swift234

SILPassManager: A new method to reduce the number of SIL pass runs.

It avoids that a pass runs a second time if didn't make any changes in the previous run and no other pass changed the function in between.
rdar://problem/20336764

In this change I also removed the CompleteFunctions analysis which is now obsolete.

Some measurements with swiftbench (-wmo, single threaded):
It reduces the number of pass runs by about 28%. Because only passes are skipped that don't do anything, the effect on compile time is not so dramatic.
The time spent in runSILOptimizationPasses is reduced by ~9% which gives a total compile time reduction of about 3%.




Swift SVN r26757