Avoid allocations in `splitAtList` (#18535)
Avoid allocations in splitAtList
(#18535)
As suspected by @simonpj in #18535, avoiding allocations in
GHC.Utils.Misc.splitAtList
when there are no leftover arguments is
beneficial for performance:
On CI validate-x86_64-linux-deb9-hadrian:
T12227 -7%
T12545 -12.3%
T5030 -10%
T9872a -2%
T9872b -2.1%
T9872c -2.5%