The idea of this patch is to continue the scheduler state over a MBB boundary in the case where the successor block has only one predecessor. This means that the scheduler will continue in the successor block (after emitting any branch instructions) with e.g. maintained processor resource counters. Benchmarks seem to benefit from this.
In order to do this the single HazardRecognizer is replaced with a map so that each MBB gets its own HazardRecognizer. This represent the outgoing state of that MBB. Another block which is only reached from MBB can then later take that state before beginning its first region.
*All* instructions are emitted, so that the state of the scheduler is as good as possible at the entry of the region. This means branches and also singular instructions before regions / in small MBBs.
Special care is taken for blocks with a call (which is about the only scheduling boundary on SystemZ), so that only the instructions after the call are part of the final scheduler state.
The only common code change needed is to set the MachineLoopInfo* pointer (that analysis pass seems to have been required also for post-RA scheduling, but not used for some reason).