Today we continue to read the WRL research report on the Swift Java Compiler. We were discussing method splitting and the criteria for the splitting point. We now look at Global Common SubExpression elimination and global code motion. Swift applies CSE to any two values that are equivalent no matter where they occur in the control flow graph. Even if neither of the two values are dominant, one value is replaced by the other. Global CSE is followed by a pass of global code motion, which places values in blocks so that all the values dominate all their users.
Two values are considered equivalent if they have identical operations and equivalent inputs. During the CSE, Swift computes equivalent values via a partitioning algorithm that splits all values into initial partitions based solely on their operation fields and puts the partitions on a work-list.  The work list is the set of values that are not necessarily equivalent. Each time it takes a partition P of the work list, it builds the set of values Si which takes one of the values in the partition as the ith input. If there is a partition Q which has some set of its values Q prime but not all of its values in Si, then it is split up into Q prime and the remaining and the smaller of the two partitions is added to the wordlist. This way Swift builds up each partition to have all values equivalent
Double GetAlternateOddNumberRangeSumCubeRootFourthSquare (Double [] A)

{

if (A == null) return 0;

Return A.AlternateOddNumberRangeSumCubeRootFourthSquare();

}