This minor change to translate_chunk() reduces the checkout time of ^/subversion/trunk/subversion in my profiler by about 1% for me. If this has the same result on production code then this patch will probably safe quite a few trees.
This part of the code was imported from stefan2's performance branch. More profiling results (especially from stefan2) welcome.
* subversion/libsvn_subr/subst.c (translate_chunk): Lose temporary variable and use boolean operators instead of bitwise.