Remove redundant NOPs during bytecode optimization.
NOP instruction is required iff one of the following is true:
(a) it is a first bytecode instruction in a try-catch block (JVM BE assumption);
(b) it is a sole bytecode instruction in a source code line (breakpoints on that line will not work).
All other NOP instructions can be removed.
Note that it doesn't really affect the performance for mature JVM implementations.
However, the perceived quality of the generated code is somewhat improved :).
Related: KT-15609
Revert changes for "tolerant to uninitialized values" in OptimizationBasicInterpreter:
this approach doesn't converge for some specific cases where local variable is reused
(e.g., in several inlined functions - see https://youtrack.jetbrains.com/issue/KT-15112).
Instead, treat fake always-false conditional jump in the beginning of the post-condition loop as a "reference point" for stack on loop break / continue.
This requires an extra abstraction layer in FixStackAnalyzer, since we can't perform fine-grain manipulations on Frames
(such as "combine frame C from local variables of frame A and stack of frame B").
NB additional NOPs will be generated for post-condition loops.
Should make a separate bytecode postprocessing pass to get rid of unnecessary NOPs
(several YT issues for perceived quality of the generated bytecode are about such NOPs).
Otherwise linenumber for previous instruction will be used in debugger. That can lead to error stepping
because it might be line that isn't reachable on current iteration.
#KT-13059 Fixed
Dmitry Petrov