PR84068, PR83459: Fix sort order of SCHED_PRESSURE_MODEL

PR84068, PR83459: Fix sort order of SCHED_PRESSURE_MODEL

The comparison function for SCHED_PRESSURE_MODEL is incorrect.  If either
instruction is not in target_bb, the ordering is not well defined.
Since all instructions outside the target_bb get the highest model_index,
all we need to do is sort on model_index.  If the model_index is the same
we defer to RFS_DEP_COUNT and/or RFS_TIE.

    gcc/
	PR rtl-optimization/84068
	PR rtl-optimization/83459
	* haifa-sched.c (rank_for_schedule): Fix SCHED_PRESSURE_MODEL sorting.

    gcc/testsuite
	PR rtl-optimization/84068
	PR rtl-optimization/83459
	* gcc.dg/pr84068.c: New test.

From-SVN: r257481