gcse.c: Update comment at top.

gcse.c: Update comment at top.

        * gcse.c: Update comment at top.
        Update comment on mem handling.
        mem_last_set, mem_first_set, mem_set_in_block: gone.
        Declaration of reg_set_info: gone.
        (oprs_unchanged_p): Don't use mem_*set_* anymore. They are
        pointless with load_killed_in_block_p (they are *more*
        conservative then it, not less, and less accurate).
        (oprs_not_set_p): Ditto.
        (alloc_gcse_mem): Don't allocate mem_set_in_block
        (free_gcse_mem): Don't free it, either.
        (record_last_mem_set_info): Update comment in front, remove
        mem_*set_* stuff. Note the reason we don't handle stores directly
        here.
        (compute_hash_table): Update comments to reflect reality. Remove
        mem_*set_* references.
        (reset_opr_set_tables): Remove mem_*set_* references.
        (mark_call): Ditto.
        (mark_set): Ditto.  Also remove double sets of bitmaps for REG's.
        (mark_clobber): Ditto (on both parts, we double set here too).
        (expr_killed_p): Remove mem_set_in_block test.
        (compute_transp): Remove mem_set_in_block test.

From-SVN: r44055