I would like to keep the time spent in the optimizer itself to a minimum.  Also, it should keep focused on patterns that actually occur in code as opposed to contrived bits of code.   Tim and Guido let us put it the optimizer only on the condition that it be kept simple and with low overhead.   The work that has been needed for a long time was to move a number of the optimizations (such as constant folding) out of the peepholer optimizer and replace them with AST manipulations just upstream from code generation (to reduce the need for the peepholer to partially disassemble and re-interpret the bytecode).