tree 1d181363feb40c317a1bd40c908320090f874030
parent 0c8b7cdb5a97f1132859459bbbd132a22c6c6829
author Daniel Dunbar <daniel_dunbar@apple.com> 1494492521 -0700
committer Daniel Dunbar <daniel_dunbar@apple.com> 1494498406 -0700

Intern build description strings.

 - It is common to have many duplicated strings in a loaded build description
   file (typically from command line arguments), so this patch optimizes the
   memory use of the build description by interning these strings while loading.

 - While we pay some cost for the interning itself, on the other hand this
   allows avoiding what would otherwise be additional allocations in many cases,
   so the interning ends up paying for itself while reducing memory footprint &
   improving cache locality. On the balance my tests indicate this is a wash to
   small improvement in terms of CPU use.

 - <rdar://problem/32128433> Intern build description strings