The following patch improves inheritance for PR64317 testcase

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64317

   I ran a lot SPEC2000 benchmarks to get better default parameter value 
for EBB_PROBABILITY_CUTOFF in LRA inheritance. The new default parameter 
value improves SPECInt2000 by 0.4% on x86-64 without changing SPECFP2000 
rate.  The code size changes are insignificant (0.002% increase for 
SPECInt and 0.01% decrease for SPECFP).

The patch was bootstrapped and tested on x86-64.

Committed as rev.221070.

2015-02-27  Vladimir Makarov  <vmakarov@redhat.com>

         PR target/64317
         * params.def (PARAM_LRA_INHERITANCE_EBB_PROBABILITY_CUTOFF): New.
         * params.h (LRA_INHERITANCE_EBB_PROBABILITY_CUTOFF): New.
         * lra-constraints.c (EBB_PROBABILITY_CUTOFF): Use
         LRA_INHERITANCE_EBB_PROBABILITY_CUTOFF.
         (lra_inheritance): Use '<' instead of '<=' for
         EBB_PROBABILITY_CUTOFF.
         * doc/invoke.texi (lra-inheritance-ebb-probability-cutoff):
         Document change.