This patch is an effort to simplify cascading jumps to return label in such case:

This patch is an effort to simplify cascading jumps to return label in such case:

   return (?(?(?:):(?:)):(?(?:):(?:(?:))));

In this return statement, expression is Conditional (could be recursive) but just branches to
accumulator values. In tridition, each Conditional expression would yeild a jump to 'done'
internal label, then cascading-jumps occur from inner-most one to out-most one. I think it should 
be faster to jump to 'return_label_' by single step instead of cascading jumps if following requirements are met:
1) Such Conditional expression is not encapculated as part of binary operation
2) Such Conditional expression is not encapculated as part of function arguments
Both tools/presubmit.py and tools/test.py got passed. Please kindly help review and comment.