        align_base and mask fields.  Drop unnecessary struct keyword from
        struct store_immediate_info.  Add do_merge method.
        (clear_bit_region_be): Use memset instead of loop storing zeros.
        (merged_store_group::do_merge): New method.
        (merged_store_group::merge_into): Use do_merge.  Allow gaps in between
        stores as long as the surrounding bitregions have no gaps.
        (merged_store_group::merge_overlapping): Use do_merge.
        (merged_store_group::apply_stores): Test that bitregion_{start,end}
        is byte aligned, rather than requiring that start and width are
        byte aligned.  Drop unnecessary struct keyword from
        struct store_immediate_info.  Allocate and populate also mask array.
        Make start of the arrays relative to bitregion_start rather than
        start and size them according to bitregion_{end,start} difference.
        (struct imm_store_chain_info): Drop unnecessary struct keyword from
        struct store_immediate_info.
        (pass_store_merging::gate): Punt if BITS_PER_UNIT or CHAR_BIT is not 8.
        (pass_store_merging::terminate_all_aliasing_chains): Drop unnecessary
        struct keyword from struct store_immediate_info.
        (imm_store_chain_info::coalesce_immediate_stores): Allow gaps in
        between stores as long as the surrounding bitregions have no gaps.
        Formatting fixes.
        (struct split_store): Add orig non-static data member.
        (split_store::split_store): Initialize orig to false.
        (find_constituent_stmts): Return store_immediate_info *, non-NULL
        if there is exactly a single original stmt.  Change stmts argument
        to pointer from reference, if NULL, don't push anything to it.  Add
        first argument, use it to optimize skipping over orig stmts that
        are known to be before bitpos already.  Simplify.
        (split_group): Return unsigned int count how many stores are or
        would be needed rather than a bool.  Add allow_unaligned argument.
        Change split_stores argument from reference to pointer, if NULL,
        only do a dry run computing how many stores would be produced.
        Rewritten algorithm to use both alignment and misalign if
        !allow_unaligned and handle bitfield stores with gaps.
        (imm_store_chain_info::output_merged_store): Set start_byte_pos
        from bitregion_start instead of start.  Compute allow_unaligned
        here, if true, do 2 split_group dry runs to compute which one
        produces fewer stores and prefer aligned if equal.  Punt if
        new count is bigger or equal than original before emitting any
        statements, rather than during that.  Remove no longer needed
        new_ssa_names tracking.  Replace num_stmts with
        split_stores.length ().  Use 32-bit stack allocated entries
        in split_stores auto_vec.  Try to reuse original store lhs/rhs1
        if possible.  Handle bitfields with gaps.
        (pass_store_merging::execute): Ignore bitsize == 0 stores.
        Compute bitregion_{start,end} for the stores and construct
        store_immediate_info with that.  Formatting fixes.

        * gcc.dg/store_merging_10.c: New test.
        * gcc.dg/store_merging_11.c: New test.
        * gcc.dg/store_merging_12.c: New test.
        * g++.dg/pr71694.C: Add -fno-store-merging to dg-options.

Added:
    trunk/gcc/testsuite/gcc.dg/store_merging_10.c
    trunk/gcc/testsuite/gcc.dg/store_merging_11.c
    trunk/gcc/testsuite/gcc.dg/store_merging_12.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/gimple-ssa-store-merging.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/g++.dg/pr71694.C