class MachineBlockFrequencyInfo;
/// BlockFrequencyImpl implements block frequency algorithm for IR and
-/// Machine Instructions. Algorithm starts with value 1024 (START_FREQ)
+/// Machine Instructions. Algorithm starts with value ENTRY_FREQ
/// for the entry block and then propagates frequencies using branch weights
/// from (Machine)BranchProbabilityInfo. LoopInfo is not required because
/// algorithm can find "backedges" by itself.