These MachOps are used by addIntC# and subIntC#, which in turn are

used in integer-gmp when adding or subtracting small Integers. The

following benchmark showed a ~6% speedup with an earlier version of

this commit (building with BuildFlavour=perf).

{-# LANGUAGE MagicHash #-} import GHC.Exts import Criterion.Main count :: Int -> Integer count (I# n#) = go n# 0 where go :: Int# -> Integer -> Integer go 0# acc = acc go n# acc = go (n# -# 1#) $! acc + 1 main = defaultMain [bgroup "count" [bench "100" $ whnf count 100]]