This function is responsible for 2.2% of all heap allocation (calls) in CL.
This change avoids all of them in the (presumably) common case where none of
the parameters require splitting. It also slightly reduces the compiler's
instruction count.
This function is responsible for 8.5% of all heap allocation (calls) in CL.
This change avoids almost all of them by using a SmallVec::<[Value; 32]>
instead. Dynamic instruction count falls by 0.25%. The fixed size of 32 was
arrived at after profiling with fixed sizes of 1, 2, 4, 8, 16, 32, 64 and 128.
32 is as high as I can push it without the instruction count starting to creep
up again, and gets almost all the block-reduction win of 64 and 128.
