Considering merge optimizations from Timsort in __move_merge_adaptive, __move_merge_adaptive_backward

[jrmarsha <jrmarsha at mtu dot edu>]

Hello all,

I've been implementing a new version of Timsort in C++ using more 
standard facilities.  One thing I've come across which adds a divide 
between a larger codebase and faster code is the implementation of 
std::inplace_merge with sufficient memory.  This goes to the specific 
functions  __move_merge_adaptive, and __move_merge_adaptive_backward.  
In particular, there is an optimization where each insertion searches 
for the maximum number of elements it can move.  A brief in context 
explanation is here: 
https://en.wikipedia.org/wiki/Timsort#Individual_merges .  Would such a 
trick have a place in glibc or is the overhead likely too great in the 
general case?