[Bug optimization/12082] [3.3/3.4 regression] Inappropriate unreachable code warnings

["janis187 at us dot ibm dot com" <gcc-bugzilla@gcc.gnu.org>]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12082


janis187 at us dot ibm dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jh at suse dot cz


------- Additional Comments From janis187 at us dot ibm dot com  2003-08-29 00:09 -------
The regression in PR 12082 was introduced or exposed by this patch:

--- gcc/gcc/ChangeLog ---

Don Feb 28 11:07:36 CET 2002  Jan Hubicka  <jh@suse.cz>

        * basic-block.h (BB_REACHABLE): Renumber.
        (BB_DIRTY, BB_NEW): New flags.
        (clear_bb_flags): Declare.
        (update_life_info_in_dirty_blocks): Declare.
        * cfg.c (clear_bb_flags): New function.
        * cfgrtl.c (create_basic_block_structure): Set flags to BB_NEW.
        * emit-rtl.c (add_insn_after, add_insn_before, remove_insn,
        reorder_insns, emit_insn_after): Mark block as dirty.
        * flow.c (update_life_info): Fix clearing of PROP_LOG_LINKS.
        (update_life_info_in_dirty_blocks): New function.
        * recog.c (apply_change_group): Dirtify block.

        * cse.c (cse_insn): Reorder emitting of jump insn to keep
        cfg consistent.
        * gcse.c (delete_null_pointer_checks): Likewise.

        * toplev.c (dump_file_index): Move cse2 after bp,
        add DFI_null
        (dump_file_info): Similary.
        (rest_of_compilation): Avoid most of CFG rebuilds;
        do first if converision after null pointer checks, do cse2
        after branch prediction; avoid full liveness rebuild after
        initializing subregs.
        * invoke.texi (-d options): Document -du, renumber.

        * cfgcleanup.c (bb_flags): Remove BB_UPDATE_LIFE.
        (notice_new_block): Do not set BB_UPDATE_LIFE.
        (try_forward_edges, merge_blocks_move_predecessor_nojumps,
         merge_blocks_move_successor_nojumps, merge_blocks,
         try_crossjump_to_edge): Likewise.
        (try_optimize_cfg): Likewise; use update_life_info_in_dirty_blocks.
        * cfgrtl.c (merge_blocks_nomove): Copy b's flags to a.
        * ifcvt.c (SET_UPDATE_LIFE, UPDATE_LIFE): Kill.
        (merge_of_block): Do not use life_data_ok.
        (find_if_case_1): Do not use SET_UPDATE_LIFE.
        (if_convert): Use BB_DIRTY mechanizm to update life.
        * lcm.c (optimize_mode_switching): Update
        update_life_info_in_dirty_blocks

The regression hunt took place on i686-pc-linux-gnu using Wolfgang's
small test case from comment #7 compiled with "-O3 -Wunreachable-code".