RFA: patch solving one IRA problem reported in PR37243

[Vladimir Makarov]

The following patch solves IRA regression on pr36222 and p36246 of gcc
testsuite.  The analysis of the problem could be found in

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37243

The patch has been bootstrapped sucessfully on x86_64.  It also
improves SPEC results at least for x86.

2008-08-29  Vladimir Makarov  <vmakarov@redhat.com>

    PR rtl-opt/37243

    * ira-conflicts.c (REG_SUBREG_P, go_through_subreg): New.
    (process_regs_for_copy): Process subregs.  Refine check when cost
    is taken into account in ira-costs.c.
    (process_reg_shuffles): Use REG_SUBREG_P.
    (add_insn_allocno_copies): Ditto.  Ignore modes.

    * ira-color.c (conflict_allocno_vec): New.
    (COST_HOP_DIVISOR): New macro.
    (update_copy_costs_1): Use it.
    (update_conflict_hard_regno_costs): New function.
    (assign_hard_reg): Use it.
    (ira_color): Allocate and free conflict_allocno_vec.
    

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