POP operations are backward-propagated.
Operation can't be transformed if its result is moved within stack
(by DUP, DUP_X1, DUP_X2, DUP2, DUP2_X1, DUP2_X2, or SWAP).
Unnecessary operations are replaced with NOPs (for debugger).
Unnecessary NOPs are removed.
KT-9922 Suboptimal generation for simple safe call with unused return value
KT-11116 Optimize methods returning Unit
