This patch is the first step to implement proper usage of SHLD/SHRD on Machine Combiner level. At first the patch introduces proper sched model for these 2 instructions. And at second the patch adds new schedule test specially for SHLD/SHRD.
In the next patch I'm going to introduce the selection of the best code sequence (SHLD/SHRD or alternative) based on [latency:throughput] numbers.