On Oct 19, 2011, at 3:25 PM, Greg Ewing wrote:

                /* Simplify conditional jump to conditional jump where the

                   result of the first test implies the success of a similar

                   test or the failure of the opposite test.

                   Arises in code like:

                   "if a and b:"

                   "if a or b:"

                   "a and b or c"

                   "(a and b) and c"

                   x:JUMP_IF_FALSE_OR_POP y   y:JUMP_IF_FALSE_OR_POP z

                      -->  x:JUMP_IF_FALSE_OR_POP z

                   x:JUMP_IF_FALSE_OR_POP y   y:JUMP_IF_TRUE_OR_POP z

                      -->  x:POP_JUMP_IF_FALSE y+3

                   where y+3 is the instruction following the second test.

                */