Raymond wrote in his recent response on issue2499 (a patch that adds
unary '+' and 'not' folding to peephole optimizer):

"""
 More importantly, we decided that the peepholer is the wrong place to 
do much of this work.  Most of the peepholer is going to be migrated 
up the chain, after the AST is generated, but before the opcodes are 
generated.  That is a faster, more reliable, and more general 
approach.
""" (See msg64618.)

This looks like the relevant patch.  I would like to take a look at the
patch, but since it is more than 2 years old, maybe someone has an
updated version.  Please advise.