Things like that often will be, which is why you generally need to use the JMH harness to do microbenchmarking on the JVM. It uses internal APIs to stop the compiler treating results as dead and eliminating them.
In this case it doesn't happen because to see that the entire operation is dead requires the compiler to inline payload into main, but he says he disabled inlining for that method specifically so it wouldn't happen. Recall that the goal is to see the assembly for a block of code in isolation, not demo what the JVM can do when given free reign.
Sure, but neither javac (the Java to bytecode compiler) or HotSpot are doing that. The former tries to preserve as much as possible, and for the latter interprocedure analysis is too costly at run-time.
It is done, but for this case the problem is partial compilation. For this you'd need methods to be tagged as pure, but that assumption needs to propagate and it could be violated by a library being upgraded.
In this case it doesn't happen because to see that the entire operation is dead requires the compiler to inline payload into main, but he says he disabled inlining for that method specifically so it wouldn't happen. Recall that the goal is to see the assembly for a block of code in isolation, not demo what the JVM can do when given free reign.